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Sample records for austenitic stainless steel

  1. High Mn austenitic stainless steel

    Science.gov (United States)

    Yamamoto, Yukinori [Oak Ridge, TN; Santella, Michael L [Knoxville, TN; Brady, Michael P [Oak Ridge, TN; Maziasz, Philip J [Oak Ridge, TN; Liu, Chain-tsuan [Knoxville, TN

    2010-07-13

    An austenitic stainless steel alloy includes, in weight percent: >4 to 15 Mn; 8 to 15 Ni; 14 to 16 Cr; 2.4 to 3 Al; 0.4 to 1 total of at least one of Nb and Ta; 0.05 to 0.2 C; 0.01 to 0.02 B; no more than 0.3 of combined Ti+V; up to 3 Mo; up to 3 Co; up to 1W; up to 3 Cu; up to 1 Si; up to 0.05 P; up to 1 total of at least one of Y, La, Ce, Hf, and Zr; less than 0.05 N; and base Fe, wherein the weight percent Fe is greater than the weight percent Ni, and wherein the alloy forms an external continuous scale including alumina, nanometer scale sized particles distributed throughout the microstructure, the particles including at least one of NbC and TaC, and a stable essentially single phase FCC austenitic matrix microstructure that is essentially delta-ferrite-free and essentially BCC-phase-free.

  2. Pitting corrosion resistant austenite stainless steel

    Science.gov (United States)

    van Rooyen, D.; Bandy, R.

    A pitting corrosion resistant austenite stainless steel comprises 17 to 28 wt. % chromium, 15 to 26 wt. % nickel, 5 to 8 wt. % molybdenum, and 0.3 to 0.5 wt. % nitrogen, the balance being iron, unavoidable impurities, minor additions made in the normal course of melting and casting alloys of this type, and may optionally include up to 10 wt. % of manganese, up to 5 wt. % of silicon, and up to 0.08 wt. % of carbon.

  3. Embrittlement of austenitic stainless steel welds

    Energy Technology Data Exchange (ETDEWEB)

    David, S.A.; Vitek, J.M. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

    1997-12-31

    The microstructure of type-308 austenitic stainless steel weld metal containing {gamma} and {delta} and ferrite is shown. Typical composition of the weld metal is Cr-20.2, Ni-9.4, Mn-1.7, Si-0.5, C-0.05, N-0.06 and balance Fe (in wt %). Exposure of austenitic stainless steel welds to elevated temperatures can lead to extensive changes in the microstructural features of the weld metal. On exposure to elevated temperatures over a long period of time, a continuous network of M{sub 23}C{sub 6} carbide forms at the austenite/ferrite interface. Upon aging at temperatures between 550--850 C, ferrite in the weld has been found to be unstable and transforms to sigma phase. These changes have been found to influence mechanical behavior of the weld metal, in particular the creep-rupture properties. For aging temperatures below 550 C the ferrite decomposes spinodally into {alpha} and {alpha}{prime} phases. In addition, precipitation of G-phase occurs within the decomposed ferrite. These transformations at temperatures below 550 C lead to embrittlement of the weld metal as revealed by the Charpy impact properties.

  4. Nickel-free austenitic stainless steels for medical applications

    Directory of Open Access Journals (Sweden)

    Ke Yang and Yibin Ren

    2010-01-01

    Full Text Available The adverse effects of nickel ions being released into the human body have prompted the development of high-nitrogen nickel-free austenitic stainless steels for medical applications. Nitrogen not only replaces nickel for austenitic structure stability but also much improves steel properties. Here we review the harmful effects associated with nickel in medical stainless steels, the advantages of nitrogen in stainless steels, and emphatically, the development of high-nitrogen nickel-free stainless steels for medical applications. By combining the benefits of stable austenitic structure, high strength and good plasticity, better corrosion and wear resistances, and superior biocompatibility compared to the currently used 316L stainless steel, the newly developed high-nitrogen nickel-free stainless steel is a reliable substitute for the conventional medical stainless steels.

  5. Transformation in Austenitic Stainless Steel Sheet under Different Loading Directions

    NARCIS (Netherlands)

    Boogaard, van den A.H.; Krauer, J.; Hora, P.

    2011-01-01

    The stress-strain relation for austenitic stainless steels is based on 2 main contributions: work hardening and a phase transformation from austenite to martensite. The transformation is highly temperature dependent. In most models for phase transformation from austenite to martensite, the stress tr

  6. The sub-zero Celsius treatment of precipitation hardenable semi-austenitic stainless steel

    DEFF Research Database (Denmark)

    Villa, Matteo; Hansen, Mikkel Fougt; Somers, Marcel A. J.

    2015-01-01

    A precipitation hardenable semi-austenitic stainless steel AISI 632 grade was austenitized according to industrial specifications and thereafter subjected to isothermal treatment at sub-zero Celsius temperatures. During treatment, austenite transformed to martensite. The isothermal austenite...

  7. Solidification cracking in austenitic stainless steel welds

    Indian Academy of Sciences (India)

    V Shankar; T P S Gill; S L Mannan; S Sundaresan

    2003-06-01

    Solidification cracking is a significant problem during the welding of austenitic stainless steels, particularly in fully austenitic and stabilized compositions. Hot cracking in stainless steel welds is caused by low-melting eutectics containing impurities such as S, P and alloy elements such as Ti, Nb. The WRC-92 diagram can be used as a general guide to maintain a desirable solidification mode during welding. Nitrogen has complex effects on weld-metal microstructure and cracking. In stabilized stainless steels, Ti and Nb react with S, N and C to form low-melting eutectics. Nitrogen picked up during welding significantly enhances cracking, which is reduced by minimizing the ratio of Ti or Nb to that of C and N present. The metallurgical propensity to solidification cracking is determined by elemental segregation, which manifests itself as a brittleness temperature range or BTR, that can be determined using the varestraint test. Total crack length (TCL), used extensively in hot cracking assessment, exhibits greater variability due to extraneous factors as compared to BTR. In austenitic stainless steels, segregation plays an overwhelming role in determining cracking susceptibility.

  8. Oxidation resistant high creep strength austenitic stainless steel

    Science.gov (United States)

    Brady, Michael P.; Pint, Bruce A.; Liu, Chain-Tsuan; Maziasz, Philip J.; Yamamoto, Yukinori; Lu, Zhao P.

    2010-06-29

    An austenitic stainless steel displaying high temperature oxidation and creep resistance has a composition that includes in weight percent 15 to 21 Ni, 10 to 15 Cr, 2 to 3.5 Al, 0.1 to 1 Nb, and 0.05 to 0.15 C, and that is free of or has very low levels of N, Ti and V. The alloy forms an external continuous alumina protective scale to provide a high oxidation resistance at temperatures of 700 to 800.degree. C. and forms NbC nanocarbides and a stable essentially single phase fcc austenitic matrix microstructure to give high strength and high creep resistance at these temperatures.

  9. COLD ROLLING ORTHODONTIC WIRES OF AUSTENITIC STAINLESS STEEL AISI 304

    Directory of Open Access Journals (Sweden)

    Rodrigo Santos Messner

    2013-03-01

    Full Text Available Austenitic stainless steels wires are widely used in the final stages of orthodontic treatment. The objective of this paper is to study the process of conformation of rectangular wires from round wires commercial austenitic stainless steel AISI 304 by the process of cold rolling. The wire quality is evaluated by means of dimensional analysis, microhardness measurements, tensile strength and fractographic analysis of the wires subjected to tensile tests. Also a study on the application of finite element method to simulate the process, comparing the force and rolling stress obtained in the rolling is done. The simulation results are consistent with those obtained in the actual process and the rolled wires show ductile fracture, tensile strength and dimensional variations appropriate to orthodontic standards. The fracture morphology shows the model cup-cone type besides the high deformation and hardness inherent in the cold rolling process.

  10. Accurate modelling of anisotropic effects in austenitic stainless steel welds

    Science.gov (United States)

    Nowers, O. D.; Duxbury, D. J.; Drinkwater, B. W.

    2014-02-01

    The ultrasonic inspection of austenitic steel welds is challenging due to the formation of highly anisotropic and heterogeneous structures post-welding. This is due to the intrinsic crystallographic structure of austenitic steel, driving the formation of dendritic grain structures on cooling. The anisotropy is manifested as both a `steering' of the ultrasonic beam and the back-scatter of energy due to the macroscopic granular structure of the weld. However, the quantitative effects and relative impacts of these phenomena are not well-understood. A semi-analytical simulation framework has been developed to allow the study of anisotropic effects in austenitic stainless steel welds. Frequency-dependent scatterers are allocated to a weld-region to approximate the coarse grain-structures observed within austenitic welds and imaged using a simulated array. The simulated A-scans are compared against an equivalent experimental setup demonstrating excellent agreement of the Signal to Noise (S/N) ratio. Comparison of images of the simulated and experimental data generated using the Total Focusing Method (TFM) indicate a prominent layered effect in the simulated data. A superior grain allocation routine is required to improve upon this.

  11. STRUCTURAL STABILITY OF HIGH NITROGEN AUSTENITIC STAINLESS STEELS

    Directory of Open Access Journals (Sweden)

    Jana Bakajová

    2011-05-01

    Full Text Available This paper deals with the structural stability of an austenitic stainless steel with high nitrogen content. The investigated steel was heat treated at 800°C using different annealing times. Investigation was carried out using light microscopy, transmission electron microscopy and thermodynamic calculations. Three phases were identified by electron diffraction: Cr2N, sigma – phase and M23C6. The thermodynamic prediction is in good agreement with the experimental result. The only is the M23C6 carbide phase which is not thermodynamically predicted. Cr2N is the majority secondary phase and occurs in the form of discrete particles or cells (lamellas of Cr2N and austenite.

  12. Development of Cast Alumina-Forming Austenitic Stainless Steels

    Science.gov (United States)

    Muralidharan, G.; Yamamoto, Y.; Brady, M. P.; Walker, L. R.; Meyer, H. M., III; Leonard, D. N.

    2016-09-01

    Cast Fe-Ni-Cr chromia-forming austenitic stainless steels with Ni levels up to 45 wt.% are used at high temperatures in a wide range of industrial applications that demand microstructural stability, corrosion resistance, and creep strength. Although alumina scales offer better corrosion protection at these temperatures, designing cast austenitic alloys that form a stable alumina scale and achieve creep strength comparable to existing cast chromia-forming alloys is challenging. This work outlines the development of cast Fe-Ni-Cr-Al austenitic stainless steels containing about 25 wt.% Ni with good creep strength and the ability to form a protective alumina scale for use at temperatures up to 800-850°C in H2O-, S-, and C-containing environments. Creep properties of the best alloy were comparable to that of HK-type cast chromia-forming alloys along with improved oxidation resistance typical of alumina-forming alloys. Challenges in the design of cast alloys and a potential path to increasing the temperature capability are discussed.

  13. Development of Cast Alumina-Forming Austenitic Stainless Steels

    Science.gov (United States)

    Muralidharan, G.; Yamamoto, Y.; Brady, M. P.; Walker, L. R.; Meyer, H. M., III; Leonard, D. N.

    2016-11-01

    Cast Fe-Ni-Cr chromia-forming austenitic stainless steels with Ni levels up to 45 wt.% are used at high temperatures in a wide range of industrial applications that demand microstructural stability, corrosion resistance, and creep strength. Although alumina scales offer better corrosion protection at these temperatures, designing cast austenitic alloys that form a stable alumina scale and achieve creep strength comparable to existing cast chromia-forming alloys is challenging. This work outlines the development of cast Fe-Ni-Cr-Al austenitic stainless steels containing about 25 wt.% Ni with good creep strength and the ability to form a protective alumina scale for use at temperatures up to 800-850°C in H2O-, S-, and C-containing environments. Creep properties of the best alloy were comparable to that of HK-type cast chromia-forming alloys along with improved oxidation resistance typical of alumina-forming alloys. Challenges in the design of cast alloys and a potential path to increasing the temperature capability are discussed.

  14. Austenite Formation from Martensite in a 13Cr6Ni2Mo Supermartensitic Stainless Steel

    NARCIS (Netherlands)

    Bojack, A.; Zhao, L.; Morris, P.F.; Sietsma, J.

    2016-01-01

    The influence of austenitization treatment of a 13Cr6Ni2Mo supermartensitic stainless steel (X2CrNiMoV13-5-2) on austenite formation during reheating and on the fraction of austenite retained after tempering treatment is measured and analyzed. The results show the formation of austenite in two stage

  15. Surface treatment and corrosion behaviour of austenitic stainless steel biomaterial

    Science.gov (United States)

    Oravcová, M.; Palček, P.; Zatkalíková, V.; Tański, T.; Król, M.

    2017-02-01

    In this article results from corrosion behaviour of austenitic stainless steel AISI 316L after different surface treatments are published. “As received” surface and surface after grinding resulted in lower resistance to pitting corrosion in physiological solution than electrochemically polished in H3PO4+H2SO4+H2O. Electropolishing also improved the surface roughness in comparison with the “as received” surface. Deposition of Al2O3 nanometric ALD coating improves the corrosion resistance of stainless steel in chloride-containing environment by shifting the breakdown potential toward more positive values. This oxide coating not only improves the corrosion resistance but it also affects the wettability of the surface, resulting in hydrophobic surface.

  16. Effect of shot peening on metastable austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Fargas, G., E-mail: gemma.fargas@upc.edu [CIEFMA - Departament de Ciència dels Materials i Enginyeria Metallúrgica, Universitat Politècnica de Catalunya, 08028 Barcelona (Spain); CRnE, Centre de Recerca en Nanoenginyeria, Universitat Politècnica de Catalunya, 08028 Barcelona (Spain); Roa, J.J.; Mateo, A. [CIEFMA - Departament de Ciència dels Materials i Enginyeria Metallúrgica, Universitat Politècnica de Catalunya, 08028 Barcelona (Spain); CRnE, Centre de Recerca en Nanoenginyeria, Universitat Politècnica de Catalunya, 08028 Barcelona (Spain)

    2015-08-12

    In this work, shot peening was performed in a metastable austenitic stainless steel EN 1.4318 (AISI 301LN) in order to evaluate its effect on austenite to martensite phase transformation and also the influence on the fatigue limit. Two different steel conditions were considered: annealed, i.e., with a fully austenitic microstructure, and cold rolled, consisting of a mixture of austenite and martensite. X-ray diffraction, electron back-scattered diffraction and focus ion beam, as well as nanoindentation techniques, were used to elucidate deformation mechanisms activated during shot peening and correlate with fatigue response. Results pointed out that extensive plastic deformation and phase transformation developed in annealed specimens as a consequence of shot peening. However, the increase of roughness and the generation of microcracks led to a limited fatigue limit improvement. In contrast, shot peened cold rolled specimens exhibited enhanced fatigue limit. In the latter case, the main factor that determined the influence on the fatigue response was the distance from the injector, followed successively by the exit speed of the shots and the coverage factor.

  17. Oxidation of molecular tritium in austenitic stainless steel containments

    Energy Technology Data Exchange (ETDEWEB)

    Blet, V.; Brossard, P.; Falanga, A.; Guidon, H.; Le Sergent, C. (CEA, BP 12, 91680 Bruyeres-le-Chatel (FR)); Clavier, B. (USSI Ingenierie, BP 72, 92223 Bagneux (FR))

    1992-03-01

    This paper discusses the rate of oxidation of molecular tritium. determined at room temperature in closed austenitic stainless steel containments versus the tritium concentration of tritium-oxygen gaseous mixtures. With our experimental conditions, the overall rate of oxidation is found to depend not only on tritium concentration but also on initial oxygen concentration. The tritiated water which is produced, does not remain in the gaseous phase but is partially trapped on the surface oxides. In addition, kinetics of reaction are strongly dependent on the geometry of the cylindrical containments. When the vessel diameter is smaller than 4 mm, tritiated water formation is significantly reduced.

  18. High Nitrogen Austenitic Stainless Steel Precipitation During Isothermal Annealing

    Directory of Open Access Journals (Sweden)

    Maria Domankova

    2016-07-01

    Full Text Available The time-temperature-precipitation in high-nitrogen austenitic stainless steel was investigated using light optical microscopy, transmission electron microscopy, selected area diffraction and energy-dispersive X-ray spectroscopy. The isothermal precipitation kinetics curves and the corresponding precipitation activation energy were obtained. The diffusion activation energy of M2N precipitation is 129 kJ/mol. The results show that critical temperature for M2N precipitation is about 825°C with the corresponding incubation period 2.5 min.

  19. Corrosion resistance of kolsterised austenitic 304 stainless steel

    Science.gov (United States)

    Abudaia, F. B.; Khalil, E. O.; Esehiri, A. F.; Daw, K. E.

    2015-03-01

    Austenitic stainless suffers from low wear resistance in applications where rubbing against other surfaces is encountered. This drawback can be overcome by surface treatment such as coating by hard materials. Other treatments such as carburization at relatively low temperature become applicable recently to improve hardness and wear resistance. Carburization heat treatment would only be justified if the corrosion resistance is unaffected. In this work samples of 304 stainless steels treated by colossal supersaturation case carburizing (known as Kolsterising) carried out by Bodycote Company was examined for pitting corrosion resistance at room temperature and at 50 °C. Comparison with results obtained for untreated samples in similar testing conditions show that there is no deterioration in the pitting resistance due to the Kolsterising heat treatment. X ray diffraction patterns obtained for Kolsterising sample showed that peaks correspond to the austenite phase has shifted to lower 2θ values compared with those of the untreated sample. The shift is an indication for expansion of austenite unit cells caused by saturation with diffusing carbon atoms. The XRD of Kolsterising samples also revealed additional peaks appeared in the patterns due to formation of carbides in the kolsterised layer. Examination of these additional peaks showed that these peaks are attributed to a type of carbide known as Hagg carbide Fe2C5. The absence of carbides that contain chromium means that no Cr depletion occurred in the layer and the corrosion properties are maintained. Surface hardness measurements showed large increase after Kolsterising heat treatment.

  20. Corrosion resistance of kolsterised austenitic 304 stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Abudaia, F. B., E-mail: fabudaia@yahoo.com; Khalil, E. O., E-mail: ekhalil9@yahoo.com; Esehiri, A. F., E-mail: Hope-eseheri@hotmail.co.uk; Daw, K. E., E-mail: Khawladaw@yahoo.com [University of Tripoli Department of Materials and Metallurgical Eng, Tripoli-Libya P.O.Box13589 (Libya)

    2015-03-30

    Austenitic stainless suffers from low wear resistance in applications where rubbing against other surfaces is encountered. This drawback can be overcome by surface treatment such as coating by hard materials. Other treatments such as carburization at relatively low temperature become applicable recently to improve hardness and wear resistance. Carburization heat treatment would only be justified if the corrosion resistance is unaffected. In this work samples of 304 stainless steels treated by colossal supersaturation case carburizing (known as Kolsterising) carried out by Bodycote Company was examined for pitting corrosion resistance at room temperature and at 50 °C. Comparison with results obtained for untreated samples in similar testing conditions show that there is no deterioration in the pitting resistance due to the Kolsterising heat treatment. X ray diffraction patterns obtained for Kolsterising sample showed that peaks correspond to the austenite phase has shifted to lower 2θ values compared with those of the untreated sample. The shift is an indication for expansion of austenite unit cells caused by saturation with diffusing carbon atoms. The XRD of Kolsterising samples also revealed additional peaks appeared in the patterns due to formation of carbides in the kolsterised layer. Examination of these additional peaks showed that these peaks are attributed to a type of carbide known as Hagg carbide Fe{sub 2}C{sub 5}. The absence of carbides that contain chromium means that no Cr depletion occurred in the layer and the corrosion properties are maintained. Surface hardness measurements showed large increase after Kolsterising heat treatment.

  1. EBSD study of a hot deformed austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Mirzadeh, H., E-mail: h-m@gmx.com [Departamento de Ciencia de los Materiales e Ingenieria Metalurgica, ETSEIB, Universitat Politecnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain); Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Cabrera, J.M. [Departamento de Ciencia de los Materiales e Ingenieria Metalurgica, ETSEIB, Universitat Politecnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain); Fundacio CTM Centre Tecnologic, Av. Bases de Manresa 1, 08242 Manresa (Spain); Najafizadeh, A. [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Calvillo, P.R. [Departamento de Ciencia de los Materiales e Ingenieria Metalurgica, ETSEIB, Universitat Politecnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain); Fundacio CTM Centre Tecnologic, Av. Bases de Manresa 1, 08242 Manresa (Spain)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer Microstructural characterization of an austenitic stainless steel by EBSD. Black-Right-Pointing-Pointer The role of twins in the nucleation and growth of dynamic recrystallization. Black-Right-Pointing-Pointer Grain refinement through the discontinuous dynamic recrystallization. Black-Right-Pointing-Pointer Determination of recrystallized fraction using the grain average misorientation. Black-Right-Pointing-Pointer Relationship between recrystallization and the frequency of high angle boundaries. - Abstract: The microstructural evolution of a 304 H austenitic stainless steel subjected to hot compression was studied by the electron backscattered diffraction (EBSD) technique. Detailed data about the boundaries, coincidence site lattice (CSL) relationships and grain size were acquired from the orientation imaging microscopy (OIM) maps. It was found that twins play an important role in the nucleation and growth of dynamic recrystallization (DRX) during hot deformation. Moreover, the conventional discontinuous DRX (DDRX) was found to be in charge of grain refinement reached under the testing conditions studied. Furthermore, the recrystallized fraction (X) was determined from the grain average misorientation (GAM) distribution based on the threshold value of 1.55 Degree-Sign . The frequency of high angle boundaries showed a direct relationship with X. A time exponent of 1.11 was determined from Avrami analysis, which was related to the observed single-peak behavior in the stress-strain flow curves.

  2. Mechanical Properties of Austenitic Stainless Steel Made by Additive Manufacturing.

    Science.gov (United States)

    Luecke, William E; Slotwinski, John A

    2014-01-01

    Using uniaxial tensile and hardness testing, we evaluated the variability and anisotropy of the mechanical properties of an austenitic stainless steel, UNS S17400, manufactured by an additive process, selective laser melting. Like wrought materials, the mechanical properties depend on the orientation introduced by the processing. The recommended stress-relief heat treatment increases the tensile strength, reduces the yield strength, and decreases the extent of the discontinuous yielding. The mechanical properties, assessed by hardness, are very uniform across the build plate, but the stress-relief heat treatment introduced a small non-uniformity that had no correlation to position on the build plate. Analysis of the mechanical property behavior resulted in four conclusions. (1) The within-build and build-to-build tensile properties of the UNS S17400 stainless steel are less repeatable than mature engineering structural alloys, but similar to other structural alloys made by additive manufacturing. (2) The anisotropy of the mechanical properties of the UNS S17400 material of this study is larger than that of mature structural alloys, but is similar to other structural alloys made by additive manufacturing. (3) The tensile mechanical properties of the UNS S17400 material fabricated by selective laser melting are very different from those of wrought, heat-treated 17-4PH stainless steel. (4) The large discontinuous yielding strain in all tests resulted from the formation and propagation of Lüders bands.

  3. Fabrication of high nitrogen austenitic stainless steels with excellent mechanical and pitting corrosion properties

    Institute of Scientific and Technical Information of China (English)

    Hua-bing Li; Zhou-hua Jiang; Yang Cao; Zu-rui Zhang

    2009-01-01

    18Cr18Mn2Mo0.9N high nitrogen austenitic stainless steel exhibits high strength and good ductility at room temperature. The steel shows typical duc-tile-brittle transition behavior and excellent pitting corrosion resistance properties.

  4. Small punch creep test in a 316 austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Saucedo-Munoz, M. L.; Komazaki, S. I.; Hashida, T.; Lopez-Hirata, V. M.

    2015-03-30

    The small punch creep test was applied to evaluate the creep behavior of a 316 type austenitic stainless steel at temperatures of 650, 675 and 700 degree centigrade. The small punch test was carried out using a creep tester with a specimen size of 10x10x0.3 mm at 650, 675 and 700 degree centigrade using loads from 199 to 512 N. The small punch creep curves show the three stages found in the creep curves of the conventional uniaxial test. The conventional creep relationships which involve parameters such as creep rate, stress, time to rupture and temperature were followed with the corresponding parameters of small punch creep test and they permitted to explain the creep behavior in this steel. The mechanism and activation energy of the deformation process were the grain boundary sliding and diffusion, respectively, during creep which caused the intergranular fracture in the tested specimens. (Author)

  5. Salt spray corrosion behaviour of austenitic stainless steel matrix composites

    Energy Technology Data Exchange (ETDEWEB)

    Velasco, F.; Abenojar, J.; Torralba, J.M. [Dept. de Ciencia de Materiales e Ing. Metalurgica, Univ. Carlos III de Madrid, Leganes (Spain); Lima, W.M. [Univ. Estadual de Maringa, Maringa PR (Brazil); Marce, R.; Bas, J.A. [AMES S.A., Sant Vicenc dels Horts Barcelona (Spain)

    2001-07-01

    This work deals with the possibility of using intermetallics as addition to P/M stainless steel in order to try to sinter these steels in nitrogen-base atmospheres. 316L was chosen as stainless steel matrix, and two intermetallics (from Ti-Al and Cr-Al binary systems), with a sieve size of less than 80 {mu}m, were added in the amount of 3% vol. to obtain MMCs. Powders were mixed, compacted at 700 MPa by uniaxial compacting, and then sintered at two temperatures (1120 and 1230 C) in five different atmospheres (95N{sub 2}/5H{sub 2}, 80N{sub 2}/20H{sub 2}, 25N{sub 2}/75H{sub 2}, hydrogen and vacuum). A complete microstructural study was carried out both by optical and scanning electron microscopy (SEM). Corrosion tests by salt spray fog were done in order to measure the possible improvements of intermetallic addition on the corrosion behaviour of these steels. SEM studies were also carried out on as corroded samples in order to understand the mechanisms of corrosion. Intermetallics absorb nitrogen from the nitrogen based atmospheres, and they develop a duplex (ferrite / austenite) microstructure when composite materials are sintered in hydrogen and vacuum. These microstructural features explain the results obtained in salt spray fog test. (orig.)

  6. Characterization of microstructure and texture across dissimilar super duplex/austenitic stainless steel weldment joint by austenitic filler metal

    Energy Technology Data Exchange (ETDEWEB)

    Eghlimi, Abbas, E-mail: a.eghlimi@ma.iut.ac.ir [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Shamanian, Morteza [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Eskandarian, Masoomeh [Department of Materials Engineering, Shiraz University, Shiraz 71348-51154 (Iran, Islamic Republic of); Zabolian, Azam [Department of Natural Resources, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Szpunar, Jerzy A. [Department of Mechanical Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9 (Canada)

    2015-08-15

    The evolution of microstructure and texture across an as-welded dissimilar UNS S32750 super duplex/UNS S30403 austenitic stainless steel joint welded by UNS S30986 (AWS A5.9 ER309LMo) austenitic stainless steel filler metal using gas tungsten arc welding process was evaluated by optical micrography and EBSD techniques. Due to their fabrication through rolling process, both parent metals had texture components resulted from deformation and recrystallization. The weld metal showed the highest amount of residual strain and had large austenite grain colonies of similar orientations with little amounts of skeletal ferrite, both oriented preferentially in the < 001 > direction with cub-on-cube orientation relationship. While the super duplex stainless steel's heat affected zone contained higher ferrite than its parent metal, an excessive grain growth was observed at the austenitic stainless steel's counterpart. At both heat affected zones, austenite underwent some recrystallization and formed twin boundaries which led to an increase in the fraction of high angle boundaries as compared with the respective base metals. These regions showed the least amount of residual strain and highest amount of recrystallized austenite grains. Due to the static recrystallization, the fraction of low degree of fit (Σ) coincident site lattice boundaries, especially Σ3 boundaries, was increased in the austenitic stainless steel heat affected zone, while the formation of subgrains in the ferrite phase increased the content of < 5° low angle boundaries at that of the super duplex stainless steel. - Graphical abstract: Display Omitted - Highlights: • Extensive grain growth in the HAZ of austenitic stainless steel was observed. • Intensification of < 100 > orientated grains was observed adjacent to both fusion lines. • Annealing twins with Σ3 CSL boundaries were formed in the austenite of both HAZ. • Cub-on-cube OR was observed between austenite and ferrite in the weld

  7. Influence of Martensite Fraction on the Stabilization of Austenite in Austenitic-Martensitic Stainless Steels

    Science.gov (United States)

    Huang, Qiuliang; De Cooman, Bruno C.; Biermann, Horst; Mola, Javad

    2016-05-01

    The influence of martensite fraction ( f α') on the stabilization of austenite was studied by quench interruption below M s temperature of an Fe-13Cr-0.31C (mass pct) stainless steel. The interval between the quench interruption temperature and the secondary martensite start temperature, denoted as θ, was used to quantify the extent of austenite stabilization. In experiments with and without a reheating step subsequent to quench interruption, the variation of θ with f α' showed a transition after transformation of almost half of the austenite. This trend was observed regardless of the solution annealing temperature which influenced the martensite start temperature. The transition in θ was ascribed to a change in the type of martensite nucleation sites from austenite grain and twin boundaries at low f α' to the faults near austenite-martensite (A-M) boundaries at high f α'. At low temperatures, the local carbon enrichment of such boundaries was responsible for the enhanced stabilization at high f α'. At high temperatures, relevant to the quenching and partitioning processing, on the other hand, the pronounced stabilization at high f α' was attributed to the uniform partitioning of the carbon stored at A-M boundaries into the austenite. Reduction in the fault density of austenite served as an auxiliary stabilization mechanism at high temperatures.

  8. Corrosion of an austenite and ferrite stainless steel weld

    Directory of Open Access Journals (Sweden)

    BRANIMIR N. GRGUR

    2011-07-01

    Full Text Available Dissimilar metal connections are prone to frequent failures. These failures are attributed to the difference in the mechanical properties across the weld, the coefficients of thermal expansion of the two types of steels and the resulting creep at the interface. For the weld analyzed in this research, it was shown that corrosion measurements can be used for a proper evaluation of the quality of weld material and for the prediction of whether or not the material, after the applied welding process, can be in service without failures. It was found that the corrosion of the weld analyzed in this research resulted from the simultaneous activity of different types of corrosion. In this study, electrochemical techniques including polarization and metallographic analysis were used to analyze the corrosion of a weld material of ferrite and austenitic stainless steels. Based on surface, chemical and electrochemical analyses, it was concluded that corrosion occurrence was the result of the simultaneous activity of contact corrosion (ferrite and austenitic material conjuction, stress corrosion (originating from deformed ferrite structure and inter-granular corrosion (due to chromium carbide precipitation. The value of corrosion potential of –0.53 V shows that this weld, after the thermal treatment, is not able to repassivate a protective oxide film.

  9. A review on nickel-free nitrogen containing austenitic stainless steels for biomedical applications.

    Science.gov (United States)

    Talha, Mohd; Behera, C K; Sinha, O P

    2013-10-01

    The field of biomaterials has become a vital area, as these materials can enhance the quality and longevity of human life. Metallic materials are often used as biomaterials to replace structural components of the human body. Stainless steels, cobalt-chromium alloys, commercially pure titanium and its alloys are typical metallic biomaterials that are being used for implant devices. Stainless steels have been widely used as biomaterials because of their very low cost as compared to other metallic materials, good mechanical and corrosion resistant properties and adequate biocompatibility. However, the adverse effects of nickel ions being released into the human body have promoted the development of "nickel-free nitrogen containing austenitic stainless steels" for medical applications. Nitrogen not only replaces nickel for austenitic structure stability but also much improves steel properties. Here we review the harmful effects associated with nickel and emphatically the advantages of nitrogen in stainless steel, as well as the development of nickel-free nitrogen containing stainless steels for medical applications. By combining the benefits of stable austenitic structure, high strength, better corrosion and wear resistance and superior biocompatibility in comparison to the currently used austenitic stainless steel (e.g. 316L), the newly developed nickel-free high nitrogen austenitic stainless steel is a reliable substitute for the conventionally used medical stainless steels.

  10. Thermal deformation behavior and microstructure of nuclear austenitic stainless steel

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Gleeble-1500D thermal simulation tester was employed in the hot-compression investigation of as-cast nuclear 304 austenitic stainless steel under conditions: deformation temperature 950―1200℃; deformations 30% and 50%; deformation rates 0.01 and 0.1 s?1. The results show that the flow stress decreases with temperature rise under the same strain rate and deformation, that the flow stress increases with deformation under the same temperature and strain rate, and that the flow stress increases with strain rate under the same temperature condition, i.e., work hardening becomes distinct. Materials exhibit better strength-toughness when the strain rate is 0.01 s-1, the deformation is 50%, and the temperature is 1050℃.

  11. Effect of Grain Size on Mechanical Properties of Nickel-Free High Nitrogen Austenitic Stainless Steel

    Institute of Scientific and Technical Information of China (English)

    LI Hua-bing; JIANG Zhou-hua; ZHANG Zu-rui; YANG Yan

    2009-01-01

    The fine grained structures of nickel-free high nitrogen austenitic stainless steels had been obtained by means of cold rolling and subsequent annealing.The relationship between microstructure and mechanical properties and gain size of nickel-free high nitrogen austenitic stainless steels was examined.High strength and good ductility of the steel were found.In the grain size range,the Hall-Petch dependency for yield stress,tensile strength,and hardness was valid for grain size ranges for the nickel-free high nitrogen austenitic stainless steel.In the present study,the ductility of cold rolled nickel-free high nitrogen austenitic stainless steel decreased with annealing time when the grain size was refined.The fracture surfaces of the tensile specimens in the grain size range were covered with dimples as usually seen in a ductile fracture mode.

  12. General and Localized corrosion of Austenitic and Borated Stainless Steels in Simulated Concentrated Ground Waters

    Energy Technology Data Exchange (ETDEWEB)

    D. Fix; J. Estill; L. Wong; R. Rebak

    2004-05-28

    Boron containing stainless steels are used in the nuclear industry for applications such as spent fuel storage, control rods and shielding. It was of interest to compare the corrosion resistance of three borated stainless steels with standard austenitic alloy materials such as type 304 and 316 stainless steels. Tests were conducted in three simulated concentrated ground waters at 90 C. Results show that the borated stainless were less resistant to corrosion than the witness austenitic materials. An acidic concentrated ground water was more aggressive than an alkaline concentrated ground water.

  13. General and Localized Corrosion of Austenitic And Borated Stainless Steels in Simulated Concentrated Ground Waters

    Energy Technology Data Exchange (ETDEWEB)

    Estill, J C; Rebak, R B; Fix, D V; Wong, L L

    2004-03-11

    Boron containing stainless steels are used in the nuclear industry for applications such as spent fuel storage, control rods and shielding. It was of interest to compare the corrosion resistance of three borated stainless steels with standard austenitic alloy materials such as type 304 and 316 stainless steels. Tests were conducted in three simulated concentrated ground waters at 90 C. Results show that the borated stainless were less resistant to corrosion than the witness austenitic materials. An acidic concentrated ground water was more aggressive than an alkaline concentrated ground water.

  14. Microstructural evolution in fast-neutron-irradiated austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Stoller, R.E.

    1987-12-01

    The present work has focused on the specific problem of fast-neutron-induced radiation damage to austenitic stainless steels. These steels are used as structural materials in current fast fission reactors and are proposed for use in future fusion reactors. Two primary components of the radiation damage are atomic displacements (in units of displacements per atom, or dpa) and the generation of helium by nuclear transmutation reactions. The radiation environment can be characterized by the ratio of helium to displacement production, the so-called He/dpa ratio. Radiation damage is evidenced microscopically by a complex microstructural evolution and macroscopically by density changes and altered mechanical properties. The purpose of this work was to provide additional understanding about mechanisms that determine microstructural evolution in current fast reactor environments and to identify the sensitivity of this evolution to changes in the He/dpa ratio. This latter sensitivity is of interest because the He/dpa ratio in a fusion reactor first wall will be about 30 times that in fast reactor fuel cladding. The approach followed in the present work was to use a combination of theoretical and experimental analysis. The experimental component of the work primarily involved the examination by transmission electron microscopy of specimens of a model austenitic alloy that had been irradiated in the Oak Ridge Research Reactor. A major aspect of the theoretical work was the development of a comprehensive model of microstructural evolution. This included explicit models for the evolution of the major extended defects observed in neutron irradiated steels: cavities, Frank faulted loops and the dislocation network. 340 refs., 95 figs., 18 tabs.

  15. HYDROGEN-ASSISTED FRACTURE IN FORGED TYPE 304L AUSTENITIC STAINLESS STEEL

    Energy Technology Data Exchange (ETDEWEB)

    Switzner, Nathan; Neidt, Ted; Hollenbeck, John; Knutson, J.; Everhart, Wes; Hanlin, R. [University of Missouri-Kansas City; Bergen, R. [Precision Metal Products; Balch, D. K. [Sandia Natl Laboratory

    2012-09-06

    Austenitic stainless steels generally have good resistance to hydrogen-assisted fracture; however, structural designs for high-pressure gaseous hydrogen are constrained by the low strength of this class of material. Forging is used to increase the low strength of austenitic stainless steels, thus improving the efficiency of structural designs. Hydrogen-assisted racture, however, depends on microstructural details associated with manufacturing. In this study, hydrogen-assisted fracture of forged type 304L austenitic stainless steel is investigated. Microstructural variation in multi-step forged 304L was achieved by forging at different rates and temperatures, and by process annealing. High internal hydrogen content in forged type 304L austenitic stainless steel is achieved by thermal precharging in gaseous hydrogen and results in as much as 50% reduction of tensile ductility.

  16. Plasma Nitriding of Austenitic Stainless Steel with Severe Surface Deformation Layer

    Institute of Scientific and Technical Information of China (English)

    JI Shi-jun; GAO Yu-zhou; WANG Liang; SUN Jun-cai; HEI Zu-kun

    2004-01-01

    The dc glow discharge plasma nitriding of austenite stainless steel with severe surface deformation layer is used to produce much thicker surface modified layer. This kind of layers has useful properties such as a high surface hardness of about 1500 Hv 0.1 and high resistance to frictional wear. This paper presents the structures and properties of low temperature plasma nitrided austenitic stainless steel with severe surface deformation layer.

  17. X-ray fractography studies on austenitic stainless steels

    NARCIS (Netherlands)

    Rajanna, K.; Pathiraj, B.; Kolster, B.H.

    1996-01-01

    In this investigation, the fracture surfaces of SS 304 and SS 316 austenitic steels were analysed using the X-ray fractography technique. In both cases, a decrease in the austenite content was observed at the fracture surface as a result of deformation induced martensite, indicating a linear relatio

  18. Austenite Formation from Martensite in a 13Cr6Ni2Mo Supermartensitic Stainless Steel

    OpenAIRE

    2016-01-01

    The influence of austenitization treatment of a 13Cr6Ni2Mo supermartensitic stainless steel (X2CrNiMoV13-5-2) on austenite formation during reheating and on the fraction of austenite retained after tempering treatment is measured and analyzed. The results show the formation of austenite in two stages. This is probably due to inhomogeneous distribution of the austenite-stabilizing elements Ni and Mn, resulting from their slow diffusion from martensite into austenite and carbide and nitride dis...

  19. Study of biocompatibility of medical grade high nitrogen nickel-free austenitic stainless steel in vitro.

    Science.gov (United States)

    Li, Menghua; Yin, Tieying; Wang, Yazhou; Du, Feifei; Zou, Xingzheng; Gregersen, Hans; Wang, Guixue

    2014-10-01

    Adverse effects of nickel ions being released into the living organism have resulted in development of high nitrogen nickel-free austenitic stainless steels for medical applications. Nitrogen not only replaces nickel for austenitic structure stability but also improves steel properties. The cell cytocompatibility, blood compatibility and cell response of high nitrogen nickel-free austenitic stainless steel were studied in vitro. The mechanical properties and microstructure of this stainless steel were compared to the currently used 316L stainless steel. It was shown that the new steel material had comparable basic mechanical properties to 316L stainless steel and preserved the single austenite organization. The cell toxicity test showed no significant toxic side effects for MC3T3-E1 cells compared to nitinol alloy. Cell adhesion testing showed that the number of MC3T3-E1 cells was more than that on nitinol alloy and the cells grew in good condition. The hemolysis rate was lower than the national standard of 5% without influence on platelets. The total intracellular protein content and ALP activity and quantification of mineralization showed good cell response. We conclude that the high nitrogen nickel-free austenitic stainless steel is a promising new biomedical material for coronary stent development.

  20. Stress corrosion cracking of austenitic stainless steel core internal welds.

    Energy Technology Data Exchange (ETDEWEB)

    Chung, H. M.; Park, J.-H.; Ruther, W. E.; Sanecki, J. E.; Strain, R. V.; Zaluzec, N. J.

    1999-04-14

    Microstructural analyses by several advanced metallographic techniques were conducted on austenitic stainless steel mockup and core shroud welds that had cracked in boiling water reactors. Contrary to previous beliefs, heat-affected zones of the cracked Type 304L, as well as 304 SS core shroud welds and mockup shielded-metal-arc welds, were free of grain-boundary carbides, which shows that core shroud failure cannot be explained by classical intergranular stress corrosion cracking. Neither martensite nor delta-ferrite films were present on the grain boundaries. However, as a result of exposure to welding fumes, the heat-affected zones of the core shroud welds were significantly contaminated by oxygen and fluorine, which migrate to grain boundaries. Significant oxygen contamination seems to promote fluorine contamination and suppress thermal sensitization. Results of slow-strain-rate tensile tests also indicate that fluorine exacerbates the susceptibility of irradiated steels to intergranular stress corrosion cracking. These observations, combined with previous reports on the strong influence of weld flux, indicate that oxygen and fluorine contamination and fluorine-catalyzed stress corrosion play a major role in cracking of core shroud welds.

  1. Ultrasonic inspection for circumferential butt joint of austenitic stainless steel with carbon steel

    Institute of Scientific and Technical Information of China (English)

    Wan Shengyun; Xiong Lasen

    2006-01-01

    Tthe practical application of ultrasonic wave inspection in welded joint by austenitic stainless steel with carbon steel is presented. It is shown from the experimental results that the high frequency narrow-pulsed longitudinal ultrasonic wave inspection technique can detect the defects in deferent sound path and location within the tested welded joint clearly and exactly. The study in the paper may provide a new approach for further application of ultrasonic inspection in coarse-grained materials.

  2. Influence of Simulated Outside-Reactor Irradiation on Anticorrosion Property of Austenitic Stainless Steel

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The influence of γ-ray irradiation on the properties of inside-reactor stainless steel structures was studied by simulating the working condition of pressurized water reactor (PWR) first circuit and the outside-reactor γ-ray irradiation. The result shows that the simulated outside-reactor irradiation (irradiation dose 4.4 × 104 Gy) has no influence on anticorrosion properties of solutionized SUS304 austenitic stainless steel, including intergranular corrosion (IC) and stress corrosion cracking (SCC). Anticorrosion properties (IC, SCC) of sensitized SUS304 austenitic stainless steel are reduced by simulated outside-reactor irradiation. The longer the sensitizedtime is, the more obvious the influence is.

  3. Kinetics analysis of two-stage austenitization in supermartensitic stainless steel

    DEFF Research Database (Denmark)

    Nießen, Frank; Villa, Matteo; Hald, John

    2017-01-01

    The martensite-to-austenite transformation in X4CrNiMo16-5-1 supermartensitic stainless steel was followed in-situ during isochronal heating at 2, 6 and 18 K min−1 applying energy-dispersive synchrotron X-ray diffraction at the BESSY II facility. Austenitization occurred in two stages, separated...

  4. In Situ Techniques for the Investigation of the Kinetics of Austenitization of Supermartensitic Stainless Steel

    DEFF Research Database (Denmark)

    Nießen, Frank; Villa, Matteo; Apel, Daniel

    2016-01-01

    The austenitization and inter-critical annealing of X4CrNiMo16-5-1 (1.4418) supermartensitic stainless steel were investigated in-situ with synchrotron X-ray diffraction (XRD), dilatometry and differential scanning calorimetry (DSC) under isochronal heating conditions. Austenitization occurred...

  5. The study of high speed fine turning of austenitic stainless steel

    Directory of Open Access Journals (Sweden)

    W.S. Lin

    2008-04-01

    Full Text Available Purpose: The purpose of this research paper is focused on the surface roughness variation in high speed fine turning of the austenitic stainless steel.Design/methodology/approach: A series of experimental tests have been done to evaluate the possibility of high speed fine turning of the austenitic stainless steel from the surface roughness variation and machining stability.Findings: It was found that, the smaller the feed rate, the smaller the surface roughness value. But when the feed rate smaller than the critical feed rate, the chatter will occurs and the surface roughness of the work piece would be deteriorated.The higher the cutting speed is, the higher the cutting temperature of cutting tool is. The cutting tool will be soften and the surface roughness of the workpiece will be deteriorated.Research limitations/implications: The tool chattering would caused poor surface roughness in high speed fine turning for feed rate smaller than 0.02 mm/rev. The chatter suppression method must be considered when high speed fine turning of austenitic stainless steel.Originality/value: Most of the stainless steel machining proceeds at low cutting speed because the austenitic stainless steel is a hard machining material. The research result of this paper indicated that high speed fine turning of austenitic stainless steel is possible.

  6. The adhesion of hot-filament CVD diamond films on AISI type 316 austenitic stainless steel

    NARCIS (Netherlands)

    Buijnsters, J.G.; Shankar, P.; Enckevort, W.J.P. van; Schermer, J.J.; Meulen, J.J. ter

    2004-01-01

    Steel ball indentation and scratch adhesion testing of hot filament chemical vapour deposited diamond films onto AISI type 316 austenitic stainless steel substrates using two different interlayer systems, namely chromium nitride and borided steel, have been investigated. In order to compare the adhe

  7. The influence of texture on phase transformation in metastable austenitic stainless steel

    NARCIS (Netherlands)

    Hilkhuijsen, P.

    2013-01-01

    Metastable austenitic stainless steels are used in many applications, from shavers and kitchen sinks to various applications in the food industry. The diversity in applications of this type of steels is possible due to the many positive properties of the steel. It is not only esthetically pleasing,

  8. Grain Boundary Assemblies in Dynamically-Recrystallized Austenitic Stainless Steel

    Directory of Open Access Journals (Sweden)

    Marina Tikhonova

    2016-11-01

    Full Text Available The grain boundary misorientation distributions associated with the development of dynamic recrystallization were studied in a high-nitrogen austenitic stainless steel subjected to hot working. Under conditions of discontinuous dynamic recrystallization, the relationships between the grain or subgrain sizes and flow stresses can be expressed by power law functions with different grain/subgrain size exponents of about −0.76 (for grain size or −1.0 (for subgrain size. Therefore, the mean grain size being much larger than the subgrain size under conditions of low flow stress gradually approaches the size of the subgrains with an increase in the flow stress. These dependencies lead to the fraction of high-angle boundaries being a function of the flow stress. Namely, the fraction of ordinary high-angle boundaries in dynamically-recrystallized structures decreases with a decrease in the flow stress. On the other hand, the fraction of special boundaries, which are associated with annealing twins, progressively increases with a decrease of the flow stress.

  9. Antibacterial and corrosive properties of copper implanted austenitic stainless steel

    Institute of Scientific and Technical Information of China (English)

    Juan Xiong; Bo-fan Xu; Hong-wei Ni

    2009-01-01

    Copper ions were implanted into austenitic stainless steel (SS) by metal vapor vacuum arc with a energy of 100 keV and an ions dose range of (0.5-8.0)x 1017 cm-2. The Cu-implanted SS was annealed in an Ar atmosphere furnace. Glancing X-ray diffraction (GXRD), transmission electron microscopy (TEM) and Auger electron spectroscopy (AES) were used to reveal the phase com-positions, microstructures, and concentration profiles of copper ions in the implanted layer. The results show that the antibacterialproperty of Cu-implanted SS is attributed to Cu9.9Fe0.1 which precipitated as needles. The depth of copper in Cu-implanted SS with annealing treatment is greater than that in Cu-implanted SS without annealing treatment, which improves the antibacterial property against S. Aureus. The salt wetting-drying combined cyclic test was used to evaluate the corrosion-resistance of antibacterial SS, and the results reveal that the antibacterial SS has a level of corrosion-resistance equivalent to that of un-implanted SS.

  10. TEM studies of plasma nitrided austenitic stainless steel.

    Science.gov (United States)

    Stróz, D; Psoda, M

    2010-03-01

    Cross-sectional transmission electron microscopy and X-ray phase analysis were used to study the structure of a layer formed during nitriding the AISI 316L stainless steel at temperature 440 degrees C. It was found that the applied treatment led to the formation of 6-microm-thick layer of the S-phase. There is no evidence of CrN precipitation. The X-ray diffraction experiments proved that the occurred austenite lattice expansion - due to nitrogen atoms - depended on the crystallographic direction. The cross-sectional transmission electron microscopy studies showed that the layer consisted of a single cubic phase that contained a lot of defects such as dislocations, stacking faults, slip bands and twins. The high-resolution electron microscopy observations were applied to study the defect formation due to the nitriding process. It was shown that the presence of great number of stacking faults leads to formation of nanotwins. Weak, forbidden {100} reflections were still another characteristic feature of the S-phase. These were not detected in the X-ray spectra of the phase. Basing on the high-resolution electron microscopy studies it can be suggested that the short-range ordering of the nitrogen atoms in the octahedral sites inside the f.c.c. matrix lattice takes place and gives rise to appearance of these spots. It is suggested that the cubic lattice undergoes not only expansion but also slight rombohedral distortion that explains differences in the lattice expansion for different crystallographic directions.

  11. Dissimilar Friction Stir Welding Between UNS S31603 Austenitic Stainless Steel and UNS S32750 Superduplex Stainless Steel

    Science.gov (United States)

    Theodoro, Maria Claudia; Pereira, Victor Ferrinho; Mei, Paulo Roberto; Ramirez, Antonio Jose

    2015-02-01

    In order to verify the viability of dissimilar UNS S31603 austenitic and UNS S32750 superduplex stainless steels joined by friction stir welding, 6-mm-thick plates were welded using a PCBN-WRe tool. The welded joints were performed in position control mode at rotational speeds of 100 to 300 rpm and a feed rate of 100 mm/min. The joints performed with 150 and 200 rpm showed good appearance and no defects. The metallographic analysis of both joints showed no internal defects and that the material flow pattern is visible only in the stirred zone (SZ) of the superduplex steel. On the SZ top, these patterns are made of regions of different phases (ferrite and austenite), and on the bottom and central part of the SZ, these patterns are formed by alternated regions of different grain sizes. The ferrite grains in the superduplex steel are larger than those in the austenitic ones along the SZ and thermo-mechanically affected zone, explained by the difference between austenite and ferrite recrystallization kinetics. The amount of ferrite islands present on the austenitic steel base metal decreased near the SZ interface, caused by the dissolving of the ferrite in austenitic matrix. No other phases were found in both joints. The best weld parameters were found to be 200 rpm rotation speed, 100 mm/min feed rate, and tool position control.

  12. Plastic deformation effect of the corrosion resistance in case of austenitic stainless steel

    Science.gov (United States)

    Haraszti, F.; Kovacs, T.

    2017-02-01

    The corrosion forms are different in case of the austenitic steel than in case of carbon steels. Corrosion is very dangerous process, because that corrosion form is the intergranular corrosion. The austenitic stainless steel shows high corrosion resistance level. It knows that plastic deformation and the heat treating decrease it’s resistance. The corrosion form in case of this steel is very special and the corrosion tests are difficult. We tested the selected steel about its corrosion behaviour after high rate deformation. We wanted to find a relationship between the corrosion resistance decreasing and the rate of the plastic deformation. We wanted to show this behaviour from mechanical and electrical changing.

  13. Corrosion fatigue behaviour of 317LN austenitic stainless steel in phosphoric acid

    Energy Technology Data Exchange (ETDEWEB)

    Onoro, J. [Ingenieria y Ciencia de los Materiales, ETSI Industriales, Universidad Politecnica de Madrid, c/Jose Gutierrez Abascal, 2, 28006 Madrid (Spain)], E-mail: javier.onoro@upm.es

    2009-10-15

    The corrosion fatigue crack-growth behaviour of AISI 317LN stainless steel was evaluated in air and in 85% phosphoric acid at 20 deg. C. Austenitic stainless steels with high molybdenum content have high corrosion resistance and good mechanical properties. However, this increase in the molybdenum content and other elements such as nitrogen can also modify the microstructure. This leads to a modification of its mechanical properties. The corrosion fatigue crack-growth rate was higher in phosphoric acid immersion than in air. Austenitic stainless steels with a fully austenitic microstructure were more ductile, tough, and behave better against corrosion fatigue. The higher resistance to corrosion fatigue was directly associated to its higher resistance to corrosion.

  14. Antibacterial Properties of an Austenitic Antibacterial Stainless Steel and Its Security for Human Body

    Institute of Scientific and Technical Information of China (English)

    Ke YANG; Manqi L(U)

    2007-01-01

    An austenitic antibacterial stainless steel is reported in this paper. The very fine and dispersive ε-Cu precipitations in the matrix of the antibacterial steel after the antibacterial treatment endow the steel with antibacterial function. The antibacterial function is strong, long-term and broad-spectrum, and can be maintained even after repeated wear and long time dipping in water. The steel is safe for human body and could be used widely in daily application.

  15. Small punch creep test in a 316 austenitic stainless steel

    Directory of Open Access Journals (Sweden)

    Saucedo-Muñoz, Maribel L.

    2015-03-01

    Full Text Available The small punch creep test was applied to evaluate the creep behavior of a 316 type austenitic stainless steel at temperatures of 650, 675 and 700 °C. The small punch test was carried out using a creep tester with a specimen size of 10×10×0.3 mm at 650, 675 and 700 °C using loads from 199 to 512 N. The small punch creep curves show the three stages found in the creep curves of the conventional uniaxial test. The conventional creep relationships which involve parameters such as creep rate, stress, time to rupture and temperature were followed with the corresponding parameters of small punch creep test and they permitted to explain the creep behavior in this steel. The mechanism and activation energy of the deformation process were the grain boundary sliding and diffusion, respectively, during creep which caused the intergranular fracture in the tested specimens.El ensayo de termofluencia por indentación se utilizó para evaluar el comportamiento a la termofluencia en un acero inoxidable austenítico 316. Este ensayo se realizó en una máquina de indentación con muestras de 10×10×0,3 mm a temperaturas de 650, 675 y 700 °C con cargas de 199 a 512 N. Las curvas de termofluencia del ensayo mostraron las tres etapas características observadas en el ensayo convencional de tensión. Asimismo, las principales relaciones de termofluencia entre parámetros como velocidad de termofluencia, esfuerzo, tiempo de ruptura y temperatura se observaron en los parámetros correspondientes al ensayo de indentación, lo que permitió caracterizar el comportamiento de termofluencia en este acero. El mecanismo y la energía de activación del proceso de deformación en la termofluencia corresponden al deslizamiento de los límites de grano y la difusión a través de los mismos, respectivamente, lo cual causó la fractura intergranular en las muestras ensayadas.

  16. The effect of grain size on the mechanical response of a metastable austenitic stainless steel

    Directory of Open Access Journals (Sweden)

    Sinclair C.W.

    2013-11-01

    Full Text Available The combination of high environmental resistance and excellent strength, elongation and energy absorption make austenitic stainless steels potentially attractive for transportation applications. In the case of metastable grades that undergo a strain induced martensitic transformation it is possible to significantly change the mechanical properties simply by changing the austenite grain size. Predicting such behaviour using physically based models is, however, extremely challenging. Here, some recent work on the coupling between grain size and mechanical response will be presented for a metastable AISI 301 LN stainless steel. Successes and continuing challenges will be highlighted.

  17. Key Technique of Austenitic Stainless Steel on-line Solution Treatment

    Institute of Scientific and Technical Information of China (English)

    LI Sheng-li; LI Wei-juan; LIU Shuang; LI Ying; ZHAO Fei

    2004-01-01

    Generally the methods of solution treatment of austenitic stainless steel are bifurcated on-line solution and off-line solution . For a founded enterprise, it is necessary to find out how to get across alterations and search a measure of on -line solution disposal with less investment and higher efficiency. By studying and analysingin laboratory, several key points and the methods settle them are presented, which offers a new route to realize austenitic stainless steel on-line solution. By reducing the cost greatly, it makes the enterprise larger benefits.

  18. Expanded austenite in nitrided layers deposited on austenitic and super austenitic stainless steel grades; Analise da austenita expandida em camadas nitretadas em acos inoxidaveis austeniticos e superaustenitico

    Energy Technology Data Exchange (ETDEWEB)

    Casteletti, L.C.; Fernandes, F.A.P.; Heck, S.C. [Universidade de Sao Paulo (EESC/USP), Sao Carlos, SP (Brazil). Escola de Engenharia. Dept. de Engenharia de Materais, Aeronautica e Automobilistica; Oliveira, A.M. [Instituto de Educacao, Ciencia e Tecnologia do Maranhao (IFMA), Sao Luis, MA (Brazil); Gallego, J., E-mail: gallego@dem.feis.unesp.b [UNESP, Ilha Solteira, SP (Brazil). Dept. Engenharia Mecanica

    2010-07-01

    In this work nitrided layers deposited on austenitic and super austenitic stainless steels were analyzed through optical microscopy and X-rays diffraction analysis (XRD). It was observed that the formation of N supersaturated phase, called expanded austenite, has promoted significant increment of hardness (> 1000HV). XRD results have indicated the anomalous displacement of the diffracted peaks, in comparison with the normal austenite. This behavior, combined with peaks broadening, it was analyzed in different nitriding temperatures which results showed good agreement with the literature. (author)

  19. Effect of Austenitizing Heat Treatment on the Microstructure and Hardness of Martensitic Stainless Steel AISI 420

    Science.gov (United States)

    Barlow, L. D.; Du Toit, M.

    2012-07-01

    The effect of austenitizing on the microstructure and hardness of two martensitic stainless steels was examined with the aim of supplying heat-treatment guidelines to the user that will ensure a martensitic structure with minimal retained austenite, evenly dispersed carbides and a hardness of between 610 and 740 HV (Vickers hardness) after quenching and tempering. The steels examined during the course of this examination conform in composition to medium-carbon AISI 420 martensitic stainless steel, except for the addition of 0.13% vanadium and 0.62% molybdenum to one of the alloys. Steel samples were austenitized at temperatures between 1000 and 1200 °C, followed by oil quenching. The as-quenched microstructures were found to range from almost fully martensitic structures to martensite with up to 35% retained austenite after quenching, with varying amounts of carbides. Optical and scanning electron microscopy was used to characterize the microstructures, and X-ray diffraction was employed to identify the carbide present in the as-quenched structures and to quantify the retained austenite contents. Hardness tests were performed to determine the effect of heat treatment on mechanical properties. As-quenched hardness values ranged from 700 to 270 HV, depending on the amount of retained austenite. Thermodynamic predictions (using the CALPHAD™ model) were employed to explain these microstructures based on the solubility of the carbide particles at various austenitizing temperatures.

  20. A Feasibility Study on Low Temperature Thermochemical Treatments of Austenitic Stainless Steel in Fluidized Bed Furnace

    Science.gov (United States)

    Haruman, Esa; Sun, Yong; Triwiyanto, Askar; Manurung, Yupiter H. P.; Adesta, Erry Y.

    2011-04-01

    In this work, the feasibility of using an industrial fluidized bed furnace to perform low temperature thermochemical treatments of austenitic stainless steels has been studied, with the aim to produce expanded austenite layers with combined wear and corrosion resistance, similar to those achievable by plasma and gaseous processes. Several low temperature thermochemical treatments were studied, including nitriding, carburizing, combined nitridingcarburizing (hybrid treatment), and sequential carburizing and nitriding. The results demonstrate that it is feasible to produce expanded austenite layers on the investigated austenitic stainless steel by the fluidized bed heat treatment technique, thus widening the application window for the novel low temperature processes. The results also demonstrate that the fluidized bed furnace is the most effective for performing the hybrid treatment, which involves the simultaneous incorporation of nitrogen and carbon together into the surface region of the component in nitrogen and carbon containing atmospheres. Such hybrid treatment produces a thicker and harder layer than the other three processes investigated.

  1. Effect of Harmonic Microstructure on the Corrosion Behavior of SUS304L Austenitic Stainless Steel

    Science.gov (United States)

    Rai, Prabhat K.; Shekhar, S.; Nakatani, M.; Ota, M.; Vajpai, S. K.; Ameyama, K.; Mondal, K.

    2016-12-01

    Corrosion behavior of a harmonic structured SUS304L austenitic stainless steel was examined and compared with nonharmonic structured SUS304L stainless steel and conventional 304 stainless steel in 3.5 pct NaCl solution. The study was performed using linear polarization, potentiodynamic polarization, cyclic polarization, and a salt fog exposure test for 30 days. Characterization was accomplished using a scanning electron microscope, an electron probe microanalyzer, and Raman spectroscopy. Improved pitting corrosion resistance was found in the case of the harmonic structured steel as compared to that of the nonharmonic and the conventional 304 stainless steel. Harmonically distributed fine-grained structure, less porosity, and higher fraction of passive α-FeOOH are attributed to the improvement in corrosion resistance of the harmonic structured steel.

  2. KINETICS OF α'-MARTENSITE FORMATION DURING FATIGUE DEFORMATION IN METASTABLE AUSTENITIC STAINLESS STEEL

    OpenAIRE

    Tsuzaki, K.; T. Maki; Tamura, I.

    1982-01-01

    The effect of applied total strain range on the critical condition necessary for the onset of α'-martensitic transformation kinetics during the fatigue deformation was studied in AISI type 304 metastable austenitic stainless steel at room temperature. In the case of fatigue deformation, the α'-martensite formation was observed even in the condition that the saturated stress amplitude of austenite phase is smaller than the critical applied stress for the onset of α'-martensite formation for th...

  3. Effect of electromagnetic stirring on solidification structure of austenitic stainless steel in horizontal continuous casting

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    An investigation on the influence of low frequency rotary electromagnetic stirring on solidification structure of austenitic stainless steel in horizontal continuous casting was experimentally conducted and carried out on an industrial trial basis. The results show that application of appropriate electromagnetic stirring parameters can obviously improve the macrostructure of austenitic stainless steel, in which both columnar and equiaxed grains can be greatly refined and shrinkage porosity or cavity zone along centerline can be remarkably decreased due to eliminating intracrystalline and enlarging equiaxed grains zone. The industrial trials verify that the electromagnetic stirring intensity of austenitic stainless steel should be higher than that of plain carbon steel. Electromagnetic stirring has somewhat affected the macrostructure of austenitic stainless steel even if the magnetic flux density of the electromagnetic stirring reaches 90 mT (amplitude reaches 141 mT ) in average at frequency f=3-4Hz, which provides a reference for the optimization of design and process parameters when applying the rotary electromagnetic stirrer

  4. Effect of electromagnetic stirring on solidification structure of austenitic stainless steel in horizontal continuous casting

    Directory of Open Access Journals (Sweden)

    ZHOU Shu-cai

    2007-08-01

    Full Text Available An investigation on the influence of low frequency rotary electromagnetic stirring on solidification structure of austenitic stainless steel in horizontal continuous casting was experimentally conducted and carried out on an industrial trial basis. The results show that application of appropriate electromagnetic stirring parameters can obviously improve the macrostructure of austenitic stainless steel, in which both columnar and equiaxed grains can be greatly refined and shrinkage porosity or cavity zone along centerline can be remarkably decreased due to eliminating intracrystalline and enlarging equiaxed grains zone. The industrial trials verify that the electromagnetic stirring intensity of austenitic stainless steel should be higher than that of plain carbon steel. Electromagnetic stirring has somewhat affected the macrostructure of austenitic stainless steel even if the magnetic flux density of the electromagnetic stirring reaches 90 mT (amplitude reaches 141 mT in average at frequency f=3-4Hz, which provides a reference for the optimization of design and process parameters when applying the rotary electromagnetic stirrer.

  5. Cytotoxicity study of plasma-sprayed hydroxyapatite coating on high nitrogen austenitic stainless steels.

    Science.gov (United States)

    Ossa, C P O; Rogero, S O; Tschiptschin, A P

    2006-11-01

    Stainless steel has been frequently used for temporary implants but its use as permanent implants is restricted due to its low pitting corrosion resistance. Nitrogen additions to these steels improve both mechanical properties and corrosion resistance, particularly the pitting and crevice corrosion resistance. Many reports concerning allergic reactions caused by nickel led to the development of nickel free stainless steel; it has excellent mechanical properties and very high corrosion resistance. On the other hand, stainless steels are biologically tolerated and no chemical bonds are formed between the steel and the bone tissue. Hydroxyapatite coatings deposited on stainless steels improve osseointegration, due their capacity to form chemical bonds (bioactive fixation) with the bone tissue. In this work hydroxyapatite coatings were plasma-sprayed on three austenitic stainless steels: ASTM-F138, ASTM-F1586 and the nickel-free Böhler-P558. The coatings were analyzed by SEM and XDR. The cytotoxicity of the coatings/steels was studied using the neutral red uptake method by quantitative evaluation of cell viability. The three uncoated stainless steels and the hydroxyapatite coated Böhler-P558 did not have any toxic effect on the cell culture. The hydroxyapatite coated ASTM-F138 and ASTM-F1586 stainless steels presented cytotoxicity indexes (IC50%) lower than 50% and high nickel contents in the extracts.

  6. Modeling of Ni Diffusion Induced Austenite Formation in Ferritic Stainless Steel Interconnects

    DEFF Research Database (Denmark)

    Chen, Ming; Molin, Sebastian; Zhang, L.

    2015-01-01

    Ferritic stainless steel interconnect plates are widely used in planar solid oxide fuel cell (SOFC) or electrolysis cell (SOEC) stacks. During stack production and operation, nickel from the Ni/YSZ fuel electrode or from the Ni contact component diffuses into the IC plate, causing transformation...... of the ferritic phase into an austenitic phase in the interface region. This is accompanied with changes in volume and in mechanical and corrosion properties of the IC plates. In this work, kinetic modeling of the inter-diffusion between Ni and FeCr based ferritic stainless steel was conducted, using the CALPHAD...... approach with the DICTRA software. The kinetics of inter-diffusion and austenite formation was explored in full detail, as functions of layer thickness, temperature, time, and steel composition. The simulation was further validated by comparing with experimental results. Growth of the austenite phase...

  7. Austenite Formation from Martensite in a 13Cr6Ni2Mo Supermartensitic Stainless Steel

    Science.gov (United States)

    Bojack, A.; Zhao, L.; Morris, P. F.; Sietsma, J.

    2016-05-01

    The influence of austenitization treatment of a 13Cr6Ni2Mo supermartensitic stainless steel (X2CrNiMoV13-5-2) on austenite formation during reheating and on the fraction of austenite retained after tempering treatment is measured and analyzed. The results show the formation of austenite in two stages. This is probably due to inhomogeneous distribution of the austenite-stabilizing elements Ni and Mn, resulting from their slow diffusion from martensite into austenite and carbide and nitride dissolution during the second, higher temperature, stage. A better homogenization of the material causes an increase in the transformation temperatures for the martensite-to-austenite transformation and a lower retained austenite fraction with less variability after tempering. Furthermore, the martensite-to-austenite transformation was found to be incomplete at the target temperature of 1223 K (950 °C), which is influenced by the previous austenitization treatment and the heating rate. The activation energy for martensite-to-austenite transformation was determined by a modified Kissinger equation to be approximately 400 and 500 kJ/mol for the first and the second stages of transformation, respectively. Both values are much higher than the activation energy found during isothermal treatment in a previous study and are believed to be effective activation energies comprising the activation energies of both mechanisms involved, i.e., nucleation and growth.

  8. Research on High-Speed Drilling Performances of Austenitic Stainless Steels

    Institute of Scientific and Technical Information of China (English)

    J.W.Zhong; Y.P.Ma; F.H.Sun; M.Chen

    2004-01-01

    Due to specific properties arising from their structure (high ductility, high toughness,strong tenacious and low heat conductivity), the stainless steels have poor machinability. The drilling of the stainless steels becomes the machining difficulty for their serious work-hardening and abrasion of tools. In this paper, the austenitic stainless steel is used as the work-piece to perform the contrastive experiments with the TiN coated and TiAlN-coated high-speed steel drills. The cutting force, torque, cutting temperature, and the abrasion of drills and tool life are tested and analyzed in the process of high-speed drilling. Experiment results show the effect of drilling speed on cutting force, cutting temperature, and drill wear. TiAlN-coated drills demonstrate better performances in high speed drilling. The research results will be of great benefit in the selection of drills and in the control of tool wear in high speed drilling of stainless steels.

  9. Very high cycle regime fatigue of thin walled tubes made from austenitic stainless steel

    DEFF Research Database (Denmark)

    Carstensen, J.V.; Mayer, H.; Brøndsted, P.

    2002-01-01

    Fatigue life data of cold worked tubes (diameter 4 mm, wall thicknesses 0.25 and 0.30 mm) of an austenitic stainless steel, AISI 904 L, were measured in the regime ranging from 2 × 105 to 1010 cycles to failure. The influence of the loading frequency was investigated as data were obtained...

  10. Influence of Plastic Deformation on Low Temperature Surface Hardening of Austenitic Stainless Steel by Gaseous Nitriding

    DEFF Research Database (Denmark)

    Bottoli, Federico; Winther, Grethe; Christiansen, Thomas Lundin;

    2015-01-01

    This article addresses an investigation of the influence of plastic deformation on low temperature surface hardening by gaseous nitriding of two commercial austenitic stainless steels: AISI 304 and EN 1.4369. The materials were plastically deformed to different equivalent strains by uniaxial...

  11. Experimental determination of the constitutive behaviour of a metastable austenitic stainless steel

    NARCIS (Netherlands)

    Post, J.; Nolles, H.; Datta, K.; Geijselaers, H.J.M.

    2008-01-01

    This article presents measurements to describe the constitutive behaviour of a semi-austenitic precipitation hardenable stainless steel called Sandvik Nanoflex™, during metal forming and hardening. The material is metastable, which causes strain-induced transformation during forming. Depending on th

  12. Stress and Composition of Carbon Stabilized Expanded Austenite on Stainless Steel

    DEFF Research Database (Denmark)

    Christiansen, Thomas; Somers, Marcel A. J.

    2009-01-01

    Low-temperature gaseous carburizing of stainless steel is associated with a colossal supersaturation of the fcc lattice with carbon, without the development of carbides. This article addresses the simultaneous determination of stress and composition profiles in layers of carbon xpanded austenite...

  13. Numerical simulation and experimental investigation of laser dissimilar welding of carbon steel and austenitic stainless steel

    Science.gov (United States)

    Nekouie Esfahani, M. R.; Coupland, J.; Marimuthu, S.

    2015-07-01

    This study reports an experimental and numerical investigation on controlling the microstructure and brittle phase formation during laser dissimilar welding of carbon steel to austenitic stainless steel. The significance of alloying composition and cooling rate were experimentally investigated. The investigation revealed that above a certain specific point energy the material within the melt pool is well mixed and the laser beam position can be used to control the mechanical properties of the joint. The heat-affected zone within the high-carbon steel has significantly higher hardness than the weld area, which severely undermines the weld quality. A sequentially coupled thermo-metallurgical model was developed to investigate various heat-treatment methodology and subsequently control the microstructure of the HAZ. Strategies to control the composition leading to dramatic changes in hardness, microstructure and service performance of the dissimilar laser welded fusion zone are discussed.

