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Sample records for superalloy haynes alloy

  1. Dynamic strain aging in Haynes 282 superalloy

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    Hörnqvist Magnus

    2014-01-01

    Full Text Available Haynes 282 is a newly introduced Ni-based superallony, developed to provide a combination of high-temperature mechanical properties, thermal stability and processability. The present contribution investigates the effect of dynamic strain aging (DSA on the deformation behaviour of Haynes 282 during monotonic and cyclic loading. It is shown that DSA (presumably related to carbon diffusion based on rough estimates of the activation energy completely dominates the development of the stress during cycling at intermediate temperatures, leading to extensive cyclic hardening and serrated yielding. However, no clear effects on the fatigue life or the resulting dislocation structure could be observed. The tensile properties were not severely affected, in spite of the presence of extensive serrated yielding, although a reduction in ductility was observed in the DSA temperature regime. During monotonic loading at lower strain rates indications of an additional DSA mechanism due to substitutional elements were observed.

  2. Corrosion behavior of Haynes {sup registered} 230 {sup registered} nickel-based super-alloys for integrated coal gasification combined cycle syngas plants. A plant exposure study

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    Lee, Sungkyu; Lee, Jieun; Kang, Suk-Hwan; Lee, Seung-Jong; Yun, Yongseung [Institute for Advanced Engineering (IAE), Gyeonggi-do (Korea, Republic of). Plant Engineering Center; Kim, Min Jung [Sungkyunkwan Univ, Gyeonggi-do (Korea, Republic of). Advanced Materials Technology Research Center

    2015-07-01

    The corrosion behavior of commercially available Haynes {sup registered} 230 {sup registered} nickel-based alloy samples was investigated by exposure to coal-gasifying integrated coal gasification combined cycle pilot plant facilities affiliated with the Institute for Advanced Engineering (2.005 MPa and 160-300 C). The morphological and microstructural analyses of the exposed samples were conducted using scanning electron microscopy and energy-dispersive X-ray spectroscopy analysis on the external surface of the recovered corrosion test samples to obtain information of the corrosion scale. These analyses based on the pre- and post-exposure corrosion test samples combined with thermodynamic Ellingham-Pourbaix stability diagrams provided preliminary insight into the mechanism of the observed corrosion behavior prevailing in the piping materials that connected the particulate removal unit and water scrubber of the integrated coal gasification combined cycle pilot plant. Uniform material wastage was observed after 46 hours of operation, and a preliminary corrosion mechanism was suggested: the observed material waste and corrosion behavior of the Haynes {sup registered} 230 {sup registered} nickel-based alloy samples cut off from the coal syngas integrated coal gasification combined cycle plant were explained by the formation of discontinuous (complex) oxide phases and subsequent chlorine-induced active oxidation under the predominantly reducing environment encountered. This contribution continues the already published studies of the Fe-Ni-Cr-Co alloy Haynes {sup registered} 556 {sup registered}.

  3. Corrosion behavior of Haynes registered 230 registered nickel-based super-alloys for integrated coal gasification combined cycle syngas plants. A plant exposure study

    International Nuclear Information System (INIS)

    Lee, Sungkyu; Lee, Jieun; Kang, Suk-Hwan; Lee, Seung-Jong; Yun, Yongseung; Kim, Min Jung

    2015-01-01

    The corrosion behavior of commercially available Haynes registered 230 registered nickel-based alloy samples was investigated by exposure to coal-gasifying integrated coal gasification combined cycle pilot plant facilities affiliated with the Institute for Advanced Engineering (2.005 MPa and 160-300 C). The morphological and microstructural analyses of the exposed samples were conducted using scanning electron microscopy and energy-dispersive X-ray spectroscopy analysis on the external surface of the recovered corrosion test samples to obtain information of the corrosion scale. These analyses based on the pre- and post-exposure corrosion test samples combined with thermodynamic Ellingham-Pourbaix stability diagrams provided preliminary insight into the mechanism of the observed corrosion behavior prevailing in the piping materials that connected the particulate removal unit and water scrubber of the integrated coal gasification combined cycle pilot plant. Uniform material wastage was observed after 46 hours of operation, and a preliminary corrosion mechanism was suggested: the observed material waste and corrosion behavior of the Haynes registered 230 registered nickel-based alloy samples cut off from the coal syngas integrated coal gasification combined cycle plant were explained by the formation of discontinuous (complex) oxide phases and subsequent chlorine-induced active oxidation under the predominantly reducing environment encountered. This contribution continues the already published studies of the Fe-Ni-Cr-Co alloy Haynes registered 556 registered .

  4. Effects of electrical discharge surface modification of superalloy Haynes 230 with aluminum and molybdenum on oxidation behavior

    International Nuclear Information System (INIS)

    Bai, C.-Y.

    2007-01-01

    The effects of the electrical discharge alloying (EDA) process on improving the high temperature oxidation resistance of the Ni-based superalloy Haynes 230 have been investigated. The 85 at.% Al and 15 at.% Mo composite electrode provided the surface alloying materials. An Al-rich layer is produced on the surface of the EDA specimen alloyed with positive electrode polarity, whereas, many discontinuous piled layers are attached to the surface of the EDA superalloy when negative electrode polarity is selected. The oxidation resistance of the specimen alloyed with positive electrode polarity is better than that of the unalloyed superalloy, and the effective temperature of oxidation resistance of the alloyed layer can be achieved to 1100 o C. Conversely, the oxidation resistance of the other EDA specimen alloyed with negative electrode polarity is even worse than that of the unalloyed superalloy

  5. Thermo-Viscoplastic Behavior of Ni-Based Superalloy Haynes 282 and Its Application to Machining Simulation

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    Marcos Rodríguez-Millán

    2017-12-01

    Full Text Available Ni-based superalloys are extensively used in high-responsibility applications in components of aerospace engines and gas turbines with high temperature service lives. The wrought, γ’-strengthened superalloy Haynes 282 has been recently developed for applications similar to other common superalloys, such as Waspaloy or Inconel 718, with improved creep behavior, thermal stability, and fabrication ability. Despite the potential of Haynes 282, there are still important gaps in the knowledge of the mechanical behavior of this alloy. In fact, it was not possible to find information concerning the mechanical behavior of the alloy under impulsive loading. This paper focuses on the mechanical characterization of the Haynes 282 at strain rates ranging from 0.1 to 2800 s−1 and high temperatures ranging from 293 to 523 K using Hopkinson bar compression tests. The experimental results from the thermo-mechanical characterization allowed for calibration of the Johnson–Cook model widely used in modeling metallic alloy’s responses under dynamic loading. Moreover, the behavior of Haynes 282 was compared to that reported for Inconel 718, and the results were used to successfully model the orthogonal cutting of Haynes 282, being a typical case of dynamic loading requiring previous characterization of the alloy.

  6. Microstructural analysis of laser weld fusion zone in Haynes 282 superalloy

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    Osoba, L.O. [Department of Mechanical and Manufacturing Engineering, University of Manitoba, Winnipeg, Manitoba, R3T 5V6 (Canada); Ding, R.G. [Department of Metallurgy and Materials Engineering, University of Birmingham, Birmingham B15 2TT (United Kingdom); Ojo, O.A., E-mail: ojo@cc.umanitoba.ca [Department of Mechanical and Manufacturing Engineering, University of Manitoba, Winnipeg, Manitoba, R3T 5V6 (Canada)

    2012-03-15

    Analytical electron microscopy and spectroscopy analyses of the fusion zone (FZ) microstructure in autogenous laser beam welded Haynes 282 (HY 282) superalloy were performed. The micro-segregation patterns observed in the FZ indicate that Co, Cr and Al exhibited a nearly uniform distribution between the dendrite core and interdendritic regions while Ti and Mo were rejected into the interdendritic liquid during the weld solidification. Transmission electron diffraction analysis and energy dispersive X-ray microanalysis revealed the second phase particles formed along the FZ interdendritic region to be Ti-Mo rich MC-type carbide particles. Weld FZ solidification cracking, which is sometimes associated with the formation of {gamma}-{gamma}' eutectic in {gamma}' precipitation strengthened nickel-base superalloys, was not observed in the HY 282 superalloy. Modified primary solidification path due to carbon addition in the newly developed superalloy is used to explain preclusion of weld FZ solidification cracking in the material. - Highlights: Black-Right-Pointing-Pointer A newly developed superalloy was welded by CO{sub 2} laser beam joining technique. Black-Right-Pointing-Pointer Electron microscopy characterization of the weld microstructure was performed. Black-Right-Pointing-Pointer Identified interdendritic microconstituents consist of MC-type carbides. Black-Right-Pointing-Pointer Modification of primary solidification path is used to explain cracking resistance.

  7. Microstructural analysis of laser weld fusion zone in Haynes 282 superalloy

    International Nuclear Information System (INIS)

    Osoba, L.O.; Ding, R.G.; Ojo, O.A.

    2012-01-01

    Analytical electron microscopy and spectroscopy analyses of the fusion zone (FZ) microstructure in autogenous laser beam welded Haynes 282 (HY 282) superalloy were performed. The micro-segregation patterns observed in the FZ indicate that Co, Cr and Al exhibited a nearly uniform distribution between the dendrite core and interdendritic regions while Ti and Mo were rejected into the interdendritic liquid during the weld solidification. Transmission electron diffraction analysis and energy dispersive X-ray microanalysis revealed the second phase particles formed along the FZ interdendritic region to be Ti–Mo rich MC-type carbide particles. Weld FZ solidification cracking, which is sometimes associated with the formation of γ–γ' eutectic in γ' precipitation strengthened nickel-base superalloys, was not observed in the HY 282 superalloy. Modified primary solidification path due to carbon addition in the newly developed superalloy is used to explain preclusion of weld FZ solidification cracking in the material. - Highlights: ► A newly developed superalloy was welded by CO 2 laser beam joining technique. ► Electron microscopy characterization of the weld microstructure was performed. ► Identified interdendritic microconstituents consist of MC-type carbides. ► Modification of primary solidification path is used to explain cracking resistance.

  8. HAYNES 244 alloy – a new 760 ∘C capable low thermal expansion alloy

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    Fahrmann Michael G.

    2014-01-01

    Full Text Available HAYNES® 244TM alloy is a new 760∘C capable, high strength low thermal expansion (CTE alloy. Its nominal chemical composition in weight percent is Ni – 8 Cr – 22.5 Mo – 6 W. Recently, a first mill-scale heat of 244 alloy was melted by Haynes International, and processed to various product forms such as re-forge billet, plate, and sheet. This paper presents key attributes of this new alloy (CTE, strength, low-cycle fatigue performance, oxidation resistance, thermal stability as they pertain to the intended use in rings and seals of advanced gas turbines.

  9. Weldability of the superalloys Haynes 188 and Hastelloy X by Nd:YAG

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    Graneix Jérémie

    2014-01-01

    Full Text Available The requirements for welded aircraft parts have become increasingly severe, especially in terms of the reproducibility of the geometry and metallurgical grade of the weld bead. Laser welding is a viable method of assembly to meet these new demands, because of automation, to replace the manual TIG welding process. The purpose of this study is to determine the weldability of Hastelloy X and Haynes 188 alloys by the butt welding process with a Nd:YAG laser. To identify the influential parameters of the welding process (laser power, feed rate, focal diameter and flow of gas while streamlining testing, an experimental design was established with the CORICO software using the graphic correlation method. The position of the focal point was fixed at 1/3 of the thickness of the sheet. The gas flow rate and the power of the beam have a major effect on the mechanical properties and geometry of the weld. The strength of the weld is comparable to that of the base metal. However, there is a significant decrease in the elongation at break of approximately 30%. The first observations of the cross section of the weld by scanning electron microscopy coupled with EBSD analysis show a molten zone presenting dendritic large grains compared to the equiaxed grains of the base metals without a heat affected zone.

  10. Fatigue Crack Growth Behavior of Nickel-base Superalloy Haynes 282 at 550-750 °C

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    Rozman, K. A.; Kruzic, J. J.; Hawk, J. A.

    2015-08-01

    The fatigue crack growth rates for nickel-based superalloy Haynes 282 were measured at temperatures of 550, 650, and 750 °C using compact tension specimens with a load ratio of 0.1 and cyclic loading frequencies of 25 Hz and 0.25 Hz. Increasing the temperature from 550 to 750 °C caused the fatigue crack growth rates to increase from ~20 to 60% depending upon the applied stress intensity level. The effect of reducing the applied loading frequency increased the fatigue crack growth rates from ~20 to 70%, also depending upon the applied stress intensity range. The crack path was observed to be transgranular for the temperatures and frequencies used during fatigue crack growth rate testing. At 750 °C, there were some indications of limited intergranular cracking excursions at both loading frequencies; however, the extent of intergranular crack growth was limited and the cause is not understood at this time.

  11. Fatigue Crack Growth Mechanisms for Nickel-based Superalloy Haynes 282 at 550-750 °C

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    Rozman, Kyle A.; Kruzic, Jamie J.; Sears, John S.; Hawk, Jeffrey A.

    2015-10-01

    The fatigue crack growth rates for nickel-based superalloy Haynes 282 were measured at 550, 650, and 750 °C using compact tension specimens with a load ratio of 0.1 and cyclic loading frequencies of 25 and 0.25 Hz. The crack path was observed to be primarily transgranular for all temperatures, and the observed effect of increasing temperature was to increase the fatigue crack growth rates. The activation energy associated with the increasing crack growth rates over these three temperatures was calculated less than 60 kJ/mol, which is significantly lower than typical creep or oxidation mechanisms; therefore, creep and oxidation cannot explain the increase in fatigue crack growth rates. Transmission electron microscopy was done on selected samples removed from the cyclic plastic zone, and a trend of decreasing dislocation density was observed with increasing temperature. Accordingly, the trend of increasing crack growth rates with increasing temperature was attributed to softening associated with thermally assisted cross slip and dislocation annihilation.

  12. Effects of long-term high temperature exposure on the microstructure of Haynes alloy 230

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    Veverkova, J.; Strang, A.; Atkinson, H.V. [Leicester Univ. (United Kingdom). Dept. of Engineering; Marchant, G.R. [Siemens Industrial Turbomachinery Ltd., Lincoln (United Kingdom)

    2010-07-01

    Haynes Alloy 230 was specifically designed to have excellent long-term thermal stability and resistance to the precipitation of damaging phases. This paper describes in detail studies on the effects of long-term high temperature exposure on the hardness, microstructural changes and tensile properties of thermally exposed samples of Haynes Alloy 230. The samples from the 2mm thick sheet material have been investigated using X-Ray diffraction and advanced electron microscopy techniques (FEGSEM, TEM etc.). The evolution of the precipitating phases was monitored across a wide range of temperatures (from 500 C to 1170 C) and durations (from 24 hours up to 30000 hours) and several key phases have been identified. In addition to the primary W-rich carbide and the precipitation of Cr-rich M{sub 23}C{sub 6}, a new brittle phase/carbide was observed within the microstructure at the highest exposure temperatures (above 930 C). (orig.)

  13. Optimization of Cutting Parameters of the Haynes 718 Nickel Alloy With Gas CO2 Laser

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    Jana PETRŮ

    2011-06-01

    Full Text Available This article deals with the application of laser technology and the optimization of parameters in the area of nickel alloy laser cutting intended for application in the aircraft industry. The main goal is to outline possibilities of use of the laser technology, primarily its application in the area of 3D material cutting. This experiment is focused on the optimization of cutting parameters of the Haynes 718 alloy with a gas CO2 laser. Originating cuts are evaluated primarily from the point of view of cut quality and accompanying undesirable phenomena occurring in the process of cutting. In conclusion the results achieved in the metallographic laboratory are described and analyzed.

  14. Proceedings of the Conference on Refractory Alloying Elements in Superalloys

    International Nuclear Information System (INIS)

    1984-01-01

    Some papers about the use of refractory metals in superalloys are presented. Mechanical properties, thermodynamics properties, use for nuclear fuels and corrosion resistance of those alloys are studied. (E.G.) [pt

  15. Microstructure of Haynes® 282® Superalloy after Vacuum Induction Melting and Investment Casting of Thin-Walled Components

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    Krzysztof J. Kurzydlowski

    2013-11-01

    Full Text Available The aim of this work was to characterize the microstructure of the as-cast Haynes® 282® alloy. Observations and analyses were carried out using techniques such as X-ray diffraction (XRD, light microscopy (LM, scanning electron microscopy (SEM, transmission electron microscopy (TEM, X-ray spectroscopy (EDS, wave length dispersive X-ray spectroscopy (WDS, auger electron spectroscopy (AES and electron energy-loss spectrometry (EELS. The phases identified in the as-cast alloy include: γ (gamma matrix, γʹ (matrix strengthening phase, (TiMoCrC (primary carbide, TiN (primary nitride, σ (sigma-TCP phase, (TiMo2SC (carbosulphide and a lamellar constituent consisting of molybdenum and chromium rich secondary carbide phase together with γ phase. Within the dendrites the γʹ appears mostly in the form of spherical, nanometric precipitates (74 nm, while coarser (113 nm cubic γʹ precipitates are present in the interdendritic areas. Volume fraction content of the γʹ precipitates in the dendrites and interdendritic areas are 9.6% and 8.5%, respectively. Primary nitrides metallic nitrides (MN, are homogeneously dispersed in the as-cast microstructure, while primary carbides metallic carbides (MC, preferentially precipitate in interdendritic areas. Such preference is also observed in the case of globular σ phase. Lamellar constituents characterized as secondary carbides/γ phases were together with (TiMo2SC phase always observed adjacent to σ phase precipitates. Crystallographic relations were established in-between the MC, σ, secondary carbides and γ/γʹ matrix.

  16. Low-cycle fatigue deformation characteristics of Haynes {reg{underscore}sign} HR-120{reg{underscore}sign} alloy

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    Liaw, P.K.; He, Y.H.; Miller, L.; Huang, M.; Brooks, C.R.; Seeley, R.R.; Klarstrom, D.L.

    1999-07-01

    Low-cycle fatigue deformation characteristics of HAYNES HR-120 alloy at room and high temperatures were studied under axial strain control. Test results show that there is a significant effect of test temperature on the low-cycle fatigue behavior of HAYNES HR-120 alloy. It was found that the alloy could cyclically harden at moderately high temperatures (649 C and 871 C), but generally cyclically soften at room temperature (24 C) and high temperature (982 C). However, the variation of the stress amplitude with cycles at the temperatures of 24 C and 982 C depended on the total strain range. The significant cyclic hardening of the alloy occurred at the high total strain ranges of 1.5% and 2.0% during the beginning state of the test at both 24C and 982 C. Microstructural analyses indicated that the cyclic hardening behavior of the alloy at the test temperature of 649 C could be related to the formation of a number of deformation bands. Nevertheless, increasing the test temperature to 871 C, cyclic hardening was attributed to the precipitation of secondary-phase particles. Furthermore, it was also found that the coarsening of secondary-phase particles brought about cyclic softening of the alloy at the high temperature of 982 C. Coffin-Manson equations and Holloman equations were given for HAYNES HR-120 alloy at different temperatures.

  17. Surface alloying of nickel based superalloys by laser

    International Nuclear Information System (INIS)

    Rodriguez, G.P.; Garcia, I.; Damborenea, J.J. de

    1998-01-01

    Ni based superalloys present a high oxidation resistance at high temperature as well as good mechanical properties. But new technology developments force to research in this materials to improve their properties at high temperature. In this work, two Ni based superalloys (Nimonic 80A and Inconel 600) were surface alloyed with aluminium using a high power laser. SEM and EDX were used to study the microstructure of the obtained coatings. Alloyed specimens were tested at 1.273 K between 24 and 250 h. Results showed the generation of a protective and continuous coating of alumina on the laser treated specimens surface that can improve oxidation resistance. (Author) 8 refs

  18. Tensile and Creep-Rupture Evaluation of a New Heat of Haynes Alloy 25

    International Nuclear Information System (INIS)

    Shingledecker, J.P.; Glanton, D.B.; Martin, R.L.; Sparks, B.L.; Swindeman, R.W.

    2007-01-01

    From 1999 to 2006, a program was undertaken within the Materials Science and Technology Division, formerly the Metals and Ceramics Division, of Oak Ridge National Laboratory to characterize the tensile and creep-rupture properties of a newly produced heat of Haynes alloy 25 (L-605). Tensile properties from room temperature to 1100 C were evaluated for base material and welded joints aged up to 12,000 hours at 675 C. Creep and creep-rupture tests were conducted on base metal and cross-weldments from 650 to 950 C. Pressurized tubular creep tests were conducted to evaluate multiaxial creep-rupture response of the material. Over 800,000 hours of creep test data were generated during the test program with the longest rupture tests extending beyond 38,000 hours, and the longest creep-rate experiments exceeding 40,000 hours

  19. Research on 16Mo3 (16M Steel Pipes Overlaid with Haynes Nicro625 Alloy Using MIG (131 Method / Badania Rur Ze Stali 16Mo3 (16M Napawanych Metodą MIG (131 Stopem Haynes Nicro625

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    Golański G.

    2015-12-01

    Full Text Available The paper presents the research on the microstructure and mechanical properties of a pipe made of 16Mo3 steel, overlaid with superalloy based on Haynes NiCro625 nickel. The overlay weld was overlaid using the MIG (131 method. The performed macro - and microscopic tests have shown the correct structure of the overlay weld without any welding unconformities. The examined overlay weld was characterized by a dendritic structure of the primary crystals accumulating towards the heat removal. It has been proved that the content of iron in the surface zone does not exceed 7%, and the steel-superalloy joint shows the highest properties in comparison with the materials joined.

  20. Mechanical characterization of superalloys for space reactors

    International Nuclear Information System (INIS)

    Duchesne, J.

    1989-01-01

    The aim of this work is the selection of structural materials that can be used in the temperature range 600-900 0 C for a gas cooled space reactor producing electricity. Superalloys fit best the temperature range required. Five nickel base alloys are chosen for their good mechanical behaviour: HAYNES 230, HASTELLOY S, HASTELLOY X, HASTELLOY XR and PYRAD 38D. Metallography, tensile and hardness tests are realized. Sample contraction is evidenced for some creep tests, under low stress: 20MPa at 800 0 C, on HAYNES 230 and HASTELLOY X, probably related to the structural evolution of these materials corresponding to a decrease of the crystal parameter [fr

  1. Design of high entropy alloys based on the experience from commercial superalloys

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    Wang, Z.; Huang, Y.; Wang, J.; Liu, C. T.

    2015-01-01

    High entropy alloys (HEAs) have been drawing increasing attention recently and gratifying results have been obtained. However, the existing metallurgic rules of HEAs could not provide specific information of selecting candidate alloys for structural applications. Our brief survey reveals that many commercial superalloys have medium and even to high configurational entropies. The experience of commercial superalloys provides a clue for helping us in the development of HEAs for structural applications.

  2. Alloying effects of refractory elements in the dislocation of Ni-based single crystal superalloys

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    Shiyu Ma

    2016-12-01

    Full Text Available The alloying effects of W, Cr and Re in the [100] (010 edge dislocation cores (EDC of Ni-based single crystal superalloys are investigated using first-principles based on the density functional theory (DFT. The binding energy, Mulliken orbital population, density of states, charge density and radial distribution functions are discussed, respectively. It is clearly demonstrated that the addition of refractory elements improves the stability of the EDC systems. In addition, they can form tougher bonds with their nearest neighbour (NN Ni atoms, which enhance the mechanical properties of the Ni-based single crystal superalloys. Through comparative analysis, Cr-doped system has lower binding energy, and Cr atom has evident effect to improve the systemic stability. However, Re atom has the stronger alloying effect in Ni-based single crystal superalloys, much more effectively hindering dislocation motion than W and Cr atoms.

  3. Gamma Prime Stability in Haynes 282: Theoretical and Experimental Considerations

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    Hawk, Jeffrey A.; Cheng, Tian-Le; Sears, John S.; Jablonski, Paul D.; Wen, You-Hai

    2015-11-01

    The life cycle requirements for advanced Ni alloys are very demanding and can be on the order of several hundreds of thousands of hours. Results are presented on a wrought Ni-based superalloy designed within the nominal chemistry range of Haynes 282 with a fixed amount of γ' strengthening phase, and either low Al or Ti (within the alloy specification) to give different ratios of Ti/Al, and thus, different γ' misfit with the γ matrix. The effect that these changes have on the γ' misfit and its relevance to long-term microstructural stability is being explored both experimentally as well as with computational modeling with results through almost 10,000 h. The basics of the modeling approach are presented as are the procedures for evaluating the γ' volume fractions from transmission electron microscopy (TEM) micrographs and correcting these volume fractions for truncation error due to TEM foil thickness. Results on each alloy formulation are compared and discussed with respect to possible γ' coarsening due to the different Ti/Al ratio and what this might mean for the long-term stability of the alloy.

  4. Mechanical characterization of superalloys for space reactors

    International Nuclear Information System (INIS)

    Duchesne, J.

    1989-01-01

    The purpose of this work is the choice of materials usable between 600 and 900 0 C for nuclear space reactor structures. The main criterion of selection for these materials is their good creep behaviour. Consequently, macroscopic theories of creep and several extrapolation methods were described. Superalloys seem the best materials for the studied range of temperatures. Five of them, base nickel, ones unusual in nuclear industry were selected for their good mechanical properties. Three of them are industrial alloys: the first, HAYNES 230 is a recent one, HASTELLOY S and X are more standard materials. The last two, HASTELLOY XR and PYRAD 38 D are issued from special fabrications. Creep tests metallographic investigations, hardness and tensile tests were performed. A contraction of samples was observed during some creep tests under a low stress, 20MPa at 800 0 C, for HAYNES 230 and HASTELLOY X. This could be due to a structural evolution of these materials connected to a decrease of the cristalline parameter. In addition, correlations were observed between certain characteristics determined from slow tensile tests and short duration creep tests. These correlations present a large interest because, at the present time, creep tests cannot be executed on irradiated materials in our laboratories. Consequently creep behaviour of irradiated materials seem may be deduced. Further studies are needed to explain and confirm the behaviour of the most interesting materials under low stresses: HAYNES 230 and HASTELLOY XR to anticipate their behaviour in working conditions [fr

  5. Creep and residual mechanical properties of cast superalloys and oxide dispersion strengthened alloys

    Science.gov (United States)

    Whittenberger, J. D.

    1981-01-01

    Tensile, stress-rupture, creep, and residual tensile properties after creep testing were determined for two typical cast superalloys and four advanced oxide dispersion strengthened (ODS) alloys. The superalloys examined included the nickel-base alloy B-1900 and the cobalt-base alloy MAR-M509. The nickel-base ODS MA-757 (Ni-16CR-4Al-0.6Y2O3 and the iron-base ODS alloy MA-956 (Fe-20Cr-5Al-0.8Y2O3) were extensively studied, while limited testing was conducted on the ODS nickel-base alloys STCA (Ni-16Cr-4.5Al-2Y2O3) with a without Ta and YD-NiCrAl (Ni-16Cr-5Al-2Y2O3). Elevated temperature testing was conducted from 114 to 1477 K except for STCA and YD-NiCrAl alloys, which were only tested at 1366 K. The residual tensile properties of B-1900 and MAR-M509 are not reduced by prior creep testing (strains at least up to 1 percent), while the room temperature tensile properties of ODS nickel-base alloys can be reduced by small amounts of prior creep strain (less than 0.5 percent). The iron-base ODS alloy MA-956 does not appear to be susceptible to creep degradation at least up to strains of about 0.25 percent. However, MA-956 exhibits unusual creep behavior which apparently involves crack nucleation and growth.

  6. Computational Design of Creep-Resistant Alloys and Experimental Validation in Ferritic Superalloys

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    Liaw, Peter

    2014-12-31

    A new class of ferritic superalloys containing B2-type zones inside parent L21-type precipitates in a disordered solid-solution matrix, also known as a hierarchical-precipitate strengthened ferritic alloy (HPSFA), has been developed for high-temperature structural applications in fossil-energy power plants. These alloys were designed by the addition of the Ti element into a previously-studied NiAl-strengthened ferritic alloy (denoted as FBB8 in this study). In the present research, systematic investigations, including advanced experimental techniques, first-principles calculations, and numerical simulations, have been integrated and conducted to characterize the complex microstructures and excellent creep resistance of HPSFAs. The experimental techniques include transmission-electron microscopy, scanningtransmission- electron microscopy, neutron diffraction, and atom-probe tomography, which provide detailed microstructural information of HPSFAs. Systematic tension/compression creep tests revealed that HPSFAs exhibit the superior creep resistance, compared with the FBB8 and conventional ferritic steels (i.e., the creep rates of HPSFAs are about 4 orders of magnitude slower than the FBB8 and conventional ferritic steels.) First-principles calculations include interfacial free energies, anti-phase boundary (APB) free energies, elastic constants, and impurity diffusivities in Fe. Combined with kinetic Monte- Carlo simulations of interdiffusion coefficients, and the integration of computational thermodynamics and kinetics, these calculations provide great understanding of thermodynamic and mechanical properties of HPSFAs. In addition to the systematic experimental approach and first-principles calculations, a series of numerical tools and algorithms, which assist in the optimization of creep properties of ferritic superalloys, are utilized and developed. These numerical simulation results are compared with the available experimental data and previous first

  7. Atom probe tomography of Ni-base superalloys Allvac 718Plus and Alloy 718

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    Viskari, L., E-mail: viskari@chalmers.se [Chalmers University of Technology, Gothenburg (Sweden); Stiller, K. [Chalmers University of Technology, Gothenburg (Sweden)

    2011-05-15

    Atom probe tomography (APT) allows near atomic scale compositional- and morphological studies of, e.g. matrix, precipitates and interfaces in a wide range of materials. In this work two Ni-base superalloys with similar compositions, Alloy 718 and its derivative Allvac 718Plus, are subject for investigation with special emphasis on the latter alloy. The structural and chemical nuances of these alloys are important for their properties. Of special interest are grain boundaries as their structure and chemistry are important for the materials' ability to resist rapid environmentally induced crack propagation. APT has proved to be suitable for analyses of these types of alloys using voltage pulsed APT. However, for investigations of specimens containing grain boundaries and other interfaces the risk for early specimen fracture is high. Analyses using laser pulsing impose lower electrical field on the specimen thereby significantly increasing the success rate of investigations. Here, the effect of laser pulsing was studied and the derived appropriate acquisition parameters were then applied for microstructural studies, from which initial results are shown. Furthermore, the influence of the higher evaporation field experienced by the hardening {gamma}' Ni{sub 3}(Al,Nb) precipitates on the obtained results is discussed. -- Research highlights: {yields} Laser pulsed APT is shown to be a good method for analysis of Ni-based superalloys. {yields} The evaporation field is shown to be different for different phases which affects reconstructions. {yields} B and P are shown to segregate to grain boundaries. {yields} Initial results of {delta}-phase analysed by APT are shown.

  8. Refractory metal superalloys: Design of yttrium aluminum garnet passivating niobium alloys

    Science.gov (United States)

    Bryan, David

    A systems-based approach, integrating computational modeling with experimental techniques to approach engineering problems in a time and cost efficient manner, was employed to design a Nb-based refractory superalloy for use at 1300°C. Ashby-type selection criteria for both thermodynamic and kinetic parameters were employed to identify a suitable protective oxide for Nb alloys. Yttrium aluminum garnet (YAG) was selected as the most promising candidate for its excellent combination of desirable properties. The alloy microstructural concept was based upon the gamma - gamma' nickel-based superalloys in which the multifunctional gamma' phase serves as both a creep strengthening dispersion and a source of reactive elements for oxide passivation. Candidate ternary Pd-Y-Al and Pt-Y-Al compounds were fabricated and characterized by XRD and DTA. Of the intermetallics studied, only PtYAl had a high enough melting point (1580°C) for use in an alloy operating at 1300°C. The alloy matrix design was based upon Wahl's extension of Wagner's criterion for protective oxidation, requiring a reduction of the product N ODO/DAl by 5 orders of magnitude relative to binary Nb-Al. A thermodynamic and kinetic analysis identified elements with large oxygen affinities as the most beneficial for reducing the magnitude of the quantity NOD O. Construction of a combined thermodynamic and mobility database identified increased Al solubility as the best approach for increasing D Al. Utilizing the thermodynamic and mobility databases, obtained from a combination of model alloys, oxidation experiments, and first principles calculations, theoretical designs predicted the large changes in solubility and transport parameters were achievable. Several prototype alloys were then fabricated and evaluated via oxidation tests at both 1300°C and 1100°C. YAG formation was demonstrated as part of multicomponent oxide scales in the alloys that exhibited the greatest reduction in oxidation rates. The oxidation

  9. Effect of long-term aging at 8150C on the tensile properties and microstructural stability of four cobalt- and nickel-base superalloys

    International Nuclear Information System (INIS)

    Hammond, J.P.

    1976-08-01

    Two heats of Haynes alloy 25 and one heat each of Haynes alloy 188, Hastelloy N, and Inconel 625 were tensile tested after aging for 11,000 h at 816 0 C. Yield strength, ultimate tensile strength, and elongation were determined 24, 316, 760, and 982 0 C and compared with typical properties for these materials in the solution annealed condition. Toughness values were determined for these materials from their engineering stress-strain curves. The long-term aging treatment degraded ductility and toughness at room temperature but, contrary to behavior expected for overaging, enhanced them over those for the solution annealed condition in tests at 760 0 C. The tensile properties of the aged superalloys were correlated with mode of fracture and the amounts, identity, and morphology of the precipitates. Aging substantially depleted the hardener tungsten from the matrix in the cobalt-base alloys

  10. Design of a braze alloy for fast epitaxial brazing of superalloys

    Science.gov (United States)

    Piegert, S.; Laux, B.; Rösier, J.

    2012-07-01

    For the repair of directionally solidified turbine components made of nickel-based superalloys, a new high-temperature brazing method has been developed. Utilising heterogeneous nucleation on the crack surface, the microstructure of the base material can be reproduced, i.e. single crystallinity can be maintained. In contrast to commonly used eutectic braze alloys, such as nickel-boron or nickel-silicon systems, the process is not diffusion controlled but works with a consolute binary base system. The currently applied epitaxial brazing methods rely on isothermal solidification diffusing the melting point depressants into the base material until their concentration is reduced so that the liquid braze solidifies. Contrary, the identified Ni-Mn consolute system enables a temperature driven epitaxial solidification resulting in substantially reduced process duration. The development of the braze alloys was assisted using the CALPHAD software Thermo-Calc. The solidification behaviour was estimated by kinetic calculations with realistic boundary conditions. Finally, the complete system, including braze alloy as well as substrate material, was modelled by means of DICTRA. Subsequently, the thermodynamic properties of the braze alloys were experimentally analysed by DSC measurements. For brazing experiments 300 μm wide parallel gaps were used. Complete epitaxial solidification, i.e. the absence of high-angle grain boundaries, could be achieved within brazing times being up to two orders of magnitude shorter compared to diffusion brazing processes. Theoretically and experimentally evaluated process windows reveal similar shapes. However, a distinct shift has to be stated which can be ascribed to the limited accuracy of the underlying thermodynamic databases.

  11. Microstructural evolution of cold-sprayed Inconel 625 superalloy coatings on low alloy steel substrate

    International Nuclear Information System (INIS)

    Chaudhuri, Atanu; Raghupathy, Y.; Srinivasan, Dheepa; Suwas, Satyam; Srivastava, Chandan

    2017-01-01

    This study illustrates microstructural evolution of INCONEL 625 superalloy coatings cold-sprayed on a 4130 chrome alloy steel with medium carbon content. INCONEL 625 powder (5–25 μm) were successfully cold sprayed without any oxidation. The comprehensive microstructure analysis of the as-sprayed coatings and of the substrate-coating interface was carried out using EBSD, TEM, and XRD. The coating microstructure at the substrate-coating interface was markedly different from the microstructure away from the interface. The coating microstructure at steel-coating interface consisted of a fine layer of small grains. The microstructure beyond this fine layer can be divided into splats, inter splat and intra splat boundaries. Both splat and splat boundaries exhibited deformation induced dislocations. Dynamic recovery of dislocations-ridden regions inside the splat was responsible for the development of sub grain structure inside a splat with both low and high angle grain boundaries. Splat-splat (inter splat) boundary consisted of a relatively high density of dislocations and shear bands as a result of adiabatic shear flow localisation. This flow instability is believed to enhance the microstructural integrity by eliminating porosity at splat-splat boundaries. Based on the microstructural analysis using electron microscopy, a plausible mechanism for the development of microstructure has been proposed in this work. Cold spray technique can thus be deployed to develop high quality coatings of commercial importance. - Graphical abstract: Schematics of the evolution of microstructure at the 4130 steel substrate close to interface. i) initial deformation close to interface. ii) Accumulation of dislocation in the substrate. iii) Formation of cell structure due to dislocation tangling and arrangement. iv) Dislocation rearrangement and subgrain formation. v.a) Formation HAGB from dislocation accumulation into LAGB. v.b) HAGB formation through DRX by progressive lattice rotation

  12. Haynes, Ray oral history interviews

    OpenAIRE

    Interviewee: Haynes, Ray; Interviewer: Walliser, Andrea; Interviewer: Bauder, Ken; Principal Investigator: Hall, Peter V

    2013-01-01

    Ray Haynes is a former president of the BC Federation of Labour. As a young man Haynes worked at Hudson’s Bay Company Wholesale, a division of the Hudson’s Bay Company, where he reported earning a low wage and working in poor conditions. He then worked at Canadian White Pine sawmill where he learned about labour and other social issues from union members who were communist, Leninist, and Trotskyist. He worked at White Pine for only 18 months even though he was earning a high wage. Haynes told...

  13. Effects of alloying element and temperature on the stacking fault energies of dilute Ni-base superalloys.

    Science.gov (United States)

    Shang, S L; Zacherl, C L; Fang, H Z; Wang, Y; Du, Y; Liu, Z K

    2012-12-19

    A systematic study of stacking fault energy (γ(SF)) resulting from induced alias shear deformation has been performed by means of first-principles calculations for dilute Ni-base superalloys (Ni(23)X and Ni(71)X) for various alloying elements (X) as a function of temperature. Twenty-six alloying elements are considered, i.e., Al, Co, Cr, Cu, Fe, Hf, Ir, Mn, Mo, Nb, Os, Pd, Pt, Re, Rh, Ru, Sc, Si, Ta, Tc, Ti, V, W, Y, Zn, and Zr. The temperature dependence of γ(SF) is computed using the proposed quasistatic approach based on a predicted γ(SF)-volume-temperature relationship. Besides γ(SF), equilibrium volume and the normalized stacking fault energy (Γ(SF) = γ(SF)/Gb, with G the shear modulus and b the Burgers vector) are also studied as a function of temperature for the 26 alloying elements. The following conclusions are obtained: all alloying elements X studied herein decrease the γ(SF) of fcc Ni, approximately the further the alloying element X is from Ni on the periodic table, the larger the decrease of γ(SF) for the dilute Ni-X alloy, and roughly the γ(SF) of Ni-X decreases with increasing equilibrium volume. In addition, the values of γ(SF) for all Ni-X systems decrease with increasing temperature (except for Ni-Cr at higher Cr content), and the largest decrease is observed for pure Ni. Similar to the case of the shear modulus, the variation of γ(SF) for Ni-X systems due to various alloying elements is traceable from the distribution of (magnetization) charge density: the spherical distribution of charge density around a Ni atom, especially a smaller sphere, results in a lower value of γ(SF) due to the facility of redistribution of charges. Computed stacking fault energies and the related properties are in favorable accord with available experimental and theoretical data.

  14. Modeling Long-term Creep Performance for Welded Nickel-base Superalloy Structures for Power Generation Systems

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Chen [GE Global Research, NIskayuna, NY (United States); Gupta, Vipul [GE Global Research, NIskayuna, NY (United States); Huang, Shenyan [GE Global Research, NIskayuna, NY (United States); Soare, Monica [GE Global Research, NIskayuna, NY (United States); Zhao, Pengyang [GE Global Research, NIskayuna, NY (United States); Wang, Yunzhi [GE Global Research, NIskayuna, NY (United States)

    2017-02-28

    The goal of this project is to model long-term creep performance for nickel-base superalloy weldments in high temperature power generation systems. The project uses physics-based modeling methodologies and algorithms for predicting alloy properties in heterogeneous material structures. The modeling methodology will be demonstrated on a gas turbine combustor liner weldment of Haynes 282 precipitate-strengthened nickel-base superalloy. The major developments are: (1) microstructure-property relationships under creep conditions and microstructure characterization (2) modeling inhomogeneous microstructure in superalloy weld (3) modeling mesoscale plastic deformation in superalloy weld and (4) a constitutive creep model that accounts for weld and base metal microstructure and their long term evolution. The developed modeling technology is aimed to provide a more efficient and accurate assessment of a material’s long-term performance compared with current testing and extrapolation methods. This modeling technology will also accelerate development and qualification of new materials in advanced power generation systems. This document is a final technical report for the project, covering efforts conducted from October 2014 to December 2016.

  15. Kinetics of Grain Growth in 718 Ni-Base Superalloy

    Directory of Open Access Journals (Sweden)

    Huda Z.

    2014-10-01

    Full Text Available The Haynes® 718 Ni-base superalloy has been investigated by use of modern material characterization, metallographic and heat treatment equipment. Grain growth annealing experiments at temperatures in the range of 1050 – 1200 oC (1323–1473K for time durations in the range of 20 min-22h have been conducted. The kinetic equations and an Arrhenius-type equation have been applied to compute the grain-growth exponent n and the activation energy for grain growth, Qg, for the investigated alloy. The grain growth exponent, n, was computed to be in the range of 0.066-0.206; and the n values have been critically discussed in relation to the literature. The activation energy for grain growth, Qg, for the investigated alloy has been computed to be around 440 kJ/mol; and the Qg data for the investigated alloy has been compared with other metals and alloys and ceramics; and critically analyzed in relation to our results.

  16. Numerical multi-criteria optimization methods for alloy design. Development of new high strength nickel-based superalloys and experimental validation

    Energy Technology Data Exchange (ETDEWEB)

    Rettig, Ralf; Mueller, Alexander; Ritter, Nils C.; Singer, Robert F. [Institute of Science and Technology of Metals, Department of Materials Science and Engineering, University of Erlangen (Germany)

    2016-07-01

    A new approach for the design of optimum balanced metallic alloys is presented. It is based on a mathematical multi-criteria optimization method which uses different property models to predict the alloy behavior in dependency of composition. These property models are mostly based on computational thermodynamics (CALPHAD-method). The full composition range of the alloying elements can be considered using these models. In alloy design usually several contradicting goals have to be fulfilled. This is handled by the calculation of so-called Pareto-fronts. The aim of our approach is to guide the experimental research towards new alloy compositions that have a high probability of having very good properties. Consequently the number of required test alloys can be massively reduced. The approach will be demonstrated for the computer-aided design of a new Re-free superalloy with nearly identical creep strength as that of Re-containing superalloys. Our starting point for the design was to maintain the good properties of the gamma prime-phase in well-known alloys like CMSX-4 and to maximize the solid solution strengthening of W and Mo. The presented experimental measurements proof the excellent properties.

  17. Influence of the alloy composition on the oxidation and internal-nitridation behaviour of nickel-base superalloys

    International Nuclear Information System (INIS)

    Krupp, U.; Christ, H.-J.

    1999-01-01

    Internal nitridation of nickel-base superalloys takes place as a consequence of the failure of protecting oxide scales (Al 2 O 3 and Cr 2 O 3 , respectively) and leads to a deterioration of the material properties due to near-surface embrittlement caused by the nitrides precipitated (TiN and AlN, respectively) and due to near-surface dissolution of the γ' phase. By using thermogravimetric methods in a temperature range between 800 C and 1100 C supplemented by microstructural examinations, the failure potential due to internal nitridation could be documented. A quantification was carried out by extending the experimental program to thermogravimetric studies in a nearly oxygen-free nitrogen atmosphere which was also applied to various model alloys of the system Ni-Cr-Al-Ti. It could be shown that the nitrogen diffusivity and solubility in nickel-base alloys is influenced particularly by the chromium concentration. An increasing chromium content leads to an enhanced internal-nitridation attack. (orig.)

  18. Recent Advances in Creep Modelling of the Nickel Base Superalloy, Alloy 720Li.

    Science.gov (United States)

    Harrison, William; Whittaker, Mark; Williams, Steve

    2013-03-20

    Recent work in the creep field has indicated that the traditional methodologies involving power law equations are not sufficient to describe wide ranging creep behaviour. More recent approaches such as the Wilshire equations however, have shown promise in a wide range of materials, particularly in extrapolation of short term results to long term predictions. In the aerospace industry however, long term creep behaviour is not critical and more focus is required on the prediction of times to specific creep strains. The current paper illustrates the capability of the Wilshire equations to recreate full creep curves in a modern nickel superalloy. Furthermore, a finite-element model based on this method has been shown to accurately predict stress relaxation behaviour allowing more accurate component lifing.

  19. Solidification and solid state phenomena during TLP bonding of IN718 superalloy using Ni–Si–B ternary filler alloy

    Energy Technology Data Exchange (ETDEWEB)

    Pouranvari, M., E-mail: mpouranvari@yahoo.com [Department of Materials Science and Engineering, Sharif University of Technology, Tehran 11365-11155 (Iran, Islamic Republic of); Ekrami, A.; Kokabi, A.H. [Department of Materials Science and Engineering, Sharif University of Technology, Tehran 11365-11155 (Iran, Islamic Republic of)

    2013-06-25

    Highlights: ► Microstructure evolution during TLP bonding of IN718 using Ni–Si–B filler. ► Athermal solidification path is influenced by severe segregation of B and Si in residual liquid. ► High hardness of ASZ microconstituents necessitates designing a PBHT to avert brittleness. ► Diffusion induced Cr–Mo–Nb based boride precipitation was observed in DAZ. ► Boride precipitates in DAZ influence the corrosion resistance and aging behavior. -- Abstract: This paper addresses solidification and solid state precipitation phenomena during transient liquid phase (TLP) bonding of wrought IN718 nickel base superalloy using Ni–4.5Si–3.2B (wt.%) ternary filler alloy. The solidification sequence of the residual liquid in the joint centerline was found to be (1) formation of proeutectic γ, followed by (2) γ/Ni{sub 3}B eutectic reaction, followed by (3) ternary eutectic of γ/Ni{sub 3}B/Ni{sub 6}Si{sub 2}B. Extensive fine Ni{sub 3}Si formed within the eutectic-γ via solid state precipitation during cooling. Extensive Cr–Mo–Nb rich boride precipitates were formed in the substrate region due to boron diffusion into the base metal during bonding process. The implications of the phase transformations on the mechanical properties, corrosion resistance and aging behavior of the joint, which are pertinent to the development of an optimum post bond heat treatment, are highlighted.

  20. Solidification and solid state phenomena during TLP bonding of IN718 superalloy using Ni–Si–B ternary filler alloy

    International Nuclear Information System (INIS)

    Pouranvari, M.; Ekrami, A.; Kokabi, A.H.

    2013-01-01

    Highlights: ► Microstructure evolution during TLP bonding of IN718 using Ni–Si–B filler. ► Athermal solidification path is influenced by severe segregation of B and Si in residual liquid. ► High hardness of ASZ microconstituents necessitates designing a PBHT to avert brittleness. ► Diffusion induced Cr–Mo–Nb based boride precipitation was observed in DAZ. ► Boride precipitates in DAZ influence the corrosion resistance and aging behavior. -- Abstract: This paper addresses solidification and solid state precipitation phenomena during transient liquid phase (TLP) bonding of wrought IN718 nickel base superalloy using Ni–4.5Si–3.2B (wt.%) ternary filler alloy. The solidification sequence of the residual liquid in the joint centerline was found to be (1) formation of proeutectic γ, followed by (2) γ/Ni 3 B eutectic reaction, followed by (3) ternary eutectic of γ/Ni 3 B/Ni 6 Si 2 B. Extensive fine Ni 3 Si formed within the eutectic-γ via solid state precipitation during cooling. Extensive Cr–Mo–Nb rich boride precipitates were formed in the substrate region due to boron diffusion into the base metal during bonding process. The implications of the phase transformations on the mechanical properties, corrosion resistance and aging behavior of the joint, which are pertinent to the development of an optimum post bond heat treatment, are highlighted

  1. Thermomechanical behavior of different Ni-base superalloys during cyclic loading at elevated temperatures

    Directory of Open Access Journals (Sweden)

    Huber Daniel

    2014-01-01

    Full Text Available The material behavior of three Ni-base superalloys (Inconel® 718, Allvac® 718PlusTM and Haynes® 282® during in-phase cyclic mechanical and thermal loading was investigated. Stress controlled thermo-mechanical tests were carried out at temperatures above 700 ∘C and different levels of maximum compressive stress using a Gleeble® 3800 testing system. Microstructure investigations via light optical microscopy (LOM and field emission gun scanning electron microscopy (FEG-SEM as well as numerical precipitation kinetics simulations were performed to interpret the obtained results. For all alloys, the predominant deformation mechanism during deformation up to low plastic strains was identified as dislocation creep. The main softening mechanism causing progressive increase of plastic strain after preceding linear behavior is suggested to be recrystallization facilitated by coarsening of grain boundary precipitates. Furthermore, coarsening and partial transformation of strengthening phases was observed. At all stress levels, Haynes® 282® showed best performance which is attributable to its stable microstructure containing a high phase fraction of small, intermetallic precipitates inside grains and different carbides evenly distributed along grain boundaries.

  2. Multiaxial Creep-Fatigue and Creep-Ratcheting Failures of Grade 91 and Haynes 230 Alloys Toward Addressing Design Issues of Gen IV Nuclear Power Plants

    Energy Technology Data Exchange (ETDEWEB)

    Hassan, Tasnim [North Carolina State Univ., Raleigh, NC (United States); Lissenden, Cliff [Penn State Univ., University Park, PA (United States); Carroll, Laura [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-04-01

    The proposed research will develop systematic sets of uniaxial and multiaxial experimental data at a very high temperature (850-950°C) for Alloy 617. The loading histories to be prescribed in the experiments will induce creep-fatigue and creep-ratcheting failure mechanisms. These experimental responses will be scrutinized in order to quantify the influences of temperature and creep on fatigue and ratcheting failures. A unified constitutive model (UCM) will be developed and validated against these experimental responses. The improved UCM will be incorporated into the widely used finite element commercial software packages ANSYS. The modified ANSYS will be validated so that it can be used for evaluating the very high temperature ASME-NH design-by-analysis methodology for Alloy 617 and thereby addressing the ASME-NH design code issues.

  3. Multiaxial Creep-Fatigue and Creep-Ratcheting Failures of Grade 91 and Haynes 230 Alloys Toward Addressing Design Issues of Gen IV Nuclear Power Plants

    International Nuclear Information System (INIS)

    Hassan, Tasnim; Lissenden, Cliff; Carroll, Laura

    2015-01-01

    The proposed research will develop systematic sets of uniaxial and multiaxial experimental data at a very high temperature (850-950°C) for Alloy 617. The loading histories to be prescribed in the experiments will induce creep-fatigue and creep-ratcheting failure mechanisms. These experimental responses will be scrutinized in order to quantify the influences of temperature and creep on fatigue and ratcheting failures. A unified constitutive model (UCM) will be developed and validated against these experimental responses. The improved UCM will be incorporated into the widely used finite element commercial software packages ANSYS. The modified ANSYS will be validated so that it can be used for evaluating the very high temperature ASME-NH design-by-analysis methodology for Alloy 617 and thereby addressing the ASME-NH design code issues.

  4. Carbide Transformation in Haynes 230 during Long-term Exposure at High Temperature

    International Nuclear Information System (INIS)

    Lee, Ho Jung; Kim, Hyunmyung; Hong, Sunghoon; Jang, Changheui

    2014-01-01

    Long-term aging behaviors of a solid solution hardened Ni-base superalloy, Haynes 230 at high temperature have not been fully investigated yet. In this study, long-term aging tests of Haynes 230 was carried out to evaluate microstructure changes especially in carbide evolution. In addition, its consequential effects on tensile property such as tensile strength and elongation were discussed. In Haynes 230, a nucleation of the secondary carbides was dominant at 800 .deg. C ageing while growth at 900 .deg. C ageing. In addition, after aging at 800 .deg. C, transition of primary W-rich M 6 C carbides (break down) were observed and it showed high W content (up to 70 at.% W) compared to un-aged W-rich M 6 C carbides (around 30 at.% W). Coarsened Cr- and Ni-rich phase surrounded by carbide depleted region and high W-rich M 6 C carbide along the grain boundary were formed only at 900 .deg. C after long-term exposure above 10000 h. Tensile strength of aged Haynes 230 increased at 800 .deg. C while decreased at 900 .deg. C due to the formation of secondary carbide within the grains at 800 .deg. C. Decrease in elongation would be resulted from the coarsened and continuous carbides at the grain boundary as well as Cr- and Ni-rich phase along the grain boundary

  5. High-Strength Aluminium Alloys and Their Use in Foundry Industry of Nickel Superalloys

    Directory of Open Access Journals (Sweden)

    Pysz S.

    2014-08-01

    Full Text Available Of great importance in the selection of materials for cast structures is keeping a proper balance between the mechanical and plastic properties, while preserving the relevant casting properties. This study has been devoted to an analysis of the choice and application of high-strength aluminium-based alloys maintaining sufficient level of casting properties. The high level of tensile strength (Rm > 500 MPa matched with satisfactory elongation (A > 3% is important because materials of this type are used for cast parts operating in the aerospace, automotive, and military industries. These beneficial relationships between the high tensile strength and toughness are relatively easy to obtain in the Al-Zn-Mg-Cu alloys subjected to plastic forming and proper heat treatment. In gravity cast products, on the other hand, whether poured into sand moulds or metal moulds (dies, obtaining this favourable combination of properties poses a number of research problems (mostly resulting from the alloy chemical composition as well as technical and technological difficulties.

  6. Effect of alloying by lanthanum and high rhenium superalloys on the basis of Ni-Al-Cr on the structure and phase composition

    Energy Technology Data Exchange (ETDEWEB)

    Kozlov, Eduard, E-mail: kozlov@tsuab.ru; Tsedrik, Elena, E-mail: tsedrik@sibmail.ru; Koneva, Nina, E-mail: koneva@tsuab.ru [Tomsk State University of Architecture and Building, 2, Solyanaya Sq., 634003, Tomsk (Russian Federation); Popova, Natalya, E-mail: natalya-popova-44@mail.ru [Tomsk State University of Architecture and Building, 2, Solyanaya Sq., 634003, Tomsk (Russian Federation); Institute of Strength Physics and Materials Science, SB RAS, 2/4, Academicheskii Av., 634055, Tomsk (Russian Federation); Nikonenko, Elena, E-mail: vilatomsk@mail.ru [Tomsk State University of Architecture and Building, 2, Solyanaya Sq., 634003, Tomsk (Russian Federation); National Research Tomsk Polytechnic University, 30, Lenin Av., 634050, Tomsk (Russian Federation); Fedoricheva, Marina, E-mail: fed-mv@mail.ru [Institute of Strength Physics and Materials Science, SB RAS, 2/4, Academicheskii Av., 634055, Tomsk (Russian Federation); National Research Tomsk Polytechnic University, 30, Lenin Av., 634050, Tomsk (Russian Federation)

    2016-01-15

    This paper presents transmission and scanning electronic microscope investigations of Ni-Al-Cr superalloy alloyed with additional Re and La elements. This superalloy is obtained by the directional solidification method and subsequently is subjected to two-stage high-temperature annealing: 1) at T = 1150°C, the test time is 1 hour; 2) at T = 1100°C, the testing time is 1430 hours. It was found that the γ- and γ′-phases are the main phases in the two states on the basis of fcc lattice. Where γ is the disordered fcc solid solution and γ′-phase is the main phase with an ordered arrangement of atoms having the L1{sub 2} superstructure. It is shown that such additional elements as Re and La result in the formation of new phases in Ni-Al-Cr accompanied by considerable modifications of quasi-cuboid structure in its γ′-phase. The phase composition and morphology of the phases are studied.

  7. Fatigue of superalloys and intermetallics

    International Nuclear Information System (INIS)

    Stoloff, N.S.

    1993-01-01

    The fatigue behavior of intermetallic alloys and their composites is contrasted to that of nickel-base superalloys. The roles of microstructure and slip planarity are emphasized. Obstacles to use of intermetallics under cyclic loading conditions are described and future research directions are suggested

  8. Forging Oxide-Dispersion-Strengthened Superalloys

    Science.gov (United States)

    Harf, F. H.; Glasgow, T. K.; Moracz, D. J.; Austin, C. M.

    1986-01-01

    Cladding of mild steel prevents surface cracking when alloy contacts die. Continual need for improvements in properties of alloys capable of withstanding elevated temperatures. Accomplished by using oxide-dispersion-strengthed superalloys such as Inconel Alloy MA 6000. Elevated tensile properties of forged alloy equal those of hot-rolled MA 6000 bar. Stress-rupture properties somewhat lower than those of bar stock but, at 1,100 degrees C, exceed those of strongest commercial single crystal, directionally solidified and conventionally cast superalloys.

  9. Creep strength and microstructure in 23Cr-45Ni-7W Alloy (HR6W) and Ni-base superalloys for advanced USC boilers

    Energy Technology Data Exchange (ETDEWEB)

    Semba, Hiroyuki; Okada, Hirokazu; Yonemura, Mitsuharu; Igarashi, Masaaki [Sumitomo metal Industries, Ltd., Hyogo (Japan). Corporate Research and Development Labs.

    2008-07-01

    Establishment of materials technologies on piping and tubing for advanced ultra super critical (A-USC) plants operated at steam temperatures above 700 C is a critical issue to achieve its hard target. 23Cr-45Ni-7W alloy (HR6W) has been developed in Japan, originally as a high strength tubing material for 650 C USC boilers. In order to clarify the capability of HR6W as a material applied to A-USC plants, creep strength and microstructure of HR6W were investigated in comparison with {gamma}'-strengthened Alloy 617 and other Ni-base superalloys, such as Alloy 263. It has been revealed that the amount of added W is intimately correlated with precipitation amount of Laves phase and thus it is a crucial factor controlling creep strength. Stability of long term creep strength and superior creep rupture ductility have been proved by creep rupture tests at 650-800 C up to 60000h. The 10{sup 5}h extrapolated creep rupture strengths are estimated to be 88MPa at 700 C and 64MPa at 750 C. Microstructural stability closely related with long term creep strength and toughness has also been confirmed by microstructural observations after creep tests and aging. Creep rupture strength of Alloy 617 has been found to be much higher than that of HR6W at 700 and 750 C, while comparable at 800 C. A thermodynamic calculation along with microstructural observation indicates that the amount of Laves phase in HR6W gradually decreases with increasing temperature, while that of {gamma}' in Alloy 617 rapidly decreases with increasing temperature and {gamma}' almost dissolves at 800 C. This may lead to an abrupt drop in creep strength of Alloy 617 above 750 C. Alloy 263, in which more {gamma}' precipitates than Alloy 617, shows much higher creep strength. However, it is suggested that inhomogeneous creep deformation is enhanced compared with HR6W and Alloy 617. Capability of HR6W as a material for A-USC plants was discussed in terms of creep properties, microstructural stability and other

  10. Elevated temperature axial and torsional fatigue behavior of Haynes 188

    Science.gov (United States)

    Bonacuse, Peter J.; Kalluri, Sreeramesh

    1992-06-01

    The results of high-temperature axial and torsional low-cycle fatigue experiments performed on Haynes 188, a wrought cobalt-base superalloy, are reported. Fatigue tests were performed at 760 C in air on thin-walled tubular specimens at various ranges under strain control. Data are also presented for coefficient of thermal expansion, elastic modulus, and shear modulus at various temperatures from room to 1000 C, and monotonic and cyclic stress-strain curves in tension and in shear at 760 C. The data set is used to evaluate several multiaxial fatigue life models (most were originally developed for room temperature multiaxial life prediction) including von Mises equivalent strain range (ASME boiler and pressure vessel code), Manson-Halford, Modified Multiaxiality Factor (proposed here), Modified Smith-Watson-Topper, and Fatemi-Socie-Kurath. At von Mises equivalent strain ranges (the torsional strain range divided by the square root of 3, taking the Poisson's ratio to be 0.5), torsionally strained specimens lasted, on average, factors of 2 to 3 times longer than axially strained specimens. The Modified Multiaxiality Factor approach shows promise as a useful method of estimating torsional fatigue life from axial fatigue data at high temperatures. Several difficulties arose with the specimen geometry and extensometry used in these experiments. Cracking at extensometer probe indentations was a problem at smaller strain ranges. Also, as the largest axial and torsional strain range fatigue tests neared completion, a small amount of specimen buckling was observed.

  11. Introduction to superalloys

    International Nuclear Information System (INIS)

    Li-Chenggong

    1995-01-01

    Throughout history, humans have developed mechanical devices to satisfy their needs, Jet aircraft was thrust into public awareness with the 1937 flight of Hans Von Ohains turbine engine Heinkel in Germany and an independent development, the 1939 flight of Whittle's engine in England. Since that time, progress in jet propulsion and industrial gas turbines has been a growing engineering technology of immense importance. This opened a new era of engineering material called superalloy. Superalloy is an alloy developed for elevated temperature service usually based on group VIIA elements, where relatively severe mechanical stressing is encountered, and where high surface stability is frequently required. The title of the speech is T he Effect of a Changing Environment on the requirements of Engine Materials . In this speech, the author emphasized that may changes in the business environment have occurred in recent years, the aircraft engine business is rapidly changing from a military focus to a commercial one, speed to market will assume greater importance in the engine industry, and greater attention to customer value will be required to remain competitive etc. However the superalloys will continue to be developed in the future. (author) 14 figs

  12. The metallurgy of superalloys part 1

    International Nuclear Information System (INIS)

    Abdelazim, M.E.; Hammad, F.H.

    1990-01-01

    This is part I of the report titled 'the metallurgy of superalloys'. In this part the structure, phases and systems of superalloys are reviewed. The role of alloying elements in the design of superalloys and the mechanical properties of superalloys are also reviewed. Superalloys are important in high temperature technology, especially above 700 degree c. They are 'super' mainly because their creep and stress rupture resistances are very high. Superalloys are based on an austenitic matrix including secondary phases, mainly gamma precipitates, inter and intragranular carbides mainly M 23 C 6 and M 6 C. They are classified into three systems, Ni-base, Fe-Ni base and Ce-base alloys. Different alloying elements mainly Cr, Mo, Al, Ti are added to increase the strength either by solid solution hardening (Cr, Mo, Al), precipitation hardening (A 1, Ti to produce gamma) or by dispersion hardening (Cr, Mo to form M 23 C 6 and M 6 C carbides) and to increase the oxidation resistance (Cr, Al). 3 tab., 2 fig

  13. Cast Alloys for Advanced Ultra Supercritical Steam Turbines

    Energy Technology Data Exchange (ETDEWEB)

    G. R. Holcomb, P. Wang, P. D. Jablonski, and J. A. Hawk,

    2010-05-01

    The proposed steam inlet temperature in the Advanced Ultra Supercritical (A-USC) steam turbine is high enough (760 °C) that traditional turbine casing and valve body materials such as ferritic/martensitic steels will not suffice due to temperature limitations of this class of materials. Cast versions of several traditionally wrought Ni-based superalloys were evaluated for use as casing or valve components for the next generation of industrial steam turbines. The full size castings are substantial: 2-5,000 kg each half and on the order of 100 cm thick. Experimental castings were quite a bit smaller, but section size was retained and cooling rate controlled to produce equivalent microstructures. A multi-step homogenization heat treatment was developed to better deploy the alloy constituents. The most successful of these cast alloys in terms of creep strength (Haynes 263, Haynes 282, and Nimonic 105) were subsequently evaluated by characterizing their microstructure as well as their steam oxidation resistance (at 760 and 800 °C).

  14. Effects of carbon and hafnium concentrations in wrought powder-metallurgy superalloys based on nasa 2b-11 alloy

    International Nuclear Information System (INIS)

    Miner, R.V. Jr.

    1976-01-01

    A candidate alloy for advanced-temperature turbine engine disks and four modifications of that alloy with various C and Hf concentrations were produced as cross-rolled disks from prealloyed powder that was hot isostatically compacted. The mechanical properties, microstructures, and phase relations of the alloys are discussed in terms of their C and Hf concentrations. A low-C and high-Hf modification of IIB-11 had the best balance of mechanical properties for service below about 750 C. Because of their finer grain sizes, none of the powder-metallurgy alloys produced had the high-temperature rupture strength of conventionally cast and wrought IIB-11. (Author)

  15. Development of Wrought Superalloy in China

    Directory of Open Access Journals (Sweden)

    DU Jinhui

    2016-06-01

    Full Text Available Wrought superalloy development in China was reviewed in recent ten years. The achievement of basic research and development of industrial manufacture technologies were systematically described from the aspects of new alloys, new technologies of hot deformation. New alloys include: new disc materials 718Plus, GH4720Li and GH4065 alloy, combustion chamber alloy GH3230, and GH4706 alloy for gas turbine engines. New technologies include: ERS-CDS new technology of easy segregation materials, multi upsetting-drawing for improving the microstructure uniformity of bars, slow cooling and multi-cycle thermomechanical treatment for increasing hot plasticity of hard-to-work alloys. Finally, the further development of wrought superalloys was prospected.

  16. Effects of helium impurities on superalloys

    International Nuclear Information System (INIS)

    Selle, J.E.

    1977-07-01

    A review of the literature on the effects of helium impurities on superalloys at elevated temperatures was undertaken. The actual effects of these impurities vary depending on the alloy, composition of the gas atmosphere, and temperature. In general, exposure in helium produces significant but not catastrophic changes in the structure and properties of the alloys. The effects of these treatments on the structure, creep, fatigue, and mechanical properties of the various alloys are reviewed and discussed. Suggestions for future work are presented

  17. Mechanical properties of Ni-base superalloys in high temperature steam environments

    International Nuclear Information System (INIS)

    Jang, Changheui; Kim, Donghoon; Sah, Injin; Lee, Ho Jung

    2015-01-01

    The effects of environmental damages on the mechanical properties of Ni-base superalloys, Alloy 617 and Haynes 230, were evaluated for VHTR-HTSE applications. Tensile tests were carried out at room temperature after ageing at 900 deg. C in vacuum, steam, and steam + 20 vol.% H2 environments up to 3 000 h. Also, creep rupture test were performed in air, steam, and steam + 20 vol.% H2 environments. The degradations such as oxidation, decarburization, and redistribution of carbides were studied in view of the interaction of materials with the environment. During the long-term ageing at 900 deg. C in vacuum, secondary phases such as M23C6 and M6C were precipitated and coarsened, which caused increase in tensile strength and decrease in ductility. For the specimens aged in steam environments, surface and internal oxides acted as preferential sites for crack initiation and consequently, decreased the tensile and creep strength. Also, the formation of decarburization region resulted in glide plane failure during tensile test and reduction in creep rupture life due to grain boundary migration and recrystallisation. During creep tests, tensile stress caused the crack and void formation in oxide layer. Consequently, fast diffusion of oxidant occurred and environmental damage were accelerated. Among the test conditions, such environmental damage was much severe in steam environments. (authors)

  18. Experimental and modeling results of creep fatigue life of Inconel 617 and Haynes 230 at 850 C

    International Nuclear Information System (INIS)

    Chen, Xiang; Sokolov, Mikhail A.; Sham, Sam; Erdman, Donald L. III; Busby, Jeremy T.; Mo, Kun; Stubbins, James

    2013-01-01

    Creep fatigue testing of Ni-based superalloy Inconel 617 and Haynes 230 were conducted in the air at 850 C. Tests were performed with fully reversed axial strain control at a total strain range of 0.5%, 1.0% or 1.5% and hold time at maximum tensile strain for 3, 10 or 30 min. In addition, two creep fatigue life prediction methods, i.e. linear damage summation and frequency-modified tensile hysteresis energy modeling, were evaluated and compared with experimental results. Under all creep fatigue tests, Haynes 230 performed better than Inconel 617. Compared to the low cycle fatigue life, the cycles to failure for both materials decreased under creep fatigue test conditions. Longer hold time at maximum tensile strain would cause a further reduction in both material creep fatigue life. The linear damage summation could predict the creep fatigue life of Inconel 617 for limited test conditions, but considerably underestimated the creep fatigue life of Haynes 230. In contrast, frequency-modified tensile hysteresis energy modeling showed promising creep fatigue life prediction results for both materials.

  19. Low temperature gaseous nitriding of Ni based superalloys

    DEFF Research Database (Denmark)

    Eliasen, K. M.; Christiansen, Thomas Lundin; Somers, Marcel A. J.

    2010-01-01

    In the present work the nitriding response of selected Ni based superalloys at low temperatures is addressed. The alloys investigated are nimonic series nos. 80, 90, 95 and 100 and nichrome (Ni/Cr......In the present work the nitriding response of selected Ni based superalloys at low temperatures is addressed. The alloys investigated are nimonic series nos. 80, 90, 95 and 100 and nichrome (Ni/Cr...

  20. Weldability of superalloys alloy 718 and ATI {sup registered} 718Plus trademark. A study performed by Varestraint testing

    Energy Technology Data Exchange (ETDEWEB)

    Jacobsson, Jonny [The Production Technology Centre Univ. West, Trollhaettan (Sweden). GKN Aerospace Sweden; Chalmers Univ. of Technology, Gothenburg (Sweden). Dept. of Industrial and Material Science; Andersson, Joel [The Production Technology Centre Univ. West, Trollhaettan (Sweden). Dept. of Engineering Science; Brederholm, Anssi; Haenninen, Hannu [Aalto Univ., Helsinki (Finland). Dept. of Engineering Design and Production

    2017-11-01

    In this study, the old and well-known alloy 718 is compared with the newly developed ATI {sup registered} 718Plus trademark from the weldability point of view. This is done in order to gain new information that have not been documented and established yet among the high-temperature materials with high strength, oxidation resistance, thermal stability and sufficient weldability, yet. ATI {sup registered} 718Plus trademark shows a lower sensitivity to hot cracking than alloy 718 with approximately 10 mm total crack length (TCL) difference in Varestraint testing. In the solution-annealed condition at 982 C for 4.5 h followed by air cooling, the crack sensitivity is decreased as compared to the mill-annealed condition. Along the crack path and also ahead of the crack tip, γ-Laves eutectic is present in both alloys. The microhardness measurements showed similar hardness level of 250 HV in the weld metal of both alloys and even in the parent material of alloy 718. ATI {sup registered} 718Plus trademark parent metal had hardness of 380 HV and a small increase of less than 50 HV was observed for both studied alloys in the heat affected zone (HAZ). For the same grain size of ATI {sup registered} 718Plus trademark (8.3 μm) and alloy 718 (15.6 μm), the susceptibility to liquation cracking may increase with increasing grain size. With a small grain size, there is a possibility to accommodate more trace elements (B, S, P) due to the larger grain boundary area. The impurity elements were found in relatively small precipitates, typically borides (0.2 μm), phosphides (0.1 to 0.5 μm) and carbo-sulphides. The solidification sequence of alloy 718 and ATI {sup registered} 718Plus trademark is relatively similar, where the liquid starts to solidify as γ-phase followed by γ/MC reaction at about 1260 C and then final γ/Laves eutectic reaction at around 1150 C. Detailed knowledge about weldability of alloy 718 and ATI {sup registered} 718Plus trademark can be used for material

  1. Studying the effect of Ruthenium on High Temperature Mechanical Properties of Nickel Based Superalloys and Determining the Universal Behavior of Ruthenium at Atomic Scale with respect to alloying elements, Stress and Temperature

    Directory of Open Access Journals (Sweden)

    Sriswaroop Dasari

    2016-10-01

    Full Text Available Any property of a material is a function of its microstructure and microstructure is a function of material composition. So, to maximize the desired properties of a material, one has to understand the evolution of microstructure which in turn is nothing but the reflection of the role of alloying elements. Research has not been done to understand the universal behavior of a certain base/alloying element. Let’s take the example of Cl- ion in HCl, we all know that in general, chloride ion can only be replaced by Fluoride or oxygen ion and that no other ion can replace it. But when you consider a metal like Ni, Co, Cr, Fe etc. there is no establishment that it behaves only in a certain way. Though I concord to the fact that discovery of universal behavior of Ni is lot complex than chloride ion, I think that future research should be focused in this direction also. Superalloys are the candidate materials required to improve thermal efficiency of a gas turbine by allowing higher turbine inlet gas temperatures. Gas turbines are the heart of local power systems, next generation jet engines and high performance space rockets. Recent research in superalloys showed that addition of some alloying elements in minor quantities can result in drastic change in properties. Such an alloying element is Ruthenium (Ru. Addition of Ruthenium to superalloys has shown improvement in mechanical properties by an order of magnitude. However reasons for such improvement are not known yet. Hence, there is a need to identify its role and discover the universal behavior of ruthenium to utilize it efficiently. In this proposal, we study materials with different compositions that are derived based on one ruthenium containing superalloy, and different thermomechanical history. Based on the evolution of microstructures and results of mechanical testing, we plan to determine the exact role of Ruthenium and prediction of its behavior with respect to other elements in the material

  2. Beyond Ni-based superalloys: Development of CoRe-based alloys for gas turbine applications at very high temperatures

    Czech Academy of Sciences Publication Activity Database

    Mukherji, D.; Roesler, J.; Strunz, Pavel; Gilles, R.; Schumacher, G.; Piegert, S.

    2011-01-01

    Roč. 102, č. 9 (2011), s. 1125-1132 ISSN 1862-5282 R&D Projects: GA ČR(CZ) GAP204/11/1453 Institutional research plan: CEZ:AV0Z10480505 Keywords : Co-base alloy * Rhenium * Electron microscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.830, year: 2011

  3. Mechanical behavior of superalloys

    International Nuclear Information System (INIS)

    Floreen, S.

