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Sample records for austenitic steels approche

  1. Anelasticity in austenitic stainless steel

    International Nuclear Information System (INIS)

    Time-dependent anelastic deformation mechanisms arise in austenitic stainless steel when load is removed during a high-temperature creep test. This phenomenon is investigated by conducting creep tests, with intermittent load removal, on AISI Type 316H austenitic stainless steel at 550 and 650 °C, supported by in situ measurement of creep-induced intergranular residual strains by neutron diffraction. All the cyclic tests exhibit anelastic behaviour on unloading and develop substantially lower load-on creep strain rates, reduced ductility and longer rupture times than baseline steady-load creep tests at similar conditions. The mechanisms underlying the observed anelastic behaviour and changes in macroscopic creep properties are discussed with reference to the development of intergranular strains and dislocation behaviour.

  2. Consitutive modeling of metastable austenitic stainless steel

    NARCIS (Netherlands)

    Perdahcioglu, Emin Semih; Perdahcioglu, Emin Semih

    2008-01-01

    Metastable austenitic stainless steels combine high formability and high strength, which are generally opposing properties in materials. This property is a consequence of the martensitic phase transformation that takes place during deformation. This transformation is purely mechanically induced

  3. Expanded austenite in nitrided layers deposited on austenitic and super austenitic stainless steel grades

    International Nuclear Information System (INIS)

    Casteletti, L.C.; Fernandes, F.A.P.; Heck, S.C.; Gallego, J.

    2010-01-01

    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)

  4. Recycle of radiologically contaminated austenitic stainless steels

    International Nuclear Information System (INIS)

    Imrich, K.J.; Leader, D.R.; Iyer, N.C.; Louthan, M.R. Jr.

    1995-01-01

    The United States Department of Energy owns large quantities of radiologically contaminated austenitic stainless steel which could by recycled for reuse if appropriate release standards were in place. Unfortunately, current policy places the formulation of a release standard for USA industry years, if not decades, away. The Westinghouse Savannah River Company, Idaho National Engineering Laboratory and various university and industrial partners are participating in initiative to recycle previously contaminated austenitic stainless steels into containers for the storage and disposal of radioactive wastes. This paper describes laboratory scale experiments which demonstrated the decontamination and remelt of stainless steel which had been contaminated with radionuclides

  5. Austenitic stainless steels for cryogenic service

    International Nuclear Information System (INIS)

    Dalder, E.N.C.; Juhas, M.C.

    1985-01-01

    Presently available information on austenitic Fe-Cr-Ni stainless steel plate, welds, and castings for service below 77 K are reviewed with the intent (1) of developing systematic relationships between mechanical properties, composition, microstructure, and processing, and (2) of assessing the adequacy of these data bases in the design, fabrication, and operation of engineering systems at 4 K

  6. 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.

  7. Local approach: fracture at high temperature in an austenitic stainless steel submitted to thermomechanical loadings. Calculations and experimental validations; Approche locale: fissuration a haute temperature dans un acier inoxydable austenitique sous chargements thermomecaniques. Simulations numeriques et validations experimentales

    Energy Technology Data Exchange (ETDEWEB)

    Poquillon, D

    1997-10-01

    Usually, for the integrity assessment of defective components, well established rules are used: global approach to fracture. A more fundamental way to deal with these problems is based on the local approach to fracture. In this study, we choose this way and we perform numerical simulations of intergranular crack initiation and intergranular crack propagation. This type of damage can be find in components of fast breeder reactors in 316 L austenitic stainless steel which operate at high temperatures. This study deals with methods coupling partly the behaviour and the damage for crack growth in specimens submitted to various thermomechanical loadings. A new numerical method based on finite element computations and a damage model relying on quantitative observations of grain boundary damage is proposed. Numerical results of crack initiation and growth are compared with a number of experimental data obtained in previous studies. Creep and creep-fatigue crack growth are studied. Various specimen geometries are considered: compact Tension Specimens and axisymmetric notched bars tested under isothermal (600 deg C) conditions and tubular structures containing a circumferential notch tested under thermal shock. Adaptative re-meshing technique and/or node release technique are used and compared. In order to broaden our knowledge on stress triaxiality effects on creep intergranular damage, new experiments are defined and conducted on sharply notched tubular specimens in torsion. These isothermal (600 deg C) Mode II creep tests reveal severe intergranular damage and creep crack initiation. Calculated damage fields at the crack tip are compared with the experimental observations. The good agreement between calculations and experimental data shows the damage criterion used can improve the accuracy of life prediction of components submitted to intergranular creep damage. (author) 200 refs.

  8. 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.

  9. Ultrasonic testing of austenitic stainless steel welds

    International Nuclear Information System (INIS)

    Nishino, Shunichi; Hida, Yoshio; Yamamoto, Michio; Ando, Tomozumi; Shirai, Tasuku.

    1982-05-01

    Ultrasonic testing of austenitic stainless steel welds has been considered difficult because of the high noise level and remarkable attenuation of ultrasonic waves. To improve flaw detectability in this kind of steel, various inspection techniques have been studied. A series of tests indicated: (1) The longitudinal angle beam transducers newly developed during this study can detect 4.8 mm dia. side drilled holes in dissimilar metal welds (refraction angle: 55 0 from SUS side, 45 0 from CS side) and in cast stainless steel welds (refraction angle: 45 0 , inspection frequency: 1 MHz). (2) Cracks more than 5% t in depth in the heat affected zones of fine-grain stainless steel pipe welds can be detected by the 45 0 shear wave angle beam method (inspection frequency: 2 MHz). (3) The pattern recognition method using frequency analysis technology was presumed useful for discriminating crack signals from spurious echoes. (author)

  10. Solidification cracking in austenitic stainless steel welds

    Indian Academy of Sciences (India)

    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 ...

  11. Static strain aging in austenitic stainless steels

    International Nuclear Information System (INIS)

    Monteiro, S.N.

    1978-07-01

    The static strain aging effects were investigated in austenitic stainless steels by measuring the yield points developed in tensile tests following the arrest of the crosshead for some period of time. The results appear to indicate that the dragging of dislocations in the interval of temperatures from 100 to 300 0 C, where the strain aging is effective, does not apparently depend on the Cottrell's atmosphere. Moreover the influence of the pre-deformation and time on the yield point intensity displayed the existence of stages. The strain aging mechanics and the reasons for the stages were discussed. (Author) [pt

  12. Ion-nitriding of austenitic stainless steels

    International Nuclear Information System (INIS)

    Pacheco, O.; Hertz, D.; Lebrun, J.P.; Michel, H.

    1995-01-01

    Although ion-nitriding is an extensively industrialized process enabling steel surfaces to be hardened by nitrogen diffusion, with a resulting increase in wear, seizure and fatigue resistance, its direct application to stainless steels, while enhancing their mechanical properties, also causes a marked degradation in their oxidation resistance. However, by adaption of the nitriding process, it is possible to maintain the improved wear resistant properties while retaining the oxidation resistance of the stainless steel. The controlled diffusion permits the growth of a nitrogen supersaturated austenite layer on parts made of stainless steel (AISI 304L and 316L) without chromium nitride precipitation. The diffusion layer remains stable during post heat treatments up to 650 F for 5,000 hrs and maintains a hardness of 900 HV. A very low and stable friction coefficient is achieved which provides good wear resistance against stainless steels under diverse conditions. Electrochemical and chemical tests in various media confirm the preservation of the stainless steel characteristics. An example of the application of this process is the treatment of Reactor Control Rod Cluster Assemblies (RCCAs) for Pressurized Water Nuclear Reactors

  13. Cast alumina forming austenitic stainless steels

    Science.gov (United States)

    Muralidharan, Govindarajan; Yamamoto, Yukinori; Brady, Michael P

    2013-04-30

    An austenitic stainless steel alloy consisting essentially of, in terms of weight percent ranges 0.15-0.5C; 8-37Ni; 10-25Cr; 2.5-5Al; greater than 0.6, up to 2.5 total of at least one element selected from the group consisting of Nb and Ta; up to 3Mo; up to 3Co; up to 1W; up to 3Cu; up to 15Mn; up to 2Si; up to 0.15B; up to 0.05P; up to 1 total of at least one element selected from the group consisting of Y, La, Ce, Hf, and Zr; steel alloys is also disclosed.

  14. Nickel-free austenitic stainless steels for medical applications.

    Science.gov (United States)

    Yang, Ke; Ren, Yibin

    2010-02-01

    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.

  15. Low-temperature creep of austenitic stainless steels

    Science.gov (United States)

    Reed, R. P.; Walsh, R. P.

    2017-09-01

    Plastic deformation under constant load (creep) in austenitic stainless steels has been measured at temperatures ranging from 4 K to room temperature. Low-temperature creep data taken from past and unreported austenitic stainless steel studies are analyzed and reviewed. Creep at cryogenic temperatures of common austenitic steels, such as AISI 304, 310 316, and nitrogen-strengthened steels, such as 304HN and 3116LN, are included. Analyses suggests that logarithmic creep (creep strain dependent on the log of test time) best describe austenitic stainless steel behavior in the secondary creep stage and that the slope of creep strain versus log time is dependent on the applied stress/yield strength ratio. The role of cold work, strain-induced martensitic transformations, and stacking fault energy on low-temperature creep behavior is discussed. The engineering significance of creep on cryogenic structures is discussed in terms of the total creep strain under constant load over their operational lifetime at allowable stress levels.

  16. Prediction on Austenite Grain Growth in High Carbon Steel

    Directory of Open Access Journals (Sweden)

    MA Han

    2017-01-01

    Full Text Available The austenite grain growth behavior of Ti-bearing and Ti-free steel was investigated using confocal laser scanning microscope (CLSM and transmission electron microscope (TEM.Samples were held for 60min at 1123-1473K and then austenite grain sizes for different holding time at a series of temperatures were measured.The results show that austenite grain size of both steels increases with the increase of temperature.Besides,the austenite grain size of both steels grows with the holding time,which meets parabolic equation.The second phase particle was observed.The equation of Ostwald ripening was introduced to calculate the size of particle,and the volume fraction equation of second phase particle was applied to calculate the volume fraction of particle.Meanwhile,the modified Gladman model was adopted to predict austenite grain growth.The predicted results agree well with the measured results.

  17. High cycle fatigue of austenitic stainless steels

    International Nuclear Information System (INIS)

    Gauthier, J.P.; Lehmann, D.; Picker

    1990-01-01

    This study concerns the evaluation of material data to be used in LMFBR design codes. High cycle fatigue properties of three austenitic stainless steels are evaluated: type AISI 316 (UKAEA tests), type AISI 316L (CEA tests) and type AISI 304 (Interatom tests). The data on these steels comprised some 550 data points from 14 casts. This data set covered a wide range of testing parameters: temperature from 20-625 0 C, frequency from 1-20 000 Hz, constant amplitude and random fatigue loading, with and without mean stress, etc. However, the testing conditions chosen by the three partners differed considerably because they had been fixed independently and not harmonized prior to the tests. This created considerable difficulties for the evaluations. Experimental procedures and statistical treatments used for the three subsets of data are described and discussed. Results are presented in tables and graphs. Although it is often difficult to single out the influence of each parameter due to the different testing conditions, several interesting conclusions can be drawn: The HCF properties of the three steels are consistent with the 0.2% proof stress, the fatigue limit being larger than the latter at temperatures above 550 0 C. The type 304 steel has lower tensile properties than the two other steels and hence also lower HCF properties. Parameters which clearly have a significant effect of HCF behaviour are mean stress or R-ratio (less in the non-endurance region than in the endurance region), temperature, cast or product. Other parameters have probably a weak or no effect but it is difficult to conclude due to insufficient data: environment, specimen orientation, frequency, specimen geometry

  18. Abnormal growth of austenite grain of low-carbon steel

    International Nuclear Information System (INIS)

    Yu Qingbo; Sun Ying

    2006-01-01

    Niobium is an important alloying element for the steel. To know further the effect of Nb in the steel, the contrast experiments on the austenite grain growth of the 0.015%Nb and free Nb steels were carried out using Gleeble 1500 thermomechanical simulator. The experimental results indicate that the austenite grain of 0.015%Nb steel is finer than that of Nb free steel at 1150-1230 deg. C. And when the heating temperature arrives the critical temperature 1240 deg. C, the austenite grain of Nb steel suddenly grows up, while the austenite grain of Nb free steel changes little. Finally, the austenite grain of Nb steel is obviously coarser than that of Nb free steel. By transmission electron microscopy (TEM) using a carbon extraction replica technique, the precipitates of Nb(C,N) were not observed in the 0.015%Nb steel. It is concluded that the grain-boundary internal adsorption of Nb atoms leads to the result

  19. Microstructural evolution in deformed austenitic TWinning Induced Plasticity steels

    NARCIS (Netherlands)

    Van Tol, R.T.

    2014-01-01

    This thesis studies the effect of plastic deformation on the stability of the austenitic microstructure against martensitic transformation and diffusional decomposition and its role in the phenomenon of delayed fracture in austenitic manganese (Mn)-based TWinning Induced Plasticity (TWIP) steels.

  20. Nanostructured Bainite-Austenite Steel for Armours Construction

    Directory of Open Access Journals (Sweden)

    Burian W.

    2014-10-01

    Full Text Available Nanostructured bainite-austenite steels are applied in the armours construction due to their excellent combination of strength and ductility which enables to lower the armour weight and to improve the protection efficiency. Mechanical properties of the bainite-austenite steels can be controlled in the wide range by chemical composition and heat treatment. In the paper the results of investigation comprising measuring of quasi - static mechanical properties, dynamic yield stress and firing tests of bainite-austenite steel NANOS-BA® are presented. Reported results show that the investigated bainite-austenite steel can be used for constructing add-on armour and that the armour fulfils requirements of protection level 2 of STANAG 4569. Obtained reduction in weight of the tested NANOS-BA® plates in comparison with the present solutions is about 30%.

  1. Effects of austenitizing temperature in quenched niobium steels

    International Nuclear Information System (INIS)

    Mello, F.B.C. de; Assuncao, F.C.R.

    1980-01-01

    Three steel compositions with varying Nb content were austenitized at different temperatures and quenched in cold water. Metallographic examination and hardness measurements provided a basis for explaining the hardening mechanism and the role of Nb on the process. (Author) [pt

  2. Reverted austenite in PH 13-8 Mo maraging steels

    International Nuclear Information System (INIS)

    Schnitzer, Ronald; Radis, Rene; Noehrer, Matthias; Schober, Michael; Hochfellner, Rainer; Zinner, Silvia; Povoden-Karadeniz, E.; Kozeschnik, Ernst; Leitner, Harald

    2010-01-01

    The mechanical properties of maraging steels are strongly influenced by the presence of reverted austenite. In this study, the morphology and chemical composition of reverted austenite in a corrosion resistant maraging steel was characterized using transmission electron microscopy (TEM) and atom probe tomography (APT). Two types of austenite, i.e. granular and elongated, are present after aging at 575 o C, whereby the content of the latter increases during aging. The investigations revealed that the austenite phase is enriched in Ni, which prevents the transformation to martensite during cooling. Inside and next to the austenitc areas, Mo and Cr-rich carbides, which form during the aging treatment, were found. Various aging treatments were performed to obtain the activation energy for the formation of reverted austenite. Additionally, the experimental data are compared with thermodynamic and kinetic simulations. Based on these results and the chemical composition changes of the phases, a model for the formation of reverted austenite is presented. It is concluded that precipitation of B2-ordered NiAl and formation of reverted austenite take place simultaneously during aging and that dissolution of precipitates is not essential for the initial formation of reverted austenite.

  3. Interpretation of dynamic tensile behavior by austenite stability in ferrite-austenite duplex lightweight steels.

    Science.gov (United States)

    Park, Jaeyeong; Jo, Min Cheol; Jeong, Hyeok Jae; Sohn, Seok Su; Kwak, Jai-Hyun; Kim, Hyoung Seop; Lee, Sunghak

    2017-11-16

    Phenomena occurring in duplex lightweight steels under dynamic loading are hardly investigated, although its understanding is essentially needed in applications of automotive steels. In this study, quasi-static and dynamic tensile properties of duplex lightweight steels were investigated by focusing on how TRIP and TWIP mechanisms were varied under the quasi-static and dynamic loading conditions. As the annealing temperature increased, the grain size and volume fraction of austenite increased, thereby gradually decreasing austenite stability. The strain-hardening rate curves displayed a multiple-stage strain-hardening behavior, which was closely related with deformation mechanisms. Under the dynamic loading, the temperature rise due to adiabatic heating raised the austenite stability, which resulted in the reduction in the TRIP amount. Though the 950 °C-annealed specimen having the lowest austenite stability showed the very low ductility and strength under the quasi-static loading, it exhibited the tensile elongation up to 54% as well as high strain-hardening rate and tensile strength (1038 MPa) due to appropriate austenite stability under dynamic loading. Since dynamic properties of the present duplex lightweight steels show the excellent strength-ductility combination as well as continuously high strain hardening, they can be sufficiently applied to automotive steel sheets demanded for stronger vehicle bodies and safety enhancement.

  4. Austenitic stainless steel for high temperature applications

    International Nuclear Information System (INIS)

    Johnson, G. D.; Powell, R. W.

    1985-01-01

    This invention describes a composition for an austenitic stainless steel which has been found to exhibit improved high temperature stress rupture properties. The composition of this alloy is about (in wt. %): 12.5 to 14.5 Cr; 14.5 to 16.5 Ni; 1.5 to 2.5 Mo; 1.5 to 2.5 Mn; 0.1 to 0.4 Ti; 0.02 to 0.08 C; 0.5 to 1.0 Si; 0.01 maximum, N; 0.02 to 0.008 P; 0.002 to 0.008 B; 0.004-0.0010 S; 0.02-0.05 Nb; 0.01-0.05 V; 0.005-0.02 Ta; 0.02-0.05 Al; 0.01-0.04 Cu; 0.02-0.05 Co; 0.03 maximum, As; 0.01 maximum, O; 0.01 maximum, Zr; and with the balance of the alloy being essentially iron. The carbon content of the alloy is adjusted such that wt. % Ti/(wt. % C+wt. % N) is between 4 and 6, and most preferably about 5. In addition the sum of the wt. % P+wt. % B+wt. % S is at least 0.03 wt. %. This alloy is believed to be particularly well suited for use as fast breeder reactor fuel element cladding

  5. Solidification behavior of austenitic stainless steel filler metals

    International Nuclear Information System (INIS)

    David, S.A.; Goodwin, G.M.; Braski, D.N.

    1980-02-01

    Thermal analysis and interrupted solidification experiments on selected austenitic stainless steel filler metals provided an understanding of the solidification behavior of austenitic stainless steel welds. The sequences of phase separations found were for type 308 stainless steel filler metal, L + L + delta + L + delta + γ → γ + delta, and for type 310 stainless steel filler metal, L → L + γ → γ. In type 308 stainless steel filler metal, ferrite at room temperature was identified as either the untransformed primary delta-ferrite formed during the initial stages of solidification or the residual ferrite after Widmanstaetten austenite precipitation. Microprobe and scanning transmission electron microscope microanalyses revealed that solute extensively redistributes during the transformation of primary delta-ferrite to austenite, leading to enrichment and stabilization of ferrite by chromium. The type 310 stainless steel filler metal investigated solidifies by the primary crystallization of austenite, with the transformation going to completion at the solidus temperature. In our samples residual ferrite resulting from solute segregation was absent at the intercellular or interdendritic regions

  6. Effect of Austenite Stability on Pack Aluminizing of Austenitic Stainless Steels

    Science.gov (United States)

    Lopez, Christopher; Kvryan, Armen; Kasnakjian, Shahan; Coronado, Armando; Sujittosakul, Sutine; Villalpando, Obed; Ravi, Vilupanur A.

    2015-01-01

    Aluminide coatings were applied to the surfaces of several austenitic stainless steels—UNS S30300, S30400, S30900, S31000, and S31600 (Type 303, 304, 309, 310, and 316)—by the halide activated pack cementation process. The coating compositions, microstructures, and hardness were determined for the different steels coated at 850°C for 25 h. The stability of the austenite phase for each type of steel was calculated by determining the ratio of the nickel to the chromium equivalents based on their nominal compositions. The thickness of the inner diffusion zone in the coating was shown to be inversely related to the austenite stability of the steels. Microhardness measurements were obtained across the coating thickness and into the substrate. The hardness values followed the same trends as the aluminum composition profile into the substrate.

  7. Precipitation reactions in austenitic stainless steels

    International Nuclear Information System (INIS)

    Hoch, M.; Yung-Shih Chen

    1979-01-01

    The precipitation reactions for commercial austenitic stainless steels (AISI type 347, 321, 316, 316L, 304 and 304L) and Ti-modified AISI type 316 SS were studied in the temperature range of 750 0 C-1350 0 C. Specimens were held at the temperature for 15 to 25 hours to ensure that equilibrium conditions were reached and followed by a water quench to prevent further precipitation reactions during cooling process. The precipitates were extracted from bulk specimens by anodic dissolution and identified by x-ray diffraction analysis. In Ti-stabilized 321 SS, large TiN and Ti 2 S (Ti 4 C 2 S2) precipitates were present in solution treated and subsequent annealed specimens. Small TiC precipitates were present in specimens annealed below 1150 0 C. The M 23 C 6 precipitates were found to be present after annealing at 850 0 C for 25 hours. The amount of M 23 C 6 was found to increase with decreased Ti content as shown in the Ti-motified 316 SS. In Nb-stabilized 347 SS, Nb(CN) precipitates were present in solution treated as well as annealed specimens. The M 23 C 6 precipitates were detected at an annealing temperature of 1050 0 C, which is higher than the precipitation temperature detected in 321 SS. Thermodynamic calculations were carried out to obtain the temperature where precipitation starts, and the temperatures where 50, 90 and 99% of the precipitates should be formed. The experimental results are in very good agreement with the calculations. (orig.) [de

  8. Failure of austenitic stainless steel tubes during steam generator operation

    OpenAIRE

    M. Głowacka; J. Łabanowski; S. Topolska

    2012-01-01

    Purpose: of this study is to analyze the causes of premature failure of steam generator coil made of austenitic stainless steel. Special attention is paid to corrosion damage processes within the welded joints.Design/methodology/approach: Examinations were conducted several segments of the coil made of seamless cold-formed pipes Ø 23x2.3 mm, of austenitic stainless steel grade X6CrNiTi18-10 according to EN 10088-1:2007. The working time of the device was 6 months. The reason for the withdrawa...

  9. Modeling of Non-isothermal Austenite Formation in Spring Steel

    Science.gov (United States)

    Huang, He; Wang, Baoyu; Tang, Xuefeng; Li, Junling

    2017-12-01

    The austenitization kinetics description of spring steel 60Si2CrA plays an important role in providing guidelines for industrial production. The dilatometric curves of 60Si2CrA steel were measured using a dilatometer DIL805A at heating rates of 0.3 K to 50 K/s (0.3 °C/s to 50 °C/s). Based on the dilatometric curves, a unified kinetics model using the internal state variable (ISV) method was derived to describe the non-isothermal austenitization kinetics of 60Si2CrA, and the abovementioned model models the incubation and transition periods. The material constants in the model were determined using a genetic algorithm-based optimization technique. Additionally, good agreement between predicted and experimental volume fractions of transformed austenite was obtained, indicating that the model is effective for describing the austenitization kinetics of 60Si2CrA steel. Compared with other modeling methods of austenitization kinetics, this model, which uses the ISV method, has some advantages, such as a simple formula and explicit physics meaning, and can be probably used in engineering practice.

  10. Residual stress studies of austenitic and ferritic steels

    International Nuclear Information System (INIS)

    Chrenko, R.M.

    1978-01-01

    Residual studies have been made on austenitic and ferritic steels of the types used as structural materials. The residual stress results presented here will include residual stress measurements in the heat-affected zone on butt welded Type 304 stainless steel pipes, and the stresses induced in Type 304 austenitic stainless steel and Type A508 ferritic steel by several surface preparations. Such surface preparation procedures as machining and grinding can induce large directionality effects in the residual stresses determined by X-ray techniques and some typical data will be presented. A brief description is given of the mobile X-ray residual stress apparatus used to obtain most of the data in these studies. (author)

  11. To the corrosion of austenitic steels in sodium loops

    International Nuclear Information System (INIS)

    Schad, M.

    1978-03-01

    This report describes the comparison between experimental corrosion and calculated corrosion effects on austenitic steels exposed to liquid sodium. As basis for the calculations served a diffusion model. The comparison showed that the model is able to predict the corrosion effects. In addition the model was used to calculate the corrosion effect along an actual fuel rod. (orig.) [de

  12. Cyclic deformation behaviour of austenitic steels at ambient and ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    Abstract. The aim of the present investigation is to characterise cyclic deforma- tion behaviour and plasticity-induced martensite formation of metastable austenitic stainless steels at ambient and elevated temperatures, taking into account the influ- ence of the alloying elements titanium and niobium. Titanium and niobium are.

  13. Retained austenite stability investigation in TRIP steel using neutron diffraction

    Czech Academy of Sciences Publication Activity Database

    Zrník, J.; Muránsky, Ondrej; Lukáš, Petr; Nový, Z.; Šittner, Petr; Horňák, P.

    2006-01-01

    Roč. 437, č. 1 (2006), s. 114-119 ISSN 0921-5093 Institutional research plan: CEZ:AV0Z10480505; CEZ:AV0Z10100520 Keywords : TRIP steel * austenite conditioning * neutron diffraction Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.490, year: 2006

  14. Influence of titanium on the tempering structure of austenitic steels

    International Nuclear Information System (INIS)

    Ghuezaiel, M.J.

    1985-10-01

    The microstructure of titanium-stabilized and initially deformed (approximately 20%) austenitic stainless steels used in structures of fast neutrons reactors has been studied after one hour duration annealings (500 0 C) by X-ray diffraction, optical microscopy, microhardness and transmission electron microscopy. The studied alloys were either of industrial type CND 17-13 (0.23 to 0.45 wt% Ti) or pure steels (18% Cr, 14% Ni, 0 or 0.3 wt% Ti). During tempering, the pure steels presented some restauration before recristallization. In the industrial steels, only recristallization occurred, and this only in the most deformed steel. Precipitation does not occur in the titanium-free pure steel. In industrial steels, many intermetallic phases are formed when recristallization starts [fr

  15. Thermal fatigue cracking of austenitic stainless steels

    International Nuclear Information System (INIS)

    Fissolo, A.

    2001-01-01

    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 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 50μm to 150□m long crack is observed. Additional SPLASH tests were performed for N >> N 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 tests confirm that

  16. Effect of austenitization conditions on kinetics of isothermal transformation of austenite of structural steels

    International Nuclear Information System (INIS)

    Konopleva, E.V.; Bayazitov, V.M.; Abramov, O.V.; Kozlova, A.G.

    1987-01-01

    Effect of austenization of kinetics of pearlite and bainite transformations for steels with different carbon content differing by alloying character and degree has been investigated. Austenization temperature increase is shown to leads to retardation of ferrite-pearlite transformation in low- and medium-carbon alloyed steels. Step-like holding in the region of austenite stable state (850, 950 deg) after high-temperature heating (1100 deg C) increases the rate of transformation partially recovering its kinetics and decomposition velocity after low-temperature heating in steels alloyed advantageously with carbide-forming elements (08Kh2G2F, 30Kh3) and does not affect kinetics in the 35Kh, 30KhGSN2A, 45N5 steels. Increase of heating temperature and growth of an austenite grain cause considerable acceleration of bainite transformation, increase of the temperaure of bainite transformation beginning and increase of the transformation amplitude in the 08Kh2G2F, 30Kh3 steels and affect weakly kinetics in steels with mixed alloying (30KhGSN2A) or low-alloy one (35Kh). The bainite transformation rate in the 45N5 steelite does not depend on austenization. The effect of additional acceleration of bainite transformation as a result holding after high-temperature heating in those steels, where activation of transformation occurs with increase of heating temperature

  17. 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.

  18. Cryogenic properties of austenitic stainless steels for superconducting magnet

    International Nuclear Information System (INIS)

    Nohara, K.; Kato, T.; Ono, Y.; Sasaki, T.; Suzuki, S.

    1983-01-01

    The present study examines the magnetic and mechanical properties of a variety of austenitic stainless steels and high maganese steel which are candidate materials for the superconducting magnet attached to high energy particle accelerators. The effect of a specified heat treatment for the precipitation of intermetallic compound Nb3Sn to be used as superconductor on ductility and toughness are especially examined. It is found that nitrogen-strengthened austenitic stainless steels have high strength and good ductility and toughness, but that these are destroyed by precipitation treatment. The poor ductility and toughness after precipitation are caused by a weakening of the grain boundaries due to the agglomerated chromium carbide percipitates. The addition of vanadium suppresses this effect by refining the grain. Austenitic steels are found to have low magnetic permeabilities and Neel temperatures, and show serrated flow in traction test due to strained martensitic transformation. High manganese steel has extremely low permeability, a Neel temperature about room temperature, and has a serrated flow in traction test due to adiabatic deformation at liquid helium temperature

  19. Microstructural and Mechanical Characterization of Solidified Austenitic Stainless Steels

    Directory of Open Access Journals (Sweden)

    Aktaş Çelik G.

    2017-09-01

    Full Text Available Among the family of stainless steels, cast austenitic stainless steels (CASSs are preferably used due to their high mechanical properties and corrosion resistance. These steels owe their properties to their microstructural features consisting of an austenitic matrix and skeletal or lathy type δ-ferrite depending on the cooling rate. In this study, the solidification behavior of CASSs (304L and 316L grades was studied using ThermoCalc software in order to determine the solidification sequence and final microstructure during cooling. Theoretical findings were supported by the microstructural examinations. For the mechanical characterization, not only hardness measurements but also tribological studies were carried out under dry sliding conditions and worn surfaces were examined by microscopy and 3D profilometric analysis. Results were discussed according to the type and amount of microstructural features.

  20. Austenite stability in the high strength metastable stainless steels

    OpenAIRE

    S.J. Pawlak

    2007-01-01

    Purpose: The aim of the present paper was to study the peculiarities of the austenite to martensite phase transformation (A-M), which is an essential step in the production technology of the high strength metastable stainless steels.Design/methodology/approach: The desired control over A-M transformation have been achieved by proper design of the steel chemistry, cold working and heat treatment.Findings: For a range of steel compositions, it was shown that severe cold working leads to fully m...

  1. 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...

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

    International Nuclear Information System (INIS)

    Eghlimi, Abbas; Shamanian, Morteza; Eskandarian, Masoomeh; Zabolian, Azam; Szpunar, Jerzy A.

    2015-01-01

    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

  3. 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

  4. Measurement and tailoring of residual stress in expanded austenite on austenitic stainless steel

    DEFF Research Database (Denmark)

    Fernandes, Frederico Augusto Pires; Christiansen, Thomas Lundin; Winther, Grethe

    2017-01-01

    Expanded austenite on stainless steel with a high interstitial nitrogen content is characterized by elasto-plastic accommodation of the large composition-induced lattice expansion leading to huge compressive residual stress. The elasto-plastic accommodation as well as the (steep) concentration...... profile has implications for the measurement strategy to determine lattice strains and associated residual stresses with X-ray diffraction. Lattice strain measurements were performed on nitrided as well as subsequently de-nitrided expanded austenite on AISI 316L stainless steel, for various grazing...... incidence angles. It is demonstrated that keeping the information depth constant by choosing appropriate combinations of grazing incidence and tilt angle leads to reliable results for the 111 reflection, while the 200 reflection should be avoided. Further, it is shown for the first time that the residual...

  5. Effect of multiple austenitizing treatments on HT-9 steels

    International Nuclear Information System (INIS)

    Emigh, R.A.

    1985-12-01

    The effect of multiple austenitizing treatments on the toughness of an Fe-12Cr-1.0Mo-0.5W-0.3V (HT-9) steel was studied. The resulting microstructures were characterized by their mechanical properties, precipitated carbide distribution, and fracture surface appearance. It was proposed that multiple transformations would refine the martensite structure and improve toughness. Optical and scanning electron microscopic observations revealed that the martensite packet structure was somewhat refined by a second austenite transformation. Transmission electron microscopy studies of carbon extraction replicas showed that this multiple step treatment had eliminated grain boundary carbide films seen in single treated specimens on prior austenite grain boundaries. The 0.2% yield strength, tensile strength, and elongation were relatively unchanged, but the toughness measured by fatigue pre-cracked Charpy impact tests increased for the multiple step specimens

  6. Hydrogen induced ductility losses in austenitic stainless steel welds

    Energy Technology Data Exchange (ETDEWEB)

    Brooks, J.A.; West, A.J.

    1978-06-01

    The effect of hydrogen on the tensile behavior of austenitic stainless steel welds was studied in two AISI 300 series alloys and two nitrogen strengthened alloys. The microstructure of these welds typically contained several percent ferrite in an austenite matrix. Hydrogen was found to reduce the ductility of all welds; however, the severity of ductility loss decreased with increasing stacking fault energy, as observed in previous studies on wrought material. In the lowest stacking fault energy welds, 304L and 308L, hydrogen changed the fracture mode from simple rupture to a mixed mode of ductile and brittle fracture associated with the austenite ferrite interface. Higher stacking fault energy welds, 309S and 22-13-5, showed smaller losses in ductility. In these materials hydrogen assisted the ductile rupture process by aiding void growth and coalescence, without changing the fracture mode. Varying the amount of ferrite from approximately one to 10 percent had no significant effect on performance in hydrogen.

  7. Diagnostic experimental results on the hydrogen embrittlement of austenitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Gavriljuk, V.G.; Shivanyuk, V.N.; Foct, J

    2003-03-14

    Three main available hypotheses of hydrogen embrittlement are analysed in relation to austenitic steels based on the studies of the hydrogen effect on the interatomic bonds, phase transformations and microplastic behaviour. It is shown that hydrogen increases the concentration of free electrons, i.e. enhances the metallic character of atomic interactions, although such a decrease in the interatomic bonding cannot be a reason for brittleness and rather assists an increased plasticity. The hypothesis of the critical role of the hydrogen-induced {epsilon} martensite was tested in the experiment with the hydrogen-charged Si-containing austenitic steel. Both the fraction of the {epsilon} martensite and resistance to hydrogen embrittlement were increased due to Si alloying, which is at variance with the pseudo-hydride hypothesis. The hydrogen-caused early start of the microplastic deformation and an increased mobility of dislocations, which are usually not observed in the common mechanical tests, are revealed by the measurements of the strain-dependent internal friction, which is consistent with the hypothesis of the hydrogen-enhanced localised plasticity. An influence of alloying elements on the enthalpy E{sub H} of hydrogen migration in austenitic steels is studied using the temperature-dependent internal friction and a correlation is found between the values of E{sub H} and hydrogen-caused decrease in plasticity. A mechanism for the transition from the hydrogen-caused microplasticity to the apparent macrobrittle fracture is proposed based on the similarity of the fracture of hydrogenated austenitic steels to that of high nitrogen steels.

  8. Solidification cracking in austenitic stainless steel welds

    Indian Academy of Sciences (India)

    M. Senthilkumar (Newgen Imaging) 1461 1996 Oct 15 13:05:22

    V Shankar et al. Although much research experience exists on the nature of hot cracking in stainless steels ... that crack-resistant weld deposits could be produced if the composition is adjusted to result in 5–35% fer- .... A large volume of literature is devoted to the prediction and measurement of δ-ferrite in stainless steel ...

  9. Effect of shot peening on metastable austenitic stainless steels

    International Nuclear Information System (INIS)

    Fargas, G.; Roa, J.J.; Mateo, A.

    2015-01-01

    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

  10. Laser borided composite layer produced on austenitic 316L steel

    Directory of Open Access Journals (Sweden)

    Mikołajczak Daria

    2016-12-01

    Full Text Available Abstract Austenitic 316L steel is well-known for its good resistance to corrosion and oxidation. Therefore, this material is often used wherever corrosive media or high temperatures are to be expected. The main drawback of this material is very low hardness and low resistance to mechanical wear. In this study, the laser boriding was used in order to improve the wear behavior of this material. As a consequence, a composite surface layer was produced. The microstructure of laser-borided steel was characterized by only two zones: re-melted zone and base material. In the re-melted zone, a composite microstructure, consisting of hard ceramic phases (borides and a soft austenitic matrix, was observed. A significant increase in hardness and wear resistance of such a layer was obtained.

  11. Carbides nucleation and growth processes in austenitic stainless steel

    International Nuclear Information System (INIS)

    Calvo, F.A.; Otero, E.; Ballester, A.; Leiro, J.

    1986-01-01

    The nucleation and growth process at some carbides with high chromium content inside an austenitic matrix corresponding to a 304 type inoxidable steel are studied. The precipitate growth seems to be controlled, at least at temperatures above 973 K, by the diffusion of carbon atoms from the matrix phase to the beginning of the second phase which is normally placed in the grain boundaries. A relationship between the percentage of precipitated carbide, as a function of the carbon excess in the saturated austenitic solid solution, and the time employed for each work temperature is established. From these data, some aspects relating to the morphologie, the carbide localization and the influence of these factors in the steel sensibilization to the grain corrosion, are interpreted. (author)

  12. Creep embrittlement of austenitic stainless steels with titanium addition

    International Nuclear Information System (INIS)

    Felsen, M.F.

    1983-04-01

    Some cold-worked austenitic stainless steels of the 316 type with titanium addition exhibit a low creep ductility and a notch sensitivity in the temperature range of 550 0 C to 750 0 C and for times to rupture from 10 to 10000 hours. It has been shown that this embrittlement increases highly with cold-work percentage, with solution annealing temperature, and depends on chemical composition because these factors can modify the difference of hardness between grains and grain boundaries

  13. Internal frictions of austenitic stainless steels at low temperature

    Science.gov (United States)

    Tsubono, K.; Owa, S.; Mio, N.; Akasaka, N.; Hirakawa, H.

    Internal frictions were measured for three types of austenitic stainless steel, AISI 304, 310S and 316, in the temperature range 4-300 K. The intrinsic friction is presented in terms of the quality factor of a 20 kHz eigenmode vibration of discs made from each material. Temperature dependence is also given for the resonant frequency of each disc. These mechanical properties show some peculiarities at low temperature.

  14. Evaluation of Microstructure and Mechanical Properties in Dissimilar Austenitic/Super Duplex Stainless Steel Joint

    Science.gov (United States)

    Rahmani, Mehdi; Eghlimi, Abbas; Shamanian, Morteza

    2014-10-01

    To study the effect of chemical composition on microstructural features and mechanical properties of dissimilar joints between super duplex and austenitic stainless steels, welding was attempted by gas tungsten arc welding process with a super duplex (ER2594) and an austenitic (ER309LMo) stainless steel filler metal. While the austenitic weld metal had vermicular delta ferrite within austenitic matrix, super duplex stainless steel was mainly comprised of allotriomorphic grain boundary and Widmanstätten side plate austenite morphologies in the ferrite matrix. Also the heat-affected zone of austenitic base metal comprised of large austenite grains with little amounts of ferrite, whereas a coarse-grained ferritic region was observed in the heat-affected zone of super duplex base metal. Although both welded joints showed acceptable mechanical properties, the hardness and impact strength of the weld metal produced using super duplex filler metal were found to be better than that obtained by austenitic filler metal.

  15. 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)

  16. Resistance Element Welding of Magnesium Alloy/austenitic Stainless Steel

    Science.gov (United States)

    Manladan, S. M.; Yusof, F.; Ramesh, S.; Zhang, Y.; Luo, Z.; Ling, Z.

    2017-09-01

    Multi-material design is increasingly applied in the automotive and aerospace industries to reduce weight, improve crash-worthiness, and reduce environmental pollution. In the present study, a novel variant of resistance spot welding technique, known as resistance element welding was used to join AZ31 Mg alloy to 316 L austenitic stainless steel. The microstructure and mechanical properties of the joints were evaluated. It was found that the nugget consisted of two zones, including a peripheral fusion zone on the stainless steel side and the main fusion zone. The tensile shear properties of the joints are superior to those obtained by traditional resistance spot welding.

  17. Non-uniformity of hot plastic strain of stainless steels with austenitic-ferritic structure

    International Nuclear Information System (INIS)

    Laricheva, L.P.; Peretyat'ko, V.N.; Rostovtsev, A.N.; Levius, A.M.

    1987-01-01

    Non-uniformity of hot strain of stainless steels of various alloying was investigated. Steels with austenite and δ-ferrite structure of two classes were chosen for investigation: 08Kh18N10T steel of austenitic class and 08Kh21N5T steel of austenitic-ferritic class. Tests were conducted for samples subjected to preliminary thermal treatment: heating up to 1250 deg C, holding during 0.5 h, cooling in water. The heat treatment enabled to produce large grains of austenite and δ-ferrite (about 30 μm) in 08Kh21N5T steel, and sufficient amount of δ-ferrite (up to 50%) in 08Kh18N10T steel. It is shown that hot strain of austenitic-ferritic steels is non-uniform. δ-ferrite strain is more pronounced as compared to austenite. The ratio of mean δ-ferrite strain to the mean austenite strain grows with increase of the degree of general steel strain and temperature. The ratio of mean phase strains in 08Kh18N10T steel is higher as compared to 08Kh21N5T steel, general strain and temperature being equal. Temperature effect on the ratio of δ-ferrite and austenite strains is more pronounced for 08Kh18N10T steel. It is explaind by the value of ratios of phase strain resistance and temperature effect on them

  18. Market Opportunities for Austenitic Stainless Steels in SO2 Scrubbers

    Science.gov (United States)

    Michels, Harold T.

    1980-10-01

    Recent U.S. federal legislation has created new opportunities for SO2 scrubbers because all coals, even low-sulfur western coals, will probably require scrubbing to remove SO2 from gaseous combustion products. Scrubbing, the chemical absorption of SO2 by vigorous contact with a slurry—usually lime or limestone—creates an aggressive acid-chloride solution. This presents a promising market for pitting-resistant austenitic stainless steels, but there is active competition from rubber and fiberglass-lined carbon steel. Since the latter are favored on a first-cost basis, stainless steels must be justified on a cost/performance or life-cost basis. Nickel-containing austenitic alloys are favored because of superior field fabricability. Ferritic stainless steels have little utility in this application because of limitations in weldability and resulting poor corrosion resistance. Inco corrosion test spools indicate that molybdenum-containing austenitic alloys are needed. The leanest alloys for this application are 316L and 317L. Low-carbon grades of stainless steel are specified to minimize corrosion in the vicinity of welds. More highly alloyed materials may be required in critical areas. At present, 16,000 MW of scrubber capacity is operational and 17,000 MW is under construction. Another 29,000 MW is planned, bringing the total to 62,000 MW. Some 160,000 MW of scrubber capacity is expected to be placed in service over the next 10 years. This could translate into a total potential market of 80,000 tons of alloy plate for new power industry construction in the next decade. Retrofitting of existing power plants plus scrubbers for other applications such as inert gas generators for oil tankers, smelters, municipal incinerators, coke ovens, the pulp and paper industry, sulfuric acid plants, and fluoride control in phosphoric acid plants will add to this large market.

  19. Phase Transformation of Metastable Austenite in Steel during Nano indentation

    International Nuclear Information System (INIS)

    Ahn, Taehong; Lee, Sung Bo; Han, Heung Nam; Park, Kyungtae

    2013-01-01

    These can produce geometrical softening accompanied by a sudden displacement excursion during load-controlled nanoindentation, which referred to in the literature as a pop-in. In this study, phase transformation of metastable austenite to stress-induced ε martensite which causes pop-ins during nanoindentation of steel will be reported and discussed. This study investigated the relationship between pop-in behavior of austenite in the early stage of nanoindentation and formation of ε martensite based on microstructural analyses. The load-displacement curve obtained from nanoindentation revealed stepwise pop-ins in the early stage of plastic deformation. From analyses of high resolution TEM images, a cluster of banded structure under the indent turned out a juxtaposition of (111) planes of γ austenite and (0001) planes of ε martensite. The calculation of displacement along indentation axis for (111) slip system by formation of ε martensite showed that geometrical softening can also occur by ε martensite formation when considering that the stress-induced ε martensite transformation is the predominant deformation mode in the early stage of plastic deformation and its monopartial nature as well. These microstructural investigations strongly suggest that the pop-in behavior in the early stage of plastic deformation of austenite is closely related to the formation of ε martensite

  20. Phase Transformation of Metastable Austenite in Steel during Nano indentation

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Taehong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Lee, Sung Bo; Han, Heung Nam [Seoul National Univ., Seoul (Korea, Republic of); Park, Kyungtae [Hanbat National Univ., Daejeon (Korea, Republic of)

    2013-05-15

    These can produce geometrical softening accompanied by a sudden displacement excursion during load-controlled nanoindentation, which referred to in the literature as a pop-in. In this study, phase transformation of metastable austenite to stress-induced ε martensite which causes pop-ins during nanoindentation of steel will be reported and discussed. This study investigated the relationship between pop-in behavior of austenite in the early stage of nanoindentation and formation of ε martensite based on microstructural analyses. The load-displacement curve obtained from nanoindentation revealed stepwise pop-ins in the early stage of plastic deformation. From analyses of high resolution TEM images, a cluster of banded structure under the indent turned out a juxtaposition of (111) planes of γ austenite and (0001) planes of ε martensite. The calculation of displacement along indentation axis for (111) slip system by formation of ε martensite showed that geometrical softening can also occur by ε martensite formation when considering that the stress-induced ε martensite transformation is the predominant deformation mode in the early stage of plastic deformation and its monopartial nature as well. These microstructural investigations strongly suggest that the pop-in behavior in the early stage of plastic deformation of austenite is closely related to the formation of ε martensite.

  1. Determination of delta ferrite volumetric fraction in austenitic stainless steel

    International Nuclear Information System (INIS)

    Almeida Macedo, W.A. de.

    1983-01-01

    Measurements of delta ferrite volumetric fraction in AISI 304 austenitic stainless steels were done by X-ray diffraction, quantitative metallography (point count) and by means of one specific commercial apparatus whose operational principle is magnetic-inductive: The Ferrite Content Meter 1053 / Institut Dr. Foerster. The results obtained were comparated with point count, the reference method. It was also investigated in these measurements the influence of the martensite induced by mechanical deformation. Determinations by X-ray diffraction, by the ratio between integrated intensities of the ferrite (211) and austenite (311) lines, are in excelent agreement with those taken by point count. One correction curve for the lectures of the commercial equipment in focus was obtained, for the range between zero and 20% of delta ferrite in 18/8 stainless steels. It is demonstrated that, depending on the employed measurement method and surface finishing of the material to be analysed, the presence of martensite produced by mechanical deformation of the austenitic matrix is one problem to be considered. (Author) [pt

  2. Determination of delta ferrite volumetric fraction in austenitic stainless steels

    International Nuclear Information System (INIS)

    Almeida Macedo, W.A. de.