  14. On the Plasma (ion) Carburized Layer of High Nitrogen Austenitic Stainless Steel

    Institute of Scientific and Technical Information of China (English)

    Y. Ueda; N. Kanayama; K. Ichii; T. Oishi; H. Miyake

    2004-01-01

    The manganese concentration of austenitic stainless steel decreases from the inner layer towards the surface of the plasma (ion) carburized layer due to the evaporation of manganese from the specimen surface. The carbon concentration in the carburized layer is influenced by alloyed elements such as Ct, Ni, Si, and Mo, as well as Nitrogen. This study examined the effects of nitrogen on the properties of the carburized layer of high nitrogen stainless steel. Plasma (ion)carburizing was carried out for 14.4 ks at 1303 K in an atmosphere of CH4+H2 gas mixtures under a pressure of 350 Pa. The plasma carburized layer of the high nitrogen stainless steel was thinner than that of an austentric stainless steel containing no nitrogen. This suggested that the nitrogen raised the activity of carbon in the plasma carburized layer, GDOES measurement indicated that the nitrogen level in the layer did not vary after plasma (ion) carburizing.

  15. Microstructures of Austenitic Stainless Steel Produced by Twin-Roll Strip Caster

    Institute of Scientific and Technical Information of China (English)

    HUANG Fu-xiang; WANG Xin-hua; WANG Wan-jun

    2012-01-01

    The microstructures of austenitic stainless steel strip were studied using color metallographic method and electron probe micro analysis (EPMA). In the cast strips, there are three kinds of solidification structures: fine cel- lular dendrite in the surface layer, equiaxed grains in the center and fine dendrite between them. The solidification mode in the surface layer is the primary austenite AF mode because of extremely high cooling rate, with the retained ferrite located around the primary cellular austenite. In the fine dendrite zone, the solidification mode of molten stainless steel changes to FA mode and the residual ferrite with fish-bone morphology is located at the core of the dendrite. The retained ferrite of equiaxed grains in the center is located in the center of broken primary ferrite dendrite with vermicular morphology.

  16. On qualification of TOFD technique for austenitic stainless steel welds inspection

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Ona, R. [Tecnatom, San Sebastian de los Reyes (Spain); Viggianiello, S.; Bleuze, A. [Metalscan, Saint-Remy (France)

    2006-07-01

    Time of Flight Diffraction (TOFD) technique is gaining ground as a solid method for detection and sizing of defects. It has been reported that TOFD technique provides good results on the inspection of fine grain steels. However, there are few results regarding the application and performance of this technique on austenitic stainless steels. A big challenge of these inspections is the coarse grain structure that produces low signal to noise ratio and may mask the diffraction signals. Appropriate transducer design, selection of technique parameters and analysis tools could overcome the actual difficulties. In this paper, the main design aspects and parameters of the TOFD technique for austenitic steels are presented. It follows the description of qualification tests carried out to validate the technique for inspecting stainless steels welds. To conclude, discussion of results from actual inspections is shown. (orig.)

  17. Influence of surface texture on the galling characteristics of lean duplex and austenitic stainless steels

    DEFF Research Database (Denmark)

    Wadman, Boel; Eriksen, J.; Olsson, M.;

    2010-01-01

    of sheet materials and lubricants. The strip reduction test, a severe sheet forming tribology test was used to simulate the conditions during ironing. This investigation shows that the risk of galling is highly dependent on the surface texture of the duplex steel. Trials were also performed......Two simulative test methods were used to study galling in sheet forming of two types of stainless steel sheet: austenitic (EN 1.4301) and lean duplex LDX 2101 (EN 1.4162) in different surface conditions. The pin-on-disc test was used to analyse the galling resistance of different combinations...... in an industrial tool used for high volume production of pump components, to compare forming of LDX 2101 and austenitic stainless steel with equal thickness. The forming forces, the geometry and the strains in the sheet material were compared for the same component. It was found that LDX steels can be formed...

  18. The sub-zero Celsius treatment of precipitation hardenable semi-austenitic stainless steel

    DEFF Research Database (Denmark)

    Villa, Matteo; Hansen, Mikkel Fougt; Somers, Marcel A. J.

    2015-01-01

    A precipitation hardenable semi-austenitic stainless steel AISI 632 grade was austenitized according to industrial specifications and thereafter subjected to isothermal treatment at sub-zero Celsius temperatures. During treatment, austenite transformed to martensite. The isothermal austenite-to-martensite...... treatment. Magnetometry showed that the additional thermal step in boiling nitrogen yields a minor increment of the fraction of martensite, but has a noteworthy accelerating effect on the transformation kinetics, which more pronounced when the isothermal holding is performed at a higher temperature. Data...... transformation was monitored in situ by magnetometry and data was used to sketch a TTT diagram for transformation. As an alternative treatment, after austenitization the material was immersed in boiling nitrogen and up-quenched to room temperature by immersion in water prior to be subjected to isothermal...

  19. Synergistic Computational and Microstructural Design of Next- Generation High-Temperature Austenitic Stainless Steels

    Energy Technology Data Exchange (ETDEWEB)

    Karaman, Ibrahim [Texas A& M Engineering Experiment Station, College Station, TX (United States); Arroyave, Raymundo [Texas A& M Engineering Experiment Station, College Station, TX (United States)

    2015-07-31

    The purpose of this project was to: 1) study deformation twinning, its evolution, thermal stability, and the contribution on mechanical response of the new advanced stainless steels, especially at elevated temperatures; 2) study alumina-scale formation on the surface, as an alternative for conventional chromium oxide, that shows better oxidation resistance, through alloy design; and 3) design new generation of high temperature stainless steels that form alumina scale and have thermally stable nano-twins. The work involved few baseline alloys for investigating the twin formation under tensile loading, thermal stability of these twins, and the role of deformation twins on the mechanical response of the alloys. These baseline alloys included Hadfield Steel (Fe-13Mn-1C), 316, 316L and 316N stainless steels. Another baseline alloy was studied for alumina-scale formation investigations. Hadfield steel showed twinning but undesired second phases formed at higher temperatures. 316N stainless steel did not show signs of deformation twinning. Conventional 316 stainless steel demonstrated extensive deformation twinning at room temperature. Investigations on this alloy, both in single crystalline and polycrystalline forms, showed that deformation twins evolve in a hierarchical manner, consisting of micron–sized bundles of nano-twins. The width of nano-twins stays almost constant as the extent of strain increases, but the width and number of the bundles increase with increasing strain. A systematic thermomechanical cycling study showed that the twins were stable at temperatures as high as 900°C, after the dislocations are annealed out. Using such cycles, volume fraction of the thermally stable deformation twins were increased up to 40% in 316 stainless steel. Using computational thermodynamics and kinetics calculations, we designed two generations of advanced austenitic stainless steels. In the first generation, Alloy 1, which had been proposed as an alumina

  20. Nitriding Process Characterization of Cold Worked AISI 304 and 316 Austenitic Stainless Steels

    Directory of Open Access Journals (Sweden)

    Waldemar Alfredo Monteiro

    2017-01-01

    Full Text Available The nitriding behavior of austenitic stainless steels (AISI 304 and 316 was studied by different cold work degree (0% (after heat treated, 10%, 20%, 30%, and 40% before nitride processing. The microstructure, layer thickness, hardness, and chemical microcomposition were evaluated employing optical microscopy, Vickers hardness, and scanning electron microscopy techniques (WDS microanalysis. The initial cold work (previous plastic deformations in both AISI 304 and 306 austenitic stainless steels does not show special influence in all applied nitriding kinetics (in layer thicknesses. The nitriding processes have formed two layers, one external layer formed by expanded austenite with high nitrogen content, followed by another thinner layer just below formed by expanded austenite with a high presence of carbon (back diffusion. An enhanced diffusion can be observed on AISI 304 steel comparing with AISI 316 steel (a nitrided layer thicker can be noticed in the AISI 304 steel. The mechanical strength of both steels after nitriding processes reveals significant hardness values, almost 1100 HV, on the nitrided layers.

  1. Hydrogen solubility and diffusion in austenitic stainless steels studied with thermal desorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Yagodzinskyy, Y.; Todoshchenko, O.; Papula, S.; Haenninen, H. [Laboratory of Engineering Materials, School of Science and Technology, Aalto University, Espoo (Finland)

    2011-01-15

    Hydrogen solubility and diffusion in austenitic stainless steels, namely AISI 310, AISI 301LN and AISI 201, are studied with thermal desorption spectroscopy (TDS) after electrochemical potentiostatic hydrogen pre-charging. Temperature dependencies of hydrogen desorption for all studied steels manifest a complex main peak caused by hydrogen releasing from the steel lattice by diffusion. Depending on the steel and heating rate the peak is situated from 350 to 500 K and its shape reflects a specific of hydrogen diffusion in stainless steels, which are multicomponent alloys. Analysis of the TDS curves is based on the hydrogen diffusion model taking into account trapping of hydrogen atoms in the energetically deep interstitial positions in the steel crystal lattice. Diffusion coefficient of hydrogen and its total content after the same charging procedure are obtained from the TDS curves and compared for the studied steels. (Copyright copyright 2011 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. On the measurement of austenite in supermartensitic stainless steel by X-ray diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Tolchard, Julian Richard, E-mail: tolchard@material.ntnu.no [Department of Materials Science and Engineering, Norwegian University of Science and Technology, Trondheim (Norway); Sømme, Astri; Solberg, Jan Ketil [Department of Materials Science and Engineering, Norwegian University of Science and Technology, Trondheim (Norway); Solheim, Karl Gunnar [Statoil, Stavanger (Norway)

    2015-01-15

    Sections of a 13Cr supermartensitic stainless steel were investigated to determine the optimum sample preparation for measurement of the austenite content by X-ray diffraction. The surface of several samples was mechanically ground or polished using media of grit sizes in the range 1–120 μm. The strained surface layer was afterwards removed stepwise by electropolishing, and the austenite content measured at each step. It was found that any level of mechanical grinding or polishing results in a reduction of the measured austenite fraction relative to the true bulk value, and that coarser grinding media impart greater damage and greater reduction in the measured austenite content. The results thus highlight the importance of the electropolishing step in preparation of such samples, but suggest that the American Society for Testing and Materials standard E975-03 substantially overestimates the amount of material which needs to be removed to recover the true “bulk” content. - Highlights: • Quantitative Rietveld analysis of austenite/martensite ratio in supermartensitic stainless steels • Critical evaluation of sample preparation for residual austenite measurements by X-ray diffraction • Highlighting of the importance of electropolishing as a final preparation step.

  3. THE EFFECT OF SHIELDING-GAS COMPOSITIONS ON THE MICROSTRUCTURE AND MECHANICAL PROPERTIES OF AUSTENITIC STAINLESS STEEL WELDMENTS

    Directory of Open Access Journals (Sweden)

    Ramazan YILMAZ

    2005-03-01

    Full Text Available Recently, austenitic stainless steel is becoming very important and widely used in the industry due to their superior properties. Therefore, welding process of those has gained popularity in the construction of stainless steel. Gas metal arc welding (GMAW and gas tungsten arc welding (GTAW processes are easily used and more suitable compared with the other welding process for the austenitic stainless steel welding applications. In this study, the effect of shielding gases used in the welding process on the microstructure and mechanical properties of austenitic stainless steel weldments has been investigated using the knowledge available in the literature. It is stressed in the study that shielding-gas composition has great influence on the microstructure and mechanical properties of stainless steel weldment. The gases of Ar+H2, Ar+CO2, Ar+N2 used for welding process effects on microstructure therefore, mechanical properties of weldments.

  4. Depth distribution analysis of Martensitic transformations in Xe implanted austenitic stainless steel

    DEFF Research Database (Denmark)

    Johnson, E.; Gerritsen, E.; Chechenin, N.G.

    1989-01-01

    In recent years the implantation of noble gases in metals has been found to induce some exciting phenomena such as formation of inclusions containing solid gas at extremely high pressures. In stainless steels these inclusions are the origin of a stress-induced martensitic fcc → bcc phase...... transformation in the implanted layer. In this work we present results from a depth distribution analysis of the martensitic phase change occurring in Xe implanted single crystals of austenitic stainless steel. Analysis was done by in situ RBS/channeling analysis, X-ray diffraction and cross-section transmission...

  5. Performance evaluation of vegetable-based oils in drilling austenitic stainless steel

    DEFF Research Database (Denmark)

    Belluco, Walter; De Chiffre, Leonardo

    2004-01-01

    The efficiency of six cutting oils was evaluated in drilling AISI 316L austenitic stainless steel using conventional HSS-Co tools by measurements of tool life, tool wear, cutting forces and chip formation. Seven tools were tested with each fluid to catastrophic failure. Cutting forces and chip...... in a measurement capability comparable to that obtained using tool life as a performance criterion. As a consequence, it is suggested that drilling thrust can be used to assess the performance of cutting fluids in drilling stainless steel, resulting in considerable time savings and cost reduction with respect...

  6. Hydrogen Silsesquioxane based silica glass coatings for the corrosion protection of austenitic stainless steel

    DEFF Research Database (Denmark)

    Lampert, Felix; Jensen, Annemette Hindhede; Din, Rameez Ud

    2016-01-01

    The application of stainless steels in hostile environments, such as concentrated acid or hot sea water, requires additional surface treatments, considering that the native surface oxide does not guarantee sufficient corrosion protection under these conditions. In the present work, silica-like thin......-film barrier coatings were deposited on AISI 316L grade austenitic stainless steel with 2B surface finish from Hydrogen Silsesquioxane (HSQ) spin-on-glass precursor and thermally cured to tailor the film properties. Results showed that curing at 500 °C resulted in a film-structure with a polymerized siloxane...

  7. Surface stability and conductivity of a high Cr and Ni austenitic stainless steel plates for PEMFC

    Institute of Scientific and Technical Information of China (English)

    TIAN Rujin; SUN Juncai; WANG Jianli

    2006-01-01

    In order to use stainless steel as bipolar plate for PEMFC, electrochemical behavior of a high Cr and Ni austenitic stainless steel was studied in the solutions containing different concentration of H2SO4 and 2 mg·L-1 F-, and interfacial contact resistance was measured after corrosion tests. The experimental results show that the passive current density lowers with decreasing the concentration of H2SO4. The interfacial contact resistance between carbon paper and passive film formed in the simulated PEMFC environment is higher than the goal of bipolar plate for PEMFC. Surface conductivity should be further reduced by surface modification.

  8. The Change of Austenitic Stainless Steel Elements Content in the Inner Parts of VVER-440 Reactor during Operation

    Science.gov (United States)

    Smutný, Vladimír; Hep, Jaroslav; Novosad, Petr

    2009-08-01

    Neutron activation induces the element transmutation in materials surrounding the reactor active core. The objective of the present paper is to calculate and evaluate the change of austenitic stainless steel 08Ch18N10T elements content through neutron induced activation, in inner parts of VVER-440 - in the baffle and in the barrel. Particularly the content changes of Mn in austenitic stainless steel. The neutron flux density and then the neutron activation of austenitic stainless steel elements in parts at the core are calculated. Neutron activation represents a measure of austenitic stainless steel elements transmutation. The power distribution is determined as an average value of several cycles power distribution in the middle of a cycle for the NPP Dukovany. The power distribution is calculated with the code MOBY-DICK [1]. The neutron flux density is calculated with the code TORT [2]. The neutron activation of austenitic stainless steel elements in the baffle and in the barrel is calculated with the system EASY-2007 containing the code FISPACT-2007 [3]. The calculation of the changing austenitic stainless steel elements content is performed depending on the moment of the supposed end of reactor operation - 40 years. There is also necessary monitoring and benchmarking of steel element content change, because the neutron flux calculation, particularly in thermal region, shows a considerable uncertainty, e.g. [4]. The motivation for this work is the study focused to stress corrosion cracking of austenitic stainless steels induced by radiation inside PWR and BWR, e.g. [5]. The paper could be a suggestion to estimation of austenitic stainless steel corrosion damage induced by neutrons in inner parts of VVER-440 reactor.

  9. Handbook for tensile properties of austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, D. W.; Ryu, W. S.; Jang, J. S.; Kim, S. H.; Kim, W. G.; Chung, M. K.; Han, C. H. [Korea Atomic Energy Research Institute, Taejeon (Korea)

    2000-03-01

    Database system of nuclear materials has not been developed and the physical and mechanical properties of materials used in nuclear power plant are not summarized systematically in Korea. Although Korea designs nuclear power plant, many materials used in nuclear power plant are imported because we do not have database system of nuclear material yet and it was hard to select a proper material for the structural materials of nuclear power plant. To develop database system of nuclear materials, data of mechanical, corrosion, irradiation properties are needed. Of theses properties, tensile properties are tested and summarized in this report. Tensile properties of stainless steel used in nuclear reactor internal were investigated. Data between Korea Atomic Energy Research Institute and foreign laboratory were compared to determine the precision of the result. To develope database system, materials, chemical composition, heat treatment, manufacturing process, and grain size were classified. Tensile properties were tested and summarized to use input data of database system. 9 figs., 9 tabs. (Author)

  10. Creep-fatigue interactions in an austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Majumdar, S; Maiya, P S

    1978-01-01

    A phenomenological model of the interaction between creep and fatigue in Type 304 stainless steel at elevated temperatures is presented. The model is based on a crack-growth equation and an equation governing cavity growth, expressed in terms of current plastic strain and plastic strain rate. Failure is assumed to occur when a proposed interaction equation is satisfied. Various parameters of the equations can be obtained by correlation with continuously cycling fatigue and monotonic creep-rupture test data, without the use of any hold-time fatigue tests. Effects of various wave shapes such as tensile, compressive, and symmetrical hold on the low-cycle fatigue life can be computed by integrating the damage-rate equations along the appropriate loading path. Microstructural evidence in support of the proposed model is also discussed.

  11. Microstructural and Stress Corrosion Cracking Characteristics of Austenitic Stainless Steels Containing Silicon

    Science.gov (United States)

    Andresen, Peter L.; Chou, Peter H.; Morra, Martin M.; Lawrence Nelson, J.; Rebak, Raul B.

    2009-12-01

    Austenitic stainless steels (SSs) core internal components in nuclear light water reactors (LWRs) are susceptible to irradiation-assisted stress corrosion cracking (IASCC). One of the effects of irradiation is the hardening of the SS and a change in the dislocation distribution in the alloy. Irradiation may also alter the local chemistry of the austenitic alloys; for example, silicon may segregate and chromium may deplete at the grain boundaries. The segregation or depletion phenomena at near-grain boundaries may enhance the susceptibility of these alloys to environmentally assisted cracking (EAC). The objective of the present work was to perform laboratory tests in order to better understand the role of Si in the microstructure, properties, electrochemical behavior, and susceptibility to EAC of austenitic SSs. Type 304 SS can dissolve up to 2 pct Si in the bulk while maintaining a single austenite microstructure. Stainless steels containing 12 pct Cr can dissolve up to 5 pct bulk Si while maintaining an austenite structure. The crack growth rate (CGR) results are not conclusive about the effect of the bulk concentration of Si on the EAC behavior of SSs.

  12. Review of environmental effects on fatigue crack growth of austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Shack, W.J.; Kassner, T.F. [Argonne National Lab., IL (United States)

    1994-05-01

    Fatigue and environmentally assisted cracking of piping, pressure vessel cladding, and core components in light water reactors are potential concerns to the nuclear industry and regulatory agencies. The degradation processes include intergranular stress corrosion cracking of austenitic stainless steel (SS) piping in boiling water reactors (BWRs), and propagation of fatigue or stress corrosion cracks (which initiate in sensitized SS cladding) into low-alloy ferritic steels in BWR pressure vessels. Crack growth data for wrought and cast austenitic SSs in simulated BWR water, developed at Argonne National Laboratory under US Nuclear Regulatory Commission sponsorship over the past 10 years, have been compiled into a data base along with similar data obtained from the open literature. The data were analyzed to develop corrosion-fatigue curves for austenitic SSs in aqueous environments corresponding to normal BWR water chemistries, for BWRs that add hydrogen to the feedwater, and for pressurized water reactor primary-system-coolant chemistry.

  13. On the formation of stacking fault tetrahedra in irradiated austenitic stainless steels – A literature review

    Energy Technology Data Exchange (ETDEWEB)

    Schibli, Raluca, E-mail: raluca.stoenescu@gmail.com; Schäublin, Robin

    2013-11-15

    Irradiated austenitic stainless steels, because of their low stacking fault energy and high shear modulus, should exhibit a high ratio of stacking fault tetrahedra relative to the overall population of radiation induced nanometric defects. Experimental observations of stacking fault tetrahedra by transmission electron microscopy in commercial-purity stainless steels are however scarce, while they abundantly occur in high-purity or model austenitic alloys irradiated at both low and high temperatures, but not at around 673 K. In commercial alloys, the little evidence of stacking fault tetrahedra does not follow such a trend. These contradictions are reviewed and discussed. Reviewing the three possible formation mechanisms identified in the literature, namely the Silcox and Hirsch Frank loop dissociation, the void collapse and the stacking fault tetrahedra growth, it seems that the later dominates under irradiation.

  14. Film-induced stress enhancing stress corrosion cracking of austenitic stainless steel

    Institute of Scientific and Technical Information of China (English)

    李金许; 陈浩; 王燕斌; 乔利杰; 褚武扬

    2001-01-01

    A constant deflection device designed for use within a transmission electron microscopy (TEM) was used to investigate the change in dislocation configuration ahead of a crack tip during stress corrosion cracking (SCC) of type 310 austenitic stainless steel in a boiling MgCl2 solution, and the initiation process of stress corrosion microcrack. Results showed that corrosion process during SCC enhanced dislocation emission, multiplication and motion. Microcracks of SCC were initiated when the corrosion-enhanced dislocation emission and motion reached critical state.   A passive film formed during corrosion of austenitic stainless steel in the boiling MgCl2 solution generated a tensile stress. During SCC, the additive tensile stress generated at the metal/passive film interface helps enhance dislocation emission and motion.

  15. Diffusion of nitrogen in austenitic phase: Application to nitriding of stainless steels

    Directory of Open Access Journals (Sweden)

    Torchane Lazhar

    2014-04-01

    Full Text Available The nitriding treatment of the martensitic stainless steels aims to harden and to introduce compressive stresses on the surface of steel. Hardening is resulting of the martensitic transformation of the austenitic matrix enriched into nitrogen during cooling and of the germination and the nitride growth. In order to preserve the stainless character of the nitrided layer, it is imperative to control precipitation within the zone affected by the treatment. Our task consists in showing that is possible to control the composition of the gas atmosphere containing ammonia and argon and to carry out on the surface of nitrided samples at 1050°C two types of configuration of layers : a single phase layer made up by martensite enriched in nitrogen α’N and or a two phase layer made up by austenite γN and martensite α’N enriched in nitrogen.

  16. Corrosion properties of S-phase layers formed on medical grade austenitic stainless steel.

    Science.gov (United States)

    Buhagiar, Joseph; Dong, Hanshan

    2012-02-01

    The corrosion properties of S-phase surface layers formed in AISI 316LVM (ASTM F138) and High-N (ASTM F1586) medical grade austenitic stainless steels by plasma surface alloying with nitrogen (at 430°C), carbon (at 500°C) and both carbon and nitrogen (at 430°C) has been investigated. The corrosion behaviour of the S-phase layers in Ringer's solutions was evaluated using potentiodynamic and immersion corrosion tests. The corrosion damage was evaluated using microscopy, hardness testing, inductive coupled plasma mass spectroscopy and X-ray diffraction. The experimental results have demonstrated that low-temperature nitriding, carburising and carbonitriding can improve the localised corrosion resistance of both industrial and medical grade austenitic stainless steels as long as the threshold sensitisation temperature is not reached. Carburising at 500°C has proved to be the best hardening treatment with the least effect on the corrosion resistance of the parent alloy.

  17. The Gibbs Thomson effect in magnetron-sputtered austenitic stainless steel films

    Science.gov (United States)

    Cusenza, S.; Borchers, C.; Carpene, E.; Schaaf, P.

    2007-03-01

    Magnetron sputtering of austenitic stainless steel AISI 316, which has a face-centred cubic structure (γ), leads to films exhibiting a body-centred cubic (α) structure or a mixture of α- and γ-phases. The microstructure of the deposited films was studied by Mössbauer spectroscopy, x-ray diffraction and transmission electron microscopy. With increasing deposition temperature a phase transformation from α- to γ-phase was observed in these films. Instantaneous recording of the electromotive force shows that nickel content and deposition temperature are crucial factors for phase stability and phase formation. In room temperature deposited stainless steel films, the phase transformation after vacuum annealing can be described by the Johnson-Mehl-Avrami kinetic model. These phase transformations in stainless steel films during annealing can be explained with the Gibbs-Thomson effect, where the grain boundary energy raises the Gibbs free energy.

  18. The Gibbs-Thomson effect in magnetron-sputtered austenitic stainless steel films

    Energy Technology Data Exchange (ETDEWEB)

    Cusenza, S [Universitaet Goettingen, II Physikalisches Institut, Friedrich-Hund-Platz 1, 37077 Goettingen (Germany); Borchers, C [Universitaet Goettingen, II Physikalisches Institut, Friedrich-Hund-Platz 1, 37077 Goettingen (Germany); Carpene, E [Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo da Vinci 32, 20133 Milan (Italy); Schaaf, P [Universitaet Goettingen, II Physikalisches Institut, Friedrich-Hund-Platz 1, 37077 Goettingen (Germany)

    2007-03-14

    Magnetron sputtering of austenitic stainless steel AISI 316, which has a face-centred cubic structure ({gamma}), leads to films exhibiting a body-centred cubic ({alpha}) structure or a mixture of {alpha}- and {gamma}-phases. The microstructure of the deposited films was studied by Moessbauer spectroscopy, x-ray diffraction and transmission electron microscopy. With increasing deposition temperature a phase transformation from {alpha}- to {gamma}-phase was observed in these films. Instantaneous recording of the electromotive force shows that nickel content and deposition temperature are crucial factors for phase stability and phase formation. In room temperature deposited stainless steel films, the phase transformation after vacuum annealing can be described by the Johnson-Mehl-Avrami kinetic model. These phase transformations in stainless steel films during annealing can be explained with the Gibbs-Thomson effect, where the grain boundary energy raises the Gibbs free energy.

  19. Modeling of Ni Diffusion Induced Austenite Formation in Ferritic Stainless Steel Interconnects

    OpenAIRE

    Chen, Ming; Molin, Sebastian; Zhang, L.; Ta, Na; Hendriksen, Peter Vang; Kiebach, Wolff-Ragnar; Du, Y

    2015-01-01

    Ferritic stainless steel interconnect plates are widely used in planar solid oxide fuel cell (SOFC) or electrolysis cell (SOEC) stacks. During stack production and operation, nickel from the Ni/YSZ fuel electrode or from the Ni contact component diffuses into the IC plate, causing transformation of the ferritic phase into an austenitic phase in the interface region. This is accompanied with changes in volume and in mechanical and corrosion properties of the IC plates. In this work, kinetic mo...

  20. Delta ferrite-containing austenitic stainless steel resistant to the formation of undesirable phases upon aging

    Science.gov (United States)

    Leitnaker, James M.

    1981-01-01

    Austenitic stainless steel alloys containing delta ferrite, such as are used as weld deposits, are protected against the transformation of delta ferrite to sigma phase during aging by the presence of carbon plus nitrogen in a weight percent 0.015-0.030 times the volume percent ferrite present in the alloy. The formation of chi phase upon aging is controlled by controlling the Mo content.

  1. Corrosion Behavior of the Stressed Sensitized Austenitic Stainless Steels of High Nitrogen Content in Seawater

    Directory of Open Access Journals (Sweden)

    A. Almubarak

    2013-01-01

    Full Text Available The purpose of this paper is to study the effect of high nitrogen content on corrosion behavior of austenitic stainless steels in seawater under severe conditions such as tensile stresses and existence of sensitization in the structure. A constant tensile stress has been applied to sensitized specimens types 304, 316L, 304LN, 304NH, and 316NH stainless steels. Microstructure investigation revealed various degrees of stress corrosion cracking. SCC was severe in type 304, moderate in types 316L and 304LN, and very slight in types 304NH and 316NH. The electrochemical polarization curves showed an obvious second current peak for the sensitized alloys which indicated the existence of second phase in the structure and the presence of intergranular stress corrosion cracking. EPR test provided a rapid and efficient nondestructive testing method for showing passivity, degree of sensitization and determining IGSCC for stainless steels in seawater. A significant conclusion was obtained that austenitic stainless steels of high nitrogen content corrode at a much slower rate increase pitting resistance and offer an excellent resistance to stress corrosion cracking in seawater.

  2. Development of a robust modeling tool for radiation-induced segregation in austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Ying [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Field, Kevin G [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Allen, Todd R. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Busby, Jeremy T [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2015-09-01

    Irradiation-assisted stress corrosion cracking (IASCC) of austenitic stainless steels in Light Water Reactor (LWR) components has been linked to changes in grain boundary composition due to irradiation induced segregation (RIS). This work developed a robust RIS modeling tool to account for thermodynamics and kinetics of the atom and defect transportation under combined thermal and radiation conditions. The diffusion flux equations were based on the Perks model formulated through the linear theory of the thermodynamics of irreversible processes. Both cross and non-cross phenomenological diffusion coefficients in the flux equations were considered and correlated to tracer diffusion coefficients through Manning’s relation. The preferential atomvacancy coupling was described by the mobility model, whereas the preferential atom-interstitial coupling was described by the interstitial binding model. The composition dependence of the thermodynamic factor was modeled using the CALPHAD approach. Detailed analysis on the diffusion fluxes near and at grain boundaries of irradiated austenitic stainless steels suggested the dominant diffusion mechanism for chromium and iron is via vacancy, while that for nickel can swing from the vacancy to the interstitial dominant mechanism. The diffusion flux in the vicinity of a grain boundary was found to be greatly influenced by the composition gradient formed from the transient state, leading to the oscillatory behavior of alloy compositions in this region. This work confirms that both vacancy and interstitial diffusion, and segregation itself, have important roles in determining the microchemistry of Fe, Cr, and Ni at irradiated grain boundaries in austenitic stainless steels.

  3. Extended X-Ray Absorption Fine Structure Investigation of Carbon Stabilized Expanded Austenite and Carbides in Stainless Steel AISI 316

    DEFF Research Database (Denmark)

    Oddershede, Jette; Christiansen, Thomas; Ståhl, Kenny;

    2011-01-01

    Low temperature carburized AISI 316 stainless steel - carbon expanded austenite - was investigated with EXAFS and synchrotron diffraction together with synthesized carbides of the type M3C2, M7C3 and M23C6. It was found that the chemical environment of carbon expanded austenite is not associated ...

  4. Microstructure and Mechanical Properties of a Dissimilar Friction Stir Weld between Austenitic Stainless Steel and Low Carbon Steel

    Institute of Scientific and Technical Information of China (English)

    M.Jafarzadegan; A.Abdollah-zadeh; A.H.Feng; T.Saeid; J.Shen; H.Assadi

    2013-01-01

    Dissimilar fusion welding of austenitic stainless steels to carbon steels has some metallurgical and technical problems.It was suggested that the solid-state nature of friction stir welding (FSW) can overcome these problems and produce a sound weld with reliable mechanical properties.In this study,plates of 304 stainless steel and st37 steel were welded together by FSW at tool rotational speed of 600 r/min and welding speed of 50 mm/min.In the stir zone (SZ) of 304 stainless steel,the results showed a refined grain structure with some features of metadynamic recrystallization.In the SZ of st37 steel,the hot deformation of material in the austenite region produced small austenite grains.These grains transformed to fine ferrite and pearlite by cooling the material after FSW.The production of fine grains increased the hardness and tensile strength in the SZ of both sides with respect to their base metals (BMs).

  5. Stress Induce Martensitic Transformations in Hydrogen Embrittlement of Austenitic Stainless Steels

    Science.gov (United States)

    Rozenak, Paul

    2014-01-01

    In austenitic type stainless steels, hydrogen concentration gradients formed during electrochemical charging and followed by hydrogen loss during aging, at room temperature, surface stresses, and martensitic phases α'-BCC and ɛ-HCP developed. The basic relationship between the X-ray diffraction peak broadening and the hydrogen gradients, formed during charging and aging at room temperature in such austenitic stainless steels, were analyzed. The results demonstrate that the impact of stresses must be considered in the discussion of phase transformations due to hydrogenation. Austenitic stainless steels based on iron-nickel-chromium, have relatively low stacking fault energy γSFE and undergo: quenching to low temperatures, plastic deformation, sensitization heat treatments, high pressure (≥3-5 × 109 Pa) by hydrogen or other gases, electrochemical charging (when the sample is cathode) and when is irradiation by various ions the samples in vacuum. All the above mentioned induce formation of ɛ and α' in the face-centered cubic (FCC) austenite γ matrix. The highest stresses cause formation of mainly α' phase and ɛ-martensite, and both are involved in plastic deformation processes and promoting crack propagation at the surface. In 310 steel, the crack propagation is based on deformation processes following ɛ-martensitic formation only. Formations of ɛ- and α'-martensites were noted along the fracture surfaces and ahead of the crack tip. The cracks propagated through the ɛ-martensitic plates, which formed along the active slip planes, while α' phase was always found in the high-stress region on the ends of the ligaments from both sides of the crack surfaces undergoing propagation.

  6. An Investigation on Low-Temperature Thermochemical Treatments of Austenitic Stainless Steel in Fluidized Bed Furnace

    Science.gov (United States)

    Haruman, E.; Sun, Y.; Triwiyanto, A.; Manurung, Y. H. P.; Adesta, E. Y.

    2012-03-01

    In this study, the feasibility of using an industrial fluidized bed furnace to perform low-temperature thermochemical treatments of austenitic stainless steels has been studied, with the aim to produce expanded austenite layers with combined wear and corrosion resistance, similar to those achievable by plasma and gaseous processes. Several low-temperature thermochemical treatments were studied, including nitriding, carburizing, combined nitriding-carburizing (hybrid treatment), and sequential carburizing and nitriding. The results demonstrate that it is feasible to produce expanded austenite layers on the investigated austenitic stainless steel by the fluidized bed heat treatment technique, thus widening the application window for the novel low-temperature processes. The results also demonstrate that the fluidized bed furnace is the most effective for performing the hybrid treatment, which involves the simultaneous incorporation of nitrogen and carbon together into the surface region of the component in nitrogen- and carbon-containing atmospheres. Such hybrid treatment produces a thicker and harder layer than the other three processes investigated.

  7. Experimental Determination of the Primary Solidification Phase dependency on the solidification velocity for 17 different austenitic stainless steel compositions

    DEFF Research Database (Denmark)

    Laursen, Birthe Nørgaard; Olsen, Flemming Ove; Yardy, John;

    1997-01-01

    to the austenite phase.Most stainless steels are weldable by conventional welding techniques. However, during laser weldng the solidification velocities can be very much higher than by conventional welding techniques. By increasing the solidification velocity to a critical value known as the transition velocity......, the primary solidification phase is found to change from ferrite to austenite.A novel laser remelting technique has been modified to enable the transition velocity for laser welded austenitic stainless steels to be deermined experimentally and on the basis of results from 17 different alloy compositions...... an equation for the calculation of the transition velocity from alloy composition is proposed....

  8. Unraveling the Effect of Thermomechanical Treatment on the Dissolution of Delta Ferrite in Austenitic Stainless Steels

    Science.gov (United States)

    Rezayat, Mohammad; Mirzadeh, Hamed; Namdar, Masih; Parsa, Mohammad Habibi

    2016-02-01

    Considering the detrimental effects of delta ferrite stringers in austenitic stainless steels and the industrial considerations regarding energy consumption, investigating, and optimizing the kinetics of delta ferrite removal is of vital importance. In the current study, a model alloy prone to the formation of austenite/delta ferrite dual phase microstructure was subjected to thermomechanical treatment using the wedge rolling test aiming to dissolve delta ferrite. The effect of introducing lattice defects and occurrence of dynamic recrystallization (DRX) were investigated. It was revealed that pipe diffusion is responsible for delta ferrite removal during thermomechanical process, whereas when the DRX is dominant, the kinetics of delta ferrite dissolution tends toward that of the static homogenization treatment for delta ferrite removal that is based on the lattice diffusion of Cr and Ni in austenite. It was concluded that the optimum condition for dissolution of delta ferrite can be defined by the highest rolling temperature and strain in which DRX is not pronounced.

  9. Swelling analysis of austenitic stainless steels by means of ion irradiation and kinetic modeling

    Energy Technology Data Exchange (ETDEWEB)

    Kohyama, Akira [Kyoto Univ., Institute of Advanced Energy, Uji, Kyoto (Japan); Donomae, Takako [Japan Nuclear Cycle Development Inst., Oarai, Ibaraki (Japan). Oarai Engineering Center

    1999-03-01

    The influences of irradiation environment on the swelling behavior of austenitic stainless steel has been studied, to aid understanding the origin of the difference in swelling response of PNC316 stainless steel in fuel-pin environment and in materials irradiation capsules, in terms of irradiation conditions, damage mechanism and material conditions. This work focused on the theoretical investigation of the influence of temperature variation on microstructural development of austenitic stainless steels during irradiation, using a kinetic rate theory model. A modeling and calculation on non-steady irradiation effects were first carried out. A fully dynamic model of point defect evolution and extended defect development, which accounts for cascade damage, was developed and successfully applied to simulate the interstitial loop evolution in low temperature regimes. The influence of cascade interstitial clustering on dislocation loop formation has also been assessed. The establishment of a basis for general assessment of non-steady irradiation effects in austenitic stainless steels was advanced. The developed model was applied to evaluate the influences of temperature variation in formerly carried out CMIR and FFTF/MFA-1 FBR irradiation experiments. The results suggested the gradual approach of microstructural features to equilibrium states in all the temperature variation conditions and no sign of anomalous behavior was noted. On the other hand, there is the influence of temperature variation on microstructural development under the neutron irradiation, like CMIR. So there are some possibilities of the work of mechanism which is not taken care on this model, for example the effect of the precipitate behavior which is sensitive to irradiation temperature. (author)

  10. Hardness analysis of welded joints of austenitic and duplex stainless steels

    Science.gov (United States)

    Topolska, S.

    2016-08-01

    Stainless steels are widely used in the modern world. The continuous increase in the use of stainless steels is caused by getting greater requirements relating the corrosion resistance of all types of devices. The main property of these steels is the ability to overlap a passive layer of an oxide on their surface. This layer causes that they become resistant to oxidation. One of types of corrosion-resistant steels is ferritic-austenitic steel of the duplex type, which has good strength properties. It is easily formable and weldable as well as resistant to erosion and abrasive wear. It has a low susceptibility to stress-corrosion cracking, to stress corrosion, to intercrystalline one, to pitting one and to crevice one. For these reasons they are used, among others, in the construction of devices and facilities designed for chemicals transportation and for petroleum and natural gas extraction. The paper presents the results which shows that the particular specimens of the ][joint representing both heat affected zones (from the side of the 2205 steel and the 316L one) and the weld are characterized by higher hardness values than in the case of the same specimens for the 2Y joint. Probably this is caused by machining of edges of the sections of metal sheets before the welding process, which came to better mixing of native materials and the filler metal. After submerged arc welding the 2205 steel still retains the diphase, austenitic-ferritic structure and the 316L steel retains the austenitic structure with sparse bands of ferrite σ.

  11. The Formation of Multipoles during the High-Temperature Creep of Austenitic Stainless Steels

    DEFF Research Database (Denmark)

    Howell, J.; Nielsson, O.; Horsewell, Andy

    1981-01-01

    It is shown that multipole dislocation configurations can arise during power-law creep of certain austenitic stainless steels. These multipoles have been analysed in some detail for two particular steels (Alloy 800 and a modified AISI 316L) and it is suggested that they arise either during...... instantaneous loading or during the primary creep stage. Trace analysis has shown that the multipoles are confined to {1 1 1} planes during primary creep but are not necessarily confined to these planes during steady-state creep unless they are pinned by interstitials....

  12. Large size austenitic stainless steel forgings for nuclear and cryogenic application - development, manufacturing and properties

    Energy Technology Data Exchange (ETDEWEB)

    Ohnishi, Keizo; Suzuki, Komei; Sato, Ikuo; Murai, Etuso (Japan Steel Works Ltd., Muroran Plant, Hokkaido (Japan))

    1992-01-01

    The high quality one-piece large austenetic stainless steel forgings are required in the several components such as nuclear reactors and run tanks for rocket engine test stand in order to assure the structural integrity and to make it easy to fabricate and inspect the components. When the austenitic stainless steel forgings are increased in size, various problems must be overcome to assure the high quality forgings. The ingot making and hot working play an important role in determining the quality of the products. In such points, the lastest manufacturing techniques such as steel making of large size ingot and hot working to get uniform and fine grains are discussed together with the fundamental data of the material properties. (orig.).

  13. RESULTS OF CHARACTERIZATION TESTS OF THE SURFACES OF A COMMERCIALLY CARBURIZED AUSTENITIC STAINLESS STEEL

    Energy Technology Data Exchange (ETDEWEB)

    Farrell, K

    2004-01-07

    A commercial surface carburization treatment that shows promise for hardening the surfaces of the stainless steel target vessel of the Spallation Neutron Source against cavitation erosion and pitting caused by the action of pulsed pressure waves in the liquid mercury target has been investigated. To verify promotional claims for the treatment and to uncover any factors that might be of concern for the integrity of a carburized target vessel, some characterization tests of the nature of the surface layers of carburized austenitic 316LN stainless steel were conducted. The findings support most of the claims. The carburized layer is about 35 {micro}m thick. Its indentation hardness is about five times larger than that of the substrate steel and declines rapidly with depth into the layer. The surface is distorted by the treatment, and the austenite lattice is enlarged. The corrosion resistance of the carburized layer in an acid medium is greater than that for untreated austenite. The layer is not brittle; it is plastically deformable and is quite resistant to cracking during straining. Contrary to the provider's assertations, the maximum carbon content of the layer is much less than 6-7 wt% carbon, and the carbon is not simply contained in supersaturated solid solution; some of it is present in a previously unreported iron carbide phase located at the very surface. Large variations were found in the thickness of the layer, and they signify that controls may be needed to ensure a uniform thickness for treatment of the SNS target vessel. Inclusion stringers and {delta}-ferrite phase embraced in the treated layer are less resistant to chemical attack than the treated austenite. From a cavitation pitting perspective under SNS bombardment, such non-austenitic phases may provide preferential sites for pitting. The shallow depth of the hardened layer will require use of protection measures to avoid mishandling damage to the layer during assembly and installation of a

  14. Crack growth rates and fracture toughness of irradiated austenitic stainless steels in BWR environments.

    Energy Technology Data Exchange (ETDEWEB)

    Chopra, O. K.; Shack, W. J.

    2008-01-21

    In light water reactors, austenitic stainless steels (SSs) are used extensively as structural alloys in reactor core internal components because of their high strength, ductility, and fracture toughness. However, exposure to high levels of neutron irradiation for extended periods degrades the fracture properties of these steels by changing the material microstructure (e.g., radiation hardening) and microchemistry (e.g., radiation-induced segregation). Experimental data are presented on the fracture toughness and crack growth rates (CGRs) of wrought and cast austenitic SSs, including weld heat-affected-zone materials, that were irradiated to fluence levels as high as {approx} 2x 10{sup 21} n/cm{sup 2} (E > 1 MeV) ({approx} 3 dpa) in a light water reactor at 288-300 C. The results are compared with the data available in the literature. The effects of material composition, irradiation dose, and water chemistry on CGRs under cyclic and stress corrosion cracking conditions were determined. A superposition model was used to represent the cyclic CGRs of austenitic SSs. The effects of neutron irradiation on the fracture toughness of these steels, as well as the effects of material and irradiation conditions and test temperature, have been evaluated. A fracture toughness trend curve that bounds the existing data has been defined. The synergistic effects of thermal and radiation embrittlement of cast austenitic SS internal components have also been evaluated.

  15. Intergranular Corrosion Behavior of Low-Nickel and 304 Austenitic Stainless Steels

    Science.gov (United States)

    Bansod, Ankur V.; Patil, Awanikumar P.; Moon, Abhijeet P.; Khobragade, Nilay N.

    2016-09-01

    Intergranular corrosion (IGC) susceptibility for Cr-Mn austenitic stainless steel and 304 austenitic stainless steel (ASS) was estimated using electrochemical techniques. Optical and SEM microscopy studies were carried out to investigate the nature of IGC at 700 °C with increasing time (15, 30, 60, 180, 360, 720, 1440 min) according to ASTM standard 262 A. Quantitative analysis was performed to estimate the degree of sensitization (DOS) using double loop electrochemical potentiokinetic reactivation (DLEPR) and EIS technique. DLEPR results indicated that with the increase in thermal aging duration, DOS becomes more severe for both types of stainless steel. The DOS for Cr-Mn ASS was found to be higher (65.12% for 1440 min) than that of the AISI 304 ASS (23% for 1440 min). The higher degree of sensitization resulted in lowering of electrical charge capacitance resistance. Chronoamperometry studies were carried out at a passive potential of 0.4 V versus SCE and was observed to have a higher anodic dissolution of the passive film of Cr-Mn ASS. EDS studies show the formation of chromium carbide precipitates in the vicinity of the grain boundary. The higher Mn content was also observed for Cr-Mn ASS at the grain boundary.

  16. Effects of the Process Parameters on Austenitic Stainless Steel by TIG-Flux Welding

    Institute of Scientific and Technical Information of China (English)

    Heryueh HUANG; Shengwen SHYU; Kuanghung TSENG; Changpin CHOU

    2006-01-01

    The effects of the process parameters of TIG (tungsten inset gas)-flux welding on the welds morphology,angular distortion, ferrite content and hot cracking in austenitic stainless steel were investigated. Autogenous TIG welding process was applied to the type 304 stainless steel through a thin layer of activating flux to produce a bead on plate welded joint. TiO2, SiO2, Fe2O3, Cr2O3, ZnO and MnO2 were used as the activating fluxes. The experimental results indicated that the TIG-flux welding can increase the weld depth/width ratio and reduce the HAZ (heat affected zone) range, and therefore the angular distortion of the weldment can be reduced. It was also found that the retained ferrite content within the TIG-flux welds is increased, and has a beneficial effect in reducing hot cracking tendency for stainless steels of the austenitic type weld metals. A plasma column constriction increases the current density at the anode spot and then a substantial increase in penetration of the TIG-flux welds can be obtained.

  17. Internal hydrogen-induced subcritical crack growth in austenitic stainless steels

    Science.gov (United States)

    Huang, J. H.; Altstetter, C. J.

    1991-11-01

    The effects of small amounts of dissolved hydrogen on crack propagation were determined for two austenitic stainless steel alloys, AISI 301 and 310S. In order to have a uniform distribution of hydrogen in the alloys, they were cathodically charged at high temperature in a molten salt electrolyte. Sustained load tests were performed on fatigue precracked specimens in air at 0 ‡C, 25 ‡C, and 50 ‡C with hydrogen contents up to 41 wt ppm. The electrical potential drop method with optical calibration was used to continuously monitor the crack position. Log crack velocity vs stress intensity curves had definite thresholds for subcritical crack growth (SCG), but stage II was not always clearly delineated. In the unstable austenitic steel, AISI 301, the threshold stress intensity decreased with increasing hydrogen content or increasing temperature, but beyond about 10 wt ppm, it became insensitive to hydrogen concentration. At higher concentrations, stage II became less distinct. In the stable stainless steel, subcritical crack growth was observed only for a specimen containing 41 wt ppm hydrogen. Fractographic features were correlated with stress intensity, hydrogen content, and temperature. The fracture mode changed with temperature and hydrogen content. For unstable austenitic steel, low temperature and high hydrogen content favored intergranular fracture while microvoid coalescence dominated at a low hydrogen content. The interpretation of these phenomena is based on the tendency for stress-induced phase transformation, the different hydrogen diffusivity and solubility in ferrite and austenite, and outgassing from the crack tip. After comparing the embrittlement due to internal hydrogen with that in external hydrogen, it is concluded that the critical hydrogen distribution for the onset of subcritical crack growth is reached at a location that is very near the crack tip.

  18. Analysis of Magnetism in High Nitrogen Austenitic Stainless Steel and Its Elimination by High Temperature Gas Nitriding

    Institute of Scientific and Technical Information of China (English)

    Peng Wan; Yibin Ren; Bingchun Zhang; Ke Yang

    2011-01-01

    Stable austenitic structure in medical stainless steels is basically required for surgical implantation. A weak magnetism was found in a high nitrogen nickel-free austenitic stainless steel for cardiovascular stent application. This magnetic behavior in high nitrogen stainless steel was investigated by optical microscopy, X-ray diffraction (XRD), electron probe microanalysis (EPMA) and superconducting quantum interference device (SQUID). The results showed that the magnetism came from the composition segregation of ferrite formation elements such as Cr and Mo in the steel and some δ-ferrites were locally formed during the pressurized electroslag remelting process. The magnetism of high nitrogen stainless steel could be eliminated by a proper high temperature gas nitriding (HTGN).

  19. Enhanced mechanical properties of type AISI301LN austenitic stainless steel through advanced thermo mechanical process

    Energy Technology Data Exchange (ETDEWEB)

    Huang Junxia, E-mail: huangjunxia@baosteel.com [Shanghai Baosteel Research Institute, Shanghai 200431 (China); Ye Xiaoning; Gu Jiaqing; Chen Xu [Shanghai Baosteel Research Institute, Shanghai 200431 (China); Xu Zhou [School of Material Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240 (China)

    2012-01-15

    Highlights: Black-Right-Pointing-Pointer 69% of strain induced martensite were obtained after 80% thickness reduction at 0 Degree-Sign C. Black-Right-Pointing-Pointer The best annealing regime was determined for diffusional controlled reversion. Black-Right-Pointing-Pointer The effect of grain size on mechanical properties conforms with the H-P relationship. - Abstract: The effect of annealing temperature and time on the grain size of reversed austenite and mechanical properties was studied based on AISI301LN austenitic stainless steel in this paper. Cold rolling at 0 Degree-Sign C was employed to obtain the strain-induced martensite, followed by annealing treatment at the temperature range of 650-900 Degree-Sign C for 1-20 min. The relationship between the volume fraction of strain-induced martensite and cold reduction was analyzed by Ferritescope MP30 and X-ray diffraction. The grain growth of reversed austenite was observed by FEG-SEM and the mechanical properties were determined by tensile tests and Vickers hardness tests. Austenite grain sizes under 3 {mu}m can be obtained after annealing in the range of 700-900 Degree-Sign C for 1-20 min. The finest austenite grain size was produced after annealing at 700 Degree-Sign C for 20 min, which had a good combination of yield strength ( Almost-Equal-To 830 MPa), tensile strength ( Almost-Equal-To 953 MPa) and elongation ( Almost-Equal-To 36%).

  20. Evaluation of the corrosion resistance of plasma nitrided austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Mareci, Daniel; Bolat, Georgiana [Technical Univ. Iasi (Romania). Faculty of Chemical Engineering and Environmental Protection; Strugaru, Sorin Iacob; Munteanu, Corneliu [Technical Univ. Iasi (Romania). Faculty of Mechanical Engineering; Souto, Ricardo M. [Univ. of La Laguna, Tenerife (Spain). Dept. of Chemistry

    2015-03-15

    Plasma nitriding at 500 C for 14 h was applied to austenitic 304 stainless steel for surface hardening. The effect of surface treatment on the corrosion resistance of the material was investigated in naturally-aerated 0.5 M NaCl solution for 30 days using linear potentiodynamic polarization and electrochemical impedance spectroscopy methods. Both as-cast and plasma nitrided stainless steel samples underwent spontaneous passivation, though the nitrided sample exhibited more positive zero current potential, higher breakdown potential, and lower anodic current densities than the as-cast material. Impedance spectra were interpreted in terms of a duplex passive film, corrosion resistance mainly arising from a thin inner compact layer, whereas the outer layer was more porous and less sealing. Capacitive behaviour and high corrosion resistance were observed in the low and medium frequency ranges for the nitrided samples.

  1. Effect Of Temperature Variation On Wear Behaviour Of Austenitic Stainless Steel

    Science.gov (United States)

    Alias, S. K.; Ahmad, S.; Abdullah, B.; Pahroraji, H. F.; Hamami, G.

    2016-11-01

    The effects of boronizing temperatures on the wear and hardness properties of austenitic stainless steel were investigated in this study. The samples were prepared in accordance to standard samples preparation for wear and hardness test. Pack boronizing were conducted using EKabor®1 powder medium at two different temperatures which are 850°C and 950°C. The wear resistance properties were evaluated though pin on disk test and the surface characterization was analyzed through scanning electron microscopy (SEM), observation. Vickers microhardness tester was performed to obtain the hardness of the samples. The results indicated that there are presences of FeB and Fe2B phases on both samples, but thicker FeB phase was produced at Po-950 samples. This resulted in reduction of abrasion wear properties but major improvement of the hardness properties of boronized stainless steel.

  2. Synergistic Computational and Microstructural Design of Next- Generation High-Temperature Austenitic Stainless Steels

    Energy Technology Data Exchange (ETDEWEB)

    Karaman, Ibrahim [Texas A& M Engineering Experiment Station, College Station, TX (United States); Arroyave, Raymundo [Texas A& M Engineering Experiment Station, College Station, TX (United States)

    2015-07-31

    The purpose of this project was to: 1) study deformation twinning, its evolution, thermal stability, and the contribution on mechanical response of the new advanced stainless steels, especially at elevated temperatures; 2) study alumina-scale formation on the surface, as an alternative for conventional chromium oxide, that shows better oxidation resistance, through alloy design; and 3) design new generation of high temperature stainless steels that form alumina scale and have thermally stable nano-twins. The work involved few baseline alloys for investigating the twin formation under tensile loading, thermal stability of these twins, and the role of deformation twins on the mechanical response of the alloys. These baseline alloys included Hadfield Steel (Fe-13Mn-1C), 316, 316L and 316N stainless steels. Another baseline alloy was studied for alumina-scale formation investigations. Hadfield steel showed twinning but undesired second phases formed at higher temperatures. 316N stainless steel did not show signs of deformation twinning. Conventional 316 stainless steel demonstrated extensive deformation twinning at room temperature. Investigations on this alloy, both in single crystalline and polycrystalline forms, showed that deformation twins evolve in a hierarchical manner, consisting of micron–sized bundles of nano-twins. The width of nano-twins stays almost constant as the extent of strain increases, but the width and number of the bundles increase with increasing strain. A systematic thermomechanical cycling study showed that the twins were stable at temperatures as high as 900°C, after the dislocations are annealed out. Using such cycles, volume fraction of the thermally stable deformation twins were increased up to 40% in 316 stainless steel. Using computational thermodynamics and kinetics calculations, we designed two generations of advanced austenitic stainless steels. In the first generation, Alloy 1, which had been proposed as an alumina

  3. Effects of high-pressure hydrogen charging on the structure of austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Hoelzel, M. [Institute for Materials Science, Darmstadt University of Technology, Petersenstrasse 23, 64287 Darmstadt (Germany)]. E-mail: Markus.Hoelzel@frm2.tum.de; Danilkin, S.A. [Hahn-Meitner-Institut, SF2, Glienicker Str. 100, 14109 Berlin (Germany); Ehrenberg, H. [Institute for Materials Science, Darmstadt University of Technology, Petersenstrasse 23, 64287 Darmstadt (Germany); Toebbens, D.M. [Hahn-Meitner-Institut, SF2, Glienicker Str. 100, 14109 Berlin (Germany); Udovic, T.J. [NIST Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, MS 8562, Gaithersburg, MD 20899-8562 (United States); Fuess, H. [Institute for Materials Science, Darmstadt University of Technology, Petersenstrasse 23, 64287 Darmstadt (Germany); Wipf, H. [Darmstadt University of Technology, Institute for Solid State Physics, Hochschulstrasse 6, 64289 Darmstadt (Germany)

    2004-10-25

    The effects of high-pressure hydrogen and deuterium charging on the structure of AISI type 304 and AISI type 310 austenitic stainless steels have been investigated by neutron and X-ray diffraction. Rietveld analyses of the neutron diffraction data revealed that hydrogen atoms occupy exclusively the octahedral interstitial sites in both steels. No phase transformations have been observed in 310 stainless steel within the whole range of hydrogen-to-metal atomic ratios H/Me up to {approx} 1. In 304 stainless steel, the formation of {epsilon}-martensite was observed not only after hydrogenation at 3.0 GPa (H/Me = 0.56), but also after applying a pressure of 4.0 GPa without hydrogen. The results differ significantly from published studies on cathodically hydrogenated samples, where high amounts of {epsilon}-martensite were observed in both steels. High-pressure hydrogenation and cathodic hydrogen charging result in different phase transformation behaviour. The discrepancies can be explained by different hydrogen distributions resulting in quite different stress states.

  4. Laser etching of austenitic stainless steels for micro-structural evaluation

    Science.gov (United States)

    Baghra, Chetan; Kumar, Aniruddha; Sathe, D. B.; Bhatt, R. B.; Behere, P. G.; Afzal, Mohd

    2015-06-01

    Etching is a key step in metallography to reveal microstructure of polished specimen under an optical microscope. A conventional technique for producing micro-structural contrast is chemical etching. As an alternate, laser etching is investigated since it does not involve use of corrosive reagents and it can be carried out without any physical contact with sample. Laser induced etching technique will be beneficial especially in nuclear industry where materials, being radioactive in nature, are handled inside a glove box. In this paper, experimental results of pulsed Nd-YAG laser based etching of few austenitic stainless steels such as SS 304, SS 316 LN and SS alloy D9 which are chosen as structural material for fabrication of various components of upcoming Prototype Fast Breeder Reactor (PFBR) at Kalpakkam India were reported. Laser etching was done by irradiating samples using nanosecond pulsed Nd-YAG laser beam which was transported into glass paneled glove box using optics. Experiments were carried out to understand effect of laser beam parameters such as wavelength, fluence, pulse repetition rate and number of exposures required for etching of austenitic stainless steel samples. Laser etching of PFBR fuel tube and plug welded joint was also carried to evaluate base metal grain size, depth of fusion at welded joint and heat affected zone in the base metal. Experimental results demonstrated that pulsed Nd-YAG laser etching is a fast and effortless technique which can be effectively employed for non-contact remote etching of austenitic stainless steels for micro-structural evaluation.

  5. Effects of Strain Rate and Plastic Work on Martensitic Transformation Kinetics of Austenitic Stainless Steel 304

    Institute of Scientific and Technical Information of China (English)

    Fang PENG; Xiang-huai DONG; Kai LIU; Huan-yang XIE

    2015-01-01

    The martensitic transformation behavior and mechanical properties of austenitic stainless steel 304 were studied by both experiments and numerical simulation. Room temperature tensile tests were carried out at various strain rates to investigate the effect on volume fraction of martensite, temperature increase and flow stress. The results show that with increasing strain rate, the local temperature increases, which suppresses the transformation of martensite. To take into account the dependence on strain level, strain rate sensitivity and thermal effects, a kinetic model of martensitic transformation was proposed and constitutive modeling on stress-strain response was conducted. The validity of the proposed model has been proved by comparisons between simulation results and experimental ones.

  6. Microstructural evolution and change in hardness during creep of NF709 austenitic stainless steel

    Institute of Scientific and Technical Information of China (English)

    Yan ZHAO; Jie ZHAO; Xiaona LI

    2011-01-01

    Microstructural evolution and the change in hardness during creep deformation of NF709 austenitic stainless steel were investigated. Creep tests were carried out at 650 ℃ for 2932 h under a load of 210 MPa for comparison with aging specimen at 650 ℃ for 3000 h. The hardness results indicated that applied stress during creep process induced hardness increase. Analysis of longitudinal section microstructure showed that the creep damage caused by pores and the grain boundary hardening caused by elongated grains could be the factors leading to hardness differences. The G phase dispersedly precipitated in intragranular and interacted with dislocations during creep process, indicating strain hardening.

  7. Deformation and Damage Mechanisms in Ultrafine-Grained Austenitic Stainless Steel During Cyclic Straining

    Science.gov (United States)

    Hamada, Atef S.

    2013-04-01

    The ultrafine-grained (UFG) structure of an austenitic stainless steel (Type 301LN), processed by controlled phase-reversion annealing, was fatigued to study the deformation and damage mechanisms during cyclic straining. Fatigue cracking along the grain boundaries and the formation of extended persistent slip band-like shear bands (SBs) were observed to be the fatigue-induced microstructural features in the ultrafine-grained structure. Characterization of SBs was performed by electron backscattered diffraction and atomic force microscopy to study the fine features.

  8. Fatigue damage evaluation of austenitic stainless steel using nonlinear ultrasonic waves in low cycle regime

    Science.gov (United States)

    Zhang, Jianfeng; Xuan, Fu-Zhen

    2014-05-01

    The interrupted low cycle fatigue test of austenitic stainless steel was conducted and the dislocation structure and fatigue damage was evaluated subsequently by using both transmission electron microscope and nonlinear ultrasonic wave techniques. A "mountain shape" correlation between the nonlinear acoustic parameter and the fatigue life fraction was achieved. This was ascribed to the generation and evolution of planar dislocation structure and nonplanar dislocation structure such as veins, walls, and cells. The "mountain shape" correlation was interpreted successfully by the combined contribution of dislocation monopole and dipole with an internal-stress dependent term of acoustic nonlinearity.

  9. Joining silicon carbide to austenitic stainless steel through diffusion welding; Stellingen behorende bij het proefschrift

    Energy Technology Data Exchange (ETDEWEB)

    Krugers, Jan-Paul

    1993-01-19

    In this thesis, the results are presented of a study dealing with joining silicon carbide to austenitic stainless steel AIS316 by means of diffusion welding. Welding experiments were carried out without and with the use of a metallic intermediate, like copper, nickel and copper-nickel alloys at various conditions of process temperature, process time, mechanical pressure and interlayer thickness. Most experiments were carried out in high vacuum. For reasons of comparison, however, some experiments were also carried out in a gas shielded environment of 95 vol.% Ar and 5 vol.% H2.

  10. Improved Accident Tolerance of Austenitic Stainless Steel Cladding through Colossal Supersaturation with Interstitial Solutes

    Energy Technology Data Exchange (ETDEWEB)

    Ernst, Frank [Case Western Reserve Univ., Cleveland, OH (United States)

    2016-10-13

    We proposed a program-supporting research project in the area of fuel-cycle R&D, specifically on the topic of advanced fuels. Our goal was to investigate whether SECIS (surface engineering by concentrated interstitial solute – carbon, nitrogen) can improve the properties of austenitic stainless steels and related structural alloys such that they can be used for nuclear fuel cladding in LWRs (light-water reactors) and significantly excel currently used alloys with regard to performance, safety, service life, and accident tolerance.

  11. Micromagnetic and Mössbauer spectroscopic investigation of strain-induced martensite in austenitic stainless steel

    Science.gov (United States)

    Mészáros, L.; Kéldor, M.; Hidasi, B.; Vértes, A.; Czakó-Nagy, I.

    1996-08-01

    Strain-induced martensite in 18/8 austenitic stainless steel was studied. Magnetic measurements and Mössbauer spectroscopic investigations were performed to characterize the amount of α’-martensite due to room-temperature plastic tensile loading. The effects of cold work and annealing heat treatment were explored using magnetic Barkhausen noise, saturation polarization, coercive force, hardness, and conversion electron Mössbauer spectra measurements. The results of the magnetic measurements were compared to results obtained by Mössbauer spectroscopy. The suggested Barkhausen noise measurement technique proved to be a useful quantitative and nondestructive method for determining the ferromagnetic phase ratio of the studied alloy.

  12. OPTIMIZATION OF SURFACE ROUGHNESS OF AISI 304 AUSTENITIC STAINLESS STEEL IN DRY TURNING OPERATION USING TAGUCHI DESIGN METHOD

    Directory of Open Access Journals (Sweden)

    D. PHILIP SELVARAJ

    2010-09-01

    Full Text Available The present work is concentrated with the dry turning of AISI 304 Austenitic Stainless Steel (ASS. This paper presents the influence of cutting parameters like cutting speed, feed rate and depth of cut on the surface roughness of austenitic stainless steel during dry turning. A plan of experiments based on Taguchi’s technique has been used to acquire the data. An orthogonal array, the signal to noise (S/N ratio and the analysis of variance (ANOVA are employed to investigate the cutting characteristics of AISI 304 austenitic stainless steel bars using TiC and TiCN coated tungsten carbide cutting tool. Finally the confirmation tests that have been carried out to compare the predicted values with the experimental values confirm its effectiveness in the analysis of surface roughness.

  13. Effect of Austenitic and Austeno-Ferritic Electrodes on 2205 Duplex and 316L Austenitic Stainless Steel Dissimilar Welds

    Science.gov (United States)

    Verma, Jagesvar; Taiwade, Ravindra V.

    2016-09-01

    This study addresses the effect of different types of austenitic and austeno-ferritic electrodes (E309L, E309LMo and E2209) on the relationship between weldability, microstructure, mechanical properties and corrosion resistance of shielded metal arc welded duplex/austenitic (2205/316L) stainless steel dissimilar joints using the combined techniques of optical, scanning electron microscope, energy-dispersive spectrometer and electrochemical. The results indicated that the change in electrode composition led to microstructural variations in the welds with the development of different complex phases such as vermicular ferrite, lathy ferrite, widmanstatten and intragranular austenite. Mechanical properties of welded joints were diverged based on compositions and solidification modes; it was observed that ferritic mode solidified weld dominated property wise. However, the pitting corrosion resistance of all welds showed different behavior in chloride solution; moreover, weld with E2209 was superior, whereas E309L exhibited lower resistance. Higher degree of sensitization was observed in E2209 weld, while lesser in E309L weld. Optimum ferrite content was achieved in all welds.

  14. Effect of Austenitic and Austeno-Ferritic Electrodes on 2205 Duplex and 316L Austenitic Stainless Steel Dissimilar Welds

    Science.gov (United States)

    Verma, Jagesvar; Taiwade, Ravindra V.

    2016-11-01

    This study addresses the effect of different types of austenitic and austeno-ferritic electrodes (E309L, E309LMo and E2209) on the relationship between weldability, microstructure, mechanical properties and corrosion resistance of shielded metal arc welded duplex/austenitic (2205/316L) stainless steel dissimilar joints using the combined techniques of optical, scanning electron microscope, energy-dispersive spectrometer and electrochemical. The results indicated that the change in electrode composition led to microstructural variations in the welds with the development of different complex phases such as vermicular ferrite, lathy ferrite, widmanstatten and intragranular austenite. Mechanical properties of welded joints were diverged based on compositions and solidification modes; it was observed that ferritic mode solidified weld dominated property wise. However, the pitting corrosion resistance of all welds showed different behavior in chloride solution; moreover, weld with E2209 was superior, whereas E309L exhibited lower resistance. Higher degree of sensitization was observed in E2209 weld, while lesser in E309L weld. Optimum ferrite content was achieved in all welds.

  15. Effect of martensite to austenite reversion on the formation of nano/submicron grained AISI 301 stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Karimi, M.; Najafizadeh, A. [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Kermanpur, A., E-mail: ahmad_k@cc.iut.ac.ir [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Eskandari, M. [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of)

    2009-11-15

    The martensite to austenite reversion behavior of 90% cold rolled AISI 301 stainless steel was investigated in order to refine the grain size. Cold rolled specimens were annealed at 600-900 deg. C, and subsequently characterized by scanning electron microscopy, X-ray diffraction, Feritscope, and hardness measurements. The effects of annealing parameters on the formation of fully-austenitic nano/submicron grained structure and the mechanisms involved were studied. It was found that annealing at 800 deg. C for 10 s exhibited the smallest average austenite grain size of 240 {+-} 60 nm with an almost fully-austenitic structure.

  16. High Nitrogen Austenitic Stainless Steels Manufactured by Nitrogen Gas Alloying and Adding Nitrided Ferroalloys

    Institute of Scientific and Technical Information of China (English)

    LI Hua-bing; JIANG Zhou-hua; SHEN Ming-hui; YOU Xiang-mi

    2007-01-01

    A simple and feasible method for the production of high nitrogen austenitic stainless steels involves nitrogen gas alloying and adding nitrided ferroalloys under normal atmospheric conditions. Alloying by nitrogen gas bubbling in Fe-Cr-Mn-Mo series alloys was carried out in MoSi2 resistance furnace and air induction furnace under normal atmospheric conditions. The results showed that nitrogen alloying could be accelerated by increasing nitrogen gas flow rate, prolonging residence time of bubbles, increasing gas/molten steel interfaces, and decreasing the sulphur and oxygen contents in molten steel. Nitrogen content of 0.69% in 18Cr18Mn was obtained using air induction furnace by bubbling of nitrogen gas from porous plug. In addition, the nickel-free, high nitrogen austenitic stainless steels with sound and compact macrostructure had been produced in the laboratory using vacuum induction furnace and electroslag remelting furnace under nitrogen atmosphere by the addition of nitrided alloy with the maximum nitrogen content of 0.81 %. Pores were observed in the ingots obtained by melting and casting in vacuum induction furnace with the addition of nitrided ferroalloys and under nitrogen atmosphere. After electroslag remelting of the cast ingots, they were all sound and were free of pores. The yield of nitrogen increased with the decrease of melting rate in the ESR process. Due to electroslag remelting under nitrogen atmosphere and the consequential addition of aluminum as deoxidizer to the slag, the loss of manganese decreased obviously. There existed mainly irregular Al2O3 inclusions and MnS inclusions in ESR ingots, and the size of most of the inclusions was less than 5 μm. After homogenization of the hot rolled plate at 1 150 ℃× 1 h followed by water quenching, the microstructure consisted of homogeneous austenite.

  17. HEALING OF HYDROGEN ATTACK CRACK IN AUSTENITE STAINLESS STEEL UNDER HEAT TREATMENT

    Institute of Scientific and Technical Information of China (English)

    X.G. Li; C.F. Dong; H. Chen

    2002-01-01

    The specimens of 304 austenite stainless steel with the hydrogen attack bubbles orcracks were heat treated at 600℃ for 6h. The SEM and TEM observations on thespecimens before and after the heat treatment showed that the bubbles or cracks could behealed completely by heat treatment. The healing of hydrogen attack bubbles or cracksis closely related to heat diffusion of Fe and C atoms in austenite. The driving forceof crack healing results fram the plastic deforming energy Es induced by the growthof hydrogen attack bubbles or cracks. The critical condition of healing of bubbles orcracks is Es ≥ 2γ/r (where γγ is the surface tension, r is the radius of bubbles or halflength of crack). During healing of the hydrogen attack bubbles or cracks, the recovery,polygonization and recrystallization of the sub-grain also occured.

  18. A powder metallurgy austenitic stainless steel for application at very low temperatures

    CERN Document Server

    Sgobba, Stefano; Liimatainen, J; Kumpula, M

    2000-01-01

    The Large Hadron Collider to be built at CERN will require 1232 superconducting dipole magnets operating at 1.9 K. By virtue of their mechanical properties, weldability and improved austenite stability, nitrogen enriched austenitic stainless steels have been chosen as the material for several of the structural components of these magnets. Powder Metallurgy (PM) could represent an attractive production technique for components of complex shape for which dimension tolerances, dimensional stability, weldability are key issues during fabrication, and mechanical properties, ductility and leak tightness have to be guaranteed during operation. PM Hot Isostatic Pressed test plates and prototype components of 316LN-type grade have been produced by Santasalo Powdermet Oy. They have been fully characterized and mechanically tested down to 4.2 K at CERN. The fine grained structure, the absence of residual stresses, the full isotropy of mechanical properties associated to the low level of Prior Particle Boundaries oxides ...

  19. OPTIMIZATION OF SURFACE ROUGHNESS OF AISI 304 AUSTENITIC STAINLESS STEEL IN DRY TURNING OPERATION USING TAGUCHI DESIGN METHOD

    OpenAIRE

    D. PHILIP SELVARAJ; Chandramohan, P.

    2010-01-01

    The present work is concentrated with the dry turning of AISI 304 Austenitic Stainless Steel (ASS). This paper presents the influence of cutting parameters like cutting speed, feed rate and depth of cut on the surface roughness of austenitic stainless steel during dry turning. A plan of experiments based on Taguchi’s technique has been used to acquire the data. An orthogonal array, the signal to noise (S/N) ratio and the analysis of variance (ANOVA) are employed to investigate the cutting cha...