    1986-04-01

    Recent developments affecting the mechanical behavior of superalloys over three ranges of operating temperatures are reviewed. At lower temperatures, activity has been focused on stress corrosion cracking susceptibility in light water reactor and sour gas well environments. The susceptibility to intergranular crack growth is critically dependent upon the grain boundary chemistry, and a method of minimizing the sensitivity of the boundaries to attack has been pursued. At intermediate temperatures, considerable effort has been directed toward increasing the tensile and fatigue strengths. The higher strength materials, however, show increased fracture sensitivity. In particular, embrittlement due to diffusion into the grain boundaries of aggressive species, such as oxygen or sulfur from the environments, becomes a problem. Minor element alloying additions of boron, zirconium, magnesium, etc., are helpful in retarding the degradation caused by the environment. At higher temperatures, the major thrust is toward improving the creep strength. The weak link in the materials, which is the transverse grain boundaries, has been eliminated by the use of specialized processing steps to produce either directionally solidified materials with minimum transverse grain boundaries, or single crystal materials. Single crystal materials permit alloying and heat treating modifications that further enhance the creep strength. The materials are very anisotropic in properties, but are successfully used in turbine blades and could be useful in other special applications

  4. Modelling and simulation of superalloys. Book of abstracts

    Energy Technology Data Exchange (ETDEWEB)

    Rogal, Jutta; Hammerschmidt, Thomas; Drautz, Ralf (eds.)

    2014-07-01

    Superalloys are multi-component materials with complex microstructures that offer unique properties for high-temperature applications. The complexity of the superalloy materials makes it particularly challenging to obtain fundamental insight into their behaviour from the atomic structure to turbine blades. Recent advances in modelling and simulation of superalloys contribute to a better understanding and prediction of materials properties and therefore offer guidance for the development of new alloys. This workshop will give an overview of recent progress in modelling and simulation of materials for superalloys, with a focus on single crystal Ni-base and Co-base alloys. Topics will include electronic structure methods, atomistic simulations, microstructure modelling and modelling of microstructural evolution, solidification and process simulation as well as the modelling of phase stability and thermodynamics.

  5. Superalloy applications in the fast breeder reactor

    International Nuclear Information System (INIS)

    Powell, R.W.

    1976-01-01

    The economics of the LMFBR are dependent on the breeding of new fuel in the reactor core and this can be improved by the use of advanced alloys as core structural components. The environment of the core makes superalloys a natural choice for these components, but phenomena related directly to neutron irradiation necessitate extensive testing. Consequently, commercially-available superalloys, together with a number of developmental alloys are being tested in existing LMFBR's and by simulation techniques to determine the best alloy for use in the LMFBR core. It presently appears that such materials will indeed be capable of the performance required, and will greatly facilitate the commercial realization of the fast breeder reactor

  6. Processing of Advanced Cast Alloys for A-USC Steam Turbine Applications

    Science.gov (United States)

    Jablonski, Paul D.; Hawk, Jeffery A.; Cowen, Christopher J.; Maziasz, Philip J.

    2012-02-01

    The high-temperature components within conventional supercritical coal-fired power plants are manufactured from ferritic/martensitic steels. To reduce greenhouse-gas emissions, the efficiency of pulverized coal steam power plants must be increased to as high a temperature and pressure as feasible. The proposed steam temperature in the DOE/NETL Advanced Ultra Supercritical power plant is high enough (760°C) that ferritic/martensitic steels will not work for the majority of high-temperature components in the turbine or for pipes and tubes in the boiler due to temperature limitations of this class of materials. Thus, Ni-based superalloys are being considered for many of these components. Off-the-shelf forged nickel alloys have shown good promise at these temperatures, but further improvements can be made through experimentation within the nominal chemistry range as well as through thermomechanical processing and subsequent heat treatment. However, cast nickel-based superalloys, which possess high strength, creep resistance, and weldability, are typically not available, particularly those with good ductility and toughness that are weldable in thick sections. To address those issues related to thick casting for turbine casings, for example, cast analogs of selected wrought nickel-based superalloys such as alloy 263, Haynes 282, and Nimonic 105 have been produced. Alloy design criteria, melt processing experiences, and heat treatment are discussed with respect to the as-processed and heat-treated microstructures and selected mechanical properties. The discussion concludes with the prospects for full-scale development of a thick section casting for a steam turbine valve chest or rotor casing.

  7. Processing of Advanced Alloys for A-USC Steam Turbine Applications

    Energy Technology Data Exchange (ETDEWEB)

    Jablonski, P. D. [National Energy Technology Laboratory (NETL); Hawk, Jeffrey A. [National Energy Technology Laboratory (NETL); Cowen, Christopher J. [National Energy Technology Laboratory (NETL); Maziasz, Philip J [ORNL

    2010-01-01

    The high-temperature components within conventional supercritical coal-fired power plants are manufactured from ferritic/martensitic steels. To reduce greenhouse-gas emissions, the efficiency of pulverized coal steam power plants must be increased to as high a temperature and pressure as feasible. The proposed steam temperature in the DOE/NETL Advanced Ultra Supercritical power plant is high enough (760 C) that ferritic/martensitic steels will not work for the majority of high-temperature components in the turbine or for pipes and tubes in the boiler due to temperature limitations of this class of materials. Thus, Ni-based superalloys are being considered for many of these components. Off-the-shelf forged nickel alloys have shown good promise at these temperatures, but further improvements can be made through experimentation within the nominal chemistry range as well as through thermomechanical processing and subsequent heat treatment. However, cast nickel-based superalloys, which possess high strength, creep resistance, and weldability, are typically not available, particularly those with good ductility and toughness that are weldable in thick sections. To address those issues related to thick casting for turbine casings, for example, cast analogs of selected wrought nickel-based superalloys such as alloy 263, Haynes 282, and Nimonic 105 have been produced. Alloy design criteria, melt processing experiences, and heat treatment are discussed with respect to the as-processed and heat-treated microstructures and selected mechanical properties. The discussion concludes with the prospects for full-scale development of a thick section casting for a steam turbine valve chest or rotor casing.

  8. FRAUD/SABOTAGE Killing Nuclear-Reactors!!! ``Super"alloys GENERIC ENDEMIC Wigner's-Disease IN-stability!!!

    Science.gov (United States)

    Asphahani, Aziz; Siegel, Sidney; Siegel, Edward

    2010-03-01

    Siegel [[J.Mag.Mag.Mtls.7,312(78); PSS(a)11,45(72); Semis.& Insuls.5(79)] (at: ORNL, ANS, Westin``KL"ouse, PSEG, IAEA, ABB) warning of old/new nuclear-reactors/spent-fuel-casks/refineries/ jet/missile/rocket-engines austenitic/FCC Ni/Fe-based (so MIS- called)``super"alloys(182/82;Hastelloy-X; 600;304/304L-SSs; 690 !!!) GENERIC ENDEMIC EXTANT detrimental(synonyms): Wigner's- diseas(WD)[J.Appl.Phys.17,857(46)]; Ostwald-ripening; spinodal- decomposition; overageing-embrittlement; thermomechanical- INstability: Mayo[Google: ``If Leaks Could Kill"; at flickr.com search on ``Giant-Magnotoresistance"; find: [SiegelPolitics(79)]; Hoffman[animatedsoftware.com],...what DOE/NRC MISlabels as ``butt-welds" ``stress-corrosion cracking" endpoint's ROOT-CAUSE ULTIMATE-ORIGIN is WD overageing-embrit- tlement caused brittle-fracture cracking from early/ongoing AEC/DOE-n``u''tional-la``v''atories sabotage!!!

  9. Development of a Refractory High Entropy Superalloy (Postprint)

    Science.gov (United States)

    2016-03-17

    hardened with HfC precipitates [2], Co-Re- or Co-Al-W-based alloys [3] or two-phase ( FCC + L12) refractory superalloys based on platinum group metals...Ni-based superalloys consisting of cuboids with the ordered L12 structure embedded in an FCC solid-solution matrix. Based on this microstructural...and 5). A comparison of the average atomic radii with the measured lattice parameters allows us to conclude that the disordered BCC phase forming

  10. Predicting the morphologies of {\\gamma}' precipitates in cobalt-based superalloys

    OpenAIRE

    Jokisaari, Andrea M.; Naghavi, Shahab S.; Wolverton, Chris; Voorhees, Peter W.; Heinonen, Olle G.

    2017-01-01

    Cobalt-based alloys with {\\gamma}/{\\gamma}' microstructures have the potential to become the next generation of superalloys, but alloy compositions and processing steps must be optimized to improve coarsening, creep, and rafting behavior. While these behaviors are different than in nickel-based superalloys, alloy development can be accelerated by understanding the thermodynamic factors influencing microstructure evolution. In this work, we develop a phase field model informed by first-princip...

  11. Biaxial thermal creep of Inconel 617 and Haynes 230 at 850 and 950 °C

    International Nuclear Information System (INIS)

    Tung, Hsiao-Ming; Mo, Kun; Stubbins, James F.

    2014-01-01

    The biaxial thermal creep behavior of Inconel 617 and Haynes 230 at 850 and 950 °C was investigated. Biaxial stresses were generated using the pressurized tube technique. The detailed creep deformation and fracture mechanism have been studied. Creep curves for both alloys showed that tertiary creep accounts for a greater portion of the materials’ life, while secondary creep only accounts for a small portion. Fractographic examinations of the two alloys indicated that nucleation, growth, and coalescence of creep voids are the dominant micro-mechanisms for creep fracture. At 850 °C, alloy 230 has better creep resistance than alloy 617. When subjected to the biaxial stress state, the creep rupture life of the two alloys was considerably reduced when compared to the results obtained by uniaxial tensile creep tests. The Monkman–Grant relation proves to be a promising method for estimating the long-term creep life for alloy 617, whereas alloy 230 does not follow the relation. This might be associated with the significant changes in the microstructure of alloy 230 at high temperatures

  12. Fatigue studies of superalloys in Japan

    International Nuclear Information System (INIS)

    Kitagawa, Masaki

    1985-01-01

    In the past 15 years, several national projects were advanced to develop high temperature machinery, such as high temperature gas-cooled reactors, gas turbines and fusion reactors. Before, the studies on the strength of superalloys were rarely carried out, however, by the above research works, superalloys are in rapid progress. Because these machinery are subjected to temperature cycles and vibration stress, the fatigue failure is the main concern in the safety analysis of the components. The purpose of this paper is to summarize the present status of the fatigue research on the alloys for high temperature use in Japan. The superalloys used for gas turbine and HTGR components are listed, and the materials tested were mostly the alloys of nickel base, cobalt base or iron base. In the above national projects, the main purpose was to clarify the high temperature properties including fatigue properties, to develop the method of forecasting the life span and to develop better materials. As the topics about the fatigue research on superalloys, the development of the method for forecasting the life span, the effect of directional solidification, coating and HIP process on the fatigue strength of gas turbine materials, the effect of helium and aging on the fatigue strength of HTGR materials, the fatigue strength of weldment of HTGR materials and others are reported. (Kako, I.)

  13. Thermomechanical fatigue in single crystal superalloys

    Directory of Open Access Journals (Sweden)

    Moverare Johan J.

    2014-01-01

    Full Text Available Thermomechanical fatigue (TMF is a mechanism of deformation which is growing in importance due to the efficiency of modern cooling systems and the manner in which turbines and associated turbomachinery are now being operated. Unfortunately, at the present time, relatively little research has been carried out particularly on TMF of single crystal (SX superalloys, probably because the testing is significantly more challenging than the more standard creep and low cycle fatigue (LCF cases; the scarcity and relative expense of the material are additional factors. In this paper, the authors summarise their experiences on the TMF testing of SX superalloys, built up over several years. Emphasis is placed upon describing: (i the nature of the testing method, the challenges involved in ensuring that an given testing methodology is representative of engine conditions (ii the behaviour of a typical Re-containing second generation alloy such as CMSX-4, and its differing performance in out-of-phase/in-phase loading and crystallographic orientation and (iii the differences in behaviour displayed by the Re-containing alloys and new Re-free variants such as STAL15. It is demonstrated that the Re-containing superalloys are prone to different degradation mechanisms involving for example microtwinning, TCP precipitation and recrystallisation. The performance of STAL15 is not too inferior to alloys such as CMSX-4, suggesting that creep resistance itself does not correlate strongly with resistance to TMF. The implications for alloy design efforts are discussed.

  14. Refractory metal based superalloys

    International Nuclear Information System (INIS)

    Alonso, Paula R.; Vicente, Eduardo E.; Rubiolo, Gerardo H.

    1999-01-01

    Refractory metals are looked as promising materials for primary circuits in fission reactors and even as fusion reactor components. Indeed, superalloys could be developed which take advantage of their high temperature properties together with the benefits of a two- phase (intermetallic compound-refractory metal matrix) coherent structure. In 1993, researchers of the Office National d'Etudes et de Recherches Aerospatiales of France reported the observation of such a coherent structure in the Ta-Ti-Zr-Al-Nb-Mo system although the exact composition is not reported. The intermetallic compound would be Ti 2 AlMo based. However, the formation of this compound and its possible coexistence with a disordered bcc phase in the ternary system Ti-Al-Mo is a controversial subject in the related literature. In this work we develop a technique to obtain homogeneous alloys samples with 50 Ti-25 Al-25 Mo composition. The resulting specimens were characterized by optical and electronic metallography (SEM), microprobe composition measurements (EPMA) and X-ray diffraction (XRD) analyses. The results show the evidence for a bcc (A2→B2) ordering reaction in the Ti-Al-Mo system in the 50 Ti-25 Al-25 Mo composition. (author)

  15. High temperature properties of polycrystalline γ"'-strengthened cobalt-base superalloys

    International Nuclear Information System (INIS)

    Bauer, Alexander

    2016-01-01

    The recent discovery of a stable γ"'-phase in Co-based superalloys opened up a pathway for the development of a new high temperature material class, which is similar in microstructure and properties to the modern γ"'-hardened Ni-based superalloys. In this work, the first attempt was done to check the influence of several for Ni-based superalloys typical alloying elements on the properties of the new Co-based superalloys. It became clear that the basic characteristics of the first experimental alloys are similar to those of the γ"'-hardened Ni-based alloys. The results of the multinary experimental alloys show that, based on the insight gained so far, targeted alloy development is possible. These materials have the potential to be used as disc materials in turbines.

  16. Erosion–corrosion behaviour of Ni-based superalloy Superni-75 in ...

    Indian Academy of Sciences (India)

    microscopy/energy-dispersive analysis (SEM/EDAX) and electron probe micro ... gas turbines and they have designated this alloy as superalloy Superni-75. ... The nickel-based superalloy Superni-75 (19·5Cr-3Fe-0·3Ti-0·1C- Balance Ni) was ...

  17. A high-throughput search for new ternary superalloys

    Science.gov (United States)

    Nyshadham, Chandramouli; Hansen, Jacob; Oses, Corey; Curtarolo, Stefano; Hart, Gus

    In 2006 an unexpected new superalloy, Co3[Al,W], was discovered. This new alloy is cobalt-based, in contrast to conventional superalloys, which are nickel-based. Inspired by this new discovery, we performed first-principles calculations, searching through 2224 ternary metallic systems of the form A3[B0.5C0.5], where A = Ni/Co/Fe and [B, C] = all binary combinations of 40 different elements chosen from the periodic table. We found 175 new systems that are better than the Co3[Al, W] superalloy. 75 of these systems are brand new--they have never been reported in experimental literature. These 75 new potential superalloys are good candidates for further experiments. Our calculations are consistent with current experimental literature where data exists. Work supported under: ONR (MURI N00014-13-1-0635).

  18. The Mechanical Properties of Candidate Superalloys for a Hybrid Turbine Disk

    Science.gov (United States)

    Gabb, Timothy P.; MacKay, Rebecca A.; Draper, Susan L.; Sudbrack, Chantal K.; Nathal, Michael V.

    2013-01-01

    The mechanical properties of several cast blade superalloys and one powder metallurgy disk superalloy were assessed for potential use in a dual alloy hybrid disk concept of joined dissimilar bore and web materials. Grain size was varied for each superalloy class. Tensile, creep, fatigue, and notch fatigue tests were performed at 704 to 815 degC. Typical microstructures and failure modes were determined. Preferred materials were then selected for future study as the bore and rim alloys in this hybrid disk concept. Powder metallurgy superalloy LSHR at 15 micron grain size and single crystal superalloy LDS-1101+Hf were selected for further study, and future work is recommended to develop the hybrid disk concept.

  19. STABILITY ANALYSIS OF RADIAL TURNING PROCESS FOR SUPERALLOYS

    Directory of Open Access Journals (Sweden)

    Alberto JIMÉNEZ

    2017-07-01

    Full Text Available Stability detection in machining processes is an essential component for the design of efficient machining processes. Automatic methods are able to determine when instability is happening and prevent possible machine failures. In this work a variety of methods are proposed for detecting stability anomalies based on the measured forces in the radial turning process of superalloys. Two different methods are proposed to determine instabilities. Each one is tested on real data obtained in the machining of Waspalloy, Haynes 282 and Inconel 718. Experimental data, in both Conventional and High Pressure Coolant (HPC environments, are set in four different states depending on materials grain size and Hard-ness (LGA, LGS, SGA and SGS. Results reveal that PCA method is useful for visualization of the process and detection of anomalies in online processes.

  20. Recrystallization of the ODS superalloy PM-1000

    International Nuclear Information System (INIS)

    Sandim, H.R.Z.; Hayama, A.O.F.; Raabe, D.

    2006-01-01

    The primary recrystallization of a -fiber textured coarse-grained oxide dispersion strengthened nickel-based superalloy (PM-1000) has been investigated by high-resolution electron backscatter diffraction. The annealing behavior of this alloy is quite complex. Even at high annealing temperatures (e.g. 1200 deg. C), recrystallization is only partial. The microstructure of this superalloy in the annealed state consists of a blurred subgrain structure, coarse grains with sizes of about 10-20 μm at the pre-existing grain boundaries and a significant fraction of small crystals in the interior of the recovered grains. These small grains are elongated and display anisotropic growth. In the present paper we present a detailed explanation for this peculiar microstructure. Particular focus is placed on the origin of the new grains in the recovered structure in a [1 0 0]-oriented grain

  1. Influence of Powder Surface Contamination in the Ni-Based Superalloy Alloy718 Fabricated by Selective Laser Melting and Hot Isostatic Pressing

    Directory of Open Access Journals (Sweden)

    Yen-Ling Kuo

    2017-09-01

    Full Text Available The aim of this study was to gain a deep understanding of the microstructure-mechanical relationship between solid-state sintering and full-melting processes. The IN718 superalloy was fabricated by hot isostatic pressing (HIP and selective laser melting (SLM. Continuous precipitates were clearly localized along the prior particle boundary (PPB in the HIP materials, while SLM materials showed a microstructure free of PPB. The mechanical properties of specimens that underwent SLM + solution treatment and aging were comparable to those of conventional wrought specimens both at room temperature and 650 °C. However, a drop was observed in the ductility of HIP material at 650 °C. The brittle particles along the PPB were found to affect the HIP materials’ creep life and ductility during solid-state sintering.

  2. Creep-fatigue of low cobalt superalloys

    Science.gov (United States)

    Halford, G. R.

    1982-01-01

    Testing for the low cycle fatigue and creep fatigue resistance of superalloys containing reduced amounts of cobalt is described. The test matrix employed involves a single high temperature appropriate for each alloy. A single total strain range, again appropriate to each alloy, is used in conducting strain controlled, low cycle, creep fatigue tests. The total strain range is based upon the level of straining that results in about 10,000 cycles to failure in a high frequency (0.5 Hz) continuous strain-cycling fatigue test. No creep is expected to occur in such a test. To bracket the influence of creep on the cyclic strain resistance, strain hold time tests with ore minute hold periods are introduced. One test per composition is conducted with the hold period in tension only, one in compression only, and one in both tension and compression. The test temperatures, alloys, and their cobalt compositions that are under study are given.

  3. Barrier Coatings for Refractory Metals and Superalloys

    International Nuclear Information System (INIS)

    SM Sabol; BT Randall; JD Edington; CJ Larkin; BJ Close

    2006-01-01

    In the closed working fluid loop of the proposed Prometheus space nuclear power plant (SNPP), there is the potential for reaction of core and plant structural materials with gas phase impurities and gas phase transport of interstitial elements between superalloy and refractory metal alloy components during service. Primary concerns are surface oxidation, interstitial embrittlement of refractory metals and decarburization of superalloys. In parallel with kinetic investigations, this letter evaluates the ability of potential coatings to prevent or impede communication between reactor and plant components. Key coating requirements are identified and current technology coating materials are reviewed relative to these requirements. Candidate coatings are identified for future evaluation based on current knowledge of design parameters and anticipated environment. Coatings were identified for superalloys and refractory metals to provide diffusion barriers to interstitial transport and act as reactive barriers to potential oxidation. Due to their high stability at low oxygen potential, alumina formers are most promising for oxidation protection given the anticipated coolant gas chemistry. A sublayer of iridium is recommended to provide inherent diffusion resistance to interstitials. Based on specific base metal selection, a thin film substrate--coating interdiffusion barrier layer may be necessary to meet mission life

  4. Barrier Coatings for Refractory Metals and Superalloys

    Energy Technology Data Exchange (ETDEWEB)

    SM Sabol; BT Randall; JD Edington; CJ Larkin; BJ Close

    2006-02-23

    In the closed working fluid loop of the proposed Prometheus space nuclear power plant (SNPP), there is the potential for reaction of core and plant structural materials with gas phase impurities and gas phase transport of interstitial elements between superalloy and refractory metal alloy components during service. Primary concerns are surface oxidation, interstitial embrittlement of refractory metals and decarburization of superalloys. In parallel with kinetic investigations, this letter evaluates the ability of potential coatings to prevent or impede communication between reactor and plant components. Key coating requirements are identified and current technology coating materials are reviewed relative to these requirements. Candidate coatings are identified for future evaluation based on current knowledge of design parameters and anticipated environment. Coatings were identified for superalloys and refractory metals to provide diffusion barriers to interstitial transport and act as reactive barriers to potential oxidation. Due to their high stability at low oxygen potential, alumina formers are most promising for oxidation protection given the anticipated coolant gas chemistry. A sublayer of iridium is recommended to provide inherent diffusion resistance to interstitials. Based on specific base metal selection, a thin film substrate--coating interdiffusion barrier layer may be necessary to meet mission life.

  5. Low-Cobalt Powder-Metallurgy Superalloy

    Science.gov (United States)

    Harf, F. H.

    1986-01-01

    Highly-stressed jet-engine parts made with less cobalt. Udimet 700* (or equivalent) is common nickel-based superalloy used in hot sections of jet engines for many years. This alloy, while normally used in wrought condition, also gas-atomized into prealloyed powder-metallurgy (PM) product. Product can be consolidated by hot isostatically pressing (HIPPM condition) and formed into parts such as turbine disk. Such jet-engine disks "see" both high stresses and temperatures to 1,400 degrees F (760 degrees C).

  6. Composition and Antimicrobial Activity of Euphrasia rostkoviana Hayne Essential Oil

    OpenAIRE

    Novy, Pavel; Davidova, Hana; Serrano-Rojero, Cecilia Suqued; Rondevaldova, Johana; Pulkrabek, Josef; Kokoska, Ladislav

    2015-01-01

    Eyebright, Euphrasia rostkoviana Hayne (Scrophulariaceae), is a medicinal plant traditionally used in Europe for the treatment of various health disorders, especially as eyewash to treat eye ailments such as conjunctivitis and blepharitis that can be associated with bacterial infections. Some Euphrasia species have been previously reported to contain essential oil. However, the composition and bioactivity of E. rostkoviana oil are unknown. Therefore, in this study, we investigated the chemica...

  7. Experimental Design for Evaluation of Co-extruded Refractory Metal/Nickel Base Superalloy Joints

    International Nuclear Information System (INIS)

    ME Petrichek

    2005-01-01

    Prior to the restructuring of the Prometheus Program, the NRPCT was tasked with delivering a nuclear space reactor. Potential NRPCT nuclear space reactor designs for the Prometheus Project required dissimilar materials to be in contact with each other while operating at extreme temperatures under irradiation. As a result of the high reactor core temperatures, refractory metals were the primary candidates for many of the reactor structural and cladding components. They included the tantalum-base alloys ASTAR-811C and Ta-10W, the niobium-base alloy FS-85, and the molybdenum base alloys Moly 41-47.5 Rhenium. The refractory metals were to be joined to candidate nickel base alloys such as Haynes 230, Alloy 617, or Nimonic PE 16 either within the core if the nickel-base alloys were ultimately selected to form the outer core barrel, or at a location exterior to the core if the nickel-base alloys were limited to components exterior to the core. To support the need for dissimilar metal joints in the Prometheus Project, a co-extrusion experiment was proposed. There are several potential methods for the formation of dissimilar metal joints, including explosive bonding, friction stir welding, plasma spray, inertia welding, HIP, and co-extrusion. Most of these joining methods are not viable options because they result in the immediate formation of brittle intermetallics. Upon cooling, intermetallics form in the weld fusion zone between the joined metals. Because brittle intermetallics do not form during the initial bonding process associated with HIP, co-extrusion, and explosive bonding, these three joining procedures are preferred for forming dissimilar metal joints. In reference to a Westinghouse Astronuclear Laboratory report done under a NASA sponsored program, joints that were fabricated between similar materials via explosive bonding had strengths that were directly affected by the width of the diffusion barrier. It was determined that the diffusion zone should not exceed

  8. Welding and Weldability of Directionally Solidified Single Crystal Nickel-Base Superalloys

    Energy Technology Data Exchange (ETDEWEB)

    Vitek, J M; David, S A; Reed, R W; Burke, M A; Fitzgerald, T J

    1997-09-01

    Nickel-base superalloys are used extensively in high-temperature service applications, and in particular, in components of turbine engines. To improve high-temperature creep properties, these alloys are often used in the directionally-solidified or single-crystal form. The objective of this CRADA project was to investigate the weldability of both experimental and commercial nickel-base superalloys in polycrystalline, directionally-solidified, and single-crystal forms.

  9. Noburnium: Systems design of niobium superalloys

    Science.gov (United States)

    Misra, Abhijeet

    2005-11-01

    A systems-based approach, integrating quantum mechanical calculations with efficient experimentation, was employed to design niobium-based superalloys. The microstructural concept of gamma-gamma' nickel-based superalloys was adopted, where, the coherent gamma ' aluminides act both as the strengthening phase and a source of aluminum for Al2O3 passivation. Building on previous research, the selected bcc-type ordered aluminide was L2 1 structured Pd2HfAl phase. Comprehensive phase relations were measured on Nb-Pd-Hf-Al prototype alloys, and key tie-tetrahedra were identified. Aluminide precipitation in a bcc matrix was demonstrated in designed Nb+Pd2HfAl alloys. Thermodynamic databases were developed by integrating first-principles calculations with measured phase relations. Atomic volume models were developed for the bcc matrix and the Pd2HfAl phase and matrix elements which would reduce lattice misfit were identified. An experimental 2-phase alloy demonstrated a misfit of 3%. A modified Wagner's model was used to predict the required transient properties to form external Al2O3. The principal oxidation design goal was to decrease the oxygen permeability ( NSOx DO ) divided by the aluminum diffusivity (DAl) by 5 orders of magnitude. A multicomponent mobility database was developed to predict the diffusivities. Guided by first-principles calculations the effect of alloying elements on the oxygen diffusivity in Nb was measured, and the mobility database was experimentally validated. Based on the mobility database, it was found that increasing Al solubility in the bcc matrix greatly increased Al diffusivity. Alloying elements were identified that would increase Al solubility in the bcc matrix. Prototype alloys were prepared and the best oxidation performance was exhibited by a bcc+Nb2Al Nb-Hf-Al alloy, which exhibited parabolic oxidation behavior at 1300°C. The alloy was shown to have achieved the required 5 orders of magnitude reduction in the design parameter. The

  10. Current status of Co-Re-based alloys being developed to supplement Ni-based superalloys for ultra-high temperature applications in gas turbines

    Czech Academy of Sciences Publication Activity Database

    Mukherji, D.; Strunz, Pavel; Gilles, R.; Karge, L.; Rösler, J.

    2015-01-01

    Roč. 53, č. 4 (2015), s. 287-294 ISSN 0023-432X EU Projects: European Commission(XE) 283883 - NMI3-II Institutional support: RVO:61389005 Keywords : Co-base alloy * scanning electron microscopy (SEM) * neutron scattering Subject RIV: JG - Metallurgy Impact factor: 0.365, year: 2015

  11. Evaluation of powder metallurgy superalloy disk materials

    Science.gov (United States)

    Evans, D. J.

    1975-01-01

    A program was conducted to develop nickel-base superalloy disk material using prealloyed powder metallurgy techniques. The program included fabrication of test specimens and subscale turbine disks from four different prealloyed powders (NASA-TRW-VIA, AF2-1DA, Mar-M-432 and MERL 80). Based on evaluation of these specimens and disks, two alloys (AF2-1DA and Mar-M-432) were selected for scale-up evaluation. Using fabricating experience gained in the subscale turbine disk effort, test specimens and full scale turbine disks were formed from the selected alloys. These specimens and disks were then subjected to a rigorous test program to evaluate their physical properties and determine their suitability for use in advanced performance turbine engines. A major objective of the program was to develop processes which would yield alloy properties that would be repeatable in producing jet engine disks from the same powder metallurgy alloys. The feasibility of manufacturing full scale gas turbine engine disks by thermomechanical processing of pre-alloyed metal powders was demonstrated. AF2-1DA was shown to possess tensile and creep-rupture properties in excess of those of Astroloy, one of the highest temperature capability disk alloys now in production. It was determined that metallographic evaluation after post-HIP elevated temperature exposure should be used to verify the effectiveness of consolidation of hot isostatically pressed billets.

  12. High temperature deformation mechanisms of L12-containing Co-based superalloys

    Science.gov (United States)

    Titus, Michael Shaw

    Ni-based superalloys have been used as the structural material of choice for high temperature applications in gas turbine engines since the 1940s, but their operating temperature is becoming limited by their melting temperature (Tm =1300degrees C). Despite decades of research, no viable alternatives to Ni-based superalloys have been discovered and developed. However, in 2006, a ternary gamma' phase was discovered in the Co-Al-W system that enabled a new class of Co-based superalloys to be developed. These new Co-based superalloys possess a gamma-gamma' microstructure that is nearly identical to Ni-based superalloys, which enables these superalloys to achieve extraordinary high temperature mechanical properties. Furthermore, Co-based alloys possess the added benefit of exhibiting a melting temperature of at least 100degrees C higher than commercial Ni-based superalloys. Superalloys used as the structural materials in high pressure turbine blades must withstand large thermomechanical stresses imparted from the rotating disk and hot, corrosive gases present. These stresses induce time-dependent plastic deformation, which is commonly known as creep, and new superalloys must possess adequate creep resistance over a broad range of temperature in order to be used as the structural materials for high pressure turbine blades. For these reasons, this research focuses on quantifying high temperature creep properties of new gamma'-containing Co-based superalloys and identifying the high temperature creep deformation mechanisms. The high temperature creep properties of new Co- and CoNi-based alloys were found to be comparable to Ni-based superalloys with respect to minimum creep rates and creep-rupture lives at 900degrees C up to the solvus temperature of the gamma' phase. Co-based alloys exhibited a propensity for extended superlattice stacking fault formation in the gamma' precipitates resulting from dislocation shearing events. When Ni was added to the Co-based compositions

  13. High temperature properties of polycrystalline γ{sup '}-strengthened cobalt-base superalloys; Hochtemperatureigenschaften polykristalliner γ{sup '}-gehaerteter Kobaltbasis-Superlegierungen

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, Alexander

    2016-07-01

    The recent discovery of a stable γ{sup '}-phase in Co-based superalloys opened up a pathway for the development of a new high temperature material class, which is similar in microstructure and properties to the modern γ{sup '}-hardened Ni-based superalloys. In this work, the first attempt was done to check the influence of several for Ni-based superalloys typical alloying elements on the properties of the new Co-based superalloys. It became clear that the basic characteristics of the first experimental alloys are similar to those of the γ{sup '}-hardened Ni-based alloys. The results of the multinary experimental alloys show that, based on the insight gained so far, targeted alloy development is possible. These materials have the potential to be used as disc materials in turbines.

  14. Influence of Short-time Oxidation on Corrosion Properties of Directionally Solidified Superalloys with Different Orientations

    Directory of Open Access Journals (Sweden)

    MA Luo-ning

    2016-07-01

    Full Text Available In order to investigate the corrosion performance on intersecting and longitudinal surfaces of unoxidized and oxidized directionally solidified superalloys, Ni-base directionally solidified superalloy DZ125 and Co-base directionally solidified superalloy DZ40M were selected. Oxidation behavior on both alloys with different orientations was investigated at 1050℃ at different times, simulating the oxidation process of vanes or blades in service; subsequent electrochemical performance in 3.5%NaCl aqueous solution was studied on two orientations of unoxidized and oxidized alloys, simulating the corrosion process of superalloy during downtime. The results show that grain boundaries and sub-boundaries of directionally solidified superalloys are susceptible to corrosion and thus longitudinal surface with lower area fraction of grain boundaries has higher corrosion resistance. Compared to intersecting surface of alloys, the structure of grain boundaries of longitudinal surface is less conducive to diffusion and thus the oxidation rate on longitudinal surface is lower. Formation of oxide layers on alloys after short-time oxidation provides protective effect and enhances the corrosion resistance.

  15. Microstructural Evolution and Creep-Rupture Behavior of Fusion Welds Involving Alloys for Advanced Ultrasupercritical Power Generation

    Science.gov (United States)

    Bechetti, Daniel H., Jr.

    Projections for large increases in the global demand for electric power produced by the burning of fossil fuels, in combination with growing environmental concerns surrounding these fuel sources, have sparked initiatives in the United States, Europe, and Asia aimed at developing a new generation of coal fired power plant, termed Advanced Ultrasupercritical (A-USC). These plants are slated to operate at higher steam temperatures and pressures than current generation plants, and in so doing will offer increased process cycle efficiency and reduced greenhouse gas emissions. Several gamma' precipitation strengthened Ni-based superalloys have been identified as candidates for the hottest sections of these plants, but the microstructural instability and poor creep behavior (compared to wrought products) of fusion welds involving these alloys present significant hurdles to their implementation and a gap in knowledge that must be addressed. In this work, creep testing and in-depth microstructural characterization have been used to provide insight into the long-term performance of these alloys. First, an investigation of the weld metal microstructural evolution as it relates to creep strength reductions in A-USC alloys INCONELRTM 740, NIMONICRTM 263 (INCONEL and NIMONIC are registered trademarks of Special Metals Corporation), and HaynesRTM 282RTM (Haynes and 282 are registered trademarks of Haynes International) was performed. gamma'-precipitate free zones were identified in two of these three alloys, and their development was linked to the evolution of phases that precipitate at the expense of gamma'. Alloy 282 was shown to avoid precipitate free zone formation because the precipitates that form during long term aging in this alloy are poor in the gamma'-forming elements. Next, the microstructural evolution of INCONELRTM 740H (a compositional variant of alloy 740) during creep was investigated. Gleeble-based interrupted creep and creep-rupture testing was used to

  16. Creep properties of heat-resistant superalloys for nuclear plants in helium

    International Nuclear Information System (INIS)

    Shimizu, Shigeki; Satoh, Keisuke; Honda, Yoshio; Matsuda, Shozo; Murase, Hirokazu

    1979-01-01

    Creep properties of candidate superalloys for VHTR components in a helium environment at both temperatures of 800 0 C and 900 0 C were compared with those of the same alloys in the atmospheric condition, and the superalloys were contrasted with each other from the viewpoint of high temperature structural design. At 800 0 C, no significant effect of a helium environment on creep properties of the superalloys is observed. At 900 0 C, however, creep strength of Inconel 617, Incoloy 800 and Incoloy 807 in the helium environment decrease more than in the atmospheric environment. In Hastelloy X and Inconel 625, there is no significant difference between creep strengths in helium and those in the atmospheric condition. Concerning So and St values in helium at 900 0 C, Inconel 617 and Hastelloy X are clearly superior to other superalloys. (author)

  17. FRAUD/SABOTAGE Killing Nuclear-Reactors Need Modeling!!!: "Super"alloys GENERIC ENDEMIC Wigner's-Disease/.../IN-stability: Ethics? SHMETHICS!!!

    Science.gov (United States)

    Asphahani, Aziz; Siegel, Sidney; Siegel, Edward

    2010-03-01

    Carbides solid-state chemistry domination of old/new nuclear- reactors/spent-fuel-casks/refineries/jet/missile/rocket-engines in austenitic/FCC Ni/Fe-based(so miscalled)``super"alloys(182/82; Hastelloy-X,600,304/304L-SSs,...,690!!!) GENERIC ENDEMIC EXTANT detrimental(synonyms): Wigner's-diseas(WD)[J.Appl.Phys.17,857 (1946)]/Ostwald-ripening/spinodal-decomposition/overageing- embrittlement/thermal-leading-to-mechanical(TLTM)-INstability: Mayo[Google:``If Leaks Could Kill"; at flickr.com search on ``Giant-Magnotoresistance"; find: Siegel[J.Mag.Mag.Mtls.7,312 (1978)]Politics(1979)]-Hoffman[animatedsoftware.com], what DOE/NRC MISlabels as ``butt-welds" ``stress-corrosion cracking" endpoint's ROOT-CAUSE ULTIMATE-ORIGIN is WD overageing-embritt- lement caused brittle-fracture cracking from early/ongoing AEC/ DOE-n"u"tional-la"v"atories sabotage!!!

  18. Measurement and modeling of residual stress in a welded Haynes[reg] 25 cylinder

    International Nuclear Information System (INIS)

    Larsson, C.; Holden, T.M.; Bourke, M.A.M.; Stout, M.; Teague, J.; Lindgren, L.-E.

    2005-01-01

    An experimental and simulation study of residual stresses was made in the vicinity of a gas tungsten arc weld, used to join a hemispherical end cap to a cylinder. The capped cylinder is used in a satellite application and was fabricated from a Co-based Haynes[reg] 25 alloy. The cylinder was 34.7 mm in outer diameter and 3.3 mm in thickness. The experimental measurements were made by neutron diffraction and the simulation used the implicit Marc finite element code. The experimental resolution was limited to approximately 3 mm parallel to the axis of the cylinder (the weld was 6 mm in the same direction) and comparison over the same volume of the finite element prediction showed general agreement. Subject to the limited spatial resolution, the largest experimentally measured tensile residual stress was 180 MPa, located at the middle of the weld. However, the predictions suggest that there are regions in the weld where average tensile residual stresses as much as 400 MPa exist. One qualitative disparity between the model and the experiments was that the measurement included a larger degree of asymmetry on either side of the weld than predicted by the model

  19. Measurement and modeling of residual stress in a welded Haynes[reg] 25 cylinder

    Energy Technology Data Exchange (ETDEWEB)

    Larsson, C. [Div. of Eng. Mat., Department of Mech. Eng., Linkoeping University, 58183 Linkoeping (Sweden)]. E-mail: clarsson@cfl.rr.com; Holden, T.M. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Bourke, M.A.M. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Stout, M. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Teague, J. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Lindgren, L.-E. [Div. Comp. Aided Design, Lulea University of Technology and Dalarna University, 97187 Lulea (Sweden)

    2005-06-15

    An experimental and simulation study of residual stresses was made in the vicinity of a gas tungsten arc weld, used to join a hemispherical end cap to a cylinder. The capped cylinder is used in a satellite application and was fabricated from a Co-based Haynes[reg] 25 alloy. The cylinder was 34.7 mm in outer diameter and 3.3 mm in thickness. The experimental measurements were made by neutron diffraction and the simulation used the implicit Marc finite element code. The experimental resolution was limited to approximately 3 mm parallel to the axis of the cylinder (the weld was 6 mm in the same direction) and comparison over the same volume of the finite element prediction showed general agreement. Subject to the limited spatial resolution, the largest experimentally measured tensile residual stress was 180 MPa, located at the middle of the weld. However, the predictions suggest that there are regions in the weld where average tensile residual stresses as much as 400 MPa exist. One qualitative disparity between the model and the experiments was that the measurement included a larger degree of asymmetry on either side of the weld than predicted by the model.

  20. Microstructural causes of negative creep in cast superalloys

    International Nuclear Information System (INIS)

    Frank, G.

    1990-01-01

    The dissertation examines by means of microstructural investigations and modelling calculations two types of superalloys: the nickel-base cast alloy IN 738 LC (γ'-hardened, containing MC and M 23 C 6 carbides), and the cobalt-base cast alloy FSX 414 (containing M 23 C 6 carbides, solid solution-hardened). The task was to determine the causes of microstructural volume contraction, in order to improve and facilitate explanation and extrapolation of the materials' long-term behaviour at high temperatures, and to derive if possible information on appropriate measures preventing negative creep, which may lead to critical damage of bolted joints, for instance. (orig./MM) [de

  1. Creep-rupture behavior of iron superalloys in high-pressure hydrogen

    Science.gov (United States)

    Bhattacharyya, S.; Peterman, W.

    1984-01-01

    The creep-rupture properties of five iron-base and one cobalt-base high temperature alloys were investigated to assess the feasibility of using the alloys as construction materials in a Stirling engine. The alloys were heat treated and hardness measurements were taken. Typical microstructures of the alloys are shown. The creep-rupture properties of the alloys were determined at 760 and 815 C in 15.0 MPa H2 for 200 to 1000 hours. Plots of rupture life versus stress for the six superalloys are presented along with creep strain-time plots.

  2. A comparative study of the corrosion resistance of incoloy MA 956 and PM 2000 superalloys

    Directory of Open Access Journals (Sweden)

    Maysa Terada

    2010-12-01

    Full Text Available Austenitic stainless steels, titanium and cobalt alloys are widely used as biomaterials. However, new medical devices require innovative materials with specific properties, depending on their application. The magnetic properties are among the properties of interest for some biomedical applications. However, due to the interaction of magnetic materials with Magnetic Resonance Image equipments they might used only as not fixed implants or for medical devices. The ferromagnetic superalloys, Incoloy MA 956 and PM 2000, produced by mechanical alloying, have similar chemical composition, high corrosion resistance and are used in high temperature applications. In this study, the corrosion resistance of these two ferritic superalloys was compared in a phosphate buffer solution. The electrochemical results showed that both superalloys are passive in this solution and the PM 2000 present a more protective passive film on it associated to higher impedances than the MA 956.

  3. Cobalt-free nickel-base superalloys

    International Nuclear Information System (INIS)

    Koizumi, Yutaka; Yamazaki, Michio; Harada, Hiroshi

    1979-01-01

    Cobalt-free nickel-base cast superalloys have been developed. Cobalt is considered to be a beneficial element to strengthen the alloys but should be eliminated in alloys to be used for direct cycle helium turbine driven by helium gas from HTGR (high temp. gas reactor). The elimination of cobalt is required to avoid the formation of radioactive 60 Co from the debris or scales of the alloys. Cobalt-free alloys are also desirable from another viewpoint, i.e. recently the shortage of the element has become a serious problem in industry. Cobalt-free Mar-M200 type alloys modified by the additions of 0.15 - 0.2 wt% B and 1 - 1.5 wt% Hf were found to have a creep rupture strength superior or comparable to that of the original Mar-M200 alloy bearing cobalt. The ductility in tensile test at 800 0 C, as cast or after prolonged heating at 900 0 C (the tensile test was done without removing the surface layer affected by the heating), was also improved by the additions of 0.15 - 0.2% B and 1 - 1.5% Hf. The morphology of grain boundaries became intricated by the additions of 0.15 - 0.2% B and 1 - 1.5% Hf, to such a degree that one can hardly distinguish grain boundaries by microscopes. The change in the grain boundary morphology was considered, as suggested previously by one of the authors (M.Y.), to be the reason for the improvements in the creep rupture strength and tensile ductility. (author)

  4. Hydrogen Annealing Of Single-Crystal Superalloys

    Science.gov (United States)

    Smialek, James L.; Schaeffer, John C.; Murphy, Wendy

    1995-01-01

    Annealing at temperature equal to or greater than 2,200 degrees F in atmosphere of hydrogen found to increase ability of single-crystal superalloys to resist oxidation when subsequently exposed to oxidizing atmospheres at temperatures almost as high. Supperalloys in question are principal constituents of hot-stage airfoils (blades) in aircraft and ground-based turbine engines; also used in other high-temperature applications like chemical-processing plants, coal-gasification plants, petrochemical refineries, and boilers. Hydrogen anneal provides resistance to oxidation without decreasing fatigue strength and without need for coating or reactive sulfur-gettering constituents. In comparison with coating, hydrogen annealing costs less. Benefits extend to stainless steels, nickel/chromium, and nickel-base alloys, subject to same scale-adhesion and oxidation-resistance considerations, except that scale is chromia instead of alumina.

  5. MGI-oriented High-throughput Measurement of Interdiffusion Coefficient Matrices in Ni-based Superalloys

    Directory of Open Access Journals (Sweden)

    TANG Ying

    2017-01-01

    Full Text Available One of the research hotspots in the field of high-temperature alloys was to search the substitutional elements for Re in order to prepare the single-crystal Ni-based superalloys with less or even no Re addition. To find the elements with similar or even lower diffusion coefficients in comparison with that of Re was one of the effective strategies. In multicomponent alloys, the interdiffusivity matrix were used to comprehensively characterize the diffusion ability of any alloying elements. Therefore, accurate determination of the composition-dependant and temperature-dependent interdiffusivities matrices of different elements in γ and γ' phases of Ni-based superalloys was high priority. The paper briefly introduces of the status of the interdiffusivity matrices determination in Ni-based superalloys, and the methods for determining the interdiffusivities in multicomponent alloys, including the traditional Matano-Kirkaldy method and recently proposed numerical inverse method. Because the traditional Matano-Kirkaldy method is of low efficiency, the experimental reports on interdiffusivity matrices in ternary and higher order sub-systems of the Ni-based superalloys were very scarce in the literature. While the numerical inverse method newly proposed in our research group based on Fick's second law can be utilized for high-throughput measurement of accurate interdiffusivity matrices in alloys with any number of components. After that, the successful application of the numerical inverse method in the high-throughput measurement of interdiffusivity matrices in alloys is demonstrated in fcc (γ phase of the ternary Ni-Al-Ta system. Moreover, the validation of the resulting composition-dependant and temperature-dependent interdiffusivity matrices is also comprehensively made. Then, this paper summarizes the recent progress in the measurement of interdiffusivity matrices in γ and γ' phases of a series of core ternary Ni-based superalloys achieved in

  6. N18, powder metallurgy superalloy for disks: Development and applications

    Energy Technology Data Exchange (ETDEWEB)

    Guedou, J.Y.; Lautridou, J.C.; Honnorat, Y. (SNECMA, Evry (France). Materials and Processes Dept.)

    1993-08-01

    The preliminary industrial development of a powder metallurgy (PM) superalloy, designated N18, for disk applications has been completed. This alloy exhibits good overall mechanical properties after appropriate processing of the material. These properties have been measured on both isothermally forged and extruded billets, as well as on specimens cut from actual parts. The temperature capability of the alloy is about 700 C for long-term applications and approximately 750 C for short-term use because of microstructural instability. Further improvements in creep and crack propagation properties, without significant reduction in tensile strength, are possible through appropriate thermomechanical processing, which results in a large controlled grain size. Spin pit tests on subscale disks have confirmed that the N18 alloy has a higher resistance than PM Astrology and is therefore an excellent alloy for modern turbine disk applications.

  7. Analysis of laser beam weldability of Inconel 738 superalloy

    International Nuclear Information System (INIS)

    Egbewande, A.T.; Buckson, R.A.; Ojo, O.A.

    2010-01-01

    The susceptibility of pre-weld heat treated laser beam welded IN 738 superalloy to heat affected zone (HAZ) cracking was studied. A pre-weld heat treatment that produced the minimal grain boundary liquation resulted in a higher level of cracking compared to those with more intergranular liquation. This deviation from the general expectation of influence of intergranular liquation extent on HAZ microfissuring is attributable to the reduction in the ability of the base alloy to accommodate welding tensile stress that accompanied a pre-weld heat treatment condition designed to minimize intergranular liquation. Furthermore, in contrast to what has been generally reported in other nickel-based superalloys, a decrease in laser welding speed resulted in increased HAZ cracking in the IN 738, which can be attributed to exacerbated process instability at lower welding speeds.

  8. Effect of tensile mean stress on fatigue behavior of single-crystal and directionally solidified superalloys

    Science.gov (United States)

    Kalluri, Sreeramesh; Mcgaw, Michael A.

    1990-01-01

    Two nickel base superalloys, single crystal PWA 1480 and directionally solidified MAR-M 246 + Hf, were studied in view of the potential usage of the former and usage of the latter as blade materials for the turbomachinery of the space shuttle main engine. The baseline zero mean stress (ZMS) fatigue life (FL) behavior of these superalloys was established, and then the effect of tensile mean stress (TMS) on their FL behavior was characterized. At room temperature these superalloys have lower ductilities and higher strengths than most polycrystalline engineering alloys. The cycle stress-strain response was thus nominally elastic in most of the fatigue tests. Therefore, a stress range based FL prediction approach was used to characterize both the ZMS and TMS fatigue data. In the past, several researchers have developed methods to account for the detrimental effect of tensile mean stress on the FL for polycrystalline engineering alloys. However, the applicability of these methods to single crystal and directionally solidified superalloys has not been established. In this study, these methods were applied to characterize the TMS fatigue data of single crystal PWA 1480 and directionally solidified MAR-M 246 + Hf and were found to be unsatisfactory. Therefore, a method of accounting for the TMS effect on FL, that is based on a technique proposed by Heidmann and Manson was developed to characterize the TMS fatigue data of these superalloys. Details of this method and its relationship to the conventionally used mean stress methods in FL prediction are discussed.

  9. Heat affected zone liquation cracking in electron beam welded third generation nickel base superalloys

    International Nuclear Information System (INIS)

    Ojo, O.A.; Wang, Y.L.; Chaturvedi, M.C.

    2008-01-01

    The weldability of directionally solidified nickel base superalloy TMS-75 and TMS-75+C was investigated by autogenous bead-on-plate electron beam welding. The analysis of microsegregation that occurred during solidification of the as-cast alloys indicated that while W and Re segregated into the γ dendrites of both the alloys, Ta, Hf and C were rejected into the interdendritic liquid in the TMS-75+C. Heat affected zone intergranular liquation cracking was observed in both the materials and was observed to be closely associated with liquated γ-γ' eutectic microconstituent. The TMS-75+C alloy, however, exhibited a reduced extent of HAZ cracking compared to TMS-75. Suppression of terminal solidification reaction involving non-invariant γ-γ' eutectic transformation due to modification of primary solidification path by carbon addition is suggested to be an important factor contributing to reduced susceptibility of TMS-75+C alloy to HAZ liquation cracking relative to the TMS-75 superalloy

  10. Effect of cobalt on microstructural parameters and mechanical properties of Ni-base single crystal superalloys

    International Nuclear Information System (INIS)

    Suzuki, Takanobu; Imai, Hachiro; Yokokawa, Tadaharu; Kobayashi, Toshiharu; Koizumi, Yutaka; Harada, Hiroshi

    2007-01-01

    The alloying effect of Cobalt (Co) to microstructural parameters and mechanical properties, such as partitioning ratios of alloying elements and creep strength, of Re-bearing Ni-base single crystal superalloys have been investigated. The second generation single crystal superalloys, TMS-82+, Ni-7.8Co-4.9Cr-1.9Mo-8.7W-5.3Al-6.0Ta-2.4Re-0.1Hf, in mass% (8Co) was compared to a Co-free (0Co) and 15 mass% Co (15Co) alloy which had the same chemical composition as TMS-82+ except that Co was changed. It was shown that the partitioning ratios of alloying elements trend to k(=X γ /X' γ )=1, as the content of Co was increased. Furthermore, it was found that there was suitable content of Co for the creep strength under various temperature-stress conditions. (author)

  11. Composition and Antimicrobial Activity of Euphrasia rostkoviana Hayne Essential Oil

    Science.gov (United States)

    Novy, Pavel; Davidova, Hana; Serrano-Rojero, Cecilia Suqued; Rondevaldova, Johana; Pulkrabek, Josef

    2015-01-01

    Eyebright, Euphrasia rostkoviana Hayne (Scrophulariaceae), is a medicinal plant traditionally used in Europe for the treatment of various health disorders, especially as eyewash to treat eye ailments such as conjunctivitis and blepharitis that can be associated with bacterial infections. Some Euphrasia species have been previously reported to contain essential oil. However, the composition and bioactivity of E. rostkoviana oil are unknown. Therefore, in this study, we investigated the chemical composition and antimicrobial activity of the eyebright essential oil against some organisms associated with eye infections: Enterococcus faecalis, Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, S. epidermidis, Pseudomonas aeruginosa, and Candida albicans. GC-MS analysis revealed more than 70 constituents, with n-hexadecanoic acid (18.47%) as the main constituent followed by thymol (7.97%), myristic acid (4.71%), linalool (4.65%), and anethole (4.09%). The essential oil showed antimicrobial effect against all organisms tested with the exception of P. aeruginosa. The best activity was observed against all Gram-positive bacteria tested with the minimum inhibitory concentrations of 512 µg/mL. This is the first report on the chemical composition of E. rostkoviana essential oil and its antimicrobial activity. PMID:26000025

  12. Composition and Antimicrobial Activity of Euphrasia rostkoviana Hayne Essential Oil.

    Science.gov (United States)

    Novy, Pavel; Davidova, Hana; Serrano-Rojero, Cecilia Suqued; Rondevaldova, Johana; Pulkrabek, Josef; Kokoska, Ladislav

    2015-01-01

    Eyebright, Euphrasia rostkoviana Hayne (Scrophulariaceae), is a medicinal plant traditionally used in Europe for the treatment of various health disorders, especially as eyewash to treat eye ailments such as conjunctivitis and blepharitis that can be associated with bacterial infections. Some Euphrasia species have been previously reported to contain essential oil. However, the composition and bioactivity of E. rostkoviana oil are unknown. Therefore, in this study, we investigated the chemical composition and antimicrobial activity of the eyebright essential oil against some organisms associated with eye infections: Enterococcus faecalis, Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, S. epidermidis, Pseudomonas aeruginosa, and Candida albicans. GC-MS analysis revealed more than 70 constituents, with n-hexadecanoic acid (18.47%) as the main constituent followed by thymol (7.97%), myristic acid (4.71%), linalool (4.65%), and anethole (4.09%). The essential oil showed antimicrobial effect against all organisms tested with the exception of P. aeruginosa. The best activity was observed against all Gram-positive bacteria tested with the minimum inhibitory concentrations of 512 µg/mL. This is the first report on the chemical composition of E. rostkoviana essential oil and its antimicrobial activity.

  13. Composition and Antimicrobial Activity of Euphrasia rostkoviana Hayne Essential Oil

    Directory of Open Access Journals (Sweden)

    Pavel Novy

    2015-01-01

    Full Text Available Eyebright, Euphrasia rostkoviana Hayne (Scrophulariaceae, is a medicinal plant traditionally used in Europe for the treatment of various health disorders, especially as eyewash to treat eye ailments such as conjunctivitis and blepharitis that can be associated with bacterial infections. Some Euphrasia species have been previously reported to contain essential oil. However, the composition and bioactivity of E. rostkoviana oil are unknown. Therefore, in this study, we investigated the chemical composition and antimicrobial activity of the eyebright essential oil against some organisms associated with eye infections: Enterococcus faecalis, Escherichia coli, Klebsiella pneumoniae, Staphylococcus aureus, S. epidermidis, Pseudomonas aeruginosa, and Candida albicans. GC-MS analysis revealed more than 70 constituents, with n-hexadecanoic acid (18.47% as the main constituent followed by thymol (7.97%, myristic acid (4.71%, linalool (4.65%, and anethole (4.09%. The essential oil showed antimicrobial effect against all organisms tested with the exception of P. aeruginosa. The best activity was observed against all Gram-positive bacteria tested with the minimum inhibitory concentrations of 512 µg/mL. This is the first report on the chemical composition of E. rostkoviana essential oil and its antimicrobial activity.

  14. Mechanical Behavior of Three-Dimensional Braided Nickel-Based Superalloys Synthesized via Pack Cementation

    Science.gov (United States)

    Lippitz, Nicolas; Erdeniz, Dinc; Sharp, Keith W.; Dunand, David C.

    2018-03-01

    Braided tubes of Ni-based superalloys are fabricated via three-dimensional (3-D) braiding of ductile Ni-20Cr (wt pct) wires followed by post-textile gas-phase alloying with Al and Ti to create, after homogenization and aging, γ/ γ' strengthened lightweight, porous structures. Tensile tests reveal an increase in strength by 100 MPa compared to as-braided Ni-20Cr (wt pct). An interrupted tensile test, combined with X-ray tomographic scans between each step, sheds light on the failure behavior of the braided superalloy tubes.

  15. A sulfidation-resistant nickel-base alloy

    International Nuclear Information System (INIS)

    Lai, G.Y.

    1989-01-01

    For applications in mildly to moderately sulfidizing environments, stainless steels, Fe-Ni-Cr alloys (e.g., alloys 800 and 330), and more recently Fe-Ni-Cr-Co alloys (e.g., alloy 556) are frequently used for construction of process equipment. However, for many highly sulfidizing environments, few existing commercial alloys have adequate performance. Thus, a new nickel-based alloy containing 27 wt.% Co, 28 wt.% Cr, 4 wt.% Fe, 2.75 wt.% Si, 0.5 wt.% Mn and 0.05 wt.% C (Haynes alloy HR-160) was developed

  16. σ and η Phase formation in advanced polycrystalline Ni-base superalloys

    Energy Technology Data Exchange (ETDEWEB)

    Antonov, Stoichko, E-mail: santonov@hawk.iit.edu [Illinois Institute of Technology, 10 W. 32nd Street, Chicago, IL 60616 (United States); Huo, Jiajie; Feng, Qiang [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Isheim, Dieter; Seidman, David N. [Department of Materials Science and Engineering, Northwestern University, 2220 Campus Drive, Evanston, IL 60208 (United States); Northwestern University Center for Atom Probe Tomography (NUCAPT), 2220 Campus Drive, Evanston, IL 60208 (United States); Helmink, Randolph C.; Sun, Eugene [Rolls-Royce Corporation, 450 S. Meridian Street, Indianapolis, IN 46225 (United States); Tin, Sammy [Illinois Institute of Technology, 10 W. 32nd Street, Chicago, IL 60616 (United States)

    2017-02-27

    In polycrystalline Ni-base superalloys, grain boundary precipitation of secondary phases can be significant due to the effects they pose on the mechanical properties. As new alloying concepts for polycrystalline Ni-base superalloys are being developed to extend their temperature capability, the effect of increasing levels of Nb alloying additions on long term phase stability and the formation of topologically close packed (TCP) phases needs to be studied. Elevated levels of Nb can result in increased matrix supersaturation and promote the precipitation of secondary phases. Long term thermal exposures on two experimental powder processed Ni-base superalloys containing various levels of Nb were completed to assess the stability and precipitation of TCP phases. It was found that additions of Nb promoted the precipitation of η-Ni{sub 6}AlNb along the grain boundaries in powder processed, polycrystalline Ni-base superalloys, while reduced Nb levels favored the precipitation of blocky Cr and Mo – rich σ phase precipitates along the grain boundary. Evaluation of the thermodynamic stability of these two phases in both alloys using Thermo-calc showed that while σ phase predictions are fairly accurate, predictions of the η phase are limited.

  17. High temperature oxidation characteristics of developed Ni-Cr-W superalloys in air

    International Nuclear Information System (INIS)

    Suzuki, Tomio; Shindo, Masami

    1996-11-01

    For expanding utilization of the Ni-Cr-W superalloy, which has been developed as one of new high temperature structural materials used in the advanced High Temperature Gas-cooled Reactors (HTGRs), in various engineering fields including the structural material for heat utilization system, the oxidation behavior of this alloy in air as one of high oxidizing environments becomes one of key factors. The oxidation tests for the industrial scale heat of Ni-Cr-W superalloy with the optimized chemical composition and five kinds of experimental Ni-Cr-W alloys with different Cr/W ratio were carried out at high temperatures in the air compared with Hastelloy XR. The conclusions were obtained as follows. (1) The oxidation resistance of the industrial scale heat of Ni-Cr-W superalloy with the optimized chemical composition was superior to that of Hastelloy XR. (2) The most excellent oxidation resistance was obtained in an alloy with 19% Cr of the industrial scale heat of Ni-Cr-W superalloy. (author)

  18. Superalloy Lattice Block Developed for Use in Lightweight, High-Temperature Structures

    Science.gov (United States)

    Hebsur, Mohan G.; Whittenberger, J. Daniel; Krause, David L.

    2003-01-01

    Successful development of advanced gas turbine engines for aircraft will require lightweight, high-temperature components. Currently titanium-aluminum- (TiAl) based alloys are envisioned for such applications because of their lower density (4 g/cm3) in comparison to superalloys (8.5 g/cm3), which have been utilized for hot turbine engine parts for over 50 years. However, a recently developed concept (lattice block) by JAMCORP, Inc., of Willmington, Massachusetts, would allow lightweight, high-temperature structures to be directly fabricated from superalloys and, thus, take advantage of their well-known, characterized properties. In its simplest state, lattice block is composed of thin ligaments arranged in a three dimensional triangulated trusslike configuration that forms a structurally rigid panel. Because lattice block can be fabricated by casting, correctly sized hardware is produced with little or no machining; thus very low cost manufacturing is possible. Together, the NASA Glenn Research Center and JAMCORP have extended their lattice block methodology for lower melting materials, such as Al alloys, to demonstrate that investment casting of superalloy lattice block is possible. This effort required advances in lattice block pattern design and assembly, higher temperature mold materials and mold fabrication technology, and foundry practice suitable for superalloys (ref. 1). Lattice block panels have been cast from two different Ni-base superalloys: IN 718, which is the most commonly utilized superalloy and retains its strength up to 650 C; and MAR M247, which possesses excellent mechanical properties to at least 1100 C. In addition to the open-cell lattice block geometry, same-sized lattice block panels containing a thin (1-mm-thick) solid face on one side have also been cast from both superalloys. The elevated-temperature mechanical properties of the open cell and face-sheeted superalloy lattice block panels are currently being examined, and the

  19. Study of the oxidation kinetics of the MA 956 superalloy

    International Nuclear Information System (INIS)

    Garcia-Alonso, M.C.; Gonzalez-Carrasco, J.L.; Escudero, M.L.

    1998-01-01

    This work deals with the oxidation kinetics of the MA 956 superalloy in the temperature range of 800-1,200 degree centigree for up to 200 h exposure. During oxidation the alloy develops a fine, compact and very well adhered α-alumina layer, the thickness of which increases with increasing time and temperature. The oxidation kinetics obeys a sub parabolic type behaviour. The scale growth seems to occur by two different oxidation mechanisms; above 1,050 degree centigree, the oxidation process would be controlled by α-alumina, and below 900 degree centigree by γ-alumina. (Author) 17 refs

  20. Expert systems for superalloy studies

    Science.gov (United States)

    Workman, Gary L.; Kaukler, William F.

    1990-01-01

    There are many areas in science and engineering which require knowledge of an extremely complex foundation of experimental results in order to design methodologies for developing new materials or products. Superalloys are an area which fit well into this discussion in the sense that they are complex combinations of elements which exhibit certain characteristics. Obviously the use of superalloys in high performance, high temperature systems such as the Space Shuttle Main Engine is of interest to NASA. The superalloy manufacturing process is complex and the implementation of an expert system within the design process requires some thought as to how and where it should be implemented. A major motivation is to develop a methodology to assist metallurgists in the design of superalloy materials using current expert systems technology. Hydrogen embrittlement is disasterous to rocket engines and the heuristics can be very complex. Attacking this problem as one module in the overall design process represents a significant step forward. In order to describe the objectives of the first phase implementation, the expert system was designated Hydrogen Environment Embrittlement Expert System (HEEES).

  1. Thermodynamic assessment of liquid composition change during solidification and its effect on freckle formation in superalloys

    International Nuclear Information System (INIS)

    Long Zhengdong; Liu Xingbo; Yang Wanhong; Chang, K.-M.; Barbero, Ever

    2004-01-01

    The solidification macrosegregation, i.e. freckle, becomes more and more concerned with ever increasing demand for the large ingot size of superalloys. The evaluation of freckle formation is very difficult because of the less understanding of freckle formation mechanism and complex solidification behaviors of multi-component superalloys. The macrostructure of typical Nb-bearing and Ti-bearing superalloys in horizontally directional solidification and vacuum arc remelting (VAR) ingots were investigated to clarify the freckle formation mechanism. The thermodynamic approach was proposed to simulate the solidification behaviors. The relative Ra numbers, a reliable criterion, of freckle formation for some alloys were obtained based on the results of thermodynamic calculations. This thermodynamic approach was evaluated through comparison of the calculations from semi-experimental results. The Ra numbers obtained by thermodynamic approach are in good agreement with the ingot size capability of the industry melting shops, which is limited mainly by freckle defects

  2. Degradation of creep properties in a long-term thermally exposed nickel base superalloy

    International Nuclear Information System (INIS)

    Zrnik, J.; Strunz, P.; Vrchovinsky, V.; Muransky, O.; Novy, Z.; Wiedenmann, A.

    2004-01-01

    When exposed for long time at elevated temperatures of 430 and 650 deg. C the nickel base superalloy EI 698 VD can experience a significant decrease in creep resistance. The cause of the creep degradation of nickel base superalloy is generally attributed to the microstructural instability at prolonged high temperature exposure. In this article, the creep-life data, generated on long thermally exposed nickel base superalloy EI698 VD were related to the local microstructural changes observed using SEM and TEM analysing techniques. While structure analysis provided supporting evidence concerning the changes associated with grain boundary carbide precipitation, no persuasive evidence of a morphological and/or dimensional gamma prime change was showed. For clarifying of the role of gamma prime precipitates on alloy on creep degradation, the SANS (small angle neutron scattering) experiment was crucial in the characterization of the bulk-averaged gamma prime morphology and its size distribution with respect to the period of thermal exposure

  3. Microstructure of the Nickel-Base Superalloy CMSX-4 Fabricated by Selective Electron Beam Melting

    Science.gov (United States)

    Ramsperger, Markus; Singer, Robert F.; Körner, Carolin

    2016-03-01

    Powder bed-based additive manufacturing (AM) processes are characterized by very high-temperature gradients and solidification rates. These conditions lead to microstructures orders of magnitude smaller than in conventional casting processes. Especially in the field of high performance alloys, like nickel-base superalloys, this opens new opportunities for homogenization and alloy development. Nevertheless, the high susceptibility to cracking of precipitation-hardenable superalloys is a challenge for AM. In this study, electron beam-based AM is used to fabricate samples from gas-atomized pre-alloyed CMSX-4 powder. The influence of the processing strategy on crack formation is investigated. The samples are characterized by optical and SEM microscopy and analyzed by microprobe analysis. Differential scanning calorimetry is used to demonstrate the effect of the fine microstructure on characteristic temperatures. In addition, in situ heat treatment effects are investigated.

  4. Soft Computing Methods in Design of Superalloys

    Science.gov (United States)

    Cios, K. J.; Berke, L.; Vary, A.; Sharma, S.

    1996-01-01

    Soft computing techniques of neural networks and genetic algorithms are used in the design of superalloys. The cyclic oxidation attack parameter K(sub a), generated from tests at NASA Lewis Research Center, is modelled as a function of the superalloy chemistry and test temperature using a neural network. This model is then used in conjunction with a genetic algorithm to obtain an optimized superalloy composition resulting in low K(sub a) values.

  5. Burst Testing and Analysis of Superalloy Disks With a Dual Grain Microstructure

    Science.gov (United States)

    Gayda, John; Kantzos, Pete

    2006-01-01

    Elastic-plastic finite element analyses of room temperature burst tests on four superalloy disks were conducted and reported in this paper. Two alloys, Rene 104 (General Electric Aircraft Engines) and Alloy 10 (Honeywell Engines & Systems), were studied. For both alloys an advanced dual microstructure disk, fine grain bore and coarse grain rim, were analyzed and compared with conventional disks with uniform microstructures, coarse grain for Rene 104 and fine grain for Alloy 10. The analysis and experimental data were in good agreement up to burst. At burst, the analysis underestimated the speed and growth of the Rene 104 disks, but overestimated the speed and growth of the Alloy 10 disks. Fractography revealed that the Alloy 10 disks displayed significant surface microcracking and coalescence in comparison to Rene 104 disks. This phenomenon may help explain the differences between the Alloy 10 disks and the Rene 104 disks, as well as the observed deviations between analytical and experimental data at burst.

  6. Solid solution strengthening and diffusion in nickel- and cobalt-based superalloys

    Energy Technology Data Exchange (ETDEWEB)

    Rehman, Hamad ur

    2016-07-01

    Nickel and cobalt-based superalloys with a γ-γ{sup '} microstructure are known for their excellent creep resistance at high temperatures. Their microstructure is engineered using different alloying elements, that partition either to the fcc γ matrix or to the ordered γ{sup '} phase. In the present work the effect of alloying elements on their segregation behaviour in nickel-based superalloys, diffusion in cobalt-based superalloys and the temperature dependent solid solution strengthening in nickel-based alloys is investigated. The effect of dendritic segregation on the local mechanical properties of individual phases in the as-cast, heat treated and creep deformed state of a nickel-based superalloy is investigated. The local chemical composition is characterized using Electron Probe Micro Analysis and then correlated with the mechanical properties of individual phases using nanoindentation. Furthermore, the temperature dependant solid solution hardening contribution of Ta, W and Re towards fcc nickel is studied. The room temperature hardening is determined by a diffusion couple approach using nanoindentation and energy dispersive X-ray analysis for relating hardness to the chemical composition. The high temperature properties are determined using compression strain rate jump tests. The results show that at lower temperatures, the solute size is prevalent and the elements with the largest size difference with nickel, induce the greatest hardening consistent with a classical solid solution strengthening theory. At higher temperatures, the solutes interact with the dislocations such that the slowest diffusing solute poses maximal resistance to dislocation glide and climb. Lastly, the diffusion of different technically relevant solutes in fcc cobalt is investigated using diffusion couples. The results show that the large atoms diffuse faster in cobalt-based superalloys similar to their nickel-based counterparts.

  7. Solid solution strengthening and diffusion in nickel- and cobalt-based superalloys

    International Nuclear Information System (INIS)

    Rehman, Hamad ur

    2016-01-01

    Nickel and cobalt-based superalloys with a γ-γ ' microstructure are known for their excellent creep resistance at high temperatures. Their microstructure is engineered using different alloying elements, that partition either to the fcc γ matrix or to the ordered γ ' phase. In the present work the effect of alloying elements on their segregation behaviour in nickel-based superalloys, diffusion in cobalt-based superalloys and the temperature dependent solid solution strengthening in nickel-based alloys is investigated. The effect of dendritic segregation on the local mechanical properties of individual phases in the as-cast, heat treated and creep deformed state of a nickel-based superalloy is investigated. The local chemical composition is characterized using Electron Probe Micro Analysis and then correlated with the mechanical properties of individual phases using nanoindentation. Furthermore, the temperature dependant solid solution hardening contribution of Ta, W and Re towards fcc nickel is studied. The room temperature hardening is determined by a diffusion couple approach using nanoindentation and energy dispersive X-ray analysis for relating hardness to the chemical composition. The high temperature properties are determined using compression strain rate jump tests. The results show that at lower temperatures, the solute size is prevalent and the elements with the largest size difference with nickel, induce the greatest hardening consistent with a classical solid solution strengthening theory. At higher temperatures, the solutes interact with the dislocations such that the slowest diffusing solute poses maximal resistance to dislocation glide and climb. Lastly, the diffusion of different technically relevant solutes in fcc cobalt is investigated using diffusion couples. The results show that the large atoms diffuse faster in cobalt-based superalloys similar to their nickel-based counterparts.

  8. Effects of cobalt in nickel-base superalloys

    Science.gov (United States)

    Tien, J. K.; Jarrett, R. N.

    1983-01-01

    The role of cobalt in a representative wrought nickel-base superalloy was determined. The results show cobalt affecting the solubility of elements in the gamma matrix, resulting in enhanced gamma' volume fraction, in the stabilization of MC-type carbides, and in the stabilization of sigma phase. In the particular alloy studied, these microstructural and microchemistry changes are insufficient in extent to impact on tensile strength, yield strength, and in the ductilities. Depending on the heat treatment, creep and stress rupture resistance can be cobalt sensitive. In the coarse grain, fully solutioned and aged condition, all of the alloy's 17% cobalt can be replaced by nickel without deleteriously affecting this resistance. In the fine grain, partially solutioned and aged condition, this resistance is deleteriously affected only when one-half or more of the initial cobalt content is removed. The structure and property results are discussed with respect to existing theories and with respect to other recent and earlier findings on the impact of cobalt, if any, on the performance of nickel-base superalloys.

  9. Materials for Advanced Ultrasupercritical Steam Turbines Task 4: Cast Superalloy Development

    Energy Technology Data Exchange (ETDEWEB)

    Thangirala, Mani

    2015-09-30

    The Steam Turbine critical stationary structural components are high integrity Large Shell and Valve Casing heavy section Castings, containing high temperature steam under high pressures. Hence to support the development of advanced materials technology for use in an AUSC steam turbine capable of operating with steam conditions of 760°C (1400°F) and 35 Mpa (5000 psia), Casting alloy selection and evaluation of mechanical, metallurgical properties and castability with robust manufacturing methods are mandated. Alloy down select from Phase 1 based on producability criteria and creep rupture properties tested by NETL-Albany and ORNL directed the consortium to investigate cast properties of Haynes 282 and Haynes 263. The goals of Task 4 in Phase 2 are to understand a broader range of mechanical properties, the impact of manufacturing variables on those properties. Scale up the size of heats to production levels to facilitate the understanding of the impact of heat and component weight, on metallurgical and mechanical behavior. GE Power & Water Materials and Processes Engineering for the Phase 2, Task 4.0 Castings work, systematically designed and executed casting material property evaluation, multiple test programs. Starting from 15 lbs. cylinder castings to world’s first 17,000 lbs. poured weight, heavy section large steam turbine partial valve Haynes 282 super alloy casting. This has demonstrated scalability of the material for steam Turbine applications. Activities under Task 4.0, Investigated and characterized various mechanical properties of Cast Haynes 282 and Cast Nimonic 263. The development stages involved were: 1) Small Cast Evaluation: 4 inch diam. Haynes 282 and Nimonic 263 Cylinders. This provided effects of liquidus super heat range and first baseline mechanical data on cast versions of conventional vacuum re-melted and forged Ni based super alloys. 2) Step block castings of 300 lbs. and 600 lbs. Haynes 282 from 2 foundry heats were evaluated which

  10. Superalloys. Volume 2. 1977-February 1978 (citations from the NTIS data base). Report for 1977--Feb 78

    International Nuclear Information System (INIS)

    Smith, M.F.