    1983-01-01

    Measurements of delta ferrite volumetric fraction in AISI 304 austenitic stainless steels were done by X-ray difraction, quantitative metallography (point count) and by means of one specific commercial apparatus whose operational principle is magnetic-inductive: The Ferrite Content Meter 1053 / Institut Dr. Forster. The results obtained were comparated with point count, the reference method. It was also investigated in these measurements the influence of the martensite induced by mechanical deformation. Determinations by X-ray diffraction, by the ratio between integrated intensities of the ferrite (211) and austenite (311) lines, are in excelent agreement with those taken by point count. One correction curve for the lectures of the commercial equipment in focus was obtained, for the range between zero and 20% of delta ferrite in 18/8 stainless steels. It is demonstrated that, depending on the employed measurement method and surface finishing of the material to be analysed, the presence of martensite produced by mechanical deformation of the austenitic matrix is one problem to be considered. (Author) [pt

  3. Phase stability of high manganese austenitic steels for cryogenic applications

    CERN Document Server

    Couturier, K

    2000-01-01

    The aim of this work is to study the austenitic stability against a' martensitic transformation of three non-magnetic austenitic steels : a new stainless steel X2CrMnNiMoN 19-12-11-1 grade, a traditional X8CrMnNiN 19-11-6 grade and a high manganese X8MnCrNi 28-7-1 grade. Measurements of relative magnetic susceptibility at room temperature are performed on strained tensile specimens at 4.2 K. A special extensometer for high precision strain measurements at low temperature has been developed at CERN to test specimens up to various levels of plastic strain. Moreover, the high precision strain recording of the extensometer enables a detailed study of the serrated yield phenomena associated with 4.2 K tensile testing and their influence on the evolution of magnetic susceptibility. The results show that high Mn contents increase the stability of the austenitic structure against a' martensitic transformation, while keeping high strength at cryogenic temperature. Moreover, proper elaboration through primary and possi...

  4. Fatigue behavior of welded austenitic stainless steel in different environments

    Directory of Open Access Journals (Sweden)

    D.S. Yawas

    2014-01-01

    Full Text Available The fatigue behavior of welded austenitic stainless steel in 0.5 M hydrochloric acid and wet steam corrosive media has been investigated. The immersion time in the corrosive media was 30 days to simulate the effect on stainless steel structures/equipment in offshore and food processing applications and thereafter annealing heat treatment was carried out on the samples. The findings from the fatigue tests show that seawater specimens have a lower fatigue stress of 0.5 × 10−5 N/mm2 for the heat treated sample and 0.1 × 10−5 N/mm2 for the unheat-treated sample compared to the corresponding hydrochloric acid and steam samples. The post-welding heat treatment was found to increase the mechanical properties of the austenitic stainless steel especially tensile strength but it reduces the transformation and thermal stresses of the samples. These findings were further corroborated by the microstructural examination of the stainless steel specimen.

  5. austenitic steel corrosion by oxygen-containing liquid sodium

    International Nuclear Information System (INIS)

    Rivollier, Matthieu

    2017-01-01

    France is planning to construct the 4. generation of nuclear reactors. They will use liquid sodium as heat transfer fluid and will be made of 316L(N) austenitic steel as structural materials. To guarantee optimal operation on the long term, the behavior of this steel must be verified. This is why corrosion phenomena of 316L(N) steel by liquid sodium have to be well-understood. Literature points out that several corrosion phenomena are possible. Dissolved oxygen in sodium definitely influences each of the corrosion phenomenon. Therefore, the austenitic steel corrosion in oxygen-containing sodium is proposed in this study. Thermodynamics data point out that sodium chromite formation on 316L(N) steel is possible in sodium containing roughly 10 μg.g -1 of oxygen for temperature lower than 650 C (reactor operating conditions).The experimental study shows that sodium chromite is formed at 650 C in the sodium containing 200 μg.g -1 of oxygen. At the same concentration and at 550 C, sodium chromite is clearly observed only for long immersion time (≥ 5000 h). Results at 450 C are more difficult to interpret. Furthermore, the steel is depleted in chromium in all cases.The results suggest the sodium chromite is dissolved in the sodium at the same time it is formed. Modelling of sodium chromite formation - approached by chromium diffusion in steel (in grain and grain boundaries -, and dissolution - assessed by transport in liquid metal - show that simultaneous formation and dissolution of sodium chromite is a possible mechanism able to explain our results. (author) [fr

  6. A review of hot cracking in austenitic stainless steel weldments

    International Nuclear Information System (INIS)

    Shankar, V.; Gill, T.P.S.; Mannan, S.L.; Rodriguez, P.

    1991-01-01

    The occurrence of hot cracking in austenitic stainless steel weldments is discussed with respect to its origin and metallurgical contributory factors. Of the three types of hot cracking, namely solidification cracking, liquation and ductility dip cracking, solidification cracking occurs in the interdendritic regions in weld metal while liquation and ductility dip cracking occur intergranularly in the heat-affected zone (HAZ). Segregation of impurity and minor elements such as sulphur, phosphorous, silicon, niobium, boron etc to form low melting eutectic phases has been found to be the major cause of hot cracking. Control of HAZ cracking requires minimisation of impurity elements in the base metal. In stabilized stainless steels containing niobium, higher amounts of delta-ferrite have been found necessary to prevent cracking than in unstabilized compositions. Titanium compounds have been found to cause liquation cracking in maraging steels and titanium containing stainless steels and superalloys. In nitrogen added stainless steels, cracking resistance decreases when the solidification mode changes to primary austenitic due to nitrogen addition. A review of the test methods to evaluate hot cracking behaviour showed that several external restraint and semi-self-restraint tests are available. The finger Test, WRC Fissure Bend Test, the PVR test and the Varestraint Test are described along with typical test results. Hot ductility testing to reveal HAZ cracking tendency during welding is described, which is of particular importance to stabilized stainless steels. Based on the literature, recommendations are made for welding stabilized and nitrogen added steels, indicating areas of further work. (author). 81 refs., 30 figs., 1 tab

  7. Electron microscopy and plastic deformation of industrial austenitic stainless steels

    International Nuclear Information System (INIS)

    Thomas, Barry

    1976-01-01

    The different mechanisms of plastic deformation observed in austenitic stainless steels are described and the role of transmission electron microscopy in the elucidation of the mechanisms is presented. At temperatures below 0,5Tm, different variants of dislocation glide are competitive: slip of perfect and partial dislocations, mechanical twinning and strain-induced phase transformations. The predominance of one or other of these mechanisms can be rationalized in terms of the temperature and composition dependence of the stacking fault energy and the thermodynamic stability of the austenite. At temperatures above 0,5Tm dislocation climb and diffusion of point defects become increasingly important and at these temperatures recovery, recrystallization and precipitation can also occur during deformation [fr

  8. Controlling radiation induced segregation in austenitic stainless steels

    International Nuclear Information System (INIS)

    Ahmedabadi, Parag M.; Kain, Vivekanand

    2011-01-01

    In-core components of austenitic stainless steels in light water reactors (LWRs) are susceptible to irradiation assisted stress corrosion cracking (IASCC) in high temperature and high pressure oxygenated water at temperature around 300 deg C . Though, the exact mechanism for IASCC is not fully understood, radiation-induced segregation (RIS) is considered to be a part of a complex process that leads to IASCC. Therefore, controlling RIS in austenitic stainless steels may lead to improvement in resistance to IASCC. RIS is non-equilibrium segregation/depletion of alloying elements in austenitic stainless steels at LWR operating temperatures. RIS occurs due to adsorption of point defects at grain boundaries and leads to segregation of Si and P and depletion of Cr at grain boundaries. Thus by controlling point defect flux towards grain boundaries, the extent of RIS at grain boundaries can be controlled. An extensive study was carried out to simulate and control RIS in austenitic stainless steels using proton irradiation at 300 deg C . The primary aim of this study was to reduce point defect flux towards grain boundaries. Various approaches viz. grain boundary engineering, addition of oversized alloying element, residual strain within matrix and presence of fine precipitates within the grains and at grain boundaries were employed to control RIS in austenitic stainless steels. A novel approach involving combination of electrochemical technique followed by atomic force microscopic (AFM) examination has been used to examine the nature and the extent of RIS. Type 304, 316 and 347 stainless steels were irradiated at 300 deg C (in FOTIA and PELLETRON) in the range of 0.2 to 1.0 dpa using proton beam. The results obtained so far have indicated that a small amount of pre-strain within the grains is very effective in reducing the flux of point defects towards grain boundaries and reducing the extent of RIS at grain boundaries. The presence of NbC precipitates within the grains is

  9. Single pit propagation on austenitic stainless steel

    International Nuclear Information System (INIS)

    Heurtault, Stephane

    2016-01-01

    The electrochemical characterization of metastable events such as pitting corrosion of stainless steel in chloride electrolyte remains complex because many individual processes may occur simultaneously on the alloy surface. To overcome these difficulties, an experimental setup, the flow micro-device, has been developed to achieve the initiation of a single pit and to propagate the single pit in three dimensions. In this work, we take advantage of such a device in order to revisit the pitting process on a 316L stainless steel in a chloride - sulphate bulk. In a first step, the time evolution of the pit geometry (depth, radius) and the chemical evolution of the pit solution investigated using in situ Raman spectroscopy have shown that the pit depth propagation depends on the formation of a metal chloride and sulphate gel in the pit solution, and is controlled by the metallic cations diffusion from the pit bottom to the pit mouth. The pit radius growth is defined by the initial surface de-passivation, by the presence of a pit cover and by the gel development in the solution. all of these phenomena are function of applied potential and chemical composition of the solution. In a last step, it was demonstrated that a critical chloride concentration is needed in order to maintain the pit propagation. This critical concentration slightly increases with the pit depth. From statistical analysis performed on identical experiments, a zone diagram showing the pit stability as a function of the chloride concentration and the pit dimensions was built. (author) [fr

  10. Reaction of uranium and plutonium carbides with austenitic steels

    International Nuclear Information System (INIS)

    Mouchnino, M.

    1967-01-01

    The reaction of uranium and plutonium carbides with austenitic steels has been studied between 650 and 1050 deg. C using UC, steel and (UPu)C, steel diffusion couples. The steels are of the type CN 18.10 with or without addition of molybdenum. The carbides used are hyper-stoichiometric. Tests were also carried out with UCTi, UCMo, UPuCTi and UPuCMo. Up to 800 deg. C no marked diffusion of carbon into stainless steel is observed. Between 800 and 900 deg. C the carbon produced by the decomposition of the higher carbides diffuses into the steel. Above 900 deg. C, decomposition of the monocarbide occurs according to a reaction which can be written schematically as: (U,PuC) + (Fe,Ni,Cr) → (U,Pu) Fe 2 + Cr 23 C 6 . Above 950 deg. C the behaviour of UPuCMo and that of the titanium (CN 18.12) and nickel (NC 38. 18) steels is observed to be very satisfactory. (author) [fr

  11. Enhanced stress corrosion resistance from steels having a dual-phase austenite-martensite microstructure

    International Nuclear Information System (INIS)

    Venkatasubramanian, T.V.; Baker, T.J.

    1983-01-01

    A high strength steel with an austenite-martensite duplex microstructure has been produced by extruding nickel coated steel powder. The austenite is present as a continuous network surrounding a high strength martensite. The steel exhibits superior resistance to stress corrosion cracking in 3.5 pct NaCl solution, the effectiveness of the austenite in improving stress corrosion cracking resistance increases as yield strength increases. The austenite reduces the effective stress intensity at the advancing crack tip and at the same time shields the crack tip from the corrosive environment

  12. Monitoring of Fatigue Degradation in Austenitic Stainless Steels

    International Nuclear Information System (INIS)

    Kalkhof, D.; Niffenegger, M.; Leber, H.J.

    2004-01-01

    During cyclic loading of austenitic stainless steel, it was observed that microstructural changes occurred; these affect both the mechanical and physical properties of the material. For certain steels, a strain-induced martensite phase transformation was seen. The investigations showed that, for the given material and loading conditions, the volume fraction of martensite depends on the cycle number, temperature and initial material state. It was also found that the martensite content continuously increased with the cycle number. Therefore, the volume fraction of martensite was used as an indication of fatigue usage. It was noted that the temperature dependence of the martensite formation could be described by a Boltzmann function, and that the martensite content decreased with increasing temperature. Two different heats of the austenitic stainless steel X6CrNiTi18-10 (AISI 321, DIN 1.4541) were investigated. It was found that the martensite formation rate was much higher for the cold-worked than for the solution-annealed material. All applied techniques - neutron diffraction and advanced magnetic methods - were successful in detecting the presence of martensite in the differently fatigued specimens. (author)

  13. 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.

  14. Residual stresses associated with welds in austenitic steel

    International Nuclear Information System (INIS)

    Fidler, R.

    1978-01-01

    Two exploratory welds have been made with AISI 316 austenitic steel and Armex GT electrodes by the manual metal-arc process, and residual stress measurements made in the as-welded condition and after various periods of stress relief. The results show that substantial stress relief occurs at temperatures of 850 0 and 750 0 C after 1 hr, but is not complete. The stress distributions are compared with those obtained from ferritic welds and the effect of differences in thermal expansion coefficients is examined using finite element analysis. (author)

  15. Void swelling behaviour of austenitic stainless steel during electron irradiation

    International Nuclear Information System (INIS)

    Sheng Zhongqi; Xiao Hong; Peng Feng; Ti Zhongxin

    1994-04-01

    The irradiation swelling behaviour of 00Cr17Ni14Mo2 austenitic stainless steel (AISI 316L) was investigated by means of high voltage electron microscope. Results showed that in solution annealed condition almost no swelling incubation period existed, and the swelling shifted from the transition period to the steady-state one when the displacement damage was around 40 dpa. In cold rolled condition there was evidently incubation period, and when the displacement damage was up to 84 dpa the swelling still remained in the transition period. The average size and density of voids in both conditions were measured, and the factors, which influenced the void swelling, were discussed. (3 figs.)

  16. Mechanical properties of austenitic stainless steels in sodium

    International Nuclear Information System (INIS)

    Lloyd, G.J.

    1978-03-01

    A detailed review of the mechanical properties of austenitic stainless steels in liquid sodium is presented. Consideration has been given to the influence of the of the impurities in reactor sodium and metallurgical variables upon the stress rupture life, the low cycle fatigue and combined creep/fatigue resistance, elastic-plastic crack propagation rates, the high cycle fatigue life, tensile properties and fracture toughness. The effects of exposure to contaminated sodium prior to testing are also discussed. Examples of the success of mechanistic interpretations of materials behaviour in sodium are given and additionally, the extent to which mechanical properties in sodium may be predicted with the use of appropriate data. (author)

  17. Deformation Behavior of An Austenitic Steel by Neutron Diffraction

    Science.gov (United States)

    Harjo, Stefanus; Abe, Jun; Aizawa, Kazuya; Gong, Wu; Iwahashi, Takaaki

    An austenitic stainless steel type 304, which is one of the most popular materials in use, was tensile deformed and in situ neutron diffraction measurement was performed. The neutron diffraction measurement was conducted using an engineering materials diffractometer installed at MLF/J-PARC. Because of the combination of the high neutron intensity, the high counting rate and an event data recording method, in situ neutron diffraction during tensile loading at plastic deformation could be performed without any interruption for load or displacement. Intergranular strains and bulky stress observed during deformation were discussed on the crystal orientation dependence.

  18. Corrosion resistance of kolsterised austenitic 304 stainless steel

    International Nuclear Information System (INIS)

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

    2015-01-01

    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 Fe 2 C 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

  19. Analysis of the retained austenite stability in TRIP steels by X-ray and neutron diffraction

    International Nuclear Information System (INIS)

    Son, Dong Min; Choi, Il Dong; Shin, Eun Joo

    2005-01-01

    The energy absorption of an automotive sheet steel during crash, that is, at a high speed deformation is very important to the safety of passengers. Therefore, property data and deformation mechanisms of materials under high strain rate conditions are needed to choose proper materials for automobiles. Dynamic mechanical properties of low carbon TRIP steels with varying retained austenite stabilities were evaluated over a wide range of strain rates using a high-velocity hydraulic tensile testing machine. The effect of retained austenite stability on high speed deformation behavior can be evaluated by the proper estimation of transformation in retained austenite. The quantity of transformed retained austenite after deformation was analyzed by X-ray diffraction and high resolution neutron diffraction and compared the results from two test methods. The carbon in retained austenite was analyzed by neutron diffraction. High stability retained austenite has higher carbon content than low stability retained austenite and transformed slowly

  20. Austenitic stainless steel-to-ferritic steel transition joint welding for elevated temperature service

    International Nuclear Information System (INIS)

    King, J.F.; Goodwin, G.M.; Slaughter, G.M.

    1978-01-01

    Transition weld joints between ferritic steels and austenitic stainless steels are required for fossil-fired power plants and proposed nuclear plants. The experience with these dissimilar-metal transition joints has been generally satisfactory, but an increasing number of failures of these joints is occurring prematurely in service. These concerns with transition joint service history prompted a program to develop more reliable joints for application in proposed nuclear power plants

  1. High nitrogen-dosed austenitic-stainless steels and duplex steels

    International Nuclear Information System (INIS)

    Harzenmoser, M.A.E.

    1990-01-01

    The austenitic grades represent the most important group in the family of stainless steels. Nitrogen addition to austenitic stainless steels provides much higher yield strength. It was the goal of the present work to develop new high strength austenitic and duplex stainless steels and to investigate the beneficial influence of nitrogen. More than 40 small ingots up to a weight of 1.5 kg were melted in a specially developed high pressure induction furnace. In addition 20 more alloys produced by a pressurized electro slag remelting facility were included in this investigation. The nitrogen content was varied between 0.37 and 1.47 wt.%. New coefficients are proposed for the nickel equivalent in the Schaeffler diagram; these are from 0.12 to 0.24 for manganese and 18 for nitrogen. The increase in yield strength by interstitially dissolved nitrogen is due to solid solution hardening and to increased grain boundary hardening. The addition of 1% nitrogen gives a yield strength of more than 759 MPa. The toughness remains very good. At room temperature nitrogen alloyed Fe-Cr-Mn austenitic steels give the highest product of strength and toughness. Nitrogen containing austenitic stainless steels show a substantial increase in strength at low temperature. From room temperature to 4K the yield strength is more than tripled. Nitrogen alloyed Fe-Cr-Mn austenitic stainless steels exhibit a ductile to brittle transition as the temperature is lowered. This is due to a planar deformation mode which could be caused by low stacking fault energy. Nickel improves the low temperature toughness and also raises the stacking fault energy. In the temperature range from 600 to 900 o C, Cr 2 N precipitate. The minimal time for precipitation is longer by a factor of 10 than in Fe-Cr-Ni grade. Nitrogen decreases the corrosion rate in austenitic and duplex stainless steels. The resistance to pitting corrosion can be described by the equation W L = %Cr + 3.3 %Mo + 30 %N. (author) figs., tabs., refs

  2. Surface protection of austenitic steels by carbon nanotube coatings

    Science.gov (United States)

    MacLucas, T.; Schütz, S.; Suarez, S.; Mücklich, F.

    2018-03-01

    In the present study, surface protection properties of multiwall carbon nanotubes (CNTs) deposited on polished austenitic stainless steel are evaluated. Electrophoretic deposition is used as a coating technique. Contact angle measurements reveal hydrophilic as well as hydrophobic wetting characteristics of the carbon nanotube coating depending on the additive used for the deposition. Tribological properties of carbon nanotube coatings on steel substrate are determined with a ball-on-disc tribometer. Effective lubrication can be achieved by adding magnesium nitrate as an additive due to the formation of a holding layer detaining CNTs in the contact area. Furthermore, wear track analysis reveals minimal wear on the coated substrate as well as carbon residues providing lubrication. Energy dispersive x-ray spectroscopy is used to qualitatively analyse the elemental composition of the coating and the underlying substrate. The results explain the observed wetting characteristics of each coating. Finally, merely minimal oxidation is detected on the CNT-coated substrate as opposed to the uncoated sample.

  3. Characteristic of Low Temperature Carburized Austenitic Stainless Steel

    Science.gov (United States)

    Istiroyah; Pamungkas, M. A.; Saroja, G.; Ghufron, M.; Juwono, A. M.

    2018-01-01

    Low temperature carburizing process has been carried out on austenitic stainless steel (ASS) type AISI 316L, that contain chromium in above 12 at%. Therefore, conventional heat treatment processes that are usually carried out at high temperatures are not applicable. The sensitization process due to chromium migration from the grain boundary will lead to stress corrosion crack and decrease the corrosion resistance of the steel. In this study, the carburizing process was carried out at low temperatures below 500 °C. Surface morphology and mechanical properties of carburized specimens were investigated using optical microscopy, non destructive profilometer, and Vicker microhardness. The surface roughness analysis show the carburising process improves the roughness of ASS surface. This improvement is due to the adsorption of carbon atoms on the surface of the specimen. Likewise, the hardness test results indicate the carburising process increases the hardness of ASS.

  4. Fracture of Fe--Cr--Mn austenitic steel

    International Nuclear Information System (INIS)

    Caskey, G.R. Jr.

    1979-01-01

    Tensile tests of Tenelon (U.S. Steel), a nitrogen-strengthened iron-base alloy containing 18% chromium and 15% manganese, demonsterated that cleavage fracture can occur in some austenitic steels and is promoted by the presence of hydrogen. Tensile failure of Tenelon at 78 0 K occurred with no detectable necking at low strain levels. The fracture surface contained cleavage facets that lay along coherent twin boundaries oriented transversely to the tensile axis. Charging gaseous hydrogen at 679 MPa pressure and 650 0 K had no significant effect on the mechanical behavior or fracture mode at 78 0 K, but raised the ductile-to-brittle transition temperature from less than 200 0 K to about 250 0 K

  5. Magnetic properties of the austenitic stainless steels at cryogenic temperatures

    International Nuclear Information System (INIS)

    Kobayashi, T.; Tsuchiya, K.; Itoh, K.; Kobayashi, S.

    2002-01-01

    The magnetization was measured for the austenitic stainless steel of SUS304, SUS304L, SUS316, and SUS316L with the temperature from 5K to 300K and the magnetic field from 0T to 10T. The field dependences of the magnetizations changed at about 0.7T and 4T. The dependence was analyzed with ranges of 0-0.5T, 1-3T, and 5-10T. There was not so much difference between those stainless steels for the usage at small fields and 300 K. The SUS316 and SUS316L samples showed large non-linearity at high fields and 5K. Therefore, SUS304 was recommended for usage at high fields and low temperatures to design superconducting magnets with the linear approximation of the field dependence of magnetization

  6. Overview of Intergranular Fracture of Neutron Irradiated Austenitic Stainless Steels

    Directory of Open Access Journals (Sweden)

    Anna Hojná

    2017-09-01

    Full Text Available Austenitic stainless steels are normally ductile and exhibit deep dimples on fracture surfaces. These steels can, however, exhibit brittle intergranular fracture under some circumstances. The occurrence of intergranular fracture in the irradiated steels is briefly reviewed based on limited literature data. The data are sorted according to the irradiation temperature. Intergranular fracture may occur in association with a high irradiation temperature and void swelling. At low irradiation temperature, the steels can exhibit intergranular fracture at low or even at room temperatures during loading in air and in high temperature water (~300 °C. This paper deals with the similarities and differences for IG fractures and discusses the mechanisms involved. The intergranular fracture occurrence at low temperatures might be correlated with decohesion or twinning and strain martensite transformation in local narrow areas around grain boundaries. The possibility of a ductile-to-brittle transition is also discussed. In case of void swelling higher than 3%, quasi-cleavage at low temperature might be expected as a consequence of ductile-to-brittle fracture changes with temperature. Any existence of the change in fracture behavior in the steels of present thermal reactor internals with increasing irradiation dose should be clearly proven or disproven. Further studies to clarify the mechanism are recommended.

  7. 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.

  8. Tailoring plasticity of austenitic stainless steels for nuclear applications: Review of mechanisms controlling plasticity of austenitic steels below 400 °C

    Energy Technology Data Exchange (ETDEWEB)

    Meric de Bellefon, G., E-mail: mericdebelle@wisc.edu [University of Wisconsin-Madison (United States); Duysen, J.C. van [EDF R& D (France); University of Tennessee-Knoxville (United States); Unité Matériaux et Transformation (UMET) CNRS, Université de Lille (France)

    2016-07-15

    AISI 304 and 316 austenitic stainless steels were invented in the early 1900s and are still trusted by materials and mechanical engineers in numerous sectors because of their good combination of strength, ductility, and corrosion resistance, and thanks to decades of experience and data. This article is part of an effort focusing on tailoring the plasticity of both types of steels to nuclear applications. It provides a synthetic and comprehensive review of the plasticity mechanisms in austenitic steels during tensile tests below 400 °C. In particular, formation of twins, extended stacking faults, and martensite, as well as irradiation effects and grain rotation are discussed in details. - Highlights: • This article is part of an effort to tailor the plasticity of 304L and 316L steels for nuclear applications. • It reviews mechanisms controlling plasticity of austenitic steels during tensile tests. • Formation of twins, extended stacking faults, and martensite, grain rotation, and irradiation effects are discussed.

  9. Diffusion Couple Alloying of Refractory Metals in Austenitic and Ferritic/Martensitic Steels

    Science.gov (United States)

    2012-03-01

    temperature (DBTT) and lower upper shelf energy (USE) obtained via a Charpy impact test (austenitic steels , however, do not experience DBTT) as seen in...ALLOYING OF REFRACTORY METALS IN AUSTENITIC AND FERRITIC/MARTENSITIC STEELS by Alexander L. McGinnis March 2012 Thesis Advisor: Luke...Ferritic/Martensitic Steels 5. FUNDING NUMBERS 6. AUTHOR(S) Alexander L. McGinnis 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Naval

  10. Corrosion And Thermal Processing In Cold Gas Dynamic Spray Deposited Austenitic Stainless Steel Coatings

    Science.gov (United States)

    2016-06-01

    testing (ASTM G5) of low pressure cold spray austenitic stainless steel coatings. Several different powders and heat treatments will be applied to...diffusion eliminating the local low chromium region. The low carbon type stainless steel alloys as used here are generally considered to be...maximum 200words) This thesis presents research on the corrosion properties and effects of heat treatment on austenitic stainless steel coatings

  11. 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.

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

    International Nuclear Information System (INIS)

    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

  13. Corrosion Behavior of Austenitic and Duplex Stainless Steels in Lithium Bromide

    Directory of Open Access Journals (Sweden)

    Ayo Samuel AFOLABI

    2009-07-01

    Full Text Available The corrosion behavior of austenitic and duplex stainless steels in various concentrations of lithium, bromide solution was investigated by using the conventional weight loss measurement method. The results obtained show that corrosion of these steels occurred due to the aggressive bromide ion in the medium. Duplex stainless steel shows a greater resistance to corrosion than austenitic stainless steel in the medium. This was attributed to equal volume proportion of ferrite and austenite in the structure of duplex stainless steel coupled with higher content of chromium in its composition. Both steels produced electrochemical noise at increased concentrations of lithium bromide due to continuous film breakdown and repair caused by reduction in medium concentration by the alkaline corrosion product while surface passivity observed in duplex stainless steel is attributed to film stability on this steel.

  14. Tailoring plasticity of austenitic stainless steels for nuclear applications: Review of mechanisms controlling plasticity of austenitic steels below 400 °C

    Science.gov (United States)

    Meric de Bellefon, G.; van Duysen, J. C.

    2016-07-01

    AISI 304 and 316 austenitic stainless steels were invented in the early 1900s and are still trusted by materials and mechanical engineers in numerous sectors because of their good combination of strength, ductility, and corrosion resistance, and thanks to decades of experience and data. This article is part of an effort focusing on tailoring the plasticity of both types of steels to nuclear applications. It provides a synthetic and comprehensive review of the plasticity mechanisms in austenitic steels during tensile tests below 400 °C. In particular, formation of twins, extended stacking faults, and martensite, as well as irradiation effects and grain rotation are discussed in details.

  15. EFFECTS OF AUSTENITIZATION ON STRUCTURE FORMATION СHROMO-MOLYBDENUM-VANADIUM STEEL AFTER HIGH TEMPERING

    Directory of Open Access Journals (Sweden)

    V. A. Lutsenko

    2017-01-01

    Full Text Available Influence of austenitization temperature of chrome-molybdenum-vanadium steel on structure formation at the softening heat treatment is studied. It is shown that the decline of the austenitization temperature promotes to reduce the micro-hardness values due to the intensification of spheroidizing of pearlite after the overcooling and high tempering. Increasing the austenitization temperature leads to formation of an uneven structure after tempering.

  16. 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. PMID:26601037

  17. 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.

  18. Residual stresses of water-jet peened austenitic stainless steel

    International Nuclear Information System (INIS)

    Suzuki, Kenji; Shobu, Takahisa; Shiro, Ayumi

    2013-01-01

    The specimen material was austenitic stainless steel, SUS316L. The residual stress was induced by water-jet peening. The residual stress was measured using the 311 diffraction with conventional X-rays. The measured residual stress showed the equi-biaxial stress state. To investigate thermal stability of the residual stress, the specimen was aged thermally at 773K in air to 1000h. The residual stress kept the equi-biaxial stress state against the thermal aging. Lattice plane dependency of the residual stress induced by water-jet peening was evaluated using hard synchrotron X-rays. The residual stress measured by the soft lattice plane showed the equi-biaxial stress state, but the residual stress measured by the hard lattice plane did not. In addition, the distributions of the residual stress in the depth direction were measured using a strain scanning method with hard synchrotron X-rays and neutrons. (author)

  19. Temperature dependent measurement of internal damping of austenitic stainless steels

    Directory of Open Access Journals (Sweden)

    Oravcová Monika

    2018-01-01

    Full Text Available This article is aimed on the analysis of the internal damping changes of austenitic stainless steels AISI 304, AISI 316L and AISI 316Ti depending from temperature. In experimental measurements only resonance method was used which is based on continuous excitation of oscillations of the specimens and the whole apparatus vibrates at the frequency near to the resonance. Microplastic processes and dissipation of energy within the metals are evaluated and investigated by internal damping measurements. Damping capacity of materials is closely tied to the presence of defects including second phase particles and voids. By measuring the energy dissipation in the material, we can determine the elastic characteristics, Youngs modulus, the level of stress relaxation and many other.

  20. Multiaxial elastoplastic cyclic loading of austenitic 316L steel

    Directory of Open Access Journals (Sweden)

    V. Mazánová

    2017-04-01

    Full Text Available Cyclic stress-strain response and fatigue damage character has been investigated in austenitic stainless steel 316L. Hollow cylindrical specimens have been cyclically deformed in combined tension-compression and torsion under constant strain rate condition and different constant strain and shear strain amplitudes. In-phase and 90° out-of-phase cyclic straining was applied and the stress response has been monitored. Cyclic hardening/softening curves were assessed in both channels. Cyclic softening followed for higher strain amplitudes by long-term cyclic hardening was observed. Cyclic stress-strain curves were determined. Study of the surface damage in fractured specimens revealed the types and directions of principal cracks and the sources of fatigue crack initiation in slip bands.

  1. Laser Welding Of Finned Tubes Made Of Austenitic Steels

    Directory of Open Access Journals (Sweden)

    Stolecki M.

    2015-09-01

    Full Text Available This paper describes the technology of welding of finned tubes made of the X5CrNi1810 (1.4301 austenitic steel, developed at Energoinstal SA, allowing one to get high quality joints that meet the requirements of the classification societies (PN-EN 15614, and at the same time to significantly reduce the manufacturing costs. The authors described an automatic technological line equipped with a Trumph disc laser and a tube production technological process. To assess the quality of the joints, one performed metallographic examinations, hardness measurements and a technological attempt to rupture the fin. Analysis of the results proved that the laser-welded finned tubes were performed correctly and that the welded joints had shown no imperfections.

  2. Fatigue crack growth in metastable austenitic stainless steels

    International Nuclear Information System (INIS)

    Mei, Z.; Chang, G.; Morris, J.W. Jr.

    1988-06-01

    The research reported here is an investigation of the influence of the mechanically induced martensitic transformation on the fatigue crack growth rate in 304-type steels. The alloys 304L and 304LN were used to test the influence of composition, the testing temperatures 298 K and 77 K were used to study the influence of test temperature, and various load ratios (R) were used to determine the influence of the load ratio. It was found that decreasing the mechanical stability of the austenite by changing composition or lowering temperature decreases the fatigue crack growth rate. The R-ratio effect is more subtle. The fatigue crack growth rate increases with increasing R-ratio, even though this change increases the martensite transformation. Transformation-induced crack closure can explain the results in the threshold regime, but cannot explain the R-ratio effect at higher cyclic stress intensities. 26 refs., 6 figs

  3. Dynamic recrystallization in friction surfaced austenitic stainless steel coatings

    Energy Technology Data Exchange (ETDEWEB)

    Puli, Ramesh, E-mail: rameshpuli2000@gmail.com; Janaki Ram, G.D.

    2012-12-15

    Friction surfacing involves complex thermo-mechanical phenomena. In this study, the nature of dynamic recrystallization in friction surfaced austenitic stainless steel AISI 316L coatings was investigated using electron backscattered diffraction and transmission electron microscopy. The results show that the alloy 316L undergoes discontinuous dynamic recrystallization under conditions of moderate Zener-Hollomon parameter during friction surfacing. - Highlights: Black-Right-Pointing-Pointer Dynamic recrystallization in alloy 316L friction surfaced coatings is examined. Black-Right-Pointing-Pointer Friction surfacing leads to discontinuous dynamic recrystallization in alloy 316L. Black-Right-Pointing-Pointer Strain rates in friction surfacing exceed 400 s{sup -1}. Black-Right-Pointing-Pointer Estimated grain size matches well with experimental observations in 316L coatings.

  4. Study on ductile fracture evaluation for austenitic stainless steel

    International Nuclear Information System (INIS)

    Miura, Naoki; Shimakawa, Takashi; Kashima, Koichi; Michiba, Kouji; Hiramatsu, Hideki.

    1994-01-01

    In the development of Fast Breeder Reactors (FBRs), structural integrity must be assured for components subjected to high temperatures up to 550degC, even though possible defects are presumed. Nonlinear fracture mechanics is one of the most effective approaches to evaluate ductile fracture behavior of cracked components. In this study, ductile fracture tests were conducted at room temperature and 550degC for austenitic stainless steel SUS304 and 316FR, which were candidates for FBR structural material. The applicability of fracture parameters was investigated from tests using small CT specimens, small CCT specimens, and wide CCT specimens. Fracture tests under the condition of combined tension and bending loads were also performed to investigate the effect of additional bending stress due to the temperature gradient through thickness. It was ascertained that fracture load could be predicted based on the net section collapse criterion and was not so affected by an additional bending stress. (author)

  5. Effect of austenite deformation temperature on Nb clustering and precipitation in microalloyed steel

    International Nuclear Information System (INIS)

    Pereloma, E.V.; Kostryzhev, A.G.; AlShahrani, A.; Zhu, C.; Cairney, J.M.; Killmore, C.R.; Ringer, S.P.

    2014-01-01

    The effect of thermomechanical processing conditions on Nb clustering and precipitation in both austenite and ferrite in a Nb–Ti microalloyed steel was studied using electron microscopy and atom probe tomography. A decrease in the deformation temperature increased the Nb-rich precipitation in austenite and decreased the extent of precipitation in ferrite. Microstructural mechanisms that explain this variation are discussed

  6. Simulation of the Growth of Austenite from As-Quenched Martensite in Medium Mn Steels

    Science.gov (United States)

    Huyan, Fei; Yan, Jia-Yi; Höglund, Lars; Ågren, John; Borgenstam, Annika

    2018-04-01

    As part of an ongoing development of third-generation advanced high-strength steels with acceptable cost, austenite reversion treatment of medium Mn steels becomes attractive because it can give rise to a microstructure of fine mixture of ferrite and austenite, leading to both high strength and large elongation. The growth of austenite during intercritical annealing is crucial for the final properties, primarily because it determines the fraction, composition, and phase stability of austenite. In the present work, the growth of austenite from as-quenched lath martensite in medium Mn steels has been simulated using the DICTRA software package. Cementite is added into the simulations based on experimental observations. Two types of systems (cells) are used, representing, respectively, (1) austenite and cementite forming apart from each other, and (2) austenite forming on the cementite/martensite interface. An interfacial dissipation energy has also been added to take into account a finite interface mobility. The simulations using the first type of setup with an addition of interfacial dissipation energy are able to reproduce the observed austenite growth in medium Mn steels reasonably well.

  7. Intermetallic Strengthened Alumina-Forming Austenitic Steels for Energy Applications

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Bin [Dartmouth College, Hanover, NH (United States); Baker, Ian [Dartmouth College, Hanover, NH (United States)

    2016-03-31

    In order to achieve energy conversion efficiencies of >50 % for steam turbines/boilers in power generation systems, the materials required must be strong, corrosion-resistant at high temperatures (>700°C), and economically viable. Austenitic steels strengthened with Laves phase and L12 precipitates, and alloyed with aluminum to improve oxidation resistance, are potential candidate materials for these applications. The creep resistance of these alloys is significantly improved through intermetallic strengthening (Laves-Fe2Nb + L12-Ni3Al precipitates) without harmful effects on oxidation resistance. Microstructural and microchemical analyses of the recently developed alumina-forming austenitic (AFA) steels (Fe-14Cr-32Ni-3Nb-3Al-2Ti-based) indicated they are strengthened by Ni3Al(Ti) L12, NiAl B2, Fe2Nb Laves phase and MC carbide precipitates. Different thermomechanical treatments (TMTs) were performed on these stainless steels in an attempt to further improve their mechanical properties. The thermo-mechanical processing produced nanocrystalline grains in AFA alloys and dramatically increased their yield strength at room temperature. Unfortunately, the TMTs didn’t increase the yield strengths of AFA alloys at ≥700ºC. At these temperatures, dislocation climb is the dominant mechanism for deformation of TMT alloys according to strain rate jump tests. After the characterization of aged AFA alloys, we found that the largest strengthening effect from L12 precipitates can be obtained by aging for less than 24 h. The coarsening behavior of the L12 precipitates was not influenced by carbon and boron additions. Failure analysis and post-mortem TEM analysis were performed to study the creep failure mechanisms of these AFA steels after creep tests. Though the Laves and B2-NiAl phase precipitated along the boundaries can improve the creep properties, cracks were

  8. Structure and properties of high-temperature austenitic steels for superheater tubes

    Science.gov (United States)

    Blinov, V. M.

    2009-12-01

    The structure and properties of high-temperature austenitic steels intended for superheater tubes are analyzed. Widely used Kh18N10T (AISI 304) and Kh16N13M3 (AISI 316) steels are found not to ensure a stable austenitic structure and stable properties during long-term thermal holding under stresses. The hardening of austenitic steels by fine particles of vanadium and niobium carbides and nitrides and γ'-phase and Fe2W and Fe2Mo Laves phase intermetallics is considered. The role of Cr23C6 chromium carbides, the σ phase, and coarse precipitates of an M 3B2 phase and a boron-containing eutectic in decreasing the time to failure and the stress-rupture strength of austenitic steels is established. The mechanism of increasing the stress-rupture strength of steels by boron additions is described. The chemical compositions, mechanical properties, stress-rupture strength, and creep characteristics of Russian and foreign austenitic steels used or designed for superheater tubes intended for operation under stress conditions at temperatures above 600°C are presented. The conditions are found for increasing the strength, plasticity, and thermodeformation stability of austenite in steels intended for superheater tubes operating at 700°C under high stresses for a long time.

  9. 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.

  10. The influence of nickel-nitrogen ratio on the deformation behaviour of austenitic stainless steels

    CSIR Research Space (South Africa)

    Schmid, OE

    1992-01-01

    Full Text Available This study examines the effect that a partial substitution of nickel with nitrogen has on the deformation behaviour of a metastable austenitic stainless steel, AISI 301. The effect on the tensile deformation behaviour is studied in detail...

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

    NARCIS (Netherlands)

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

  12. 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. Copyright © 2013 Elsevier B.V. All rights reserved.

  13. Friction welding of Al-Cu-SiC composite to AISI 304 austenitic stainless steel

    OpenAIRE

    Özdemir, Niyazi; Balaban, Zülküf

    2017-01-01

    The present study investigates thefeasibility of joining an aluminium matrix composite reinforced with 5, 10 and15 vol. % of SiCp particles to AISI 304 austenitic stainless steel by usingfriction welding technique. In the present study, optical and electronmicroscopy as well as lap shear strength test and microhardness measurementswere used to evaluate the quality of bonding of Al-Cu-SiC and AISI 304austenitic stainless steel joints produced by friction welding

  14. Materials design of high nitrogen manganese austenitic stainless TWIP steels for strip casting

    OpenAIRE

    Mosecker, Linda

    2016-01-01

    High nitrogen manganese austenitic stainless TWIP steels achieve attractive mechanical properties and excellent strain hardening behavior. However, high nitrogen steel melting methods are generally associated with high pressures to enhance the nitrogen solubility in the melt. Thin strip casting offers an attractive option that not only shortens the process route but also allows the alloying with nitrogen at atmospheric pressure. In the present work, the materials design of austenitic Fe-Cr-Mn...

  15. Deuterium retention in ITER-grade austenitic stainless steel

    Science.gov (United States)

    Nemanič, Vincenc; Žumer, Marko; Zajec, Bojan

    2008-11-01

    In view of the construction of ITER, it is essential to confirm that the retention of tritium by the large interior surface area of stainless steel will not become an issue for safety or operating inventory reasons. Retention of deuterium in ITER-grade austenitic stainless steel samples was studied during t = 24 h exposures to pure gaseous deuterium at p = 0.01 mbar and 0.1 mbar and T = 100 °C, 250 °C and 400 °C, respectively. The required high sensitivity for distinguishing hydrogen isotopes involved in the process (H2, HD and D2) was gained after suppression of the native hydrogen concentration by a thermal treatment at T = 400 °C for t = 200 h. The quantity of retained deuterium was determined by measuring the absolute pressure change during the deuterium exposure and subsequent mass spectrometry revealing an intense isotope exchange reaction. The retained amount of 2.6 × 1016 D cm-2 was the highest at T = 400 °C and p = 0.1 mbar and noticeably less at lower deuterium pressure and temperature. Our results, when compared with similar tritium exposures, do not exceed the limits set in the generic safety analysis for the ITER. They manifest that an extremely high sensitivity for deuterium absorption and release can be gained with a precise pressure measuring technique, otherwise attributed exclusively to tritium scintillation methods.

  16. Dynamical recrystallization of high purity austenitic stainless steels

    International Nuclear Information System (INIS)

    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.)

  17. 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. Copyright © 2014 Elsevier B.V. All rights reserved.

  18. Effects of Austenitizing Conditions on the Microstructure of AISI M42 High-Speed Steel

    Directory of Open Access Journals (Sweden)

    Yiwa Luo

    2017-01-01

    Full Text Available The influences of austenitizing conditions on the microstructure of AISI M42 high-speed steel were investigated through thermodynamic calculation, microstructural analysis, and in-situ observation by a confocal scanning laser microscope (CSLM. Results show that the network morphology of carbides could not dissolve completely and distribute equably in the case of the austenitizing temperature is 1373 K. When the austenitizing temperature reaches 1473 K, the excessive increase in temperature leads to increase in carbide dissolution, higher dissolved alloying element contents, and unwanted grain growth. Thus, 1453 K is confirmed as the best austenitizing condition on temperature for the steel. In addition, variations on the microstructure and hardness of the steel are not obvious when holding time ranges from 15 to 30 min with the austenitizing temperature of 1453 K. However, when the holding time reaches 45 min, the average size of carbides tends to increase because of Ostwald ripening. Furthermore, the value of Ms and Mf decrease with the increase of cooling rate. Hence, high cooling rate can depress the martensitic transformation and increase the content of retained austenite. As a result, the hardness of the steel is the best (65.6 HRc when the austenitizing temperature reaches 1453 K and is held for 30 min.

  19. Kinetics of austenite-ferrite and austenite-pearlite transformations in a 1025 carbon steel

    Science.gov (United States)

    Hawbolt, E. B.; Chau, B.; Brimacombe, J. K.

    1985-04-01

    Isothermal and continuous-cooling transformation kinetics have been measured dilatometrically for the γ → α + γ' and γ' → P reactions in a 1025 steel. The isothermal transformation of austenite for each reaction was found to fit the Avrami equation after the fraction transformed was normalized to unity at the completion of the reaction and a transformation-start time was determined. The transformation kinetics under isothermal conditions therefore were characterized in terms of the n and b parameters from the Avrami equation together with the transformation-start times. The parameter n was found to be independent of temperature over the range studied (645 to 760 ‡C) and to have values of 0.99 and 1.33 for the ferrite and pearlite reactions, respectively. This indicates that the nucleation condition is essentially constant and site saturation occurs early in the transformation process. The continuous-cooling experiments were conducted at cooling rates of 2 to 150 ‡C per second to determine the transformation-start times for the ferrite and pearlite reactions and the completion time for transformation to pearlite under CCT conditions. Both reactions were found to obey the Additivity Principle for continuous cooling provided that the incubation (pre-transformation) period was not included in the transformation time. The isothermal transformation data and CCT transformation-start times have been incorporated in a mathematical model to predict continuous-cooling transformation kinetics that agree closely with measurements made at three cooling rates.

  20. Development of nano/sub-micron grain structures in metastable austenitic stainless steels

    Science.gov (United States)

    Rajasekhara, Shreyas

    2007-12-01

    This dissertation is a part of a collaborative work between the University of Texas, Austin-Texas, the University of Oulu, Oulu-Finland, and Outokumpu Stainless Oy, Tornio-Finland, to develop commercial austenitic stainless steels with high strength and ductility. The idea behind this work involves cold-rolling a commercial metastable austenitic stainless steel - AISI 301LN stainless steel to produce strain-induced martensite, followed by an annealing treatment to generate nano/sub-micron grained austenite. AISI 301LN stainless steel sheets are cold-rolled to 63% reduction and subsequently annealed at 600°C, 700°C, 800°C, 900°C and 1000°C for 1, 10 and 100 seconds. The samples are analyzed by X-Ray diffraction, SQUID, transmission electron microscopy, and tensile testing to fundamentally understand the microstructural evolution, the mechanism for the martensite → austenite reversion, the formation of nano/sub-micron austenite grains, and the relationship between the microstructure and the strength obtained in this stainless steel. The results show that cold-rolled AISI 301LN stainless steel consist of dislocation-cell martensite, heavily deformed lath-martensite and austenite shear bands. Subsequent annealing at 600°C for short durations of 1 and 10 seconds leads to negligible martensite to austenite reversion. These 600°C samples exhibit a similar microstructure to the cold-rolled sample. However, for samples annealed at 600°C for 100 seconds and those annealed at higher temperatures (700°C, 800°C, 900°C and 1000°C) exhibit equiaxed austenitic grains of sizes 0.2mum-10mum and secondary phase precipitates. The microstructural analysis also reveals that the martensite → austenite reversion occurs via a diffusion-type reversion mechanism. In this regard, a generalized form of Avrami's equation is used to model the kinetics of martensite → austenite phase reversion. The results from the model agree reasonably well with the experiments. Furthermore

  1. Austenitic Reversion of Cryo-rolled Ti-Stabilized Austenitic Stainless Steel: High-Resolution EBSD Investigation

    Science.gov (United States)

    Tiamiyu, A. A.; Odeshi, A. G.; Szpunar, J. A.