  20. Investigation of corrosion of welded joints of austenitic and duplex stainless steels

    Science.gov (United States)

    Topolska, S.

    2016-08-01

    Investigation of corrosion resistance of materials is one of the most important tests that allow determining their functional properties. Among these tests the special group consist electrochemical investigations, which let to accelerate the course of the process. These investigations allow rapidly estimating corrosion processes occurring in metal elements under the influence of the analysed environment. In the paper are presented results of investigations of the resistance to pitting corrosion of the steel of next grades: austenitic 316L and duplex 2205. It was also analysed the corrosion resistance of welded joints of these grades of steel. The investigations were conducted in two different corrosion environments: in the neutral one (3.5 % sodium chloride) and in the aggressive one (0.1 M sulphuric acid VI). The obtained results indicate different resistance of analysed grades of steel and their welded joints in relation to the corrosion environment. The austenitic 316L steel characterizes by the higher resistance to the pitting corrosion in the aggressive environment then the duplex 2205 steel. In the paper are presented results of potentiodynamic tests. They showed that all the specimens are less resistant to pitting corrosion in the environment of sulphuric acid (VI) than in the sodium chloride one. The 2205 steel has higher corrosion resistance than the 316L stainless steel in 3.5% NaCl. On the other hand, in 0.1 M H2SO4, the 316L steel has a higher corrosion resistance than the 2205 one. The weld has a similar, very good resistance to pitting corrosion like both steels.

  1. Influence of austenitizing temperature on microstructure and mechanical properties of AISI 431 martensitic stainless steel electron beam welds

    Energy Technology Data Exchange (ETDEWEB)

    Rajasekhar, A. [Department of Mechanical Engineering, SVITS, Mahaboob Nagar 509 001 (India)], E-mail: adula.rajasekhar@rediffmail.com; Madhusudhan Reddy, G.; Mohandas, T. [Defence Metallurgical Research Laboratory, Hyderabad 500 058 (India); Murti, V.S.R. [Department of Mechanical Engineering, SVITS, Mahaboob Nagar 509 001 (India)

    2009-05-15

    The relative effects of various austenitizing temperatures on microstructure and mechanical properties of electron beam welds of AISI 431martensitic stainless steel were studied. The post-weld heat treatments consist of austenitizing the weld samples for 1 h at various temperatures, i.e., at 950 deg. C, 1000 deg. C, 1050 deg. C, 1100 deg. C and at 1150 deg. C and air cooling followed by double tempering, i.e., tempering at 670 + 600 deg. C. In the as-welded condition the microstructure contains dendritic structure with ferrite network and retained austenite in a matrix of un-tempered martensite. The prior austenite grain size increased with increase in austenitizing temperature. Parent metal grain size was coarser as compared to grain size in the weld zone in respective conditions. Retained austenite content increased with increase in the austenitizing temperature. Presence of undissolved carbides was observed in welds and parent metal austenitized up to 1000 deg. C and they dissolved at austenitizing temperature {>=} 1050 deg. C. Coarsening of martensite laths was observed after tempering. The martensite laths were coarser in the samples subjected to higher austenitizing temperatures. Optimum mechanical properties, i.e., strength, hardness and toughness were observed when austenitized between 1050 deg. C and 1100 deg. C followed by tempering. Austenitizing at 1150 deg. C and tempering resulted in inferior mechanical properties. The mechanism for the observed trends is discussed in relation to the microstructure, fracture features and mechanical properties.

  2. Review of environmental effects on fatigue crack growth of austenitic stainless steels.

    Energy Technology Data Exchange (ETDEWEB)

    Shack, W. J.; Kassner, T. F.; Energy Technology

    1994-07-11

    Fatigue and environmentally assisted cracking of piping, pressure vessel cladding, and core components in light water reactors are potential concerns to the nuclear industry and regulatory agencies. The degradation processes include intergranular stress corrosion cracking of austenitic stainless steel (SS) piping in boiling water reactors (BWRs), and propagation of fatigue or stress corrosion cracks (which initiate in sensitized SS cladding) into low-alloy ferritic steels in BWR pressure vessels. Crack growth data for wrought and cast austenitic SSs in simulated BWR water, developed at Argonne National Laboratory under US Nuclear Regulatory Commission sponsorship over the past 10 years, have been compiled into a data base along with similar data obtained from the open literature. The data were analyzed to develop corrosion-fatigue curves for austenitic SSs in aqueous environments corresponding to normal BWR water chemistries, for BWRs that add hydrogen to the feedwater, and for pressurized water reactor primary-system-coolant chemistry. The corrosion-fatigue data and curves in water were compared with the air line in Section XI of the ASME Code.

  3. Cutting Properties of Austenitic Stainless Steel by Using Laser Cutting Process without Assist Gas

    Directory of Open Access Journals (Sweden)

    Hitoshi Ozaki

    2012-01-01

    Full Text Available Recently, laser cutting is used in many industries. Generally, in laser cutting of metallic materials, suitable assist gas and its nozzle are needed to remove the molten metal. However, because of the gas nozzle should be set closer to the surface of a workpiece, existence of the nozzle seems to prevent laser cutting from being used flexible. Therefore, the new cutting process, Assist Gas Free laser cutting or AGF laser cutting, has been developed. In this process, the pressure at the bottom side of a workpiece is reduced by a vacuum pump, and the molten metal can be removed by the air flow caused by the pressure difference between both sides of the specimen. In this study, cutting properties of austenitic stainless steel by using AGF laser cutting with 2 kW CO2 laser were investigated. Laser power and cutting speed were varied in order to study the effect of these parameters on cutting properties. As a result, austenitic stainless steel could be cut with dross-free by AGF laser cutting. When laser power was 2.0 kW, cutting speed could be increased up to 100 mm/s, and kerf width at specimen surface was 0.28 mm.

  4. Impact Toughness Properties of Nickel- and Manganese-Free High Nitrogen Austenitic Stainless Steels

    Science.gov (United States)

    Mohammadzadeh, Roghayeh; Akbari, Alireza; Mohammadzadeh, Mina

    2016-12-01

    A large amount of manganese (>10 wt pct) in nickel-free high nitrogen austenitic stainless steels (Ni-free HNASSs) can induce toxicity. In order to develop Ni-free HNASSs with low or no manganese, it is necessary to investigate their mechanical properties for biomedical applications. This work aims to study the Charpy V-notch (CVN) impact toughness properties of a Ni- and Mn-free Fe-22.7Cr-2.4Mo-1.2N HNASS plate in the temperature range of 103 K to 423 K (-170 °C to 150 °C). The results show that unlike conventional AISI 316L austenitic stainless steel, the Ni- and Mn-free HNASS exhibits a sharp ductile-to-brittle transition (DBT). The intergranular brittle fracture associated with some plasticity and deformation bands is observed on the fracture surface at 298 K (25 °C). Electron backscattered diffraction (EBSD) analysis of the impact-tested sample in the longitudinal direction indicates that deformation bands are parallel to {111} slip planes. By decreasing the temperature to 273 K, 263 K, and 103 K (0 °C, -10 °C, and -70 °C), entirely intergranular brittle fracture occurs on the fracture surface. The fracture mode changes from brittle fracture to ductile as the temperature increases to 423 K (150 °C). The decrease in impact toughness is discussed on the basis of temperature sensitivity of plastic flow and planarity of deformation mechanism.

  5. Equi-biaxial loading effect on austenitic stainless steel fatigue life

    Directory of Open Access Journals (Sweden)

    C. Gourdin

    2016-10-01

    Full Text Available Fatigue lifetime assessment is essential in the design of structures. Under-estimated predictions may result in unnecessary in service inspections. Conversely, over-estimated predictions may have serious consequences on the integrity of structures. In some nuclear power plant components, the fatigue loading may be equibiaxial because of thermal fatigue. So the potential impact of multiaxial loading on the fatigue life of components is a major concern. Meanwhile, few experimental data are available on austenitic stainless steels. It is essential to improve the fatigue assessment methodologies to take into account the potential equi-biaxial fatigue damage. Hence this requires obtaining experimental data on the considered material with a strain tensor in equibiaxial tension. Two calibration tests (with strain gauges and image correlation were used to obtain the relationship between the imposed deflection and the radial strain on the FABIME2 specimen. A numerical study has confirmed this relationship. Biaxial fatigue tests are carried out on two austenitic stainless steels for different values of the maximum deflection, and with a load ratio equal to -1. The interpretation of the experimental results requires the use of an appropriate definition of strain equivalent. In nuclear industry, two kinds of definition are used: von Mises and TRESCA strain equivalent. These results have permitted to estimate the impact of the equibiaxiality on the fatigue life of components

  6. Microstructure and Properties of Plasma Source Nitrided AISI 316 Austenitic Stainless Steel

    Science.gov (United States)

    Li, G. Y.; Lei, M. K.

    2016-11-01

    Plasma source nitriding is a relatively new nitriding technology which can overcome those inherent shortcomings associated with conventional direct current plasma nitriding technology such as the arcing surface damage, the edging effect and the hollow cathode effect. There is considerable study on the properties of nitrided samples for laboratorial scale plasma source nitriding system; however, little information has been reported on the industrial-scale plasma source nitriding system. In this work, AISI 316 austenitic stainless steel samples were nitrided by an industrial-scale plasma source nitriding system at various nitriding temperatures (350, 400, 450 and 500 °C) with a floating potential. A high-nitrogen face-centered-cubic phase (γN) formed on the surface of nitrided sample surface. As the nitriding temperature was increased, the γN phase layer thickness increased, varying from 1.5 μm for the lowest nitriding temperature of 350 °C, to 30 μm for the highest nitriding temperature of 500 °C. The maximum Vickers microhardness of the γN phase layer with a peak nitrogen concentration of 20 at.% is about HV 0.1 N 15.1 GPa at the nitriding temperature of 450 °C. The wear and corrosion experimental results demonstrated that the γN phase was formed on the surface of AISI 316 austenitic stainless steel by plasma source nitriding, which exhibits not only high wear resistance, but also good pitting corrosion resistance.

  7. Systematic Study of Nanocrystalline Plasma Electrolytic Nitrocarburising of 316L Austenitic Stainless Steel for Corrosion Protection

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A number of studies have been reported on the use of nanocrystalline plasma electrolytic nitrocarburising technology for surface hardening of stainless steels for higher corrosion resistance resulted from this technique. However, very few studies have focused on the optimization of the nanocrystalline plasma electrolytic nitrocarburising process parameters. In this study, a design of experiment (DOE) technique, the Taguchi method, has been used to optimize the nanocrystalline plasma electrolytic nitrocarburising not only for surface hardening but also for the corrosion protection of 316L austenitic stainless steel by controlling the coating process's factors. The experimental design consisted of four factors (Urea concentration, electrical conductivity of electrolyte, voltage and duration of process), each containing three levels. Potentiodynamic polarization measurements were carried out to determine the corrosion resistance of the coated samples. The results were analyzed with related software. An analysis of the mean of signal-to-noise (S/N) ratio indicated that the corrosion resistance of nanocrystalline plasma electrolytic nitrocarburised 316L stainless steel was influenced significantly by the levels in the Taguchi orthogonal array. The optimized coating parameters for corrosion resistance are 1150 g/L for urea concentration, 360 mS/cm for electrical conductivity of electrolyte, 260 V for applied voltage, 6 min for treatment time. The percentage of contribution for each factor was determined by the analysis of variance (ANOVA). The results showed that the applied voltage is the most significant factor affecting the corrosion resistance of the coatings.

  8. Corrosion sensitization behavior and mechanical properties of liquid-nitrogen-deformed austenitic 304 stainless steel

    Science.gov (United States)

    Maldonado, Julio Gerardo

    Plastic deformation of 304 stainless steel at liquid nitrogen temperature ({-}196sp°C) produces an almost complete transformation to strain-induced alphasp'/-martensite which provides the necessary conditions for a pseudo-recrystallization of the microstructure. This "so-called" pseudo-recrystallization results directly from the martensitic reversion (i.e. martensite to austenite reverse transformation) upon the application of heat treatment within the sensitization temperature range. The very fine duplex (alpha/gamma) microstructure which results (after heat treatment-0.1h-670sp°C) is also accompanied by a very extensive and homogeneous precipitation of chromium-rich carbides. The concomitant pseudo-recrystallization and precipitation processes not only have a profound positive effect on the sensitization behavior, but also affect the mechanical properties of the material. This suggests that 304 stainless steel could be thermo-mechanically treated, to in essence, heal itself and simultaneously produce an extremely fine (≈0.1mum) duplex grain structure with intermixed carbides to form a very high strength product. This might have important practical implications since 304 stainless steel is the material of choice in many engineering applications. Electrochemical testing, transmission electron microscopy, scanning electron microscopy, optical microscopy, neutron diffraction, X-ray diffraction, and mechanical testing were some of the techniques employed in this work.

  9. Modelling the evolution of composition-and stress-depth profiles in austenitic stainless steels during low-temperature nitriding

    DEFF Research Database (Denmark)

    Jespersen, Freja Nygaard; Hattel, Jesper Henri; Somers, Marcel A. J.

    2016-01-01

    that accompanies the dissolution of high nitrogen contents in expanded austenite. An intriguing phenomenon during low-temperature nitriding is that the residual stresses evoked by dissolution of nitrogen in the solid state, affect the thermodynamics and the diffusion kinetics of nitrogen dissolution......Nitriding of stainless steel causes a surface zone of expanded austenite, which improves the wear resistance of the stainless steel while preserving the stainless behaviour. During nitriding huge residual stresses are introduced in the treated zone, arising from the volume expansion....... In the present paper solid mechanics was combined with thermodynamics and diffusion kinetics to simulate the evolution of composition-depth and stress-depth profiles resulting from nitriding. The model takes into account a composition-dependent diffusion coefficient of nitrogen in expanded austenite, short range...

  10. The Effect of Constant and Pulsed Current Gas Tungsten Arc Welding on Joint Properties of 2205 Duplex Stainless Steel to 316L Austenitic Stainless Steel

    Science.gov (United States)

    Neissi, R.; Shamanian, M.; Hajihashemi, M.

    2016-05-01

    In this study, dissimilar 316L austenitic stainless steel/2205 duplex stainless steel (DSS) joints were fabricated by constant and pulsed current gas tungsten arc welding process using ER2209 DSS as a filler metal. Microstructures and joint properties were characterized using optical and electron scanning microscopy, tensile, Charpy V-notch impact and micro-hardness tests, and cyclic polarization measurements. Microstructural observations confirmed the presence of chromium nitride and delta ferrite in the heat-affected zone of DSS and 316L, respectively. In addition, there was some deviation in the austenite/ferrite ratio of the surface welding pass in comparison to the root welding pass. Besides having lower pitting potential, welded joints produced by constant current gas tungsten arc welding process, consisted of some brittle sigma phase precipitates, which resulted in some impact energy reduction. The tensile tests showed high tensile strength for the weld joints in which all the specimens were broken in 316L base metal.

  11. Microstructural and electrochemical characterization of laser deposited 18-10 austenitic stainless steel clad layers

    Energy Technology Data Exchange (ETDEWEB)

    Fouquet, F. (GEMPPM/CALFETMAT, 69 Villeurbanne (France)); Sallamand, P. (GEMPPM/CALFETMAT, 69 Villeurbanne (France)); Millet, J.P. (GEMPPM/CALFETMAT, 69 Villeurbanne (France) Physicochimie Industrielle, 69 Villeurbanne (France)); Frenk, A. (GEMPPM/CALFETMAT, 69 Villeurbanne (France) Centre de Traitement des Materiaux par Laser (CTML), Ecole Polytechnique Federale de Lausanne (Switzerland)); Wagniere, J.D. (GEMPPM/CALFETMAT, 69 Villeurbanne (France) Centre de Traitement des Materiaux par Laser (CTML), Ecole Polytechnique Federale de Lausanne (Switzerland))

    1993-11-01

    The present work reports on 18-10 stainless steel coatings produced by laser powder cladding technique on a mild steel. Uniform clad layers - about 600 [mu]m thick - have been produced through partially overlapping single cladding tracks. The clad layers thus obtained show excellent adherence, no cracks, few porosities and good chemical homogeneity. The microstructure is dendritic or cellular. Dentrites or cells have an austenitic structure and a small amount of [delta]-ferrite is detected in the interdendritic areas. The corrosion resistance of the clad layers is tested by electrochemical techniques in various neutral or acidified aqueous saline media, deaerated or naturally aerated. In every case, the coatings show an excellent uniform corrosion resistance. (orig.).

  12. Effect of Carbon and Nitrogen Content on Deformation and Fracture of AISI 304 Austenitic Stainless Steel

    Directory of Open Access Journals (Sweden)

    C. Menapace

    2008-04-01

    Full Text Available The effect of small differences in the content of carbon and nitrogen on the room temperature tensile deformation and fracture behaviour of an AISI 304 stainless steel was studied. In the steel containing the lower amount of carbon and nitrogen, a higher amount of strain induced alfa’ martensite is formed, which increases strain hardening rate and both uniform and total elongation at fracture. The presence of large martensitic areas in the cross section causes strain localization at the austenite/martensite interface, which promotes the nucleation of cracks and their propagation along the interface. This results in a decrease of Ultimate Tensile Strength. Strain induced transformation slightly reduces strain rate sensitivity, as well.

  13. Surface structure and properties of ion-nitrided austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Hannula, S.P.; Nenonen, P. (Metallurgy Lab., Technical Research Centre, Espoo (Finland)); Hirvonen, J.P. (Dept. of Physics, Univ. of Helsinki (Finland))

    1989-12-10

    The near surface structure and nitrogen concentration of the low-temperature low-pressure ion-nitrided stainless steels (SS) was studied by using X-ray diffraction (XRD), transmission electron microscopy (TEM), nuclear resonance broadening (NRB) and microhardness techniques. The surface nitrogen content as determined by NRB was found to increase with nitriding time such that at long nitriding times the surface nitrogen concentration was higher than for any equilibrium nitride in the Fe-N system. Nitrogen contents were slightly higher for type-304 than for type-316 stainless steels. Simultaneously with increasing surface nitrogen content, a strong shift and broadening of X-ray diffraction peaks occured. In the surface of the nitrided layer expanded austenite as well as {epsilon}-phase analogous to {epsilon}-martensite is formed. At long nitriding times (high nitrogen surface contents) the structure of the surface corresponds to cubic MN{sub 1-x} nitride. At intermediate nitriding times (and nitrogen contents) possibly some {epsilon}'-nitride is also formed. TEM study of the surface layer showed that after long nitriding times the expanded austenite with occasional weak primitive lattice reflections was the dominating phase and the hexagonal {epsilon}-phase was habited as thin platelets on the (111) planes of the nitrogen supersaturated austenite. The hardness of the compound layer can be as high as 25 GPa. The high hardness is suggested to result from nitrogen supersaturation, high dislocation density and thin platelets of {epsilon}-phase in the surface of the compound layer. (orig.).

  14. Grain-to-Grain Variations in NbC Particle Size Distributions in an Austenitic Stainless Steel

    DEFF Research Database (Denmark)

    Barlow, Claire; Ralph, B.; Silverman, B.;

    1979-01-01

    Quantitative information has been obtained concerning the size distributions of NbC precipitate particles in different grains in a deformed and aged austenitic stainless steel specimen. The precipitate size distributions obtained differ from one grain to another. The average disparity measured be...

  15. Effect of Grain Size on Void Formation during High-Energy Electron Irradiation of Austenitic Stainless Steel

    DEFF Research Database (Denmark)

    Singh, Bachu Narain

    1974-01-01

    Thin foils of an ‘ experimental ’ austenitic stainless steel, with and without dispersions of aluminium oxide particles, are irradiated with 1 MeV electrons in a High Voltage Electron Microscope at 600°C. Evidence of grain size dependent void nucleation, void concentration, and void volume swelling...

  16. Characterization of microstructure and texture across dissimilar super duplex/austenitic stainless steel weldment joint by super duplex filler metal

    Energy Technology Data Exchange (ETDEWEB)

    Eghlimi, Abbas, E-mail: a.eghlimi@ma.iut.ac.ir [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Shamanian, Morteza [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Eskandarian, Masoomeh [Department of Materials Engineering, Shiraz University, Shiraz 71348-51154 (Iran, Islamic Republic of); Zabolian, Azam [Department of Natural Resources, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Szpunar, Jerzy A. [Department of Mechanical Engineering, University of Saskatchewan, Saskatoon SK S7N 5A9 (Canada)

    2015-08-15

    In the present paper, microstructural changes across an as-welded dissimilar austenitic/duplex stainless steel couple welded by a super duplex stainless steel filler metal using gas tungsten arc welding process is characterized with optical microscopy and electron back-scattered diffraction techniques. Accordingly, variations of microstructure, texture, and grain boundary character distribution of base metals, heat affected zones, and weld metal were investigated. The results showed that the weld metal, which was composed of Widmanstätten austenite side-plates and allotriomorphic grain boundary austenite morphologies, had the weakest texture and was dominated by low angle boundaries. The welding process increased the ferrite content but decreased the texture intensity at the heat affected zone of the super duplex stainless steel base metal. In addition, through partial ferritization, it changed the morphology of elongated grains of the rolled microstructure to twinned partially transformed austenite plateaus scattered between ferrite textured colonies. However, the texture of the austenitic stainless steel heat affected zone was strengthened via encouraging recrystallization and formation of annealing twins. At both interfaces, an increase in the special character coincident site lattice boundaries of the primary phase as well as a strong texture with <100> orientation, mainly of Goss component, was observed. - Graphical abstract: Display Omitted - Highlights: • Weld metal showed local orientation at microscale but random texture at macroscale. • Intensification of <100> orientated grains was observed adjacent to the fusion lines. • The austenite texture was weaker than that of the ferrite in all duplex regions. • Welding caused twinned partially transformed austenites to form at SDSS HAZ. • At both interfaces, the ratio of special CSL boundaries of the primary phase increased.

  17. High temperature oxidation behavior of austenitic stainless steel AISI 304 in steam of nanofluids contain nanoparticle ZrO2

    Energy Technology Data Exchange (ETDEWEB)

    Prajitno, Djoko Hadi, E-mail: djokohp@batan.go.id; Syarif, Dani Gustaman, E-mail: djokohp@batan.go.id [Research Center for Nuclear Materials and Radiometry, Jl. Tamansari 71, Bandung 40132 (Indonesia)

    2014-03-24

    The objective of this study is to evaluate high temperature oxidation behavior of austenitic stainless steel SS 304 in steam of nanofluids contain nanoparticle ZrO{sub 2}. The oxidation was performed at high temperatures ranging from 600 to 800°C. The oxidation time was 60 minutes. After oxidation the surface of the samples was analyzed by different methods including, optical microscope, scanning electron microscope (SEM) and X-ray diffraction (XRD). X-ray diffraction examination show that the oxide scale formed during oxidation of stainless steel AISI 304 alloys is dominated by iron oxide, Fe{sub 2}O{sub 3}. Minor element such as Cr{sub 2}O{sub 3} is also appeared in the diffraction pattern. Characterization by optical microscope showed that cross section microstructure of stainless steel changed after oxidized with the oxide scale on the surface stainless steels. SEM and x-ray diffraction examination show that the oxide of ZrO{sub 2} appeared on the surface of stainless steel. Kinetic rate of oxidation of austenite stainless steel AISI 304 showed that increasing oxidation temperature and time will increase oxidation rate.

  18. High Nb, Ta, and Al creep- and oxidation-resistant austenitic stainless steel

    Science.gov (United States)

    Brady, Michael P [Oak Ridge, TN; Santella, Michael L [Knoxville, TN; Yamamoto, Yukinori [Oak Ridge, TN; Liu, Chain-tsuan [Oak Ridge, TN

    2010-07-13

    An austenitic stainless steel HTUPS alloy includes, in weight percent: 15 to 30 Ni; 10 to 15 Cr; 2 to 5 Al; 0.6 to 5 total of at least one of Nb and Ta; no more than 0.3 of combined Ti+V; up to 3 Mo; up to 3 Co; up to 1 W; up to 0.5 Cu; up to 4 Mn; up to 1 Si; 0.05 to 0.15 C; up to 0.15 B; up to 0.05 P; up to 1 total of at least one of Y, La, Ce, Hf, and Zr; less than 0.05 N; and base Fe, wherein the weight percent Fe is greater than the weight percent Ni wherein said alloy forms an external continuous scale comprising alumina, nanometer scale sized particles distributed throughout the microstructure, said particles comprising at least one composition selected from the group consisting of NbC and TaC, and a stable essentially single phase fcc austenitic matrix microstructure, said austenitic matrix being essentially delta-ferrite-free and essentially BCC-phase-free.

  19. A Hybrid Low Temperature Surface Alloying Process for Austenitic Stainless Steels

    Institute of Scientific and Technical Information of China (English)

    Y. Sun

    2004-01-01

    This paper describes a novel, hybrid process developed to engineer the surfaces of austenitic stainless steels at temperatures below 450℃ for the improvement in wear and corrosion resistance. The process is carried out in the plasma of a glow discharge containing both nitrogen and carbon reactive species, and facilitates the incorporation of both nitrogen and carbon into the austenite surface to form a dual-layer structure comprising a nitrogen-rich layer on top of a carbon-rich layer.Both layers can be precipitation-free at sufficiently low processing temperatures, and contain nitrogen and carbon respectively in supersaturated fcc austenite solid solutions. The resultant hybrid structure offers several advantages over the conventional low temperature nitriding and the newly developed carburizing processes in terms of mechanical and chemical properties, including higher surface hardness, a hardness gradient from the surface towards the layer-core interface, uniform layer thickness, and much enhanced corrosion resistance. This paper discusses the main features of this hybrid process and the various structural and properties characteristics of the resultant engineered surfaces.

  20. Stress-induced martensitic transformation in metastable austenitic stainless steels: Effect on fatigue crack growth rate

    Science.gov (United States)

    Khan, Z.; Ahmed, M.

    1996-04-01

    This paper addresses the influence of cyclic stress-induced martensitic transformation on fatigue crack growth rates in metastable austenitic stainless steels. At low applied stress and mean stress values in AISI type 301 stainless steel, fatigue crack growth rate is substantially retarded due to a cyclic stress-induced γ-α' and γ-ɛ martensitic transformation occurring at the crack-tip plastic zone. It is suggested that the transformation products produce a compressive residual stress at the tip of the fatigue crack, which essentially lowers the effective stress intensity and hence retards the fatigue crack growth rate. At high applied stress or mean stress values, fatigue crack growth rates in AISI type 301 steels become almost equal to those of stable AISI type 302 alloy. As the amount of transformed products increases (with an increase in applied or mean stress), the strain-hardening effect brought about by the transformed martensite phase appears to accelerate fatigue crack growth, offsetting the contribution from the compressive residual stress produced by the positive volume change of γ → α' or ɛ transformation.

  1. Pitting corrosion and crevice corrosion behaviors of high nitrogen austenitic stainless steels

    Institute of Scientific and Technical Information of China (English)

    Hua-bing Li; Zhou-hua Jiang; Yan Yang; Yang Cao; Zu-rui Zhang

    2009-01-01

    Pitting corrosion and crevice corrosion behaviors of high nitrogen austenitic stainless steels (HNSS) were investigated by electrochemical and immersion testing methods in chloride solution, respectively. The chemical constitution and composition in the depth of passive films formed on HNSS were analyzed by X-ray photoelectron spectrum (XPS). HNSS has excellent pitting and crevice corrosion resistance compared to 316L stainless steel. With increasing the nitrogen content in steels, pitting potentials and critical pitting temperature (CPT) increase, and the maximum, average pit depths and average weight loss decrease. The CPT of HNSS is correlated with the alloying element content through the measure of alloying for resistance to corrosion (MARC). The MARC can be expressed as an equation of CPT=2.55MARC-29. XPS results show that HNSS exhibiting excellent corrosion resis-tance is attributed to the enrichment of nitrogen on the surface of passive films, which forms ammonium ions increasing the local pH value and facilitating repassivation, and the synergistic effects of molybdenum and nitrogen.

  2. Effect of heat treatment on an AISI 304 austenitic stainless steel evaluated by the ultrasonic attenuation coefficient

    Energy Technology Data Exchange (ETDEWEB)

    Moghanizadeh, Abbas; Farzi, Abolfazl [Islamic Azad Univ., Esfarayen (Iran, Islamic Republic of). Dept. of Civil Engineering

    2016-07-01

    The properties of metals can be substantially changed by various methods, one of them is using heat treatment processes. Moreover, ultrasonic testing is the most preferred and effective, nondestructive testing technique for characterization of mechanical material properties. Austenitic stainless steel AISI 304 serves in many applications due to high strength and corrosion resistance. In certain applications, it is important to evaluate the mechanical properties of AISI 304 stainless steel. In this study, the ultrasonic method (attenuation measurement technique) is used to evaluate the hardness of AISI 304 stainless steel samples which were heat treated at different levels. Due to the heat treatment process, each sample has its specific microstructure and hardness which attenuate ultrasonic waves appropriately. The ultrasonic and hardness test show that it is possible to evaluate the hardness of AISI 304 stainless steel by ultrasonic attenuation coefficient. In addition, the relationship between ultrasonic attenuation coefficients and time of heat treatment is investigated.

  3. Prediction of microsegregation and pitting corrosion resistance of austenitic stainless steel welds by modelling

    Energy Technology Data Exchange (ETDEWEB)

    Vilpas, M. [VTT Manufacturing Technology, Espoo (Finland). Materials and Structural Integrity

    1999-07-01

    The present study focuses on the ability of several computer models to accurately predict the solidification, microsegregation and pitting corrosion resistance of austenitic stainless steel weld metals. Emphasis was given to modelling the effect of welding speed on solute redistribution and ultimately to the prediction of weld pitting corrosion resistance. Calculations were experimentally verified by applying autogenous GTA- and laser processes over the welding speed range of 0.1 to 5 m/min for several austenitic stainless steel grades. Analytical and computer aided models were applied and linked together for modelling the solidification behaviour of welds. The combined use of macroscopic and microscopic modelling is a unique feature of this work. This procedure made it possible to demonstrate the effect of weld pool shape and the resulting solidification parameters on microsegregation and pitting corrosion resistance. Microscopic models were also used separately to study the role of welding speed and solidification mode in the development of microsegregation and pitting corrosion resistance. These investigations demonstrate that the macroscopic model can be implemented to predict solidification parameters that agree well with experimentally measured values. The linked macro-micro modelling was also able to accurately predict segregation profiles and CPT-temperatures obtained from experiments. The macro-micro simulations clearly showed the major roles of weld composition and welding speed in determining segregation and pitting corrosion resistance while the effect of weld shape variations remained negligible. The microscopic dendrite tip and interdendritic models were applied to welds with good agreement with measured segregation profiles. Simulations predicted that weld inhomogeneity can be substantially decreased with increasing welding speed resulting in a corresponding improvement in the weld pitting corrosion resistance. In the case of primary austenitic

  4. Microstructural observations of HFIR-irratiated austenitic stainless steels including welds from JP9-16

    Energy Technology Data Exchange (ETDEWEB)

    Sawai, T.; Shiba, K.; Hishinuma, A.

    1996-04-01

    Austenitic stainless steels, including specimens taken from various electron beam (EB) welds, have been irradiated in HFIR Phase II capsules, JP9-16. Fifteen specimens irradiated at 300, 400, and 500{degrees}C up to 17 dpa are so far examined by a transmission electron microscope (TEM). In 300{degrees}C irradiation, cavities were smaller than 2nm and different specimens showed little difference in cavity microstructure. At 400{degrees}C, cavity size was larger, but still very small (<8 nm). At 500{degrees}C, cavity size reached 30 nm in weld metal specimens of JPCA, while cold worked JPCA contained a small (<5 nm) cavities. Inhomogeneous microstructural evolution was clearly observed in weld-metal specimens irradiated at 500{degrees}C.

  5. Effects of low temperature neutron irradiation on deformation behavior of austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Pawel, J.E.; Rowcliffe, A.F.; Alexander, D.J.; Grossbeck, M.L. [Oak Ridge National Laboratory, TN (United States); Shiba, K.

    1996-04-01

    An austenitic stainless steel, designated 316LN-IG, has been chosen for the first wall/shield (FW/S) structure for the International Thermonuclear Experimental Reactor (ITER). The proposed operational temperature range for the structure (100 to 250{degree}C) is below the temperature regimes for void swelling (400-600{degree}C) and for helium embrittlement (500-700{degree}C). However, the proposed neutron dose is such that large changes in yield strength, deformation mode, and strain hardening capacity could be encountered which could significantly affect fracture properties. Definition of the irradiation regimes in which this phenomenon occurs is essential to the establishment of design rules to protect against various modes of failure.

  6. Influence of the austenitic stainless steel microstructure on the void swelling under ion irradiation

    Directory of Open Access Journals (Sweden)

    Rouxel Baptiste

    2016-01-01

    Full Text Available To understand the role of different metallurgical parameters on the void formation mechanisms, various austenitic stainless steels were elaborated and irradiated with heavy ions. Two alloys, in several metallurgical conditions (15Cr/15Ni–Ti and 15Cr/25Ni–Ti, were irradiated in the JANNUS-Saclay facility at 600 °C with 2 MeV Fe2+ ions up to 150 dpa. Resulting microstructures were observed by Transmission Electron Microscopy (TEM. Different effects on void swelling are highlighted. Only the pre-aged samples, which were consequently solute and especially titanium depleted, show cavities. The nickel-enriched matrix shows more voids with a smaller size. Finally, the presence of nano-precipitates combined with a dense dislocation network decreases strongly the number of cavities.

  7. Effect of Plasma Nitriding Temperatures on Characteristics of Aisi 201 Austenitic Stainless Steel

    Science.gov (United States)

    Gao, Yuxin; Zheng, Shaomei

    2016-10-01

    Samples of AISI 201 austenitic stainless steel were produced by plasma nitriding at 350∘C, 390∘C, 420∘C, 450∘C and 480∘C for 5h. Systematic characterization of the nitrided layer was carried out in terms of micrograph observations, phase identification, chemical composition depth profiling, surface microhardness measurements and electrochemical corrosion tests. The results show that the surface hardness and the layer thickness increased with increasing temperature. XRD indicated that a single S-phase layer was formed during low temperature (≤420∘C), while Cr2N or CrN phase was formed besides S-phase when nitrided at 450∘C and 480∘C. The specimen treated at 390∘C presents a much enhanced corrosion resistance compared to the untreated substrate. The corrosion resistance deteriorated for samples treated above 450∘C due to the formation of chromium nitrides.

  8. Corrosion Fatigue of Austenitic Stainless Steel in Different Hot Chloride Solutions

    Energy Technology Data Exchange (ETDEWEB)

    Visser, A.; Mori, G.; Panzenboeck, M. [Montanuniversitaet Leoben, Leoben (Austria); Pippan, R. [Erich Schmid Institute of Materials Science, Austrian Academy of Science, Leoben (Austria)

    2015-08-15

    Austenitic stainless steel was investigated under cyclic loading in electrolytes with different chloride contents and pH and at different temperatures. The testing solutions were 13.2 % NaCl (80,000 ppm Cl-) at 80 °C and 43 % CaCl{sub 2} (275,000 ppm Cl-) at 120 °C. In addition to S-N curves in inert and corrosive media, the fracture surfaces were investigated with a scanning electron microscope (SEM) to analyse the type of attack. The experimental results showed that a sharp decrease in corrosion fatigue properties can be correlated with the occurrence of stress corrosion cracking. The correlation of occurring types of damage in different corrosion systems is described.

  9. Empirical modeling of shot peening parameters for welded austenitic stainless steel using grey relational analysis

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Lakhwinder; Aggarwal, M. L. [YMCA University of Science and Technology, Haryana (India); Khan, R. A. [Jamia Millia Islamia, New Delhi (India)

    2012-06-15

    The attempt of this paper is to present an effective approach for the optimization of the shot peening process of welded AISI 304 austenitic stainless steel with multi performance characteristics using Grey relational analysis (GRA) based on Taguchi orthogonal array. Twenty-seven experimental runs are performed to determine best process parameters level. An analysis of variance (ANOVA) is carried out to identify significant peening parameters. The response tables are obtained for analyzing the optimal levels of shot peening parameters and major factors that affect the quality function. The multiple performance characteristics including tensile strength, surface hardness and surface roughness are the quality functions considered for the optimization. Further mathematical models are developed using regression analysis for the tensile strength, surface hardness and surface roughness. It will be very helpful to the engineers in deciding the levels of the shot peening parameters for desired performance characteristics.

  10. Ultrasonic Sound Field Mapping Through Coarse Grained Cast Austenitic Stainless Steel Components

    Energy Technology Data Exchange (ETDEWEB)

    Crawford, Susan L.; Prowant, Matthew S.; Cinson, Anthony D.; Larche, Michael R.; Diaz, Aaron A.

    2014-08-01

    The Pacific Northwest National Laboratory (PNNL) has been involved with nondestructive examination (NDE) of coarse-grained cast austenitic stainless steel (CASS) components for over 30 years. More recent work has focused on mapping the ultrasonic sound fields generated by low-frequency phased array probes that are typically used for the evaluation of CASS materials for flaw detection and characterization. The casting process results in the formation of large grained material microstructures that are nonhomogeneous and anisotropic. The propagation of ultrasonic energy for examination of these materials results in scattering, partitioning and redirection of these sound fields. The work reported here provides an assessment of sound field formation in these materials and provides recommendations on ultrasonic inspection parameters for flaw detection in CASS components.

  11. Composite model of microstructural evolution in austenitic stainless steel under fast neutron irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Stoller, R.E.; Odette, G.R.

    1986-01-01

    A rate-theory-based model has been developed which includes the simultaneous evolution of the dislocation and cavity components of the microstructure of irradiated austenitic stainless steels. Previous work has generally focused on developing models for void swelling while neglecting the time dependence of the dislocation structure. These models have broadened our understanding of the physical processes that give rise to swelling, e.g., the role of helium and void formation from critically-sized bubbles. That work has also demonstrated some predictive capability by successful calibration to fit the results of fast reactor swelling data. However, considerable uncertainty about the values of key parameters in these models limits their usefulness as predictive tools. Hence the use of such models to extrapolate fission reactor swelling data to fusion reactor conditions is compromised.

  12. Surface Modification by Nitrogen Plasma Immersion Ion Implantation on Austenitic AISI 304 Stainless Steel

    Institute of Scientific and Technical Information of China (English)

    Miguel CASTRO-COLIN; William DURRER; Jorge ALPEZ; Enrique RAMIREZ-HOMS

    2016-01-01

    Surfaces of AISI 304 austenitic stainless steel plates nitrided by plasma immersion ion implantation (PIII) technology were studied by means of Auger electron spectroscopy (AES)and X-ray photoelectron spectroscopy (XPS)to determine the effect of the nitriding process on the surface and subjacent layers.Elemental compositions obtained by AES and XPS at varying depths indicate that the saturation of N is relatively constant as a function of depth,indicating the reliability of PIII technology for subsurface saturation.It is concluded that the concentrations of both Cr and O increase with depth,the subjacent oxide is driven by the Ar+ sputtering process used to access the lower layers,and then N is bound to Cr.

  13. Mechanical and Electrochemical Characterization of Super-Solidus Sintered Austenitic Stainless Steel (316L)

    Science.gov (United States)

    Muthuchamy, A.; Raja Annamalai, A.; Ranka, Rishabh

    2016-08-01

    The present study compares the mechanical and electrochemical behaviour of austenitic (AISI 316L) stainless steel compacted at various pressures (200, 400 and 600 MPa) and conventionally sintered at super-solidus temperature of 1,400°C. The electrochemical behaviour was investigated in 0.1 N H2SO4 solution by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The shrinkage decreased and densification has been increased with increasing pressure. The mechanical and electrochemical behaviour with pressure has been correlated with densification response and microstructure (pore type, volume and morphology). Highest densification ( 92% theoretical) achieved at 600 MPa (compaction pressure) and 1,400°C (sintering temperature) resulted in excellent combination of tensile strength and ductility (456 ± 40 MPa, 25 ± 1.1%), while showing excellent corrosion resistance (0.1 mmpy or 4.7 mpy).

  14. Correlation between locally deformed structure and oxide film properties in austenitic stainless steel irradiated with neutrons

    Science.gov (United States)

    Chimi, Yasuhiro; Kitsunai, Yuji; Kasahara, Shigeki; Chatani, Kazuhiro; Koshiishi, Masato; Nishiyama, Yutaka

    2016-07-01

    To elucidate the mechanism of irradiation-assisted stress corrosion cracking (IASCC) in high-temperature water for neutron-irradiated austenitic stainless steels (SSs), the locally deformed structures, the oxide films formed on the deformed areas, and their correlation were investigated. Tensile specimens made of irradiated 316L SSs were strained 0.1%-2% at room temperature or at 563 K, and the surface structures and crystal misorientation among grains were evaluated. The strained specimens were immersed in high-temperature water, and the microstructures of the oxide films on the locally deformed areas were observed. The appearance of visible step structures on the specimens' surface depended on the neutron dose and the applied strain. The surface oxides were observed to be prone to increase in thickness around grain boundaries (GBs) with increasing neutron dose and increasing local strain at the GBs. No penetrative oxidation was observed along GBs or along surface steps.

  15. Active flux tungsten inert gas welding of austenitic stainless steel AISI 304

    Directory of Open Access Journals (Sweden)

    D. Klobčar

    2016-10-01

    Full Text Available The paper presents the effects of flux assisted tungsten inert gas (A-TIG welding of 4 (10 mm thick austenitic stainless steel EN X5CrNi1810 (AISI 304 in the butt joint. The sample dimensions were 300 ´ 50 mm, and commercially available active flux QuickTIG was used for testing. In the planned study the influence of welding position and weld groove shape was analysed based on the penetration depth. A comparison of microstructure formation, grain size and ferrit number between TIG welding and A-TIG welding was done. The A-TIG welds were subjected to bending test. A comparative study of TIG and A-TIG welding shows that A-TIG welding increases the weld penetration depth.

  16. Effect of Electrode Types on the Solidification Cracking Susceptibility of Austenitic Stainless Steel Weld Metal

    Directory of Open Access Journals (Sweden)

    J. U. Anaele

    2015-01-01

    Full Text Available The effect of electrode types on the solidification cracking susceptibility of austenitic stainless steel weld metal was studied. Manual metal arc welding method was used to produce the joints with the tungsten inert gas welding serving as the control. Metallographic and chemical analyses of the fusion zones of the joints were conducted. Results indicate that weldments produced from E 308-16 (rutile coated, E 308-16(lime-titania coated electrodes, and TIG welded joints fall within the range of 1.5≤Creq./Nieq.≤1.9 and solidified with a duplex mode and were found to be resistant to solidification cracking. The E 308-16 weld metal had the greatest resistance to solidification cracking. Joints produced from E 310-16 had Creq./Nieq. ratio 1.9 and solidified with ferrite mode. It had a low resistance to solidification cracking.

  17. Relative merits of duplex and austenitic stainless steels for applications in the oil and gas industry

    Energy Technology Data Exchange (ETDEWEB)

    Johansson, Elisabeth; Wegrelius, Lena; Pettersson, Rachel [Outokumpu Stainless AB, Avesta (Sweden)

    2012-07-01

    The broad range of available stainless steel grades means that these materials can fulfil a wide variety of requirements within the oil and gas industry. The duplex grades have the advantage of higher strength than standard austenitic grades, while the superaustenitic grades provide a cost-effective alternative to nickel-base alloys in a number of cases. The paper presents the results of various types of laboratory testing to rank the grades in terms of resistance to pitting, crevice corrosion and stress corrosion cracking. Results from field testing in actual or simulated service conditions are discussed and a number of application examples, including process piping flexible, heat exchangers and topside equipment are presented. (author)

  18. Effects of Nitrogen Concentration on Microstructure and Antibac-terial Property of Copper-Bearing Austenite Stainless Steels

    Institute of Scientific and Technical Information of China (English)

    Zhixia ZHANG; Laizhu JIANG; Gang LIN; Zhou XU

    2008-01-01

    Austenite antibacterial stainless steels have been found to have wide applications in hospitals and food indus-tries. In recent years epsilon copper precipitation in antibacterial stainless steels has obtained much research interest due to its antibacterial action. The objective of this study was to determine the effects of nitro-gen concentration on the precipitation of epsilon copper and antibacterial property. Two kinds of austenite antibacterial stainless steels containing copper and different nitrogen concentration (0.02 and 0.08 wt pct, re-spectively) were prepared and the microstructures were characterized by a combination of electron microscopy and thermodynamic analysis. A mathematical expression was deduced to predict the effect of nitrogen con-centration on the activity coefficient of copper, In(fCu/focu)=0.53524+4.11xN-0.48x2N. Higher nitrogen was found to increase the free energy difference of copper concentration distribution between precipitation phase and austenite matrix, stimulate the aggregation of copper atoms from austenite, increase the precipitation amount and consequently enhance the antibacterial property of steel.

  19. Formation of Inclusions in Ti-Stabilized 17Cr Austenitic Stainless Steel

    Science.gov (United States)

    Yin, Xue; Sun, Yanhui; Yang, Yindong; Bai, Xuefeng; Barati, Mansoor; Mclean, Alex

    2016-12-01

    The behavior and formation mechanisms of inclusions in Ti-stabilized, 17Cr Austenitic Stainless Steel produced by the ingot casting route were investigated through systematic sampling of liquid steel and rolled products. Analysis methods included total oxygen and nitrogen contents, optical microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The results indicate that the composition of inclusions was strongly dependent on the types of added alloying agents. During the AOD refining process, after the addition of ferrosilicon alloy and electrolytic manganese, followed by aluminum, the composition of inclusions changed from manganese silicate-rich inclusions to alumina-rich inclusions. After tapping and titanium wire feeding, pure TiN particles and complex inclusions with Al2O3-MgO-TiO x cores containing TiN were found to be the dominant inclusions when [pct Ti] was 0.307 mass pct in the molten steel. These findings were confirmed by thermodynamic calculations which indicated that there was a driving force for TiN inclusions to be formed in the liquid phase due to the high contents of [Ti] and [N] in the molten steel. From the start of casting through to the rolled bar, there was no further change in the composition of inclusions compared to the titanium addition stage. Stringer-shaped TiN inclusions were observed in the rolled bar. These inclusions were elongated along the rolling direction with lengths varying from 17 to 84 µm and could have a detrimental impact on the corrosion resistance as well as the mechanical properties of the stainless steel products.

  20. Development of Advanced 9Cr Ferritic-Martensitic Steels and Austenitic Stainless Steels for Sodium-Cooled Fast Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Sham, Sam [ORNL; Tan, Lizhen [ORNL; Yamamoto, Yukinori [ORNL

    2013-01-01

    Ferritic-martensitic (FM) steel Grade 92, with or without thermomechanical treatment (TMT), and austenitic stainless steels HT-UPS (high-temperature ultrafine precipitate strengthening) and NF709 were selected as potential candidate structural materials in the U.S. Sodium-cooled Fast Reactor (SFR) program. The objective is to develop advanced steels with improved properties as compared with reference materials such as Grade 91 and Type 316H steels that are currently in nuclear design codes. Composition modification and/or processing optimization (e.g., TMT and cold-work) were performed to improve properties such as resistance to thermal aging, creep, creep-fatigue, fracture, and sodium corrosion. Testings to characterize these properties for the advanced steels were conducted by the Idaho National Laboratory, the Argonne National Laboratory and the Oak Ridge National Laboratory under the U.S. SFR program. This paper focuses on the resistance to thermal aging and creep of the advanced steels. The advanced steels exhibited up to two orders of magnitude increase in creep life compared to the reference materials. Preliminary results on the weldment performance of the advanced steels are also presented. The superior performance of the advanced steels would improve reactor design flexibility, safety margins and economics.

  1. Ultrasonic inspectability of austenitic stainless steel and dissimilar metal weld joints

    Energy Technology Data Exchange (ETDEWEB)

    Pudovikov, S.; Bulavinov, A.; Kroening, M. [Fraunhofer-Institut fuer Zerstoerungsfreie Pruefverfahren IZFP, Saarbruecken (Germany)

    2008-07-01

    Since their invention in 1912, austenitic stainless steel materials are widely used in a variety of industry sectors. In particular, austenitic stainless steel material is qualified to meet the design criteria of high quality, safety related applications, for example, the primary loop of the most of the nuclear power plants in the world, due to high durability and corrosion resistance. Certain operating conditions may cause a range of changes in the integrity of the component, and therefore require nondestructive testing at reasonable intervals. These in-service inspections are often performed using ultrasonic techniques, in particular when cracking is of specific concern. However, the coarse, dendritic grain structure of the weld material, formed during the welding process, is extreme and unpredictably anisotropic. Such structure is no longer direction-independent to the ultrasonic wave propagation; therefore, the ultrasonic beam deflects and redirects and the wave front becomes distorted. Thus, the use of conventional ultrasonic testing techniques using fixed beam angles is very limited and the application of ultrasonic Phased Array techniques becomes desirable. The ''Sampling Phased Array'' technique, invented and developed by Fraunhofer IZFP, allows the acquisition of time signals (A-scans) for each individual transducer element of the array along with image reconstruction techniques using ''SynFoc'' algorithms. The reconstruction considers the sound propagation from each image pixel to the individual sensor element. For anisotropic media, where the sound beam is deflected and the sound path is not known a-priory, we implement a new phase adjustment called ''Reverse Phase Matching'' technique. This algorithm permits the acquisition of phase-corrected A-scans that represent the actual sound propagation in the anisotropic structure; this technique can be utilized for image reconstruction. (orig.)

  2. Effect of Colouring Process on Pitting Susceptibility of Austenitic Stainless Steel

    Institute of Scientific and Technical Information of China (English)

    S.S.Mahmoud; M.M.Ahmed

    2008-01-01

    Colouring of the austenitic stainless steel alloy (20.45% Cr, 8.57% Ni) was carried out in NaNO3-KNO3 eutectic melt without and with additions of Na2O2, NaCl and their mixtures at different temperatures ranging from 400-600℃, under open-circuit and galvanostatic anodic polarization conditions. The produced colours greatly depend on the thickness of oxide films, which in turn depends on the composition of the molten bath and its temperature. The more attractive, bright, adherent and uniform coloured oxide films can be obtained at 400, 450 and 500℃ in molten nitrate bath containing NaCl and Na2O2 mixtures. The pitting corrosion susceptibility of the coloured oxide films was tested in FeCl3 and NaCl as corrosive media. The obtained results indicate that the pitting corrosion susceptibility of the coloured oxide films greatly depends on the previous operating conditions of the colouring process of the stainless steel specimens such as the composition of molten bath, temperature and technique of colouring process.

  3. INVESTIGATING SPOT WELD GROWTH ON 304 AUSTENITIC STAINLESS STEEL (2 mm SHEETS

    Directory of Open Access Journals (Sweden)

    NACHIMANI CHARDE

    2013-02-01

    Full Text Available Resistance spot welding (RSW has revolutionized automotive industries since early 1970s for its mechanical assemblies. To date one mechanical assembly out five is welded using spot welding technology in various industries and stainless steel became very popular among common materials. As such this research paper analyses the spot weld growth on 304 austenitic stainless steels with 2mm sample sheets. The growth of a spot weld is primarily determined by its parameters such as current, weld time, electrode tip and force. However other factors such as electrode deformations, corrosions, dissimilar materials and material properties are also affect the weld growth. This paper is intended to analyze only the effects of nuggets growth due to the current and weld time increment with constant force and unchanged electrode tips. A JPC 75kVA spot welder was used to accomplish it and the welded samples were undergone tensile test, hardness test and metallurgical test to characterize the formation of weld nuggets.

  4. Estimation of the kinetics of martensitic transformation in austenitic stainless steels by conventional and novel approaches

    Energy Technology Data Exchange (ETDEWEB)

    Shirdel, M., E-mail: mshirdel1989@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Mirzadeh, H., E-mail: hmirzadeh@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Advanced Metalforming and Thermomechanical Processing Laboratory, School of Metallurgy and Materials Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Parsa, M.H., E-mail: mhparsa@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Center of Excellence for High Performance Materials, School of Metallurgy and Materials Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Advanced Metalforming and Thermomechanical Processing Laboratory, School of Metallurgy and Materials Engineering, University of Tehran, Tehran (Iran, Islamic Republic of)

    2015-01-29

    A comparative study was carried out on the kinetics of the martensitic transformation in a 304L stainless steel during cold rolling by conventional and novel approaches. The phase analysis based on X-ray diffraction patterns and metallography and also magnetic measurements based on ferritescope readings were utilized to elucidate the kinetics of the martensitic transformation. A straightforward magnetic measurement approach for evaluating the amount of strain-induced martensite in metastable austenitic stainless steels has been introduced in this study. This technique collects the data throughout the bulk of the material to give a realistic estimate of the amount of ferromagnetic martensite. This is an advantage over the surface collecting methods such as ferritescope readings, which overestimates the amount of martensite due to its inhomogeneous distribution through the thickness based on the frictional effects between the rolls and the specimen surface. The proposed approach can be applied in various designs for static/continuous magnetic measurement of bulk materials that is advantageous compared with the conventional vibrating sample magnetometer technique which is useful for static measurement of bulk materials with specific shapes. Moreover, in analogy to ferritescope, the output data of the developed device is directly related to the amount of martensite.

  5. High-cycle fatigue behavior of ultrafine-grained austenitic stainless and TWIP steels

    Energy Technology Data Exchange (ETDEWEB)

    Hamada, A.S. [Materials Engineering Laboratory (4KOMT), Box 4200, University of Oulu, 90014 Oulu (Finland); Metallurgical and Materials Engineering Department, Faculty of Petroleum and Mining Engineering, Suez Canal University, Box 43721, Suez (Egypt); Karjalainen, L.P., E-mail: pentti.karjalainen@oulu.fi [Materials Engineering Laboratory (4KOMT), Box 4200, University of Oulu, 90014 Oulu (Finland)

    2010-08-20

    High-cycle fatigue behavior of ultrafine-grained (UFG) 17Cr-7Ni Type 301LN austenitic stainless and high-Mn Fe-22Mn-0.6C TWIP steels were investigated in a reversed plane bending fatigue and compared to the behavior of steels with conventional coarse grain (CG) size. Optical, scanning and transmission electron microscopy were used to examine fatigue damage mechanisms. Testing showed that the fatigue limits leading to fatigue life beyond 4 x 10{sup 6} cycles were about 630 MPa for 301LN while being 560 MPa for TWIP steel, and being 0.59 and 0.5 of the tensile strength respectively. The CG counterparts were measured to have the fatigue limits of 350 and 400 MPa. The primary damage caused by fatigue took place by grain boundary cracking in UFG 301LN, while slip band cracking occurred in CG 301LN. However, in the case of TWIP steel, the fatigue damage mechanism is similar in spite of the grain size. In the course of cycling neither the formation of a martensite structure nor mechanical twinning occurs, but intense slip bands are created with extrusions and intrusions. Fatigue crack initiates preferentially on grain and twin boundaries, and especially in the intersection sites of slip bands and boundaries.

  6. Investigations on structure–property relationships of activated flux TIG weldments of super-duplex/austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Devendranath Ramkumar, K., E-mail: ramdevendranath@gmail.com; Bajpai, Ankur; Raghuvanshi, Shubham; Singh, Anshuman; Chandrasekhar, Aditya; Arivarasu, M.; Arivazhagan, N.

    2015-06-25

    This research work articulated the effect of SiO{sub 2} flux assisted tungsten inert gas (TIG) welding on the microstructure and mechanical properties of marine grade stainless steel weldments, such as super-duplex stainless steel (UNS S32750) and austenitic stainless steel (AISI 316L). The studies showed that the use of flux decreased the heat input required to obtain complete penetration. Microstructure studies revealed the presence of ferrite at the heat affected zone of AISI 316L and the fusion zone which obviated the hot cracking tendency. Tensile studies corroborated that the joint strength was sufficiently greater than that of the parent metals. Impact toughness slightly impoverished owing to the presence of large platelets of Widmanstätten austenite in the fusion zone. The study also explored the structure–property relationships of the flux assisted weldments using the combined techniques of optical and scanning electron microscopy analysis. Owing to the better metallurgical and mechanical properties, this study recommends the use of SiO{sub 2} flux for joining the dissimilar metals involving austenitic and super-duplex stainless steels.

  7. The Prediction of Long-Term Thermal Aging in Cast Austenitic Stainless Steel

    Energy Technology Data Exchange (ETDEWEB)

    Byun, Thak Sang; Yang, Ying; Lach, Timothy G.

    2017-02-15

    Cast austenitic stainless steel (CASS) materials are extensively used for many massive primary coolant system components of light water reactors (LWRs) including coolant piping, valve bodies, pump casings, and piping elbows. Many of these components are operated in complex and persistently damaging environments of elevated temperature, high pressure, corrosive environment, and sometimes radiation for long periods of time. Since a large number of CASS components are installed in every nuclear power plant and replacing such massive components is prohibitively expensive, any significant degradation in mechanical properties that affects structural integrity, cracking resistance in particular, of CASS components will raise a serious concern on the performance of entire power plant. The CASS materials for nuclear components are highly corrosion-resistant Fe-Cr-Ni alloys with 300 series stainless steel compositions and mostly austenite (γ)–ferrite (δ) duplex structures, which result from the casting processes consisting of alloy melting and pouring or injecting liquid metal into a static or spinning mold. Although the commonly used static and centrifugal casting processes enable the fabrication of massive components with proper resistance to environmental attacks, the alloying and microstructural conditions are not highly controllable in actual fabrication, especially in the casting processes of massive components. In the corrosion-resistant Fe-Cr-Ni alloy system, the minor phase (i.e., the δ-ferrite phase) is inevitably formed during the casting process, and is in a non-equilibrium state subject to detrimental changes during exposure to elevated temperature and/or radiation. In general, relatively few critical degradation modes are expected within the current design lifetime of 40 years, given that the CASS components have been processed properly. It has been well known, however, that both the thermal aging and the neutron irradiation can cause degradation of static

  8. Crack initiation in smooth fatigue specimens of austenitic stainless steel in light water reactor environments.

    Energy Technology Data Exchange (ETDEWEB)

    Chopra, O. K.; Smith, J. L.

    1999-04-08

    The fatigue design curves for structural materials specified in Section III of the ASME Boiler and Pressure Vessel Code are based on tests of smooth polished specimens at room temperature in air. The effects of light water reactor (LWR) coolant environments are not explicitly addressed by the Code design curves; however, recent test data illustrate the detrimental effects of LWR coolant environments on the fatigue resistance of austenitic stainless steels (SSs). Certain loading and environmental conditions have led to test specimen fatigue lives that are significantly shorter than those obtained in air. Results of fatigue tests that examine the influence of reactor environments on crack initiation and crack growth of austenitic SSs are presented. Block loading was used to mark the fracture surface to determine crack length as a function of fatigue cycles in water environments, Crack lengths were measured by scanning electron microscopy. The mechanism for decreased fatigue life in LWR environments is discussed, and crack growth rates in the smooth fatigue specimens are compared with existing data from studies of crack growth rates.

  9. Flexural Strength and Toughness of Austenitic Stainless Steel Reinforced High-Cr White Cast Iron Composite

    Science.gov (United States)

    Sallam, H. E. M.; Abd El-Aziz, Kh.; Abd El-Raouf, H.; Elbanna, E. M.

    2013-12-01

    Flexural behavior of high-Cr white cast iron (WCI) reinforced with different shapes, i.e., I- and T-sections, and volume fractions of austenitic stainless steel (310 SS) were examined under three-point bending test. The dimensions of casted beams used for bending test were (50 × 100 × 500 mm3). Carbon and alloying elements diffusion enhanced the metallurgical bond across the interface of casted beams. Carbon diffusion from high-Cr WCI into 310 SS resulted in the formation of Cr-carbides in 310 SS near the interface and Ni diffusion from 310 SS into high-Cr WCI led to the formation of austenite within a network of M7C3 eutectic carbides in high-Cr WCI near the interface. Inserting 310 SS plates into high-Cr WCI beams resulted in a significant improvement in their toughness. All specimens of this metal matrix composite failed in a ductile mode with higher plastic deformation prior to failure. The high-Cr WCI specimen reinforced with I-section of 310 SS revealed higher toughness compared to that with T-section at the same volume fraction. The presence of the upper flange increased the reinforcement efficiency for delaying the crack growth.

  10. Dynamic recrystallization and precipitation in high manganese austenitic stainless steel during hot compression

    Institute of Scientific and Technical Information of China (English)

    Amir Momeni; Shahab Kazemi; Golam Ebrahimi; Alireza Maldar

    2014-01-01

    Dynamic recrystallization and precipitation in a high manganese austenitic stainless steel were investigated by hot compression tests over temperatures of 950-1150°C at strain rates of 0.001 s-1-1 s-1. All the flow curves within the studied deformation regimes were typ-ical of dynamic recrystallization. A window was constructed to determine the value of apparent activation energy as a function of strain rate and deformation temperature. The kinetics of dynamic recrystallization was analyzed using the Avrami kinetics equation. A range of apparent activation energy for hot deformation from 303 kJ/mol to 477 kJ/mol is obtained at different deformation regimes. Microscopic characterization confirms that under a certain deformation condition (medium Zener-Hollomon parameter (Z) values), dynamic recrystalliza-tion appears at first, but large particles can not inhibit the recrystallization. At low or high Z values, dynamic recrystallization may occur be-fore dynamic precipitation and proceeds faster. In both cases, secondary phase precipitation is observed along prior austenite grain bounda-ries. Stress relaxation tests at the same deformation temperatures also confirm the possibility of dynamic precipitation. Unexpectedly, the Avrami's exponent value increases with the increase of Z value. It is associated with the priority of dynamic recrystallization to dynamic pre-cipitation at higher Z values.

  11. Feasibility of surface-coated friction stir welding tools to join AISI 304 grade austenitic stainless steel

    Institute of Scientific and Technical Information of China (English)

    A.K. LAKSHMINARAYANAN; C.S.RAMACHANDRAN; V.BALASUBRAMANIAN

    2014-01-01

    An attempt is made to develop the tools that are capable enough to withstand the shear, impact and thermal forces that occur during friction stir welding of stainless steels. The atmospheric plasma spray and plasma transferred arc hardfacing processes are employed to deposit refractory ceramic based composite coatings on the Inconel 738 alloy. Five different combinations of self-fluxing alloy powder and 60% ceramic rein-forcement particulate mixtures are used for coating. The best friction stir welding tool selected based on tool wear analysis is used to fabricate the austenitic stainless steel joints.

  12. Crack growth behavior of warm-rolled 316L austenitic stainless steel in high-temperature hydrogenated water

    Science.gov (United States)

    Choi, Kyoung Joon; Yoo, Seung Chang; Jin, Hyung-Ha; Kwon, Junhyun; Choi, Min-Jae; Hwang, Seong Sik; Kim, Ji Hyun

    2016-08-01

    To investigate the effects of warm rolling on the crack growth of 316L austenitic stainless steel, the crack growth rate was measured and the oxide structure was characterized in high-temperature hydrogenated water. The warm-rolled specimens showed a higher crack growth rate compared to the as-received specimens because the slip bands and dislocations produced during warm rolling served as paths for corrosion and cracking. The crack growth rate increased with the dissolved hydrogen concentration. This may be attributed to the decrease in performance and stability of the protective oxide layer formed on the surface of stainless steel in high-temperature water.

  13. In vitro Study on a New High Nitrogen Nickel-free Austenitic Stainless Steel for Coronary Stents

    Institute of Scientific and Technical Information of China (English)

    Yibin Ren; Peng Wan; Feng Liu; Bingchun Zhang; Ke Yang

    2011-01-01

    Most commercialized coronary stents are made of 316L stainless steels due to its good combination of properties, and currently some new stents are made of cobalt-based alloy owing to its higher mechanical properties. However, the presence of high quantity of nickel and/or cobalt elements in these materials, which are known to trigger the toxic and allergic responses, has caused many concerns. Nickel-free austenitic stainless steels have been developed in order to solve these problems. In this paper, based on the development of a new FeCr-Mn-Mo-N type high nitrogen nickel-free austenitic stainless steel, properties such as mechanical property, corrosion resistance in Hank′s solution, and in vitro blood compatibility including the kinetic clotting time and the platelets adhesion, were investigated in comparison to the above two conventional materials, a 316L stainless steel and a Co-28Cr-6Mo alloy. The results showed that the new high nitrogen steel possessed better combination of mechanical properties, corrosion resistance and blood compatibility than those of 316L steel and the Co-28Cr-6Mo alloy, and can be a promising alternative material for manufacture of coronary stents.

  14. Impact of the nanostructuration on the corrosion resistance and hardness of irradiated 316 austenitic stainless steels

    Science.gov (United States)

    Hug, E.; Prasath Babu, R.; Monnet, I.; Etienne, A.; Moisy, F.; Pralong, V.; Enikeev, N.; Abramova, M.; Sauvage, X.; Radiguet, B.

    2017-01-01

    The influence of grain size and irradiation defects on the mechanical behavior and the corrosion resistance of a 316 stainless steel have been investigated. Nanostructured samples were obtained by severe plastic deformation using high pressure torsion. Both coarse grain and nanostructured samples were irradiated with 10 MeV 56Fe5+ ions. Microstructures were characterized using transmission electron microscopy and atom probe tomography. Surface mechanical properties were evaluated thanks to hardness measurements and the corrosion resistance was studied in chloride environment. Nanostructuration by high pressure torsion followed by annealing leads to enrichment in chromium at grain boundaries. However, irradiation of nanostructured samples implies a chromium depletion of the same order than depicted in coarse grain specimens but without metallurgical damage like segregated dislocation loops or clusters. Potentiodynamic polarization tests highlight a definitive deterioration of the corrosion resistance of coarse grain steel with irradiation. Downsizing the grain to a few hundred of nanometers enhances the corrosion resistance of irradiated samples, despite the fact that the hardness of nanocrystalline austenitic steel is only weakly affected by irradiation. These new experimental results are discussed in the basis of couplings between mechanical and electrical properties of the passivated layer thanks to impedance spectroscopy measurements, hardness properties of the surfaces and local microstructure evolutions.

  15. Damage structure of austenitic stainless steel 316LN irradiated at low temperature in HFIR

    Energy Technology Data Exchange (ETDEWEB)

    Hashimoto, N.; Robertson, J.P.; Grossbeck, M.L.; Rowcliffe, A.F. [Oak Ridge National Lab., TN (United States); Wakai, E. [Japan Atomic Energy Research Inst. (Japan)

    1998-03-01

    TEM disk specimens of austenitic stainless steel 316LN irradiated to damage levels of about 3 dpa at irradiation temperatures of either about 90 C or 250 C have been investigated by using transmission electron microscopy. The irradiation at 90 C and 250 C induced a dislocation loop density of 3.5 {times} 10{sup 22} m{sup {minus}3} and 6.5 {times} 10{sup 22} m{sup {minus}3}, a black dot density of 2.2 {times} 10{sup 23} m{sup {minus}3} and 1.6 {times} 10{sup 23} m{sup {minus}3}, respectively, in the steels, and a high density (<1 {times} 10{sup 22} m{sup {minus}3}) of precipitates in matrix. Cavities could be observed in the specimens after the irradiation. It is suggested that the dislocation loops, the black dots, and the precipitates cause irradiation hardening, an increase in the yield strength and a decrease in the uniform elongation, in the 316LN steel irradiated at low temperature.

  16. Effects of Mo on the Precipitation Behaviors in High-Nitrogen Austenitic Stainless Steels

    Institute of Scientific and Technical Information of China (English)

    Feng Shi; Yang Qi; Chunming Liu

    2011-01-01

    Precipitation behaviors of Fe-18Cr-18Mn-0.63N and Fe-18Cr-18Mn-2Mo-0.69N high-nitrogen austenitic stainless steels during isothermally aging at 850℃ have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The experimental results show that precipitation displays a discontinuous cellular way and the precipitates are identified as Cr2N in Fe-18Cr-18Mn-0.63N steel. The addition of Mo makes precipitation occur not only at the grain boundary but also inside the grain and precipitation also displays discontinuous cellular way. The precipitates at the grain boundary and in the cell are both identified as G2N phase and χ phase and the precipitates inside the grain are identified as χ phase in Fe-18Cr-18Mn-2Mo-0.69N steel. The nucleations of χ phase and Cr2N phase at the grain boundary are both governed by the diffusion of Cr atoms. The formation and growth of χ phase inside the grain are induced by the impoverishment of N atoms with increasing aging time.

  17. Irradiation-Assisted Stress Corrosion Cracking of Austenitic Stainless Steels in BWR Environments

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Y. [Argonne National Lab. (ANL), Argonne, IL (United States); Chopra, O. K. [Argonne National Lab. (ANL), Argonne, IL (United States); Gruber, Eugene E. [Argonne National Lab. (ANL), Argonne, IL (United States); Shack, William J. [Argonne National Lab. (ANL), Argonne, IL (United States)

    2010-06-01

    The internal components of light water reactors are exposed to high-energy neutron irradiation and high-temperature reactor coolant. The exposure to neutron irradiation increases the susceptibility of austenitic stainless steels (SSs) to stress corrosion cracking (SCC) because of the elevated corrosion potential of the reactor coolant and the introduction of new embrittlement mechanisms through radiation damage. Various nonsensitized SSs and nickel alloys have been found to be prone to intergranular cracking after extended neutron exposure. Such cracks have been seen in a number of internal components in boiling water reactors (BWRs). The elevated susceptibility to SCC in irradiated materials, commonly referred to as irradiation-assisted stress corrosion cracking (IASCC), is a complex phenomenon that involves simultaneous actions of irradiation, stress, and corrosion. In recent years, as nuclear power plants have aged and irradiation dose increased, IASCC has become an increasingly important issue. Post-irradiation crack growth rate and fracture toughness tests have been performed to provide data and technical support for the NRC to address various issues related to aging degradation of reactor-core internal structures and components. This report summarizes the results of the last group of tests on compact tension specimens from the Halden-II irradiation. The IASCC susceptibility of austenitic SSs and heat-affected-zone (HAZ) materials sectioned from submerged arc and shielded metal arc welds was evaluated by conducting crack growth rate and fracture toughness tests in a simulated BWR environment. The fracture and cracking behavior of HAZ materials, thermally sensitized SSs and grain-boundary engineered SSs was investigated at several doses (≤3 dpa). These latest results were combined with previous results from Halden-I and II irradiations to analyze the effects of neutron dose, water chemistry, alloy compositions, and welding and processing conditions on IASCC

  18. A low-temperature study to examine the role of epsilon-martensite during strain-induced transformations in metastable austenitic stainless steels

    NARCIS (Netherlands)

    Datta, K.; Delhez, R.; Bronsveld, P.M.; Beyer, J.; Geijselaers, H.J.M.; Post, J.

    2009-01-01

    A low-temperature study of the mechanical behaviour of a metastable semi-austenitic stainless steel was carried out. This class of stainless steels is found to show a characteristic hump followed by softening in their stress–strain curves, especially at low temperatures, much like dynamically recrys

  19. A low-temperature study to examine the role of epsilon-martensite during strain-induced transformations in metastable austenitic stainless steels

    NARCIS (Netherlands)

    Datta, K.; Delhez, R.; Bronsveld, P. M.; Beyer, J.; Geijselaers, H. J. M.; Post, J.