    1978-03-01

    Federally-funded research on cobalt- and nickel-based superalloys is cited. Casting and powder metallurgy of these alloys are covered. Properties such as heat resistance, corrosion resistance, microstructure, fracture, and creep are described. The use of these materials in nuclear reactors, gas turbine parts, and high-temperature equipment is a major part of this compilation

  11. Computer aided design of nickel-base superalloys

    International Nuclear Information System (INIS)

    Lawrence, P.J.

    1988-01-01

    This paper describes a computer aided design process for Ni-base superalloys developed and employed at ASEA Brown Boveri. The technique involves a series of modules each of which predicts a particular property of a hypothetical new composition. In the first stage of the development of this design techniques modules were produced to predict phase stability, using PHACOMP, and high temperature creep strength and hot corrosion resistance, using multiple linear regression equations derived from the data in the literature. Alloys designed using these technique are also discussed and, in particular, shortcomings of the design process are highlighted. This information was then used to produce a revamped design methodology involving extra modules, including prediction of an alloy's gamma-prime content. (orig.)

  12. Metallurgical optimisation of PM superalloy N19

    Directory of Open Access Journals (Sweden)

    Locq Didier

    2014-01-01

    Full Text Available Microstructures of the new PM superalloy N19 have been investigated for various heat treatments in order to reach the best compromise between static strength and cyclic resistance. One subsolvus and several supersolvus heat treatments were applied to produce fine (7 μm and medium (25 μm grain sizes, respectively. The alloy is shown to be quite sensitive to the cooling conditions after solutioning as the γ′ hardening precipitates, both secondary and tertiary, have a direct influence on mechanical properties. Two cooling conditions after solutioning produce a high crack propagation resistance at 650 °C with dwell time cycles, which is one of the basic requirements. The low cycle fatigue behaviour appears to be correlated to the grain size, which determines the origin of crack initiation (from ceramic inclusions or not. The other mechanical properties (tensile, creep remain above target levels. Despite the medium size grain microstructure in the supersolvus condition, a high level of mechanical strength is observed in N19 at elevated temperature. It is understood that further improvement in properties can be achieved by developing coarse grain microstructures.

  13. Titanium and titanium alloys: fundamentals and applications

    National Research Council Canada - National Science Library

    Leyens, C; Peters, M

    2003-01-01

    ... number of titanium alloys have paved the way for light metals to vastly expand into many industrial applications. Titanium and its alloys stand out primarily due to their high specific strength and excellent corrosion resistance, at just half the weight of steels and Ni-based superalloys. This explains their early success in the aerospace and the...

  14. Influence of cobalt, tantalum, and tungsten on the microstructure and mechanical properties of superalloy single crystals

    International Nuclear Information System (INIS)

    Nathal, M.V.; Ebert, L.J.

    1982-01-01

    The influence of Co, Ta, and W on the microstructure and mechanical properties of nickel base super-alloy single crystals was investigated. A matrix of alloys was based on Mar-M 247 stripped of C, B, Zr, and Hf. The microstructures of the alloys were examined using optical and electron microscopy, phase extraction, X-ray diffraction, and differential thermal analysis. Tensile and creep-rupture tests were performed at 1000 C. An increase in tensile and creep strength resulted when Co was removed from alloys containing high refractory metal contents, but Co effects were negligible for alloys with lower refractory metal levels. In the composition range studied, W was more effective than Ta in increasing the creep resistance. The mechanical properties are discussed in relation to the microstructures of the alloys

  15. Influence of cobalt, tantalum, and tungsten on the microstructure and mechanical properties of superalloy single crystals

    Science.gov (United States)

    Nathal, M. V.; Ebert, L. J.

    1982-01-01

    The influence of Co, Ta, and W on the microstructure and mechanical properties of nickel base super-alloy single crystals was investigated. A matrix of alloys was based on Mar-M 247 stripped of C, B, Zr, and Hf. The microstructures of the alloys were examined using optical and electron microscopy, phase extraction, X-ray diffraction, and differential thermal analysis. Tensile and creep-rupture tests were performed at 1000 C. An increase in tensile and creep strength resulted when Co was removed from alloys containing high refractory metal contents, but Co effects were negligible for alloys with lower refractory metal levels. In the composition range studied, W was more effective than Ta in increasing the creep resistance. The mechanical properties are discussed in relation to the microstructures of the alloys.

  16. Computer Aided Design of Ni-Based Single Crystal Superalloy for Industrial Gas Turbine Blades

    Science.gov (United States)

    Wei, Xianping; Gong, Xiufang; Yang, Gongxian; Wang, Haiwei; Li, Haisong; Chen, Xueda; Gao, Zhenhuan; Xu, Yongfeng; Yang, Ming

    The influence of molybdenum, tungsten and cobalt on stress-rupture properties of single crystal superalloy PWA1483 has been investigated using the simulated calculation of JMatPro software which ha s been widely used to develop single crystal superalloy, and the effect of alloying element on the stability of strengthening phase has been revealed by using the Thermo-Calc software. Those properties calculation results showed that the increasing of alloy content could facilitate the precipitation of TCP phases and increase the lattice misfit between γ and γ' phase, and the effect of molybdenum, tantalum was the strongest and that of cobalt was the weakest. Then the chemical composition was optimized, and the selected compositions showed excellent microstructure stability and stress-rupture properties by the confirmation of d-electrons concept and software calculation.

  17. Phase Transformations in Nickel base Superalloy Inconel 718 during Cyclic Loading at High Temperature

    Directory of Open Access Journals (Sweden)

    Michal Jambor

    2017-06-01

    Full Text Available Nickel base superalloys are hi-tech materials intended for high temperature applications. This property owns a complex microstructure formed by matrix of Ni and variety of precipitates. The type, form and the amount of these phases significantly affect the resulting properties of these alloys. At sufficiently long exposure to high temperatures, the transformation phase can occur, which can lead to degradation of properties of these alloys. A cyclic plastic deformation can accelerate these changes, and they could occur at significantly lower temperatures or in shorter time of exposure. The aim of this study is to describe phase transformation, which can occur by a cyclic plastic deformation at high temperatures in nickel base superalloy Inconel 718.

  18. A Review on Inertia and Linear Friction Welding of Ni-Based Superalloys

    Science.gov (United States)

    Chamanfar, Ahmad; Jahazi, Mohammad; Cormier, Jonathan

    2015-04-01

    Inertia and linear friction welding are being increasingly used for near-net-shape manufacturing of high-value materials in aerospace and power generation gas turbines because of providing a better quality joint and offering many advantages over conventional fusion welding and mechanical joining techniques. In this paper, the published works up-to-date on inertia and linear friction welding of Ni-based superalloys are reviewed with the objective to make clarifications on discrepancies and uncertainties reported in literature regarding issues related to these two friction welding processes as well as microstructure, texture, and mechanical properties of the Ni-based superalloy weldments. Initially, the chemical composition and microstructure of Ni-based superalloys that contribute to the quality of the joint are reviewed briefly. Then, problems related to fusion welding of these alloys are addressed with due consideration of inertia and linear friction welding as alternative techniques. The fundamentals of inertia and linear friction welding processes are analyzed next with emphasis on the bonding mechanisms and evolution of temperature and strain rate across the weld interface. Microstructural features, texture development, residual stresses, and mechanical properties of similar and dissimilar polycrystalline and single crystal Ni-based superalloy weldments are discussed next. Then, application of inertia and linear friction welding for joining Ni-based superalloys and related advantages over fusion welding, mechanical joining, and machining are explained briefly. Finally, present scientific and technological challenges facing inertia and linear friction welding of Ni-based superalloys including those related to modeling of these processes are addressed.

  19. Looking for New Polycrystalline MC-Reinforced Cobalt-Based Superalloys Candidate to Applications at 1200°C

    OpenAIRE

    Patrice Berthod

    2017-01-01

    For applications for which temperatures higher than 1150°C can be encountered the currently best superalloys, the γ/γ′ single crystals, cannot be used under stress because of the disappearance of their reinforcing γ′ precipitates at such temperatures which are higher than their solvus. Cobalt-based alloys strengthened by refractory and highly stable carbides may represent an alternative solution. In this work the interest was focused on MC carbides of several types. Alloys were elaborated wit...

  20. Niobium-base superalloys via powder metallurgy technology

    International Nuclear Information System (INIS)

    Loria, E.A.

    1987-01-01

    This paper provides some insight into an area that has been neglected, namely the possibility of developing high-strength, niobium-base alloys by improved oxidation resistance via the consolidation of rapidly solidified powders. Powder metallurgy (P/M) is an attractive processing technique because of its flexibility and versatility, and it may provide the alloys with properties and workability not obtainable via metal casting. A critical review of both U.S. and Russian literature is presented along with suggestions on the most promising compositions and processing techniques available to meet these competing goals. Previous work on many niobium alloys reveals that long term properties are retained well above those obtained on nickel-base superalloys. Cast and wrought alloys extend specific strength beyond 1200 0 C (2200 0 F), but lack oxidation resistance. Remarkable oxidation resistance is obtained, however, on miniature castings of certain ternary alloys which are too brittle for any processing. A better understanding of the oxidation mechanism is necessary before the proper P/M (RST) approach is taken on compositions which could provide compatibility between the two competing goals through grain refinement and a homogeneous distribution of the contributory phases. Finally, ways to up-scale production of Nb powder are discussed, including thermodynamic feasibility for the direct reduction of NbCl/sub 5/ in a 1.5 MW plasma reactor

  1. Computational and Experimental Design of Fe-Based Superalloys for Elevated-Temperature Applications

    Energy Technology Data Exchange (ETDEWEB)

    Liaw, Peter K. [Univ. of Tennessee, Knoxville, TN (United States); Fine, Morris E. [Northwestern Univ., Evanston, IL (United States); Ghosh, Gautam [Northwestern Univ., Evanston, IL (United States); Asta, Mark D. [Univ. of California, Berkeley, CA (United States); Liu, Chain T. [Auburn Univ., AL (United States); Sun, Zhiqian [Univ. of Tennessee, Knoxville, TN (United States); Huang, Shenyan [Univ. of Tennessee, Knoxville, TN (United States); Teng, Zhenke [Univ. of Tennessee, Knoxville, TN (United States); Wang, Gongyao [Univ. of Tennessee, Knoxville, TN (United States)

    2012-04-13

    Analogous to nickel-based superalloys, Fe-based superalloys, which are strengthened by coherent B2- type precipitates are proposed for elevated-temperature applications. During the period of this project, a series of ferritic superalloys have been designed and fabricated by methods of vacuum-arc melting and vacuum-induction melting. Nano-scale precipitates were characterized by atom-probe tomography, ultrasmall- angle X-ray scattering, and transmission-electron microscopy. A duplex distribution of precipitates was found. It seems that ferritic superalloys are susceptible to brittle fracture. Systematic endeavors have been devoted to understanding and resolving the problem. Factors, such as hot rolling, precipitate volume fractions, alloy compositions, precipitate sizes and inter-particle spacings, and hyperfine cooling precipitates, have been investigated. In order to understand the underlying relationship between the microstructure and creep behavior of ferric alloys at elevated temperatures, in-situ neutron studies have been carried out. Based on the current result, it seems that the major role of β' with a 16%-volume fraction in strengthening ferritic alloys is not load sharing but interactions with dislocations. The oxidation behavior of one ferritic alloy, FBB8 (Fe-6.5Al-10Ni-10Cr-3.4Mo-0.25Zr-0.005B, weight percent), was studied in dry air. It is found that it possesses superior oxidation resistance at 1,023 and 1,123 K, compared with other creep-resistant ferritic steels [T91 (modified 9Cr-1Mo, weight percent) and P92 (9Cr-1.8W-0.5Mo, weight percent)]. At the same time, the calculation of the interfacial energies between the -iron and B2-type intermetallics (CoAl, FeAl, and NiAl) has been conducted.

  2. Discussion of "Investigation of Oxide Bifilms in Investment Cast Superalloy IN100 Parts I and II"*

    Science.gov (United States)

    Campbell, John

    2017-10-01

    Fuchs and Kaplan carried out experiments in an attempt to ascertain whether oxide bifilms were present in a vacuum-cast Ni-base superalloy but concluded negatively. Although this author challenged their interpretation of their findings, both parties had overlooked the presence in the alloy of boron which is now known to inhibit bifilm formation. However, even though boron can help significantly, improved filling system designs remain important if other damaging entrainment defects are to be avoided.

  3. Analysis of microstructure in electro-spark deposited IN718 superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Anisimov, E.; Khan, A.K.; Ojo, O.A., E-mail: olanrewaju.ojo@umanitoba.ca

    2016-09-15

    The microstructure of electro-spark deposited (ESD) superalloy IN718 was studied by the use of scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) techniques. In converse to general assumption, the extremely high cooling rate involved in the ESD process did not produce partitionless solidification that is devoid of second phase microconstituents in the material, nano-sized Laves phase and MC carbide particles were observed within the deposited layer. Notwithstanding the several thermal cycles involved in the process, the extremely low heat input of the process produced a deposited region that is free of the main strengthening phase of the alloy, γ″ phase precipitates, which is in contrast to what have been reported on laser deposition. Nevertheless, application of the standard full heat treatment of the alloy resulted in extensive formation of the γ″ phase precipitates and δ phase precipitates, the most stable secondary phase of the alloy, with nearly, if not complete, dissolution of the Laves phase particles. Furthermore, the XPS analysis done in the study revealed the formation of nano-oxides within the deposited layer, which increased the microhardness of the superalloy in the as-deposited condition and inhibited its grain growth during post-process heat treatment. The microstructure analysis done in this work is crucial to the understanding of properties of the superalloy processed by the ESD technique. - Highlights: •Electron microscopy analyses of electro-spark deposited IN 718 superalloy were performed. •Nano-sized secondary phase particles were observed within the deposited layer. •The study shows that the ESD did not produce partitionless solidification of the alloy.

  4. Behaviour and damage of a superalloy prepared by hot isostatic compression

    International Nuclear Information System (INIS)

    Dubiez-Le-Goff, Sophie

    2003-01-01

    This work deals with the behavior and damage of Udimet 720 superalloy prepared by hot isostatic compression. This alloy is considered for manufacturing turbine disks of high temperature reactors (HTR). The material choice for HTR turbine disk depends on the following criteria: a good creep resistance until 700 C, a good behaviour under an helium impure atmosphere, a possible implementation under a disk of 1.5 m diameter. (author) [fr

  5. Development of advanced P/M Ni-base superalloys for turbine disks

    Directory of Open Access Journals (Sweden)

    Garibov Genrikh S.

    2014-01-01

    Full Text Available In the process of evolution of powder metallurgy in Russia the task permanently formulated was the following: to improve strength properties of P/M superalloys without application of additional complex HIPed blanks deformation operation. On the other hand development of a turbine disk material structure to ensure an improvement in aircraft engine performance requires the use of special HIP and heat treatment conditions. To ensure maximum strength properties of disk materials it is necessary to form a structure which would have optimum size of solid solution grains, γ′-phases and carbides. Along with that heating of the material up to a temperature determined by solvus of an alloy ensures a stable and reproducible level of mechanical properties of the disks. The above-said can be illustrated by successful mastering of new complex-alloyed VVP-class superalloys with the use of powder size − 100 μm. Application of special HIP and heat treatment conditions for these superalloys to obtain the desired grain size and the strengthening γ′-phase precipitates allowed a noticeable improvement in ultimate tensile strength and yield strength up to ≥1600 MPa and ≥1200 MPa respectively. 100 hrs rupture strength at 650 ∘C and 750 ∘C was improved up to 1140 MPa and 750 MPa respectively. P/M VVP nickel-base superalloys offer higher characteristics in comparison with many superalloys designed for the same purposes. HIPed disc compacts manufactured from PREP-powder have a homogeneous micro- and macrostructure, a stable level of mechanical properties.

  6. Detection of creep damage in a nickel base superalloy using NDE techniques

    International Nuclear Information System (INIS)

    Carreon, H.; Mora, B.; Barrera, G.

    2009-10-01

    Due to elevated temperatures, excessive stresses and severed corrosion conditions, turbine engine components are subject to creep processes that limit the components life such as a turbine bucket. The failure mechanism of a turbine bucket is related primarily to creep and corrosion and secondarily to thermal fatigue. As a result, it is desirable to assess the current conditions of such turbine component. This study uses the eddy current nondestructive evaluation technique in an effort to monitor the creep damage in a nickel base super-alloy, turbine bucket after service. The experimental results show an important electrical conductivity variation in eddy current images on the creep damage zone of nickel base super-alloy samples cut from a turbine bucket. Thermoelectric power measurements were also conducted in order to obtain a direct correlation between the presence of material changes due to creep damage and the electrical conductivity measurements. This research work shows an alternative non-destructive method in order to detect creep damage in a nickel base super-alloy turbine bucket. (Author)

  7. Oxidation behavior of HVOF sprayed Ni-5Al coatings deposited on Ni- and Fe-based superalloys under cyclic condition

    International Nuclear Information System (INIS)

    Mahesh, R.A.; Jayaganthan, R.; Prakash, S.

    2008-01-01

    Ni-5Al coating was obtained on three superalloy substrates viz. Superni 76, Superni 750 and Superfer 800 using high velocity oxy-fuel (HVOF) spray process. Oxidation studies were carried out on both bare and coated superalloy substrates in air at 900 deg. C for 100 cycles. The weight change was measured at the end of each cycle and observed that the weight gain was high in Superni 750 alloy when compared to Superni 76 and Superfer 800. A nearly parabolic oxidation behavior was observed for Ni-5Al coated Superni 750 and Superfer 800 alloys but a Ni-5Al coated Superni 76 substrate showed a slight deviation. The scale was analysed using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) and electron probe microanalysis (EPMA). The coating increased the oxidation resistance for all the alloy substrates at 900 deg. C. Among the three-coated superalloys, Superfer 800 substrate has shown the best resistance to oxidation. The protective nature of the Ni-5Al coated superalloys was due to the formation of protective oxide scales such as NiO, Al 2 O 3 and Cr 2 O 3

  8. Superalloy applications in the nuclear field

    International Nuclear Information System (INIS)

    Ramanathan, L.V.; Padilha, A.F.

    1984-01-01

    The process conditions in the areas of nuclear fuel processing, fabrication, utilization, reprocessing and disposal are severe, demanding therefore the use of materials with high temperature mechanical strength and corrosion resistance. A number of refractory metal containing superalloys have found application in the diferrent areas of the nuclear field. The main aspects of the microstructure, strengthening mechanisms and corrosion resistance of 3 superalloys, namely Incoloy 825, Inconel 718 and Hastelloy C have been discussed. The role of the refractory metal elements in influencing the mechanical strength and corrosion resistance of superalloys has been emphasised. (Author) [pt

  9. Computational thermodynamics and genetic algorithms to design affordable γ′-strengthened nickel–iron based superalloys

    International Nuclear Information System (INIS)

    Tancret, F

    2012-01-01

    Computational thermodynamics based on the CALPHAD approach (Thermo-Calc software) are used to design creep-resistant and affordable superalloys for large-scale applications such as power plants. Cost is reduced by the introduction of iron and by avoiding the use of expensive alloying elements such as Nb, Ta, Mo, Co etc. Strengthening is ensured by the addition of W, and of Al and Ti to provoke the precipitation of γ′. However, the addition of iron reduces the maximum possible volume fraction of γ′. The latter is maximized automatically using a genetic algorithm during simulation, while keeping the alloys free of undesirable phases at high temperatures. New superalloys with 20 wt% Cr are designed, with Fe content up to 37 wt%. They should be forgeable, weldable, oxidation resistant and significantly cheaper than existing alloys with equivalent properties. (paper)

  10. Very High Cycle Fatigue of Ni-Based Single-Crystal Superalloys at High Temperature

    Science.gov (United States)

    Cervellon, A.; Cormier, J.; Mauget, F.; Hervier, Z.; Nadot, Y.

    2018-05-01

    Very high cycle fatigue (VHCF) properties at high temperature of Ni-based single-crystal (SX) superalloys and of a directionally solidified (DS) superalloy have been investigated at 20 kHz and a temperature of 1000 °C. Under fully reversed conditions (R = - 1), no noticeable difference in VHCF lifetimes between all investigated alloys has been observed. Internal casting pores size is the main VHCF lifetime-controlling factor whatever the chemical composition of the alloys. Other types of microstructural defects (eutectics, carbides), if present, may act as stress concentration sites when the number of cycles exceed 109 cycles or when porosity is absent by applying a prior hot isostatic pressing treatment. For longer tests (> 30 hours), oxidation also controls the main crack initiation sites leading to a mode I crack initiation from oxidized layer. Under such conditions, alloy's resistance to oxidation has a prominent role in controlling the VHCF. When creep damage is present at high ratios (R ≥ 0.8), creep resistance of SX/DS alloys governs VHCF lifetime. Under such high mean stress conditions, SX alloys developed to retard the initiation and creep propagation of mode I micro-cracks from pores have better VHCF lifetimes.

  11. The metallurgy of superalloys part 2

    International Nuclear Information System (INIS)

    Abdelazim, M.E.; Hammad, F.H.

    1990-01-01

    This is part II of the report titled 'the metallurgy of superalloys'. It deals with the effect of heat treatment and operating conditions (thermal exposure and environment) on the mechanical properties of superalloys. The heat treatment is important in the development of superalloys through that it controls type, amount, size shape and distribution of the precipitate and the grain size of the matrix. The thermal exposure leads to reduction in the amount of the primary carbides and to precipitation of secondary carbides. Also it leads to the agglomeration and coarsening of gamma or the transformation of gamma phase to phase. The environment may lead to the internal oxidation, carburization, decarburization or sulphidization of the superalloys which may result in the degradation of their mechanical properties. This part gives also an example of applications of superalloys in the field of nuclear reactors especially high temperature-gas cooled reactors. Joined with this part a table which contains the major superalloys including its chemical analysis, creep rupture strength and some of its applications. 1 tab

  12. Optimising mechanical properties of hot forged nickel superalloy 625 components

    Science.gov (United States)

    Singo, Nthambe; Coles, John; Rosochowska, Malgorzata; Lalvani, Himanshu; Hernandez, Jose; Ion, William

    2018-05-01

    Hot forging and subsequent heat treatment were resulting in substandard mechanical properties of nickel superalloy, Alloy 625, components. The low strength was found to be due to inadequate deformation during forging, excessive grain growth and precipitation of carbides during subsequent heat treatment. Experimentation in a drop forging company and heat treatment facility led to the establishment of optimal parameters to minimise grain size and mitigate the adverse effects of carbide precipitation, leading to successful fulfilment of mechanical property specifications. This was achieved by reducing the number of operations, maximising the extent of deformation by changing the slug dimensions and its orientation in the die, and minimising the time of exposure to elevated temperatures in both the forging and subsequent heat treatment processes to avoid grain growth.

  13. Electron-microscopic investigations of dispersion-strengthened superalloys

    International Nuclear Information System (INIS)

    Schroeder, J.H.; Arzt, E.

    1988-01-01

    Oxide dispersion strengthened (ODS) superalloys possess a high creep strength up to temperatures above 1000 0 C. This is due to a fine dispersion of incoherent Y 2 O 3 particles in connection with a highly elongated grain structure. To investigate the production and properties of ODS alloys, the grain structure was studied and the shape and distribution of dispersoids were characterized after each of the various production steps. Because the interactions between lattice dislocations and dispersoids control the deformation behaviour at high temperatures, the dislocation-dispersoid configurations in crept specimens have been studied by a TEM stereo technique and under weak-beam conditions. It was possible to detect strain fields around the dispersoids using TEM. The results lead to an improved understanding of dispersion strengthening at high temperatures and provide guidelines for the optimum use of this strengthening mechanism. (orig.) [de

  14. Microstructural response to heat affected zone cracking of prewelding heat-treated Inconel 939 superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, M.A., E-mail: mgonzalez@comimsa.com.mx [Facultad de Ingenieria Mecanica y Electrica (FIME-UANL), Av. Universidad s/n. Ciudad Universitaria, C.P.66451 San Nicolas de los Garza, N.L. (Mexico); Martinez, D.I., E-mail: dorairma@yahoo.com [Facultad de Ingenieria Mecanica y Electrica (FIME-UANL), Av. Universidad s/n. Ciudad Universitaria, C.P.66451 San Nicolas de los Garza, N.L. (Mexico); Perez, A., E-mail: betinperez@hotmail.com [Facultad de Ingenieria Mecanica y Electrica (FIME-UANL), Av. Universidad s/n. Ciudad Universitaria, C.P.66451 San Nicolas de los Garza, N.L. (Mexico); Guajardo, H., E-mail: hguajardo@frisa.com [FRISA Aerospace, S.A. de C.V., Valentin G. Rivero No. 200, Col. Los Trevino, C.P. 66150, Santa Caterina N.L. (Mexico); Garza, A., E-mail: agarza@comimsa.com [Corporacion Mexicana de Investigacion en Materiales S.A. de C.V. (COMIMSA), Ciencia y Tecnologia No.790, Saltillo 400, C.P. 25295 Saltillo Coah. (Mexico)

    2011-12-15

    The microstructural response to cracking in the heat-affected zone (HAZ) of a nickel-based IN 939 superalloy after prewelding heat treatments (PWHT) was investigated. The PWHT specimens showed two different microstructures: 1) spherical ordered {gamma} Prime precipitates (357-442 nm), with blocky MC and discreet M{sub 23}C{sub 6} carbides dispersed within the coarse dendrites and in the interdendritic regions; and 2) ordered {gamma} Prime precipitates in 'ogdoadically' diced cube shapes and coarse MC carbides within the dendrites and in the interdendritic regions. After being tungsten inert gas welded (TIG) applying low heat input, welding speed and using a more ductile filler alloy, specimens with microstructures consisting of spherical {gamma} Prime precipitate particles and dispersed discreet MC carbides along the grain boundaries, displayed a considerably improved weldability due to a strong reduction of the intergranular HAZ cracking associated with the liquation microfissuring phenomena. - Highlights: Black-Right-Pointing-Pointer Homogeneous microstructures of {gamma} Prime spheroids and discreet MC carbides of Ni base superalloys through preweld heat treatments. Black-Right-Pointing-Pointer {gamma} Prime spheroids and discreet MC carbides reduce the intergranular HAZ liquation and microfissuring of Nickel base superalloys. Black-Right-Pointing-Pointer Microstructure {gamma} Prime spheroids and discreet blocky type MC carbides, capable to relax the stress generated during weld cooling. Black-Right-Pointing-Pointer Low welding heat input welding speeds and ductile filler alloys reduce the HAZ cracking susceptibility.

  15. Tensile properties and temperature-dependent yield strength prediction of GH4033 wrought superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Jianzuo [State Key Laboratory of Coal Mine Disaster Dynamics and Control and College of Aerospace Engineering, Chongqing University, Chongqing 400030 (China); Li, Weiguo, E-mail: wgli@cqu.edu.cn [State Key Laboratory of Coal Mine Disaster Dynamics and Control and College of Aerospace Engineering, Chongqing University, Chongqing 400030 (China); Zhang, Xianhe; Kou, Haibo; Shao, Jiaxing; Geng, Peiji; Deng, Yong [State Key Laboratory of Coal Mine Disaster Dynamics and Control and College of Aerospace Engineering, Chongqing University, Chongqing 400030 (China); Fang, Daining [LTCS and College of Engineering, Peking University, Beijing 100871 (China)

    2016-10-31

    The tensile properties of superalloy GH4033 have been evaluated at temperatures ranging from room temperature to 1000 °C. Fracture surfaces and precipitation were observed using a field-emission scanning electron microscope (FE-SEM). The alloy mainly consisted of γ’ precipitate particles homogeneously dispersed in the γ matrix interior. The effects of dynamic strain aging and precipitation on the strength were verified. A temperature-dependent yield strength model was developed to describe the temperature and precipitation effects on the alloy's yield behaviour. The model is able to consider the effect of precipitation strengthening on the yield strength. The yield behaviour of the precipitation-strengthened superalloy was demonstrated to be adequately predictable over a wide range of temperatures. Note that this model reflects the quantitative relationship between the yield strength of the precipitation-strengthened superalloy and the temperature, the elastic modulus, the specific heat capacity at constant pressure, Poisson's ratio, the precipitate particle size and the volume fraction of the particles.

  16. Welding Metallurgy of Nickel-Based Superalloys for Power Plant Construction

    Science.gov (United States)

    Tung, David C.

    Increasing the steam temperature and pressure in coal-fired power plants is a perpetual goal driven by the pursuit of increasing thermal cycle efficiency and reducing fuel consumption and emissions. The next target steam operating conditions, which are 760°C (1400°F) and 35 MPa (5000 psi) are known as Advanced Ultra Supercritical (AUSC), and can reduce CO2 emissions up to 13% but this cannot be achieved with traditional power plant construction materials. The use of precipitation-strengthened Nickel-based alloys (superalloys) is required for components which will experience the highest operating temperatures. The leading candidate superalloys for power plant construction are alloys 740H, 282, and 617. Superalloys have excellent elevated temperature properties due to careful microstructural design which is achieved through very specific heat treatments, often requiring solution annealing or homogenization at temperatures of 1100 °C or higher. A series of postweld heat treatments was investigated and it was found that homogenization steps before aging had no noticeable effect on weld metal microhardness, however; there were clear improvements in weld metal homogeneity. The full abstract can be viewed in the document itself.

  17. The High Temperature Tensile and Creep Behaviors of High Entropy Superalloy.

    Science.gov (United States)

    Tsao, Te-Kang; Yeh, An-Chou; Kuo, Chen-Ming; Kakehi, Koji; Murakami, Hideyuki; Yeh, Jien-Wei; Jian, Sheng-Rui

    2017-10-04

    This article presents the high temperature tensile and creep behaviors of a novel high entropy alloy (HEA). The microstructure of this HEA resembles that of advanced superalloys with a high entropy FCC matrix and L1 2 ordered precipitates, so it is also named as "high entropy superalloy (HESA)". The tensile yield strengths of HESA surpass those of the reported HEAs from room temperature to elevated temperatures; furthermore, its creep resistance at 982 °C can be compared to those of some Ni-based superalloys. Analysis on experimental results indicate that HESA could be strengthened by the low stacking-fault energy of the matrix, high anti-phase boundary energy of the strengthening precipitate, and thermally stable microstructure. Positive misfit between FCC matrix and precipitate has yielded parallel raft microstructure during creep at 982 °C, and the creep curves of HESA were dominated by tertiary creep behavior. To the best of authors' knowledge, this article is the first to present the elevated temperature tensile creep study on full scale specimens of a high entropy alloy, and the potential of HESA for high temperature structural application is discussed.

  18. Initial Mechanical Testing of Superalloy Lattice Block Structures Conducted

    Science.gov (United States)

    Krause, David L.; Whittenberger, J. Daniel

    2002-01-01

    The first mechanical tests of superalloy lattice block structures produced promising results for this exciting new lightweight material system. The testing was performed in-house at NASA Glenn Research Center's Structural Benchmark Test Facility, where small subelement-sized compression and beam specimens were loaded to observe elastic and plastic behavior, component strength levels, and fatigue resistance for hundreds of thousands of load cycles. Current lattice block construction produces a flat panel composed of thin ligaments arranged in a three-dimensional triangulated trusslike structure. Investment casting of lattice block panels has been developed and greatly expands opportunities for using this unique architecture in today's high-performance structures. In addition, advances made in NASA's Ultra-Efficient Engine Technology Program have extended the lattice block concept to superalloy materials. After a series of casting iterations, the nickel-based superalloy Inconel 718 (IN 718, Inco Alloys International, Inc., Huntington, WV) was successfully cast into lattice block panels; this combination offers light weight combined with high strength, high stiffness, and elevated-temperature durability. For tests to evaluate casting quality and configuration merit, small structural compression and bend test specimens were machined from the 5- by 12- by 0.5-in. panels. Linear elastic finite element analyses were completed for several specimen layouts to predict material stresses and deflections under proposed test conditions. The structural specimens were then subjected to room-temperature static and cyclic loads in Glenn's Life Prediction Branch's material test machine. Surprisingly, the test results exceeded analytical predictions: plastic strains greater than 5 percent were obtained, and fatigue lives did not depreciate relative to the base material. These assets were due to the formation of plastic hinges and the redundancies inherent in lattice block construction

  19. Evaluation of Heat Capacity and Resistance to Cyclic Oxidation of Nickel Superalloys

    Directory of Open Access Journals (Sweden)

    Przeliorz R.

    2014-08-01

    Full Text Available Paper presents the results of evaluation of heat resistance and specific heat capacity of MAR-M-200, MAR-M-247 and Rene 80 nickel superalloys. Heat resistance was evaluated using cyclic method. Every cycle included heating in 1100°C for 23 hours and cooling for 1 hour in air. Microstructure of the scale was observed using electron microscope. Specific heat capacity was measured using DSC calorimeter. It was found that under conditions of cyclically changing temperature alloy MAR-M-247 exhibits highest heat resistance. Formed oxide scale is heterophasic mixture of alloying elements, under which an internal oxidation zone was present. MAR-M-200 alloy has higher specific heat capacity compared to MAR-M-247. For tested alloys in the temperature range from 550°C to 800°C precipitation processes (γ′, γ″ are probably occurring, resulting in a sudden increase in the observed heat capacity.

  20. Effects of cobalt on structure, microchemistry and properties of a wrought nickel-base superalloy

    Science.gov (United States)

    Jarrett, R. N.; Tien, J. K.

    1982-01-01

    The effect of cobalt on the basic mechanical properties and microstructure of wrought nickel-base superalloys has been investigated experimentally by systematically replacing cobalt by nickel in Udimet 700 (17 wt% Co) commonly used in gas turbine (jet engine) applications. It is shown that the room temperature tensile yield strength and tensile strength only slightly decrease in fine-grained (disk) alloys and are basically unaffected in coarse-grained (blading) alloys as cobalt is removed. Creep and stress rupture resistances at 760 C are found to be unaffected by cobalt level in the blading alloys and decrease sharply only when the cobalt level is reduced below 8 vol% in the disk alloys. The effect of cobalt is explained in terms of gamma prime strengthening kinetics.

  1. Liquation Cracking in the Heat-Affected Zone of IN738 Superalloy Weld

    Directory of Open Access Journals (Sweden)

    Kai-Cheng Chen

    2018-05-01

    Full Text Available The main scope of this study investigated the occurrence of liquation cracking in the heat-affected zone (HAZ of IN738 superalloy weld, IN738 is widely used in gas turbine blades in land-based power plants. Microstructural examinations showed considerable amounts of γ’ uniformly precipitated in the γ matrix. Electron probe microanalysis (EPMA maps showed the γ-γ’ colonies were rich in Al and Ti, but lean in other alloy elements. Moreover, the metal carbides (MC, fine borides (M3B2 and M5B3, η-Ni3Ti, σ (Cr-Co and lamellar Ni7Zr2 intermetallic compounds could be found at the interdendritic boundaries. The fracture morphologies and the corresponding EPMA maps confirmed that the liquation cracking in the HAZ of the IN738 superalloy weld resulted from the presence of complex microconstituents at the interdendritic boundaries.

  2. Intermediate Co/Ni-base model superalloys — Thermophysical properties, creep and oxidation

    International Nuclear Information System (INIS)

    Zenk, Christopher H.; Neumeier, Steffen; Engl, Nicole M.; Fries, Suzana G.; Dolotko, Oleksandr; Weiser, Martin; Virtanen, Sannakaisa; Göken, Mathias

    2016-01-01

    The mechanical properties of γ′-strengthened Co–Ni–Al–W–Cr model superalloys extending from pure Ni-base to pure Co-base superalloys have been assessed. Differential scanning calorimetry measurements and thermodynamic calculations match well and show that the γ′ solvus temperature decreases with increasing Co-content. The γ/γ′ lattice misfit is negative on the Ni- and positive on the Co-rich side. High Ni-contents decelerate the oxidation kinetics up to a factor of 15. The creep strength of the Ni-base alloy increases by an order of magnitude with additions of Co before it deteriorates strongly upon higher additions despite an increasing γ′ volume fraction.

  3. On post-weld heat treatment cracking in tig welded superalloy ATI 718Plus

    Science.gov (United States)

    Asala, G.; Ojo, O. A.

    The susceptibility of heat affected zone (HAZ) to cracking in Tungsten Inert Gas (TIG) welded Allvac 718Plus superalloy during post-weld heat treatment (PWHT) was studied. Contrary to the previously reported case of low heat input electron beam welded Allvac 718Plus, where HAZ cracking occurred during PWHT, the TIG welded alloy is crack-free after PWHT, notwithstanding the presence of similar micro-constituents that caused cracking in the low input weld. Accordingly, the formation of brittle HAZ intergranular micro-constituents may not be a sufficient factor to determine cracking propensity, the extent of heat input during welding may be another major factor that influences HAZ cracking during PWHT of the aerospace superalloy Allvac 718Plus.

  4. Grain Boundary Engineering the Mechanical Properties of Allvac 718Plus(Trademark) Superalloy

    Science.gov (United States)

    Gabb, Timothy P.; Telesman, Jack; Garg, Anita; Lin, Peter; Provenzano, virgil; Heard, Robert; Miller, Herbert M.

    2010-01-01

    Grain Boundary Engineering can enhance the population of structurally-ordered "low S" Coincidence Site Lattice (CSL) grain boundaries in the microstructure. In some alloys, these "special" grain boundaries have been reported to improve overall resistance to corrosion, oxidation, and creep resistance. Such improvements could be quite beneficial for superalloys, especially in conditions which encourage damage and cracking at grain boundaries. Therefore, the effects of GBE processing on high-temperature mechanical properties of the cast and wrought superalloy Allvac 718Plus (Allvac ATI) were screened. Bar sections were subjected to varied GBE processing, and then consistently heat treated, machined, and tested at 650 C. Creep, tensile stress relaxation, and dwell fatigue crack growth tests were performed. The influences of GBE processing on microstructure, mechanical properties, and associated failure modes are discussed.

  5. The effects of Re addition to the nanostructure of a Ni-Cr-Al model superalloy

    International Nuclear Information System (INIS)

    Yoon, K.E.; Seidman, D.N.; Noebe, R.D.

    2004-01-01

    Full text: The refractory elements, such as W, Mo, Ta, and Re, have been at the center of focus since the late 1970s for the development of single-crystal turbine-blades, and they have improved significantly the high-temperature properties of Ni-based superalloys. The optimum mechanical properties and operating temperature of single-crystal blades are achieved by increasing the total amounts of refractory elements. In spite of the improvement of mechanical properties of Ni-based superalloys utilizing the addition of refractory elements, their effects on the microstructure of superalloys are mostly unidentified at the subnano- to nanoscale. Rhenium (2 at.%) was added to a model ternary Ni-8.5 at.% Cr-10 at.% Al superalloy to study its effects on the temporal evolution. The temporal evolution of γ' (L1 2 ) precipitates in a Ni-Cr-AI-Re FCC alloy, aged at 1073 K from 0.25 to 264 h, is investigated by transmission-electron and three-dimensional atom-probe (3DAP) microscopies. The coarsening kinetics of γ' precipitates is investigated by measuring the mean radius, number density of precipitates and matrix supersaturation, and compared with Umantsev-Olson's (UO) coarsening theory for multicomponent alloys. The coarsening experiments do not agree with the time dependencies prediction of UO theory. The cluster-diffusion-coagulation mechanism is involved in coarsening, as well as evaporation-condenzation mechanism, and is suggested to generate discrepancy between the experiments and theory. The addition of Re reduces the lattices parameter misfit between the matrix and precipitates. Therefore, unlike other Ni-based superalloys, this Ni-Cr-AI-Re alloy does not undergo the sphere-to-cube morphological transition and maintains the spheroidal morphology of the γ' precipitates for extended aging times. In addition, the γ' precipitates do not align along [100] direction, even at the longest aging time of 264 h. Contrary to a commercial superalloy Rene N6, significant Re

  6. Computational design and performance prediction of creep-resistant ferritic superalloys

    Energy Technology Data Exchange (ETDEWEB)

    Liaw, Peter K. [Univ. of Tennessee, Knoxville, TN (United States); Wang, Shao-Yu [Univ. of Tennessee, Knoxville, TN (United States); Dunand, David C. [Northwestern Univ., Evanston, IL (United States); Ghosh, Gautum [Northwestern Univ., Evanston, IL (United States); Song, Gian [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Rawlings, Michael [Univ. of Tennessee, Knoxville, TN (United States); Baik, Sung Il [Northwestern Univ., Evanston, IL (United States)

    2017-12-04

    Ferritic superalloys containing the B2 phase with the parent L21 phase precipitates in a disordered solid-solution matrix, also known as a hierarchical-precipitate-strengthened ferritic alloy (HPSFA), had been developed for high-temperature structural applications in fossil-energy power plants. These alloys were designed by adding Ti into a previously-studied NiAl-strengthened ferritic alloy (denoted as FBB8 in this study). Following with the concept of HPSFAs, in the present research, a systematic investigation on adding other elements, such as Hf and Zr, and optimizing the Ti content within the alloy system, has been conducted, in order to further improve the creep resistance of the model alloys. Studies include advanced experimental techniques, first-principles calculations on thermodynamic and mechanical properties, and numerical simulations on precipitation hardening, have been integrated and conducted to characterize the complex microstructures and excellent creep resistance of alloys. The experimental techniques include transmission-electron microscopy (TEM), scanning-electron microscopy (SEM), neutron diffraction (ND), and atom-probe tomography (APT), which provide the detailed microstructural information of the model alloys. Systematic tension/compression creep tests have also been conducted in order to verify the creep resistance of the potential alloy compositions. The results show that when replacing Ti with Hf and Zr, it does not form the L21 phase. Instead, the hexagonal Laves phase forms and distributes majorly along the grain boundary, or large segregation within grains. Since the Laves phase does not form parent to the B2-phase precipitates, it cannot bring the strengthening effect of HPSFAs. As a result, the FBB8 + 2 wt. % Hf and FBB8 + 2 wt. % Zr alloys have similar mechanical properties to the original FBB8. The FBB8 + Ti series alloys had also been studied, from the creep tests and microstructural characterizations, the FBB8 + 3.5 wt.% Ti

  7. Designing Nanoscale Precipitates in Novel Cobalt-based Superalloys to Improve Creep Resistance and Operating Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Dunand, David C. [Northwestern Univ., Evanston, IL (United States); Seidman, David N. [Northwestern Univ., Evanston, IL (United States); Wolverton, Christopher [Northwestern Univ., Evanston, IL (United States); Saal, James E. [Northwestern Univ., Evanston, IL (United States); Bocchini, Peter J. [Northwestern Univ., Evanston, IL (United States); Sauza, Daniel J. [Northwestern Univ., Evanston, IL (United States)

    2014-10-01

    High-temperature structural alloys for aerospace and energy applications have long been dominated by Ni-base superalloys, whose strength and creep resistance can be attributed to microstructures consisting of a large volume fraction of ordered (L12) γ'-precipitates embedded in a disordered’(f.c.c.) γ-matrix. These alloys exhibit excellent mechanical behavior and thermal stability, but after decades of incremental improvement are nearing the theoretical limit of their operating temperatures. Conventional Co-base superalloys are solid-solution or carbide strengthened; although they see industrial use, these alloys are restricted to lower-stress applications because the absence of an ordered intermetallic phase places an upper limit on their mechanical performance. In 2006, a γ+γ' microstructure with ordered precipitates analogous to (L12) Ni3Al was first identified in the Co-Al-W ternary system, allowing, for the first time, the development of Co-base alloys with the potential to meet or even exceed the elevated-temperature performance of their Ni-base counterparts. The potential design space for these alloys is complex: the most advanced Ni-base superalloys may contain as many as 8-10 minor alloying additions, each with a specified purpose such as raising the γ' solvus temperature or improving creep strength. Our work has focused on assessing the effects of alloying additions on microstructure and mechanical behavior of γ'-strengthened Co-base alloys in an effort to lay the foundations for understanding this emerging alloy system. Investigation of the size, morphology, and composition of γ' and other relevant phases is investigated utilizing scanning electron microscopy (SEM) and 3-D picosecond ultraviolet local electrode atom probe tomography (APT). Microhardness, compressive yield stress at ambient and elevated temperatures, and compressive high-temperature creep measurements are employed to

  8. Morphology Dependent Flow Stress in Nickel-Based Superalloys in the Multi-Scale Crystal Plasticity Framework

    Directory of Open Access Journals (Sweden)

    Shahriyar Keshavarz

    2017-11-01

    Full Text Available This paper develops a framework to obtain the flow stress of nickel-based superalloys as a function of γ-γ’ morphology. The yield strength is a major factor in the design of these alloys. This work provides additional effects of γ’ morphology in the design scope that has been adopted for the model developed by authors. In general, the two-phase γ-γ’ morphology in nickel-based superalloys can be divided into three variables including γ’ shape, γ’ volume fraction and γ’ size in the sub-grain microstructure. In order to obtain the flow stress, non-Schmid crystal plasticity constitutive models at two length scales are employed and bridged through a homogenized multi-scale framework. The multi-scale framework includes two sub-grain and homogenized grain scales. For the sub-grain scale, a size-dependent, dislocation-density-based finite element model (FEM of the representative volume element (RVE with explicit depiction of the γ-γ’ morphology is developed as a building block for the homogenization. For the next scale, an activation-energy-based crystal plasticity model is developed for the homogenized single crystal of Ni-based superalloys. The constitutive models address the thermo-mechanical behavior of nickel-based superalloys for a large temperature range and include orientation dependencies and tension-compression asymmetry. This homogenized model is used to obtain the morphology dependence on the flow stress in nickel-based superalloys and can significantly expedite crystal plasticity FE simulations in polycrystalline microstructures, as well as higher scale FE models in order to cast and design superalloys.

  9. A continuum approach to combined $\\gamma/\\gamma'$ evolution and dislocation plasticity in Nickel-based superalloys

    OpenAIRE

    Wu, Ronghai; Zaiser, Michael; Sandfeld, Stefan

    2017-01-01

    Creep in single crystal Nickel-based superalloys has been a topic of interest since decades, and nowadays simulations are more and more able to complement experiments. In these alloys, the $\\gamma/\\gamma'$ phase microstructure co-evolves with the system of dislocations under load, and understanding the mutual interactions is essential for understanding the resulting creep properties. Predictive modeling thus requires multiphysics frameworks capable of modeling and simulating both the phase an...

  10. Design of Novel Precipitate-Strengthened Al-Co-Cr-Fe-Nb-Ni High-Entropy Superalloys

    Science.gov (United States)

    Antonov, Stoichko; Detrois, Martin; Tin, Sammy

    2018-01-01

    A series of non-equiatomic Al-Co-Cr-Fe-Nb-Ni high-entropy alloys, with varying levels of Co, Nb and Fe, were investigated in an effort to obtain microstructures similar to conventional Ni-based superalloys. Elevated levels of Co were observed to significantly decrease the solvus temperature of the γ' precipitates. Both Nb and Co in excessive concentrations promoted the formation of Laves and NiAl phases that formed either during solidification and remained undissolved during homogenization or upon high-temperature aging. Lowering the content of Nb, Co, or Fe prevented the formation of the eutectic type Laves. In addition, lowering the Co content resulted in a higher number density and volume fraction of the γ' precipitates, while increasing the Fe content led to the destabilization of the γ' precipitates. Various aging treatments were performed which led to different size distributions of the strengthening phase. Results from the microstructural characterization and hardness property assessments of these high-entropy alloys were compared to a commercial, high-strength Ni-based superalloy RR1000. Potentially, precipitation-strengthened high-entropy alloys could find applications replacing Ni-based superalloys as structural materials in power generation applications.

  11. Characterisation of As-deformed microstructure of ODS NI-Base superalloy and ODS ferritic steel prior to directional recrystallisation

    International Nuclear Information System (INIS)

    Baloch, M.M.; Memon, S.A.

    2007-01-01

    The materials studied are unusual in the sense that they have been prepared from mechanically alloyed procedures, including compaction and hot extrusion. It was felt necessary to characterise the initial microstructure thoroughly prior to directional recrystallisation of the alloys. Following consolidation by hot extrusion, dispersion strengthened superalloys appear to display a very fine sub-micron grain size consisting of both dislocation free recrystallised material and un- recrystallised regions of high dislocation density. It is found that there is a very fine dislocation cell structure in the ODS (Oxide Dispersion Strengthened) Ferritic stainless Steel prior to recrystallisation treatment, which shows that alloy is in old-deformed condition after mechanical alloying, extrusion I hot-working. This is in contrast to the mechanically alloyed Nickel Base Superalloy, which have consistently been found to be in primary recrystallisation state following extrusion. In order to understand the recrystallisation behaviour of the two mechanically illoyed materials with commercial designations MA6000 and MA956, a measurement of the orientation relationship between adjacent grains in the as- deformed ODS alloys has also been carried out using Transmission Electron microscope. (author)

  12. Segregation to grain boundaries in nimonic PE16 superalloy

    International Nuclear Information System (INIS)

    Nettleship, D.J.; Wild, R.K.

    1990-01-01

    Nimonic PE16 alloy is a nickel-based superalloy containing 34 wt.% iron and 16wt.% chromium with additions of molybdenum, titanium and aluminium. It is used in the fuel assembly of the UK advanced gas-cooled reactors (AGR). This component supports significant loads in service and its mechanical integrity is therefore of paramount importance. Mechanical properties may be influenced by the grain size and grain boundary composition, both of which can themselves alter during service. Scanning Auger microscopy is a well-established method for investigating grain boundaries, and has now been applied to the study of PE16. In order to expose PE16 grain boundary surfaces it is necessary to hydrogen charge samples and fracture by pulling in tension at a slow strain rate within the ultra-high vacuum chamber of the Auger microprobe. A series of casts of nimonic PE16 alloy that have received a range of thermal ageing treatments have been fractured in an intergranular manner and the grain boundary composition determined. Segregation of trace and minority elements, particularly Mo and P, has been detected at grain boundaries. Significant variations between different as-manufactured casts were observed, whilst ageing brought about the growth of chromium-rich particles on the grain boundaries. Ductile fracture in PE16 followed a path through Ti(C, N) particles. Many of these particles incorporated large amounts of sulphur. (author)

  13. Friction Freeform Fabrication of Superalloy Inconel 718: Prospects and Problems

    Science.gov (United States)

    Dilip, J. J. S.; Janaki Ram, G. D.

    2014-01-01

    Friction Freeform Fabrication is a new solid-state additive manufacturing process. The present investigation reports a detailed study on the prospects of this process for additive part fabrication in superalloy Inconel 718. Using a rotary friction welding machine and employing alloy 718 consumable rods in solution treated condition, cylindrical-shaped multi-layer friction deposits (10 mm diameter) were successfully produced. In the as-deposited condition, the deposits showed very fine grain size with no grain boundary δ phase. The deposits responded well to direct aging and showed satisfactory room-temperature tensile properties. However, their stress rupture performance was unsatisfactory because of their layered microstructure with very fine grain size and no grain boundary δ phase. The problem was overcome by heat treating the deposits first at 1353 K (1080 °C) (for increasing the grain size) and then at 1223 K (950 °C) (for precipitating the δ phase). Overall, the current study shows that Friction Freeform Fabrication is a very useful process for additive part fabrication in alloy 718.

  14. Advances in titanium alloys

    International Nuclear Information System (INIS)

    Seagle, S.R.; Wood, J.R.

    1993-01-01

    As described above, new developments in the aerospace market are focusing on higher temperature alloys for jet engine components and higher strength/toughness alloys for airframe applications. Conventional alloys for engines have reached their maximum useful temperature of about 1000 F (540 C) because of oxidation resistance requirements. IMI 834 and Ti-1100 advanced alloys show some improvement, however, the major improvement appears to be in gamma titanium aluminides which could extend the maximum usage temperature to about 1500 F (815 C). This puts titanium alloys in a competitive position to replace nickel-base superalloys. Advanced airframe alloys such as Ti-6-22-22S, Beta C TM , Ti-15-333 and Ti-10-2-3 with higher strength than conventional Ti-6-4 are being utilized in significantly greater quantities, both in military and commercial applications. These alloys offer improved strength with little or no sacrifice in toughness and improved formability, in some cases. Advanced industrial alloys are being developed for improved corrosion resistance in more reducing and higher temperature environments such as those encountered in sour gas wells. Efforts are focused on small precious metal additions to optimize corrosion performance for specific applications at a modest increase in cost. As these applications develop, the usage of titanium alloys for industrial markets should steadily increase to approach that for aerospace applications. (orig.)

  15. Microstructural aspects of Ni-based superalloy 693

    International Nuclear Information System (INIS)

    Dutta, R.S.; Sengupta, P.; Tewari, R.; Kain, V.; Dey, G.K.; Sharma, A.K.; Raj, K.

    2009-01-01

    Alloy 693 is an austenitic, precipitation-hardenable Ni-based superalloy. It is a promising material for high temperature fuel cell, petrochemical processing industry, high temperature waste and biomass incinerators and as thermal processing equipment, burner nozzles, melter pot material and in other areas. Microstructure plays quite often a major role in regulating the properties of the materials. Keeping this in view, optical microscope, scanning electron microscope (SEM) and transmission electron microscope (TEM) were employed to characterize the microstructure of Alloy 693. Microanalyses of the phases were performed by using electron probe microanalysis (EPMA) and TEM along with energy dispersive spectroscopy (EDS). The alloy in as-received condition under an optic microscope and SEM revealed the presence of predominantly finer intergranular precipitates and randomly distributed coarser precipitates of various morphologies. EPMA of spherical-shaped coarse precipitate indicated that the major constituent of this precipitate has been chromium. Besides this, niobium-rich irregular-shaped coarse precipitate was also detected. The finer grain boundary precipitates in the alloy appeared to be of Cr-carbide. TEM examination on as-received alloy indicated very uniform distribution of a large volume fraction of fine precipitates in the austenite matrix. Selected area diffraction (SAD) pattern, dark-field TEM and detailed analyses confirmed that these fine precipitates have been ordered Ni 3 Al type phase. TEM investigation also revealed the presence of coarse particles of various morphologies. Analyses of such particles indicated this phase as M 6 C type. EDS analyses indicated that the major constituents of these coarse particles have been Cr and Ni. Minor elements like Fe, Al and Nb were also detected in all the particles with some variation of their contents from particle to particle. TEM investigation on annealed (1373 K/30 minutes, WQ) specimen of Alloy 693

  16. Microstructure, Lattice Misfit, and High-Temperature Strength of γ'-Strengthened Co-Al-W-Ge Model Superalloys

    Science.gov (United States)

    Zenk, Christopher H.; Bauer, Alexander; Goik, Philip; Neumeier, Steffen; Stone, Howard J.; Göken, Mathias

    2016-05-01

    The quaternary alloy system Co-Al-W-Ge was investigated and it was found that a continuous γ /γ ^' two-phase field extends between the systems Co-Al-W and Co-Ge-W. All alloys examined comprised cuboidal L1_2 precipitates coherently embedded in an A1 matrix. Differential scanning calorimetry measurements revealed that the liquidus, solidus, and γ ^' -solvus temperatures decrease when the Ge content is increased. The lower liquidus temperature and the capability of γ ^' -strengthening in the Ge-rich alloys make them interesting as potential candidates for brazing applications of Co-base superalloys. The γ /γ ^' lattice misfit was determined by high-resolution X-ray diffraction and found to be positive for all alloys investigated, decreasing with increasing Ge content. The mechanical properties of the Al-rich alloys surpass those rich in Ge.

  17. Statistical Study of the Effects of the Composition on the Oxidation Resistance of Ni-Based Superalloys

    Directory of Open Access Journals (Sweden)

    Si-Jun Park

    2015-01-01

    Full Text Available The effects of alloying elements (Co, Cr, Mo, W, Al, Ti, and Ta on the oxidation resistance of Ni-based superalloys are studied using the Response Surface Methodology (RSM. The statistical analysis showed that Al and Ta generally improve the oxidation resistance of the alloy, whereas Ti and Mo degrade the oxidation resistance. Co, Cr, and W did not alter oxidation rate significantly when examined by the mass gain averaged for all model alloys. However, it is remarkable that the degree of the effects of alloying elements varied with the concentration of other elements. Further, the effect of each element was sometimes found to be reversed for alloy groups specified by the concentration of another element.

  18. Cyclic Oxidation and Hot Corrosion Behavior of Nickel-Iron-Based Superalloy

    Science.gov (United States)

    Chellaganesh, D.; Adam Khan, M.; Winowlin Jappes, J. T.; Sathiyanarayanan, S.

    2018-01-01

    The high temperature oxidation and hot corrosion behavior of nickel-iron-based superalloy are studied at 900 ° and 1000 °C. The significant role of alloying elements with respect to the exposed medium is studied in detail. The mass change per unit area was catastrophic for the samples exposed at 1000 °C and gradual increase in mass change was observed at 900 °C for both the environments. The exposed samples were further investigated with SEM, EDS and XRD analysis to study the metallurgical characteristics. The surface morphology has expressed the in situ nature of the alloy and its affinity toward the environment. The EDS and XRD analysis has evidently proved the presence of protective oxides formation on prolonged exposure at elevated temperature. The predominant oxide formed during the exposure at high temperature has a major contribution toward the protection of the samples. The nickel-iron-based superalloy is less prone to oxidation and hot corrosion when compared to the existing alloy in gas turbine engine simulating marine environment.

  19. Characterization and Modeling of Microstructure Development in Nickel-base Superalloy Welds

    Energy Technology Data Exchange (ETDEWEB)

    Babu, S.S.; David, S.A.; Miller, M.K.; Vitek, J.M.

    1999-11-01

    Welding is important for economical reuse and reclamation of used and failed nickel-base superalloy blades, respectively [1]. Solidification and solid state decomposition of {gamma} (Face Centered Cubic, FCC) phase into {gamma}{prime} (L1{sub 2}-ordered) phase control the properties of these welds. In previous publications, the microstructure development in electron beam welds of PWA-1480 alloy [2] and laser beam welds of CMSX-4 alloy [3] were presented. These results showed that the weld cracking in these alloys were associated with low melting point eutectic at the dendrite boundaries [1,2]. The eutectic-{gamma}{prime} precipitation was reduced at rapid weld cooling rates and the partitioning between {gamma}-{gamma}{prime} phase was found to be far from equilibrium conditions [3,4]. This observation was related to diffusional growth of {gamma}{prime} precipitate into {gamma} phase. Subsequent to the above work, the precipitation characteristics of {gamma}{prime} phase from {gamma} phase were evaluated during continuous cooling conditions [5]. The results show that the number density of {gamma} precipitates increased with an increase in cooling rate. However, the details of this decomposition and also the fine-scale elemental partitioning characteristics between {gamma}-{gamma}{prime} were not investigated. In this paper, the precipitation characteristics of {gamma}{prime} from {gamma} during continuous cooling conditions were investigated with transmission electron microscopy, and atom probe field ion microscopy. In addition, thermodynamic and kinetic models were used to describe microstructure development in Ni-base superalloy welds.

  20. Synergistic effect of rhenium and ruthenium in nickel-based single-crystal superalloys

    Energy Technology Data Exchange (ETDEWEB)

    Yu, X.X. [Department of Physics, Tsinghua University, Beijing 100084 (China); Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Wang, C.Y., E-mail: cywang@mail.tsinghua.edu.cn [Department of Physics, Tsinghua University, Beijing 100084 (China); Central Iron and Steel Research Institute, Beijing 100081 (China); Zhang, X.N. [Institute of Microstructure and Property of Advanced Materials, Beijing University of Technology, Beijing 100124 (China); Yan, P. [Central Iron and Steel Research Institute, Beijing 100081 (China); Zhang, Z., E-mail: zezhang@zju.edu.cn [State Key Laboratory of Silicon Materials, Department of Materials Science and Engineering, Zhejiang University, Hangzhou 310027 (China)

    2014-01-05

    Highlights: • Re and Ru synergistic effects in nickel-based superalloys are investigated. • The Al site occupation of Re atom in the γ′ phase is observed directly. • The addition of Ru results in the repartitioning of Re to γ phase. -- Abstract: The microstructures of ternary Ni–Al–Re and quaternary Ni–Al–Re–Ru single-crystal alloys were investigated at atomic and electronic levels to clarify the synergistic effect of Re and Ru in nickel-based single-crystal superalloys. In the Ni–Al–Re alloy, it was directly observed that Re atom occupied the Al site of γ′ phase. In the Ni–Al–Re–Ru alloy, the mechanisms of Re repartition between γ and γ′ phases were proposed. In the dendritic cores, high concentrations of Re exceeded the solubility limit of γ′ phase and partitioned to γ phase, which led to the homogenization. In the interdendritic regions, Ru resulted in the repartitioning of Re to γ phase which was proved by transmission electron microscopy and first-principles calculations.

  1. Formation and Dissolution of gamma ' Precipitates in IN792 Superalloy at Elevated Temperatures

    Czech Academy of Sciences Publication Activity Database

    Strunz, Pavel; Petrenec, Martin; Polák, Jaroslav; Gasser, U.; Farkas, G.

    2016-01-01

    Roč. 6, č. 2 (2016), č. článku 37. ISSN 2075-4701 R&D Projects: GA ČR GB14-36566G; GA MŠk(CZ) LM2011019 EU Projects: European Commission(XE) 283883 - NMI3-II Institutional support: RVO:61389005 ; RVO:68081723 Keywords : metals * high temperature alloys * superalloy * precipitation * neutron scattering * in-situ neutron diffraction * small-angle neutron scattering Subject RIV: BM - Solid Matter Physics ; Magnetism; JL - Materials Fatigue, Friction Mechanics (UFM-A) Impact factor: 1.984, year: 2016

  2. Development of a Ni-based superalloy with cellular structure and interconnected micro porosity

    International Nuclear Information System (INIS)

    Bernabe, A.; Lopez, E.; Gil-Sevillano, J.

    1998-01-01

    A cellular metallic material with interconnected porosity of controlled size of an order of 10 μm has been developed by electrochemical dissolution of tungsten grains in a W-Ni-Fe heavy alloy. The nickel superalloy with sponge structure and high surface/volume ratio can also be processed recycling chips from heavy metal machining (Patent number p9700191, 1997). Applications for the new materials could be found as support for catalysts, high temperature filters for corrosive fluids, burners, etc. (Author) 10 refs

  3. Phase transformation and liquid density redistribution during solidification of Ni-based superalloy Inconel 718

    Directory of Open Access Journals (Sweden)

    Wang Ling

    2012-08-01

    Full Text Available The influences of chemical segregation and phase transformation on liquid density variation during solidification of Ni-based supperalloy Inconel 718 were investigated using SEM and EDS. It was found that significant segregation in liquid prompts high Nb phase to precipitate directly from liquid, which results in the redistribution of alloy elements and liquid density in their vicinity. The term “inter-precipitate liquid density” is therefore proposed and this concept should be applied to determine the solidification behavior of superalloy Inconel 718.

  4. Chemical driving force for rafting in superalloys

    CSIR Research Space (South Africa)

    Nabarro, FRN

    1997-08-15

    Full Text Available The author provides a brief overview of the chemical driving forces for rafting in superalloys. Until recently, all theories of the driving force for rafting have considered the compositions of the two phases to be fixed, although accepting...

  5. Effects of stacking fault energy on the creep behaviors of Ni-base superalloy

    International Nuclear Information System (INIS)

    Tian, Chenggang; Han, Guoming; Cui, Chuanyong; Sun, Xiaofeng

    2014-01-01

    Highlights: • The decrease of SFE could promote the dislocation dissociation. • The creep mechanisms were significantly affected by the SFE of the alloys. • The creep properties of the alloys improved with the decrease of SFE by facilitating the microtwinning process. - Abstract: Cobalt in a 23 wt.% Co containing Ni-base superalloys was systematically substituted by Ni in order to study the effects of stacking fault energy (SFE) on the creep mechanisms. The deformation microstructures of the alloys during different creep stages at 725 °C and 630 MPa were investigated by transmission electron microscopy (TEM). The results showed that the creep life increased as the SFE decreased corresponding to the increase of Co content in the alloys. At primary creep stage, the dislocation was difficult to dissociate independent of SFE. In contrast, at secondary and tertiary creep stages the dislocations dissociated at γ/γ′ interface and the partial dislocation started to shear γ′ precipitates, leaving isolated faults (IFs) in high SFE alloy, while the dislocations dissociated in the matrix and the partials swept out the matrix and γ′ precipitates creating extended stacking faults (ESFs) or deformation microtwins which were involved in diffusion-mediated reordering in low SFE alloy. It is suggested that the deformation microtwinning process should be favorable with the decrease of SFE, which could enhance the creep resistance and improve the creep properties of the alloys

  6. Effects of cobalt on creep rupture properties and dislocation structures in nickel base superalloys

    International Nuclear Information System (INIS)

    Wang, W.Z.; Jin, T.; Jia, J.H.; Liu, J.L.; Hu, Z.Q.

    2015-01-01

    The influences of cobalt (Co) on creep rupture lives and dislocation structures in nickel base superalloys with and without rhenium (Re) are investigated. The creep rupture test conditions were high temperature low stress (1100 °C/150 MPa), intermediate temperature and stress (982 °C, 1010 °C) and low temperature high stress (850 °C/586 MPa). The results show that increasing Co content could enhance the creep rupture lives at low and intermediate temperature, and does not degrade the creep rupture lives of alloys at high temperature. In Re-containing alloys, at high temperature low stress (1100 °C/150 MPa), the effects of Co on the dislocation structures are negligible, while at low temperature high stress (850 °C/586 MPa), stacking faults are generated in alloy with 12% Co, and in alloy with 3% Co and free of Co, gamma prime particles are sheared by dislocation pairs. In Re-free alloys, at intermediate temperature and stress (1010 °C/248 MPa), large quantities of stacking faults appear in alloy without Co, while in alloy having 12% Co, gamma prime particles are sheared by dislocation pairs coupled by anti-phase boundary (APB). The gamma prime sheared by stacking faults or by dislocation pairs coupled by APB depends on the competition of stacking faults energy and APB energy which is affected by temperature and the interaction of Re and Co

  7. Chemical constituents in the Peedee and Castle Hayne aquifers: Porters Neck area, New Hanover County, North Carolina

    Science.gov (United States)

    Roberts, T.L.; Harris, W.B.

    2004-01-01

    Concerns about overuse and potential contamination of major aquifers in the southeastern part of North Carolina resulted in the initiation of a subsurface water quality study in February 2001. The focus of this study was to examine variations in nutrients (NO3-, TRP, SO42- Cl-, NH4+) and total dissolved Fe in the Cretaceous Peedee and Tertiary Castle Hayne Limestone aquifers of northeastern New Hanover County. Water samples were collected monthly for one year from sixteen wells located in the Porters Neck area (west of the Intracoastal Waterway and south of Futch Creek) and four springs located on the south side of Futch Creek. Variations in selective nutrient concentrations were measured between and within each aquifer. Concentrations of NH4+ and Fe increased in the Peedee sandstone aquifer during the warmer summer and early fall months. In late summer to early fall, Fe, NO 3-, NH4+, and TRP concentrations in the Castle Hayne Limestone aquifer were significantly higher than in the spring and winter months. Chloride and SO 42- concentrations for the Castle Hayne Limestone aquifer both increased during the warmer months, probably as a result of saltwater intrusion. Factors considered for nutrient and Fe variance include: temperature variation, anaerobic conditions, subsurface stratigraphy/structure, recharge locations, site location and surface fertilization. The shallower Castle Hayne Limestone aquifer showed seasonal variability in the study area, whereas the Peedee sandstone aquifer showed little to no seasonal variability. Increases in NO3- and TRP lagged slightly behind periods of high fertilization and were more prevalent down-dip of a major golf course. Nutrient content and seasonal variation of Futch Creek springs indicated that they originate from the Castle Hayne Limestone aquifer.

  8. Cyclic Oxidation of High Mo, Reduced Density Superalloys

    Directory of Open Access Journals (Sweden)

    James L. Smialek

    2015-11-01

    Full Text Available Cyclic oxidation was characterized as part of a statistically designed, 12-alloy compositional study of 2nd generation single crystal superalloys as part of a broader study to co-optimize density, creep strength, and cyclic oxidation. The primary modification was a replacement of 5 wt. % W by 7% or 12% Mo for density reductions of 2%–7%. Compositions at two levels of Mo, Cr, Co, and Re were produced, along with a midpoint composition. Initially, polycrystalline vacuum induction samples were screened in 1100 °C cyclic furnace tests using 1 h cycles for 200 h. The behavior was primarily delimited by Cr content, producing final weight changes of −40 mg/cm2 to −10 mg/cm2 for 0% Cr alloys and −2 mg/cm2 to +1 mg/cm2 for 5% Cr alloys. Accordingly, a multiple linear regression fit yielded an equation showing a strong positive Cr effect and lesser negative effects of Co and Mo. The results for 5% Cr alloys compare well to −1 mg/cm2, and +0.5 mg/cm2 for Rene′ N4 and Rene′ N5 (or Rene′ N6, respectively. Scale phases commonly identified were Al2O3, NiAl2O4, NiTa2O6, and NiO, with (Ni,CoMoO4 found only on the least resistant alloys having 0% Cr and 12% Mo. Scale microstructures were complex and reflected variations in the regional spallation history. Large faceted NiO grains and fine NiTa2O6 particles distributed along NiAl2O4 grain boundaries were typical distinctive features. NiMoO4 formation, decomposition, and volatility occurred for a few high Mo compositions. A creep, density, phase stability, and oxidation balanced 5% Cr, 10% Co, 7% Mo, and 3% Re alloy was selected to be taken forward for more extensive evaluations in single crystal form.

  9. The influence of cooling rate from annealing temperature on the microstructure of Haynes 230

    International Nuclear Information System (INIS)

    Sah, Injin; Hong, Sunghoon; Jang, Changheui

    2015-01-01

    The effects of cooling rate from annealing temperature, which simulated the diffusion bonding process, on the microstructure of Haynes 230 (Ni-22Cr-14W-5Co) were investigated. While the grain boundaries are slightly covered with Cr-rich M 23 C 6 carbides for the diffusion-bonded and quenched condition, precipitates were extensively present on/near the grain boundaries for the furnace-cooled specimens. For the furnace-cooled specimens, lamellar precipitates were extensively formed near the grain boundaries below 1 000 deg. C, with intervals of a few hundred nanometers. Also, grain boundaries were severely serrated for the furnace-cooled specimens. Through electron probe micro analysis and transmission electron microscope, the lamellar precipitates were identified as (Cr,W)-rich M 23 C 6 -type lamellar carbides. Despite the differences in microstructure, tensile properties were not much affected by the cooling rate. Creep tests are underway and results will be presented. (authors)

  10. Thermodynamic Assessment of Hot Corrosion Mechanisms of Superalloys Hastelloy N and Haynes 242 in Eutectic Mixture of Molten Salts KF and ZrF4

    Energy Technology Data Exchange (ETDEWEB)

    Michael V. Glazoff

    2012-02-01

    The KF - ZrF4 system was considered for the application as a heat exchange agent in molten salt nuclear reactors (MSRs) beginning with the work carried out at ORNL in early fifties. Based on a combination of excellent properties such as thermal conductivity, viscosity in the molten state, and other thermo-physical and rheological properties, it was selected as one of possible candidates for the nuclear reactor secondary heat exchanger loop.

  11. Effect of Crystal Orientation on Fatigue Failure of Single Crystal Nickel Base Turbine Blade Superalloys

    Science.gov (United States)

    Arakere, Nagaraj K.; Swanson, Gregory R.

    2000-01-01

    High Cycle Fatigue (HCF) induced failures in aircraft gas-turbine engines is a pervasive problem affecting a wide range of components and materials. HCF is currently the primary cause of component failures in gas turbine aircraft engines. Turbine blades in high performance aircraft and rocket engines are increasingly being made of single crystal nickel superalloys. Single-crystal Nickel-base superalloys were developed to provide superior creep, stress rupture, melt resistance and thermomechanical fatigue capabilities over polycrystalline alloys previously used in the production of turbine blades and vanes. Currently the most widely used single crystal turbine blade superalloys are PWA 1480/1493 and PWA 1484. These alloys play an important role in commercial, military and space propulsion systems. PWA1493, identical to PWA1480, but with tighter chemical constituent control, is used in the NASA SSME (Space Shuttle Main Engine) alternate turbopump, a liquid hydrogen fueled rocket engine. Objectives for this paper are motivated by the need for developing failure criteria and fatigue life evaluation procedures for high temperature single crystal components, using available fatigue data and finite element modeling of turbine blades. Using the FE (finite element) stress analysis results and the fatigue life relations developed, the effect of variation of primary and secondary crystal orientations on life is determined, at critical blade locations. The most advantageous crystal orientation for a given blade design is determined. Results presented demonstrates that control of secondary and primary crystallographic orientation has the potential to optimize blade design by increasing its resistance to fatigue crack growth without adding additional weight or cost.

  12. Comparison of Thermodynamic Predictions and Experimental Observations on B Additions in Powder-Processed Ni-Based Superalloys Containing Elevated Concentrations of Nb

    Science.gov (United States)

    Antonov, Stoichko; Huo, Jiajie; Feng, Qiang; Isheim, Dieter; Seidman, David N.; Sun, Eugene; Tin, Sammy

    2018-03-01

    Boron additions to Ni-based superalloys are considered to be beneficial to the creep properties of the alloy, as boron has often been reported to increase grain boundary cohesion, increase ductility, and promote the formation of stable boride phases. Despite the importance, it is not well understood whether these improvements are associated with the presence of elemental boron or stable borides along the grain boundaries. In this investigation, two experimental powder-processed Ni-based superalloys containing elevated levels of Nb were found to exhibit increased solubility for B in the γ matrix when compared to similar commercial Ni-based superalloys. This resulted in an overall lower B concentration at grain boundaries that suppressed boride formation. As the predictive capability of CALPHAD database models for Ni-based superalloys have improved over the years, some discrepancies may still persist around compositionally heterogeneous features such as grain boundaries. Improved quantification of the characteristic partitioning of B as a function of the bulk alloy composition is required for understanding and predicting the stability of borides.