    2018-02-01

    In this study, AISI 321 austenitic stainless steel (ASS) was cryo-rolled and subsequently annealed at 650 and 800 °C to reverse BCC α'-martensite to FCC γ-austenite. The texture evolution associated with the reversion at the selected temperatures was investigated using high-resolution EBSD. After the reversion, TiC precipitates were observed to be more stable in 650 °C-annealed specimens than those reversed at 800 °C. {110} texture was mainly developed in specimens subjected to both annealing temperatures. However, specimens reversed at 650 °C have stronger texture than those annealed at 800 °C, even at the higher annealing time. The strong intensity of {110} texture component is attributed to the ability of AISI 321 ASS to memorize the crystallographic orientation of the deformed austenite, a phenomenon termed texture memory. The development of weaker texture in 800 °C-annealed specimens is attributed to the residual strain relief in grains, dissolution of grain boundary precipitates, and an increase in atomic migration along the grain boundaries. Based on the observed features of the reversed austenite grains and estimation from an existing model, it is suspected that the austenite reversion at 650 and 800 °C undergone diffusional and martensitic shear reversion, respectively.

  2. Upset Resistance Welding of Carbon Steel to Austenitic Stainless Steel Narrow Rods

    Science.gov (United States)

    Ozlati, Ashkaan; Movahedi, Mojtaba; Mohammadkamal, Helia

    2016-11-01

    Effects of welding current (at the range of 2-4 kA) on the microstructure and mechanical properties of upset resistance welds of AISI-1035 carbon steel to AISI-304L austenitic stainless steel rods were investigated. The results showed that the joint strength first increased by raising the welding current up to 3 kA and then decreased beyond it. Increasing trend was related to more plastic deformation, accelerated diffusion, reduction of defects and formation of mechanical locks at the joint interface. For currents more than 3 kA, decrease in the joint strength was mainly caused by formation of hot spots. Using the optimum welding current of 3 kA, tensile strength of the joint reached to 76% of the carbon steel base metal strength. Microstructural observations and microhardness results confirmed that there was no hard phase, i.e., martensite or bainite, at the weld zone. Moreover, a fully austenitic transition layer related to carbon diffusion from carbon steel was observed at the weld interface.

  3. Numerical Modelling of Micro-Stresses in Carbonised Austenitic Cast Steel under Rapid Cooling Conditions

    Directory of Open Access Journals (Sweden)

    Tuleja J.

    2017-06-01

    Full Text Available The paper presents a method of the numerical modelling of micro-stresses in carbonised austenitic cast steel being developed during rapid cooling due to differences in the values of thermal expansion coefficients for this material phases – carbides and austenitic matrix. Micro-stresses are indicated as the main cause of crack initiation in the tooling elements of carburising furnaces being mainly made of austenitic cast steel. A calculation model of carbonised and thermally fatigued austenitic cast steel was developed based on the microstructure images obtained using light microscopy techniques and the phase composition evaluated with the X-ray diffraction method. The values of the stress tensor components and the reduced stress in the complex models of test material structure were determined numerically by the finite element method. The effort analysis was performed and the areas where development of cracks is to be expected were identified, which was experimentally confirmed.

  4. Fundamental study of the austenite formation and decomposition in low-silicon, aluminum added TRIP steels

    Science.gov (United States)

    Garcia-Gonzalez, Jose Enrique

    2005-11-01

    TRIP (Transformation Induced Plasticity) steels are under development for automotive applications that require high strength and excellent formability. Conventional TRIP steels consist of a multiphase microstructure comprised of a ferrite matrix with a dispersion of bainite and metastable retained austenite. The high ductility exhibited by these steels results from the transformation of the metastable retained austenite to martensite during straining. In conventional TRIP steel processing, the multiphase microstructure is obtained by controlled cooling from the alpha + gamma region to an isothermal holding temperature. During this holding, bainite forms and carbon is rejected out into the austenite, which lowers the Ms temperature and stabilizes the austenite to room temperature. In this research project, a fundamental study of a low-Si, Mo-Nb added cold rolled TRIP steel with and without Al additions was conducted. In this study, the recrystallization of cold-rolled ferrite, the formation of austenite during intercritical annealing and the characteristics of the decomposition of the intercritically annealed austenite by controlled cooling rates were systematically assessed. Of special interest were: (i) the effect of the initial hot band microstructure, (ii) the formation of epitaxial ferrite during cooling from the intercritical annealing temperature to the isothermal holding temperature, (iii) the influence of the intercritically annealed austenite on the formation of bainite during the isothermal holding temperature, and (iv) the influence of the processing variables on the type, amount, composition and stability of the retained austenite. During this research study, techniques such as OM, SEM, EBSD, TEM, XRD and Magnetometry were used to fully characterize the microstructures. Furthermore, a Gleeble 3500 unit at US Steel Laboratories was used for dilatometry studies and to simulate different CGL processing routes, from which specimens were obtained to evaluate

  5. 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.

  6. Dissolution mechanism of austenitic stainless steels in lead-bismuth eutectic at 500 deg. C

    International Nuclear Information System (INIS)

    Roy, M.

    2012-01-01

    In the framework of the future nuclear power plants studies, lead-bismuth eutectic (LBE) is foreseen as a coolant in the primary or the secondary circuit in three nuclear systems. The use of this liquid alloy induces corrosion issues for structural steels. In liquid lead alloys, steels can undergo two corrosion phenomena: dissolution or oxidation depending on the temperature and the dissolved oxygen content in LBE. The goal of this study is to identify the dissolution mechanisms of austenitic steels in LBE at 500 deg. C. Four Fe-Cr-Ni model austenitic steels, the 316L steel and five other industrial steels were corroded in LBE up to, respectively, 3000, 6000 and 200 h. The dissolution mechanism is identical for all steels: it starts by a preferential dissolution of chromium and nickel. This dissolution leads to the formation of a ferritic corrosion layer penetrated by LBE and containing between 5 and 10 at% of chromium and almost no nickel. This study demonstrates that dissolutions of nickel and chromium are linked. Otherwise, the corrosion kinetics is linear whatever the tested austenitic steel. The controlling steps of the austenitic steels' corrosion rates have been identified. Natural convection in the LBE bath leads to the formation of a diffusion boundary layer at the steel surface. Chromium diffusion in this diffusion boundary layer seems to control the corrosion rates of the model and industrial austenitic steels except the 316L steel. Indeed, the corrosion rate of the 316L steel is controlled by an interfacial reaction which is either the simultaneous dissolution of nickel and chromium in Ni, Cr compounds or the nickel and chromium dissolution catalyzed by the dissolved oxygen in LBE. This study has permitted to highlight the major role of chromium on the corrosion mechanisms and the corrosion rates of austenitic steels: the corrosion rate increases when chromium activity increases. Finally, the impact of the dissolved oxygen and the minor alloying

  7. Surface modification of austenitic stainless steel by titanium ion implantation

    International Nuclear Information System (INIS)

    Evans, P.J.; Hyvarinen, J.; Samandi, M.

    1995-01-01

    The wear properties of AISI 316 austenitic stainless steel implanted with Ti were investigated for ion doses in the range (2.3-5.4)x10 16 ionscm -2 and average ion energies of 60 and 90keV. The implanted layer was examined by Rutherford backscattering, from which the retained doses were determined, and glow discharge optical emission spectroscopy. Following implantation, the surface microhardness was observed to increase with the greatest change occurring at higher ion energy. Pin-on-disc wear tests and associated friction measurements were also performed under both dry and lubricated conditions using applied loads of 2N and 10N. In the absence of lubrication, breakthrough of the implanted layer occurred after a short sliding time; only for a dose of 5.1x10 16 ionscm -2 implanted at an average energy of 90keV was the onset of breakthrough appreciably delayed. In contrast, the results of tests with lubrication showed a more gradual variation, with the extent of wear decreasing with implant dose at both 2N and 10N loads. Finally, the influence of Ti implantation on possible wear mechanisms is discussed in the light of information provided by several surface characterization techniques. ((orig.))

  8. High cycle fatigue of austenitic stainless steels under random loading

    International Nuclear Information System (INIS)

    Gauthier, J.P.; Petrequin, P.

    1987-08-01

    To investigate reactor components, load control random fatigue tests were performed at 300 0 C and 550 0 C, on specimens from austenitic stainless steels plates in the transverse orientation. Random solicitations are produced on closed loop servo-hydraulic machines by a mini computer which generates random load sequence by the use of reduced Markovian matrix. The method has the advantage of taking into account the mean load for each cycle. The solicitations generated are those of a stationary gaussian process. Fatigue tests have been mainly performed in the endurance region of fatigue curve, with scattering determination using stair case method. Experimental results have been analysed aiming at determining design curves for components calculations, depending on irregularity factor and temperature. Analysis in term of mean square root fatigue limit calculation, shows that random loading gives more damage than constant amplitude loading. Damage calculations following Miner rule have been made using the probability density function for the case where the irregularity factor is nearest to 100 %. The Miner rule is too conservative for our results. A method using design curves including random loading effects with irregularity factor as an indexing parameter is proposed

  9. 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.

  10. Dynamic Recrystallization during Hot Deformation of 304 Austenitic Stainless Steel

    Science.gov (United States)

    Marchattiwar, A.; Sarkar, A.; Chakravartty, J. K.; Kashyap, B. P.

    2013-08-01

    The kinetics of dynamic recrystallization (DRX) during hot compression of 304 austenitic stainless steel was studied over the temperature range of 900-1200 °C and strain rate range of 0.002-0.1 s-1. The initiation and evolution of DRX were investigated using the process variables derived from flow curves. By the regression analysis for conventional hyperbolic sine equation, the activation energy for DRX was determined as Q = 475 kJ mol-1. The temperature and strain rate domain where DRX occurred were identified from the strain rate sensitivity contour map. The critical stress (and strain) for the initiation of DRX was determined from the inflection point on the work hardening rate (θ = dσ/ dɛ) versus flow stress (σ) curve. The saturation stress of the dynamic recovery (DRV) curve was calculated from the θ-σ plot at the same condition at which DRX occurred. Progress of fraction recrystallization was determined from the difference between the generated DRV curve and the experimental DRX curve. In addition, the microstructural evolution at different strain levels during DRX was characterized and compared with the calculated fraction recrystallization.

  11. Residual stress distribution in ferritic-austenitic steel joints made by laser welding

    OpenAIRE

    Iordachescu, Mihaela; Ocaña Moreno, José Luis

    2013-01-01

    The present investigation addresse the influence of laser welding process-ing parameters used for joining dis-similar metals (ferritic to austenitic steel), on the induced residual stress field. Welding was performed on a Nd:YAG laser DY033 (3300 W) in a continuous wave (CW), keyhole mode. The base metals (BM) employed in this study are AISI 1010 carbon steel (CS) and AISI 304L austenitic stainless steel (SS). Pairs of dissimilar plates of 200 mm x 45 mm x 3 mm were butt joined by laser weldi...

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

    International Nuclear Information System (INIS)

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

    2004-01-01

    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. Forgings made of austenitic chromium-nickel steels for the low temperature range

    International Nuclear Information System (INIS)

    Gruendler, O.; Schwarz, W.; Koren, M.

    1981-01-01

    The authors discuss the low temperature application of austenitic chromium-nickel steels for energy production and process techniques. Material requirements are presented, and the behaviour, mechanical and physical properties of such steels are discussed. The manufacture of forgings is considered and test results presented. (Auth.)

  14. Forgings made of austenitic chromium-nickel steels for the low temperature range

    Energy Technology Data Exchange (ETDEWEB)

    Gruendler, O.; Schwarz, W.; Koren, M. (Vereinigte Edelstahlwerke A.G. (VEW), Kapfenberg (Austria))

    1981-09-01

    The authors discuss the low temperature application of austenitic chromium-nickel steels for energy production and process techniques. Material requirements are presented, and the behaviour, mechanical and physical properties of such steels are discussed. The manufacture of forgings is considered and test results presented.

  15. 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...

  16. Discontinuous precipitation in a nickel-free high nitrogen austenitic stainless steel on solution nitriding

    DEFF Research Database (Denmark)

    Mohammadzadeh, Roghayeh; Akbari, Alireza; Grumsen, Flemming Bjerg

    2017-01-01

    Chromium-rich nitride precipitates in production of nickel-free austenitic stainless steel plates via pressurised solution nitriding of Fe–22.7Cr–2.4Mo ferritic stainless steel at 1473 K (1200 °C) under a nitrogen gas atmosphere was investigated. The microstructure, chemical and phase composition...

  17. Modeling of the Recrystallization and Austenite Formation Overlapping in Cold-Rolled Dual-Phase Steels During Intercritical Treatments

    Science.gov (United States)

    Ollat, M.; Massardier, V.; Fabregue, D.; Buscarlet, E.; Keovilay, F.; Perez, M.

    2017-10-01

    Austenite formation kinetics of a DP1000 steel was investigated from a ferrite-pearlite microstructure (either fully recrystallized or cold-rolled) during typical industrial annealing cycles by means of dilatometry and optical microscopy after interrupted heat treatments. A marked acceleration of the kinetics was found when deformed ferrite grains were present in the microstructure just before austenite formation. After having described the austenite formation kinetics without recrystallization and the recrystallization kinetics of the steel without austenite formation by simple JMAK laws, a mixture law was used to analyze the kinetics of the cold-rolled steel for which austenite formation and recrystallization may occur simultaneously. In the case where the interaction between these two phenomena is strong, three main points were highlighted: (i) the heating rate greatly influences the austenite formation kinetics, as it affects the degree of recrystallization at the austenite start temperature; (ii) recrystallization inhibition above a critical austenite fraction accelerates the austenite formation kinetics; (iii) the austenite fractions obtained after a 1 hour holding deviate from the local equilibrium fractions given by Thermo-Calc, contrary to the case of the recrystallized steel. This latter result could be due to the fact that the dislocations of the deformed ferrite matrix could promote the diffusion of the alloying elements of the steel and accelerate austenite formation.

  18. Strength of "Light" Ferritic and Austenitic Steels Based on the Fe - Mn - Al - C System

    Science.gov (United States)

    Kaputkina, L. M.; Svyazhin, A. G.; Smarygina, I. V.; Kindop, V. E.

    2017-01-01

    The phase composition, the hardness, the mechanical properties at room temperature, and the resistance to hot (950 - 1000°C) and warm (550°C) deformation are studied for cast deformable "light" ferritic and austenitic steels of the Fe - (12 - 25)% Mn - (0 - 15)% Al - (0 - 2)% C system alloyed additionally with about 5% Ni. The high-aluminum high-manganese low-carbon and carbonless ferritic steels at a temperature of about 0.5 T melt have a specific strength close to that of the austenitic steels and may be used as weldable scale-resistant and wear-resistant materials. The high-carbon Fe - (20 - 24)% Mn - (5 - 9)% Al - 5% Ni - 1.5% C austenitic steels may be applied as light high-strength materials operating at cryogenic temperatures after a solution treatment and as scale- and heat-resistant materials in an aged condition.

  19. Image based EFIT simulation for nondestructive ultrasonic testing of austenitic steel

    International Nuclear Information System (INIS)

    Nakahata, Kazuyuki; Hirose, Sohichi; Schubert, Frank; Koehler, Bernd

    2009-01-01

    The ultrasonic testing (UT) of an austenitic steel with welds is difficult due to the acoustic anisotropy and local heterogeneity. The ultrasonic wave in the austenitic steel is skewed along crystallographic directions and scattered by weld boundaries. For reliable UT, a straightforward simulation tool to predict the wave propagation is desired. Here a combined method of elastodynamic finite integration technique (EFIT) and digital image processing is developed as a wave simulation tool for UT. The EFIT is a grid-based explicit numerical method and easily treats different boundary conditions which are essential to model wave propagation in heterogeneous materials. In this study, the EFIT formulation in anisotropic and heterogeneous materials is briefly described and an example of a two dimensional simulation of a phased array UT in an austenitic steel bar is demonstrated. In our simulation, a picture of the surface of the steel bar with a V-groove weld is scanned and fed into the image based EFIT modeling. (author)

  20. Wearing Quality of Austenitic, Duplex Cast Steel, Gray and Spheroidal Graphite Iron

    Directory of Open Access Journals (Sweden)

    S. Pietrowski

    2012-04-01

    Full Text Available The current work presents the research results of abrasion wear and adhesive wear at rubbing and liquid friction of new austenitic, austenitic-ferritic (“duplex” cast steel and gray cast iron EN-GJL-250, spheroidal graphite iron EN-GJS-600-3, pearlitic with ledeburitic carbides and spheroidal graphite iron with ledeburitic carbides with a microstructure of the metal matrix: pearlitic, upper bainite, mixture of upper and lower bainite, martensitic with austenite, pearlitic-martensitic-bainitic-ausferritic obtained in the raw state. The wearing quality test was carried out on a specially designed and made bench. Resistance to abrasion wear was tested using sand paper P40. Resistance to adhesive wear was tested in interaction with steel C55 normalized, hardened and sulfonitrided. The liquid friction was obtained using CASTROL oil. It was stated that austenitic cast steel and “duplex” are characterized by a similar value of abrasion wear and adhesive wear at rubbing friction. The smallest decrease in mass was shown by the cast steel in interaction with the sulfonitrided steel C55. Austenitic cast steel and “duplex��� in different combinations of friction pairs have a higher wear quality than gray cast iron EN-GJL- 250 and spheroidal graphite iron EN-GJS-600-3. Austenitic cast steel and “duplex” are characterized by a lower wearing quality than the spheroidal graphite iron with bainitic-martensitic microstructure. In the adhesive wear test using CASTROL oil the tested cast steels and cast irons showed a small mass decrease within the range of 1÷2 mg.

  1. Determination of local carbon content in austenite during intercritical annealing of dual phase steels by PEELS analysis

    International Nuclear Information System (INIS)

    Garcia-Junceda, A.; Caballero, F.G.; Capdevila, C.; Garcia de Andres, C.

    2007-01-01

    Parallel electron energy loss spectroscopy has allowed to analyse and quantify local variations in the carbon concentration of austenite islands transformed during the intercritical annealing treatment of commercial dual-phase steels. These changes in the carbon content of different austenite regions are responsible for the different volume fractions of tempered martensite, martensite and retained austenite obtained after intercritical annealing and overaging treatment. This technique reveals how carbon distribution in austenite evolves as the transformation process advances

  2. Radio-induced brittleness of austenitic stainless steels at high temperatures

    International Nuclear Information System (INIS)

    Barre, Bertrand

    1969-02-01

    In a first part, the author recalls some metallurgical characteristics and properties of iron (atomic properties, crystalline structure, transformation), of iron carbon systems and steels (ferrite, austenite, cementite, martensite, bainite, phase diagrams of iron chromium alloy and iron nickel alloy), aspects regarding the influence of addition elements in the case of stainless steels (mutual interaction of carbon, chromium and nickel in their iron alloys, indication of the various stainless steels, i.e. martensitic, ferritic, austenitic, austenitic-ferritic, and non ferrous), and presents and discusses various mechanical tests (tensile tests, torsion tests, resilience tests, hardness tests, creep tests). In a second part, he discusses the effects of irradiation on austenitic stainless steels: irradiation and deformation under low temperature, irradiation at intermediate temperature, irradiation at high temperature. The third part addresses mechanisms of intergranular fracture in different temperature ranges (400-600, 700-750, and about 800 C). The author then discusses the effect of Helium on the embrittlement of austenitic steels, and finally evokes the perspective of development of a damage model

  3. Rapid nickel diffusion in cold-worked type 316 austenitic steel at 360-500 C

    International Nuclear Information System (INIS)

    Arioka, Koji; Iijima, Yoshiaki

    2017-01-01

    The diffusion coefficient of nickel in cold-worked Type 316 austenitic steel was determined by the diffusion couple method in the temperature range between 360 and 500 C. A diffusion couple was prepared by electroless nickel plating on the surface of a 20 % cold-worked Type 316 austenitic steel specimen. The growth in width of the interdiffusion zone was proportional to the square root of diffusion time until 14 055 h. The diffusion coefficient of nickel (D Ni ) in cold-worked Type 316 austenitic steel was determined by extrapolating the concentration-dependent interdiffusion coefficient to 11 at.% of nickel. The value of D Ni at 360 C was about 5 000 times higher than the lattice diffusion coefficient of nickel in Type 316 austenitic steel. The determined activation energy 117 kJ mol -1 was 46.6 % of the activation energy 251 kJ mol -1 for the lattice diffusion of nickel in Type 316 austenitic steel.

  4. Rapid nickel diffusion in cold-worked type 316 austenitic steel at 360-500 C

    Energy Technology Data Exchange (ETDEWEB)

    Arioka, Koji [Institute of Nuclear Safety Systems, Inc., Mihama (Japan); Iijima, Yoshiaki [Tohoku Univ., Sendai (Japan). Dept. of Materials Science; Miyamoto, Tomoki [Kobe Material Testing Laboratory Co. Ltd., Harima (Japan)

    2017-10-15

    The diffusion coefficient of nickel in cold-worked Type 316 austenitic steel was determined by the diffusion couple method in the temperature range between 360 and 500 C. A diffusion couple was prepared by electroless nickel plating on the surface of a 20 % cold-worked Type 316 austenitic steel specimen. The growth in width of the interdiffusion zone was proportional to the square root of diffusion time until 14 055 h. The diffusion coefficient of nickel (D{sub Ni}) in cold-worked Type 316 austenitic steel was determined by extrapolating the concentration-dependent interdiffusion coefficient to 11 at.% of nickel. The value of D{sub Ni} at 360 C was about 5 000 times higher than the lattice diffusion coefficient of nickel in Type 316 austenitic steel. The determined activation energy 117 kJ mol{sup -1} was 46.6 % of the activation energy 251 kJ mol{sup -1} for the lattice diffusion of nickel in Type 316 austenitic steel.

  5. Residual stress distribution in ferritic to austenitic steel joints made by laser welding,

    OpenAIRE

    Iordachescu, Mihaela; Ruiz Hervías, Jesús; Luzin, V.; Scutelnicu, Elena; Valiente Cancho, Andrés; Ocaña Moreno, José Luis

    2013-01-01

    In this study, autogenous laser welding was used to join thin plates of low carbon ferritic and austenitic stainless steel. Due to the differences in the thermo-physical properties of base metals, this kind of weld exhibits a complex microstructure, which frequently leads to an overall loss of joint quality. Four welded samples were prepared by using different sets of processing parameters, with the aim of minimizing the induced residual stress field. The dissimilar austenitic-ferritic joints...

  6. Austenite stability in reversion-treated structures of a 301LN steel under tensile loading

    Czech Academy of Sciences Publication Activity Database

    Järvenpää, A.; Jaskari, M.; Man, Jiří; Karjalainen, L. P.

    2017-01-01

    Roč. 127, MAY (2017), s. 12-26 ISSN 1044-5803 R&D Projects: GA ČR GA13-32665S Institutional support: RVO:68081723 Keywords : austenitic stainless steel * austenite stability * grain size * reversion annealing * tensile straining * deformation induced martensite Subject RIV: JL - Materials Fatigue, Friction Mechanics OBOR OECD: Audio engineering, reliability analysis Impact factor: 2.714, year: 2016

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

    OpenAIRE

    Monteiro, Waldemar Alfredo; Pereira, Silvio Andre Lima; Vatavuk, Jan

    2017-01-01

    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 ...

  8. The radiation swelling effect on fracture properties and fracture mechanisms of irradiated austenitic steels. Part I. Ductility and fracture toughness

    Energy Technology Data Exchange (ETDEWEB)

    Margolin, B., E-mail: mail@crism.ru; Sorokin, A.; Shvetsova, V.; Minkin, A.; Potapova, V.; Smirnov, V.

    2016-11-15

    The radiation swelling effect on the fracture properties of irradiated austenitic steels under static loading has been studied and analyzed from the mechanical and physical viewpoints. Experimental data on the stress-strain curves, fracture strain, fracture toughness and fracture mechanisms have been represented for austenitic steel of 18Cr-10Ni-Ti grade (Russian analog of AISI 321 steel) irradiated up to neutron dose of 150 dpa with various swelling. Some phenomena in mechanical behaviour of irradiated austenitic steels have been revealed and explained as follows: a sharp decrease of fracture toughness with swelling growth; untypical large increase of fracture toughness with decrease of the test temperature; some increase of fracture toughness after preliminary cyclic loading. Role of channel deformation and channel fracture has been clarified in the properties of irradiated austenitic steel and different tendencies to channel deformation have been shown and explained for the same austenitic steel irradiated at different temperatures and neutron doses.

  9. Effect of Prior Austenite Grain Size on the Morphology of Nano-Bainitic Steels

    Science.gov (United States)

    Singh, Kritika; Kumar, Avanish; Singh, Aparna

    2018-04-01

    The strength in nanostructured bainitic steels primarily arises from the fine platelets of bainitic ferrite embedded in carbon-enriched austenite. However, the toughness is dictated by the shape and volume fraction of the retained austenite. Therefore, the exact determination of processing-morphology relationships is necessary to design stronger and tougher bainite. In the current study, the morphology of bainitic ferrite in Fe-0.89C-1.59Si-1.65Mn-0.37Mo-1Co-0.56Al-0.19Cr (wt pct) bainitic steel has been investigated as a function of the prior austenite grain size (AGS). Specimens were austenitized at different temperatures ranging from 900 °C to 1150 °C followed by isothermal transformation at 300 °C. Detailed microstructural characterization has been carried out using scanning electron microscopy and X-ray diffraction. The results showed that the bainitic laths transformed in coarse austenite grains are finer resulting in higher hardness, whereas smaller austenite grains lead to the formation of thicker bainitic laths with a large fraction of blocky type retained austenite resulting in lower hardness.

  10. 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...... by a temperature region in which the transformation was strongly decelerated. The region of limited transformation was more concise and occurred at higher austenite phase fractions and temperatures for higher heating rates. The two-step kinetics was reproduced by kinetics modeling in DICTRA. The model indicates...

  11. Crack growth in an austenitic stainless steel at high temperature

    International Nuclear Information System (INIS)

    Polvora, J.P.

    1998-01-01

    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* 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)

  12. The effects of fast-neutron irradiation on the mechanical properties of austenitic stainless steel

    International Nuclear Information System (INIS)

    Dalton, J.H.

    1978-01-01

    The paper reviews the effects of fast-neutron irradiation on the tensile properties of austenitic stainless steels at irradiation temperatures of less than 400 degrees Celcius, using as an example, work carried out at Pelindaba on an AISI 316 type steel produced in South Africa. Damage produced in these steels at higher irradiation temperatures and fluences is also briefly discussed. The paper concludes with a discussion of some methods of overcoming or decreasing the effects of irradiation damage [af

  13. Shot-peening effect on the structure, microhardness, and compressive stresses of the austenitic steel 1.4539

    Directory of Open Access Journals (Sweden)

    Barbara Nasiłowska

    2015-06-01

    Full Text Available This article presents shot-peening effect on the structure, microhardness, and compressive stresses of the austenitic steel 1.4539. The research shows strengthening of the top layer and the formation of compressive stresses in the subsurface layers of the shot-peening elements.[b]Keyword[/b]: austenitic steel 1.4539, residual stresses, Waisman-Phillips’a method

  14. Influence of Ti on the Hot Ductility of High-manganese Austenitic Steels

    Science.gov (United States)

    Liu, Hongbo; Liu, Jianhua; Wu, Bowei; Su, Xiaofeng; Li, Shiqi; Ding, Hao

    2017-07-01

    The influence of Ti addition ( 0.10 wt%) on hot ductility of as-cast high-manganese austenitic steels has been examined over the temperature range 650-1,250 °C under a constant strain rate of 10-3 s-1 using Gleeble3500 thermal simulation testing machine. The fracture surfaces and particles precipitated at different tensile temperatures were characterized by means of scanning electron microscope and X-ray energy dispersive spectrometry (SEM-EDS). Hot ductility as a function of reduction curves shows that adding 0.10 wt% Ti made the ductility worse in the almost entire range of testing temperatures. The phases' equilibrium diagrams of precipitates in Ti-bearing high-Mn austenitic steel were calculated by the Thermo-Calc software. The calculation result shows that 0.1 wt% Ti addition would cause Ti(C,N) precipitated at 1,499 °C, which is higher than the liquidus temperature of high-Mn austenitic steel. It indicated that Ti(C,N) particles start forming in the liquid high-Mn austenitic steel. The SEM-EDS results show that Ti(C,N) and TiC particles could be found along the austenite grain boundaries or at triple junction, and they would accelerate the extension of the cracks along the grain boundaries.

  15. High temperature strength and aging behavior of 12%Cr-15%Mn austenitic steels

    International Nuclear Information System (INIS)

    Miyahara, Kazuya; Bae, Dong-Su; Sakai, Hidenori; Hosoi, Yuzo

    1993-01-01

    High Mn-Cr austenitic steels are still considered to be an important high temperature structural material from the point of view of reduced radio-activation. The objective of the present study is to make a fundamental research of mechanical properties and microstructure of 12%Cr-15%Mn austenitic steels. Especially the effects of alloying elements of V and Ti on the mechanical properties and microstructure evolution of high Mn-Cr steels were studied. Precipitation behaviors of carbides, nitrides and σ phase are investigated and their remarkable effects on the high temperature strength are found. The addition of V was very effective for strengthening the materials with the precipitation of fine VN. Ti was also found to be beneficial for the improvement of high temperature strength properties. The results of high temperature strengths of the 12Cr-15Mn austenitic steels were compared with those of the other candidate and/or reference materials, for example, JFMS (modified 9Cr-2Mo ferritic stainless steel) and JPCAs (modified 316 austenitic stainless steels). (author)

  16. 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.

  17. Environmental Degradation of Dissimilar Austenitic 316L and Duplex 2205 Stainless Steels Welded Joints

    Directory of Open Access Journals (Sweden)

    Topolska S.

    2017-12-01

    Full Text Available The paper describes structure and properties of dissimilar stainless steels welded joints between duplex 2205 and austenitic 316L steels. Investigations were focused on environmentally assisted cracking of welded joints. The susceptibility to stress corrosion cracking (SCC and hydrogen embrittlement was determined in slow strain rate tests (SSRT with the strain rate of 2.2 × 10−6 s−1. Chloride-inducted SCC was determined in the 35% boiling water solution of MgCl2 environment at 125°C. Hydrogen assisted SCC tests were performed in synthetic sea water under cathodic polarization condition. It was shown that place of the lowest resistance to chloride stress corrosion cracking is heat affected zone at duplex steel side of dissimilar joins. That phenomenon was connected with undesirable structure of HAZ comprising of large fractions of ferrite grains with acicular austenite phase. Hydrogen assisted SCC tests showed significant reduction in ductility of duplex 2205 steel while austenitic 316L steel remains almost immune to degradation processes. SSR tests of dissimilar welded joints revealed a fracture in the area of austenitic steel.

  18. Influence of Silicon on Swelling and Microstructure in Russian Austenitic Stainless Steels Irradiated to High Neutron Doses

    International Nuclear Information System (INIS)

    Porollo, S.I.; Shulepin, S.V.; Konobeev, Y.V.; Garner, F.

    2007-01-01

    Full text of publication follows: For some applications in fusion devices austenitic stainless steels are still considered to be candidates for use as structural components, but high neutron exposures must be endured by the steels. Operational experience of fast reactors in Western Europe, USA and Japan provides evidence of the possible use of austenitic steels up to ∼ 150 dpa. Studies aimed at improvement of existing Russian austenitic steels are being carried out in Russia. For improvement of irradiation resistance of Russian steels it is necessary to understand the basic mechanisms responsible for deterioration of steel properties. This understanding can be achieved by continuing detailed investigations of the microstructure of cladding steels after irradiation to high doses. By investigating the evolution of radiation-induced microstructure in neutron irradiated steels of different chemical composition one can study the effect of chemical variations on steel properties. Silicon is one of the most important chemical elements that strongly influence the behavior of austenitic steel properties under irradiation. In this paper results are presented of investigations of the effect of silicon additions on void swelling and microstructure of base austenitic stainless steel EI-847 (0.06C-16Cr-15Ni- 3Mo-Nb) irradiated as fuel pin cladding of both regular and experimental assemblies in the BOR-60, BN-350 and BN-600 fast reactors to neutron doses up to 49 dpa. The possible mechanisms of silicon's effect on void swelling in austenitic stainless steels are presented and analyzed. (authors)

  19. Measurement techniques of magnetic properties for evaluation of neutron irradiation damage on austenitic stainless steels

    International Nuclear Information System (INIS)

    Yamagata, Ichiro; Konno, Shotaro; Hayashi, Takehiro; Takaya, Shigeru

    2012-01-01

    The remote-controlled equipment for measurement of magnetic flux density has been developed in order to evaluate the irradiation damage of austenitic stainless steels. Magnetic flux densities by neutron irradiation in austenitic stainless steels, SUS304 and Fast Breeder Reactor grade type 316 (316FR), have been measured by the equipment. The results show that irradiation damage affected to magnetic flux density, and indicate the measuring method of magnetic flux density using a small magnetizer with a permanent magnet of 2 mm in diameter is less affected by specimen shape. (author)

  20. Effect of cold working on nitriding process of AISI 304 and 316 austenitic stainless steel

    International Nuclear Information System (INIS)

    Pereira, Silvio Andre de Lima

    2012-01-01

    The nitriding behavior of AISI 304 and 316 austenitic stainless steel was studied by different cold work degree before nitriding processes. The microstructure, thickness, microhardness and chemical micro-composition were evaluated through optical microscopy, microhardness, scanner electronic microscopy and x ray diffraction techniques. Through them, it was observed that previous plastic deformations do not have influence on layer thickness. However, a nitrided layer thicker can be noticed in the AISI 304 steel. In addition, two different layers can be identified as resulted of the nitriding, composed for austenitic matrix expanded by nitrogen atoms and another thinner immediately below expanded by Carbon atoms. (author)

  1. Impact Strength of Austenitic and Ferritic-Austenitic Cr-Ni Stainless Cast Steel in -40 and +20°C Temperature

    Directory of Open Access Journals (Sweden)

    Kalandyk B.

    2014-10-01

    Full Text Available Studies described in this paper relate to common grades of cast corrosion resistant Cr-Ni steel with different matrix. The test materials were subjected to heat treatment, which consisted in the solution annealing at 1060°C followed by cooling in water. The conducted investigations, besides the microstructural characteristics of selected cast steel grades, included the evaluation of hardness, toughness (at a temperature of -40 and +20oC and type of fracture obtained after breaking the specimens on a Charpy impact testing machine. Based on the results of the measured volume fraction of ferrite, it has been found that the content of this phase in cast austenitic steel is 1.9%, while in the two-phase ferritic-austenitic grades it ranges from 50 to 58%. It has been demonstrated that within the scope of conducted studies, the cast steel of an austenitic structure is characterised by higher impact strength than the two-phase ferritic-austenitic (F-A grade. The changing appearance of the fractures of the specimens reflected the impact strength values obtained in the tested materials. Fractures of the cast austenitic Cr-Ni steel obtained in these studies were of a ductile character, while fractures of the cast ferritic-austenitic grade were mostly of a mixed character with the predominance of brittle phase and well visible cleavage planes.

  2. Impact of Reversed Austenite on the Impact Toughness of the High-Strength Steel of Low Carbon Medium Manganese

    Science.gov (United States)

    Su, Guanqiao; Gao, Xiuhua; Zhang, Dazheng; Du, Linxiu; Hu, Jun; Liu, Zhenguang

    2018-01-01

    We elucidate the relationship between the volume fraction of austenite and the Charpy impact toughness in a medium-Mn steel in terms of microstructural evolution with impact temperature. Different from retained austenite in the matrix after direct quenching, sub-micron lath-shaped morphology-reversed austenite in medium-Mn steel was produced by intercritical annealing. We found that reversed austenite steadily affected the fracture mode; only ductile fractures and dimples decreased with decreasing impact temperature. After the impact fracture test, the content of reversed austenite in the matrix increased slightly with a decreasing impact temperature due to the stability of the austenite grains caused by recrystallization of α' martensite. Reversed austenite slightly decreased during the impact process with a decreasing impact temperature.

  3. Corrosion of austenitic and ferritic-martensitic steels exposed to supercritical carbon dioxide

    International Nuclear Information System (INIS)

    Tan, L.; Anderson, M.; Taylor, D.; Allen, T.R.

    2011-01-01

    Highlights: → Oxidation is the primary corrosion phenomenon for the steels exposed to S-CO 2 . → The austenitic steels showed significantly better corrosion resistance than the ferritic-martensitic steels. → Alloying elements (e.g., Mo and Al) showed distinct effects on oxidation behavior. - Abstract: Supercritical carbon dioxide (S-CO 2 ) is a potential coolant for advanced nuclear reactors. The corrosion behavior of austenitic steels (alloys 800H and AL-6XN) and ferritic-martensitic (FM) steels (F91 and HCM12A) exposed to S-CO 2 at 650 deg. C and 20.7 MPa is presented in this work. Oxidation was identified as the primary corrosion phenomenon. Alloy 800H had oxidation resistance superior to AL-6XN. The FM steels were less corrosion resistant than the austenitic steels, which developed thick oxide scales that tended to exfoliate. Detailed microstructure characterization suggests the effect of alloying elements such as Al, Mo, Cr, and Ni on the oxidation of the steels.

  4. High temperature crack initiation in an austenitic stainless steel

    International Nuclear Information System (INIS)

    Laiarinandrasana, Lucien

    1994-01-01

    The study deals with crack initiation at 600 deg. C and 650 deg. C, on an austenitic stainless steel referenced by Z2 CND 17 12. The behaviour laws of the studied plate were updated 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, monitored by electrical potential drop technique. The time necessary for the crack to initiate is predicted with fracture mechanics global and local approaches, with the help of microstructural observations and finite element results. An identification of a 'Paris' law' for continuous cyclic loading and of a unique correlation between the initiation time and C h * 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 h * 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 decrease 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

  5. Crack initiation at high temperature on an austenitic stainless steel

    International Nuclear Information System (INIS)

    Laiarinandrasana, L.

    1994-01-01

    The study deals with crack initiation at 600 degrees Celsius 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, monitored by electrical potential drop technique. 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 * 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 * 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

  6. Characterization of the Carbon and Retained Austenite Distributions in Martensitic Medium Carbon, High Silicon Steel

    Science.gov (United States)

    Sherman, Donald H.; Cross, Steven M.; Kim, Sangho; Grandjean, Fernande; Long, Gary J.; Miller, Michael K.

    2007-08-01

    The retained austenite content and carbon distribution in martensite were determined as a function of cooling rate and temper temperature in steel that contained 1.31 at. pct C, 3.2 at. pct Si, and 3.2 at. pct noniron metallic elements. Mössbauer spectroscopy, transmission electron microscopy (TEM), transmission synchrotron X-ray diffraction (XRD), and atom probe tomography were used for the microstructural analyses. The retained austenite content was an inverse, linear function of cooling rate between 25 and 560 K/s. The elevated Si content of 3.2 at. pct did not shift the start of austenite decomposition to higher tempering temperatures relative to SAE 4130 steel. The minimum tempering temperature for complete austenite decomposition was significantly higher (>650 °C) than for SAE 4130 steel (˜300 °C). The tempering temperatures for the precipitation of transition carbides and cementite were significantly higher (>400 °C) than for carbon steels (100 °C to 200 °C and 200 °C to 350 °C), respectively. Approximately 90 pct of the carbon atoms were trapped in Cottrell atmospheres in the vicinity of the dislocation cores in dislocation tangles in the martensite matrix after cooling at 560 K/s and aging at 22 °C. The 3.2 at. pct Si content increased the upper temperature limit for stable carbon clusters to above 215 °C. Significant autotempering occurred during cooling at 25 K/s. The proportion of total carbon that segregated to the interlath austenite films decreased from 34 to 8 pct as the cooling rate increased from 25 to 560 K/s. Developing a model for the transfer of carbon from martensite to austenite during quenching should provide a means for calculating the retained austenite. The maximum carbon content in the austenite films was 6 to 7 at. pct, both in specimens cooled at 560 K/s and at 25 K/s. Approximately 6 to 7 at. pct carbon was sufficient to arrest the transformation of austenite to martensite. The chemical potential of carbon is the same in

  7. Effects of austenitization temperature on the microstructure of 15BCr30 and PL22 boron steels

    Directory of Open Access Journals (Sweden)

    C. A. Suski

    2013-01-01

    Full Text Available This paper studies boron precipitation and segregation at austenitic grain boundaries for low carbon boron steels types: PL22 and 15BCr30. The following parameters were evaluated: percentage of martensite/bainite, size and nucleation sites of austenitic grains and precipitates sizes. Three austenitization temperatures were studied (870, 1050 and 1200 °C. The highest martensite percentage occurred for 1050 °C. Iron-borocarbides were detected at grain boundaries for all tested temperatures. At 870 °C the coarse iron-borocarbides are due to non-solubility and coalescence. The highest martensite percentage at 1050 °C is caused by the discrete precipitation of iron-borocarbides at austenitic grains boundaries. The discrete precipitation was due to the low non-equilibrium segregation of boron at grain boundaries. The low non-equilibrium segregation and the small grain size at 1050 °C reduce the total boron concentration at grain boundaries.

  8. Relationship between austenite stability and martensite formation in modified 9Cr-1Mo steel

    International Nuclear Information System (INIS)

    Ning, Baoqun; Zhao, Jie

    2014-01-01

    Aimed at investigating the relationship between austenite stability and martensite formation in modified 9Cr-1Mo steel, the fully austenitized steel was cooled to a temperature above or below the start temperature of martensite transformation (M s o , 406 C), which occurs upon continuous cooling from the austenitizing temperature to room temperature, and held for different times (10 min, 25 min, and 45 min) followed by cooling to room temperature. The concept of primary and secondary martensite is introduced to indicate that two different, sequential, martensites formed in this processing. When cooled to 650 C or 450 C for different times, the austenite stability decreased with prolonged holding time, and during the subsequent cooling the primary martensite start temperature (M s ) was raised to a value higher than M s o . In contrast, M s was reduced to a level lower than M s o when cooled to 420 C or 410 C for 45 min. On the other hand, as the steel was isothermally quenched at temperatures below M s o , during the subsequent cooling a secondary martensite reaction could be observed, and the secondary martensite start temperature (M s ') decreased with holding time. Retained austenite in the form of thin films along martensite lath boundaries was obtained when cooled to 380 C or below for different times. (orig.)

  9. Microstructural investigations and monitoring of low-cycle fatigue degradation in meta-stable austenitic steel

    International Nuclear Information System (INIS)

    Grosse, M.; Kalkhof, D.; Niffenegger, M.

    2000-01-01

    The microstructural changes in the pre-crack stage of low-cycle fatigue (LCF) damage in austenitic pipework steels have been characterised by neutron and X-ray diffraction. The LCF damage evolution in the meta-stable austenitic steel causes a deformation-induced phase transformation from austenite to martensite. Thresholds exist for the formation of martensite as a function of both the load amplitude and the number of LCF cycles. Magnetic stray field and eddy-current measurements were chosen to transfer the results of material characterisation to an on-line monitoring non destructive testing (NDT) method. The density and distribution of martensite obtained from neutron diffraction experiments were used for the calibration of these methods. Both techniques were able to detect the very low amount of martensite in the different-aged specimens (0.5 - 3.1 vol % martensite, usage factors from 0 to 1). (authors)

  10. Effect of austenitizing temperature on microstructure in 16Mn steel treated by cerium

    Science.gov (United States)

    Wen, Bin; Song, Bo; Pan, Ning; Hu, Qing-Yun; Mao, Jing-Hong

    2011-12-01

    The change of inclusions and microstructure of 16Mn steel treated by Ce were observed, and the effect of austenitizing temperature on the microstructure was also examined. The results show that the inclusions are transformed from Si-Mn-Al composite oxide and MnS into AlCeO3, Ce2O2S, and MnS composite inclusions after being treated by Ce. Plenty of intragranular ferrites are formed in 16Mn steel containing ˜0.017wt% Ce. A large amount of intragranular acicular ferrites are formed after being austenitized for 20 min at 1473 K. The prior austenite grain size fit for the formation of intragranular acicular ferrites is about 120 μm.

  11. The effect of variations in carbon activity on the carburization of austenitic steels in sodium

    International Nuclear Information System (INIS)

    Gwyther, J.R.; Hobdell, M.R.; Hooper, A.J.

    1978-07-01

    Experience has shown that the liquid sodium coolant of fast breeder reactors is an effective carbon-transport medium; the resulting carburization of thin austenitic stainless steel components (eg IHX and fuel cladding) could adversely affect their mechanical integrity. The degree and nature of steel carburization depend, inter alia, on the carbon activity of the sodium environment. Exploratory tests are described in which specimens of austenitic stainless steel were carburized in sodium, the carbon activity of which was continuously monitored by a BNL electrochemical carbon meter. The sodium carbon activity was initially high, but decreased with time, simulating conditions equivalent to plant start-up or coolant clean-up following accidental oil ingress. The extent and nature of steel carburization was identified by metallography, electron microscopy, X-ray crystallography and chemical analysis. (author)

  12. Influence of laser shock peening on irradiation defects in austenitic stainless steels

    Science.gov (United States)

    Lu, Qiaofeng; Su, Qing; Wang, Fei; Zhang, Chenfei; Lu, Yongfeng; Nastasi, Michael; Cui, Bai

    2017-06-01

    The laser shock peening process can generate a dislocation network, stacking faults, and deformation twins in the near surface of austenitic stainless steels by the interaction of laser-driven shock waves with metals. In-situ transmission electron microscopy (TEM) irradiation studies suggest that these dislocations and incoherent twin boundaries can serve as effective sinks for the annihilation of irradiation defects. As a result, the irradiation resistance is improved as the density of irradiation defects in laser-peened stainless steels is much lower than that in untreated steels. After heating to 300 °C, a portion of the dislocations and stacking faults are annealed out while the deformation twins remain stable, which still provides improved irradiation resistance. These findings have important implications on the role of laser shock peening on the lifetime extension of austenitic stainless steel components in nuclear reactor environments.

  13. Studies Regarding the Elaboration of the Manganese Austenitic Steel in the Induction Electric Furnace with Acid Coating

    Directory of Open Access Journals (Sweden)

    Constantin Marta

    2010-10-01

    Full Text Available The paper forwards a method of elaborating the manganese austenitic steel in induction electric furnaces with a capacity of 250 Kg having an acid furnace coating. Considering the fact that when elaborating the manganese austenitic steel sulphur can be obtained under 0.02% constitutes an additional reason to attempt the elaboration of this steel in the electric furnaces through induction with acid coating, even if the load has over 0.02% S.

  14. 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

    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...