    2009-01-01

    A low-temperature study of the mechanical behaviour of a metastable semi-austenitic stainless steel was carried out. This class of stainless steels is found to show a characteristic hump followed by softening in their stress-strain curves, especially at low temperatures, much like dynamically recrys

  20. Effect of Treatment Time on the Microstructure of Austenitic Stainless Steel During Low-Temperature Liquid Nitrocarburizing

    Science.gov (United States)

    Wang, Jun; Lin, Yuanhua; Zhang, Qiang; Zeng, Dezhi; Fan, Hongyuan

    2014-09-01

    The effect of treatment time on the microstructure of AISI 304 austenitic stainless steel during liquid nitrocarburizing (LNC) at 703 K (430 °C) was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Experimental results revealed that the modified layer was covered with the alloy surface and the modified layer depth increased extensively from 2 to 33.4 μm with increasing treatment time. SEM and XRD showed that when the 304 stainless steel sample was subjected to LNC at 703 K (430 °C) for less than 4 hours, the main phase of the modified layer was expanded austenite. When the treatment time was prolonged to 8 hours, the abundant expanded austenite was formed and it partially transformed into CrN and ferrite subsequently. With the increased treatment time, more and more CrN precipitate transformed in the overwhelming majority zone in the form of a typical dendritic structure in the nearby outer part treated for 40 hours. Still there was a single-phase layer of the expanded austenite between the CrN part and the inner substrate. TEM showed the expanded austenite decomposition into the CrN and ferrite after longtime treatment even at low temperature.

  1. Influence of Plastic Deformation on Low Temperature Surface Hardening of Austenitic and Precipitation Hardening Stainless Steels by Gaseous Nitriding

    DEFF Research Database (Denmark)

    Bottoli, Federico; Winther, Grethe; Christiansen, Thomas Lundin;

    2015-01-01

    This article addresses an investigation of the influence of plastic deformation on low temperature surface hardening by gaseous nitriding of three commercial austenitic stainless steels: AISI 304, EN 1.4369 and Sandvik Nanoflex® with various degrees of austenite stability. The materials were...... plastically deformed to different equivalent strains by uniaxial tension. Gaseous nitriding of the strained material was performed in ammonia gas at atmospheric pressure at 703 K (430 °C) and 693 K (420 °C) depending on the material. Microstructural characterization of the as-deformed states and the nitrided...

  2. OPTIMIZATION OF SURFACE ROUGHNESS AND TOOL FLANK WEAR IN TURNING OF AISI 304 AUSTENITIC STAINLESS STEEL WITH CVD COATED TOOL

    Directory of Open Access Journals (Sweden)

    M. KALADHAR

    2013-04-01

    Full Text Available AISI 304 austenitic stainless steel is a popularly used grade in the various fields of manufacturing because of its high ductility, high durability and excellent corrosion resistance. High work hardening, low heat conductivity and high built up edge (BUE formation made this as difficult-to- machine material. Poor surface quality and rapid tool wear are the common problems encountered while machining it. In the present work, an attempt has been made to explore the influence of machining parameters on the performance measures, surface roughness and flank wear in turning of AISI 304 austenitic stainless steel with a two layer Chemical vapour deposition(CVD coated tool. In order to achieve this, Taguchi approach has been employed. The results revealed that the cutting speed most significantly, influences both surface roughness and flank wear. In addition to this the optimal setting of process parameters and optimal ranges of performance measures are predicted.

  3. Narrow gap TIG and electron beam weld inspection in austenitic stainless steel using pulse echo, TOFD and phased array ultrasonics

    Energy Technology Data Exchange (ETDEWEB)

    Quirk, K.P.; Turner, J.L. [Phoenix Inspection Systems Limited, Warrington (United Kingdom)

    2004-07-01

    'Full-text:' Narrow gap Tungsten Inert Gas (TIG) and Electron Beam (EB) welding techniques are being considered for the splice joint welds on the austenitic stainless steel Vacuum Vessel in the next generation of experimental Fusion Power stations under the ITER programme. Under the programme there is a requirement to develop automated ultrasonic NDT techniques to inspect material up to 60 mm thick in both weld types. These narrow welds are difficult to inspect because of the steep fusion faces made more difficult in this project by the beam scattering effects of austenitic stainless steel welds and the very limited access from only one side of the vessel. The paper details the development of the combined Pulse Echo, TOFD and Phased Array techniques on behalf of ITER. The authors describe the philosophy behind the inspections, results and possible transfer of the technology to other sectors of industry. (author)

  4. Assessment of void swelling in austenitic stainless steel PWR core internals.

    Energy Technology Data Exchange (ETDEWEB)

    Chung, H. M.; Energy Technology

    2006-01-31

    As many pressurized water reactors (PWRs) age and life extension of the aged plants is considered, void swelling behavior of austenitic stainless steel (SS) core internals has become the subject of increasing attention. In this report, the available database on void swelling and density change of austenitic SSs was critically reviewed. Irradiation conditions, test procedures, and microstructural characteristics were carefully examined, and key factors that are important to determine the relevance of the database to PWR conditions were evaluated. Most swelling data were obtained from steels irradiated in fast breeder reactors at temperatures >385 C and at dose rates that are orders of magnitude higher than PWR dose rates. Even for a given irradiation temperature and given steel, the integral effects of dose and dose rate on void swelling should not be separated. It is incorrect to extrapolate swelling data on the basis of 'progressive compounded multiplication' of separate effects of factors such as dose, dose rate, temperature, steel composition, and fabrication procedure. Therefore, the fast reactor data should not be extrapolated to determine credible void swelling behavior for PWR end-of-life (EOL) or life-extension conditions. Although the void swelling data extracted from fast reactor studies is extensive and conclusive, only limited amounts of swelling data and information have been obtained on microstructural characteristics from discharged PWR internals or steels irradiated at temperatures and at dose rates comparable to those of a PWR. Based on this relatively small amount of information, swelling in thin-walled tubes and baffle bolts in a PWR is not considered a concern. As additional data and relevant research becomes available, the newer results should be integrated with existing data, and the worthiness of this conclusion should continue to be scrutinized. PWR baffle reentrant corners are the most likely location to experience high swelling

  5. Parameters influencing the transgranular stress corrosion cracking behaviour of austenitic stainless steels in systems conveying reactor coolant

    Energy Technology Data Exchange (ETDEWEB)

    Kilian, R.; Wesseling, U. [Framatome ANP (Germany); Wachter, O. [E.ON Kernkraft (Germany); Widera, M. [RWE Power (Germany); Brummer, G. [HEW - (Germany); Ilg, U. [EnBW - (Germany)

    2002-07-01

    During replacement of an auxiliary system in the German PWR KKS (NPP Stade) a damage was detected in a valve housing and in the connected piping both made from stabilised austenitic stainless steel. During operation stagnant conditions are present in this area. Based on the failure analysis chloride induced stress corrosion cracking (SCC) was found as the dominating root cause. In the open literature many cases of corrosion observed in the water/steam interface in valve components as well as in adjacent portions of auxiliary circuits made of un-stabilized stainless steels are mentioned. A common feature of the reported cases is that transgranular cracking was found. Extensive laboratory investigations revealed that non-stabilised austenitic stainless steels are also sensitive to transgranular cracking in boric acid solutions particularly in concentrated solutions. Often these solutions are contaminated with chlorides and/or oxygen is present. Taking into account the literature data the question could arise whether the above mentioned cracking may be also caused by boric acid attack. Thus, for stabilised stainless steels laboratory exposure tests at 80 C in saturated aerated boric acid solution and at 300 C in (at 100 C) saturated, oxygen free boric acid solution have been performed. Double-U-bend specimens and wedge loaded 1T-CT specimens made of Ti- and Nb-stabilised austenitic stainless steels were used. The results revealed no evidence of crack initiation and crack growth. Based on the laboratory results and the literature data an attempt is undertaken to separate parameters influencing chloride induced SCC from the effect of boric acid. (authors)

  6. Effect of cold work on low-temperature sensitization behaviour of austenitic stainless steels

    Science.gov (United States)

    Kain, V.; Chandra, K.; Adhe, K. N.; De, P. K.

    2004-09-01

    The effects of cold work and low-temperature sensitization heat treatment of non-sensitized austenitic stainless steels have been investigated and related to the cracking in nuclear power reactors. Types 304, 304L and 304LN developed martensite after 15% cold working. Heat treatment of these cold worked steels at 500 °C led to sensitization of grain boundaries and the matrix and a desensitization effect was seen in 11 days due to fast diffusion rate of chromium in martensite. Types 316L and 316LN did not develop martensite upon cold rolling due to its chemical composition suppressing the martensite transformation (due to deformation) temperature, hence these were not sensitized at 500 °C. The sensitization of the martensite phase was always accompanied by a hump in the reactivation current peak in the double loop electrochemical potentiokinetic reactivation test, thus providing a test to detect such sensitization. It was shown that bending does not produce martensite and therefore, is a better method to simulate weld heat affected zone. Bending and heating at 500 °C for 11 days led to fresh precipitation due to increased retained strain and desensitization of 304LN due to faster diffusion rate of chromium along dislocations. The as received or solution annealed 304 and 304LN with 0.15% nitrogen showed increased sensitization after heat treatment at 500 °C, indicating the presence of carbides/nitrides.

  7. Influence of combined thermomechanical treatment on impurity segregation in ferritic-martensitic and austenitic stainless steels

    Science.gov (United States)

    Ilyin, A. M.; Neustroev, V. S.; Shamardin, V. K.; Shestakov, V. P.; Tazhibaeva, I. L.; Krivchenkoa, V. A.

    2000-12-01

    In this study 13Cr2MoVNb ferritic-martensitic steel (FMS) and 16Cr15Ni3MoNb austenitic stainless steel (ASS) tensile specimens were subjected to standard heat treatments and divided into two groups. Specimens in group 1 (FMS only) were aged at 400°C in a stress free and in an elastically stressed state with a tensile load (100 MPa) then doped with hydrogen in an electrolytic cell. Specimens in group 2 were subjected to cold work (up to 10%) and exposed to short-time heating at 500° for 0.5 h. All specimens were fractured at room temperature in an Auger spectrometer and Auger analysis of the fracture surfaces was performed in situ after fracturing. A noticeable increase of N and P segregation levels and a widening of the depth distribution on the grain boundary facets were observed in the FMS after aging in the stressed state. Cold-worked FMS and ASS showed a ductile dimple mode of fracture, but relatively high levels of S, P and N were observed on the dimple surfaces. We consider the origin of such effects in terms of the stressed state and plastic-deformation-enhanced segregation.

  8. Fatigue behavior in austenitic stainless steels in high-temperature water

    Science.gov (United States)

    Smith, Jean Laverty

    The fatigue life of Type 304 and Type 316NG austenitic stainless steel has been shown to be significantly lower in light water reactor environments than in air at 288°C. The focus of this study was to determine the effect of dissolved oxygen (DO) on fatigue crack initiation and early crack growth at 288°C using fully-reversed, constant strain, axial fatigue tests. The fatigue tests were chosen to evaluate fracture surface appearance, fatigue crack lengths, and fatigue crack growth rates. Additional studies were conducted to evaluate the oxide film growth kinetics of Type 304 and Type 316NG stainless steel in high-temperature water. Corrosion coupons were exposed for intervals up to 50 days to high-temperature water at 288°C with two different levels of dissolved oxygen. The coupons were evaluated for weight change, oxide film thickness, and oxide film composition. The fatigue testing and oxide evaluations conducted in this study indicate that in low-DO water, the bulk environment does not allow a passive film to form, and newly created metal surfaces do not oxidize. Fatigue cracks propagate as Mode I tensile cracks normal to the stress axis from the onset. The apparent lack of Stage I crack growth in low-DO water accounts for the significant reduction in life in this environment as compared to air. In high-DO water, the bulk environment supports the formation of a passive film and prevents the evolution of hydrogen. Crack growth initially occurs only along primary slip planes at angles 45° to the applied stress. As the crack length increases, the crack tip environment becomes increasingly independent of the bulk environment, water at the crack tip becomes unstable, and the newly created surfaces no longer re-oxidize. Subsequently, the increasing stress intensity allows slip to occur on additional planes, and the fatigue crack propagates as a Mode I tensile crack.

  9. Effect of heat treatment on the microstructure and mechanical properties of martensitic stainless-steel joints welded with austenitic stainless-steel fillers: Vpliv toplotne obdelave na mikrostrukturo in mehanske lastnosti martenzitnih nerjavnih spojev, varjenih z avstenitnimi nerjavnimi elektrodami:

    OpenAIRE

    Calik, Adnan; Mustafa Serdar KARAKAŞ

    2013-01-01

    AISI 422 martensitic stainless steels were welded according to the ISO 15792-1 standard with austenitic stainless-steel filler. The effects of tempering and preheating heat treatments were also evaluated. The microstructures of the welds were characterized with optical microscopy. Mechanical properties were determined via microhardness, tensile and fatigue tests, and compared to those of the unwelded AISI 422 steel. X-ray diffraction was used to characterize the phases present in the weld. Ch...

  10. Irradiation-assisted stress corrosion cracking behavior of austenitic stainless steels applicable to LWR core internals.

    Energy Technology Data Exchange (ETDEWEB)

    Chung, H. M.; Shack, W. J.; Energy Technology

    2006-01-31

    This report summarizes work performed at Argonne National Laboratory on irradiation-assisted stress corrosion cracking (IASCC) of austenitic stainless steels that were irradiated in the Halden reactor in simulation of irradiation-induced degradation of boiling water reactor (BWR) core internal components. Slow-strain-rate tensile tests in BWR-like oxidizing water were conducted on 27 austenitic stainless steel alloys that were irradiated at 288 C in helium to 0.4, 1.3, and 3.0 dpa. Fractographic analysis was conducted to determine the fracture surface morphology. Microchemical analysis by Auger electron spectroscopy was performed on BWR neutron absorber tubes to characterize grain-boundary segregation of important elements under BWR conditions. At 0.4 and 1.4 dpa, transgranular fracture was mixed with intergranular fracture. At 3 dpa, transgranular cracking was negligible, and fracture surface was either dominantly intergranular, as in field-cracked core internals, or dominantly ductile or mixed. This behavior indicates that percent intergranular stress corrosion cracking determined at {approx}3 dpa is a good measure of IASCC susceptibility. At {approx}1.4 dpa, a beneficial effect of a high concentration of Si (0.8-1.5 wt.%) was observed. At {approx}3 dpa, however, such effect was obscured by a deleterious effect of S. Excellent resistance to IASCC was observed up to {approx}3 dpa for eight heats of Types 304, 316, and 348 steel that contain very low concentrations of S. Susceptibility of Types 304 and 316 steels that contain >0.003 wt.% S increased drastically. This indicates that a sulfur related critical phenomenon plays an important role in IASCC. A sulfur content of <0.002 wt.% is the primary material factor necessary to ensure good resistance to IASCC. However, for Types 304L and 316L steel and their high-purity counterparts, a sulfur content of <0.002 wt.% alone is not a sufficient condition to ensure good resistance to IASCC. This is in distinct contrast to

  11. Effects of a high magnetic field on fracture toughness at 4. 2 K for austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Murase, S.; Kobatake, S.; Tanaka, M.; Tashiro, I.; Horigami, O.; Ogiwara, H. (Toshiba R and D Center, Kawasaki (Japan)); Shibata, K. (Univ. Tokyo, Bunkyo (Japan)); Nagai, K.; Ishikawa, K. (National Research Inst. for Metals, Sengen, Tsukuba (Japan))

    1993-01-01

    Structural stainless steels for cryogenic use in superconducting magnets for fusion reactors are used under high magnetic field and stress. The authors have performed fracture thoughness tests, using the unloading compliance method at 4.2 K on SUS304, 316LN and 304L stainless steels precracked at 77 K, in a varying magnetic field (0 and 8 T). Fracture toughness values (J[sub IC]) for 304 and 316LN steels at 8 T decreased by 17 and 20%, respectively, as compared with the 0 T condition. On the other hand, J[sub IC] for 304L steel was 30% increased by applying a high magnetic field of 8 T. Details of martensite formation and austenite stability are considered in discussion. (orig.).

  12. Development of Stronger and More Reliable Cast Austenitic Stainless Steels (H-Series) Based on Scientific and Design Methodology

    Energy Technology Data Exchange (ETDEWEB)

    Pankiw, Roman I; Muralidharan, G. (Murali); Sikka, Vinod K.

    2006-06-30

    The goal of this project was to increase the high-temperature strength of the H-Series of cast austenitic stainless steels by 50% and the upper use temperature by 86 to 140 degrees fahrenheit (30 to 60 degrees celsius). Meeting this goal is expected to result in energy savings of 35 trillion Btu/year by 2020 and energy cost savings of approximately $230 million/year. The higher-strength H-Series cast stainless steels (HK and HP type) have applications for the production of ethylene in the chemical industry, for radiant burner tubes and transfer rolls for secondary processing of steel in the steel industry, and for many applications in the heat treating industry, including radiant burner tubes. The project was led by Duraloy Technologies, Inc., with research participation by Oak Ridge National Laboratory (ORNL) and industrial participation by a diverse group of companies.

  13. Methods for the In-Situ Characterization of Cast Austenitic Stainless Steel Microstructures

    Science.gov (United States)

    Ramuhalli, P.; Good, M. S.; Harris, R. J.; Bond, L. J.; Ruud, C. O.; Diaz, A. A.; Anderson, M. T.

    2011-06-01

    Cast austenitic stainless steel (CASS) that was commonly used in U.S. nuclear power plants is a coarse-grained, elastically anisotropic material. Its engineering properties made it a material of choice for selected designs of nuclear power reactor systems. However, the material manufacturing and fabrication processes result in a variety of coarse-grain microstructures that make current ultrasonic in-service inspection of components quite challenging. To address inspection needs, new ultrasonic inspection approaches are being sought. However, overcoming the deleterious and variable effects of the microstructure on the interrogating ultrasonic beam may require knowledge of the microstructure, for potential optimization of inspection parameters to enhance the probability of detection (POD). The ability to classify microstructure type (e.g. polycrystalline or columnar) has the potential to guide selection of optimal NDE approaches. This paper discusses the application of ultrasonic and electromagnetic methods for classifying CASS microstructures, when making measurements from the outside surface of the component. Results to date demonstrate the potential of these measurements to discriminate between two consistent microstructures—equiaxed-grain material versus columnar-grain material. The potential for fusion of ultrasonic and electromagnetic measurements for in-situ microstructure characterization in CASS materials will be explored.

  14. Methods for the In-Situ Characterization of Cast Austenitic Stainless Steel Microstructures

    Energy Technology Data Exchange (ETDEWEB)

    Ramuhalli, Pradeep; Good, Morris S.; Harris, Robert V.; Bond, Leonard J.; Ruud, Clayton O.; Diaz, Aaron A.; Anderson, Michael T.

    2011-06-29

    Cast austenitic stainless steel (CASS) that was commonly used in U.S. nuclear power plants is a coarse-grained, elastically anisotropic material. Its engineering properties made it a material of choice for selected designs of nuclear power reactor systems. However, the fabrication processes result in a variety of coarse-grain microstructures that make current ultrasonic in-service inspection of components quite challenging. To address inspection needs, new ultrasonic inspection approaches are being sought. However, overcoming the deleterious and variable effects of the microstructure on the interrogating ultrasonic beam may require knowledge of the microstructure, for potential optimization of inspection parameters to enhance the probability of detection (POD). The ability to classify microstructure type (e.g. polycrystalline or columnar) has the potential to guide selection of optimal NDE approaches. This paper discusses the application of ultrasonic and electromagnetic methods for classifying CASS microstructures, when making measurements from the outside surface of the component. Results to date demonstrate the potential of these measurements to discriminate between two consistent microstructures - equiaxed-grain material versus columnar-grain material. The potential for fusion of ultrasonic and electromagnetic measurements for in-situ microstructure characterization in CASS materials will be explored.

  15. The evolution of mechanical property change in irradiated austenitic stainless steels

    Science.gov (United States)

    Lucas, G. E.

    1993-11-01

    The evolution of mechanical properties in austenitic stainless steels during irradiation is reviewed. Changes in strength, ductility and fracture toughness are strongly related to the evolution of the damage microstructure and microstructurally-based models for strengthening reasonably correlate the data. Irradiation-induced defects promote work softening and flow localization which in turn leads to significant reductions in ductility and fracture toughness beyond about 10 dpa. The effects of irradiation on fatigue appear to be modest except at high temperature where helium embrittlement becomes important. The swelling-independent component of irradiation creep strain increases linearly with dose and is relatively insensitive to material variables and irradiation temperature, except at low temperatures where accelerated creep may occur as a result of low vacancy mobility. Creep rupture life is a strong function of helium content, but is less sensitive to metallurgical conditions. Irradiation-induced stress corrosion cracking appears to be related to the evolution of radiation-induced segregation/depletion at grain boundaries, and hence may not be significant at low irradiation temperatures.

  16. Microstructural evolution in austenitic stainless steel irradiated with triple-beam

    Energy Technology Data Exchange (ETDEWEB)

    Hamada, Shozo; Miwa, Yukio; Yamaki, Daiju [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Zhang Yichuan

    1997-03-01

    An austenitic stainless steel was simultaneously irradiated with nickel, helium and hydrogen ions at the temperature range of 573-673 K. The damage level and injected concentration of He and H ions in the triple-beam irradiated region are 57 dpa, 19000 and 18000 at.ppm, respectively. Following to irradiation, the cross sectional observation normal to the incident surface of the specimen was carried out with a transmission electron microscope. Two bands parallel to the incident surface were observed in the irradiated specimen, which consist of dislocation loops and lines of high number density. These locate in the range of the depth of 0.4 to 1.3 {mu}m and 1.8 to 2.4 {mu}m from the incident surface, respectively. The region between two bands, which corresponds to the triple beam irradiated region, shows very low number density of dislocations than that in each band. Observation with higher magnification of this region shows that fine cavities with high number density uniformly distribute in the matrix. (author)

  17. Tensile properties of a titanium modified austenitic stainless steel and the weld joints after neutron irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Shiba, K.; Ioka, I.; Jitsukawa, S.; Hamada, A.; Hishinuma, A. [and others

    1996-10-01

    Tensile specimens of a titanium modified austenitic stainless steel and its weldments fabricated with Tungsten Inert Gas (TIG) and Electron Beam (EB) welding techniques were irradiated to a peak dose of 19 dpa and a peak helium level of 250 appm in the temperature range between 200 and 400{degrees}C in spectrally tailored capsules in the Oak Ridge Research Reactor (ORR) and the High Flux Isotope Reactor (HFIR). The He/dpa ratio of about 13 appm/dpa is similar to the typical helium/dpa ratio of a fusion reactor environment. The tensile tests were carried out at the irradiation temperature in vacuum. The irradiation caused an increase in yield stress to levels between 670 and 800 MPa depending on the irradiation temperature. Total elongation was reduced to less than 10%, however the specimens failed in a ductile manner. The results were compared with those of the specimens irradiated using irradiation capsules producing larger amount of He. Although the He/dpa ratio affected the microstructural change, the impact on the post irradiation tensile behavior was rather small for not only base metal specimens but also for the weld joint and the weld metal specimens.

  18. Comparison of hydrogen gas embrittlement of austenitic and ferritic stainless steels

    Science.gov (United States)

    Perng, T. P.; Altstetter, C. J.

    1987-01-01

    Hydrogen-induced slow crack growth (SCG) was compared in austenitic and ferritic stainless steels at 0 to 125 °Cand 11 to 216 kPa of hydrogen gas. No SCG was observed for AISI 310, while AISI 301 was more susceptible to hydrogen embrittlement and had higher cracking velocity than AL 29-4-2 under the same test conditions. The kinetics of crack propagation was modeled in terms of the hydrogen transport in these alloys. This is a function of temperature, microstructure, and stress state in the embrittlement region. The relatively high cracking velocity of AISI 301 was shown to be controlled by the fast transport of hydrogen through the stress-induced α' martensite at the crack tip and low escape rate of hydrogen through the γ phase in the surrounding region. Faster accumulation rates of hydrogen in the embrittlement region were expected for AISI 301, which led to higher cracking velocities. The mechanism of hydrogen-induced SCG was discussed based upon the concept of hydrogen-enhanced plasticity.

  19. Parametric optimization during machining of AISI 304 Austenitic Stainless Steel using CVD coated DURATOMIC cutting insert

    Directory of Open Access Journals (Sweden)

    M. Kaladhar

    2012-08-01

    Full Text Available In this work, Taguchi method is applied to determine the optimum process parameters for turning of AISI 304 austenitic stainless steel on CNC lathe. A Chemical vapour deposition (CVD coated cemented carbide cutting insert is used which is produced by DuratomicTM technology of 0.4 and 0.8 mm nose radii. The tests are conducted at four levels of Cutting speed, feed and depth of cut. The influence of these parameters are investigated on the surface roughness and material removal rate (MRR. The Analysis Of Variance (ANOVA is also used to analyze the influence of cutting parameters during machining. The results revealed that cutting speed significantly (46.05% affected the machined surface roughness values followed by nose radius (23.7%. The influence of the depth of cut (61.31% in affecting material removal rate (MRR is significantly large. The cutting speed (20.40% is the next significant factor. Optimal range and optimal level of parameters are also predicted for responses.

  20. Void Swelling and Microstructure of Austenitic Stainless Steels Irradiated in the BOR - 60 Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Y. [Argonne National Lab. (ANL), Argonne, IL (United States); Yang, Yong [Argonne National Lab. (ANL), Argonne, IL (United States); Huang, Yina [Argonne National Lab. (ANL), Argonne, IL (United States); Allen, T. [Argonne National Lab. (ANL), Argonne, IL (United States); Alexandreanu, B. [Argonne National Lab. (ANL), Argonne, IL (United States); Natesan, K. [Argonne National Lab. (ANL), Argonne, IL (United States)

    2012-11-01

    As nuclear power plants age and neutron fluence increases, detrimental effects resulting from radiation damage have become an increasingly important issue for the operational safety and structural integrity of core internal components. In this study, irradiated specimens of reactor core internal components were characterized by transmission electron microscopy. The specimens had been irradiated to 5.5-45 dpa in the BOR-60 reactor at a dose rate close to 10-6 dpa/s and temperature of about 320°C. No voids were observed in the austenitic stainless steels and nickel alloys at all doses. Despite the possibility that fine voids below the TEM resolution limit may be present, it was clear that void swelling was insignificant in all examined alloys up to 45 dpa. Irradiated microstructures of the studied alloys were dominated by a high density of Frank loops. The mean size and density of the Frank loops varied from one material to another, but saturated with increasing dose above ~10 dpa. While no irradiation-induced precipitations were present below 24.5 dpa, fine precipitates were evident in several alloys at 45 dpa.

  1. On the crystal structure of Cr2N precipitates in high-nitrogen austenitic stainless steel.

    Science.gov (United States)

    Lee, Tae-Ho; Oh, Chang-Seok; Han, Heung Nam; Lee, Chang Gil; Kim, Sung-Joon; Takaki, Setsuo

    2005-04-01

    The crystal structure of Cr(2)N precipitates in high-nitrogen austenitic stainless steel was investigated by transmission electron microscopy (TEM). Based on the analyses of selected area diffraction (SAD) patterns, the crystal structure of Cr(2)N was confirmed to be trigonal (P31m) and was characterized by three sets of superlattice reflections: (001), ((11/33)0)and ((11/33)1). These could be explained in terms of the epsilon-type occupational ordering of nitrogen. The static concentration waves (SCWs) method was applied to describe the ordered superstructure of Cr(2)N. The occupation probability function (OPF) for describing the distribution of N atoms in the Cr(2)N superstructure was derived based on the superlattice reflections obtained in the SAD patterns and could be expressed as: n(r)=c-1/6eta1cos2piz+4/3eta3cos(2pi/3)(x+y+3z). The crystallographic models for epsilon-type ordering, mainly suggested in the Fe-N system, were discussed in comparison to the present model.

  2. Precipitation Kinetics of Cr2N in High Nitrogen Austenitic Stainless Steel

    Institute of Scientific and Technical Information of China (English)

    SHI Feng; WANG Li-jun; CUI Wen-fang; LIU Chun-ming

    2008-01-01

    The precipitation behavior of Cr2N during isothermal aging in the temperature range from 700℃to 950℃ in Fe-18Cr-12Mn-0.48N(in mass percent)high nitrogen austenitic stainless steel,including morphology and content of precipitate,was investigated using optical microscopy,scanning electron microscopy,and transmission electron microscopy.The isothermal precipitation kinetics curve of Cr2N and the corresponding precipitation activation energy were obtained.The results show that Cr2N phase precipitates in a cellular way and its morphology is transformed from initial granular precipitates to lamellar ones in the cell with increasing aging time.The nose temperature of Cr2N precipitation is about 800℃,with a corresponding incubation period of 30 min,and the ceiling temperature of Cr2N precipitation is 950℃.The diffusion activation energy of Cr2N precipitation is 296 kJ/mol.

  3. Preparation of high nitrogen and nickel-free austenitic stainless steel by powder injection molding

    Institute of Scientific and Technical Information of China (English)

    Dawei Cui; Junsheng Jiang; Guangming Cao; Enzhong Xiao; Xuanhui Qu

    2008-01-01

    High nitrogen and nickel-free austenitic stainless steel has received much recognition worldwide because it can solve the problem of "nickel-allergy" and has outstanding mechanical and physical properties. In this article, 0Cr17Mn11Mo3N was prepared by powder injection molding (PIM) technique accompanied with solid-nitriding. The results show that the critical solid loading can achieve up to 64vo1% by use of gas-atomized powders with the average size of 17.4 μm. The optimized sintering conditions are de- termined to be 1300℃,2 h in flowing nitrogen atmosphere, at which the relative density reaches to 99% and the N content is as high as 0.78wt%. After solution annealing at 1150℃for 90 min and water quench, the 0.2% yield strength, ultimate tensile strength (UTS), elongation, reduction in area, and hardness can reach as high as 580 MPa, 885 MPa, 26.0%, 29.1%, and Hv 222, respectively. C 2008 University of Science and Technology Beijing. All rights reserved.

  4. Thermomechanical processing optimization for 304 austenitic stainless steel using artificial neural network and genetic algorithm

    Science.gov (United States)

    Feng, Wen; Yang, Sen

    2016-12-01

    Thermomechanical processing has an important effect on the grain boundary character distribution. To obtain the optimal thermomechanical processing parameters is the key of grain boundary engineering. In this study, genetic algorithm (GA) based on artificial neural network model was proposed to optimize the thermomechanical processing parameters. In this model, a back-propagation neural network (BPNN) was established to map the relationship between thermomechanical processing parameters and the fraction of low-Σ CSL boundaries, and GA integrated with BPNN (BPNN/GA) was applied to optimize the thermomechanical processing parameters. The validation of the optimal thermomechanical processing parameters was verified by an experiment. Moreover, the microstructures and the intergranular corrosion resistance of the base material (BM) and the materials produced by the optimal thermomechanical processing parameters (termed as the GBEM) were studied. Compared to the BM specimen, the fraction of low-Σ CSL boundaries was increased from 56.8 to 77.9% and the random boundary network was interrupted by the low-Σ CSL boundaries, and the intergranular corrosion resistance was improved in the GBEM specimen. The results indicated that the BPNN/GA model was an effective and reliable means for the thermomechanical processing parameters optimization, which resulted in improving the intergranular corrosion resistance in 304 austenitic stainless steel.

  5. Mechanical Behaviors of Ultrafine-Grained 301 Austenitic Stainless Steel Produced by Equal-Channel Angular Pressing

    Science.gov (United States)

    Huang, C. X.; Yang, G.; Wang, C.; Zhang, Z. F.; Wu, S. D.

    2011-07-01

    The technique of equal-channel angular pressing (ECAP) was used to refine the microstructure of an AISI 301 austenitic stainless steel (SS). An ultrafine-grained (UFG) microstructure consisting mainly of austenite and a few martensite was achieved in 301 steel after ECAP processing for four passes at 523 K (250 °C). By submitting the as-ECAP rods to annealing treatment in the temperature range from 853 K to 893 K (580 °C to 620 °C) for 60 minutes, fully austenitic microstructures with grain sizes of 210 to 310 nm were obtained. The uniaxial tensile tests indicated that UFG 301 austenitic SS had an excellent combination of high yield strength (>1.0 GPa) and high elongation-to-fracture (>30 pct). The tensile stress-strain curves exhibited distinct yielding peak followed by obvious Lüders deformation. Measurements showed that Lüders elongation increased with an increase in strength as well as a decrease in grain size. The microstructural changes in ultrafine austenite grains during tensile deformation were tracked by X-ray diffraction and transmission electron microscope. It was found that the strain-induced phase transformation from austenite to martensite took place soon after plastic deformation. The transformation rate with strain and the maximum strain-induced martensite were promoted significantly by ultrafine austenite grains. The enhanced martensitic transformation provided extra strain-hardening ability to sustain the propagation of Lüders bands and large uniform plastic deformation. During tensile deformation, the Lüders bands and martensitic transformation interacted with each other and made great contribution to the excellent mechanical properties in UFG austenitic SS.

  6. Electron work functions of ferrite and austenite phases in a duplex stainless steel and their adhesive forces with AFM silicon probe.

    Science.gov (United States)

    Guo, Liqiu; Hua, Guomin; Yang, Binjie; Lu, Hao; Qiao, Lijie; Yan, Xianguo; Li, Dongyang

    2016-02-12

    Local electron work function, adhesive force, modulus and deformation of ferrite and austenite phases in a duplex stainless steel were analyzed by scanning force microscopy. It is demonstrated that the austenite has a higher electron work function than the ferrite, corresponding to higher modulus, smaller deformation and larger adhesive force. Relevant first-principles calculations were conducted to elucidate the mechanism behind. It is demonstrated that the difference in the properties between austenite and ferrite is intrinsically related to their electron work functions.

  7. Microscopic investigation of pitting corrosion in plasma nitrided austenitic stainless steel; Mikroskopische Untersuchung von Lochkorrosion an plasmanitriertem austenitischem rostfreiem Stahl

    Energy Technology Data Exchange (ETDEWEB)

    Escalada, Lisandro; Simison, Silvia N. [Univ. of Mar del Plata (Argentina). Faculty of Engineering; Bruehl, Sonia P. [National Univ. of Technology, Concepcion del Uruguay (Argentina). Surface Engineering Group

    2014-10-01

    UNS 31603 austenitic stainless steel was nitrided using different techniques, and pitting corrosion resistance was analysed in a chloride solution. All nitriding techniques, LEII, PI. and convectional DC nitriding produced a nitrided layer called S phase which is corrosion resistant. Pits morphology and layer structure was investigated using optical and electronic microscopy, SEM-FIB, EDS, and a 3D reconstruction of a pit was assessed using FIB tomography. It was concluded that pits are initiated in MnS inclusions and a channel was generated passing through the nitrided layer, connecting the steel with the electrolyte. Base alloy dissolution was observed beneath the nitrided layer.

  8. Material Characterization of Fatigue Specimens made from Meta-stable Austenitic Stainless Steel

    Energy Technology Data Exchange (ETDEWEB)

    Niffenegger, M.; Grosse, M.; Kalkhof, D.; Leber, H. [Paul Scherrer Institut Villigen (Switzerland); Vincent, A.; Pasco, L.; Morin, M. [Insa de Lyon (France)

    2003-07-01

    defects, - Metallographic investigations to determine shape and size of grains and martensite. Based on results from former investigations, main attention was paid to the content of martensitic phase as an indicator for fatigue. Since most NDT-methods are considered as indirect methods for the detection of martensite, neutron diffraction was applied as a reference method for a quantitative determination of martensite. Differences between the three investigated metastable austenitic stainless steels concerning their microstructure and affinity for martensitic transformation were observed. After a short description of the measuring methods some representative results are presented and discussed in this report. Finally, some conclusions in respect to the application of NDT-methods are summarised. (author)

  9. Effect of copper on the formation of strain-induced martensite in two austenitic stainless steels AISI 304

    Energy Technology Data Exchange (ETDEWEB)

    Gilapa, Leonidas Cayo Mamani, E-mail: leonidas@ifsc.edu.br [Instituto Federal de Santa Catarina, Rua Pavão, 1337, Bairro Costa e Silva, Joinville, SC CEP 89220-200 (Brazil); Oliveira, Carlos Augusto Silva de, E-mail: carlos.a@ufsc.br [Universidade Federal de Santa Catarina, Campus Universitário Reitor João David Ferreira Lima, Trindade, Florianópolis, SC CEP 88040-970 (Brazil); Silva, Manoel Ribeiro da, E-mail: mrsilva@unifei.edu.br [Universidade Federal de Itajubá, Instituto de Ciências, Itajubá (Brazil)

    2015-01-12

    The transformation of strain-induced martensite in two metastable austenitic stainless steels, AISI 304, with the same basic composition and concentrations of Cu variables was characterized by transmission electron microscopy and magnetic measurements. The deformations to induce the formation of martensite were performed using the test of conformability with Nakajima tooling at room temperature. The results obtained for the various samples showed that the steel with lower content of Cu presented higher degree of magnetization. Also it was observed that the martensite magnetic α′ and paramagnetic ε are formed at the intersection of dislocation, in the grain boundary, inside and at the edge of twinned and the stacking faults in the austenite.

  10. A review of irradiation effects on LWR core internal materials - IASCC susceptibility and crack growth rates of austenitic stainless steels

    Science.gov (United States)

    Chopra, O. K.; Rao, A. S.

    2011-02-01

    Austenitic stainless steels (SSs) are used extensively as structural alloys in the internal components of light water reactor (LWR) pressure vessels because of their relatively high strength, ductility, and fracture toughness. However, exposure to neutron irradiation for extended periods changes the microstructure (radiation hardening) and microchemistry (radiation-induced segregation) of these steels, and degrades their fracture properties. Irradiation-assisted stress corrosion cracking (IASCC) is another degradation process that affects LWR internal components exposed to neutron radiation. The existing data on irradiated austenitic SSs were reviewed to evaluate the effects of key parameters such as material composition, irradiation dose, and water chemistry on IASCC susceptibility and crack growth rates of these materials in LWR environments. The significance of microstructural and microchemistry changes in the material on IASCC susceptibility is also discussed. The results are used to determine (a) the threshold fluence for IASCC and (b) the disposition curves for cyclic and IASCC growth rates for irradiated SSs in LWR environments.

  11. Modeling of the Austenite-Martensite Transformation in Stainless and TRIP Steels

    NARCIS (Netherlands)

    Geijselaers, H.J.M.; Hilkhuijsen, P.; Bor, T.C.; Perdahcioglu, E.S.; Boogaard, van den A.H.; Zhang, S.-H.; Liu, X.-H.; Gheng, M.; Li, J.

    2013-01-01

    The transformation of austenite to martensite is a dominant factor in the description of the constitutive behavior during forming of TRIP assisted steels. To predict this transformation different models are currently available. In this paper the transformation is regarded as a stress induced process

  12. Effect of titanium on passive state stability of austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Cihal, V.; Blahetova, M.; Krhutova, Z.; Lasek, St.; Mikel, P. [Ostrava VSB-Technical Univ. (Czech Republic); Cihal, V.; Kalabisova, E. [SVUOM Ltd. Prague (Czech Republic); Burda, J.; Karnik, D. [Nuclear Research Institute Rez, plc. (Czech Republic)

    2009-07-01

    In view of the wide application range of austenitic stainless steels and alloys, it is indispensable for these materials to retain adequate passivity when exposed to aggressive media under a variety of conditions. Stability of the passive state is the function mainly of the chemical composition, structural sensitivity, and the state of stressing of the metal, coupled with the specific chemistry of the environment, as is also the case e.g., with boiling water and pressure water reactors. Sensitization of higher-carbon steels was eventually coped with by stabilization i.e., bonding the carbon with titanium and columbium, and by lowering the carbon content. In the case of steels stabilized with titanium and columbium, the effects of these elements when present in the form of carbides as well as their influence in the solid solution on potential passive film breakdown require attention, owing to the danger of provoking pitting corrosion, stress corrosion cracking, intergranular corrosion, or dissolution in highly oxidizing media. The effects of titanium and columbium in the solid solution on passive state stability of CrNi and CrNiMo steels as well as on their localized corrosion are compared. Experimental heats of low-carbon (max 0.02%) alloys containing 17.5-18.0% Cr, 12-15% Ni and 2.5-2.7% Mo, modified with graduated additions of Ti and Nb (0.4-1.2%), were subjected to chemical and metallographic analyses and to phase identification procedures. Electrochemical polarization measurements involving reactivation from the outset of the passive region (at 0.1 or 0.0 V{sub SCE}) indicated a reduction of the critical reactivation current density for the titanium-stabilized steels. The reactivation ratios derived from measurements by the DL-EPR method (according to ISO12732-2006) exhibit slightly lower values, on the average, for the steels with titanium than for those with columbium. The significant effect of titanium has also been confirmed by reactivation measurements run

  13. Biocompatibility studies of low temperature nitrided and collagen-I coated AISI 316L austenitic stainless steel.

    Science.gov (United States)

    Martinesi, M; Stio, M; Treves, C; Borgioli, F

    2013-06-01

    The biocompatibility of austenitic stainless steels can be improved by means of surface engineering techniques. In the present research it was investigated if low temperature nitrided AISI 316L austenitic stainless steel may be a suitable substrate for bioactive protein coating consisting of collagen-I. The biocompatibility of surface modified alloy was studied using as experimental model endothelial cells (human umbilical vein endothelial cells) in culture. Low temperature nitriding produces modified surface layers consisting mainly of S phase, the supersaturated interstitial solid solution of nitrogen in the austenite lattice, which allows to enhance surface microhardness and corrosion resistance in PBS solution. The nitriding treatment seems to promote the coating with collagen-I, without chemical coupling agents, in respect of the untreated alloy. For biocompatibility studies, proliferation, lactate dehydrogenase levels and secretion of two metalloproteinases (MMP-2 and MMP-9) were determined. Experimental results suggest that the collagen protection may be favourable for endothelial cell proliferation and for the control of MMP-2 release.

  14. An investigation on microstructure and mechanical propertiesof a Nb-microalloyed nano/ultrafine grained 201 austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Samaei Baghbadorani, H., E-mail: h.samaeibaghbadorani@ma.iut.ac.ir [Department of Materials Engineering, Isfahan University of Technology, 84156-83111 Isfahan (Iran, Islamic Republic of); Kermanpur, A. [Department of Materials Engineering, Isfahan University of Technology, 84156-83111 Isfahan (Iran, Islamic Republic of); Najafizadeh, A. [Department of Materials Engineering, Isfahan University of Technology, 84156-83111 Isfahan (Iran, Islamic Republic of); Fould Institute of Technology, Fouldshare 84916-63763 (Iran, Islamic Republic of); Behjati, P.; Rezaee, A.; Moallemi, M. [Department of Materials Engineering, Isfahan University of Technology, 84156-83111 Isfahan (Iran, Islamic Republic of)

    2015-06-11

    The present study was aimed to investigate the mechanical properties of a nano/ultrafine grained Nb-containing 201 austenitic stainless steel. For this purpose, 90% cold rolled sheets with fully martensitic microstructure were isothermally annealed at 900 °C for different times of 1 to 1800 s, leading to the reversion of strain- induced α′-martensite to austenite and significant grain refinement. Ferritescopy, X-ray diffractometery and optical/electron microscopy techniques along with hardness measurements and tensile tests were used to study the evolution in microstructure and mechanical properties in the course of annealing. It was found that heavy cold-rolling promoted formation of Nb-rich carbonitrides which effectively retarded the growth of fine reverted austenite grains. The obtained results showed that the complete transformation of martensite to austenite took about 60 s with the corresponding austenite grain size of about 90 nm. This sample had an ultrahigh yield strength of 1170 MPa, which was almost four times higher than that of the raw material and outstanding elongation of 37%. Further, the true stress–strain curves of the reversion annealed samples revealed two distinct uniform elongation stages (stage I and stage II), whereas, the onset of stage II was concurrent with pronounced strain hardening. This was related to the sharp increase in the formation of α′-martensite upon tensile straining.

  15. Gigacycle fatigue behaviour of austenitic stainless steels used for mercury target vessels

    Science.gov (United States)

    Naoe, Takashi; Xiong, Zhihong; Futakawa, Masatoshi

    2016-01-01

    A mercury enclosure vessel for the pulsed spallation neutron source manufactured from a type 316L austenitic stainless steel, a so-called target vessel, suffers the cyclic loading caused by the proton beam induced pressure waves. A design criteria of the JSNS target vessel which is defined based on the irradiation damage is 2500 h at 1 MW with a repetition rate of 25 Hz, that is, the target vessel suffers approximately 109 cyclic loading while in operation. Furthermore, strain rate of the beam window of the target vessel reaches 50 s-1 at the maximum, which is much higher than that of the conventional fatigue. Gigacycle fatigue strength up to 109 cycles for solution annealed 316L (SA) and cold-worked 316L (CW) were investigated through the ultrasonic fatigue tests. Fatigue tests were performed under room temperature and 250 °C which is the maximum temperature evaluated at the beam window in order to investigate the effect of temperature on fatigue strength of SA and CW 316L. The results showed that the fatigue strength at 250 °C is clearly reduced in comparison with room temperature, regardless of cold work level. In addition, residual strength and microhardness of the fatigue tested specimen were measured to investigate the change in mechanical properties by cyclic loading. Cyclic hardening was observed in both the SA and CW 316L, and cyclic softening was observed in the initial stage of cyclic loading in CW 316L. Furthermore, abrupt temperature rising just before fatigue failure was observed regardless of testing conditions.

  16. Effects of molybdenum on the composition and nanoscale morphology of passivated austenitic stainless steel surfaces.

    Science.gov (United States)

    Maurice, Vincent; Peng, Hao; Klein, Lorena H; Seyeux, Antoine; Zanna, Sandrine; Marcus, Philippe

    2015-01-01

    Surface analysis by time-of-flight secondary ion mass spectrometry, X-ray photoelectron spectroscopy and scanning tunnelling microscopy has been applied to provide new insight on Mo effects on the composition and nanostructure of the passive films grown in sulfuric acid on well-controlled Fe-17Cr-14.5Ni-2.3Mo(100) austenitic stainless steel single crystal surfaces. A duplex hydroxylated oxide matrix, 1.8-1.9 nm thick, is formed with a strong partition between Cr(iii) and Fe(iii) in the inner and outer layers, respectively. Cr(iii) is increasingly enriched by preferential iron oxide dissolution upon passivation and ageing. Ni, only present as oxide traces in the film, is enriched in the alloy underneath. Mo, mostly present as Mo(iv) in the Cr-rich inner layer prior to anodic polarisation, becomes increasingly enriched (up to 16% of cations) mostly as Mo(vi) in the Fe-rich outer layer of the passive film, with ageing promoting this effect. Metallic Mo is not significantly enriched below the passive film produced from the native oxide covered surface. Mo does not markedly impact the nanogranular morphology of the native oxide film nor its local thickness variations assigned to substrate site effects on Cr(iii) enrichment. Site specific preferential passivation still takes place at the (native) oxide-covered step edges of the alloy surface, and transient dissolution remains preferentially located on the terraces. Nanostructures, possibly Mo-containing, and healing local depressions formed by transient dissolution during passivation, appear as a specific effect of the Mo presence. Another Mo effect, observed even after 20 h of passivation, is to prevent crystallisation at least in the Fe-rich outer part of the passive film where it is concentrated mostly as Mo(vi) (i.e. molybdate) species.

  17. Hot Ductility Characterization of Sanicro-28 Super-Austenitic Stainless Steel

    Science.gov (United States)

    Mirzaei, A.; Zarei-Hanzaki, A.; Abedi, H. R.

    2016-05-01

    The hot ductility behavior of a super-austenitic stainless steel has been studied using tensile testing method in the temperature range from 1073 K to 1373 K (800 °C to 1100 °C) under the strain rates of 0.1, 0.01, and 0.001 s-1. The hot compression tests were also performed at the same deformation condition to identify the activated restoration mechanisms. At lower temperatures [ i.e., 1073 K and 1173 K (800 °C and 900 °C)], the serration of initial grain boundaries confirms the occurrence of dynamic recovery as the predominant restoration process. However, in the course of applied deformation, the initial microstructure is recrystallized at higher temperatures [ i.e., 1273 K and 1373 K (1000 °C and 1100 °C)]. In this respect, annealing the twin boundaries could well stimulate the recrystallization kinetic through initiation new annealing twins on prior annealing twin boundaries. The hot tensile results show that there is a general trend of increasing ductility by temperature. However, two regions of ductility drop are recognized at 1273 K and 1373 K (1000°C)/0.1s-1 and (1100°C)/0.01s-1. The ductility variations at different conditions of temperature and strain rate are discussed in terms of simultaneous activation of grain boundary sliding and restoration processes. The observed ductility troughs are attributed to the occurrence of grain boundary sliding and the resulting R-type and W-type cracks. The occurrence of dynamic recrystallization is also considered as the main factor increasing the ductility at higher temperatures. The enhanced ductility is primarily originated from the post-uniform elongation behavior, which is directly associated with the strain rate sensitivity of the experimental material.

  18. Pitting corrosion in austenitic stainless steel water tanks of hotel trains

    Directory of Open Access Journals (Sweden)

    Moreno, D. A.

    2011-12-01

    Full Text Available The water storage tanks of hotel trains suffered pitting corrosion. To identify the cause, the tanks were subjected to a detailed metallographic study and the chemical composition of the austenitic stainless steels used in their construction was determined. Both the tank water and the corrosion products were further examined by physicochemical and microbiological testing. Corrosion was shown to be related to an incompatibility between the chloride content of the water and the base and filler metals of the tanks. These findings formed the basis of recommendations aimed at the prevention and control of corrosion in such tanks.

    Se han detectado problemas de corrosión por picaduras en los depósitos de agua de trenes hotel. Para identificar las causas se llevó a cabo un detallado estudio metalográfico así como de la composición química de los aceros inoxidables austeníticos utilizados en su construcción. También se realizaron estudios fisicoquímicos y microbiológicos de los productos de corrosión. Se ha encontrado que los problemas de corrosión están relacionados con la incompatibilidad entre el contenido en cloruros del agua y los metales base y de aporte de la soldadura de los tanques. En base a estos hallazgos se proponen una serie de recomendaciones encaminadas a la prevención y control de la corrosión de dichos depósitos.

  19. Signal quality enhancement using higher order wavelets for ultrasonic TOFD signals from austenitic stainless steel welds.

    Science.gov (United States)

    Praveen, Angam; Vijayarekha, K; Abraham, Saju T; Venkatraman, B

    2013-09-01

    Time of flight diffraction (TOFD) technique is a well-developed ultrasonic non-destructive testing (NDT) method and has been applied successfully for accurate sizing of defects in metallic materials. This technique was developed in early 1970s as a means for accurate sizing and positioning of cracks in nuclear components became very popular in the late 1990s and is today being widely used in various industries for weld inspection. One of the main advantages of TOFD is that, apart from fast technique, it provides higher probability of detection for linear defects. Since TOFD is based on diffraction of sound waves from the extremities of the defect compared to reflection from planar faces as in pulse echo and phased array, the resultant signal would be quite weak and signal to noise ratio (SNR) low. In many cases the defect signal is submerged in this noise making it difficult for detection, positioning and sizing. Several signal processing methods such as digital filtering, Split Spectrum Processing (SSP), Hilbert Transform and Correlation techniques have been developed in order to suppress unwanted noise and enhance the quality of the defect signal which can thus be used for characterization of defects and the material. Wavelet Transform based thresholding techniques have been applied largely for de-noising of ultrasonic signals. However in this paper, higher order wavelets are used for analyzing the de-noising performance for TOFD signals obtained from Austenitic Stainless Steel welds. It is observed that higher order wavelets give greater SNR improvement compared to the lower order wavelets.

  20. Three-dimensional transient thermoelectric currents in deep penetration laser welding of austenite stainless steel

    Science.gov (United States)

    Chen, Xin; Pang, Shengyong; Shao, Xinyu; Wang, Chunming; Xiao, Jianzhong; Jiang, Ping

    2017-04-01

    The existence of thermoelectric currents (TECs) in workpieces during the laser welding of metals has been common knowledge for more than 15 years. However, the time-dependent evolutions of TECs in laser welding remain unclear. The present study developed a novel three-dimensional theoretical model of thermoelectric phenomena in the fiber laser welding of austenite stainless steel and used it to observe the time-dependent evolutions of TECs for the first time. Our model includes the complex physical effects of thermal, electromagnetic, fluid and phase transformation dynamics occurring at the millimeter laser ablated zone, which allowed us to simulate the TEC, self-induced magnetic field, Lorentz force, keyhole and weld pool behaviors varying with the welding time for different parameters. We found that TECs are truly three-dimensional, time-dependent, and uneven with a maximum current density of around 107 A/m2 located at the liquid-solid (L/S) interface near the front or bottom part of the keyhole at a laser power of 1.5 kW and a welding speed of 3 m/min. The TEC formed three-dimensional circulations moving from the melting front to solidification front in the solid part of workpiece, after which the contrary direction was followed in the liquid part. High frequency oscillation characteristics (2.2-8.5 kHz) were demonstrated in the TEC, which coincides with that of the keyhole instability (2.0-5.0 kHz). The magnitude of the self-induced magnetic field and Lorentz force can reach 0.1 mT and 1 kN/m3, respectively, which are both consistent with literature data. The predicted results of the weld dimensions by the proposed model agree well with the experimental results. Our findings could enhance the fundamental understanding of thermoelectric phenomena in laser welding.

  1. Defocusing Techniques for Multi-pass Laser Welding of Austenitic Stainless Steel

    Science.gov (United States)

    Karhu, Miikka; Kujanpää, Veli

    This study introduces an experimental work carried out in multi-pass laser welding with cold filler wire and laser-arc hybrid welding of thick section austenitic stainless steel. As it has been demonstrated earlier, hybrid and cold wire welding with a keyhole-mode can offer very efficient way to produce multi-pass welds in narrow gap thick section joints. However, when multi-pass welding is applied to one pass per layer method without e.g. scanning or defocusing, the used groove width needs to be very narrow in order to ensure the proper melting of groove side walls and thus to avoid lack of fusion/cold-run defects. As a consequence of the narrow groove, particularly in thick section joints, the accessibility of an arc torch or a wire nozzle into the very bottom of a groove in root pass welding can be considerably restricted. In an alternative approach described in this paper, a power density of a laser beam spot was purposely dispersed by using a defocusing technique. In groove filling experiments, a power density of defocused laser beam was kept in the range, which led the welding process towards to conduction limited regime and thus enabled to achieve broader weld cross-sections. The object was to study the feasibility of defocusing as a way to fill and bridge wider groove geometries than what can be welded with focused keyhole-mode welding with filler addition. The paper covers the results of multi-pass welding of up to 60 mm thick joints with single side preparations.

  2. In Situ Thermo-magnetic Investigation of the Austenitic Phase During Tempering of a 13Cr6Ni2Mo Supermartensitic Stainless Steel

    Science.gov (United States)

    Bojack, A.; Zhao, L.; Morris, P. F.; Sietsma, J.

    2014-12-01

    The formation of austenite during tempering of a 13Cr6Ni2Mo supermartensitic stainless steel (X2CrNiMoV13-5-2) was investigated using an in situ thermo-magnetic technique to establish the kinetics of the martensite to austenite transformation and the stability of austenite. The austenite fraction was obtained from in situ magnetization measurements. It was found that during heating to the tempering temperature 1 to 2 vol pct of austenite, retained during quenching after the austenitization treatment, decomposed between 623 K and 753 K (350 °C and 480 °C). The activation energy for martensite to austenite transformation was found by JMAK-fitting to be 233 kJ/mol. This value is similar to the activation energy for Ni and Mn diffusion in iron and supports the assumption that partitioning of Ni and Mn to austenite are mainly rate determining for the austenite formation during tempering. This also indicates that the stability of austenite during cooling after tempering depends on these elements. With increasing tempering temperature the thermal stability of austenite is decreasing due to the lower concentrations of austenite-stabilizing elements in the increased fraction of austenite. After cooling from the tempering temperature the retained austenite was further partially decomposed during holding at room temperature. This appears to be related to previous martensite formation during cooling.

  3. COMPETITION BEETWEN DYNAMIC RECUPERATION AND RECRYSTALLIZATION OF ASTM F 138 AUSTENITIC STAINLESS STEEL UTILIZED IN MEDICAL DEVICES

    Directory of Open Access Journals (Sweden)

    Fabio Henrique Casarini Geronimo

    2013-06-01

    Full Text Available ASTM F 138 austenitic stainless steel has being used in the manufacture of orthopedical devices by hot forging. In this work, the flow stress curves are determined by hot torsion tests in a wide range of temperatures and strain rates. With the observed microestrutural evolution by optical microscopy in different hot forming conditions in addiction with EBSD (Electron Backscatter Diffraction techniques it is possible to obtained the recrystallized volume fraction and the misorientation angles of the samples. Due to the intermediate level of stacking fault energy of this material, during the dynamic softening occurs a competition between recrystallization and recovery. The aim of this work is to identify the softening mechanisms in this stainless steel, as well as in which hot work conditions they become more active.

  4. Automated Flaw Detection Scheme For Cast Austenitic Stainless Steel Weld Specimens Using Hilbert Huang Transform Of Ultrasonic Phased Array Data

    Energy Technology Data Exchange (ETDEWEB)

    Khan, T.; Majumdar, Shantanu; Udpa, L.; Ramuhalli, Pradeep; Crawford, Susan L.; Diaz, Aaron A.; Anderson, Michael T.

    2012-01-01

    The objective of this work is to develop processing algorithms to detect and localize the flaws using NDE ultrasonic data. Data was collected using cast austenitic stainless steel (CASS) weld specimens on-loan from the U.S. nuclear power industry’s Pressurized Water Reactor Owners Group (PWROG) specimen set. Each specimen consists of a centrifugally cast stainless steel (CCSS) pipe section welded to a statically cast (SCSS) or wrought (WRSS) section. The paper presents a novel automated flaw detection and localization scheme using low frequency ultrasonic phased array inspection signals in the weld and heat affected zone of the base materials. The major steps of the overall scheme are preprocessing and region of interest (ROI) detection followed by the Hilbert Huang transform (HHT) of A-scans in the detected ROIs. HHT offers time-frequency-energy distribution for each ROI. The accumulation of energy in a particular frequency band is used as a classification feature for the particular ROI.

  5. Stress Corrosion Cracking of an Austenitic Stainless Steel in Nitrite-Containing Chloride Solutions

    Directory of Open Access Journals (Sweden)

    R. K. Singh Raman

    2014-12-01

    Full Text Available This article describes the susceptibility of 316L stainless steel to stress corrosion cracking (SCC in a nitrite-containing chloride solution. Slow strain rate testing (SSRT in 30 wt. % MgCl2 solution established SCC susceptibility, as evidenced by post-SSRT fractography. Addition of nitrite to the chloride solution, which is reported to have inhibitive influence on corrosion of stainless steels, was found to increase SCC susceptibility. The susceptibility was also found to increase with nitrite concentration. This behaviour is explained on the basis of the passivation and pitting characteristics of 316L steel in chloride solution.

  6. Thermodynamic Calculation Study on Effect of Manganese on Stability of Austenite in High Nitrogen Stainless Steels

    Science.gov (United States)

    Wang, Qingchuan; Zhang, Bingchun; Yang, Ke

    2016-07-01

    A series of high nitrogen steels were studied by using thermodynamic calculations to investigate the effect of manganese on the stability of austenite. Surprisingly, it was found that the austenite stabilizing ability of manganese was strongly weakened by chromium, but it was strengthened by molybdenum. In addition, with an increase of manganese content, the ferrite stabilizing ability of chromium significantly increased, but that of molybdenum decreased. Therefore, strong interactions exist between manganese and the other alloying elements, which should be the main reason for the difference among different constituent diagrams.

  7. The formation of radiation-induced segregation at twin bands in ion-irradiated austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Hyung-Ha; Lee, Gyeong-Geun; Kwon, Junhyun; Hwang, Seong Sik [Nuclear Materials Division, Korea Atomic Energy Research Institute, 1045 Daedeok-daero, Yuseong-gu, Daejeon 305-353 (Korea, Republic of); Shin, Chansun, E-mail: c.shin@mju.ac.kr [Department of Materials Science and Engineering, Myongji University, 116 Myongji-ro, Cheoin-gu, Youngin, Gyeonggi-do 449-728 (Korea, Republic of)

    2014-11-15

    Radiation-induced segregation (RIS) at twins was investigated using transmission electron microscopy (TEM) for ion-irradiated austenitic stainless steel. Significant RIS was found to occur at twin boundaries. TEM analysis indicates that interfacial dislocations at partially coherent twin boundaries are potential sites for strong RIS phenomenon. The RIS causes the formation of thin bands having a higher Ni and lower Cr concentration in twin bands with a width less than 15 nm. In wider twin bands, strong RIS occurs only at the outer twin boundaries, but not inside the band. The possible mechanism for the formation of the RIS thin band is discussed.

  8. Effects of Thermocapillary Forces during Welding of 316L-Type Wrought, Cast and Powder Metallurgy Austenitic Stainless Steels

    CERN Document Server

    Sgobba, Stefano

    2003-01-01

    The Large Hadron Collider (LHC) is now under construction at the European Organization for Nuclear Research (CERN). This 27 km long accelerator requires 1248 superconducting dipole magnets operating at 1.9 K. The cold mass of the dipole magnets is closed by a shrinking cylinder with two longitudinal welds and two end covers at both extremities of the cylinder. The end covers, for which fabrication by welding, casting or Powder Metallurgy (PM) was considered, are dished-heads equipped with a number of protruding nozzles for the passage of the different cryogenic lines. Structural materials and welds must retain high strength and toughness at cryogenic temperature. AISI 316L-type austenitic stainless steel grades have been selected because of their mechanical properties, ductility, weldability and stability of the austenitic phase against low-temperature spontaneous martensitic transformation. 316LN is chosen for the fabrication of the end covers, while the interconnection components to be welded on the protrud...

  9. Activated flux tungsten inert gas welding of 8 mm-thick AISI 304 austenitic stainless steel

    Institute of Scientific and Technical Information of China (English)

    刘观辉; 刘美华; 易耀勇; 张宇鹏; 罗子艺; 许磊

    2015-01-01

    AISI 304 stainless steel plates were welded with activated flux tungsten inert gas (A-TIG) method by utilizing self-developed activated flux. It is indicated from the experimental results that for 8 mm-thick AISI 304 stainless steel plate, weld joint of full penetration and one-side welding with good weld appearance can be obtained in a single pass without groove preparation by utilizing A-TIG welding. Moreover, activated flux powders do not cause significant effect on the microstructure of TIG weld and the mechanical properties of A-TIG weld joints are also superior to those of C-TIG (conventional TIG) welding.

  10. Low-Temperature Nitriding of Deformed Austenitic Stainless Steels with Various Nitrogen Contents Obtained by Prior High-Temperature Solution Nitriding

    Science.gov (United States)

    Bottoli, Federico; Winther, Grethe; Christiansen, Thomas L.; Dahl, Kristian Vinter; Somers, Marcel A. J.

    2016-08-01

    In the past decades, high nitrogen steels (HNS) have been regarded as substitutes for conventional austenitic stainless steels because of their superior mechanical and corrosion properties. However, the main limitation to their wider application is their expensive production process. As an alternative, high-temperature solution nitriding has been applied to produce HNS from three commercially available stainless steel grades (AISI 304L, AISI 316, and EN 1.4369). The nitrogen content in each steel alloy is varied and its influence on the mechanical properties and the stability of the austenite investigated. Both hardness and yield stress increase and the alloys remain ductile. In addition, strain-induced transformation of austenite to martensite is suppressed, which is beneficial for subsequent low-temperature nitriding of the surface of deformed alloys. The combination of high- and low-temperature nitriding results in improved properties of both bulk and surface.

  11. Characterization of Low Temperature Ferrite/Austenite Transformations in the Heat Affected Zone of 2205 Duplex Stainless Steel Arc Welds

    Energy Technology Data Exchange (ETDEWEB)

    Palmer, T A; Elmer, J W; Babu, S S; Vitek, J M

    2003-08-20

    Spatially Resolved X-Ray Diffraction (SRXRD) has been used to identify a previously unobserved low temperature ferrite ({delta})/austenite({gamma}) phase transformation in the heat affected zone (HAZ) of 2205 Duplex Stainless Steel (DSS) welds. In this ''ferrite dip'' transformation, the ferrite transforms to austenite during heating to peak temperatures on the order of 750 C, and re-transforms to ferrite during cooling, resulting in a ferrite volume fraction equivalent to that in the base metal. Time Resolved X-Ray Diffraction (TRXRD) and laser dilatometry measurements during Gleeble{reg_sign} thermal simulations are performed in order to verify the existence of this low temperature phase transformation. Thermodynamic and kinetic models for phase transformations, including both local-equilibrium and para-equilibrium diffusion controlled growth, show that diffusion of substitutional alloying elements does not provide a reasonable explanation for the experimental observations. On the other hand, the diffusion of interstitial alloying elements may be rapid enough to explain this behavior. Based on both the experimental and modeling results, two mechanisms for the ''ferrite dip'' transformation, including the formation and decomposition of secondary austenite and an athermal martensitic-type transformation of ferrite to austenite, are considered.

  12. PRECIPITATION BEHAVIOR OF M2N IN A HIGH-NITROGEN AUSTENITIC STAINLESS STEEL DURING ISOTHERMAL AGING

    Institute of Scientific and Technical Information of China (English)

    F. Shi; L.J. Wang; W.F. Cui; C.M. Liu

    2007-01-01

    The precipitation behavior of M2N and the microstructural evolution in a Cr-Mn austenitic stainless steel with a high nitrogen content of 0.43mass% during isothermal aging has been investigated using optical microscopy (OM), scanning electron microscopy ( SEM), and transmission electron microscopy (TEM). The aging treatments have led to the decomposition of nitrogen supersaturated austenitic matrix through discontinuous cellular precipitation. The precipitated cells comprise alternate lamellae of M2N precipitate and austenitic matrix. This kind of precipitate morphology is similar to that of pearlite. However, owing to the non-eutectoidic mechanism of the reaction, the growth characteristic of the cellular precipitates is different from that of pearlite in Fe-C binary alloys. M2N precipitate in the cell possesses a hexagonal crystal structure with the parameters a=0.4752nm and c=0.4429nm, and the orientation relationship between the MN precipitates and austenite determined from the SADP is [01110]M2N// [101]γ,[2-1-10]M2N// [010]γ.

  13. In Situ Observation of Solidification Process of AISI 304 Austenitic Stainless Steel

    Institute of Scientific and Technical Information of China (English)

    HUANG Fu-xiang; WANG Xin-hua; ZHANG Jiong-ming; JI Chen-xi; FANG Yuan; YU Yan

    2008-01-01

    The solidification process of AISI 304 stainless steel during cooling at a rate of 0.05 K/s has been observed in situ using a confocal scanning laser microscope(CSLM).The results show that the δ phase appeared first in liquid steel,as the temperature decreased,the γ phase precipitated prior at δ-grain boundary at 1452.2℃,the liquid steel disappeared at 1431.3℃,and then theγphase precipitated on the δ ferrite.Based on the Scheil-GulliVer solidification model,the solidification processes of AISI 304 stainless steel are simulated using the Scheil model in Thermo-Calc.and the simulation results agree well with the results observed in the experiment.

  14. Aspects and mechanisms of austenitic stainless steel corrosion in case of sodium leaks under mineral wool insulation

    Energy Technology Data Exchange (ETDEWEB)

    Bertrand, C.; Ardellier, A. [Commissariat a l`Energie Atomique, Saint-Paul-Lez-Durance (France)

    1996-10-01

    Sodium pipe rupture tests representative of Fast Reactors accidents have been carried out on austenitic stainless steel surfaces. These tests improve the authors knowledge of small sodium leakage propagation in mineral wool insulation. Furthermore, they explain the new and unexpected aspects of the crevice corrosion phenomenon which has been observed on austenitic stainless steel external pipe surfaces. Experimental results show that the corrosion is limited to a peripheral annular zone, which extends out in concentric waves. The diameter of this corrosion zone is practically constant. Furthermore, the tests show that sodium does not expand directly on the pipe surface. The sodium sprays through the mineral wool insulation, where chemical reactions between silica fibers, occluded oxygen and water vapor occur at the same time. Simultaneously, there is a diffusion phenomenon of liquid sodium droplets on the mineral wool fibers. The study allows to prove the electrochemical nature of the corrosion. The excess liquid sodium, spraying as droplets on the pipe surface, induces an anodic dissolution mechanism by differential aeration. This phenomenon explains the random microscopic and macroscopic aspects of material removal.

  15. Aspects and mechanisms of austenitic stainless steel corrosion in case of sodium leaks under mineral wool insulation

    Energy Technology Data Exchange (ETDEWEB)

    Bertrand, C.; Ardellier, A.

    1996-12-31

    Sodium pipe rupture tests representative of Fast Reactors Accidents have been carried out on austenitic stainless steel surfaces. These tests improve our knowledge of small sodium leakage propagation in mineral wool insulation. They explain the new and unexpected aspects of the crevice corrosion phenomenon which has been observed on austenitic stainless steel pipe surfaces. Experimental results show that corrosion is limited to a peripheral annular zone, which extends out in concentric waves. The diameter of this corrosion zone is practically constant. Tests show that sodium does not expand directly on the pipe surface. Sodium sprays through mineral wool insulation, where chemical reaction between silica fibers, occluded oxygen and water vapor occur at the same time. Simultaneously, there is a diffusion phenomenon of liquid Na droplets on the mineral wool fibers. The study allows to prove the electrochemical nature of the corrosion. The excess liquid Na, spraying as droplets induces an anodic dissolution mechanism by differential aeration. This phenomenon explains the random microscopic and macroscopic aspects of material removal. (authors). 1 ref., 16 figs.

  16. Cast, heat-resistant austenitic stainless steels having reduced alloying element content

    Energy Technology Data Exchange (ETDEWEB)

    Muralidharan, Govindarajan [Knoxville, TN; Sikka, Vinod Kumar [Oak Ridge, TN; Maziasz, Philip J [Oak Ridge, TN; Pankiw, Roman I [Greensburg, PA

    2010-07-06

    A cast, austenitic steel composed essentially of, expressed in weight percent of the total composition, about 0.4 to about 0.7 C, about 20 to about 30 Cr, about 20 to about 30 Ni, about 0.5 to about 1 Mn, about 0.6 to about 2 Si, about 0.05 to about 1 Nb, about 0.05 to about 1 W, about 0.05 to about 1.0 Mo, balance Fe, the steel being essentially free of Ti and Co, the steel characterized by at least one microstructural component selected from the group consisting of MC, M.sub.23C.sub.6, and M(C, N).

  17. Cast, heat-resistant austenitic stainless steels having reduced alloying element content

    Energy Technology Data Exchange (ETDEWEB)

    Muralidharan, Govindarajan [Knoxville, TN; Sikka, Vinod Kumar [Oak Ridge, TN; Maziasz, Philip J [Oak Ridge, TN; Pankiw, Roman I [Greensburg, PA

    2011-08-23

    A cast, austenitic steel composed essentially of, expressed in weight percent of the total composition, about 0.4 to about 0.7 C, about 20 to about 30 Cr, about 20 to about 30 Ni, about 0.5 to about 1 Mn, about 0.6 to about 2 Si, about 0.05 to about 1 Nb, about 0.05 to about 1 W, about 0.05 to about 1.0 Mo, balance Fe, the steel being essentially free of Ti and Co, the steel characterized by at least one microstructural component selected from the group consisting of MC, M.sub.23C.sub.6, and M(C, N).