  13. Subsurface characterization of an oxidation-induced phase transformation and twinning in nickel-based superalloy exposed to oxy-combustion environments

    International Nuclear Information System (INIS)

    Zhu Jingxi; Holcomb, Gordon R.; Jablonski, Paul D.; Wise, Adam; Li Jia; Laughlin, David E.; Sridhar, Seetharaman

    2012-01-01

    Highlights: ►Oxidation products of Ni-based superalloy were studied in oxy-fuel combustion conditions. ► An oxidation-induced phase transformation occurred in the subsurface region. ► One of the two product phases was not in the Ni database of Thermo-Calc. ► This unknown phase is an ordered derivative of FCC structure of Ni–Ti(–Ta) system. ► This phase is likely detrimental to the mechanical integrity of the alloy in use. - Abstract: In the integration of oxy-fuel combustion to turbine power generation system, turbine alloys are exposed to high temperature and an atmosphere comprised of steam, CO 2 and O 2 . While surface and internal oxidation of the alloy takes place, the microstructure in the subsurface region also changes due to oxidation. In this study, bare metal coupons of Ni-base superalloys were exposed in oxy-fuel combustion environment for up to 1000 h and the oxidation-related microstructures were examined. Phase transformation occurred in the subsurface region in Ni-based superalloy and led to twinning. The transformation product phases were analyzed through thermodynamic equilibrium calculations and various electron microscopy techniques, including scanning electron microscopy (SEM), orientation imaging microscopy (OIM) and transmission electron microscopy (TEM). The mechanism by which the phase transformation and the formation of the microstructure occurred was also discussed. The possible effects of the product phases on the performance of the alloy in service were discussed.

  14. Castability of Traditionally Wrought Ni-Based Superalloys for USC Steam Turbines

    Energy Technology Data Exchange (ETDEWEB)

    Jablonski, P D; Cowen, C J; Hawk, J A; Evens, N; Maziasz, P

    2011-02-27

    The high temperature components within conventional coal fired power plants are manufactured from ferritic/martensitic steels. In order to reduce greenhouse gas emissions the efficiency of pulverized coal steam power plants must be increased. The proposed steam temperature in the Advanced Ultra Supercritical (A-USC) power plant is high enough (760°C) that ferritic/martensitic steels will not work due to temperature limitations of this class of materials; thus Ni-based superalloys are being considered. The full size castings are quite substantial: ~4in thick, several feet in diameter and weigh 5-10,000lb each half. Experimental castings were quite a bit smaller, but section size was retained and cooling rate controlled in order to produce relevant microstructures. A multi-step homogenization heat treatment was developed in order to better deploy the alloy constituents. The castability of two traditionally wrought Ni-based superalloys to which minor alloy adjustments have been made in order to improve foundry performance is further explored.

  15. High Temperature Degradation of Powder-processed Ni-based Superalloy

    Directory of Open Access Journals (Sweden)

    Natália Luptáková

    2015-05-01

    Full Text Available The aim of present work is to study the high temperature degradation of the powder-processed polycrystalline superalloy Ni-15Cr-18Co-4Al-3.5Ti-5Mo. This superalloy has been applied as material for grips of a creep machine. The material was exposed at 1100 °C for about 10 days at 10 MPa stress. During the creep test occurred unacceptable creep deformation of grips as well as severe surface oxidation with scales peeling off. Three types of the microstructure were observed in the studied alloy: (i unexposed state; (ii heat treated (annealing - 10 min/1200 °C and (iii after using as a part of the equipment of the creep machine during the creep test. It is shown that the microstructure degradation resulting from the revealed γ´ phase fcc Ni3(Al,Ti particles preferentially created at the grain boundaries of the samples after performing creep tests affects mechanical properties of the alloy and represents a significant contribution to all degradation processes affecting performance and service life of the creep machine grips. Based on investigation and obtained results, the given material is not recommended to be used for grips of creep machine at temperatures above 1000 °C.

  16. Control of microstructure and mechanical properties of laser solid formed Inconel 718 superalloy by electromagnetic stirring

    Science.gov (United States)

    Liu, Fencheng; Cheng, Hongmao; Yu, Xiaobin; Yang, Guang; Huang, Chunping; Lin, Xin; Chen, Jing

    2018-02-01

    The coarse columnar grains and special interface in laser solid formed (LSFed) Inconel 718 superalloy workpieces seriously affect their mechanical properties. To improve the microstructure and mechanical properties of LSFed Inconel 718 superalloy, electromagnetic stirring (EMS) was introduced to alter the solidification process of the molten pool during LSF. The results show that EMS could not completely eliminate the epitaxially growing columnar grains, however, the strong convection of liquid metals can effectively influence the solid-liquid interface growing mode. The segregation of alloying elements on the front of solid-liquid interface is inhibited and the degree of constitutional supercooling decreases correspondingly. Comparing the microstructures of samples formed under different process parameters, the size and amount of the γ+Laves eutectic phases formed in interdendritic area decrease along with the increasing magnetic field intensity, resulting in more uniformly distributed alloying elements. The residual stress distribution is proved to be more uniform, which is beneficial to the grain refinement after recrystallilzaiton. Mechanical properties testing results show an improvement of 100 MPa in tensile strength and 22% in elongation was obtained after EMS was used. The high cycle fatigue properties at room temperature was also improved from 4.09 × 104 cycles to 8.21 × 104 cycles for the as-deposited samples, and from 5.45 × 104 cycles to 12.73 × 104 cycles for the heat treated samples respectively.

  17. Effects of Thermal Exposure on Structures of DD6 Single Crystal Superalloy with Thermal Barrier Coatings

    Directory of Open Access Journals (Sweden)

    DONG Jianmin

    2016-10-01

    Full Text Available In order to investigate the effect of water grit-blasting and high temperature thermal exposure on the microstructures of DD6 alloy with TBCs, DD6 single crystal superalloy specimens were water grit-blasted with 0.3 MPa pressure, then the specimens were coated with thermal barrier coatings by electron beam physical vapor deposition (EB-PVD. Specimens with TBCs were exposed at 1100℃ for 50 and 100 hours in the air respectively, and then these specimens were subjected to stress-rupture tests under the condition of 1100℃/130 MPa. The results show that grit-blasting doesn't lead into the recrystallization, thermal exposure can induce element interdiffusion between the bond coat and alloy substrate, the residual stress and element diffusion lead into the changes of γ' phase coarsing direction. After stress rupture tests, the secondary reaction zone emerges into a local area.

  18. Low Cycle Fatigue of Single Crystal Nickel-based Superalloy DD6 at 1100℃

    Directory of Open Access Journals (Sweden)

    ZHANG Shichao

    2018-02-01

    Full Text Available The total strain-controlled low cycle fatigue(LCF behaviors of a single crystal superalloy DD6 at 1100℃ for R=-1 and 0.05 were investigated. The results of LCF tests indicated that the cyclic hardening/softening behavior of the alloy not only has the relationship with the microstructure of the material, but also the loading status. The mean stress relaxation occurred under asymmetric straining. The rate of mean stress relaxation increased with the increasing of strain amplitude; when R=-1, the alloy shows tension-compression asymmetry behavior. All the LCF data obtain under various ratios were well correlated by three models for lifetime prediction, the precision rates predicted are fallen into the factor of±2 times scatter band.

  19. Study on the hot corrosion behavior of a cast Ni-base superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Wang, W.; Guo, J.T.; Zhang, J.; Yuan, C.; Zhou, L.Z.; Hu, Z.Q. [Chinese Academy of Sciences, Shenyang (China). Inst. of Metal Research

    2010-07-01

    Hot corrosion behavior of Nickel-base cast superalloy K447 in 90% Na{sub 2}SO{sub 4} + 10% NaCl melting salt at 850 C and 900 C was studied. The hot corrosion kinetic of the alloy follows parabolic rate law under the experimental conditions. The external layer is mainly Cr{sub 2}O{sub 3} scale which is protective to the alloy, the intermediate layer is the Ti-rich phase, and the internal layer is mainly the international oxides and sulfides. With increased corrosion time and temperature, the oxide scales are gradually dissolved in the molten salt and then precipitate as a thick and non-protective scale. Chlorides cause the formation of volatile species, which makes the oxide scale disintegrate and break off. The corrosion kinetics and morphology examinations tend to support the basic dissolution model for hot corrosion mechanisms. (orig.)

  20. Dynamic precipitation of nickel-based superalloys undergoing severe deformation below the solvus temperature

    Energy Technology Data Exchange (ETDEWEB)

    Nowotnik, Andrzej; Rokicki, Pawel; Mrowka-Nowotnik, Grazyna; Sieniawski, Jan [Rzeszow Univ. of Technology (Poland). Dept. of Material Science

    2015-07-15

    The authors performed uniaxial compression tests of nickel-based superalloys: single crystal CMSX-4, also precipitation hardened; Inconel 718 and X750, at temperatures below the γ' solvus, in order to study the effect of temperature and strain rate on their flow stress and microstructural development. On the basis of the obtained flow stress values, the activation energy of a high-temperature deformation process was estimated. Microstructural observations of the deformed samples at high temperatures, previously solution heat treated and aged CMSX-4 and Inconel alloys revealed non-uniform deformation effects. Distribution of either molybdenum- or niobium-rich carbides was found to be affected by localized flow within the investigated strain range at relatively low deformation temperatures, 720-850 C. Microstructural examination of the alloys also showed that shear banding and cavity growth were responsible for the decrease in flow stress and a specimen fracture at larger strains.

  1. High Temperature Deformation Mechanisms in a DLD Nickel Superalloy

    Directory of Open Access Journals (Sweden)

    Sean Davies

    2017-04-01

    Full Text Available The realisation of employing Additive Layer Manufacturing (ALM technologies to produce components in the aerospace industry is significantly increasing. This can be attributed to their ability to offer the near-net shape fabrication of fully dense components with a high potential for geometrical optimisation, all of which contribute to subsequent reductions in material wastage and component weight. However, the influence of this manufacturing route on the properties of aerospace alloys must first be fully understood before being actively applied in-service. Specimens from the nickel superalloy C263 have been manufactured using Powder Bed Direct Laser Deposition (PB-DLD, each with unique post-processing conditions. These variables include two build orientations, vertical and horizontal, and two different heat treatments. The effects of build orientation and post-process heat treatments on the materials’ mechanical properties have been assessed with the Small Punch Tensile (SPT test technique, a practical test method given the limited availability of PB-DLD consolidated material. SPT testing was also conducted on a cast C263 variant to compare with PB-DLD derivatives. At both room and elevated temperature conditions, differences in mechanical performances arose between each material variant. This was found to be instigated by microstructural variations exposed through microscopic and Energy Dispersive X-ray Spectroscopy (EDS analysis. SPT results were also compared with available uniaxial tensile data in terms of SPT peak and yield load against uniaxial ultimate tensile and yield strength.

  2. The precipitation behavior of superalloy ATI Allvac 718Plus

    Energy Technology Data Exchange (ETDEWEB)

    Zickler, Gerald A.; Schnitzer, Ronald; Leitner, Harald [Department of Physical Metallurgy and Materials Testing, Christian Doppler Laboratory Early Stages of Precipitation, Montanuniversitaet Leoben (Austria); Radis, Rene [Christian Doppler Laboratory Early Stages of Precipitation, Institute of Materials Science and Technology, Vienna University of Technology (Austria); Institute for Materials Science and Welding, Graz University of Technology (Austria); Kozeschnik, Ernst [Christian Doppler Laboratory Early Stages of Precipitation, Institute of Materials Science and Technology, Vienna University of Technology (Austria); Stockinger, Martin [Boehler Schmiedetechnik GmbH and Co. KG., Kapfenberg (Austria)

    2010-03-15

    ATI Allvac 718Plus is a novel nickel-based superalloy, which was designed for heavy-duty applications in aerospace gas turbines. The precipitation kinetics of the intermetallic {delta} (Ni{sub 3}Nb) and {gamma}' (Ni{sub 3}(Al,Ti)) phases in this alloy are of scientific as well as technological interest because of their significant influence on the mechanical properties. Important parameters like grain size are controlled by coarse {delta} precipitates located at grain boundaries, whereas small {gamma}' precipitates are responsible for strengthening by precipitation hardening. In the present study, the microstructure is investigated by three-dimensional atom probe tomography and simulated by computer modeling using the thermo-kinetic software MatCalc. The results of numerical simulations and experimental data are compared and critically discussed. It is shown that the chemical compositions of the phases change during isothermal aging, and the precipitation kinetics of {delta} and {gamma}' phases interact with each other as shown in a time temperature precipitation (TTP) plot. The TTP plot shows C-shaped curves with characteristic discontinuities in the temperature range, where simultaneous and concurrent precipitation of the {delta} and {gamma}' phases occurs. This leads to a competition in the diffusion of Nb and Al, which are partly present in both phases. Thus, the present study gives important information on heat treatments for ATI Allvac 718Plus in order to achieve the desired microstructure and mechanical properties. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  3. ISOTHERMAL AND THERMOMECHANICAL FATIGUE OF A NICKEL-BASE SUPERALLOY

    Directory of Open Access Journals (Sweden)

    Carlos Carvalho Engler-Pinto Júnior

    2014-06-01

    Full Text Available Thermal gradients arising during transient regimes of start-up and shutdown operations produce a complex thermal and mechanical fatigue loading which limits the life of turbine blades and other engine components operating at high temperatures. More accurate and reliable assessment under non-isothermal fatigue becomes therefore mandatory. This paper investigates the nickel base superalloy CM 247LC-DS under isothermal low cycle fatigue (LCF and thermomechanical fatigue (TMF. Test temperatures range from 600°C to 1,000°C. The behavior of the alloy is strongly affected by the temperature variation, especially in the 800°C-1,000°C range. The Ramberg-Osgood equation fits very well the observed isothermal behavior for the whole temperature range. The simplified non-isothermal stress-strain model based on linear plasticity proposed to represent the thermo-mechanical fatigue behavior was able to reproduce the observed behavior for both in-phase and out-of-phase TMF cycling.

  4. Microstructure and Mechanical Properties in Gamma(face-centered cubic) + Gamma Prime(L12) Precipitation-Strengthened Cobalt-based Superalloys

    Science.gov (United States)

    Bocchini, Peter J.

    High-temperature structural alloys for aerospace and energy applications have long been dominated by Ni-based superalloys, whose high-temperature strength and creep resistance can be attributed to a two-phase microstructure consisting of a large volume fraction of ordered gamma'(L12)-precipitates embedded in a disordered gamma(f.c.c.)-matrix. These alloys exhibit excellent mechanical behavior and thermal stability, but after decades of incremental improvement, are nearing the theoretical limit of their operating temperatures. In 2006, an analogous gamma(f.c.c.) + gamma'(L12) microstructure was identified in the Co-Al-W ternary system with liquidus and solidus temperatures 50-150 °C higher than conventional Ni-based superalloys. The work herein focuses on assessing the effects of alloying additions on microstructure and mechanical behavior in an effort to lay the foundations for understanding this emerging alloy system. A variety of Co-based superalloys are investigated in order to study fundamental materials properties and to address key engineering challenges. Coarsening rate constants and temporal exponents are measured for gamma'(L1 2)-precipitates in a ternary Co-Al-W alloy aged at 650 °C and 750 °C. A series of Co-Al-W-B-Zr alloys are cast to study the influence of segregation of B and Zr to grain boundaries (GBs) on mechanical properties. Co-Ni-Al-W-Ti alloys with various amounts of Al, W, and Ti are cast in order to fabricate Co-based superalloys with decreased density and increased gamma'(L1 2)-solvus temperature. 2-D dislocation dynamics modeling is employed to predict how gamma'(L12)-precipitate size and volume fraction affect the mechanical properties of Ni- and Co-based superalloys. Compositional information such as phase concentrations, partitioning behavior, and GB segregation are measured with local electrode atom probe (LEAP) tomography in alloys with fine microstructures and with scanning electron microscope (SEM) electron dispersive x

  5. 75 FR 67100 - Superalloy Degassed Chromium From Japan

    Science.gov (United States)

    2010-11-01

    ... Chromium From Japan AGENCY: United States International Trade Commission. ACTION: Institution of a five-year review concerning the antidumping duty order on superalloy degassed chromium from Japan. SUMMARY... order on superalloy degassed chromium from Japan would be likely to lead to continuation or recurrence...

  6. 76 FR 8773 - Superalloy Degassed Chromium From Japan

    Science.gov (United States)

    2011-02-15

    ... INTERNATIONAL TRADE COMMISSION [Investigation No. 731-TA-1090 (Review)] Superalloy Degassed Chromium From Japan AGENCY: United States International Trade Commission. ACTION: Termination of five-year... revocation of the antidumping duty order on superalloy degassed chromium from Japan would be likely to lead...

  7. Relationship of heat treatment-mechanical properties of nickel base superalloys

    International Nuclear Information System (INIS)

    Zamora R, L.

    1997-01-01

    The nickel-base superalloys have high strength, excellent corrosion resistant, and good creep and fatigue resistance. These alloy improved properties at high temperature derive their mechanical and creep behavior on γ precipitate morphology, and the evolution of such morphology during different heat treatment conditions. The main microstructural variable of Nickel-based superalloys, responsible for the mechanical properties are: a) amount and morphology of precipitates; b) size and shape of grains; and c) carbide distribution. In this work, a Nickel-base superalloy Nimonic 80A, modified little with Zr prepared by melting and casting practices of materials electrolytic in vacuum-induction melting (VIM) type Balzers, to obtain five alloys different and ingots of 2 Kg and 1 Kg, with composition in weight % of Nimonic 80-A is: Ni = bal (76.66), C = 0.01, Cr = 19.83, Fe = 2.4, Mn = 0.17, Si 0.47, Al = 0.19, Zr = 0.4. The solidification process is made in a steel mold. After having realized four thermal treatments, the most representative microstructures there were obtained. The results from tensile tests performed on Instron Servohydraulic testing systems at uniaxial dynamic testing, at constant speeds to ,0.2 cm/min, were: the yield strength, the ultimate strength value, percentage elongation and area reduction. Creep tests were performed at in stress of 90 and 129 MPa, at a temperature of 600 and 680 Centigrades at different times and width of specimen of 1 mm. The alloys were analyzed by MEB(JEOL 35CF) at different magnifications. The nucleation and growth of intergranular cavities during creep of alloy Nimonic M3, were investigated. One sample was deformed in creep at 129 MPa and 680 Centigrades during 110 hs. Creep samples were annealing heat treated at 800 Centigrades, during 7 days. After a careful sample preparation procedure, 3100 of cavities were measured in the sample . The cavity size distributions in the sample were obtained. The cavity growth rate, was

  8. Relationship of microstructure to fracture topography in orthopedic alloys

    International Nuclear Information System (INIS)

    Gilbertson, L.N.

    1976-01-01

    Two major alloys used for orthopedic implants are 316L stainless steel and a cast cobalt--chromium--molybdenum alloy similar to Haynes Stellite 21. Another alloy that is just being introduced is Ti--6Al--4V. All three of these alloys are used in different conditions with different microstructures. Standard specimens with typical microstructures encountered in orthopedic applications were loaded to fracture in both overload and fatigue modes. Different rates of loading were also used in some cases. The fracture surfaces of these standard samples were analyzed in the Scanning Electron Microscope. An attempt was made to relate the fracture behavior, as evidenced by the fracture typography, to the microstructure of the alloy as revealed by metallography

  9. Influence of different etchants on the representation of microstructures in nickel alloys; Einfluss verschiedener Aetzmittel auf die Gefuegedarstellung in Nickellegierungen

    Energy Technology Data Exchange (ETDEWEB)

    Speicher, Magdalena; Scheck, Rudi; Maile, Karl [Stuttgart Univ. (Germany). Materialpruefungsanstalt

    2016-04-15

    This work presents a comparison of selected nickel alloys of the same condition which were treated by means of specifically chosen etching techniques. Microstructures on microscope images of wrought Alloy 617, a casting variant of Alloy 625, a polycrystalline casting alloy IN-738 LC, as well as of a monocrystalline superalloy CM 247 LC SX, respectively, are juxtaposed and evaluated. This approach allows for a comprehensive optical microscopy characterization of the characteristic microstructural features.

  10. Handbook of International alloy Compositions and Designations. Volume II. Superalloys

    Science.gov (United States)

    1978-12-01

    Aubert et Duval, 92200 Neuilly-sur-Seine, Paris, France C-0180 August Dreckshage Eisen und Stahl, 4800 Bielefeld, West Germany C-0021 Avesta Jernverks...Aktiebolag, 774 01 Avesta , Sweden B C-0087 Babcock & Wilcox, Beaver Falls, Pennsylvania 15010 C-0126 Bergische Stahl-lndustrie, (BSD 5630 Remscheid...C-0033) C-0021 Avesta Jernverks Aktiebolag, 774 01 Avesta , Sweden C-0022 Howmet Turbine Components Corporation, (Div. of PUG), Muskegon, Michigan

  11. Chemical composition and nutritional evaluation of the seeds of Acacia tortilis (Forssk.) Hayne ssp. raddiana.

    Science.gov (United States)

    Embaby, Hassan E; Rayan, Ahmed M

    2016-06-01

    Chemical composition and nutritional evaluation as well as physicochemical and functional properties of seed flour of Acacia tortilis (Forssk.) Hayne ssp. raddiana were studied. The results indicated that seeds contained 5.30% moisture, 3.99% ash, 9.19% fat, 14.31% fiber, 27.21% protein and 45.30% carbohydrates. Potassium was the predominant element followed by calcium and then phosphorous. Phytic acid, tannins and trypsin inhibitor as antinutrients were detected. The amino acid profile compared well with FAO/WHO recommended pattern except for cystine/methionine, isoleucine, tyrosine/phenylalanine, lysine and threonine. Also, the first limiting amino acid was lysine. Fatty acid composition showed that linoleic acid was the major fatty acid, followed by palmitic, stearic, oleic and arachidic acids. The seed oil showed absorbance in the ultraviolet ranges, thus it can be used as a broad spectrum UV protectant. For physicochemical and functional properties, acacia seeds flour had excellent water holding index, swelling index, foaming capacity and foam stability. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. Phase I decontamination of the J.C. Haynes site, Newark, Ohio. Final report

    International Nuclear Information System (INIS)

    Emswiler, T.R.

    1985-11-01

    Phase I consisted of the primary decontamination, packaging, and shipment of all 241 Am-contaminated gloveboxes, vent system, and miscellaneous waste items located in the laboratory restricted area in the J.C. Haynes house. The primary goals of Phase I were to locate and account for a major quantity of 241 Am which was unaccounted for and to remove all radioactive materials and contamination posing an imminent hazard to public health and safety. All Phase I operations were conducted under a Quality Assurance (QA) Program Plan and QA procedures written specifically for this program. In addition, certain generic Battelle QA procedures were used for routine tasks. All operations were conducted under strict health physics supervision and procedures. Cognizant ORAU and US Nuclear Regulatory Commission (NRC) personnel were on site during the entire Phase I operation and provided support and approval in the daily operations. All staff members had participated in previous decontamination and decommissioning programs involving transuranic waste and completed Phase I in a well controlled, timely, and safe manner

  13. Fabrication of tungsten wire reinforced nickel-base alloy composites

    Science.gov (United States)

    Brentnall, W. D.; Toth, I. J.

    1974-01-01

    Fabrication methods for tungsten fiber reinforced nickel-base superalloy composites were investigated. Three matrix alloys in pre-alloyed powder or rolled sheet form were evaluated in terms of fabricability into composite monotape and multi-ply forms. The utility of monotapes for fabricating more complex shapes was demonstrated. Preliminary 1093C (2000F) stress rupture tests indicated that efficient utilization of fiber strength was achieved in composites fabricated by diffusion bonding processes. The fabrication of thermal fatigue specimens is also described.

  14. Sintering and microstructure evolution of columnar nickel-based superalloy sheets prepared by EB-PVD

    International Nuclear Information System (INIS)

    Chen, S.; Qu, S.J.; Liang, J.; Han, J.C.

    2010-01-01

    Research highlights: → EB-PVD technology is commonly used to deposit thermal barrier coatings (TBCs) and columnar structure is commonly seen in EB-PVD condensates. The unique columnar structure can provide outstanding resistance against thermal shock and mechanical strains for TBCs. However, a number of researchers have found that the columnar structure can affect the mechanical properties of EB-PVD alloy thin sheet significantly. As yet, works on how to reduce this kind of effects are seldom done. In the present article, we tried to reveal the sintering effects on microstructure evolution and mechanical properties of columnar Ni-based superalloy sheet. The results suggests that after sintering, the columnar structure degrades. Degradation depends on sintering temperature and time. Both the ultimate tensile strength and the elongation percentage are effectively improved after sintering. - Abstract: A ∼0.15 mm-thick columnar nickel-based superalloy sheet was obtained by electron beam physical vapor deposition (EB-PVD). The as-deposited alloy sheet was sintered at different conditions. The microstructure of the specimens before and after sintering was characterized by using scanning electron microscopy. An X'Pert texture facility was used to determine the crystallographic orientation of the as-deposited alloy sheet. The phase transformation was investigated by X-ray diffraction. Tensile tests were conducted at room temperature on as-deposited and sintered specimens. The results show that the as-deposited sheet is composed of typical columnar structures. After sintering, however, the columnar structure degrades. The degradation depends on sintering temperature and time. Both the ultimate tensile strength and the elongation percentage are effectively improved after sintering.

  15. Effect of processing on microstructure and physical properties of three nickel-based superalloys with different hardening mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Strondl, Annika; Frommeyer, Georg [Department of Materials Technology, Max-Planck-Institut fuer Eisenforschung GmbH, Max-Planck-Strasse 1, D-40237 Duesseldorf (Germany); Klement, Uta [Department of Materials and Manufacturing Technology, Chalmers University of Technology, SE-412 96 Gothenburg (Sweden); Milenkovic, Srdjan; Schneider, Andre

    2012-07-15

    The nickel-based superalloys Inconel alloy 600, Udimet alloy 720, and Inconel alloy 718 were produced by electron beam melting (EBM), casting, and directional solidification (DS). The distance between dendrites and the size of the precipitates indicated the difference in solidification rates between the three processes. In this study, the solidification rate was fastest with EBM, closely followed by casting, whereas it was much slower with DS. In the directional solidified materials the <100> direction was the fastest and thus, preferred growth direction. The EBM samples show a sharp (001)[100] texture in the building direction and in the two scanning directions of the electron beam. Macrosegregation was observed in some cast and directionally solidified samples, but not in the EBM samples. The melting temperatures are in good agreement with literature and the narrow melting interval of IN600 compare to UD720 and IN718 might reduce the risk of incipient melting during EBM processing. Porosity was observed in the EBM samples and the reasons are discussed. However, EBM seems to be a feasible process route to produce nickel-based superalloys with well-defined texture, no macrosegregation and a rapidly solidified microstructure. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. Integrated design of Nb-based superalloys: Ab initio calculations, computational thermodynamics and kinetics, and experimental results

    International Nuclear Information System (INIS)

    Ghosh, G.; Olson, G.B.

    2007-01-01

    An optimal integration of modern computational tools and efficient experimentation is presented for the accelerated design of Nb-based superalloys. Integrated within a systems engineering framework, we have used ab initio methods along with alloy theory tools to predict phase stability of solid solutions and intermetallics to accelerate assessment of thermodynamic and kinetic databases enabling comprehensive predictive design of multicomponent multiphase microstructures as dynamic systems. Such an approach is also applicable for the accelerated design and development of other high performance materials. Based on established principles underlying Ni-based superalloys, the central microstructural concept is a precipitation strengthened system in which coherent cubic aluminide phase(s) provide both creep strengthening and a source of Al for Al 2 O 3 passivation enabled by a Nb-based alloy matrix with required ductile-to-brittle transition temperature, atomic transport kinetics and oxygen solubility behaviors. Ultrasoft and PAW pseudopotentials, as implemented in VASP, are used to calculate total energy, density of states and bonding charge densities of aluminides with B2 and L2 1 structures relevant to this research. Characterization of prototype alloys by transmission and analytical electron microscopy demonstrates the precipitation of B2 or L2 1 aluminide in a (Nb) matrix. Employing Thermo-Calc and DICTRA software systems, thermodynamic and kinetic databases are developed for substitutional alloying elements and interstitial oxygen to enhance the diffusivity ratio of Al to O for promotion of Al 2 O 3 passivation. However, the oxidation study of a Nb-Hf-Al alloy, with enhanced solubility of Al in (Nb) than in binary Nb-Al alloys, at 1300 deg. C shows the presence of a mixed oxide layer of NbAlO 4 and HfO 2 exhibiting parabolic growth

  17. Development of welding technology for improving the metallurgical and mechanical properties of 21st century nickel based superalloy 686

    Energy Technology Data Exchange (ETDEWEB)

    Arulmurugan, B. [School of Mechanical Engineering, VIT University, Vellore 632014 (India); KPR Institute of Engineering and Technology, Coimbatore (India); Manikandan, M., E-mail: mano.manikandan@gmail.com [School of Mechanical Engineering, VIT University, Vellore 632014 (India)

    2017-04-13

    Alloy 686 is a highly corrosion resistant 21st-Century Nickel based superalloy derived from Ni-Cr-Mo ternary system. The alloying elements chromium (Cr) and molybdenum (Mo) are added to improve the resistance to corrosion in the broad range of service environment. The presence of a higher percentage of alloying elements Cr and Mo lead to microsegregation and end up with hot cracking in the fusion zone of Nickel-based superalloys. However, there is scanty of information regarding the welding of alloy 686 with respect to the microsegregation of alloying elements. The present study investigates the possibility of bringing down the microsegregation to cut down the formation of secondary phases in the fusion zone. The weld joints were fabricated by Gas Tungsten Arc Welding (GTAW) and Pulsed current gas tungsten arc welding (PCGTAW) with ERNiCrMo-10 filler and without filler wire (autogenous) mode. The microstructural properties of the weld joints were studied with optical and Scanning Electron Microscope (SEM). The joints fabricated by pulsed current (PC) technique shows refined microstructure, narrower weld bead and practically no heat affected zone (HAZ). Scanning Electron Microscope demonstrates the presence of secondary phases in the interdendritic regions of GTAW case. Energy Dispersive X-ray Spectroscopy (EDS) analysis was carried out to evaluate the microsegregation of alloying element. The results show that the segregation of Mo noticed in the interdendritic zone of GTAW both autogenous and filler wire. Tensile and Impact tests were done to evaluate the strength, ductility, and toughness of the weld joints. The results show that the PCGTA helps to obtain improved strength, ductility and toughness of the weld joints compared to their respective GTAW. Bend test did not lead to cracking irrespective of the type of welding adopted in the present study.

  18. Characterization of Phase Chemistry and Partitioning in a Family of High-Strength Nickel-Based Superalloys

    Science.gov (United States)

    Lapington, M. T.; Crudden, D. J.; Reed, R. C.; Moody, M. P.; Bagot, P. A. J.

    2018-06-01

    A family of novel polycrystalline Ni-based superalloys with varying Ti:Nb ratios has been created using computational alloy design techniques, and subsequently characterized using atom probe tomography and electron microscopy. Phase chemistry, elemental partitioning, and γ' character have been analyzed and compared with thermodynamic predictions created using Thermo-Calc. Phase compositions and γ' volume fraction were found to compare favorably with the thermodynamically predicted values, while predicted partitioning behavior for Ti, Nb, Cr, and Co tended to overestimate γ' preference over the γ matrix, often with opposing trends vs Nb concentration.

  19. THERMAL FATIGUE OF INCONEL ALLOY DA718

    Science.gov (United States)

    2016-10-27

    this material meets the required improvement and offers a low cost alternative to powder metallurgy Rene’95. However, its thermal fatigue resistance...chromel-alumel thermocouple, spot- welded to the mid-length of the specimen. The thermal strain, induced by the expansion and contraction of the...12 FOR OFFICIAL USE ONLY 13. J. F. Radavich, “The Physical Metallurgy of Cast and Wrought Alloy 718,” in Superalloy 718 – Metallurgy and

  20. Enhancing the Oxidation Performance of Wrought Ni-Base Superalloy by Minor Additions of Active Elements

    Science.gov (United States)

    Tawancy, H. M.

    2016-12-01

    We show that the oxidation performance of Cr2O3-forming superalloy based upon the Ni-Cr-W system is significantly improved by the presence of minor concentrations of La, Si and Mn, which outweigh the detrimental effect of high W concentration in the alloy. Although Cr2O3 is known to transform into volatile CrO3 at temperatures ≥950 °C, the respective protection is extended to temperatures reaching 1150 °C, which has also been correlated with the beneficial effects of La, Si and Mn. During high-temperature oxidation, an inner protective La- and Si-modified layer of α-Cr2O3 in contact with the superalloy substrate is developed and shielded by an outermost layer of MnCr2O4. The distribution of La and Si in the inner oxide layer has been characterized down to the scale of transmission electron microscopy, and the possible mechanisms underlying their beneficial effects are elucidated.

  1. Additive Manufacturing of Nickel Superalloys: Opportunities for Innovation and Challenges Related to Qualification

    Science.gov (United States)

    Babu, S. S.; Raghavan, N.; Raplee, J.; Foster, S. J.; Frederick, C.; Haines, M.; Dinwiddie, R.; Kirka, M. K.; Plotkowski, A.; Lee, Y.; Dehoff, R. R.

    2018-06-01

    Innovative designs for turbines can be achieved by advances in nickel-based superalloys and manufacturing methods, including the adoption of additive manufacturing. In this regard, selective electron beam melting (SEBM) and selective laser melting (SLM) of nickel-based superalloys do provide distinct advantages. Furthermore, the direct energy deposition (DED) processes can be used for repair and reclamation of nickel alloy components. The current paper explores opportunities for innovation and qualification challenges with respect to deployment of AM as a disruptive manufacturing technology. In the first part of the paper, fundamental correlations of processing parameters to defect tendency and microstructure evolution will be explored using DED process. In the second part of the paper, opportunities for innovation in terms of site-specific control of microstructure during processing will be discussed. In the third part of the paper, challenges in qualification of AM parts for service will be discussed and potential methods to alleviate these issues through in situ process monitoring, and big data analytics are proposed.

  2. High-temperature γ (FCC/γ′ (L12 Co-Al-W based superalloys

    Directory of Open Access Journals (Sweden)

    Knop Matthias

    2014-01-01

    Full Text Available Interim results from the development of a polycrystalline Co-Al-W based superalloy are presented. Cr has been added to provide oxidation resistance and Ni has then been added to widen and stabilise the γ′ phase field. The alloy presented has a solvus of 1010 °C and a density of 8.7 g cm−3. The room temperature flow stress is over 1000 MPa and this reduces dramatically above 800 °C. The flow stress anomaly is observed. A microstructure with both ∼ 50 nm γ′ produced on cooling and larger 100–200 nm γ′ can be obtained. Isothermal oxidation at 800 °C in air for 200 h gave a mass gain of 0.96 mg cm−2. After hot deformation in the 650–850 °C temperature range, both anti phase boundaries (APBs and stacking faults could be observed. An APB energy of 71 mJ m−2 was measured, which is comparable to that found in commercial nickel superalloys.

  3. Spray forming and mechanical properties of a new type powder metallurgy superalloy

    International Nuclear Information System (INIS)

    Jia Chong-Lin; Ge Chang-Chun; Xia Min; Gu Tian-Fu

    2015-01-01

    The deposited billet of a new type powder metallurgy (PM) superalloy FGH4095M for use in turbine disk manufacturing has been fabricated using spray forming technology. The metallurgical quality of the deposited billet was analyzed in terms of density, texture, and grain size. Comparative research was done on the microstructure and mechanical properties between the flat disk preform prepared with hot isostatic pressing (HIP) and the same alloy forgings prepared with HIP followed by isothermal forging (IF). The results show that the density of the spray-formed and nitrogen-atomized deposit billet is above 99% of the theoretical density, indicating a compact structure. The grains are uniform and fine. The billet has weak texture with a random distribution in the spray deposition direction and perpendicular to the direction of deposition. A part of atomizing nitrogen exists in the preform in the form of carbonitride. Nitrogen-induced microporosity causes the density reduction of the preform. Compared with the process of HIP+IF, the superalloy FGH4095M after HIP has better mechanical properties at both room temperature and high temperature. The sizes of the γ′ phase are finer in microstructure of the preform after HIP in comparison with the forgings after HIP+IF. This work shows that SF+HIP is a viable processing route for FGH4095M as a turbine-disk material. (paper)

  4. The effects of Ta on the stress rupture properties and microstructural stability of a novel Ni-base superalloy for land-based high temperature applications

    International Nuclear Information System (INIS)

    Zheng, Liang; Zhang, Guoqing; Lee, Tung L.; Gorley, Michael J.; Wang, Yue; Xiao, Chengbo; Li, Zhou

    2014-01-01

    Highlights: • An equiaxed superalloy has high rupture life equivalent to single crystal alloy DD3. • Low Cr and high W superalloys possess good microstructrual stability at 850–1100 °C. • Tantalum promotes, strengthens and stabilizes the eutectic γ′ and MC carbides. • Excessive Ta leads to form harmful abnormal primary α and plate-like M 6 C phases. • Proper Ta can improve the stress rupture life at intermediate and high temperatures. - Abstract: A novel polycrystalline Ni-base superalloy was developed for land-based high temperature applications, such as isothermal forging dies and industrial gas turbines. The alloy possessed surprisingly high stress rupture life of 52 h at 1100 °C/118 MPa which is comparable to the first generation single crystal (SC) superalloy and exhibited good microstructural stability. The effects of Ta addition on the phase change, stress rupture properties and microstructural stability of the alloy were investigated. The results indicated that Ta is a γ′-former and promotes the formation of eutectic γ′. The alloys with ∼7 vol.% eutectic γ′ possess higher stress rupture life at 1100 °C/118 MPa than the alloys with higher ∼20 vol.% eutectic. However, ∼20 vol.% excessive eutectic phases will enhance the stress rupture life at intermediate temperature of 760 °C for 686 MPa but weaken high temperature stress rupture properties. The (Al + Ta) content over 14.4 at.% led to the formation of large amounts of eutectic γ′ and exceeded the solubility of W and Mo in the residue liquid pool, which then promoted the precipitation of primary α-(W,Mo) and M 6 C phases. Tantalum was also found as a strong MC carbides forming element. The order of ability to form monocarbide decreased from NbC to TaC to TiC. 6Al–0Ta (wt.%) alloys possessed good microstructural stability with no harmful topologically close-packed (TCP) phases being observed after thermal exposure at 850 °C/3000 h, 900 °C/1000 h. Only trace amounts of

  5. Measurement and analyses of molten Ni-Co alloy density

    Institute of Scientific and Technical Information of China (English)

    XIAO Feng; K. MUKAI; FANG Liang; FU Ya; YANG Ren-hui

    2006-01-01

    With the advent of powerful mathematical modeling techniques for material phenomena, there is renewed interest in reliable data for the density of the Ni-based superalloys. Up to now, there has been few report on the density of molten Ni-Co alloy.In order to obtain more accurate density data for molten Ni-Co alloy, the density of molten Ni-Co alloy was measured with a modified sessile drop method, and the accommodation of different atoms in molten Ni-Co alloy was analyzed. The density of alloy is found to decrease with increasing temperature and Co concentration in the alloy. The molar volume of molten Ni-Co alloy increases with increasing Co concentration. The molar volume of Ni-Co alloy determined shows a positive deviation from the linear molar volume, and the deviation of molar volume from ideal mixing increases with increasing Co concentration over the experimental concentration range.

  6. Grinding of Inconel 713 superalloy for gas turbines

    Czech Academy of Sciences Publication Activity Database

    Čapek, J.; Kyncl, J.; Kolařík, K.; Beránek, L.; Pitrmuc, Z.; Medřický, Jan; Pala, Z.

    2016-01-01

    Roč. 16, č. 1 (2016), s. 14-15 ISSN 1213-2489 Institutional support: RVO:61389021 Keywords : Casting defects * Gas turbine * Grinding * Nickel superalloy * Residual stresses Subject RIV: JJ - Other Materials

  7. Microstructural Evolution and Creep-Rupture Behavior of A-USC Alloy Fusion Welds

    Science.gov (United States)

    Bechetti, Daniel H.; DuPont, John N.; Siefert, John A.; Shingledecker, John P.

    2016-09-01

    Characterization of the microstructural evolution of fusion welds in alloys slated for use in advanced ultrasupercritical (A-USC) boilers during creep has been performed. Creep-rupture specimens involving INCONEL® 740, NIMONIC® 263 (INCONEL and NIMONIC are registered trademarks of Special Metals Corporation), and Haynes® 282® (Haynes and 282 are registered trademarks of Haynes International) have been analyzed via light optical microscopy, scanning electron microscopy, X-ray diffraction, and thermodynamic and kinetic modeling. Focus has been given to the microstructures that develop along the grain boundaries in these alloys during creep at temperatures relevant to the A-USC process cycle, and particular attention has been paid to any evidence of the formation of local γ'-denuded or γ'-free zones. This work has been performed in an effort to understand the microstructural changes that lead to a weld strength reduction factor (WSRF) in these alloys as compared to solution annealed and aged alloy 740 base metal. γ' precipitate-free zones have been identified in alloy 740 base metal, solution annealed alloy 740 weld metal, and alloy 263 weld metal after creep. Their development during long-term thermal exposure is correlated with the stabilization of phases that are rich in γ'-forming elements ( e.g., η and G) and is suppressed by precipitation of phases that do not contain the γ' formers ( e.g., M23C6 and μ). The location of failure and creep performance in terms of rupture life and WSRF for each welded joint is presented and discussed.

  8. Micromorphology of the floral nectary of red horse chestnut (Aesculus ×carnea Hayne

    Directory of Open Access Journals (Sweden)

    Elżbieta Weryszko-Chmielewska

    2014-04-01

    Full Text Available In Europe Aesculus ×carnea Hayne is planted in cities as an avenue tree. Compared to A. hippocastanum L., it is more drought resistant, but less resistant to low temperatures. A. ×carnea is a lower tree than A. hippocastanum and develops a smaller corolla. It produces dark green, shiny and crinkled leaves. Its flowers have different colours, from bright pink to carmine red. The nectary glands secrete nectar abundantly. Due to the long corolla tube, nectar is difficult to reach for bees. The aim of this study was to investigate the topography and micromorphology of the nectaries of A. ×carnea using scanning electron microscopy. The study shows that the nectary gland of red horse chestnut forms an incomplete ring around the base of the staminal filaments, surrounding only four stamens out of the seven that occur in the flower. Three stamens are outside the nectary. In its widest place, the nectary diameter reaches 2.7 mm. Three expanded portions of the gland can bee seen in the marginal part of the nectary, adjoining the petals. The part of the nectary adjacent to the filaments forms a convex protrusion with a wavy appearance (shape, which results from the vicinity of the filaments. Nectar is secreted through numerous stomata located beneath the convex part of the nectary. The stoma length is 21.7 μm, while the width 23.3 μm. In the material examined, most stomata had open pores. Secretion was observed in many places. The stomata were surrounded by 6-7 guard cells; this allows them to be classified as the cyclocytic type. The cells of the stomatal complex were raised above the surface of the other epidermal cells. The walls of the guard cells and of the adjacent epidermal cells were covered by a cuticle with irregular striation.

  9. Changes in the properties of superalloys by long term heating

    International Nuclear Information System (INIS)

    Susukida, H.; Tsuji, I.; Kawai, H.

    1976-01-01

    A laboratory study was conducted in order to determine the effect of long term heating (max. 10000h at 850 0 and 950 0 C) on the microstructure, tensile properties, hardness and stress rupture properties of four kinds of superalloys. These superalloys are two kinds of solid solution hardened Ni-base superalloys Hastelloy X and Inconel 617 and two kinds of dispersion strengthened Ni-base superalloys TD-Ni and TD-NiCr. The result of the study can be summarized as follows: (1) Solid solution hardened superalloys: Many precipitates were observed in the grains and on the grain boundaries after 100 hours of heating, and the precipitates became coarse-grained by over 1000 hours of heating. This tendency was remarkable when they were heated at 950 0 C. With the change of their microstructure, their mechanical properties also changed, particularly their tensile ductility decreased remarkably. (2) Dispersion strengthened superalloys: Their microstructure and mechanical properties were almost unchanged by long term heating. (3) The authors proposed ''solid solution hardening value'' in order to grasp quantitatively the solid solution hardening which has been discussed by the content of each element hitherto. (auth.)

  10. Tensile behavior of nickel-base single-crystal superalloy DD6

    Energy Technology Data Exchange (ETDEWEB)

    Xiong, Xinhong, E-mail: xiongxh@whut.edu.cn [School of Logistics Engineering, Wuhan University of Technology, Wuhan 430063 (China); Quan, Dunmiao; Dai, Pengdan; Wang, Zhiping [School of Logistics Engineering, Wuhan University of Technology, Wuhan 430063 (China); Zhang, Qiaoxin [School of Mechanical and Electronic Engineering, Wuhan University of Technology, Wuhan 430070 (China); Yue, Zhufeng [School of Mechanics Civil Engineering and Architecture, Northwestern Polytechnical University, Xi' an 710072 (China)

    2015-06-11

    Tensile behavior of the nickel-base single-crystal superalloy DD6 was studied from room temperature to 1020 °C. The plate specimens were along [001] orientation parallel to the loading axis in tension. The microstructures on the surface and fracture morphology were investigated after tensile test to rupture by scanning electron microscopy (SEM). The results of the present investigation indicate that the yield strength at 650 °C is superior to that at room temperature, 850 °C and 1020 °C. Low ductility and serrated flow in stress–strain curves were also observed at 650 °C. The microstructures on the surface of the plate specimens and fracture morphology observation indicated that localized slip which resulted in glide plane decohesion caused the low ductility of DD6 alloy.

  11. Phase-field modelling of as-cast microstructure evolution in nickel-based superalloys

    Energy Technology Data Exchange (ETDEWEB)

    Warnken, N., E-mail: n.warnken@bham.ac.uk [University of Birmingham, Department of Metallurgy and Materials, Edgbaston, Birmingham B15 2TT (United Kingdom); Ma, D. [Foundry Institute of the RWTH-Aachen, Intzestr. 5, 52072 Aachen (Germany); Drevermann, A. [ACCESS e.V., Intzestr. 5, 52072 Aachen (Germany); Reed, R.C. [University of Birmingham, Department of Metallurgy and Materials, Edgbaston, Birmingham B15 2TT (United Kingdom); Fries, S.G. [SGF Consultancy, 52064 Aachen (Germany)] [ICAMS, Ruhr University Bochum, Stiepeler Strasse 129, D-44780 Bochum (Germany); Steinbach, I. [ICAMS, Ruhr University Bochum, Stiepeler Strasse 129, D-44780 Bochum (Germany)

    2009-11-15

    A modelling approach is presented for the prediction of microstructure evolution during directional solidification of nickel-based superalloys. A phase-field model is coupled to CALPHAD thermodynamic and kinetic (diffusion) databases, so that a multicomponent alloy representative of those used in industrial practice can be handled. Dendritic growth and the formation of interdendritic phases in an isothermal (2-D) cross-section are simulated for a range of solidification parameters. The sensitivity of the model to changes in the solidification input parameters is investigated. It is demonstrated that the predicted patterns of microsegregation obtained from the simulations compare well to the experimental ones; moreover, an experimentally observed change in the solidification sequence is correctly predicted. The extension of the model to 3-D simulations is demonstrated. Simulations of the homogenization of the as-cast structure during heat treatment are presented.

  12. Microstructure and mechanical properties of the superalloy ATI Allvac 718Plus

    International Nuclear Information System (INIS)

    Zickler, Gerald A.; Schnitzer, Ronald; Radis, Rene; Hochfellner, Rainer; Schweins, Ralf; Stockinger, Martin; Leitner, Harald

    2009-01-01

    ATI Allvac 718Plus is a novel nickel-based superalloy, which was designed for heavy-duty applications in aerospace turbines. In the present study the high-resolution investigation techniques, atom probe tomography, electron microscopy and in situ high-temperature small-angle neutron scattering were used for a comprehensive microstructural characterization. The alloy contains nanometer-sized spherical γ' phase precipitates (Ni 3 (Al,Ti)) and plate-shaped δ phase precipitates (Ni 3 Nb) of micrometer size. The precipitation kinetics of the γ' phase can be described by a classical model for coarsening. The precipitation strongly influences the mechanical properties and is of high scientific and technological interest.

  13. Phase-field modelling of as-cast microstructure evolution in nickel-based superalloys

    International Nuclear Information System (INIS)

    Warnken, N.; Ma, D.; Drevermann, A.; Reed, R.C.; Fries, S.G.; Steinbach, I.

    2009-01-01

    A modelling approach is presented for the prediction of microstructure evolution during directional solidification of nickel-based superalloys. A phase-field model is coupled to CALPHAD thermodynamic and kinetic (diffusion) databases, so that a multicomponent alloy representative of those used in industrial practice can be handled. Dendritic growth and the formation of interdendritic phases in an isothermal (2-D) cross-section are simulated for a range of solidification parameters. The sensitivity of the model to changes in the solidification input parameters is investigated. It is demonstrated that the predicted patterns of microsegregation obtained from the simulations compare well to the experimental ones; moreover, an experimentally observed change in the solidification sequence is correctly predicted. The extension of the model to 3-D simulations is demonstrated. Simulations of the homogenization of the as-cast structure during heat treatment are presented.

  14. TEM microstructural analysis of creep deformed CM186LC single crystal Ni-base superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Dubiel, B.; Czyrska-Filemonowicz, A. [AGH Univ. of Science and Technology, Krakow (Poland); Blackler, M. [Howmet Ltd., Exeter (United Kingdom); Barnard, P.M. [ALSTOM Power Turbo-Systems Technology Centre, Rugby (United Kingdom)

    2006-07-01

    The nickel based single crystal superalloy CM186LC was extensively investigated as a potential low cost material for industrial gas turbine vanes within the COST522 programme. The alloy exhibits inhomogeneous structure consisting of dendritic regions and eutectic colonies. In the present work attention is focused on microstructural changes observed in single crystal CM186LC following creep deformation at 750 C. Creep tests were conducted at 750 C with an applied stress of 560 or 675 MPa for up to 11440 hours. The microstructure o ruptured and terminated specimens was investigated by scanning (SEM) and transmission (TEM) electron microscopy. TEM analysis revealed the microstructural changes in the CM186LC at primary and secondary creep as well as after creep rupture. (orig.)

  15. High temperature low cycle fatigue behavior of Ni-base superalloy M963

    International Nuclear Information System (INIS)

    He, L.Z.; Zheng, Q.; Sun, X.F.; Guan, H.R.; Hu, Z.Q.; Tieu, A.K.; Lu, C.; Zhu, H.T.

    2005-01-01

    The cyclic stress-strain response and the low cycle fatigue life behavior of solution treated Ni-base superalloy M963 were studied. Fully reversed strain-controlled tests were performed at temperature range from 700 to 950 deg. C in air at a constant total strain rate. The dislocation characteristics and failed surface observation were evaluated through scanning electron microscopy and transmission electron microscopy, respectively. The alloy exhibited the cyclic hardening, softening, or stable cyclic stress response, which was dependent on the temperature and total strain range. The fracture surface observation revealed that fatigue crack initiation was transgranular and closely related to the total strain range; however, fatigue crack propagation exhibited a strong dependence on testing temperature. The dramatic reduction in fatigue life and intergranular cracking observed at 900 and 950 deg. C were attributed to oxidation

  16. Microstructural response of an Al-modified Ni-Cr-Fe ternary alloy during thermal processing

    Energy Technology Data Exchange (ETDEWEB)

    Akinlade, D.A. [Department of Mechanical and Manufacturing Engineering, University of Manitoba, Winnipeg, MB (Canada)], E-mail: dotun172@yahoo.co.uk; Caley, W.F. [Department of Process Engineering and Applied Science, Dalhousie University, Halifax, NS (Canada); Richards, N.L.; Chaturvedi, M.C. [Department of Mechanical and Manufacturing Engineering, University of Manitoba, Winnipeg, MB (Canada)

    2008-07-15

    A thermodynamic package was used to predict the phase transformations that occurred during thermal processing of a superalloy based on the composition of a ternary Ni-Cr-Fe alloy. The effect of the addition of 6 w/o Al on phase transformation in the material sintered were estimated and compared with results obtained experimentally by X-ray diffraction and metallography, while the transformation temperature of the modified alloy was corroborated by differential scanning calorimetry (DSC). Mechanical property of the alloy was estimated in terms of Vickers hardness. These results suggest that despite potential problems encountered in high-temperature powder processing of superalloys that often tend to influence the feasibility of using thermodynamic predictions to model such alloy systems, the software and predictions used in this study offer a way to simulate both design and characterisation of the experimental alloy.

  17. New concept of composite strengthening in Co-Re based alloys for high temperature applications in gas turbines

    Energy Technology Data Exchange (ETDEWEB)

    Mukherji, D.; Roesler, J.; Fricke, T.; Schmitz, F. [Technische Univ. Braunschweig (DE). Inst. fuer Werkstoffkunde (IfW); Piegert, S. [Siemens AG, Berlin (DE). Energy Sector (F PR GT EN)

    2010-07-01

    High temperature material development is mainly driven by gas turbine needs. Today, Ni-based superalloys are the dominant material class in the hot section of turbines. Material development will continue to push the maximum service temperature of Ni-superalloys upwards. However, this approach has a fundamental limit and can not be sustained indefinitely, as the Ni-superalloys are already used very close to their melting point. Within the frame work of a DFG Forschergruppe program (FOR 727) - ''Beyond Ni-base Superalloys'' - Co-Re based alloys are being developed as a new generation of high temperature materials that can be used at +100 C above single crystal Ni-superalloys. Along with other strengthening concepts, hardening by second phase is explored to develop a two phase composite alloy. With quaternary Co-Re-Cr-Ni alloys we demonstrate this development concept, where Co{sub 2}Re{sub 3}-type {sigma} phase is used in a novel way as the hardening phase. Thermodynamic calculation was used for designing model alloy compositions. (orig.)

  18. Atomic Species Associated with the Portevin-Le Chatelier Effect in Superalloy 718 Studied by Mechanical Spectroscopy

    Science.gov (United States)

    Max, B.; San Juan, J.; Nó, M. L.; Cloue, J. M.; Viguier, B.; Andrieu, E.

    2018-06-01

    In many Ni-based superalloys, dynamic strain aging (DSA) generates an inhomogeneous plastic deformation resulting in jerky flow known as the Portevin-Le Chatelier (PLC) effect. This phenomenon has a deleterious effect on the mechanical properties and, at high temperature, is related to the diffusion of substitutional solute atoms toward the core of dislocations. However, the question about the nature of the atomic species responsible for the PLC effect at high temperature still remains open. The goal of the present work is to answer this important question; to this purpose, three different 718-type and a 625 superalloy were studied through a nonconventional approach by mechanical spectroscopy. The internal friction (IF) spectra of all the studied alloys show a relaxation peak P 718 (at 885 K for 0.1 Hz) in the same temperature range, 700 K to 950 K, as the observed PLC effect. The activation parameters of this relaxation peak have been measured, E a( P 718) = 2.68 ± 0.05 eV, τ 0 = 2·10-15 ± 1 s as well as its broadening factor β = 1.1. Experiments on different alloys and the dependence of the relaxation strength on the amount of Mo attribute this relaxation to the stress-induced reorientation of Mo-Mo dipoles due to the short distance diffusion of one Mo atom by exchange with a vacancy. Then, it is concluded that Mo is the atomic species responsible for the high-temperature PLC effect in 718 superalloy.

  19. Creep Behaviour of Modified Mar-247 Superalloy

    Directory of Open Access Journals (Sweden)

    Cieśla M.

    2016-06-01

    Full Text Available The paper presents the results of analysis of creep behaviour in short term creep tests of cast MAR-247 nickel-based superalloy samples made using various modification techniques and heat treatment. The accelerated creep tests were performed under temperature of 982 °C and the axial stresses of σ = 150 MPa (variant I and 200 MPa (variant II. The creep behaviour was analysed based on: creep durability (creep rupture life, steady-state creep rate and morphological parameters of macro- and microstructure. It was observed that the grain size determines the creep durability in case of test conditions used in variant I, durability of coarse-grained samples was significantly higher.

  20. Mechanical Property and Its Comparison of Superalloys for High Temperature Gas Cooled Reactor

    International Nuclear Information System (INIS)

    Kim, Woo Gon; Kim, D. W.; Ryu, W. S.; Han, C. H.; Yoon, J. H.; Chang, J.

    2005-01-01

    Since structural materials for high temperature gas cooled reactor are used during long period in nuclear environment up to 1000 .deg. C, it is important to have good properties at elevated temperature such as mechanical properties (tensile, creep, fatigue, creep-fatigue), microstructural stability, interaction between metal and gas, friction and wear, hydrogen and tritium permeation, irradiation behavior, corrosion by impurity in He. Thus, in order to select excellent materials for the high temperature gas cooled reactor, it is necessary to understand the material properties and to gather the data for them. In this report, the items related to material properties which are needed for designing the high temperature gas cooled reactor were presented. Mechanical properties; tensile, creep, and fatigue etc. were investigated for Haynes 230, Hastelloy-X, In 617 and Alloy 800H, which can be used as the major structural components, such as intermediate heat exchanger (IHX), hot duct and piping and internals. Effect of He and irradiation on these structural materials was investigated. Also, mechanical properties; physical properties, tensile properties, creep and creep crack growth rate were compared for them, respectively. These results of this report can be used as important data to select superior materials for high temperature gas reactor

  1. Production and Characterization of WC-Reinforced Co-Based Superalloy Matrix Composites

    Science.gov (United States)

    Özgün, Özgür; Dinler, İlyas

    2018-05-01

    Cobalt-based superalloy matrix composite materials were produced through the powder metallurgy technique using element powders at high purity and nano-sized wolfram carbide (WC) reinforcement in this study. An alloy that had the same chemical composition as the Stellite 6 alloy but not containing carbon was selected as the matrix alloy. The powder mixtures obtained as a result of mixing WC reinforcing member and element powders at the determined ratio were shaped by applying 300 MPa of pressure. The green components were sintered under argon atmosphere at 1240 °C for 120 minutes. The densities of the sintered components were determined by the Archimedes' principle. Microstructural characterization was performed via X-ray diffraction analysis, scanning electron microscope examinations, and energy-dispersive spectrometry. Hardness measurements and tensile tests were performed for determining mechanical characteristics. The relative density values of the sintered components increased by increasing the WC reinforcement ratio and they could almost reach the theoretical density. It was determined from the microstructural examinations that the composite materials consisted of fine and equiaxed grains and coarse carbides demonstrating a homogeneous dispersion along the microstructure at the grain boundaries. As it was the case in the density values, the hardness and strength values of the composites increased by increasing the WC ratio.

  2. Effect of carbides on the creep properties of a Ni-base superalloy M963

    International Nuclear Information System (INIS)

    He, L.Z.; Zheng, Q.; Sun, X.F.; Guan, H.R.; Hu, Z.Q.; Tieu, A.K.; Lu, C.; Zhu, H.T.

    2005-01-01

    Effect of carbides on the creep properties of a cast Ni-base superalloy M963 tested at 800 and 900 deg. C over a broad stress range has been investigated. Correlation between the carbides and creep properties of the alloy is enabled through scanning electron microscopy (SEM) and transmission electron microscopy (TEM). During high temperature creep tests, the primary MC carbide decomposes sluggishly and a large amount of secondary carbides precipitate. The cubic and acicular M 6 C carbide precipitates at the dendritic core region. Extremely fine chromium-rich M 23 C 6 carbide precipitates preferentially at grain boundaries. The M 6 C and M 23 C 6 carbides are found to be beneficial to the creep properties of the alloy. At lower temperature (800 deg. C), the interface of MC carbide with matrix is one of the principal sites for crack initiation. At higher temperature (900 deg. C), the oxidation and the precipitation of μ phase are the main factors for significant loss in creep strength of the alloy

  3. A New Superalloy Enabling Heavy Duty Gas Turbine Wheels for Improved Combined Cycle Efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Detor, Andrew [General Electric Company, Niskayuna, NY (United States). GE Global Research; DiDomizio, Richard [General Electric Company, Niskayuna, NY (United States). GE Global Research; McAllister, Don [The Ohio State Univ., Columbus, OH (United States); Sampson, Erica [General Electric Company, Niskayuna, NY (United States). GE Global Research; Shi, Rongpei [The Ohio State Univ., Columbus, OH (United States); Zhou, Ning [General Electric Company, Niskayuna, NY (United States). GE Global Research

    2017-01-03

    The drive to increase combined cycle turbine efficiency from 62% to 65% for the next-generation advanced cycle requires a new heavy duty gas turbine wheel material capable of operating at 1200°F and above. Current wheel materials are limited by the stability of their major strengthening phase (gamma double prime), which coarsens at temperatures approaching 1200°F, resulting in a substantial reduction in strength. More advanced gamma prime superalloys, such as those used in jet engine turbine disks, are also not suitable due to size constraints; the gamma prime phase overages during the slow cooling rates inherent in processing thick-section turbine wheels. The current program addresses this need by screening two new alloy design concepts. The first concept exploits a gamma prime/gamma double prime coprecipitation reaction. Through manipulation of alloy chemistry, coprecipitation is controlled such that gamma double prime is used only to slow the growth of gamma prime during slow cooling, preventing over-aging, and allowing for subsequent heat treatment to maximize strength. In parallel, phase field modeling provides fundamental understanding of the coprecipitation reaction. The second concept uses oxide dispersion strengthening to improve on two existing alloys that exhibit excellent hold time fatigue crack growth resistance, but have insufficient strength to be considered for gas turbine wheels. Mechanical milling forces the dissolution of starting oxide powders into a metal matrix allowing for solid state precipitation of new, nanometer scale oxides that are effective at dispersion strengthening.

  4. Laser Cladding of Ultra-Thin Nickel-Based Superalloy Sheets.

    Science.gov (United States)

    Gabriel, Tobias; Rommel, Daniel; Scherm, Florian; Gorywoda, Marek; Glatzel, Uwe

    2017-03-10

    Laser cladding is a well-established process to apply coatings on metals. However, on substrates considerably thinner than 1 mm it is only rarely described in the literature. In this work 200 µm thin sheets of nickel-based superalloy 718 are coated with a powder of a cobalt-based alloy, Co-28Cr-9W-1.5Si, by laser cladding. The process window is very narrow, therefore, a precisely controlled Yb fiber laser was used. To minimize the input of energy into the substrate, lines were deposited by setting single overlapping points. In a design of experiments (DoE) study, the process parameters of laser power, laser spot area, step size, exposure time, and solidification time were varied and optimized by examining the clad width, weld penetration, and alloying depth. The microstructure of the samples was investigated by optical microscope (OM) and scanning electron microscopy (SEM), combined with electron backscatter diffraction (EBSD) and energy dispersive X-ray spectroscopy (EDX). Similarly to laser cladding of thicker substrates, the laser power shows the highest influence on the resulting clad. With a higher laser power, the clad width and alloying depth increase, and with a larger laser spot area the weld penetration decreases. If the process parameters are controlled precisely, laser cladding of such thin sheets is manageable.

  5. Laser Cladding of Ultra-Thin Nickel-Based Superalloy Sheets

    Directory of Open Access Journals (Sweden)

    Tobias Gabriel

    2017-03-01

    Full Text Available Laser cladding is a well-established process to apply coatings on metals. However, on substrates considerably thinner than 1 mm it is only rarely described in the literature. In this work 200 µm thin sheets of nickel-based superalloy 718 are coated with a powder of a cobalt-based alloy, Co–28Cr–9W–1.5Si, by laser cladding. The process window is very narrow, therefore, a precisely controlled Yb fiber laser was used. To minimize the input of energy into the substrate, lines were deposited by setting single overlapping points. In a design of experiments (DoE study, the process parameters of laser power, laser spot area, step size, exposure time, and solidification time were varied and optimized by examining the clad width, weld penetration, and alloying depth. The microstructure of the samples was investigated by optical microscope (OM and scanning electron microscopy (SEM, combined with electron backscatter diffraction (EBSD and energy dispersive X-ray spectroscopy (EDX. Similarly to laser cladding of thicker substrates, the laser power shows the highest influence on the resulting clad. With a higher laser power, the clad width and alloying depth increase, and with a larger laser spot area the weld penetration decreases. If the process parameters are controlled precisely, laser cladding of such thin sheets is manageable.

  6. Fabrication development for ODS-superalloy, air-cooled turbine blades

    Science.gov (United States)

    Moracz, D. J.

    1984-01-01

    MA-600 is a gamma prime and oxide dispersion strengthened superalloy made by mechanical alloying. At the initiation of this program, MA-6000 was available as an experimental alloy only and did not go into production until late in the program. The objective of this program was to develop a thermal-mechanical-processing approach which would yield the necessary elongated grain structure and desirable mechanical properties after conventional press forging. Forging evaluations were performed to select optimum thermal-mechanical-processing conditions. These forging evaluations indicated that MA-6000 was extremely sensitive to die chilling. In order to conventionally hot forge the alloy, an adherent cladding, either the original extrusion can or a thick plating, was required to prevent cracking of the workpiece. Die design must reflect the requirement of cladding. MA-6000 was found to be sensitive to the forging temperature. The correct temperature required to obtain the proper grain structure after recrystallization was found to be between 1010-1065 C (1850-1950 F). The deformation level did not affect subsequent crystallization; however, sharp transition areas in tooling designs should be avoided in forming a blade shape because of the potential for grain structure discontinuities. Starting material to be used for forging should be processed so that it is capable of being zone annealed to a coarse elongated grain structure as bar stock. This conclusion means that standard processed bar materials can be used.

  7. Assessing phase stability and element distribution in Co-base superalloys at elevated temperatures by in situ TEM heating experiments

    Energy Technology Data Exchange (ETDEWEB)

    Eggeler, Yolita; Mueller, Julian; Spiecker, Erdmann [Lehrstuhl fuer Mikro- und Nanostrukturforschung and Center for Nanoanalysis and Electron Microscopy (CENEM), Department Werkstoffwissenschaften, Universitaet Erlangen-Nuernberg, Erlangen (Germany)

    2016-07-01

    Co-based alloys, of a composition of Co-12Al-9W, form a stable two phase γ/γ{sup '} microstructure at 900 C. γ{sup '} cubes, consisting of the L12 crystal structure are coherently embedded in a solid solution fcc (A1) γ matrix. To ensure precipitate hardening at temperatures, which are relevant to practical applications, 700-1100 C, as experienced in gas turbine applications, the stability of the γ/γ{sup '} phases is of fundamental importance. In this analysis in situ TEM studies with chip-based heating systems (by DENS solution) are applied on new Co-based superalloys. After in situ heating at apr. 900 C and controlled quenching with different quenching rates the elemental distribution at the γ/γ{sup '} interface is measured using ChemiSTEM EDX. Exploiting the driving force for interface movement resulting from temperature-dependent volume fraction of γ and γ{sup '} insight into the diffusion of individual alloying elements and the relationship between local chemistry and ordering can be gained from transient phenomena. The experimental results will be compared with theoretical calculations. This work has been carried out within the framework of the SFB-TR 103 ''Single Crystal Superalloys''.

  8. Effect of tensile holds on the deformation behaviour of a nickel base superalloy subjected to low cycle fatigue

    Energy Technology Data Exchange (ETDEWEB)

    Zrnik, J.; Semenak, J.; Wangyao, P.; Vrchovinsky, V.; Hornak, P. [Dept. of Materials Science, Technical Univ. of Kosice, Kosice (Slovakia)

    2002-07-01

    The deformation behaviour of the wrought nickel base superalloy EI698 VD has been investigated in conditions of low cycle fatigue. The tensile hold periods, imposing a constant stress into the fatigue loading, have been introduced at the maximum stress value. The individual hold periods were in the range of 1 minute to 10 hours. The fatigue tests were of tension-tension type defined by a stress ratio R = 0.027 and were conducted at temperature of 650 C. The tests were performed until fracture. The time to failure, the time to failure corresponding to total load at peak amplitude and the number of cycles to failure have been criteria to evaluate the deformation behaviour of the alloy subjected to complex cyclic creep loading. In order to predict lifetime of alloy, regarding the respective types cyclic test, the Kitagawa's modified the linear cumulative damage criterion has been considered. The two regression functions for applied hold period interval were proposed time to calculate the time to failure. The formulae can be used to predict the life of nickel base superalloy considering the specific conditions of low cycle fatigue with tensile hold period introduced at stress amplitude peaks. The failure analysis of fracture surfaces contributed to evaluation of the role of repeatedly reduced stress in damage process. (orig.)

  9. Life prediction of Ni-base superalloy

    Indian Academy of Sciences (India)

    mean stress exponent, n, and the mean activation energy for creep were calculated from the experimental results. The accelerated creep life of the alloy was evaluated by using iso-stress parametric equations and Monkman–Grant method. Keywords. ... This alloy is age-hardenable by a fine dispersion of γ par- ticles, which ...

  10. The effect of lattice misfit on the dislocation motion in superalloys during high-temperature low-stress creep

    International Nuclear Information System (INIS)

    Zhang, J.X.; Wang, J.C.; Harada, H.; Koizumi, Y.

    2005-01-01

    The development of dislocation configurations in two single-crystal superalloys during high-temperature low-stress creep (1100 deg C, 137 MPa) was investigated with the use of transmission electron microscopy. Detailed analysis showed that the lattice misfit has an important influence on the dislocation movement. For an alloy with a large negative lattice misfit, the dislocations are able to move smoothly by cross-slip in the horizontal γ channels. During subsequent formation of γ/γ' rafted structure, the dislocations on the surface of γ' cuboids rapidly re-orientate themselves from to direction and form a complete network. For an alloy with a small lattice misfit, the dislocations move by the combination of climbing and gliding processes, and the resultant γ/γ' interfacial dislocation network is incomplete. A good explanation of the creep curves is obtained from these differences in the microstructures

  11. On the Time-Temperature-Transformation Behavior of a New Dual-Superlattice Nickel-Based Superalloy

    Science.gov (United States)

    Mignanelli, P. M.; Jones, N. G.; Hardy, M. C.; Stone, H. J.

    2018-03-01

    Recent research has identified compositions of nickel-based superalloys with microstructures containing appreciable and comparable volume fractions of γ' and γ″ precipitates. In this work, an alloy capable of forming such a dual-superlattice microstructure was subjected to a range of thermal exposures between 873 K and 1173 K (600 °C and 900 °C) for durations of 1 to 1000 hours. The microstructures and nature of the precipitating phases were characterized using synchrotron X-ray diffraction and electron microscopy. These data have enabled the construction of a T-T-T diagram for the precipitating phases. Hardness measurements following each thermal exposure have identified the age-hardening behavior of this alloy and allowed preliminary mechanical properties to be assessed.

  12. Modeling Long-term Creep Performance for Welded Nickel-base Superalloy Structures for Power Generation Systems

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Chen

    2015-01-01

    We report here a constitutive model for predicting long-term creep strain evolution in’ strengthened Ni-base superalloys. Dislocation climb-bypassing’, typical in intermediate’ volume fraction (~20%) alloys, is considered as the primary deformation mechanism. Dislocation shearing’ to anti-phase boundary (APB) faults and diffusional creep are also considered for high-stress and high-temperature low-stress conditions, respectively. Additional damage mechanism is taken into account for rapid increase in tertiary creep strain. The model has been applied to Alloy 282, and calibrated in a temperature range of 1375-1450°F, and stress range of 15-45ksi. The model parameters and a MATLAB code are provided. This report is prepared by Monica Soare and Chen Shen at GE Global Research. Technical discussions with Dr. Vito Cedro are greatly appreciated. This work was supported by DOE program DE-FE0005859

  13. Gamma prime precipitation modeling and strength responses in powder metallurgy superalloys

    Science.gov (United States)

    Mao, Jian

    Precipitation-hardened nickel-based superalloys have been widely used as high temperature structural materials in gas turbine engine applications for more than 50 years. Powder metallurgy (P/M) technology was introduced as an innovative manufacturing process to overcome severe segregation and poor workability of alloys with high alloying contents. The excellent mechanical properties of P/M superalloys also depend upon the characteristic microstructures, including grain size and size distribution of gamma' precipitates. Heat treatment is the most critical processing step that has ultimate influences on the microstructure, and hence, on the mechanical properties of the materials. The main objective of this research was to study the gamma ' precipitation kinetics in various cooling circumstances and also study the strength response to the cooling history in two model alloys, Rne88DT and U720LI. The research is summarized below: (1) An experimental method was developed to allow accurate simulation and control of any desired cooling profile. Two novel cooling methods were introduced: continuous cooling and interrupt cooling. Isothermal aging was also carried out. (2) The growth and coarsening kinetics of the cooling gamma' precipitates were experimentally studied under different cooling and aging conditions, and the empirical equations were established. It was found that the cooling gamma' precipitate versus the cooling rate follows a power law. The gamma' precipitate size versus aging time obeys the LSW cube law for coarsening. (3) The strengthening of the material responses to the cooling rate and the decreasing temperature during cooling was investigated in both alloys. The tensile strength increases with the cooling rate. In addition, the non-monotonic response of strength versus interrupt temperature is of great interest. (4) An energy-driven model integrated with the classic growth and coarsen theories was successfully embedded in a computer program developed to

  14. Coupling effects of tungsten and molybdenum on microstructure and stress-rupture properties of a nickel-base cast superalloy

    Directory of Open Access Journals (Sweden)

    Tongjin Zhou

    2018-02-01

    Full Text Available In order to comprehensively understand the forming mechanism of abnormal phases solidified in a nickel-base cast superalloy with additives of tungsten and molybdenum, the coupling effects of W and Mo on the microstructure and stress-rupture properties were investigated in this paper. The results indicated that the precipitation of primary α-(W, Mo phase depended tremendously on the amount of W and Mo addition. When the total amount of W and Mo was greater than 5.79 at%, α-(W, Mo phase became easily precipitated in the alloy. With increasing of Mo/W ratio, the dendrite-like α-(W, Mo phases were apt to convert into small bars or blocky-like phases at the vicinities of γ′/γ eutectic. The morphological changes of α-(W, Mo phase can be interpreted as the non-equilibrium solidification of W and Mo in the alloy. Since the large sized α-(W, Mo phase has detrimental effects on stress-rupture properties in as-cast conditions, secondary cracks may mainly initiate at and then propagate along the interfaces of brittle phases and soft matrix. During exposing at 1100 ℃ for 1000 h, the α-(W, Mo phases transformed gradually into bigger and harder M6C carbide, which results in decreasing of stress-rupture properties of the alloy. Finally, the alloy with an addition of 14W-1Mo(wt% maintained the longest stress lives at high temperatures and therefore it revealed the best microstructure stability after 1100 ℃/1000 h thermal exposure. Keywords: Superalloy, Tungsten and molybdenum, Cast, Microstructure, Stress-rupture properties

  15. Improved creep strength of nickel-base superalloys by optimized γ/γ′ partitioning behavior of solid solution strengthening elements

    International Nuclear Information System (INIS)

    Pröbstle, M.; Neumeier, S.; Feldner, P.; Rettig, R.; Helmer, H.E.; Singer, R.F.; Göken, M.