  15. Dependence of corrosion properties of AISI 304L stainless steel on the austenite grain size

    Energy Technology Data Exchange (ETDEWEB)

    Sabooni, Soheil; Rashtchi, Hamed; Eslami, Abdoulmajid; Karimzadeh, Fathallah; Enayati, Mohammad Hossein; Raeissi, Keyvan; Imani, Reihane Faghih [Isfahan Univ. of Technology, Isfahan (Iran, Islamic Republic of). Dept. of Materials Engineering; Ngan, Alfonso Hing Wan [The Univ. of Hong Kong (China). Dept. of Mechanical Engineering

    2017-07-15

    The corrosion resistance of austenitic stainless steels is known to be hampered by the loss of chromium available for passive surface layer formation as a result of chromium carbide precipitation at austenite grain boundaries during annealing treatments. Although high-temperature annealing can promote carbide dissolution leading to better corrosion resistance, grain coarsening also results, which would lead to poorer mechanical properties. Processing methods to achieve both good corrosion resistance and mechanical properties are thus highly desirable for austenitic stainless steels. In the present study, we show that the corrosion resistance of AISI 304L stainless steel can be improved by grain refinement into the ultrafine-grained regime. Specifically, samples with different austenite grain sizes in the range of 0.65-12 μm were studied by potentiodynamic polarization and electrochemical impedance spectroscopy tests in a 3.5 wt.% NaCl solution. All samples showed a typical passive behavior with similar corrosion potential, but the corrosion current density decreased significantly with decreasing grain size. The results show that the sample with the finest grain size had the best corrosion resistance due to a higher resistance of the passive layer to pitting attacks. This study indicates that grain refinement which improves mechanical properties can also significantly improve the corrosion resistance of AISI 304L stainless steel.

  16. Weld metal characterization of 316L(N) austenitic stainless steel by ...

    African Journals Online (AJOL)

    The present work is focused on EBW of 316L(N) austenitic stainless steel varying the welding parameters such as beam power and welding speed. This study is carried out by analyzing the mechanical and metallurgical properties of the welded material. The mechanical properties have been evaluated using tensile, impact, ...

  17. 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...

  18. Microstructure of super-austenitic steels after long-term annealing

    Czech Academy of Sciences Publication Activity Database

    Kraus, M.; Kroupa, Aleš; Miodownik, P.; Svoboda, Milan; Vřešťál, J.

    2010-01-01

    Roč. 101, č. 6 (2010), s. 729-735 ISSN 1862-5282 R&D Projects: GA ČR(CZ) GA106/07/1078 Institutional research plan: CEZ:AV0Z20410507 Keywords : phase equilibria * microstructure * super-austenitic steel Subject RIV: BJ - Thermodynamics Impact factor: 0.860, year: 2010

  19. 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 ...

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

    NARCIS (Netherlands)

    Geijselaers, Hubertus J.M.; Hilkhuijsen, P.; Bor, Teunis Cornelis; Perdahcioglu, Emin Semih; van den Boogaard, Antonius 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

  1. The efficiency of ion nitriding of austenitic stainless steel 304 using the “active screen”

    OpenAIRE

    M. Ogórek; Z. Skuza; T. Frączek

    2015-01-01

    The study examined layers were formed on the outer surface of austenitic stainless steel 304 under glow discharge conditions in the low-temperature and short-term ion nitriding. The outer layers analyzed in the work produced in parallel in the classical process of cathode and a novel method of “active screen”, intensifying the process of nitriding.

  2. The efficiency of ion nitriding of austenitic stainless steel 304 using the “active screen”

    Directory of Open Access Journals (Sweden)

    M. Ogórek

    2015-01-01

    Full Text Available The study examined layers were formed on the outer surface of austenitic stainless steel 304 under glow discharge conditions in the low-temperature and short-term ion nitriding. The outer layers analyzed in the work produced in parallel in the classical process of cathode and a novel method of “active screen”, intensifying the process of nitriding.

  3. Effect of metallurgical variables on the austenite stability in fatigued AISI 304 type steels

    Czech Academy of Sciences Publication Activity Database

    Man, Jiří; Smaga, M.; Kuběna, Ivo; Eifler, D.; Polák, Jaroslav

    2017-01-01

    Roč. 185, NOV (2017), s. 139-159 ISSN 0013-7944 Institutional support: RVO:68081723 Keywords : Austenitic stainless steel * Chemical banding * Color metallography * Deformation induced martensite * Low cycle fatigue Subject RIV: JL - Materials Fatigue, Friction Mechanics OBOR OECD: Audio engineering, reliability analysis Impact factor: 2.151, year: 2016

  4. Nanotwin Formation in High-Manganese Austenitic Steels Under Explosive Shock Loading

    Science.gov (United States)

    Canadinc, D.; Uzer, B.; Elmadagli, M.; Guner, F.

    2018-04-01

    The micro-deformation mechanisms active in a high-manganese austenitic steel were investigated upon explosive shock loading. Single system of nanotwins forming within primary twins were shown to govern the deformation despite the elevated temperatures attained during testing. The benefits of nanotwin formation for potential armor materials were demonstrated.

  5. Investigation of retained austenite stability in Mn-Si TRIP steel in tensile deformation condition

    OpenAIRE

    O. Muránsky; P. Horňak; P. Lukáš; J. Zrník; P. Šittner

    2005-01-01

    Purpose: The aim of this study is to contribute to a better understanding of the role of the key factors governing the formation of multiphase TRIP aided steel.Design/methodology/approach: The present work reports the results of in-situ neutron diffraction experiments focused on monitoring the phase evolution in three TRIP steel samples subjected to different thermomechanical processing and mechanical loading to evaluate the stability of retained austenite.Findings: In-situ neutron diffractio...

  6. Neutron diffraction analysis of retained austenite stability in Mn-Si steel during plastic deformation

    International Nuclear Information System (INIS)

    Muransky, Ondrej; Lukas, Petr; Zrnik, Jozef; Sittner, Petr

    2006-01-01

    High strength and ductility of the transformation-induced plasticity (TRIP) steels is attributed to the transformation-induced plasticity effect resulting from the strain-induced martensitic transformation of the retained austenite in the multiphase (ferrite, bainite) microstructure. This paper reports the results of in situ neutron diffraction experiments focused on monitoring the evolution of the phase fractions and phase stresses in three different TRIP steel samples subjected to tensile loading at room temperature

  7. Factors which determine the swelling rate of austenitic stainless steels

    International Nuclear Information System (INIS)

    Garner, F.A.; Wolfer, W.G.

    1983-01-01

    Once void nucleation subsides, the swelling rate of many austenitic alloys becomes rather insensitive to variables that control the transient regime of swelling. Models are presented which describe the roles of nickel, chromium and silicon in void nucleation. The relative insensitivity of steady-state swelling to temperature, displacement rate and composition is also discussed

  8. Summary of the PISC round robin results on wrought and cast austenitic steel welds

    International Nuclear Information System (INIS)

    Lemaitre, P.; Koble, T.D.; Crutzen, S.

    1995-01-01

    Within the framework of Action 4 of the third phase of the Programme for the Inspection of Steel Components (PISC III) three capability studies on stainless steel welds have been conducted. The first capability study used a series of 6 wrought-to-wrought stainless steel assemblies that contained a number of flaws such as intergranular stress corrosion cracks, mechanical and thermal fatigue cracks and PISC type A flaws. The second capability study used two wrought-to-cast austenitic steel assemblies that contained lack of fusion flaws and PISC type A flaws. The third capability study used three cast-to-cast austenitic steel assemblies that contained lack of fusion flaws, mechanical fatigue cracks and PISC type A flaws. In total more than 25 teams from 10 different countries participated. A lot of information was obtained on the performance of the inspection techniques used with respect to detection, false calls, depth and length sizing. Different flaw categories were considered to identify those difficult to detect. Furthermore an analysis at the level of techniques was performed which identified some of the more effective techniques and procedures. In this paper the main conclusions from these capabilities studies on austenitic steel welds will be discussed. (author). 12 refs, 14 figs, 1 tab

  9. Effect of hydrogen on the microstructure, mechanical properties and phase transformations in austenitic steels

    International Nuclear Information System (INIS)

    Li, Y.Y.; Xing, Z.S.

    1989-01-01

    Effect of high-pressure hydrogen charging on the microstructure, mechanical properties and phase transformations in austenitic steels has been investigated and discussed. The results show that the strength and impact toughness of the steels increase slightly and that the ductility decreases after hydrogen charging. The existence of δ-ferrite deteriorates the resistance to hydrogen embrittlement (HE) of the steels. The occurrence of carbide in the steel resulted from aging reduces the ductility of the steel and makes the steel sensitive to HE. The existence of sufficient hydrogen promotes the ε-martensitic transformation and suppresses the α'-martensitic transformation. The permeabilities and diffusivities of hydrogen in the steels have also been determined. (orig.)

  10. Theoretical and experimental study of carburisation and decarburisation of a meta-stable austenitic steel

    Directory of Open Access Journals (Sweden)

    Charles West

    2005-12-01

    Full Text Available Metastable austenitic stainless steels are known to undergo a partial transformation of austenite to martensite as a consequence of plastic deformation. In the case of cyclic loading, a certain level of plastic strain must be exceeded, and phase formation takes place after an incubation period, during which the necessary amount of plastic deformation is accumulated. The susceptibility of the austenitic phase to deformation-induced martensite formation is strongly affected by the temperature of loading and the stability of austenite, which itself depends on the chemical composition. A key element in this regard is carbon which stabilizes the austenitic phase. It is shown in this study that the carbon concentration can be analysed systematically and reproducible by means of annealing treatments, if the parameters of these treatments are carefully defined on the basis of advanced theoretical thermodynamic and kinetic considerations. First results on the effect of carbon concentration and temperature of fatigue testing on the austenite/martensite transformation are presented, in order to illustrate the significance of these parameters on the martensite formation rate.

  11. Partial transformation of austenite in Al-Mn-Si TRIP steel upon tensile straining: an in situ EBSD study

    DEFF Research Database (Denmark)

    Lomholt, Trine Nybo; Adachi, Y.; da Silva Fanta, Alice Bastos

    2013-01-01

    of the stability of austenite grains against strain-induced transformation, with particular focus on the grain size and the location of the austenite grains. The findings confirm that size and location of austenite grains are significant parameters for their stability. Small austenite grains were observed......The transformation of austenite to martensite in an Al–Mn–Si transformation-induced plasticity steel was investigated with in situ electron backscatter diffraction (EBSD) measurements under tensile straining. The visualisation of the microstructure upon straining allows for an investigation...... to be more stable than large grains, while austenite grains located beside bainitic ferrite are the most stable. Moreover, it is demonstrated that austenite grains transform gradually...

  12. Austenitic steels of the new generation used for power plant installations with supercritical parameters and their welding

    International Nuclear Information System (INIS)

    Brozda, J.

    2006-01-01

    Combustion of bituminous coal and lignite in power boilers brings into the atmosphere a lot of contaminations. The emission of pollutants can be reduced by the application of supercritical steam parameters, which also improves the efficiency of power units, but in that case constructional materials of the new generation are needed, among them austenitic steels. The development of power units with supercritical and ultra supercritical steam parameters is presented as well as applied structural materials. Austenitic steels used in power boiler constructions are listed. Basic characteristics of austenitic steels of the new generation are given and principles of their forming and welding. (author)

  13. The effect of chemical composition and austenite conditioning on the transformation behavior of microalloyed steels

    International Nuclear Information System (INIS)

    Mousavi Anijdan, S.H.; Rezaeian, Ahmad; Yue, Steve

    2012-01-01

    In this investigation, by using continuous cooling torsion (CCT) testing, the transformation behavior of four microalloyed steels under two circumstances of austenite conditioning and non-conditioning was studied. A full scale hot-rolling schedule containing a 13-pass deformation was employed for the conditioning of the austenite. The CCT tests were then employed till temperature of ∼ 540 °C and the flow curves obtained from this process were analyzed. The initial and final microstructures of the steels were studied by optical and electron microscopes. Results show that alloying elements would decrease the transformation temperature. This effect intensifies with the gradual increase of Mo, Nb and Cu as alloying elements added to the microalloyed steels. As well, austenite conditioning increased the transformation start temperature due mainly to the promotion of polygonal ferrite formation that resulted from a pancaked austenite. The final microstructures also show that CCT alone would decrease the amount of bainite by inducing ferrite transformation in the two phase region. In addition, after the transformation begins, the deformation might result in the occurrence of dynamic recrystallization in the ferrite region. This could lead to two different ferrite grain sizes at the end of the CCT. Moreover, the Nb bearing steels show no sign of decreasing the strength level after the transformation begins in the non-conditioned situation and their microstructure is a mix of polygonal ferrite and bainite indicating an absence of probable dynamic recrystallization in this condition. In the conditioned cases, however, these steels show a rapid decrease of the strength level and their final microstructures insinuate that ferrite could have undergone a dynamic recrystallization due to deformation. Consequently, no bainite was seen in the austenite conditioned Nb bearing steels. The pancaking of austenite in the latest cases produced fully polygonal ferrite structures

  14. Role of Austenite in Brittle Fracture of Bond Region of Super Duplex Stainless Steel

    Science.gov (United States)

    Kitagawa, Yoshihiko; Ikeuchi, Kenji; Kuroda, Toshio

    Weld simulation of heat-affected zone (HAZ) was performed to investigate the mechanism by which austenite affects the toughness of super duplex stainless steel. Thermal cycles of various peak temperatures in the range from 1373 K to 1673 K corresponding to the HAZ were applied to SAF2507 super duplex stainless steel specimens. Charpy impact test was carried out using the specimens after the weld simulation, and the fracture surfaces were observed by SEM using three-dimensionally reconstruction technique. Austenite content decreased with increasing the peak temperature when the peak temperature exceeded 1473 K and the impact value decreased with increasing the peak temperature and decreasing the austenite content. The thermal cycle of the peak temperature of 1673 K corresponding to weld bond region caused decreasing of austenite content which was 22% lower than that of the base metal. The ductile-brittle transition temperature was measured. As a result the temperature increased rapidly in the weld bond region, the peak temperature of which exceeded 1623 K by the grain growth of ferrite matrix occurring subsequently to the completely dissolution of austenite. The morphology of the fracture surfaces after impact testing at 77 K showed cleavage fracture of ferrite. The {100} orientations of cleavage fracture facets were measured using three-dimensional images of the fracture surfaces and the results were visualized as the orientation color maps. The results showed that there were cleavage fractures consisting of a few facets parallel to each other. It was considered that a few facets existed in one ferrite grain. It was concluded that Widmanstätten austenite divided the large fracture into smaller cleavage facets in a ferrite grain and then suppressed the degradation of bond toughness of duplex stainless steel.

  15. Overlaying of type 316 austenitic stainless steel with type 430 ferritic stainless steel

    International Nuclear Information System (INIS)

    Sujith, S.; Gill, T.P.S.

    1993-01-01

    Overlaying of type 316 austenitic stainless steel vessel with type 430 ferritic stainless is proposed for liquid magnesium service. The interface in this type of bimetallic configuration has been shown to be a cause for concern as it contains a hard and brittle martensite micro constituent which becomes susceptible to cracking under certain conditions. This study was carried out to standardize the welding conditions and characterise the interface in order to obtain sound overlay. Some tests were also conducted to simulate the elevated temperature service. The investigation has shown that the interface hardness approaches 400 VPN when no preheating is employed. However, in the preheated samples, appreciable reduction in the peak hardness was observed. This has been attributed to a decrease in the cooling rate of the clad metal with an increase in the preheating temperature which results in softening of the martensite. The minimum recommended preheat is 473 K. The samples exposed to thermal cycle tests to a peak temperature of 1223 K to simulate the service condition did not show any cracking at the interface after 20 cycles of testing. Therefore, this study has demonstrated the stability of the interface between type 316 and 430 stainless steels at the intended temperature of service. (author)

  16. Ferrittic steels sodium cooled fast reactor piping: an alternative to austenitic stainless steels

    International Nuclear Information System (INIS)

    Dubey, J.K.; Athmalingam, S.; Balasubramaniyan, V.; Srinivasan, G.

    2016-01-01

    Piping for Nuclear Steam Supply System (NSSS) in sodium cooled fast reactor constitutes a significant portion of the total plant cost. Optimal choice of piping material is therefore essential from the economy consideration. Material selection also plays an important role in reliable and safe operation of fast breeder reactor. The major factors considered in the selection of material include compatibility of material, operating conditions, availability of design data in nuclear codes, ease of fabrication, international experience, cost etc. Cost reduction is an important aspect for the future fast breeder reactor to be competitive. There are several components for which cheaper materials may satisfy the design requirements. Sodium piping in fast reactor is designed for low pressure and high temperature when compared to fossil power plant steam piping. Hence sodium piping is thin walled. Sodium piping has to be designed for normal, possible design basis events and transient load like seismic and sodium-water reaction pressure. This paper explores the various aspect of ferritic steel as alternative to austenitic stainless steel for piping of sodium cooled fast reactor

  17. Hydrogen Absorption Induced Slow Crack Growth in Austenitic Stainless Steels for Petrochemical Pressure Vessel Industries

    Directory of Open Access Journals (Sweden)

    Ronnie Rusli

    2011-05-01

    Full Text Available Type 304Land type 309 austenitic stainless steels were tested either by exposed to gaseous hydrogen or undergoing polarized cathodic charging. Slow crack growth by straining was observed in type 304L, and the formation of α‘ martensite was indicated to be precursor for such cracking. Gross plastic deformation was observed at the tip of the notch, and a single crack grew slowly from this region in a direction approximately perpendicular to the tensile axis. Martensite formation is not a necessary condition for hydrogen embrittlement in the austenitic phase.

  18. Effect of bainite transformation and retained austenite on mechanical properties of austempered spheroidal graphite cast steel

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Toshio; Abe, Toshihiko; Tada, Shuji [Tohoku National Industrial Research Inst., Sendai (Japan). Materials Engineering Div.

    1996-06-01

    Austempered ductile iron (ADI) has excellent mechanical properties, but its Young`s modulus is low. Austempered spheroidal graphite cast steel (AGS) has been developed in order to obtain a new material with superior mechanical properties to ADI. Its carbon content (approximately 1.0 pct) is almost one-third that of a standard ADI; thus, the volume of graphite is also less. Young`s modulus of AGS is 195 to 200 GPa and is comparable to that of steel. Austempered spheroidal graphite cast steel has an approximately 200 MPa higher tensile strength than ADI and twice the Charpy absorbed energy of ADI. The impact properties and the elongation are enhanced with increasing volume fraction of carbon-enriched retained austenite. At the austempering temperature of 650 K, the volume fraction of austenite is approximately 40 pct for 120 minutes in the 2.4 pct Si alloy, although it decreases rapidly in the 1.4 pct Si alloy. The X-ray diffraction analysis shows that appropriate quantity of silicon retards the decomposition of the carbon-enriched retained austenite. For austempering at 570 K, the amount of the carbon-enriched austenite decreases and the ferrite is supersaturated with carbon, resulting in high tensile strength but low toughness.

  19. 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.

  20. Austenitic-ferritic stainless steels: A state-of-the-art review

    Science.gov (United States)

    Voronenko, B. I.

    1997-10-01

    Austenitic-ferritic stainless steels, more commonly known as duplex stainless steels, or DSS for short, consist of two basic phases. One is austenite, A, and the other is ferrite, F, present in about equal amounts (but not less than 30% each). The two phases owe their corrosion resistance to the high chromium content. Compared to austenitic stainless steels, ASS, they are stronger (without sacrificing ductility), resist corrosion better, and cost less due to their relatively low nickel content. DSS can be used in an environment where standard ASS are not durable enough, such as chloride solutions (ships, petrochemical plant, etc.). Due to their low nickel content and the presence of nickel, DSS have good weldability. However, they have a limited service temperature range (from -40 to 300°) because heating may cause them to give up objectionable excess phases and lower the threshold of cold brittleness in the heat-affected zone of welded joints. State-of-the art DSS are alloyed with nitrogen to stabilize their austenite, and in this respect the nitrogen does the job of nickel. Also, nitrogen enhances the strength and resistance to pitting and improves the structure of welds.

  1. Quantitative determination of retained austenite in the continuous annealing production line of cold-rolled steel

    International Nuclear Information System (INIS)

    Ichikawa, Fumihiko; Kitagawa, Hajime.

    1987-01-01

    An X-ray diffraction method has been developed for quantitative determination of retained austenite in the continuous annealing production line, CAL, of cold rolled steel sheets. A new unit of diffractometer(Cr-K α source with two proportional counters) was specially designed for the CAL. Intensities of {220} austenite reflection, I γ , and background, I BG , are measured separately by the two detectors. From I γ and I BG , real-time calculation of normalized intensity of austenite, I S , is executed by the following equation ; I S = (I γ -I BG )/I BG . I S was little affected by the fluctuation of the distance between the diffractometer and travelling material. Normalized intensity is well correlated both with the tensile strength and with volume fraction of martensite, of high strength ''dual-phase'' steel sheets. From this findings, the presently developed X-ray diffractometer unit is proved to be successfully employable in the CAL as an effectual method for control of material properties in the high strength ''dual-phase'' steel sheet by monitoring the normalized intensity of austenite. (author)

  2. Features of austenite formation in low-carbon steel upon heating in the intercritical temperature range

    Science.gov (United States)

    Panov, D. O.; Smirnov, A. I.

    2017-11-01

    The features of austenite formation upon continuous heating of low-carbon steel at the rates of 90-0.15 K/s in the intercritical temperature range (ICTR) have been studied. It has been found that, in the initially high-tempered, initially quenched, and initially cold-deformed steel, the α → γ transition in the ICTR consists of three stages. The thermokinetic diagrams of the austenite formation with the indication of the positions of the critical points Ac 1 and Ac 3 and also of the temperature ranges of the development of each identified stage of the α → γ transformation have been constructed. A complex of structural studies has been carried out, and a scheme of the austenite formation upon continuous heating at a rate of 90 K/s in the ICTR for the initially high-tempered steel, initially quenched steel, and initially cold-deformed low-carbon steel has been suggested, which reflects all stages of this process.

  3. Phase Equilibrium and Austenite Decomposition in Advanced High-Strength Medium-Mn Bainitic Steels

    Directory of Open Access Journals (Sweden)

    Adam Grajcar

    2016-10-01

    Full Text Available The work addresses the phase equilibrium analysis and austenite decomposition of two Nb-microalloyed medium-Mn steels containing 3% and 5% Mn. The pseudobinary Fe-C diagrams of the steels were calculated using Thermo-Calc. Thermodynamic calculations of the volume fraction evolution of microstructural constituents vs. temperature were carried out. The study comprised the determination of the time-temperature-transformation (TTT diagrams and continuous cooling transformation (CCT diagrams of the investigated steels. The diagrams were used to determine continuous and isothermal cooling paths suitable for production of bainite-based steels. It was found that the various Mn content strongly influences the hardenability of the steels and hence the austenite decomposition during cooling. The knowledge of CCT diagrams and the analysis of experimental dilatometric curves enabled to produce bainite-austenite mixtures in the thermomechanical simulator. Light microscopy (LM, scanning electron microscopy (SEM, and transmission electron microscopy (TEM were used to assess the effect of heat treatment on morphological details of produced multiphase microstructures.

  4. Fatigue behaviors and damage mechanism of a Cr-Mn-N austenitic steel

    DEFF Research Database (Denmark)

    Lv, Z.; Cai, P.; Yu, Tianbo

    2017-01-01

    Four-point bending fatigue tests were conducted on a Cr-Mn-N austenitic steel at room temperature, at frequency of 20 Hz and the stress ratio of R = 0.1, in air. The fatigue strength of this Cr-Mn-N austenitic steel was measured to be 503 MPa in the maximum stress from the S-N curve obtained....... It was found that multi-site crack nucleation took place on the surface of the steel during fatigue, and that the crack population (i.e., fatigue weak-links) was found to be a Weibull function of the applied stress. Usually only one or two of the initiated cracks could lead to the final failure of the samples...

  5. Effect of residual stress on fatigue crack propagation at 200 C in a welded joint austenitic stainless steel - ferritic steel

    International Nuclear Information System (INIS)

    Zahouane, A.I.; Gauthier, J.P.; Petrequin, P.

    1988-01-01

    Fatigue resistance of heterogeneous welded joints between austenitic stainless steels and ferritic steels is evaluated for reactor components and more particularly effect of residual stress on fatigue crack propagation in a heterogeneous welded joint. Residual stress is measured by the hole method in which a hole is drilled through the center of a strain gage glued the surface of the materials. In the non uniform stress field a transmissibility function is used for residual stress calculation. High compression residual stress in the ferritic metal near the interface ferritic steel/weld slow down fatigue crack propagation. 5 tabs., 15 figs., 19 refs [fr

  6. In-situ investigation of strain-induced martensitic transformation kinetics in an austenitic stainless steel by inductive measurements

    NARCIS (Netherlands)

    Alonso de Celada Casero, C.; Kooiker, Harm; Groen, Manso; Post, J; San Martin, D

    2017-01-01

    An inductive sensor developed by Philips ATC has been used to study in-situ the austenite (γ) to martensite (α′) phase transformation kinetics during tensile testing in an AISI 301 austenitic stainless steel. A correlation between the sensor output signal and the volume fraction of α′-martensite

  7. 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...

  8. 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 ...

  9. Interpretation of the influences of irradiation upon fatigue crack propagation in austenitic stainless steels

    International Nuclear Information System (INIS)

    Lloyd, G.J.

    1982-04-01

    An interpretation of the influences of neutron irradiation upon fatigue crack propagation in austenitic stainless steels is given. The approach has been to extend a previously developed rationalisation of the effects of various test and materials variables upon fatigue crack propagation in unirradiated stainless steels to include irradiated stainless steels. Irradiation has diverse influences upon the rate of fatigue crack propagation depending on the exact irradiation and test conditions. It has been shown that by considering the underlying mechanisms of failure, some confidence is established in trends in data in a subject where information is very scarce and difficult to obtain. (author)

  10. Interim fatigue design curves for carbon, low-alloy, and austenitic stainless steels in LWR environments

    International Nuclear Information System (INIS)

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

    1993-01-01

    Both temperature and oxygen affect fatigue life; at the very low dissolved-oxygen levels in PWRs and BWRs with hydrogen water chemistry, environmental effects on fatigue life are modest at all temperatures (T) and strain rates. Between 0.1 and 0.2 ppM, the effect of dissolved-oxygen increases rapidly. In oxygenated environments, fatigue life depends strongly on strain rate and T. A fracture mechanics model is developed for predicting fatigue lives, and interim environmentally assisted cracking (EAC)-adjusted fatigue curves are proposed for carbon steels, low-alloy steels, and austenitic stainless steels

  11. Austenite Continuous Cooling Transformation of Wear-Resistant Steel with Hardness 500HBW

    Science.gov (United States)

    Yong, Feng; Xiaodong, Liu; Demin, Sun

    The phase transformation rule, microstructures and properties of 500HBW wear-resistant steel produced in Jinan Company of Shandong Iron and Steel Co. ltd. have been investigated in this paper. When the chemical composition of steel is given, the cooling rates after austeniting affect on the properties of steel greatly. The hardness and tensile strength increasing as increasing of cooling rates. The main cause is due to appearance and increasing of Bainite and Martensite other than Ferrite and Pearlite at room temperature. The cooling rate has distinct effects upon the mechanical properties of steel plates. With the 3-55°C/s cooling rate, the tensile strength vary in 979-1690MPa, the hardness changed from 341 to 596HV10. In the procedure of manufacture of 500HBW wear-resistant steels, the quickly cooling rate should be got to keep suitable microstructure and good hardness and toughness.

  12. A study of ion-induced phase transformation in austenitic stainless steel

    International Nuclear Information System (INIS)

    Sakamoto, Isao

    1993-01-01

    The phase stability of austenitic stainless steel in an irradiation environment using low-nickel 17/7, 17/13 steel and commercial steel such as 304 and 316 steel as well as high-nickel 310 steel in order to investigate a mechanism of the ion-induced phase transformation were studied. The irradiation in steel was performed with steel constituent elements (Fe, Cr and Ni ions) and also with rare-gas elements such as Ar, Kr and Xe ions at room temperature. In addition, He, H, D and N 2 ions were irradiated in steel complementarily. The modification in the near surface region of the irradiated steel has been observed by means of conversion electron Moessbauer spectroscopy (CEMS), glancing angle X-ray diffraction (GXRD), Rutherford backscattering (RBS) and particle-induced X-ray emission (PIXE). It has been considered that the phase transformation in steel after irradiation of Ni ions was stress-induced due to a stress field around damages accumulated by irradiation. On the other hand, for Fe ion irradiation in steel, we have confirmed that the increase of Fe constituent atoms induced the phase transformation. For rare-gas ion irradiation in steel, it has been suggested that implanted rare-gas atoms aggregated and formed highly pressurized rare-gas inclusion. In both metal ion and rare-gas ion irradiation, the austenite stability was demonstrated to be well correlated with the phase conditions of the Schaffler diagram, and it has been established that the primary contribution to the driving force for these transformation comes from relief of high stress levels in the implanted layer. (J.P.N.) 76 refs

  13. Application of Moessbauer effect to the study of austenite retained in low carbon steels

    International Nuclear Information System (INIS)

    Azevedo, A.L.T. de; Silva, E.G. da

    1979-01-01

    Moessbauer effect measurements were performed in two samples of low carbon, low alloy steels, one with a bainite granular microstructure and the other a martensitic one. The concentration of the retained austenite was determined in both samples by Moessbauer spectrometry and X radiation, a very good agreement for the sample with a greater austenite content having been observed. From the assumption that the carbon atoms in the f.c.c. matrix repel one another due to Coulomb interactions, giving origin to quadrupolar interactions, it was possible to determine carbon concentration in the MA (Martensite Austenite) components of bainite, the results being in good agreement with the one obtained from metallographic considerations. (I.C.R.) [pt

  14. A macroscopic model to simulate the mechanically induced martensitic transformation in metastable austenitic stainless steels

    International Nuclear Information System (INIS)

    Perdahcıoğlu, E.S.; Geijselaers, H.J.M.

    2012-01-01

    Mechanically induced martensitic transformation and the associated transformation plasticity phenomena in austenitic stainless steels are studied. The mechanisms responsible for the transformation are investigated and put into perspective based on experimental evidence. The stress and strain partitioning into the austenite and martensite phases are formulated using a mean-field homogenization approach. At this intermediate length-scale the average stress in the austenite phase is computed and utilized to compute the mechanical driving force resolved in the material. The amount of transformation and the transformation plasticity is derived as a function of the driving force. The mechanical response of the material is obtained by combining the homogenization and the transformation models. The model is verified by mechanical tests under biaxial loading conditions during which different transformation rates are observed. As a final verification of the model, a bending test is used which manifests the stress-state dependency of the transformation.

  15. 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.

  16. Influence of Austenitizing Parameters on Mechanical Behavior of Press Hardened Steels

    Science.gov (United States)

    Golem, Lindsay

    Recent increases in the Corporate Average Fuel Economy standard have led to an increased focus on lightweight materials for use in vehicle architectures. In particular, press hardened steels (PHS) have been identified as suitable materials to reduce vehicle mass while maintaining or possibly improving vehicle crash performance. A fundamental understanding of the mechanical behavior of PHS with respect to changes in processing conditions is critical to their proper use. In this work, 22MnB5 Al-Si coated blanks were austenitized at several different times and temperatures to produce a range of prior austenite grain sizes. Mechanical behavior was evaluated using smooth sided tensile testing, double edge notch tensile testing, and free bend testing. Metrics, such as notch tensile strength, notch strength ratio, and notch displacement, which is based on the fracture mechanics parameter crack tip opening displacement, were derived from double edge notch tensile testing to assess material notch sensitivity and toughness as a function of processing conditions. Additionally, bend angle at maximum load, post uniform bending slope, and energy for fracture were measured using free bend testing to provide another means for evaluating mechanical behavior. Increasing the austenitizing temperature and hold time resulted in an increase in the measured prior austenite grain size; however, elevated austenitizing temperatures also increased the thickness of the coating interdiffusion layer. In the coated material, tensile strength decreased with increasing prior austenite grain size for both notched and smooth sided tensile samples, but minimal difference was observed in the strain to failure results. Notch displacement, bend angle at maximum load, and energy for fracture during free bend testing all decreased with increasing prior austenite grain size in the coated PHS and also showed a significant drop in measured behavior for the 1025 °C for 30 minutes austenitizing condition

  17. Comprehensive Deformation Analysis of a Newly Designed Ni-Free Duplex Stainless Steel with Enhanced Plasticity by Optimizing Austenite Stability

    DEFF Research Database (Denmark)

    Moallemi, Mohammad; Zarei-Hanzaki, Abbas; Eskandari, Mostafa

    2017-01-01

    A new metastable Ni-free duplex stainless steel has been designed with superior plasticity by optimizing austenite stability using thermodynamic calculations of stacking fault energy and with reference to literature findings. Several characterization methods comprising optical microscopy, magneti...

  18. Low-temperature nitriding of austenitic steel in a vibrofluidized bed

    Science.gov (United States)

    Baraz, V. R.; Grachev, S. V.

    1999-11-01

    The prospects for use of a vibrofluidized bed (VFB) for low-temperature nitrogen saturation of high-strength austenitic steel based on Cr-Ni-Mn (12Kh17N8G2S2MF) are considered. The positive effect of preliminary plastic deformation on the intensity of nitriding is described. The temperature and time parameters of nitriding in a VFB for strain-aging austenitic steel 12Kh17N8G2S2MF are shown to be adequate for the regimes of the final heat-treatment operation of aging. This creates the possibility of combining the operations of surface alloying and strain aging into a single cycle. This combined treatment increases substantially the resistance of the steel to cyclic loads while preserving the strength parameters. It is shown that the presented method of low-temperature nitriding in a VFB is expedient for improving the service characteristics of austenitic steel 12Kh17N8G2S2MF used for production of force springs of automobile brake systems.

  19. Austenite stability in TRIP steels studied by synchrotron radiation

    NARCIS (Netherlands)

    Blondé, R.

    2014-01-01

    TRIP steel is a material providing great mechanical properties. Such steels show a good balance between high-strength and ductility, not only as a result of the fine microstructure, but also because of the well-known TRIP effect. The Transformation Induced-Plasticity (TRIP) phenomenon is the

  20. Characterization of friction stir welded joint of low nickel austenitic stainless steel and modified ferritic stainless steel

    Science.gov (United States)

    Mondal, Mounarik; Das, Hrishikesh; Ahn, Eun Yeong; Hong, Sung Tae; Kim, Moon-Jo; Han, Heung Nam; Pal, Tapan Kumar

    2017-09-01

    Friction stir welding (FSW) of dissimilar stainless steels, low nickel austenitic stainless steel and 409M ferritic stainless steel, is experimentally investigated. Process responses during FSW and the microstructures of the resultant dissimilar joints are evaluated. Material flow in the stir zone is investigated in detail by elemental mapping. Elemental mapping of the dissimilar joints clearly indicates that the material flow pattern during FSW depends on the process parameter combination. Dynamic recrystallization and recovery are also observed in the dissimilar joints. Among the two different stainless steels selected in the present study, the ferritic stainless steels shows more severe dynamic recrystallization, resulting in a very fine microstructure, probably due to the higher stacking fault energy.

  1. Quantification of retained austenite by X-ray diffraction and saturation magnetization in a supermartensitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Sicupira, Felipe Lucas [Departamento de Engenharia Metalúrgica e de Materiais - Escola de Engenharia da UFMG, 31270–901 Belo Horizonte, MG (Brazil); Sandim, Maria José R.; Sandim, Hugo R.Z. [Escola de Engenharia de Lorena – USP, 12600–970 Lorena, SP (Brazil); Santos, Dagoberto Brandão [Departamento de Engenharia Metalúrgica e de Materiais - Escola de Engenharia da UFMG, 31270–901 Belo Horizonte, MG (Brazil); Renzetti, Reny Angela, E-mail: renzetti.ra@gmail.com [Universidade Federal de Itajubá - UNIFEI, 35903–087 Itabira, MG (Brazil)

    2016-05-15

    The good performance of supermartensitic stainless steels is strongly dependent on the volume fraction of retained austenite at room temperature. The present work investigates the effect of secondary tempering temperatures on this phase transformation and quantifies the amount of retained austenite by X-ray diffraction and saturation magnetization. The steel samples were tempered for 1 h within a temperature range of 600–800 °C. The microstructure was characterized using scanning electron microscopy and electron backscatter diffraction. Results show that the amount of retained austenite decreased with increasing secondary tempering temperature in both quantification methods. - Highlights: • The phase transformation during secondary tempering temperatures was observed. • Phases were quantified by X-ray diffraction and DC-saturation magnetization. • More retained austenite forms with increasing secondary tempering temperature. • The retained austenite is mainly located at the grain and lath boundaries.

  2. The thermal expansion of austenitic manganese and manganese-chromium steels

    International Nuclear Information System (INIS)

    Richter, F.

    1977-01-01

    The linear coefficient of thermal expansion was determined by dilatometer for 5 Mn steels and 6 Mn-Cr steels between -196 and +500 0 C. Because of the antiferromagnetic properties, the thermal expansion of austenitic Mn and Mn-Cr steels is determined by the position of the magnetic changeover temperature (Neel temperature), which depends on the chemical composition of the steel. Below the Neel temperature, the thermal coefficient of expansion is greatly reduced by volumetric magnetostriction (Invar effect). For this reason, one can only give approximate values for thermal expansion for all Mn and Mn-Cr steels in the temperature range of -100 0 C to about +100 0 C. (GSC) [de

  3. In-situ neutron diffraction analysis on deformation behavior of duplex high Mn steel containing austenite and ɛ-martensite

    Science.gov (United States)

    Kwon, Ki Hyuk; Jeong, Jae Suk; Choi, Jong-Kyo; Koo, Yang Mo; Tomota, Yo; Kim, Nack J.

    2012-10-01

    The deformation behavior of Fe-17Mn-0.02C steel containing ɛ-martensite within austenite matrix has been investigated via in-situ neutron diffraction study at 298 K and 77 K. Based on the analyses of changes in phase fraction and lattice strain, it has been shown that the steel shows the deformation-induced phase transformation of austenite → ɛ-martensite → α'-martensite and the direct transformation of austenite → α'-martensite at both temperatures. However, the kinetics of such transformations vary with temperature, resulting in a higher and more persistent work hardening at 77 K than at 298 K.

  4. On the capability of austenitic steel to withstand cyclic deformations during service at elevated temperatures

    International Nuclear Information System (INIS)

    Etienne, C.F.; Dortland, W.; Zeedijk, H.B.

    1975-01-01

    Safe design for structures with steels for elevated temperatures necessitates screening these materials on the basis of objective criteria for ductility, besides screening them on elevated temperature strength. Because creep and fatigue damage may occur during operation, the ductility of a steel after a long operation time is more important than the ductility in the as delivered condition. This paper describes results of an investigation into the ductility of some austenitic Cr-Ni-steels. In order to determine the capability of the steels to withstand cyclic plastic deformation in the aged condition, various ageing treatments were applied before determining the ductility in low-cycle fatigue testing. Correlating the ductility with the sizes of the carbide precipitates made it possible to predict the ductility behaviour during long service times. This led to the conclusion that for an austenitic steel with a high thermal stability (17.5 per cent Cr-11 per cent Ni) the ductility can decrease considerably during service at elevated temperature. Nevertheless it is expected that the remaining ductility of such steels in aged condition will be amply sufficient to withstand the cyclic deformations that occur during normal service. (author)

  5. Capability of austenitic steel to withstand cyclic deformations during service at elevated temperatures

    International Nuclear Information System (INIS)

    Etienne, C.F.; Dortland, W.; Zeedijk, H.B.

    1975-01-01

    Safe design for structures with steels for elevated temperatures necessitates screening these materials on the basis of objective criteria for ductility, besides screening them on elevated temperature strength. Because creep and fatigue damage may occur during operation, the ductility of a steel after a long operation time is more important than the ductility in the as delivered condition. Results of an investigation into the ductility of austenitic Cr--Ni-steels are described. In order to determine the capability of the steels to withstand cyclic plastic deformations in the aged condition, various aging treatments were applied before determining the ductility in low-cycle fatigue testing. Correlating the ductility with the sizes of the carbide precipitates made it possible to predict the ductility behavior during long service times. This led to the conclusion that for an austenitic steel with a high thermal stability (17.5 percent Cr--11 percent Ni) the ductility can decrease considerably during service at elevated temperature. Nevertheless it is expected that the remaining ductility of such steels in aged condition will be amply sufficient to withstand the cyclic deformations that occur during normal service

  6. Development of Creep-Resistant and Oxidation-Resistant Austenitic Stainless Steels for High Temperature Applications

    Science.gov (United States)

    Maziasz, Philip J.

    2018-01-01

    Austenitic stainless steels are cost-effective materials for high-temperature applications if they have the oxidation and creep resistance to withstand prolonged exposure at such conditions. Since 1990, Oak Ridge National Laboratory (ORNL) has developed advanced austenitic stainless steels with creep resistance comparable to Ni-based superalloy 617 at 800-900°C based on specially designed "engineered microstructures" utilizing a microstructure/composition database derived from about 20 years of radiation effect data on steels. The wrought high temperature-ultrafine precipitate strengthened (HT-UPS) steels with outstanding creep resistance at 700-800°C were developed for supercritical boiler and superheater tubing for fossil power plants in the early 1990s, the cast CF8C-Plus steels were developed in 1999-2001 for land-based gas turbine casing and diesel engine exhaust manifold and turbocharger applications at 700-900°C, and, in 2015-2017, new Al-modified cast stainless steels with oxidation and creep resistance capabilities up to 950-1000°C were developed for automotive exhaust manifold and turbocharger applications. This article reviews and summarizes their development and their properties and applications.

  7. A Basic Study on the Defect Detectability of Austenitic Stainless Steel Weldments using Ultrasonic Testing

    International Nuclear Information System (INIS)

    Park, M. H.; Park, K. H.; Seo, D. M.; Yoon, K. S.

    1989-01-01

    This paper presents the ultrasonic characteristics of weldment and detectability of defects of weldment in Austenitic Stainless Steel Type 304 that is composed of mostly coolant piping system in nuclear power plants. The results of this experiment show as follows: 1. When the ultrasonic beam detects the defects on the side of base metal and on the opposite side of weldment, the indications which was detected on the screen show different amplitude and different metal path each. 2. The ultrasonically estimated notch depth is generally oversized than actual notch depth. 3. It is easy for the false indication to show up on the screen because of columnar structure of weldment in austenitic stainless steel. 4. The higher frequencies of transducer have more difficulties to detect the defects of the opposite side of weldment because of ultrasonic attenuation in weldment and the longitudinal transmitter-receiver transducer is the most effective in detecting the opposite side defects of weldment

  8. Correlation Between Microstructure and Mechanical Properties Before and After Reversion of Metastable Austenitic Stainless Steels

    Science.gov (United States)

    Fargas, Gemma; Zapata, Ana; Roa, Joan Josep; Sapezanskaia, Ina; Mateo, Antonio

    2015-12-01

    Reversion treatments are a way to improve the mechanical response of metastable austenitic stainless steels by means of grain refinement. To effectively apply those treatments, the steel must be previously deformed to induce a significant amount of martensitic transformation. In this work, the effect of reversion treatments was studied on a commercial AISI 301LN grade subjected to an industrial cold rolling process, with thickness reductions not higher than 40 pct. Microstructural changes and evolution of both monotonic and cyclic mechanical properties were investigated after cold rolling and upon reversion treatments. Results revealed that the finer austenitic microstructure obtained after reversion leads to an interesting combination of properties, with strong increments in hardness and yield strength, and also fatigue limit improvement, as compared to the initial annealed condition.

  9. Fatigue crack growth of 316NG austenitic stainless steel welds at 325 °C

    Science.gov (United States)

    Li, Y. F.; Xiao, J.; Chen, Y.; Zhou, J.; Qiu, S. Y.; Xu, Q.

    2018-02-01

    316NG austenitic stainless steel is a commonly-used material for primary coolant pipes of pressurized water reactor systems. These pipes are usually joined together by automated narrow gap welding process. In this study, welds were prepared by narrow gap welding on 316NG austenitic stainless steel pipes, and its microstructure of the welds was characterized. Then, fatigue crack growth tests were conducted at 325 °C. Precipitates enriched with Mn and Si were found in the fusion zone. The fatigue crack path was out of plane and secondary cracks initiated from the precipitate/matrix interface. A moderate acceleration of crack growth was also observed at 325°Cair and water (DO = ∼10 ppb) with f = 2 Hz.

  10. Effect of chlorides and sulfates on the EAC of austenitic stainless steel in PWR environment

    International Nuclear Information System (INIS)

    Couvant, T.; Herms, E.; Combrade, P.; Vaillant, F.; De Curieres, I.; Boursier, J.M.; Raquet, O.; De Bouvier, O.

    2007-01-01

    Austenitic stainless steels are widely used in primary and auxiliary circuits of Pressurized Water Reactors (PWRs). Moreover, some components (Canopy or Omega seals, dead legs, etc.) suffer from environmentally assisted cracking (EAC) that is, in a most cases related to the presence of tiny concentrations of pollutants. Stress corrosion tests were conducted on austenitic stainless steels (AISI 304L, 316L) in polluted simulated PWR primary environment at temperatures from 150 o C to 300 o C. When sulfates were present (> 1 μg.g -1 ), shallow cracking indicating some sensitivity to EAC was observed in Constant Elongation Rate Tests (CERTs) in deaerated environment but not in aerated environment. When chlorides were present, EAC was only observed in aerated environment, depending on the chloride and sulfate contents. In aerated environment a significant synergy between chlorides and sulfates led to an increase in the susceptibility to EAC. A deleterious effect of the cold work was also noted. (author)

  11. Influence of impact energy on work hardening ability of austenitic manganese steel and its mechanism

    Directory of Open Access Journals (Sweden)

    Li Xiaoyun

    2012-08-01

    Full Text Available To further understand the hardening mechanism of austenitic manganese steel under actual working conditions, the work hardening ability was studied and the microstructures of austenitic manganese steel were observed under different impact energies. The work hardening mechanism was also analyzed. The results show that the best strain hardening effect could be received only when the impact energy reaches or exceeds the critical impact energy. The microstructural observations reveal that dislocations, stacking faults and twins increase with raising impact energy of the tested specimens. The hardening mechanism changes at different hardening degrees. It is mainly dislocation and slip hardening below the critical impact energy, but it changes to the twinning hardening mechanism when the impact energy is above the critical impact energy.

  12. Mechanism of fatigue crack initiation in austenitic stainless steels in light water reactor environments

    International Nuclear Information System (INIS)

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

    2003-01-01

    This paper examines the mechanism of fatigue crack initiation in austenitic stainless steels (SSs) in light water reactor (LWR) coolant environments. The effects of key material and loading variables on the fatigue lives of wrought and cast austenitic SSs in air and LWR environments have been evaluated. The influence of reactor coolant environments on the formation and growth of fatigue cracks in polished smooth SS specimens is discussed. The results indicate that the fatigue lives of these steels are decreased primarily by the effects of the environment on the growth of cracks <200 μm and, to a lesser extent, on enhanced growth rates of longer cracks. The fracture morphology in the specimens has been characterized. Exploratory fatigue tests were conducted to study the effects of surface micropits or minor differences in the surface oxide on fatigue crack initiation. (author)

  13. A review of compatibility of IFR fuel and austenitic stainless steel

    International Nuclear Information System (INIS)

    Keiser, D.D. Jr.