  18. Influence of plastic strain localization on the stress corrosion cracking of austenitic stainless steels; Influence de la localisation de la deformation plastique sur la CSC d'aciers austenitiques inoxydables

    Energy Technology Data Exchange (ETDEWEB)

    Cisse, S.; Tanguy, B. [CEA Saclay, DEN, SEMI, 91 - Gif-sur-Yvette (France); Andrieu, E.; Laffont, L.; Lafont, M.Ch. [Universite de Toulouse. CIRIMAT, UPS/INPT/CNRS, 31 - Toulous (France)

    2010-03-15

    The authors present a research study of the role of strain localization on the irradiation-assisted stress corrosion cracking (IASCC) of vessel steel in PWR-type (pressurized water reactor) environment. They study the interaction between plasticity and intergranular corrosion and/or oxidation mechanisms in austenitic stainless steels with respect to sublayer microstructure transformations. The study is performed on three austenitic stainless grades which have not been sensitized by any specific thermal treatment: the A286 structurally hardened steel, and the 304L and 316L austenitic stainless steels

  19. Atomic-scale decoration for improving the pitting corrosion resistance of austenitic stainless steels

    Science.gov (United States)

    Zhou, Y. T.; Zhang, B.; Zheng, S. J.; Wang, J.; San, X. Y.; Ma, X. L.

    2014-01-01

    Stainless steels are susceptible to the localized pitting corrosion that leads to a huge loss to our society. Studies in the past decades confirmed that the pitting events generally originate from the local dissolution in MnS inclusions which are more or less ubiquitous in stainless steels. Although a recent study indicated that endogenous MnCr2O4 nano-octahedra within the MnS medium give rise to local nano-galvanic cells which are responsible for the preferential dissolution of MnS, effective solutions of restraining the cells from viewpoint of electrochemistry are being tantalizingly searched. Here we report such a galvanic corrosion can be greatly resisted via bathing the steels in Cu2+-containing solutions. This chemical bath generates Cu2-δS layers on the surfaces of MnS inclusions, invalidating the nano-galvanic cells. Our study provides a low-cost approach via an atomic scale decoration to improve the pitting corrosion resistance of stainless steels in a volume-treated manner.

  20. Contribution of deformation mechanisms to strength and ductility in two Cr-Mn grade austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Hamada, A.S., E-mail: atef_saleh@s-petrol.suez.edu.eg [Materials Engineering Laboratory, Box 4200, University of Oulu, 90014 Oulu (Finland); Metallurgical and Materials Engineering Department, Faculty of Petroleum and Mining Engineering, Suez Canal University, Box 43721, Suez (Egypt); Karjalainen, L.P. [Materials Engineering Laboratory, Box 4200, University of Oulu, 90014 Oulu (Finland); Misra, R.D.K. [Center for Structural and Functional Materials and Chemical Engineering Department, University of Louisiana at Lafayette, P.O. Box 44130, Lafayette, LA 70504-4130, USA. (United States); Talonen, J. [Outokumpu Oyj, Box 140, FI-02201 Espoo (Finland)

    2013-01-01

    The role of different deformation mechanisms in controlling mechanical properties were studied in two low-Ni, Cr-Mn austenitic stainless steel grades (Types 201 and 201L) by tensile testing and microstructure examinations. Tensile tests were carried out at two different strain rates, 5 Multiplication-Sign 10{sup -4} and 10{sup -2} s{sup -1}, in the temperature range from -80 Degree-Sign C to 200 Degree-Sign C. It was observed that the flow properties and work hardening rate are affected significantly by temperature and strain rate for the concerned steels through variation of deformation mechanism. Deformation-induced austenite-to-martensite transformation (TRIP effect) is the dominant mechanism at temperatures below room temperature. From 50 Degree-Sign C up to 200 Degree-Sign C, plastic deformation is controlled by mechanical twinning (TWIP effect) and dislocation glide. The electron backscattered diffraction (EBSD) technique and transmission electron microscopy (TEM) were employed to study the plastic deformation accommodation and identify the primary deformation mechanisms operating in the deformed steels.

  1. Modeling precipitation thermodynamics and kinetics in type 316 austenitic stainless steels with varying composition as an initial step toward predicting phase stability during irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Shim, Jae-Hyeok, E-mail: jhshim@kist.re.kr [Department of Nuclear Engineering, University of Tennessee, Knoxville, TN 37996 (United States); High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Povoden-Karadeniz, Erwin [Christian Doppler Laboratory for Early Stages of Precipitation, Vienna University of Technology, A-1040 Vienna (Austria); Kozeschnik, Ernst [Institute of Materials Science and Technology, Vienna University of Technology, A-1040 Vienna (Austria); Wirth, Brian D. [Department of Nuclear Engineering, University of Tennessee, Knoxville, TN 37996 (United States)

    2015-07-15

    Highlights: • We model the precipitation kinetics in irradiated 316 austenitic stainless steels. • Radiation-induced phases are predicted to form at over 10 dpa segregation conditions. • The Si content is the most critical for the formation of radiation-induced phases. - Abstract: The long-term evolution of precipitates in type 316 austenitic stainless steels at 400 °C has been simulated using a numerical model based on classical nucleation theory and the thermodynamic extremum principle. Particular attention has been paid to the precipitation of radiation-induced phases such as γ′ and G phases. In addition to the original compositions, the compositions for radiation-induced segregation at a dose level of 5, 10 or 20 dpa have been used in the simulation. In a 316 austenitic stainless steel, γ′ appears as the main precipitate with a small amount of G phase forming at 10 and 20 dpa. On the other hand, G phase becomes relatively dominant over γ′ at the same dose levels in a Ti-stabilized 316 austenitic stainless steel, which tends to suppress the formation of γ′. Among the segregated alloying elements, the concentration of Si seems to be the most critical for the formation of radiation-induced phases. An increase in dislocation density as well as increased diffusivity of Mn and Si significantly enhances the precipitation kinetics of the radiation-induced phases within this model.

  2. Evaluation of ageing-induced embrittlement in an austenitic stainless steel by instrumented impact testing

    Science.gov (United States)

    Samuel, K. G.; Sreenivasan, P. R.; Ray, S. K.; Rodriguez, P.

    1987-09-01

    Fracture properties of a thermally aged Type 316 stainless steel have been investigated at room temperature by an instrumented impact test. The impact energy is found to depend on the heat treatment conditions. Several alternative estimates for toughness are evaluated and compared with the conventional Charpy impact energy, C v, to assess the degree of embrittlement. Sensitivity of these parameters to monitor the ageing-induced embrittlement in comparison with C v is discussed.

  3. Effect of heat input on the microstructure, residual stresses and corrosion resistance of 304L austenitic stainless steel weldments

    Energy Technology Data Exchange (ETDEWEB)

    Unnikrishnan, Rahul, E-mail: rahulunnikrishnannair@gmail.com [Department of Metallurgical and Materials Engineering, Visvesvaraya National Institute of Technology (VNIT), South Ambazari Road, Nagpur 440010, Maharashtra (India); Idury, K.S.N. Satish, E-mail: satishidury@gmail.com [Department of Metallurgical and Materials Engineering, Visvesvaraya National Institute of Technology (VNIT), South Ambazari Road, Nagpur 440010, Maharashtra (India); Ismail, T.P., E-mail: tpisma@gmail.com [Department of Metallurgical and Materials Engineering, Visvesvaraya National Institute of Technology (VNIT), South Ambazari Road, Nagpur 440010, Maharashtra (India); Bhadauria, Alok, E-mail: alokbhadauria1@gmail.com [Department of Metallurgical and Materials Engineering, Visvesvaraya National Institute of Technology (VNIT), South Ambazari Road, Nagpur 440010, Maharashtra (India); Shekhawat, S.K., E-mail: satishshekhawat@gmail.com [Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay (IITB), Powai, Mumbai 400076, Maharashtra (India); Khatirkar, Rajesh K., E-mail: rajesh.khatirkar@gmail.com [Department of Metallurgical and Materials Engineering, Visvesvaraya National Institute of Technology (VNIT), South Ambazari Road, Nagpur 440010, Maharashtra (India); Sapate, Sanjay G., E-mail: sgsapate@yahoo.com [Department of Metallurgical and Materials Engineering, Visvesvaraya National Institute of Technology (VNIT), South Ambazari Road, Nagpur 440010, Maharashtra (India)

    2014-07-01

    Austenitic stainless steels are widely used in high performance pressure vessels, nuclear, chemical, process and medical industry due to their very good corrosion resistance and superior mechanical properties. However, austenitic stainless steels are prone to sensitization when subjected to higher temperatures (673 K to 1173 K) during the manufacturing process (e.g. welding) and/or certain applications (e.g. pressure vessels). During sensitization, chromium in the matrix precipitates out as carbides and intermetallic compounds (sigma, chi and Laves phases) decreasing the corrosion resistance and mechanical properties. In the present investigation, 304L austenitic stainless steel was subjected to different heat inputs by shielded metal arc welding process using a standard 308L electrode. The microstructural developments were characterized by using optical microscopy and electron backscattered diffraction, while the residual stresses were measured by X-ray diffraction using the sin{sup 2}ψ method. It was observed that even at the highest heat input, shielded metal arc welding process does not result in significant precipitation of carbides or intermetallic phases. The ferrite content and grain size increased with increase in heat input. The grain size variation in the fusion zone/heat affected zone was not effectively captured by optical microscopy. This study shows that electron backscattered diffraction is necessary to bring out changes in the grain size quantitatively in the fusion zone/heat affected zone as it can consider twin boundaries as a part of grain in the calculation of grain size. The residual stresses were compressive in nature for the lowest heat input, while they were tensile at the highest heat input near the weld bead. The significant feature of the welded region and the base metal was the presence of a very strong texture. The texture in the heat affected zone was almost random. - Highlights: • Effect of heat input on microstructure, residual

  4. Thermal fatigue cracking of austenitic stainless steels; Fissuration en fatigue thermique des aciers inoxydables austenitiques

    Energy Technology Data Exchange (ETDEWEB)

    Fissolo, A

    2001-07-01

    This report deals with the thermal fatigue cracking of austenitic stainless steels as AISI 316 LN and 304 L. Such damage has been clearly observed for some components used in Fast Breeder reactors (FBR) and Pressure Water Reactor (PWR). In order to investigate thermal fatigue, quasi-structural specimen have been used. In this frame, facilities enforcing temperature variations similar to those found under the operation conditions have been progressively developed. As for components, loading results from impeded dilatation. In the SPLASH facility, the purpose was to establish accurate crack initiation conditions in order to check the relevance of the usual component design methodology. The tested specimen is continuously heated by the passage of an electrical DC current, and submitted to cyclic thermal down shock (up to 1000 deg C/s) by means of periodical spraying of water on two opposite specimen faces. The number of cycles to crack initiation N{sub i} is deduced from periodic examinations of the quenched surfaces, by means of optical microscopy. It is considered that initiation occurs when at least one 50{mu}m to 150{open_square}m long crack is observed. Additional SPLASH tests were performed for N >> N{sub i}, with a view to investigate the evolution of a surface multiple cracking network with the number of cycles N. The CYTHIA test was mainly developed for the purpose of assessing crack growth dynamics of one isolated crack in thermal fatigue conditions. Specimens consist of thick walled tubes with a 1 mm circular groove is spark-machined at the specimen centre. During the test, the external wall of the tube is periodically heated by using a HF induction coil (1 MHz), while its internal wall is permanently cooled by flowing water. Total crack growth is derived from post-mortem examinations, whereby the thermal fatigue final rupture surface is oxidized at the end of the test. The specimen is broken afterwards under mechanical fatigue at room temperature. All the

  5. Surface analysis of localized corrosion of austenitic 316L and duplex 2205 stainless steels in simulated body solutions

    Energy Technology Data Exchange (ETDEWEB)

    Conradi, Marjetka, E-mail: marjetka.conradi@imt.si [Institute of Metals and Technology, Lepi pot 11, 1000 Ljubljana (Slovenia); Schoen, Peter M. [Materials Science and Technology of Polymers and MESA Institute for Nanotechnology, University of Twente, Enschede 7500 AE (Netherlands); Kocijan, Aleksandra; Jenko, M. [Institute of Metals and Technology, Lepi pot 11, 1000 Ljubljana (Slovenia); Vancso, G. Julius [Materials Science and Technology of Polymers and MESA Institute for Nanotechnology, University of Twente, Enschede 7500 AE (Netherlands)

    2011-10-17

    Highlights: {yields} In situ steel surface morphology observations in simulated body solutions. {yields} Pitting, square-like and elliptic-like corrosion products. {yields} Corrosion products' shapes related to the growth of Cr and Fe oxides. {yields} Direct relation of the size of the deposition products to surface roughness. - Abstract: We report on cyclic voltammetry and in situ electrochemical atomic force microscopy (EC-AFM) studies of localized corrosion of duplex 2205 stainless steel (DSS 2205) and austenitic stainless steel of the type AISI 316L in two model solutions, including artificial saliva (AS) and a simulated physiological solution known as - Hank's solution (PS). The AFM topography analysis illustrated the higher corrosion resistance of DSS 2205 steel for the chosen range of electrochemical potentials that were applied to the steel surface in both solutions. In contrast, pitting corrosion was observed at the surface of AISI 316L steel, with the pits becoming more evident, larger and deeper, when the sample was electrochemically treated in the PS. On both surfaces the growth of corrosion products formed during the oxidation process was observed. As a result, depending on the sample's metallurgical structure, different types of oxides covered the surface close to the breakdown potential. We distinguished between the square-like type of oxides on the surface of the DSS 2205, and the AISI 316L with its ellipse-like oxide deposits. The X-ray photoelectron spectroscopy (XPS) revealed the chemical composition of the deposition products, which consisted of two main elements, Fe and Cr. However, the oxides of the alloying elements Ni and Mo were negligible compared to the bulk.

  6. Role of Microstructural Constituents on Surface Crack Formation During Hot Rolling of Standard and Low Nickel Austenitic Stainless Steels

    Institute of Scientific and Technical Information of China (English)

    Manidipto Mukherjee; Tapan Kumar Pal

    2013-01-01

    The effect of alloy segregation and delta (δ) ferrite contents on surface cracking of three standard (i.e.AISI 304L,AISI 310S and AISI 321) and two low nickel (i.e.LNi-1 and LNi-0.3) austenitic stainless steels (ASS)during hot rolling was investigated using optical microscopy (OM),automatic image analyzer,scanning electron microscopy (SEM),energy dispersive X-ray spectroscopy (EDX) and electron probe micro analyzer (EPMA).It was observed that the amount of δ-ferrite varied among different grades and also distributed heterogeneously across the width of the steel plates.In general,low nickel ASS showed higher amount of δ-ferrite compared to the standard ASS grades.The tendency to surface cracking during hot rolling gradually increased with increasing δ-ferrite content.Interestingly,carbon and nitrogen exerted maximum effect on δ-ferrite formation.The higher carbon and nitrogen content in the steel decreased δ-ferrite content.In addition,the segregation of Cu and Mn plays significant role in low nickel ASS and Ni-Cr in case of standard ASS has profound effect on surface cracking of the steel plates.A possible cause of surface crack formation/origination in steel plates during hot rolling was discussed.

  7. Effect of Hydrogen Charging on the Tensile and Constant Load Properties of an Austenitic Stainless Steel Weldment

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The effect of cathodic hydrogen charging on the tensile and constant load properties was determined for an austenitic stainless steel weldment comprising a 304L steel in the solution treated condition as a base metal and a 308L filler steel as a weld metal. Part of the 304L solution treated steel was separately given additional sensitization treatment to simulate the microstructure that would develop in the heat affected zone. Tests were performed at room temperature on notched round bar specimens. Hydrogen charging resulted in a pronounced embrittlement of the tested materials. This was manifested mainly as a considerable loss in the dluctility of tensile specimens and a decrease in the time to failure and threshold stress of constant load specimens. The 308L weld metal exhibited the highest, and the 304L solution treated steel the lowest, resistance to hydrogen embrittlement. Hydrogen embrittlement was associated with the formation of strain induced martensite as well as a transition from brittle to ductile fracture morphology onwards the centre of the specimens.

  8. Mechanical Properties and Microstructure Evolution of Cold-deformed High-nitrogen Nickel-free Austenitic Stainless Steel during Annealing

    Institute of Scientific and Technical Information of China (English)

    XU Mingzhou; WANG Jianjun; LIU Chunming

    2012-01-01

    The mechanical properties and microstructure evolution of cold-deformed CrMnN austenitic stainless steel annealed in a temperature ranging from 50 ℃ to 650 ℃ for 90 min and at 550 ℃ for different time were investigated by tensile test,micro hardness test,and Transmission Electron Microscope (TEM).The steel was strengthened when it got annealed at temperatures ranging from 100 ℃ to 550 ℃,while it was softened when it got annealed at temperatures ranging from 550 ℃ to 650 ℃.Annealing temperature had stronger effect on mechanical properties than annealing time.TEM observations showed that nano-sized precipitates formed when the steel was annealed at 150 ℃ for 90 min,but the size and density of precipitates had no noticeable change with annealing temperature and time.Recrystallization occurred when the steel was annealed at temperatures above 550 ℃ for 90 min,and its scale increased with annealing temperature.Nanosized annealing twins were observed.The mechanisms that controlled the mechanical behaviors of the steel were discussed.

  9. Improvement of the Corrosion Resistance of High Alloyed Austenitic Cr-Ni-Mo Stainless Steels by Solution Nitriding

    Institute of Scientific and Technical Information of China (English)

    Christine Eckstein; Heinz- Joachim Spies; Jochen Albrecht

    2004-01-01

    Characteristic features of austenitic steel grades combine a good corrosion resistance with a low hardness, wear resistance and scratch resistance. An interesting possibility for improving the wear behaviour of these steels without loss of their corrosion resistance lies in enriching the near surface region with nitrogen. The process of a solution nitriding allows the rise of the solution of nitrogen in the solid phase. On this state nitrogen increases the corrosion resistance and the tribilogical load-bearing capacity. The aim of the study was, to investigate the improvement of the pitting corrosion behaviour by solution nitriding. A special topic was to observe the effect of nitrogen by different molybdenum content. So austenitic stainless steels (18% Cr, 12% Ni, Mo gradation between 0.06 to 3.6%) had been solution nitrided. The samples could be prepared with various surface content of nitrogen from 0.04 to 0.45% with a step-by-step grinding. The susceptibility against pitting corrosion of these samples had been tested by determination of the stable pitting potential in 0.5M and 1M NaCl at 25℃. For the investigated steel composition and the used corrosion system there is no influence of molybdenum on the effectiveness of nitrogen. The influence of nitrogen to all of the determined parameters can be corrosion tests. Additionally surface investigations with an acid elektolyte (0,1M HCl + 0,4M NaCI) were performed. In this case the passivation effective nitrogen content increases markedly with rising molybdenum concentration of the steel.Obviously an interaction of Mo and N is connected with a strongly acid electrolyte.

  10. Comparison of Roller Burnishing Method with Other Hole Surface Finishing Processes Applied on AISI 304 Austenitic Stainless Steel

    Science.gov (United States)

    Akkurt, Adnan

    2011-08-01

    Component surface quality and selection of the optimum material are the main factors determining the performance of components used in machine manufacturing. The level of hole surface quality can be evaluated by the measurements regarding surface roughness, micro-hardness, and cylindricity. In this study, data had been obtained for different hole drilling methods. The characteristics of materials obtained after applications were compared for different hole-finishing processes to identify best hole drilling method. AISI 304 austenitic stainless steel material was used. Surface finishing of holes were performed using drilling, turning, reaming, grinding, honing, and roller burnishing methods. The results of the study show that the roller burnishing method gives the best results for mechanical, metallurgical properties, and hole surface quality of the material. On the other hand, the worst characteristics were obtained in the drilling method.

  11. MAGNETIC PROPERTY CHANGE IN AN AUSTENITIC STAINLESS STEEL SUBJECTED TO DAMAGE AT ELEVATED TEMPERATURE - MICROSTRUCTURE RESPONSIBLE FOR MAGNETIC PROPERTY

    Institute of Scientific and Technical Information of China (English)

    Y.Nagae; K.Aoto

    2004-01-01

    It has been found that magnetic property changes in austenitic stainless steel subjected to creep at high temperature. The change of magnetic property is mainly due to decrease the chromium concentration in the vicinity of grain boundary and transform into martensite in the area. However this result is for short-term creep. It is necessary to evaluate the long-term creep in order to develop non-destructive technique for plants. Moreover it is important to evaluate the fatigue. The change of magnetic property for those damages at high temperatures is investigated. The transformation into martensite is observed for both the long-term creep and fatigue. The magnetic regions are observed in sever deformed area and near crack. Then the formation of magnetic phases is related to the damage. The damage at high temperature can be universally evaluated.

  12. Constitutive modeling of hot horming of austenitic stainless steel 316LN by accounting for recrystallization in the dislocation evolution

    Science.gov (United States)

    Kooiker, H.; Perdahcioğlu, E. S.; van den Boogaard, A. H.

    2016-08-01

    Hot compression test data taken from Zhang [1] of metastable austenitic stainless steel AISI 316LN over a range of strain rates and temperatures shows typical dynamic recovery and recrystallization behavior. It is proposed to model this behavior by incorporating not only the hardening and recovery into the Bergstrom dislocation evolution equation, but also the recrystallization. It is shown that the initial mechanical response before recrystallization can be accurately represented by assuming that the mean free path evolves as the microstructure evolves from homogeneously spaced dislocations to cell-pattern. Results show that this novel continuum mechanical model can predict the observed behavior, showing a good match to the experimental data and capturing the transition from recrystallization to (almost) no recrystallization.

  13. Corrosion resistance of multilayer hybrid sol-gel coatings deposited on the AISI 316L austenitic stainless steel

    Science.gov (United States)

    Caballero, Y. T.; Rondón, E. A.; Rueda, L.; Hernández Barrios, C. A.; Coy, A.; Viejo, F.

    2016-02-01

    In the present work multilayer hybrid sol-gel coatings were synthesized on the AISI 316L austenitic stainless steel employed in the fabrication of orthopaedic implants. Hybrid sols were obtained from a mixture of inorganic precursor, TEOS, and organic, GPTMS, using ethanol as solvent, and acetic acid as catalyst. The characterization of the sols was performed using pH measurements, rheological tests and infrared spectroscopy (FTIR) for different ageing times. On the other hand, the coatings were characterized by scanning electron microscopy (SEM), while the corrosion resistance was evaluated using anodic potentiodynamic polarization in SBF solution at 37±2°C. The results confirmed that sol-gel synthesis employing TEOS-GPTMS systems produces uniform and homogeneous coatings, which enhanced the corrosion resistance with regard to the parent alloy. Moreover, corrosion performance was retained after applying more than one layer (multilayer coatings).

  14. Fatigue and fracture properties of a super-austenitic stainless steel at 295 K and 4 K

    Science.gov (United States)

    McRae, D. M.; Walsh, R. P.; Dalder, E. N. C.; Litherland, S.; Trosen, M.; Kuhlmann, D. J.

    2014-01-01

    The tie plate structure for the ITER Central Solenoid (CS) is required to have high strength and good fatigue and fracture behavior at both room temperature and 4 K. A super-austenitic stainless steel - UNS 20910, commonly referred to by its trade name, Nitronic 50 (N50) - has been chosen for consideration to fulfill this task, due to its good room temperature and cryogenic yield strengths and weldability. Although N50 is often considered for cryogenic applications, little published data exists at 4 K. Here, a full series of tests have been conducted at 295 K and 4 K, and static tensile properties of four forgings of commercially-available N50 are reported along with fatigue life, fatigue crack growth rate (FCGR), and fracture toughness data. This study makes a significant contribution to the cryogenic mechanical properties database of high strength, paramagnetic alloys with potential for superconducting magnet applications.

  15. Effects of hydrogen gas environment on non-propagation phenomena of a type 304 austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Aoki, Y.; Matsuyama, T.; Oda, Y.; Noguchi, H.; Higashida, K. [Hakozaki, Higashi-ku, Fukuoka (Japan)

    2005-07-01

    In order to investigate the hydrogen gas effect on non-propagation phenomena of a type 304 austenitic stainless steel, fatigue tests with in-situ observation using a Scanning Laser Microscope were performed in air, in 0.18 MPa hydrogen gas and in 0.18 MPa nitrogen gas. A non-propagating crack was observed during the fatigue test in air. At almost the same stress level of non-propagating in air, non-propagating cracks were also observed in fatigue tests in hydrogen and in nitrogen. Stress level of the non-propagation is not sufficiently different in the three environments. However, the process up to non-propagation differs from each other, for example, the crack path and debris. (orig.)

  16. Characteristics of oxide scale formed on Cu-bearing austenitic stainless steel during early stages of high temperature oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Swaminathan, Srinivasan, E-mail: swaminathan@kist.re.kr [Metallurgy & Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seongbuk-gu, Seoul 136 791 (Korea, Republic of); Krishna, Nanda Gopala [Metallurgy & Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Kim, Dong-Ik, E-mail: dongikkim@kist.re.kr [High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seongbuk-gu, Seoul 136 791 (Korea, Republic of)

    2015-10-30

    Highlights: • Initial oxidation characteristics of Cu-bearing austenitic stainless steel at 650 °C were studied. • Strong segregation and oxidation of Mn and Nb were found in the entire oxide scale. • Surface coverage by metallic Cu-rich precipitates increases with exposure time. • Chemical heterogeneity of oxide scale revealed initial oxidation to be non-selective. • Fe-Cr and Mn-Cr mixed oxides were realized along with binary oxides of Fe, Cr and Mn. - Abstract: Oxide scale evolution on Cu-bearing austenitic stainless steel 304H at 650 °C, in ambient air, for exposure times 100, 300, 500 and 1000 h, has been investigated. Surface morphology and chemistry of the oxide scale grown were examined using SEM/EDX and XPS. The oxidation kinetics was determined by measuring the weight change using an electronic balance. At the initial stage, up to 500 h of exposure time, the oxidation rate was rapid due to surface reactions governed primarily by oxygen ingress, and then, dropped to a low rate after prolonged oxidation for 1000 h. The diffusion of reactants through the initially formed oxide scale limits the oxidation rate at longer times, thus, the progress of reaction followed the parabolic kinetics. The formed oxide scale was enriched significantly with segregation and subsequent oxidation of Nb, and finely dispersed metallic Cu particles. Within the time frame of oxidation, the oxide scale was mainly composed of mixed oxides such as FeCr{sub 2}O{sub 4} and MnCr{sub 2}O{sub 4} along with the binary oxides of Fe, Cr and Mn. Moreover, the precipitation fraction of Cu-rich particles on the oxide scale increased markedly with increase of exposure times. The chemical heterogeneity of oxide scale suggests that the oxidation occurred in a non-selective manner.

  17. Comparison of the microstructure, deformation and crack initiation behavior of austenitic stainless steel irradiated in-reactor or with protons

    Energy Technology Data Exchange (ETDEWEB)

    Stephenson, Kale J., E-mail: kalejs@umich.edu; Was, Gary S.

    2015-01-15

    Highlights: • Dislocation loops were the prominent defect, but neutron irradiation caused higher loop density. • Grain boundaries had similar amounts of radiation-induced segregation. • The increment in hardness and yield stress due to irradiation were very similar. • Relative IASCC susceptibility was nearly identical. • The effect of dislocation channel step height on IASCC was similar. - Abstract: The objective of this study was to compare the microstructures, microchemistry, hardening, susceptibility to IASCC initiation, and deformation behavior resulting from proton or reactor irradiation. Two commercial purity and six high purity austenitic stainless steels with various solute element additions were compared. Samples of each alloy were irradiated in the BOR-60 fast reactor at 320 °C to doses between approximately 4 and 12 dpa or by a 3.2 MeV proton beam at 360 °C to a dose of 5.5 dpa. Irradiated microstructures consisted mainly of dislocation loops, which were similar in size but lower in density after proton irradiation. Both irradiation types resulted in the formation of Ni–Si rich precipitates in a high purity alloy with added Si, but several other high purity neutron irradiated alloys showed precipitation that was not observed after proton irradiation, likely due to their higher irradiation dose. Low densities of small voids were observed in several high purity proton irradiated alloys, and even lower densities in neutron irradiated alloys, implying void nucleation was in process. Elemental segregation at grain boundaries was very similar after each irradiation type. Constant extension rate tensile experiments on the alloys in simulated light water reactor environments showed excellent agreement in terms of the relative amounts of intergranular cracking, and an analysis of localized deformation after straining showed a similar response of cracking to surface step height after both irradiation types. Overall, excellent agreement was observed

  18. Corrosion behaviour of austenitic stainless steel, nickel-base alloy and its weldments in aqueous LiBr solutions

    Energy Technology Data Exchange (ETDEWEB)

    Blasco-Tamarit, E.; Igual-Munoz, A.; Garcia Anton, J.; Garcia-Garcia, D. [Departamento de Ingenieria Quimica y Nuclear. E.T.S.I.Industriales, Universidad Politecnica de Valencia, P.O. Box 22012 E-46071 Valencia (Spain)

    2004-07-01

    With the advances in materials production new alloys have been developed, such as High- Alloy Austenitic Stainless Steels and Nickel-base alloys, with high corrosion resistance. These new alloys are finding applications in Lithium Bromide absorption refrigeration systems, because LiBr is a corrosive medium which can cause serious corrosion problems, in spite of its favourable properties as absorbent. The objective of the present work was to study the corrosion resistance of a highly alloyed austenitic stainless steel (UNS N08031) used as base metal, a Nickel-base alloy (UNS N06059) used as its corresponding filler metal, and the weld metal obtained by the Gas Tungsten Arc Welding (GTAW) procedure. The materials have been tested in different LiBr solutions (400 g/l, 700 g/l, 850 g/l and a commercial 850 g/l LiBr heavy brine containing Lithium Chromate as corrosion inhibitor), at 25 deg. C. Open Circuit Potential tests and potentiodynamic anodic polarization curves have been carried out to obtain information about the general electrochemical behaviour of the materials. The polarization curves of all the alloys tested were typical of passivable materials. Pitting corrosion susceptibility has been evaluated by means of cyclic potentiodynamic curves, which provide parameters to analyse re-passivation properties. The galvanic corrosion generated by the electrical contact between the welded and the base material has been estimated from the polarization diagrams according to the Mixed Potential Method. Samples have been etched to study the microstructure by Scanning Electron Microscopy (SEM). The results demonstrate that the pitting resistance of all these materials increases as the LiBr concentration decreases. In general, the presence of chromate tended to shift the pitting potential to more positive values than those obtained in the 850 g/l LiBr solution. (authors)

  19. An experience with in-service fabrication and inspection of austenitic stainless steel piping in high temperature sodium system

    Energy Technology Data Exchange (ETDEWEB)

    Ravi, S., E-mail: sravi@igcar.gov.in; Laha, K.; Sakthy, S.; Mathew, M.D.; Bhaduri, A.K.

    2015-04-01

    Highlights: • Procedure for changing 304L SS pipe to 316L SS in sodium loop has been established. • Hot leg made of 304L SS was isolated from existing cold leg made of 316LN SS. • Innovative welding was used in joining the new 316L SS pipe with existing 316LN SS. • The old components of 304L SS piping have been integrated with the new piping. - Abstract: A creep testing facility along with dynamic sodium loop was installed at Indira Gandhi Centre for Atomic Research, Kalpakkam, India to assess the creep behavior of fast reactor structural materials in flowing sodium. Type 304L austenitic stainless steel was used in the low cross section piping of hot-leg whereas 316LN austenitic stainless steel in the high cross section cold-leg of the sodium loop. The intended service life of the sodium loop was 10 years. The loop has performed successfully in the stipulated time period. To enhance its life time, it has been decided to replace the 304L piping with 316L piping in the hot-leg. There were more than 300 welding joints involved in the integration of cold-leg with the new 316L hot-leg. Continuous argon gas flow was maintained in the loop during welding to avoid contamination of sodium residue with air. Several innovative welding procedures have been adopted for joining the new hot-leg with the existing cold-leg in the presence of sodium residue adopting TIG welding technique. The joints were inspected for 100% X-ray radiography and qualified by performing tensile tests. The components used in the discarded hot-leg were retrieved, cleaned and integrated in the renovated loop. A method of cleaning component of sodium residue has been established. This paper highlights the in-service fabrication and inspection of the renovation.

  20. Cracking behavior and microstructure of austenitic stainless steels and alloy 690 irradiated in BOR-60 reactor, phase I.

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Y.; Chopra, O. K.; Soppet, W. K.; Shack, W. J.; Yang, Y.; Allen, T. R.; Univ. of Wisconsin at Madison

    2010-02-16

    Cracking behavior of stainless steels specimens irradiated in the BOR-60 at about 320 C is studied. The primary objective of this research is to improve the mechanistic understanding of irradiation-assisted stress corrosion cracking (IASCC) of core internal components under conditions relevant to pressurized water reactors. The current report covers several baseline tests in air, a comparison study in high-dissolved-oxygen environment, and TEM characterization of irradiation defect structure. Slow strain rate tensile (SSRT) tests were conducted in air and in high-dissolved-oxygen (DO) water with selected 5- and 10-dpa specimens. The results in high-DO water were compared with those from earlier tests with identical materials irradiated in the Halden reactor to a similar dose. The SSRT tests produced similar results among different materials irradiated in the Halden and BOR-60 reactors. However, the post-irradiation strength for the BOR-60 specimens was consistently lower than that of the corresponding Halden specimens. The elongation of the BOR-60 specimens was also greater than that of their Halden specimens. Intergranular cracking in high-DO water was consistent for most of the tested materials in the Halden and BOR-60 irradiations. Nonetheless, the BOR-60 irradiation was somewhat less effective in stimulating IG fracture among the tested materials. Microstructural characterization was also carried out using transmission electron microscopy on selected BOR-60 specimens irradiated to {approx}25 dpa. No voids were observed in irradiated austenitic stainless steels and cast stainless steels, while a few voids were found in base and grain-boundary-engineered Alloy 690. All the irradiated microstructures were dominated by a high density of Frank loops, which varied in mean size and density for different alloys.

  1. Dynamical recrystallization of high purity austenitic stainless steels; Recristallisation dynamique d'aciers inoxydables austenitiques de haute purete

    Energy Technology Data Exchange (ETDEWEB)

    Gavard, L

    2001-01-01

    The aim of this work is to optimize the performance of structural materials. The elementary mechanisms (strain hardening and dynamical regeneration, germination and growth of new grains) occurring during the hot working of metals and low pile defect energy alloys have been studied for austenitic stainless steels. In particular, the influence of the main experimental parameters (temperature, deformation velocity, initial grain size, impurities amount, deformation way) on the process of discontinuous dynamical recrystallization has been studied. Alloys with composition equal to those of the industrial stainless steel-304L have been fabricated from ultra-pure iron, chromium and nickel. Tests carried out in hot compression and torsion in order to cover a wide range of deformations, deformation velocities and temperatures for two very different deformation ways have allowed to determine the rheological characteristics (sensitivity to the deformation velocity, apparent activation energy) of materials as well as to characterize their microstructural deformations by optical metallography and electron back-scattered diffraction. The influence of the initial grain size and the influence of the purity of the material on the dynamical recrystallization kinetics have been determined. An analytical model for the determination of the apparent mobility of grain boundaries, a semi-analytical model for the dynamical recrystallization and at last an analytical model for the stationary state of dynamical recrystallization are proposed as well as a new criteria for the transition between the refinement state and the state of grain growth. (O.M.)

  2. Study of the corrosion behaviors of 304 austenite stainless steel specimens exposed to static liquid lithium at 600 K

    Science.gov (United States)

    Meng, Xiancai; Zuo, Guizhong; Ren, Jun; Xu, Wei; Sun, Zhen; Huang, Ming; Hu, Wangyu; Hu, Jiansheng; Deng, Huiqiu

    2016-11-01

    Investigation of corrosion behavior of stainless steel served as one kind of structure materials exposed to liquid lithium (Li) is one of the keys to apply liquid Li as potential plasma facing materials (PFM) or blanket coolant in the fusion device. Corrosion experiments of 304 austenite stainless steel (304 SS) were carried out in static liquid Li at 600 K and up to1584 h at high vacuum with pressure less than 4 × 10-4 Pa. After exposure to liquid Li, it was found that the weight of 304 SS slightly decreased with weight loss rate of 5.7 × 10-4 g/m2/h and surface hardness increased by about 50 HV. Lots of spinel-like grains and holes were observed on the surface of specimens measured by SEM. By further EDS, XRD and metallographic analyzing, it was confirmed that the main compositions of spinel-like grains were M23C6 carbides, and 304 SS produced a non-uniform corrosion behavior by preferential grain boundary attack, possibly due to the easy formation of M23C6 carbides and/or formation of Li compound at grain boundaries.

  3. Investigation of phase transformation for ferrite–austenite structure in stainless steel thin films

    Energy Technology Data Exchange (ETDEWEB)

    Merakeb, Noureddine [Laboratory of Physical Metallurgy and Property of Materials (LM2PM), Metallurgy and Materials Engineering Department, Badji Mokhtar University, P.O. Box 12, Annaba 23000 (Algeria); Messai, Amel [Laboratoire d' Ingénierie et Sciences des Matériaux Avancés (ISMA), Institut des Sciences et Technologie, Abbès Laghrour University, Khenchela 40000 (Algeria); Ayesh, Ahmad I., E-mail: ayesh@qu.edu.qa [Department of Mathematics, Statistics and Physics, Qatar University, Doha (Qatar)

    2016-05-01

    In this work we report on phase transformation of 304 stainless steel thin films due to heat treatment. Ex-situ annealing was applied for evaporated 304 stainless steel thin films inside an ultra-high vacuum chamber with a pressure of 3 × 10{sup −7} Pa at temperatures of 500 °C and 600 °C. The structure of thin films was studied by X-ray diffraction (XRD) and conversion electron Mössbauer spectroscopy (CEMS) techniques. The results revealed a transformation from α-phase that exhibits a body-centered cubic structure (BCC) to γ-phase that exhibits a face-centered cubic (FCC) due to annealing. In addition, the percentage of γ-phase structure increased with the increase of annealing temperature. Annealing thin films increased the crystal size of both phases (α and γ), however, the increase was nonlinear. The results also showed that phase transformation was produced by recrystallization of α and γ crystals with a temporal evolution at each annealing temperature. The texture degree of thin films was investigated by XRD rocking curve method, while residual stress was evaluated using curvature method. - Highlights: • Stainless steel thin films were fabricated by thermal evaporation on quartz. • Alpha to gamma phase transformation of thin films was investigated. • Annealing of thin films reduces disruption in crystal lattice. • The stress of as-grown thin films was independent on the thin film thickness. • The stress of the thin films was reduced due to annealing.

  4. Novel approaches to determining residual stresses by ultramicroindentation techniques: Application to sandblasted austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Frutos, E. [Centro de Bioingenieria, Biomateriales y Nanomedicina, CIBER-BBN, Instituto de Salud Carlos III (Spain)] [Centro Nacional de Investigaciones Metalurgicas, CENIM-CSIC, 28040 Madrid (Spain); Multigner, M. [Centro Nacional de Investigaciones Metalurgicas, CENIM-CSIC, 28040 Madrid (Spain)] [Centro de Bioingenieria, Biomateriales y Nanomedicina, CIBER-BBN, Instituto de Salud Carlos III (Spain); Gonzalez-Carrasco, J.L., E-mail: jlg@cenim.csic.es [Centro Nacional de Investigaciones Metalurgicas, CENIM-CSIC, 28040 Madrid (Spain)] [Centro de Bioingenieria, Biomateriales y Nanomedicina, CIBER-BBN, Instituto de Salud Carlos III (Spain)

    2010-07-15

    This research addresses the determination of residual stresses in sandblasted austenitic steel by ultramicroindentation techniques using a sharp indenter, of which the sensitivity to residual stress effects is said to be inferior to that of spherical ones. The introduction of an angular correction in the model of Wang et al. which relates variations in the maximum load to the presence of residual stresses is proposed. Similarly, the contribution to the hardness of grain size refinement and work hardening, developed as a consequence of the severe plastic deformation during blasting, is determined in order to avoid overestimation of the residual stresses. Measurements were performed on polished cross sections along a length of several microns, thus obtaining a profile of the residual stresses. Results show good agreement with those obtained by synchrotron radiation on the same specimens, which validates the method and demonstrates that microindentation using sharp indenters may be sensitive to the residual stress effect.

  5. Investigation of the Mechanical Properties of AISI 316 Austenitic Stainless Steel and St 37 Low Carbon Steel Dissimilar Joint by Friction Stir Welding

    Directory of Open Access Journals (Sweden)

    A.H. Khosrovaninezhad

    2015-07-01

    Full Text Available This paper reports on the mechanical properties of the dissimilar joints between AISI 316 austenitic stainless steel and St 37 low carbon steel achieved using friction stir welding technique. The welding was carried out by means of rotational speed of 800 rpm and linear speeds of 50,100,150 mm/min. EDS and XRD techniques were employed in order to determine possible phase transformations. Tensile test, shear punch test and microhardness measurements were conducted to evaluate the mechanical properties of the joints. The results of phase investigations showed that no carbide and brittle phase were detected at the joint boundary. Also, tensile test results demonstrated that failure occurred in the St 37 base metal. According to the shear punch test, the highest ultimate shear strength and yield shear strength was achieved for the sample welded at rotational speed of 800 rpm and linear speed of 150 mm/min, while this sample showed the least elongation. In addition, the highest microhardness was measured in the stir zone of austenitic stainless steel sample welded in the above mentioned welding condition, which can be attributed to the decrease in grain size caused by recrystallization process.

  6. Simultaneous chromizing and aluminizing using chromium oxide and aluminum: (II) on austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Heo, N.H.; Kim, M.T.; Shin, J.H.; Kim, C.Y. [Korea Electr. Power Res. Inst., Taejon (Korea). Machinery and Mater. Group

    2000-02-01

    For pt.I see ibid., vol.123, p.227-30, 2000. The codeposition of Cr and Al on 304 stainless steel has been investigated, using the conversion reaction of Cr{sub 2}O{sub 3} to halide. An increase in ratio of Cr{sub 2}O{sub 3} to Al in the pack composition tends to form a chromide coating, which is very poor in high temperature oxidation resistance. A codeposited coating layer, which shows high oxidation resistance, is mainly characterized by three zones: an outer layer of iron aluminide, a nickel-rich iron aluminide, and an interdiffusion zone consisting of alpha ferrite and nickel aluminide precipitates. Oxidation resistance increased as the thickness of the outer iron aluminide layer increased. This means that the aluminum in the outer layer, rather than that in nickel aluminide precipitates or alpha ferrite, acts as a strong aluminum source forming a protective Al{sub 2}O{sub 3} scale at the coating surface. Using a pack mixture containing 10 wt.% Cr{sub 2}O{sub 3} and 10 wt.% Al, a coating, which shows excellent oxidation resistance at 1100 C, was obtained after codeposition of aluminum and chromium on 304 stainless steel at 1050 C for about 6-8 h. (orig.)

  7. Microstructure influence on fatigue behaviour of austenitic stainless steels with high molybdenum content; Influencia de la microestructura en el comportamiento a fatiga de aceros inoxidables austeniticos con alto contenido en molibdeno

    Energy Technology Data Exchange (ETDEWEB)

    Onoro, J.; Gamboa, R.; Ranninger, C.

    2006-07-01

    Austenitic stainless steels with molybdenum present high mechanical properties and corrosion resistance to aggressive environments. These steels have been used to tank and vessel components for high liquids as phosphoric, nitric and sulphuric acids. These materials with low carbon and nitrogen addition have been proposed candidates as structural materials for the international thermonuclear experimental reactor (ITER) in-vessel components. Molybdenum addition in austenitic stainless steel improves mechanical and corrosion properties, but with it can produce the presence of nitrogen microstructure modifications by presence or precipitation of second phases. This paper summarises the fatigue and corrosion fatigue behaviour of two 317LN stainless steels with different microstructure. Fully austenitic steel microstructure show better fatigue, corrosion fatigue resistance and better ductility than austenitic steel with delta ferrite microstructure, mainly at low stresses. (Author)

  8. In situ TEM study of G-phase precipitates under heavy ion irradiation in CF8 cast austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Wei-Ying [Argonne National Laboratory, Argonne, IL 60439 (United States); University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); Li, Meimei; Zhang, Xuan; Kirk, Marquis A.; Baldo, Peter M. [Argonne National Laboratory, Argonne, IL 60439 (United States); Lian, Tiangan [Electric Power Research Institute, Palo Alto, CA 94304 (United States)

    2015-09-15

    Thermally-aged cast austenitic stainless steels (CASS) CF8 was irradiated with 1 MeV Kr ions at 300, 350 and 400 °C to 1.88 × 10{sup 19} ions/m{sup 2} (∼3 dpa) at the IVEM-Tandem Facility at the Argonne National Laboratory. Before irradiation, the distribution of G-phase precipitates in the ferrite showed spatial variations, and both their size and density were affected by the ferrite–austenite phase boundary and presence of M{sub 23}C{sub 6} carbides. Under 300 °C irradiation, in situ TEM observation showed G-phase precipitates were relatively unchanged in the vicinity of the phase boundary M{sub 23}C{sub 6} carbides, while the density of G-phase precipitates increased with increasing dose within the ferrite matrix. Coarsening of G-phase precipitates was observed in the vicinity of phase boundary M{sub 23}C{sub 6} carbides at 350 °C and 400 °C.

  9. Swelling and microstructure of austenitic stainless steel ChS-68 CW after high dose neutron irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Porollo, S.I.; Konobeev, Yu.V. [State Scientific Center of Russian Federation - Institute of Physics and Power Engineering (IPPE), Obninsk, Kaluga Region (Russian Federation); Garner, F.A., E-mail: frank.garner@dslextreme.co [Radiation Effects Consulting, 2003 Howell Avenue, Richland, WA 99354 (United States)

    2009-08-15

    Austenitic stainless steel ChS-68 serving as fuel pin cladding was irradiated in the 20% cold-worked condition in the BN-600 fast reactor in the range 56-84 dpa. This steel was developed to replace EI-847 which was limited by its insufficient resistance to void swelling. Comparison of swelling between EI-847 and ChS-68 under similar irradiation conditions showed improvement of the latter steel by an extended transient regime of an additional approx10 dpa. Concurrent with swelling was the development of a variety of phases. In the temperature range 430-460 deg. S where the temperature peak of swelling was located, the principal type of phase generated during irradiation was G-phase, with volume fraction increasing linearly with dose to approx0.5% at 84 dpa. While the onset of swelling is concurrent with formation of G-phase, the action of G-phase cannot be confidently ascribed to significant removal from solution of swelling-suppressive elements such as silicon. A plausible mechanism for the higher resistance to void swelling of ChS-68 as compared with EI-847 may be related to an observed higher stability of faulted dislocation loops in ChS-68 that impedes the formation of a glissile dislocation network. The higher level of boron in ChS-68 is thought to be one contributor that might play this role.

  10. Structural Transformations in Austenitic Stainless Steel Induced by Deuterium Implantation: Irradiation at 295 K

    Science.gov (United States)

    Morozov, Oleksandr; Zhurba, Volodymir; Neklyudov, Ivan; Mats, Oleksandr; Progolaieva, Viktoria; Boshko, Valerian

    2016-02-01

    Deuterium thermal desorption spectra were investigated on the samples of austenitic steel 18Cr10NiTi pre-implanted at 295 K with deuterium ions in the dose range from 8 × 1014 to 2.7 × 1018 D/cm2. The kinetics of structural transformation development in the steel layer was traced from deuterium thermodesorption spectra as a function of deuterium concentration. Three characteristic regions with different low rates of deuterium amount desorption as the implantation dose increases were revealed: I—the linear region of low implantation doses (up to 1 × 1017 D/cm2); II—the nonlinear region of medium implantation doses (1 × 1017 to 8 × 1017 D/cm2); III—the linear region of high implantation doses (8 × 1017 to 2.7 × 1018 D/cm2). During the process of deuterium ion irradiation, the coefficient of deuterium retention in steel varies in discrete steps. Each of the discrete regions of deuterium retention coefficient variation corresponds to different implanted-matter states formed during deuterium ion implantation. The low-dose region is characterized by formation of deuterium-vacancy complexes and solid-solution phase state of deuterium in the steel. The total concentration of the accumulated deuterium in this region varies between 2.5 and 3 at.%. The medium-dose region is characterized by the radiation-induced action on the steel in the presence of deuterium with the resulting formation of the energy-stable nanosized crystalline structure of steel, having a developed network of intercrystalline boundaries. The basis for this developed network of intercrystalline boundaries is provided by the amorphous state, which manifests itself in the thermodesorption spectra as a widely temperature-scale extended region of deuterium desorption (structure formation with a varying activation energy). The total concentration of the accumulated deuterium in the region of medium implantation doses makes 7 to 8 at.%. The resulting structure shows stability against the action of

  11. Low temperature surface hardening of stainless steel; the role of plastic deformation

    DEFF Research Database (Denmark)

    Bottoli, Federico; Jespersen, Freja Nygaard; Hattel, Jesper Henri;

    2016-01-01

    Thermochemical surface engineering by nitriding of austenitic stainless steel transforms the surface zone into expanded austenite, which improves the wear resistance of the stainless steel while preserving the stainless behavior. As a consequence of the thermochemical surface engineering, huge re...

  12. EFFECT OF COPPER IMPLANTATION ON ANTIBACTERIAL ACTIVITY OF AUSTENITIC STAINLESS STEEL

    Institute of Scientific and Technical Information of China (English)

    J. Xiong; B.F. Xu; H.W. Ni; P.Y. Xiong; Z.G. Dan

    2004-01-01

    Antibacterial activity has been studied by copper ion implantation into 0Cr18Ni9 stainless steel.Ions extracted from a metal vapor vacuum arc (MEWA) are sourced with 60-100keV energy and a dose range (0.2-2.0)×1017 ions cm-2. Saturation doses, surface concentration were calculated and the relationships between energy, dose and antibacterial activity were analyzed.Novel phases such as Fe4Cu3 and Cu0.81Ni0-19 were found after copper implantation by X-ray diffraction. The novel phases effects on antibacterial activity have been investigated. The results show that saturation dose varies with the ions′energy. Antibacterial activity has close relation with copper's concentration in implanted layer and Cu-rich phase.

  13. SCC crack growth rate of cold-worked austenitic stainless steels in PWR primary water conditions

    Energy Technology Data Exchange (ETDEWEB)

    Guerre, C.; Raquet, O.; Herms, E. [Commissariat a l' Energie Atomique (CEA), DEN/DPC/SCCME/LECA, Gif-sur-Yvette Cedex (France); Marie, S. [Commissariat a l' Energie Atomique (CEA), DEN/DM2S/SEMT/LISN, Gif-sur-Yvette Cedex (France); Le Calvar, M. [Inst. for Radiological Protection and Nuclear Safety (IRSN), DSR/SAMS, Fontenay-aux-Roses Cedex (France)

    2007-07-01

    Stress corrosion cracking (SCC) of stainless steels (SS) is a significant cause of failure in the pressurized water reactors (PWR). Most of the reported case history failures of SS in PWR can be attributed to pollutants (chloride, sulphate) and / or locally oxygenated environments, even to sensitisation of the SS. However, some failures have been attributed to heavy cold work (CW) of SS. In laboratory tests, SCC initiation of cold-worked SS has been obtained using slow strain rate tests (SSRT) in nominal PWR environment. This paper describes constant load and cyclic crack growth rate (CGR) tests on cold-worked SS, on CT specimens. 304L and 316L have been tested with a CW up to 60 %. CW 316L is more prone to cracking than 304L. Over 30 % of CW, 316L is susceptible to crack propagation under constant load. CW is the main controlling parameter for cracking. (author))

  14. Laser power coupling efficiency in conduction and keyhole welding of austenitic stainless steel

    Indian Academy of Sciences (India)

    A K Nath; R Sridhar; P Ganesh; R Kaul

    2002-06-01

    Laser welding of thin sheets of AISI 304 stainless steel was carried out with high power CW CO2 laser. The laser power utilized in the welding process was estimated using the experimental results and the dimensionless parameter model for laser welding; and also the energy balance equation model. Variation of laser welding efficiency with welding speed and mode of welding was studied. Welding efficiency was high for high-speed conduction welding of thin sheets and also in keyhole welding process at high laser powers. Effect of pre-oxidization of the surface and powder as filler material on laser power coupling is also reported. The paper also discusses effect of microstructure on the cracking susceptibility of laser welds.

  15. Optimization of CO2 laser cutting parameters on Austenitic type Stainless steel sheet

    Science.gov (United States)

    Parthiban, A.; Sathish, S.; Chandrasekaran, M.; Ravikumar, R.

    2017-03-01

    Thin AISI 316L stainless steel sheet widely used in sheet metal processing industries for specific applications. CO2 laser cutting is one of the most popular sheet metal cutting processes for cutting of sheets in different profile. In present work various cutting parameters such as laser power (2000 watts-4000 watts), cutting speed (3500mm/min – 5500 mm/min) and assist gas pressure (0.7 Mpa-0.9Mpa) for cutting of AISI 316L 2mm thickness stainless sheet. This experimentation was conducted based on Box-Behenken design. The aim of this work is to develop a mathematical model kerf width for straight and curved profile through response surface methodology. The developed mathematical models for straight and curved profile have been compared. The Quadratic models have the best agreement with experimental data, and also the shape of the profile a substantial role in achieving to minimize the kerf width. Finally the numerical optimization technique has been used to find out best optimum laser cutting parameter for both straight and curved profile cut.

  16. Evaluation of Electrochemical Characteristics on Graphene Coated Austenitic and Martensitic Stainless Steels for Metallic Bipolar Plates in PEMFC Fabricated with Hydrazine Reduction Methods

    Energy Technology Data Exchange (ETDEWEB)

    Cha, Seong-Yun; Lee, Jae-Bong [School of Advanced Materials Engineering, Kookmin University, Seoul (Korea, Republic of)

    2016-04-15

    Graphene was coated on austenitic and martensitic stainless steels to simulate the metallic bipolar plate of proton exchange membrane fuel cell (PEMFC). Graphene oxide (GO) was synthesized and was reduced to reduced graphene oxide (rGO) via a hydrazine process. rGO was confirmed by FE-SEM, Raman spectroscopy and XPS. Interfacial contact resistance (ICR) between the bipolar plate and the gas diffusion layer (GDL) was measured to confirm the electrical conductivity. Both ICR and corrosion current density decreased on graphene coated stainless steels. Corrosion resistance was also improved with immersion time in cathodic environments and satisfied the criteria of the Department of Energy (DOE), USA. The total concentrations of metal ions dissolved from graphene coated stainless steels were reduced. Furthermore hydrophobicity was improved by increasing the contact angle.

  17. Factors Affecting the Development of Oxide Scales on Austenitic Stainless Steels during Hot Rolling in Steckel Mills

    Science.gov (United States)

    Cobo, S. J.; Rainforth, W. M.

    2008-10-01

    The hot rolling of austenitic stainless steels in Steckel Mills introduces particular characteristics to the development of oxides scales and surface structures. In this work, the formation of oxide structures during multipass hot rolling of 302 steel was studied under different sets of processing parameters in a laboratory system designed for the simulation of the Steckel process. The resulting surface structures were characterized by a set of complementary techniques involving scanning electron microscopy, energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), and glow discharge optical spectroscopy (GDOS). The surface analysis revealed two alternative surface structures: one consisting in a thin protective oxide layer rich in Cr2O3 and the other consisting in thick complex structures containing several successive nonprotective oxide scale and metal layers resulting from a cyclic oxidation pattern involving stages of protective oxidation, chemical breakaway, and duplex oxidation. The critical condition that determined the activation of one mechanism or the other was identified associated with the parabolic rate constant for Cr2O3 growth and the diffusivity of Cr in the alloy. The effects of changes in temperature, deformation, and furnace atmosphere are discussed. Alternatives for controlling scale development are presented.

  18. Microstructure and Property Relationships in Resistance Spot Weld between 7114 Interstitial Free Steel and 304 Austenitic Stainless Steel

    Institute of Scientific and Technical Information of China (English)

    Ahmet Hasanba(s)o(g)lu; Ramazan Ka(c)ar

    2006-01-01

    Due to the differences in physical, chemical and mechanical properties of the base metals, the resistance spot welding of dissimilar materials is generally more challenging than that of similar materials. The influence of the primary welding parameters affecting the heat input such as peak current on the morphology, microhardness,and tensile shear load bearing capacity of dissimilar welds between 304 grades austenitic and 7114 grade interstitial free steel has been investigated in this study. The optimum welding parameters producing maximum joint strength were established at a peak current of 9 kA, where the electrode force is kept 6×10-5 Pa and weld time is kept constant 17 cycles, respectively. The primary cause of weakening the weldment is identified as the excessive grain growing region of heat affected zone (HAZ) in case of 7114 grade interstitial free steel.

  19. Phase diffusionless γ↔α transformations and their effect on physical, mechanical and corrosion properties of austenitic stainless steels irradiated with neutrons and charged particles

    Science.gov (United States)

    Maksimkin, O. P.

    2016-04-01

    The work presents relationships of γ→α' and α'→γ-transformations in reactor 12Cr18Ni10Ti and 08Cr16Ni11Mo3 austenitic stainless steels induced by cold work, irradiation and/or temperature. Energy and mechanical parameters of nucleation and development of deformation-induced martensitic α'-phase in the non-irradiated and irradiated steels are given. The mechanisms of localized static deformation were investigated and its effect on martensitic γ→α' transformation is determined. It has been shown that irradiation of 12Cr18Ni10Ti steel with heavy Kr ions (1.56MeV/nucleon, fluence of 1·1015 cm-2) results in formation of α'-martensite in near-surface layer of the sample. Results of systematic research on reversed α'→γ-transformation in austenitic metastable stainless steels irradiated with slow (VVR-K) and fast (BN-350) neutrons are presented. The effect of annealing on strength and magnetic characteristics was determined. It was found that at the temperature of 400 °C in the irradiated with neutrons samples (59 dpa) an increase of ferromagnetic α'-phase and microhardness was observed. The obtained results could be used during assessment of operational characteristics of highly irradiated austenitic steels during transportation and storage of Fuel Assemblies for fast nuclear reactors.

  20. Strain induced grain boundary migration effects on grain growth of an austenitic stainless steel during static and metadynamic recrystallization

    Energy Technology Data Exchange (ETDEWEB)

    Paggi, A., E-mail: alpaggi@tenaris.com [Tenaris Dalmine R& D, Dalmine S.p.A., Piazza Caduti 6 Luglio 1944 n.1, 24044 Dalmine (Italy); Angella, G.; Donnini, R. [National Research Council (CNR), Institute for Energetics and Interphases (IENI), Via Roberto Cozzi 53, 20125 Milano (Italy)

    2015-09-15

    Static and metadynamic recrystallization of an AISI 304L austenitic stainless steel was investigated at 1100 °C and 10{sup −} {sup 2} s{sup −} {sup 1} strain rate. The kinetics of recrystallization was determined through double hit compression tests. Two strain levels were selected for the first compression hit: ε{sub f} = 0.15 for static recrystallization (SRX) and 0.25 for metadynamic recrystallization (MDRX). Both the as-deformed and the recrystallized microstructures were investigated through optical microscopy and electron back-scattered diffraction (EBSD) technique. During deformation, strain induced grain boundary migration appeared to be significant, producing a square-like grain boundary structure aligned along the directions of the maximum shear stresses in compression. EBSD analysis revealed to be as a fundamental technique that the dislocation density was distributed heterogeneously in the deformed grains. Grain growth driven by surface energy reduction was also investigated, finding that it was too slow to explain the experimental data. Based on microstructural results, it was concluded that saturation of the nucleation sites occurred in the first stages of recrystallization, while grain growth driven by strain induced grain boundary migration (SIGBM) dominated the subsequent stages. - Highlights: • Recrystallization behavior of a stainless steel was investigated at 1100 °C. • EBSD revealed that the dislocation density distribution was heterogeneous during deformation. • Saturation of nucleation sites occurred in the first stages of recrystallization. • Strain induced grain boundary migration (SIGBM) effects were significant. • Grain growth driven by SIGBM dominated the subsequent stages.

  1. Influence of temperature histories during reactor startup periods on microstructural evolution and mechanical properties of austenitic stainless steel irradiated with neutrons

    Science.gov (United States)

    Kasahara, Shigeki; Kitsunai, Yuji; Chimi, Yasuhiro; Chatani, Kazuhiro; Koshiishi, Masato; Nishiyama, Yutaka

    2016-11-01

    This paper addresses influence of two different temperature profiles during startup periods in the Japan Materials Testing Reactor and a boiling water reactor upon microstructural evolution and mechanical properties of austenitic stainless steel irradiated with neutrons to about 1 dpa and 3 dpa. One of the temperature profiles was that the specimens experienced neutron irradiation in both reactors, under which the irradiation temperature transiently increased to 290 °C from room temperature with increasing reactor power during reactor startup periods. Another was that the specimens were pre-heated to about 150 °C prior to the irradiation to suppress the transient temperature increase. Tensile tests at 290 °C and Vickers hardness tests at room temperature were carried out, and their microstructures were observed by FEG-TEM. Difference of the temperature profiles was observed obviously in interstitial cluster formation, in particular, growth of Frank loops. Although influence of neutron irradiation involving transient temperature increase to 290 °C from room temperature on the yield strength and the Vickers hardness is buried in the trend curves of existing data, the influence was also found certainly in increment of in yield strength, existence of modest yield drop, and loss of strain hardening capacity and ductility. As a result, Frank loops, which were observed in austenitic stainless steel irradiated at doses of 1 dpa or more, seemed to have important implications regarding the interpretation of not irradiation hardening, but deformation of the austenitic stainless steel.

  2. Ultrasonic Characterization of Cast Austenitic Stainless Steel Microstructure: Discrimination between Equiaxed- and Columnar-Grain Material – An Interim Study

    Energy Technology Data Exchange (ETDEWEB)

    Ramuhalli, Pradeep; Good, Morris S.; Diaz, Aaron A.; Anderson, Michael T.; Watson, Bruce E.; Peters, Timothy J.; Dixit, Mukul; Bond, Leonard J.

    2009-10-27

    Ultrasonic nondestructive evaluation (NDE) and inspection of cast austenitic stainless steel (CASS) components used in the nuclear power industry is neither as effective nor reliable as is needed due to detrimental effects upon the interrogating ultrasonic beam and interference from ultrasonic backscatter. The root cause is the coarse-grain microstructure inherent to this class of materials. Some ultrasonic techniques perform better for particular microstructural classifications and this has led to the hypothesis that an ultrasonic inspection can be optimized for a particular microstructural class, if a technique exists to reliably classify the microstructure for feedback to the inspection. This document summarizes scoping experiments of in-situ ultrasonic methods for classification and/or characterization of the material microstructures in CASS components from the outside surface of a pipe. The focus of this study was to evaluate ultrasonic methods and provide an interim report that documents results and technical progress. An initial set of experiments were performed to test the hypothesis that in-service characterization of cast austenitic stainless steel (CASS) is feasible, and that, if reliably performed, such data would provide real-time feedback to optimize in-service inspections in the field. With this objective in mind, measurements for the experiment were restricted to techniques that should be robust if carried forward to eventual field implementation. Two parameters were investigated for their ability to discriminate between different microstructures in CASS components. The first parameter was a time-of-flight ratio of a normal incidence shear wave to that of a normal incidence longitudinal wave (TOFRSL). The ratio removed dependency on component thickness which may not be accurately reported in the field. The second parameter was longitudinal wave attenuation. The selected CASS specimens provided five equiaxed-grain material samples and five columnar

  3. Effect of relative humidity in high temperature oxidation of ceria nanoparticles coating on 316L austenitic stainless steel

    Science.gov (United States)

    Giraldez Pizarro, Luis Miguel

    A solution of 20 wt. % colloidal dispersion of Cerium Oxide (CeO2) in 2.5% of acetic acid, was used for depositing a coating film on an austenitic stainless steel 316L. Cerium compounds have been distinguished as potential corrosion inhibitors in coatings over several alloys. The oxidation behavior of the cerium oxide coating on 316L austenitic stainless steel alloy was evaluated in dry and humid environments, the weight changes (W/A) was monitored as a function of time using a custom built Thermogravimetrical Analysis (TGA) instrument at temperatures of 750°C, 800°C and 850°C, and different relative humidity levels (0%, 10% and 20%) respectively. The parabolic oxidation rate and activation energy is calculated experimentally for each relative humidity level. A measurement of the effective diameter size of the ceria nanoparticles was performed using a Light Scattering technique. A characterization of the film morphology and thickness before the oxidation was executed using Atomic Force Microscopy (AFM). Microstructure and chemical composition of the oxidized coated substrates were analyzed using Scanning Electronic Microscopy (SEM) with energy dispersive spectroscopy (EDS). X-Ray Diffractometer (XRD) was used to characterize oxides formed in the surface upon isothermal treatment. A comparison of activation energy values obtained to identify the influence of relative humidity in the oxidation process at high temperature was conducted. Cerium oxides coating may prevent crevice corrosion and increase pitting resistance of 316L relative to the uncoated substrate at high temperatures and different levels of relative humidity acting as a protective oxidation barrier. The calculated parabolic rate constants, kp, at the experimental temperatures tend to increase as a function of humidity levels. The activation energy tends to increase proportionally to higher level of humidity exposures. At 0% relative humidity a value of 319.29 KJ/mol of activation energy is being

  4. Development of Stronger and More Reliable Cast Austenitic Stainless Steels (H-Series) Based on Scientific Design Methodology

    Energy Technology Data Exchange (ETDEWEB)

    Muralidharan, G.; Sikka, V.K.; Pankiw, R.I.

    2006-04-15

    The goal of this program was to increase the high-temperature strength of the H-Series of cast austenitic stainless steels by 50% and upper use temperature by 86 to 140 F (30 to 60 C). Meeting this goal is expected to result in energy savings of 38 trillion Btu/year by 2020 and energy cost savings of $185 million/year. The higher strength H-Series of cast stainless steels (HK and HP type) have applications for the production of ethylene in the chemical industry, for radiant burner tubes and transfer rolls for secondary processing of steel in the steel industry, and for many applications in the heat-treating industry. The project was led by Duraloy Technologies, Inc. with research participation by the Oak Ridge National Laboratory (ORNL) and industrial participation by a diverse group of companies. Energy Industries of Ohio (EIO) was also a partner in this project. Each team partner had well-defined roles. Duraloy Technologies led the team by identifying the base alloys that were to be improved from this research. Duraloy Technologies also provided an extensive creep data base on current alloys, provided creep-tested specimens of certain commercial alloys, and carried out centrifugal casting and component fabrication of newly designed alloys. Nucor Steel was the first partner company that installed the radiant burner tube assembly in their heat-treating furnace. Other steel companies participated in project review meetings and are currently working with Duraloy Technologies to obtain components of the new alloys. EIO is promoting the enhanced performance of the newly designed alloys to Ohio-based companies. The Timken Company is one of the Ohio companies being promoted by EIO. The project management and coordination plan is shown in Fig. 1.1. A related project at University of Texas-Arlington (UT-A) is described in Development of Semi-Stochastic Algorithm for Optimizing Alloy Composition of High-Temperature Austenitic Stainless Steels (H-Series) for Desired

  5. Study of austenitic stainless steel welded with low alloy steel filler metal. [tensile and impact strength tests

    Science.gov (United States)

    Burns, F. A.; Dyke, R. A., Jr.

    1979-01-01

    The tensile and impact strength properties of 316L stainless steel plate welded with low alloy steel filler metal were determined. Tests were conducted at room temperature and -100 F on standard test specimens machined from as-welded panels of various chemical compositions. No significant differences were found as the result of variations in percentage chemical composition on the impact and tensile test results. The weldments containing lower chromium and nickel as the result of dilution of parent metal from the use of the low alloy steel filler metal corroded more severely in a marine environment. The use of a protective finish, i.e., a nitrile-based paint containing aluminum powder, prevented the corrosive attack.

  6. The role of niobium carbide in radiation induced segregation behaviour of type 347 austenitic stainless steel

    Science.gov (United States)

    Ahmedabadi, Parag; Kain, Vivekanand; Gupta, Manu; Samajdar, I.; Sharma, S. C.; Bhagwat, P.; Chowdhury, R.

    2011-08-01

    The effect of niobium carbide precipitates on radiation induced segregation (RIS) behaviour in type 347 stainless steel was investigated. The material in the as-received condition was irradiated using double-loop 4.8 MeV protons at 300 °C for 0.43 dpa (displacement per atom). The RIS in the proton irradiated specimen was characterized using double-loop electrochemical potentiokinetic reactivation (DL-EPR) test followed by atomic force microscopic examination. The nature of variation of DL-EPR values with the depth matched with the variation of the calculated irradiation damage (dpa) with the depth. The attack on grain boundaries during EPR tests was negligible indicating absence of chromium depletion zones. The interface between niobium carbide and the matrix acts as a sink for point defects generated during irradiation and this had reduced point defect flux toward grain boundaries. The attack was noticed at a few large cluster of niobium carbide after the DL-EPR test at the depth of maximum attack for the irradiated specimen. Pit-like features were not observed within the matrix indicating the absence of chromium depletion regions within the matrix.

  7. Electrochemical behaviour and surface conductivity of niobium carbide-modified austenitic stainless steel bipolar plate

    Science.gov (United States)

    Wang, Lixia; Sun, Juncai; Kang, Bin; Li, Song; Ji, Shijun; Wen, Zhongsheng; Wang, Xiaochun

    2014-01-01

    A niobium carbide diffusion layer with a cubic NbC phase surface layer (∼6 μm) and a Nb and C diffusion subsurface layer (∼1 μm) is fabricated on the surface of AISI 304 stainless steel (304 SS) bipolar plate in a proton exchange membrane fuel cell (PEMFC) using plasma surface diffusion alloying. The electrochemical behaviour of the niobium carbide diffusion-modified 304 SS (Nb-C 304 SS) is investigated in simulated PEMFC environments (0.5 M H2SO4 and 2 ppm HF solution at 80 °C). Potentiodynamic, potentiostatic polarisation and electrochemical impedance spectroscopy measurements reveal that the niobium carbide diffusion layer considerably improves the corrosion resistance of 304 SS compared with untreated samples. The corrosion current density of Nb-C 304 SS is maintained at 0.058 μA cm-2 and 0.051 μA cm-2 under simulated anodic and cathodic conditions, respectively. The interfacial contact resistance of Nb-C 304 SS is 8.47 mΩ cm2 at a compaction force of 140 N cm-2, which is significantly lower than that of the untreated sample (100.98 mΩ cm2). Moreover, only a minor increase in the ICR of Nb-C 304 SS occurs after 10 h potentiostatic tests in both cathodic and anodic environments.

  8. Low-temperature plasma nitriding of sintered PIM 316L austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Mendes, Aecio Fernando; Scheuer, Cristiano Jose; Joanidis, Ioanis Labhardt; Cardoso, Rodrigo Perito; Mafra, Marcio; Klein, Aloisio Nelmo; Brunatto, Silvio Francisco, E-mail: brunatto@ufpr.br [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil). Dept. de Engenharia Mecanica. Grupo de Tecnologia de Fabricacao Assistida pro Plasma e Metalurgia do Po

    2014-08-15

    This work reports experimental results on sintered PIM 316L stainless steel low-temperature plasma nitriding. The effect of treatment temperature and time on process kinetics, microstructure and surface characteristics of the nitrided samples were investigated. Nitriding was carried out at temperatures of 350, 380, 410 and 440 °C , and times of 4, 8 and 16 h, using a gas mixture composed by 60% N2 + 20% H2 + 20% Ar, at a gas flow rate of 5.00 X 10{sup 6} Nm{sup 3-1}, and a pressure of 800 Pa. The treated samples were characterized by scanning electron microscopy, X-ray diffractometry and microhardness measurements. Results indicate that low-temperature plasma nitriding is a diffusion controlled process. The calculated activation energy for nitrided layer growth was 111.4 kJmol{sup -1}. Apparently precipitation-free layers were produced in this study. It was also observed that the higher the treatment temperature and time the higher is the obtained surface hardness. Hardness up to 1343 HV{sub 0.025} was verified for samples nitrided at 440 °C. Finally, the characterization of the treated surface indicates the formation of cracks, which were observed in regions adjacent to the original pores after the treatment. (author)

  9. Cumulative creep-fatigue damage evolution in an austenitic stainless steel

    Science.gov (United States)

    Mcgaw, Michael A.