    2016-01-01

    Solid solution strengthening of the γ matrix is one key factor for improving the creep strength of single crystal nickel-base superalloys at high temperatures. Therefore a strong partitioning of solid solution hardening elements to the matrix is beneficial for high temperature creep strength. Different Rhenium-free alloys which are derived from CMSX-4 are investigated. The alloys have been characterized regarding microstructure, phase compositions as well as creep strength. It is found that increasing the Titanium (Ti) as well as the Tungsten (W) content causes a stronger partitioning of the solid solution strengtheners, in particular W, to the γ phase. As a result the creep resistance is significantly improved. Based on these ideas, a Rhenium-free alloy with an optimized chemistry regarding the partitioning behavior of W is developed and validated in the present study. It shows comparable creep strength to the Rhenium containing second generation alloy CMSX-4 in the high temperature / low stress creep regime and is less prone to the formation of deleterious topologically close packed (TCP) phases. This more effective usage of solid solution strengtheners can enhance the creep properties of nickel-base superalloys while reducing the content of strategic elements like Rhenium.

  16. First approach for thermodynamic modelling of the high temperature oxidation behaviour of ternary γ′-strengthened Co–Al–W superalloys

    International Nuclear Information System (INIS)

    Klein, L.; Zendegani, A.; Palumbo, M.; Fries, S.G.; Virtanen, S.

    2014-01-01

    Highlights: • Thermodynamic modelling of the oxidation behaviour of a novel Co-base superalloy. • Calculated oxide layer sequence is in good agreement with formed oxide scales. • Prediction of an optimised alloy composition with increased phase stability. • Prediction of the influence of oxygen partial pressure on Al 2 O 3 formation. - Abstract: In the present work, thermodynamic modelling of the high temperature oxidation behaviour of a γ′-strengthened Co-base superalloy is presented. The ternary Co–9Al–9W alloy (values in at%) was isothermally oxidised for 500 h at 800 and 900 °C in air. Results reveal that the calculated oxide layer sequence (Thermo-Calc, TCNI6) is in good agreement with the formed oxide scales on the alloy surface. Furthermore, prediction of the influence of oxygen partial pressure on Al 2 O 3 formation is presented. The modelling results indicate pathways for alloy development or possible pre-oxidation surface treatments for improved oxidation resistance of the material

  17. Effect of carbon additions on the as-cast microstructure and defect formation of a single crystal Ni-based superalloy

    International Nuclear Information System (INIS)

    Al-Jarba, K.A.; Fuchs, G.E.

    2004-01-01

    In an effort to reduce grain defects in large single crystal Ni-base superalloy components, carbon is intentionally added. In this study, the effect of carbon additions on the microstructure and solidification defect formation of a model Ni-based superalloy, LMSX-1, was examined. The results show that the tendency of the alloy to form all types of solidification defects decreased as the carbon content increased. The as-cast microstructures also exhibited a decrease in the amount of γ-γ' eutectic structure and an increase in the volume fraction of carbides and porosity, as the carbon content was increased. The carbides formed in these alloys were mostly of script-type MC carbides which formed continuous, dendritic networks in the interdendritic region. Microprobe analysis of the as-cast structures showed that the partitioning coefficients did not change with carbon additions. Therefore, the reduction in defect formation with increasing carbon content could not be attributed to changes in segregation behavior of alloying elements. Instead, the presence of these carbides in the interdendritic regions of the alloy appeared to have prevented the thermosolutal fluid flow

  18. Relationship of heat treatment-mechanical properties of nickel base superalloys.; Relacion tratamiento termico-propiedades mecanicas de una superaleacion base niquel.

    Energy Technology Data Exchange (ETDEWEB)

    Zamora R, L

    1997-12-01

    The nickel-base superalloys have high strength, excellent corrosion resistant, and good creep and fatigue resistance. These alloy improved properties at high temperature derive their mechanical and creep behavior on {gamma} precipitate morphology, and the evolution of such morphology during different heat treatment conditions. The main microstructural variable of Nickel-based superalloys, responsible for the mechanical properties are: (a) amount and morphology of precipitates; (b) size and shape of grains; and (c) carbide distribution. In this work, a Nickel-base superalloy Nimonic 80A, modified little with Zr prepared by melting and casting practices of materials electrolytic in vacuum-induction melting (VIM) type Balzers, to obtain five alloys different and ingots of 2 Kg and 1 Kg, with composition in weight % of Nimonic 80-A is: Ni = bal (76.66), C = 0.01, Cr = 19.83, Fe = 2.4, Mn = 0.17, Si 0.47, Al = 0.19, Zr = 0.4. The solidification process is made in a steel mold. After having realized four thermal treatments, the most representative microstructures there were obtained. The results from tensile tests performed on Instron Servohydraulic testing systems at uniaxial dynamic testing, at constant speeds to ,0.2 cm/min, were: the yield strength, the ultimate strength value, percentage elongation and area reduction. Creep tests were performed at in stress of 90 and 129 MPa, at a temperature of 600 and 680 Centigrades at different times and width of specimen of 1 mm. The alloys were analyzed by MEB(JEOL 35CF) at different magnifications. The nucleation and growth of intergranular cavities during creep of alloy Nimonic M3, were investigated. One sample was deformed in creep at 129 MPa and 680 Centigrades during 110 hs. Creep samples were annealing heat treated at 800 Centigrades, during 7 days. After a careful sample preparation procedure, 3100 of cavities were measured in the sample . The cavity size distributions in the sample were obtained. (Abstract Truncated)

  19. Microstructural, mechanical and weldability assessments of the dissimilar welds between γ′- and γ″-strengthened nickel-base superalloys

    Energy Technology Data Exchange (ETDEWEB)

    Naffakh Moosavy, Homam, E-mail: homam_naffakh@iust.ac.ir [School of Metallurgy and Materials Engineering, Iran University of Science and Technology (IUST), Tehran 16846-13114 (Iran, Islamic Republic of); Aboutalebi, Mohammad-Reza; Seyedein, Seyed Hossein [School of Metallurgy and Materials Engineering, Iran University of Science and Technology (IUST), Tehran 16846-13114 (Iran, Islamic Republic of); Mapelli, Carlo [Dipartimento di Meccanica, Politecnico di Milano, Via La Massa 34, Milan 20156 (Italy)

    2013-08-15

    Dissimilar welding of γ′- and γ″-strengthened nickel-base superalloys has been investigated to identify the relationship between the microstructure of the welds and the resultant mechanical and weldability characteristics. γ′-Strengthened nickel-base Alloy 500 and γ″-strengthened nickel-base Alloy 718 were used for dissimilar welding. Gas tungsten arc welding operations were utilized for performing the autogenous dissimilar welding. Alloy 500 and Alloy 718 base metals showed various types of phases, carbides, intermetallics and eutectics in their microstructure. The results for Alloy 500 weld metal showed severe segregation of titanium to the interdendritic regions. The Alloy 718 weld metal compositional analysis confirmed the substantial role of Nb in the formation of low-melting eutectic-type morphologies which can reduce the weldability. The microstructure of dissimilar weld metal with dilution level of 65% wt.% displayed semi-developed dendritic structure. The less segregation and less formation of low-melting eutectic structures caused to less susceptibility of the dissimilar weld metal to the solidification cracking. This result was confirmed by analytic modeling achievements. Dissolution of γ″-Ni{sub 3}Nb precipitations took place in the Alloy 718 heat-affected zone leading to sharp decline of the microhardness in this region. Remelted and resolidified regions were observed in the partially-melted zone of Alloy 500 and Alloy 718. Nevertheless, no solidification and liquation cracking happened in the dissimilar welds. Finally, this was concluded that dissimilar welding of γ′- and γ″-strengthened nickel-base superalloys can successfully be performed. - Highlights: • Dissimilar welding of γ′- and γ″-strengthened nickel-base superalloys is studied. • Microstructural, mechanical and weldability aspects of the welds are assessed. • Microstructure of welds, bases and heat-affected zones is characterized in detail. • The type

  20. Preparation of Inconel 740 superalloy by electron beam smelting

    Energy Technology Data Exchange (ETDEWEB)

    You, Xiaogang [School of Materials Science and Engineering, Dalian University of Technology, Dalian 116023 (China); Laboratory for New Energy Material Energetic Beam Metallurgical Equipment Engineering of Liaoning Province, Dalian 116024 (China); Tan, Yi, E-mail: tanyi@dlut.edu.cn [School of Materials Science and Engineering, Dalian University of Technology, Dalian 116023 (China); Laboratory for New Energy Material Energetic Beam Metallurgical Equipment Engineering of Liaoning Province, Dalian 116024 (China); You, Qifan; Shi, Shuang; Li, Jiayan [School of Materials Science and Engineering, Dalian University of Technology, Dalian 116023 (China); Laboratory for New Energy Material Energetic Beam Metallurgical Equipment Engineering of Liaoning Province, Dalian 116024 (China); Ye, Fei [School of Materials Science and Engineering, Dalian University of Technology, Dalian 116023 (China); Wei, Xin [School of Materials Science and Engineering, Dalian University of Technology, Dalian 116023 (China); Laboratory for New Energy Material Energetic Beam Metallurgical Equipment Engineering of Liaoning Province, Dalian 116024 (China)

    2016-08-15

    A novel method, namely electron beam smelting (EBS) technology was used to prepare the Inconel 740 superalloy. The microstructures, hardness and oxidation behavior were characterized and compared with the traditionally prepared Inconel 740 superalloy. The results imply that the solution treatment gives rise to the coarsening of γ′ precipitates, with further aging treatment, the γ′ precipitates with size of less than 30 nm are distributed dispersively in the matrix, leading to a decreasing of the lattice parameters and an increasing of the misfit. The γ′ precipitates result in shearing mechanism of weakly pair coupling. The EBS 740 superalloy produces better properties than that prepared in the traditional method in both precipitation strengthening effect and oxidation resistance. - Highlights: • Electron beam smelting, a new method, was used to prepare the Inconel 740 superalloy. • The EBS 740 shows higher strengthening effect than 740 made in traditional method. • The EBS 740 shows better oxidation resistance than traditional 740. • It shows application prospect of EBS technology in preparing Ni-base superalloys.

  1. 3D digital image correlation investigation of PLC effect in a new Ni-Co base superalloy

    Science.gov (United States)

    Gao, Y.; Fu, S. H.; Cheng, T.; Huo, X.; Zhang, Q. C.

    2013-06-01

    Repeated plastic instability accompanying serrated yielding in stress-strain curves and localization of deformation is observed during plastic deformation of many metallic alloys when tensile specimens are deformed under certain experimental conditions of temperature, strain rate, and pre-deformation. This phenomenon is referred to as the Portevin- Le Chatelier (PLC) effect. TMW alloy, a newly developed Ni-Co base superalloy for aircraft engine application, also exhibit PLC effect during tensile test at temperatures ranging from 300 ° to 600 °, which are also the temperature range for engine working. In this paper, a 3D digital image correlation (3D DIC) measurement system was established to observe the localization of deformation (PLC band) in a tensile test performed on TMW alloy specimen at temperature of 400 °. The 3D DIC system, with displacement measurement accuracy up to 0.01 pixels and strain measurement accuracy up to 100 μɛ, has a high performance in displacement field calculation with more than 10000 points every second on a 3.1G Hz CPU computer. The test result shows that, the PLC bands are inclined at an angle of about 60° to the tensile axis. Unlike tensile test performed on aluminums alloy, the widths of PLC bands of TMW alloy specimen, ranging from 4 mm to 4.5 mm, are much greater than the specimen thickness (0.25 mm).

  2. Solute transport during the cyclic oxidation of Ni-Cr-Al alloys. M.S. Thesis

    Science.gov (United States)

    Nesbitt, J. A.

    1982-01-01

    Important requirements for protective coatings of Ni-Cr-Al alloys for gas turbine superalloys are resistance to oxidation accompanied by thermal cycling, resistance to thermal fatigue cracking. The resistance to oxidation accompanied by thermal cycling is discussed. The resistance to thermal fatigue cracking is also considered.

  3. Mechanical properties of modified low cobalt powder metallurgy Udimet 700 type alloys

    Science.gov (United States)

    Harf, Fredric H.

    1989-01-01

    Eight superalloys derived from Udimet 700 were prepared by powder metallurgy, hot isostatically pressed, heat treated and their tensile and creep rupture properties determined. Several of these alloys displayed properties superior to those of Udimet 700 similarly prepared, in one case exceeding the creep rupture life tenfold. Filter clogging by extracted gamma prime, its measurement and significance are discussed in an appendix.

  4. High Velocity Oxidation and Hot Corrosion Resistance of Some ODS Alloys

    Science.gov (United States)

    Lowell, C. E.; Deadmore, D. L.

    1977-01-01

    Several oxide dispersion strengthened (ODS) alloys were tested for cyclic, high velocity, oxidation, and hot corrosion resistance. These results were compared to the resistance of an advanced, NiCrAl coated superalloy. An ODS FeCrAl were identified as having sufficient oxidation and hot corrosion resistance to allow potential use in an aircraft gas turbine without coating.

  5. Employing various metallography methods at high temperature alloy fatigue tests evaluation

    Directory of Open Access Journals (Sweden)

    Juraj Belan

    2016-12-01

    Full Text Available . Microstructures of superalloys have dramatically changed throughout the years, as modern technology of its casting or forging has become more sophisticated. The first superalloys have polyedric microstructure consisting of gamma solid solution, some fraction of gamma prime and of course grain boundaries. As demands on higher performance of aero jet engine increases, the changes in superalloys microstructure become more significant. A further step in microstructure evolution was directionally solidified alloys with columnar gamma prime particles. The latest microstructures are mostly monocrystalline, oriented in [001] direction of FCC gamma matrix. All microstructure changes bring necessity of proper preparation and evaluation of microstructure. Except for the already mentioned structures have gamma double prime and various carbides form can be seen. These structural parameters have mainly positive influence on important mechanical properties of superalloys. The paper deals with a microstructural evaluation of both groups of alloys – cast and as well as wrought. Microstructure evaluation helps to describe mechanism at various loading and failure of progressive superalloys. Such an example where microstructure evaluation is employed is fractography of failure surfaces after fatigue tests, which are examples of metallography evaluation described in this paper as a secondary objective.

  6. Studies on phase kinetics of new superalloys

    International Nuclear Information System (INIS)

    Weisbrodt, A.; Penkalla, H.J.; Schubert, F.; Nickel, H.

    1990-08-01

    At the development of new ODS (Oxide-Dispersion-Strengthened) alloys for components being exposed to hot-gas temperatures nickel-base alloys and ODS alloys have been investigated. The experimental work mainly referred to phase investigations of thermally loaded samples. The addition of alloying elements will have a decisive influence on the γ'-phase fraction, γ'-lattice parameter, the morphology as well as the coarsening behaviour of the γ'-phase under temperature load. The main characteristics of ODS alloys are Y,Al-mixed oxides and microstructural inhomogenities. As for MA6000 a Time-Temperature-Precipitation diagram has been elaborated. By means of the improved computer programme PHASCALC for phase and N v (= average electron vacancy concentration) - value calculation many microstructural parameters such as the γ/γ'-misfit, the solution of the γ'-phase and melting temperatures can be determined. Tensile tests made at temperatures above 900deg C have shown that the strengthening parameters are dependent on alloy composition, temperature conditions, γ'-phase fraction and oxide dispersion content. (orig.) [de

  7. Elastic Properties of Novel Co- and CoNi-Based Superalloys Determined through Bayesian Inference and Resonant Ultrasound Spectroscopy

    Science.gov (United States)

    Goodlet, Brent R.; Mills, Leah; Bales, Ben; Charpagne, Marie-Agathe; Murray, Sean P.; Lenthe, William C.; Petzold, Linda; Pollock, Tresa M.

    2018-06-01

    Bayesian inference is employed to precisely evaluate single crystal elastic properties of novel γ -γ ' Co- and CoNi-based superalloys from simple and non-destructive resonant ultrasound spectroscopy (RUS) measurements. Nine alloys from three Co-, CoNi-, and Ni-based alloy classes were evaluated in the fully aged condition, with one alloy per class also evaluated in the solution heat-treated condition. Comparisons are made between the elastic properties of the three alloy classes and among the alloys of a single class, with the following trends observed. A monotonic rise in the c_{44} (shear) elastic constant by a total of 12 pct is observed between the three alloy classes as Co is substituted for Ni. Elastic anisotropy ( A) is also increased, with a large majority of the nearly 13 pct increase occurring after Co becomes the dominant constituent. Together the five CoNi alloys, with Co:Ni ratios from 1:1 to 1.5:1, exhibited remarkably similar properties with an average A 1.8 pct greater than the Ni-based alloy CMSX-4. Custom code demonstrating a substantial advance over previously reported methods for RUS inversion is also reported here for the first time. CmdStan-RUS is built upon the open-source probabilistic programing language of Stan and formulates the inverse problem using Bayesian methods. Bayesian posterior distributions are efficiently computed with Hamiltonian Monte Carlo (HMC), while initial parameterization is randomly generated from weakly informative prior distributions. Remarkably robust convergence behavior is demonstrated across multiple independent HMC chains in spite of initial parameterization often very far from actual parameter values. Experimental procedures are substantially simplified by allowing any arbitrary misorientation between the specimen and crystal axes, as elastic properties and misorientation are estimated simultaneously.

  8. Quantitative characterization and comparison of precipitate and grain shape in Nickel -base superalloys using moment invariants

    Science.gov (United States)

    Callahan, Patrick Gregory

    A fundamental objective of materials science and engineering is to understand the structure-property-processing-performance relationship. We need to know the true 3-D microstructure of a material to understand certain geometric properties of a material, and thus fulfill this objective. Focused ion beam (FIB) serial sectioning allows us to find the true 3-D microstructure of Ni-base superalloys. Once the true 3-D microstructure is obtained, an accurate quantitative description and characterization of precipitate and/or grain shapes is needed to understand the microstructure and describe it in an unbiased way. In this thesis, second order moment invariants, the shape quotient Q, a convexity measure relating the volume of an object to the volume of its convex hull, V/Vconv, and Gaussian curvature have been used to compare an experimentally observed polycrystalline IN100 microstructure to three synthetic microstructures. The three synthetic microstructures used different shape classes to produce starting grain shapes. The three shape classes are ellipsoids, superellipsoids, and the shapes generated when truncating a cube with an octahedron. The microstructures are compared using a distance measure, the Hellinger distance. The Hellinger distance is used to compare distributions of shape descriptors for the grains in each microstructure. The synthetic microstructure that has the smallest Hellinger distance, and so best matched the experimentally observed microstructure is the microstructure that used superellipsoids as a starting grain shape. While it has the smallest Hellinger distance, and is approaching realistic grain morphologies, the superellipsoidal microstructure is still not realistic. Second order moment invariants, Q, and V/V conv have also been used to characterize the γ' precipitate shapes from four experimental Ru-containing Ni-base superalloys with differences in alloying additions. The superalloys are designated UM-F9, UM-F18, UM-F19, and UM-F22. The

  9. Mathematical modelling of brittle phase precipitation in complex ruthenium containing nickel-based superalloys

    International Nuclear Information System (INIS)

    Rettig, Ralf

    2010-01-01

    A new model has been developed in this work which is capable of simulating the precipitation kinetics of brittle phases, especially TCP-phases (topologically close packed phases) in ruthenium containing superalloys. The model simultaneously simulates the nucleation and the growth stage of precipitation for any number of precipitating phases. The CALPHAD method (Calculation of Phase Diagrams) is employed to calculate thermodynamic properties, such as the driving force or phase compositions in equilibrium. For calculation of diffusion coefficients, kinetic mobility databases which are also based on the CALPHAD-method are used. The model is fully capable of handling multicomponent effects, which are common in complex superalloys. Metastable phases can be treated and will automatically be dissolved if they get unstable. As the model is based on the general CALPHAD method, it can be applied to a broad range of precipitation processes in different alloys as long as the relevant thermodynamic and kinetic databases are available. The developed model proves that the TCP-phases precipitate in a sequence of phases. The first phase that is often formed is the metastable σ-phase because it has the lowest interface energy due to low-energy planes at the interface between matrix and precipitate. After several hundred hours the stable μ- and P-phases start to precipitate by nucleating at the σ-phase which is energetically favourable. During the growth of these stable phases the sigma-phase is continuously dissolved. It can be shown by thermodynamic CALPHAD calculations that the sigma-phase has a lower Gibbs free enthalpy than the μ- and P-phase. All required parameters of the model, such as interface energy and nucleate densities, have been estimated. The mechanisms of suppression of TCP-phase precipitation in the presence of ruthenium in superalloys were investigated with the newly developed model. It is shown by the simulations that ruthenium mostly affects the nucleation

  10. Boride particles in a powder metallurgy superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Witt, M C; Charles, J A

    1985-12-01

    Using optical and electron metallography, the composition, morphology, and distribution of M/sub 3/B/sub 2/ borides in as-hipped (hot isostatically pressed) samples of the powder metallurgy superalloy Nimonic AP1 have been determined. Two types of boride are present depending on the HIP temperature. Hipping below the boride solvus results in low-aspect ratio particles, distributed both inter- and intragranularly. Hipping above the boride solvus produces high-aspect ratio particles which are exclusively intergranular. A small difference in both lattice parameter and composition has been measured. Electron energy loss spectroscopy of the particles has confirmed the presence of boron, and laser ion-induced mass analysis has indicated a low carbon level. The higher susceptibility to edge cracking during forging of material hipped above the boride solvus is related to the boride morphology. Studies of the subsequent recrystallization of the forged samples have indicated that necklace formation is neither inhibited nor accelerated by the presence of grain boundary borides. 18 references.

  11. Microstructures and oxidation behavior of some Molybdenum based alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ray, Pratik Kumar [Iowa State Univ., Ames, IA (United States)

    2011-01-01

    The advent of Ni based superalloys revolutionized the high temperature alloy industry. These materials are capable of operating in extremely harsh environments, comprising of temperatures around 1050 C, under oxidative conditions. Demands for increased fuel efficiency, however, has highlighted the need for materials that can be used under oxidative conditions at temperatures in excess of 1200 C. The Ni based superalloys are restricted to lower temperatures due to the presence of a number of low melting phases that melt in the 1250 - 1450 C, resulting in softening of the alloys above 1000 C. Therefore, recent research directions have been skewed towards exploring and developing newer alloy systems. This thesis comprises a part of such an effort. Techniques for rapid thermodynamic assessments were developed and applied to two different systems - Mo-Si alloys with transition metal substitutions (and this forms the first part of the thesis) and Ni-Al alloys with added components for providing high temperature strength and ductility. A hierarchical approach towards alloy design indicated the Mo-Ni-Al system as a prospective candidate for high temperature applications. Investigations on microstructures and oxidation behavior, under both isothermal and cyclic conditions, of these alloys constitute the second part of this thesis. It was seen that refractory metal systems show a marked microstructure dependence of oxidation.

  12. Hot corrosion behavior of Ni based Inconel 617 and Inconel 738 superalloys

    Energy Technology Data Exchange (ETDEWEB)

    El-Awadi, G.A., E-mail: gaberelawdi@yahoo.com [Atomic Energy Authority, NRC, Cyclotron Project, Abo-zabal, 13759 Cairo (Egypt); Abdel-Samad, S., E-mail: salem_abdelsamad@yahoo.com [Atomic Energy Authority, NRC, Cyclotron Project, Abo-zabal, 13759 Cairo (Egypt); Elshazly, Ezzat S. [Atomic Energy Authority, NRC, Metallurgy Dept., Abo-zabal, 13759 Cairo (Egypt)

    2016-08-15

    Highlights: • Supperalloy good resistance to high temperature oxidation. • Ni-base alloy IN738 and Inconel 617 good resistance to hot corrosion. • Corrosion resistance of supperalloys depending on environment of abrasive ions such as (NaCl or NaSO{sub 4}). • Hot corrosion resistance depend on what the oxides phases where formed. - Abstract: Superalloys are extensively used at high temperature applications due to their good oxidation and corrosion resistance properties in addition to their high stability were made at high temperature. Experimental measurements of hot corrosion at high temperature of Inconel 617 and Inconel 738 superalloys. The experiments were carried out at temperatures 700 °C, 800 °C and 900 °C for different exposure times to up to 100 h. The corrosive media was NaCl and Na{sub 2}SO{sub 4} sprayed on the specimens. Seven different specimens were used at each temperature. The corrosion process is endothermic and the spontaneity increased by increasing temperature. The activation energy was found to be Ea = 23.54 and E{sub a} = 25.18 KJ/mol for Inconel 738 and Inconel 617 respectively. X-ray diffraction technique (XRD) was used to analyze the formed scale. The morphology of the specimen and scale were examined by scanning electron microscopy (SEM). The results show that the major corrosion products formed were NiCr{sub 2}O{sub 4}, and Co Cr{sub 2}O{sub 4} spinles, in addition to Cr{sub 2}O{sub 3}.

  13. High temperature corrosion kinetics study of IN-657 and HK-40 superalloys in contact with an 82% K[sub 2]S[sub 2]O[sub 7]-18% V[sub 2]O[sub 5] eutectic melt. Estudio de la cinetica de corrosion a alta temperatura de las superaleaciones IN-657 y HK-40 en presencia de la mezcla eutectica fundida 82% K[sub 2]S[sub 2]O[sub 7]-18% V[sub 2]O[sub 5

    Energy Technology Data Exchange (ETDEWEB)

    Pardo, A.; Otero, E.; Perez, F.J.; Alvarez, J.F.; Utrilla, M. V. (Universidad Complutense de Madrid (Spain). Facultad de Ciencias Quimicas)

    1993-01-01

    Electrochemical methods are used to study the corrosion kinetics of the IN-657 and HK-40 super-alloys in contact with the eutectic melt 82% K[sub 2]S[sub 2]O[sub 7]-18% V[sub 2]O[sub 5] with different carbon contents and at different temperatures (773 and 823 K). The results obtained are discussed in relation with the chemistry of the process. The kinetics equations of the corrosion process are given to the two super-alloys studied and at different test conditions. (Author) 18 refs.

  14. Influence of γ' precipitates on Portevin–Le Chatelier effect of Ni-based superalloys

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Yulong [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); CAS Key Laboratory of Mechanical Behavior and Design of Materials, University of Science and Technology of China, Hefei 230027 (China); Tian, Chenggang [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Fu, Shihua, E-mail: fushihua@ustc.edu.cn [CAS Key Laboratory of Mechanical Behavior and Design of Materials, University of Science and Technology of China, Hefei 230027 (China); Han, Guoming [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Cui, Chuanyong, E-mail: chycui@imr.ac.cn [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Zhang, Qingchuan, E-mail: zhangqc@ustc.edu.cn [CAS Key Laboratory of Mechanical Behavior and Design of Materials, University of Science and Technology of China, Hefei 230027 (China)

    2015-06-25

    The γ′ precipitate plays a critical role in improving the mechanical properties of Ni-based superalloys. An undesirable phenomenon referred to as the Portevin–Le Chatelier (PLC) effect always appears in Ni-based superalloys deformed within specific ranges of strain rate and temperature. In order to systematically investigate the influence of the γ′ precipitates on the PLC effect, four Ni-based superalloys with various γ′ contents were designed and fabricated. Microscopic observations from transmission electron microscopy (TEM) indicated that the volume fraction of the γ′ phase was consistent with the designed value. Furthermore, analysis of energy dispersive spectroscopy (EDS) results revealed that the γ matrix of all the alloys consisted of the same components. Uniaxial tensile tests were performed at strain rates and temperatures ranging from 1×10{sup −4} to 3×10{sup −3} s{sup −1} and 300–500 °C, respectively. We found that the ultimate strength increased while the elongation decreased with increasing γ′ content. In addition, the serration changed from type A to type B and to type C with increasing temperature, decreasing strain rate or increasing γ′ content; the amplitude of type B serrations was described by unimodal or bimodal distributions. Increasing volume fraction of γ′ precipitates shifted the region in which the PLC effect occurred, to the range of low temperatures and high strain rates. Moreover, the serration amplitude increased with increasing γ′ content at a given temperature, which indicated that the γ′ precipitate increases the dynamic strain ageing (DSA) effect.

  15. The role of particle ripening on the creep acceleration of Nimonic 263 superalloy

    Directory of Open Access Journals (Sweden)

    Angella Giuliano

    2014-01-01

    Full Text Available Physically based constitutive equations need to incorporate the most relevant microstructural features of materials to adequately describe their mechanical behaviour. To accurately model the creep behaviour of precipitation hardened alloys, the value and the evolution of strengthening particle size are important parameters to be taken into account. In the present work, creep tests have been run on virgin and overaged (up to 3500 h at 800 ∘C Nimonic 263, a polycrystalline nickel base superalloy used for combustion chambers of gas turbines. The experimental results suggest that the reinforcing particle evolution is not the main reason for the creep acceleration that seems to be better described by a strain correlated damage, such as the accumulation of mobile dislocations or the grain boundary cavitation. The coarsened microstructure, obtained by overageing the alloy at high temperature before creep testing, mainly influences the initial stage of the creep, resulting in a higher minimum creep rate and a corresponding reduction of the creep resistance.

  16. High temperature low cycle fatigue behavior of a directionally solidified Ni-base superalloy DZ951

    International Nuclear Information System (INIS)

    Chu Zhaokuang; Yu Jinjiang; Sun Xiaofeng; Guan Hengrong; Hu Zhuangqi

    2008-01-01

    Total strain-controlled low cycle fatigue (LCF) tests were performed at a temperature range from 700 to 900 deg. C in ambient air condition on a directionally solidified Ni-base superalloy DZ951. The fatigue life of DZ951 alloy does not monotonously decrease with increasing temperature, but exhibits a strong dependence on the total strain range. The dislocation characteristics and failed surface observation were evaluated through transmission electron microscopy and scanning electron microscopy. The alloy exhibits cyclic hardening, softening or cyclic stability as a whole, which is dependent on the testing temperature and total strain range. At 700 deg. C, the cyclic plastic deformation process is the main cause of fatigue failure. At 900 deg. C, the failure mostly results from combined fatigue and creep damage under total strain range from 0.6 to 1.2% and the reduction in fatigue life can be taken as the cause of oxidation, creep and cyclic plastic deformation under total strain range of 0.5%

  17. Creep lifing methodologies applied to a single crystal superalloy by use of small scale test techniques

    Energy Technology Data Exchange (ETDEWEB)

    Jeffs, S.P., E-mail: s.p.jeffs@swansea.ac.uk [Institute of Structural Materials, Swansea University, Singleton Park SA2 8PP (United Kingdom); Lancaster, R.J. [Institute of Structural Materials, Swansea University, Singleton Park SA2 8PP (United Kingdom); Garcia, T.E. [IUTA (University Institute of Industrial Technology of Asturias), University of Oviedo, Edificio Departamental Oeste 7.1.17, Campus Universitario, 33203 Gijón (Spain)

    2015-06-11

    In recent years, advances in creep data interpretation have been achieved either by modified Monkman–Grant relationships or through the more contemporary Wilshire equations, which offer the opportunity of predicting long term behaviour extrapolated from short term results. Long term lifing techniques prove extremely useful in creep dominated applications, such as in the power generation industry and in particular nuclear where large static loads are applied, equally a reduction in lead time for new alloy implementation within the industry is critical. The latter requirement brings about the utilisation of the small punch (SP) creep test, a widely recognised approach for obtaining useful mechanical property information from limited material volumes, as is typically the case with novel alloy development and for any in-situ mechanical testing that may be required. The ability to correlate SP creep results with uniaxial data is vital when considering the benefits of the technique. As such an equation has been developed, known as the k{sub SP} method, which has been proven to be an effective tool across several material systems. The current work now explores the application of the aforementioned empirical approaches to correlate small punch creep data obtained on a single crystal superalloy over a range of elevated temperatures. Finite element modelling through ABAQUS software based on the uniaxial creep data has also been implemented to characterise the SP deformation and help corroborate the experimental results.

  18. Creep lifing methodologies applied to a single crystal superalloy by use of small scale test techniques

    International Nuclear Information System (INIS)

    Jeffs, S.P.; Lancaster, R.J.; Garcia, T.E.

    2015-01-01

    In recent years, advances in creep data interpretation have been achieved either by modified Monkman–Grant relationships or through the more contemporary Wilshire equations, which offer the opportunity of predicting long term behaviour extrapolated from short term results. Long term lifing techniques prove extremely useful in creep dominated applications, such as in the power generation industry and in particular nuclear where large static loads are applied, equally a reduction in lead time for new alloy implementation within the industry is critical. The latter requirement brings about the utilisation of the small punch (SP) creep test, a widely recognised approach for obtaining useful mechanical property information from limited material volumes, as is typically the case with novel alloy development and for any in-situ mechanical testing that may be required. The ability to correlate SP creep results with uniaxial data is vital when considering the benefits of the technique. As such an equation has been developed, known as the k SP method, which has been proven to be an effective tool across several material systems. The current work now explores the application of the aforementioned empirical approaches to correlate small punch creep data obtained on a single crystal superalloy over a range of elevated temperatures. Finite element modelling through ABAQUS software based on the uniaxial creep data has also been implemented to characterise the SP deformation and help corroborate the experimental results

  19. Thermo-mechanical Fatigue Failure of Thermal Barrier Coated Superalloy Specimen

    Science.gov (United States)

    Subramanian, Rajivgandhi; Mori, Yuzuru; Yamagishi, Satoshi; Okazaki, Masakazu

    2015-09-01

    Failure behavior of thermal barrier coated (TBC) Ni-based superalloy specimens were studied from the aspect of the effect of bond coat material behavior on low cycle fatigue (LCF) and thermo-mechanical fatigue (TMF) at various temperatures and under various loading conditions. Initially, monotonic tensile tests were carried out on a MCrAlY alloy bond coat material in the temperature range of 298 K to 1273 K (25 °C to 1000 °C). Special attention was paid to understand the ductile to brittle transition temperature (DBTT). Next, LCF and TMF tests were carried out on the thermal barrier coated Ni-based alloy IN738 specimen. After these tests, the specimens were sectioned to understand their failure mechanisms on the basis of DBTT of the bond coat material. Experimental results demonstrated that the LCF and TMF lives of the TBC specimen were closely related to the DBTT of the bond coat material, and also the TMF lives were different from those of LCF tests. It has also been observed that the crack density in the bond coat in the TBC specimen was significantly dependent on the test conditions. More importantly, not only the number of cracks but also the crack penetration probability into substrate were shown to be sensitive to the DBTT.

  20. Computer simulation of phase transformation and plastic deformation in IN718 superalloy: Microstructural evolution during precipitation

    International Nuclear Information System (INIS)

    Zhou, N.; Lv, D.C.; Zhang, H.L.; McAllister, D.; Zhang, F.; Mills, M.J.; Wang, Y.

    2014-01-01

    Microstructural evolution during co-precipitation of γ′, γ″ and δ phases from a supersaturated γ matrix during aging of superalloy Inconel 718 (IN718) is investigated by computer simulation using the phase-field method. The precipitation model is quantitative, using as model inputs ab initio calculations of elastic constants, experimental data on lattice parameters, precipitate–matrix orientation relationship, interfacial energy of each individual precipitate phase and interdiffusivities, and a Ni–Nb–Al pseudo-ternary thermodynamic database specifically developed for IN718. In order to simulate statistically representative multiphase microstructures observed in the alloy, the Kim–Kim–Suzuki treatment of interfaces is employed. Simulation results show how alloy composition, lattice misfit, external stress, temperature and time affect precipitate microstructure and variant selection during isothermal aging, without any a priori assumptions about key microstructural features including size, shape, volume fraction and spatial distribution of different types of precipitates and different variants of the same precipitate phase. The shapes of precipitates and their coarsening kinetics are analyzed based on the two-dimensional moment invariant. The various multiphase microstructures generated by the simulations have been used as model inputs in a study to investigate how precipitate microstructure (in particular shape and spatial distribution) influences the strength of IN718

  1. Microstructural stability and mechanical properties of a boron modified Ni–Fe based superalloy for steam boiler applications

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Changshuai, E-mail: cswang@imr.ac.cn; Guo, YongAn; Guo, Jianting; Zhou, Lanzhang, E-mail: lzz@imr.ac.cn

    2015-07-15

    Ni–Fe based superalloys are being considered as boiler materials in 700 °C advanced ultra-supercritical (A-USC) coal fired power plants due to their excellent oxidation and hot corrosion resistance, outstanding workability and low cost. In this paper, the microstructural stability and mechanical properties of a boron (B) modified Ni–Fe based superalloy designed for 700 °C A-USC during thermal exposure at 650–750 °C for up to 5000 h were investigated. The results show that adding boron has no apparent influence on the major precipitates, including spherical γ′ and blocky MC. However, the amount of M{sub 23}C{sub 6} decreases markedly after standard heat treatment. During long-term thermal exposure, the addition of boron has no influence on γ′ coarsening, η phase precipitation and primary MC degeneration, but decreases the growth rate of M{sub 23}C{sub 6} along grain boundary. The stress rupture life and ductility are obviously improved after the addition of B. Meanwhile, the yield strength of B-doped alloy almost keeps the same level as that without boron addition. The fracture surface characterization exhibits that the dimples increase significantly after adding boron. During long-term thermal exposure, the elongation of the alloy with B addition increases slightly, but, for the alloy without B addition, the elongation obviously increases. The improvement of the stress rupture life and ductility can be attributed to the increase of grain boundary strength and the optimization of M{sub 23}C{sub 6} carbide distribution at grain boundary.

  2. Microstructural stability and mechanical properties of a boron modified Ni–Fe based superalloy for steam boiler applications

    International Nuclear Information System (INIS)

    Wang, Changshuai; Guo, YongAn; Guo, Jianting; Zhou, Lanzhang

    2015-01-01

    Ni–Fe based superalloys are being considered as boiler materials in 700 °C advanced ultra-supercritical (A-USC) coal fired power plants due to their excellent oxidation and hot corrosion resistance, outstanding workability and low cost. In this paper, the microstructural stability and mechanical properties of a boron (B) modified Ni–Fe based superalloy designed for 700 °C A-USC during thermal exposure at 650–750 °C for up to 5000 h were investigated. The results show that adding boron has no apparent influence on the major precipitates, including spherical γ′ and blocky MC. However, the amount of M 23 C 6 decreases markedly after standard heat treatment. During long-term thermal exposure, the addition of boron has no influence on γ′ coarsening, η phase precipitation and primary MC degeneration, but decreases the growth rate of M 23 C 6 along grain boundary. The stress rupture life and ductility are obviously improved after the addition of B. Meanwhile, the yield strength of B-doped alloy almost keeps the same level as that without boron addition. The fracture surface characterization exhibits that the dimples increase significantly after adding boron. During long-term thermal exposure, the elongation of the alloy with B addition increases slightly, but, for the alloy without B addition, the elongation obviously increases. The improvement of the stress rupture life and ductility can be attributed to the increase of grain boundary strength and the optimization of M 23 C 6 carbide distribution at grain boundary

  3. Coarsening behaviour and interfacial structure of γ′ precipitates in Co-Al-W based superalloys

    International Nuclear Information System (INIS)

    Vorontsov, V.A.; Barnard, J.S.; Rahman, K.M.; Yan, H.-Y.; Midgley, P.A.; Dye, D.

    2016-01-01

    This work discusses the effects of alloying on the coarsening behaviour of the L1 2 ordered γ ′ phase and the structure of the γ/γ ′ interfaces in three Co-Al-W base superalloys aged at ∼90 °C below the respective solvus temperatures: Co-7Al-7W, Co-10Al-5W-2Ta and Co-7Al-7W-20Ni (at.%). The coarsening kinetics are adequately characterised by the classical Lifshitz-Slyozov-Wagner model for Ostwald ripening. Co-7Al-7W exhibited much slower coarsening than its quaternary derivatives. Alloying can be exploited to modify the coarsening kinetics either by increasing the solvus temperature by adding tantalum, or by adding nickel to shift the rate controlling mechanism towards dependence on the diffusion of aluminium rather than tungsten. Lattice resolution STEM imaging was used to measure the widths of the order-disorder (structural) and Z-contrast (compositional) gradients across the γ/γ ′ interfaces. Similarly to nickel base superalloys, the compositional gradient was found to be wider than the structural. Co-7Al-7W-20Ni had much wider interface gradients than Co-7Al-7W and Co-10Al-5W-2Ta, which suggests that its γ ′ phase stoichiometry is less constrained. A possible correlation between temperature and misfit normalised r vs. t 1/3 coarsening rate coefficients and the structural gradient width has also been identified, whereby alloys with wider interfaces exhibit faster coarsening rates.

  4. Additive Manufacturing of IN100 Superalloy Through Scanning Laser Epitaxy for Turbine Engine Hot-Section Component Repair: Process Development, Modeling, Microstructural Characterization, and Process Control

    Science.gov (United States)

    Acharya, Ranadip; Das, Suman

    2015-09-01

    This article describes additive manufacturing (AM) of IN100, a high gamma-prime nickel-based superalloy, through scanning laser epitaxy (SLE), aimed at the creation of thick deposits onto like-chemistry substrates for enabling repair of turbine engine hot-section components. SLE is a metal powder bed-based laser AM technology developed for nickel-base superalloys with equiaxed, directionally solidified, and single-crystal microstructural morphologies. Here, we combine process modeling, statistical design-of-experiments (DoE), and microstructural characterization to demonstrate fully metallurgically bonded, crack-free and dense deposits exceeding 1000 μm of SLE-processed IN100 powder onto IN100 cast substrates produced in a single pass. A combined thermal-fluid flow-solidification model of the SLE process compliments DoE-based process development. A customized quantitative metallography technique analyzes digital cross-sectional micrographs and extracts various microstructural parameters, enabling process model validation and process parameter optimization. Microindentation measurements show an increase in the hardness by 10 pct in the deposit region compared to the cast substrate due to microstructural refinement. The results illustrate one of the very few successes reported for the crack-free deposition of IN100, a notoriously "non-weldable" hot-section alloy, thus establishing the potential of SLE as an AM method suitable for hot-section component repair and for future new-make components in high gamma-prime containing crack-prone nickel-based superalloys.

  5. The development of platinum-based alloys and their thermodynamic database

    OpenAIRE

    Cornish L.A.; Hohls J.; Hill P.J.; Prins S.; Süss R.; Compton D.N.

    2002-01-01

    A series of quaternary platinum-based alloys have been demonstrated to exhibit the same two-phase structure as Ni-based superalloys and showed good mechanical properties. The properties of ternary alloys were a good indication that the quaternary alloys, with their better microstructure, will be even better. The quaternary alloy composition has been optimised at Pt84:Al11:Ru2:Cr3 for the best microstructure and hardness. Work has begun on establishing a thermodynamic database for Pt-Al-Ru-Cr ...

  6. Suppression of Boride Formation in Transient Liquid Phase Bonding of Pairings of Parent Superalloy Materials with Different Compositions and Grain Structures and Resulting Mechanical Properties

    Science.gov (United States)

    Steuer, Susanne; Singer, Robert F.

    2014-07-01

    Two Ni-based superalloys, columnar grained Alloy 247 and single-crystal PWA1483, are joined by transient liquid phase bonding using an amorphous brazing foil containing boron as a melting point depressant. At lower brazing temperatures, two different morphologies of borides develop in both base materials: plate-like and globular ones. Their ratio to each other is temperature dependent. With very high brazing temperatures, the deleterious boride formation in Alloy 247 can be totally avoided, probably because the three-phase-field moves to higher alloying element contents. For the superalloy PWA1483, the formation of borides cannot be completely avoided at high brazing temperatures as incipient melting occurs. During subsequent solidification of these areas, Chinese-script-like borides precipitate. The mechanical properties (tensile tests at room and elevated temperatures and short-term creep rupture tests at elevated temperatures) for brazed samples without boride precipitation are very promising. Tensile strengths and creep times to 1 pct strain are comparable, respectively, higher than the ones of the weaker parent material for all tested temperatures and creep conditions (from 90 to 100 pct rsp. 175 to 250 pct).

  7. Precipitation in solid solution and structural transformations in single crystals of high rhenium ruthenium-containing nickel superalloys at high-temperature creep

    Energy Technology Data Exchange (ETDEWEB)

    Alekseev, A.A.; Petrushin, N.V.; Zaitsev, D.V.; Treninkov, I.A.; Filonova, E.V. [All-Russian Scientific Research Institute of Aviation Materials (VIAM), Moscow (Russian Federation)

    2010-07-01

    The phase composition and structure of single crystals of two superalloys (alloy 1 and alloy 2) were investigated in this work. For alloy 1 (Re - 9 wt%) the kinetics of precipitation in solid solution at heat treatment (HT) was investigated. TEM and X-Ray examinations have revealed that during HT rhombic phase (R-phase) precipitation (Immm class (BCR)) occurs. The TTT diagram is plotted, it contains the time-temperature area of the existence of R-phase particles. The element content of R-phase is identified (at. %): Re- 51.5; Co- 23.5; Cr- 14.8; Mo- 4.2; W- 3.3; Ta- 2.7. For alloy 2 (Re - 6.5 wt %, Ru - 4 wt %) structural transformations at high-temperature creep are investigated. By dark-field TEM methods it is established, that in alloy 2 the additional phase with a rhombic lattice is formed during creep. Particles of this phase precipitate in {gamma}-phase and their quantity increases during high-temperature creep. It is revealed that during creep 3-D dislocation network is formed in {gamma}-phase. At the third stage of creep the process of inversion structure formation is observed in the alloy, i.e. {gamma}'-phase becomes a matrix. Thus during modeling creep the volume fraction of {gamma}'-phase in the samples increases from 30% (at creep duration of 200 hrs) up to 55% (at 500 hrs). The processes of structure formation in Re and Ru-containing nickel superalloys are strongly affected by decomposition of solid solution during high-temperature creep that includes precipitation of additional TCP-phases. (orig.)

  8. NASA/ORNL/AFRL Project Work on EBM LSHR: Additive Manufacturing of High-Temperature Gamma-Prime Strengthened Ni-Based Superalloys

    Science.gov (United States)

    Sudbrack, Chantal K.; Kirka, Michael M.; Dehoff, Ryan R.; Carter, Robert W.; Semiatin, Sheldon L.; Gabb, Timothy P.

    2016-01-01

    Powder-bed fabrication of aerospace alloys may revolutionize production by eliminating the need for extensive machining and expensive tooling. Heated-bed electron-beam melting (EBM) offers advantages over non-heated laser additive manufacturing (AM) methods, including lower residual stress, reduced risk of contamination, slower cooling rates, and faster build times. NASA Glenn Research Center has joint project work with Oak Ridge National Lab and the Air Force Research Laboratory to explore the feasibility of fabricating advanced Ni-based gamma-prime superalloys with EBM AM.

  9. Nanosize boride particles in heat-treated nickel base superalloys

    International Nuclear Information System (INIS)

    Zhang, H.R.; Ojo, O.A.; Chaturvedi, M.C.

    2008-01-01

    Grain boundary microconstituents in aged nickel-based superalloys were studied by transmission electron microscopy techniques. A nanosized M 5 B 3 boride phase, possibly formed by intergranular solute desegregation-induced precipitation, was positively identified. The presence of these intergranular nanoborides provides reasonable clarification of a previously reported reduction of grain boundary liquation temperature during the weld heat affected zone thermal cycle

  10. Multiscale modelling of single crystal superalloys for gas turbine blades

    NARCIS (Netherlands)

    Tinga, T.

    2009-01-01

    Gas turbines are extensively used for power generation and for the propulsion of aircraft and vessels. Their most severely loaded parts, the turbine rotor blades, are manufactured from single crystal nickel-base superalloys. The superior high temperature behaviour of these materials is attributed to

  11. Double minimum creep of single crystal Ni-base superalloys

    Czech Academy of Sciences Publication Activity Database

    WU, X.; Wollgramm, P.; Somsen, C.; Dlouhý, Antonín; Kostka, A.; Eggeler, G.

    2016-01-01

    Roč. 112, JUN (2016), s. 242-260 ISSN 1359-6454 R&D Projects: GA ČR(CZ) GA14-22834S Institutional support: RVO:68081723 Keywords : Single crystal Ni-base superalloys * Primary creep * Transmission electron microscopy * Dislocations * Stacking faults Subject RIV: JG - Metallurgy Impact factor: 5.301, year: 2016

  12. High-temperature steam oxidation testing of select advanced replacement alloys for potential core internals

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Lizhen [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Pint, Bruce A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-05-19

    Coupons from a total of fourteen commercial and custom fabricated alloys were exposed to 1 bar full steam with ~10 ppb oxygen content at 600 and 650°C. The coupons were weighed at 500-h intervals with a total exposure time of 5,000 h. The fourteen alloys are candidate alloys selected under the ARRM program, which include three ferritic steels (Grade 92, 439, and 14YWT), three austenitic stainless steels (316L, 310, and 800), seven Ni-base superalloys (X750, 725, C22, 690, 625, 625 direct-aging, and 625- plus), and one Zr-alloy (Zr–2.5Nb). Among the alloys, 316L and X750 are served as reference alloys for low- and high-strength alloys, respectively. The candidate Ni-base superalloy 718 was procured too late to be included in the tests. The corrosion rates of the candidate alloys can be approximately interpreted by their Cr, Ni and Fe content. The corrosion rate was significantly reduced with increasing Cr content and when Ni content is above ~15 wt%, but not much further reduced when Fe content is less than ~55 wt%. Simplified thermodynamics analyses of the alloy oxidation provided reasonable indications for the constituents of oxide scales formed on the alloys and explanations for the porosity and exfoliation phenomena because of the nature of specific types of oxides.

  13. Influences of Processing and Fatigue Cycling on Residual Stresses in a NiCrY-Coated Powder Metallurgy Disk Superalloy

    Science.gov (United States)

    Gabb, T. P.; Rogers, R. B.; Nesbitt, J. A.; Miller, R. A.; Puleo, B. J.; Johnson, D.; Telesman, J.; Draper, S. L.; Locci, I. E.

    2017-11-01

    Oxidation and corrosion can attack superalloy disk surfaces exposed to increasing operating temperatures in some turbine engine environments. Any potential protective coatings must also be resistant to harmful fatigue cracking during service. The objective of this study was to investigate how residual stresses evolve in one such coating. Fatigue specimens of a powder metallurgy-processed disk superalloy were coated with a NiCrY coating, shot peened, and then subjected to fatigue in air at room and high temperatures. The effects of this processing and fatigue cycling on axial residual stresses and other aspects of the coating were assessed. While shot peening did induce beneficial compressive residual stresses in the coating and substrate, these stresses relaxed in the coating with subsequent heating. Several cast alloys having compositions near the coating were subjected to thermal expansion and tensile stress relaxation tests to help explain this response of residual stresses in the coating. For the coated fatigue specimens, this response contributed to earlier cracking of the coating than for the uncoated surface during long intervals of cycling at 760 °C. Yet, substantial compressive residual stresses still remained in the substrate adjacent to the coating, which were sufficient to suppress fatigue cracking there. The coating continued to protect the substrate from hot corrosion pitting, even after fatigue cracks initiated in the coating.

  14. Heredity of medium-range order structure from melts to the microstructure of Ni-Cr-W superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Zhongtang; Hu, Rui; Wang, Jun; Li, Jinshan [Northwestern Polytechnical University, State Key Laboratory of Solidification Processing, Xi' an (China)

    2015-07-15

    The structure factor S(Q), intensities and pair distribution function g(r) of liquid Ni-Cr-W superalloy at different temperatures have been measured by a high-temperature X-ray diffractometer. Coordination N{sub min}, correlation radius r{sub c}, the nearest atomic distance r{sub 1}, solidification microstructure and compression performance have been studied. The results show that a pre-peak exists on the structure factor curve at the liquidus temperature, and a fine structure of equiaxed, globular and non-dendritic primary grains can be achieved by casting the alloy at liquidus temperature. Liquid structure feature of Ni-Cr-W superalloy is found to depend on temperature. During the solidification, some structural information carried by the medium-range order (MRO) structure is inherited from the melt to the microstructure, which is beneficial for grain refinement. The maximum yield strength measured from typical microstructure of the equiaxed and non-dendritic grains at 1400 C is 543 MPa. The results show that refinement and non-dendritic grain is beneficial to the improvement of the yield strength. (orig.)

  15. Effect of microstructure on high-temperature mechanical behavior of nickel-base superalloys for turbine disc applications

    Science.gov (United States)

    Sharpe, Heather Joan

    2007-05-01

    Engineers constantly seek advancements in the performance of aircraft and power generation engines, including, lower costs and emissions, and improved fuel efficiency. Nickel-base superalloys are the material of choice for turbine discs, which experience some of the highest temperatures and stresses in the engine. Engine performance is proportional to operating temperatures. Consequently, the high-temperature capabilities of disc materials limit the performance of gas-turbine engines. Therefore, any improvements to engine performance necessitate improved alloy performance. In order to take advantage of improvements in high-temperature capabilities through tailoring of alloy microstructure, the overall objectives of this work were to establish relationships between alloy processing and microstructure, and between microstructure and mechanical properties. In addition, the projected aimed to demonstrate the applicability of neural network modeling to the field of Ni-base disc alloy development and behavior. The first phase of this work addressed the issue of how microstructure varies with heat treatment and by what mechanisms these structures are formed. Further it considered how superalloy composition could account for microstructural variations from the same heat treatment. To study this, four next-generation Ni-base disc alloys were subjected to various controlled heat-treatments and the resulting microstructures were then quantified. These quantitative results were correlated to chemistry and processing, including solution temperature, cooling rate, and intermediate hold temperature. A complex interaction of processing steps and chemistry was found to contribute to all features measured; grain size, precipitate distribution, grain boundary serrations. Solution temperature, above a certain threshold, and cooling rate controlled grain size, while cooling rate and intermediate hold temperature controlled precipitate formation and grain boundary serrations. Diffusion

  16. Corrosion studies and recommendation of alloys for an incinerator of glove-boxes wastes

    International Nuclear Information System (INIS)

    Devisme, F.; Garnier, M.H.

    1992-01-01

    In the framework of the development of an incineration process for high chlorinated wastes, commercial alloys have been investigated by means of parametric laboratory tests in HCl containing gas mixtures and also in field tests. Recommendations may be formulated for the three main components i.e. pyrolyser, calciner and cooler. In very low oxygen-potential atmospheres, the alloys Hastelloy C276 and Inconel 625 present the best behaviours. For the calciner, alloy Inconel 601 is more satisfactory than AISI 310 steel. As for the cooler, only the alloy Haynes 214 appears acceptable at 1100 deg C. Because of the very low stress level affecting the components, thermomechanical properties do not modify these recommendations based on corrosion behaviour

  17. Inspection report of unauthorized possession and use of unsealed americium-241 and subsequent confiscation, J.C. Haynes Company, Newark, Ohio

    International Nuclear Information System (INIS)

    1985-11-01

    This US Nuclear Regulatory Commission report documents the circumstances surrounding the March 26, 1985, confiscation and subsequent decontamination activities related to the use of unauthorized quantities of americium-241 at the John C. Haynes Company (licensee) of Newark, Ohio. It focuses on the period from early February to July 26, 1985. The incident started when NRC Region III recieved information that John C. Haynes possessed unauthorized quantities of americium-241 and was conducting unauthorized activities (diamond irradiation). By July 26, 1985, the decontamination activities at the licensee's laboratory were concluded. The licensee's actions with diamond irradiation resulted in contamination in restricted and unrestricted areas of the facility. The confiscation and decontamination activities required the combined efforts of NRC, Federal Bureau of Investigation, US Department of Energy, Oak Ridge Associated Universities, the State of Ohio, and the US Environmental Protection Agency. The report describes the factual information and significant findings associated with the confiscation and decontamination activities

  18. High temperature oxidation and electrochemical studies on novel co-base superalloys

    Energy Technology Data Exchange (ETDEWEB)

    Klein, Leonhard

    2013-02-27

    Isothermal oxidation in air was carried out on novel γ'-strengthened Cobalt-base superalloys of the system Co-Al-W-B. After fast initial oxide formation, a multi-layered structure establishes, consisting of an outer cobalt oxide layer, a middle spinel-containing layer, and an inner Al{sub 2}O{sub 3}-rich region. Ion diffusion in outward direction is hindered by the development of Al{sub 2}O{sub 3}, that can be either present as a continuous and protective layer or as a discontinuous Al{sub 2}O{sub 3}-rich area without comparable protective effect. Furthermore, high temperature oxidation leads to phase transformation (from γ/γ' into γ/Co{sub 3}W) at the alloy/oxide layer interface due to aluminium depletion. Pure cobalt and ternary Co-Al-W alloys exhibit parabolic oxide growth due to the lack or insufficient amounts of protective oxides, whereas quaternary Co-Al-W-B alloys possess sub-parabolic oxidation behaviour (at 900 C). At lower temperatures (800 C), even a blockage of further oxidation can be observed. High amounts of B (0.12 at%) significantly improve oxidation resistance mainly due to its beneficial effect on inner Al{sub 2}O{sub 3}-formation at the alloy/oxide interface. Furthermore, B prevents decohesion of high temperature scales due to the formation of B-rich phases (presumably tungsten borides) in the middle oxide layer. Appropriate amounts of chromium (8 at%) as additional alloying element to Co-Al-W-B alloys lead to the formation of an inner duplex layer composed of protective Cr{sub 2}O{sub 3} and Al{sub 2}O{sub 3} phases. In this respect, chromium also benefits selective oxidation of aluminium, which results in higher Al{sub 2}O{sub 3}-contents compared to chromium-free alloys. Major drawbacks of chromium additions are, on the one hand, the formation of volatile chromium-containing species at temperatures exceeding 1000 C and on the other hand, the instability of the γ/γ'-microstructure. Titanium and silicon additions lead to

  19. Precipitation in Powder Metallurgy, Nickel Base Superalloys: Review of Modeling Approach and Formulation of Engineering (Postprint)

    Science.gov (United States)

    2016-12-01

    AFRL-RX-WP-JA-2016-0333 PRECIPITATION IN POWDER- METALLURGY , NICKEL-BASE SUPERALLOYS: REVIEW OF MODELING APPROACH AND FORMULATION OF...PRECIPITATION IN POWDER- METALLURGY , NICKEL- BASE SUPERALLOYS: REVIEW OF MODELING APPROACH AND FORMULATION OF ENGINEERING (POSTPRINT) 5a...and kinetic parameters required for the modeling of γ′ precipitation in powder- metallurgy (PM), nickel-base superalloys are summarized. These

  20. A Comparison of the Plastic Flow Response of a Powder Metallurgy Nickel Base Superalloy (Postprint)

    Science.gov (United States)

    2017-04-01

    AFRL-RX-WP-JA-2017-0225 A COMPARISON OF THE PLASTIC-FLOW RESPONSE OF A POWDER- METALLURGY NICKEL-BASE SUPERALLOY (POSTPRINT) S.L...COMPARISON OF THE PLASTIC-FLOW RESPONSE OF A POWDER- METALLURGY NICKEL-BASE SUPERALLOY (POSTPRINT) 5a. CONTRACT NUMBER IN-HOUSE 5b. GRANT...behavior at hot-working temperatures and strain rates of the powder- metallurgy superalloy LSHR was determined under nominally-isothermal and transient

  1. Microstructure evolution of a pre-compression nickel-base single crystal superalloy during tensile creep

    International Nuclear Information System (INIS)

    Yu Xingfu; Tian Sugui; Du Hongqiang; Yu Huichen; Wang Minggang; Shang Lijuan; Cui Shusen

    2009-01-01

    By pre-compressive creep treatment, the cubical γ' phase in the nickel-base single crystal superalloy is transformed into the P-type rafted structure along the direction parallel to the applied stress axis. And the microstructure evolution of the P-type γ' rafted alloy during tensile creep is investigated by means of the measurement of the creep curve and microstructure observation. Results show that the P-type γ' rafted phase in the alloy is transformed into the N-type structure along the direction perpendicular to the applied stress axis in the initial stage of the tensile creep. In the role of the tensile stress at high temperature, the change of the element's equilibrium concentration in the different regions of P-type γ' rafted phase occurs, which promotes the inhomogeneous coarsening of the P-type γ' phase. And then, the decomposition of the P-type γ' rafted phase in the alloy occurs to form the groove structure. As of result of the directional diffusion of the elements, the fact that the P-type γ' rafted phase is decomposed to transform into the cubical-like structure is attributed to the increment of the solute elements M(Ta, Al) chemical potential in the groove regions. Further, the lattice constriction in the horizontal interfaces of the cubical-like γ' phase may repel out the Al and Ta atoms with higher radius due to the role of the shearing stress, and the lattice expanding in the upright interfaces of the cubical-like γ' phase, due to the role of the tension stress, may trap the Ta and Al atoms, which promotes the directional growing of γ' phase into the N-type rafted structure. Therefore, the change of the strain energy density in different interfaces of the cubical-like γ' phase is thought to be the driving force of the elements diffusing and the directional coarsening of γ' phase

  2. Corrosion of high Ni-Cr alloys and Type 304L stainless steel in HNO3-HF

    International Nuclear Information System (INIS)

    Ondrejcin, R.S.; McLaughlin, B.D.

    1980-04-01

    Nineteen alloys were evaluated as possible materials of construction for steam heating coils, the dissolver vessel, and the off-gas system of proposed facilities to process thorium and uranium fuels. Commercially available alloys were found that are satisfactory for all applications. With thorium fuel, which requires HNO 3 -HF for dissolution, the best alloy for service at 130 0 C when complexing agents for fluoride are used is Inconel 690; with no complexing agents at 130 0 C, Inconel 671 is best. At 95 0 C, six other alloys tested would be adequate: Haynes 25, Ferralium, Inconel 625, Type 304L stainless steel, Incoloy 825, and Haynes 20 (in order of decreasing preference); based on composition, six untested alloys would also be adequate. The ions most effective in reducing fluoride corrosion were the complexing agents Zr 4+ and Th 4+ ; Al 3+ was less effective. With uranium fuel, modestly priced Type 304L stainless steel is adequate. Corrosion will be most severe in HNO 3 -HF used occasionally for flushing and in solutions of HNO 3 and corrosion products (ferric and dichromate ions). HF corrosion can be minimized by complexing the fluoride ion and by passivation of the steel with strong nitric acid. Corrosion caused by corrosion products can be minimized by operating at lower temperatures

  3. Recent trends in superalloys research for critical aero-engine components

    Energy Technology Data Exchange (ETDEWEB)

    Remy, Luc [Mine ParisTech, CNRS UMR 7633, 91 - Evry (France). Centre des Materiaux; Guedou, Jean-Yves [Snecma Safran Group, Moissy-Cramayel (France). Materials and Processes Dept.

    2010-07-01

    This paper is a brief survey of common research activity on superalloys for aero-engines between Snecma and Mines ParisTech Centre des Materiaux during recent years. First in disks applications, the development of new powder metallurgy superalloys is shown. Then grain boundary engineering is investigated in a wrought superalloy. Secondly, design oriented research on single crystals blades is shown: a damage model for low cycle fatigue is used for life prediction when cracks initiated at casting pores. The methodology developed for assessing coating life is illustrated for thermal barrier coating deposited on AMI single crystal superalloy. (orig.)

  4. Microstructure-sensitive Crystal Viscoplasticity for Ni-base Superalloys Targeting Long-term Creep-Fatigue Interaction Modeling

    Energy Technology Data Exchange (ETDEWEB)

    Neu, Richard W.

    2017-09-30

    The aim of this project is to develop a microstructure-sensitive crystal viscoplasticity (CVP) model for single-crystal Ni-base superalloys to model the behavior of the material and components in the hot gas path sections of industrial gas turbines (IGT). Microstructure degradation associated with aging critical to predicting long-term creep-fatigue interactions will be embedded into the model through the γ' precipitate morphology evolution by coupling the coarsening drivers and kinetics into the constitutive equations of the CVP model. Model parameters will be determined using new experimental protocols that involve systematically artificially aging the alloy under different stress conditions to determine the relationship between the size and morphology g' precipitates on the creep and thermomechanical fatigue response.

  5. Microstructure and Mechanical Properties of Laser Welded Joints of DZ125L and IN718 Nickel Base Superalloys

    Science.gov (United States)

    Liang, Taosha; Wang, Lei; Liu, Yang; Song, Xiu

    2018-05-01

    The microstructure and mechanical properties of the laser welded joint of DZ125L and IN718 nickel base superalloys were investigated. The results show that the fusion zone (FZ) mainly consists of fine dendrite structure with fine γ', Laves phases and MC carbides inhomogeneously distributed. The high welding temperature induces the partial dissolution of γ' in the heat-affected zone (HAZ) of DZ125L and liquation of grain boundaries in both of the HAZs. After post-weld heat treatment (PWHT), fine γ″ and γ' phases precipitate in the FZ, IN718 HAZ and IN718 base metal (BM), and fine γ' precipitate in the γ channel of the HAZ and BM of DZ125L. With tensile testing, the joints after PWHT show higher strengths than that of the weaker DZ125L alloy. Plastic deformation mainly concentrates in the weaker DZ125L and the joint finally fails in the DZ125L BM.

  6. Effect of Process Variables on the Inertia Friction Welding of Superalloys LSHR and Mar-M247

    Science.gov (United States)

    Mahaffey, D. W.; Senkov, O. N.; Shivpuri, R.; Semiatin, S. L.

    2016-08-01

    The effect of inertia friction welding process parameters on microstructure evolution, weld plane quality, and the tensile behavior of welds between dissimilar nickel-base superalloys was established. For this purpose, the fine-grain, powder metallurgy alloy LSHR was joined to coarse-grain cast Mar-M247 using a fixed level of initial kinetic energy, but different combinations of the flywheel moment of inertia and initial rotation speed. It was found that welds made with the largest moment of inertia resulted in a sound bond with the best microstructure and room-temperature tensile strength equal to or greater than that of the parent materials. A relationship between the moment of inertia and weld process efficiency was established. The post-weld tensile behavior was interpreted in the context of observed microstructure gradients and weld-line defects.

  7. Investigation of selected thermo-physical properties in the Co-based superalloy: Experiment and application study

    Directory of Open Access Journals (Sweden)

    J. Kasala

    2010-01-01

    Full Text Available Thermo-physical properties are the critical input parameters in computational models of solidification and casting simulations. In thermodynamics, the enthalpy is quotient of thermodynamic potential of a system, which can be used to calculate the useful work obtainable from a closed thermodynamic system under constant pressure. Differential thermal analysis has been used to study melting and solidification paths in the cobalt based superalloy FSX-414. The temperature enthalpy curve was determined from differential thermal analysis curves obtained from solidification curves. A solidification simulation of a cobalt base multi-component alloy casting was carried out to predict cooling and shrinkage porosity in the casting of a turbine engine vane segment. The effect of latent heat on the heat transfer calculation was considered by enthalpy method.

  8. Life Prediction of Low Cycle Fatigue for Ni-base Superalloy GTD111 DS at Elevated Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jin Yeol; Yoon, Dong Hyun; Kim, Jae Hoon [Chungnam Nat’l Univ., Daejeon (Korea, Republic of); Bae, Si Yeon; Chang, Sung Yong; Chang, Sung Ho [KEPCO Research Institute, Daejeon (Korea, Republic of)

    2017-08-15

    GTD111 DS of nickel base superalloy has been used for gas turbine blades. In this study, low cycle fatigue test was conducted on the GTD111 DS alloy by setting conditions similar to the real operating environment. The low cycle fatigue tests were conducted at room temperature, 760 °C, 870 °C, and various strain amplitudes. Test results showed that fatigue life decreased with increasing total strain amplitude. Cyclic hardening response was observed at room temperature and 760 °C; however, tests conducted at 870 °C showed cyclic softening response. Stress relaxation was observed at 870 °C because creep effects occurred from holding time. A relationship between fatigue life and total strain range was obtained from the Coffin-Manson method. The fratography using a SEM was carried out at the crack initiation and propagation regions.

  9. Microstructure-sensitive Crystal Viscoelasticity for Ni-base Superalloys Targeting Long-term Creep-Fatigue Interaction Modeling

    Energy Technology Data Exchange (ETDEWEB)

    Neu, Richard W

    2016-09-30

    The aim of this project is to develop a microstructure-sensitive crystal viscoplasticity (CVP) model for single-crystal Ni-base superalloys to model the behavior of the material and components in the hot gas path sections of industrial gas turbines (IGT). Microstructure degradation associated with aging critical to predicting long-term creep-fatigue interactions will be embedded into the model through the γ' precipitate morphology evolution by coupling the coarsening drivers and kinetics into the constitutive equations of the CVP model. Model parameters will be determined using new experimental protocols that involve systematically artificially aging the alloy under different stress conditions to determine the relationship between the size and morphology g' precipitates on the creep and thermomechanical fatigue response.

  10. The erosion/corrosion of small superalloy turbine rotors operating in the effluent of a PFB coal combustor

    Science.gov (United States)

    Zellars, G. R.; Benford, S. M.; Rowe, A. P.; Lowell, C. E.

    1979-01-01

    The operation of a turbine in the effluent of a pressurized fluidized bed (PFB) coal combustor presents serious materials problems. Synergistic erosion/corrosion and deposition/corrosion interactions may favor the growth of erosion-resistant oxides on blade surfaces, but brittle cracking of these oxides may be an important source of damage along heavy particle paths. Integrally cast alloy 713LC and IN792 + Hf superalloy turbine rotors in a single-stage turbine with 6% partial admittance have been operated in the effluent of a PFB coal combustor for up to 164 hr. The rotor erosion pattern exhibits heavy particle separation with severe erosion at the leading edge, pressure side center, and suction side trailing edge at the tip. The erosion distribution pattern gives a spectrum of erosion/oxidation/deposition as a function of blade position. The data suggest that preferential degradation paths may exist even under the targeted lower loadings (less than 20 ppm).

  11. Formation of carbides and their effects on stress rupture of a Ni-base single crystal superalloy

    International Nuclear Information System (INIS)

    Liu, L.R.; Jin, T.; Zhao, N.R.; Sun, X.F.; Guan, H.R.; Hu, Z.Q.

    2003-01-01

    Creep tests of a nickel-base single crystal superalloy with minor C addition and non-carbon were carried out at different temperatures and stresses. Correlations between microstructural change and testing temperature and stress were enabled through scanning electron microscopy (SEM) and transmission electron microscopy (TEM), detailing the rafting microstucture and carbides precipitation. The results showed that minor carbon addition prolonged the second stage of creep strain curves and improved creep properties. Some carbide was precipitated during creep tests in modified alloy. M 23 C 6 carbide precipitated at lower temperature (871-982 deg. C), while (M 6 C) 2 carbide precipitated at higher temperature (>1000 deg. C), all of which was considered to be beneficial to creep properties. A small amount of MC carbide formed during solidification and its decomposition product (M 6 C) 1 were detrimental to mechanical properties, which together with micropores provided the site of initiation of cracks and led to the final fracture

  12. The Influence of Impurities in Feed Ingots on the Quality of Castings Made from Nickel Superalloy IN-713C

    Directory of Open Access Journals (Sweden)

    Binczyk F.

    2013-12-01

    Full Text Available The paper presents the results of research on the impact of impurities in the feed ingots (master heat on the precipitation of impurities in the ATD thermal analysis probe castings. This impurities occur mostly inside shrinkage cavities and in interdendritic space. Additionally, insufficient filtration of liquid alloy during pouring promotes the transfer of impurities into the casting. The technology of melting superalloys in vacuum furnace prevents the removal of slag from the surface of molten metal. Because of that, the effective method of quality assessment of feed ingots in order to evaluate the existence of impurities is needed. The effectiveness of ATD analysis in evaluation of purity of feed ingots was researched. In addition the similarities of non-metallic inclusions in feed ingots and in castings were observed.

  13. The characteristic of deformability and quantitative description of the microstructure of hot-deformed Ni-Fe superalloy

    Directory of Open Access Journals (Sweden)

    Ducki K. J.

    2017-03-01

    Full Text Available The paper presents the results of research concerning the influence of hot plastic working parameters on the deformability and microstructure of a Ni-Fe superalloy. The research was performed on a torsion plastometer in the range of temperatures of 900-1150°C, at a strain rates 0.1 and 1.0 s-1. Plastic properties of the alloy were characterized by the worked out flow curves and the temperature relationships of flow stress and strain limit. The structural inspections were performed on microsections taken from plastometric samples after so-called “freezing”. The stereological parameters as the recrystallized grain size, inhomogenity and grain shape have been determined. Functional relations between the Zener-Hollomon parameter and the maximum yield stress and the average grain area have been developed and the activation energy for hot working has been estimated.

  14. Fatigue properties of MA 6000E, a gamma-prime strengthened ODS alloy. [Oxide Dispersion Strengthened Ni-base alloy for gas turbine blade applications

    Science.gov (United States)

    Kim, Y. G.; Merrick, H. F.

    1980-01-01

    MA 6000E is a corrosion resistant, gamma-prime strengthened ODS alloy under development for advanced turbine blade applications. The high temperature, 1093 C, rupture strength is superior to conventional nickel-base alloys. This paper addresses the fatigue behavior of the alloy. Excellent properties are exhibited in low and high cycle fatigue and also thermal fatigue. This is attributed to a unique combination of microstructural features, i.e., a fine distribution of dispersed oxides and other nonmetallics, and the highly elongated grain structure which advantageously modify the deformation characteristics and crack initiation and propagation modes from that characteristic of conventional gamma-prime hardened superalloys.