    1996-01-01

    Interdiffusion experiments have been conducted to investigate the compatibility of various austenitic stainless steels with U-Pu-Zr alloys, which are alloys to be employed as fuel for the Integral Fast Reactor being developed by Argonne National Laboratory. These tests have also studied the compatibility of austenitic stainless steels with fission products, like the minor actinides (Np and Am) and lanthanides (Ce and Nd), that are generated during the fission process in an IFR. This paper compares the results of these investigations in the context of fuel-cladding compatibility in IFR fuel elements, specifically focusing on the relative Interdiffusion behavior of the components and the types of phases that develop based on binary phase diagrams. Results of Interdiffusion tests are assessed in the light of observations derived from post-test examinations of actual irradiated fuel elements

  14. In situ TEM study of stress corrosion cracking of austenitic stainless steel

    International Nuclear Information System (INIS)

    Li, J.X.; Chu, W.Y.; Wang, Y.B.; Qiao, L.J.

    2003-01-01

    A constant deflection device designed for use within a transmission electron microscope (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 MgCl 2 solution, and the initiation of stress corrosion microcracking. Results showed that crack tip corrosion processes during SCC-enhanced dislocation emission, multiplication and motion. SCC microcracks initiated when the corrosion-enhanced dislocation emission and motion had fully develop. A passive film formed during corrosion of austenitic stainless steel in the boiling MgCl 2 solution generated a tensile stress. During SCC, the additive tensile stress generated at the metal/passive film interface assists the applied stress to enhance dislocation emission and motion

  15. Evaluation of High Temperature Corrosion Resistance of Finned Tubes Made of Austenitic Steel And Nickel Alloys

    Directory of Open Access Journals (Sweden)

    Turowska A.

    2016-06-01

    Full Text Available The purpose of the paper was to evaluate the resistance to high temperature corrosion of laser welded joints of finned tubes made of austenitic steel (304,304H and nickel alloys (Inconel 600, Inconel 625. The scope of the paper covered the performance of corrosion resistance tests in the atmosphere of simulated exhaust gases of the following chemical composition: 0.2% HCl, 0.08% SO2, 9.0% O2 and N2 in the temperature of 800°C for 1000 hours. One found out that both tubes made of austenitic steel and those made of nickel alloy displayed good resistance to corrosion and could be applied in the energy industry.

  16. Solid state alloying by plasma nitriding and diffusion annealing treatment for austenitic stainless steel

    International Nuclear Information System (INIS)

    Pinedo, C.E.; Vatavuk, J.; Oliveira, S.D. de; Tschiptschin, A.P.

    1999-01-01

    Nitrogen has been added to stainless steels to improve mechanical strength and corrosion resistance. High nitrogen steel production is limited by high gas pressure requirements and low nitrogen solubility in the melt. One way to overcome this limitation is the addition of nitrogen in solid state because of its higher solubility in austenite. However, gas and salt bath nitriding have been done at temperatures around 550 C, where nitrogen solubility in the steel is still very low. High temperature nitriding has been, thus proposed to increase nitrogen contents in the steel but the presence of oxide layers on top of the steel is a barrier to nitrogen intake. In this paper a modified plasma nitriding process is proposed. The first step of this process is a hydrogen plasma sputtering for oxide removal, exposing active steel surface improving nitrogen pickup. This is followed by a nitriding step where high nitrogen contents are introduced in the outermost layer of the steel. Diffusion annealing is then performed in order to allow nitrogen diffusion into the core. AISI 316 austenitic stainless steel was plasma nitrided and diffusion annealed at 1423K, for 6 hours, with 0.2 MPa nitrogen pressure. The nitrided steel presented ∝60 μm outermost compact layer of (Fe,Cr) 3 N and (Fe,Cr) 4 N with 11 wt.% N measured by surface depth profiling chemical analysis - GDS system. During the annealing treatment the nitride layer was dissolved and nitrogen diffused to the core of the sample leaving more even nitrogen distribution into the steel. Using this technique one-millimetre thick sample were obtained having high nitrogen content and uniform distribution through the thickness. (orig.)

  17. 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

    When studying laser welding of austenitic stainless steel, hot cracking is frequently observed. To prevent hot cracking in laser welded stainless steel it is advantageous to obtain primary solidification of the ferrite phase that subsequently, on cooling, transforms in the solid state to the aust......When studying laser welding of austenitic stainless steel, hot cracking is frequently observed. To prevent hot cracking in laser welded stainless steel it is advantageous to obtain primary solidification of the ferrite phase that subsequently, on cooling, transforms in the solid state...

  18. The use of different techniques for determination of pitting corrosion potential of austenitic stainless steel

    International Nuclear Information System (INIS)

    Eskelinen, P.; Forsen, O.; Onnela, J.; Ylaesaari, S.; Haenninen, H.

    1992-01-01

    Three different techniques for pitting corrosion potential measurement on austenitic stainless steel (Fe18Cr10Ni) were compared: conventional polarization method, a new Avesta electrochemical corrosion measurement cell and a scratch technique. Special attention was paid to the effects of crevice corrosion during pitting corrosion potential measurement and to their elimination. Development of a rapid test technique for reliable pitting corrosion potential determination was aimed at and resulted from comparison of the different techniques

  19. Use of Direct Current Resistivity Measurements to Assess AISI 304 Austenitic Stainless Steel Sensitization

    OpenAIRE

    Mesquita, Ramaiany Carneiro; Mecury, José Manoel Rivas; Tanaka, Auro Atsumi; Sousa, Regina Célia de

    2015-01-01

    This paper describes the feasibility of using direct current electrical resistivity measurements to evaluate AISI 304 austenitic stainless steel sensitization. ASTM A262 – Practice A and double loop electrochemical potentiodynamic reactivation (DL-EPR) tests were performed to assess the degree of sensitization (DoS) qualitatively and quantitatively, and electrical resistivity (ER) was measured by the four-point direct-current potential drop method. The results indicate that the DoS incr...

  20. The Similar and Dissimilar Spot Welding of 304 and 316L Austenitic Stainless Steels

    OpenAIRE

    ÇINAR, Özgür; ALYANAKOĞLU, Ahmet Erdem; ÇAKIR, Talha; ÇETİNER, Burcu Nilgün; TOPCU, İsmail; EKİCİ, Bülent; GÜLLÜOĞLU, Arif Nihat

    2017-01-01

    Being one of the eldest electric welding process, theresistance spot welding offers practical and time saving applications in thefield of joining metals of several manufacturing industries such as automotive,white goods and machinery. Even light weight metals, i.e. aluminum andmagnesium has lately been taking attention of researchers and producers, thesteels, especially austenitic stainless steels are still being used in widerange of applications due to their combination of excellent corrosio...

  1. Microstructural and Texture Development in Two Austenitic Steels with High-Manganese Content

    DEFF Research Database (Denmark)

    Bhattacharya, Basudev; Ray, Ranjit Kumar; Leffers, Torben

    2015-01-01

    Two austenitic steels, Fe-21.3Mn-3.44Si-3.74Al-0.5C and Fe-29.8Mn-2.96Si-2.73Al-0.52C, were subjected to cold rolling with 30 to 80 pct reduction with an increment of 10 pct and subsequently the development of their microstructures and textures were studied. The overall texture after 80 pct cold ...

  2. Characterization of strain-induced martensitic transformation in a metastable austenitic stainless steel

    International Nuclear Information System (INIS)

    Hausild, P.; Davydov, V.; Drahokoupil, J.; Landa, M.; Pilvin, P.

    2010-01-01

    Kinetics of deformation-induced martensitic transformation in metastable austenitic steel AISI 301 was characterized by several techniques including classical light metallography, scanning electron microscopy, X-ray diffraction, neutron diffraction and electron back scattered diffraction. In situ monitoring of magnetic properties, acoustic emission and temperature increase during tensile tests at different strain rates was also performed. Results obtained by different methods are compared and discussed.

  3. Stability of austenitic 316L steel against martensite formation during cyclic straining

    Czech Academy of Sciences Publication Activity Database

    Man, Jiří; Obrtlík, Karel; Petrenec, Martin; Beran, Přemysl; Smaga, M.; Weidner, A.; Dluhoš, J.; Kruml, Tomáš; Biermann, H.; Eifler, D.; Polák, Jaroslav

    2011-01-01

    Roč. 10, - (2011), s. 1279-1284 E-ISSN 1877-7058. [ICM11 -International Conference on The Mechanical Behavior of Materials /11./. Lake Como, 05.06.2011-09.06.2011] R&D Projects: GA ČR GAP108/10/2371 Institutional research plan: CEZ:AV0Z10480505; CEZ:AV0Z20410507 Keywords : low cycle fatigue * 316L austenitic stainless steel * deformation-induced martensite Subject RIV: JL - Materials Fatigue, Friction Mechanics

  4. Development of Ultra-Fine-Grained Structure in AISI 321 Austenitic Stainless Steel

    Science.gov (United States)

    Tiamiyu, A. A.; Szpunar, J. A.; Odeshi, A. G.; Oguocha, I.; Eskandari, M.

    2017-12-01

    Ultra-fine-grained (UFG) structure was developed in AISI 321 austenitic stainless steel (ASS) using cryogenic rolling followed by annealing treatments at 923 K, 973 K, 1023 K, and 1073 K (650 °C, 700 °C, 750 °C, and 800 °C) for different lengths of time. The α'-martensite to γ-austenite reversion behavior and the associated texture development were analyzed in the cryo-rolled specimens after annealing. The activation energy, Q, required for the reversion of α'-martensite to γ-austenite in the steel was estimated to be 80 kJ mol-1. TiC precipitates and unreversed triple junction α'-martensite played major roles in the development of UFG structure through the Zener pinning of grain boundaries. The optimum annealing temperature and time for the development of UFG structure in the cryo-rolled AISI 321 steel are (a) 923 K (650 °C) for approximately 28800 seconds and (b) 1023 K (750 °C) for 600 seconds, with average grain sizes of 0.22 and 0.31 µm, respectively. Annealing at 1023 K (750 °C) is considered a better alternative since the volume fraction of precipitated carbides in specimens annealed at 1023 K (750 °C) are less than those annealed at 923 K (650 °C). More so, the energy consumption during prolonged annealing time to achieve an UFG structure at 923 K (650 °C) is higher due to low phase reversion rate. The hardness of the UFG specimens is 195 pct greater than that of the as-received steel. The higher volume fraction of TiC precipitates in the UFG structure may be an additional source of hardening. Micro and macrotexture analysis indicated {110}〈uvw〉 as the major texture component of the austenite grains in the UFG structure. Its intensity is stronger in the specimen annealed at low temperatures.

  5. Effect of metallurgical variables on the austenite stability in fatigued AISI 304 type steels

    Czech Academy of Sciences Publication Activity Database

    Man, Jiří; Smaga, M.; Kuběna, Ivo; Eifler, D.; Polák, Jaroslav

    2017-01-01

    Roč. 185, NOV (2017), s. 139-159 ISSN 0013-7944. [XVIII International Colloquium Mechanical Fatigue of Metals. Gijón, 05.11.2016-07.11.2016] R&D Projects: GA ČR GA13-32665S Institutional support: RVO:68081723 Keywords : Austenitic stainless steel * Deformation induced martensite * Color metallography * Chemical banding * Low cycle fatigue Subject RIV: JL - Materials Fatigue, Friction Mechanics OBOR OECD: Audio engineering, reliability analysis Impact factor: 2.151, year: 2016

  6. Numerical simulation of hydrogen-assisted crack initiation in austenitic-ferritic duplex steels

    International Nuclear Information System (INIS)

    Mente, Tobias

    2015-01-01

    Duplex stainless steels have been used for a long time in the offshore industry, since they have higher strength than conventional austenitic stainless steels and they exhibit a better ductility as well as an improved corrosion resistance in harsh environments compared to ferritic stainless steels. However, despite these good properties the literature shows some failure cases of duplex stainless steels in which hydrogen plays a crucial role for the cause of the damage. Numerical simulations can give a significant contribution in clarifying the damage mechanisms. Because they help to interpret experimental results as well as help to transfer results from laboratory tests to component tests and vice versa. So far, most numerical simulations of hydrogen-assisted material damage in duplex stainless steels were performed at the macroscopic scale. However, duplex stainless steels consist of approximately equal portions of austenite and δ-ferrite. Both phases have different mechanical properties as well as hydrogen transport properties. Thus, the sensitivity for hydrogen-assisted damage is different in both phases, too. Therefore, the objective of this research was to develop a numerical model of a duplex stainless steel microstructure enabling simulation of hydrogen transport, mechanical stresses and strains as well as crack initiation and propagation in both phases. Additionally, modern X-ray diffraction experiments were used in order to evaluate the influence of hydrogen on the phase specific mechanical properties. For the numerical simulation of the hydrogen transport it was shown, that hydrogen diffusion strongly depends on the alignment of austenite and δ-ferrite in the duplex stainless steel microstructure. Also, it was proven that the hydrogen transport is mainly realized by the ferritic phase and hydrogen is trapped in the austenitic phase. The numerical analysis of phase specific mechanical stresses and strains revealed that if the duplex stainless steel is

  7. 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.

  8. Characterization of the sodium corrosion behavior of commercial austenitic steels

    International Nuclear Information System (INIS)

    Shiels, S.A.; Bagnall, C.; Keeton, A.R.; Witkowski, R.E.; Anantatmula, R.P.

    1980-01-01

    During the course of an on-going evaluation of austenitic alloys for potential liquid metal fast breeder reactor (LMFBR) fuel pin cladding application, a series of commercial alloys was selected for study. The data obtained led to the recognition of an underlying pattern of behavior and enabled the prediction of surface chemistry changes. The changes in surface topographical development from alloy to alloy are shown and the important role played by the element molybdenum in this development is indicated. The presentation also illustrates how a total damage equation was evolved to encompass all aspects of weight loss and metal/sodium interactions: wall thinning ferrite layer formation and intergranular attack. The total damage equation represents a significant departure from the classical description of sodium corrosion in which weight loss is simply translated into wall thinning

  9. The Influence of Porosity on Corrosion Attack of Austenitic Stainless Steel

    Science.gov (United States)

    Abdullah, Z.; Ismail, A.; Ahmad, S.

    2017-10-01

    Porous metals also known as metal foams is a metallic body having spaces orpores through which liquid or air may pass. Porous metals get an attention from researchers nowadays due to their unique combination of properties includes excellent mechanical and electrical, high energy absorption, good thermal and sound insulation and water and gas permeability. Porous metals have been applied in numerous applications such as in automotive, aerospace and also in biomedical applications. This research reveals the influence of corrosion attack in porous austenitic stainless steel 316L. The cyclic polarization potential analysis was performed on the porous austenitic stainless steel 316L in 3.5% NaCl solution. The morphology and the element presence on the samples before and after corrosion attack was examined using scanning electron microscopy (SEM) and energy dispersive x-ray (EDX) respectively to determine the corrosion mechanism structure. The cyclic polarization potential analysis showed the result of (E corr ) for porous austenitic stainless steel type 316L in the range of -0.40v to -0.60v and breakdown potential (E b ) is -0.3v to -0.4v in NaCl solution.

  10. A simplified LBB evaluation procedure for austenitic and ferritic steel piping

    Energy Technology Data Exchange (ETDEWEB)

    Gamble, R.M.; Wichman, K.R.

    1997-04-01

    The NRC previously has approved application of LBB analysis as a means to demonstrate that the probability of pipe rupture was extremely low so that dynamic loads associated with postulated pipe break could be excluded from the design basis (1). The purpose of this work was to: (1) define simplified procedures that can be used by the NRC to compute allowable lengths for circumferential throughwall cracks and assess margin against pipe fracture, and (2) verify the accuracy of the simplified procedures by comparison with available experimental data for piping having circumferential throughwall flaws. The development of the procedures was performed using techniques similar to those employed to develop ASME Code flaw evaluation procedures. The procedures described in this report are applicable to pipe and pipe fittings with: (1) wrought austenitic steel (Ni-Cr-Fe alloy) having a specified minimum yield strength less than 45 ksi, and gas metal-arc, submerged arc and shielded metal-arc austentic welds, and (2) seamless or welded wrought carbon steel having a minimum yield strength not greater than 40 ksi, and associated weld materials. The procedures can be used for cast austenitic steel when adequate information is available to place the cast material toughness into one of the categories identified later in this report for austenitic wrought and weld materials.

  11. Growth of creep life of type-347H austenitic stainless steel by micro-alloying elements

    International Nuclear Information System (INIS)

    Research highlights: → B, Ce and N can improve the creep life significantly at high temperature. → The precipitate of B element at the grain boundaries can improve the creep life. → The removing O through Ce provided the steel with longer creep life. → N increased the creep life by stabilizing austenite and solid solution strengthening. - Abstract: The creep life of type-347H austenitic stainless steel modified with B, Ce and N was measured, and microstructures were analyzed by optical microscope, X-ray diffraction, scanning electron microscope and transmission electron microscope equipped with energy dispersive spectroscopy. The results indicate that B, Ce and N can improve the creep life significantly at high temperature. The growth of creep life was mainly due to the precipitate of B in the elemental form at the grain boundaries and the removing O through Ce. N addition made for solid solution strengthening and effectively suppressed the precipitate of δ-ferrite at high temperature. The micro-alloying elements have a beneficial effect on creep life of type-347H austenitic stainless steel at high temperature.

  12. 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.

  13. The microstructural dependence of wear resistance in austenite containing plate steels

    Science.gov (United States)

    Wolfram, Preston Charles

    The purpose of this project was to examine the microstructural dependence of wear resistance of various plate steels, with interests in exploring the influence of retained austenite (RA). Materials resistant to abrasive wear are desirable in the industrial areas of agriculture, earth moving, excavation, mining, mineral processing, and transportation. Abrasive wear contributes to significant financial cost associated with wear to the industry. The motivation for the current study was to determine whether it would be beneficial from a wear resistance perspective to produce plate steels with increased amounts of retained austenite. This thesis investigates this motivation through a material matrix containing AR400F, Abrasive (0.21 wt pct C, 1.26 wt pct Mn, 0.21 wt pct Si, 0.15 wt pct Ni, 0.18 wt pct Mo), Armor (0.46 wt pct C, 0.54 wt pct Mn, 0.36 wt pct Si, 1.74 wt pct Ni, 0.31 wt pct Mo), 9260, 301SS, Hadfield, and SAE 4325 steels. The Abrasive, Armor and 9260 steels were heat treated using different methods such as quench and temper, isothermal bainitic hold, and quench and partitioning (Q&P). These heat treatments yielded various microstructures and the test matrix allowed for investigation of steels with similar hardness and varying levels of RA. The wear test methods used consisted of dry sand rubber wheel (DSRW), impeller-tumbler impact-abrasion (impeller), and Bond abrasion wear testing. DSRW and impeller wear resistance was found to increase with hardness and retained austenite levels at certain hardness levels. Some Q&P samples exhibited similar or less wear than the Hadfield steels in DSRW and impeller tests. Scanning electron microscopy investigation of wear surfaces revealed different wear mechanisms for the different wear test methods ranging from micro-plowing, to micro-cutting and to fragmentation.

  14. Tunneling corrosion mechanism of the hot forged austenitic stainless steel in highly oxidizing nitric acid

    International Nuclear Information System (INIS)

    Nagano, Hiroo; Kajimura, Haruhiko

    1993-01-01

    Austenitic Stainless Steels have been used for reprocessing plants where spent nuclear fuels are dealt with in hot nitric acid. Conventional stainless steels are resistant enough to nitric acid. However, they are prone to localized corrosion when nitric acid becomes highly oxidizing with birth of oxidants such as Ce 4+ or Cr 6+ ion during the reprocessing. Pitting type corrosion, so-called tunneling or end-grain corrosion occurred on the forgings of 25%-20%-Nb stainless steel (310Nb stainless steel) in such nitric acid solutions because of transpassive corrosion. It has been well known that metal surfaces of steel products casted, forged or rolled are susceptible to the tunneling corrosion in aggressive corrosion media. Nevertheless, neither clear explanations of the mechanism nor definite countermeasures have been proposed yet. This paper describes the mechanism and countermeasures on the tunneling corrosion of stainless steels in nitric acid relevant to spent nuclear fuel reprocessing. The results obtained are as follows: both general and intergranular corrosion occur on austenitic stainless steels in boiling 8N HNO 3 with Cr 6+ ions. Tunneling corrosion is initiated and propagates at the metal surfaces of 310Nb stainless steel forgings along chromium depleted areas vertical to metal flows. The grooves due to the tunneling corrosion are of diameters of 0.5 to 2 mm with a maximum depth of 6mm depending on exposure time and Cr 6+ concentration in nitric acid. Tunneling corrosion proceeds by build up of galvanic corrosion cells with Cr depleted parts as anodes and their neighborhoods as cathodes. The Cr depleted parts are formed during solidification of ingots and still retained parallel to the metal flow even after forging. The ESR (Electro Slag Remelting) is one of the useful preventive methods to tunneling corrosion from the view point of steel homogenization

  15. 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...

  16. Effect of plastic deformation on the magnetic properties of selected austenitic stainless steels

    Directory of Open Access Journals (Sweden)

    Tatiana Oršulová

    2017-04-01

    Full Text Available Austenitic stainless steels are materials, that are widely used in various fields of industry, architecture and biomedicine. Their specific composition of alloying elements has got influence on their deformation behavior. The main goal of this study was evaluation of magnetic properties of selected steels, caused by plastic deformation. The samples were heat treated in different intervals of temperature before measuring. Then the magnetic properties were measured on device designed for measuring of magnetism. From tested specimens, only AISI 304 confirmed effect of plastic deformation on the magnetic properties. Magnetic properties changed with increasing temperature.

  17. Determination of Thermal Diffusivity of Austenitic Steel Using Pulsed Infrared Thermography

    Directory of Open Access Journals (Sweden)

    Kochanowski K.

    2014-10-01

    Full Text Available The simple method of determining thermal diffusivity of solid materials at room temperature using the pulsed infrared thermography (IRT is proposed. The theoretical basis of the method and experimental results are presented. The study was conducted on austenitic steel 316L. Theobtained results show that the thermal diffusivity value of the tested steel determined by means of pulsed infrared thermography is very approximate to the values given in the literature, obtained by using more complicated methods. The differences between these values are 0.5%.

  18. Potential high fluence response of pressure vessel internals constructed from austenitic stainless steels

    International Nuclear Information System (INIS)

    Garner, F.A.; Greenwood, L.R.; Harrod, D.L.

    1993-08-01

    Many of the in-core components in pressurized water reactors are constructed of austenitic stainless steels. The potential behavior of these components can be predicted using data on similar steels irradiated at much higher displacement rates in liquid-metal reactors or water-cooled mixed-spectrum reactors. Consideration of the differences between the pressurized water environment and that of the other reactors leads to the conclusion that significant amounts of void swelling, irradiation creep, and embrittlement will occur in some components, and that the level of damage per atomic displacement may be larger in the pressurized water environment

  19. Austenite grain growth and microstructure control in simulated heat affected zones of microalloyed HSLA steel

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Lei [Department of Machine Tools and Factory Management, Technical University of Berlin, Pascalstraße 8 – 9, 10587, Berlin (Germany); Federal Institute for Materials Research and Testing, Unter den Eichen 87, 12205, Berlin (Germany); Kannengiesser, Thomas [Federal Institute for Materials Research and Testing, Unter den Eichen 87, 12205, Berlin (Germany); Institute of Materials and Joining Technology, Otto von Guericke University Magdeburg, Universitetsplatz 2, 39106, Magdeburg (Germany)

    2014-09-08

    The roles of microalloying niobium, titanium and vanadium for controlling austenite grain growth, microstructure evolution and hardness were investigated at different simulated heat affected zones (HAZ) for high strength low alloy (HSLA) S690QL steel. High resolution FEG-SEM has been used to characterize fine bainitic ferrite, martensite and nanosized second phases at simulated coarse and fine grain HAZs. It was found that for Ti bearing steel (Ti/N ratio is 2) austenite grain had the slowest growth rate due to the presence of most stable TiN. The fine cuboidal particles promoted intragranular acicular ferrite (IGF) formation. Nb bearing steel exhibited relatively weaker grain growth retardation compared with titanium bearing steels and a mixed microstructure of bainite and martensite was present for all simulated HAZs. IGF existed at coarse grain HAZ of Ti+V bearing steel but it was totally replaced by bainite at fine grain HAZs. Hardness result was closely related to the morphology of bainitic ferrite, intragranular ferrite and second phases within ferrite. The microstructure and hardness results of different simulated HAZs were in good agreement with welded experimental results.

  20. Overview of microstructural evolution in neutron-irradiated austenitic stainless steels

    International Nuclear Information System (INIS)

    Maziasz, P.J.

    1993-01-01

    Austenitic stainless steels are important structural materials common to several different reactor systems, including light water and fast breeder fission, and magnetic fusion reactors (LWR, FBR, and MFR, respectively). The microstructures that develop in 300 series austenitic stainless steels during neutron irradiation at 60-700 C include combinations of dislocation loops and networks, bubbles and voids, and various kinds of precipitate phases (radiation-induced, or -enhanced or -modified thermal phases). Many property changes in these steels during neutron irradiation are directly or indirectly related to radiation-induced microstructural evolution. Even more important is the fact that radiation-resistance of such steels during either FBR or MFR irradiation is directly related to control of the evolving microstructure during such irradiation. The purpose of this paper is to provide an overview of the large and complex body of data accumulated from various fission reactor irradiation experiments conducted over the many years of research on microstructural evolution in this family of steels. The data can be organized into several different temperature regimes which then define the nature of the dominant microstructural components and their sensitivities to irradiation parameters (dose, helium/dpa ratio, dose rate) or metallurgical variables (alloy composition, pretreatment). The emphasis in this paper will be on the underlying mechanisms driving the microstructure to evolve during irradiation or those enabling microstructural stability related to radiation resistance. (orig.)

  1. Compatibility of austenitic and martensitic steels behaviour in semi-stagnant Pb17Li

    International Nuclear Information System (INIS)

    Sannier, J.; Dufrenoy, T.; Flament, T.; Terlain, A.

    1991-01-01

    Compatibility tests between Pb17Li and 316L austenitic or 1.4914 martensitic steels have been performed with experimental conditions simulating the special features of the water-cooled lithium-lead blanket (low Pb17Li velocity, significant radial thermal gradient and short distances between hot and cold zones). In the 420-475 deg C temperature range, the results show that corrosion kinetics for both 316L and 1.4914 steels are quasi-linear and about 3 times lower compared to turbulent condition. From amount of recovered deposits, the mass transfer of 316L steel at 450 deg C appears to be equivalent to that of 1.1914 steel at 475 deg C. The same relationship was observed in flowing Pb17Li condition

  2. Microstructural changes within similar coronary stents produced from two different austenitic steels.

    Science.gov (United States)

    Weiss, Sabine; Meissner, Andreas; Fischer, Alfons

    2009-04-01

    Coronary heart disease has become the most common source for death in western industrial countries. Since 1986, a metal vessel scaffold (stent) is inserted to prevent the vessel wall from collapsing [Puel, J., Joffre, F., Rousseau, H., Guermonprez, B., Lancelin, B., Valeix, B., Imbert, G., Bounhoure, J.P, 1987. Endo-prothéses coronariennes autoexpansives dans la Préevention des resténoses apés angioplastie transluminale. Archives des Maladies du Coeur et des Vaisseaux, 1311--1312]. Most of these coronary stents are made from CrNiMo-steel (AISI 316L). Due to its austenitic structure, the material shows strength and ductility combined with corrosion resistance and a satisfactory biocompatibility. However, recent studies indicate that Nickel is under discussion as to its allergenic potential. Other typically used materials like Co-Base L605 or Tantalum alloys are relatively expensive and are not used so often. Newly developed austenitic high-nitrogen CrMnMoN-steels (AHNS) may offer an alternative. Traditional material tests revealed that strength and ductility, as well as corrosion resistance and biocompatibility, are as good as or even better than those of 316L [Vogt, J.B., Degallaix, S., Foct J., 1984. Low cycle fatigue life enhancement of 316L stainless steel by nitrogen alloying. International Journal of Fatigue 6 (4), 211-215, Menzel, J., Stein, G., 1996. High nitrogen containing Ni-free austenitic steels for medical applications. ISIJ Intern 36 (7), 893-900, Gavriljuk, V.G., Berns, H., 1999. High nitrogen steels, Springer Verlag, Berlin, Heidelberg]. However, because of a strut diameter of about 100 microm, the cross section consists of about five to ten crystal grains (oligo-crystalline). Thus very few, or even just one, grain can be responsible for the success or failure of the whole stent. During implantation, the structure of coronary artery stents is subjected to distinct inhomogeneous plastic deformation due to crimping and dilation.

  3. Pitting corrosion of low-Cr austenitic stainless steels

    International Nuclear Information System (INIS)

    Bullard, S.J.; Covino, B.S. Jr.

    1996-01-01

    The Albany Research Center has investigated the pitting corrosion resistance of experimental low-Cr stainless steels and several commercial stainless steels in chloride-containing aqueous and atmospheric environments. Previous research had shown the experimental alloys to be as corrosion resistant as commercial stainless steels in chloride-free acid environments. The alloys studied were Fe-8Cr-16Ni-5.5Si-1Cu-(0-1)Mo, 304 SS, and 316 SS. These alloys were examined by immersion and electrochemical tests in 3.5 wt. pct. NaCl and 6 wt.pct.FeCl 3 . Results of these tests showed that the addition of one weight percent Mo improved the pitting resistance of the low-Cr alloy and that the Mo-containing experimental alloy was as resistant to pitting as the commercial alloys. Electrochemical tests did, however, show the experimental alloys to be slightly less resistant to pitting than the commercial alloys. Because of these results, the low-Cr alloy with one weight percent Mo and 304 SS were exposed for one year to a marine atmospheric environment on the coast of Oregon. The marine atmospheric corrosion resistance of the low-Cr alloy was found to be comparable to that for type 304 stainless steel

  4. Cyclic deformation behaviour of austenitic steels at ambient and ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    stainless steels at ambient and elevated temperatures, taking into account the influ- ence of the alloying elements titanium and ... 5 Hz and triangular load-time waveforms. Stress–strain-hysteresis and temperature measurements were used at ambient tem- ...... Eng. Design 198: pp 185–191. Nebel T, Martin U, Eifler D 2001 ...

  5. Tensile properties of shielded metal arc welded dissimilar joints of nuclear grade ferritic steel and austenitic stainless steel

    Science.gov (United States)

    Karthick, K.; Malarvizhi, S.; Balasubramanian, V.; Krishnan, S. A.; Sasikala, G.; Albert, Shaju K.

    2016-12-01

    In nuclear power plants, modified 9Cr-1Mo ferritic steel (Grade 91 or P91) is used for constructing steam generators (SG's) whereas austenitic stainless steel (AISI 316LN) is a major structural member for intermediate heat exchanger (IHX). Therefore, a dissimilar joint between these materials is unavoidable. In this investigation, dissimilar joints were fabricated by Shielded Metal Arc Welding (SMAW) process with Inconel 82/182 filler metals. Transverse tensile properties and Charpy V-notch impact toughness for different regions of dissimilar joints of modified 9Cr-1Mo ferritic steel and AISI 316LN austenitic stainless steel were evaluated as per the standards. Microhardness distribution across the dissimilar joint was recorded. Microstructural features of different regions were characterized by optical and scanning electron microscopy. The transverse tensile properties of the joint is found to be inferior to base metals. Impact toughness values of different regions of dissimilar metal weld joint (DMWJ) is slightly higher than the prescribed value. Formation of a soft zone at the outer edge of the HAZ will reduce the tensile properties of DMWJ. The complex microstructure developed at the interfaces of DMWJ will reduce the impact toughness values.

  6. Martensite transformations influence in austenite stainless steel fractures

    International Nuclear Information System (INIS)

    Fonseca, H.; Monteiro, S.N.

    1976-07-01

    The influence of martensitic transformation on the fracture of tensile specimens of type AISI 310, and type 302, stainless steels was studied in the temperature interval from 25 0 C to -196 0 C. The influence of the metastability through the amount and rate of martensite transformation leading to high stresses and work hardening, apparently explains the brittle characteristics observed in the fracture of type 302 alloy as well as its ductile nature at -196 0 C [pt

  7. Multiaxial elastoplastic cyclic loading of austenitic 316L steel

    Czech Academy of Sciences Publication Activity Database

    Mazánová, Veronika; Polák, Jaroslav; Škorík, Viktor; Kruml, Tomáš

    2017-01-01

    Roč. 11, č. 40 (2017), s. 162-169 ISSN 1971-8993 R&D Projects: GA ČR(CZ) GA13-23652S; GA MŠk LM2015069; GA MŠk(CZ) LQ1601; GA ČR GA15-08826S Institutional support: RVO:68081723 Keywords : 316L steel * Crack initiation * Cyclic stress-strain curve * Multiaxial cyclic loading Subject RIV: JL - Materials Fatigue, Friction Mechanics OBOR OECD: Audio engineering, reliability analysis

  8. Thermal and mechanical stability of retained austenite in aluminum-containing multiphase TRIP steels

    CERN Document Server

    Zwaag, S; Kruijver, S O; Sietsma, J

    2002-01-01

    Stability of retained austenite is the key issue to understand transformation-induced plasticity (TRIP) effect. In this work, both thermal stability and mechanical stability are investigated by thermo-magnetic as well as in situ conventional X-ray diffraction and micro synchrotron radiation diffraction measurements. The thermal stability in a 0.20C-1.52Mn-0.25Si-0.96Al (wt%) TRIP steel is studied in the temperature range between 5 and 300 K under a constant magnetic field of 5T. It is found that almost all austenite transforms thermally to martensite upon cooling to 5K and M sub s and M sub f temperatures are analyzed to be 355 and 115 K. Transformation kinetics on the fraction versus temperature relation are well described by a model based on thermodynamics. From the in situ conventional X-ray and synchrotron diffraction measurements in a 0.17C-1.46Mn-0.26Si-1.81Al (wt%) steel, the volume fraction of retained austenite is found to decrease as the strain increases according to Ludwigson and Berger relation. T...

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

    NARCIS (Netherlands)

    Conradi, Marjetka; Schön, Peter Manfred; Kocijan, Aleksandra; Jenko, M.; Vancso, Gyula J.

    2011-01-01

    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

  10. Gas bubbles evolution peculiarities in ferritic-martensitic and austenitic steels and alloys under helium-ion irradiation

    NARCIS (Netherlands)

    Chernov, [No Value; Kalashnikov, AN; Kahn, BA; Binyukova, SY

    2003-01-01

    Transmission electron microscopy has been used to investigate the gas bubble evolution in model alloys of the Fe C system, ferritic-martensitic steels of 13Cr type, nickel and austenitic steels under 40-keV helium-ion it. radiation up to a fluence of 5 x 10(20) m(-2) at the temperature of 920 K. It

  11. Surface hardening of austenitic stainless steels via low-temperature colossal supersaturation

    Science.gov (United States)

    Cao, Yan

    The Swagelok Company has recently developed a low-temperature (470°C) carburization technology for austenitic stainless steels, that increases the surface hardness from 200 to 1200 HV25 without sacrificing corrosion resistance. In order to investigate the microstructural changes responsible for these outstanding properties, bulk specimens, thin foils, and powder specimens of several different low-temperature carburized 316 stainless steels have been studied. XRD studies revealed that the low-temperature carburization of 316 austenitic stainless steels lead to a colossal supersaturation of interstitial carbon in the austenite. While the equilibrium solubility of carbon is 0.03 at% at the carburization temperature of 470°C, high-precision XRD determination of the lattice parameter after carburization indicated a carbon concentration of >10at% in solid solution---a colossal supersaturation! This astonishing result was confirmed by a completely independent experimental method, X-ray photoelectron spectrometry (XPS). Residual stress measurements indicated that low-temperature carburization caused an enormous compressive residual stress of 2 GPa at the surface. The enormous compressive residual stress and a high density of stacking faults caused broadening and shifting of the austenite peaks in X-ray diffraction scans. Analysis of the underlying thermodynamics and kinetics indicate that the key to colossal supersaturation is to kinetically suppress the formation of M23C6. The colossal supersaturation of carbon in the austenite is the dominant feature responsible for the unusual hardness. Only during the extended (>40h) carburization times, M5C 2 carbide (Hagg carbide), instead of M23C6, was observed to form. In addition, TEM studies indicated the presence of a small amount of a second carbide phase, M7C3. The particles of both carbides have the shape of long needles, containing a high density of planar defects normal to the long axis of the needles. The concept of "low

  12. Development of advanced austenitic stainless steels resistant to void swelling under irradiation

    International Nuclear Information System (INIS)

    Rouxel, Baptiste

    2016-01-01

    In the framework of studies about Sodium Fast Reactors (SFR) of generation IV, the CEA is developing new austenitic steel grades for the fuel cladding. These steels demonstrate very good mechanical properties but their use is limited because of the void swelling under irradiation. Beyond a high irradiation dose, cavities appear in the alloys and weaken the material. The reference material in France is a 15Cr/15Ni steel, named AIM1, stabilized with titanium. This study try to understand the role played by various chemical elements and microstructural parameters on the formation of the cavities under irradiation, and contribute to the development of a new grade AIM2 more resistant to swelling. In an analytical approach, model materials were elaborated with various chemical compositions and microstructures. Ten grades were cast with chemical variations in Ti, Nb, Ni and P. Four specific microstructures for each alloy highlighted the effect of dislocations, solutes or nano-precipitates on the void swelling. These materials were characterized using TEM and SANS, before irradiation with Fe 2+ (2 MeV) ions in the order to simulate the damages caused by neutrons. Comparing the irradiated microstructures, it is demonstrated that the solutes have a dominating effect on the formation of cavities. Specifically titanium in solid solution reduces the swelling whereas niobium does not show this effect. Finally, a matrix enriched by 15% to 25% of nickel is still favorable to limit swelling in these advanced austenitic stainless steels. (author) [fr

  13. 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.

  14. Crystal structure and lattice dynamics of Fe-Cr-Mn-Ni-N austenitic steels

    International Nuclear Information System (INIS)

    Beskrovni, A.; Jadrowski, E.; Danilkin, S.; Fuess, H.; Wieder, T.; Neova-Baeva, M.

    1999-01-01

    Complete text of publication follows. High nitrogen austenitic steels are of high strength, corrosion resistance and offer structural stability. The properties of these steels depend on the interstitial (N) and substitution (Cr, Ni, Mn) atom content. The present study investigates the effect of the Mn and Cr content on crystal structure and interatomic bonding. Nitrogen austenitic steels with composition Fe-19Cr-xMn-0.5N (x = 9/23 wt.%) and Fe-xCr-11Ni-0.5N (x=15/29 wt.%) were studied with X-Ray and neutron scattering methods. It was found that Mn and Cr expand FCC lattice in the both steels. However modification of the metal atom frequency spectrum, g(ε), is different. Mn additions cause the decrease of metal atom frequencies. The softening of the Me-Me interaction is an agreement with the theoretical model predictions based on volume changes. Modification of g(ε) caused by Cr atoms is more complicated. It was concluded that alloying with Cr alters the electronic states. The decrease of the width of the nitrogen localised vibrations with increasing Cr content was noted and is probably connected with stress-induced ordering. (author)

  15. Effects of metallurgical variables on swelling of modified 316 and higher Ni austenitic stainless steels

    International Nuclear Information System (INIS)

    Shibahara, Itaru; Akasaka, Naoaki; Onose, Shoji

    1996-01-01

    The effects of solute elements and cold-work on swelling in modified 316 and higher Ni advanced austenitic stainless steels developed for FBR core material were investigated together with the posted model alloys. The Si, P, B, Ti, Nb modified and cold-worked steels exhibited an improved swelling resistance. In the temperature range between 400 and 500 C, the swelling was suppressed significantly by an addition of 0.8 wt% Si. The beneficial effect of Si appears to be reduced in the steels without Ti and Nb tending to form γ' precipitates. In the temperature range between 500 and 600 C, a needle-like phosphide precipitates played an important role in suppressing void growth. Additions of Ti and/or Nb were found to stabilize the phosphide phase and extended the swelling incubation period. In the improved austenitic steels, the synergistic effect of cold-working and P, B, Ti, Nb additions act beneficially to stabilize the dislocation structure and to form finely dispersed precipitates during irradiation

  16. Comparison of material property specifications of austenitic steels in fast breeder reactor technology

    International Nuclear Information System (INIS)

    Vanderborck, Y.; Van Mulders, E.

    1985-01-01

    Austenitic stainless steels are very widely used in components for European Fast Breeder Reactors. The Activity Group Nr.3 ''Materials'', within Working Group ''Codes and Standards'' of the Fast Reactor Co-Ordination Committee of the European Communities, has decided to initiate a study to compare the material property specifications of the austenitic stainless steel used in the European Fast Breeder Technology. Hence, this study would allow one to view rapidly the designation of a particular steel grade in different European countries and to compare given property values for a same grade. There were dissimilarities, differences or voids appear, it could lead to an attempt to complete and/or to uniformize the nationally given values, so that on a practical level interchangeability, availability and use ease design and construction work. A selection of the materials and of their properties has been made by the Working Group. Materials examined are Stainless Steel AISI 304, 304 L, 304 LN, 316, 316 L, 316 LN, 316''Ti stab.'', 316''Nb stab''., 321, 347

  17. Effect of deformation temperature on niobium clustering, precipitation and austenite recrystallisation in a Nb–Ti microalloyed steel

    International Nuclear Information System (INIS)

    Kostryzhev, Andrii G.; Al Shahrani, Abdullah; Zhu, Chen; Ringer, Simon P.; Pereloma, Elena V.

    2013-01-01

    The effect of deformation temperature on Nb solute clustering, precipitation and the kinetics of austenite recrystallisation were studied in a steel containing 0.081C–0.021Ti–0.064 Nb (wt%). Thermo-mechanical processing was carried out using a Gleeble 3500 simulator. The austenite microstructure was studied using a combination of optical microscopy, transmission electron microscopy, and atom probe microscopy, enabling a careful characterisation of grain size, as well as Nb-rich clustering and precipitation processes. A correlation between the austenite recrystallisation kinetics and the chemistry, size and number density of Nb-rich solute atom clusters, and NbTi(C,N) precipitates was established via the austenite deformation temperature. Specifically, we have determined thresholds for the onset of recrystallisation: for deformation levels above 75% and temperatures above 825 °C, Nb atom clusters <8 nm effectively suppressed austenite recrystallisation

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

    International Nuclear Information System (INIS)

    Kohyama, Akira; Donomae, Takako

    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)

  19. Improvement of corrosion resistance in austenitic stainless steel by grain boundary character distribution control

    International Nuclear Information System (INIS)

    Wang, Yun; Kaneda, Junya; Kasahara, Shigeki; Shigenaka, Naoto

    2012-01-01

    Strauss test, Coriou test and Huey test were conducted on a Type 316L austenitic stainless steel. Improvement in grain boundary corrosion resistance was verified after raising low Σ coincidence site lattice (CSL) grain boundary (GB) frequency by controlling grain boundary character distribution (GBCD). During crevice corrosion test under gamma-ray irradiation, initiation frequency of GB corrosion after GBCD controlled specimens decreased to 1/10 of GBCD uncontrolled counterpart along with lower depth of corrosion. Stress corrosion cracking (SCC) propagation rate of GBCD controlled specimen decreased to less than 1/2 of GBCD uncontrolled specimen in high temperature and high pressure water. Based on these results, we expect that GBCD control will improve corrosion resistance of austenitic material in a wide range of application and environment. (author)

  20. 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 ...

  1. Design of Wear-Resistant Austenitic Steels for Selective Laser Melting

    Science.gov (United States)

    Lemke, J. N.; Casati, R.; Lecis, N.; Andrianopoli, C.; Varone, A.; Montanari, R.; Vedani, M.

    2018-03-01

    Type 316L stainless steel feedstock powder was modified by alloying with powders containing carbide/boride-forming elements to create improved wear-resistant austenitic alloys that can be readily processed by Selective Laser Melting. Fe-based alloys with high C, B, V, and Nb contents were thus produced, resulting in a microstructure that consisted of austenitic grains and a significant amount of hard carbides and borides. Heat treatments were performed to modify the carbide distribution and morphology. Optimal hard-phase spheroidization was achieved by annealing the proposed alloys at 1150 °C for 1 hour followed by water quenching. The total increase in hardness of samples containing 20 pct of C/B-rich alloy powder was of 82.7 pct while the wear resistance could be increased by a factor of 6.

  2. Empirical Formulas for the Calculations of the Hardness of Steels Cooled From the Austenitizing Temperature

    Directory of Open Access Journals (Sweden)

    Trzaska J.

    2016-09-01

    Full Text Available In this paper, the equations applied for the purpose of the calculations of the hardness of continuously cooled structural steels upon the basis of the temperature of austenitizing. The independent variables of the hardness model were: the mass concentrations of elements, the austenitizing temperature and the cooling rate. The equations were developed with the application of the following methods: multiple regression and logistic regression. In this paper, attention was paid to preparing data for the purpose of calculations, to the methodology of the calculations, and also to the assessment of the quality of developed formulas. The collection of empirical data was prepared upon the basis of more than 500 CCT diagrams.

  3. Static Recrystallized Grain Size of Coarse-Grained Austenite in an API-X70 Pipeline Steel

    Science.gov (United States)

    Sha, Qingyun; Li, Guiyan; Li, Dahang

    2013-12-01

    The effects of initial grain size and strain on the static recrystallized grain size of coarse-grained austenite in an API-X70 steel microalloyed with Nb, V, and Ti were investigated using a Gleeble-3800 thermomechanical simulator. The results indicate that the static recrystallized grain size of coarse-grained austenite decreases with decreasing initial grain size and increasing applied strain. The addition of microalloying elements can lead to a smaller initial grain size for hot deformation due to the grain growth inhibition during reheating, resulting in decreasing of static recrystallized grain size. Based on the experimental data, an equation for the static recrystallized grain size was derived using the least square method. The grain sizes calculated using this equation fit well with the measured ones compared with the equations for fine-grained austenite and for coarse-grained austenite of Nb-V microalloyed steel.

  4. Creep rupture properties of oxidised 20%Cr austenitic stainless steels

    International Nuclear Information System (INIS)

    Lobb, R.C.; Ecob, R.C.