    1992-01-01

    A model of cumulative creep-fatigue damage has been developed which is based on the use of damage curve equations to describe the evolution of creep-fatigue damage for four basic creep-fatigue cycle types. These cycle types correspond to the four fundamental cycles of the Strain Range Partitioning Life Prediction approach of Manson, Halford, and Hirschberg. A concept referred to as Damage Coupling is introduced to analytically account for the differences in the nature of the damage introduced by each cycle type. For application of this model, the cumulative creep-fatigue damage behavior of type 316 stainless steel at 816 C has been experimentally established for the two-level loading cases involving fatigue and creep-fatigue, in various permutations. The tests were conducted such that the lower life (high strain) cycling was applied first, for a controlled number of cycles, and the higher life (lower strain) cycling was conducted at the second level, to failure. The proposed model correlated the majority of the observed cumulative creep-fatigue data.

  10. Effects of stop-start features on residual stresses in a multipass austenitic stainless steel weld

    Energy Technology Data Exchange (ETDEWEB)

    Turski, M., E-mail: Mark.Turski@magnesium-elektron.com [School of Materials, University of Manchester, Grosvenor Street, Manchester M1 7HS (United Kingdom); Francis, J.A. [School of Materials, University of Manchester, Grosvenor Street, Manchester M1 7HS (United Kingdom)] [Materials Engineering, Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); Hurrell, P.R. [Rolls-Royce Plc., Raynesway, Derby DE21 7XX (United Kingdom); Bate, S.K. [Serco Technical Services, Birchwood Park, Warrington, Cheshire WA3 6GA (United Kingdom); Hiller, S. [Materials Engineering, Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom); Withers, P.J. [School of Materials, University of Manchester, Grosvenor Street, Manchester M1 7HS (United Kingdom)

    2012-01-15

    In this article we describe experiments that characterise and quantify the localised perturbations in residual stress associated with both ramped and abrupt stop-start features in a multipass weld. Residual stress distributions in AISI Grade 304L/308L stainless steel groove-welded specimens, containing weld interruptions that were introduced in a controlled manner, have been characterised using both neutron diffraction and the incremental deep hole drilling method. The extent to which the localised stresses associated with the interruptions were annealed by overlayed passes was also assessed. The results suggest that, regardless of the type of interruption, there can be significant localised increases in residual stress if the stop-start feature is left exposed. If further weld passes are deposited, then the localised increases in stress are likely to persist if the interruption was abrupt, whereas for a ramped interruption they may be dissipated. - Highlights: Black-Right-Pointing-Pointer In this study the residual stress-field surrounding weld interruptions was measured. Black-Right-Pointing-Pointer Localised stresses were found to increase at weld interruptions. Black-Right-Pointing-Pointer Both ramped and abrupt weld interruptions were investigated. Black-Right-Pointing-Pointer After subsequent weld passes, localised stresses persisted for abrupt interruptions. Black-Right-Pointing-Pointer After subsequent weld passes, localised stresses dissipated for ramped interruptions.

  11. Aging Degradation of Austenitic Stainless Steel Weld Probed by Electrochemical Method and Impact Toughness Evaluation

    Science.gov (United States)

    Singh, Raghuvir; Das, Goutam; Mahato, B.; Singh, P. K.

    2017-03-01

    The present study discriminates the spinodal decomposition and G-phase precipitation in stainless steel welds by double loop electrochemical potentio-kinetic reactivation method and correlates it with the degradation in toughness property. The welds produced with different heat inputs were aged up to 10,000 hours at 673 K to 723 K (400 to 450 °C) and evaluated subsequently for the degree of sensitization (DOS) and impact toughness. The DOS values obtained were attributed to the spinodal decomposition and precipitation of G-phase. Study shows that the DOS correlates well with the impact toughness of the 304LN weld. Prolonged aging at 673 K and 723 K (400 °C and 450 °C) increased the DOS values while the impact toughness was decreased. The weld fabricated at 1 kJ/mm of heat input, produced higher DOS, compared to that at 3 kJ/mm. The geometrical location along the weld is shown to influence the DOS; higher values were obtained at the root than at the topside of the weld. Vermicular and columnar microstructure, in addition to the spinodal decomposition and G-phase precipitation, observed in the root side of the weld appear risky for the impact toughness.

  12. Ferrite Measurement in Austenitic and Duplex Stainless Steel Castings - Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Lundin, C.D.; Zhou, G.; Ruprecht, W.

    1999-08-01

    The ability to determine ferrite rapidly, accurately and directly on a finished casting, in the solution annealed condition, can enhance the acceptance, save on manufacturing costs and ultimately improve service performance of duplex stainless steel cast products. If the suitability of a non-destructive ferrite determination methodology can be demonstrated for standard industrial measurement instruments, the production of cast secondary standards for calibration of these instruments is a necessity. With these concepts in mind, a series of experiments were carried out to demonstrate, in a non-destructive manner, the proper methodology for determining ferrite content. The literature was reviewed, with regard to measurement techniques and vagaries, an industrial ferrite measurement round-robin was conducted, the effects of casting surface finish, preparation of the casting surface for accurate measurement and the evaluation of suitable means for the production of cast secondary standards for calibration were systematically investigated. The data obtained from this research program provide recommendations to ensure accurate, repeatable, and reproducible ferrite measurement and qualifies the Feritscope for field use on production castings.

  13. Aging Degradation of Austenitic Stainless Steel Weld Probed by Electrochemical Method and Impact Toughness Evaluation

    Science.gov (United States)

    Singh, Raghuvir; Das, Goutam; Mahato, B.; Singh, P. K.

    2017-01-01

    The present study discriminates the spinodal decomposition and G-phase precipitation in stainless steel welds by double loop electrochemical potentio-kinetic reactivation method and correlates it with the degradation in toughness property. The welds produced with different heat inputs were aged up to 10,000 hours at 673 K to 723 K (400 to 450 °C) and evaluated subsequently for the degree of sensitization (DOS) and impact toughness. The DOS values obtained were attributed to the spinodal decomposition and precipitation of G-phase. Study shows that the DOS correlates well with the impact toughness of the 304LN weld. Prolonged aging at 673 K and 723 K (400 °C and 450 °C) increased the DOS values while the impact toughness was decreased. The weld fabricated at 1 kJ/mm of heat input, produced higher DOS, compared to that at 3 kJ/mm. The geometrical location along the weld is shown to influence the DOS; higher values were obtained at the root than at the topside of the weld. Vermicular and columnar microstructure, in addition to the spinodal decomposition and G-phase precipitation, observed in the root side of the weld appear risky for the impact toughness.

  14. Ferrite Measurement in Austenitic and Duplex Stainless Steel Castings - Literature Review

    Energy Technology Data Exchange (ETDEWEB)

    Lundin, C.D.; Zhou, G.; Ruprecht, W.

    1999-08-01

    The ability to determine ferrite rapidly, accurately and directly on a finished casting, in the solution annealed condition, can enhance the acceptance, save on manufacturing costs and ultimately improve service performance of duplex stainless steel cast products. If the suitability of a non-destructive ferrite determination methodology can be demonstrated for standard industrial measurement instruments, the production of cast secondary standards for calibration of these instruments is a necessity. With these concepts in mind, a series of experiments were carried out to demonstrate, in a non-destructive manner, the proper methodology for determining ferrite content. The literature was reviewed, with regard to measurement techniques and vagaries, an industrial ferrite measurement round-robin was conducted, the effects of casting surface finish, preparation of the casting surface for accurate measurement and the evaluation of suitable means for the production of cast secondary standards for calibration were systematically investigated. The data obtained from this research program provides recommendations to insure accurate, repeatable and reproducible ferrite measurement and qualifies the Feritscope for field use on production castings.

  15. Modeling of residual stress mitigation in austenitic stainless steel pipe girth weldment

    Energy Technology Data Exchange (ETDEWEB)

    Li, M.; Atteridge, D.G.; Anderson, W.E. [Oregon Graduate Inst., Portland, OR (United States); West, S.L. [Westinghouse Savannah River Co., Aiken, SC (United States)

    1994-03-01

    This study provides numerical procedures to model 40-cm-diameter, schedule 40, Type 304L stainless steel pipe girth welding and a newly proposed post-weld treatment. The treatment can be used to accomplish the goal of imparting compressive residual stresses at the inner surface of a pipe girth weldment to prevent/retard the intergranular stress corrosion cracking (IGSCC) of the piping system in nuclear reactors. This new post-weld treatment for mitigating residual stresses is cooling stress improvement (CSI). The concept of CSI is to establish and maintain a certain temperature gradient across the pipe wall thickness to change the final stress state. Thus, this process involves sub-zero low temperature cooling of the inner pipe surface of a completed girth weldment, while simultaneously keeping the outer pipe surface at a slightly elevated temperature with the help of a certain heating method. Analyses to obtain quantitative results on pipe girth welding and CSI by using a thermo-elastic-plastic finite element model are described in this paper. Results demonstrate the potential effectiveness of CSI for introducing compressive residual stresses to prevent/retard IGSCC. Because of the symmetric nature of CSI, it shows great potential for industrial application.

  16. Improvement of the strength of a metastable austenitic stainless steel by cyclic deformation-induced martensitic transformation at 103 K

    Energy Technology Data Exchange (ETDEWEB)

    Bayerlein, M.; Mughrabi, H. (Inst. fuer Werkstoffwissenschaften, Lehrstuhl 1, Univ. Erlangen-Nuernberg, Erlangen (Germany)); Kesten, M.; Meier, B. (Messer Griesheim GmbH, Koeln (Germany))

    1992-12-15

    Specimens of a metastable austenitic stainless steel were cyclically deformed at 103 K under constant plastic strain control with constant plastic strain ranges [Delta][epsilon][sub pl] = 1% and 2%. The tests were performed both with a symmetrical plastic strain amplitude (mean plastic strain anti [epsilon][sub pl] = 0) and with an asymetrical plastic strain amplitude (anti [epsilon][sub pl] > 0) with the minimum plastic strain equal to zero. The cyclic deformation behaviour was investigated, especially in the stage of cyclic hardening, and correlated with the deformation-induced formation of martensitic phases which could be detected by transmission electron microscopy. The effect of the transformed martensite on the mechanical properties of the steel was quantified by subsequent tensile tests at room temperature with the cyclically deformed specimens. In contrast to results of earlier studies at room temperature, no cumulative plastic ''incubation'' strain was necessary at 103 K to trigger the deformation-induced martensitic transformation. At [Delta][epsilon][sub pl] = 2% and anti [epsilon][sub pl] = 0 the maximum cyclic range was attained after only 18 cycles. In the reference test with an asymmetrical plastic strain amplitude (anti [epsilon][sub pl] = 1%) 23 cycles were required to reach the maximum cyclic stress range. Tension tests revealed an increase of up to 200% in the 1% offset yield stress and a 75% increase in the tensile strength at room temperature after cycling the specimens to the maximum stress range with either symmetrical or asymmetrical plastic strain amplitudes. The ductility and the toughness of the steel remained surprisingly high with an elongation after failure of 45%. (orig.).

  17. CRADA NFE-08-01456 Evaluation of Alumina-Forming Austenitic Stainless Steel Alloys in Industrial Gas Turbines

    Energy Technology Data Exchange (ETDEWEB)

    Brady, Michael P [ORNL; Pint, Bruce A [ORNL; Unocic, Kinga A [ORNL; Yamamoto, Yukinori [ORNL; Kumar, Deepak [ORNL; Lipschutz, Mark D. [Solar Turbines, Inc.

    2011-09-01

    Oak Ridge National Laboratory (ORNL) and Solar Turbines Incorporated (Solar) participated in an in-kind cost share cooperative research and development agreement (CRADA) effort under the auspices of the Energy Efficiency and Renewable Energy (EERE) Technology Maturation Program to explore the feasibility for use of developmental ORNL alumina-forming austenitic (AFA) stainless steels as a material of construction for industrial gas turbine recuperator components. ORNL manufactured lab scale foil of three different AFA alloy compositions and delivered them to Solar for creep properties evaluation. One AFA composition was selected for a commercial trial foil batch. Both lab scale and the commercial trial scale foils were evaluated for oxidation and creep behavior. The AFA foil exhibited a promising combination of properties and is of interest for future scale up activities for turbine recuperators. Some issues were identified in the processing parameters used for the first trial commercial batch. This understanding will be used to guide process optimization of future AFA foil material production.

  18. TEM study of the nucleation of bubbles induced by He implantation in 316L industrial austenitic stainless steel

    Science.gov (United States)

    Jublot-Leclerc, S.; Lescoat, M.-L.; Fortuna, F.; Legras, L.; Li, X.; Gentils, A.

    2015-11-01

    10 keV He ions were implanted in-situ in a TEM into thin foils of 316L industrial austenitic stainless steel at temperatures ranging from 200 to 550 °C. As a result, overpressurized nanometric bubbles are created with density and size depending strongly on both the temperature and fluence of implantation. An investigation on their nucleation and growth is reported through a rigorous statistical analysis whose procedure, including the consideration of free surface effects, is detailed. In the parameter range considered, the results show that an increase of fluence promotes both the nucleation and growth of the bubbles whilst an increase of temperature enhances the growth of the bubbles at the expense of their nucleation. The confrontation of resulting activation energies with existing models for bubble nucleation enables the identification of the underlying mechanisms. In spite of slight differences resulting from different conditions of implantation among which the He concentration, He production rate and He/dpa ratio, it appears that the dominating mechanisms are the same as those obtained in metals in previous studies, which, in addition to corroborating literature results, shows the suitability of in-situ TEM experiments to simulate the production of helium in nuclear materials.

  19. Phased Array Ultrasonic Sound Field Mapping through Large-Bore Coarse Grained Cast Austenitic Stainless Steel (CASS) Components

    Energy Technology Data Exchange (ETDEWEB)

    Crawford, Susan L.; Cinson, Anthony D.; Prowant, Matthew S.; Coble, Jamie B.; Diaz, Aaron A.; Anderson, Michael T.

    2012-09-01

    A sound field beam mapping exercise was conducted to assist in understanding the effects of coarse-grained microstructures found in cast austenitic stainless steel (CASS) materials on acoustic longitudinal wave propagation. Ultrasonic laboratory measurements were made on three specimens representing four different grain structures. Phased array (PA) probes were fixed on each specimen surface and excited in the longitudinal mode at specific angles while a point receiver was scanned in a raster pattern over the end of the specimen, generating a transmitted sound field image. Three probes operating at nominal frequencies of 0.5, 0.8, and 1.0 MHz were used. A 6.4 mm (0.25-in.) thick slice was removed from the specimen end and beam mapping was repeated three times, yielding four full sets of beam images. Data were collected both with a constant part path for each configuration (probe, specimen and slice, angle, etc.) and with a variable part path (fixed position on the surface). The base specimens and slices were then polished and etched to reveal measureable grain microstructures that were compared to the sound field interactions and scattering effects seen in the collected data.

  20. A new alloy design concept for austenitic stainless steel with tungsten modification for bipolar plate application in PEMFC

    Science.gov (United States)

    Kim, Kwang Min; Kim, Kyoo Young

    The feasibility of a new alloy design concept utilizing the principle of 'tungsten bronze effect' is critically evaluated for the development of metallic bipolar plates for proton exchange membrane fuel cell (PEMFC). An austenitic stainless steel (ASS) is modified with W and La to improve the stability of the passive film in an acidic environment as well as to reduce the contact resistance by the tungsten bronze effect. The experimental ASS containing W and La was evaluated in a simulated PEMFC environment of H 3PO 4 and H 2SO 4 solutions at 80 °C, and the electrical property was evaluated by performing a contact resistance test. The test results show that the ASS modified with W and La has good passive film stability for corrosion resistance and low contact resistance. The X-ray photoelectron spectroscopy (XPS) analysis clearly suggests the possibility of the tungsten bronze effect from the change in valency state of W 6+ to W 5+ in the passive film formed on the modified ASS. The feasibility of a new alloy design concept utilizing the 'tungsten bronze effect' is well demonstrated; however, more study is highly required for the development of metallic bipolar plates of PEMFC.

  1. Effects of Low Temperature on Hydrogen-Assisted Crack Growth in Forged 304L Austenitic Stainless Steel

    Science.gov (United States)

    Jackson, Heather; San Marchi, Chris; Balch, Dorian; Somerday, Brian; Michael, Joseph

    2016-08-01

    The objective of this study was to evaluate effects of low temperature on hydrogen-assisted crack propagation in forged 304L austenitic stainless steel. Fracture initiation toughness and crack-growth resistance curves were measured using fracture mechanics specimens that were thermally precharged with 140 wppm hydrogen and tested at 293 K or 223 K (20 °C or -50 °C). Fracture initiation toughness for hydrogen-precharged forgings decreased by at least 50 to 80 pct relative to non-charged forgings. With hydrogen, low-temperature fracture initiation toughness decreased by 35 to 50 pct relative to room-temperature toughness. Crack growth without hydrogen at both temperatures was microstructure-independent and indistinguishable from blunting, while with hydrogen microcracks formed by growth and coalescence of microvoids. Initiation of microvoids in the presence of hydrogen occurred where localized deformation bands intersected grain boundaries and other deformation bands. Low temperature additionally promoted fracture initiation at annealing twin boundaries in the presence of hydrogen, which competed with deformation band intersections and grain boundaries as sites of microvoid formation and fracture initiation. A common ingredient for fracture initiation was stress concentration that arose from the intersection of deformation bands with these microstructural obstacles. The localized deformation responsible for producing stress concentrations at obstacles was intensified by low temperature and hydrogen. Crack orientation and forging strength were found to have a minor effect on fracture initiation toughness of hydrogen-supersaturated 304L forgings.

  2. Modelling the attenuation in the ATHENA finite elements code for the ultrasonic testing of austenitic stainless steel welds.

    Science.gov (United States)

    Chassignole, B; Duwig, V; Ploix, M-A; Guy, P; El Guerjouma, R

    2009-12-01

    Multipass welds made in austenitic stainless steel, in the primary circuit of nuclear power plants with pressurized water reactors, are characterized by an anisotropic and heterogeneous structure that disturbs the ultrasonic propagation and makes ultrasonic non-destructive testing difficult. The ATHENA 2D finite element simulation code was developed to help understand the various physical phenomena at play. In this paper, we shall describe the attenuation model implemented in this code to give an account of wave scattering phenomenon through polycrystalline materials. This model is in particular based on the optimization of two tensors that characterize this material on the basis of experimental values of ultrasonic velocities attenuation coefficients. Three experimental configurations, two of which are representative of the industrial welds assessment case, are studied in view of validating the model through comparison with the simulation results. We shall thus provide a quantitative proof that taking into account the attenuation in the ATHENA code dramatically improves the results in terms of the amplitude of the echoes. The association of the code and detailed characterization of a weld's structure constitutes a remarkable breakthrough in the interpretation of the ultrasonic testing on this type of component.

  3. Systematic study of polycrystalline flow during tension test of sheet 304 austenitic stainless steel at room temperature

    Energy Technology Data Exchange (ETDEWEB)

    Muñoz-Andrade, Juan D., E-mail: jdma@correo.azc.uam.mx [Departamento de Materiales, División de Ciencias Básicas e Ingeniería, Universidad Autónoma Metropolitana Unidad Azcapotzalco, Av. San Pablo No. 180, Colonia Reynosa Tamaulipas, C.P. 02200, México Distrito Federal (Mexico)

    2013-12-16

    By systematic study the mapping of polycrystalline flow of sheet 304 austenitic stainless steel (ASS) during tension test at constant crosshead velocity at room temperature was obtained. The main results establish that the trajectory of crystals in the polycrystalline spatially extended system (PCSES), during irreversible deformation process obey a hyperbolic motion. Where, the ratio between the expansion velocity of the field and the velocity of the field source is not constant and the field lines of such trajectory of crystals become curved, this accelerated motion is called a hyperbolic motion. Such behavior is assisted by dislocations dynamics and self-accommodation process between crystals in the PCSES. Furthermore, by applying the quantum mechanics and relativistic model proposed by Muñoz-Andrade, the activation energy for polycrystalline flow during the tension test of 304 ASS was calculated for each instant in a global form. In conclusion was established that the mapping of the polycrystalline flow is fundamental to describe in an integral way the phenomenology and mechanics of irreversible deformation processes.

  4. Understanding the effect of uniaxial tensile strain on the early stages of sensitization in AISI 304 austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Chowdhury, P.S., E-mail: psc0126@gmail.com [Techno India Agartala, Maheshkhola, Agartala, West Tripura PIN – 799004 (India); Guchhait, S.K.; Mitra, P.K. [Department of Metallurgical and Material Engineering, Jadavpur University, Kolkata 700032 (India); Mukherjee, P.; Gayathri, N. [Variable Energy Cyclotron Centre (VECC), 1/AF Bidhan Nagar, Kolkata 700064 (India); Mitra, M.K. [Department of Metallurgical and Material Engineering, Jadavpur University, Kolkata 700032 (India)

    2015-04-01

    In the present study, an attempt has been made to understand the effect of different competing mechanisms controlling the overall degree of sensitization (DOS) of deformed austenitic stainless steel at the early stage of sensitization. The Double Loop Electrochemical Potentiokinetic Reactivation (DL-EPR) studies were performed to characterize the Degree of Sensitization (DOS) as a function of both pre-defined strain and sensitization temperature. X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) were used to explain the phenomena qualitatively. A non monotonous behaviour in the variation of DOS has been observed with deformation and sensitization temperature. The presence of Deformation Induced Martensites (DIM) and their transformation into tempered martensites (α + M{sub 23}C{sub 6}) at higher temperatures was found to play major roles in controlling the overall sensitization and desensitization processes. - Highlights: • Interplay of various dynamic processes (four) in the early sensitization. • Deformation induced martensite (α′) playing major role at low temperature. • α (Tempered martensite) induced processes plays a vital role at higher temperatures. • Results in non monotonous variation in degree of sensitisation (DOS)

  5. Nickel-based alloy/austenitic stainless steel dissimilar weld properties prediction on asymmetric distribution of laser energy

    Science.gov (United States)

    Zhou, Siyu; Ma, Guangyi; Chai, Dongsheng; Niu, Fangyong; Dong, Jinfei; Wu, Dongjiang; Zou, Helin

    2016-07-01

    A properties prediction method of Nickel-based alloy (C-276)/austenitic stainless steel (304) dissimilar weld was proposed and validated based on the asymmetric distribution of laser energy. Via the dilution level DC-276 (the ratio of the melted C-276 alloy), the relations between the weld properties and the energy offset ratio EC-276 (the ratio of the irradiated energy on the C-276 alloy) were built, and the effects of EC-276 on the microstructure, mechanical properties and corrosion resistance of dissimilar welds were analyzed. The element distribution Cweld and EC-276 accorded with the lever rule due to the strong convention of the molten pool. Based on the lever rule, it could be predicted that the microstructure mostly consists of γ phase in each weld, the δ-ferrite phase formation was inhibited and the intermetallic phase (P, μ) formation was promoted with the increase of EC-276. The ultimate tensile strength σb of the weld joint could be predicted by the monotonically increasing cubic polynomial model stemming from the strengthening of elements Mo and W. The corrosion potential U, corrosion current density I in the active region and EC-276 also met the cubic polynomial equations, and the corrosion resistance of the dissimilar weld was enhanced with the increasing EC-276, mainly because the element Mo could help form a steady passive film which will resist the Cl- ingress.

  6. Influence of the solution temperature on the corrosion behavior of an austenitic stainless steel in phosphoric acid medium

    Energy Technology Data Exchange (ETDEWEB)

    Ibanez-Ferrandiz, M.V.; Blasco-Tamarit, E.; Garcia-Garcia, D.M.; Garcia-Anton, J. [Valencia Univ. Politecnica, Dept. de Ingenieria Quimica y Nuclear. ETSI Industriales, Valencia (Spain); Guenbour, A.; Bakour, S.; Benckokroun, A. [University Mohammed V-Agdal, Lab. Corrosion-Electrochimie, Faculty of Sciences, Rabat (Morocco)

    2009-07-01

    The objective of the present work is to study the effect of the solution temperature on the corrosion resistance of a highly alloyed austenitic stainless steel (UNS N08031) used as base metal, the welded metal obtained by TIG (Tungsten Inert Gas) welding using a Nickel-base alloy (UNS N06059) as filler metal, and the Heat Affected Zone (HAZ) of the base metal. The materials were tested in 5.5 M phosphoric acid solution at 25 C, 40 C, 60 C and 80 C. Open Circuit Potential tests and potentiodynamic anodic polarization curves have been carried out to obtain information about the electrochemical behavior of the materials. Corrosion potentials and corrosion current densities were obtained from Tafel analysis. The critic potentials and passivation current densities of the studied materials were also analyzed. The galvanic corrosion generated by the electrical contact between the welded metal, the base metal and the HAZ, was estimated from the polarisation diagrams according to the Mixed Potential Theory. The samples were etched to study their microstructure by Optical Microscopy. Results demonstrated that the corrosion potential values shift to more anodic potentials as temperature increases. The corrosion current densities and the passive current densities increased with temperature. Open circuit potential values were located in the passive zone of the potentiodynamic curves, which means that the materials passivated spontaneously. (authors)

  7. Cluster dynamics modeling of the effect of high dose irradiation and helium on the microstructure of austenitic stainless steels

    Science.gov (United States)

    Brimbal, Daniel; Fournier, Lionel; Barbu, Alain

    2016-01-01

    A mean field cluster dynamics model has been developed in order to study the effect of high dose irradiation and helium on the microstructural evolution of metals. In this model, self-interstitial clusters, stacking-fault tetrahedra and helium-vacancy clusters are taken into account, in a configuration well adapted to austenitic stainless steels. For small helium-vacancy cluster sizes, the densities of each small cluster are calculated. However, for large sizes, only the mean number of helium atoms per cluster size is calculated. This aspect allows us to calculate the evolution of the microstructural features up to high irradiation doses in a few minutes. It is shown that the presence of stacking-fault tetrahedra notably reduces cavity sizes below 400 °C, but they have little influence on the microstructure above this temperature. The binding energies of vacancies to cavities are calculated using a new method essentially based on ab initio data. It is shown that helium has little effect on the cavity microstructure at 300 °C. However, at higher temperatures, even small helium production rates such as those typical of sodium-fast-reactors induce a notable increase in cavity density compared to an irradiation without helium.

  8. Effect of cold working on biocompatibility of Ni-free high nitrogen austenitic stainless steels using Dalton's Lymphoma cell line.

    Science.gov (United States)

    Talha, Mohd; Kumar, Sanjay; Behera, C K; Sinha, O P

    2014-02-01

    The aims of the present work are to explore the effect of cold working on in-vitro biocompatibility of indigenized low cost Ni-free nitrogen containing austenitic stainless steels (HNSs) and to compare it with conventionally used biomedical grade, i.e. AISI 316L and 316LVM, using Dalton's Lymphoma (DL) cell line. The MTT assay [3-(4,5-dimethythiazol 2-yl)-2,5-diphenyltetrazolium bromide] was performed on DL cell line for cytotoxicity evaluation and cell adhesion test. As a result, it was observed that the HNS had higher cell proliferation and cell growth and it increases by increasing nitrogen content and degree of cold working. The surface wettability of the alloys was also investigated by water contact angle measurements. The value of contact angles was found to decrease with increase in nitrogen content and degree of cold working. This indicates that the hydrophilic character increases with increasing nitrogen content and degree of cold working which further attributed to enhance the surface free energy (SFE) which would be conducive to cell adhesion which in turn increases the cell proliferation.

  9. Effect of aging and oxidation on strain hardening behaviour of a nickel-free high nitrogen austenitic stainless steel

    Science.gov (United States)

    Karthik, B.; Veerababu, R.; Satyanarayana, D. V. V.

    2016-05-01

    Effect of aging and oxidation on strain hardening behaviour of a nickel-free high nitrogen austenitic stainless steel has been investigated using room temperature tensile tests and TEM. The alloy in both oxidised and unoxidised conditions exhibits a transition in flow behaviour that can be described best by the Ludwigson flow relationship as evident from the lowest values of the sum of residual squares, χ 2, of the fit. The transition in macroscopic flow behaviour with strain has been correlated to change in deformation mechanism from planar slip in the low strain regime (LSR) to deformation twinning and slip in the high strain regime (HSR) in solution treated (ST) condition of the alloy. However, the LSR of the alloy aged for longer times (>100 h) is characterized by the formation of dislocation tangles, while the HSR is marked by the formation of well-defined finer dislocation cell structure. This difference in deformation sub-structures in low and high strain regimes between ST and long term aged samples has been correlated to the change in stacking fault energy due to the precipitation of Cr2N and σ-phases. Further, the alloy in ST condition exhibits the highest strain hardening rate, which then progressively decreases with aging time.

  10. Characteristics of oxide scale formed on Cu-bearing austenitic stainless steel during early stages of high temperature oxidation

    Science.gov (United States)

    Swaminathan, Srinivasan; Krishna, Nanda Gopala; Kim, Dong-Ik

    2015-10-01

    Oxide scale evolution on Cu-bearing austenitic stainless steel 304H at 650 °C, in ambient air, for exposure times 100, 300, 500 and 1000 h, has been investigated. Surface morphology and chemistry of the oxide scale grown were examined using SEM/EDX and XPS. The oxidation kinetics was determined by measuring the weight change using an electronic balance. At the initial stage, up to 500 h of exposure time, the oxidation rate was rapid due to surface reactions governed primarily by oxygen ingress, and then, dropped to a low rate after prolonged oxidation for 1000 h. The diffusion of reactants through the initially formed oxide scale limits the oxidation rate at longer times, thus, the progress of reaction followed the parabolic kinetics. The formed oxide scale was enriched significantly with segregation and subsequent oxidation of Nb, and finely dispersed metallic Cu particles. Within the time frame of oxidation, the oxide scale was mainly composed of mixed oxides such as FeCr2O4 and MnCr2O4 along with the binary oxides of Fe, Cr and Mn. Moreover, the precipitation fraction of Cu-rich particles on the oxide scale increased markedly with increase of exposure times. The chemical heterogeneity of oxide scale suggests that the oxidation occurred in a non-selective manner.

  11. Intergranular corrosion testing of austenitic stainless steels in nitric acid solutions

    Energy Technology Data Exchange (ETDEWEB)

    Whillock, G.O.H.; Dunnett, B. F. [British Nuclear Fuels plc, BNFL, B170, Sellafield, Seascale, Cumbria CA20 1PG (United Kingdom)

    2004-07-01

    In hot strong nitric acid solutions, stainless steels exhibit intergranular corrosion. Corrosion rates are often measured from immersion testing of specimens manufactured from the relevant material (e.g. plate or pipe). The corrosion rates, measured from weight loss, are found to increase with time prior to reaching steady state, which can take thousands of hours to achieve. The apparent increase in corrosion rate as a function of time was found to be an artefact due to the surface area of the specimen's being used in the corrosion rate calculations, rather than that of the true area undergoing active corrosion i.e. the grain boundaries. The steady state corrosion rate coincided with the onset of stable grain dropping, where the use of the surface area of the specimen to convert the weight loss measurements to corrosion rates was found to be appropriate. This was confirmed by sectioning of the specimens and measuring the penetration depths. The rate of penetration was found to be independent of time and no induction period was observed. A method was developed to shorten considerably the testing time to reach the steady state corrosion rate by use of a pre-treatment that induces grain dropping. The long-term corrosion rates from specimens which were pre-treated was similar to that achieved after prolonged testing of untreated (i.e. initially ground) specimens. The presence of cut surfaces is generally unavoidable in the simple immersion testing of specimens in test solutions. However, inaccuracy in the results may occur as the measured corrosion rate is often influenced by the orientation of the microstructure, the highest rates typically being observed on the cut surfaces. Two methods are presented which allow deconvolution of the corrosion rates from immersion testing of specimens containing cut surfaces, thus allowing reliable prediction of the long-term corrosion rate of plate surfaces. (authors)

  12. The role of niobium carbide in radiation induced segregation behaviour of type 347 austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Ahmedabadi, Parag, E-mail: adit@barc.gov.in [Materials Science Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Kain, Vivekanand [Materials Science Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Gupta, Manu [PEC University of Technology, Chandigarh (India); Samajdar, I. [Department of Metallurgical Engineering and Materials Science, Indian Institute of Technology Bombay, Powai, Mumbai 400 076 (India); Sharma, S.C.; Bhagwat, P.; Chowdhury, R. [Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)

    2011-08-01

    Highlights: > Characterization of radiation-induced segregation done by EPR and AFM examination. > Variation of DL-EPR values with depth showed trend similar to that of variation of dpa with depth, calculated by SRIM. > Niobium carbides had reduced defect flux toward grain boundaries leading to reduced chromium depletion levels. > Adsorption of point defects at carbide-matrix interface leading to chromium depletion at large carbide clusters. - Abstract: The effect of niobium carbide precipitates on radiation induced segregation (RIS) behaviour in type 347 stainless steel was investigated. The material in the as-received condition was irradiated using double-loop 4.8 MeV protons at 300 deg. C for 0.43 dpa (displacement per atom). The RIS in the proton irradiated specimen was characterized using double-loop electrochemical potentiokinetic reactivation (DL-EPR) test followed by atomic force microscopic examination. The nature of variation of DL-EPR values with the depth matched with the variation of the calculated irradiation damage (dpa) with the depth. The attack on grain boundaries during EPR tests was negligible indicating absence of chromium depletion zones. The interface between niobium carbide and the matrix acts as a sink for point defects generated during irradiation and this had reduced point defect flux toward grain boundaries. The attack was noticed at a few large cluster of niobium carbide after the DL-EPR test at the depth of maximum attack for the irradiated specimen. Pit-like features were not observed within the matrix indicating the absence of chromium depletion regions within the matrix.

  13. Changes in the passive layer of corrugated austenitic stainless steel of low nickel content due to exposure to simulated pore solutions

    Energy Technology Data Exchange (ETDEWEB)

    Bautista, A. [Departamento de Ciencia e Ingenieria de Materiales e Ingenieria Quimica, Universidad Carlos III de Madrid, Avda Universidad no. 30, 28911 Leganes, Madrid (Spain)], E-mail: mbautist@ing.uc3m.es; Blanco, G.; Velasco, F. [Departamento de Ciencia e Ingenieria de Materiales e Ingenieria Quimica, Universidad Carlos III de Madrid, Avda Universidad no. 30, 28911 Leganes, Madrid (Spain); Gutierrez, A.; Soriano, L. [Departamento de Fisica Aplicada and Instituto de Ciencia de Materiales Nicolas Cabrera, Universidad Autonoma de Madrid, Cantoblanco, 28049 Madrid (Spain); Palomares, F.J. [Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Cientificas (CSIC), Cantoblanco, Madrid (Spain); Takenouti, H. [UPR-15 du CNRS, UPMC, 4 place Jussieu, 75252 Paris Cedex 05 (France)

    2009-04-15

    In this work, changes undergone at the passive layer of a new type of corrugated austenitic stainless steel (low Ni, high Mn 204Cu type) when exposed to solutions simulating that contained in the pores of concrete have been studied. Changes in the nature of the passive layer have been characterized by X-ray photoelectronic spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). Particular focus has been put on the influence of the presence of chlorides and/or carbonation in the solution. Changes in the passive layer due to the passivation treatment that is often applied to corrugated stainless steels during manufacturing processes have also been considered. The results obtained on the 204Cu type steel have been compared with those obtained on more traditional, high Ni, austenitic AISI 304 grade and duplex SAF 2205 grade. During the immersion in simulated pore solutions, 204Cu type suffers more intense redox processes than other studied stainless steels. Moreover, it shows less Cr-rich protective passive layers in these media.

  14. Effect of Plastic Pre-straining on Residual Stress and Composition Profiles in Low-Temperature Surface-Hardened Austenitic Stainless Steel

    DEFF Research Database (Denmark)

    Bottoli, Federico; Christiansen, Thomas Lundin; Winther, Grethe

    2016-01-01

    The present work deals with the evaluation of the residual stress profiles in expanded austenite by applying grazing incidence X-ray diffraction (GI-XRD) combined with successive sublayer removal. Annealed and deformed (εeq=0.5) samples of stable stainless steel EN 1.4369 were nitrided...... deformation in the steel prior to thermochemical treatment has a hardly measurable influence on the nitrogen-rich zone, while it has a measurable effect on the stresses and depth of the carbon-rich zone....

  15. Characteristics of vacuum sintered stainless steels

    OpenAIRE

    Z. Brytan; L.A. Dobrzański; M. Actis Grande; Rosso, M.

    2009-01-01

    Purpose: In the present study duplex stainless steels were sintered in vacuum. using rapid cooling form the mixture of prealloyed and alloying element powders The purpose of this paper was to describe the obtained microstructures after sintering as well as the main mechanical properties of sintered stainless steels.Design/methodology/approach: In presented work duplex stainless steels were obtained through powder metallurgy starting from austenitic 316L or ferritic 410L prealloyed stainless s...

  16. Nano/ultrafine grained austenitic stainless steel through the formation and reversion of deformation-induced martensite: Mechanisms, microstructures, mechanical properties, and TRIP effect

    Energy Technology Data Exchange (ETDEWEB)

    Shirdel, M., E-mail: mshirdel1989@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Mirzadeh, H., E-mail: hmirzadeh@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Advanced Metalforming and Thermomechanical Processing Laboratory, School of Metallurgy and Materials Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Parsa, M.H., E-mail: mhparsa@ut.ac.ir [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Center of Excellence for High Performance Materials, School of Metallurgy and Materials Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Advanced Metalforming and Thermomechanical Processing Laboratory, School of Metallurgy and Materials Engineering, University of Tehran, Tehran (Iran, Islamic Republic of)

    2015-05-15

    A comprehensive study was carried out on the strain-induced martensitic transformation, its reversion to austenite, the resultant grain refinement, and the enhancement of strength and strain-hardening ability through the transformation-induced plasticity (TRIP) effect in a commercial austenitic 304L stainless steel with emphasis on the mechanisms and the microstructural evolution. A straightforward magnetic measurement device, which is based on the measurement of the saturation magnetization, for evaluating the amount of strain-induced martensite after cold rolling and reversion annealing in metastable austenitic stainless steels was used, which its results were in good consistency with those of the X-ray diffraction (XRD) method. A new parameter called the effective reduction in thickness was introduced, which corresponds to the reasonable upper bound on the obtainable martensite fraction based on the saturation in the martensitic transformation. By means of thermodynamics calculations, the reversion mechanisms were estimated and subsequently validated by experimental results. The signs of thermal martensitic transformation at cooling stage after reversion at 850 °C were found, which was attributed to the rise in the martensite start temperature due to the carbide precipitation. After the reversion treatment, the average grain sizes were around 500 nm and the nanometric grains of the size of ~ 65 nm were also detected. The intense grain refinement led to the enhanced mechanical properties and observation of the change in the work-hardening capacity and TRIP effect behavior. A practical map as a guidance for grain refining and characterizing the stability against grain growth was proposed, which shows the limitation of the reversion mechanism for refinement of grain size. - Graphical abstract: Display Omitted - Highlights: • Nano/ultrafine grained austenitic stainless steel through martensite treatment • A parameter descriptive of a reasonable upper bound on

  17. Influence of Partial Replacement of Nickel by Nitrogen on Microstructure and Mechanical Properties of Austenitic Stainless Steel

    Directory of Open Access Journals (Sweden)

    A. Ahmed

    2011-01-01

    Furthermore, the produced forged steels were subjected to solution treatment at different temperatures. The microstructure of produced stainless steels was observed. The X-ray diffractmeter and Mossbauer effect spectroscopy were used to follow the phase change in reference and modified steels after different heat treatment temperatures. The influence of grain-size, soluble, and insoluble nitrogen on tensile strength and hardness was investigated. The major phase in the modified steel has a fcc structure similar to the reference one, but with finer grains and more expanded lattice. The yield strength and hardness of the nitrogen-modified stainless steel are higher than the reference steel. On the other hand, the increase of nitrogen content deteriorates the steel ductility.

  18. Elastic interaction between twins during tensile deformation of austenitic stainless steel

    DEFF Research Database (Denmark)

    Juul, Nicolai Ytterdal; Winther, Grethe; Dale, Darren

    2016-01-01

    In austenite, the twin boundary normal is a common elastically stiff direction shared by the two twins, which may induce special interactions. By means of three-dimensional X-ray diffraction this elastic interaction has been analysed and compared to grains separated by conventional grain boundaries....... However, the components of the Type II stress normal to the twin boundary plane exhibit the same large variations as for the grain boundaries. Elastic grain interactions are therefore complex and must involve the entire set of neighbouring grains. The elastic-regime stress along the tensile direction...

  19. Alumina-Forming Austenitics: A New Approach to Thermal and Degradation Resistant Stainless Steels for Industrial Use

    Energy Technology Data Exchange (ETDEWEB)

    David A Helmick; John H Magee; Michael P Brady

    2012-05-31

    A series of developmental AFA alloys was selected for study based on: 25 Ni wt.% (alloys A-F), 20 wt% Ni (alloys G-H), and 12 Ni wt.% (alloys I-L). An emphasis in this work was placed on the lower alloy content direction for AFA alloys to reduce alloy raw material cost, rather than more highly alloyed and costly AFA alloys for higher temperature performance. Alloys A-D explored the effects of Al (3-4 wt.%) and C (0.05-0.2 wt.%) in the Fe-25Ni-14Cr-2Mn-2Mo-1W-1Nb wt.% base range; alloys E and F explored the effects of removing costly Mo and W additions in a Fe-25Ni-14Cr-4Al-2.5Nb-2Mn-0.2C base, alloys G and H examined Nb (1-2.5wt.%) and removal of Mo, W in a Fe-20Ni-14Cr-3Al-2Mn-0.2 C wt.% base; and alloys I-L examined effects of C (0.1-0.2 wt.%) and Mn (5-10 wt.%) on a low cost Fe-14Cr-12Ni-3Cu-2.5Al wt.% base (no Mo, W additions). Creep testing resulted in elemental trends that included the beneficial effect of higher carbon and lower niobium in 20-25%Ni AFA alloys and, the beneficial of lower Mn in 12%Ni AFA alloys. Corrosion tests in steam and sulfidation-oxidation environments showed, in general, these alloys were capable of a ten-fold improvement in performance when compared to conventional austenitic stainless steels. Also, corrosion test results in metal-dusting environments were promising and, warrant further investigation.

  20. An exponential strain dependent Rusinek–Klepaczko model for flow stress prediction in austenitic stainless steel 304 at elevated temperatures

    Directory of Open Access Journals (Sweden)

    Amit Kumar Gupta

    2014-10-01

    Full Text Available In this paper, to predict flow stress of Austenitic Stainless Steel (ASS 304 at elevated temperatures the extended Rusinek–Klepaczko (RK model has been modified using an exponential strain dependent term for dynamic strain aging (DSA region. Isothermal tensile tests are conducted on ASS 304 for a temperature range of 323–923 K with an interval of 50 K and at strain rates of 0.0001 s−1, 0.001 s−1, 0.01 s−1 and 0.1 s−1. DSA phenomenon is observed from 623 to 923 K at 0.0001 s−1, 0.001 s−1 and 0.01 s−1. Material constants are calculated using data obtained from these tensile tests for non-DSA and DSA region separately. The predicted results from the RK model are compared with the experimental data to check the accuracy of the constitutive relation. It is observed that to find out the constants of this model, some initial assumptions are required, and these initial values affect the predicted values. Hence, Genetic Algorithm (GA is used to optimize the constants for RK model. Statistical measures such as the correlation coefficient, the average absolute error and standard deviation are used to measure the accuracy of the model. The resulting values of the correlation coefficient for ASS 304 for non-DSA and DSA region using modified extended RK model are 0.9828 and 0.9701. This modified, extended RK model is compared with Johnson–Cook (JC, Zerilli–Armstrong (ZA and Arrhenius models and it is observed that specifically in DSA region, the modified extended RK model gives highly accurate predictions.

  1. The role of nanocrystalline titania coating on nanostructured austenitic stainless steel in enhancing osteoblasts functions for regeneration of tissue

    Energy Technology Data Exchange (ETDEWEB)

    Shah, J.S.; Venkatsurya, P.K.C.; Thein-Han, W.W. [Biomaterials and Biomedical Engineering Research Laboratory, Center for Structural and Functional Materials, University of Louisiana at Lafayette, P.O. Box 44130, Lafayette, LA 70504 (United States); Misra, R.D.K., E-mail: dmisra@louisiana.edu [Biomaterials and Biomedical Engineering Research Laboratory, Center for Structural and Functional Materials, University of Louisiana at Lafayette, P.O. Box 44130, Lafayette, LA 70504 (United States); Pesacreta, T.C. [Department of Biology, University of Louisiana at Lafayette, P.O. Box 42451, Lafayette, LA 70504 (United States); Somani, M.C.; Karjalainen, L.P. [Department of Mechanical Engineering, University of Oulu, P.O. Box 4200, 90014 Oulu (Finland)

    2011-03-12

    In the context of osseointegration of metallic implants, while nanostructuring the surface favorably modulates cellular response, the disinfective attributes required during the healing process are not available. Thus, in the present study, we demonstrate that nanocrystalline titania provides cumulative benefit of enhancing osteoblasts functions to promote the efficacy of metal implants together with the disinfective attributes. To this end, the primary objective here is to examine the select functions of bone forming cells (osteoblasts) on electrocrystallized nanonodular titania-coated nanograined/ultrafine grained (NG/UFG) austenitic stainless steel. The accompanying objective is to study the disinfective/antimicrobial activity. To the best of our understanding this is the first study of nanophase titania on a non-titanium substrate. The osteoblasts functions were investigated in terms of cell attachment, proliferation, and quantitative analysis of proteins, actin and vinculin. In comparison to the bare NG/UFG substrate, the nanophase titania-coated substrate exhibited higher degree of cell attachment and proliferation which are regulated via cellular and molecular interactions with proteins, actin and vinculin. The enhanced functions of osteoblasts suggest that nanophase titania adsorbs extracellular matrix proteins, fibronectin and vitronectin from serum enhancing protein, with subsequent binding of integrins and osteoblasts precursor to titania. The antimicrobial attributes assessed in terms of degradation of methyl orange and effectiveness in killing E. coli supports the viewpoint that large surface area of titania would be instrumental in reducing the detrimental effect of biologically reactive oxygen species produced by macrophages in the vicinity of the metal bone/implant interface. In summary, the study provides some new insights concerning nanostructuring of metallic substrates with specific physical and surface properties for medical devices with

  2. Inhibition effect of 2-amino-5-ethyl-1, 3, 4-thiadiazole on corrosion behaviour of austenitic stainless steel type 304 in dilute HCl solution

    Institute of Scientific and Technical Information of China (English)

    Roland T Loto; Cleophas A Loto; Abimbola P Popoola; Tatiana Fedotova

    2016-01-01

    The corrosion inhibition of type 304 austenitic stainless steel by 2-amino-5-ethyl-1, 3, 4-thiadiazole (TTD) compound and the electrochemical behaviour in dilute HCl solution were investigated through potentiodynamic polarization test, mass loss techniques and potential measurements. The results show that the organic derivative is highly effective with a maximum inhibition efficiency of 70.22% from mass loss analysis, while 74.2% is obtained from polarization tests. Observation of the scanning electron micrographs shows the absence of corrosion products due to electrochemical influence of TTD on the surface morphology of the steel. X-ray diffractometry reveals the absence of phase compounds and complexes on the steel samples after exposure. TTD adsorption on the steel surface obeys the Langmuir, Frumkin and Freundlich adsorption isotherms. Corrosion thermodynamic calculations reveal the inhibition mechanism occurs through chemisorption process and results from statistical analysis depict the strong influence of inhibitor concentration on the electrochemical performance of the TTD.

  3. Influence of low-temperature nitriding on the strain-induced martensite and laser-quenched austenite in a magnetic encoder made from 304L stainless steel.

    Science.gov (United States)

    Leskovšek, Vojteh; Godec, Matjaž; Kogej, Peter

    2016-08-05

    We have investigated the possibility of producing a magnetic encoder by an innovative process. Instead of turning grooves in the encoder bar for precise positioning, we incorporated the information in 304L stainless steel by transforming the austenite to martensite after bar extrusion in liquid nitrogen and marking it with a laser, which caused a local transformation of martensite back into austenite. 304L has an excellent corrosion resistance, but a low hardness and poor wear resistance, which limits its range of applications. However, nitriding is a very promising way to enhance the mechanical and magnetic properties. After low-temperature nitriding at 400 °C it is clear that both ε- and α'-martensite are present in the deformed microstructure, indicating the simultaneous stress-induced and strain-induced transformations of the austenite. The effects of a laser surface treatment and the consequent appearance of a non-magnetic phase due to the α' → γ transformation were investigated. The EDS maps show a high concentration of nitrogen in the alternating hard surface layers of γN and α'N (expanded austenite and martensite), but no significantly higher concentration of chromium or iron was detected. The high surface hardness of this nitride layer will lead to steels and encoders with better wear and corrosion resistance.

  4. Study of structural modifications induced by ion implantation in austenitic stainless steel; Etude des modifications structurales induites par implantation ionique dans les aciers austenitiques

    Energy Technology Data Exchange (ETDEWEB)

    Dudognon, J

    2006-12-15

    Ion implantation in steels, although largely used to improve the properties of use, involves structural modifications of the surface layer, which remain still prone to controversies. Within this context, various elements (N, Ar, Cr, Mo, Ag, Xe and Pb) were implanted (with energies varying from 28 to 280 keV) in a 316LVM austenitic stainless steel. The implanted layer has a thickness limited to 80 nm and a maximum implanted element concentration lower than 10 % at. The analysis of the implanted layer by grazing incidence X ray diffraction highlights deformations of austenite lines, appearance of ferrite and amorphization of the layer. Ferritic phase which appears at the grain boundaries, whatever the implanted element, is formed above a given 'threshold' of energy (produced of fluency by the energy of an ion). The formation of ferrite as well as the amorphization of the implanted layer depends only on energy. In order to understand the deformations of austenite diffraction lines, a simulation model of these lines was elaborated. The model correctly describes the observed deformations (broadening, shift, splitting) with the assumption that the expansion of the austenitic lattice is due to the presence of implanted element and is proportional to the element concentration through a coefficient k'. This coefficient only depends on the element and varies linearly with its radius. (author)

  5. Influence of low-temperature nitriding on the strain-induced martensite and laser-quenched austenite in a magnetic encoder made from 304L stainless steel

    Science.gov (United States)

    Leskovšek, Vojteh; Godec, Matjaž; Kogej, Peter

    2016-08-01

    We have investigated the possibility of producing a magnetic encoder by an innovative process. Instead of turning grooves in the encoder bar for precise positioning, we incorporated the information in 304L stainless steel by transforming the austenite to martensite after bar extrusion in liquid nitrogen and marking it with a laser, which caused a local transformation of martensite back into austenite. 304L has an excellent corrosion resistance, but a low hardness and poor wear resistance, which limits its range of applications. However, nitriding is a very promising way to enhance the mechanical and magnetic properties. After low-temperature nitriding at 400 °C it is clear that both ε- and α‧-martensite are present in the deformed microstructure, indicating the simultaneous stress-induced and strain-induced transformations of the austenite. The effects of a laser surface treatment and the consequent appearance of a non-magnetic phase due to the α‧ → γ transformation were investigated. The EDS maps show a high concentration of nitrogen in the alternating hard surface layers of γN and α‧N (expanded austenite and martensite), but no significantly higher concentration of chromium or iron was detected. The high surface hardness of this nitride layer will lead to steels and encoders with better wear and corrosion resistance.

  6. Tensile and Impact Properties of Shielded Metal Arc Welded AISI 409M Ferritic Stainless Steel Joints

    Institute of Scientific and Technical Information of China (English)

    K.Shanmugam; A.K.Lakshminarayanan; V.Balasubramanian

    2009-01-01

    The present study is concerned with the effect of filler metals such as austenitic stainless steel, ferritic stainless steel and duplex stainless steel on tensile and impact properties of the ferritic stainless steel conforming to AISI 409M grade. Rolled plates of 4 mm thickness were used as the base material for preparing single pass butt welded joints. Tensile and impact properties, microhardness, microstructure and fracture surface morphology of the joints fabricated by austenitic stainless steel, ferritic stainless steel and duplex stainless steel filler metals were evaluated and the results were reported. From this investigation, it is found that the joints fabricated by duplex stainless steel filler metal showed higher tensile strength and hardness compared to the joints fabricated by austenitic and ferritic stainless steel filler metals. Joints fabricated by austenitic stainless steel filler metal exhibited higher ductility and impact toughness compared with the joints fabricated by ferritic stainless steel and duplex stainless steel filler metals.

  7. Automatic TIG welding of austenitic stainless steels in nitrogen and nitrogen-based gas mixtures

    Directory of Open Access Journals (Sweden)

    Zorc, B.

    2011-02-01

    Full Text Available The paper treats studies of TIG gas-shielded arc welding using pure nitrogen, N2+ 5-20 % Ar gas mixtures and N2 + 2-10 % H2 gas mixtures. A weld root shielding was provided by nitrogen gas. Welding in N2 requires by 40 % lower welding current than welding in argon. The study showed that porosity was an issue due to overalloying of N2 in the weld pool; it can, however, be avoided with adequate welding parameters, particularly sufficiently high welding speed and controlled low heat input. The microstructure of all-weld metal is fully austenitic (γ. Hydrogen reduces nitrogen solubility in the weld pool and produces an austenitic-ferritic (γ+δ microstructure. Titanium increases nitrogen solubility in the weld pool and strongly reacts with nitrogen. Consequently, there is a high fraction of TiN inclusions in the weld metal.

    Hemos efectuado las investigaciones de la soldadura TIG en nitrógeno puro, las mezclas de gas N2 + 5 hasta un 20 % Ar, así como también N2 + 2 hasta un 10 % H2. Para la protección se utilizó nitrógeno. Para la soldadura se necesitan aproximadamente un 40 % menos de corriente de soldadura, comparado con la soldadura de argón. La investigación ha mostrado que la porosidad es un problema de absorción excesiva de la fundición con nitrógeno y que es posible suprimir la porosidad mediante parámetros adecuados de soldadura, sobre todo con una suficiente velocidad de soldadura y, con ella, una pequeña emisión controlada de calor. El hidrógeno reduce la solubilidad del nitrógeno en la fundición y acciona la segregación de ferrita. El titanio aumenta la solubilidad del nitrógeno en la fundición y reacciona fuertemente con el nitrógeno, de tal modo que en la soldadura hay una gran parte de inclusiones TiN.

  8. Anisotropic Radiation-Induced Segregation in 316L Austenitic Stainless Steel with Grain Boundary Character

    Energy Technology Data Exchange (ETDEWEB)

    Christopher M. Barr; Gregory A. Vetterick; Kinga A. Unocic; Khalid Hattar; Xian-Ming Bai; Mitra L. Taheri

    2014-04-01

    Radiation-induced segregation (RIS) and subsequent depletion of chromium along grain boundaries has been shown to be an important factor in irradiation-assisted stress corrosion cracking in austenitic face-centered cubic (fcc)-based alloys used for nuclear energy systems. A full understanding of RIS requires examination of the effect of the grain boundary character on the segregation process. Understanding how specific grain boundary structures respond under irradiation would assist in developing or designing alloys that are more efficient at removing point defects, or reducing the overall rate of deleterious Cr segregation. This study shows that solute segregation is dependent not only on grain boundary misorientation, but also on the grain boundary plane, as highlighted by markedly different segregation behavior for the __3 incoherent and coherent grain boundaries. The link between RIS and atomistic modeling is also explored through molecular dynamic simulations of the interaction of vacancies at different grain boundary structures through defect energetics in a simple model system. A key insight from the coupled experimental RIS measurements and corresponding defect–grain boundary modeling is that grain boundary–vacancy formation energy may have a critical threshold value related to the major alloying elements’ solute segregation.

  9. Strengthening of austenitic stainless steel wires by heavily cold-drawing%奥氏体不锈钢弹簧丝的大变形拉拔强化

    Institute of Scientific and Technical Information of China (English)

    史世凤; 李窘

    2011-01-01

    Austenitic stainless steel spring wire with tensile strength of 1980 MPa was prepared by severely cold-drawing at reduction of 97.7%.The cold-drawing strengthening behavior of austenitic stainless steel was investigated by optical microscope(OM) and X-ray diffraction(XRD).The results indicate that with the increase of the reduction,Vickers hardness and tensile strength of the steel increase,and volume fraction of martensite transformed from austenite increases and fiber microstructure forms at heavy reduction.The possible explanation of the strengthening for the heavily deformed steel is associated with work hardening,fiber strengthening and martensitic trarsformation strengthening.%借助于光学显微镜和X射线衍射仪等研究了奥氏体不锈钢弹簧丝在经过97.7%的大变形后抗拉强度高达1980 MPa的强化现象。结果表明,钢丝的硬度和抗拉强度随着变形量的增加而升高。在大变形量时,沿拉拔方向的组织趋向纤维化,变形马氏体的体积分数在增加,拉拔钢丝的抗拉强度值升高的幅度增加。分析认为变形强化,纤维组织强化和马氏体相变强化是大变形强化的主要原因。

  10. Fatigue strain-life behavior of carbon and low-alloy steels, austenitic stainless steels, and Alloy 600 in LWR environments

    Energy Technology Data Exchange (ETDEWEB)

    Keisler, J.; Chopra, O.K.; Shack, W.J. [Argonne National Lab., IL (United States)

    1995-08-01

    The existing fatigue strain vs. life (S-N) data, foreign and domestic, for carbon and low-alloy steels, austenitic stainless steels, and Alloy 600 used in the construction of nuclear power plant components have been compiled and categorized according to material, loading, and environmental conditions. Statistical models have been developed for estimating the effects of the various service conditions on the fatigue life of these materials. The results of a rigorous statistical analysis have been used to estimate the probability of initiating a fatigue crack. Data in the literature were reviewed to evaluate the effects of size, geometry, and surface finish of a component on its fatigue life. The fatigue S-N curves for components have been determined by adjusting the probability distribution curves for smooth test specimens for the effect of mean stress and applying design margins to account for the uncertainties due to component size/geometry and surface finish. The significance of the effect of environment on the current Code design curve and on the proposed interim design curves published in NUREG/CR-5999 is discussed. Estimations of the probability of fatigue cracking in sample components from BWRs and PWRs are presented.

  11. Effect of Cold-Rolling on Precipitation Phenomena in Sensitized Type 316L and 340L Austenitic Stainless Steels

    Institute of Scientific and Technical Information of China (English)

    H.Tsubakino; A.Yamamoto; T. Yamada; L.Liu; M.Terasawa; S.Nakahigashi; H.Harada

    2004-01-01

    Precipitation phenomena in Type 316L and 304L stainless steels were studied mainly by transmission electron microscopic (TEM) observations after cold-rolling ranging from 0% (as solution annealed) to 80% reduction in thickness,and then by sensitization treatment. Precipitates were identified by electron diffraction analysis and EDS analysis.Precipitates observed in sensitized 316L stainless steel were sigma and chi phases, whereas carbide and sigma were observed in sensitized 304L stainless steel. Recrystallized grains were formed in 30% cold-rolled and sensitized 304L.However, the tendency toward recrystallization in sensitized 316L was much lower than in 304L. Precipitation of sigma and chi phases was accelerated by cold-rolling and they were observed at grain boundaries in lower cold-rolling; they were also seen, in grain interiors in higher cold-rolling. Higher deformation induced partially recrystallization combined with precipitation, resulting in the formation of heterogeneous microstructures.

  12. Changes in the mechanical properties and microstructure of anisotropic austenitic stainless sheet steel after uniaxial tensile test

    Directory of Open Access Journals (Sweden)

    Yankov Emil

    2017-01-01

    Full Text Available The aim of the investigation is to study the changes in the characteristics of an austenitic sheet material X5CrNi18-10 (1.4301, AISI 304 after a plastic deformation. Samples are cut out from the sheet material at three different directions - 0°, 45° and 90° angle to the rolling direction. The changes in the mechanical properties and microstructure of the anisotropic austenitic steel are investigated by mechanical tests (uniaxial tension tests and hardness measurements and structural analyses (optical and scanning electron microscopy, X-ray diffraction. It is established that the strain induced phase transformation of the metastable austenite to martensite during the tension tests changes the magnetic properties of the steel. It is found out that the sheet anisotropy effect on the uniform deformation, the thickness reduction and structure of the austenite sheet material is more essential for the plastic deformation behaviour than the strain-induced γ → α′ phase transformation.

  13. The Portevin-Le Châtelier Effect in a Metastable Austenitic Stainless Steel

    Science.gov (United States)

    Müller, Alexandra; Segel, Christian; Linderov, Mikhail; Vinogradov, Alexei; Weidner, Anja; Biermann, Horst

    2016-01-01

    The Portevin-Le Châtelier (PLC) effect was investigated in a high-alloy metastable CrMnNi cast steel during tensile tests for the range of deformation temperatures between 293 K and 413 K (20 °C and 140 °C) and for nominal strain rates ranging between 10-4 and 10-1 s-1. Analysis of the stress-strain curves was complemented by in situ measurements of thermal and acoustic emissions as well as by digital image correlation, enabling determination of various local characteristics of plastic flow and clarification of individual contributions of different microscopic mechanisms involved in plastic deformation. It was shown that the PLC effect in the investigated CrMnNi steel was caused by the diffusion of interstitial atoms in the bcc phases.

  14. Effect of nitrogen and cold working on structural and mechanical behavior of Ni-free nitrogen containing austenitic stainless steels for biomedical applications

    Energy Technology Data Exchange (ETDEWEB)

    Talha, Mohd; Behera, C.K.; Sinha, O.P., E-mail: opsinha.met@itbhu.ac.in

    2015-02-01

    This investigation deals with the evaluation of structural and mechanical behavior of deformed (10% and 20% cold work) and annealed (at 1050 °C for 15 min followed by water quenching) Ni-free high nitrogen austenitic stainless steels (HNSs). The microstructure was observed by optical micrograph and the mechanical properties were determined by macrohardness and tensile tests. Both stress strain behavior and work hardening behavior were evaluated. HNSs have smaller grain size as compared to low nitrogen steels and no formation of martensite was observed after 20% cold working. Further, it was found that hardness; yield strength and ultimate tensile strength of the steels linearly increases and elongation decreased with nitrogen content and degree of cold working. The strength coefficient was observed to be higher for the high nitrogen steels; it decreased to some extent with degree of cold working. The work hardening exponent was also observed to decrease with degree of cold working. Influence of nitrogen on mechanical properties was mainly related to its effect on solid solution strengthening. X-ray diffraction analysis of annealed as well as deformed alloys further confirmed no evidence for formation of martensite or any other secondary phases. SEM fractography of the annealed and deformed samples after tensile tests indicates predominantly ductile fracture in all specimens. - Graphical abstract: Effect of cold working on mechanical properties of indigenized Ni-free nitrogen containing austenitic stainless steels was explored. Hardness, yield strength and ultimate tensile strength of the steels increased and elongation decreased with nitrogen content and degree of cold working. X-ray diffraction analysis of annealed as well as deformed alloys confirmed no evidence for formation of martensite or any other secondary phases. SEM fractography of the annealed and deformed samples indicates predominantly ductile fracture. - Highlights: • Effect of cold working on

  15. Investigation of low-cycle fatigue behavior of austenitic stainless steel for cold-stretched pressure vessels

    Institute of Scientific and Technical Information of China (English)

    Cun-jian MIAO; Jin-yang ZHENG; Xiao-zhe GAO; Ze HUANG; A-bin GUO; Du-yi YE; Li MA

    2013-01-01

    Cold-stretched pressure vessels from austenitic stainless steels (ASS) are widely used for storage and transportation of liquefied gases,and have such advantages as thin wall and light weight.Fatigue is an important concern in these pressure vessels,which are subjected to alternative loads.Even though several codes and standards have guidelines on these pressure vessels,there are no relevant design methods on fatigue failure.To understand the fatigue properties of ASS 1.4301 (equivalents include UNS S30400 and AISI 304) in solution-annealed (SA) and cold-stretched conditions (9% strain level) and the response of fatigue properties to cold stretching (CS),low-cycle fatigue (LCF) tests were performed at room temperature,with total strain amplitudes ranging from ±0.4% to ±0.8%.Martensite transformations were measured during the tests.Comparisons on cyclic stress response,cyclic stress-strain behavior,and fatigue life were carried out between SA and CS materials.Results show that CS reduces the initial hardening stage,but prolongs the softening period in the cyclic stress response.Martensite transformation helps form a stable regime and subsequent secondary hardening.The stresses of monotonic and cyclic stress-strain curves are improved by CS,which leads to a lower plastic strain and a much higher elastic strain.The fatigue resistance of the CS material is better than that of the SA material,which is approximately 1 x l03 to 2×104 cycles.The S-N curve of the ASME standard for ASS is compared with the fatigue data and is justified to be suitable for the fatigue design of cold-stretched pressure vessels.However,considering the CS material has a better fatigue resistance,the S-N curve will be more conservative.The present study would be helpful in making full use of the advantages of CS to develop a new S-N curve for fatigue design of cold-stretched pressure vessels.

  16. Investigation of the Effects of Solution Temperature on the Corrosion Behavior of Austenitic Low-Nickel Stainless Steels in Citric Acid using Impedance and Polarization Measurements

    Directory of Open Access Journals (Sweden)

    Mulimbayan Francis M.

    2015-01-01

    Full Text Available Stainless steels may be classified according to alloy microstructure – ferritic, austenitic, martensitic, duplex, and precipitation hardening grades. Among these, austenitic grade has the largest contribution to market due to the alloy’s numerous industrial and domestic applications. In this study, the corrosion behavior of low-Nickel stainless steel in citric acid was investigated using potentiodynamic polarization techniques and Electrochemical Impedance Spectroscopy (EIS. The corrosion current density which is directly related to corrosion rate was extracted from the generated anodic polarization curve. Increasing the temperature of the citric acid resulted to increased corrosion current densities indicating higher corrosion rates at initial corrosion condition. EIS was performed to generate Nyquist plots whose shape and size depicts the corrosion mechanism and corrosion resistance of the alloy in citric acid, respectively. All the generated Nyquist plots have depressed semi-circle shapes implying that corrosion process takes place with charge-transfer as the rate-determining step. Based from the extracted values of polarization resistance (Rp, the temperature of the solution has negative correlation with the corrosion resistance of the studied alloy.

  17. Thermally Nitrided Stainless Steels for Polymer Electrolyte Membrane Fuel Cell Bipolar Plates: Part 1 Model Ni-50Cr and Austenitic 349TM alloys

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Heli [National Renewable Energy Laboratory (NREL); Brady, Michael P [ORNL; Turner, John [National Renewable Energy Laboratory (NREL)

    2004-01-01

    Thermal nitridation of a model Ni-50Cr alloy at 1100 C for 2 h in pure nitrogen resulted in the formation of a continuous, protective CrN/Cr{sub 2}N surface layer with a low interfacial contact resistance. Application of similar nitridation parameters to an austenitic stainless steel, 349{sup TM}, however, resulted in a discontinuous mixture of discrete CrN, Cr{sub 2}N and (Cr,Fe){sub 2}N{sub 1-x} (x = 0--0.5) phase surface particles overlying an exposed {gamma} austenite-based matrix, rather than a continuous nitride surface layer. The interfacial contact resistance of the 349{sup TM} was reduced significantly by the nitridation treatment. However, in the simulated PEMFC environments (1 M H{sub 2}SO{sub 4} + 2 ppm F{sup -} solutions at 70 C sparged with either hydrogen or air), very high corrosion currents were observed under both anodic and cathodic conditions. This poor behavior was linked to the lack of continuity of the Cr-rich nitride surface formed on 349{sup TM} Issues regarding achieving continuous, protective Cr-nitride surface layers on stainless steel alloys are discussed.

  18. Multi performance characteristic optimization of shot peening process for AISI 304 austenitic stainless steel using grey relational analysis with principal component analysis and Taguchi method

    Directory of Open Access Journals (Sweden)

    Dr. Lakhwinder Singh

    2013-10-01

    Full Text Available Shot peening is a cold working process. It impact on thin surface layer of the material and is used to enhance the mechanical and surface properties. The manufacturer is in demand to reduce the cost and improve the process productivity. He is always in search of an optimization technique which involves multiple performance characteristics. From this work, an optimal combination of shot peening parameters is generated by using a Grey relational analysis (GRA with Principal component analysis (PCA and Taguchi method. The present study shows that there are many factors that affect the properties of the AISI 304 austenitic stainless steel. Mechanisms to compensate for surface tractions and further enhancement of mechanical properties are described. The shot peening is discussed to enhance the mechanical and surface properties of AISI 304 austenitic stainless steel. The optimization of shot pening process is done by including multi performance characteristics i.e. tensile strength, surface hardness an fatigue strengths. The analysis includes pressure, shot size, exposure time, nozzle distance and nozzle angle as process parameters. The complete analysis will be helpful to the manufacturer in deciding the shot peening parameters for required performance characteristics.

  19. Influence of Plastic Deformation on Low-Temperature Surface Hardening of Austenitic Stainless Steel by Gaseous Nitriding

    DEFF Research Database (Denmark)

    Bottoli, Federico; Winther, Grethe; Christiansen, Thomas Lundin

    2015-01-01

    This article addresses an investigation of the influence of plastic deformation on low-temperature surface hardening by gaseous nitriding of two commercial stainless steels: EN 1.4369 and AISI 304. The materials were plastically deformed to several levels of equivalent strain by conventional...

  20. Acoustic wave propagation in austenitic stainless steel AISI 304L: Application examples

    Energy Technology Data Exchange (ETDEWEB)

    Dahmene, F., E-mail: fethidahmen@yahoo.fr [Laboratoire Roberval Unite Mixte 6066 CNRS, UTC, BP20592, 60205 Compiegne (France)] [Ecole des Mines de Douai, Departement Technologies des Polymeres et Composites and Ingenierie Mecanique, 941 rue Charles Bourseul, BP. 10838, 59508 Douai Cedex (France); Laksimi, A. [Laboratoire Roberval Unite Mixte 6066 CNRS, UTC, BP20592, 60205 Compiegne (France); Hariri, S. [Ecole des Mines de Douai, Departement Technologies des Polymeres et Composites and Ingenierie Mecanique, 941 rue Charles Bourseul, BP. 10838, 59508 Douai Cedex (France); Herve, C.; Jaubert, L.; Cherfaoui, M. [Pole EPI, Equipements sous Pression et Ingenierie d' Instrumentation, CETIM, 52, Avenue Felix-Lauat, BP80067, 60304 Senlis (France); Mouftiez, A. [Ecole des Mines de Douai, Departement Technologies des Polymeres et Composites and Ingenierie Mecanique, 941 rue Charles Bourseul, BP. 10838, 59508 Douai Cedex (France)

    2012-04-15

    Prior to the detection and monitoring by acoustic emission of defects in steel, this paper deals with the use of waveguide that avoids direct contact between the sensor and monitoring structure when working at high temperature. The study of the waveguide effect on elastic wave transmission shows that waveguide deforms the waveform but it does not affect its frequency. Waveguide length does not affect signal magnitude. An experimental example of compact tensile specimen monitoring by acoustic emission is given. The monitoring of the damage at low and high temperature '450 Degree-Sign C' by acoustic emission enables us to identify crack propagation stages and their acoustic signature. - Highlights: Black-Right-Pointing-Pointer This paper deals with the use of waveguide that avoids direct contact between the sensor and monitoring structure when working at high temperature. Black-Right-Pointing-Pointer The objective is the development of nondestructive testing by acoustic emission (AE) of pressure equipment (PE) operating at high temperature. Black-Right-Pointing-Pointer The use of AE in this work has underlined high temperature mechanical behavior in terms of damage and crack propagation.