  15. Effect of carbon content on the microstructure and creep properties of a 3rd generation single crystal nickel-base superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Li, X.W.; Liu, T. [Superalloys Division, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Wang, L., E-mail: wangli@imr.ac.cn [Superalloys Division, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Liu, X.G.; Lou, L.H. [Superalloys Division, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Zhang, J. [Superalloys Division, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)

    2015-07-15

    Effect of carbon content on the microstructure and creep properties of a 3rd generation single crystal nickel-base superalloy has been investigated by the scanning electron microscope, X-ray computed tomography and electron probe microanalyzer. With the increase of the carbon content, MC carbides evolve from octahedral to well-developed dendrite, which promotes the formation of microporosity. Moreover, the volume fraction of porosity increases in the experimental alloys after solution heat treatment. As a result, the increase in the size of MC carbides and the porosity has a detrimental effect on the low temperature and high stress creep behavior of the alloys. The specimen crept at 850 °C and 586 MPa with the carbon content of 430 ppm shows the shortest rupture life due to the largest primary creep strain. However, the creep behavior of the alloy at 1120 °C and 140 MPa gets better as the carbon content increases from 88 to 430 ppm. TCP phase is observed near the fracture surfaces of the alloys, which explores as a potential cause for the creep rupture. However, the formation of TCP phase is effectively suppressed for decreasing segregation of the alloying elements, which results in the improvement of the creep life in the alloy with 430 ppm carbon at 1120 °C and 140 MPa.

  16. Hydrogeology, hydraulic characteristics, and water-quality conditions in the surficial, Castle Hayne and Peedee aquifers of the greater New Hanover County area, North Carolina, 2012-13

    Science.gov (United States)

    McSwain, Kristen Bukowski; Gurley, Laura N.; Antolino, Dominick J.

    2014-01-01

    A major issue facing the greater New Hanover County, North Carolina, area is the increased demand for drinking water resources as a result of rapid growth. The principal sources of freshwater supply in the greater New Hanover County area are withdrawals of surface water from the Cape Fear River and groundwater from the underlying Castle Hayne and Peedee aquifers. Industrial, mining, irrigation, and aquaculture groundwater withdrawals increasingly compete with public-supply utilities for freshwater resources. Future population growth and economic expansion will require increased dependence on high-quality sources of fresh groundwater. An evaluation of the hydrogeology and water-quality conditions in the surficial, Castle Hayne, and Peedee aquifers was conducted in New Hanover, eastern Brunswick, and southern Pender Counties, North Carolina. A hydrogeologic framework was delineated by using a description of the geologic and hydrogeologic units that compose aquifers and their confining units. Current and historic water-level, water-quality, and water-isotope data were used to approximate the present boundary between freshwater and brackish water in the study area. Water-level data collected during August–September 2012 and March 2013 in the Castle Hayne aquifer show that recharge areas with the highest groundwater altitudes are located in central New Hanover County, and the lowest are located in a discharge area along the Atlantic Ocean. Between 1964 and 2012, groundwater levels in the Castle Hayne aquifer in central New Hanover County have rebounded by about 10 feet, but in the Pages Creek area groundwater levels declined in excess of 20 feet. In the Peedee aquifer, the August–September 2012 groundwater levels were affected by industrial withdrawals in north-central New Hanover County. Groundwater levels in the Peedee aquifer declined more than 20 feet between 1964 and 2012 in northeastern New Hanover County because of increased withdrawals. Vertical gradients

  17. Microstructural Characterization and Modeling of SLM Superalloy 718

    Science.gov (United States)

    Smith, Tim M.; Sudbrack, Chantal K.; Bonacuse, Pete; Rogers, Richard

    2017-01-01

    Superalloy 718 is an excellent candidate for selective laser melting (SLM) fabrication due to a combination of excellent mechanical properties and workability. Predicting and validating the microstructure of SLM-fabricated Superalloy 718 after potential post heat-treatment paths is an important step towards producing components comparable to those made using conventional methods. At present, obtaining accurate volume fraction and size measurements of gamma-double-prime, gamma-prime and delta precipitates has been challenging due to their size, low volume fractions, and similar chemistries. A technique combining high resolution distortion corrected SEM imaging and with x-ray energy dispersive spectroscopy has been developed to accurately and independently measure the size and volume fractions of the three precipitates. These results were further validated using x-ray diffraction and phase extraction methods and compared to the precipitation kinetics predicted by PANDAT and JMatPro. Discrepancies are discussed in context of materials properties, model assumptions, sampling, and experimental errors.

  18. Phase Stability of a Powder Metallurgy Disk Superalloy

    Science.gov (United States)

    Gabb, Timothy P.; Gayda, John; Kantzos, P.; Telesman, Jack; Gang, Anita

    2006-01-01

    Advanced powder metallurgy superalloy disks in aerospace turbine engines now entering service can be exposed to temperatures approaching 700 C, higher than those previously encountered. They also have higher levels of refractory elements, which can increase mechanical properties at these temperatures but can also encourage phase instabilities during service. Microstructural changes including precipitation of topological close pack phase precipitation and coarsening of existing gamma' precipitates can be slow at these temperatures, yet potentially significant for anticipated disk service times exceeding 1,000 h. The ability to quantify and predict such potential phase instabilities and degradation of capabilities is needed to insure structural integrity and air worthiness of propulsion systems over the full life cycle. A prototypical advanced disk superalloy was subjected to high temperature exposures, and then evaluated. Microstructural changes and corresponding changes in mechanical properties were quantified. The results will be compared to predictions of microstructure modeling software.

  19. Microstructure evolution during dynamic recrystallization of hot deformed superalloy 718

    International Nuclear Information System (INIS)

    Wang, Y.; Shao, W.Z.; Zhen, L.; Zhang, X.M.

    2008-01-01

    Microstructure evolution during dynamic recrystallization (DRX) of superalloy 718 was studied by optical microscope and electron backscatter diffraction (EBSD) technique. Compression tests were performed at different strains at temperatures from 950 deg. C to 1120 deg. C with a strain rate of 10 -1 s -1 . Microstructure observations show that the recrystallized grain size as well as the fraction of new grains increases with the increasing temperature. A power exponent relationship is obtained between the dynamically recrystallized grain size and the peak stress. It is found that different nucleation mechanisms for DRX are operated in hot deformed superalloy 718, which is closely related to deformation temperatures. DRX nucleation and development are discussed in consideration of subgrain rotation or twinning taking place near the original grain boundaries. Particular attention is also paid to the role of continuous dynamic recrystallization (CDRX) at both higher and lower temperatures

  20. Comparative Studies on Microstructure, Mechanical and Pitting Corrosion of Post Weld Heat Treated IN718 Superalloy GTA and EB Welds

    Science.gov (United States)

    Dilkush; Mohammed, Raffi; Madhusudhan Reddy, G.; Srinivasa Rao, K.

    2018-03-01

    In the present study, an attempt has been made to weld Inconel 718 nickel-base superalloy (IN718 alloy) using gas tungsten arc welding (GTAW) and electron beam welding (EBW) processes. Both the weldments were subjected to post-weld heat treatment condition as follows -980°C / 20 min followed by direct aging condition (DA) as 720°C/8 h/FC followed by 620°C/8 h/AC. The GTA and EB welds of IN718 alloy were compared in two conditions as-received and 980STA conditions. Welds were characterized to observe mechanical properties, pitting corrosion resistance by correlating with observed microstructures. The rate of higher cooling ranges, the fusion zone of EBW exhibited discrete and relative finer lave phases whereas the higher niobium existed laves with coarser structure were observed in GTAW. The significant dissolution of laves were observed at 980STA of EBW. Due to these effects, the EBW of IN718 alloy showed the higher mechanical properties than GTAW. The electrochemical potentiostatic etch test was carried out in 3.5wt% sodium chloride (NaCl) solution to study the pitting corrosion behaviour of the welds. Results of the present investigation established that mechanical properties and pitting corrosion behaviour are significantly better in post weld heat treated condition. The comparative studies showed that the better combination of mechanical properties and pitting corrosion resistance were obtained in 980STA condition of EBW than GTAW.

  1. The influence of cobalt, tantalum, and tungsten on the elevated temperature mechanical properties of single crystal nickel-base superalloys

    Science.gov (United States)

    Nathal, M. V.; Ebert, L. J.

    1985-01-01

    The influence of composition on the tensile and creep strength of 001-line oriented nickel-base superalloy single crystals at temperatures near 1000 C was investigated. Cobalt, tantalum, and tungsten concentrations were varied according to a matrix of compositions based on the single crystal version of MAR-M247. For alloys with the baseline refractory metal level of 3 wt pct Ta and 10 wt pct W, decreases in Co level from 10 to 0 wt pct resulted in increased tensile and creep strength. Substitution of 2 wt pct W for 3 wt pct Ta resulted in decreased creep life at high stresses, but improved life at low stresses. Substitution of Ni for Ta caused large reductions in tensile strength and creep resistance, and corresponding increases in ductility. For these alloys with low Ta-plus-W totals, strength was independent of Co level. The effects of composition on properties were related to the microstructural features of the alloys. In general, high creep strength was associated with high levels of gamma-prime volume fraction, gamma-gamma-prime lattice mismatch, and solid solution hardening.

  2. Predictive Analysis for the Thermal Diffusion of the Plasma-Assisted Machining of Superalloy Inconel-718 Based on Exponential Smoothing

    Directory of Open Access Journals (Sweden)

    Chen Shao-Hsien

    2018-01-01

    Full Text Available Nickel base and titanium base materials have been widely applied to engines in aerospace industry, and these engines are essential components of airplanes. The machining characteristics of aerospace materials may cause machining cutters to be worn down in a short time and thus reduce the accuracy of processing. The plasma-assisted machining adopted in the research is a kind of the complex machining method. In the cases of nickel base and titanium base alloys, the method can heat workpieces in an extremely short duration to soften the materials for the ease of cutting so that the cutting force, cutter wear, and machining cost will all be reduced. The research adopted plasma heating to soften parts of the materials and aimed to explore the heating of nickel base alloy. The temperature variation of the materials was investigated and measured by adjusting the current and feed velocity. Moreover, Inconel-718 superalloy was adopted for the comparison with nickel base alloy for the observation of the influence and change brought by heat, and the method of exponential smoothing was adopted to conduct the prediction and analysis of thermal diffusion for understanding the influence and change brought by electric current on nickel base materials. Finally, given the current from 20 A to 80 A and feed velocity from 1,000 mm/min to 3,000 mm/min, the influence of thermal diffusion was investigated and the related model was built.

  3. Partitioning and nanostructural evolution in model Ni-based superalloys containing W, Re, and Ru studied on a subnanometer scale

    International Nuclear Information System (INIS)

    Isheim, D.; Seidman, D.N.

    2004-01-01

    Full text: Modern Ni-based sueralloys, for example, Rene N6, rely on a complex microstructure and microchemistry to achieve their superior mechanical and physical properties with up to 10 or more alloying additions. Refractory metal additions are known to improve the high-temperature creep-resistance and the influence and interactions with various alloying additions have drawn much attention. We study partitioning behavior of the alloying elements, growth and coarsening kinetics of γ' (L1 2 structure) precipitates in a series of model superalloys containing W, Re, and Ru in the earlier stages of the transformation with precipitates several tens of nanometers in diameter. The three-dimensional elemental spatial distribution with respect to γ' (L1 2 structure) precipitates, their heterophase interfaces, and their temporal evolution with high-temperature aging are characterized by 3D atom-probe (3DAP) microscopy with subnanometer resolution. The overall microstructure is characterized by transmission electron microscopy (TEM), which helps in the spanning of length scales. The experimental characterization provides important input parameters for modeling of partitioning and nanostructural evolution by ThermoCalc and PrecipiCalc and thus allows for a critical test of the predictive capabilities of these models. (author)

  4. Surface modification, microstructure and mechanical properties of investment cast superalloy

    OpenAIRE

    M. Zielińska; K. Kubiak; J. Sieniawski

    2009-01-01

    Purpose: The aim of this work is to determine physical and chemical properties of cobalt aluminate (CoAl2O4) modifiers produced by different companies and the influence of different types of modifiers on the grain size, the microstructure and mechanical properties of high temperature creep resisting superalloy René 77.Design/methodology/approach: The first stage of the research work took over the investigations of physical and chemical properties of cobalt aluminate manufactured by three diff...

  5. Powder-metallurgy superalloy strengthened by a secondary gamma phase.

    Science.gov (United States)

    Kotval, P. S.

    1971-01-01

    Description of experiments in which prealloyed powders of superalloy compositions were consolidated by extrusion after the strengthening by precipitation of a body-centered tetragonal gamma secondary Ni3 Ta phase. Thin foil electron microscopy showed that the mechanical properties of the resultant powder-metallurgy product were correlated with its microstructure. The product exhibited high strength at 1200 F without loss of ductility, after thermomechanical treatment and aging.

  6. The effect of heat treatment on the micro-structure and the mechanical properties of high-temperature nickel-base-superalloys

    International Nuclear Information System (INIS)

    Schubert, R.; Horn, E.

    1974-01-01

    General review of heat treatment applied to high-temperature nickel-base-superalloys as a function of the volume percent of the γ'-phase. Heat treatment schedule. γ'-morphology and γ'-distribution as well as their effect on mechanical properties. Values obtained from tensile tests up to 1,000 0 C. Results obtained from creep tests. Limitation for the heat treatment of alloys having an unstable γ'-phase. Alloys X 5 NiCrTi 26 15, ATS 270 (approximately INCO 718), NiCr 20 TiAl, NiCr 20 Co 18 Ti, ATS 342 (approximately Waspaloy), ATS 354 (approximately Udimet 520), NiCo 20 Cr 15 MoAlTi, ATS 382 (approximately Udimet 710), ATS 381-G (approximately Mar M 246), FIS 145 and ATS 391-G (aproximately IN 100). (orig.) [de

  7. Effects of Rhenium Addition on the Temporal Evolution of the Nanostructure and Chemistry of a Model Ni-Cr-Al Superalloy. 1; Experimental Observations

    Science.gov (United States)

    Yoon, Kevin E.; Noebe, Ronald D.; Seidman, David N.

    2006-01-01

    The temporal evolution of the nanostructure and chemistry of a model Ni-8.5 at.% Cr-10 at. % Al alloy, with the addition of 2 at.% Re, aged at 1073 K from 0.25 to 264 h, was studied. Transmission electron microscopy and atom-probe tomography were used to measure the number density and mean radius of the gamma prime (L1(sub 2) structure)-precipitates and the chemistry of the gamma prime-precipitates and the gamma (face-centered cubic)-matrix, including the partitioning behavior of all alloying elements between the gamma- and gamma prime-phases and the segregation behavior at gamma/gamma prime interfaces. The precipitates remained spheroidal for an aging time of up to 264 h and, unlike commercial nickel-based superalloys containing Re, there was not confined (nonmonotonic) Re segregation at the gamma/gamma prime interfaces.

  8. High temperature corrosion of nickel alloys by molten calcium chloride in an oxidising environment

    International Nuclear Information System (INIS)

    Barnett, Roger; Gittos, Mike

    2012-09-01

    A series of nickel alloys was submerged in molten calcium chloride (a molten salt proposed for and used in the nuclear industry for a variety of applications), at 850 deg. C for 72 hours under an oxidising environment. The samples were analysed in detail, in order to determine their corrosion behaviour and suitability for use under these conditions. 310 stainless steel was used as a reference material. Extensive corrosion occurred and the observed attack on the metal substrates was general and massive with corrosion rates ranging from 1.17 mm/year, for Haynes 214, to 13.3 mm/year, for 310 stainless steel. All materials showed selective leaching of chromium from the samples but the oxide layer formed was not protective, spalling away easily. The severity of the attack was not immediately visible from the corrosion rate alone: samples showed a friable scale on the surface and deep penetration of the attack beneath, up to 0.63 mm for 310 stainless steel. In some cases, the attack was clearly intergranular with chromium being depleted along the grain boundaries, whereas in others, the attack was more general. No simple correlation between alloying elements and corrosion rate was apparent, with additions of aluminium and silicon appearing to have little or no protective effect. Alloys 600 and Haynes HR-160 showed promise, with relatively low corrosion rates and penetration depths. (authors)

  9. Focused Ion Beam Nanotomography of ruthenium-bearing nickel-base superalloys with focus on cast-microstructure and phase stability

    International Nuclear Information System (INIS)

    Cenanovic, Samir

    2012-01-01

    The influence of rhenium and ruthenium on the multi component system nickel-base superalloy is manifold and complex. An experimental nickel-base superalloy containing rhenium and ruthenium within defined contents, named Astra, was used to investigate the influences of these two elements on the alloy system. The last stage solidification of nickel-base superalloys after Bridgman casting and the high temperature phase stability of these alloys, could be explored with the aid of focused ion beam nanotomography. FIB-nt therefore was introduced and realized at the chair of General Materials Properties of the University Erlangen-Nuremberg. Cast Astra alloys are like other nickel-base superalloys morphologically very inhomogeneous and affected by segregation. In the interdendritic region different structures with huge γ' precipitates are formed. These inhomogeneities and remaining eutectics degrade the mechanical properties, witch makes an understanding of the subsiding processes at solidification of residual melt important for the casting process and the heat treatment. This is why the last stage solidification in the interdendritic region was analyzed. With the help of focused ion beam nanotomography, three different structures identified from 2-D sections could be assigned to one original 3-D structure. It was pointed out, that only the orientation of the plane of the 2-D cut influences the appearance in the 2-D section. The tomography information was used to explain the development during solidification and to create a model of last stage solidification. The interdendritic region is solidifying under the development of eutectic islands. The structure nucleates eutectically epitaxially at primary dendrite arms, with formation of fine γ/γ' precipitates. During solidification the γ' precipitates coarsen in a rod-like structure, and end up in large γ' precipitates. Simulations and other investigations could approve this model. First three

  10. Competing fatigue failure behaviors of Ni-based superalloy FGH96 at elevated temperature

    International Nuclear Information System (INIS)

    Miao, Guolei; Yang, Xiaoguang; Shi, Duoqi

    2016-01-01

    Fatigue experiments were performed on a polycrystalline P/M processed nickel-based superalloy, FGH96 at 600 °C to investigate competing fatigue failure behaviors of the alloy. The experiments were performed at four levels of stress (from high cycle fatigue to low cycle fatigue) at stress ratio of 0.05. There was large variability in fatigue life at both high and low stresses. Scanning electron microscopy (SEM) was used to analyze the failure surfaces. Three types of competing failure modes were observed (surface, sub-surface and internal initiated failures). Crack initiation sites were gradually changed from the surface to the interior with the decreasing of stress level. Roles of microstructures in competing failure mechanism were analyzed. There were six kinds of fatigue crack initiation modes: (1) surface inclusion initiated; (2) surface facet initiated; (3) sub-surface inclusion initiated; (4) sub-surface facet initiated; (5) internal inclusion initiated; (6) internal facet initiated. Inclusions at surface were the life-limiting microstructures at higher stress levels. The probability of occurrence of inclusions initiated is gradually reduced with decreasing of stress level, simultaneously the probability of occurrence of facets initiated is increasing. The existence of the inclusions resulted in large life variability at higher stress levels, while heterogeneity of material caused by random combinations of grains was the main cause of fatigue variability at lower stress levels.

  11. On the compatibility of single crystal superalloys with a thermal barrier coating system

    Energy Technology Data Exchange (ETDEWEB)

    Wu, R.T. [Department of Materials, Imperial College London, Prince Consort Road, London SW7 2BP (United Kingdom); Reed, R.C. [Department of Materials, Imperial College London, Prince Consort Road, London SW7 2BP (United Kingdom)], E-mail: r.reed@birmingham.ac.uk

    2008-02-15

    The compatibility of three Co-containing prototype single crystal nickel-based superalloys with a thermal barrier coating (TBC) system is examined. These contain 2.1, 8.4 and 12.6 at.% Co; the concentrations of Al, Cr, Ta, W, Re, Hf are identical and chosen to be representative of advanced grades of these alloys. The TBC consists of an yttria-stabilized zirconia (YSZ) layer formed by electron beam physical vapour deposition (EB-PVD) and a bond coat made by electrodeposited platinum with a subsequent interdiffusion heat treatment - a so-called 'platinum-diffused' bond coat. The resistance to spallation of the TBC system is degraded as the Co content of the substrate increases. Wavelength-dispersive X-ray analysis and secondary ion mass spectrometry indicate that quantities of Co are present in the thermally grown oxide (TGO) by the time that failure occurs, this effect being most pronounced when the Co content of the substrate is high; the TGO is then more wavy and convoluted. The bond coat consists exclusively of the {gamma} and {gamma}' phases, with the balance shifting towards {gamma} with increasing thermal exposure; the loss of Al from the bond coat due to TGO formation means that the TGO is eventually in contact with the {gamma} phase solely, which is enriched in Co.

  12. Effect of Sulfur and Chlorine on Fireside Corrosion Behavior of Inconel 740 H Superalloy

    Science.gov (United States)

    Jin-tao, Lu; Yan, Li; Zhen, Yang; Jin-yang, Huang; Ming, Zhu; Gu, Y.

    2018-03-01

    Fireside corrosion behavior of Inconel 740H superalloy was studied at 750 °C in simulated coal ash/flue gas environments by means of XRD, SEM and EDS. The results indicated that the corrosion behavior was strongly related to the SO2 levels and was significantly affected by NaCl additions. In presence of the atmospheres with 0.1 % SO2, the alloy exhibited the highest corrosion resistance due to formation of a stable and dense Cr2O3 film. In presence of the atmosphere with 1.5 % SO2, however, a non-coherent and porous Cr2O3 film was formed. The thickness of film and internal sulfides were substantially increased. The NaCl additions significantly accelerated the corrosion process. A non-protective outer oxide film was formed, composed by multiple layers with serious inner sulfide and spallation. The depths of internal oxidizing and sulfuration zones were significantly increased. The mechanism of ash corrosion formation was also discussed.

  13. Competing fatigue failure behaviors of Ni-based superalloy FGH96 at elevated temperature

    Energy Technology Data Exchange (ETDEWEB)

    Miao, Guolei [School of Energy and Power Engineering, Beihang University, Beijing 100191 (China); Yang, Xiaoguang [School of Energy and Power Engineering, Beihang University, Beijing 100191 (China); Collaborative Innovation Center of Advanced Aero-engine(CICAAE), Beihang University, Beijing 100191 (China); Shi, Duoqi, E-mail: shdq@buaa.edu.cn [School of Energy and Power Engineering, Beihang University, Beijing 100191 (China); Collaborative Innovation Center of Advanced Aero-engine(CICAAE), Beihang University, Beijing 100191 (China)

    2016-06-21

    Fatigue experiments were performed on a polycrystalline P/M processed nickel-based superalloy, FGH96 at 600 °C to investigate competing fatigue failure behaviors of the alloy. The experiments were performed at four levels of stress (from high cycle fatigue to low cycle fatigue) at stress ratio of 0.05. There was large variability in fatigue life at both high and low stresses. Scanning electron microscopy (SEM) was used to analyze the failure surfaces. Three types of competing failure modes were observed (surface, sub-surface and internal initiated failures). Crack initiation sites were gradually changed from the surface to the interior with the decreasing of stress level. Roles of microstructures in competing failure mechanism were analyzed. There were six kinds of fatigue crack initiation modes: (1) surface inclusion initiated; (2) surface facet initiated; (3) sub-surface inclusion initiated; (4) sub-surface facet initiated; (5) internal inclusion initiated; (6) internal facet initiated. Inclusions at surface were the life-limiting microstructures at higher stress levels. The probability of occurrence of inclusions initiated is gradually reduced with decreasing of stress level, simultaneously the probability of occurrence of facets initiated is increasing. The existence of the inclusions resulted in large life variability at higher stress levels, while heterogeneity of material caused by random combinations of grains was the main cause of fatigue variability at lower stress levels.

  14. Microstructure properties relationship in transient liquid phase diffusion bonds made in MA 758 superalloy

    International Nuclear Information System (INIS)

    Ekrami, A.

    2003-01-01

    Transient liquid phase diffusion bonding procedure was used to join an ODS Ma 758 superalloy in two conditions, wrought fine grains, and recrystallised grains. An Ni-Cr-B-Si alloy was used as an interlayer. Bonding was carried out at 1100 d ig C for bonding hold times of 15,30, and 60 minutes under vacuum of 6x10 -4 torr. Bonded samples were homogenized at 1360 d ig C for one hour and then cooled with a rate of 15 d ig C /min. Shear and fatigue strengths of bonds were determined. The results showed that there is no effect of bonding hold times on shear strength after bonding hold time of 30 minutes. At a given bonding hold time, the shear strength of bonds made in the recrystallized condition was greater than the shear strength of bonds made in the fine grain condition. The same was true for fatigue strength at a given cycle to fracture. Transient liquid phase bonding was also carried out under pressure of 0.1 Mpa under the same temperature and bonding hold time for fine grain material. Microstructure studies of bonds made under pressure showed no effects of pressure on bond region grain size. Shear tests results also demonstrate little effects of pressure on shear strength of bonds

  15. The structure and properties of a nickel-base superalloy produced by osprey atomization-deposition

    Science.gov (United States)

    Bricknell, Rodger H.

    1986-04-01

    The production of a nickel-base superalloy, René* 80, by the Osprey atomization-deposition process has been investigated. Dense (>99 pct) material with a fine-grained equiaxed microstructure was deposited using either argon or nitrogen as the atomizing gas. Defects present in the material included a chill region at the collector plate interface, entrapped recirculated particles, porosity, and ceramic particles from the melting and dispensing system. In contrast to other rapid solidification techniques, low oxygen pick-ups are noted in the current technique. Tensile strengths above those displayed by castings are found in both nitrogen and argon atomized material, and in both the as-deposited and heat treated conditions. In addition, no profound mid-temperature ductility loss is displayed by this low oxygen material, in contrast to results on other rapidly solidified material with high oxygen contents. These results are explained in terms of oxygen embrittlement. In view of the excellent properties measured, the attractive economics of the process, and the fact that fine control of the gas/metal flow ratio is shown to be unnecessary, it is concluded that atomization-deposition presents an attractive potential production route for advanced alloys.

  16. Effect of Microstructure on Electrical Conductivity of Nickel-Base Superalloys

    Science.gov (United States)

    Nagarajan, Balasubramanian; Castagne, Sylvie; Annamalai, Swaminathan; Fan, Zheng; Chan, Wai Luen

    2017-08-01

    Eddy current spectroscopy is one of the promising non-destructive methods for residual stress evaluation along the depth of subsurface-treated nickel-base superalloys, but it is limited by its sensitivity to microstructure. This paper studies the influence of microstructure on the electrical conductivity of two nickel-base alloys, RR1000 and IN100. Different microstructures were attained using heat treatment cycles ranging from solution annealing to aging, with varying aging time and temperature. Eddy current conductivity was measured using conductivity probes of frequencies ranging between 1 and 5 MHz. Qualitative and quantitative characterization of the microstructure was performed using optical and scanning electron microscopes. For the heat treatment conditions between the solution annealing and the peak aging, the electrical conductivity of RR1000 increased by 6.5 pct, which is duly substantiated by the corresponding increase in hardness (12 pct) and the volume fraction of γ' precipitates (41 pct). A similar conductivity rise of 2.6 pct for IN100 is in agreement with the increased volume fraction of γ' precipitates (12.5 pct) despite an insignificant hardening between the heat treatment conditions. The observed results with RR1000 and IN100 highlight the sensitivity of electrical conductivity to the minor microstructure variations, especially the volume fraction of γ' precipitates, within the materials.

  17. Morphological changes of gamma prime precipitates in nickel-base superalloy single crystals

    International Nuclear Information System (INIS)

    Mackay, R.A.

    1984-07-01

    Changes in the morphology of the gamma prime precipitate were examined during tensile creep at temperatures between 927 and 1038 C in 001-oriented single crystals of a Ni-Al-Mo-Ta superalloy. In this alloy, which has a large negative misfit of -0.80%, the gamma prime particles link together during creep to form platelets, or rafts, which are aligned with their broad faces perpendicular to the applied tensile axis. The dimensions of the gamma and gamma prime phases were measured as directional coarsening developed in an attempt to trace the changing morphology under various stress levels. In addition, the effects of initial microstructure, as well as slight compositional variations, were related to raft development and creep properties. The results showed that directional coarsening of gamma prime began during primary creep, and under certain conditions, continued to develop after the onset of steady-state creep. The length of the rafts increased linearly with time up to a plateau region. The thickness of the rafts, however, remained equal to the initial gamma prime size at least up through the onset of tertiary creep this is a clear indication of the stability of the finely-spaced gamma-gamma prime lamellar structure. It was found that the single crystals with the finest gamma prime size exhibited the longest creep lives, because the resultant rafted structure had a larger number of gamma-gamma prime interfaces per unit volume of material

  18. Investigations on Microstructure and Corrosion behavior of Superalloy 686 weldments by Electrochemical Corrosion Technique

    Science.gov (United States)

    Arulmurugan, B.; Manikandan, M.

    2018-02-01

    In the present study, microstructure and the corrosion behavior of Nickel based superalloy 686 and its weld joints has been investigated by synthetic sea water environment. The weldments were fabricated by Gas Tungsten Arc Welding (GTAW) and Pulsed Current Gas Tungsten Arc Welding (PCGTAW) techniques with autogenous mode and three different filler wires (ERNiCrMo-4, ERNiCrMo-10 and ERNiCrMo-14). Microstructure and Scanning electron microscope examination was carried out to evaluate the structural changes in the fusion zones of different weldments. Energy Dispersive X-ray Spectroscopy (EDS) analysis was carried out to evaluate the microsegregation of alloying elements in the different weld joints. Potentiodynamic polarization study was experimented on the base metal and weld joints in the synthetic sea water environment to evaluate the corrosion rate. Tafel’s interpolation technique was used to obtain the corrosion rate. The microstructure examination revealed that the fine equiaxed dendrites were observed in the pulsed current mode. EDS analysis shows the absence of microsegregation in the current pulsing technique. The corrosion rates of weldments are compared with the base metal. The results show that the fine microstructure with the absence of microsegregation in the PCGTA weldments shows improved corrosion resistance compared to the GTAW. Autogenous PCGTAW shows higher corrosion resistance irrespective of all weldments employed in the present study.

  19. Nucleation of recrystallisation in castings of single crystal Ni-based superalloys

    International Nuclear Information System (INIS)

    Mathur, Harshal N.; Panwisawas, Chinnapat; Jones, C. Neil; Reed, Roger C.; Rae, Catherine M.F.

    2017-01-01

    Recrystallisation in single crystal Ni-based superalloys during solution heat treatment results in a significant cost to the investment casting industry. In this paper two sources of surface nucleation have been identified in the alloy CMSX-4 ® . Firstly, Electron Backscattered Diffraction (EBSD) has revealed micro-grains of γ′, between 2 and 30 μm diameter in the layer of surface eutectic found in the upper part of the casting. These have high angle boundaries with respect to the bulk single crystal and a fraction coarsen during solution heat treatment. Secondly, in the lower regions where surface eutectic does not form, locally deformed regions, 5–20 μm deep, form where the metal adheres to the mould. The local strain causes misorientations up to ≈20° with respect the bulk single crystal, and after heat treatment these regions develop into small grains of similar low-angle misorientations. However, they also form twins to produce further grains which have mobile high-angle boundaries with respect to the bulk single crystal. Experiments have shown that micro-grains at the surface grow to cause full recrystallisation where there is sufficient strain in the bulk material, and by removing these surface defects, recrystallisation can be completely mitigated. Etching of the cast surface is demonstrated to be an effective method of achieving this.

  20. On the formation of white-spot defects in a superalloy VAR ingot

    Energy Technology Data Exchange (ETDEWEB)

    Grignard, Jean Francois; Soller, Aude; Jourdan, Julien; Bellot, Jean-Pierre; Jardy, Alain [Institut Jean Lamour (UMR 7198), Ecole des Mines de Nancy, Parc de Saurupt, Nancy Cedex (France)

    2011-07-15

    For the production of nickel-based superalloys for the aerospace industry, strict control of the macrostructure of the product is necessary to avoid the appearance of potentially fatal defects. Our study focuses on the prevention of ''white spots'' in the alloy IN 718. These defects, which are small volumes of a few millimeters of characteristic length, are depleted in niobium. They are known to result from the fall of metal fragments in the liquid pool during VAR processing. According to their history in the liquid metal, these fragments could not being remelted before being trapped in the mushy zone and then give rise to defects. A model calculates the heat transfer in such a precursor to simulate its melting during his stay in the bath. The validation of the predicted melting kinetics requires a series of immersive experiences of synthetic defects in a metal bath. The model and experiments have demonstrated the initial solidification of a layer of metal around the precursor. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Microstructure and Mechanical Properties of Laser Melting Deposited GH4169 Superalloy

    Directory of Open Access Journals (Sweden)

    DU Bo-rui

    2017-01-01

    Full Text Available The block samples of a Ni-based superalloy named GH4169 were prepared by laser melting deposited method using the corresponding GH4169 alloy powders,and then were heat treated with solution treatment followed by double aging.The microstructure and element segregation analysis of both as-deposited and heat treated samples were studied by scanning electron microscopy (SEM and energy dispersive spectroscopy (EDS.The microhardness as well as tensile properties at room and elevated temperatures were tested.The results indicate that the microstructure of as-deposited sample mainly consists of columnar dendritic crystals that grow along with different directions.Grains are refined after solution and aging heat treatment,but remain dendritic crystals substructure inside.Compared with the as-deposited sample,the microhardness and tensile strength of the heat treated sample increase substantially,but the plasticity somewhat decreases.Nonetheless the tensile properties are superior to the standard values of forgings.The fracture surface exhibits ductile transcrystalline fracture mode.

  2. Microstructural Changes during High Temperature Service of a Cobalt-Based Superalloy First Stage Nozzle

    Directory of Open Access Journals (Sweden)

    A. Luna Ramírez

    2016-01-01

    Full Text Available Superalloys are a group of alloys based on nickel, iron, or cobalt, which are used to operate at high temperatures (T > 540°C and in situations involving very high stresses like in gas turbines, particularly in the manufacture of blades, nozzles, combustors, and discs. Besides keeping its high resistance to temperatures which may approach 85% of their melting temperature, these materials have excellent corrosion resistance and oxidation. However, after long service, these components undergo mechanical and microstructural degradation; the latter is considered a major cause for replacement of the main components of gas turbines. After certain operating time, these components are very expensive to replace, so the microstructural analysis is an important tool to determine the mode of microstructure degradation, residual lifetime estimation, and operating temperature and most important to determine the method of rehabilitation for extending its life. Microstructural analysis can avoid catastrophic failures and optimize the operating mode of the turbine. A case study is presented in this paper.

  3. Effect of laser shock on tensile deformation behavior of a single crystal nickel-base superalloy

    International Nuclear Information System (INIS)

    Lu, G.X.; Liu, J.D.; Qiao, H.C.; Zhou, Y.Z.; Jin, T.; Zhao, J.B.; Sun, X.F.; Hu, Z.Q.

    2017-01-01

    This investigation focused on the tensile deformation behavior of a single crystal nickel-base superalloy, both in virgin condition and after laser shock processing (LSP) with varied technology parameters. Nanoindention tests were carried out on the sectioned specimens after LSP treatment to characterize the surface strengthening effect. Stress strain curves of tensile specimens were analyzed, and microstructural observations of the fracture surface and the longitudinal cross-sections of ruptured specimens were performed via scanning electron microscope (SEM), in an effort to clarify the fracture mechanisms. The results show that a surface hardening layer with the thickness of about 0.3–0.6 mm was gained by the experimental alloys after LSP treatment, but the formation of surface hardening layer had not affected the yield strength. Furthermore, fundamental differences in the plastic responses at different temperatures due to LSP treatment had been discovered. At 700 °C, the slip deformation was held back when it extended to the surface hardening layer and the ensuing slip steps improved the plasticity; however, at 1000 °C, surface hardening layer hindered the macro necking, which resulted in the relatively lower plasticity.

  4. Factors Influencing Dwell Fatigue Cracking in Notches of Powder Metallurgy Superalloys

    Science.gov (United States)

    Gabb, T. P.; Telesman, J.; Ghosn, L.; Garg, A.; Gayda, J.

    2011-01-01

    The influences of heat treatment and cyclic dwells on the notch fatigue resistance of powder metallurgy disk superalloys were investigated for low solvus high refractory (LSHR) and ME3 disk alloys. Disks were processed to produce material conditions with varied microstructures and associated mechanical properties. Notched specimens were first subjected to baseline dwell fatigue cycles having a dwell at maximum load, as well as tensile, stress relaxation, creep rupture, and dwell fatigue crack growth tests at 704 C. Several material heat treatments displayed a bimodal distribution of fatigue life with the lives varying by two orders-of-magnitude, while others had more consistent fatigue lives. This response was compared to other mechanical properties, in search of correlations. The wide scatter in baseline dwell fatigue life was observed only for material conditions resistant to stress relaxation. For selected materials and conditions, additional tests were then performed with the dwells shifted in part or in total to minimum tensile load. The tests performed with dwells at minimum load exhibited lower fatigue lives than max dwell tests, and also exhibited early crack initiation and a substantial increase in the number of initiation sites. These results could be explained in part by modeling evolution of peak stresses in the notch with continued dwell fatigue cycling. Fatigue-environment interactions were determined to limit life for the fatigue cycles with dwells.

  5. Effect of laser shock on tensile deformation behavior of a single crystal nickel-base superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Lu, G.X. [Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China); University of Chinese Academy of Sciences, 19 Yuquan Road, Beijing 100049 (China); Liu, J.D., E-mail: jdliu@imr.ac.cn [Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China); Qiao, H.C. [Shenyang Institute of Automation, Chinese Academy of Sciences, 114 Nanta Road, Shenyang 110016 (China); Zhou, Y.Z. [Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China); Jin, T., E-mail: tjin@imr.ac.cn [Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China); Zhao, J.B. [Shenyang Institute of Automation, Chinese Academy of Sciences, 114 Nanta Road, Shenyang 110016 (China); Sun, X.F.; Hu, Z.Q. [Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China)

    2017-02-16

    This investigation focused on the tensile deformation behavior of a single crystal nickel-base superalloy, both in virgin condition and after laser shock processing (LSP) with varied technology parameters. Nanoindention tests were carried out on the sectioned specimens after LSP treatment to characterize the surface strengthening effect. Stress strain curves of tensile specimens were analyzed, and microstructural observations of the fracture surface and the longitudinal cross-sections of ruptured specimens were performed via scanning electron microscope (SEM), in an effort to clarify the fracture mechanisms. The results show that a surface hardening layer with the thickness of about 0.3–0.6 mm was gained by the experimental alloys after LSP treatment, but the formation of surface hardening layer had not affected the yield strength. Furthermore, fundamental differences in the plastic responses at different temperatures due to LSP treatment had been discovered. At 700 °C, the slip deformation was held back when it extended to the surface hardening layer and the ensuing slip steps improved the plasticity; however, at 1000 °C, surface hardening layer hindered the macro necking, which resulted in the relatively lower plasticity.

  6. Experimental study on creep-fatigue interaction behavior of GH4133B superalloy

    International Nuclear Information System (INIS)

    Hu Dianyin; Wang Rongqiao

    2009-01-01

    The creep-fatigue tests have been conducted with nickel-based superalloy GH4133B at 600 deg. C in three cases of type loading to study the creep-fatigue behavior of the alloy and the loading history effect on the creep-fatigue damage. Since the conventional linear cumulative damage rule failed in evaluating the creep-fatigue life based on experimental data, a continuous non-linear model proposed by Mao et al. was employed to describe the creep-fatigue interaction. The creep-fatigue damage in the cases of continuous cyclic creep loading (CF) and prior fatigue followed by creep loading (F + C) was larger than unity and smaller than unity when the type loading was prior creep followed by fatigue loading (C + F). Scanning electron microscope (SEM) analyses of the fracture surface showed that the cracks initiated from the specimen surface and the fracture modes in different loading history were different. The crack mode at CF loading depended on the cyclic period. In the case of F + C loading, the primary fracture mode was transgranular, and in the condition where the type of waveform was C + F, the fracture mode was of mixed transgranular and intergranular type. In addition, the origin of the history effect on creep-fatigue interaction was explained by the SEM observations.

  7. Looking for New Polycrystalline MC-Reinforced Cobalt-Based Superalloys Candidate to Applications at 1200°C

    Directory of Open Access Journals (Sweden)

    Patrice Berthod

    2017-01-01

    Full Text Available For applications for which temperatures higher than 1150°C can be encountered the currently best superalloys, the γ/γ′ single crystals, cannot be used under stress because of the disappearance of their reinforcing γ′ precipitates at such temperatures which are higher than their solvus. Cobalt-based alloys strengthened by refractory and highly stable carbides may represent an alternative solution. In this work the interest was focused on MC carbides of several types. Alloys were elaborated with atomically equivalent quantities in M element (among Ti, Ta, Nb, Hf, or Zr and in C. Script-like eutectic TiC, TaC, NbC, HfC, and ZrC carbides were successfully obtained in the interdendritic spaces. Unfortunately, only one type, HfC, demonstrated high morphological stability during about 50 hours at 1200°C. The concerned alloy, of the Co-25Cr-0.5C-7.4Hf type (in wt.%, was further characterized in flexural creep resistance and air-oxidation resistance at the same temperature. The creep behaviour was very good, notably by comparison with a more classical Co-25Cr-0.5C-7.5Ta alloy, proving that the interest of HfC is higher than the TaC one. In contrast the oxidation by air was faster and its behaviour not really chromia-forming. Significant improvements of this chemical resistance are expected before taking benefit from the mechanical superiority of this alloy.

  8. Rafting in single crystal nickel-base superalloys – An overview

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    Page 1 ... aircraft engines as well as land-based power generation applications. Microstruc- ture and high temperature mechanical properties are the major factors controlling the performance of SX ... Single crystal (SX) superalloys are a group of nickel-base superalloys. They exhibit superior high temperatur mechanical ...

  9. Ontogênese, anatomia e ultra-estrutura dos nectários extraflorais de Hymenaea stigonocarpa Mart. ex Hayne (Fabaceae - Caesalpinioideae Ontogenesis, anatomy, and ultrastructure of Hymenaea stigonocarpa Mart. ex Hayne (Fabaceae - Caesalpinioideae extrafloral nectaries

    Directory of Open Access Journals (Sweden)

    Élder Antônio Sousa Paiva

    2006-06-01

    Full Text Available O jatobá-do-cerrado (Hymenaea stigonocarpa Mart. ex Hayne apresenta nectários extraflorais (NEFs, os quais são descritos pela primeira vez no gênero. Neste trabalho foram estudadas a distribuição, ontogênese, estrutura e ultra-estrutura dos nectários extraflorais (NEFs. Amostras de folhas em várias fases de desenvolvimento foram coletadas, fixadas e processadas para estudos em microscopia de luz e eletrônica de transmissão e varredura, segundo técnicas convencionais. Testes histoquímicos foram empregados para determinar a natureza química da secreção. Os NEFs estão distribuídos por todo o limbo, sendo mais concentrados nos terços basal e médio de cada folíolo. Estes nectários são embutidos no mesofilo, apresentam tecido secretor envolvido por uma endoderme e são vascularizados por xilema e floema. A atividade secretora dos NEFs é limitada à fase juvenil da folha. Nas folhas mais velhas, os NEFs tornam-se não funcionais. O tecido secretor dos NEFs é formado a partir da protoderme, enquanto a endoderme tem origem no meristema fundamental. No tecido secretor de nectários funcionais as células apresentam citoplasma denso, núcleo volumoso, mitocôndrias, plastídios com sistema de membranas pouco desenvolvido, gotas de óleo dispersas no citosol, dictiossomos e segmentos de retículo endoplasmático liso. A secreção é liberada por meio de rupturas cuticulares e apresenta polissacarídeos e lipídios.Hymenaea stigonocarpa Mart. ex Hayne, known as "jatobá-do-cerrado" has extrafloral nectaries (EFNs, which are reported for the first time in Hymenaea genus. In this research the origin, distribution, structure, and ultrastructure of the EFNs were studied. Samples of leaflets at different developmental stages were collected, fixed and processed by standard methods for analyses at light and electronic microscopes; histochemical tests were employed to determine the nature of secretion products. EFNs are distributed all over

  10. High temperature oxidation and corrosion behavior of Ni-base superalloy in He environment

    International Nuclear Information System (INIS)

    Lee, Gyoeng Geun; Park, Ji Yeon; Jung, Su jin

    2010-11-01

    Ni-base superalloy is considered as a IHX (Intermediate Heat Exchanger) material for VHTR (Very High Temperature Gas-Cooled Reactor). The helium environment in VHTR contains small amounts of impure gases, which cause oxidation, carburization, and decarburization. In this report, we conducted the literature survey about the high temperature behavior of Ni-base superalloys in air and He environments. The basic information of Ni-base superalloy and the basic metal-oxidation theory were briefly stated. The He effect on the corrosion of Ni-base superalloy was also summarized. This works would provide a brief suggestion for the next research topic for the application of Ni-base superalloy to VHTR

  11. Oxidation of Inconel 625 superalloy upon treatment with oxygen or hydrogen plasma at high temperature

    Energy Technology Data Exchange (ETDEWEB)

    Vesel, Alenka; Drenik, Aleksander; Elersic, Kristina; Mozetic, Miran; Kovac, Janez [Jozef Stefan Institute, Jamova 39, SI-1000 Ljubljana (Slovenia); Gyergyek, Tomaz [University of Ljubljana, Faculty of Electrical Engineering, Trzaska 25, SI-1000 Ljubljana (Slovenia); Stockel, Jan; Varju, Jozef; Panek, Radomir [Institute of Plasma Physics, Academy of Sciences of the Czech Republic, Ze Slovankou 3, Praha 8 (Czech Republic); Balat-Pichelin, Marianne, E-mail: marianne.balat@promes.cnrs.fr [PROMES-CNRS Laboratory, 7 rue du four solaire, 66120 Font Romeu Odeillo (France)

    2014-06-01

    Initial stages of Inconel 625 superalloy (Ni{sub 60}Cr{sub 30}Mo{sub 10}Ni{sub 4}Nb{sub 1}) oxidation upon short treatment with gaseous plasma at different temperatures up to about 1600 K were studied. Samples were treated for different periods up to a minute by oxygen or hydrogen plasma created with a microwave discharge in the standing-wave mode at a pressure of 40 Pa and a power 500 W. Simultaneous heating of the samples was realized by focusing concentrated solar radiation from a 5 kW solar furnace directly onto the samples. The morphological changes upon treatment were monitored using scanning electron microscopy, compositional depth profiling was performed using Auger electron spectroscopy, while structural changes were determined by X-ray diffraction. The treatment in oxygen plasma caused formation of metal oxide clusters of three dimensional crystallites initially rich in nickel oxide with the increasing chromium oxide content as the temperature was increasing. At about 1100 K iron and niobium oxides prevailed on the surface causing a drop of the material emissivity at 5 μm. Simultaneously the NiCr{sub 2}O{sub 4} compound started growing at the interface between the oxide film and bulk alloy and the compound persisted up to temperatures close to the Inconel melting point. Intensive migration of minority alloying elements such as Fe and Ti was observed at 1600 K forming mixed surface oxides of sub-micrometer dimensions. The treatment in hydrogen plasma with small admixture of water vapor did not cause much modification unless the temperature was close to the melting point. At such conditions aluminum segregated on the surface and formed well-defined Al{sub 2}O{sub 3} crystals.

  12. Oxidation of Inconel 625 superalloy upon treatment with oxygen or hydrogen plasma at high temperature

    Science.gov (United States)

    Vesel, Alenka; Drenik, Aleksander; Elersic, Kristina; Mozetic, Miran; Kovac, Janez; Gyergyek, Tomaz; Stockel, Jan; Varju, Jozef; Panek, Radomir; Balat-Pichelin, Marianne

    2014-06-01

    Initial stages of Inconel 625 superalloy (Ni60Cr30Mo10Ni4Nb1) oxidation upon short treatment with gaseous plasma at different temperatures up to about 1600 K were studied. Samples were treated for different periods up to a minute by oxygen or hydrogen plasma created with a microwave discharge in the standing-wave mode at a pressure of 40 Pa and a power 500 W. Simultaneous heating of the samples was realized by focusing concentrated solar radiation from a 5 kW solar furnace directly onto the samples. The morphological changes upon treatment were monitored using scanning electron microscopy, compositional depth profiling was performed using Auger electron spectroscopy, while structural changes were determined by X-ray diffraction. The treatment in oxygen plasma caused formation of metal oxide clusters of three dimensional crystallites initially rich in nickel oxide with the increasing chromium oxide content as the temperature was increasing. At about 1100 K iron and niobium oxides prevailed on the surface causing a drop of the material emissivity at 5 μm. Simultaneously the NiCr2O4 compound started growing at the interface between the oxide film and bulk alloy and the compound persisted up to temperatures close to the Inconel melting point. Intensive migration of minority alloying elements such as Fe and Ti was observed at 1600 K forming mixed surface oxides of sub-micrometer dimensions. The treatment in hydrogen plasma with small admixture of water vapor did not cause much modification unless the temperature was close to the melting point. At such conditions aluminum segregated on the surface and formed well-defined Al2O3 crystals.

  13. Effect of boron and carbon on thermomechanical fatigue of IN 718 superalloy

    International Nuclear Information System (INIS)

    Xiao, L.; Chen, D.L.; Chaturvedi, M.C.

    2006-01-01

    Stress-controlled thermomechanical fatigue (TMF) behavior of IN 718 superalloy with different concentrations of boron (B) and carbon (C) was studied with temperature varying between 350 and 650 deg. C at different cyclic stress ranges and at a stress ratio of R = 0.1. Initial cyclic softening followed by a significant cyclic hardening was observed in the in-phase (IP) TMF, while continuous cyclic hardening occurred during out-of-phase (OP) TMF. Tensile cyclic creep was observed in all the TMF deformation regimes, and the creep strain increased with increasing number of cycles and stress range. B and C additions were found to retard the cyclic creep, leading to an effective improvement in the fatigue life of IP-TMF. Among the four alloys tested, the alloy with 29 ppm B and 225 ppm C exhibited the lowest creep strain and the highest IP-TMF life at the lower stress range. In the OP-TMF, the fatigue life increased with increasing B concentration at the higher stress range, and with C concentration at the lower stress range. The IP-TMF life was observed to be much shorter than that of the OP-TMF, with a crossover occurring at the higher stress range. Fractographic examinations showed that the fracture was predominantly intergranular in the IP-TMF mode, and transgranular, as characterized by typical fatigue striations, in the OP-TMF mode of deformation. The difference in the fracture mechanisms between the IP and OP-TMF mode of deformation was the primary reason for a significant influence of the loading mode on the TMF lifetime

  14. High-temperature mechanical properties of high-purity 70 mass% Cr-Fe alloy

    Energy Technology Data Exchange (ETDEWEB)

    Asahina, M.; Harima, N.; Takaki, S.; Abiko, K. [Tohoku Univ., Sendai (Japan). Inst. for Materials Research

    2002-01-16

    An ingot of high-purity 70 mass% Cr-Fe alloy was prepared by high-frequency induction melting in a high-purity argon atmosphere using a cold copper crucible. Its tensile properties such as hot-ductility and tensile strength were measured, and compared with the results for a high-purity 50 mass% Cr-Fe alloy, a high-purity 60 mass% Cr-Fe alloy and a Ni-based super-alloy. The formation of {sigma}-phase was also examined. The purity of a 70Cr-Fe alloy (70 mass% Cr-Fe alloy) ingot is more than 99.98 mass% and the total amount of gaseous impurities (C, N, O, S, H) in the 70Cr-Fe alloy is 69.9 mass ppm. The strength of the 70Cr-Fe alloy is higher than those of the 60Cr-Fe alloy and the 50Cr-Fe alloy at the temperatures between 293 and 1573 K, without decrease in ductility with increasing Cr content. The 70Cr-Fe alloy also possesses excellent high-temperature ductility. The {sigma}-phase was not observed after aging of 3.6 Ms at 873 K. Consequently, the 70Cr-Fe alloy is an excellent alloy as the base of super heat-resistant alloys. (orig.)

  15. Molybdenum-A Key Component of Metal Alloys

    Science.gov (United States)

    Kropschot, S.J.

    2010-01-01

    Molybdenum, whose chemical symbol is Mo, was first recognized as an element in 1778. Until that time, the mineral molybdenite-the most important source of molybdenum-was believed to be a lead mineral because of its metallic gray color, greasy feel, and softness. In the late 19th century, French metallurgists discovered that molybdenum, when alloyed (mixed) with steel in small quantities, creates a substance that is remarkably tougher than steel alone and is highly resistant to heat. The alloy was found to be ideal for making tools and armor plate. Today, the most common use of molybdenum is as an alloying agent in stainless steel, alloy steels, and superalloys to enhance hardness, strength, and resistance to corrosion.

  16. γ' Precipitation Study of a Co-Ni-Based Alloy

    Science.gov (United States)

    Locq, D.; Martin, M.; Ramusat, C.; Fossard, F.; Perrut, M.

    2018-05-01

    A Co-Ni-based alloy strengthened by γ'-(L12) precipitates was utilized to investigate the precipitation evolution after various cooling rates and several aging conditions. In this study, the precipitate size and volume fraction have been studied via scanning electron microscopy and transmission electron microscopy. The influence of the precipitation evolution was measured via microhardness tests. The cooling rate study shows a more sluggish γ' precipitation reaction compared to that observed in a Ni-based superalloy. Following a rapid cooling rate, the application of appropriate double aging treatments allows for the increase of the γ' volume fraction as well as the control of the size and distribution of the precipitates. The highest hardness values reach those measured on supersolvus cast and wrought Ni-based superalloys. The observed γ' precipitation behavior should have implications for the production, the heat treatment, the welding, or the additive manufacturing of this new class of high-temperature materials.

  17. Near-surface residual stresses and microstructural changes after turning of a nickel-based superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Schlauer, Christian

    2003-07-01

    Nickel-based superalloys are precipitation hardened alloys with complex compositions. They are used in aircraft engines and land-based gas turbines in load bearing structural components that are exposed to high temperatures. Failure mechanisms in this environment are high and low cycle fatigue, creep, and corrosion. During manufacturing, residual stresses are often introduced into the material due to inhomogeneous plastic deformations, both intentionally and unintentionally. One such manufacturing process is metal cutting, which introduces residual stresses in the surface layer. The stress state in the near-surface zone of components is of special interest as the surface often experiences peak loads and cracks have their starting point there. In this thesis, near-surface residual stress distributions and microstructural changes are studied in the nickel-based superalloy Inconel 718 for two different turning operations, face grooving and facing. Process variables are in both cases cutting speed and feed that have been varied between (10 and 1200) m/min and (0.01 and 0.5) mm, respectively. The first turning technique face grooving, which gives cutting conditions similar to orthogonal cutting, showed a clear dependency of the residual stresses on the cutting speed. The tensile stress at the surface, the maximum compressive stress below the surface, and the thickness of the affected layer increase with increasing cutting speed. The tensile stresses are constrained to a thin surface layer and compressive residual stresses below the surface dominate the depth profile of the residual stresses. Only at low cutting speed, residual stresses were largely avoided. The second turning technique facing confirmed the dependency of the residual stresses on the cutting speed and revealed a similar dependency on the feed. Microstructural investigations of near-surface cross-sections by means of transmission electron microscopy showed a zone where the grains had undergone plastic

  18. The development of platinum-based alloys and their thermodynamic database

    Directory of Open Access Journals (Sweden)

    Cornish L.A.

    2002-01-01

    Full Text Available A series of quaternary platinum-based alloys have been demonstrated to exhibit the same two-phase structure as Ni-based superalloys and showed good mechanical properties. The properties of ternary alloys were a good indication that the quaternary alloys, with their better microstructure, will be even better. The quaternary alloy composition has been optimised at Pt84:Al11:Ru2:Cr3 for the best microstructure and hardness. Work has begun on establishing a thermodynamic database for Pt-Al-Ru-Cr alloys, and further work will be done to enhance the mechanical and oxidation properties of the alloys by adding small amounts of other elements to the base composition of Pt84:Al11:Ru2:Cr3.

  19. Ni/boride interfaces and environmental embrittlement in Ni-based superalloys: A first-principles study

    International Nuclear Information System (INIS)

    Sanyal, Suchismita; Waghmare, Umesh V.; Hanlon, Timothy; Hall, Ernest L.

    2011-01-01

    Highlights: ► Fracture strengths of Ni/boride interfaces through first-principles calculations. ► Fracture strengths of Ni/boride interfaces are higher than Ni/Ni 3 Al and NiΣ5 grain boundaries. ► Ni/boride interfaces have higher resistance to O-embrittlement than Ni/Ni 3 Al and NiΣ5 grain boundaries. ► CrMo-borides are more effective than Cr-borides in resisting O-embrittlement. ► Electronegativity differences between alloying elements correlate with fracture strengths. - Abstract: Motivated by the vital role played by boride precipitates in Ni-based superalloys in improving mechanical properties such as creep rupture strength, fatigue crack growth rates and improved resistance towards environmental embrittlement , we estimate fracture strength of Ni/boride interfaces through determination of their work of separation using first-principles simulations. We find that the fracture strength of Ni/boride interfaces is higher than that of other commonly occurring interfaces in Ni-alloys, such as Ni Σ-5 grain boundaries and coherent Ni/Ni 3 Al interfaces, and is less susceptible to oxygen-induced embrittlement. Our calculations show how the presence of Mo in Ni/M 5 B 3 (M = Cr, Mo) interfaces leads to additional reduction in oxygen-induced embrittlement. Through Electron-Localization-Function based analyses, we identify the electronic origins of effects of alloying elements on fracture strengths of these interfaces and observe that chemical interactions stemming from electronegativity differences between different atomic species are responsible for the trends in calculated strengths. Our findings should be useful towards designing Ni-based alloys with higher interfacial strengths and reduced oxygen-induced embrittlement.

  20. Fatigue crack growth behavior of a new single crystal nickel-based superalloy (CMSX-4) at 650 C

    International Nuclear Information System (INIS)

    Sengupta, A.; Putatunda, S.K.

    1994-01-01

    CMSX-4 is a recently developed rhenium containing single crystal nickel-based superalloy. This alloy has potential applications in many critical high-temperature applications such as turbine blades, rotors, nuclear reactors, etc. The fatigue crack growth rate and the fatigue threshold data of this material is extremely important for accurate life prediction, as well as failure safe design, at elevated temperatures. In this paper, the fatigue crack growth behavior of CMSX-4 has been studied at 650 C. The investigation also examined the influence of γ' precipitates (size and distribution) on the near-threshold fatigue crack growth rate and the fatigue threshold. The influence of load ratio on the fatigue crack growth rate and the fatigue threshold was also examined. Detailed fractographic studies were carried out to determine the crack growth mechanism in fatigue in the threshold region. Compact tension specimens were prepared from the single crystal nickel-based superalloy CMSX-4 with [001] orientation as the tensile loading axis direction. These specimens were given three different heat treatments to produce three different γ' precipitate sizes and distributions. Fatigue crack growth behavior of these specimens was studied at 650 C in air. The results of the present investigation indicate that the near-threshold fatigue crack growth rate decreases and that the fatigue threshold increases with an increase in the γ' precipitate size at 650 C. The fatigue threshold decreased linearly with an increase in load ratio. Fractographs at 650 C show a stage 2 type of crack growth along {100} type of crystal planes in the threshold region, and along {111} type of crystal planes in the high ΔK region

  1. Innovative technologies for powder metallurgy-based disk superalloys: Progress and proposal

    Science.gov (United States)

    Chong-Lin, Jia; Chang-Chun, Ge; Qing-Zhi, Yan

    2016-02-01

    Powder metallurgy (PM) superalloys are an important class of high temperature structural materials, key to the rotating components of aero engines. In the purview of the present challenges associated with PM superalloys, two novel approaches namely, powder preparation and the innovative spray-forming technique (for making turbine disk) are proposed and studied. Subsequently, advanced technologies like electrode-induction-melting gas atomization (EIGA), and spark-plasma discharge spheroidization (SPDS) are introduced, for ceramic-free superalloy powders. Presently, new processing routes are sought after for preparing finer and cleaner raw powders for disk superalloys. The progress of research in spray-formed PM superalloys is first summarized in detail. The spray-formed superalloy disks specifically exhibit excellent mechanical properties. This paper reviews the recent progress in innovative technologies for PM superalloys, with an emphasis on new ideas and approaches, central to the innovation driving techniques like powder processing and spray forming. Project supported by the National Natural Science Foundation of China (Grant Nos. 50974016 and 50071014).

  2. Microstructural and mechanical characterization of injection molded 718 superalloy powders

    Energy Technology Data Exchange (ETDEWEB)

    Özgün, Özgür [Bingol University, Faculty of Engineering and Architecture, Mechanical Eng. Dep., 12000 Bingol (Turkey); Gülsoy, H. Özkan, E-mail: ogulsoy@marmara.edu.tr [Marmara University, Technology Faculty, Metallurgy and Materials Eng. Dep., 34722 Istanbul (Turkey); Yılmaz, Ramazan [Sakarya University, Technology Faculty, Metallurgy and Materials Eng. Dep., 54187 Sakarya (Turkey); Fındık, Fehim [Sakarya University, Technology Faculty, Metallurgy and Materials Eng. Dep., 54187 Sakarya (Turkey) and International University of Sarajevo, Faculty of Engineering and Natural Sciences, Department of Mechanical Engineering, 71000 Sarajevo, Bosnia and Herzegovina (Bosnia and Herzegowina)

    2013-11-05

    Highlights: •Microstructural and mechanical properties of injection molded Nickel 718 superalloy were studied. •The maximum sintered density achieved this study was 97.3% at 1290 °C for 3 hours. •Tensile strength of 1022 MPa and elongation of 5.3% were achieved for sintered-heat treated samples. -- Abstract: This study concerns with the determination of optimum production parameters for injection molding 718 superalloy parts. And at the same time, microstructural and mechanical characterization of these produced parts was also carried out. At the initial stage, 718 superalloy powders were mixed with a multi-component binder system for preparing feedstock. Then the prepared feedstock was granulated and shaped by injection molding. Following this operation, the shaped samples were subjected to the debinding process. These samples were sintered at different temperatures for various times. Samples sintered under the condition that gave way to the highest relative density (3 h at 1290 °C) were solution treated and aged respectively. Sintered, solution treated and aged samples were separately subjected to microstructural and mechanical characterization. Microstructural characterization operations such as X-ray diffraction, optical microscope (OM), scanning electron microscope (SEM), transmission electron microscope (TEM) and elemental analysis showed that using polymeric binder system led to plentiful carbide precipitates to be occurred in the injection molded samples. It is also observed that the volume fractions of the intermetallic phases (γ′ and γ″) obtained by aging treatment were decreased due to the plentiful carbide precipitation in the samples. Mechanical characterization was performed by hardness measurements and tensile tests.

  3. Hot deformation behavior of delta-processed superalloy 718

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Y., E-mail: wangyanhit@yahoo.cn [State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083 (China); School of Aeronautics and Astronautics, Central South University, Changsha 410083 (China); Shao, W.Z.; Zhen, L.; Zhang, B.Y. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)

    2011-03-25

    Research highlights: {yields} The peak stress for hot deformation can be described by the Z parameter. {yields} The grain size of DRX was inversely proportional to the Z parameter. {yields} The dissolution of {delta} phases was greatly accelerated under hot deformation. {yields}The {delta} phase stimulated nucleation can serve as the main DRX mechanism. - Abstract: Flow stress behavior and microstructures during hot compression of delta-processed superalloy 718 at temperatures from 950 to 1100 deg. C with strain rates of 10{sup -3} to 1 s{sup -1} were investigated by optical microscopy (OM), electron backscatter diffraction (EBSD) technique and transmission electron microscopy (TEM). The relationship between the peak stress and the deformation conditions can be expressed by a hyperbolic-sine type equation. The activation energy for the delta-processed superalloy 718 is determined to be 467 kJ/mol. The change of the dominant deformation mechanisms leads to the decrease of stress exponent and the increase of activation energy with increasing temperature. The dynamically recrystallized grain size is inversely proportional to the Zener-Hollomon (Z) parameter. It is found that the dissolution rate of {delta} phases under hot deformation conditions is much faster than that under static conditions. Dislocation, vacancy and curvature play important roles in the dissolution of {delta} phases. The main nucleation mechanisms of dynamic recrystallization (DRX) for the delta-processed superalloy 718 include the bulging of original grain boundaries and the {delta} phase stimulated DRX nucleation, which is closely related to the dissolution behavior of {delta} phases under certain deformation conditions.

  4. Influence of composition on precipitation behavior and stress rupture properties in INCONEL RTM740 series superalloys

    Science.gov (United States)

    Casias, Andrea M.

    Increasing demands for energy efficiency and reduction in CO2 emissions have led to the development of advanced ultra-supercritical (AUSC) boilers. These boilers operate at temperatures of 760 °C and pressures of 35 MPa, providing efficiencies close to 50 pct. However, austenitic stainless steels typically used in boiler applications do not have sufficient creep or oxidation resistance. For this reason, nickel (Ni)-based superalloys, such as IN740, have been identified as potential materials for AUSC boiler tube components. However, IN740 is susceptible to heat-affected-zone liquation cracking in the base metal of heavy section weldments. To improve weldability, IN740H was developed. However, IN740H has lower stress rupture ductility compared to IN740. For this reason, two IN740H modifications have been produced by lowering carbon content and increasing boron content. In this study, IN740, IN740H, and the two modified IN740H alloys (modified 1 and 2) were produced with equiaxed grain sizes of 90 ìm (alloys IN740, IN740H, and IN740H modified 1 alloys) and 112 µm (IN740H modified 2 alloy). An aging study was performed at 800 °C on all alloys for 1, 3, 10, and 30 hours to assess precipitation behavior. Stress rupture tests were performed at 760 °C with the goal of attaining stress levels that would yield rupture at 1000 hours. The percent reduction in area was measured after failure as a measure of creep ductility. Light optical, scanning electron, and transmission electron microscopy were used in conjunction with X-ray diffraction to examine precipitation behavior of annealed, aged, and stress rupture tested samples. The amount and type of precipitation that occurred during aging prior to stress rupture testing or in-situ during stress rupture testing influenced damage development, stress rupture life, and ductility. In terms of stress rupture life, IN740H modified 2 performed the best followed by IN740H modified 1 and IN740, which performed similarly, and IN740

  5. Oxidation behavior and compositional analysis of aluminized superalloy

    International Nuclear Information System (INIS)

    Khalid, F.A.; Nawaz, F.

    2003-01-01

    The high temperature oxidation behavior of superalloy specimens used for the manufacture of turbine blades has been examined using scanning electron microscopy (SEM) and fine-probe spot and line scan EDS microanalysis techniques. The performance of aluminized coating applied to the specimens has also been examined. It was observed that complex oxides are formed in both coated and uncoated specimens. However the coated specimens revealed a greater stability of gamma phase and integrity of aluminized coating as compared with uncoated specimens. The microchemical and microstructural changes that occurred during oxidation have been analyzed to examine characteristics of oxide layers. (author)

  6. Intermediate temperature embrittlement of one new Ni-26W-6Cr based superalloy for molten salt reactors

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Li [Thorium Molten Salts Reactor Center, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); University of Chinese Academy of Science, Beijing 100049 (China); Ye, Xiangxi [University of Chinese Academy of Science, Beijing 100049 (China); Cui, Chuanyong [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Huang, Hefei; Leng, Bin [Thorium Molten Salts Reactor Center, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Li, Zhijun, E-mail: lizhijun@sinap.ac.cn [Thorium Molten Salts Reactor Center, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China); Zhou, Xingtai [Thorium Molten Salts Reactor Center, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 (China)

    2016-06-21

    Ni-26W-6Cr based superalloy is considered a potential structure material for the molten salt reactors due to its high strength and good compatibility with the fluoride salt. In the present work, the temperature dependence of the tensile behavior of the alloy was studied by tensile tests in the temperature range of 25–850 °C. This alloy exhibited a good ductility at RT and 450 °C, a ductility minimum from 650 to 750 °C and an intermediate ductility at 850 °C. TEM and EBSD characterization was performed on specimens tested at three typical temperature points (RT, 650 °C and 850 °C) to determine the deformation and fracture mechanisms accounting for the intermediate temperature embrittlement. At RT, the grain boundaries can accommodate enough dislocations to provide compatibility of the sliding between adjacent grains, then M{sub 6}C carbides act as crack origins and cause the fracture. In case of 650 °C, the grain boundaries cannot withstand the local stress even if only a small number of dislocation pile-ups exist. The premature cracks at grain boundaries impede the development of plastic deformation from single slips to multiple ones and cause the low ductility. If tested at 850 °C, the fracture process is retarded by the dynamic recovery and local dynamic recrystallization at crack tips.

  7. Characterization of defects and nanostructural alterations in the Nimonic 80A superalloy by using Transmission Electron Microscopy

    International Nuclear Information System (INIS)

    Guillen Giron, Teodolito; Leon Salazar, Jose Luis

    2015-01-01

    TEM (Transmission Electron Microscopy) probes are analyzed in aeronautical applications. Intercrystalline defects present in the Nimonic 80A superalloy are studied after being thermally treated and then subjecting the specimens to cyclic stresses. The TEM test specimens are pre-tested under high frequency (1 000 Hz and 20 000 Hz) fatigue at the University of Siegen in Germany simulating the working conditions of this alloy in aircraft turbines or other types of aeronautical applications. The mechanical stress has generated many deformations and nanometric defects in this material, evidenced in the dislocations. Defects are observed using very powerful microscopy techniques such as TEM. The results are obtained from the TEM analysis and have revealed characteristic precipitates in the Nimonic 80A sample when subjected to thermal treatments. The alloy has evidenced the formation of dislocations resulting from the mechanical stresses of the specimens. The influence of rainfall is evidenced in the mechanism of formation, grouping and movement of the dislocations in the microstructure of the samples used. (author) [es

  8. A ternary phase-field model incorporating commercial CALPHAD software and its application to precipitation in superalloys

    International Nuclear Information System (INIS)

    Wen, Y.H.; Lill, J.V.; Chen, S.L.; Simmons, J.P.

    2010-01-01

    A ternary phase-field model was developed that is linked directly to commercial CALPHAD software to provide quantitative thermodynamic driving forces. A recently available diffusion mobility database for ordered phases is also implemented to give a better description of the diffusion behavior in alloys. Because the targeted application of this model is the study of precipitation in Ni-based superalloys, a Ni-Al-Cr model alloy was constructed. A detailed description of this model is given in the paper. We have considered the misfit effects of the partitioning of the two solute elements. Transformation rules of the dual representation of the γ+γ ' microstructure by CALPHAD and by the phase field are established and the link with commercial CALPHAD software is described. Proof-of-concept tests were performed to evaluate the model and the results demonstrate that the model can qualitatively reproduce observed γ ' precipitation behavior. Uphill diffusion of Al is observed in a few diffusion couples, showing the significant influence of Cr on the chemical potential of Al. Possible applications of this model are discussed.

  9. Factors which influence directional coarsening of Gamma prime during creep in nickel-base superalloy single crystals

    International Nuclear Information System (INIS)

    Mackay, R.A.; Ebert, L.J.

    1984-01-01

    Changes in the morphology of the gamma prime precipitate were examined as a function of time during creep at 982 C in 001 oriented single crystals of a Ni-Al-Mo-Ta superalloy. In this alloy, which has a large negative misfit of -0.80 pct., the gamma prime particles link together during creep to form platelets, or rafts, which are aligned with their broad faces perpendicular to the applied tensile axis. The effects of initial microstructure and alloy composition of raft development and creep properties were investigated. Directional coarsening of gamma prime begins during primary creep and continues well after the onset of second state creep. The thickness of the rafts remains constant up through the onset of tertiary creep a clear indication of the stability of the finely-spaced gamma/gamma prime lamellar structure. The thickness of the rafts which formed was equal to the initial gamma prime size which was present prior to testing. The single crystals with the finest gamma prime size exhibited the longest creep lives, because the resultant rafted structure had a larger number of gamma/gamma prime interfaces per unit volume of material. Reducing the Mo content by only 0.73 wt. pct. increased the creep life by a factor of three, because the precipitation of a third phase was eliminated

  10. Improvement of creep-rupture properties by serrated grain boundaries in high-tungsten cobalt-base superalloys

    International Nuclear Information System (INIS)

    Tanaka, Manabu

    1993-01-01

    The improvement of creep-rupture properties by serrated grain boundaries was investigated using cobalt-base superalloys containing about 14 to 20 wt.% tungsten at 1089 and 1311 K. Serrated grain boundaries improved both the rupture life and the ductility, especially under lower stresses at 1089 K. The increase in rupture life was larger in the alloys containing a larger amount of W. Ductile grain boundary fracture surfaces, which involved dimple patterns and grain boundary ledges, were observed in the specimens with serrated grain boundaries whereas brittle grain boundary facets were observed in the specimens with normal straight grain boundaries ruptured at 1089 K. The strengthening by serrated grain boundaries was also effective at 1311 K, but there was little difference in rupture life between the specimens with serrated grain boundaries and those with straight grain boundaries under lower stresses, since serrated grain boundaries developed also in the specimens with straight grain boundaries according to grain boundary precipitates forming during creep at 1311 K. The increase in W content of the alloys led to the increase in rupture life of the specimens with serrated grain boundaries at 1089 and 1311 K. (orig.) [de

  11. The effect of strain distribution on microstructural developments during forging in a newly developed nickel base superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Buckingham, R.C. [Institute of Structural Materials, Swansea University, Bay Campus, Fabian Way, Swansea SA1 8EN (United Kingdom); Argyrakis, C.; Hardy, M.C. [Rolls-Royce plc, PO Box 31, Derby DE24 8BJ (United Kingdom); Birosca, S., E-mail: 522042@swansea.ac.uk [Institute of Structural Materials, Swansea University, Bay Campus, Fabian Way, Swansea SA1 8EN (United Kingdom)

    2016-01-27

    In the current study, the effect of strain distribution in a simple forging geometry on the propensity for recrystallization, and its impact on mechanical properties has been investigated in a newly developed experimental nickel-based superalloy. The new alloy was produced via a Powder Metallurgy (PM) route and was subsequently Hot Isostatic Processed (HIP), isothermally forged, and heat treated to produce a coarse grain microstructure with average grain size of 23–32 μm. The alloy was examined by means of Electron Back-Scatter Diffraction (EBSD) to characterise the microstructural features such as grain orientation and morphology, grain boundary characteristics and the identification of potential Prior Particle Boundaries (PPBs) throughout each stage of the processing route. Results at the central region of the cross-section plane parallel to the loading direction showed significant microstructural differences across the forging depth. This microstructural variation was found to be highly dependent on the value of local strain imparted during forging such that areas of low effective strain showed partial recrystallisation and a necklace grain structure was observed following heat treatment. Meanwhile, a fully recrystallised microstructure with no PPBs was observed in the areas of high strain values, in the central region of the forging.