    1989-02-01

    Sheet specimens of stabilised 20%Cr/25%Ni/Nb and nitrided 20%Cr/25%Ni/Ti stainless steels, both used as fuel cladding materials in CAGRs, have been oxidised in simulated reactor gas (Co 2 /1-2%CO) for up to l.9kh at 850 0 C, including intermediate thermal cycles to room temperature. The oxidised specimens have been creep tested subsequently at 750 0 C, under conditions of constant stress. The creep rupture properties are affected differently for the two materials. For 20%Cr/25%Ni/Nb stainless steel, there was no effect of oxidation on the intrinsic microstructure, when compared with thermally aged, non-oxidised material. Any differences in creep ductility were ascribed to geometric effects in specimens of this alloy. Lower ductilities were associated with an increased incidence of pitting attack (higher oxide spallation) and it was concluded that the extent of local, rather than general, loss of section controlled the ductility. For nitrided 20%Cr/25%Ni/Ti stainless steel, the intrinsic microstructure was affected by oxidation, such that increased grain boundary precipitation of M 23 C 6 occurred. The resultant effect was for a greater tendency for intergranular failure at lower ductility than for the thermally aged material. The magnitude of this reduction could not be quantified because the specimen geometry was also changed by oxidation. In this instance, the oxidation mode that produced the most severe loss of section was grain boundary, rather than pitting, attack. This mode of attack was not linked directly to oxide fracture/spallation, but to the period of oxidation. (author)

  5. Physical properties of the AISI 348 L* austenitic stainless steel

    International Nuclear Information System (INIS)

    Teodoro, Celso Antonio; Lucki, Georgi; Silva, Jose Eduardo Rosa da; Terremoto, Luis Antanio Albiac; Castanheira, Myrthes; Damy, Margaret de Almeida

    2005-01-01

    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 * stainless steel utilized as a structural material of the fuel elements of PWR, in comparison with the AISI 304. (author)

  6. Study of cumulative fatigue damage on an austenitic steel

    International Nuclear Information System (INIS)

    Baudry, G.; Amzallag, C.; Bernard, J.L.

    1984-01-01

    The validity of Palmgren-Miner rule is verified for working life between about 500 and 1,000,000 cycles for two damages: one corresponding to complete rupture of smooth test piece and the other corresponding to initiation of a fatigue crack in a high stress area. Material studied is a stainless steel Z3CND17-12 (AISI 316) used in nuclear industry. Validity of the rule is better verified in the case of small cracks than for a smooth sample. (15 references are given) [fr

  7. Hydrogen embrittlement of super austenitic stainless steel welded joints; Fragilizacao por hidrogenio em juntas soldadas de acos inoxidaveis superausteniticos

    Energy Technology Data Exchange (ETDEWEB)

    Paredes, Ramon S. Cortes [Parana Univ., Curitiba, PR (Brazil). Centro Politecnico. Inst. de Tecnologia para o Desenvolvimento (LACTEC); Berthier, Thiana; Kuromoto, Neide K. [Parana Univ., Curitiba, PR (Brazil). Lab. de Materiais e Tratamento de Superficies. Lab. de Nanopropriedades Mecanicas

    2004-09-15

    The austenitic stainless steel embrittlement is usually present on sulphurous medium due to the hydrogen presence, resulting on cracks and corrosion on acid medium. Several researches carried out on the behaviour of hydrogenated stainless steel structures, had shown that the hydrogen induces superficial phase transformation during hydrogenation period and cracks formation after this period. These are due to the permeation of the hydrogen into the material, which is apprehended on preferential site, resulting on high pressure zones of molecular hydrogen. These zones may lead the crack formation, compromising the mechanical properties. There are few results on austenitic and super austenitic stainless steel, considering the transformations induced on welded unions. This work evaluates the cracks nucleation on welded unions of super austenitic stainless steel AISI 904L exposed to hydrogen rich environments and its relation to the reduction of material ductility. The samples were welded by the Mig/Mag process, followed by hydrogenation which were cathodic on sulfuric acid solution at room temperature. The results showed that the tested super austenitic stainless steel has a significant amount of cracks and no phase transformation has occurred after hydronization. (author)

  8. Adaptation of fuel code for light water reactor with austenitic steel rod cladding

    Energy Technology Data Exchange (ETDEWEB)

    Gomes, Daniel de Souza; Silva, Antonio Teixeira, E-mail: dsgomes@ipen.br, E-mail: teixeira@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Giovedi, Claudia, E-mail: claudia.giovedi@labrisco.usp.br [Universidade de Sao Paulo (POLI/USP), Sao Paulo, SP (Brazil). Lab. de Analise, Avaliacao e Gerenciamento de Risco

    2015-07-01

    Light water reactors were used with steel as nuclear fuel cladding from 1960 to 1980. The high performance proved that the use of low-carbon alloys could substitute the current zirconium alloys. Stainless steel is an alternative that can be used as cladding. The zirconium alloys replaced the steel. However, significant experiences in-pile occurred, in commercial units such as Haddam Neck, Indian Point, and Yankee experiences. Stainless Steel Types 347 and 348 can be used as cladding. An advantage of using Stainless Steel was evident in Fukushima when a large number of hydrogens was produced at high temperatures. The steel cladding does not eliminate the problem of accumulating free hydrogen, which can lead to a risk of explosion. In a boiling water reactor, environments easily exist for the attack of intergranular corrosion. The Stainless Steel alloys, Types 321, 347, and 348, are stabilized against attack by the addition of titanium, niobium, or tantalum. The steel Type 348 is composed of niobium, tantalum, and cobalt. Titanium preserves type 321, and niobium additions stabilize type 347. In recent years, research has increased on studying the effects of irradiation by fast neutrons. The impact of radiation includes changes in flow rate limits, deformation, and ductility. The irradiation can convert crystalline lattices into an amorphous structure. New proposals are emerging that suggest using a silicon carbide-based fuel rod cladding or iron-chromium-aluminum alloys. These materials can substitute the classic zirconium alloys. Once the steel Type 348 was chosen, the thermal and mechanical properties were coded in a library of functions. The fuel performance codes contain all features. A comparative analysis of the steel and zirconium alloys was made. The results demonstrate that the austenitic steel alloys are the viable candidates for substituting the zirconium alloys. (author)

  9. Adaptation of fuel code for light water reactor with austenitic steel rod cladding

    International Nuclear Information System (INIS)

    Gomes, Daniel de Souza; Silva, Antonio Teixeira; Giovedi, Claudia

    2015-01-01

    Light water reactors were used with steel as nuclear fuel cladding from 1960 to 1980. The high performance proved that the use of low-carbon alloys could substitute the current zirconium alloys. Stainless steel is an alternative that can be used as cladding. The zirconium alloys replaced the steel. However, significant experiences in-pile occurred, in commercial units such as Haddam Neck, Indian Point, and Yankee experiences. Stainless Steel Types 347 and 348 can be used as cladding. An advantage of using Stainless Steel was evident in Fukushima when a large number of hydrogens was produced at high temperatures. The steel cladding does not eliminate the problem of accumulating free hydrogen, which can lead to a risk of explosion. In a boiling water reactor, environments easily exist for the attack of intergranular corrosion. The Stainless Steel alloys, Types 321, 347, and 348, are stabilized against attack by the addition of titanium, niobium, or tantalum. The steel Type 348 is composed of niobium, tantalum, and cobalt. Titanium preserves type 321, and niobium additions stabilize type 347. In recent years, research has increased on studying the effects of irradiation by fast neutrons. The impact of radiation includes changes in flow rate limits, deformation, and ductility. The irradiation can convert crystalline lattices into an amorphous structure. New proposals are emerging that suggest using a silicon carbide-based fuel rod cladding or iron-chromium-aluminum alloys. These materials can substitute the classic zirconium alloys. Once the steel Type 348 was chosen, the thermal and mechanical properties were coded in a library of functions. The fuel performance codes contain all features. A comparative analysis of the steel and zirconium alloys was made. The results demonstrate that the austenitic steel alloys are the viable candidates for substituting the zirconium alloys. (author)

  10. Deformation in type 304 austenitic stainless steel. Final report

    International Nuclear Information System (INIS)

    Kumar, V.; Mukherjee, S.; Huang, F.H.; Li, C.Y.

    1979-12-01

    Extensive experimental and theoretical work on Type 304 stainless steel to demonstrate the applicability of a state variable approach in materials testing and in stress analysis are reported. The state variable approach adopted has been shown recently to be able to describe the deformation properties of a variety of materials accurately with constitutive equations in the form of mechanical equation of state. It has been shown that the effort required in materials testing to determine the parameters of the constitutive equations is considerably less compared to that required for equations based on the traditional approach. During the course of the work a set of constitutive equations based on state variables for Type 304 stainless steel were established with all the required parameters determined experimentally. Numerical codes for uniaxial deformation and for bending of a beam were developed and used to predict the results of component testing. The code predictions were found to agree well with experimental data. The same constitutive equations were also incorporated into two versions of NONFIN, a finite element stress analysis code; one for Honeywell Computers and the other for IBM Computers. Both versions ran successfully and economically

  11. Two strain-hardening mechanisms in nanocrystalline austenitic steel: An in situ synchrotron X-ray diffraction study

    International Nuclear Information System (INIS)

    Schloth, P.; Weisser, M.A.; Van Swygenhoven, H.; Van Petegem, S.; Susila, P.; Subramanya Sarma, V.; Murty, B.S.; Lauterbach, S.; Heilmaier, M.

    2012-01-01

    The mechanical behaviour of nanocrystalline austenitic steels with and without yttria particles was investigated using in situ synchrotron diffraction during tensile deformation. Two different strain-hardening regimes were found. The first regime can be assigned predominantly to a martensitic phase transformation, the second to deformation twinning in the fragmented retained austenite. The kinetics of martensitic phase transformation is remarkably enhanced in the nanocrystalline structure.

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

    Science.gov (United States)

    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).

  13. Influence of TiC precipitation in austenitic stainless steel on strength, ductility and helium embrittlement

    International Nuclear Information System (INIS)

    Kesternich, W.; Matta, M.K.; Rothaut, J.

    1984-01-01

    Creep experiments were performed on 1.4970 (German DIN standard) and 316 (AISI standard) type austenitic steels after various thermomechanical pretreatments and after α-implantation. The microstructure introduced by the pretreatments was characterized by transmission electron microscopy and the behaviour of strength and ductility is correlated to the dislocation and precipitate distributions. He embrittlement can be suppressed in these simulation experiments when dispersive TiC precipitate distributions are produced by the proper pretreatments or are allowed to form during creep testing. It is shown that adequate pretreatment results in a significantly superior behaviour of the 1.4970 steel as compared to the 316 type steel in all three investigated properties, i.e. strength, ductility and resistance to He embrittlement. (orig.)

  14. Diffusion bonding of silicon carbide and silicon nitride to austenitic stainless steel

    International Nuclear Information System (INIS)

    Krugers, J.P.; Ouden, G. den

    1989-01-01

    In this paper the results are reported of a study dealing with diffusion bonding of silicon carbide and silicon nitride (both reaction-bonded and hot-pressed) to austenitic stainless steel (type AISI 316). Experiments were carried out in high vacuum (in the range of 10 -3 -10 -4 Pa) and in an inert gas atmosphere (95 vol% Ar, 5 vol% H 2 ), at temperatures between 1000 and 1300deg C and at various pressures. It was found that under specific conditions the steel could be bonded to both grades of silicon nitride. It was not possible, however, to produce an acceptable bond between steel and silicon carbide. The bonded combinations were tested mechanically by means of shear strength testing. It was found that the higher the process temperature or the longer the process time the stronger the bond. (orig.)

  15. Localised corrosion processes of austenitic stainless steel bipolar plates for polymer electrolyte membrane fuel cells

    Science.gov (United States)

    Mele, Claudio; Bozzini, Benedetto

    This research addresses the problem of localised corrosion of stainless steel PEMFC bipolar plates. The susceptibility to pitting and crevice corrosion of austenitic AISI 304 stainless steel has been investigated both by post-mortem microscopic analysis of the end-plates of a laboratory single-cell and by studies of electrochemically corroded stainless steels, in the presence of specially-designed crevice-formers simulating the operating conditions of a PEMFC. This work is based on optical and scanning-electron microscopies as well as potentiostatic and potentiodynamic measurements. The crevice-formers we considered were: Teflon, graphite and AISI 304. The samples, coupled to the crevice-formers have been tested in aqueous solutions containing Cl -, SO 4 2- and F -. From the E-log i plot, the values of corrosion, pitting, crevice and protection potential have been obtained and perfect and imperfect passivity conditions have been identified.

  16. Recent Developments of Advanced Austenitic and Duplex Stainless Steels for Oil and Gas Industry

    Science.gov (United States)

    Chai, Guocai; Kangas, Pasi

    The demands for fuel and the development of the fuel exploitation processes have made it economically possible to produce oil-gas from deeper and more corrosive wells where the parameters such as high chloride, H2S or CO2 content, high temperature and pressure, erosion and bioactivities in seawater should be considered. In these applications, special grades of stainless steels with greater corrosion resistance at a broad range of temperatures and high strength have to be used to meet the requirements. This paper provides an overview on the development, properties and applications of these advanced materials for oil & gas industry. They include recently developed advanced super austenitic stainless steels with high Mo, Ni, Cr and N contents with a PRE (pitting resistance equivalent) number up to 52 and hyper duplex stainless steels.

  17. Effects of Austenitizing and Forging on Mechanical Properties of MIL A-12560/AISI 4340 Steel

    Science.gov (United States)

    Herbirowo, S.; Adjiantoro, B.; Romijarso, T. B.

    2017-05-01

    Laterite steels might be used for alternative armored steels. Their properties can be improved in various ways, such as by heat treatment. This paper reports the influences of tempering temperature on the hardness and microstructure of the modified MIL A-12560/AISI 4340 steels. Samples were austenitized at 1200, 1000, and 800°C and forged at 100, 75, and 50 tons. Mechanical properties consisted of Hardness measurement was conducted by Brinell indentation and metallographic observation was conducted by scanning electron microscopy (SEM). The results showed that increasing forging force until 100 tons can decrease hardness. The formation of the microstructure consists of tempered martensite containing ferrite and dual phase perlite. The presence of void and porous can also decrease hardness. Decreasing austenizing temperature from 1200 °C to 800°C can increase material strength and hardness.

  18. Influence of Ti(C,N precipitates on austenite growth of micro-alloyed steel during continuous casting

    Directory of Open Access Journals (Sweden)

    Liu Yang

    2017-11-01

    Full Text Available Austenite grain size is an important influence factor for ductility of steel at high temperatures during continuous casting. Thermodynamic and kinetics calculations were performed to analyze the characteristics of Ti(C,N precipitates formed during the continuous casting of micro-alloyed steel. Based on Andersen-Grong equation, a coupling model of second phase precipitation and austenite grain growth has been established, and the influence of second precipitates on austenite grain growth under different cooling rates is discussed. Calculations show that the final sizes of austenite grains are 2.155, 1.244, 0.965, 0.847 and 0.686 mm, respectively, under the cooling rate of 1, 3, 5, 7, and 10 ℃·s-1, when ignoring the pinning effect of precipitation on austenite growth. Whereas, if taking the pinning effect into consideration, the grain growth remains stable from 1,350 ℃, the calculated final sizes of austenite grains are 1.46, 1.02, 0.80, 0.67 and 0.57 mm, respectively. The sizes of final Ti(C,N precipitates are 137, 79, 61, 51 and 43 nm, respectively, with the increase of cooling rate from 1 to 10 ℃·s-1. Model validation shows that the austenite size under different cooling rates coincided with the calculation results. Finally, the corresponding measures to strengthen cooling intensity at elevated temperature are proposed to improve the ductility and transverse crack of slab.

  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. Mitigating the Risk of Stress Corrosion of Austenitic Stainless Steels in Advanced Gas Cooled Reactor Boilers

    International Nuclear Information System (INIS)

    Bull, A.; Owen, J.; Quirk, G.; G, Lewis; Rudge, A.; Woolsey, I.S.

    2012-09-01

    Advanced Gas-Cooled Reactors (AGRs) operated in the UK by EDF Energy have once-through boilers, which deliver superheated steam at high temperature (∼500 deg. C) and pressure (∼150 bar) to the HP turbine. The boilers have either a serpentine or helical geometry for the tubing of the main heat transfer sections of the boiler and each individual tube is fabricated from mild steel, 9%Cr1%Mo and Type 316 austenitic stainless steel tubing. Type 316 austenitic stainless steel is used for the secondary (final) superheater and steam tailpipe sections of the boiler, which, during normal operation, should operate under dry, superheated steam conditions. This is achieved by maintaining a specified margin of superheat at the upper transition joint (UTJ) between the 9%Cr1%Mo primary superheater and the Type 316 secondary superheater sections of the boiler. Operating in this mode should eliminate the possibility of stress corrosion cracking of the Type 316 tube material on-load. In recent years, however, AGRs have suffered a variety of operational problems with their boilers that have made it difficult to maintain the specified superheat margin at the UTJ. In the case of helical boilers, the combined effects of carbon deposition on the gas side and oxide deposition on the waterside of the tubing have resulted in an increasing number of austenitic tubes operating with less than the specified superheat margin at the UTJ and hence the possibility of wetting the austenitic section of the boiler. Some units with serpentine boilers have suffered creep-fatigue damage of the high temperature sections of the boiler, which currently necessitates capping the steam outlet temperature to prevent further damage. The reduction in steam outlet temperature has meant that there is an increased risk of operation with less than the specified superheat margin at the UTJ and hence stress corrosion cracking of the austenitic sections of the boiler. In order to establish the risk of stress

  1. Influence of Short Austenitization Treatments on the Mechanical Properties of Low-Alloy Steels for Hot Forming Applications

    Science.gov (United States)

    Holzweissig, Martin Joachim; Lackmann, Jan; Konrad, Stefan; Schaper, Mirko; Niendorf, Thomas

    2015-07-01

    The current work elucidates an improvement of the mechanical properties of tool-quenched low-alloy steel by employing extremely short austenitization durations utilizing a press heating arrangement. Specifically, the influence of different austenitization treatments—involving austenitization durations ranging from three to 15 seconds—on the mechanical properties of low-alloy steel in comparison to an industrial standard furnace process was examined. A thorough set of experiments was conducted to investigate the role of different austenitization durations and temperatures on the resulting mechanical properties such as hardness, bending angle, tensile strength, and strain at fracture. The most important finding is that the hardness, the bending angle as well as the tensile strength increase with shortened austenitization durations. Furthermore, the ductility of the steels exhibits almost no difference following the short austenitization durations and the standard furnace process. The enhancement of the mechanical properties imposed by the short heat treatments investigated, is related to a refinement of microstructural features as compared to the standard furnace process.

  2. Fatigue crack growth in austenitic stainless steel piping

    International Nuclear Information System (INIS)

    Bethmont, M.; Cheissoux, J.L.; Lebey, J.

    1981-04-01

    The study presented in this paper is being carried out with a view to substantiating the calculations of the fatigue crack growth in pipes made of 316 L stainless steel. The results obtained may be applied to P.W.R. primary piping. It is divided into two parts. First, fatigue tests (cyclic pressure) are carried out under hot and cold conditions with straight pipes machined with notches of various dimensions. The crack propagation and the fatigue crack growth rate are measured here. Second, calculations are made in order to interpret experimental results. From elastic calculations the stress intensity factor is assessed to predict the crack growth rate. The results obtained until now and presented in this paper relate to longitudinal notches

  3. Microstructural observation of ion-irradiated austenitic stainless steel

    International Nuclear Information System (INIS)

    Sawai, T.; Hamada, S.; Hishinuma, A.

    1992-01-01

    Type 316 stainless steel, base metal and weld metal obtained from an electron beam weld joint, was irradiated with 90 MeV Br +6 in the JAERI tandem accelerator. Cross-sectional TEM specimens were obtained by nickel plating. Microstructural observation revealed a band of tiny dislocation loops was observed around the mean projected range and the measured distance from the surface was 6.75±0.15μm. This is slightly larger than the calculated value using Ziegler's stopping power. Defect clusters were also observed around defect sinks within the mean projected range, suggesting cascade-sink interaction. These sinks are the grain boundary in the base metal specimen and preexisting dislocation lines in the weld metal specimen. Surface roughness of polished specimen was detected at the shallower side of the peak damage band, although no visible crystalline defect cluster was observed. This suggests radiation-induced microchemical evolution prior to sever microstructural evolution. (author)

  4. Analysis of elevated temperature cyclic deformation of austenitic stainless steels

    International Nuclear Information System (INIS)

    Rohde, R.W.; Swearengen, J.C.

    1977-01-01

    The stress relaxation behavior of 304 and 316 stainless steels during cyclic deformation at 538 and 650 0 C with various hold times and strain amplitudes has been analyzed in terms of a power-law equation of state which includes internal stress and drag stress as structure variables. At 650 0 C the internal sress in 304 appears to be zero and microstructural recovery plays an important role in the kinetics of stress relaxation. For deformation at 538 0 C, the internal stress in 304 is nonzero and microstructural recovery appears minimal. In 316 tested at 650 0 C the internal stress is zero and again recovery is important. However, the kinetics of recovery differ from those measured in 304. These observations are explained physically in terms of strain and temperature-induced recovery of the structural variables, and provide insights into the procedures for calculating accumulated ''creep'' damage in reactor components

  5. Structure, mechanical, and tribotechnical properties of an austenitic nitrogen steel after frictional treatment

    Science.gov (United States)

    Narkevich, N. A.; Shulepov, I. A.; Mironov, Yu. P.

    2017-04-01

    The features of the structure and the mechanical and tribotechnical properties of an austenitic nitrogen steel (Cr16.5, Mn18.8, C0.07, N0.53, Si0.52 wt %, and Fe for balance) after frictional treatment have been studied. It has been shown that, along with twinning, the nitrogen austenite upon frictional treatment undergoes a γ → stacking fault → ɛ transformation. The strengthening of the steel by the frictional treatment manifests in a delay of the onset of the plastic flow. In the structure of the surface layer with a thickness of 5 μm, a high concentration of stacking faults has been detected. The mechanical properties depend on the orientation of the acting stresses relative to the direction of the frictional treatment. Upon the sliding friction of a ball made of hard alloy (94%WC + 6%Co) on the strengthened surface, an anomalously low coefficient of friction of 0.13 is observed. The coefficient of friction in the presence of abrasive particles in the form of wear debris increases to 0.50; however, the wear rate is almost two times lower compared to the same characteristic for a nonstrengthened surface of the nitrogen steel tested under the same conditions.

  6. Effect of prior cold work on creep properties of a titanium modified austenitic stainless steel

    International Nuclear Information System (INIS)

    Vijayanand, V.D.; Parameswaran, P.; Nandagopal, M.; Panneer Selvi, S.; Laha, K.; Mathew, M.D.

    2013-01-01

    Prior cold worked (PCW) titanium-modified 14Cr–15Ni austenitic stainless steel (SS) is used as a core-structural material in fast breeder reactor because of its superior creep strength and resistance to void swelling. In this study, the influence of PCW in the range of 16–24% on creep properties of IFAC-1 SS, a titanium modified 14Cr–15Ni austenitic SS, at 923 K and 973 K has been investigated. It was found that PCW has no appreciable effect on the creep deformation rate of the steel at both the test temperatures; creep rupture life increased with PCW at 923 K and remained rather unaffected at 973 K. The dislocation structure along with precipitation in the PCW steel was found to change appreciably depending on creep testing conditions. A well-defined dislocation substructure was observed on creep testing at 923 K; a well-annealed microstructure with evidences of recrystallization was observed on creep testing at 973 K

  7. Ensemble Empirical Mode Decomposition based methodology for ultrasonic testing of coarse grain austenitic stainless steels.

    Science.gov (United States)

    Sharma, Govind K; Kumar, Anish; Jayakumar, T; Purnachandra Rao, B; Mariyappa, N

    2015-03-01

    A signal processing methodology is proposed in this paper for effective reconstruction of ultrasonic signals in coarse grained high scattering austenitic stainless steel. The proposed methodology is comprised of the Ensemble Empirical Mode Decomposition (EEMD) processing of ultrasonic signals and application of signal minimisation algorithm on selected Intrinsic Mode Functions (IMFs) obtained by EEMD. The methodology is applied to ultrasonic signals obtained from austenitic stainless steel specimens of different grain size, with and without defects. The influence of probe frequency and data length of a signal on EEMD decomposition is also investigated. For a particular sampling rate and probe frequency, the same range of IMFs can be used to reconstruct the ultrasonic signal, irrespective of the grain size in the range of 30-210 μm investigated in this study. This methodology is successfully employed for detection of defects in a 50mm thick coarse grain austenitic stainless steel specimens. Signal to noise ratio improvement of better than 15 dB is observed for the ultrasonic signal obtained from a 25 mm deep flat bottom hole in 200 μm grain size specimen. For ultrasonic signals obtained from defects at different depths, a minimum of 7 dB extra enhancement in SNR is achieved as compared to the sum of selected IMF approach. The application of minimisation algorithm with EEMD processed signal in the proposed methodology proves to be effective for adaptive signal reconstruction with improved signal to noise ratio. This methodology was further employed for successful imaging of defects in a B-scan. Copyright © 2014. Published by Elsevier B.V.

  8. Atypical transitions in material response during constant strain rate, hot deformation of austenitic steel

    Science.gov (United States)

    Borah, Utpal; Aashranth, B.; Samantaray, Dipti; Kumar, Santosh; Davinci, M. Arvinth; Albert, Shaju K.; Bhaduri, A. K.

    2017-10-01

    Work hardening, dynamic recovery and dynamic recrystallization (DRX) occurring during hot working of austenitic steel have been extensively studied. Various empirical models describe the nature and effects of these phenomena in a typical framework. However, the typical model is sometimes violated following atypical transitions in deformation mechanisms of the material. To ascertain the nature of these atypical transitions, researchers have intentionally introduced discontinuities in the deformation process, such as interrupting the deformation as in multi-step rolling and abruptly changing the rate of deformation. In this work, we demonstrate that atypical transitions are possible even in conventional single-step, constant strain rate deformation of austenitic steel. Towards this aim, isothermal, constant true strain rate deformation of austenitic steel has been carried out in a temperature range of 1173-1473 K and strain rate range of 0.01-100 s-1. The microstructural response corresponding to each deformation condition is thoroughly investigated. The conventional power-law variation of deformation grain size (D) with peak stress (σp) during DRX is taken as a typical model and experimental data is tested against it. It is shown that σp-D relations exhibit an atypical two-slope linear behaviour rather than a continuous power law relation. Similarly, the reduction in σp with temperature (T) is found to consist of two discrete linear segments. In practical terms, the two linear segments denote two distinct microstructural responses to deformation. As a consequence of this distinction, the typical model breaks down and is unable to completely relate microstructural evolution to flow behaviour. The present work highlights the microstructural mechanisms responsible for this atypical behavior and suggests strategies to incorporate the two-slope behaviour in the DRX model.

  9. 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.

  10. The role of nitrogen in improving pitting corrosion resistance of high-alloy austenitic and duplex stainless steel welds

    International Nuclear Information System (INIS)

    Vilpas, M.; Haenninen, H.

    1999-01-01

    The effects of nitrogen alloyed shielding gas on weld nitrogen content and pitting corrosion resistance of super austenitic (6%Mo) and super duplex stainless steels have been studied with special emphasis on microsegregation behaviour of Cr, Mo and N. The measurements performed with the 6%Mo steel indicate that all these elements segregate interdendritically in the fully austenitic weld metal. With nitrogen addition to the shielding gas the enrichment of nitrogen to the interdendritic regions is more pronounced than to the dendrite cores due to which the pitting corrosion resistance of the dendrite cores increases only marginally. In the super duplex steel welds nitrogen enriches in austenite increasing its pitting corrosion resistance more effectively. In these welds the pitting corrosion resistance of the ferrite phase remains lower. (orig.)

  11. 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...... tension. Gaseous nitriding of the strained material was performed in ammonia gas at atmospheric pressure at 703 K. Microstructural characterization of the as-deformed states and the nitrided case produced included X-ray diffraction analysis, reflected light microscopy, microhardness testing. The results...

  12. Fatigue hardening and softening studies on strain hardened 18-8 austenitic stainless steel

    International Nuclear Information System (INIS)

    Ramakrishna Prasad, C.; Vasudevan, R.

    1976-01-01

    Metals when subjected to fatigue harden or soften depending on their previous mechanical history. Annealed or mildly cold worked metals are known to harden while severely cold worked metals soften when subjected to fatigue loading. In the present work samples of austenitic 18-8 steel cold worked to 11% and 22% reduction in area were mounted in a vertical pulsator and fatigued in axial tension-compression. Clear cut effects were produced and it was noticed that these depended on the extent of cold work, the amplitude as well as the number of cycles of fatigue and mean stress if any. (orig.) [de

  13. 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.

  14. Elastic constants of an Fe-5Cr-26Mn austenitic steel, 76 to 400 K

    International Nuclear Information System (INIS)

    Ledbetter, H.M.; Austin, M.W.

    1983-01-01

    By measuring longitudinal-mode and transverse-mode sound velocities at frequencies near 10 MHz, we determined the complete engineering elastic constants - bulk modulus, shear modulus, Young modulus, Poisson ratio - for an Fe-5Cr-26Mn austenitic steel between 76 and 400 K. Due to a magnetic transition, all elastic constants behave anomalously below about 360 K. The bulk modulus begins to soften during cooling at some higher temperature. Except for Poisson's ratio, below the 360-K magnetic transition, all elastic constants resume an apparently normal temperature dependence. After increasing abruptly at the magnetic transition, Poisson's ratio increases with decreasing temperature

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

    OpenAIRE

    Klobčar, D.; Tušek; Bizjak, M.; Simončič, S.; Lešer, V.

    2016-01-01

    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 a...

  16. Martensitic transformation in an intergranular corrosion area of austenitic stainless steel during thermal cycling

    International Nuclear Information System (INIS)

    La Fontaine, Alexandre; Yen, Hung-Wei; Trimby, Patrick; Moody, Steven; Miller, Sarah; Chensee, Martin; Ringer, Simon; Cairney, Julie

    2014-01-01

    An oxidation-assisted martensitic phase transformation was observed in an austenitic stainless steel after thermal cycling up to 970 °C in air in a solar thermal steam reformer. The intergranular corrosion areas were investigated by electron backscatter diffraction (EBSD), transmission Kikuchi diffraction (TKD) and transmission electron microscopy (TEM). The structural-and-chemical maps revealed that within intergranular corrosion areas this martensitic transformation primarily occurs in oxidation-induced chromium-depleted zones, rather than due to only sensitization. This displacive transformation may also play a significant role in the rate at which intergranular corrosion takes place

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

    DEFF Research Database (Denmark)

    Chen, Ming; Alimadadi, Hossein; Molin, Sebastian

    2017-01-01

    Ferritic stainless steel interconnect plates are widely used in planar solid oxide fuel cell and electrolysis cell stacks. During stack production and operation, nickel from the Ni/yttria stabilized zirconia fuel electrode or from the Ni contact component layer diffuses into the interconnect 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 interconnect plates. In this work, kinetic modeling of the inter-diffusion between Ni and FeCr based ferritic...

  18. The effect of oxidation on the creep behavior of austenitic stainless steels

    International Nuclear Information System (INIS)

    Assis, A.M.C.A.; Monteiro, S.N.

    1979-01-01

    The manifestation of superficial oxidation in creep rupture tests performed with three austenitic, stainless steels under constant load in furnaces open to the atmosphere, between the temperature of 550 0 C and 800 0 C is discussed. There is experimental evidence that the superficial oxidation effects are associated, in each material, to the testing temperature, to the duration of the test and to the degree of deformation reached. The influence of the oxidatio is related to the acting deformation mechanisms. The possible corrosion action on the characteristics of the mechanical behavior of the materials under creep is analysed. (Author) [pt

  19. On the Cutting Performance of Coated HSS Taps When Machining of Austenitic Steel

    Science.gov (United States)

    Sliwkova, Petra; Piska, Miroslav

    2014-12-01

    The paper deals with a quality of the PVD coated HSS taps when cutting the stainless austenitic chromiumnickel non-stabilized steel DIN 1.4301 (X5CrNi 18-10). The main attention is focused on the analysis of loading (cutting moment, specific energy) of the HSS taps by means of pieso-electrical dynamometer Kistler 9272 and the relation between the quality of duplex and triplex PVD coatings and their effects on the quality of machined thread surfaces and tool life of the taps. The results showed a safe and stabilized cutting with acceptable quality of threads for HSSE with the TiN+TiCN+DLC coating.

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

    International Nuclear Information System (INIS)

    Moreno, D. A.; Garcia, A. M.; Ranninger, C.; Molina, B.

    2011-01-01

    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. (Author) 18 refs.

  1. Quantitative description of changes in the structure in austenitic steels after hot temperature deformation

    International Nuclear Information System (INIS)

    Kuc, D.; Rodak, K.; Niewielski, G.; Hetmanczyk, M.

    1998-01-01

    An investigation on the structural changes in austenitic hard deformable Cr-Mn and Cr-Ni steels during dynamic recrystallization has been presented in the paper. The influence of the factors (strain rate, deformation, temperature) on the geometric characteristic of grains has been taken into consideration. Investigation of the structure were performed using metallographic microscope and transmission electron microscope. The results of researched should widen the theoretical background in order to the model of phenomena, which accompany the dynamic recovery and dynamic recrystallization. (author)

  2. Stress Corrosion Cracking Behaviour of Dissimilar Welding of AISI 310S Austenitic Stainless Steel to 2304 Duplex Stainless Steel

    Directory of Open Access Journals (Sweden)

    Thiago AmaroVicente

    2018-03-01

    Full Text Available The influence of the weld metal chemistry on the stress corrosion cracking (SCC susceptibility of dissimilar weldments between 310S austenitic stainless steel and 2304 duplex steels was investigated by constant load tests and microstructural examination. Two filler metals (E309L and E2209 were used to produce fusion zones of different chemical compositions. The SCC results showed that the heat affected zone (HAZ on the 2304 base metal side of the weldments was the most susceptible region to SCC for both filler metals tested. The SCC results also showed that the weldments with 2209 duplex steel filler metal presented the best SCC resistance when compared to the weldments with E309L filler metal. The lower SCC resistance of the dissimilar joint with 309L austenitic steel filler metal may be attributed to (1 the presence of brittle chi/sigma phase in the HAZ on the 2304 base metal, which produced SC cracks in this region and (2 the presence of a semi-continuous delta-ferrite network in the fusion zone which favored the nucleation and propagation of SC cracks from the fusion zone to HAZ of the 2304 stainless steel. Thus, the SC cracks from the fusion zone associated with the SC cracks of 2304 HAZ decreased considerably the time-of-fracture on this region, where the fracture occurred. Although the dissimilar weldment with E2209 filler metal also presented SC cracks in the HAZ on the 2304 side, it did not present the delta ferrite network in the fusion zone due to its chemical composition. Fractography analyses showed that the mixed fracture mode was predominant for both filler metals used.

  3. Tensile Fracture Behavior of 316L Austenitic Stainless Steel Manufactured by Hot Isostatic Pressing

    Science.gov (United States)

    Cooper, A. J.; Brayshaw, W. J.; Sherry, A. H.

    2018-02-01

    Herein we investigate how the oxygen content in hot isostatically pressed (HIP'd) 316L stainless steel affects the mechanical properties and tensile fracture behavior. This work follows on from previous studies, which aimed to understand the effect of oxygen content on the Charpy impact toughness of HIP'd steel. We expand on the work by performing room-temperature tensile testing on different heats of 316L stainless steel, which contain different levels of interstitial elements (carbon and nitrogen) as well as oxygen in the bulk material. Throughout the work we repeat the experiments on conventionally forged 316L steel as a reference material. The analysis of the work indicates that oxygen does not contribute to a measureable solution strengthening mechanism, as is the case with carbon and nitrogen in austenitic stainless steels (Werner in Mater Sci Eng A 101:93-98, 1988). Neither does oxygen, in the form of oxide inclusions, contribute to precipitation hardening due to the size and spacing of particles. However, the oxide particles do influence fracture behavior; fractography of the failed tension test specimens indicates that the average ductile dimple size is related to the oxygen content in the bulk material, the results of which support an on-going hypothesis relating oxygen content in HIP'd steels to their fracture mechanisms by providing additional sites for the initiation of ductile damage in the form of voids.

  4. Radiation-induced grain boundary segregation in austenitic stainless steels

    International Nuclear Information System (INIS)

    Bruemmer, S.M.; Charlot, L.A.; Vetrano, J.S.; Simonen, E.P.

    1994-11-01

    Radiation-induced segregation (RIS) to grain boundaries in Fe-Ni-Cr-Si stainless alloys has been measured as a function of irradiation temperature and dose. Heavy-ion irradiation was used to produce damage levels from 1 to 20 displacements per atom (dpa) at temperatures from 175 to 550 degrees C. Measured Fe, Ni, and Cr segregation increased sharply with irradiation dose (from G to 5 dpa) and temperature (from 175 to about 350 degrees C). However, grain boundary concentrations did not change significantly as dose or temperatures were further increased. Although interfacial compositions were similar, the width of radiation-induced enrichment or depletion profiles increased consistently with increasing dose or temperature. Impurity segregation (Si and P) was also measured, but only Si enrichment appeared to be radiation-induced. Grain boundary Si peaked at levels approaching 10 at% after irradiation doses to 10 dpa at an intermediate temperature of 325 degrees C. No evidence of grain boundary silicide precipitation was detected after irradiation at any temperature. Equilibrium segregation of P was measured in the high-P alloys, but interfacial concentration did not increase with irradiation exposure. Comparisons to reported RIS in neutron-irradiated stainless steels revealed similar grain boundary compositional changes for both major alloying and impurity elements

  5. Standard practice for X-Ray determination of retained austenite in steel with near random crystallographic orientation

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2003-01-01

    1.1 This practice covers the determination of retained austenite phase in steel using integrated intensities (area under peak above background) of X-ray diffraction peaks using chromium Kα or molybdenum Kα X-radiation. 1.2 The method applies to carbon and alloy steels with near random crystallographic orientations of both ferrite and austenite phases. 1.3 This practice is valid for retained austenite contents from 1 % by volume and above. 1.4 If possible, X-ray diffraction peak interference from other crystalline phases such as carbides should be eliminated from the ferrite and austenite peak intensities. 1.5 Substantial alloy contents in steel cause some change in peak intensities which have not been considered in this method. Application of this method to steels with total alloy contents exceeding 15 weight % should be done with care. If necessary, the users can calculate the theoretical correction factors to account for changes in volume of the unit cells for austenite and ferrite resulting from vari...

  6. Moessbauer effect and neutron scattering in austenitic high nitrogen steel Fe-19Cr-19Mn-0.9N

    International Nuclear Information System (INIS)

    Nadutov, V.M.; Garamus, V.M.; Islamov, A.Kh.

    1999-01-01

    Austenitic high nitrogen Fe-19Cr-19Mn-0.9N steel was studied by means of Moessbauer analysis and neutron diffraction and small-angle neutron scattering (SANS) after solution treatment at 1125 C and ageing at 250-350 C. The redistribution of nitrogen atoms in austenite after ageing was detected in Moessbauer measurements. SANS was observed in annealed and aged samples characterizing an existence of the inhomogeneities in steel of atomic and magnetic nature. The linear size and shape of inhomogeneities is estimated on the basis of analysis of the integral parameters of scattering curves. (orig.)

  7. Work hardening mechanism in high nitrogen austenitic steel studied by in situ neutron diffraction and in situ electron backscattering diffraction

    International Nuclear Information System (INIS)

    Ojima, M.; Adachi, Y.; Tomota, Y.; Ikeda, K.; Kamiyama, T.; Katada, Y.

    2009-01-01

    With a focus on microstructural hierarchy, work hardening behaviour in high nitrogen-bearing austenitic steel (HNS) was investigated mainly by a combined technique of in situ neutron diffraction and in situ electron backscattering diffraction (EBSD). Stress partitioning due to difference in deformability among grains is enhanced in HNS. The larger stress partitioning among [h k l]-oriented family grains seems to realize high work hardening at a small strain. At a larger strain, dislocation density is higher in HNS than in low nitrogen austenitic steel (LNS), which is a possible reason for high work hardening after straining proceeds, resulting in large uniform elongation.

  8. 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.

  9. The radiation swelling effect on fracture properties and fracture mechanisms of irradiated austenitic steels. Part II. Fatigue crack growth rate

    Energy Technology Data Exchange (ETDEWEB)

    Margolin, B., E-mail: margolinbz@yandex.ru; Minkin, A.; Smirnov, V.; Sorokin, A.; Shvetsova, V.; Potapova, V.

    2016-11-15

    The experimental data on the fatigue crack growth rate (FCGR) have been obtained for austenitic steel of 18Cr-10Ni-Ti grade (Russian analog of AISI 321 steel) irradiated up to neutron dose of 150 dpa with various radiation swelling. The performed study of the fracture mechanisms for cracked specimens under cyclic loading has explained why radiation swelling affects weakly FCGR unlike its effect on fracture toughness. Mechanical modeling of fatigue crack growth has been carried out and the dependencies for prediction of FCGR in irradiated austenitic steel with and with no swelling are proposed and verified with the obtained experimental results. As input data for these dependencies, FCGR for unirradiated steel and the tensile mechanical properties for unirradiated and irradiated steels are used.

  10. Welding hot cracking in an austenitic stainless steel

    International Nuclear Information System (INIS)

    Kerrouault, N.

    2001-01-01

    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

  11. INFLUENCE OF AUSTENITE GRAIN SIZE TO DEVELOPMENT OF DECARBONIZATION IN PRODUCTION OF ROLLED STEEL

    Directory of Open Access Journals (Sweden)

    PARUSOV E. V.

    2016-08-01

    ]. The paper [11] acknowledges the influence of micro-additives of boron on changes in the austenite grain size and accordingly the length of borders in high-carbon steels with austenitizing temperature increase within the range of 900…1 100ºС. The purpose of work is to research the effect of austenite grain size on the decarburization depth in carbon (base steel and boron micro-alloyed steel.

  12. The Effect of Calcium Treatment on Pitting Corrosion of Type 316L Austenitic Stainless steel

    International Nuclear Information System (INIS)

    Lee, Yong Heon; LeeSoo Chan; Kim, Yong Hwan; Kim, Hee San

    2001-01-01

    Pitting in chloride containing aqueous solution occurs mainly on manganese sulphide. Adding a slight amount of Ca as an alloying element prevents the MnS formation, since Ca is a stronger sulphide former than Mn. In this work, calcium treated Type 316L austenitic stainless steels have been investigated electrochemically to evaluate the effect of modified inclusions on pitting corrosion. Staircase polarization measurements were performed in 3.5% NaCl solution, where the occurrence of pits in materials caused current spikes. During staircase polarization test, steels with calcium treatment show low and discontinuous current spikes while those without calcium treatment show high and continuous current spikes. The results show that calcium treatment in Ca/S ratio of 1 ∼ 2 leads to an increase in the pitting potential of several hundred mV. A relationship between the calcium treatment and pit initiation sites was described

  13. Discrimination of ultrasonic indications from austenitic stainless-steel pipe welds

    International Nuclear Information System (INIS)

    Singh, G.P.; Manning, R.C.

    1983-01-01

    The inspection of butt-welded stainless-steel pipe joints in nuclear power plants is routinely performed using ultrasonic non-destructive evaluation methods. However, discrimination between crack and geometric/weld (malignant versus benign) indications is principally based on operator experience, variations in signal amplitude, and the location of the reflector. In response to the inspection problem, a pattern-recognition methodology has been developed to discriminate intergranular stress-corrosion cracking from geometric/weld reflectors in austenitic stainless-steel pipes. Results demonstrate that the algorithm can provide discrimination comparable to or better than those supplied by well trained operators. Preliminary results show that the pattern-recognition algorithm approach yields a better than 90% index of performance. (author)

  14. Testing of intergranular and pitting corrosion in sensitized welded joints of austenitic stainless steel

    Directory of Open Access Journals (Sweden)

    Bore V. Jegdic

    2017-06-01

    Full Text Available Pitting corrosion resistance and intergranular corrosion of the austenitic stainless steel X5Cr Ni18-10 were tested on the base metal, heat affected zone and weld metal. Testing of pitting corrosion was performed by the potentiodynamic polarization method, while testing of intergranular corrosion was performed by the method of electrochemical potentiokinetic reactivation with double loop. The base metal was completely resistant to intergranular corrosion, while the heat affected zone showed a slight susceptibility to intergranular corrosion. Indicators of pitting corrosion resistance for the weld metal and the base metal were very similar, but their values are significantly higher than the values for the heat affected zone. This was caused by reduction of the chromium concentration in the grain boundary areas in the heat affected zone, even though the carbon content in the examined stainless steel is low (0.04 wt. % C.

  15. Perspective on present and future alloy development efforts on austenitic stainless steels for fusion application

    Energy Technology Data Exchange (ETDEWEB)

    Maziasz, P.J.

    1984-01-01

    The purpose of this paper is to address important questions concerning how to effect further alloy development of austenitic stainless steels for resistance, and to what extent the behavior of other properties under irradiation, such as strength/embrittlement, fatigue/irradiation creep, corrosion (under irradiation), and radiation-induced activation must be influenced. To summarize current understanding, helium has been found to have major effects on swelling and embrittlement, but several metallurgical avenues are available for significant improvement relative to type 316 stainless steel. Studies on fatigue and irradiation creep, particularly including helium effects, are preliminary but have yet to reveal engineering problems requiring additional alloy development remedies. The effects of irradiation on corrosion behavior are unknown, but higher alloy nickel contents make thermal corrosion in lithium worse. 67 refs. (JDB)

  16. Structure and composition of phases occurring in austenitic stainless steels in thermal and irradiation environments

    International Nuclear Information System (INIS)

    Lee, E.H.; Maziasz, P.J.; Rowcliffe, A.F.

    1980-01-01

    Transmission electron diffraction techniques coupled with quantitative x-ray energy dispersive spectroscopy have been used to characterize the phases which develop in austenitic stainless steels during exposure to thermal and to irradiation environments. In AISI 316 and Ti-modified stainless steels some thirteen phases have been identified and characterized in terms of their crystal structure and chemical composition. Irradiation does not produce any completely new phases. However, as a result of radiation-induced segregation, principally of Ni and Si, and of enhanced diffusion rates, several major changes in phase relationships occur during irradiation. Firstly, phases characteristic of remote regions of the phase diagram appear unexpectedly, and dissolve during postirradiation annealing (radiation-induced phases). Secondly, some phases develop with their compositions significantly altered by the incorporation of Ni or Si (radiation-modified phases). In addition, several phases develop at significantly lower temperaures during neutron irradiation (radiation-enhanced phases). 18 figures, 9 tables

  17. 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.

  18. Perspective on present and future alloy development efforts on austenitic stainless steels for fusion application

    International Nuclear Information System (INIS)

    Maziasz, P.J.

    1984-01-01

    The purpose of this paper is to address important questions concerning how to effect further alloy development of austenitic stainless steels for resistance, and to what extent the behavior of other properties under irradiation, such as strength/embrittlement, fatigue/irradiation creep, corrosion (under irradiation), and radiation-induced activation must be influenced. To summarize current understanding, helium has been found to have major effects on swelling and embrittlement, but several metallurgical avenues are available for significant improvement relative to type 316 stainless steel. Studies on fatigue and irradiation creep, particularly including helium effects, are preliminary but have yet to reveal engineering problems requiring additional alloy development remedies. The effects of irradiation on corrosion behavior are unknown, but higher alloy nickel contents make thermal corrosion in lithium worse. 67 refs

  19. Investigations on the creep-rupture behaviour of the austenitic stainless steel AISI 316 NET

    International Nuclear Information System (INIS)

    Schirra, M.; Heger, S.; Ritter, B.