  1. Effects of Solution Depletion and Segregation Oxidation on Morphology of Modified 310 Austenitic Stainless Steel

    Institute of Scientific and Technical Information of China (English)

    Hong-ying SUN; Qiang HE; Zhang-jian ZHOU; Man WANG; Guang-ming ZHANG; Shao-fu LI

    2016-01-01

    The oxidation morphologies of modified 310 steel exposed in 900 and 1 100 ℃ air were investigated.A double layer morphology consisting of a (Cr,Mn)-rich outer layer and a fine Cr-rich inner layer was formed at 900 ℃.It was related to the breakaway oxidation induced by the Cr-depletion and the Mn-segregation in inner layer.Some Cr-rich oxides with amorphous state were formed along grain boundaries.And some new finer oxide grains,voids and Cr-rich precipitates were observed in spallation areas at 1 100 ℃.Correspondingly,the oxidation kinetic curve dropped with the spallation of scale and increased with the formation of some new oxide grains.It was caused by segregation of Cr and the transformation of oxides from Cr2 O 3 to the volatile oxides at elevated temperature.XRD analysis showed that the precipitates were mainly composed of CrO 3 .Segregation and depletion for solutions were also dis-cussed by oxidation diffusion mechanisms.

  2. Improved Creep Behavior of a High Nitrogen Nb-Stabilized 15Cr-15Ni Austenitic Stainless Steel Strengthened by Multiple Nanoprecipitates

    Science.gov (United States)

    Ha, Vu The; Jung, Woo Sang; Suh, Jin Yoo

    2011-11-01

    Austenitic stainless steels are expected to be a major material for boiler tubes and steam turbines in future ultra-supercritical (USC) fossil power plants. It is of great interest to maximize the creep strength of the materials without increasing the cost. Precipitation strengthening was found to be the best and cheapest way for increasing the creep strength of such steels. This study is concerned with improving creep properties of a high nitrogen Nb-stabilized 15Cr-15Ni austenitic alloy through introducing a high number of nanosized particles into the austenitic matrix. The addition of around 4 wt pct Mn and 0.236 wt pct N into the 15Cr-15Ni-0.46Si-0.7Nb-1.25Mo-3Cu-Al-B-C matrix in combination with a special multicycled aging-quenching heat treatment resulted in the fine dispersion of abundant quantities of thermally stable (Nb,Cr,Fe)(C,N) precipitates with sizes of 10 to 20 nm. Apart from the carbonitrides, it was found that a high number of coherent copper precipitates with size 40 to 60 nm exist in the microstructure. Results of creep tests at 973 K and 1023 K (700 °C and 750 °C) showed that the creep properties of the investigated steel are superior compared to that of the commercial NF709 alloy. The improved creep properties are attributed to the improved morphology and thermal stability of the carbonitrides as well as to the presence of the coherent copper precipitates inside the austenitic matrix.

  3. Irradiation creep and stress-enhanced swelling of Fe-16Cr-15Ni-Nb austenitic stainless steel in BN-350

    Energy Technology Data Exchange (ETDEWEB)

    Vorobjev, A.N.; Porollo, S.I.; Konobeev, Yu.V. [Institute of Physics and Power Engineering, Obninsk (Russian Federation)] [and others

    1997-04-01

    Irradiation creep and void swelling will be important damage processes for stainless steels when subjected to fusion neutron irradiation at elevated temperatures. The absence of an irradiation device with fusion-relevant neutron spectra requires that data on these processes be collected in surrogate devices such as fast reactors. This paper presents the response of an annealed austenitic steel when exposed to 60 dpa at 480{degrees}C and to 20 dpa at 520{degrees}C. This material was irradiated as thin-walled argon-pressurized tubes in the BN-350 reactor located in Kazakhstan. These tubes were irradiated at hoop stresses ranging from 0 to 200 MPa. After irradiation both destructive and non-destructive examination was conducted.

  4. Effect of Plastic Pre-straining on Residual Stress and Composition Profiles in Low-Temperature Surface-Hardened Austenitic Stainless Steel

    Science.gov (United States)

    Bottoli, Federico; Christiansen, Thomas L.; Winther, Grethe; Somers, Marcel A. J.

    2016-08-01

    The present work deals with the evaluation of the residual stress profiles in expanded austenite by applying grazing incidence X-ray diffraction (GI-XRD) combined with successive sublayer removal. Annealed and deformed ( ɛ eq=0.5) samples of stable stainless steel EN 1.4369 were nitrided or nitrocarburized. The residual stress profiles resulting from the thermochemical low-temperature surface treatment were measured. The results indicate high-residual compressive stresses of several GPa's in the nitrided region, while lower-compressive stresses are produced in the carburized case. Plastic deformation in the steel prior to thermochemical treatment has a hardly measurable influence on the nitrogen-rich zone, while it has a measurable effect on the stresses and depth of the carbon-rich zone.

  5. Ultrasonic Phased Array Testing of Austenitic Stainless Steel Welds%奥氏体不锈钢焊缝的相控阵超声检测

    Institute of Scientific and Technical Information of China (English)

    胡栋; 王强; 肖琨; 刘富君

    2013-01-01

    The ultrasonic testing(UT) of austenitic stainless steel welds defects is always difficult because its coarse-grained material and anisotropic structure which lead to aberration and scattering of the ultrasonic waves. In this paper, ultrasonic testing properties of austenitic welds were analyzed. Ultrasonic test and ultrasonic phased array test were performed in an austenitic stainless steel welds test block. The results reveal that 14 dB signal-to-noise ratio (SNR) is obtained by ultrasonic phased array test while by ultrasonic test only 6 dB SNR is obtained to the defects in 10 mm depth. But both of these two tests cannot detect the defects in 30 mm depth.%由于奥氏体不锈钢焊缝晶粒组织粗大以及结构的各向异性导致超声声束的散射和畸变,其超声检测比较困难.本文分析了奥氏体不锈钢焊缝超声检测特性,在奥氏体不锈钢焊缝试块上进行了常规超声和相控阵超声检测试验.研究结果表明:对于10 mm深焊缝缺陷,相控阵超声检测信噪比可达14 dB,而常规超声技术仅获得6 dB的信噪比,对于30 mm深内部缺陷,均未取得较好的效果.

  6. Evolution of Microstructure in Brazed Joints of Austenitic-Martensitic Stainless Steel with Pure Silver Obtained with Ag-27Cu-5Sn Brazing Filler Material

    Science.gov (United States)

    Gangadharan, S.; Sivakumar, D.; Venkateswaran, T.; Kulkarni, Kaustubh

    2016-12-01

    Brazing of an austenitic-martensitic stainless steel (AMSS) with pure silver was carried out at 1053 K, 1073 K, and 1093 K (780 °C, 800 °C, and 820 °C) with Ag-27Cu-5Sn (wt pct) as brazing filler material (BFM). Wettability of the liquid BFM over base AMSS surface was found to be poor. Application of nickel coating to the steel was observed to enhance the wettability and to enable the formation of a good bond between BFM and the steel. The mechanism responsible for enhanced metallurgical bonding of the BFM with AMSS in the presence of nickel coating was explained based on diffusional interactions and uphill diffusion of iron, chromium and nickel observed in the brazed microstructure. Good diffusion-assisted zone was observed to form on silver side at all three temperatures. Four phases were encountered within the joint including silver solid solution, copper solid solution, Cu3Sn intermetallic and Ni-Fe solid solution. The Cu3Sn intermetallic was present in small amounts in the joints brazed at 1053 K and 1073 K (780 °C and 800 °C). The joint formed at 1093 K (820 °C) exhibited the absence of Cu3Sn, fewer defects and larger diffusion-assisted zone. Hardness of base AMSS was found to reduce during brazing due to austenite reversion and post-brazing sub-zero treatment for 2.5 hours was found suitable to recover the hardness.

  7. Low temperature gaseous surface hardening of stainless steel

    DEFF Research Database (Denmark)

    Christiansen, Thomas; Somers, Marcel A. J.

    2011-01-01

    The present contribtion gives an overview of some of the technological aspects of low temperature thermochemical treatment of stainless steel. Examples of low temperature gaseous nitriding, carburising and nitrocarburising of stainless steel are presented and discussed. In particular......, the morphology, microstructure and characteristics of so-called expanded austenite "layers" on stainless steel are addressed....

  8. 21 CFR 872.3350 - Gold or stainless steel cusp.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Gold or stainless steel cusp. 872.3350 Section 872...) MEDICAL DEVICES DENTAL DEVICES Prosthetic Devices § 872.3350 Gold or stainless steel cusp. (a) Identification. A gold or stainless steel cusp is a prefabricated device made of austenitic alloys or...

  9. Tribocorrosion wear of austenitic and martensitic steels

    Directory of Open Access Journals (Sweden)

    G. Rozing

    2016-07-01

    Full Text Available This paper explores the impact of tribocorrosion wear caused by an aggressive acidic media. Tests were conducted on samples made of stainless steel AISI 316L, 304L and 440C. Austenitic steels were tested in their nitrided state and martensitic in quenched and tempered and then induction hardened state. Electrochemical corrosion resistance testing and analysis of the microstructure and hardness in the cross section was carried out on samples of selected steels. To test the possibility of applying surface modification of selected materials in conditions of use, tests were conducted on samples/parts in a worm press for final pressing.

  10. Electrochemical and passivation behavior investigation of ferritic stainless steel in simulated concrete pore media

    OpenAIRE

    Hong Luo; Huaizhi Su; Chaofang Dong; Kui Xiao; Xiaogang Li

    2015-01-01

    The applications of stainless steel are one of the most reliable solutions in concrete structures to reduce chloride-induced corrosion problems and increase the structures service life, however, due to high prices of nickel, especially in many civil engineering projects, the austenitic stainless steel is replaced by the ferritic stainless steels. Compared with austenite stainless steel, the ferritic stainless steel is known to be extremely resistant of stress corrosion cracking and other prop...

  11. EFFECTS OF MODIFICATION OF THE CARBIDE CHARACTERISTICS THROUGH GRAIN BOUNDARY SERRATION ON CREEP-FATIGUE LIFE IN AUSTENITIC STAINLESS STEELS

    Institute of Scientific and Technical Information of China (English)

    K.J.Kim; H.U.Hong; K.S.Min; S.W.Nam

    2004-01-01

    Modification of the carbide characteristics through the grain boundary serration is investigated, using an AISI 316 and 304 stainless steels. In both steels, triangular carbides were observed at straight grain boundaries while planar carbides vere observed at the serrated grain boundaries. The serrated grain boundary energy is observed to be much lower than that of the straight one. Therefore, the carbide morphology is found to be changed from triangular to planar along the serrated boundary to reduce the interfacial energy between the carbide and the matrix. The creep-fatigue properties of these steels at 873K have been investigated. The creep-fatigue life of the sample vith planar carbide at the serrated grain boundary was found to be much longer than that with triangular carbide at the straight one. These results imply that the planar carbides with lower interfacial energy have higher cavitation resistance, resulting in the retardation of cavity nucleation and growth to increase creep-fatigue life.

  12. Response of Triaxial State of Stress to Creep Rupture Life and Ductility of 316 LN Austenitic Stainless Steel

    Science.gov (United States)

    Goyal, Sunil; Laha, K.; Bhaduri, A. K.

    2017-02-01

    In the present investigation, the effect of triaxial state of stress on creep rupture life and ductility of 316 LN stainless steel has been assessed. The creep tests were carried out on both smooth and notched specimens of the steel at 873 K in the stress range of 270-340 MPa. The notched specimens had root radius ranging from 0.83 mm to 5 mm. The detailed finite element analysis has been carried out to assess the triaxial state of stress across the notch incorporating Norton's law as creep deformation governing mechanism. The creep rupture life of the steel increased in presence of triaxial stresses and extent of which was more at lower net applied stresses and higher triaxiality (sharper notch). The reduction in effective stress in presence of notch resulted in higher creep rupture life of the steel under triaxial stresses. The fracture surfaces revealed mixed mode failure consisting of dimple ductile and intergranular creep cavitation for all testing conditions, however, extent of cavitation was higher for relatively higher triaxialities and lower net applied stresses. The creep ductility of the steel was found to decrease drastically under triaxial state of stress. The triaxial rupture life and creep ductility of the steel have been assessed based on different models on incorporating different components of stresses at the skeletal point.

  13. Response of Triaxial State of Stress to Creep Rupture Life and Ductility of 316 LN Austenitic Stainless Steel

    Science.gov (United States)

    Goyal, Sunil; Laha, K.; Bhaduri, A. K.

    2016-12-01

    In the present investigation, the effect of triaxial state of stress on creep rupture life and ductility of 316 LN stainless steel has been assessed. The creep tests were carried out on both smooth and notched specimens of the steel at 873 K in the stress range of 270-340 MPa. The notched specimens had root radius ranging from 0.83 mm to 5 mm. The detailed finite element analysis has been carried out to assess the triaxial state of stress across the notch incorporating Norton's law as creep deformation governing mechanism. The creep rupture life of the steel increased in presence of triaxial stresses and extent of which was more at lower net applied stresses and higher triaxiality (sharper notch). The reduction in effective stress in presence of notch resulted in higher creep rupture life of the steel under triaxial stresses. The fracture surfaces revealed mixed mode failure consisting of dimple ductile and intergranular creep cavitation for all testing conditions, however, extent of cavitation was higher for relatively higher triaxialities and lower net applied stresses. The creep ductility of the steel was found to decrease drastically under triaxial state of stress. The triaxial rupture life and creep ductility of the steel have been assessed based on different models on incorporating different components of stresses at the skeletal point.

  14. EXAMINATION OF THE CUTTING FORCES OF AISI 304 AUSTENITIC STAINLESS STEEL IN THE TURNING PROCESS WITH TITANIUM CARBIDE COATED CUTTING TOOLS

    Directory of Open Access Journals (Sweden)

    Özgür TEKASLAN

    2007-02-01

    Full Text Available In this study, cutting forces occurring in the machining process of AISI 304 austenitic stainless steel specimen using titanium coated cutting tools are investigated experimentally and the results are compared to theoretical calculations. In the experimental study, various cutting speeds, feed rates and cutting depths are considered. Cutting forces are measured by 3-dimensional Kistler dynamometer. In the theoretically study, cutting forces are determined by Kienzle formulation. Consequently, it is found that the calculation of cutting forces in the theoretical method doesn't yield the exact results because of various factors and there is a % 25 average differences in accordance with the experimental results. Hence it is evaluated that the experimental technique in the determination of cutting forces yields more accurate results.

  15. Effect of post weld heat treatment on the microstructure and mechanical properties of ITER-grade 316LN austenitic stainless steel weldments

    Science.gov (United States)

    Xin, Jijun; Fang, Chao; Song, Yuntao; Wei, Jing; Xu, Shen; Wu, Jiefeng

    2017-04-01

    The effect of postweld heat treatment (PWHT) on the microstructure and mechanical properties of ITER-grade 316LN austenitic stainless steel joints with ER316LMn filler material was investigated. PWHT aging was performed for 1 h at four different temperatures of 600 °C, 760 °C, 870 °C and 920 °C, respectively. The microstructure revealed the sigma phase precipitation occurred in the weld metals heat-treated at the temperature of 870 °C and 920 °C. The PWHT temperatures have the less effect on the tensile strength, and the maximum tensile strength of the joints is about 630 MPa, reaching the 95% of the base metal, whereas the elongation is enhanced with the rise of PWHT temperatures. Meanwhile, the sigma phase precipitation in the weld metals reduces the impact toughness.

  16. Investigation of high temperature annealing effectiveness for recovery of radiation-induced structural changes and properties of 18Cr-10Ni-Ti austenitic stainless steels

    Science.gov (United States)

    Gurovich, B. A.; Kuleshova, E. A.; Frolov, A. S.; Maltsev, D. A.; Prikhodko, K. E.; Fedotova, S. V.; Margolin, B. Z.; Sorokin, A. A.

    2015-10-01

    A complex study of structural state and properties of 18Cr-10Ni-Ti austenitic stainless steel after irradiation in BOR-60 fast research reactor (in the temperature range 330-400 °C up to damaging doses of 145 dpa) and in VVER-1000 light water reactor (at temperature ∼320 °C and damaging doses ∼12-14 dpa) was performed. The possibility of recovery of structural-phase state and mechanical properties to the level almost corresponding to the initial state by the recovery annealing was studied. The principal possibility of the recovery annealing of pressurized water reactor internals that ensures almost complete recovery of its mechanical properties and microstructure was shown. The optimal mode of recovery annealing was established: 1000 °C during 120 h.

  17. Grain boundary engineering for intergranular corrosion resistant austenitic stainless steel%抗晶间腐蚀奥氏体不锈钢的晶界工程

    Institute of Scientific and Technical Information of China (English)

    粉川博之

    2005-01-01

    Sensitization by chromium depletion due to chromium carbide precipitation at grain boundaries in austenitic stainless steels can not be prevented perfectly only by previous conventional techniques, such as reduction of carbon content, stabilization-treatment, local solution-heat-treatment, etc. Recent studies on grain boundary structure have revealed that the sensitization depends strongly on grain boundary character and atomic structure, and that low energy grain boundaries such as coincidence-site-lattice (CSL) boundaries have strong resistance to intergranular corrosion. The concept of 'grain boundary design and control' has been developed as grain boundary engineering (GBE). GBEed materials are characterized by high frequencies of CSL boundaries which are resistant to intergranular deterioration of materials, such as intergranular corrosion. A thermomechanical treatment was tried to improve the resistance to the sensitization by GBE. A type 304 austenitic stainless steel was cold-rolled and solution-heat-treated, and then sensitization-heat-treated. The grain boundary character distribution was examined by orientation imaging microscopy (OIM). The intergranular corrosion resistance was evaluated by electrochemical potentiokinetic reactivation (EPR) and ferric sulfate-sulfuric acid tests. The sensitivity to intergranular corrosion was reduced by the thermomechanical treatment and indicated a minimum at a small roll-reduction. The frequency of CSL boundaries indicated a maximum at the small reduction. The ferric sulfate-sulfuric acid test showed much smaller corrosion rate in the thermomechanical-treated specimen than in the base material. A high density of annealing twins were observed in the thermomechanical-treated specimen. The results suggest that the therrmomechanical treatment can introduce low energy segments in the grain boundary network by annealing twins and can arrest the percolation of intergranular corrosion from the surface. The effects of carbon

  18. In vitro response of human peripheral blood mononuclear cells to AISI 316L austenitic stainless steel subjected to nitriding and collagen coating treatments.

    Science.gov (United States)

    Stio, Maria; Martinesi, Maria; Treves, Cristina; Borgioli, Francesca

    2015-02-01

    Surface modification treatments can be used to improve the biocompatibility of austenitic stainless steels. In the present research two different modifications of AISI 316L stainless steel were considered, low temperature nitriding and collagen-I coating, applied as single treatment or in conjunction. Low temperature nitriding produced modified surface layers consisting mainly of S phase, which enhanced corrosion resistance in PBS solution. Biocompatibility was assessed using human peripheral blood mononuclear cells (PBMC) in culture. Proliferation, lactate dehydrogenase (LDH) levels, release of cytokines (TNF-α, IL-1β, IL-12, IL-10), secretion of metalloproteinase (MMP)-9 and its inhibitor TIMP-1, and the gelatinolytic activity of MMP-9 were determined. While the 48-h incubation of PBMC with all the sample types did not negatively influence cell proliferation, LDH and MMP-9 levels, suggesting therefore a good biocompatibility, the release of the pro-inflammatory cytokines was always remarkable when compared to that of control cells. However, in the presence of the nitrided and collagen coated samples, the release of the pro-inflammatory cytokine IL-1β decreased, while that of the anti-inflammatory cytokine IL-10 increased, in comparison with the untreated AISI 316L samples. Our results suggest that some biological parameters were ameliorated by these surface treatments of AISI 316L.

  19. The corrosion and stress corrosion cracking behavior of a novel alumina-forming austenitic stainless steel in supercritical water

    Science.gov (United States)

    Sun, Hongying; Yang, Haijie; Wang, Man; Giron-Palomares, Benjamin; Zhou, Zhangjian; Zhang, Lefu; Zhang, Guangming

    2017-02-01

    The general corrosion and stress corrosion behavior of Fe-27Ni-15Cr-5Al-2Mo-0.4Nb alumina-forming austenitic (AFA) steel were investigated in supercritical water under different conditions. A double layer oxide structure was formed: a Fe-rich outer layer (Fe2O3 and Fe3O4) and an Al-Cr-rich inner layer. And the inner layer has a low growth rate with exposing time, which is good for improvement of corrosion resistance. Additionally, some internal nodular Al-Cr-rich oxides were also observed, which resulted in a local absence of inner layer. Stress corrosion specimens exhibited a combination of high strength, good ductility and low susceptibility. The stress strength and elongation was reduced by increasing temperature and amount of dissolved oxygen. In addition, the corresponding susceptibility was increased with decreased temperatures and increased oxygen contents.

  20. Study on Structure and Corrosion Resistance Analysis of Carburizing Organization of Austenitic Stainless Steel%奥氏体不锈钢渗碳层的组织及耐蚀强化性能研究

    Institute of Scientific and Technical Information of China (English)

    李朋; 潘邻; 张良界; 杨闽红; 朱云峰; 马飞; 王成虎

    2013-01-01

    针对常规渗碳工艺会削弱奥氏体不锈钢耐蚀性的问题,通过对现有气体渗碳技术进行改进,采用前处理活化、降低渗碳温度的方法,实现了奥氏体不锈钢渗碳兼顾表面强度与耐蚀性能的目标.采用该工艺对AISI304和AISI316奥氏体不锈钢进行渗碳处理,并分析渗层组织和性能,结果表明,在470℃条件下,AISI316不锈钢经气体渗碳处理后,渗碳层具有优异的耐蚀强化性能.%In view of the conventional carburization weakening austenitic stainless steel corrosion resistance problem,based on the existing gas carburizing technology was improved,using pretreatment activation,carburizing temperature reduction methods,realized the austenitic stainless steel carburized surface strength and corrosion resistant properties of the target.Using this process on AISI304,AISI316 austenitic stainless steel carburizing processing,and get the austenitic stainless steel for low temperature carburizing organization performance carries on the analysis and research,research shows that under the condition of 470 ℃,AISI316 stainless steel carburization treated by low temperature gas carburizing layer has excellent corrosion resistance improved performance.

  1. The corrosion behaviour of austenitic and duplex stainless steels in artificial saliva with the addition of fluoride

    Energy Technology Data Exchange (ETDEWEB)

    Kocijan, Aleksandra, E-mail: Aleksandra.Kocijan@imt.s [Institute of Metals and Technology, Lepi pot 11, 1000 Ljubljana (Slovenia); Merl, Darja Kek [Jozef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia); Jenko, Monika [Institute of Metals and Technology, Lepi pot 11, 1000 Ljubljana (Slovenia)

    2011-02-15

    Research highlights: The corrosion behaviour of AISI 316L and 2205 DSS in orthodontics. The increased passive range for DSS 2205 compared to AISI 316L in artificial saliva. Higher R{sub p} values of DSS compared to AISI 316L in artificial saliva. The main constituent of the passive layers on DSS at the OCP in saliva was Cr-oxide. DSS 2205 is suitable for orthodontic applications in artificial saliva. - Abstract: The evolution of the passive films on 2205 duplex stainless steel (2205 DSS) and AISI 316L stainless steel in artificial saliva, and with the addition of fluoride, was studied using electrochemical impedance spectroscopy (EIS) and potentiodynamic measurements. The extent of the passive range increased for the 2205 DSS compared to the AISI 316L in both solutions. The formation of the passive film was studied by EIS at the open-circuit potential (OCP). The passive layers were studied at the OCP by X-ray photoelectron spectroscopy (XPS). The passive films on both materials predominantly contained Cr-oxides, whereas the Fe species were markedly depleted.

  2. Influence of Material Model on Prediction Accuracy of Welding Residual Stress in an Austenitic Stainless Steel Multi-pass Butt-Welded Joint

    Science.gov (United States)

    Deng, Dean; Zhang, Chaohua; Pu, Xiaowei; Liang, Wei

    2017-03-01

    Both experimental method and numerical simulation technology were employed to investigate welding residual stress distribution in a SUS304 steel multi-pass butt-welded joint in the current study. The main objective is to clarify the influence of strain hardening model and the yield strength of weld metal on prediction accuracy of welding residual stress. In the experiment, a SUS304 steel butt-welded joint with 17 passes was fabricated, and the welding residual stresses on both the upper and bottom surfaces of the middle cross section were measured. Meanwhile, based on ABAQUS Code, an advanced computational approach considering different plastic models as well as annealing effect was developed to simulate welding residual stress. In the simulations, the perfect plastic model, the isotropic strain hardening model, the kinematic strain hardening model and the mixed isotropic-kinematic strain hardening model were employed to calculate the welding residual stress distributions in the multi-pass butt-welded joint. In all plastic models with the consideration of strain hardening, the annealing effect was also taken into account. In addition, the influence of the yield strength of weld metal on the simulation result of residual stress was also investigated numerically. The conclusions drawn by this work will be helpful in predicting welding residual stresses of austenitic stainless steel welded structures used in nuclear power plants.

  3. Observations of Ferrite/Austenite Transformations in the Heat Affected Zone of 2205 Duplex Stainless Steel Spot Welds Using Time Resolved X-Ray Diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Palmer, T; Elmer, J; Babu, S

    2003-10-29

    Time Resolved X-Ray Diffraction (TRXRD) measurements are made in the Heat Affected Zone (HAZ) of 2205 Duplex Stainless Steel (DSS) spot welds. Both the {gamma} {yields} {delta} and {delta} {yields} {gamma} transformations are monitored as a function of time during the rapid spot weld heating and cooling cycles. These observations are then correlated with calculated thermal cycles. Where the peak temperatures are highest ({approx}1342 C), the {gamma} {yields} {delta} transformation proceeds to completion, leaving a ferritic microstructure at the end of heating. With lower peak temperatures, the {gamma} {yields} {delta} transformation proceeds to only partial completion, resulting in a microstructure containing both transformed and untransformed austenite. Further analyses of the individual diffraction patterns show shifts in the peak positions and peak widths as a function of both time and temperature. In addition, these changes in the peak characteristics are correlated with measured changes in the ferrite volume fraction. Such changes in the peak positions and widths during the {gamma} {yields} {delta} transformation provide an indication of changes occurring in each phase. These changes in peak properties can be correlated with the diffusion of nitrogen and other substitutional alloying elements, which are recognized as the primary mechanisms for this transformation. Upon cooling, the {delta} {yields} {gamma} transformation is observed to proceed from both the completely and partially transformed microstructural regions in the TRXRD data. An examination of the resulting microstructures confirms the TRXRD observation as the evidence shows that austenite both nucleates and grows from the ferritic microstructure at locations closest to the fusion zone boundary and grows from untransformed austenite grains at locations further from this boundary.

  4. Extreme embrittlement of austenitic stainless steel irradiated to 75--81 dpa at 335--360 C

    Energy Technology Data Exchange (ETDEWEB)

    Porollo, S.I.; Vorobjev, A.N.; Konobeev, Yu.V. [Inst. of Physics and Power Engineering, Obninsk (Russian Federation); Garner, F.A. [Pacific Northwest National Lab., Richland, WA (United States)

    1998-03-01

    This paper presents the results of an experiment conducted in the BN-350 fast reactor in Kazakhstan that involved the irradiation of argon-pressurized thin-walled tubes (0--2000 MPa hoop stress) constructed from Fe-16Cr-15Ni-3Mo-Nb stabilized steel in contact with the sodium coolant, which enters the reactor at {approximately}270 C. Tubes in the annealed condition reached 75 dpa at 335 C, and another set in the 20% cold-worked condition reached 81 dpa at 360 C. Upon disassembly all tubes, except those in the stress-free condition, were found to have failed in an extremely brittle fashion. The stress-free tubes exhibited diameter changes that imply swelling levels ranging from 9 to 16%. It is expected that stress-enhancement of swelling induced even larger swelling levels in the stressed tubes. The embrittlement is explained in terms of the sensitivity of the swelling regime to displacement rate and the large, unprecedented levels of swelling reached at 335--360 C at these high neutron fluences. The failure mechanism appears to be identical to that observed at similar swelling levels in other austenitic steels irradiated in US fast reactors at 400--425 C, whereby stress-concentration between voids and nickel segregation at void surfaces predisposes the steel to an epsilon martensite transformation followed by formation of alpha martensite at crack tips. The very slow strain rate inherent in such creep tests and the relatively high helium levels may also contribute to the failure.

  5. Modelling the grain orientation of austenitic stainless steel multipass welds to improve ultrasonic assessment of structural integrity

    Energy Technology Data Exchange (ETDEWEB)

    Moysan, J.; Apfel, A.; Corneloup, G.; Chassignole, B

    2003-02-01

    Knowledge of the grain orientation quantifies the material anisotropy which helps to ensure the good ultrasonic testing of welded assemblies and the assessment of their mechanical integrity. The model described here concerns the weld solidification of 316L stainless steel. The solidification of multipass welds made with a shielded electrode raises many unsolved modelling questions as it involves heat and fluid flow modelling in addition to solute redistribution models. To overcome these difficulties we have developed the MINA model to predict the resulting grain orientations without using a complete solidification model. This model relies upon a phenomenological description of grain orientations from macrograph analysis. One important advance of this model is to include data reporting in the welding notebook that ensures the generality of the model. This model allows us to accurately simulate the ultrasonic testing of welded components and to propose a new tool to associate welding design with the ultrasonic assessment of structural integrity.

  6. Finite element modeling of the effect of welding parameters on solidification cracking of Austenitic Stainless Steel 310

    Directory of Open Access Journals (Sweden)

    Eslam Ranjbarnodeh

    2016-12-01

    Full Text Available A transient thermo-mechanical model is employed to study the effects of welding parameters on the occurrence of solidification cracking. A finite element program, ANSYS, is employed to solve the thermal and mechanical equations while the different variables such as welding current, speed and sequence are considered in the simulation. The studied geometry was butt joint of two stainless steel plates with the thickness of 2 mm. Then, the samples were welded by TIG method without filler. To verify the numerical results, the model outputs were checked with the experimental observations and good agreement was observed. It was found that the increasing of welding current from 70 A to 100 A resulted in the increase in transverse tensile strain from 1.2 to 2.1 which can facilitate the occurrence of solidification cracking. Furthermore, the application of symmetric welding layout is an effective method to prevent solidification cracking.

  7. Tribological behavior of AISI302 austenitic stainless steel modified by elevated temperature nitrogen plasma immersion ion implantation

    Institute of Scientific and Technical Information of China (English)

    JIANG Shao-qun; MA Xin-xin; SUN Yue

    2004-01-01

    AISI302 stainless steel samples were modified by elevated temperature nitrogen plasma immersion ion implantation at temperature ranging from 330 ℃ to 450 ℃. The tribological behaviors of the implanted layers of the samples were investigated. The samples were characterized by Auger electron spectroscopy (AES), glancing angle X-ray diffraction (GXRD), and nanoindentation. The results show that the implantation temperature plays an important rule on the microstructure and surface properties of the implanted layers. The thickness of the modified layer implanted at 390 ℃ is about 9 μm. It is improved about two orders compared with that of the implanted at room temperature. The surface nanohardness and the wear resistance of elevated temperature implanted layers increase significantly, and the friction coefficient decreases obviously in comparison with the unimplanted one. These data suggests that the improvement results from the formation of new phases such as ε-(Fe, Cr, Ni)2+xN, or noncrystal phase.

  8. High Energy Rate Forming Induced Phase Transition in Austenitic Steel

    Science.gov (United States)

    Kovacs, T.; Kuzsella, L.

    2017-02-01

    In this study, the effects of explosion hardening on the microstructure and the hardness of austenitic stainless steel have been studied. The optimum explosion hardening technology of austenitic stainless steel was researched. In case of the explosive hardening used new idea means indirect hardening setup. Austenitic stainless steels have high plasticity and can be cold formed easily. However, during cold processing the hardening phenomena always occurs. Upon the explosion impact, the deformation mechanism indicates a plastic deformation and this deformation induces a phase transformation (martensite). The explosion hardening enhances the mechanical properties of the material, includes the wear resistance and hardness [1]. In case of indirect hardening as function of the setup parameters specifically the flayer plate position the hardening increased differently. It was find a relationship between the explosion hardening setup and the hardening level.

  9. Radiation-induced instability of MnS precipitates and its possible consequences on IASCC of austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Chung, H.M. [Argonne National Lab., IL (United States); Garner, F.A. [Pacific Northwest National Lab., Richland, WA (United States)

    1996-10-01

    Irradiation assisted stress corrosion cracking (IASCC) continues to be a significant materials issue for the light water reactor industry and may also pose a problem for fusion power devices that employ water cooling. Although a number of potential mechanisms have been proposed to participate in this phenomenon, at this time it is not clear that any of these candidate mechanisms are sufficient to rationalize the observed failures. A new mechanism is proposed in this paper that involves the radiation-induced release into solution of elements not usually thought to participate in IASCC. It is shown in this paper that MnS precipitates, which contain most of the sulphur in stainless steels, are probably unstable under irradiation. First, the Mn transmutes very strongly to Fe in highly thermalized neutron spectra. Second, the combination of cascade-induced disordering and the inverse-Kirkendall effect operating at the incoherent interfaces of MnS precipitates will probably act as a pump to export Mn from the precipitate surface into the alloy matrix. Both of these processes will most likely allow some of the sulphur to re-enter the alloy matrix. Sulphur is known to exert a deleterious influence on grain boundary cracking. MnS precipitates are also thought to be a reservoir of other deleterious impurities such as fluorine which could be also released due to radiation-induced instability of the precipitates. This possibility has been confirmed by Auger electron spectroscopy of Types 304, 316, and 348 stainless steel specimens sectioned from several BWR components irradiated up to 3.5x10{sup 21} n/cm{sup 2} (E > 1 MeV).

  10. Extreme embrittlement of austenitic stainless steel irradiated to 75-81 dpa at 335-360{degrees}C

    Energy Technology Data Exchange (ETDEWEB)

    Porollo, S.I.; Vorobjev, A.N.; Konobeev, Yu.V. [Institute of Physics and Power Engineering, Obninsk (Russian Federation)] [and others

    1997-04-01

    It is generally accepted that void swelling of austenitic steels ceases below some temperature in the range 340-360{degrees}C, and exhibits relatively low swelling rates up to {approximately}400{degrees}C. This perception may not be correct at all irradiation conditions, however, since it was largely developed from data obtained at relatively high displacement rates in fast reactors whose inlet temperatures were in the range 360-370{degrees}C. There is an expectation, however, that the swelling regime can shift to lower temperatures at low displacement rates via the well-known {open_quotes}temperature shift{close_quotes} phenomenon. It is also known that the swelling rates at the lower end of the swelling regime increase continuously at a sluggish rate, never approaching the terminal 1%/dpa level within the duration of previous experiments. This paper presents the results of an experiment conducted in the BN-350 fast reactor in Kazakhstan that involved the irradiation of argon-pressurized thin-walled tubes (0-200 MPa hoop stress) constructed from Fe-16Cr-15Ni-3Mo-Nb stabilized steel in contact with the sodium coolant, which enters the reactor at {approx}270{degrees}C. Tubes in the annealed condition reached 75 dpa at 335{degrees}C, and another set in the 20% cold-worked condition reached 81 dpa at 360{degrees}C. Upon disassembly all tubes, except those in the stress-free condition, were found to have failed in an extremely brittle fashion. The stress-free tubes exhibited diameter changes that imply swelling levels ranging from 9 to 16%. It is expected that stress-enhancement of swelling induced even larger swelling levels in the stressed tubes.

  11. Tensile strength and creep behaviour of austenitic stainless steel type 18Cr - 12Ni with niobium additions at 700{sup 0}C

    Energy Technology Data Exchange (ETDEWEB)

    Sordi, V L; Bueno, L O, E-mail: sordi@ufscar.b [Federal University of Sao Carlos, Materials Engineering Department, Sao Carlos (SP), 13565-905 (Brazil)

    2010-07-01

    The effect of niobium additions up to 2.36 wt% on the creep behavior of a series of seven extra low carbon 18Cr-12Ni austenitic stainless steels at 700{sup 0}C has been investigated. Grain size and hardness measurements, hot tensile tests and constant stress creep tests from 90 to 180 MPa were carried out for each alloy, in the solution treated condition at 1050, 1200 and 1300{sup 0}C followed by quench in water. The mechanical behavior at high temperature was related to the amount of NbC precipitation occurring during the tests. Solid solution and intermetallic compound effects were also considered. Creep data analysis was done to determine the parameters of the creep power-law equation {epsilon}-dot = A.{sigma}{sup n} and the Monkman-Grant relation {epsilon}-dot .t{sup m}{sub R} = K. Niobium-carbide precipitation in these steels reduces the secondary stage dependence of strain rate with applied stress, resulting in n-values which indicate the possibility of operation of various creep mechanisms. The creep strength during the secondary stage is primarily controlled by the amount of NbC available for precipitation. However, the rupture times increase progressively with niobium content, as the amount of undissolved carbide particles in grain boundaries and the Laves phase precipitation increase.

  12. Effect of Oxygen Content Upon the Microstructural and Mechanical Properties of Type 316L Austenitic Stainless Steel Manufactured by Hot Isostatic Pressing

    Science.gov (United States)

    Cooper, Adam J.; Cooper, Norman I.; Dhers, Jean; Sherry, Andrew H.

    2016-09-01

    Although hot isostatic pressing (HIP) has been shown to demonstrate significant advances over more conventional manufacture routes, it is important to appreciate and quantify the detrimental effects of oxygen involvement during the HIP manufacture process on the microstructural and material properties of the resulting component. This paper quantifies the effects of oxygen content on the microstructure and Charpy impact properties of HIP'd austenitic stainless steel, through combination of detailed metallographic examination and mechanical testing on HIP'd Type 316L steel containing different concentrations (100 to 190 ppm) of oxygen. Micron-scale pores were visible in the microstructure of the HIP'd materials postmetallographic preparation, which result from the removal of nonmetallic oxide inclusions during metallographic preparation. The area fraction of the resulting pores is shown to correlate with the oxygen concentration which influences the Charpy impact toughness over the temperature range of 77 K to 573 K (-196 °C to 300 °C), and demonstrates the influence of oxygen involved during the HIP manufacture process on Charpy toughness. The same test procedures and microstructural analyses were performed on commercially available forged 316L. This showed comparatively fewer inclusions and exhibited higher Charpy impact toughness over the tested temperature range.

  13. Study on strain induced martensite in 304 austenitic stainless steel%304奥氏体不锈钢应变诱发马氏体的研究

    Institute of Scientific and Technical Information of China (English)

    杨钒; 黄建龙

    2012-01-01

    用X射线衍射(XRD)、磁针法、力学性能和显微分析研究了商用热轧态和冷轧态304奥氏体不锈钢在不同变形方式下应变诱发马氏体的行为。结果表明:304钢热轧态由于存在多量碳化物和组织不均匀性,其奥氏体稳定性低,拉伸应变诱发马氏体量达40%,冷轧(固溶)态组织均匀、奥氏体稳定性高,拉伸应变诱发马氏体量仅9%;304冷轧板材扩孔、杯突成形时其切向和径向的二向拉应力有助于γ→α'转变,诱发马氏体量(30%~35%)多于单向拉应力的拉伸诱发马氏体量(8%~10%)。对于冷轧304不锈钢,在20%以上拉伸工程应变的驱动下才能较明显地诱发马氏体。304明显的强化效果(△σ达320~400 MPa)来自应变硬化和马氏体相变强化两方面:冷轧304钢的强化主要来自应变硬化本身;热轧304钢的强化不光有应变硬化的贡献,还有应变诱发的多量马氏体的重要贡献,而且后者是主要的。%Behavior of strain induced martensite(SIM) by different deformation processes for commercial hot rolled and cold rolled 304 austenitic stainless steel was studied by means of XRD,magnetic method,optical microscope observation and mechanical property tests.The results show that amount of SIM of hot rolled 304 steel reaches 40% after tension deformation,because of precipitation of alloy carbides,un-uniform microstructure resulting in low austenite stability,and that of cold rolled and solution-treated 304 steel is only 9% due to the uniform microstructure and high austenite stability.The amount of SIM in hole expansion and cupping forming of cold rolled 304 steel,which is 30%-35%,is much more than that of uniaxial tension,because biaxial tension stresses in the former deformation are favourable for γ→α′ transformation.It is found that the obvious SIM can be observed in cold rolled 304 steel with tensile strain more than 20%.The strengthening mechanism of the 304 steel

  14. On the Carbon Solubility in Expanded Austenite and Formation of Hägg Carbide in AISI 316 Stainless Steel

    DEFF Research Database (Denmark)

    Christiansen, Thomas Lundin; Ståhl, Kenny; Brink, Bastian;

    2016-01-01

    –420 °C and 465–470 °C, respectively. Hägg carbide (x-M5C2)develops when the carbon content in the expanded austenite exceeds the metastable solubility limit; the transformation of carbon expanded austenite into Hägg carbide occurs irrespective of carburizing temperature in the investigated temperature...

  15. Study of stress relief cracking in titanium stabilized austenitic stainless steel; Etude de la fissuration differee par relaxation d'un acier inoxydable austenitique stabilise au titane

    Energy Technology Data Exchange (ETDEWEB)

    Chabaud-Reytier, M

    1999-07-01

    The heat affected zone (HAZ) of titanium stabilised austenitic stainless steel welds (AISI 321) may exhibit a serious form of intercrystalline cracking during service at high temperature. This type of cracking, called 'stress relief cracking', is known to be due to work hardening but also to ageing: a fine and abundant intragranular Ti(C,N) precipitation appears near the fusion line and modifies the mechanical behaviour of the HAZ. This study aims to better know the accused mechanism and to succeed in estimating the risk of such cracking in welded junctions of 321 stainless steel. To analyse this embrittlement mechanism, and to assess the lifetime of real components, different HAZ are simulated by heat treatments applied to the base material which is submitted to various cold rolling and ageing conditions in order to reproduce the HAZ microstructure. Then, we study the effects of work hardening and ageing on the titanium carbide precipitation, on the mechanical (tensile and creep) behaviour of the resulting material and on its stress relief cracking sensitivity. It is shown that work hardening is the main parameter of the mechanism and that ageing do not favour crack initiation although it leads to titanium carbide precipitation. The role of this precipitation is also discussed. Moreover, a creep damage model is identified by a local approach to fracture. Materials sensitive to stress relief cracking are selected. Then, creep tests are carried out on notched bars in order to quantify the intergranular damage of these different materials; afterwards, these measurements are combined with calculated mechanical fields. Finally, it is shown that the model gives good results to assess crack initiation for a compact tension (CT) specimen during relaxation tests, as well as for a notched tubular specimen tested at 600 deg. C under a steady torque. (author)

  16. Austenitic Stainless Steel AISI 316L Corrosion Test Research%奥氏体不锈钢AISI 316L腐蚀试验研究

    Institute of Scientific and Technical Information of China (English)

    王金刚; 刘江涛; 程珊珊

    2014-01-01

    在精对苯二甲酸(PTA)生产中,选取干燥机BM302壳体常用材料奥氏体不锈钢AISI 316L为研究对象,在醋酸环境中,对AISI 316L 受Br-及Cl-作用的电化学极化试验和电化学阻抗试验进行腐蚀性试验研究。试验结果表明,Br-或Cl-浓度的增加都会导致AISI 316L不锈钢腐蚀速率增加、击穿电位降低、腐蚀反应电阻减小,导致其耐腐蚀性能下降,腐蚀加剧。为PTA设备腐蚀的现场监测和设备维护提供参考依据。%In purified terephthalic acid (PTA) production, selected the drying machine BM302 shell commonly use material austenitic stainless steel AISI 316L as the research object. In the acetic acid environment, for corrosive test research of AISI 316L, through Br-and Cl-the role of electrochemical polarization test and electrochemical impedance test. The test results show that Br-or Cl-will lead to the increasing of the concentration of seawater AISI 316L stainless steel corrosion rate increase, breakdown voltage is reduced, and the corrosion reaction resistance decreases, and lead to its corrosion resistance drop, corrosion intensifies. That will provide reference for PTA equipment corrosion field monitoring and equipment maintenance.

  17. Effect of sigma phase in the repassivation potential of austenitic-ferritic stainless steel SEW 410 Nr. 14517; Efeito da fase sigma no potencial de repassivacao do aco inoxidavel austeno-ferritico SEW 410 Nr. 14517

    Energy Technology Data Exchange (ETDEWEB)

    Itman Filho, A.; Pimenta, C.C.; Santos, C.M.L. [Instituto Federal do Espirito Santo, Vitoria (Brazil)], e-mail: andrei@ifes.edu.br; Casteletti, L.C. [Escola de Engenharia de Sao Carlos - EESC/USP, SP (Brazil)

    2010-07-01

    The austenitic-ferritic stainless steels, due to the optimum compromise between mechanical properties and corrosion resistance, are being used in many applications, as chemical and oil industries. In the oil exploitation, the effect of erosion-corrosion in acid environment is responsible for the increment in the equipment maintenance costs. Regarding the interest in researches of deep water oil exploitation, the proposal of this study was to evaluate the effect of the heat treatment at 850 degree C of the austenitic-ferritic stainless steel SEW 410 Nr.14517. Microstructural characterizations, microhardness measurements of the phases and corrosion tests were accomplished to evaluate the samples. The pitting potential values were obtained by galvanostatic tests in H{sub 2}SO{sub 4} acid solution. The results showed that the volumetric percentages of sigma phase increased while the ferritic phase percentages decreased, when the heat treatment time increased. The sigma phase promoted hardness increase with little corrosion resistance decrease in the austenitic-ferritic stainless steel, too. (author)

  18. Assessment of surface relief and short cracks under cyclic creep in a type 316LN austenitic stainless steel

    Science.gov (United States)

    Sarkar, Aritra; Nagesha, A.; Parameswaran, P.; Sandhya, R.; Laha, K.

    2015-12-01

    Formation of surface relief and short cracks under cyclic creep (stress-controlled fatigue) in type 316LN stainless steel was studied at temperatures ranging from ambient to 923 K using scanning electron microscopy technique. The surface topography and crack distribution behaviour under cyclic creep were found to be strong functions of testing temperature due to the difference in strain accumulation. At 823 K, surface relief mainly consisted of fine slip markings due to negligible accumulation of strain as a consequence of dynamic strain ageing (DSA) which led to an increase in the cyclic life. Persistent slip markings (PSM) with distinct extrusions containing minute cracks were seen to prevail in the temperature range 873-923 K, indicating a higher slip activity causing higher strain accumulation in the absence of DSA. Besides, a large number of secondary cracks (both transgranular and intergranular) which were partially accentuated by severe oxidation, were observed. Extensive cavitation-induced grain boundary cracking took place at 923 K, which coalesced with PSM-induced transgranular cracks resulting in failure dominated by creep that in turn led to a drastic reduction in cyclic life. Investigations on the influence of stress rate were also carried out which underlined the presence of DSA at 823 K. At 923 K, lowering the stress rate caused further strengthening of the contribution from creep damage marked by a shift in the damage mechanism from cyclic slip to diffusion.

  19. Brazing of stainless steel; Stainless ko no rozuke

    Energy Technology Data Exchange (ETDEWEB)

    Matsu, T.

    1996-04-01

    This paper explains brazing of stainless steel as to its processing materials, brazing materials, brazing methods, and brazing works. When performing brazing at higher than 800{degree}C on a martensite-based stainless steel represented by the 13Cr steel, attention is required on cracking caused by quenching. When a ferrite-based stainless steel represented by the 18Cr steel is heated above 900{degree}C, crystalline particles grow coarser, causing their tenacity and corrosion resistance to decline. High-temperature long-time heating in brazing in a furnace demands cautions. Austenite-based stainless steel represented by the 18Cr-8Ni steel has the best brazing performance. However, since the steel has large thermal expansion coefficient and low thermal conductivity, attention is required on strain and deformation due to heating, and on localized overheating. Deposition hardened stainless steel made of the Cr-Ni alloy steel added with aluminum and titanium has poor wettability in a brazing work, hence pretreatment is required for the purpose of activation. 9 figs., 7 tabs.

  20. Sigma phase formation kinetics in stainless steel laminate composites

    Energy Technology Data Exchange (ETDEWEB)

    Wenmen, D.W.; Olson, D.L.; Matlock, D.K. [Colorado School of Mines, Golden, CO (United States)] [and others

    1994-12-31

    Stainless steel laminate composites were made to simulate weld microstructures. The use of laminates with variations in chemical composition allows for one dimensional analysis of phase transformation associated with the more complex three-dimensional solidification experience of weld metal. Alternate layers of austenitic (304L and 316L) and ferritic (Ebrite) stainless steels allowed for the study of sigma phase formation at the austenite-ferrite interface in duplex stainless steel. Two austenitic stainless steels, 304L (18.5Cr-9.2Ni-0.3Mo) and 316L (16.2Cr-10.1Ni-2.6Mo), and one ferritic stainless steel, Ebrite (26.3Cr-0Ni-1.0Mo) were received in the form of sheet which was laboratory cold rolled to a final thickness of 0.25 mm (0.030 in.). Laminate composites were prepared by laboratory hot rolling a vacuum encapsulated compact of alternating layers of the ferrite steel with either 304L or 316L stainless steel sheets. Laminate composite specimens, which simulate duplex austenite-ferrite weld metal structure, were used to establish the kinetics of nucleation and growth of sigma phase. The factors affecting sigma phase formation were identified. The effects of time, temperature, and transport of chromium and nickel were evaluated and used to establish a model for sigma phase formation in the austenite-ferrite interfacial region. Information useful for designing stainless steel welding consumables to be used for high temperature service was determined.

  1. Ne Implantation Induced Transformation in Stainless Steel

    NARCIS (Netherlands)

    Noordhuis, J.; Hosson, J.Th.M. De

    1990-01-01

    This paper reports a microstructural investigation of the changes induced by Ne implantation in stainless steel of the austenitic type. At a critical dose of 2.3 · 10^17/cm^2 a martensitic phase transformation was observed. In particular, attention has been paid to the effect of the stress held of n

  2. Controlled dissolution of colossal quantities of nitrogen in stainless steel

    DEFF Research Database (Denmark)

    Christiansen, Thomas; Somers, Marcel A. J.

    2006-01-01

    The solubility of nitrogen in austenitic stainless steel was investigated thermogravimetrically by equilibrating thin foils of AISI 304 and AISI 316 in ammonia/hydrogen gas mixtures. Controlled dissolution of colossal amounts of nitrogen under metastable equilibrium conditions was realized...

  3. Effect of Continuous and Pulsed Current Gas Tungsten Arc Welding on Dissimilar Weldments Between Hastelloy C-276/AISI 321 Austenitic Stainless Steel

    Science.gov (United States)

    Sharma, Sumitra; Taiwade, Ravindra V.; Vashishtha, Himanshu

    2017-02-01

    In the present investigation, an attempt has been made to join Hastelloy C-276 nickel-based superalloy and AISI 321 austenitic stainless steel using ERNiCrMo-4 filler. The joints were fabricated by continuous and pulsed current gas tungsten arc welding processes. Experimental studies to ascertain the structure-property co-relationship with or without pulsed current mode were carried out using an optical microscope and scanning electron microscope. Further, the energy-dispersive spectroscope was used to evaluate the extent of microsegregation. The microstructure of fusion zone was obtained as finer cellular dendritic structure for pulsed current mode, whereas columnar structure was formed with small amount of cellular structure for continuous current mode. The scanning electron microscope examination witnessed the existence of migrated grain boundaries at the weld interfaces. Moreover, the presence of secondary phases such as P and μ was observed in continuous current weld joints, whereas they were absent in pulsed current weld joints, which needs to be further characterized. Moreover, pulsed current joints resulted in narrower weld bead, refined morphology, reduced elemental segregation and improved strength of the welded joints. The outcomes of the present investigation would help in obtaining good quality dissimilar joints for industrial applications and AISI 321 ASS being cheaper consequently led to cost-effective design also.

  4. Statistical analysis of AISI304 austenitic stainless steel machining using Ti(C, N/Al2O3/TiN CVD coated carbide tool

    Directory of Open Access Journals (Sweden)

    Sofiane Berkani

    2015-09-01

    Full Text Available The present research work investigated the machining of AISI304 austenitic stainless steel in terms of machining force evolution, power consumption, specific cutting force and surface roughness where a factorial experiment design and analysis of variance technique were used and several factors were evaluated for their effects on each level. The case of dry turning process was studied based on design of experiments in order to obtain empirical equations characterizing material machinability according to cutting conditions such as cutting speed, feed rate and depth of cut and the latter ones were put in relationship with the machining output variables (Ra, Fc, Kc and Pc through the response surface methodology (RSM. Results revealed that feed rate was the most preponderant factor affecting surface roughness (71.04%. However, the depth of cut affects considerably cutting force and cutting power by (60.74% and 67.11%, respectively. In addition, the specific cutting force was found affected significantly by cutting speed with a contribution of 41.43%. The quadratic model of RSM associated with response optimization technique and composite desirability was used to find optimum values of machining parameters (104.54 m/min, 0.08 mm/rev and 0.295 mm.

  5. Cyclic Deformation Behavior of Fe-18Cr-18Mn-0.63N Nickel-Free High-Nitrogen Austenitic Stainless Steel

    Science.gov (United States)

    Shao, C. W.; Shi, F.; Li, X. W.

    2015-04-01

    Cyclic deformation and damage behavior of a Ni-free high-nitrogen austenitic stainless steel with a composition of Fe-18Cr-18Mn-0.63N (weight pct) were studied, and the internal stress and effective stress were estimated by partitioning the hysteresis loop during cyclic straining at total strain amplitudes ranging from 3.0 × 10-3 to 1.0 × 10-2. It is found that immediate cyclic softening takes place at all strain amplitudes and subsequently a saturation or quasi-saturation state develops and occupies the main part of the whole fatigue life. The internal stress increases with increasing strain amplitude, while the variation of effective stress with strain amplitude is somewhat complicated. Such a phenomenon is discussed in terms of dislocation structures and the short-range ordering caused by the interaction between nitrogen atoms and substitutional atoms. The relationship of fatigue life vs plastic strain amplitude ( N f-Δ ɛ pl/2) follows a bilinear Coffin-Manson rule, resulting from the variation in slip deformation mode with the applied strain amplitude. At the low strain amplitude, cracks initiate along slip bands, and planar slip dislocation configurations dominate the major characteristic of internal microstructures. At high strain amplitudes, intergranular (mostly along grain boundaries and few along twin boundaries) cracks are generally found, and the deformation microstructures are mainly composed of dislocation cells, stacking faults and a small amount of deformation twins, in addition to planar slip dislocation structures.

  6. Interaction between recrystallization and strain-induced precipitation in a high Nb- and N-bearing austenitic stainless steel: Influence of the interpass time

    Energy Technology Data Exchange (ETDEWEB)

    Silva, M.B.R., E-mail: marianabdrs@gmail.com [Department of Materials Engineering, UFSCar, Via Washington Luis, Km 235, 13565-905 São Carlos, SP (Brazil); Gallego, J. [Department of Mechanical Engineering, UNESP, Avenida Brasil, 56, 15385-000 Ilha Solteira, SP (Brazil); Cabrera, J.M. [Department of Materials Science and Metallurgical Engineering, Polytechnic University of Catalunya, Avenida Diagonal 647, 08028 Barcelona (Spain); Fundacio CTM Centre Tecnologic, Plaza de la Ciencia 2, 08243 Manresa (Spain); Balancin, O. [Department of Materials Engineering, UFSCar, Via Washington Luis, Km 235, 13565-905 São Carlos, SP (Brazil); Jorge, A.M., E-mail: moreira@dema.ufscar.br [Department of Materials Engineering, UFSCar, Via Washington Luis, Km 235, 13565-905 São Carlos, SP (Brazil)

    2015-06-18

    In this work, we studied the influence of the interpass time (20 and 5 s) on the interaction between recrystallization and strain-induced precipitation occurring during multiple passes' deformations under continuous cooling conditions in a high niobium- and nitrogen-bearing austenitic stainless steel (ISO 5832-9). The correlation between microstructure evolution and hot mechanical properties was performed by physical simulation using hot torsion tests. The microstructure evolution was analyzed by optical microscopy, transmission electron microscopy and electron back scattered diffraction (EBSD). This technique indicated that dynamic recrystallization occurred at the first passes promoting an excellent grain refinement. On the other hand, shorter interpass time (5 s) allowed higher volume fraction of smallest precipitates than larger interpass time (20 s). After soaking, only TiNbN precipitates were found, whereas, Z-phase (CrNbN) and NbN were formed during thermomechanical processing. Particles with sizes between 20 and 50 nm were effective to pin grain boundaries and dislocations.

  7. Effect of Continuous and Pulsed Current Gas Tungsten Arc Welding on Dissimilar Weldments Between Hastelloy C-276/AISI 321 Austenitic Stainless Steel

    Science.gov (United States)

    Sharma, Sumitra; Taiwade, Ravindra V.; Vashishtha, Himanshu

    2017-03-01

    In the present investigation, an attempt has been made to join Hastelloy C-276 nickel-based superalloy and AISI 321 austenitic stainless steel using ERNiCrMo-4 filler. The joints were fabricated by continuous and pulsed current gas tungsten arc welding processes. Experimental studies to ascertain the structure-property co-relationship with or without pulsed current mode were carried out using an optical microscope and scanning electron microscope. Further, the energy-dispersive spectroscope was used to evaluate the extent of microsegregation. The microstructure of fusion zone was obtained as finer cellular dendritic structure for pulsed current mode, whereas columnar structure was formed with small amount of cellular structure for continuous current mode. The scanning electron microscope examination witnessed the existence of migrated grain boundaries at the weld interfaces. Moreover, the presence of secondary phases such as P and μ was observed in continuous current weld joints, whereas they were absent in pulsed current weld joints, which needs to be further characterized. Moreover, pulsed current joints resulted in narrower weld bead, refined morphology, reduced elemental segregation and improved strength of the welded joints. The outcomes of the present investigation would help in obtaining good quality dissimilar joints for industrial applications and AISI 321 ASS being cheaper consequently led to cost-effective design also.

  8. Effect of Welding Current and Time on the Microstructure, Mechanical Characterizations, and Fracture Studies of Resistance Spot Welding Joints of AISI 316L Austenitic Stainless Steel

    Science.gov (United States)

    Kianersi, Danial; Mostafaei, Amir; Mohammadi, Javad

    2014-09-01

    This article aims at investigating the effect of welding parameters, namely, welding current and welding time, on resistance spot welding (RSW) of the AISI 316L austenitic stainless steel sheets. The influence of welding current and welding time on the weld properties including the weld nugget diameter or fusion zone, tensile-shear load-bearing capacity of welded materials, failure modes, energy absorption, and microstructure of welded nuggets was precisely considered. Microstructural studies and mechanical properties showed that the region between interfacial to pullout mode transition and expulsion limit is defined as the optimum welding condition. Electron microscopic studies indicated different types of delta ferrite in welded nuggets including skeletal, acicular, and lathy delta ferrite morphologies as a result of nonequilibrium phases, which can be attributed to a fast cooling rate in the RSW process. These morphologies were explained based on Shaeffler, WRC-1992, and pseudo-binary phase diagrams. The optimum microstructure and mechanical properties were achieved with 8-kA welding current and 4-cycle welding time in which maximum tensile-shear load-bearing capacity or peak load of the welded materials was obtained at 8070 N, and the failure mode took place as button pullout with tearing from the base metal. Finally, fracture surface studies indicated that elongated dimples appeared on the surface as a result of ductile fracture in the sample welded in the optimum welding condition.

  9. Analytical modeling of the thermomechanical behavior of ASTM F-1586 high nitrogen austenitic stainless steel used as a biomaterial under multipass deformation.

    Science.gov (United States)

    Bernardes, Fabiano R; Rodrigues, Samuel F; Silva, Eden S; Reis, Gedeon S; Silva, Mariana B R; Junior, Alberto M J; Balancin, Oscar

    2015-06-01

    Precipitation-recrystallization interactions in ASTM F-1586 austenitic stainless steel were studied by means of hot torsion tests with multipass deformation under continuous cooling, simulating an industrial laminating process. Samples were deformed at 0.2 and 0.3 at a strain rate of 1.0s(-1), in a temperature range of 900 to 1200°C and interpass times varying from 5 to 80s. The tests indicate that the stress level depends on deformation temperature and the slope of the equivalent mean stress (EMS) vs. 1/T presents two distinct behaviors, with a transition at around 1100°C, the non-recrystallization temperature (Tnr). Below the Tnr, strain-induced precipitation of Z-phase (NbCrN) occurs in short interpass times (tpass<30s), inhibiting recrystallization and promoting stepwise stress build-up with strong recovery, which is responsible for increasing the Tnr. At interpass times longer than 30s, the coalescence and dissolution of precipitates promote a decrease in the Tnr and favor the formation of recrystallized grains. Based on this evidence, the physical simulation of controlled processing allows for a domain refined grain with better mechanical properties.

  10. Cultures and co-cultures of human blood mononuclear cells and endothelial cells for the biocompatibility assessment of surface modified AISI 316L austenitic stainless steel.

    Science.gov (United States)

    Stio, Maria; Martinesi, Maria; Treves, Cristina; Borgioli, Francesca

    2016-12-01

    Samples of AISI 316L austenitic stainless steel were subjected either to grinding and polishing procedure, or to grinding and then low temperature glow-discharge nitriding treatment, or to grinding, nitriding and subsequently coating with collagen-I. Nitrided samples, even if only ground, show a higher corrosion resistance in PBS solution, in comparison with ground and polished AISI 316L. Biocompatibility was evaluated in vitro by incubating the samples with either peripheral blood mononuclear cells (PBMC) or human umbilical vein endothelial cells (HUVEC), tested separately or in co-culture. HUVEC-PBMC co-culture and co-incubation of HUVEC with PBMC culture medium, after the previous incubation of PBMC with metallic samples, allowed to determine whether the incubation of PBMC with the different samples might affect HUVEC behaviour. Many biological parameters were considered: cell proliferation, release of cytokines, matrix metalloproteinases (MMPs) and sICAM-1, gelatinolytic activity of MMPs, and ICAM-1 protein expression. Nitriding treatment, with or without collagen coating of the samples, is able to ameliorate some of the biological parameters taken into account. The obtained results point out that biocompatibility may be successfully tested in vitro, using cultures of normal human cells, as blood and endothelial cells, but more than one cell line should be used, separately or in co-culture, and different parameters should be determined, in particular those correlated with inflammatory phenomena.

  11. Localized Corrosion Behavior of 6% Mo Super Austenitic & 316L Stainless Steels in Low pH 3% NaCl Solution

    Institute of Scientific and Technical Information of China (English)

    M.M.A.Gad; H.G.Salem; A.M. Nasreldin; H.Sabry; A.A.El-Sayed

    2005-01-01

    Electrochemical techniques were applied to study the crevice corrosion resistance of two types of stainless steel alloys namely, conventional 316L and 6% Mo super austenitic in acidified 3% NaCl solution at room temperature.Potentiodynamic results showed that 6% Mo alloy possessed a remarkable resistance to crevice corrosion compared with 316L alloy when they are tested in the same solution. The breakdown potential at which passivity broke down for 316L alloy was 0.00 mV (SCE). The corresponding value for 6% Mo alloy could not reach up to the potential value of 700 mV (SCE). 316L alloy suffered extremely from crevice corrosion at room temperature (about 25℃), which indicates that the critical crevice corrosion temperature, below which crevice corrosion does not occur, was lower than the test temperature. For 6% Mo alloy, the critical crevice corrosion temperature was higher than the testing temperature. Electrochemical parameters indicated that 6% Mo alloy exhibited higher crevice corrosion resistance than 316L alloy.

  12. A Stem Analysis of Two Rapidly Solidified Stainless Steels.

    Science.gov (United States)

    1980-03-25

    slightly faster rate than the 303 stainless steel powder and therefore few usable specimens were obtained by electropolishing . The unsuccessful...CONCLUSIONS Rapid solidification processing of a high- sulphur austenitic type 303 stainless steel produces a significant refinement in the...A STEM ANALYSTS OF TWO RAPIDLY SOLIDIFIED STAINLESS STEELS . (U) UN D MAR 80 T F KELLY, J B VANDER SANDE NOBOI-76-C-0171 UNLSSFE7Minrnc UNCLASSIFIED

  13. Welding hot cracking in an austenitic stainless steel; Fissuration a chaud en soudage d'un acier inoxydable austenitique

    Energy Technology Data Exchange (ETDEWEB)

    Kerrouault, N

    2001-07-01

    The occurrence of hot cracking is linked to several conditions, in particular, the composition of the material and the local strains due to clambering. The aim of this study is to better analyse the implied mechanisms and to lead to a local thermomechanical criterion for hot cracking. The example studied is an AISI 321-type stainless steel (X10CrNiTi18-12) strongly prone to cracking. Two weldability tests are studied: - the first one consists in carrying out a fusion line by the TIG process on a thin sheet. In the case of the defect occurrence, the crack is longitudinal and follows the back of the molten bath. The influence of the operating conditions welding (speed, welding heat input, width test sample) is studied. - the second one is the Varestraint test. It is widely used to evaluate the sensitivity of a material to hot cracking. It consists in loading the material by bending during a fusion line by the TIG process and in characterising the defects quantity (length, number). Various thermal and mechanical instrumentation methods were used. The possibilities of a local instrumentation instrumentation being limited because of the melting, the experimental results were complemented by a numerical modelling whose aim is to simulate the thermomechanical evolution of the loading thanks to the finite element analysis code ABAQUS. First, the heat input for thermal simulation is set by the use of an inverse method in order to optimise the energy deposit mode during welding in the calculation. Then, the mechanical simulation needs the input of a constitutive law that fits the mechanical behaviour over a wide temperature range from ambient to melting temperature. Thus, a mechanical characterization is performed by selecting strain values and strain rates representative of what the material undergoes during the tests. The results come from tensile and compressive tests and allow to settle an elasto-visco-plastic constitutive law over temperatures up to liquidus. Once

  14. Characteristics of vacuum sintered stainless steels

    Directory of Open Access Journals (Sweden)

    Z. Brytan

    2009-04-01

    Full Text Available Purpose: In the present study duplex stainless steels were sintered in vacuum. using rapid cooling form the mixture of prealloyed and alloying element powders The purpose of this paper was to describe the obtained microstructures after sintering as well as the main mechanical properties of sintered stainless steels.Design/methodology/approach: In presented work duplex stainless steels were obtained through powder metallurgy starting from austenitic 316L or ferritic 410L prealloyed stainless steels powders by controlled addition of alloying elements powder. Prepared mixes were sintered in a vacuum furnace in 1250°C for 1h. After sintering rapid cooling (6°C/s using nitrogen under pressure was applied. Sintered compositions were subjected to structural examinations by scanning and optical microscopy and EDS analysis as well as X-ray analysis. Mechanical properties were studied through tensile tests and Charpy impact test.Findings: It was demonstrated that austenitic-ferritic microstructures with regular arrangement of both phases and absence of precipitates can be obtained with properly designed powder mix composition as well as sintering cycle with rapid cooling rate. Obtained sintered duplex stainless steels shows good mechanical properties which depends on phases ratio in the microstructure and elements partitioning (Cr/Ni between phases.Research limitations/implications: Basing on alloys characteristics applied cooling rate and powder mix composition seems to be a good compromise to obtain balanced sintered duplex stainless steel microstructures.Practical implications: Mechanical properties of obtained sintered duplex stainless steels structures are rather promising, especially with the aim of extending their field of possible applications.Originality/value: The utilization of vacuum sintering process with rapid cooling after sintering combined with use of elemental powders added to a stainless steel base powder shows its advantages in terms

  15. Technical Letter Report Assessment of Ultrasonic Phased Array Testing for Cast Austenitic Stainless Steel Pressurizer Surge Line Piping Welds and Thick Section Primary System Cast Piping Welds JCN N6398, Task 2A

    Energy Technology Data Exchange (ETDEWEB)

    Diaz, Aaron A.; Denslow, Kayte M.; Cinson, Anthony D.; Morra, Marino; Crawford, Susan L.; Prowant, Matthew S.; Cumblidge, Stephen E.; Anderson, Michael T.

    2008-07-21

    Research is being conducted for the NRC at PNNL to assess the effectiveness and reliability of advanced NDE methods for the inspection of LWR components. The scope of this research encompasses primary system pressure boundary materials including cast austenitic stainless steels (CASS), dissimilar metal welds (DMWs), piping with corrosion-resistant cladding, weld overlays, and far-side examinations of austenitic piping welds. A primary objective of this work is to evaluate various NDE methods to assess their ability to detect, localize, and size cracks in coarse-grained steel components. This interim technical letter report (TLR) provides a synopsis of recent investigations at PNNL aimed at evaluating the capabilities of phased-array (PA) ultrasonic testing (UT) methods as applied to the inspection of CASS welds in nuclear reactor piping. A description of progress, recent developments and interim results are provided.

  16. Wear behavior of austenite containing plate steels

    Science.gov (United States)

    Hensley, Christina E.

    As a follow up to Wolfram's Master of Science thesis, samples from the prior work were further investigated. Samples from four steel alloys were selected for investigation, namely AR400F, 9260, Hadfield, and 301 Stainless steels. AR400F is martensitic while the Hadfield and 301 stainless steels are austenitic. The 9260 exhibited a variety of hardness levels and retained austenite contents, achieved by heat treatments, including quench and tempering (Q&T) and quench and partitioning (Q&P). Samples worn by three wear tests, namely Dry Sand/Rubber Wheel (DSRW), impeller tumbler impact abrasion, and Bond abrasion, were examined by optical profilometry. The wear behaviors observed in topography maps were compared to the same in scanning electron microscopy micrographs and both were used to characterize the wear surfaces. Optical profilometry showed that the scratching abrasion present on the wear surface transitioned to gouging abrasion as impact conditions increased (i.e. from DSRW to impeller to Bond abrasion). Optical profilometry roughness measurements were also compared to sample hardness as well as normalized volume loss (NVL) results for each of the three wear tests. The steels displayed a relationship between roughness measurements and observed wear rates for all three categories of wear testing. Nanoindentation was used to investigate local hardness changes adjacent to the wear surface. DSRW samples generally did not exhibit significant work hardening. The austenitic materials exhibited significant hardening under the high impact conditions of the Bond abrasion wear test. Hardening in the Q&P materials was less pronounced. The Q&T microstructures also demonstrated some hardening. Scratch testing was performed on samples at three different loads, as a more systematic approach to determining the scratching abrasion behavior. Wear rates and scratch hardness were calculated from scratch testing results. Certain similarities between wear behavior in scratch testing

  17. Influence of localized deformation on A-286 austenitic stainless steel stress corrosion cracking in PWR primary water; Influence de la localisation de la deformation sur la corrosion sous contrainte de l'acier inoxydable austenitique A-286 en milieu primaire des REP

    Energy Technology Data Exchange (ETDEWEB)

    Savoie, M

    2007-01-15

    Irradiation-assisted stress corrosion cracking (IASCC) of austenitic stainless steels is known to be a critical issue for structural components of nuclear reactor cores. The deformation of irradiated austenitic stainless steels is extremely heterogeneous and localized in deformation bands that may play a significant role in IASCC. In this study, an original approach is proposed to determine the influence of localized deformation on austenitic stainless steels SCC in simulated PWR primary water. The approach consists in (i) performing low cycle fatigue tests on austenitic stainless steel A-286 strengthened by {gamma}' precipitates Ni{sub 3}(Ti,Al) in order to shear and dissolve the precipitates in intense slip bands, leading to a localization of the deformation within and in (ii) assessing the influence of these {gamma}'-free localized deformation bands on A-286 SCC by means of comparative CERT tests performed on specimens with similar yield strength, containing or not {gamma}'-free localized deformation bands. Results show that strain localization significantly promotes A-286 SCC in simulated PWR primary water at 320 and 360 C. Moreover, A-286 is a precipitation-hardening austenitic stainless steel used for applications in light water reactors. The second objective of this work is to gain insights into the influence of heat treatment and metallurgical structure on A-286 SCC susceptibility in PWR primary water. The results obtained demonstrate a strong correlation between yield strength and SCC susceptibility of A-286 in PWR primary water at 320 and 360 C. (author)

  18. Thermodynamic calculation of phase equilibria in stainless steels

    Directory of Open Access Journals (Sweden)

    Klančnik G.