  12. Electroslag remelting of cobalt-base superalloys

    International Nuclear Information System (INIS)

    Nafziger, R.H.; Lincoln, R.L.

    1974-01-01

    A study was undertaken to determine the feasibility and possible advantages of electroslag remelting of MAR-M 302, MAR-M 509 and X-45. The alloys were electroslag remelted (ESR) in an inert gas using single-phase a.c. power and CaF 2 -CaO-(MgO)-Al 2 O 3 fluxes. Comparisons of ESR ingots with vacuum-arc remelted (VAR) ones were made on the basis of composition, surface condition, macrostructure, hardness, microstructure, room- and elevated-temperature tensile strength and ductility, and high-temperature stress-rupture strength. Minimal differences in non-metallic inclusions, chemical refinement (except perhaps for reduced S and P contents), hardness, and tensile properties were observed in ESR ingots as compared with VAR material. Microstructures of VAR ingots and of ESR ingots prepared with the quaternary flux contained larger intergranular eutectic lamellae than ESR material obtained using ternary fluxes. As regards the stress-rupture data, the MAR-M 302 ESR material exhibited, at the temperatures tested, a rupture strength approximately 10% superior to that of the VAR material in terms of sustained stress for a given life. As regards MAR-M 509, the ESR material was only slightly superior to the VAR material at 815 0 C (1,500 0 F); moreover, at 1,095 0 C (2,000 0 F), there is a crossover of the two curves, and the VAR material stands out as considerably superior at lower stress. Finally, the stress withstood for a given rupture life at 760 0 C (1,400 0 F) was approximately 10% greater for ESR X-45 than for the corresponding VAR material; at 1,040 0 C (1,900 0 F), a crossover of the two curves also occurs, though the advantage to the VAR material at lower stress levels is smaller than was the case for MAR-M 509. (orig.) [de

  13. Microstructural evolutions and mechanical behaviour of the nickel based alloys 617 and 230 at high temperature

    International Nuclear Information System (INIS)

    Chomette, S.

    2009-11-01

    High Temperature Reactors (HTR), is one of the innovative nuclear reactor designed to be inherently safer than previous generation and to produce minimal waste. The most critical metallic component in that type of reactor is the Intermediate Heat exchanger (IHX). The constraints imposed by the conception and the severe operational conditions (high temperature of 850 C to 950 C, lifetime of 20,000 h) have guided the IHX material selection toward two solid solution nickel base alloys, the Inconel 617 and the Haynes 230. Inconel 617 is the primary candidate alloy thanks to its good high temperature mechanical and corrosion properties and the large data base developed in previous programs. However, its high cobalt content has to be considered as an issue (nuclear activation). The more recent alloy Haynes 230, in which most of the cobalt has been replaced by tungsten, present characteristics similar to the 617 alloy. The objective of this thesis is to study the high temperature mechanical behaviour of both alloys in relation with their microstructural evolutions. The as received microstructural observations have revealed primary carbides (M 6 C). Most of this precipitates are evenly distributed in the materials. Few M 23 C 6 secondary carbides are observed in both alloys in the as received state. Thermal ageing treatments at 850 C lead to an important M 23 C 6 precipitation on slip lines and at grain boundaries. The size of this carbides increases and their number decreases with increasing ageing duration. The intragranular precipitation of secondary carbides at 950 C is more limited and the intergranular evolution more important than at 850 C. The microstructural observations and the hardness evolution of both alloys show that the main microstructural evolutions occur before 1,000 h at both studied temperatures. The mechanical properties of the Inconel 617 and the Haynes 230 have been studied using tensile, creep, fatigue and relaxation-fatigue tests. Particularly, the

  14. Thermal Analysis in the Technological “Step” Test of H282 Nickel Alloy

    Directory of Open Access Journals (Sweden)

    Pirowski Z.

    2015-03-01

    Full Text Available Superalloys show a good combination of mechanical strength and resistance to surface degradation under the influence of chemically active environments at high temperature. They are characterized by very high heat and creep resistance. Their main application is in gas turbines, chemical industry, and in all those cases where resistance to creep and the aggressive corrosion environment is required. Modern jet engines could never come into use if not for progress in the development of superalloys. Superalloys are based on iron, nickel and cobalt. The most common and the most interesting group includes superalloys based on nickel. They carry loads at temperatures well in excess of the eighty percent of the melting point. This group includes the H282 alloy, whose nominal chemical composition is as follows (wt%: Ni - base, Fe - max. 1.5%, Al - 1.5% Ti - 2.1%, C - 0.06% Co - 10% Cr - 20% Mo - 8.5%. This study shows the results of thermal analysis of the H282 alloy performed on a cast step block with different wall thickness. Using the results of measurements, changes in the temperature of H282 alloy during its solidification were determined, and the relationship dT / dt = f (t was derived. The results of the measurements taken at different points in the cast step block allowed identifying a number of thermal characteristics of the investigated alloy and linking the size of the dendrites formed in a metal matrix (DAS with the thermal effect of solidification. It was found that the time of solidification prolonged from less than ome minute at 10 mm wall thickness to over seven minutes at the wall thickness of 44 mm doubled the value of DAS.

  15. Effect of standard heat treatment on the microstructure and mechanical properties of hot isostatically pressed superalloy inconel 718

    International Nuclear Information System (INIS)

    Rao, G. Appa; Kumar, Mahendra; Srinivas, M.; Sarma, D.S.

    2003-01-01

    Ni-Fe base superalloy, Inconel 718, was processed through powder metallurgy (P/M) hot isostatic pressing (HIP) route. In order to balance the strength and ductility, the HIPed material was given the standard heat treatment, viz. solution treatment at 980 deg. C for 1 h/water quenched (WQ) to room temperature and a two-step ageing treatment consisting of 720 deg. C for 8 h/furnace cooling (FC) at 55 deg. C h -1 to 620 deg. C and holding at 620 deg. C for 8 h before air cooling (AC) to room temperature. Optical microscopy and scanning electron microscopy (SEM) studies on the heat treated alloy have shown a homogeneous microstructure with fine grain size (25 μm) along with the presence of prior particle boundary (PPB) networks. Transmission electron microscopy (TEM) on the heat treated material has revealed the presence of oxides, MC carbides and δ-precipitates at the grain boundaries and a uniform precipitation of fine γ'' and γ' strengthening phases in the matrix. Tensile and stress rupture tests were performed on the heat treated material. While the yield strength (YS) and ultimate tensile strength (UTS) of the HIPed and heat treated alloy at room temperature and 650 deg. C were comparable to those of conventionally processed wrought IN 718, its ductility was lower. The stress rupture life of the HIPed alloy improved marginally due to heat treatment and met the minimum specification requirement of life hours but the rupture ductility was found to be inferior to that of the wrought material. The fractography of the failed samples has revealed the transgranular ductile mode of fracture in the as-solution treated alloy, while intergranular mode of failure with the decohesion of PPBs occurred more predominantly in the aged condition. This change of fracture mode with ageing treatment shows the ductility dependence on the relative strength of the matrix and PPBs. The TEM studies on the deformed alloy have revealed that the brittle oxides and carbides at the prior

  16. Determination of hydrogen permeability in uncoated and coated superalloys

    Science.gov (United States)

    Bhattacharyya, S.; Vesely, E. J., Jr.; Hill, V. L.

    1981-01-01

    Hydrogen permeability, diffusivity, and solubility data were obtained for eight wrought and cast high temperature alloys over the range 650 to 815 C. Data were obtained for both uncoated alloys and wrought alloys coated with four commercially available coatings. Activation energies for permeability, diffusivity and solubility were calculated.

  17. Effect of homogenization heat treatments on the cast structure and tensile properties of nickel-base superalloy ATI 718Plus in the presence of boron and zirconium additions

    Energy Technology Data Exchange (ETDEWEB)

    Hosseini, Seyed Ali, E-mail: saliho3ini@gmail.com; Madar, Karim Zangeneh; Abbasi, Seyed Mehdi

    2017-03-24

    The effect of homogenization heat treatment on cast structure, hardness, and tensile properties of the nickel-based superalloy 718plus in the presence of boron and zirconium additives were investigated. For this purpose, five alloys with different contents of boron (0.00–0.016 wt%) and zirconium (0.0–0.1 wt%) were cast by double vacuum process VIM/VAR and then were homogenized at 1075–1175 °C for 5–25 h. Microstructural investigation by OM and SEM and phase analysis by XRD were done and then hardness and high temperature tensile tests were performed on the homogenized alloys. The results show that the amount of the Laves phase is reduced by increases in time and temperature of homogenization. It was also found that increases in duration of homogenization at 1075 °C results in improving strength and ductility, while duration increase at 1175 °C is accompanied with degradation of them, which caused the reduction of needle-like delta phase on grain boundaries. Boron and zirconium had negative effects on the strength and ductility of the alloy by increasing the amount of Laves in the cast structure. By increasing these elements in alloy composition, more time is needed in order to fully eliminate the Laves by homogenization treatment.

  18. Precipitate microstructure evolution in exposed IN738LC superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Strunz, Pavel, E-mail: strunz@ujf.cas.cz [Nuclear Physics Institute ASCR, CZ-25068 Řež near Prague (Czech Republic); Petrenec, Martin [Institute of Physics of Materials of the AS CR, Brno (Czech Republic); Gasser, Urs [Laboratory for Neutron Scattering, PSI, CH-5232 Villigen (Switzerland); Tobiáš, Jiří; Polák, Jaroslav [Institute of Physics of Materials of the AS CR, Brno (Czech Republic); Šaroun, Jan [Nuclear Physics Institute ASCR, CZ-25068 Řež near Prague (Czech Republic)

    2014-03-15

    Highlights: • Evolution of γ′-phase morphology in IN738LC Ni-base superalloy was examined by SANS. • In situ tests at high temperatures revealed trimodal precipitate distribution. • Formation, dissolution and (slow) kinetics of small γ′ precipitates was determined. • Equilibrium volume fraction of γ′ phase is significantly higher than 45%. • The small γ′ precipitates arise regardless the application of the mechanical load. -- Abstract: Nickel base superalloy IN738LC has been studied after low-cycle fatigue by Small Angle Neutron Scattering (SANS). Samples subjected to high-temperature low-cycle fatigue were annealed at various temperatures to change the size and the distribution of precipitates. Ex and in situ SANS and TEM studies were performed. It was found that additional precipitates are formed either during slow cooling from high temperatures or after reheating above 570 °C. Their size and distribution were evaluated. The precipitates arise regardless the application of the mechanical load. Nevertheless, these small precipitates influence low-cycle fatigue resistance. From the SANS data, it can be also deduced that the equilibrium volume fraction of γ′-precipitates at temperatures from room temperature to 825 °C is significantly higher than 45%. The kinetics of formation of small and medium-size γ′ precipitates at 700 and 800 °C was determined as well.

  19. Failure mechanisms of superhard materials when cutting superalloys

    International Nuclear Information System (INIS)

    Focke, A.E.; Westermann, F.E.; Ermi, A.; Yavelak, J.; Hoch, M.

    1975-01-01

    The present research studies the reasons for the failure of tungsten carbide tools while cutting superalloys. There is a continuous layer of the superalloy in the bottom of the crater which from time to time is torn away locally, taking tungsten carbide crystal with it. Under recommended cutting conditions a plateau (unworn cutting surface) separates the crater from the cutting edge of the tool when cutting AISI 4340. This plateau is totally absent in all cutting of Inconel 718, even in short, two-minute tests. The crater intersects the cutting edge--only a thin wedge of carbide is left which either breaks off or deforms and wears very rapidly. Temperature measurements carried out by use of an infrared detector aimed on the corner of the tungsten carbide indicate at recommended speeds a sharp rise of the temperature at the beginning of the cutting operation, then a steady-state very slow increase as the cutting continues, and finally just before tool failure a very rapid increase in the temperature again. Scanning and replica electron microscopy through the crater and flank face shows that both under the crater and in the back of the cutting edge a fairly deep layer of ''disturbed metal'' exists in which the tungsten carbide grains are much smaller and have much more rounded edges than in the original material. 10 figures, 4 tables

  20. Microstrain evolution during creep of a high volume fraction superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Ma, S. [Materials Department, New Mexico Tech, Socorro, NM 87801 (United States); Brown, D. [Los Alamos National Laboratory, Los Alamos, NM (United States); Bourke, M.A.M. [Los Alamos National Laboratory, Los Alamos, NM (United States); Daymond, M.R. [Rutherford Appleton Laboratory, ISIS Facility, Chilton, Didcot, Oxon OX11 0QX (United Kingdom); Majumdar, B.S. [Materials Department, New Mexico Tech, Socorro, NM 87801 (United States)]. E-mail: majumdar@nmt.edu

    2005-06-15

    The creep of superalloys containing a high volume fraction of {gamma}' phase is significantly influenced by initial misfit and by the evolution of internal stresses. An in situ neutron diffraction technique was used to monitor elastic microstrains in a polycrystalline superalloy, CM247 LC. The misfit was nearly zero at room temperature and it increased to -0.17% at 900 deg. C. These values are rationalized in terms of thermal mismatch using an eigenstrain formulation and a simple formula is derived to relate the thermal mismatch to the misfit strain. During creep at 425 MPa at 900 deg. C, the material exhibited primarily tertiary behavior. For grains with [0 0 1] axis close to the loading direction, the elastic microstrain in the loading direction increased with creep time for the {gamma}' phase, whereas the opposite occurred for the {gamma} phase. These results are explained in terms of constrained deformation in the narrow {gamma} channels and by an interface dislocation buildup. TEM analysis of the crept microstructure provides evidence of the interface dislocation network.

  1. Alloy materials

    Energy Technology Data Exchange (ETDEWEB)

    Hans Thieme, Cornelis Leo (Westborough, MA); Thompson, Elliott D. (Coventry, RI); Fritzemeier, Leslie G. (Acton, MA); Cameron, Robert D. (Franklin, MA); Siegal, Edward J. (Malden, MA)

    2002-01-01

    An alloy that contains at least two metals and can be used as a substrate for a superconductor is disclosed. The alloy can contain an oxide former. The alloy can have a biaxial or cube texture. The substrate can be used in a multilayer superconductor, which can further include one or more buffer layers disposed between the substrate and the superconductor material. The alloys can be made a by process that involves first rolling the alloy then annealing the alloy. A relatively large volume percentage of the alloy can be formed of grains having a biaxial or cube texture.

  2. An overview of advanced high-strength nickel-base alloys for LWR applications

    International Nuclear Information System (INIS)

    Prybylowski, J.; Ballinger, R.G.

    1989-01-01

    This paper reviews our current understanding of the behavior of high strength nickel base alloys used in light water reactor (LWR) applications. Emphasis is placed on understanding the fundamental mechanisms controlling crack propagation in these environments. To provide a foundation for this survey, general mechanisms of stress corrosion cracking and hydrogen embrittlement are first reviewed. The behavior of high strength nickel base alloys in LWR environments, as well as in other relevant environments is then reviewed. Suggested mechanisms of crack propagation are discussed. Alternate alloys and microstructural modifications that may result in improved behavior are presented. It is now clear that, at temperatures near 100C, alloy X-750, the predominant high strength nickel base alloy used today in LWR applications, is susceptible to hydrogen embrittlement. A review of published data from hydrogen embrittlement studies of nickel base superalloys during electrolytic charging and in hydrogen sulfide/brine solutions suggests that other nickel base superalloys are available possessing resistance to hydrogen embrittlement superior to that of alloy X-750. Available results of tests in gaseous hydrogen suggest that reduced grain boundary precipitation and a fine distribution of intragranular precipitates that act as irreversible hydrogen traps is the optimum microstructure for hydrogen embrittlement resistance. 42 refs., 2 figs., 5 tabs

  3. Advanced Scale Bridging Microstructure Analysis of Single Crystal Ni-Base Superalloys

    Czech Academy of Sciences Publication Activity Database

    Parsa, A. B.; Wollgramm, P.; Buck, H.; Somsen, C.; Kostka, A.; Povstugar, I.; Choi, P.-P.; Raabe, D.; Dlouhý, Antonín; Müller, J.; Spiecker, E.; Demtroder, K.; Schreuer, J.; Neuking, K.; Eggeler, G.

    2015-01-01

    Roč. 17, č. 2 (2015), s. 216-230 ISSN 1438-1656 Institutional support: RVO:68081723 Keywords : High temperature materials * Nickel based superalloys * EPMA * HRTEM Subject RIV: JG - Metallurgy Impact factor: 1.817, year: 2015

  4. High Temperature Degradation of Powder-processed Ni-based Superalloy

    Czech Academy of Sciences Publication Activity Database

    Luptáková, Natália; Pizúrová, Naděžda; Roupcová, Pavla; Dymáček, Petr

    2015-01-01

    Roč. 22, č. 2 (2015), s. 85-94 ISSN 1335-0803 Institutional support: RVO:68081723 Keywords : powder materials * polycrystalline Ni-based superalloy * creep machine grips * oxidation Subject RIV: JG - Metallurgy

  5. Nickel-base superalloy powder metallurgy: state-of-the-art

    International Nuclear Information System (INIS)

    Allen, M.M.; Athey, R.L.; Moore, J.B.

    1975-01-01

    Development of powder metallurgical methods for fabrication of Ni-base superalloy turbine engine disks is reviewed. Background studies are summarized and current state-of-art is discussed for the F100 jet engine, advanced applications, and forging processes

  6. Recovery of creep properties of the nickel-base superalloy nimonic 105

    CSIR Research Space (South Africa)

    Girdwood, RB

    1996-01-01

    Full Text Available Uniaxial constant stress creep tests were performed on the wrought nickel-base superalloy Nimonic 105. Entire creep curves were recorded and curve shapes analysed using the Theta Projection Concept. Rejuventive procedures were applied to pre...

  7. Microstructural studies of carbides in MAR-M247 nickel-based superalloy

    Science.gov (United States)

    Szczotok, A.; Rodak, K.

    2012-05-01

    Carbides play an important role in the strengthening of microstructures of nickel-based superalloys. Grain boundary carbides prevent or retard grain-boundary sliding and make the grain boundary stronger. Carbides can also tie up certain elements that would otherwise promote phase instability during service. Various types of carbides are possible in the microstructure of nickel-based superalloys, depending on the superalloy composition and processing. In this paper, scanning electron and scanning transmission electron microscopy studies of carbides occurring in the microstructure of polycrystalline MAR-M247 nickel-based superalloy were carried out. In the present work, MC and M23C6 carbides in the MAR-M247 microstructure were examined.

  8. Design and properties of advanced {gamma}(TiAl) alloys

    Energy Technology Data Exchange (ETDEWEB)

    Appel, F; Clemens, H; Oehring, M [Institute for Materials Research, GKSS Research Centre, Max-Planck-Strasse, D-21502 Geesthacht (Germany)

    2001-07-01

    Intermetallic titanium aluminides are one of the few classes of emerging materials that have the potential to be used in demanding high-temperature structural applications whenever specific strength and stiffness are of major concern. However, in order to effectively replace the heavier nickel-base superalloys currently use, titanium aluminides must combine a wide range of mechanical property capabilities. Advanced alloy designs are tailored for strength, toughness, creep resistance, and environmental stability. Some of these concerns are addressed in the present paper through global commentary on the physical metallurgy and technology of gamma TiAl-base alloys. Particular emphasis is paid on recent developments of TiAl alloys with enhanced high-temperature capability. (author)

  9. Design and properties of advanced γ(TiAl) alloys

    International Nuclear Information System (INIS)

    Appel, F.; Clemens, H.; Oehring, M.

    2001-01-01

    Intermetallic titanium aluminides are one of the few classes of emerging materials that have the potential to be used in demanding high-temperature structural applications whenever specific strength and stiffness are of major concern. However, in order to effectively replace the heavier nickel-base superalloys currently use, titanium aluminides must combine a wide range of mechanical property capabilities. Advanced alloy designs are tailored for strength, toughness, creep resistance, and environmental stability. Some of these concerns are addressed in the present paper through global commentary on the physical metallurgy and technology of gamma TiAl-base alloys. Particular emphasis is paid on recent developments of TiAl alloys with enhanced high-temperature capability. (author)

  10. Analytical electron microscopy of neutron-irradiated reactor alloys

    International Nuclear Information System (INIS)

    Thomas, L.E.

    1982-01-01

    Exposure to the high neutron fluxes and temperatures from 400 to 650 0 C in the core region of a fast breeder reactor profoundly alters the microstructure and properties of structural steels and superalloys. The development of irradiation-induced voids, dislocations and precipitates, as well as segregation of alloying elements on a microscopic scale has been related to macroscopic swelling, creep, hardening and embrittlement which occur during prolonged exposures in reactor. Microanalytical studies using TEM/STEM methods, primarily energy dispersive x-ray (EDX) microanalysis, have greatly aided understanding of alloy behavior under irradiation. The main uses of analytical electron microscopy in studying irradiated alloys have been the identification of irradiation-induced precipitates and determination of the changes in local composition due to irradiation-induced solute segregation

  11. Toughness testing and high-temperature oxidation evaluations of advanced alloys for core internals

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Lizhen [ORNL; Pint, Bruce A [ORNL; Chen, Xiang [ORNL

    2016-09-16

    Alloy X-750 was procured from Carpenter Technology and Bodycote in this year. An appropriate TMT was developed on Alloy 439 to obtain materials with refined grain size for property screening tests. Charpy V-notch impact tests were completed for the three ferritic steels Grade 92, Alloy 439, and 14YWT. Fracture toughness tests at elevated temperatures were completed for 14YWT. The tests will be completed for the other alloys in next fiscal year. Steam oxidation tests of the three ferritic steels, 316L, and Zr–2.5Nb have been completed. The steam tests of the Ni-based superalloys and the other austenitic stainless steels will be continued and finished in next fiscal year. Performance ranking in terms of steam oxidation resistance and impact/fracture toughness of the alloys will be deduced.

  12. Identifying and Understanding Environment-Induced Crack propagation Behavior in Ni-based Superalloy INCONEL 617

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Longzhou

    2012-11-30

    The nickel-based superalloy INCONEL 617 is a candidate material for heat exchanger applications in the next-generation nuclear plant (NGNP) system. This project will study the crack propagation process of alloy 617 at temperatures of 650°C-950°C in air under static/cyclic loading conditions. The goal is to identify the environmental and mechanical damage components and to understand in-depth the failure mechanism. Researchers will measure the fatigue crack propagation (FCP) rate (da/dn) under cyclic and hold-time fatigue conditions, and sustained crack growth rates (da/dt) at elevated temperatures. The independent FCP process will be identified and the rate-controlled sustained loading crack process will be correlated with the thermal activation equation to estimate the oxygen thermal activation energy. The FCP-dependent model indicates that if the sustained loading crack growth rate, da/dt, can be correlated with the FCP rate, da/dn, at the full time dependent stage, researchers can confirm stress-accelerated grain-boundary oxygen embrittlement (SAGBOE) as a predominate effect. Following the crack propagation tests, the research team will examine the fracture surface of materials in various cracking stages using a scanning electron microscope (SEM) and an optical microscope. In particular, the microstructure of the crack tip region will be analyzed in depth using high resolution transmission electron microscopy (TEM) and electron energy loss spectrum (EELS) mapping techniques to identify oxygen penetration along the grain boundary and to examine the diffused oxygen distribution profile around the crack tip. The cracked sample will be prepared by focused ion beam nanofabrication technology, allowing researchers to accurately fabricate the TEM samples from the crack tip while minimizing artifacts. Researchers will use these microscopic and spectroscopic results to interpret the crack propagation process, as well as distinguish and understand the environment or

  13. Emission spectral analysis of nickel-base superalloys with fixed time intergration technique

    International Nuclear Information System (INIS)

    Okochi, Haruno; Takahashi, Katsuyuki; Suzuki, Shunichi; Sudo, Emiko

    1980-01-01

    Simultaneous determination of multielements (C, B, Mo, Ta, Co, Fe, Mn, Cr, Nb, Cu, Ti, Zr, and Al) in nickel-base superalloys (Ni: 68 -- 76%) was performed by emission spectral analysis. At first, samples which had various nickel contents (ni: 68 -- 76%) were prepared by using JAERI R9, nickel and other metals (Fe, Co, or Cr). It was confirmed that in the internal standard method (Ni II 227.73 nm), analytical values of all the elements examined decreased with a decrease of the integration time (ca. 3.9 -- 4.6 s), that is, an increase of the nickel content. On the other hand, according to the fixed time integration method, elements except for C, Mo, and Cr were not interfered within the range of nickel contents examined. A series of nickel-base binary alloys (Al, Si, Ti, Cr, Mn, Fe, Co, Nb, Mo, and W series) were prepared by high frequency induction melting and the centrifugal casting method and formulae for correcting interferences with near spectral lines were obtained. Various synthetic samples were prepared and analysed by this method. The equations of calibration curves were derived from the data for standard samples (JAERI R1 -- R6, NBS 1189, 1203 -- 1205, and B.S. 600B) by curve fitting with orthogonal polynomials using a computer. For the assessment of this method studied, the F-test was performed by comparison of variances of both analytical values of standard and synthetic samples. The surfaces of specimens were polished with a belt grinder using No. 80 of alumina or silicon carbide endless-paper. The preburn period and integration one were decided at 5 and 6 s respectively. A few standard samples which gave worse reproducibility in emission spectral analysis was investigated with an optical microscope and an electron probe X-ray microanalyser. (author)

  14. Monitoring alloy formation during mechanical alloying process by x-ray diffraction techniques

    International Nuclear Information System (INIS)

    Abdul Kadir Masrom; Noraizam Md Diah; Mazli Mustapha

    2002-01-01

    Monitoring alloying (MA) is a novel processing technique that use high energy impact ball mill to produce alloys with enhanced properties and microscopically homogeneous materials starting from various powder mixtures. Mechanical alloying process was originally developed to produce oxide dispersion strengthened nickel superalloys. In principal, in high-energy ball milling process, alloy is formed by the result of repeated welding, fracturing and rewelding of powder particles in a high energy ball mill. In this process a powder mixture in a ball mill is subjected to high-energy collisions among balls. MA has been shown to be capable of synthesizing a variety of materials. It is known to be capable to prepare equilibrium and non-equilibrium phases starting from blended elemental or prealloyed powders. The process ability to produce highly metastable materials such as amorphous alloys and nanostructured materials has made this process attractive and it has been considered as a promising material processing technique that could be used to produce many advanced materials at low cost. The present study explores the conditions under which aluminum alloys formation occurs by ball milling of blended aluminum and its alloying elements powders. In this work, attempt was made in producing aluminum 2024 alloys by milling of blended elemental aluminum powder of 2024 composition in a stainless steel container under argon atmosphere for up to 210 minutes. X-ray diffraction together with thermal analysis techniques has been used to monitor phase changes in the milled powder. Results indicate that, using our predetermined milling parameters, alloys were formed after 120 minutes milling. The thermal analysis data was also presented in this report. (Author)

  15. Analysis of Effective and Internal Cyclic Stress Components in the Inconel Superalloy Fatigued at Elevated Temperature

    Czech Academy of Sciences Publication Activity Database

    Šmíd, Miroslav; Petrenec, Martin; Polák, Jaroslav; Obrtlík, Karel; Chlupová, Alice

    2011-01-01

    Roč. 278, 4 July (2011), s. 393-398 ISSN 1022-6680. [European Symposium on Superalloys and their Application. Wildbad Kreuth, 25.5.2010-28.5.2010] R&D Projects: GA ČR GA106/08/1631 Institutional research plan: CEZ:AV0Z20410507 Keywords : low cycle fatigue * superalloys * high temperature * hysteresis loop * effective and internal stresses Subject RIV: JL - Materials Fatigue, Friction Mechanics; JL - Materials Fatigue, Friction Mechanics (UFM-A)

  16. Effects of cutting parameters on machinability characteristics of Ni-based superalloys: a review

    Directory of Open Access Journals (Sweden)

    Kaya Eren

    2017-12-01

    Full Text Available Nickel based superalloys offer high strength, corrosion resistance, thermal stability and superb thermal fatigue properties. However, they have been one of the most difficult materials to machine due to these properties. Although we are witnessing improved machining strategies with the developing machining, tooling and inspection technologies, machining of nickel based superalloys is still a challenging task due to in-process strains and post process part quality demands.

  17. The Effect of Forging Variables on the Supersolvus Heat-Treatment Response of Powder-Metallurgy Nickel-Base Superalloys

    Science.gov (United States)

    2014-12-01

    AFRL-RX-WP-JA-2015-0160 THE EFFECT OF FORGING VARIABLES ON THE SUPERSOLVUS HEAT-TREATMENT RESPONSE OF POWDER - METALLURGY NICKEL-BASE SUPERALLOYS... POWDER - METALLURGY NICKEL- BASE SUPERALLOYS (POSTPRINT) 5a. CONTRACT NUMBER In-house 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 62102F 6. AUTHOR...treatment (SSHT) of two powder - metallurgy , gamma–gamma prime superalloys, IN-100 and LSHR, was established. For this purpose, isothermal, hot

  18. Machine learning assisted first-principles calculation of multicomponent solid solutions: estimation of interface energy in Ni-based superalloys

    Science.gov (United States)

    Chandran, Mahesh; Lee, S. C.; Shim, Jae-Hyeok

    2018-02-01

    A disordered configuration of atoms in a multicomponent solid solution presents a computational challenge for first-principles calculations using density functional theory (DFT). The challenge is in identifying the few probable (low energy) configurations from a large configurational space before DFT calculation can be performed. The search for these probable configurations is possible if the configurational energy E({\\boldsymbol{σ }}) can be calculated accurately and rapidly (with a negligibly small computational cost). In this paper, we demonstrate such a possibility by constructing a machine learning (ML) model for E({\\boldsymbol{σ }}) trained with DFT-calculated energies. The feature vector for the ML model is formed by concatenating histograms of pair and triplet (only equilateral triangle) correlation functions, {g}(2)(r) and {g}(3)(r,r,r), respectively. These functions are a quantitative ‘fingerprint’ of the spatial arrangement of atoms, familiar in the field of amorphous materials and liquids. The ML model is used to generate an accurate distribution P(E({\\boldsymbol{σ }})) by rapidly spanning a large number of configurations. The P(E) contains full configurational information of the solid solution and can be selectively sampled to choose a few configurations for targeted DFT calculations. This new framework is employed to estimate (100) interface energy ({σ }{{IE}}) between γ and γ \\prime at 700 °C in Alloy 617, a Ni-based superalloy, with composition reduced to five components. The estimated {σ }{{IE}} ≈ 25.95 mJ m-2 is in good agreement with the value inferred by the precipitation model fit to experimental data. The proposed new ML-based ab initio framework can be applied to calculate the parameters and properties of alloys with any number of components, thus widening the reach of first-principles calculation to realistic compositions of industrially relevant materials and alloys.

  19. Determination of hydrogen permeability in commercial and modified superalloys

    Science.gov (United States)

    Bhattacharyya, S.; Peterman, W.

    1983-01-01

    The results of hydrogen permeability measurements on several iron- and cobalt-base alloys as well as on two long-ranged ordered alloys over the range of 705 to 870 C (1300 to 1600 F) are summarized. The test alloys included wrought alloys N-155, IN 800, A-286, 19-9DL, and 19-9DL modifications with aluminum, niobium, and misch metal. In addition, XF-818, CRM-6D, SA-F11, and HS-31 were evaluated. Two wrought long-range ordered alloys, Ni3Al and (Fe,Ni)3(V,Al) were also evaluated. All tests were conducted at 20.7 MPa pressure in either pure and/or 1% CO2-doped H2 for test periods as long as 133 h. Detailed analyses were conducted to determine the relative permeability rankings of these alloys and the effect of doping, exit surface oxidation, specimen design variations, and test duration on permeability coefficient, and permeation activation energies were determined. The two long-range ordered alloys had the lowest permeability coefficients in pure H2 when compared with the eight commercial alloys and their modifications. With CO2 doping, significant decrease in permeability was observed in commercial alloys--no doped tests were conducted with the long-range ordered alloys.

  20. Hardness optimization of boride diffusion layer on Astm F-75 alloy using response surface methodology

    Energy Technology Data Exchange (ETDEWEB)

    Arguelles O, J. L.; Corona R, M. A. [Universidad Autonoma de San Luis Potosi, Doctorado Institucional en Ingenieria y Ciencia de Materiales, San Luis Potosi 78000, SLP (Mexico); Marquez H, A.; Saldana R, A. L.; Saldana R, A. [Universidad de Guanajuato, Ingenieria Mecanica Agricola DICIVA, Irapuato, Guanajuato 36500 (Mexico); Moreno P, J., E-mail: amarquez@ugto.mx [Universidad de Guanajuato, Departamento de Minas, Metalurgia y Geologia, Ex-Hacienda San Matias s/n, Guanajuato, Guanajuato 36020 (Mexico)

    2017-11-01

    In this study, the Response Surface Methodology (Rsm) and Central Composite Design (Ccd) were used to optimize the hardness of boride diffusion layer on Astm F-75 alloy (also called Haynes alloy). A boronizing thermochemical treatment was carried out at different temperatures and for different time periods. Hardness tests were conducted. The boride diffusion layer was verified by the X-ray diffraction (XRD) analysis indicating the formation of Co B, Co{sub 2}B, Cr B and Mo{sub 2}B phases. An optimal hardness of 3139.7 Hv was obtained for the samples subjected to the boriding process for a duration of 6.86 h at 802.4 degrees Celsius. (Author)

  1. "I want to be a pop idol". Oscar Wilde between parody and glam re-invention in Todd Haynes' Velvet Goldmine

    Directory of Open Access Journals (Sweden)

    Pierpaolo Martino

    2017-01-01

    Full Text Available Il presente studio analizza Velvet Goldmine un film del 1998 diretto da Todd Haynes al fine di indagare come il regista americano riesca ad evidenziare la centralità del glam (emerso in Gran Bretagna nei primi anni Settanta nella cultura contemporanea, ponendo un' enfasi specifica sull’aspetto che più di ogni altro aveva caratterizzato quell’esperienza, ossia la sovversione parodica dell' idea di mascolinità normativa nei decenni precedenti. Sul palco i 'glamsters' – ossia artisti quali Bolan, Bowie, Roxy Music, Glitter – erano in grado, utilizzando segni visivi quali trucco e abiti 'glitter' di costruire un’identità di genere ibrida che si poneva in netto contrasto con il machismo di molti musicisti degli anni Sessanta. Seguendo un approccio metodologico in cui studi culturali, studi letterari e neo-musicologia finiscono per dialogare tra loro, la presente indagine crea uno stretto rapporto tra Oscar Wilde e la cultura glam – un rapporto individuato dal regista sin dalle prime battute del film – ma che qui viene declinato in un senso più specifico, in base al quale l' intero film rappresenta una parodia o reinvenzione glam dell'intera epopea wildiana e in cui le immagini e gli aforismi wildiani sembrano interrogare con la loro complessità e la loro portata dissacrante il nostro presente.  The present essay analyses Velvet Goldmine a 1998 film directed by Todd Haynes, in order to investigate how the American director points to the relevance of glam (emerged in Great Britain at the beginning of the Seventies within contemporary culture, focusing on one of its most relevant aspects, that is the parodic subversion  of the normative idea of masculinity which was dominant in the previous decades. Glamsters – that is, such artists as Bolan, Bowie, Roxy Music and Glitter – were able, using such visual signs as make-up and glitter dresses, to construct a hybrid gender identity, which sharply contrasted with the normative

  2. Microstructural tomography of a Ni{sub 70}Cr{sub 20}Al{sub 10} superalloy using focused ion beam microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Uchic, M.D. [Materials and Manufacturing Directorate, Air Force Research Laboratory, AFRL/RXLM, Wright-Patterson Air Force Base, OH 45433-7817 (United States); De Graef, M., E-mail: degraef@cmu.edu [Department of Materials Science and Engineering, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States); Wheeler, R. [UES Inc., Dayton, OH 45432 (United States); Dimiduk, D.M. [Materials and Manufacturing Directorate, Air Force Research Laboratory, AFRL/RXLM, Wright-Patterson Air Force Base, OH 45433-7817 (United States)

    2009-09-15

    A focused ion beam (FIB) microscope has been used to simultaneously depth profile and image the {gamma}-{gamma}{sup '} microstructure of a nickel base superalloy using normal incidence milling in order to characterize the precipitate microstructure in three dimensions (3D). The normal incidence milling rates of the {gamma} and {gamma}{sup '} phases in this alloy are closely matched when the orientation of the depth-profiled surface is near <001>, which allows for uniform material removal to depths up to a couple of microns. Depth-profiling experiments consisted of automated ion milling and collection of ion-generated secondary-electron images at specified intervals, and was demonstrated for a voxel resolution of roughly 15x15x16nm{sup 3}. Image-processing software was used for automated processing of the 2D image sequence to render the {gamma} precipitate structure in 3D.

  3. Evolution of precipitate in nickel-base alloy 718 irradiated with argon ions at elevated temperature

    International Nuclear Information System (INIS)

    Jin, Shuoxue; Luo, Fengfeng; Ma, Shuli; Chen, Jihong; Li, Tiecheng; Tang, Rui; Guo, Liping

    2013-01-01

    Alloy 718 is a nickel-base superalloy whose strength derives from γ′(Ni 3 (Al,Ti)) and γ″(Ni 3 Nb) precipitates. The evolution of the precipitates in alloy 718 irradiated with argon ions at elevated temperature were examined via transmission electron microscopy. Selected-area electron diffraction indicated superlattice spots disappeared after argon ion irradiation, which showing that the ordered structure of the γ′ and γ″ precipitates became disordered. The size of the precipitates became smaller with the irradiation dose increasing at 290 °C

  4. A study on microstructures and extended defects in Ni- and Co-base superalloys. Development and application of advanced TEM techniques

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, Julian

    2016-04-21

    To improve the efficiency of stationary gas turbines and air craft jet engines, it is crucial to increase the maximum temperature capabilities of single crystalline superalloys by appropriate alloy design and microstructure tuning. The mechanical properties of superalloys are largely influenced by the physical constitution of the microstructure. To develop a better understanding of fundamental aspects of creep deformation, like the stress states, defect structures and other degradation processes, it is necessary to employ scale-bridging characterization. In the present work, Ni- and Co-based superalloys are investigated by a series of advanced transmission electron microscopy techniques and by the application of specifically developed characterization methods to identify dominating processes on atomic scale and hence to make a direct correlation to the macroscopic creep behavior. For instance, the misfit between γ and γ' in the initial microstructure is of great importance, since it strongly influences the rafting process and the interfacial dislocation network. To address the stress state, on the one hand misfit measurements in undeformed samples are conducted and are directly compared to finite-element simulations. On the other hand, deformed samples are investigated to assess the influence of an initial rafting process and the formation of an interface dislocation network. For this, characterization methods are used which are based on the evaluation of atomically resolved images and on electron diffraction. Moreover, the temperature dependency of the misfit and of the microstructure stability is specifically investigated for different Co-base alloys in in situ heating experiments. The characterization of defect structures in Ni-base superalloys after creep deformation builds the second pillar of this work. Specific cutting processes of superdislocations are studied to elucidate which atomic processes take place. A series of left angle 100 right angle and

  5. Integrated computational microstructure engineering for single-crystal nickel-base superalloys

    Science.gov (United States)

    Wang, Billie

    A methodology that integrates the phase field model with simpler models was developed to study the early stages of microstructural development in nickel base superalloys under non-isothermal conditions, allowing for faster, more comprehensive examination of the experimental system. Additionally, the parameters required for calibrating a phase field model were examined for uncertainty, and a comprehensive method for linking experimental data to a model was developed. The methodology developed was applied to analyze the formation of bimodal particle size distributions during linear continuous cooling. The dynamic competition for supersaturation by growth of existing precipitates and nucleation of new particles was modeled. The nucleation rate was calculated according to classical nucleation theory as function of local supersaturation and temperature. The depletion of matrix super-saturation by growth of existing particles was calculated from fully diffusion-controlled precipitate growth in an infinite matrix. Phase field simulations of gamma' precipitation in a binary Ni-Al alloy were performed under continuous cooling conditions. Then the average and maximum matrix supersaturations were calculated and plotted onto the contours of nucleation rate and growth rate in concentration and temperature space. These methods were used iteratively to identify the window for bimodal particle size distributions. Combining the models of different complexities produced a much more comprehensive understanding of the competing dynamics involved early in microstructure formation. A systemic method for calibrating a model to experimental alloy systems was developed. Calibrated to isothermal aging data along with literature, database and parametric values, a phase field model reproduced the precipitation kinetics. Quantitative phase field modeling techniques were developed to control the influence of uncertainty in the original data sources for model inputs. Using more data sources than

  6. The influence of Ta on the solidification microstructure and segregation behavior of γ(Ni)/γ′(Ni3Al)–δ(Ni3Nb) eutectic Ni-base superalloys

    International Nuclear Information System (INIS)

    Xie, M.; Helmink, R.; Tin, S.

    2013-01-01

    Highlights: ► Ta and Nb have a nominally identical influence on equilibrium δ volume fraction. ► Ta and Nb impact the sequence and segregation differently during solidification. ► Microstructure varies with both overall Ta + Nb level and Ta/Nb ratio. ► Pandat (PanNi7) is unable to predict trends quantitatively in this system. -- Abstract: Polycrystalline γ/γ′–δ eutectic Ni-base superalloys based on the Ni–Al–Nb alloy system were recently demonstrated to possess excellent high temperature strength and creep resistance. Investigations aimed to establish the fundamental relationships between alloy chemistry, solidification behavior and cast microstructure in these novel Ni–Al–Nb γ/γ′–δ alloy systems are currently underway. This particular study is focused on understanding the influence of Ta additions on the solidification sequence, phase volume fraction, distribution coefficient and solid state partitioning parameter of this eutectic alloy system by systematically investigating a series of experimental alloys with nominally constant overall levels of Ta + Nb content but varying Ta/Nb ratios. Although many of the tendencies observed in these multi-component γ/γ′–δ eutectic alloys are in agreement with trends observed in lower order model alloy systems, Ta additions were found to significantly modify solidification characteristics of the alloys. The experimental observations were also used to critically assess the predictive capability of thermodynamic database calculations. Despite the qualitative agreement observed between the experimental results and predictions for relatively simple quaternary and quinary model alloys, comparison of the results for higher order, multi-component γ/γ′–δ eutectic alloys reveals notable differences

  7. Fiber laser welding of nickel based superalloy Inconel 625

    Science.gov (United States)

    Janicki, Damian M.

    2013-01-01

    The paper describes the application of single mode high power fiber laser (HPFL) for the welding of nickel based superalloy Inconel 625. Butt joints of Inconel 625 sheets 0,8 mm thick were laser welded without an additional material. The influence of laser welding parameters on weld quality and mechanical properties of test joints was studied. The quality and mechanical properties of the joints were determined by means of tensile and bending tests, and micro hardness tests, and also metallographic examinations. The results showed that a proper selection of laser welding parameters provides non-porous, fully-penetrated welds with the aspect ratio up to 2.0. The minimum heat input required to achieve full penetration butt welded joints with no defect was found to be 6 J/mm. The yield strength and ultimate tensile strength of the joints are essentially equivalent to that for the base material.

  8. Evaluation of powder metallurgical processing routes for multi-component niobium silicide-based high-temperature alloys

    Energy Technology Data Exchange (ETDEWEB)

    Seemueller, Hans Christoph Maximilian

    2016-03-22

    Niobium silicide-based composites are potential candidates to replace nickel-base superalloys for turbine applications. The goal of this work was to evaluate the feasibility and differences in ensuing properties of various powder metallurgical processing techniques that are capable of manufacturing net-shape turbine components. Two routes for powder production, mechanical alloying and gas atomization were combined with compaction via hot isostatic pressing and powder injection molding.

  9. Joining of ceramic Ba0.5Sr0.5Co0.8Fe0.2O3 membranes for oxygen production to high temperature alloys

    DEFF Research Database (Denmark)

    Kiebach, Wolff-Ragnar; Engelbrecht, Kurt; Kwok, Kawai

    2016-01-01

    /reactivity and their thermal expansion coefficient on the stability of the final joint was evaluated. Leak tight assemblies were obtained only for steels with a thermal expansion coefficient of > 16 [10(-6) K-1] and protective coating. Proof-of-concept oxygen flux measurements up to 830 degrees C were performed......The possibility of joining dense ceramic BCSF tubular membranes to metal alloys using a silver braze was investigated. Four different alloys (Crofer 22 APU (R), Kanthal APM (R), Haynes 214 (R) and EN 1.4841) were considered and the influence of their oxide scale stability...

  10. The Effect of Boron and Zirconium on the Structure and Tensile Properties of the Cast Nickel-Based Superalloy ATI 718Plus

    Science.gov (United States)

    Hosseini, Seyed Ali; Abbasi, Seyed Mehdi; Madar, Karim Zangeneh

    2018-04-01

    The effects of boron and zirconium on cast structure, hardness, and tensile properties of the nickel-based superalloy 718Plus were investigated. For this purpose, five alloys with different contents of boron and zirconium were cast via vacuum induction melting and then purified via vacuum arc remelting. Microstructural analysis by light-optical microscope and scanning electron microscope equipped with energy-dispersive x-ray spectroscopy and phase studies by x-ray diffraction analysis were performed. The results showed that boron and zirconium tend to significantly reduce dendritic arm spacing and increase the amount of Laves, Laves/gamma eutectic, and carbide phases. It was also found that boron led to the formation of B4C and (Cr, Fe, Mo, Ni, Ti)3B2 phases and zirconium led to the formation of intermetallic phases and ZrC carbide. In the presence of boron and zirconium, the hardness and its difference between dendritic branches and inter-dendritic spaces increased by concentrating such phases as Laves in the inter-dendritic spaces. These elements had a negative effect on tensile properties of the alloy, including ductility and strength, mainly because of the increase in the Laves phase. It should be noted that the largest degradation of the tensile properties occurred in the alloys containing the maximum amount of zirconium.

  11. On the Influence of Nb/Ti Ratio on Environmentally-Assisted Crack Growth in High-Strength Nickel-Based Superalloys

    Science.gov (United States)

    Németh, A. A. N.; Crudden, D. J.; Collins, D. M.; Kuksenko, V.; Liebscher, C. H.; Armstrong, D. E. J.; Wilkinson, A. J.; Reed, R. C.

    2018-05-01

    The effect of Nb/Ti ratio on environmentally-assisted crack growth of three prototype Ni-based superalloys is studied. For these alloys, the yield strength is unaltered with increasing Nb/Ti ratio due to an increase in grain size. This situation has allowed the rationalization of the factors influencing damage tolerance at 700 °C. Primary intergranular cracks have been investigated using energy-dispersive X-ray spectroscopy in a scanning transmission electron microscope and the analysis of electron back-scatter diffraction patterns. Any possible detrimental effect of Nb on the observed crack tip damage due to Nb-rich oxide formation is not observed. Instead, evidence is presented to indicate that the tertiary γ'-precipitates are dissolving ahead of the crack consistent with the formation of oxides such as alumina and rutile. Our results have implications for alloy design efforts; at any given strength level, both more and less damage-tolerant variants of these alloys can be designed.

  12. Micro-tensile strength of a welded turbine disc superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Oluwasegun, K.M.; Cooper, C.; Chiu, Y.L.; Jones, I.P. [School of Metallurgy and Materials, University of Birmingham, B15 2TT (United Kingdom); Li, H.Y., E-mail: h.y.li.1@bham.ac.uk [School of Metallurgy and Materials, University of Birmingham, B15 2TT (United Kingdom); Baxter, G. [Rolls-Royce plc., P.O. Box 31, Derby DE24 8BJ (United Kingdom)

    2014-02-24

    A micro-tensile testing system coupled with focussed ion beam (FIB) machining was used to characterise the micro-mechanical properties of the weld from a turbine disc alloy. The strength variations between the weld and the base alloy are rationalised via the microstructure obtained.

  13. Densities of molten Ni-(Cr, Co, W) superalloys

    Institute of Scientific and Technical Information of China (English)

    XIAO Feng; YANG Ren-hui; FANG Liang; LIU Lan-xiao; ZHAO Hong-kai

    2008-01-01

    In order to obtain more accurate density for molten Ni-(Cr, Co, W) binary alloy, the densities of molten pure Ni and Ni-Cr, Ni-Co, Ni-W alloys were measured with a sessile drop method. It is found that the measured densities of molten pure Ni and Ni-Cr, Ni-Co, Ni-W alloys decrease with increasing temperature in the experimental temperature range. The density of alloys increases with increasing W and Co concentrations while it decreases with increasing Cr concentration in the alloy at 1 773-1 873 K. The molar volume of Ni-based alloys increases with increasing W concentration while it decreases with increasing Co concentration. The effect of Cr concentration on the molar volume of the alloy is little in the studied concentration range. The accommodation among atomic species was analyzed. The deviation of molar volume from ideal mixing shows an ideal mixing of Ni-(Cr, Co, W) binary alloys.

  14. Focused Ion Beam Nanotomography of ruthenium-bearing nickel-base superalloys with focus on cast-microstructure and phase stability; Focused Ion Beam Nanotomographie von rutheniumhaltigen Nickelbasis-Superlegierungen mit Fokus auf Gussgefuege und Phasenstabilitaet

    Energy Technology Data Exchange (ETDEWEB)

    Cenanovic, Samir

    2012-12-03

    The influence of rhenium and ruthenium on the multi component system nickel-base superalloy is manifold and complex. An experimental nickel-base superalloy containing rhenium and ruthenium within defined contents, named Astra, was used to investigate the influences of these two elements on the alloy system. The last stage solidification of nickel-base superalloys after Bridgman casting and the high temperature phase stability of these alloys, could be explored with the aid of focused ion beam nanotomography. FIB-nt therefore was introduced and realized at the chair of General Materials Properties of the University Erlangen-Nuremberg. Cast Astra alloys are like other nickel-base superalloys morphologically very inhomogeneous and affected by segregation. In the interdendritic region different structures with huge γ' precipitates are formed. These inhomogeneities and remaining eutectics degrade the mechanical properties, witch makes an understanding of the subsiding processes at solidification of residual melt important for the casting process and the heat treatment. This is why the last stage solidification in the interdendritic region was analyzed. With the help of focused ion beam nanotomography, three different structures identified from 2-D sections could be assigned to one original 3-D structure. It was pointed out, that only the orientation of the plane of the 2-D cut influences the appearance in the 2-D section. The tomography information was used to explain the development during solidification and to create a model of last stage solidification. The interdendritic region is solidifying under the development of eutectic islands. The structure nucleates eutectically epitaxially at primary dendrite arms, with formation of fine γ/γ' precipitates. During solidification the γ' precipitates coarsen in a rod-like structure, and end up in large γ' precipitates. Simulations and other investigations could approve this model. First three

  15. Application of a multi-component mean field model to the coarsening behaviour of a nickel-based superalloy

    International Nuclear Information System (INIS)

    Anderson, M.J.; Rowe, A.; Wells, J.; Basoalto, H.C.

    2016-01-01

    A multi-component mean field model has been applied to predict the particle evolution of the γ′ particles in the nickel based superalloy IN738LC, capturing the transition from an initial multimodal particle distribution towards a unimodal distribution. Experiments have been performed to measure the coarsening behaviour during isothermal heat treatments using quantitative analysis of micrographs. The three dimensional size of the γ′ particles has been approximated for use in simulation. A coupled thermodynamic/mean field modelling framework is presented and applied to describe the particle size evolution. A robust numerical implementation of the model is detailed that makes use of surrogate models to capture the thermodynamics. Different descriptions of the particle growth rate of non-dilute particle systems have been explored. A numerical investigation of the influence of scatter in chemical composition upon the particle size distribution evolution has been carried out. It is shown how the tolerance in chemical composition of a given alloy can impact particle coarsening behaviour. Such predictive capability is of interest in understanding variation in component performance and the refinement of chemical composition tolerances. It has been found that the inclusion of misfit strain within the current model formulation does not have a significant affect upon predicted long term particle coarsening behaviour. Model predictions show good agreement with experimental data. In particular, the model predicts a reduced growth rate of the mean particle size during the transition from bimodal to unimodal distributions.

  16. Effects of grain refinement on cast structure and tensile properties of superalloy K4169 at high pouring temperature

    Directory of Open Access Journals (Sweden)

    Zi-qi Jie

    2016-03-01

    Full Text Available In order to improve the filling ability of large complex thin wall castings, the pouring temperature should be increased, but this will result in the grain coarsening. To overcome this problem, two kinds of grain refiners of Co-Fe-Nb and Cr-Fe-Nb ternary alloys, which contain high stability compound particles, were prepared. The effects of the refiners on the as-cast structures and tensile properties of the K4169 superalloy with different casting conditions were studied by analyzing specimens 110 mm long and 20 mm in diameter. Results showed that the mixture addition of the two refiners in the melt of K4169 can reduce the columnar grain region and decrease the equiaxed grain size greatly. After refinement, the amount of Laves phase decreases and its morphology changes from island to blocky structure. The carbides in the fine grain samples are fine and dispersive. Meanwhile, the porosity in specimens is decreased due to grain refinement. As a result, the yield strength, ultimate strength and the elongation of the specimens are increased. The grain refinement mechanisms are also discussed.

  17. Application of Finite Element, Phase-field, and CALPHAD-based Methods to Additive Manufacturing of Ni-based Superalloys.

    Science.gov (United States)

    Keller, Trevor; Lindwall, Greta; Ghosh, Supriyo; Ma, Li; Lane, Brandon M; Zhang, Fan; Kattner, Ursula R; Lass, Eric A; Heigel, Jarred C; Idell, Yaakov; Williams, Maureen E; Allen, Andrew J; Guyer, Jonathan E; Levine, Lyle E

    2017-10-15

    Numerical simulations are used in this work to investigate aspects of microstructure and microseg-regation during rapid solidification of a Ni-based superalloy in a laser powder bed fusion additive manufacturing process. Thermal modeling by finite element analysis simulates the laser melt pool, with surface temperatures in agreement with in situ thermographic measurements on Inconel 625. Geometric and thermal features of the simulated melt pools are extracted and used in subsequent mesoscale simulations. Solidification in the melt pool is simulated on two length scales. For the multicomponent alloy Inconel 625, microsegregation between dendrite arms is calculated using the Scheil-Gulliver solidification model and DICTRA software. Phase-field simulations, using Ni-Nb as a binary analogue to Inconel 625, produced microstructures with primary cellular/dendritic arm spacings in agreement with measured spacings in experimentally observed microstructures and a lesser extent of microsegregation than predicted by DICTRA simulations. The composition profiles are used to compare thermodynamic driving forces for nucleation against experimentally observed precipitates identified by electron and X-ray diffraction analyses. Our analysis lists the precipitates that may form from FCC phase of enriched interdendritic compositions and compares these against experimentally observed phases from 1 h heat treatments at two temperatures: stress relief at 1143 K (870 °C) or homogenization at 1423 K (1150 °C).

  18. Transmission Electron Microscopy of a CMSX-4 Ni-Base Superalloy Produced by Selective Electron Beam Melting

    Directory of Open Access Journals (Sweden)

    Alireza B. Parsa

    2016-10-01

    Full Text Available In this work, the microstructures of superalloy specimens produced using selective electron beam melting additive manufacturing were characterized. The materials were produced using a CMSX-4 powder. Two selective electron beam melting processing strategies, which result in higher and lower effective cooling rates, are described. Orientation imaging microscopy, scanning transmission electron microscopy and conventional high resolution transmission electron microscopy are used to investigate the microstructures. Our results suggest that selective electron beam melting processing results in near equilibrium microstructures, as far as γ′ volume fractions, the formation of small amounts of TCP phases and the partitioning behavior of the alloy elements are concerned. As expected, higher cooling rates result in smaller dendrite spacings, which are two orders of magnitude smaller than observed during conventional single crystal casting. During processing, columnar grains grow in <100> directions, which are rotated with respect to each other. There are coarse γ/γ′ microstructures in high angle boundary regions. Dislocation networks form low angle boundaries. A striking feature of the as processed selective electron beam melting specimens is their high dislocation density. From a fundamental point of view, this opens new possibilities for the investigation of elementary dislocation processes which accompany solidification.

  19. Microstructure of selective laser melted CM247LC nickel-based superalloy and its evolution through heat treatment

    Energy Technology Data Exchange (ETDEWEB)

    Divya, V.D., E-mail: dv272@cam.ac.uk [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom); Muñoz-Moreno, R.; Messé, O.M.D.M.; Barnard, J.S. [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom); Baker, S.; Illston, T. [Materials Solutions, Unit 8, Great Western Business Park, McKenzie Way, Worcester WR4 9GN (United Kingdom); Stone, H.J. [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom)

    2016-04-15

    The selective laser melting of high temperature alloys is of great interest to the aerospace industry as it offers the prospect of producing more complex geometries than can be achieved with other manufacturing methods. In this study, the microstructure of the nickel-based superalloy, CM247LC, has been characterised following selective laser melting and after a post deposition heat treatment below the γ′ solvus temperature. In the as-deposited state, scanning electron microscopy with electron backscatter diffraction revealed a fine, cellular microstructure with preferential alignment of 〈001〉 along the build direction. A high dislocation density was seen at the periphery of the cells, indicating substantial localised deformation of the material. Fine primary MC carbides were also observed in the inter-cellular regions. High-resolution transmission electron microscopy identified the occurrence of very fine γ′ precipitates, approximately 5 nm in diameter, dispersed within the gamma phase. After heat treatment, the elongated cell colonies were observed to partially coalesce, accompanied by a decrease in dislocation density, producing columnar grains along the build direction. Cuboidal γ′ precipitates approximately 500 nm in diameter were observed to form in the recrystallised grains, accompanied by larger γ′ precipitates on the grain boundaries.

  20. Strain Amount Dependent Grain Size and Orientation Developments during Hot Compression of a Polycrystalline Nickel Based Superalloy

    Directory of Open Access Journals (Sweden)

    Guoai He

    2017-02-01

    Full Text Available Controlling grain size in polycrystalline nickel base superalloy is vital for obtaining required mechanical properties. Typically, a uniform and fine grain size is required throughout forging process to realize the superplastic deformation. Strain amount occupied a dominant position in manipulating the dynamic recrystallization (DRX process and regulating the grain size of the alloy during hot forging. In this article, the high-throughput double cone specimen was introduced to yield wide-range strain in a single sample. Continuous variations of effective strain ranging from 0.23 to 1.65 across the whole sample were achieved after reaching a height reduction of 70%. Grain size is measured to be decreased from the edge to the center of specimen with increase of effective strain. Small misorientation tended to generate near the grain boundaries, which was manifested as piled-up dislocation in micromechanics. After the dislocation density reached a critical value, DRX progress would be initiated at higher deformation region, leading to the refinement of grain size. During this process, the transformations from low angle grain boundaries (LAGBs to high angle grain boundaries (HAGBs and from subgrains to DRX grains are found to occur. After the accomplishment of DRX progress, the neonatal grains are presented as having similar orientation inside the grain boundary.

  1. Microstructure of selective laser melted CM247LC nickel-based superalloy and its evolution through heat treatment

    International Nuclear Information System (INIS)

    Divya, V.D.; Muñoz-Moreno, R.; Messé, O.M.D.M.; Barnard, J.S.; Baker, S.; Illston, T.; Stone, H.J.

    2016-01-01

    The selective laser melting of high temperature alloys is of great interest to the aerospace industry as it offers the prospect of producing more complex geometries than can be achieved with other manufacturing methods. In this study, the microstructure of the nickel-based superalloy, CM247LC, has been characterised following selective laser melting and after a post deposition heat treatment below the γ′ solvus temperature. In the as-deposited state, scanning electron microscopy with electron backscatter diffraction revealed a fine, cellular microstructure with preferential alignment of 〈001〉 along the build direction. A high dislocation density was seen at the periphery of the cells, indicating substantial localised deformation of the material. Fine primary MC carbides were also observed in the inter-cellular regions. High-resolution transmission electron microscopy identified the occurrence of very fine γ′ precipitates, approximately 5 nm in diameter, dispersed within the gamma phase. After heat treatment, the elongated cell colonies were observed to partially coalesce, accompanied by a decrease in dislocation density, producing columnar grains along the build direction. Cuboidal γ′ precipitates approximately 500 nm in diameter were observed to form in the recrystallised grains, accompanied by larger γ′ precipitates on the grain boundaries.

  2. Creep deformation-induced antiphase boundaries in L12-containing single-crystal cobalt-base superalloys

    International Nuclear Information System (INIS)

    Eggeler, Yolita M.; Titus, Michael S.; Suzuki, Akane; Pollock, Tresa M.

    2014-01-01

    Creep-induced antiphase boundaries (APBs) in new Co-base single-crystal superalloys with coherent embedded L1 2 -γ′ precipitates have been observed. APBs formed during single-crystal tensile creep tests performed at 900 °C under vacuum at stresses between 275 and 310 MPa. The alloys investigated contained 30–39 at.% Ni, which was added to the Co–Al–W ternary system to expand the γ–γ′ phase field and increase the γ′-solvus. Transmission electron microscopy (TEM) using two-beam conditions with fundamental and superlattice reflections was performed for defect characterization. The Burgers vector b of dislocations associated with the APBs was determined to be of type b = a 0 /2[011] and a 0 /2[011 ¯ ]. The displacement vectors, R, of the APBs matched the dislocation Burgers vectors, with R = b = a 0 /2[011]. APBs were observed in nearly every precipitate beyond 0.5% creep strain for the compositions investigated. The implications for high-temperature properties are discussed

  3. Mechanisms of oxide layer formation and destruction on a chromia former nickel base alloy in HTR environment

    International Nuclear Information System (INIS)

    Rouillard, F.

    2007-10-01

    Haynes 230 alloy which contains 22 wt.% chromium could be a promising candidate material for structures and heat exchangers (maximum operating temperature: 850-950 C) in Very High Temperature Reactors (VHTR). The feasibility demonstration involves to valid its corrosion resistance in the reactor specific environment namely impure helium. The alloys surface reactivity was investigated at temperatures between 850 and 1000 C. We especially focused on the influence of different parameters such as concentrations of impurities in the gas phase (carbon monoxide and methane, water vapour/hydrogen ratio), alloy composition (activities of Cr and C, alloying element contents) and temperature. Two main behaviours have been revealed: the formation of a Cr/Mn rich oxide layer at 900 C and its following reduction at higher temperatures. At 900 C, the water vapour is the main oxidizing gas. However in the initial times, the carbon monoxide reacts at the metal/oxide interface which involves a gaseous transport through the scale; CO mainly oxidizes the minor alloying elements aluminium and silicon. Above a critical temperature TA, the carbon in solution in the alloy reduces chromia. To ascribe the scale destruction, a model is proposed based on thermodynamic interfacial data for the alloy, oxide layer morphology and carbon monoxide partial pressure in helium; the model is then validated regarding experimental results and observations. (author)

  4. Microstructural Evaluations of Baseline HSR/EPM Disk Alloys

    Science.gov (United States)

    Gabb, Timothy P.; Garg, Anita; Ellis, David L.

    2004-01-01

    Six alloys representing two classes of powder metallurgy nickel-based superalloys were examined by transmission electron microscopy (TEM) and phase extraction. Alloys KM4, CH98, IN-100 and 456 are based on a Ni-18Co-12Cr composition while alloys Rene' 88 DT and SR 3 have lower Al and Co and higher Cr contents. The lambda size distributions were determined from quantitative image analysis of the TEM images. The volume fraction of lambda and carbides and the composition of the phases were determined by a combination of phase extraction and TEM. The results showed many similarities in lambda size distributions, grain boundary serrations, and grain boundary carbide frequencies between alloys KM4, CH98, 456, Rene' 88 DT and SR 3 when heat treated to give an approximate grain size of ASTM 6. The density of grain boundary carbides in KM4 was shown to substantially increase as the grain size increased. IN-100 and 456 subjected to a serration cooling heat treatment had much more complex lambda size distributions with very large intergranular and intragranular secondary lambda as well as finer than average cooling and aging lambda. The grain boundary carbides in IN-100 were similar to the other alloys, but 456 given the serration cooling heat treatment had a more variable density of grain boundary carbides. Examination of the phases extracted from the matrix showed that there were significant differences in the phase chemistries and elemental partitioning ratios between the various alloys.

  5. Effect of Microstructure and Alloy Chemistry on Hydrogen Embrittlement of Precipitation-Hardened Ni-Based Alloys

    Science.gov (United States)

    Obasi, G. C.; Zhang, Z.; Sampath, D.; Morana, Roberto; Akid, R.; Preuss, M.

    2018-04-01

    The sensitivity to hydrogen embrittlement (HE) has been studied in respect of precipitation size distributions in two nickel-based superalloys: Alloy 718 (UNS N07718) and Alloy 945X (UNS N09946). Quantitative microstructure analysis was carried out by the combination of scanning and transmission electron microscopy and energy dispersive x-ray spectroscopy (EDS). While Alloy 718 is mainly strengthened by γ″, and therefore readily forms intergranular δ phase, Alloy 945X has been designed to avoid δ formation by reducing Nb levels providing high strength through a combination of γ' and γ″. Slow strain rate tensile tests were carried out for different microstructural conditions in air and after cathodic hydrogen (H) charging. HE sensitivity was determined based on loss of elongation due to the H uptake in comparison to elongation to failure in air. Results showed that both alloys exhibited an elevated sensitivity to HE. Fracture surfaces of the H precharged material showed quasi-cleavage and transgranular cracks in the H-affected region, while ductile failure was observed toward the center of the sample. The crack origins observed on the H precharged samples exhibited quasi-cleavage with slip traces at high magnification. The sensitivity is slightly reduced for Alloy 718, by coarsening γ″ and reducing the overall strength of the alloy. However, on further coarsening of γ″, which promotes continuous decoration of grain boundaries with δ phase, the embrittlement index rose again indicating a change of hydrogen embrittlement mechanism from hydrogen-enhanced local plasticity (HELP) to hydrogen-enhanced decohesion embrittlement (HEDE). In contrast, Alloy 945X displayed a strong correlation between strength, based on precipitation size and embrittlement index, due to the absence of any significant formation of δ phase for the investigated microstructures. For the given test parameters, Alloy 945X did not display any reduced sensitivity to HE compared with

  6. Atomistic simulation of processes in Ni-base alloys with account for local relaxations

    International Nuclear Information System (INIS)

    Bursik, Jiri

    2007-01-01

    Ordering in Ni-base superalloys is the crucial process controlling the development of the characteristic two-phase microstructure and subsequently the mechanical properties. Systems containing up to six alloying elements typical of advanced Ni-based superalloys are modelled in this work using a Monte Carlo approach with phenomenological Lennard-Jones pair potentials and interactions up to the third coordination sphere. Three-dimensional crystal block is used with over 10 5 atoms. Molecular dynamics approach is used to relax local atomic positions in course of ordering processes under applied stress. The importance of taking into account both relaxation of modelled block dimensions and relaxation of local atomic positions is discussed

  7. Observations of cellular transformation products in nickel-base superalloys

    International Nuclear Information System (INIS)

    Barlow, C.Y.; Ralph, B.

    1979-01-01

    Transmission electron microscopy has been used to identify the products in cellularly transformed regions of alloys based on the Nimonic 80 A composition. The commercial alloy is shown to undergo a small degree of cellular transformation even after conventional heat treatments, while recrystallization is found to increase the incidence of this reaction type. Low carbon versions of this alloy demonstrate cellular precipitation over a wider range of heat treatments. It is shown that the cellular reaction may take place in these alloys under a variety of different conditions and with a range of driving forces. Reasons for this unexpected behaviour are offeredm as is a suggestion as to why the cellular reaction occurs on a local scale. (author)

  8. The tensile behavior of GH3535 superalloy at elevated temperature

    Energy Technology Data Exchange (ETDEWEB)

    Han, F.F.; Zhou, B.M.; Huang, H.F.; Leng, B.; Lu, Y.L. [Thorium Molten Salts Reactor Center, Shanghai Institute of Applied Physics, Chinese Academy of Sciences (China); Dong, J.S. [Superalloy Division, Institute of Metal Research, Chinese Academy of Sciences (China); Li, Z.J., E-mail: lizhijun@sinap.ac.cn [Thorium Molten Salts Reactor Center, Shanghai Institute of Applied Physics, Chinese Academy of Sciences (China); Zhou, X.T. [Thorium Molten Salts Reactor Center, Shanghai Institute of Applied Physics, Chinese Academy of Sciences (China)

    2016-10-01

    The tensile behavior of GH3535 alloy has been investigated at strain rates of 8.33 × 10{sup −5}/s{sup −1}–8.33 × 10{sup −3}/s{sup −1}, in the temperature range of 25–800 °C. The results showed that the ultimate tensile strength was decreased with increasing temperature and increased with rising strain rate, whereas the yield strength kept almost a constant value at the temperature range from 550 to 800 °C in all strain rates test. The formation of M{sub 12}C carbides at the grain boundary during the tension process played an important role in increasing the yield strength of the alloy at elevated temperatures. But inhomogeneous deformation at 650 °C resulted in the minimum ductility of the alloy. Additionally, various types of serrations were noticed on the stress-strain curves for the alloy tested in the temperature range of 500–800 °C. Normal Portevin-Le Chatelier (PLC) effect and positive strain rate sensitivity were observed in this alloy. Type A and A + B serrations were presented to stress-strain curves at temperatures below 650 °C, whereas type C serration was noticed when the temperature rose above 650 °C. The analysis suggested that the interactions between substitutional solutes migration and mobile dislocations were the main reason for the serrated flow behavior in this alloy. - Highlights: • The tensile behavior of GH3535 alloy at elevated temperature was studied. • The yield strength anomaly was observed in the temperature range from 550 to 800 °C. • The formation of M{sub 12}C improves the grain boundary strength to a certain extent. • Inhomogeneous deformation at 650 °C results in the ductility loss of the alloy. • The interaction between solute atoms and dislocations results in the PLC effect.

  9. A new method in prediction of TCP phases formation in superalloys

    International Nuclear Information System (INIS)

    Mousavi Anijdan, S.H.; Bahrami, A.

    2005-01-01

    The purpose of this investigation is to develop a model for prediction of topologically closed-packed (TCP) phases formation in superalloys. In this study, artificial neural networks (ANN), using several different network architectures, were used to investigate the complex relationships between TCP phases and chemical composition of superalloys. In order to develop an optimum ANN structure, more than 200 experimental data were used to train and test the neural network. The results of this investigation shows that a multilayer perceptron (MLP) form of the neural networks with one hidden layer and 10 nodes in the hidden layer has the lowest mean absolute error (MAE) and can be accurately used to predict the electron-hole number (N v ) and TCP phases formation in superalloys

  10. Zinc-induced embrittlement in nickel-base superalloys by simulation and experiment

    Science.gov (United States)

    Otis, Richard; Waje, Mahesh; Lindwall, Greta; Jefferson, Tiffany; Lange, Jeremy; Liu, Zi-Kui

    2017-09-01

    The high cost of Re has driven interest in processes for recovering Re from scrap superalloy parts. In this work thermodynamic modelling is used to study Zn-induced embrittlement of a superalloy and to direct experiments. Treating superalloy powder with Zn vapour reduces the average particle size after milling from approximately ?m to 0.5-10 ?m, vs. ?m for untreated powder. Simulations predict the required treatment time to increase with temperature. Agreement between predictions and experiments suggests that an embrittling liquid forms in less than an hour of Zn vapour treatment between 950-1000 ?C and partial pressures of Zn between 14-34 kPa (2-5 psi).

  11. Density of liquid NiCoAlCr quarternary alloys measured by modified sessile drop method

    Institute of Scientific and Technical Information of China (English)

    FANG Liang; ZHANG Shu-fang; XIAO Feng; YANG Ling-chuan; DONG Jian-xin; CAO Chun-lan; TAO Zai-nan; K. MUKAI

    2006-01-01

    The densities of liquid NiCoAlCr quaternary alloys with a fixed molar ratio of Ni to Co to Al (x(Ni)-x(Co)-x(Al)≈73-12-15) which is close to the average value of the commercial Ni-based superalloys TMS75, INCO713, CM247LC and CMSX-4, and the mass fraction of chromium changes from 0 to 9% were measured by a modified sessile drop method. It is found that with increasing temperature and chromium concentration in the alloys, the densities of the liquid NiCoAlCr quaternary alloys decrease, whereas the molar volume of the liquid NiCoAlCr quaternary alloys increases. And the liquid densities of NiCoAlCr quaternary alloys calculated from the partial molar volumes of nickel, cobalt, aluminum and chromium in the corresponding Ni-bases binary alloys are in good agreement with the experimental ones, i.e. within the error tolerance range the densities of the liquid Ni-based multi-component alloys can be predicted from the partial volumes of elements in Ni-based binary alloys in liquid state. The molar volume of liquid NiCoAlCr binary alloy shows a negative deviation from the ideal linear mixing and the deviation changes small with the increase of chromium concentration at the same temperature.

  12. Development of a high strength, hydrogen-resistant austenitic alloy

    International Nuclear Information System (INIS)

    Chang, K.M.; Klahn, D.H.; Morris, J.W. Jr.

    1980-08-01

    Research toward high-strength, high toughness nonmagnetic steels for use in the retaining rings of large electrical generators led to the development of a Ta-modified iron-based superalloy (Fe-36 Ni-3 Ti-3 Ta-0.5 Al-1.3 Mo-0.3 V-0.01 B) which combines high strength with good toughness after suitable aging. The alloy did, however, show some degradation in fatigue resistance in gaseous hydrogen. This sensitivity was associated with a deformation-induced martensitic transformation near the fracture surface. The addition of a small amount of chromium to the alloy suppressed the martensite transformation and led to a marked improvement in hydrogen resistance

  13. Low cycle fatigue of alloy 718 in cryogenic environment

    International Nuclear Information System (INIS)

    Vergara Aimone, J.