    1991-08-01

    The report describes the creep-rupture tests carried out with a 17Cr-13Ni-2Mo-steel in the frame of the German-Spanish collaboration (KfK-CIEMAT). The material studied is the austenitic steel AISI 316(L) selected as potential first-wall material for NET (Next European Torus). The test program on base material with a NET specified batch comprises in the temperature range 500-750deg C the rupture-time-range till 40 000 h. The results permit statements on the creep- and creep-rupture behaviour and ductility. Metallographic examinations give informations about the fracture behaviour and demonstrate the complex precipitation behaviour. The results are compared with literature data and own results from two batches of the European Fast-Breeder-Program. (orig.) [de

  20. 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...... backbone and a reduced amount of Si-H moieties. The coatings showed good substrate coverage and the average thickness was between 200 and 400 nm on the rough substrate surface, however, film thicknesses of > 1400 nm were observed at substrate defects. Deposition of these films significantly improved...

  1. Grain boundary chromium concentration effects on the IGSCC and IASCC of austenitic stainless steels

    International Nuclear Information System (INIS)

    Bruemmer, S.M.; Arey, B.W.; Charlot, L.A.

    1993-08-01

    Comparisons are made between grain boundary composition and intergranular stress corrosion cracking (IGSCC) of 304 and 309 austenitic stainless steels in high-temperature water environments. Chromium depletion had the dominant effect on cracking resistance with the extent of IG cracking controlled by the interfacial chromium concentration. The minimum chromium concentration required to promote cracking was a function of the applied strain rate during slow-strain-rate tensile tests in 288 C air-saturated water. Depletion from bulk levels of 18 wt% to ∼13.5 wt% Cr at grain boundaries prompted 100% IG cracking at a strain rate of 1 x 10 -6 s -1 , while embrittlement was observed with only a slight depletion to ∼17 wt% at 2 x 10 -7 s -1 . Insights into critical interfacial compositions promoting IGSCC are discussed in reference to cracking of irradiated stainless steel nuclear reactor core components

  2. Topological characterization of static strain aging of type AISI 304 austenitic stainless steel

    International Nuclear Information System (INIS)

    Monteiro, S.N.; Miranda, P.E.V. de

    1981-01-01

    Static strain aging of type AISI 304 austenitic stainless steel was studied from room temperature up to 623K by conducting tests in which the load was held approximately constant. The aging times varied between 10s and 100h, using a plastic pre-deformation of 9%. The static strain aging of 304 steel furnished an activation energy of 23.800 cal/mol. This implies that vacancies play an important role on the aging process. The curve of the variation of the discontinuous yielding with aging time presented different stages, to which specific mathematical expressions were developed. These facts permited the conclusion that Snock type mechanisms are responsible for the aging in such conditions. (Author) [pt

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

    International Nuclear Information System (INIS)

    Hoelzel, M.; Danilkin, S.A.; Ehrenberg, H.; Toebbens, D.M.; Udovic, T.J.; Fuess, H.; Wipf, H.

    2004-01-01

    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 ∼ 1. In 304 stainless steel, the formation of ε-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 ε-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. Effects of LWR coolant environments on fatigue lives of austenitic stainless steels

    International Nuclear Information System (INIS)

    Chopra, O.K.; Gavenda, D.J.

    1997-01-01

    The ASME Boiler and Pressure Vessel Code fatigue design curves for structural materials do not explicitly address the effects of reactor coolant environments on fatigue life. Recent test data indicate a significant decrease in fatigue life of pressure vessel and piping materials in light water reactor (LWR) environments. Fatigue tests have been conducted on Types 304 and 316NG stainless steel in air and LWR environments to evaluate the effects of various material and loading variables, e.g., steel type, strain rate, dissolved oxygen (DO) in water, and strain range, on fatigue lives of these steels. The results confirm the significant decrease in fatigue life in water. The environmentally assisted decrease in fatigue life depends both on strain rate and DO content in water. A decrease in strain rate from 0.4 to 0.004%/s decreases fatigue life by a factor of ∼ 8. However, unlike carbon and low-alloy steels, environmental effects are more pronounced in low-DO than in high-DO water. At ∼ 0.004%/s strain rate, reduction in fatigue life in water containing <10 ppb D is greater by a factor of ∼ 2 than in water containing ≥ 200 ppb DO. Experimental results have been compared with estimates of fatigue life based on the statistical model. The formation and growth of fatigue cracks in austenitic stainless steels in air and LWR environments are discussed

  5. Mass transfer behavior of a modified austenitic stainless steel in lithium

    International Nuclear Information System (INIS)

    Tortorelli, P.F.; DeVan, J.H.

    1983-01-01

    An austenitic stainless steel that was developed to resist neutron damage was exposed to lithium in the high-temperature part of a thermal convection loop for 6700 h. Specimens of this Prime Candidate Alloy (PCA) composed of 65.0 Fe-15.9 Ni-13.0 Cr-1.9 Mo-1.9 Mn-1.7 Si-0.5 Ti-0.05 C (wt %) were exposed at 600 and 570 0 C in both solution annealed and cold worked forms. The dissolution process was found to be similar to other austenitic alloys in flowing lithium: weight losses of PCA eventually became linearly proportional to exposure time with the specimen surfaces exhibiting porous layers depleted in nickel and chromium. However, the measured weight losses and dissolution rates of these PCA specimens were higher than those of type 316 stainless steel exposed under similar conditions and can be attributed to the higher nickel concentration of the former alloy. The effect of cold work on dissolution rates was less definitive, particularly at 570 0 C. At longer exposure times, the annealed PCA specimen exposed at 600 0 C suffered greater dissolution than the cold worked material, while no effect of prior deformation was observed by analysis of the respective surfaces

  6. 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.

  7. High corrosion resistance of austenitic stainless steel alloyed with nitrogen in an acid solution

    Energy Technology Data Exchange (ETDEWEB)

    Metikos-Hukovic, M., E-mail: mmetik@fkit.h [Department of Electrochemistry, Faculty of Chemical Engineering and Technology, University of Zagreb, Savska 16, P.O. Box 177, 100000 Zagreb (Croatia); Babic, R. [Department of Electrochemistry, Faculty of Chemical Engineering and Technology, University of Zagreb, Savska 16, P.O. Box 177, 100000 Zagreb (Croatia); Grubac, Z. [Department of General and Inorganic Chemistry, Faculty of Chemistry and Technology, University of Split, 21000 Split (Croatia); Petrovic, Z. [Department of Electrochemistry, Faculty of Chemical Engineering and Technology, University of Zagreb, Savska 16, P.O. Box 177, 100000 Zagreb (Croatia); Lajci, N. [Faculty of Mine and Metallurgy, University of Prishtina, 10000 Prishtina, Kosovo (Country Unknown)

    2011-06-15

    Highlights: {yields} ASS alloyed with nitrogen treated at 1150 {sup o}C exhibits microstructure homogeneity. {yields} Passivation peak of ASS corresponds to oxidation of metal and absorbed hydrogen. {yields} Transfer phenomena and conductivity depend on the film formation potential. {yields} Electronic structure of the passive film and its corrosion resistance correlate well. {yields} Passive film on ASS with nitrogen is low disordered and high corrosion resistant. - Abstract: Passivity of austenitic stainless steel containing nitrogen (ASS N25) was investigated in comparison with AISI 316L in deareated acid solution, pH 0.4. A peculiar nature of the passivation peak in a potentiodynamic curve and the kinetic parameters of formation and growth of the oxide film have been discussed. The electronic-semiconducting properties of the passive films have been correlated with their corrosion resistance. Alloying austenitic stainless steel with nitrogen increases its microstructure homogeneity and decreases the concentration of charge carriers, which beneficially affects the protecting and electronic properties of the passive oxide film.

  8. Mechanical properties microstructure correlation in neutron irradiated heat-affected zones of austenitic stainless steels

    Science.gov (United States)

    Stoenescu, R.; Schaeublin, R.; Gavillet, D.; Baluc, N.

    2007-05-01

    The effects of neutron irradiation on austenitic stainless steels, usually used for the manufacturing of internal elements of nuclear reactors (e.g. the core shrouds), are the alteration of the microstructure, and, as a consequence, of the mechanical properties. The present study is aimed at extending knowledge upon the impact of neutron-irradiation on the heat-affected zone of welded materials, which was influenced by the thermal cycles upon fusion welding. An austenitic stainless steel weld type AISI 304 from a decommissioned experimental pressurised water reactor has been used in the present study. The welded material has been irradiated during 11 reactor cycles to a maximum dpa dose of 0.35 and a temperature of around 573 K. The mechanical properties and microstructure are determined on specimens from heat-affected zone and base materials, with different dose levels. The mechanical properties were determined by performing tensile tests on small flat specimens at two deformation temperatures: room temperature and about 573 K. The characterisation of the microstructure was made by transmission electron microscopy. The correlation between mechanical properties and microstructure after neutron irradiation is made using the dispersed obstacle hardening model. It was found that the measured radiation hardening cannot be explained solely by the presence of the irradiation-induced defects observed in TEM. Smaller irradiation-induced features not resolvable in TEM may also contribute to radiation hardening.

  9. The microstructural, mechanical, and fracture properties of austenitic stainless steel alloyed with gallium

    Science.gov (United States)

    Kolman, D. G.; Bingert, J. F.; Field, R. D.

    2004-11-01

    The mechanical and fracture properties of austenitic stainless steels (SSs) alloyed with gallium require assessment in order to determine the likelihood of premature storage-container failure following Ga uptake. AISI 304 L SS was cast with 1, 3, 6, 9, and 12 wt pct Ga. Increased Ga concentration promoted duplex microstructure formation with the ferritic phase having a nearly identical composition to the austenitic phase. Room-temperature tests indicated that small additions of Ga (less than 3 wt pct) were beneficial to the mechanical behavior of 304 L SS but that 12 wt pct Ga resulted in a 95 pct loss in ductility. Small additions of Ga are beneficial to the cracking resistance of stainless steel. Elastic-plastic fracture mechanics analysis indicated that 3 wt pct Ga alloys showed the greatest resistance to crack initiation and propagation as measured by fatigue crack growth rate, fracture toughness, and tearing modulus. The 12 wt pct Ga alloys were least resistant to crack initiation and propagation and these alloys primarily failed by transgranular cleavage. It is hypothesized that Ga metal embrittlement is partially responsible for increased embrittlement.

  10. 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

  11. Mechanical and microstructural aspects of severe plastic deformation of austenitic steel

    Science.gov (United States)

    Rodak, K.; Pawlicki, J.; Tkocz, M.

    2012-05-01

    The paper presents the effects of severe plastic deformation by multiple compression in the orthogonal directions on the microstructure and the mechanical properties of austenitic steel. Several deformation variants were conducted with different number of passes. FEM simulations were performed in order to evaluate the actual values of the effective strain in the examined, central parts of the compressed samples. The deformed microstructure was investigated by means of the scanning transmission electron microscopy (STEM) and the scanning electron microscopy (SEM) supported by the electron back scattered diffraction (EBSD). X-ray phase analysis was performed to evaluate the martensite volume fraction. The mechanical properties were determined by means of the digital image correlation method and hardness testing. It is shown that the applied forming technique leads to strong grain refinement in the austenitic steel. Moreover, deformation induces the martensitic γ- α' transformation. The microstructural changes cause an improvement in the strength properties. The material exhibits the ultimate tensile strength of 1560 MPa and the yield stress of 1500 MPa after reaching the effective strain of 10.

  12. Mechanical and microstructural aspects of severe plastic deformation of austenitic steel

    International Nuclear Information System (INIS)

    Rodak, K; Pawlicki, J; Tkocz, M

    2012-01-01

    The paper presents the effects of severe plastic deformation by multiple compression in the orthogonal directions on the microstructure and the mechanical properties of austenitic steel. Several deformation variants were conducted with different number of passes. FEM simulations were performed in order to evaluate the actual values of the effective strain in the examined, central parts of the compressed samples. The deformed microstructure was investigated by means of the scanning transmission electron microscopy (STEM) and the scanning electron microscopy (SEM) supported by the electron back scattered diffraction (EBSD). X-ray phase analysis was performed to evaluate the martensite volume fraction. The mechanical properties were determined by means of the digital image correlation method and hardness testing. It is shown that the applied forming technique leads to strong grain refinement in the austenitic steel. Moreover, deformation induces the martensitic γ– α' transformation. The microstructural changes cause an improvement in the strength properties. The material exhibits the ultimate tensile strength of 1560 MPa and the yield stress of 1500 MPa after reaching the effective strain of 10.

  13. Moessbauer spectroscopy of He irradiated austenitic stainless steel SUS304 at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Horii, Kiyomasa; Ishibashi, Tetsu; Toriyama, Tamotsu; Wakabayashi, Hidehiko; Iijima, Hiroshi [Musashi Inst. of Tech., Tokyo (Japan); Kawasaki, Katsunori; Hayashi, Nobuyuki; Sakamoto, Isao

    1996-04-01

    SUS 304 austenitic stainless steel causes the magnetic transition at 60 K, and the Young`s modulus lowers. In addition, its composition elements have the large (n,{alpha}) reaction cross section to high energy neutrons, and helium is apt to be generated, and this is a factor that lowers the material strength. In the He-irradiated parts in austenitic stainless steel, the precursory state of martensite transformation should exist, and its effect is considered to be observable by carrying out low temperature Moessbauer spectroscopy. As to the preparation of He-irradiation samples, the SUS 304 foils used and the irradiation conditions are described. The measurement of low temperature Moessbauer spectra for the samples without irradiation and with irradiation is reported. In order to determine the magnetic transition point, the thermal scanning measurement was carried out for the samples without or with irradiation. The martensite transformation was measured by X-ray diffraction and transmission type Moessbauer spectroscopy. In order to observe the state of the sample surfaces, the measurement by internal conversion electron Moessbauer spectroscopy was performed. These results and the temperature dependence of the Moessbauer spectra for the irradiated parts are reported. (K.I.)

  14. Microstructure and mechanical properties of resistance upset butt welded 304 austenitic stainless steel joints

    International Nuclear Information System (INIS)

    Sharifitabar, M.; Halvaee, A.; Khorshahian, S.

    2011-01-01

    Graphical abstract: Three different microstructural zones formed at different distances from the joint interface in resistance upset butt welding of 304 austenitic stainless steel. Highlights: → Evaluation of microstructure in resistance upset welding of 304 stainless steel. → Evaluation of welding parameters effects on mechanical properties of the joint. → Introducing the optimum welding condition for joining stainless steel bars. -- Abstract: Resistance upset welding (UW) is a widely used process for joining metal parts. In this process, current, time and upset pressure are three parameters that affect the quality of welded products. In the present research, resistance upset butt welding of 304 austenitic stainless steel and effect of welding power and upset pressure on microstructure, tensile strength and fatigue life of the joint were investigated. Microstructure of welds were studied using scanning electron microscopy (SEM). X-ray diffraction (XRD) analysis was used to distinguish the phase(s) that formed at the joint interface and in heat affected zone (HAZ). Energy dispersive spectroscopy (EDS) linked to the SEM was used to determine chemical composition of phases formed at the joint interface. Fatigue tests were performed using a pull-push fatigue test machine and the fatigue properties were analyzed drawing stress-number of cycles to failure (S-N) curves. Also tensile strength tests were performed. Finally tensile and fatigue fracture surfaces were studied by SEM. Results showed that there were three different microstructural zones at different distances from the joint interface and delta ferrite phase has formed in these regions. There was no precipitation of chromium carbide at the joint interface and in the HAZ. Tensile and fatigue strengths of the joint decreased with welding power. Increasing of upset pressure has also considerable influence on tensile strength of the joint. Fractography of fractured samples showed that formation of hot spots at

  15. Influence of hydrogen and temperature on the mechanical behaviour in an austenitic stainless steel

    International Nuclear Information System (INIS)

    Lamani, Emil; Jouinot, Patrice

    2003-01-01

    The mechanical behaviour of an austenitic stainless steel has been studied in this work, by means of two techniques: disk pressure embrittlement test (French standard NF E 29-723) and special biaxial tensile test. Specimens for both techniques are embedded disks, loaded by a continuously increasing gas pressure until rupture. Tests have been performed at various temperatures, between 18 o C and 655 o C, with loading speeds from 0.06 to 7 MPa/min. Their main results have been recorded as relationships between gas pressure and specimen deflection until its burst or cracking. Other observations (fracture, microstructure, etc.) are performed to assess the structural evolution with the temperature. The influence of hydrogen is evaluated by the comparison of the rupture parameters of specimens tested similarly under helium and hydrogen. The embrittlement index, E.I is determined as the ratio of the rupture pressures under helium and hydrogen taking into account also the effects of the loading speed and the gas purity. It has been noticed that the mechanical behaviour of the steel is strongly influenced by the apparition of a second phase in the austenitic structure: the deformation induced martensite, α, which presence is identified by microscopic observations and X-ray diffraction. At room temperature, the steel presents a relatively high sensitivity to the hydrogen embrittlement (2.20 ≤ E.I ≤ 2.40), while, with the temperature increasing, together with the reduction of the martensitic transformation, it was observed a rapid diminution of this sensitivity. Obtained results allow to define the performance of this steel for thin walls applications, as it is the case of expansions bellows in the chemical industry. (Original)

  16. Image analysis measurements of prior austenitic grain size of 9Cr-1Mo martensitic steels in function of the austenitization conditions. Quantification par analyse d'images de la taille de l'ancien grain austenitique d'aciers martensitiques 9Cr-1Mo

    Energy Technology Data Exchange (ETDEWEB)

    Barcelo, F.; Brachet, J.C. (CEA Centre d' Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. de Technologie des Materiaux)

    1994-02-01

    The size grain of the high temperature phase (austenite) can influence mechanical properties as well as some physical properties of 9Cr-1Mo martensitic steels. Automated image analysis makes it possible to quantify the size of an austenitic grain with respect to the heat treatment conditions of austenitization (time-temperature). The results obtained on a 9Cr-1Mo steel have made it possible to describe the growth kinetics of the austenitic grain of this steel. (authors). 21 refs., 14 figs.

  17. Bainite transformation of low carbon Mn-Si TRIP-assisted multiphase steels: influence of silicon content on cementite precipitation and austenite retention

    International Nuclear Information System (INIS)

    Jacques, P.; Catlin, T.; Geerlofs, N.; Kop, T.; Zwaag, S. van der; Delannay, F.

    1999-01-01

    Studies dealing with TRIP-assisted multiphase steels have emphasized the crucial role of the bainite transformation of silicon-rich intercritical austenite in the achievement of a good combination of strength and ductility. The present work deals with the bainite transformation in two steels differing in their silicon content. It is shown that both carbon enrichment of residual austenite and cementite precipitation influences the kinetics of the bainite transformation. A minimum silicon content is found to be necessary in order to prevent cementite precipitation from austenite during the formation of bainitic ferrite in such a way as to allow stabilisation of austenite by carbon enrichment. (orig.)

  18. Novel ferrite–austenite duplex lightweight steel with 77% ductility by transformation induced plasticity and twinning induced plasticity mechanisms

    International Nuclear Information System (INIS)

    Sohn, Seok Su; Choi, Kayoung; Kwak, Jai-Hyun; Kim, Nack J.; Lee, Sunghak

    2014-01-01

    The need for lightweight materials has been an important issue in automotive industries to reduce greenhouse gas emission and to improve fuel efficiency. In addition, automotive steels require an excellent combination of strength and ductility to sustain automotive structures and to achieve complex shapes, but the traditional approach to obtain a reduction in weight from down-gauged steels with high strength has many limitations. Here, we present a new ferrite–austenite duplex lightweight steel containing a low-density element, Al; this steel exhibits tensile elongation up to 77% as well as high tensile strength (734 MPa). The enhanced properties are attributed to the simultaneous formation of deformation-induced martensites and deformation twins and the additional plasticity due to deformation twinning in austenite grains having optimal mechanical stability. The present work gives a promise for automotive applications requiring excellent properties as well as reduced specific weight

  19. In vitro corrosion resistance of plasma source ion nitrided austenitic stainless steels.

    Science.gov (United States)

    Le, M K; Zhu, X M

    2001-04-01

    Plasma source ion nitriding has emerged as a low-temperature, low-pressure nitriding approach for low-energy implanting nitrogen ions and then diffusing them into steel and alloy. In this work, a single high nitrogen face-centered-cubic (f.c.c.) phase (gammaN) formed on the 1Cr18Ni9Ti and AISI 316L austenitic stainless steels with a high nitrogen concentration of about 32 at % was characterized using Auger electron spectroscopy, electron probe microanalysis, glancing angle X-ray diffraction, and transmission electron microscopy. The corrosion resistance of the gammaN-phase layer was studied by the electrochemical cyclic polarization measurement in Ringer's solutions buffered to pH from 3.5 to 7.2 at a temperature of 37 degrees C. No pitting corrosion in the Ringer's solutions with pH = 7.2 and 5.5 was detected for the gammaN-phase layers on the two stainless steels. The high pitting potential for the gammaN-phase layers is higher, about 500 and 600 mV, above that of the two original stainless steels, respectively, in the Ringer's solution with pH = 3.5. The corroded surface morphologies of the gammaN-phase layers observed by scanning electron microscopy are consistent with the results of the electrochemical polarization measurement.

  20. Prediction of long-term precipitate evolution in austenitic heat-resistant steels

    Energy Technology Data Exchange (ETDEWEB)

    Shim, Jae-Hyeok; Jung, Woo-Sang; Cho, Young Whan [Korea Institute of Science and Technology, Seoul (Korea, Republic of). Materials/Devices Div.; Kozeschnik, Ernst [Vienna Univ. of Technology (Austria). Inst. of Materials Science and Technology

    2010-07-01

    Numerical prediction of the long-term precipitate evolution in five different austenitic heat-resistant stainless steels, NF709, Super304H, Sanicro25, CF8C-PLUS and HTUPS has been carried out. MX and M{sub 23}C{sub 6} are predicted to remain as major precipitates during long-term aging in these steels. The addition of 3 wt% Cu produces very fine Cu-rich precipitates during aging in Super304H and Sanicro25. It is found that the amount of Z phase start to increase remarkably between 1,000 and 10,000 hours of aging at the expense of MX precipitates in the steels containing a high nitrogen content. However, the growth rate of Z phase is relatively slow and its average size reaches at most a few tens of nanometers after 100,000 hours of aging at 700 C, compared with 9-12% Cr ferritic/martensitic heat-resistant steels. The predicted precipitation sequence and precipitate size during aging are in general agreement with experimental observations. (orig.)

  1. Microstructural Evolution of a Low-Carbon Steel during Application of Quenching and Partitioning Heat Treatments after Partial Austenitization

    NARCIS (Netherlands)

    Santofimia, M.J.; Zhao, L.; Sietsma, J.

    2008-01-01

    The “quenching and partitioning” (Q&P) process has been studied in a low-carbon steel containing 1.1 wt pct aluminum by heat treatments consisting of partial austenitization at 900 °C and subsequent rapid cooling to a quenching temperature in the range between 125 °C and 175 °C, followed by an

  2. Measured resolved shear stresses and Bishop-Hill stress states in individual grains of austenitic stainless steel

    DEFF Research Database (Denmark)

    Juul, Nicolai Ytterdal; Oddershede, Jette; Beaudoin, Armand

    2017-01-01

    The full three-dimensional stress state of 172 individual bulk grains in austenitic stainless steel 316L at 0.1 and 1% sample elongation has been determined with sufficient accuracy to allow comparison with the theoretical Bishop-Hill stress states for plastically deforming grains as well...

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

    NARCIS (Netherlands)

    Kooiker, Harmen; Perdahcioglu, Emin Semih; van den Boogaard, Antonius H.

    2016-01-01

    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

  4. Comparison of damaging behavior of oxide scales grown on austenitic stainless steels using tensile test and cyclic thermogravimetry

    OpenAIRE

    Fedorova, Elena N.; Braccini, Muriel; Parry, Valérie; Pascal, Celine; Mantel, Marc; Roussel-Dherbey, Francine; Oquab, Djar; Wouters, Yves; Monceau, Daniel

    2016-01-01

    Two austenitic stainless steels, AISI 304L and AISI 303, were submitted to cyclic oxidation and to staticmechanical loading after isothermal oxidation at 1000◦C. Alloy 303 contains ten times more S than 304Land some Mn addition. During the steel process, it formed manganese sulfides that lead to the formationof a less resistant oxide scale. Both alloys showed similar behavior during thermal cycling but breakawayoxidation and intensive spallation occurred much sooner for alloy 303 than for all...

  5. A contribution to the question of stress-corrosion cracking of austenitic stainless steel cladding in nuclear power plants

    International Nuclear Information System (INIS)

    Kupka, I.; Mrkous, P.

    1977-01-01

    A brief review is presented of the basic types of corrosion damage (uniform corrosion, intergranular corrosion, stress corrosion) and their influence on operational safety are estimated. Corrosion cracking is analyzed of austenitic stainless steel cladding taking into account the adverse impact of coolant and stress (both operational and residual) in a light water reactor primary circuit. Experimental data are given of residual stresses in the stainless steel clad material, as well as their magnitude and distribution after cladding and heat treatment. (author)

  6. A Comparative Study of Fracture Toughness at Cryogenic Temperature of Austenitic Stainless Steel Welds

    Science.gov (United States)

    Aviles Santillana, I.; Boyer, C.; Fernandez Pison, P.; Foussat, A.; Langeslag, S. A. E.; Perez Fontenla, A. T.; Ruiz Navas, E. M.; Sgobba, S.

    2018-03-01

    The ITER magnet system is based on the "cable-in-conduit" conductor (CICC) concept, which consists of stainless steel jackets filled with superconducting strands. The jackets provide high strength, limited fatigue crack growth rate and fracture toughness properties to counteract the high stress imposed by, among others, electromagnetic loads at cryogenic temperature. Austenitic nitrogen-strengthened stainless steels have been chosen as base material for the jackets of the central solenoid and the toroidal field system, for which an extensive set of cryogenic mechanical property data are readily available. However, little is published for their welded joints, and their specific performance when considering different combinations of parent and filler metals. Moreover, the impact of post-weld heat treatments that are required for Nb3Sn formation is not extensively treated. Welds are frequently responsible for cracks initiated and propagated by fatigue during service, causing structural failure. It becomes thus essential to select the most suitable combination of parent and filler material and to assess their performance in terms of strength and crack propagation at operation conditions. An extensive test campaign has been conducted at 7 K comparing tungsten inert gas (TIG) welds using two fillers adapted to cryogenic service, EN 1.4453 and JK2LB, applied to two different base metals, AISI 316L and 316LN. A large set of fracture toughness data are presented, and the detrimental effect on fracture toughness of post-weld heat treatments (unavoidable for some of the components) is demonstrated. In this study, austenitic stainless steel TIG welds with various filler metals have undergone a comprehensive fracture mechanics characterization at 7 K. These results are directly exploitable and contribute to the cryogenic fracture mechanics properties database of the ITER magnet system. Additionally, a correlation between the impact in fracture toughness and microstructure

  7. Deformation localization and dislocation channel dynamics in neutron-irradiated austenitic stainless steels

    Science.gov (United States)

    Gussev, Maxim N.; Field, Kevin G.; Busby, Jeremy T.

    2015-05-01

    The dynamics of deformation localization and dislocation channel formation were investigated in situ in a neutron-irradiated AISI 304 austenitic stainless steel and a model 304-based austenitic alloy by combining several analytical techniques including optic microscopy and laser confocal microscopy, scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy (TEM). Channel formation was observed at ∼70% of the polycrystalline yield stress of the irradiated materials (σ0.2). It was shown that triple junction points do not always serve as a source of dislocation channels; at stress levels below the σ0.2, channels often formed near the middle of the grain boundary. For a single grain, the role of elastic stiffness value (Young's modulus) in channel formation was analyzed; it was shown that in the irradiated 304 steels the initial channels appeared in "soft" grains with a high Schmid factor located near "stiff" grains with high elastic stiffness. The spatial organization of channels in a single grain was analyzed; it was shown that secondary channels operating in the same slip plane as primary channels often appeared at the middle or at one-third of the way between primary channels. The twinning nature of dislocation channels was analyzed for grains of different orientation using TEM. In the AISI 304 steel, channels in grains oriented close to 〈0 0 1〉||TA (tensile axis) and 〈1 0 1〉||TA were twin free and grain with 〈1 1 1〉||TA and grains oriented close to a Schmid factor maximum contained deformation twins.

  8. Analysis Of The Austenite Grain Growth In Low-Alloy Boron Steel With High Resistance To Abrasive Wear

    Directory of Open Access Journals (Sweden)

    Białobrzeska B.

    2015-09-01

    Full Text Available Today low-alloy steels with boron achieve high resistance to abrasive wear and high strength. These features are obtained by using advanced technology of manufacturing. This makes boron steels increasingly popular and their application more diverse. Application of these steels can extend the lifetime of very expensive machine construction in many industries such as mining, the automotive, and agriculture industries. An interesting subgroup of these materials is steel with boron intended for heat treatment. These steels are supplied by the manufacturer after cold or hot rolling so that it is possible for them to be heat treated in a suitable manner by the purchaser for its specific application. Very important factor that determines the mechanical properties of final product is austenite grain growth occurring during hot working process such us quenching or hot rolling. Investigation of the effect of heating temperature and holding time on the austenite grain size is necessary to understand the growth behavior under different conditions. This article presents the result of investigation of austenite grain growth in selected low-allow boron steel with high resistance to abrasive wear and attempts to describe the influence of chemical composition on this process.

  9. 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

  10. Improvement of solidification cracking susceptibility of electron beam weld metal of fully austenitic type 316 stainless steel

    International Nuclear Information System (INIS)

    Nakao, Yoshikuni; Katsu, Shinichiro

    1986-01-01

    The effect of rare earth metals (REM) addition on the solidification cracking susceptibility of electron beam weld metals in fully austenitic Type 316 stainless steel was researched. The cracking susceptibility of this steel is put in order by REM and P or (P + S) content. Adding proper content of REM (about 0.25 % REM for 0.025 % P steel) is effective to improve the cracking susceptibility of this steel. However, the cracking susceptibility of this steel is deteriorated again by adding excess content of REM (about 0.37 % REM for 0.025 % P steel). Free P and S atoms being fixed as phosphides, oxyphosphides, sulfides and oxysulfides by REM atoms is the main reason why the cracking susceptibility of this steel is improved by adding REM. (author)

  11. Effect of Composition and Deformation on Coarse-Grained Austenite Transformation in Nb-Mo Microalloyed Steels

    Science.gov (United States)

    Isasti, N.; Jorge-Badiola, D.; Taheri, M. L.; López, B.; Uranga, P.

    2011-12-01

    Thermomechanical processing of microalloyed steels containing niobium can be performed to obtain deformed austenite prior to transformation. Accelerated cooling can be employed to refine the final microstructure and, consequently, to improve both strength and toughness. This general rule is fulfilled if the transformation occurs on a quite homogeneous austenite microstructure. Nevertheless, the presence of coarse austenite grains before transformation in different industrial processes is a usual source of concern, and regarding toughness, the coarsest high-angle boundary units would determine its final value. Sets of deformation dilatometry tests were carried out using three 0.06 pct Nb microalloyed steels to evaluate the effect of Mo alloying additions (0, 0.16, and 0.31 pct Mo) on final transformation from both recrystallized and unrecrystallized coarse-grained austenite. Continuous cooling transformation (CCT) diagrams were created, and detailed microstructural characterization was achieved through the use of optical microscopy (OM), field emission gun scanning electron microscopy (FEGSEM), and electron backscattered diffraction (EBSD). The resultant microstructures ranged from polygonal ferrite (PF) and pearlite (P) at slow cooling ranges to bainitic ferrite (BF) accompanied by martensite (M) for fast cooling rates. Plastic deformation of the parent austenite accelerated both ferrite and bainite transformation, moving the CCT curves to higher temperatures and shorter times. However, an increase in the final heterogeneity was observed when BF packets were formed, creating coarse high-angle grain boundary units.

  12. 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

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

    International Nuclear Information System (INIS)

    Chung, H.M.

    2006-01-01

    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 rates, and

  14. Microstructure, Texture, and Mechanical Property Analysis of Gas Metal Arc Welded AISI 304 Austenitic Stainless Steel

    Science.gov (United States)

    Saha, Saptarshi; Mukherjee, Manidipto; Pal, Tapan Kumar

    2015-03-01

    The present study elaborately explains the effect of welding parameters on the microstructure, texture, and mechanical properties of gas metal arc welded AISI 304 austenitic stainless steel sheet (as received) of 4 mm thickness. The welded joints were prepared by varying welding speed (WS) and current simultaneously at a fixed heat input level using a 1.2-mm-diameter austenitic filler metal (AISI 316L). The overall purpose of this study is to investigate the effect of the variation of welding conditions on: (i) Microstructural constituents using optical microscope and transmission electron microscope; (ii) Micro-texture evolution, misorientation distributions, and grain boundaries at welded regions by measuring the orientation data from electron back scattered diffraction; and (iii) Mechanical properties such as hardness and tensile strength, and their correlation with the microstructure and texture. It has been observed that the higher WS along with the higher welding current (weld metal W1) can enhance weld metal mechanical properties through alternation in microstructure and texture of the weld metal. Higher δ-ferrite formation and high-angle boundaries along with the + grain growth direction of the weld metal W1 were responsible for dislocation pile-ups, SFs, deformation twinning, and the induced martensite with consequent strain hardening during tensile deformation. Also, fusion boundary being the weakest link in the welded structure, failure took place mainly at this region.

  15. Flow Softening Index for Assessment of Dynamic Recrystallization in an Austenitic Stainless Steel

    Science.gov (United States)

    Aashranth, B.; Samantaray, Dipti; Kumar, Santosh; Dasgupta, Arup; Borah, Utpal; Albert, Shaju K.; Bhaduri, A. K.

    2017-07-01

    The present study proposes a novel technique to assess dynamic recrystallization (DRX) and related microstructural phenomena during hot deformation of austenite. A `Flow Softening Index (FSI)' has been identified on the basis of investigations on elevated temperature deformation behaviour of austenitic stainless steel. This index corresponds to dominant microstructural phenomena at different deformation conditions. For this investigation, experimental results obtained from isothermal, constant true strain rate compression tests in a temperature range of 1173 (900)-1473 K (1200 °C) and strain rate range of 0.01-100 s-1 have been used. Resultant microstructures have been quantified using average grain size and grain size distributions. The dominant microstructural phenomena have been identified at different conditions using electron backscatter diffraction. Low FSI values are associated with the grain growth, intermediate values with DRX, and high values with the work-hardening and flow localisation phenomena. FSI also quantitatively indexes the average grain size and grain size distributions at different temperature-strain rate combinations. Analysis of the specific deformation conditions, particularly where 3.4 < FSI < 3.5, indicates a common thermo-mechanical origin of flow localisation and DRX. The potential technological implications thereof are discussed and a semi-empirical model of microstructural evolution is developed for the studied material.

  16. Residual stress measurement round robin on an electron beam welded joint between austenitic stainless steel 316L(N) and ferritic steel P91

    OpenAIRE

    Javadi, Y.; Smith, M.C.; Abburi Venkata, K.; Naveed, N.; Forsey, A.N.; Francis, J.A.; Ainsworth, R.A.; Truman, C.E.; Smith, D.J.; Hosseinzadeh, F.; Gungor, S.; Bouchard, P. J.; Dey, H.C.; Bhaduri, A.K.; Mahadevan, S.

    2017-01-01

    This paper is a research output of DMW-Creep project which is part of a national UK programme through the RCUK Energy programme and India's Department of Atomic Energy. The research is focussed on understanding the characteristics of welded joints between austenitic stainless steel and ferritic steel that are widely used in many nuclear power generating plants and petrochemical industries as well as conventional coal and gas-fired power systems. The members of the DMW-Creep project have under...

  17. Effect of liquid sodium on long-term properties of austenitic steels

    International Nuclear Information System (INIS)

    Svoboda, V.; Merta, J.; Slach, J.

    The effect is discussed of liquid sodium on the long-term properties of austenitic steels corresponding to the ASI 304 and ASI 316 types, mainly of steel CSN 17348. The choice is described of test specimens and of the experimental sodium test equipment. Testing was carried out using the so-called indirect method, i.e., the liquid sodium effect was assessed using the results of creep tests of two groups of specimens, one exposed to sodium and the other to the inert argon atmosphere. Otherwise the tests proceeded under identical conditions. The sodium stand had been manufactured for exposure of test specimens to liquid sodium. The morphology of specimen surfaces was studied by the JSN-50A electron microscope. The results of testing steel CSN 17348-AKV EXTRA S exposed to liquid sodium containing 10 ppm of oxygen at a temperature of 550 degC showed a significant sodium effect on the basic mechanical properties, on long-term creep strength and on the metallurgical properties. (Oy)

  18. The mechanical properties of austenite stainless steel 304 after structural deformation through cold work

    Energy Technology Data Exchange (ETDEWEB)

    Mubarok, Naila; Manaf, Azwar, E-mail: azwar@ui.ac.id [PPS Materials Science, FMIPA-Universitas Indonesia, Depok 16424 (Indonesia); Notonegoro, Hamdan Akbar [Mechanical Engineering Dept., FT-Universitas Sultan Ageng Tirtayasa,Cilegon 42435 (Indonesia); Thosin, Kemas Ahmad Zaini [Pusat Penelitian Fisika,LIPI, Serpong (Indonesia)

    2016-06-17

    The 304 stainless steel (SS) type is widely used in oil and gas operations due to its excellent corrosion resistance. However, the presence of the fine sand particles and H{sub 2}S gas contained in crude oil could lead the erosion and abrasion in steel. In this study, cold rolled treatments were conducted to the 304 SS in order to increase the wear resistance of the steel. The cold work has resulted in thickness reduction to 20%, 40% and 60% of the original. Various microstructural characterizations were used to analyze the effect of deformation. The hardness characterization showed that the initial hardness value increased from 145 HVC to 395 HVC as the level of deformation increase. Further, the wear resistance increased with the deformation rate from 0% to 40% and subsequently decreased from 40% to 60% deformation rate. Microstructural characterization shows that the boundary change to coincide by 56 µm, 49 µm, 45 µm, and 43 µm width and the grain go to flatten and being folded like needles. The effect of deformation on the grain morphology and structure was also studied by optical metallography and X-Ray Diffraction. It is shown that the deformation by means of a cold rolled process has transformed the austenite structure into martensitic structure.

  19. Effect of composition on corrosion resistance of high-alloy austenitic stainless steel weld metals

    International Nuclear Information System (INIS)

    Marshall, P.I.; Gooch, T.G.

    1993-01-01

    The corrosion resistance of stainless steel weld metal in the ranges of 17 to 28% chromium (Cr), 6 to 60% nickel (Ni), 0 to 9% molybdenum (Mo), and 0.0 to 0.37% nitrogen (N) was examined. Critical pitting temperatures were determined in ferric chloride (FeCl 3 ). Passive film breakdown potentials were assessed from potentiodynamic scans in 3% sodium chloride (NaCl) at 50 C. Potentiodynamic and potentiostatic tests were carried out in 30% sulfuric acid (H 2 SO 4 ) ar 25 C, which was representative of chloride-free acid media of low redox potential. Metallographic examination and microanalysis were conducted on the test welds. Because of segregation of alloying elements, weld metal pitting resistance always was lower than that of matching composition base steel. The difference increased with higher Cr, Mo, and N contents. Segregation also reduced resistance to general corrosion in H 2 SO 4 , but the effect relative to the base steel was less marked than with chloride pitting. Segregation of Cr, Mo, and N in fully austenitic deposits decreased as the Ni' eq- Cr' eq ratio increased. Over the compositional range studied, weld metal pitting resistance was dependent mainly on Mo content and segregation. N had less effect than in wrought alloys. Both Mo and N enhanced weld metal corrosion resistance in H 2 SO 4

  20. Effect of light impurities on the early stage of swelling in austenitic stainless steel

    International Nuclear Information System (INIS)

    Igata, N.

    1998-01-01

    The objective of this study is to analyse the early stage of swelling and clarify the role of light impurities (nitrogen) in swelling of austenitic stainless steel. Recent results show that light impurities affect the swelling of 316 stainless steel under HVEM irradiation up to 10 dpa. At low concentration of light impurities the radiation swelling increases then decreases through the maximum as the concentration of light impurities increases. In the present paper the theoretical model is presented for the explanation of this effect. The model is based on the two factors: the influence of absorbed impurities on the voids caused by the production of an additional gas pressure in voids for their stabilization and the effect of impurities segregated around the surface of voids by the lowering of surface tension. These two affects are taken into account in the calculations of the critical size and the growth rate of cavities. The theoretical predictions on the radiation swelling rate dependent on the impurity concentration and temperature coincided with the experimental results on 316 stainless steel irradiated by HVEM. (orig.)

  1. Mechanical Properties, Short Time Creep, and Fatigue of an Austenitic Steel.

    Science.gov (United States)

    Brnic, Josip; Turkalj, Goran; Canadija, Marko; Lanc, Domagoj; Krscanski, Sanjin; Brcic, Marino; Li, Qiang; Niu, Jitai

    2016-04-20

    The correct choice of a material in the process of structural design is the most important task. This study deals with determining and analyzing the mechanical properties of the material, and the material resistance to short-time creep and fatigue. The material under consideration in this investigation is austenitic stainless steel X6CrNiTi18-10. The results presenting ultimate tensile strength and 0.2 offset yield strength at room and elevated temperatures are displayed in the form of engineering stress-strain diagrams. Besides, the creep behavior of the steel is presented in the form of creep curves. The material is consequently considered to be creep resistant at temperatures of 400 °C and 500 °C when subjected to a stress which is less than 0.9 of the yield strength at the mentioned temperatures. Even when the applied stress at a temperature of 600 °C is less than 0.5 of the yield strength, the steel may be considered as resistant to creep. Cyclic tensile fatigue tests were carried out at stress ratio R = 0.25 using a servo-pulser machine and the results were recorded. The analysis shows that the stress level of 434.33 MPa can be adopted as a fatigue limit. The impact energy was also determined and the fracture toughness assessed.

  2. Experimental and computational study of nitride precipitation in a CrMnN austenitic stainless steel

    International Nuclear Information System (INIS)

    Pettersson, Niklas; Frisk, Karin; Fluch, Rainer

    2017-01-01

    The austenitic CrMnN stainless steels are high-strength, tough, and non-magnetic, and are used in oil field applications. The steels have high alloying contents, and precipitation of Cr-nitrides and/or intermetallic phases can occur when cooling through the temperature region 950–700 °C. The nitride precipitates appear in the grain boundaries but can be difficult to observe in the microstructure due to their small size. However, there is an effect of precipitation on corrosion and impact strength and a modelling approach to predict precipitation is valuable for alloy and process development. In the present work precipitation simulations were applied to a CrMnN steel composition, and coupled to experimental investigations after heat treatments at 700 and 800 °C. The early stages, with short heat-treatment times, were studied. The simulations were performed using TC-PRISMA, a software for calculation of multiphase precipitation kinetics, using multicomponent nucleation and growth models. Dedicated thermodynamic and kinetic databases were used for the simulations. The main precipitate was identified by experiments and simulations to be the Cr 2 N nitride, and the precipitation during isothermal heat treatments was investigated. Isothermal precipitation diagrams are simulated, and the influence of precipitation kinetics on toughness is discussed.

  3. Mechanical Properties, Short Time Creep, and Fatigue of an Austenitic Steel

    Directory of Open Access Journals (Sweden)

    Josip Brnic

    2016-04-01

    Full Text Available The correct choice of a material in the process of structural design is the most important task. This study deals with determining and analyzing the mechanical properties of the material, and the material resistance to short-time creep and fatigue. The material under consideration in this investigation is austenitic stainless steel X6CrNiTi18-10. The results presenting ultimate tensile strength and 0.2 offset yield strength at room and elevated temperatures are displayed in the form of engineering stress-strain diagrams. Besides, the creep behavior of the steel is presented in the form of creep curves. The material is consequently considered to be creep resistant at temperatures of 400 °C and 500 °C when subjected to a stress which is less than 0.9 of the yield strength at the mentioned temperatures. Even when the applied stress at a temperature of 600 °C is less than 0.5 of the yield strength, the steel may be considered as resistant to creep. Cyclic tensile fatigue tests were carried out at stress ratio R = 0.25 using a servo-pulser machine and the results were recorded. The analysis shows that the stress level of 434.33 MPa can be adopted as a fatigue limit. The impact energy was also determined and the fracture toughness assessed.

  4. EBSD study of purity effects during hot working in austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    El Wahabi, M. [Centre SMS, CNRS UMR 5146, Ecole Nationale Superieure des Mines de Saint-Etienne, 158, cours Fauriel-42023, Saint-Etienne Cedex 2 (France) and Departamento de Ciencia de los Materiales e Ingenieria Metalurgica, ETSEIB, Universidad Politecnica de Cataluna, Av. Diagonal 647, Barcelona 08028 (Spain)]. E-mail: elwahabi@emse.fr; Gavard, L. [Centre SMS, CNRS UMR 5146, Ecole Nationale Superieure des Mines de Saint-Etienne, 158, cours Fauriel-42023, Saint-Etienne Cedex 2 (France); Cabrera, J.M. [Departamento de Ciencia de los Materiales e Ingenieria Metalurgica, ETSEIB, Universidad Politecnica de Cataluna, Av. Diagonal 647, Barcelona 08028 (Spain); Prado, J.M. [Departamento de Ciencia de los Materiales e Ingenieria Metalurgica, ETSEIB, Universidad Politecnica de Cataluna, Av. Diagonal 647, Barcelona 08028 (Spain); Montheillet, F. [Centre SMS, CNRS UMR 5146, Ecole Nationale Superieure des Mines de Saint-Etienne, 158, cours Fauriel-42023, Saint-Etienne Cedex 2 (France)

    2005-02-25

    The technique of electron back scattering diffraction (EBSD) is considered as a powerful instrument for the study of the microstructural changes during hot forming processes and gives the possibility to present the information in different ways (OIM, misorientation diagram and pole figures). The present work is focused on the observation by EBSD of the microstructure evolution during deformation at high temperature of three austenitic stainless steels: AISI-304H, AISI-304L and a high purity steel HP. The difference between the three steels is the content carbon and the presence of residual elements. To this aim compression tests were carried out at a constant strain rate of 0.001 s{sup -1} and different temperatures. The study showed an increase of twin boundary fractions and a diminution of substructure (low angle densities boundaries) at increasing temperatures. On the other hand, increasing carbon content promotes lower twin boundary fractions and larger amounts of low angle boundaries. This effect can be explained by the reduction of grain boundary mobility caused by increasing carbon contents, which in turn reduces the migration rate and consequently the probability of twin boundary generation. Moreover, the increment of low angle boundaries with carbon content accelerates the twin character loss. It was also found that the dynamically recrystallized grain size decreased at increasing carbon content due to a typical drag effect. No important features on textures were found during DDRX.