    2012-01-01

    Full Text Available In this paper two examples of thermodynamic investigation of stainless steels using both, experimental and modeling approach are described. The ferritic-austenitic duplex stainless steel and austenitic stainless steel were investigated using thermal analysis. The complex melting behavior was evident for both alloy systems. Experimentally obtained data were compared with the results of the thermodynamic calculations using the CALPHAD method. The equilibrium thermal events were also described by the calculated heat capacity. In spite of the complexity of both selected real alloy systems a relative good agreement was obtained between the thermodynamic calculations and experimental results.

  19. Effect of alloying and heat treatment on the structure and tribological properties of nitrogen-bearing stainless austenitic steels under abrasive and adhesive wear

    Science.gov (United States)

    Korshunov, L. G.; Goikhenberg, Yu. N.; Chernenko, N. K.

    2007-05-01

    The effect of nitrogen, silicon, and aging modes on the structure, resistance to abrasive and adhesive wear, friction factor, and mechanical properties of nitrogen-bearing (0.27-0.83% N) chromium-manganese austenitic steels is studied. It is shown that it is possible to ensure a favorable combination of mechanical and tribological properties in such steels by choosing the appropriate chemical composition and aging mode.

  20. Structure and mechanical properties of austenitic steel after cold rolling

    Directory of Open Access Journals (Sweden)

    A. Kurc-Lisiecka

    2011-02-01

    Full Text Available Purpose: The aim of the paper is to determine the influence of the cold plastic deformation within the range 18-79% and heat treatment in a temperature range of 500 to 700°C on the microstructure and mechanical properties of austenitic stainless steel grade X5CrNi18-8.Design/methodology/approach: The investigations included observations of the microstructure on a light microscope, researches of mechanical properties in a static tensile test and hardness measurements made by Vickers’s method. The analysis of the phase composition was carried out on the basis of X-ray researches. Whereas, X-ray quantitative phase analysis was carried out by the Averbach Cohen method.Findings: Heat treatment of X5CrNi18-8 stainless steel in the range 500-700°C causes a significant decrease of the mechanical properties (Rm, Rp0.2 and increase of elongation (A. Hardness of investigated steel drops with decrease of cold working degree and increase of heat treatment temperature.Research limitations/implications: The analysis of the obtained results permits to state that the heat treatment causes an essential changes of the microstructure connected with fading of cold deformation. Heating of cold rolled austenitic stainless steels can cause a reverse transformation α’ → γ.Practical implications: Two-phase structure α’+γ of austenitic Cr-Ni steel in deformed state working at elevated temperature undergo a transformation. It significantly influences mechanical properties of steel. Austenite phase undergoes a recrystallization, while martensite α’ phase undergoes reverse transformation.Originality/value: The analytic dependence of the yield point of the investigated steel on the cold working degree in cold rolling process has been confirmed. Revealing this relation is of essential practical importance for the technology of sheetmetal forming of austenitic steel.

  1. Microstructural studies of advanced austenitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Todd, J. A.; Ren, Jyh-Ching [University of Southern California, Los Angeles, CA (USA). Dept. of Materials Science

    1989-11-15

    This report presents the first complete microstructural and analytical electron microscopy study of Alloy AX5, one of a series of advanced austenitic steels developed by Maziasz and co-workers at Oak Ridge National Laboratory, for their potential application as reheater and superheater materials in power plants that will reach the end of their design lives in the 1990's. The advanced steels are modified with carbide forming elements such as titanium, niobium and vanadium. When combined with optimized thermo-mechanical treatments, the advanced steels exhibit significantly improved creep rupture properties compared to commercially available 316 stainless steels, 17--14 Cu--Mo and 800 H steels. The importance of microstructure in controlling these improvements has been demonstrated for selected alloys, using stress relaxation testing as an accelerated test method. The microstructural features responsible for the improved creep strengths have been identified by studying the thermal aging kinetics of one of the 16Ni--14Cr advanced steels, Alloy AX5, in both the solution annealed and the solution annealed plus cold worked conditions. Time-temperature-precipitation diagrams have been developed for the temperature range 600 C to 900 C and for times from 1 h to 3000 h. 226 refs., 88 figs., 10 tabs.

  2. Influence of nitrogen on the stress corrosion cracking resistance of austenitic stainless steels in chloride environment; Influence de l'azote sur la resistance a la corrosion sous contrainte d'aciers inoxydables austenitiques en milieu chlorure

    Energy Technology Data Exchange (ETDEWEB)

    Teysseyre, S

    2001-11-01

    The aim of this study is to investigate the influence of nitrogen additions on the Stress Corrosion Cracking (SSC) resistance of austenitic stainless steel in chloride environment. The investigation was carried out in two part: first, an experimental investigation with model industrial steels was carried out and secondly, numerical simulations based on the Corrosion Enhanced Plasticity Model were developed. Both slow strain rate tensile tests and constant load test of the different steels in boiling MgCl{sub 2} (153 deg C) at free potential show that, for a given plastic strain rate, nitrogen addition increases the critical stress for crack initiation without influencing the crack propagation rate. We observed that the creep rate under constant load was affected by the nitrogen content. As a consequence, the SCC behaviour (cracks density and propagation rate) depends on the nitrogen content. We thus confirm that the nitrogen content influences the corrosion - deformation interaction mechanisms via its positive contribution to the flow stress. These experimental results are reproduced semi-quantitatively by means of numerical simulations at the scale of crack. - dislocation interactions. The presence of nitrogen is modelled by an increased lattice friction stress, which in turn affects the dynamics of crack tip shielding by dislocation pile-ups. We conclude that nitrogen addition in austenitic stainless steels increases the SC crack initiation stress in proportion of the increased flow stress, without penalty in terms of SC crack propagation rate. (author)

  3. Crack growth in an austenitic stainless steel at high temperature; Propagation de fissure a haute temperature dans un acier inoxydable austenitique

    Energy Technology Data Exchange (ETDEWEB)

    Polvora, J.P

    1998-12-31

    This study deals with crack propagation at 650 deg C on an austenitic stainless steel referenced by Z2 CND 17-12 (316L(NN)). It is based on an experimental work concerning two different cracked specimens: CT specimens tested at 650 deg C in fatigue, creep and creep-fatigue with load controlled conditions (27 tests), tube specimens containing an internal circumferential crack tested in four points bending with displacement controlled conditions (10 tests). Using the fracture mechanics tools (K, J and C* parameters), the purpose here is to construct a methodology of calculation in order to predict the evolution of a crack with time for each loading condition using a fracture mechanics global approach. For both specimen types, crack growth is monitored by using a specific potential drop technique. In continuous fatigue, a material Paris law at 650 deg C is used to correlate crack growth rate with the stress intensity factor range corrected with a factor U(R) in order to take into account the effects of crack closure and loading ratio R. In pure creep on CT specimens, crack growth rate is correlated to the evolution of the C* parameter (evaluated experimentally) which can be estimated numerically with FEM calculations and analytically by using a simplified method based on a reference stress approach. A modeling of creep fatigue growth rate is obtained from a simple summation of the fatigue contribution and the creep contribution to the total crack growth. Good results are obtained when C* parameter is evaluated from the simplified expression C*{sub s}. Concerning the tube specimens tested in 4 point bending conditions, a simulation based on the actual A 16 French guide procedure proposed at CEA. (authors) 104 refs.

  4. Crack initiation at high temperature on an austenitic stainless steel; Amorcage de fissure a haute temperature dans un acier inoxydable austenitique

    Energy Technology Data Exchange (ETDEWEB)

    Laiarinandrasana, L.

    1994-11-25

    The study deals with crack initiation at 600 and 650 degrees Celsius, on an austenitic stainless steel referenced by Z2 CND 17 12. The behaviour laws of the studied plate were update in comparison with existing data. Forty tests were carried out on CT specimens, with continuous fatigue with load or displacement controlled, pure creep, pure relaxation, creep-fatigue and creep-relaxation loadings. The practical initiation definition corresponds to a small crack growth of about the grain size. The time necessary for the crack to initiate is predicted with fracture mechanics global and local approaches, with the helps of microstructural observations and finite elements results. An identification of a `Paris`law` for continuous cyclic loading and of a unique correlation between the initiation time and C{sup *}{sub k} for creep tests was established. For the local approach, crack initiation by creep can be interpreted as the reaching of a critical damage level, by using a damage incremental rule. For creep-fatigue tests, crack growth rates at initiation are greater than those of Paris`law for continuous fatigue. A calculation of a transition time between elastic-plastic and creep domains shows that crack initiation can be interpreted whether by providing Paris`law with an acceleration term when the dwell period is less than the transition time, or by calculating a creep contribution which relies on C{sup *}{sub k} parameter when the dwell period and/or the initiation times are greater than the transition time. Creep relaxation tests present crack growth rates at initiation which are less than those for `equivalent` creep-fatigue tests. These crack growth rates when increasing hold time, but also when temperature decreases. Though, for hold times which are important enough and at lower temperature, there is no effect of the dwell period insofar as crack growth rate is equal to continuous fatigue Paris law predicted ones. (Abstract Truncated)

  5. Articles comprising ferritic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Rakowski, James M.

    2016-06-28

    An article of manufacture comprises a ferritic stainless steel that includes a near-surface region depleted of silicon relative to a remainder of the ferritic stainless steel. The article has a reduced tendency to form an electrically resistive silica layer including silicon derived from the steel when the article is subjected to high temperature oxidizing conditions. The ferritic stainless steel is selected from the group comprising AISI Type 430 stainless steel, AISI Type 439 stainless steel, AISI Type 441 stainless steel, AISI Type 444 stainless steel, and E-BRITE.RTM. alloy, also known as UNS 44627 stainless steel. In certain embodiments, the article of manufacture is a fuel cell interconnect for a solid oxide fuel cell.

  6. Austenite formation in C-Mn steel

    OpenAIRE

    Savran, V.I.

    2009-01-01

    The production process of almost all modern steels involves austenitization formation of the austenite phase upon continuous heating. Many of the microstructural features and properties that are obtained upon subsequent cooling are to a large extend determined by the evolution of the microstructure and chemical inhomogeneities during austenitization. In spite of its importance, austenitization so far has received much less attention than the transformations on cooling; however, the interest i...

  7. 奥氏体不锈钢低温气体渗碳的组织性能%Structure and Properties of Anti-corrosion Carburized Layers in Austenitic Stainless Steels

    Institute of Scientific and Technical Information of China (English)

    李朋; 潘邻; 张良界; 杨闽红; 朱云峰; 马飞

    2013-01-01

    Low temperature carburizing process, such as salt bath carburizing and plasma carburizing can improve the surface strength of the austenite stainless steel, but reduce the corrosion resistant performance. A gas carburizing technology at low temperature was developed, which can both improve the surface strength and corrosion resistant performance. 304 and 316 austenitic stainless steel were carburized by low temperature carburizing process, and the hardness and performance was analized. The results show that the surface strength enhances, however, the corrosion resistance reduces with the temperature increase. The austenitic stainless steel shows good strength and corrosion resistance under the condition of 470 ℃.%低温盐浴渗碳、等离子渗碳等低温渗碳工艺在提高奥氏体不锈钢表面强度的同时,会降低其耐蚀性能.为克服上述缺陷,开发了一种高效兼顾表面强度与耐蚀性能的表面强化工艺的低温气体渗碳技术.采用该工艺对304、316奥氏体不锈钢进行渗碳处理,并对得到的奥氏体不锈钢低温渗碳组织性能进行分析.结果表明,随着温度升高,试样表面强度提高,而腐蚀性能下降.470℃是兼顾强化与耐蚀性能的低温气体渗碳工艺参数.

  8. Fatigue of stainless steel in hydrogen

    Science.gov (United States)

    Schuster, G.; Altstetter, C.

    1983-10-01

    The fatigue crack growth rates of two austenitic stainless steel alloys, AISI 301 and 302, were compared in air, argon, and hydrogen environments at atmospheric pressure and room temperature. Under the stresses at the crack tip the austenite in type 301 steel transformed martensitically to a’ to a greater extent than in type 302 steel. The steels were also tested in the cold worked condition under hydrogen or argon. Hydrogen was found to have a deleterious effect on both steels, but the effect was stronger in the unstable than in the stable alloy. Cold work decreased fatigue crack growth rates in argon and hydrogen, but the decrease was less marked in hydrogen than in argon. Metallographic, fractographic, and microhardness surveys in the vicinity of the fatigue crack were used to try to understand the reasons for the observed fatigue behavior.

  9. 奥氏体不锈钢低温气体渗碳过程中温度对渗碳层的影响%Effect of temperature on low-temperature gas carburized layer of austenitic stainless steel

    Institute of Scientific and Technical Information of China (English)

    2013-01-01

      利用扫描电镜、电子探针、显微硬度计、CS电化学工作站研究AISI316奥氏体不锈钢经低温气体渗碳处理后渗碳层显微组织及力学特性的变化。结果表明,在450,470,500℃温度条件下,在AISI316奥氏体不锈钢表面获得10~33μm的硬化层,随温度的不同,渗层深度、硬度梯度、耐蚀性能呈现不同的变化规律。%Microstructure and mechanical properties of low⁃temperature gas carburized layer of AISI316 austenitic stainless steel were investigated by means of scanning electron microscopy(SEM),micro hardness tester,CS electrochemical workstation. The experimental results indicate that the thickness of hardened layer is within the range of 10 to 33 μm,when AISI316 austenitic stainless steel is carburized at 450,470,500 ℃. With the variation of carburizing temperature,different case depth,hardness gradient and corrosion resistance are observed in the steel.

  10. 高氮奥氏体钢的韧脆转变与层错能的关系%Study on relationship between ductile to brittle transition and stacking fault energy of high nitrogen containing austenitic stainless steel

    Institute of Scientific and Technical Information of China (English)

    马玉喜

    2011-01-01

    在60℃至室温范围内,采用夏比冲击试验测定材料的韧一脆转变温度,并通过对冲击断口的X-射线测试层错能等方法,对几种不同含氮量奥氏体不锈钢在低温下发生韧一脆转变的现象进行了研究.结果表明:在超高氮奥氏体钢中,随氮质量分数的增加该钢种发生韧一脆转变的温度上升,层错能减少,韧性越来越差.%The DBTT of super-high nitrogen containing austenitic stainless steels was tested at temperatures between room-temperature and -60 ℃ by Charpy-type test, and its ductility and brittleness transition were investigated under low temperature by XRD method. The results show that the ductile to brittle transition temperature (DBTT) of high nitrogen containing austenitic stainless steels depends on the nitrogen content in the steel, and the DBTT is shifted from low temperature to high temperature. In addition,with the increase of nitrogen content, the stacking fault energy is decreased and the ductility is getting worse.

  11. Evaluation of stainless steels for their resistance to intergranular corrosion

    Science.gov (United States)

    Korostelev, A. B.; Abramov, V. Ya.; Belous, V. N.

    1996-10-01

    Austenitic stainless steels are being considered as structural materials for first wall/blanket systems in the International Thermonuclear Reactor (ITER). The uniform corrosion of stainless steels in water is well known and is not a critical issue limiting its application for the ITER design. The sensitivity of austenitic steels to intergranular corrosion (IGC) can be estimated rather accurately by means of calculation methods, considering structure and chemical composition of steel. There is a maximum permissible carbon content level, at which sensitization of stainless steel is eliminated: K = Cr eff - αC eff, where α-thermodynamic coefficient, Cr eff-effective chromium content (regarding molybdenum influence) and C eff-effective carbon content (taking into account nickel and stabilizing elements). Corrosion tests for 16Cr11Ni3MoTi, 316L and 316LN steel specimens, irradiated up to 2 × 10 22 n/cm 2 fluence have proved the effectiveness of this calculation technique for determination of austenitic steels tendency to IGC. This method is directly applicable in austenitic stainless steel production and enables one to exclude complicated experiments on determination of stainless steel susceptibility to IGC.

  12. Evaluation of stainless steels for their resistance to intergranular corrosion

    Energy Technology Data Exchange (ETDEWEB)

    Korostelev, A.B. [Research and Development Inst. of Power Engineering, Moscow (Russian Federation); Abramov, V.Ya. [Research and Development Inst. of Power Engineering, Moscow (Russian Federation); Belous, V.N. [Research and Development Inst. of Power Engineering, Moscow (Russian Federation)

    1996-10-01

    Austenitic stainless steels are being considered as structural materials for first wall/blanket systems in the international thermonuclear reactor (ITER). The uniform corrosion of stainless steels in water is well known and is not a critical issue limiting its application for the ITER design. The sensitivity of austenitic steels to intergranular corrosion (IGC) can be estimated rather accurately by means of calculation methods, considering structure and chemical composition of steel. There is a maximum permissible carbon content level, at which sensitization of stainless steel is eliminated: K=Cr{sub eff}-{alpha}C{sub eff}, where {alpha}-thermodynamic coefficient, Cr{sub eff}-effective chromium content (regarding molybdenum influence) and C{sub eff}-effective carbon content (taking into account nickel and stabilizing elements). Corrosion tests for 16Cr11Ni3MoTi, 316L and 316LN steel specimens, irradiated up to 2 x 10{sup 22} n/cm{sup 2} fluence have proved the effectiveness of this calculation technique for determination of austenitic steels tendency to IGC. This method is directly applicable in austenitic stainless steel production and enables one to exclude complicated experiments on determination of stainless steel susceptibility to IGC. (orig.).

  13. Microstructural characterization and model of hardening for the irradiated austenitic stainless steels of the internals of pressurized water reactors; Caracterisation microstructurale et modelisation du durcissement des aciers austenitiques irradies des structures internes des reacteurs a eau pressurisee

    Energy Technology Data Exchange (ETDEWEB)

    Pokor, C

    2003-07-01

    The core internals of Pressurized Water Reactors (PWR) are composed of SA 304 stainless steel plates and CW 316 stainless steel bolts. These internals undergo a neutron flux at a temperature between 280 deg C and 380 deg C which modifies their mechanical properties. These modifications are due to the changes in the microstructure of these materials under irradiation which depend on flux, dose and irradiation temperature. We have studied, by Transmission Electron Microscopy, the microstructure of stainless steels SA 304, CW 316 and CW 316Ti irradiated in a mixed flux reactor (OSIRIS at 330 deg C between 0,8 dpa et 3,4 dpa) and in a fast breeder reactor at 330 deg C (BOR-60) up to doses of 40 dpa. Moreover, samples have been irradiated at 375 deg C in a fast breeder reactor (EBR-II) up to doses of 10 dpa. The microstructure of the irradiated stainless steels consists in faulted Frank dislocation loops in the [111] planes of austenitic, with a Burgers vector of [111]. It is possible to find some voids in the solution annealed samples irradiated at 375 deg C. The evolution of the dislocations loops and voids has been simulated with a 'cluster dynamic' model. The fit of the model parameters has allowed us to have a quantitative description of our experimental results. This description of the microstructure after irradiation was coupled together with a hardening model by Frank loops that has permitted us to make a quantitative description of the hardening of SA 304, CW 316 and CW 316Ti stainless steels after irradiation at a certain dose, flux and temperature. The irradiation doses studied grow up to 90 dpa, dose of the end of life of PWR internals. (author)

  14. Development of Cast Alumina-forming Austenitic Stainless Steel Alloys for use in High Temperature Process Environments

    Energy Technology Data Exchange (ETDEWEB)

    Muralidharan, Govindarajan [ORNL; Yamamoto, Yukinori [ORNL; Brady, Michael P [ORNL; Pint, Bruce A [ORNL; Pankiw, Roman [Duraloy Technologies Inc; Voke, Don [Duraloy Technologies Inc

    2015-01-01

    There is significant interest in the development of alumina-forming, creep resistant alloys for use in various industrial process environments. It is expected that these alloys can be fabricated into components for use in these environments through centrifugal casting and welding. Based on the successful earlier studies on the development of wrought versions of Alumina-Forming Austenitic (AFA) alloys, new alloy compositions have been developed for cast products. These alloys achieve good high-temperature oxidation resistance due to the formation of protective Al2O3 scales while multiple second-phase precipitation strengthening contributes to excellent creep resistance. This work will summarize the results on the development and properties of a centrifugally cast AFA alloy. This paper highlights the strength, oxidation resistance in air and water vapor containing environments, and creep properties in the as-cast condition over the temperature range of 750°C to 900°C in a centrifugally cast heat. Preliminary results for a laboratory cast AFA composition with good oxidation resistance at 1100°C are also presented.

  15. Applications of Thermo-Calc in Research of High Nitrogen Austenitic Stainless Steels%热力学计算在高氮奥氏体不锈钢研究中的应用

    Institute of Scientific and Technical Information of China (English)

    郎宇平; 陈海涛; 翁宇庆; 屈华鹏

    2013-01-01

    采用Thermo-Calc软件,计算了碳、铬、锰、镍元素和压力因素对22Cr高氮奥氏体不锈钢氮溶解度、凝固过程中相转变以及析出相的影响,并对设计的新型高氮奥氏体不锈钢组织及析出相进行了研究.结果表明:铬元素主要增加液态钢的氮溶解度,增加0.1%(质量分数)的碳即能显著增大奥氏体不锈钢在高温凝固时的最小氮溶解度.锰元素既增加液态钢中的饱和氮溶解度,又增加凝固初期的最小氮溶解度.适当的锰含量能扩大并稳定奥氏体相区,避免“铁素体阱”的出现.少量的镍含量既增加奥氏体不锈钢高温凝固时的最小氮溶解度,缩小高温δ铁素体存在的温度区间,也能使钢在室温下有完全的奥氏体组织.加压冶炼能有效促进氮溶解度.新型高氮奥氏体不锈钢的析出相主要为Cr23C6,Cr2N.采用热力学计算工具可以对高氮奥氏体不锈钢的冶炼、组织控制、热处理和热加工提供科学的指导.%The Thermo-Calc software was used to calculate the influence of pressure factor and elements including C,Cr,Mn and Ni on the solubility of nitrogen,the phase transformation during solidification in high nitrogen austenitic stainless steel with 22% (mass fraction) Cr.The microstructures and precipitates of new designed high austenitic stainless steel were studied also.The results show that Cr increases mainly the solubility of nitrogen in liquid steel.With about 0.1%C the minimum solubility of nitrogen during higher solidification temperature is enhanced remarkably.Mn increases not only the solubility of nitrogen in liquid steel but also the minimum solubility of nitrogen during earlier solidification.With proper Mn the phase area of austenite is extended and more stably,also the "ferrite trap" can be avoided.With a little nickel less than 2 % the minimum solubility of nitrogen during higher solidification temperature is enhanced and the temperature extension of

  16. The strong influence of displacement rate on void swelling in variants of Fe-16Cr-15Ni-3Mo austenitic stainless steel irradiated in BN-350 and BOR-60

    Energy Technology Data Exchange (ETDEWEB)

    Budylkin, N.I.; Bulanova, T.M.; Mironova, E.G.; Mitrofanova, N.M.; Porollo, S.I.; Chernov, V.M.; Shamardin, V.K.; Garner, F.A. E-mail: frank.garner@pnl.gov

    2004-08-01

    Recent irradiation experiments conducted on a variety of austenitic stainless steels have shown that void swelling appears to be increased when the dpa rate is decreased, primarily by a shortening of the transient regime of swelling. This paper presents results derived from nominally similar irradiations conducted on six Russian steels, all laboratory heat variants of Fe-16Cr-15Ni-3Mo-Nb-B, with each irradiated in two fast reactors, BOR-60 and BN-350. The BN-350 irradiation proceeded at a dpa rate three times higher than that conducted in BOR-60. In all six steels, a significantly higher swelling level was attained in BOR-60, agreeing with the results of earlier studies.

  17. Phase Transformation in Cast Superaustenitic Stainless Steels

    Energy Technology Data Exchange (ETDEWEB)

    Lee Phillips, Nathaniel Steven [Iowa State Univ., Ames, IA (United States)

    2006-01-01

    Superaustenitic stainless steels constitute a group of Fe-based alloys that are compositionally balanced to have a purely austenitic matrix and exhibit favorable pitting and crevice corrosion resistant properties and mechanical strength. However, intermetallic precipitates such as sigma and Laves can form during casting or exposure to high-temperature processing, which degrade the corrosion and mechanical properties of the material. The goal of this study was to accurately characterize the solid-solid phase transformations seen in cast superaustenitic stainless steels. Heat treatments were performed to understand the time and temperature ranges for intermetallic phase formations in alloys CN3MN and CK3MCuN. Microstructures were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy and wavelength dispersive spectroscopy (EDS, WDS). The equilibrium microstructures, composed primarily of sigma and Laves within purely austenitic matrices, showed slow transformation kinetics. Factors that determine the extent of transformation, including diffusion, nucleation, and growth, are discussed.

  18. The effect of CO{sub 2} laser beam welded AISI 316L austenitic stainless steel on the viability of fibroblast cells, in vitro

    Energy Technology Data Exchange (ETDEWEB)

    Köse, Ceyhun, E-mail: ceyhun.kose@gop.edu.tr [Faculty of Natural Sciences and Engineering, Department of Mechanical Engineering, Gaziosmanpaşa University, Tokat (Turkey); Kaçar, Ramazan, E-mail: rkacar@karabuk.edu.tr [Faculty of Technology Department of Manufacturing Engineering, Karabuk University, Karabuk 78050 (Turkey); Zorba, Aslı Pınar, E-mail: aslipinarzorba@gmail.com [Graduate School of Natural and Applied Sciences, Department of Bioengineering Cell Culture and Tissue Engineering, Yıldız Technical University, Istanbul (Turkey); Bağırova, Melahat, E-mail: mbagir@yildiz.edu.tr [Department of Bioengineering Cell Culture and Tissue Engineering, Yıldız Technical University, Istanbul (Turkey); Allahverdiyev, Adil M., E-mail: adil@yildiz.edu.tr [Department of Bioengineering Cell Culture and Tissue Engineering, Yıldız Technical University, Istanbul (Turkey)

    2016-03-01

    It has been determined by the literature research that there is no clinical study on the in vivo and in vitro interaction of the cells with the laser beam welded joints of AISI 316L biomaterial. It is used as a prosthesis and implant material and that has adequate mechanical properties and corrosion resistance characteristics. Therefore, the interaction of the CO{sub 2} laser beam welded samples and samples of the base metal of AISI 316L austenitic stainless steel with L929 fibroblast cells as an element of connective tissue under in vitro conditions has been studied. To study the effect of the base metal and the laser welded test specimens on the viability of the fibroblast cells that act as an element of connective tissues in the body, they were kept in DMEMF-12 medium for 7, 14, 28 days and 18 months. The viability study was experimentally studied using the MTT method for 7, 14, 28 days. In addition, the direct interaction of the fibroblast cells seeded on 6 different plates with the samples was examined with an inverted microscope. The MTT cell viability experiment was repeated on the cells that were in contact with the samples. The statistical relationship was analyzed using a Tukey test for the variance with the GraphPad statistics software. The data regarding metallic ion release were identified with the ICP-MS method after the laser welded and main material samples were kept in cell culture medium for 18 months. The cell viability of the laser welded sample has been detected to be higher than that of the base metal and the control based on 7th day data. However, the laser welded sample's viability of the fibroblast cells has diminished by time during the test period of 14 and 28 days and base metal shows better viability when compared to the laser welded samples. On the other hand, the base metal and the laser welded sample show better cell viability effect when compared to the control group. According to the ICP-MS results of the main material and

  19. Effect of Friction-Induced Deformation on the Structure, Microhardness, and Wear Resistance of Austenitic Chromium—Nickel Stainless Steel Subjected to Subsequent Oxidation

    Science.gov (United States)

    Korshunov, L. G.; Chernenko, N. L.

    2016-03-01

    The effect of plastic deformation that occurs in the zone of the sliding friction contact on structural transformations in the 12Kh18N9T austenitic steel subjected to subsequent 1-h oxidation in air at temperatures of 300-800°C, as well as on its wear resistance, has been studied. It has been shown that severe deformation induced by dry sliding friction produces the two-phase nanocrystalline γ + α structure in the surface layer of the steel ~10 μm thick. This structure has the microhardness of 5.2 GPa. Subsequent oxidation of steel at temperatures of 300-500°C leads to an additional increase in the microhardness of its deformed surface layer to the value of 7.0 GPa. This is due to the active saturation of the austenite and the strain-assisted martensite (α') with the oxygen atoms, which diffuse deep into the metal over the boundaries of the γ and α' nanocrystals with an increased rate. The concentration of oxygen in the surface layer of the steel and in wear products reaches 8 wt %. The atoms of the dissolved oxygen efficiently pin dislocations in the γ and α' phases, which enhances the strength and wear resistance of the surface of the 12Kh18N9T steel. The oxidation of steel at temperatures of 550-800°C under a light normal load (98 N) results in the formation of a large number of Fe3O4 (magnetite) nanoparticles, which increase the resistance of the steel to thermal softening and its wear resistance during dry sliding friction in a pair with 40Kh13 steel. Under a heavy normal load (196 N), the toughness of 12Kh18N9T steel and, therefore, the wear resistance of its surface layer decrease due to the presence of the brittle oxide phase.

  20. Nickel-free Stainless Steel for Medical Applications

    Institute of Scientific and Technical Information of China (English)

    Yibin REN; Ke YANG; Bingchun ZHANG; Yaqing WANG; Yong LIANG

    2004-01-01

    BIOSS4 steel is essentially a nickel-free austenitic stainless steel developed by the Institute of Metal Research, Chinese Academy of Sciences, in response to nickel allergy problems associated with nickel-containing stainless steels that are widely used in medical applications. The high nitrogen content of this steel effectively maintains the austenitic stability and also contributes to the high levels of corrosion resistance and strength. BIOSS4 steel possesses a good combination of high strength and toughness, better corrosion resistance, and better blood compatibility, in comparison with the medical 316L stainless steel. Potential applications of BIOSS4 steel can include medical implantation material and orthodontic or orthopedic devices, as well as jewelries and other decorations.

  1. The effect of CO2 laser beam welded AISI 316L austenitic stainless steel on the viability of fibroblast cells, in vitro.

    Science.gov (United States)

    Köse, Ceyhun; Kaçar, Ramazan; Zorba, Aslı Pınar; Bağırova, Melahat; Allahverdiyev, Adil M

    2016-03-01

    It has been determined by the literature research that there is no clinical study on the in vivo and in vitro interaction of the cells with the laser beam welded joints of AISI 316L biomaterial. It is used as a prosthesis and implant material and that has adequate mechanical properties and corrosion resistance characteristics. Therefore, the interaction of the CO2 laser beam welded samples and samples of the base metal of AISI 316L austenitic stainless steel with L929 fibroblast cells as an element of connective tissue under in vitro conditions has been studied. To study the effect of the base metal and the laser welded test specimens on the viability of the fibroblast cells that act as an element of connective tissues in the body, they were kept in DMEMF-12 medium for 7, 14, 28 days and 18 months. The viability study was experimentally studied using the MTT method for 7, 14, 28 days. In addition, the direct interaction of the fibroblast cells seeded on 6 different plates with the samples was examined with an inverted microscope. The MTT cell viability experiment was repeated on the cells that were in contact with the samples. The statistical relationship was analyzed using a Tukey test for the variance with the GraphPad statistics software. The data regarding metallic ion release were identified with the ICP-MS method after the laser welded and main material samples were kept in cell culture medium for 18 months. The cell viability of the laser welded sample has been detected to be higher than that of the base metal and the control based on 7th day data. However, the laser welded sample's viability of the fibroblast cells has diminished by time during the test period of 14 and 28 days and base metal shows better viability when compared to the laser welded samples. On the other hand, the base metal and the laser welded sample show better cell viability effect when compared to the control group. According to the ICP-MS results of the main material and laser welded

  2. 铸造奥氏体不锈钢的疲劳裂纹扩展%Fatigue crack growth of cast austenitic stainless steels

    Institute of Scientific and Technical Information of China (English)

    吕绪明; 李时磊; 王西涛; 王艳丽

    2015-01-01

    用紧凑拉伸试样研究了载荷比、单峰过载和两步高-低幅加载对Z3CN20-09M铸造奥氏体不锈钢疲劳裂纹扩展速率的影响。当应力强度因子范围相同时,疲劳裂纹扩展速率随载荷比的增大而增大。单峰过载使裂纹扩展速率先有短暂的增加后长距离的减速扩展,出现裂纹扩展迟滞现象。两步高-低幅加载时,若两步的最大载荷不同,第二步裂纹扩展也会出现迟滞现象。用两参数模型和Wheeler模型能够预测恒幅载荷和变幅载荷下的疲劳裂纹扩展行为。%The influences of stress ratio, single overload and high-low loading sequence on the fatigue crack growth of Z3CN20-09M cast austenitic stainless steels were studied with compact tension specimens. When the stress intensity factor range is identical, the fatigue crack growth rate increases with the increase of stress ratio. During single overload, the fatigue crack growth rate shows a short period of acceleration followed by a significant decrease, leading to subsequent crack growth retardation. Similarly, high-low loading sequence with the maximum load in the second step lower than that in the first loading step results in significant crack growth retardation in the second loading step. A two-parameter model and Wheeler’ s model are found to predict well the crack growth behav-ior under constant-amplitude loading and variable-amplitude loading, respectively.

  3. Development of Semi-Stochastic Algorithm for Optimizing Alloy Composition of High-Temperature Austenitic Stainless Steels (H-Series) for Desired Mechanical and Corrosion Properties.

    Energy Technology Data Exchange (ETDEWEB)

    Dulikravich, George S.; Sikka, Vinod K.; Muralidharan, G.

    2006-06-01

    The goal of this project was to adapt and use an advanced semi-stochastic algorithm for constrained multiobjective optimization and combine it with experimental testing and verification to determine optimum concentrations of alloying elements in heat-resistant and corrosion-resistant H-series stainless steel alloys that will simultaneously maximize a number of alloy's mechanical and corrosion properties.

  4. Decomposition of Expanded Austenite in AISI 316 L Stainless Steel Nitrided at 450 ℃%450℃渗氮AISI 316 L不锈钢中膨胀奥氏体的分解

    Institute of Scientific and Technical Information of China (English)

    F.A.P.Fernandes; L.C.Casteletti; G.E.Totten; J.Gallego

    2014-01-01

    Expanded austenite (γN ),which can be produced during plasma nitriding of austenitic stainless steels, provides high levels of strength,toughness and corrosion resistance by comparison with traditional nitride layers. However,expanded austenite properties can be lost due to decomposition caused its thermodynamic metastability. In the present work,austenitic stainless AISI 316L steel was plasma nitrided at 450 ℃ for 5 h at 500 Pa and microstructurally characterised by X-ray diffraction (XRD ),and optical and transmission electron microscopy (TEM)which confirmed the presence of fcc expanded austenite with a lattice parameter up to 9.5% larger than untreated austenite.TEM analyses of thin foils showed that fine nitrides were formed in the N layer and some areas were observed with a singular lamellar morphology very similar to the pearlite colonies found in carbon steels. Selected area electron diffraction (SAED)analysis suggests that these areas are composed of bcc ferrite and cubic chromium nitrides produced after a localised decomposition of the expanded austenite layer.Amorphous expanded austenite was observed in some areas of the investigated samples.The occurrence of N decomposition was associated with microsegregation of ferrite stabilisers (Cr,Mo)and depletion of an austenite stabiliser (Ni)in localised regions of the expanded austenite layer.%奥氏体不锈钢等离子渗氮时会形成膨胀奥氏体(γN),其强度、韧性和耐蚀性均高于传统的氮化物层。然而,膨胀奥氏体在热力学上是亚稳的,其性能会因其发生分解而降低。本文对AISI 316L 不锈钢进行了等离子渗氮,工艺为450℃×5 h,压力500 Pa。对渗氮后试样采用XRD、OM和TEM等进行了显微组织表征。试验结果证明了面心立方膨胀奥氏体的存在,其晶格常数比未经渗氮奥氏体增加多达9.5%。薄片试样的TE M分析表明,N层中有细小的氮化物形成,并且发现一些区域呈奇特的

  5. Modeling of helium bubble nucleation and growth in austenitic stainless steels using an Object Kinetic Monte Carlo method

    Science.gov (United States)

    De Backer, A.; Adjanor, G.; Domain, C.; Lescoat, M. L.; Jublot-Leclerc, S.; Fortuna, F.; Gentils, A.; Ortiz, C. J.; Souidi, A.; Becquart, C. S.

    2015-06-01

    Implantation of 10 keV helium in 316L steel thin foils was performed in JANNuS-Orsay facility and modeled using a multiscale approach. Density Functional Theory (DFT) atomistic calculations [1] were used to obtain the properties of He and He-vacancy clusters, and the Binary Collision Approximation based code MARLOWE was applied to determine the damage and He-ion depth profiles as in [2,3]. The processes involved in the homogeneous He bubble nucleation and growth were defined and implemented in the Object Kinetic Monte Carlo code LAKIMOCA [4]. In particular as the He to dpa ratio was high, self-trapping of He clusters and the trap mutation of He-vacancy clusters had to be taken into account. With this multiscale approach, the formation of bubbles was modeled up to nanometer-scale size, where bubbles can be observed by Transmission Electron Microscopy. Their densities and sizes were studied as functions of fluence (up to 5 × 1019 He/m2) at two temperatures (473 and 723 K) and for different sample thicknesses (25-250 nm). It appears that the damage is not only due to the collision cascades but is also strongly controlled by the He accumulation in pressurized bubbles. Comparison with experimental data is discussed and sensible agreement is achieved.

  6. Microstructural evolution of austenitic stainless steels irradiated to 17 dpa in spectrally tailored experiment of the ORR and HFIR at 400{degrees}C

    Energy Technology Data Exchange (ETDEWEB)

    Wakai, E.; Hashimoto, N.; Gibson, L.T. [Oak Ridge National Lab., TN (United States)] [and others

    1997-08-01

    The microstructural evolution of austenitic JPCA aged and solution annealed JPCA, 316R, C, K, and HP steels irradiated at 400{degrees}C in spectrally tailored experiments of the ORR and HFIR has been investigated. The helium generation rates were about 12-16 appm He/dpa on the average up to 17.3 dpa. The number densities and average diameters of dislocation loops in the steels have ranges of 3.3 x 10{sup 21} m{sup -3} and 15.2-26.3 nm, respectively, except for HP steel for which they are 1.1 x 10{sup 23} m{sup -3} and 8.0 nm. Precipitates are formed in all steels except for HP steel, and the number densities and average diameters have ranges of 5.2 x 10{sup 20} - 7.7 x 10{sup 21} m{sup -3} and 3.4- 19.3 nm, respectively. In the 216R, C, and K steels, the precipitates are also formed at grain boundaries, and the mean sizes of these are about 110, 50, and 50 nm, respectively. The number densities of cavities are about 1 x 10{sup 22} m{sup -3} in all the steels. The swelling is low in the steels which form the precipitates.

  7. Microstructure and property of Cr18Mn6Ni4N nickel-saving austenite stainless steel%节镍奥氏体不锈钢 Cr18Mn6Ni4N 的组织及性能

    Institute of Scientific and Technical Information of China (English)

    房菲; 李静媛; 王一德; 秦丽雁

    2015-01-01

    为节约镍资源,研究了不同成分17.8~19.1%Cr,3.93~6.05%Mn,3.58~4.62%Ni,0.32~0.42%N节镍型奥氏体不锈钢固溶后的力学性能和耐蚀性能,以期获得可替代304不锈钢的新钢种。结果表明:Cr18.4Mn5.98Ni4.62N0.42不锈钢的力学性能和耐蚀性能与304不锈钢相当。分析了该成分不锈钢时效处理后的组织演变规律、冷变形过程中奥氏体稳定性及形变诱发马氏体相变过程。结果表明:800℃是Cr2 N相析出的鼻尖温度,随着时效时间的增加,析出相首先以颗粒状形貌沿晶界析出,而后以胞状析出方式向晶内生长。冷轧压下率18.5%时尚未发现形变诱发马氏体组织,随着变形量增大,片层状ε′马氏体含量先增加后减少至消失,而板条状α′马氏体含量逐渐增多,相对磁导率增加,但其奥氏体稳定性远高于304不锈钢。可见,Cr18.4Mn5.98Ni4.62N0.42不锈钢可替代304不锈钢。%In order to save nickel resource and obtain a new type of stainless steel that can take place of the 304 stainless steel, the mechanical properties and corrosion resistance of nickel-saving austenitic stainless steels with different alloy compositions (17.8~19.1%Cr, 3.93~6.05%Mn, 3.58~4.62%Ni, 0.32~0.42%N) were studied af-ter solution heat treatment.The results indicated that the mechanical properties and corrosion resistance of the Cr18. 4Mn5.98Ni4.62N0.42 austenitic stainless steel are similar to that of"304"stainless steel.The microstructural evo-lution after aging treatment, stability of austenite during cold working and the phase change process of martensite induced by deformation were analyzed.The results indicate that the nose temperature of Cr2N phase precipitation is 800℃, and with the increase in the annealing time, granular Cr2N phases precipitate along grain boundaries first-ly, and then lamellar precipitates begin to grow into grains

  8. 热处理工艺对超级马氏体钢逆变奥氏体的影响%Effect of heat treatment technology on reversed austenite in super martensitic stainless steel

    Institute of Scientific and Technical Information of China (English)

    姜雯; 赵昆渝; 业冬; 李俊; 苏杰; 雍岐龙

    2015-01-01

    The effect of adding different content of Cr to the super martensitic stainless steel (SMSS) on formation of re-versed austenite subjected to quenching and tempering by using optical microscope(OM),X-ray diffraction (XRD),trans-mission electron microscope (TEM) and energy dispersive spectrometer(EDS) was studied. The experimental results indi-cate that the microstructures of two tested steels were tempered martensite and reversed austenite after tempering. The vol-ume fraction and grain size of reversed austenite in two tested steels increased first and then decreased with the increase of tempering temperature,which reached the maximum at 650-700℃. When the reversed austenite re-dissolved and trans-formed to martensite,there was an effect of refinement on the matrix. Compared with 13Cr steels,the reversed austenite in 15Cr steels was more and the size was bigger. The effect of refinement on the matrix was more obvious.%试验采用光学显微镜、X射线衍射仪(XRD)、透射电镜(TEM)及能谱分析(EDS)等手段,研究不同铬含量的超级马氏体不锈钢在相同热处理工艺下逆变奥氏体含量、组织形貌及生长规律的异同。结果表明,13Cr和15Cr两试验钢经淬火+回火后的显微组织为回火马氏体和逆变奥氏体,两试验钢中逆变奥氏体含量及尺寸均随着回火温度升高先增加再减小,且在650~700℃时达到最大。两试验钢内的逆变奥氏体在回溶过程中会对基体组织产生细化作用。通过对比发现,15Cr钢中的逆变奥氏体含量更多,尺寸更大,回溶时对基体的细化作用更明显。

  9. High Temperature Softening Behaviors and Flow Stress Model for a High Molybdenum Austenitic Stainless Steel%高钼奥氏体不锈钢高温软化行为与流变应力模型

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Single-stage and double-stage interrupted hot compression tests for physical simulating hot rolling have been carried out on the THERMECMATSTOR-Z simulator for 00Cr20Ni18Mo6Cu[ N] austenitic stainless steel under high temperature (1223~1373 K) and various strain rates (0.1~60 s- 1 ). The high temperature mechanical behaviors and microstructure evolution of the steel were studied. The activation energies of hot deformation and dynamic, static and metadynamic recrystallization were calculated. Serials of perfect flow stress model considering dynamic recrystallization were established. The predicted result by the model was well agreed with the experiment data.The kinetics of metadynamic and static recrystallization had also been determined.

  10. Evaluation of Cutting Fluids in Multiple Reaming of Stainless Steel

    DEFF Research Database (Denmark)

    Belluco, Walter; Zeng, Z.; De Chiffre, Leonardo

    2001-01-01

    subsequent reaming operations were carried out on austenitic stainless steel using high-speed-steel and solid carbide tools. The tested fluids were all significantly different from the reference fluid in at least some of the tested conditions. Significant differences down to 2 percent in cutting forces and 6...

  11. Evaluation of structural behaviour and corrosion resistant of austenitic AISI 304 and duplex AISI 2304 stainless steel reinforcements embedded in ordinary Portland cement mortars; Evaluacion del comportamiento estructural y de resistencia a la corrosion de armaduras de acero inoxidable austenitico AISI 304 y duplex AISI 2304 embebidas en morteros de cemento Portland

    Energy Technology Data Exchange (ETDEWEB)

    Medina, E.; Cobo, A.; Bastidas, D. M.

    2012-07-01

    The mechanical and structural behaviour of two stainless steels reinforcements, with grades austenitic EN 1.4301 (AISI 304) and duplex EN 1.4362 (AISI 2304) have been studied, and compared with the conventional carbon steel B500SD rebar. The study was conducted at three levels: at rebar level, at section level and at structural element level. The different mechanical properties of stainless steel directly influence the behaviour at section level and structural element level. The study of the corrosion behaviour of the two stainless steels has been performed by electrochemical measurements, monitoring the corrosion potential and the lineal polarization resistance (LPR), of reinforcements embedded in ordinary Portland cement (OPC) mortar specimens contaminated with different amount of chloride over one year time exposure. Both stainless steels specimens embedded in OPC mortar remain in the passive state for all the chloride concentration range studied after one year exposure. (Author) 26 refs.

  12. Modelling of composition and stress profiles in low temperature surface engineered stainless steel

    DEFF Research Database (Denmark)

    Jespersen, Freja Nygaard; Hattel, Jesper Henri; Somers, Marcel A. J.

    2015-01-01

    Thermochemical surface engineering by nitriding/carburizing of stainless steel causes a surface zone of expanded austenite, which improves the wear resistance of the stainless steel while preserving the stainless behavior. As a consequence of the thermochemical surface engineering, huge residual...

  13. Properties of duplex stainless steels made by powder metallurgy

    OpenAIRE

    Rosso, M.; M. Actis Grande; Z. Brytan; L.A. Dobrzański

    2007-01-01

    Purpose: of this paper was to examine the mechanical properties of duplex stainless steels.Design/methodology/approach: In presented study duplex stainless steels were obtained through powder metallurgy starting from austenitic, martensitic base powders by controlled addition of alloying elements, such as Cr, Ni, Mo and Cu. In the studies behind the preparation of mixes, Schaeffler’s diagram was taken into consideration. Prepared mixes have been sintered in a vacuu...

  14. Production of Austenitic Steel for the LHC Superconducting Dipole Magnets

    CERN Document Server

    Bertinelli, F; Komori, T; Peiro, G; Rossi, L

    2006-01-01

    The austenitic-steel collars are an important component of the LHC dipole magnets, operating at cryogenic temperature under high mechanical stress. The required steel, known as YUS 130S, has been specifically developed for this application by Nippon Steel Corporation (NSC), who was awarded a CERN contract in 1999 for the supply of 11 500 tonnes. In 2005 - after six years of work - the contract is being successfully completed, with final production being ensured since October 2003 by Nippon Steel & Sumikin Stainless Steel Corporation (NSSC). The paper describes the steel properties, its manufacturing and quality control process, organization of production, logistics and contract follow-up. Extensive statistics have been collected relating to mechanical, physical and technological parameters. Specific attention is dedicated to measurements of magnetic permeability performed at cryogenic temperatures by CERN, the equipment used and statistical results. Reference is also made to the resulting precision of the...

  15. Studies of Hot Crack Properties of Laser Welded Stainless Steel

    DEFF Research Database (Denmark)

    Juhl, Thomas Winther

    During the present work crack testing concerning small and fast solidifying laser welds in austenitic stainless steel has been studied. A set of methods has been applied to investigate alloy properties, including ·Application of known information to predict solidification phases from the alloy...... investigated and recommendations are given. From studies of literature it is found that the austenitic stainless steels have lowest crack susceptibility by a solidification course leaving approximately 15% rest ferrite in the weld metal. The alloys properties and the solidification rate determines the amount...

  16. New Stainless Steel Alloys for Low Temperature Surface Hardening?

    DEFF Research Database (Denmark)

    Christiansen, Thomas Lundin; Dahl, Kristian Vinter; Somers, Marcel A. J.

    2015-01-01

    The present contribution showcases the possibility for developing new surface hardenable stainless steels containing strong nitride/carbide forming elements (SNCFE). Nitriding of the commercial alloys, austenitic A286, and ferritic AISI 409 illustrates the beneficial effect of having SNCFE present...... in the stainless steel alloys. The presented computational approach for alloy design enables “screening” of hundreds of thousands hypothetical alloy systems by use of Thermo-Calc. Promising compositions for new stainless steel alloys can be selected based on imposed criteria, i.e. facilitating easy selection...

  17. Investigation of the Hot Plasticity of Duplex Stainless Steel

    Institute of Scientific and Technical Information of China (English)

    LIN Gang; ZHANG Zhi-xia; SONG Hong-wei; TONG Jun; ZHOU Can-dong

    2008-01-01

    Hot plasticity of a nitrogen alloyed 25Cr-7Ni-4 Mo duplex stainless steel was investigated.The results indicate that thc main factors affecting the hot plasticity of duplex stainless steel are listed as follows:coalescent force of phase interface,microstructure,and the phase ratio and difference between the mechanicsl propertms of ferrite and austenite.The heat treatment and sulphur contents have a notable effect on the hot plasticity.The reasonable heat treatrnents and the irlcreased interfacial coalescent force will effectively enhance the hot plasticity of duplex stainless steel.

  18. EXAFS investigation of low temperature nitrided stainless steel

    DEFF Research Database (Denmark)

    Oddershede, Jette; Christiansen, Thomas; Ståhl, Kenny

    2008-01-01

    Low temperature nitrided stainless steel AISI 316 flakes were investigated with EXAFS and X-ray diffraction analysis. The stainless steel flakes were transformed into a mixture of nitrogen expanded austenite and nitride phases. Two treatments were carried out yielding different overall nitrogen...... contents: (1) nitriding in pure NH3 and (2)nitriding in pure NH3 followed by reduction in H2. The majority of the Cr atoms in the stainless steel after treatment 1 and 2 was associated with a nitrogen–chromium bond distance comparable to that of the chemical compound CrN. The possibility of the occurrence...

  19. Thermal treatments effect on the austenite-ferrite equilibrium in a duplex stainless steel weld beads; Effet des traitements thermiques sur l equilibre austenite - ferrite dans un cordon de soudure en acier inoxydable duplex

    Energy Technology Data Exchange (ETDEWEB)

    Belkessa, Brahim; Badji, Riad; Bettahar, Kheireddine; Maza, Halim [Division de la Metallurgie et Mecanique. Centre de Recherche Scientifique et Technique en Soudage et Controle. B.P 64, Route de Dely Ibrahim, Cheraga, Alger (Algeria)

    2006-07-01

    Heat treatments in the temperature range between 800 to 1200 C, with a keeping at high temperature of 60 min, followed by a water quenching at 20 C, have been carried out on austeno-ferritic stainless steel welds (of type SAF 2205-UNS S31803). The heat treatments carried out at temperatures below 1000 C have modified the structure of the duplex stainless steel 2205 in inducing the formation of precipitates, identified by X-ray diffraction as being the intermetallic compound {sigma} and the chromium carbides M{sub 23}C{sub 6}. The treatments applied to temperatures superior to 1000 C shift the {delta}-{gamma} equilibrium towards the {delta} phase. Indeed, the increase of the ferrite rate with the treatment temperature is approximately linear. The ferrite rates are higher in the heat-affected zone, which has been submitted to a ferritizing due to the welding thermal effects. (O.M.)

  20. Comparison of the fatigue behavior and residual stress stability of laser-shock peened and deep rolled austenitic stainless steel AISI 304 in the temperature range 25-600 deg. C

    Energy Technology Data Exchange (ETDEWEB)

    Nikitin, I. [Institute of Materials Engineering, University of Kassel (Germany)], E-mail: nikitin@uni-kassel.de; Altenberger, I. [Institute of Materials Engineering, University of Kassel (Germany)

    2007-09-15

    Laser-shock peening and deep rolling were applied to an austenitic stainless steel AISI 304 and the effects on the fatigue life were investigated. Isothermal push-pull fatigue tests were performed in the temperature range 25-600 deg. C. The results of the investigations, e.g. s/n curves, cyclic deformation curves as well as the residual stress stability of the laser-shock peened condition were compared to untreated and deep rolled conditions. Near-surface regions were characterized using X-ray diffraction methods, transmission electron microscopy (TEM) and focused ion beam microscopy (FIB). The different near-surface microstructures as well as residual stress stabilities of laser-shock peened and deep rolled specimens were investigated and discussed.

  1. Numerical simulation of austenitic stainless steel strength and ductility at room temperature%奥氏体不锈钢室温强度和塑性的数值模拟计算

    Institute of Scientific and Technical Information of China (English)

    李冬升; 戴起勋; 程晓农; 邵新中; 王国建

    2012-01-01

    Based on the experimental data and the extensive results of the author's research, the author studied the relation between elements and mechanical properties of austenitic stainless steels at room temperature. According to a large number of experimental results, the quantitative calculational equation of strength and elongation are obtained by computer processing.%在理论研究和试验的基础上,结合各研究者实验数据和作者的大量研究结果,研究了奥氏体不锈钢室温强度和塑性与合金元素的变化规律,经计算机处理得到了室温强度、伸长率的定量计算的表达式.

  2. Effects of nitrogen and pulsed mean welding current in AISI 316 austenitic stainless steel solidification cracks; Efecto del nitrogeno y la corriente media pulsada de soldadura en la formacion de grietas de solidificacion en aceros inoxidables AISI 316L

    Energy Technology Data Exchange (ETDEWEB)

    Trevisan, R. E.; Braga, E.; Fals, H. C.

    2002-07-01

    An analysis of the influence of nitrogen concentration in the weld zone and the pulsed mean welding current in the solidification crack formation is presented in this paper. The AISI 316L austenitic stainless steel was employed as the metal base. The welding was done using CC+ pulsed flux cored are welding process and AWS E316L wire type. The tests were conducted using CO{sub 2} shielding gas with four different nitrogen levels (0,5; 10 and 15%) in order to induce different nitrogen weld metal concentrations. The pulsed mean welding current was varied in three levels and the. Transvarestraint tangential strain test was fixed of 5%. The results showed that the solidification cracking decreased as the pulsed mean welding current increase. It was also verified that an increase of the weld zone nitrogen level was associated with a decrease in both the total length of solidification crack and the amount of {delta} ferrite. (AUthor) 20 refs.

  3. Cyclic plasticity of an austenitic-ferritic stainless steel under biaxial non proportional loading; Plasticite cyclique d'un acier inoxydable austeno-ferritique sous chargement biaxial non-proportionnel

    Energy Technology Data Exchange (ETDEWEB)

    Aubin, V

    2001-11-15

    Austenitic-ferritic stainless steels are supplied since about 30 years only, so they are yet not well-known. Their behaviour in cyclic plasticity was studied under uniaxial loading but not under multiaxial loading, whereas only a thorough knowledge of the phenomena influencing the mechanical behaviour of a material enables to simulate and predict accurately its behaviour in a structure. This work aims to study and model the behaviour of a duplex stainless steel under cyclic biaxial loading. A three step method was adopted. A set of tension-torsion tests on tubular specimen was first defined. We studied the equivalence between loading directions, and then the influence of loading path and loading history on the stress response of the material. Results showed that duplex stainless steel shows an extra-hardening under non proportional loading and that its behaviour depends on previous loading. Then, in order to analyse the results obtained during this first experimental stage, the yield surface was measured at different times during cyclic loading of the same kind. A very small plastic strain offset (2*10{sup -5}) was used in order not to disturb the yield surface measured. The alteration of isotropic and kinematic hardening variables were deduced from these measures. Finally, three phenomenological constitutive laws were identified with the experimental set. We focused our interest on the simulation of stabilized stress levels and on the simulation of the cyclic hardening/softening behaviour. The comparison between experimental and numerical results enabled the testing of the relevance of these models. (authors)

  4. Salt bath nitriding of 304 austenitic stainless steel at low temperature and corrosion resistance of nitriding layer%304奥氏体不锈钢低温盐浴氮化处理及其耐蚀性

    Institute of Scientific and Technical Information of China (English)

    黄润波; 闫静; 曾德志; 张太平; 胡泽晶; 罗伟; 王均

    2012-01-01

    采用低温(430℃)盐浴对304奥氏体不锈钢进行氮化处理,研究了氮化时间对渗氮层组织,显微硬度及耐蚀性的影响.分别用X射线衍射仪(XRD)、表面显微硬度计、光学显微镜分析了渗氮层的相组成、显微硬度、截面形貌和厚度.结果表明,304不锈钢表面的渗氮层厚度和显微硬度都随处理时间的延长而增大.氮化处理1h得到的渗氮层由单一的S相组成.经盐浴渗氮处理的304不锈钢,其耐Cl-点蚀性能得到改善,430℃下氮化4h得到的渗氮层耐蚀性能最好.%304 austenitic stainless steel was nitrided in a salt bath at low temperature (430 °C). The effects of nitriding time on microstructure, microhardness, and corrosion resistance of nitriding layer were studied. The phase composition, microhardness, cross-sectional morphology, and thickness of nitriding layer were examined by X-ray diffraction (XRD), microhardness tester, and optical microscopy. The results showed that the thickness and microhardness of nitriding layer on 304 stainless steel substrate are increased with the increasing of nitriding time. The layer obtained by nitriding for 1 h is composed of a single S phase. The 304 stainless steel shows improved corrosion resistance by nitriding and exhibits optimal corrosion resistance after nitriding for 4 h.

  5. On High-Temperature Materials: A Case on Creep and Oxidation of a Fully Austenitic Heat-Resistant Superalloy Stainless Steel Sheet

    Directory of Open Access Journals (Sweden)

    A. Kanni Raj

    2013-01-01

    Full Text Available The creep behavior of AISI 310S stainless steel taken from SAIL’s Salem stainless steel plant has been investigated by constant load tensile creep test at the temperatures of 973, 1023, and 1073 K and loads of 66.6, 74.8, 86.6, and 94.8 MPa. It exhibits steady-state creep behavior in most test conditions. The double logarithm plot of rupture life and applied stress yielded straight lines at all the three test temperatures indicating that power-law creep due to dislocation climb is the operating mechanism of creep deformation. Linear relationship was obtained for plots of logarithm of rupture life against inverse temperature obeying Arrhenius type of temperature dependence with activation energy of 340 kJ/mol. The stress-rupture data yielded a master curve of Larson-Miller parameter. The plot of Monkman-Grant relationship is typical indicating that rupture is controlled by growth of grain boundary cavities. The metallographic examination of crept samples revealed formation of grain boundary voids and cracks leading to intergranular creep fracture. Deformation twins and carbide precipitates were also observed. Oxidation tests were also carried out isothermally at 973 K, 1023 K, and 1073 K in dry air. The plots of mass gain versus square root time were linear at all the three test temperatures obeying parabolic kinetics of oxidation. It was found that scales are well adherent to the substrate. The plot of parabolic rate constant and inverse temperature was linear giving an activation energy value of 210 kJ/mol. The metallographic examination of an oxidized sample reveals duplex types of scales. Finally, rupture properties are compared with that of AISI 600 iron-based superalloy and oxidation weight gain analysis with surface nanocrystalline AISI 310S stainless steel to analyze quantitatively its behavior.

  6. Paraequilibrium Carburization of Duplex and Ferritic Stainless Steels

    Science.gov (United States)

    Michal, G. M.; Gu, X.; Jennings, W. D.; Kahn, H.; Ernst, F.; Heuer, A. H.

    2009-08-01

    AISI 301 and E-BRITE stainless steels were subjected to low-temperature (743 K) carburization experiments using a commercial technology developed for carburization of 316 austenitic stainless steels. The AISI 301 steel contained ~40 vol pct ferrite before carburization but had a fully austenitic hardened case, ~20- μm thick, and a surface carbon concentration of ~8 at. pct after treatment; this “colossal” paraequilibrium carbon supersaturation caused an increase in lattice parameter of ~3 pct. The E-BRITE also developed a hardened case, 12- to 18- μm thick, but underwent a more modest (~0.3 pct) increase in lattice parameter; the surface carbon concentration was ~10 at. pct. While the hardened case on the AISI 301 stainless steel appeared to be single-phase austenite, evidence for carbide formation was apparent in X-ray diffractometer (XRD) scans of the E-BRITE. Paraequilibrium phase diagrams were calculated for both AISI 301 and E-BRITE stainless steels using a CALPHAD compound energy-based interstitial solid solution model. In the low-temperature regime of interest, and based upon measured paraequilibrium carbon solubilities, more negative Cr-carbon interaction parameters for austenite than those in the current CALPHAD data base may be appropriate. A sensitivity analysis involving Cr-carbon interaction parameters for ferrite found a strong dependence of carbon solubility on relatively small changes in the magnitude of these parameters.

  7. Physical properties of the AISI 348 L{sup *} austenitic stainless steel; Propriedades fisicas do aco inoxidavel austenitico AISI 348 L{sup *}

    Energy Technology Data Exchange (ETDEWEB)

    Teodoro, Celso Antonio; Lucki, Georgi; Silva, Jose Eduardo Rosa da; Terremoto, Luis Antanio Albiac; Castanheira, Myrthes; Damy, Margaret de Almeida [Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, SP (Brazil)]. E-mail: cteodoro@ipen.br

    2005-07-01

    The study of radiation damage in metals and alloys, used as structural materials of nuclear reactors has a strategic meaning in nuclear technology, because it allows the performance evaluation of these materials in working conditions of PWR. For this sake it is necessary to know the detrimental structural changes that occur during fast neutron irradiation. The aim of the present work is to show some strain-stress results of the AISI 348 L{sup *} stainless steel utilized as a structural material of the fuel elements of PWR, in comparison with the AISI 304. (author)

  8. Austenitic Oxide Dispersion Strengthened Steels : A Review

    Directory of Open Access Journals (Sweden)

    Lavanya Raman

    2016-06-01

    Full Text Available Materials play an important role in the fast breeder reactors.  Materials used in cladding tube and fuel pins should have better creep and void swelling resistance. To overcome these difficulties, a new class of material known as oxide dispersion strengthened (ODS steels are used. There are two groups of ODS steels, the ferritic and the austenitic ODS steels based on the matrix. The present paper reviews the current status of research in austenitic ODS steels. The interaction of dislocations with finely dispersed incoherent, hard particles that governs the strength and high temperature properties of ODS materials is briefly reviewed. The synthesis route adopted for these ODS steels, which is mostly through powder metallurgy route is also discussed. The role of various oxides such as Y2O3, ZrO2and TiO2and the clusters formed in these ODS steels on the mechanical properties and void swelling characteristics is also discussed.

  9. Long term properties and microstructural evolution of 18Cr-10Ni-3Cu-Ti-Nb austenitic stainless steel for boiler tube application

    Energy Technology Data Exchange (ETDEWEB)

    Minami, Y.; Fukui, T.; Ono, T. [TenarisNKK Tubes, Kawasaki, Kanagawa (Japan); Caminada, S. [TenarisDalmine, Dalmine, BG (Italy)

    2010-07-01

    The allowable tensile stress of 0.1C-18Cr-10Ni-3Cu-Ti-Nb steel (TEMPALOY AA-1; ASME C.C. 2512) is more than 30% higher compared with that of ASME SA-213 Grade TP347H in the temperature range 600-700 C. This high creep rupture strength is obtained by the precipitation of MC and M{sub 23}C{sub 6} carbides, and Cu-rich phase. Long term creep rupture tests over 10{sup 5}h enabled to verify the superior creep rupture strength of this steel. The investigation of microstructural evolution on the creep ruptured and aged specimens has shown the high structural stability of this material. Hardness and impact properties after high temperature aging reveal similar performance as conventional 18-8 stainless steels. Excellent steam oxidation resistance can be achieved by a shot-blasting method. The scale thickness of shot-blasted tube after 1000h at 750 C is below a few micron meters. These results have revealed that the mechanical properties and environmental resistance of this steel enable the use of TEMPALOY AA-1 in the latest generation of advanced USC boiler. (orig.)

  10. Assessment of Hot Crack Properties of Laser Welded Stainless Steel

    DEFF Research Database (Denmark)

    Juhl, Thomas Winther; Olsen, Flemming Ove

    2003-01-01

    Crack testing concerning small and fast solidifying laser welds in austenitic stainless steel has been studied. A set of methods has been applied to investigate alloy properties, including (1) Application of known information to predict solidification phases, (2) Weld metal solidification rate...

  11. Low temperature gaseous nitriding and carburising of stainless steel

    DEFF Research Database (Denmark)

    Christiansen, Thomas; Somers, Marcel A.J.

    2005-01-01

    The response of various austenitic and duplex stainless steel grades to low temperature gaseous nitriding and carburising was investigated. Gaseous nitriding was performed in ammonia/hydrogen mixtures at temperatures ,723 K; gaseous carburising was carried out in carbon monoxide/hydrogen mixtures...

  12. Effect of 16Cr Austenite Stainless Steel High Frequency Welding Parameters on Weld Microstructure and Properties%16Cr奥氏体不锈钢高频焊接参数对焊缝组织性能的影响

    Institute of Scientific and Technical Information of China (English)

    毕宗岳; 严培林; 余晗; 汪海涛

    2016-01-01

    In order to analyze the effect of 16Cr stainless steel high frequency welding parameter on weld microstructure and properties, under the different high frequency welding(HFW) parameters,the change of weld microstructure and properties of 16Cr stainless steel were studied by optical microscope(OM), scanning electron microscope(SEM) tensile test and bending test. The results showed that the weld formability of 16Cr austenitic stainless steel becomes better with the increase of welding speed. The content of δ-ferrite in weld show a trend of decrease after an initial increase with the increasing of welding heat input,accompanied by brittle σ-phase precipitation. The weld of 3.4 mm thickness 16Cr austenitic stainless steel has good formability,when welding speed about 10 m/min,welding heat input 2.9 kJ/cm, and with appropriate pressing force and the opening angle. The welded joints have good matching hardness and the weld tensile strength is close to the base material tensile strength. The microstructure of weld is mainly composed of austenite and δ-ferrite. But the welded joints have poor toughness, because of the oxide inclusions in weld.%为了分析16Cr不锈钢高频焊接参数对焊缝组织性能的影响,通过光学显微镜(OM)、扫描电镜(SEM)和拉伸、弯曲试验,分析了不同高频焊接参数下1Cr17Mn6Ni5N 不锈钢(以下简称16Cr不锈钢)焊缝组织与性能的变化情况。结果表明:16Cr奥氏体不锈钢高频焊随着焊接速度的增加,焊缝成形性能变好;焊缝中δ铁素体的含量随焊接热输入的增加先增后减,同时伴随σ脆性相析出;对于壁厚3.4 mm的16Cr奥氏体不锈钢,当焊接速度为10 m/min、焊接热输入为2.9 kJ/cm、并配以适当的挤压力和开口角时,焊缝成形及焊接接头硬度匹配良好,且焊缝抗拉强度接近母材抗拉强度,焊缝显微组织以奥氏体+δ铁素体为主,但由于焊缝存在大量

  13. Experimental Study on Edge-cracking in Austenitic Stainless Steel Cr15Mn9Cu2NiN during Hot Rolling%奥氏体不锈钢热轧边裂实验研究

    Institute of Scientific and Technical Information of China (English)

    朱亮; 魏鹏; 侯国清; 苏婷婷

    2012-01-01

    Austenitic stainless steel Crl5Mn9Cu2NiN is prone to suffer from edge cracking during hot rolling. Hot rolling test is conducted on an experimental hot rolling device, which is designed cooperate with thermal simulator. Formation mechanism of edge cracks is researched through this test. The resuks show thai, when press quantity reaches to a certain amount, samples will crack on edge at all test temperatures. All the edge cracks propagate along austenitic grain boundaries. In the range of 1000~l 1 50℃ deformation, cracking tendency of samples are severe, which is related to the reduction of ductility in austenitic stainless steel. The characteristic of microstructures in hot rolled specimens is deformation substructures and twins boundaries in coarse grains in this temperature range. But at 1200℃ deformation, the grain size of specimens is smaller, and all substructures and twins boundaries disappear in the grains.%奥氏体不锈钢Cr15Mn9Cu2NiN在热轧过程中容易产生边裂.在热模拟试验机上开发出热轧实验装置,进行热轧实验,分析该不锈钢边部裂纹产生的原因.结果表明,压下量达到一定程度时,在所有变形温度下,试样边部均会产生裂纹,裂纹均沿奥氏体晶界扩展.在1000~1150℃变形时裂纹倾向较大,分析认为这与奥氏体不锈钢在此温度区间内的延性下降有关.在该温度区间内,轧后试样的微观组织具有晶粒租大和晶粒内部变形亚结构与孪晶共同存在的特征,而在1200℃变形时,晶粒尺寸较小,晶粒内部的变形亚结构和孪晶全部消失.

  14. MICROSCOPIC CORROSION STUDIES OF DUPLEX STAINLESS STEELS

    Institute of Scientific and Technical Information of China (English)

    C.Leygraf; J.Pan; M.Femenia

    2004-01-01

    Electrochemical scanning tunneling microscopy and scanning electrochemical microscopy have been used for in situ monitoring of localized corrosion processes of different Duplex stainless steels (DSS) in acidic chloride solutions. The techniques allow imaging of local dissolution events with micrometer resolution, as opposed to conventional electrochemical techniques, which only give an overall view of the corrosion behavior. In addition, combined scanning Kelvin probe force microscopy and magnetic force microscopy were used for mapping the Volta potential variation over the surface of DSSs. A significant difference in Volta potential between the austenite and ferrite phases suggests galvanic interaction between the phases. A compositional gradient appears within 2 micrometers across the phase boundary, as seen with scanning Auger microscopy (SAM). In all, the studies suggest that higher alloyed DSS exhibit a more homogeneous dissolution behavior than lower alloyed DSS, due to higher and more similar corrosion resistance of the two phases, and enhanced resistance of the ferrite/austenite phase boundary regions.

  15. Improvement of mechanical properties on metastable stainless steels by reversion heat treatments

    OpenAIRE

    Mateo García, Antonio Manuel; Zapata, A.; Fargas Ribas, Gemma

    2013-01-01

    AISI 301LN is a metastable austenitic stainless steel that offers an excellent combination of high strength and ductility. This stainless grade is currently used in applications where severe forming operations are required, such as automotive bodies. When these metastable steels are plastically deformed at room temperature, for example by cold rolling, austenite transforms to martensite and, as a result, yield strength increases but ductility is reduced. Grain refinement is ...

  16. Deformation induced martensite in an AISI 301LN stainless steel: characterization and influence on pitting corrosion resistance

    OpenAIRE

    Hamilton Ferreira Gomes de Abreu; Sheyla Santana de Carvalho; Pedro de Lima Neto; Ricardo Pires dos Santos; Válder Nogueira Freire; Paulo Maria de Oliveira Silva; Sérgio Souto Maior Tavares

    2007-01-01

    In austenitic stainless steels, plastic deformation can induce martensite formation. The induced martensite is related to the austenite (gamma) instability at temperatures close or below room temperature. The metastability of austenite stainless steels increases with the decreasing of stacking fault energy (SFE). In this work, the deformation induced martensite was analyzed by X ray diffraction, electron back scatter diffraction (EBSD), magnetic methods and atomic force microscope (AFM) in sa...