    1989-01-01

    A specially processed Ni-Fe base superalloy 718 has been selected as a structural material for a critical component in ALCATOR C-MOD, the new fusion experimental facility at the Massachusetts Institute of Technology. Draw bars made out of this material will be subjected to large alternating loads while operating at 77 0 K. Monotonic and cyclic mechanical properties were determined in order to evaluate the reactor's maintenance schedule with special emphasis in developing a Low Cycle Fatigue database for this special alloy. Improved monotonic properties over conventionally heat treated alloy 718 were observed. Partial hardening was observed at 77 0 K at 1% of the fatigue life, while softening was observed at room temperature, both relative to their respective monotonic stress strain curves. The fatigue curves were corrected for non-zero mean stress allowing satisfactory safety margin for the expected alternating stress. (author)

  14. Effects of alloying element on stabilities, electronic structures, and mechanical properties of Pd-based superalloys

    Science.gov (United States)

    Yan, Pei; Chong, Xiao-Yu; Jiang, Ye-Hua; Feng, Jing

    2017-12-01

    Not Available Project supported by the Young-Talent Support Programs of Kunming University of Science and Technology, China (Grant No. 11504146) and the National Natural Science Foundation of China (Grant No. 51762028).

  15. Chemical vapor deposition of aluminide coatings on iron, nickel and superalloys

    International Nuclear Information System (INIS)

    John, John T.; De, P.K.; Dubey, Vivekanand; Srinivasa, Raman

    2009-08-01

    Aluminide coatings are a class of intermetallic coatings applied on nickel and cobalt base superalloys and steels to protect them from different forms of environmental degradation at high temperatures. In this report a CVD system that can produce the aluminide coatings on iron, nickel and nickel base alloys has been described and the result of chemical vapor deposition of aluminide coatings on iron specimens, their characterization, and property evaluation have been presented. The CVD system consists of an AlCl 3 bath, a stainless steel retort as a hot-wall reacto, cold traps and vacuum system. Aluminium chloride vapor was carried in a stream of hydrogen gas at a flow rate of 150 SCCM (standard cubic centimeter per minute) into the CVD reactor maintained in the temperature range of 1173 - 1373 K and at a pressure of 1.33 kPa (10 Torr). Aluminum deposition takes place from aluminium subchlorides produced by reaction between AlCl 3 and pure aluminum kept in the CVD reactor. The aluminum diffuses into the iron samples and iron aluminide phases are formed at the surface. The coatings were shining bright and showed good adherence to the substrate. The coatings consisted of FeAl phase over a wide range of experimental conditions. The growth kinetics of the coating followed a parabolic rate law and the mean activation energy was 212 ±16 kJ/mol. Optical microscopic studies on the transverse section of the coating showed that the aluminide coating on iron consisted of two layers. The top layer had a thickness in the range of 20-50 μm, and the under layer had thickness ranging from 35 to 250 μm depending on coating temperature in two hours. The thickness of the aluminide layer increased with coating duration and temperature. Electron microprobe studies (EPMA) showed that the aluminum concentration decreased steadily as distance from the surface increased. TEM studies showed that the outer most layer had a B2 order (of the FeAl phase), which extended even into the under

  16. VANADIUM ALLOYS

    Science.gov (United States)

    Smith, K.F.; Van Thyne, R.J.

    1959-05-12

    This patent deals with vanadium based ternary alloys useful as fuel element jackets. According to the invention the ternary vanadium alloys, prepared in an arc furnace, contain from 2.5 to 15% by weight titanium and from 0.5 to 10% by weight niobium. Characteristics of these alloys are good thermal conductivity, low neutron capture cross section, good corrosion resistance, good welding and fabricating properties, low expansion coefficient, and high strength.

  17. Corrosion Behavior of Superalloys in Hot Lithium Molten Salt

    International Nuclear Information System (INIS)

    Cho, Soo-Haeng; Hur, Jin-Mok; Seo, Chung-Seok; Park, Seoung-Won

    2006-01-01

    The Li-reduction process involves the chemical reduction of spent fuel oxides by liquid lithium metal in a molten LiCl salt bath at 650 .deg. C followed by a separate electrochemical reduction of lithium oxide (Li 2 O), which builds up in the salt bath. This process requires a high purity inert gas atmosphere inside remote hot cell nuclear facility to prevent unwanted Li oxidation and fires during the handling of chemically active Li metal. In light of the limitations of the Li-reduction process, a direct electrolytic reduction technology is being developed by KAERI to enhance process safety and economic viability. The electrolytic reduction of spent oxide fuel involves the liberation of oxygen in a molten LiCl electrolyte, which results in a chemically aggressive environment that is too corrosive for typical structural materials. Even so, the electrochemical process vessel must be resilient at ∼ 650 .deg. C in the presence of oxygen to enable high processing rates and an extended service life. But, the mechanism and the rate of the corrosion of metals in LiCl-Li 2 O molten salt under oxidation condition are not clear. In the present work, the corrosion behavior and corrosion mechanism of superalloys have been studied in the molten salt of LiCl-Li 2 O under oxidation condition

  18. Structural Performance of Inconel 625 Superalloy Brazed Joints

    Science.gov (United States)

    Chen, Jianqiang; Demers, Vincent; Cadotte, Eve-Line; Turner, Daniel; Bocher, Philippe

    2017-02-01

    The purpose of this work was to investigate tensile and fatigue behaviors of Inconel 625 superalloy brazed joints after transient liquid-phase bonding process. Brazing was performed in a vacuum furnace using a nickel-based filler metal in a form of paste to join wrought Inconel 625 plates. Mechanical tests were carried out on single-lap joints under various lap distance-to-thickness ratios. The fatigue crack initiation and crack growth modes were examined via metallographic analysis, and the effect of local stress on fatigue life was assessed by finite element simulations. The fatigue results show that fatigue strength and endurance limit increase with overlap distance, leading to a relatively large scatter of results. Fatigue cracks nucleated in the high-stressed region of the weld fillets from brittle eutectic phases or from internal brazing cavities. The present work proposes to rationalize the results by using the local stress at the brazing fillet. When using this local stress, all fatigue-obtained results find themselves on a single S- N curve, providing a design curve for any joint configuration in fatigue solicitation.

  19. Microstructural characteristics of high-temperature oxidation in nickel-base superalloy

    International Nuclear Information System (INIS)

    Khalid, F.A.

    1997-01-01

    Superalloys are used for aerospace and nuclear applications where they can withstand high-temperature and severe oxidizing conditions. High-temperature oxidation behavior of a nickel-base superalloy is examined using optical and scanning electron microscopical techniques. The morphology of the oxide layers developed is examined, and EDX microanalysis reveals diffusion of the elements across the oxide-metal interface. Evidence of internal oxidation is presented, and the role of structural defects is considered. The morphology of the oxide-metal interface formed in the specimens exposed in steam and air is examined to elucidate the mechanism of high-temperature oxidation

  20. Process of welding gamma prime-strengthened nickel-base superalloys

    Science.gov (United States)

    Speigel, Lyle B.; White, Raymond Alan; Murphy, John Thomas; Nowak, Daniel Anthony

    2003-11-25

    A process for welding superalloys, and particularly articles formed of gamma prime-strengthened nickel-base superalloys whose chemistries and/or microstructures differ. The process entails forming the faying surface of at least one of the articles to have a cladding layer of a filler material. The filler material may have a composition that is different from both of the articles, or the same as one of the articles. The cladding layer is machined to promote mating of the faying surfaces, after which the faying surfaces are mated and the articles welded together. After cooling, the welded assembly is free of thermally-induced cracks.

  1. Influence of sub-solvus solution heat treatment on γ′ morphological instability in a new Ni–Cr–Co-based powder metallurgy superalloy

    International Nuclear Information System (INIS)

    Yang, W.P.; Liu, G.Q.; Wu, K.; Hu, B.F.

    2014-01-01

    Highlights: • A special γ′ morphological instability in a new Ni–Cr–Co-based P/M superalloy was studied. • Three heat treatments were applied to the alloy and microstructures were observed. • Microstructure of the alloy was homogenized by sub-solvus solution heat treatment. • Sub-solvus solution heat treatment influences morphology of γ′ fan-type structures. • Sub-solvus solution heat treatment makes γ′ fan-type structures regular and stable. -- Abstract: The influence of the sub-solvus solution heat treatment on the microstructure, especially the γ′ morphology (γ′ fan-type structure), and microhardness of a new Ni–Cr–Co-based powder metallurgy superalloy was studied by means of field emission scanning electron microscopy (FESEM) and microhardness testing. The results show that sub-solvus solution heat treatment changes the microstructure of an as-forged alloy. It makes large primary γ′ phases at grain boundaries smaller and the distribution of secondary γ′ phases in the interior of the grains more homogeneous. Moreover, the grain boundaries widen because of the supplementary precipitate. The sub-solvus solution heat treatment before the super-solvus solution heat treatment does not change nucleation sites of the γ′ fan-type structures which precipitate during the super-solvus solution heat treatment. However, it influences the morphology of γ′ fan-type structures. Length distribution of the secondary γ′ dendrites in fan-type structures changes from a bimodal to a unimodal distribution, which means the lengths of the secondary γ′ dendrites become more uniform. Applying a sub-solvus solution heat treatment after the super-solvus solution heat treatment causes the secondary γ′ dendrites to be broken off in the fan-type structures and a refinement of the γ′ phases, and this improves stability of the γ′ phases

  2. Microstructural characterization, formation mechanism and fracture behavior of the needle δ phase in Fe–Ni–Cr type superalloys with high Nb content

    Energy Technology Data Exchange (ETDEWEB)

    Ning, Yongquan, E-mail: luckyning@nwpu.edu.cn [School of Materials Science & Engineering, Northwestern Polytechnical University, Xi' an 710072 (China); Huang, Shibo [Anshan Iron & Steel Group Corporation Bayuquan Subsidiary Company, Bayuquan 115007 (China); Fu, M.W. [Department of Mechanical Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong (China); Dong, Jie [Inspection & Research Institute of Boiler & Pressure Vessel of Jiangxi Province, Nanchang 330029 (China)

    2015-11-15

    Microstructural characterization, formation mechanism and fracture behavior of the needle δ phase in Fe–Ni–Cr type superalloys with high Nb content (GH4169, equivalent to Inconel 718) have been quantitatively investigated in this research. The typical microstructures of δ phases with the stick, mixed and needle shapes obviously present in Inconel 718 after the isothermal upsetting at the temperature of 980–1060 °C with the initial strain rate of 10{sup −3}–10{sup −1} s{sup −1}. It is found that the shape of the δ phase has a great effect on the mechanical properties of the alloy, viz., the stick δ phase behaves good plasticity and the needle δ phase has good strength. In addition, the needle δ phase can be used to control the grain size as it can prevent grain growth. The combined effect of the localized necking and microvoid coalescence leads to the final ductile fracture of the GH4169 components with the needle δ phase. Both dislocation motion and atom diffusion are the root-cause for the needle δ phase to be firstly separated at grain boundary and then at sub-boundary. The formation mechanism of the needle δ phase is the new finding in this research. Furthermore, it is the primary mechanism for controlling the needle δ phase in Fe–Ni–Cr type superalloys with high Nb content. - Highlights: • Shape of the δ phase takes great effect on mechanical property. • Needle δ phase plays a great role to prevent grain growth. • Needle δ phase can enhance the fracture strength. • Microstructure mechanism of the needle δ phase has been investigated. • Fracture behavior of the needle δ phase has been studied.

  3. Alloying and the micromechanics of Co–Al–W–X quaternary alloys

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Hui-Yu; Coakley, James; Vorontsov, Vassili A. [Department of Materials, Royal School of Mines, Imperial College London, Prince Consort Road, London SW7 2BP (United Kingdom); Jones, Nicholas G.; Stone, Howard J. [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom); Dye, David, E-mail: ddye@ic.ac.uk [Department of Materials, Royal School of Mines, Imperial College London, Prince Consort Road, London SW7 2BP (United Kingdom)

    2014-09-08

    The lattice misfit and diffraction elastic constants in hot rolled polycrystalline Co–7Al–5W–2Ta and Co–6Al–6W–2Ti (at.%) are measured using neutron and synchrotron X-ray diffraction. The misfit in the two alloys was found to be +0.67 and +0.59%, using neutron diffraction at HRPD. The misfit was found to increase with temperature, as in Ni superalloys. This implies that the amount of coherency strengthening increases with temperature. The diffraction elastic constants measured show that the γ′ phase is less stiff than the γ matrix in all orientations, which means that load shedding will occur to the γ phase.

  4. Alloying and the micromechanics of Co–Al–W–X quaternary alloys

    International Nuclear Information System (INIS)

    Yan, Hui-Yu; Coakley, James; Vorontsov, Vassili A.; Jones, Nicholas G.; Stone, Howard J.; Dye, David

    2014-01-01

    The lattice misfit and diffraction elastic constants in hot rolled polycrystalline Co–7Al–5W–2Ta and Co–6Al–6W–2Ti (at.%) are measured using neutron and synchrotron X-ray diffraction. The misfit in the two alloys was found to be +0.67 and +0.59%, using neutron diffraction at HRPD. The misfit was found to increase with temperature, as in Ni superalloys. This implies that the amount of coherency strengthening increases with temperature. The diffraction elastic constants measured show that the γ′ phase is less stiff than the γ matrix in all orientations, which means that load shedding will occur to the γ phase

  5. Crescimento de Hymenaea courbaril L. var. stilbocarpa (Hayne Lee et Lang. e Enterolobium contortisiliquum (Vell. Morong (Leguminosae sob diferentes níveis de sombreamento Growth of Hymenaea courbaril L. var. stilbocarpa (Hayne Lee et Lang. e Enterolobium contortisiliquum (Vell. Morong (Leguminosae under different shading levels

    Directory of Open Access Journals (Sweden)

    Ana Lúcia da Silva Lima

    2010-03-01

    Full Text Available Hymenaea courbaril L. var. stilbocarpa (Hayne Lee et Lang. é uma espécie clímax tolerante a sombra, ao passo que Enterolobium contortisiliquum (Vell. Morong. é uma espécie pioneira. O desenvolvimento destas espécies pode refletir a habilidade de adaptação aos diferentes fatores ambientais (luz, água e temperatura no local em que estão crescendo. O suprimento inadequado de um desses fatores pode reduzir o vigor da planta e limitar seu desenvolvimento. O presente trabalho teve como objetivo avaliar os efeitos do nível de sombreamento no crescimento e a concentração de pigmentos fotossintéticos em duas espécies de leguminosas arbóreas, Hymenaea courbaril L. var. stilbocarpa (Hayne Lee et Lang. e Enterolobium contortisiliquum (Vell. Morong. O experimento foi conduzido no Setor de Olericultura do Centro Universitário Luterano de Ji-Paraná (CEULJI/ULBRA/Rondônia. Durante a formação das mudas, ambas as espécies foram expostas a quatro tratamentos de sombra: 0 % (controle - sol pleno; 30 %; 50 % e 80 %. Cada tratamento foi constituído com três repetições de cada espécie; o delineamento experimental foi inteiramente casualisado. Quatro meses após a semeadura, as seguintes análises foram realizadas: número de folhas, altura da planta, comprimento do sistema radicular, massa seca total e concentração de pigmentos fotossintéticos. O tratamento sob sol pleno afetou negativamente o crescimento de ambas as espécies. As mudas crescidas sob 50% e 80% apresentaram melhor desenvolvimento. Conforme o aumento do sombreamento houve um decréscimo na razão clorofila a/b e um aumento nas concentrações de clorofila total e carotenóides totais.Hymenaea courbaril L. var. stilbocarpa (Hayne Lee et Lang. is a clímax shadow tolerant specie and Enterolobium contortisiliquum (Vell. Morong., by the other hand, is considered as a pioneer specie. The development of these species may reflect its adaptation ability to different environmental

  6. Results of the Electron-Beam Button Melting of very clean Ni-base superalloys for the identification of nonmetallic inclusions

    Energy Technology Data Exchange (ETDEWEB)

    Hauner, F.; Stephan, H.; Stumpp, H.

    1986-02-01

    The reliability of components made of high strength materials is substantially influenced by their cleanliness. For example, the ductility, the fatigue-characteristics and the stress resistance of high strength alloys can be improved by increasing the cleanliness along with decreasing the inclusion size to below 25 ..mu..m. For the analysis of such high clean alloys with decreasing size of nonmetallic inclusions, the metallographic texting methods become troublesome and inexact for a dependable quality control. The Electron-Beam Button Melt Test offers a possibility for the examination and qualification of the small amounts of different inclusions in the high clean materials. During a process-controlled melting procedure, inclusions of high density sink to the bottom of a water-cooled copper crucible. Low density inclusions float to the pool surface and are concentrated in the upper center of the button by means of a controlled solidification of the melting pool. For the utilization of the process in the production quality control, development and research, we have developed the Electron-Beam Button Melting Furnace ES 1/07/30 B. In this paper we will present results of the application of the ES1/07/30 B. In this paper we will present results of the application of the ES 1/07/30 B to the EB-Button melting of the Ni-Base Superalloys IN718 and Astroloy. (orig.).

  7. Superior metallic alloys through rapid solidification processing (RSP) by design

    Energy Technology Data Exchange (ETDEWEB)

    Flinn, J.E. [Idaho National Engineering Laboratory, Idaho Falls, ID (United States)

    1995-05-01

    Rapid solidification processing using powder atomization methods and the control of minor elements such as oxygen, nitrogen, and carbon can provide metallic alloys with superior properties and performance compared to conventionally processing alloys. Previous studies on nickel- and iron-base superalloys have provided the baseline information to properly couple RSP with alloy composition, and, therefore, enable alloys to be designed for performance improvements. The RSP approach produces powders, which need to be consolidated into suitable monolithic forms. This normally involves canning, consolidation, and decanning of the powders. Canning/decanning is expensive and raises the fabrication cost significantly above that of conventional, ingot metallurgy production methods. The cost differential can be offset by the superior performance of the RSP metallic alloys. However, without the performance database, it is difficult to convince potential users to adopt the RSP approach. Spray casting of the atomized molten droplets into suitable preforms for subsequent fabrication can be cost competitive with conventional processing. If the fine and stable microstructural features observed for the RSP approach are preserved during spray casing, a cost competitive product can be obtained that has superior properties and performance that cannot be obtained by conventional methods.

  8. Strain-induced γ{sup '}-coarsening during aging of Ni-based superalloys under uniaxial load. Modeling and analysis

    Energy Technology Data Exchange (ETDEWEB)

    Mushongera, Leslie T.

    2016-07-28

    called for a regularization that enforces local equilibrium at the corners, and the method of Eggelston et al. [Physica D 150, 91 (2001)], generalized to arbitrary crystal symmetries and rotations of the crystalline axes was adapted for that context. Mechanical effects accounting for the contributions from the misfit, anisotropic and inhomogeneous elasticity and creep loading were integrated physically consistent. The mechanical effects are incorporated into the phase field model via the Allen-Cahn equation based on Steinbach [Physica D, 217, 153 (2006)] and Fleck et. al [Philos. Mag., 90, 265 (2010)]. The relaxed displacement fields required to calculate the elastic driving force was obtained by solving the mechanical equilibrium using an iterative Jacobi relaxation scheme using a staggered grid based on the finite difference method. Morphological evolution and kinetics in single crystal Ni-base superalloys was studied. To gain insight in optimized alloying, a systematic computational measure to assess and track the evolution anisotropic microstructures was integrated in the model. Previously, focusing on the solidification behavior, Heckl et al. [Metal. and Mater. Trans. A, 41, 202 (2010)] discussed Ruthenium (Ru) as a possible Rhenium (Re) replacement-candidate for next generation Ni-based superalloys. Employing phase field simulation studies, we performed virtual experiments of the coarsening behavior in Re and Ru containing alloys. The simulations revealed that the degradation of the γ-γ{sup '} microstructure via coarsening is considerably slower in Re-containing superalloys. We observed that an increase in the Re content strongly reduces the γ{sup '}-coarsening kinetics and the simulations explicitly resolved the time dependence of that slow down beyond experiment. Likewise, it was found that Ru variations have no significant effect on the coarsening kinetics. The simulations revealed the mechanism by which Re reduces coarsening kinetics. The

  9. Nonswelling alloy

    Science.gov (United States)

    Harkness, S.D.

    1975-12-23

    An aluminum alloy containing one weight percent copper has been found to be resistant to void formation and thus is useful in all nuclear applications which currently use aluminum or other aluminum alloys in reactor positions which are subjected to high neutron doses.

  10. Nonswelling alloy

    International Nuclear Information System (INIS)

    Harkness, S.D.

    1975-01-01

    An aluminum alloy containing one weight percent copper has been found to be resistant to void formation and thus is useful in all nuclear applications which currently use aluminum or other aluminum alloys in reactor positions which are subjected to high neutron doses

  11. Size dependence of the polarizability and Haynes rule for an exciton bound to an ionized donor in a single spherical quantum dot

    Energy Technology Data Exchange (ETDEWEB)

    Feddi, E., E-mail: e.feddi@um5s.net.ma; Zouitine, A. [Université Mohamed V Souissi, Ecole Normale Supérieure de l' Enseignement Technique (ENSET), Rabat (Morocco); Oukerroum, A.; Zazoui, M. [Laboratory of Condensed Matter, Faculty of Sciences and Techniques, University of Hassan II-Mohammedia, B.P. 146, 20800 Mohammedia (Morocco); Dujardin, F. [LCP-A2MC, Université de Lorraine, ICPM, 1 Bd Arago, 57070 Metz (France); Assaid, E. [Laboratoire d' Électronique et Optique des Nanostructures de Semiconducteurs, Faculté des Sciences, B. P. 20, El Jadida (Morocco)

    2015-02-14

    We study the effect of an external electric field on an exciton bound to an ionized donor (D{sup +}, X) confined in a spherical quantum dot using a perturbative-variational method where the wave function and energy are developed in series of powers of the electric field strength. After testing this new approach in the determination of the band gap for some semiconductor materials, we generalize it to the case of (D{sup +}, X) in the presence of the electric field and for several materials ZnO, PbSe, and InAs, with significant values of the mass ratio. Three interesting results can be deduced: First, we show that the present method allows to determine the ground state energy in the presence of a weak electric field in a simple way (E = E{sub 0} − αf{sup 2}) using the energy without electric field E{sub 0} and the polarizability α. The second point is that our theoretical predictions show that the polarizability of (D{sup +}, X) varies proportionally to R{sup 3.5} and follows an ordering α{sub D{sup 0}}<α{sub X}<α{sub (D{sup +},X)}. The last point to highlight is that the Haynes rule remains valid even in the presence of a weak electric field.

  12. Size dependence of the polarizability and Haynes rule for an exciton bound to an ionized donor in a single spherical quantum dot

    International Nuclear Information System (INIS)

    Feddi, E.; Zouitine, A.; Oukerroum, A.; Zazoui, M.; Dujardin, F.; Assaid, E.

    2015-01-01

    We study the effect of an external electric field on an exciton bound to an ionized donor (D + , X) confined in a spherical quantum dot using a perturbative-variational method where the wave function and energy are developed in series of powers of the electric field strength. After testing this new approach in the determination of the band gap for some semiconductor materials, we generalize it to the case of (D + , X) in the presence of the electric field and for several materials ZnO, PbSe, and InAs, with significant values of the mass ratio. Three interesting results can be deduced: First, we show that the present method allows to determine the ground state energy in the presence of a weak electric field in a simple way (E = E 0  − αf 2 ) using the energy without electric field E 0 and the polarizability α. The second point is that our theoretical predictions show that the polarizability of (D + , X) varies proportionally to R 3.5 and follows an ordering α D 0 <α X <α (D + ,X) . The last point to highlight is that the Haynes rule remains valid even in the presence of a weak electric field

  13. Thermal-stress fatigue behavior of twenty-six superalloys

    Science.gov (United States)

    Bizon, P. T.; Spera, D. A.

    1976-01-01

    The comparative thermal-stress fatigue resistances of 26 nickeland cobalt-base alloys were determined by fluidized bed tests. Cycles to cracking differed by almost three orders of magnitude for these materials, with directional solidification and surface protection showing definite benefit. The alloy-coating combination with the highest thermal-stress fatigue resistance was directionally solidified NASA TAZ-8A with an RT-SP coating. Its oxidation resistance was also excellent, showing approximately a 1/2 percent weight loss after 14,000 fluidized bed cycles.

  14. Mechanical behavior and coupling between mechanical and oxidation in alloy 718: effect of solide solution elements

    International Nuclear Information System (INIS)

    Max, Bertrand

    2014-01-01

    Alloy 718 is the superalloy the most widely used in industry due to its excellent mechanical properties, as well as oxidation and corrosion resistance in wide range of temperatures and solicitation modes. Nevertheless, it is a well-known fact that this alloy is sensitive to stress corrosion cracking and oxidation assisted cracking under loading in the range of temperatures met in service. Mechanisms explaining this phenomenon are not well understood: nevertheless, it is well established that a relation exists between a change in fracture mode and the apparition of plastic instabilities phenomenon. During this study, the instability phenomenon, Portevin-Le Chatelier effect, in alloy 718 was studied by tensile tests in wide ranges of temperatures and strain rates. Different domains of plastic instabilities have been evidenced. Their characteristics suggest the existence of interactions between dislocations and different types of solute elements: interstitials for lower temperatures and substitutionals for higher testing temperatures. Mechanical spectroscopy tests have been performed on alloy 718 and various alloys which composition is comparable to that of alloy 718. These tests prove the mobility of molybdenum atoms in the alloy in the studied temperature range. Specific tests have been performed to study interaction phenomenon between plasticity and oxidation. These results highlight the strong effect of plastic strain rate on both mechanical behavior and intergranular cracking in alloy 718. The subsequent discussion leads to propose hypothesis on coupling effects between deformation mechanisms and oxidation assisted embrittlement in the observed cracking processes. (author)

  15. Corrosion of superalloy Incoloy 800H/HT in eutectic mixture LiF-NaF-KF with different addition of chromium fluoride; Korozia superzliatiny Incoloy 800H/HT v eutektickej zmesi LiF-NaF-KF s ruznym pridavkom fluoridu chromiteho

    Energy Technology Data Exchange (ETDEWEB)

    Kontrik, M.; Pavlik, V.; Simko, F. [Slovenska Akademia Vied, Ustav Anorganickej Chemie, Oddelenie Taveninovych Sustav, 84636 Bratislava (Slovakia)

    2013-04-16

    Thesis deals with investigating the addition of chromium trifluoride to eutectic mixture of LiF-NaF-KF (46.5 - 11.5 - 42 mol %) on the corrosion of superalloy Incoloy 800H/HT with static tests. The corrosion losses of the alloy and type of corrosion attack was observed. It was found that the addition of chromium fluoride into the mixture generally increases of corrosion of the material. Several types of corrosion attacks were observed. On the surface of the samples the spotted, pitting and transgranular corrosions were found. On the cross-sections of the samples the subsurface and lamellar corrosions were detected. (authors)

  16. The Relation Between Alloy Chemistry and Hot-Cracking

    Science.gov (United States)

    Nunes, A. C., Jr.; Talia, J. E.

    2000-01-01

    Hot cracking is a problem in welding 2195 aluminum-lithium alloy. Weld wire additives seem to reduce the problem. This study proposes a model intended to clarify the way alloying elements affect hot-cracking. The brittle temperature range of an alloy extends wherever the tensile stress required to move the meniscus of the liquid film at the grain/dendrite boundaries is less than the bulks flow stress Sigma(sub B) of the grains: 2gamma/delta alloys outgas.) If the above condition is not met, the grains deform under stress and the liquid film remains in place. Curves of 2gamma/delta and sigma(sub B) vs. temperature in the range just below the melting temperature determine the hot cracking susceptibility of an alloy. Both are zero at onset of solidification. sigma(sub B) rises as the thermal activation of the slip mechanism is reduced. 2gamma/delta rises as the film thickness delta which can be estimated from the Scheil equation, drops. But, given an embrittled alloy, whether the alloy actually cracks is determined by the strain imposed upon it in the embrittled condition. A critical strain is estimated, Epsilon(sub C) on the order of Epsilon(sub C) is approximately delta/l where L = grain size and where the the volume increment due to the strain, concentrated at the liquid film, is on the order of the liquid film volume. In the early 80's an empirical critical strain cracking envelope Epsilon(sub C)(T) was incorporated into a damage criterion to estimate the effect of welding parameters on the formation of microfissures in a superalloy with good results. These concepts, liquid film decoherence vs. grain bulk deformation and critical strain, form the key elements of a quantitative theory of hot-cracking applicable for assessing the effect of alloying elements on hot-cracking during welding.

  17. High-temperature and low-stress creep anisotropy of single-crystal superalloys

    Czech Academy of Sciences Publication Activity Database

    Jacome, L. A.; Nortershauser, P.; Heyer, J. K.; Lahni, A.; Frenzel, J.; Dlouhý, Antonín; Somsen, C.; Eggeler, G.

    2013-01-01

    Roč. 61, č. 8 (2013), s. 2926-2943 ISSN 1359-6454 R&D Projects: GA ČR(CZ) GA202/09/2073 Institutional support: RVO:68081723 Keywords : superalloy single crystals * creep anisotropy * rafting * dislocations * deformation mechanisms Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.940, year: 2013

  18. Creep deformation and microstructural examination of a prior thermally exposed nickel base superalloy

    Czech Academy of Sciences Publication Activity Database

    Zrník, J.; Strunz, Pavel; Vrchovinský, V.; Muránsky, O.; Horňák, P.; Wiedenmann, A.

    2004-01-01

    Roč. 274 (2004), s. 925-930 ISSN 1013-9826 R&D Projects: GA AV ČR KSK1010104 Keywords : superalloy * thermal exposition * creep Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.278, year: 2004

  19. SANS investigation of precipitate microstructure in nickel-base superalloys Waspaloy and DT750

    Czech Academy of Sciences Publication Activity Database

    Strunz, Pavel; Zrník, J.; Seliga, T.; Penkalla, H.J.

    2006-01-01

    Roč. 2, č. 23 (2006), s. 363-368 ISSN 0044-2968 R&D Projects: GA ČR GA202/06/0601 Institutional research plan: CEZ:AV0Z10480505 Keywords : small-angle-neutron scattering * superalloys * precipitation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.897, year: 2006

  20. Ledges and grooves at γ/γ′ interfaces of single crystal superalloys

    Czech Academy of Sciences Publication Activity Database

    Parsa, A. B.; Wollgramm, P.; Buck, H.; Kostka, A.; Somsen, C.; Dlouhý, Antonín; Eggeler, G.

    2015-01-01

    Roč. 90, MAY (2015), s. 105-117 ISSN 1359-6454 R&D Projects: GA ČR(CZ) GA14-22834S Institutional support: RVO:68081723 Keywords : Ni-base single crystal superalloys * γ/γ′ interfaces * Interface dislocations * Rafting * Grooves Subject RIV: JG - Metallurgy Impact factor: 5.058, year: 2015

  1. Fundamental studies of electron beam welding of heat-resistant superalloys for nuclear plants, 5

    International Nuclear Information System (INIS)

    Arata, Yoshiaki; Terai, Kiyohide; Nagai, Hiroyoshi; Shimizu, Shigeki; Aota, Toshiichi.

    1978-01-01

    In this paper, the mechanical properties of base metal, its electron beam and TIG weld joint of superalloys for nuclear plants were made clear and compared with each other. As a result, it has been clarified that electron beam weld joint is superior to TIG weld joint and nearly comparable to base metal. (author)

  2. Microstructural study of weld fusion zone of TIG welded IN 738LC nickel-based superalloy

    International Nuclear Information System (INIS)

    Ojo, O.A.; Richards, N.L.; Chaturvedi, M.C.

    2004-01-01

    The weld fusion zone microstructure of a commercial aerospace superalloy IN 738 was examined. Elemental segregation induced interdendritic microconstituents were identified to include terminal solidification product M 3 B 2 and Ni 7 Zr 2 in association with γ-γ' eutectic constituent, which require proper consideration during the development of optimum post weld heat treatment

  3. Refractory porcelain enamel passive-thermal-control coating for high-temperature superalloys

    Science.gov (United States)

    Levin, H.; Auker, B. H.; Gardos, M. N.

    1973-01-01

    Study was conducted to match thermal expansion coefficients thereby preventing enamels from cracking. Report discusses various enamel coatings that are applied to two different high-temperature superalloys. Study may be of interest to manufacturers of chemical equipment, furnaces, and metal components intended for high-temperature applications.

  4. MC Carbide Characterization in High Refractory Content Powder-Processed Ni-Based Superalloys

    Science.gov (United States)

    Antonov, Stoichko; Chen, Wei; Huo, Jiajie; Feng, Qiang; Isheim, Dieter; Seidman, David N.; Sun, Eugene; Tin, Sammy

    2018-04-01

    Carbide precipitates in Ni-based superalloys are considered to be desirable phases that can contribute to improving high-temperature properties as well as aid in microstructural refinement of the material; however, they can also serve as crack initiation sites during fatigue. To date, most of the knowledge pertaining to carbide formation has originated from assessments of cast and wrought Ni-based superalloys. As powder-processed Ni-based superalloys are becoming increasingly widespread, understanding the different mechanisms by which they form becomes increasingly important. Detailed characterization of MC carbides present in two experimental high Nb-content powder-processed Ni-based superalloys revealed that Hf additions affect the resultant carbide morphologies. This morphology difference was attributed to a higher magnitude of elastic strain energy along the interface associated with Hf being soluble in the MC carbide lattice. The composition of the MC carbides was studied through atom probe tomography and consisted of a complex carbonitride core, which was rich in Nb and with slight Hf segregation, surrounded by an Nb carbide shell. The characterization results of the segregation behavior of Hf in the MC carbides and the subsequent influence on their morphology were compared to density functional theory calculations and found to be in good agreement, suggesting that computational modeling can successfully be used to tailor carbide features.

  5. Freckle Defect Formation near the Casting Interfaces of Directionally Solidified Superalloys.

    Science.gov (United States)

    Hong, Jianping; Ma, Dexin; Wang, Jun; Wang, Fu; Sun, Baode; Dong, Anping; Li, Fei; Bührig-Polaczek, Andreas

    2016-11-16

    Freckle defects usually appear on the surface of castings and industrial ingots during the directional solidification process and most of them are located near the interface between the shell mold and superalloys. Ceramic cores create more interfaces in the directionally solidified (DS) and single crystal (SX) hollow turbine blades. In order to investigate the location of freckle occurrence in superalloys, superalloy CM247 LC was directionally solidified in an industrial-sized Bridgman furnace. Instead of ceramic cores, Alumina tubes were used inside of the casting specimens. It was found that freckles occur not only on the casting external surfaces, but also appear near the internal interfaces between the ceramic core and superalloys. Meanwhile, the size, initial position, and area of freckle were investigated in various diameters of the specimens. The initial position of the freckle chain reduces when the diameter of the rods increase. Freckle area follows a linear relationship in various diameters and the average freckle fraction is 1.1% of cross sectional area of casting specimens. The flow of liquid metal near the interfaces was stronger than that in the interdendritic region in the mushy zone, and explained why freckle tends to occur on the outer or inner surfaces of castings. This new phenomenon suggests that freckles are more likely to occur on the outer or inner surfaces of the hollow turbine blades.

  6. Freckle Defect Formation near the Casting Interfaces of Directionally Solidified Superalloys

    Directory of Open Access Journals (Sweden)

    Jianping Hong

    2016-11-01

    Full Text Available Freckle defects usually appear on the surface of castings and industrial ingots during the directional solidification process and most of them are located near the interface between the shell mold and superalloys. Ceramic cores create more interfaces in the directionally solidified (DS and single crystal (SX hollow turbine blades. In order to investigate the location of freckle occurrence in superalloys, superalloy CM247 LC was directionally solidified in an industrial-sized Bridgman furnace. Instead of ceramic cores, Alumina tubes were used inside of the casting specimens. It was found that freckles occur not only on the casting external surfaces, but also appear near the internal interfaces between the ceramic core and superalloys. Meanwhile, the size, initial position, and area of freckle were investigated in various diameters of the specimens. The initial position of the freckle chain reduces when the diameter of the rods increase. Freckle area follows a linear relationship in various diameters and the average freckle fraction is 1.1% of cross sectional area of casting specimens. The flow of liquid metal near the interfaces was stronger than that in the interdendritic region in the mushy zone, and explained why freckle tends to occur on the outer or inner surfaces of castings. This new phenomenon suggests that freckles are more likely to occur on the outer or inner surfaces of the hollow turbine blades.

  7. Erosion–corrosion behaviour of Ni-based superalloy Superni-75

    Indian Academy of Sciences (India)

    The super-heater and re-heater tubes of the boilers used in thermal power plants are ... mechanism, resulting in the tube wall thinning and premature failure. The nickel-based superalloys can be used as boiler tube materials to increase the ...

  8. Pressure vessel code construction capabilities for a nickel-chromium-tungsten-molybdenum alloy

    International Nuclear Information System (INIS)

    Rothman, M.F.

    1990-01-01

    HAYNES alloy 230 (UNS NO6230) has achieved wide usage in a variety of high-temperature aerospace, chemical process industry and industrial heating applications since its introduction in 1981. Combining high elevated temperature strength with excellent metallurgical stability, environment-resistance and relatively straight forward fabrication characteristics, this Ni-Cr-W-Mo alloy was an excellent candidate for ASME Pressure vessel Code applications. Coverage under case No. 2063 was granted in July, 1989, for both Section I and Section VIII Division 1 construction. In this paper, the metallurgy of 230 alloy will be described, and its design strength capabilities contrasted with those for more established code materials. Other important performance capabilities, such as long-term thermal stability, oxidation-resistance, fatigue-resistance, and resistance to other forms of environmental degradation will be discussed. It will be shown that the combined properties of 230 alloy offer some significant advantages over other materials for applications such as expansion bellows, heat-exchangers, valves and other components in the fossil energy, nuclear energy and chemical process industries, among others

  9. Mechanical properties of nanostructured nickel based superalloy Inconel 718

    Energy Technology Data Exchange (ETDEWEB)

    Mukhtarov, Sh; Ermachenko, A, E-mail: shamil@anrb.r [Institute for Metals Superplasticity Problems RAS, 39, Khalturina, Ufa, 450001 (Russian Federation)

    2010-07-01

    This paper will describe the investigations of a nanostructured (NS) state of nickel based INCONEL alloy 718. This structure was generated in bulk semiproducts by severe plastic deformation (SPD) via multiple isothermal forging (MIF) of a coarse-grained alloy. The initial structure consisted of {gamma}-phase grains with disperse precipitations of {gamma}{sup -}phase in the forms of discs, 50-75 nm in diameter and 20 nm in thickness. The MIF generated structures possess a large quantity of non-coherent plates and rounded precipitations of {delta}-phase, primarily along grain boundaries. In the duplex ({gamma}+{delta}) structure the grains have high dislocation density and a large number of nonequilibrium boundaries. Investigations to determine mechanical properties of the alloy in a nanostructured state were carried out. Nanocrystalline Inconel 718 (80 nm) possesses a very high room-temperature strength after SPD. Microcrystalline (MC) and NS states of the alloy were subjected to strengthening thermal treatment, and the obtained results were compared in order to determine their mechanical properties at room and elevated temperatures.

  10. High Temperature Oxidation of Superalloys and Intermetallic Compounds

    Science.gov (United States)

    2010-02-28

    Oxid. Met. Vol.14, pp. 217-234. 1980. 20. T.A. Rannanarayanan, M. Raghavan and R. Petrovic-Luton. Metallic Yttrium Additions to High Temperatura ... Temperatura Alloys: Influence of AI2O3 Scale Properties. Oxid. Met. Vol.22, pp. 83-100. 1984. 21. High-temperature characterization of reactively

  11. Investigation of as-cast alloys in the Pt-Al-Cr system

    International Nuclear Information System (INIS)

    Suess, R.; Cornish, L.A.; Witcomb, M.J.

    2010-01-01

    Platinum-based alloys are being developed which have microstructures that are analogous to the γ/γ' microstructure of the nickel-based superalloys. These Pt-based alloys have the potential to be used for high-temperature applications. The ternary Pt-Al-Cr system was investigated as part of the continued development of a thermodynamic database for the Pt-Al-Cr-Ru system. Scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analyses were used to obtain phase equilibria data. The alloys were studied in the as-cast condition. A solidification projection was constructed and a liquidus surface derived. It was concluded that all phase regions were identified correctly since the results were self-consistent. Three ternary phases and 21 ternary invariant reactions were identified.

  12. Heat-treatment and heat-to-heat variations in the fracture toughness of Alloy 718

    International Nuclear Information System (INIS)

    Mills, W.J.

    1981-07-01

    The effect of heat-treatment and heat-to-heat variations on the J Ic fracture toughness response of Alloy 718 was examined at room and elevated temperatures using the multiple-specimen R-curve technique. Six heats of alloy 718 were tested in the conventional and modified heat-treated conditions. The fracture toughness response for the modified superalloy was found to be superior to that exhibited by the conventional material. Heat-to-heat variations in the J Ic response of Alloy 718 were observed in both heat-treated conditions; the modified treatment exhibited much larger variability. The J Ic and corresponding K Ic fracture toughness values were analyzed statistically to establish minimum expected toughness, values for use in design and safety analyses. 26 refs., 10 figs., 9 tabs

  13. Aging of vacuum plasma sprayed MCrAlY protective layers and their interaction with nickel- and cobalt-based γ/γ'-superalloys

    International Nuclear Information System (INIS)

    Terberger, Philipp J.

    2015-01-01

    γ/γ' single crystal superalloys with plasma-sprayed thermal barrier coating systems are used as turbine rotor blades in gas turbines if the blades are exposed to high temperatures and high mechanical loads. A bond coat (BC) is part of the thermal barrier coating system. It protects the substrate from oxidation and ensures good bonding of the ceramic coating that serves as a thermal insulator. MCrAlY (M=Ni,Co) alloys are commonly used as BCs. They form a protective Al 2 O 3 layer. This study investigates four different vacuum plasma-sprayed MCrAlY BCs with and without Re after thermal treatment of up to 1000 h at 1044 C in air. The employed substrates are the Ni-based superalloy ERBO1 and the novel Co-based γ/γ' superalloy ERBOCo-1. Additionally, the ternary γ/γ' alloy Co-9Al-9W (in at.%) was aged with a BC for up to 500 h at 900 C. Up to now little is known about the interaction of the Co-based substrates and the BCs. Oxidation and Al depletion of the BC as well as the interdiffusion of BCs and substrates are analysed primarily on the basis of SEM/EDX and XRD. The effect of Y and Hf on the microstructure of the oxide scale is discussed. Rate constants show that Hf results in higher oxidation rates while Re slows down the oxidation. The influence of the alloying elements on the BC microstructure is described. For example, Co prevents the formation of γ' phase, Re slows down diffusion and results in the formation of brittle phases. The choice of substrate material has no measurable influence on the oxidation. Qualitative and quantitative analysis of the interdiffusion zone (IDZ) shows that the choice of substrate surface pre-treatment (grit blasting or grinding) has a major influence on the interdiffusion behaviour with the BC. Grinding results in a thinner IDZ and fewer topologically closed packed (TCP) phases. The reason for this is the recrystallisation of the single crystal substrate. A study of the influence of the substrate crystal

  14. Electrical Resistance Alloys and Low-Expansion Alloys

    DEFF Research Database (Denmark)

    Kjer, Torben

    1996-01-01

    The article gives an overview of electrical resistance alloys and alloys with low thermal expansion. The electrical resistance alloys comprise resistance alloys, heating alloys and thermostat alloys. The low expansion alloys comprise alloys with very low expansion coefficients, alloys with very low...... thermoelastic coefficients and age hardenable low expansion alloys....

  15. ANALYSIS OF PITTING CORROSION ON AN INCONEL 718 ALLOY SUBMITTED TO AGING HEAT TREATMENT

    Directory of Open Access Journals (Sweden)

    Felipe Rocha Caliari

    2014-10-01

    Full Text Available Inconel 718 is one of the most important superalloys, and it is mainly used in the aerospace field on account of its high mechanical strength, good resistance to fatigue and creep, good corrosion resistance and ability to operate continuously at elevated temperatures. In this work the resistance to pitting corrosion of a superalloy, Inconel 718, is analyzed before and after double aging heat treatment. The used heat treatment increases the creep resistance of the alloy, which usually is used up to 0.6 Tm. Samples were subjected to pitting corrosion tests in chloride-containing aqueous solution, according to ASTM-F746-04 and the procedure described by Yashiro et al. The results of these trials show that after heat treatment the superalloy presents higher corrosion resistance, i.e., the pitting corrosion currents of the as received surfaces are about 6 (six times bigger (~0.15 mA than those of double aged surfaces (~0.025 mA.

  16. Creep-Data Analysis of Alloy 617 for High Temperature Reactor Intermediate Heat Exchanger

    International Nuclear Information System (INIS)

    Kim, Woo Gon; Ryu, Woo Seog; Kim, Yong Wan; Yin, Song Nan

    2006-01-01

    The design of the metallic components such as hot gas ducts, intermediate heat exchanger (IHX) tube, and steam reformer tubes of very high temperature reactor (VHTR) is principally determined by the creep properties, because an integrity of the components should be preserved during a design life over 30 year life at the maximum operating temperature up to 1000 .deg. C. For designing the time dependent creep of the components, a material database is needed, and an allowable design stress at temperature should be determined by using the material database. Alloy 617, a nicked based superalloy with chromium, molybdenum and cobalt additions, is considered as a prospective candidate material for the IHX because it has the highest design temperature. The alloy 617 is approved to 982 .deg. C (1800 .deg. F) and other alloys approved to 898 .deg. C (1650 .deg. C), such as alloy 556, alloy 230, alloy HX, alloy 800. Also, the alloy 617 exhibits the highest level of creep strength at high temperatures. Therefore, it is needed to collect the creep data for the alloy 617 and the creep-rupture life at the given conditions of temperature and stress should be predicted for the IHX construction. In this paper, the creep data for the alloy 617 was collected through literature survey. Using the collected data, the creep life for the alloy 617 was predicted based on the Larson-Miller parameter. Creep master curves with standard deviations were presented for a safety design, and failure probability for the alloy 617 was obtained with a time coefficient

  17. Powder metallurgy of turbine disc alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ingesten, N.G. (Dep. of Engineering Metals)

    1981-03-01

    The first part embraced a study of carbide precipitated in IN 100 and astrology powders. The powder was heat treated at temperatures between 950/sup 0/C and 1150/sup 0/C. After aging at 950-1100/sup 0/C the MC-carbides formed during atomization were replaced by M/sub 23/C/sub 6/-carbides. After 1150/sup 0/C treatments the MC carbides were present again. Precipitation comparable with that obtained in HIP:ed specimens was not observed at free particle surfaces. However, powder particles which had agglomerated during atomization often exhibited considerable precipitation at contiguous surfaces. Obviously, contact between the particles must occur if coarse precipitation at particle surfaces is to develop. Reduced PPB-precipitation was obtained by pre-heat- treatment of powder before compaction. It is suggested that the carbon otherwise available for PPB-precipitation forms carbides in the interior of the powder particles. The aim of the second part was to ..gamma..-strengthen a Co-based super-alloy (Co-15Cr-3Mo-5Ti). Here the Ti-addition gives a coherent and ordered ..gamma..-phase Co/sub 3/Ti. However, upon ageing the alloy is unstable in order to increase the stability modifications of the alloy were prepared by: leaving out the Mo-content, adding 10 % Ni and by decreasing the Ti-content to 4.2 %. In addition, the effect of enhanced grain size and of deformation was investigated. Significant reduction of the transformation rate was only obtained by decresing the Ti-content while deformation of the alloy greatly increased the transformation rate.(author).

  18. Benefits of high gradient solidification for creep and low cycle fatigue of AM1 single crystal superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Steuer, S., E-mail: Susanne.Steuer@ensma.fr [Institut Pprime, CNRS – ENSMA – Université de Poitiers, UPR CNRS 3346, Department of Physics and Mechanics of Materials, ENSMA – Téléport 2, 1 avenue Clément Ader, BP 40109, 86961 Futuroscope Chasseneuil Cedex (France); Villechaise, P. [Institut Pprime, CNRS – ENSMA – Université de Poitiers, UPR CNRS 3346, Department of Physics and Mechanics of Materials, ENSMA – Téléport 2, 1 avenue Clément Ader, BP 40109, 86961 Futuroscope Chasseneuil Cedex (France); Pollock, T.M. [Materials Department, University of California Santa Barbara, Santa Barbara, CA 93106-5050 (United States); Cormier, J. [Institut Pprime, CNRS – ENSMA – Université de Poitiers, UPR CNRS 3346, Department of Physics and Mechanics of Materials, ENSMA – Téléport 2, 1 avenue Clément Ader, BP 40109, 86961 Futuroscope Chasseneuil Cedex (France)

    2015-10-01

    The influence of high thermal gradient processing on the creep and low cycle fatigue properties of the AM1 Ni-based single crystal superalloy has been studied. Isothermal creep (from 750 °C up to 1200 °C) and low cycle fatigue (750 °C and 950 °C) experiments were performed for AM1 alloy solidified with a conventional radiation cooled (Bridgman) and higher thermal gradient liquid-metal cooled (LMC) casting process to produce coarse and finer-scaled dendritic structures, respectively. There was no significant effect of the casting technique on creep properties, due to the very similar microstructures (γ′-size and γ-channel width) established after full heat treatment of both Bridgman and LMC samples. For low cycle fatigue properties, the benefit of the higher gradient LMC process was dependent on the testing temperature. At 750 °C, cracks primarily initiated at pores created by solidification shrinkage in both Bridgman and LMC samples. Samples produced by the LMC technique demonstrated fatigue lives up to 4 times longer, compared to the Bridgman samples, due to refined porosity. At 950 °C the low cycle fatigue properties of the LMC and conventionally solidified material were not distinguishable due to a shift of crack initiation sites from internal pores to oxidized surface layers or near-surface pores. The benefit of the LMC approach was, however, apparent in fatigue at 950 °C when testing in a vacuum environment. Based on these results, a crack initiation model based on the local slip activity close to casting defect is proposed.

  19. High temperature coatings from post processing Fe-based chips and Ni-based alloys as a solution for critical raw materials

    Science.gov (United States)

    Dudziak, T.; Olbrycht, A.; Polkowska, A.; Boron, L.; Skierski, P.; Wypych, A.; Ambroziak, A.; Krezel, A.

    2018-03-01

    Due to shortage of natural resources worldwide, it is a need to develop innovative technologies, to save natural resources and secure Critical Raw Materials (CRM). On the other hand, these new technologies should move forward materials engineering in order to develop better materials for extreme conditions. One way to develop new materials is to use post processing chips of austenitic steels (i.e. 304L stainless steel: 18/10 Cr/Ni) and other materials such as Ni-based alloy with high Cr content. In this work, the results of the preliminary study on the High Velocity Oxy Fuel (HVOF) coatings developed from 304L stainless steel chips and Haynes® 282® Ni- based alloys are shown. The study obeys development of the powder for HVOF technology. The produced coatings were exposed at high temperature at 500 and 700 °C for 100 and 300 hours respectively to assess corrosion behaviour.

  20. Assessment of wrought ASTM F1058 cobalt alloy properties for permanent surgical implants.

    Science.gov (United States)

    Clerc, C O; Jedwab, M R; Mayer, D W; Thompson, P J; Stinson, J S

    1997-01-01

    The behavior of the ASTM F1058 wrought cobalt-chromium-nickel-molybdenum-iron alloy (commonly referred to as Elgiloy or Phynox) is evaluated in terms of mechanical properties, magnetic resonance imaging, corrosion resistance, and biocompatibility. The data found in the literature, the experimental corrosion and biocompatibility results presented in this article, and its long track record as an implant material demonstrate that the cobalt superalloy is an appropriate material for permanent surgical implants that require high yield strength and fatigue resistance combined with high elastic modulus, and that it can be safely imaged with magnetic resonance.

  1. Ni-base wrought alloy development for USC steam turbine rotor applications

    International Nuclear Information System (INIS)

    Penkalla, H.-J.; Schubert, F.

    2004-01-01

    For the development of a new generation of steam turbines for use in advanced power plants with prospective operating temperatures of about 700 o C the ferritic steels for rotor applications must be replaced by advanced wrought Ni-base superalloys as the most qualified candidate materials for this purpose. In this paper three different potential candidates are discussed under the aspects of fabricability, sufficient microstructural and mechanical stability. As a result of theoretical and experimental investigation suitable strategies for the development two modified alloys are proposed to improve the fabricability and microstructural stability. (author)

  2. Nitrogen alloyed material for steam turbine and generator components: an alternative to expensive nondestructive inservice inspections

    International Nuclear Information System (INIS)

    Stein, G.; Menzel, J.

    1990-01-01

    In efforts to improve the efficiency of energy conversion systems the trend in power generation is towards increased output capacities, pressures and, in particular, temperatures. If these goals are to be achieved, it will be necessary for materials displaying distinctly improved properties to be used without this involving any dramatic rise in costs, e.g. by the use of superalloys. A new steel making technique, based on pressurized electroslag remelting, has spawned a new generation of advanced engineering materials, the nitrogen alloyed steels. The paper describes the properties of these ferritic and austenitic N-steels and their potential for future applications

  3. Eddy current spectroscopy for near-surface residual stress profiling in surface treated nonmagnetic engine alloys

    Science.gov (United States)

    Abu-Nabah, Bassam A.

    Recent research results indicated that eddy current conductivity measurements can be exploited for nondestructive evaluation of near-surface residual stresses in surface-treated nickel-base superalloy components. Most of the previous experimental studies were conducted on highly peened (Almen 10-16A) specimens that exhibit harmful cold work in excess of 30% plastic strain. Such high level of cold work causes thermo-mechanical relaxation at relatively modest operational temperatures; therefore the obtained results were not directly relevant to engine manufacturers and end users. The main reason for choosing peening intensities in excess of recommended normal levels was that in low-conductivity engine alloys the eddy current penetration depth could not be forced below 0.2 mm without expanding the measurements above 10 MHz which is beyond the operational range of most commercial eddy current instruments. As for shot-peened components, it was initially felt that the residual stress effect was more difficult to separate from cold work, texture, and inhomogeneity effects in titanium alloys than in nickel-base superalloys. In addition, titanium alloys have almost 50% lower electric conductivity than nickel-base superalloys; therefore require proportionally higher inspection frequencies, which was not feasible until our recent breakthrough in instrument development. Our work has been focused on six main aspects of this continuing research, namely, (i) the development of an iterative inversion technique to better retrieve the depth-dependent conductivity profile from the measured frequency-dependent apparent eddy current conductivity (AECC), (ii) the extension of the frequency range up to 80 MHz to better capture the peak compressive residual stress in nickel-base superalloys using a new eddy current conductivity measuring system, which offers better reproducibility, accuracy and measurement speed than the previously used conventional systems, (iii) the lift-off effect on

  4. Environmental aspects on LCF-life of Ni-base superalloys during long term operation; Miljoeinverkan paa LCF-egenskaper vid laanga drifttider hos superlegeringar

    Energy Technology Data Exchange (ETDEWEB)

    Moverare, Johan; Leijon, Gunnar; Palmert, Frans

    2012-02-15

    The applicability of fine grain polycrystalline nickel base superalloys in gas or steam turbine applications is often limited by their susceptibility to fast intergranular cracking during fatigue in combination with extended hold times at high temperatures and high tensile stresses. This effect is further enhanced in corrosive environments even at moderate temperatures such as 400-600 deg In this study the negative effect of SO{sub 2} + water vapour on the low cycle fatigue resistance of three different nickel based superalloys (Nimonic 901, Inconel 718 and 718 plus) has been studied at 450 deg and 550 deg. A negative effect was found on both the crack initiation and crack propagation process. The effect increases with increasing temperature and is likely to be influenced by both the chemical composition and the grain size of the material. The negative effect of water vapour + SO{sub 2} is manifested by a decreased resistance to cyclic plastic deformation and a transition from transcrystalline to intercrystalline fracture behaviour. In Nimonic 901 this negative effect increases with the degree of plastic deformation. For lower mechanical strain amplitudes where the number of cycles and the total exposure time is increased the environmental impact is reduced. Similar trends can also be noticed for the other alloys. The surface corrosion in air and in SO{sub 2} + water vapour are found to be rather similar in this study and it is therefore concluded that the surface scale can remain adherent and protective if the strains on the oxide scale are low. However, for LCF tests with higher strain ranges, the oxide scale will rupture preferably at the grain boundaries and intergranular microcracks will initiate which promotes inward diffusion of embritteling elements such as oxygen and sulphur. Inconel 718 seems to be more sensitive to SO{sub 2} + water vapour than Nimonic 901 when tested at 450. The overall resistance to LCF is however still higher in Inconel 718 for the

  5. Fatigue behavior of ULTIMETRTM alloy: Experiment and theoretical modeling

    Science.gov (United States)

    Jiang, Liang

    ULTIMETRTM alloy is a commercial Co-26Cr-9Ni (weight percent) superalloy, which possesses excellent resistance to both wear and corrosion. In order to extend the structural applications of this alloy and improve the fundamental understanding of the fatigue damage mechanisms, stress- and strain-controlled fatigue tests were performed at various temperatures and in different environments. The stress- and strain-life data were developed for the structural design and engineering applications of this material. Fractographic studies characterized the crack-initiation and propagation behavior of the alloy. Microstructure evolution during fatigue was revealed by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Specifically, it was found that the metastable face-centered-cubic structure of this alloy in the as-received condition could be transformed into a hexagonal-close-packed structure either under the action of plastic deformation at room temperature, or due to the aging and cyclic deformation at intermediate temperatures. This interesting observation constructed a sound basis for the alloy development. The dominant mechanisms, which control the fatigue behavior of ULTIMET alloy, were characterized. High-speed, high-resolution infrared (IR) thermography, as a non-contact, full-field, and nondestructive technique, was used to characterize the damage during fatigue. The temperature variations during each fatigue cycle, which were due to the thermal-elastic-plastic effect, were observed and related to stress-strain analyses. The temperature evolution during fatigue manifested the cumulative fatigue damage process. A constitutive model was developed to predict thermal and mechanical responses of ULTIMET alloy subjected to cyclic deformation. The predicted cyclic stress-strain responses and temperature variations were found to be in good agreement with the experimental results. In addition, a fatigue life prediction model was developed

  6. Avaliação in vitro da atividade antibacteriana de um cimento odontológico à base de óleo-resina de Copaifera multijuga Hayne

    Directory of Open Access Journals (Sweden)

    Kátia Regina Felizardo Vasconcelos

    Full Text Available Um dos materiais utilizados para a adequação do meio bucal no serviço público é o cimento produzido a partir de óxido de zinco e eugenol. Entretanto, o eugenol é uma substância citotóxica que pode desencadear alguns efeitos adversos. Por essa razão, procura-se substituir o eugenol por uma substância que apresente baixa toxicidade, mantendo ou mesmo melhorando as propriedades do cimento. O óleo-resina de copaíba é um produto natural, utilizado pelas populações amazônicas e reconhecido por suas propriedades medicinais. Baseando-se nas propriedades desse óleo-resina, na ação antimicrobiana comprovada do hidróxido de cálcio e na ação anti-séptica do óxido de zinco, propôs-se formular um cimento odontológico obtido da associação do ZnO, Ca(OH2 e óleo-resina de Copaifera multijuga Hayne e avaliar sua atividade antibacteriana através do teste de diluição em meio líquido frente às cepas padrão de Streptococcus mutans (ATCC 25175 e S. sanguinis (ATCC 15300. Nesse ensaio, utilizaram-se os seguintes grupos experimentais: o cimento contendo ZnO, Ca(OH2 e óleo-resina de copaíba (G1 e cada um dos constituintes isoladamente, ZnO (G2, Ca(OH2 (G3 e óleo-resina de copaíba (G4. Todos os grupos analisados demonstraram atividade antibacteriana, o G4 apresentou os melhores resultados e o G1 mostrou-se um cimento promissor a ser utilizado em odontologia.

  7. Ductile Fracture Behaviour of Hot Isostatically Pressed Inconel 690 Superalloy

    Science.gov (United States)

    Cooper, A. J.; Brayshaw, W. J.; Sherry, A. H.

    2018-04-01

    Herein we assess the differences in Charpy impact behavior between Hot Isostatically Pressed and forged Inconel 690 alloy over the temperature range of 300 °C to - 196 °C. The impact toughness of forged 690 exhibited a relatively small temperature dependence, with a maximum difference of ca. 40 J measured between 300 °C and - 196 °C, whereas the HIP'd alloy exhibited a difference of approximately double that of the forged alloy over the same temperature range. We have conducted Charpy impact testing, tensile testing, and metallographic analyses on the as-received materials as well as fractography of the failed Charpy specimens in order to understand the mechanisms that cause the observed differences in material fracture properties. The work supports a recent series of studies which assess differences in fundamental fracture behavior between Hot Isostatically Pressed and forged austenitic stainless steel materials of equivalent grades, and the results obtained in this study are compared to those of the previous stainless steel investigations to paint a more general picture of the comparisons between HIP vs forged material fracture behavior. Inconel 690 was selected in this study since previous studies were unable to completely omit the effects of strain-induced martensitic transformation at the tip of the Chary V-notch from the fracture mechanism; Inconel 690 is unable to undergo strain-induced martensitic transformation due to the alloy's high nickel content, thereby providing a sister study with the omission of any martensitic transformation effects on ductile fracture behavior.

  8. Development of high temperature property database for Alloy 800H

    International Nuclear Information System (INIS)

    Yokoyama, Norio; Watanabe, Katsutoshi; Tsuji, Hirokazu; Nakajima, Hajime.

    1993-07-01

    JAERI Material Performance Database (JMPD) has been developed since 1989 in JAERI with a view to utilizing the various kinds of characteristic data of nuclear materials efficiently. Using relational database management system, PLANNER on the mainframe, the JMPD provides the retrieval supporting system, graphic and statistical analyses system. The data obtained with 7868 sets on characteristic data of metallic materials including fatigue crack growth data, etc. have been stored in the JMPD at the end of March in 1993. A ferritic superalloy, Alloy 800H is used for the structural material of the control rods of the High Temperature Engineering Test Reactor (HTTR). Thermal stress generates which might cause a severe creep damage at a reactor scram. It therefore needs to be designed with consideration on the fracture modes induced by creep deformation after neutron irradiation. The creep data (approximately 240 sets) and tensile data (approximately 100 sets) of Alloy 800H including the effects of test environment, aging treatment and neutron irradiation have been stored in the JMPD. Furthermore, using a personal computer, high temperature property database for Alloy 800H has been developed. The present report outlines the development of high temperature property database for Alloy 800H. (author)

  9. Microstructure Modeling of 3rd Generation Disk Alloy

    Science.gov (United States)

    Jou, Herng-Jeng

    2008-01-01

    The objective of this initiative, funded by NASA's Aviation Safety Program, is to model, validate, and predict, with high fidelity, the microstructural evolution of third-generation high-refractory Ni-based disc superalloys during heat treating and service conditions. This initiative is a natural extension of the DARPA-AIM (Accelerated Insertion of Materials) initiative with GE/Pratt-Whitney and with other process simulation tools. Strong collaboration with the NASA Glenn Research Center (GRC) is a key component of this initiative and the focus of this program is on industrially relevant disk alloys and heat treatment processes identified by GRC. Employing QuesTek s Computational Materials Dynamics technology and PrecipiCalc precipitation simulator, physics-based models are being used to achieve high predictive accuracy and precision. Combining these models with experimental data and probabilistic analysis, "virtual alloy design" can be performed. The predicted microstructures can be optimized to promote desirable features and concurrently eliminate nondesirable phases that can limit the reliability and durability of the alloys. The well-calibrated and well-integrated software tools that are being applied under the proposed program will help gas turbine disk alloy manufacturers, processing facilities, and NASA, to efficiently and effectively improve the performance of current and future disk materials.

  10. Fracture toughness evaluation of select advanced replacement alloys for LWR core internals

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Lizhen [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Chen, Xiang [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-08-01

    Life extension of the existing nuclear reactors imposes irradiation of high fluences to structural materials, resulting in significant challenges to the traditional reactor materials such as type 304 and 316 stainless steels. Advanced alloys with superior radiation resistance will increase safety margins, design flexibility, and economics for not only the life extension of the existing fleet but also new builds with advanced reactor designs. The Electric Power Research Institute (EPRI) teamed up with Department of Energy (DOE) to initiate the Advanced Radiation Resistant Materials (ARRM) program, aiming to develop and test degradation resistant alloys from current commercial alloy specifications by 2021 to a new advanced alloy with superior degradation resistance in light water reactor (LWR)-relevant environments by 2024. Fracture toughness is one of the key engineering properties required for core internal materials. Together with other properties, which are being examined such as high-temperature steam oxidation resistance, radiation hardening, and irradiation-assisted stress corrosion cracking resistance, the alloys will be down-selected for neutron irradiation study and comprehensive post-irradiation examinations. According to the candidate alloys selected under the ARRM program, ductile fracture toughness of eight alloys was evaluated at room temperature and the LWR-relevant temperatures. The tested alloys include two ferritic alloys (Grade 92 and an oxide-dispersion-strengthened alloy 14YWT), two austenitic stainless steels (316L and 310), four Ni-base superalloys (718A, 725, 690, and X750). Alloy 316L and X750 are included as reference alloys for low- and high-strength alloys, respectively. Compact tension specimens in 0.25T and 0.2T were machined from the alloys in the T-L and R-L orientations according to the product forms of the alloys. This report summarizes the final results of the specimens tested and analyzed per ASTM Standard E1820. Unlike the

  11. Cyclic Oxidation and Hot Corrosion of NiCrY-Coated Disk Superalloys

    Science.gov (United States)

    Gabb, Timothy P.; Miller, Robert A.; Sudbrack, Chantal K.; Draper, Susan L.; Nesbitt, James A.; Rogers, Richard B.; Telesman, Ignacy; Ngo, Vanda; Healy, Jonathan

    2016-01-01

    Powder metallurgy disk superalloys have been designed for higher engine operating temperatures through improvement of their strength and creep resistance. Yet, increasing disk application temperatures to 704 degrees Centigrade and higher could enhance oxidation and activate hot corrosion in harmful environments. Protective coatings could be necessary to mitigate such attack. Cylindrical coated specimens of disk superalloys LSHR and ME3 were subjected to thermal cycling to produce cyclic oxidation in air at a maximum temperature of 760 degrees Centigrade. The effects of substrate roughness and coating thickness on coating integrity after cyclic oxidation were considered. Selected coated samples that had cyclic oxidation were then subjected to accelerated hot corrosion tests. This cyclic oxidation did not impair the coating's resistance to subsequent hot corrosion pitting attack.

  12. Cyclic Oxidation and Hot Corrosion of NiCrY-Coated Disk Superalloy

    Science.gov (United States)

    Gabb, Tim; Miller, R. A.; Sudbrack, C. K.; Draper, S. L.; Nesbitt, J.; Telesman, J.; Ngo, V.; Healy, J.

    2015-01-01

    Powder metallurgy disk superalloys have been designed for higher engine operating temperatures through improvement of their strength and creep resistance. Yet, increasing disk application temperatures to 704 C and higher could enhance oxidation and activate hot corrosion in harmful environments. Protective coatings could be necessary to mitigate such attack. Cylindrical coated specimens of disk superalloys LSHR and ME3 were subjected to thermal cycling to produce cyclic oxidation in air at a maximum temperature of 760 C. The effects of substrate roughness and coating thickness on coating integrity after cyclic oxidation were considered. Selected coated samples that had cyclic oxidation were then subjected to accelerated hot corrosion tests. The effects of this cyclic oxidation on resistance to subsequent hot corrosion attack were examined.

  13. Metallurgical joining of engine parts. Inertia welding of nickel superalloy HP compressor disks

    International Nuclear Information System (INIS)

    Ferte, J.P.

    1993-01-01

    The main part of this paper describes upside metallurgical and mechanical work done at SNECMA, on inertia welding of powder metallurgy nickel base superalloys ASTROLOY and N18, allowing appliance of this process to engine parts : Inertia welding of superalloys leads to deap microstructural changes in the H.A.Z. which have been, as well as upset, correlated to process parameters, weld geometry and base material microstructure; a full mechanical testing of welds shown properties equivalent to base material ones up to 650 C except for fatigue crack growth behavior under specific conditions (T>600 C-hold time at maximum load) which is drastically reduced for in weld plane propagation. A significant improvement of this later property has been done through post-welding heat treatment and optimization of welding parameters. Last part of this paper summarize the main teachings gained, on the complete welding procedure, from welding of scale one parts. (orig.)

  14. On the microstructural origin of primary creep in nickel-base superalloys

    International Nuclear Information System (INIS)

    Heilmaier, M.; Reppich, B.

    1997-01-01

    The nature of primary creep in nickel-base superalloys is strongly correlated to the different hardening species present in the material. In fine-grained single-phase material the classical assumption of a homogeneous dislocation distribution enables the prediction of the transition from normal via sigmoidal to inverse primary creep with decreasing applied stress σ. In coarse-grained material the back stress σ b of hard subgrain boundaries evolving during plastic deformation must be additionally taken into account. Second-phase particles influence creep in a 2-fold manner via reducing the effective stress σ eff , namely directly by the stress σ p * for particle overcoming, and indirectly by increasing the dislocation density ρ. The proposed approach accounts for the observed pronounced normal primary creep in particle-strengthened superalloys. (orig.)

  15. Extension of an anisotropic creep model to general high temperature deformation of a single crystal superalloy

    International Nuclear Information System (INIS)

    Pan, L.M.; Ghosh, R.N.; McLean, M.

    1993-01-01

    A physics based model has been developed that accounts for the principal features of anisotropic creep deformation of single crystal superalloys. The present paper extends this model to simulate other types of high temperature deformation under strain controlled test conditions, such as stress relaxation and tension tests at constant strain rate in single crystals subject to axial loading along an arbitrary crystal direction. The approach is applied to the SRR99 single crystal superalloy where a model parameter database is available, determined via analysis of a database of constant stress creep curves. A software package has been generated to simulate the deformation behaviour under complex stress-strain conditions taking into account anisotropic elasticity. (orig.)

  16. Development of superalloys for 1700 C ultra-efficient gas turbines

    Energy Technology Data Exchange (ETDEWEB)

    Harada, Hiroshi [National Institute for Materials Science, Tsukuba, Ibaraki (Japan). High Temperature Materials Center

    2010-07-01

    Mitigation of global warming is one of the most outstanding issues for the humankind. The Japanese government announced that it will reduce its greenhouse gas emissions by 25% from the 1990 level by 2020 as a medium-term goal. One of the promising approaches to achieving this is to improve the efficiency of thermal power plants emitting one-third of total CO{sub 2} gas in Japan. The key to improving the thermal efficiency is high temperature materials with excellent temperature capabilities allowing higher inlet gas temperatures. In this context, new single crystal superalloys for turbine blades and vanes, new coatings and turbine disk superalloys have been successfully developed for various gas turbine applications, typically 1700 C ultra-efficient gas turbines for next generation combine cycle power plants. (orig.)

  17. Atomic force microscopy imaging to measure precipitate volume fraction in nickel-based superalloys

    International Nuclear Information System (INIS)

    Bourhettar, A.; Troyon, M.; Hazotte, A.

    1995-01-01

    In nickel-based superalloys, quantitative analysis of scanning electron microscopy images fails in providing accurate microstructural data, whereas more efficient techniques are very time-consuming. As an alternative approach, the authors propose to perform quantitative analysis of atomic force microscopy images of polished/etched surfaces (quantitative microprofilometry). This permits the measurement of microstructural parameters and the depth of etching, which is the main source of measurement bias. Thus, nonbiased estimations can be obtained by extrapolation of the measurements up to zero etching depth. In this article, the authors used this approach to estimate the volume fraction of γ' precipitates in a nickel-based superalloy single crystal. Atomic force microscopy images of samples etched for different times show definition, homogeneity, and contrast high enough to perform image analysis. The result after extrapolation is in very good agreement with volume fraction values available from published reports

  18. STUDY OF THE MECHANICAL PROPERTIES OF INCONEL 718 SUPERALLOY AFTER HOT TENSILE TESTS

    Directory of Open Access Journals (Sweden)

    Tarcila Sugahara

    2014-10-01

    Full Text Available This research work investigated some important mechanical properties of Inconel 718 superalloy using hot tensile tests like conventional yield strength to 0.2% strain (σe , ultimate strength (σr , and specific elongation (εu . Samples were strained to failure at temperatures of 600°C, 650°C, 700°C, 750°C, 800°C and 850°C and strain rate of 0.5 mm/min (2 × 10–4 s–1 according to ASTM E-8. The results showed higher values σe of yield strength at 700°C, this anomalous behavior can be attributed to the presence of hardening precipitates as observed in the TTT diagram of superalloy Inconel 718. Examination of the sample’s surfaces tensile fracture showed that with increasing temperature test the actuating mechanism changes from intergranular fracture to coalescence of the microcavities.

  19. The Effectiveness of a NiCrY-Coating on a Powder Metallurgy Disk Superalloy

    Science.gov (United States)

    Gabb, Timothy P.; Miller, Robert A.; Nesbitt, James A.; Draper, Susan L.; Rogers, Richard B.; Telesman, Jack

    2018-01-01

    Protective ductile coatings could be necessary to mitigate oxidation and corrosion attack on superalloy disks in some turbine engine applications. However, the effects of coatings on fatigue life of the disk during service are an important concern. The objective of this study was to investigate how such a coating could perform after varied post-coating processing. Cylindrical gage fatigue specimens of powder metallurgy-processed disk superalloy LSHR were coated with a NiCrY coating, shot peened, preparation treated, exposed, and then subjected to fatigue at high temperature. The effects of varied shot peening, preparation treatment, and exposures on fatigue life with and without the coating were compared. Each of these variables and several of their interactions significantly influenced fatigue life.

  20. Superconducting alloys

    International Nuclear Information System (INIS)

    Bowers, J.E.

    1976-01-01

    Reference is made to superconductors having high critical currents. The superconductor described comprises an alloy consisting of a matrix of a Type II superconductor which is a homogeneous mixture of 50 to 95 at.% Pb and 5 to 40 at.%Bi and/or 10 to 50 at.%In. Dispersed in the matrix is a material to provide pinning centres comprising from 0.01% to 20% by volume of the alloy; this material is a stable discontinuous phase of discrete crystalline particles of Cu, Mn, Te, Se, Ni, Ca, Cr, Ce, Ge or La, either in the form of the element or a compound with a component of the matrix. These particles should have an average diameter of not more than 2μ. A method for making this alloy is described. (U.K.)