  5. Beneficial effect of shot peening on steamside oxidation of 300-series austenitic steels: An electrochemical study

    Science.gov (United States)

    Bystrianský, Václav; Krausová, Aneta; Macák, Jan; Děd, Jiří; Eltai, Elsadig; Hamouda, Abdel Magid

    2018-01-01

    The formation of a protective oxide ensures the good corrosion resistance of austenitic steels in high temperature steam. However after long-term interaction even the protective oxide may tend to exfoliate and cause operational problems. With shot peening believed to be an effective method for mitigating steamside oxidation and exfoliation, we compared oxide layers formed on two materials: AISI 316H with a rugged untreated surface and Super304H with a shot-peened surface. In addition to conventional methods (SEM/EDS, Raman spectroscopy), Mott-Schottky analysis was used to characterize the oxide layers in order to determine the quality of the protective oxide. The oxides formed on Super 304H showed unexpected semiconducting behaviour with a significantly lower charge carrier density, thereby supporting the benefits of shot peening. Our findings extend the knowledge applicable to the design of more efficient coal-fired power plants.

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

    International Nuclear Information System (INIS)

    Frutos, E.; Multigner, M.; Gonzalez-Carrasco, J.L.

    2010-01-01

    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.

  7. Study of ultrasound waves attenuation: application to the nondestructive control of austenitic stainless steel welds

    International Nuclear Information System (INIS)

    Ultrasonic propagation simulation in anisotropic and heterogeneous media is essential for nondestructive testing by ultrasounds of multipass austenitic stainless steel welds that are specific of piping in nuclear power stations. Scattering at grain boundaries leads to a strong attenuation as a function of grain orientation. Attenuation measurement is complex. The implemented technique allows taking into account the physical reality of the beams and the material anisotropy. Ultrasonic propagation through the samples is modeled with transmission coefficients calculated with any incidence on a triclinic material. This method results in an increase of the attenuation versus grain orientation. For the first time, measured attenuation coefficients are integrated into a simulation code that validated them by comparison with experience. (author)

  8. The influence of He on the high temperature fracture of an austenitic stainless steel

    International Nuclear Information System (INIS)

    Saguees, A.A.

    1976-01-01

    The Ti-stabilised DIN 1.4970 austenitic stainless steel is an important candidate for high temperature - high neutron fluence applications which will create appreciable amounts of He within the matrix. In order to determine the mechanical effects associated with the presence of He alone a set of tensile specimens was cyclotron implanted to uniform He concentrations in the 10 -6 to 10 -4 at. range and later creep tested at 700 0 C and 800 0 C. The elongation to fracture values of the implanted specimens were reduced with respect to those of unimplanted controls. Scanning Electron Microscope (SEM) examination revealed that fracture starts as intergranular and subsequently propagates in a transgranular fashion, the intergranular part being much more extended in the implanted material. Transmission Electron Microscope (TEM) examination revealed He segregation at the grain boundary precipitates. A mechanism of He embrittlement is discussed in terms of the present results

  9. Effect of phosphorus on the swelling and precipitation behavior of austenitic stainless steels during irradiation

    International Nuclear Information System (INIS)

    Lee, E.H.; Mansur, L.K.; Rowcliffe, A.F.

    1983-01-01

    It has been observed that increasing the volume fraction of the needle-shaped iron phosphide phase in austenitic stainless steels tends to inhibit void swelling during neutron irradiation. An earlier analysis showed that this effect could not be accounted for in terms of enhanced point defect recombination at particle-matrix interfaces. The behavior of the iron phosphide phase has been further examined using dual ion beam irradiations. It was found that the particle-matrix interface serves as a site for the nucleation of a very fine dispersion of helium bubbles. It is thought that since a high number density of cavities lowers the number of helium atoms per cavity, the irradiation time for the cavities to accumulate the critical number of gas atoms for bias-driven growth is correspondingly increased. Although the phosphide phase nucleates rapidly, it eventually undergoes dissolution if either the G or Laves phase develops with increasing dose

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

    DEFF Research Database (Denmark)

    Belluco, Walter; De Chiffre, Leonardo

    2004-01-01

    breaking were recorded for each bore, and tool wear was measured at constant intervals. A commercial mineral-based oil was taken as reference product, and five vegetable-based cutting fluids at different levels of additivation were tested. All measured parameters were in agreement, confirming......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...... to tool life testing. All vegetable-based fluids performed better than the reference product. The best performance was obtained with a cutting fluid yielding 177% increases in tool life and 7% reduction in thrust force. (C) 2003 Elsevier B.V. All rights reserved....

  11. 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.

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

    International Nuclear Information System (INIS)

    Singh, Lakhwinder; Aggarwal, M. L.; Khan, R. A.

    2012-01-01

    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

  13. Thermal Aging Performance of Domestic Cast Austenitic Stainless Steels in Nuclear Power Plants

    Science.gov (United States)

    Chengliang, Li; Xiaoyun, Deng; Zhiying, Yin; Yuangang, Duan

    The domestic cast austenitic stainless steels (CASS) used for PWR main coolant lines face thermal aging phenomenon during long-term service at reactor operating temperatures in the range of 280-320°C. The accelerated thermal aging experiment of CASS at an elevated temperature of 400°C was carried out. The decrease regularity of absorbed energy of CASS at room temperature was obtained by Charpy impact test, and the variation trend of impacted specimen's fracture surfaces of CASS at different aging time was observed by scanning electron microscope. The experimental results show that: after 15,000 hours of accelerated thermal aging, the domestic CASS gradually reaches a thermal aging saturation, and its absorbed energy suffers a dramatic loss, dropping to almost 41-45% of the initial value, but still meets the assessment indicators for unaged state required by design specifications.

  14. Structure and phase composition of titanium nitride coating on austenitic steel

    International Nuclear Information System (INIS)

    Dubovitskaya, N.V.; Kolenchenko, L.D.; Larikov, L.N.

    1989-01-01

    Structure and phase composition of titanium nitride coating deposited on 08Kh18N10T steel substrate using ''Bulat'' device are studied. Use of complex investigation methods permitted despite small coating thickness (1μm) to aquire information on hardness, porosity, to study phase composition in all coating thickness. The surface layer (∼0.1 μm) consists of ε-Ti 2 N, TiN 0.6 , TiC 0.35 , that is formed with carbon participation from oil vacuum. In more deeper layers beside ε-Ti 2 N TiC 0.14 N 0.77 is present. Effect of carbon diffusion from substrate to forming coating is stated. Gradient of element concentrations in the substrate-coating interface causes recrystallization of austenite

  15. Shallow-Land Buriable PCA-type austenitic stainless steel for fusion application

    International Nuclear Information System (INIS)

    Zucchetti, M.

    1991-01-01

    Neutron-induced activity in the PCA (Primary Candidate Alloy) austenitic stainless steel is examined, when used for first-wall components in a DEMO fusion reactor. Some low-activity definitions, based on different waste management and disposal concepts, are introduced. Activity in the PCA is so high that any recycling of the irradiated material can be excluded. Disposal of PCA radioactive wastes in Shallow-Land Buriable (SLB) is prevented as well. Mo, Nb and some impurity elements have to be removed or limited, in order to reduce the radioactivity of the PCA. Possible low-activity versions of the PCA are introduced (PCA-la); they meet the requirements for SLB and may also be recycled under certain conditions. (author)

  16. Evaluation of residual stress distribution in austenitic stainless steel pipe butt-welded joint

    International Nuclear Information System (INIS)

    Maekawa, Akira; Noda, Michiyasu; Takahashi, Shigeru; Oumaya, Toru; Serizawa, Hisashi; Murakawa, Hidekazu

    2009-01-01

    This paper reports measured and estimated results of residual stress distributions of butt-welded austenitic stainless steel pipe in order to improve estimation accuracy of welding residual stress. Neutron diffraction and strain gauge method were employed for the measurement of the welding residual stress and its detailed distributions on inner and outer surface of the pipe as well as the distributions within the pipe wall were obtained. Finite element method was employed for the estimation. Transient and residual stresses in 3D butt-welded joint model were computed by employing Iterative Substructure Method and also commercial FEM code ABAQUS for a reference. The measured and estimated distributions presented typical characteristic of straight butt-welded pipe which had decreasing trend along the axial direction and bending type distributions through wall of the pipe. Both results were compared and the accuracy of measurement and estimation was discussed. (author)

  17. Determination of austenite vs. α-ferrite in steel by neutron and X-ray diffraction

    International Nuclear Information System (INIS)

    Als-Nielsen, J.; Clausen, K.

    1984-06-01

    Neutron and X-ray diffraction studies for determining the relative content of fcc (austenite) and bcc (α-ferrite) phases in steel samples are reported. In addition to determine the relative content of phases the diffraction method also provides information about the strain fields in the sample by the concomitant broadening of diffraction peaks. Neutron diffraction has the advantage that large sample volumes (several cc) are probed, and the effect of texture can thus be eliminated. X-ray diffraction patterns can be registered in a short time thus allowing kinetic studies of phase changes during heat treatment or mechanical treatment. In addition it is possible to probe different surface thickness by utilizing different X-ray wavelengths. Measurements of this type can be carried out on a commercial contract basis in the Solid State Physics Division at Risoe National Laboratory. (author)

  18. Cryogenic deformation microstructures of 32Mn-7Cr-1Mo-0.3N austenitic steels

    International Nuclear Information System (INIS)

    Fu Ruidong; Qiu Liang; Wang Tiansheng; Wang Cunyu; Zheng Yangzeng

    2005-01-01

    The cryogenic deformation microstructures of impact and tensile specimens of 32Mn-7Cr-1Mo-0.3N austenitic steel were investigated using light microscopy and transmission electron microscopy. The results show that the deformation microstructures of the impact specimens are mainly composed of stacking faults, network dislocation, slip bands, and a few mechanical twins and ε-martensite. These microstructures cross with each other in a crystal angle. The deformation microstructures of the tensile specimens consist only of massive slip bands, in which a few mechanical twins and ε-martenite are located. Because of the larger plastic deformation the slip band traces become bent. All the deformation microstructures are formed on the {111} planes and along the orientation

  19. Carburizing plasma in a low temperature austenitic stainless steel AISI 304

    International Nuclear Information System (INIS)

    Mota, W.T.; Ramos, F.D.; Rocha, R.C.; Barcelos, M.V.; Barcelos, M.A.

    2014-01-01

    The industrial use of thermochemical treatment assisted by the cold plasma has been widely employed in recent years, mainly oriented to the excellent results obtained in the surface modification of engineering materials, when compared to more traditional methods. In this work, we studied the plasma carburizing low temperature steel AISI 304 mechanical parts used in construction. The thermochemical treatment was performed at a fixed gas atmosphere 7% CH 4 (g) and 93 % H 2 (g), 350 ° C and times of 1, 3 and 5 hours. Samples being tested for Vickers hardness, abrasive microwear, microstructure evaluation by optical microscopy and SEM and X-ray diffraction. The results show significant improvement in surface hardness, wear resistance and good formation of expanded austenite layer and no identifiers peaks of carbides. The results achieved are due to diffusion/adsorption of carbon present in the gaseous atmosphere to the evaluated samples. (author)

  20. Analysis of the austenitic stainless steel's r-value behavior at elevated temperatures

    Directory of Open Access Journals (Sweden)

    Dušan Arsić

    2015-05-01

    Full Text Available An analysis of the anisotropy properties of austenitic steel AISI 304 (X5CrNi18-10 at elevated temperatures is presented in this paper. Considerations of the anisotropy problems are presented in the theoretical part of the paper, as well as the procedure for determination of the normal anisotropy coefficient. The experimental part of the paper describes the plan, methodology and equipment for testing of material's normal anisotropy and mechanical characteristics. The objective of conducting the experiments was to investigate influence of temperature on normal anisotropy, as well as on the mechanical properties of the considered material. The normal anisotropy was monitored by the coefficient – the so-called "r-value". Besides that, the tensile strength, yield stress and elongation at break were monitored, also. The tests were done on the 0.7 mm thick sheet metal within the temperature range 20 to 700°C.

  1. Tool Wear Analysis due to Machining In Super Austenitic Stainless Steel

    Directory of Open Access Journals (Sweden)

    Polishetty Ashwin

    2017-01-01

    Full Text Available This paper presents tool wear study when a machinability test was applied using milling on Super Austenitic Stainless Steel AL6XN alloy. Eight milling trials were performed under two cutting speeds, 100 m/min and 150 m/min, combined with two feed rates at 0.1mm/tooth and 0.15 mm/tooth and two depth of cuts at 2 mm and 3 mm. An Alicona 3D optical surface profilometer was used to scan cutting inserts flank and rake face areas for wear. Readings such as maximum and minimum deviations were extracted and used to analyse the outcomes. Results showed various types of wear were generated on the tool rake and flank faces. The common formed wear was the crater wear. The formation of the build-up edge was observed on the rake face of the cutting tool.

  2. Effect of Carbon Fraction on Stacking Fault Energy of Austenitic Stainless Steels

    Science.gov (United States)

    Lee, Tae-Ho; Ha, Heon-Young; Hwang, Byoungchul; Kim, Sung-Joon; Shin, Eunjoo

    2012-12-01

    The effect of C fraction (C/N) on stacking fault energy (SFE) of austenitic Fe-18Cr-10Mn steels with a fixed amount of C + N (0.6 wt pct) was investigated by means of neutron diffraction and transmission electron microscopy (TEM). The SFE were evaluated by the Rietveld whole-profile fitting combined with the double-Voigt size-strain analysis for neutron diffraction profiles using neutron diffraction. The measured SFE showed distinguishable difference and were well correlated with the change in deformation microstructure. Three-dimensional linear regression analyses yielded the relation reflecting the contribution of both C + N and C/N: SFE (mJ/m2) = -5.97 + 39.94(wt pct C + N) + 3.81(C/N). As C fraction increased, the strain-induced γ→ ɛ martensitic transformation was suppressed, and deformation twinning became the primary mode of plastic deformation.

  3. Bauschinger Effect in an Austenitic Steel: Neutron Diffraction and a Multiscale Approach

    Science.gov (United States)

    Fajoui, Jamal; Gloaguen, David; Legrand, Vincent; Oum, Guy; Kelleher, Joe; Kockelmann, Winfried

    2016-05-01

    The generation of internal stresses/strains arising from mechanical deformations in single-phase engineering materials was studied. Neutron diffraction measurements were performed to study the evolution of intergranular strains in austenitic steel during sequential loadings. Intergranular strains expand due to incompatibilities between grains and also resulting from single-crystal elastic and plastic anisotropy. A two-level homogenization approach was adopted in order to predict the mechanical state of deformed polycrystals in relation to the microstructure during Bauschinger tests. A mechanical description of the grain was developed through a micro-meso transition based on the Kröner model. The meso-macro transition using a self-consistent approach was applied to deduce the global behavior. Mechanical tests and neutron diffraction measurements were used to validate and assess the model.

  4. Effect of solution treatment conditions on the sensitization of austenitic stainless steel

    Directory of Open Access Journals (Sweden)

    XIAOFEI YU

    2009-11-01

    Full Text Available In this study, the impact of the conditions of solution treatment on the degree of sensitization (DOS of austenitic stainless steel (AISI 304 was investigated in detail. The results derived from the electrochemical potentiodynamic reactivation (EPR test indicated that the DOS decreased as the solution treatment temperature and time increased. The reason for this was studied via the SEM morphologies and EDS results, which indicated that the grain size influenced the DOS. Furthermore, cellular automaton (CA was utilized to simulate grain growth, the precipitation of Cr-rich carbides and the three dimensional distribution of the chromium concentration, which vividly illuminated the effect of the grain size on the DOS and was in accordance with the experiment results.

  5. Investigations on the mechanisms of PWSCC of strain hardened austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Couvant, T.; Legras, L. [EDF/R and D, Moret-sur-Loing (France); Pokor, C. [EDF/DIN/CEIDRE, DLCH, Avoine (France); Vaillant, F. [EDF/R and D, Moret-sur-Loing (France); Brechet, Y. [LTPCM/INPG, Grenoble (France); Boursier, J.M. [EDF/R and D, Moret-sur-Loing (France); Moulart, P. [EDF/DIN/CEIDRE, DLCH, Avoine (France)

    2007-07-01

    Limited cases of stress corrosion cracking (SCC) have been recently observed in French PWRs (heaters of pressurizers), in high strain hardened non-sensitized austenitic stainless steels exposed to primary environment. Consequently, a R and D program has been conducted, in addition to hot laboratories investigations, in order to understand the mechanisms responsible for PWSCC at 360{sup o}C. Stress corrosion tests were performed on AISI 304L and 316L, in hydrogenated primary environments (7.2 < pH{sub 320{sup o}C} < 9.2) at 360{sup o}C. Particular attention was directed towards the correlation between selective oxidation and strain localization due to microtwining and strain incompatibilities. Based on electron microscope examinations (SEM and TEM), a description of the possible contribution of the strain localization in the mechanism of PWSCC is proposed. Experimental results are finally compared to hot laboratory observations of pressurizer heaters. (author)

  6. Effects on Machining on Surface Residual Stress of SA 508 and Austenitic Stainless Steel

    International Nuclear Information System (INIS)

    Lee, Kyoung Soo; Lee, Seong Ho; Park, Chi Yong; Yang, Jun Seok; Lee, Jeong Geun; Park, Jai Hak

    2011-01-01

    Primary water stress corrosion cracking has occurred in dissimilar weld areas in nuclear power plants. Residual stress is a driving force in the crack. Residual stress may be generated by weld or surface machining. Residual stress due to surface machining depends on the machining method, e.g., milling, grinding, or EDM. The stress is usually distributed on or near the surface of the material. We present the measured residual stress for machining on SA 508 and austenitic stainless steels such as TP304 and F316. The residual stress can be tensile or compressive depending on the machining method. The depth and the magnitude of the residual stress depend on the material and the machining method

  7. 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.

  8. 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)

  9. 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.

  10. Effects of thermal oxidation and subsequent pickling on pitting geometry of austenitic stainless steels in chloride solutions

    Energy Technology Data Exchange (ETDEWEB)

    Alar, Vesna; Esih, Ivan; Budic, Ivan; Brod, Slavonski [Zagreb Univ. (Croatia). Dept. of Materials

    2011-07-01

    Harmful effects of thermal oxides formed on austenitic stainless steels (SS) like AISI 304 and 316L by heating in air or other oxidizing gases on their pitting liability in chloride solutions have been studied by pursuing geometric characteristics of corrosion process (pits density, their depths, and mouth areas, ie. penetrating and superficial detrimental consequences etc.). The possibility of preventing the decay of thermally oxidized austenitic SS by chemical removal (pickling) of oxides before exposure to chloride solutions was successfully applied on simple specimens but serious difficulties arose on welded parts and on parts exposed to other temperature gradients during manufacture or in exploitation. (orig.)

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

    Energy Technology Data Exchange (ETDEWEB)

    Hug, E., E-mail: eric.hug@ensicaen.fr [Laboratoire de Cristallographie et Sciences des Matériaux, Normandie Université, CNRS UMR 6508, 6 Bd Maréchal Juin, 14050 Caen (France); Prasath Babu, R. [School of Materials, University of Manchester, M13 9PL (United Kingdom); Groupe de Physique des Matériaux, UMR CNRS 6634, Université et INSA de Rouen, Normandie Université, Saint-Etienne du Rouvray Cedex (France); Monnet, I. [Centre de recherches sur les Ions, les Matériaux et la Photonique CEA-CNRS, Normandie Université, 6 Bd Maréchal Juin, 14050 Caen (France); Etienne, A. [Groupe de Physique des Matériaux, UMR CNRS 6634, Université et INSA de Rouen, Normandie Université, Saint-Etienne du Rouvray Cedex (France); Moisy, F. [Centre de recherches sur les Ions, les Matériaux et la Photonique CEA-CNRS, Normandie Université, 6 Bd Maréchal Juin, 14050 Caen (France); Pralong, V. [Laboratoire de Cristallographie et Sciences des Matériaux, Normandie Université, CNRS UMR 6508, 6 Bd Maréchal Juin, 14050 Caen (France); Enikeev, N. [Institute of Physics of Advanced Materials, Ufa (Russian Federation); Saint Petersburg State University, Laboratory of the Mechanics of Bulk Nanostructured Materials, 198504 St. Petersburg (Russian Federation); Abramova, M. [Institute of Physics of Advanced Materials, Ufa (Russian Federation); and others

    2017-01-15

    Highlights: • Impacts of nanostructuration and irradiation on the properties of 316 stainless steels are reported. • Irradiation of nanostructured samples implies chromium depletion as than depicted in coarse grain specimens. • Hardness of nanocrystalline steels is only weakly affected by irradiation. • Corrosion resistance of the nanostructured and irradiated samples is less affected by the chromium depletion. - Abstract: 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 {sup 56}Fe{sup 5+} 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.

  12. Stability of retained austenite in high carbon steel under compressive stress: an investigation from macro to nano scale

    Science.gov (United States)

    Hossain, R.; Pahlevani, F.; Quadir, M. Z.; Sahajwalla, V.

    2016-10-01

    Although high carbon martensitic steels are well known for their industrial utility in high abrasion and extreme operating environments, due to their hardness and strength, the compressive stability of their retained austenite, and the implications for the steels’ performance and potential uses, is not well understood. This article describes the first investigation at both the macro and nano scale of the compressive stability of retained austenite in high carbon martensitic steel. Using a combination of standard compression testing, X-ray diffraction, optical microstructure, electron backscattering diffraction imaging, electron probe micro-analysis, nano-indentation and micro-indentation measurements, we determined the mechanical stability of retained austenite and martensite in high carbon steel under compressive stress and identified the phase transformation mechanism, from the macro to the nano level. We found at the early stage of plastic deformation hexagonal close-packed (HCP) martensite formation dominates, while higher compression loads trigger body-centred tetragonal (BCT) martensite formation. The combination of this phase transformation and strain hardening led to an increase in the hardness of high carbon steel of around 30%. This comprehensive characterisation of stress induced phase transformation could enable the precise control of the microstructures of high carbon martensitic steels, and hence their properties.

  13. submitter Physical Properties of a High-Strength Austenitic Stainless Steel for the Precompression Structure of the ITER Central Solenoid

    CERN Document Server

    Sgobba, Stefano; Arauzo, Ana; Roussel, Pascal; Libeyre, Paul

    2016-01-01

    The ITER central solenoid (CS) consists of six independent coils kept together by a precompression support structure that must react vertical tensile loads and provide sufficient preload to maintain coil-to-coil contact when the solenoid is energized. The CS precompression system includes tie plates, lower and upper key blocks, load distribution and isolation plates and other attachment, support and insulating hardware. The tie plates operating at 4 K are manufactured starting from forgings in a high-strength austenitic stainless steel (FXM-19) with a stringent specification. Moreover, forged components for the lower and upper key blocks have to be provided in the same FXM-19 grade with comparably strict requirements. FXM-19 is a high-nitrogen austenitic stainless steel, featuring high strength and toughness, ready weldability, and forgeability. It features as well higher integral thermal contraction down to 4 K compared with the very high Mn steel grade selected for the CS coil jackets, hence providing an ad...

  14. Effect of preliminary nanostructuring frictional treatment on the efficiency of nitriding of metastable austenitic steel in electron beam plasma

    Science.gov (United States)

    Makarov, A. V.; Samoylova, G. V.; Gavrilov, N. V.; Mamaev, A. S.; Osintseva, A. L.; Kurennykh, T. E.; Savrai, R. A.

    2017-12-01

    The paper studies the effect of the temperature of nitriding in electron beam plasma, ranging between 250 and 500 °C, on the nitrogen concentration, phase composition and microhardness of the surface of the AISI 321 chromium-nickel austenitic steel in two initial states - quenched undeformed and after nanostructuring frictional treatment. The lowest nitriding temperature (350 °C) for the efficient hardening of the steel has been established. The application of frictional pretreatment with a sliding synthetic diamond indenter in an argon environment is shown to be highly efficient for increasing the depth of the layer nitrided at this temperature. The contribution of the formed S-phase (nitrogen-oversaturated austenite γN) to the intensive hardening of the steel nitrided at low temperatures (300 to 400 °C) is noted.

  15. Production, microstructure and mechanical properties of two different austenitic ODS steels

    Science.gov (United States)

    Gräning, T.; Rieth, M.; Hoffmann, J.; Möslang, A.

    2017-04-01

    This article is to summarize and examine processing parameters of novel developed austenitic oxide dispersed strengthened (ODS) steels. Comparing hot-rolled and extruded conditions after the same degree of deformation after and before annealing, are just some examples to give insights into the complex processing of austenitic ODS steels. One of the major drawbacks of the material is the more sophisticated production process. Due to a ductile matrix material with an increased stickiness during milling, a two-step milling procedure with the use of ZrO2 milling balls was applied to raise the production yield and to use the abrasion of the ZrO2 as an additional element to facilitate the formation of nano-sized precipitates. To get a better understanding how the different powder particle sizes after milling affect final properties, sieving was applied and revealed a serious effect in terms of precipitate size, distribution and mechanical properties. Grain sizes in relation to the precipitate size, annealing time and processing parameters were determined and compared to the mechanical properties. Hardness and tensile test have pointed out, that the precipitate size and number are more important in respect to the ultimate tensile strength than the grain size and that in this study hot-rolled material exhibited the better properties. The investigation of the microstructure illustrated the stability of precipitates during annealing at 1100 °C for 40 h. These heat treatments also led to a consistent grain size, due to the pinning effect of the grain boundaries, caused by precipitates.

  16. In Situ Investigation of the Evolution of Lattice Strain and Stresses in Austenite and Martensite During Quenching and Tempering of Steel

    DEFF Research Database (Denmark)

    Villa, M.; Niessen, F.; Somers, M. A. J.

    2018-01-01

    Energy dispersive synchrotron X-ray diffraction was applied to investigate in situ the evolution of lattice strains and stresses in austenite and martensite during quenching and tempering of a soft martensitic stainless steel. In one experiment, lattice strains in austenite and martensite were me...

  17. DEPENDENCE OF GRAIN SIZE OF AUSTENITE STEEL OF RAILWAY WHEEL FROM PARAMETERS OF HOT DEFORMATION

    Directory of Open Access Journals (Sweden)

    L. I. Vakulenko

    2015-03-01

    Full Text Available Purpose. The estimation of heat temperature influence and degree of hot reduction of carbon steel on the size of grain аustenite at making of railway wheels. Methodology. The material for research was carbon steel, mark 60 with carbon content of 0,55 and 0,65 %, selected from the fragments of railway wheels. The size of grain аustenite depending on a temperature (from 800 to 1 150 ºC and degrees of hot deformation (10−50 % was determined. The size of grain was determined under a light microscope with the use of quantitative metallography methods. Findings. The use of cooling in the process of hot reduction of the railway wheel will allow dispergating the structure of аustenite on large distances from the surface of the rim. The reason for this is that the volumes of metal after cooling have an increased strength and will be exposed in less degree to the plastic deformation. To compare the cooling layers near-by with the surface of rim, they are more warmed-up in internal volumes of metal. In the conditions of continuity of plastic deformation distribution, having a high temperature, they will be exposed to the reduction on the large total degree of deformation. In consequence of the resulted decisions more even austenitic structure must be formed on the section of rim of railway wheel. To obtain the effect of disperse grain of аustenite at making of the whole-rolled railway wheels it is necessary to decrease the heat temperature of billet under rolling or increase the degree of reduction on the lasts stages of shape-generating deformation. The pause by duration of 1,5 min. after reduction of 20 % at a temperature 950 ºC is sufficiently for processes completion of dynamic and static recrystalization of аustenite carbon steel of the railway wheel. Originality. Increase of plastic deformation degree, especially in the central volumes of rim is accompanied by the decrease of heterogeneity of austenitic structure on his section. The

  18. Initiation of stress corrosion cracking in pre-stained austenitic stainless steels exposed to primary water

    International Nuclear Information System (INIS)

    Huguenin, P.

    2012-01-01

    Austenitic stainless steels are widely used in primary circuits of Pressurized Water Reactors (PWR) plants. However, a limited number of cases of Intergranular Stress Corrosion Cracking (IGSCC) has been detected in cold-worked (CW) areas of non-sensitized austenitic stainless steel components in French PWRs. A previous program launched in the early 2000's identified the required conditions for SCC of cold-worked stainless steels. It was found that a high strain hardening coupled with a cyclic loading favoured SCC. The present study aims at better understanding the role of pre-straining on crack initiation and at developing an engineering model for IGSCC initiation of 304L and 316L stainless steels in primary water. Such model will be based on SCC initiation tests on notched (not pre-cracked) specimens under 'trapezoidal' cyclic loading. The effects of pre-straining (tensile versus cold rolling), cold-work level and strain path on the SCC mechanisms are investigated. Experimental results demonstrate the dominating effect of strain path on SCC susceptibility for all pre-straining levels. Initiation can be understood as crack density and crack depth. A global criterion has been proposed to integrate both aspects of initiation. Maps of SCC initiation susceptibility have been proposed. A critical crack depth between 10 and 20 μm has been demonstrated to define transition between slow propagation and fast propagation for rolled materials. For tensile pre-straining, the critical crack depth is in the range 20 - 50 μm. Experimental evidences support the notion of a KISCC threshold, whose value depends on materials, pre-straining ant load applied. The initiation time has been found to depend on the applied loading as a function of (σ max max/YV) 11,5 . The effect of both strain path and surface hardening is indirectly taken into account via the yield stress. In this study, material differences rely on strain path effect on mechanical properties. As a result, a stress

  19. Microstructural Evolutions During Annealing of Plastically Deformed AISI 304 Austenitic Stainless Steel: Martensite Reversion, Grain Refinement, Recrystallization, and Grain Growth

    Science.gov (United States)

    Naghizadeh, Meysam; Mirzadeh, Hamed

    2016-08-01

    Microstructural evolutions during annealing of a plastically deformed AISI 304 stainless steel were investigated. Three distinct stages were identified for the reversion of strain-induced martensite to austenite, which were followed by the recrystallization of the retained austenite phase and overall grain growth. It was shown that the primary recrystallization of the retained austenite postpones the formation of an equiaxed microstructure, which coincides with the coarsening of the very fine reversed grains. The latter can effectively impair the usefulness of this thermomechanical treatment for grain refinement at both high and low annealing temperatures. The final grain growth stage, however, was found to be significant at high annealing temperatures, which makes it difficult to control the reversion annealing process for enhancement of mechanical properties. Conclusively, this work unravels the important microstructural evolution stages during reversion annealing and can shed light on the requirements and limitations of this efficient grain refining approach.

  20. The Effect Of Carbon Concentration On The Retained Austenite Content And The Mechanical Properties Of TRIP Steel Wire Rod Obtained From The Stelmor Controlled Cooling Line

    Directory of Open Access Journals (Sweden)

    Muskalski Z.

    2015-09-01

    Full Text Available The austenite content of the multiphase TRIP-structure steels depends, inter alia, on the carbon concentration and the properly selected parameters of the two-stage heat treatment.

  1. Effects of Inclusions and Austenite Grain Size on the Impact Behavior of a Newly Developed Low-Carbon Steel Weld Metal

    National Research Council Canada - National Science Library

    Blackburn, J

    1999-01-01

    ... carbon steel weld metal was determined. It was concluded that austenite grain refinement was effective at improving toughness across the entire test temperature region, with the exception of the upper shelf energy when the inclusion count...

  2. Nucleation and swelling in electron irradiated austenitic stainless steels in temperature range 400∼720 degree C

    International Nuclear Information System (INIS)

    Qian Jiapu; Lu Liping; Chen Jiming; Sun Jiguang; Zhao Zhuoyong

    1994-10-01

    A study of the influence of temperature on swelling behavior in electron irradiated austenitic stainless steels has been performed with a high voltage electron microscope (HVEM) in the temperature range 400 to 720 degree C. The specimen materials were solution annealed (SA) 316 stainless steel (SS), cold worked (CW) 316 SS and Ti-modified austenitic stainless steel (Ti-mod. SS). The electron energy in HVEM was 1 MeV. The results of mean void density, mean void diameter, void swelling, swelling rate and incubation dose vs. dose and temperature are presented. It is suggested that the irradiation temperature influenced the microstructure, overall sink strength and relative strength of neutral sinks to that of biased sinks in the specimens and so made the void nucleation, void growth and swelling behavior differently in 316 SA, 316 CW and Ti-mod. SS. The influence of He pre-implantation on void nucleation in electron irradiated austenitic stainless steels has also been studied. The experiments indicated that the helium was active void nucleus but had no direct impact on void growth

  3. Effects of fluoride and other halogen ions on the external stress corrosion cracking of Type 304 austenitic stainless steel

    International Nuclear Information System (INIS)

    Whorlow, K.M.; Hutto, F.B. Jr.

    1997-07-01

    The drip procedure from the Standard Test Method for Evaluating the Influence of Thermal Insulation on External Stress Corrosion Cracking Tendency of Austenitic Stainless Steel (ASTM C 692-95a) was used to research the effect of halogens and inhibitors on the External Stress Corrosion Cracking (ESCC) of Type 304 stainless steel as it applies to Nuclear Regulatory Commission Regulatory Guide 1.36, Nonmetallic Thermal Insulation for Austenitic Stainless Steel. The solutions used in this research were prepared using pure chemical reagents to simulate the halogens and inhibitors found in insulation extraction solutions. The results indicated that sodium silicate compounds that were higher in sodium were more effective for preventing chloride-induced ESCC in Type 304 austenitic stainless steel. Potassium silicate (all-silicate inhibitor) was not as effective as sodium silicate. Limited testing with sodium hydroxide (all-sodium inhibitor) indicated that it may be effective as an inhibitor. Fluoride, bromide, and iodide caused minimal ESCC which could be effectively inhibited by sodium silicate. The addition of fluoride to the chloride/sodium silicate systems at the threshold of ESCC appeared to have no synergistic effect on ESCC. The mass ratio of sodium + silicate (mg/kg) to chloride (mg/kg) at the lower end of the NRC RG 1.36 Acceptability Curve was not sufficient to prevent ESCC using the methods of this research

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

    International Nuclear Information System (INIS)

    Devendranath Ramkumar, K.; Bajpai, Ankur; Raghuvanshi, Shubham; Singh, Anshuman; Chandrasekhar, Aditya; Arivarasu, M.; Arivazhagan, N.

    2015-01-01

    This research work articulated the effect of SiO 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 2 flux for joining the dissimilar metals involving austenitic and super-duplex stainless steels

  5. 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.

  6. A Model for Converting Dilatometric Strain Measurements to the Fraction of Phase Formed during the Transformation of Austenite to Martensite in Powder Metallurgy Steels

    Science.gov (United States)

    Warke, Virendra S.; Sisson, Richard D.; Makhlouf, Makhlouf M.

    2009-03-01

    A model is developed to allow converting dilatometric strains that occur during the continuous cooling transformation (CCT) of austenite to martensite to volume fraction martensite formed in powder metallurgy steels. Unlike existing models, this model can accurately account for the observed decrease in the measured transformation strain with increased porosity. As a demonstration, the model is used to accurately calculate the volume fraction of martensite formed during the CCT of austenite to martensite in FL-4605 PM steel.

  7. The Role of Retained Austenite on the Mechanical Properties of a Low Carbon 3Mn-1.5Ni Steel

    Science.gov (United States)

    Chen, Jun; Zhang, Wei-na; Liu, Zhen-yu; Wang, Guo-dong

    2017-12-01

    The present studies focus on the correlation between retained austenite characteristics and the cryogenic temperature Charpy impact toughness, strength, and plasticity. The steels with different volume fractions and stabilities of retained austenite were prepared by quenching followed by intercritical heat treatment, and the microstructure was characterized using scanning electron microscope, electron back-scattered diffraction, and X-ray diffraction. The grain size, dislocation density, crack initiation energy, and crack propagation energy were quantified. It has been demonstrated that the volume fraction of retained austenite plays a significant role in the reduction of the measured yield strength and the effect of tempered martensite/ferrite matrix on cryogenic temperature impact toughness can be assumed to be similar due to the similar grain size, dislocation density and element content in solution for different heat treatments. It was found that the stability of retained austenite plays a determining role in the increase of cryogenic temperature impact toughness. Furthermore, the dependence of the crack propagation energy on retained austenite is much greater than that of the crack initiation energy. Generally, an excellent UTS × TEL does not produce good cryogenic temperature impact toughness.

  8. 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

  9. Partial transient liquid phase diffusion bonding of Zircaloy-4 to stabilized austenitic stainless steel 321

    Energy Technology Data Exchange (ETDEWEB)

    Atabaki, M. Mazar, E-mail: m.mazaratabaki@gmail.com [Department of Materials Engineering, Faculty of Mechanical Engineering, University Technology Malaysia, 81310 (Malaysia); Hanzaei, A. Talebi [Department of Metallurgy and Materials Engineering, Faculty of Engineering, University of Tehran (Iran, Islamic Republic of)

    2010-10-15

    An innovative method was applied for bonding Zircaloy-4 to stabilized austenitic stainless steel 321 using an active titanium interlayer. Specimens were joined by a partial transient liquid phase diffusion bonding method in a vacuum furnace at different temperatures under 1 MPa dynamic pressure of contact. The influence of different bonding temperatures on the microstructure, microindentation hardness, joint strength and interlayer thickness has been studied. The diffusion of Fe, Cr, Ni and Zr has been investigated by scanning electron microscopy and energy dispersive spectroscopy elemental analyses. Results showed that control of the heating and cooling rate and 20 min soaking at 1223 K produces a perfect joint. However, solid-state diffusion of the melting point depressant elements into the joint metal causes the solid/liquid interface to advance until the joint is solidified. The tensile strength of all the bonded specimens was found around 480-670 MPa. Energy dispersive spectroscopy studies indicated that the melting occurred along the interface of the bonded specimens as a result of the transfer of atoms between the interlayer and the matrix during bonding. This technique provides a reliable method of bonding zirconium alloy to stainless steel.

  10. Soft tissue response to a new austenitic stainless steel with a negligible nickel content.

    Science.gov (United States)

    Tschon, M; Fini, M; Giavaresi, G; Borsari, V; Lenger, H; Bernauer, J; Chiesa, R; Cigada, A; Chiusoli, L; Giardino, R

    2005-10-01

    This study evaluates the soft tissue response to a new austenitic stainless steel with a low nickel content (P558) in comparison with a conventional stainless steel (SSt)and a titanium alloy (Ti6Al4V). Previous findings showed its in vitro biocompatibility by culturing P558 with healthy and osteoporotic osteoblasts and its in vivo effectiveness as bone implant material. Regarding its use as a material in osteosynthesis,P558 biocompatibility when implanted in soft tissues, as subcutis and muscle, was assessed. Disks and rods of these metals were implanted in rat subcutis and in rabbit muscle, respectively. Four and twelve weeks post surgery implants with surrounding tissue were retrieved for histologic and histomorphometric analysis: fibrous capsule thickness and new vessel formation were measured. Around all implanted materials, light microscopy highlighted a reactive and fibrous capsule formation coupled with ongoing neoangiogenesis both in rats and in rabbits. Histomorphometric measurements revealed a stronger inflammatory response,in terms of capsule thickness,surrounding SSt implants (9.8% Ni content) both in rat subcutis and in rabbit muscle independently of shape and site of implantation. A progressive decrease in capsule thickness around P558 (implantation. However,in the light of the previous and present studies, P558 is a good material, instead of titanium alloys, in orthopedic research.

  11. Hot Deformation Behavior and Microstructural Evolution of Antibacterial Austenitic Stainless Steel Containing 3.60% Cu

    Science.gov (United States)

    Li, Juan; Zhao, Guanghui; Ma, Lifeng; Chen, Huiqin; Li, Huaying; Huang, Qingxue; Zhang, Wei

    2018-03-01

    Hot deformation behavior of as-cast antibacterial austenitic stainless steel containing 3.60% copper was investigated in a temperature range of 900-1150 °C and strain rate range of 0.01-20 s-1. At strain rates higher than 1 s -1, the flow stress curves were corrected considering adiabatic heating. Kinetic analysis indicated that the hot deformation activation energy of steel was 376.02 kJ mol-1. The microstructural evolution under different temperatures was observed by optical microscopy. The nucleation sites for recrystallization and different orientations and twin ratios under different strain rates were analyzed by electron backscatter diffraction. The results showed that hot deformation was dominated by continuous dynamic recrystallization in the high-temperature and high-strain-rate region (1050-1150 °C, 1-20 s-1). On increasing the temperature and strain rate, the degree of recrystallization and twinning increased simultaneously. These phenomena promoted one another. Thus, the volume fraction of the recrystallized and twinned grains increased with the addition of Cu.

  12. Crack growth rates of irradiated austenitic stainless steel weld heat affected zone in BWR environments.

    Energy Technology Data Exchange (ETDEWEB)

    Chopra, O. K.; Alexandreanu, B.; Gruber, E. E.; Daum, R. S.; Shack, W. J.; Energy Technology

    2006-01-31

    Austenitic stainless steels (SSs) are used extensively as structural alloys in the internal components of reactor pressure vessels because of their superior fracture toughness. However, exposure to high levels of neutron irradiation for extended periods can exacerbate the corrosion fatigue and stress corrosion cracking (SCC) behavior of these steels by affecting the material microchemistry, material microstructure, and water chemistry. Experimental data are presented on crack growth rates of the heat affected zone (HAZ) in Types 304L and 304 SS weld specimens before and after they were irradiated to a fluence of 5.0 x 10{sup 20} n/cm{sup 2} (E > 1 MeV) ({approx} 0.75 dpa) at {approx}288 C. Crack growth tests were conducted under cycling loading and long hold time trapezoidal loading in simulated boiling water reactor environments on Type 304L SS HAZ of the H5 weld from the Grand Gulf reactor core shroud and on Type 304 SS HAZ of a laboratory-prepared weld. The effects of material composition, irradiation, and water chemistry on growth rates are discussed.

  13. Statistical properties of material strength for reliability evaluation of components of fast reactors. Austenitic stainless steels

    International Nuclear Information System (INIS)

    Takaya, Shigeru; Sasaki, Naoto; Tomobe, Masato

    2015-03-01

    Many efforts have been made to implement the System Based Code concept of which objective is to optimize margins dispersed in several codes and standards. Failure probability is expected to be a promising quantitative index for optimization of margins, and statistical information for random variables is needed to evaluate failure probability. Material strength like tensile strength is an important random variable, but the statistical information has not been provided enough yet. In this report, statistical properties of material strength such as creep rupture time, steady creep strain rate, yield stress, tensile stress, flow stress, fatigue life and cyclic stress-strain curve, were estimated for SUS304 and 316FR steel, which are typical structural materials for fast reactors. Other austenitic stainless steels like SUS316 were also used for statistical estimation of some material properties such as fatigue life. These materials are registered in the JSME code of design and construction of fast reactors, so test data used for developing the code were used as much as possible in this report. (author)

  14. A shallow land buriable low-activation austenitic stainless steel for fusion applications

    International Nuclear Information System (INIS)

    Zucchetti, M.

    1990-01-01

    First-wall components are the most activated materials in fusion reactors, but their activity can be reduced by material selection. The development of new alloys with good mechanical and physical properties and with low activation characteristics is needed. The PCA is one of the reference austenitic stainless steels for fusion structural applications in the United States. In this paper, the authors analyze the induced radioactivity in the PCA in connection with the shallow land burial (SLB) waste disposal concept. The most proper elemental substitutions is suggested for reducing the activity in the PCA. A low-activity version of the PCA is proposed. Since recycling is not possible, shallow land burial is the best achievable goal for a low-activation steel for the first wall. The PCA cannot be accepted for SLB, mainly due to the presence of molybdenum, niobium, and certain impurities. With limited elemental substitutions and impurity limitations, a new alloy (PCA-la) can be obtained. The PCA-la meets requirements for SLB. The properties of PCA-la should be comparable to those of the PCA. Fabrication and testing of specimens to check its main properties will be the next step of this work

  15. Analysis of the strain induced martensitic transformation in austenitic steel subjected to dynamic perforation

    Science.gov (United States)

    Rodríguez-Martínez, J. A.; Rusinek, A.; Pesci, R.; Zaera, R.

    2012-08-01

    An experimental and numerical analysis on the martensitic transformation in AISI 304 steel sheets subjected to perforation by conical and hemispherical projectiles is reported. Two target thicknesses are considered, 0.5 and 1.0 mm, and impact velocities range from 35 to 200 m/s. The perforation mechanisms are identified and the effect of the projectile nose-shape on the ability of the target for energy absorption is evaluated. Martensite has been detected in all the impacted samples and the role played by the projectile nose-shape on the transformation is highlighted. A 3D model implemented in ABAQUS/Explicit allowed to simulate the perforation tests. The material is defined through a constitutive description developed by the authors to describe the strain induced martensitic transformation taking place in metastable austenitic steels at high strain rates. The numerical results are compared with the experimental evidence and satisfactory matching is obtained. The numerical model succeeds in describing the perforation mechanisms associated to each projectile-target configuration analysed.

  16. Effect of triple ion beam irradiation on mechanical properties of high chromium austenitic stainless steel

    International Nuclear Information System (INIS)

    Ioka, Ikuo; Futakawa, Masatoshi; Nanjyo, Yoshiyasu; Kiuchi, Kiyoshi; Anegawa, Takefumi

    2003-01-01

    A high-chromium austenitic stainless steel has been developed for an advanced fuel cladding tube considering waterside corrosion and irradiation embrittlement. The candidate material was irradiated in triple ion (Ni, He, H) beam modes at 573 K up to 50 dpa to simulate irradiation damage by neutron and transmutation product. The change in hardness of the very shallow surface layer of the irradiated specimen was estimated from the slope of load/depth-depth curve which is in direct proportion to the apparent hardness of the specimen. Besides, the Swift's power low constitutive equation (σ=A(ε 0 + ε) n , A: strength coefficient, ε 0 : equivalent strain by cold rolling, n: strain hardening exponent) of the damaged parts was derived from the indentation test combined with an inverse analysis using a finite element method (FEM). For comparison, Type304 stainless steel was investigated as well. Though both Type304SS and candidate material were also hardened by ion irradiation, the increase in apparent hardness of the candidate material was smaller than that of Type304SS. The yield stress and uniform elongation were estimated from the calculated constitutive equation by FEM inverse analysis. The irradiation hardening of the candidate material by irradiation can be expected to be lower than that of Type304SS. (author)

  17. Experimental and Computational Investigation of Structural Integrity of Dissimilar Metal Weld Between Ferritic and Austenitic Steel

    Science.gov (United States)

    Santosh, R.; Das, G.; Kumar, S.; Singh, P. K.; Ghosh, M.

    2018-03-01

    The structural integrity of dissimilar metal welded (DMW) joint consisting of low-alloy steel and 304LN austenitic stainless steel was examined by evaluating mechanical properties and metallurgical characteristics. INCONEL 82 and 182 were used as buttering and filler materials, respectively. Experimental findings were substantiated through thermomechanical simulation of the weld. During simulation, the effect of thermal state and stress distribution was pondered based on the real-time nuclear power plant environment. The simulation results were co-related with mechanical and microstructural characteristics. Material properties were varied significantly at different fusion boundaries across the weld line and associated with complex microstructure. During in-situ deformation testing in a scanning electron microscope, failure occurred through the buttering material. This indicated that microstructure and material properties synergistically contributed to altering the strength of DMW joints. Simulation results also depicted that the stress was maximum within the buttering material and made its weakest zone across the welded joint during service exposure. Various factors for the failure of dissimilar metal weld were analyzed. It was found that the use of IN 82 alloy as the buttering material provided a significant improvement in the joint strength and became a promising material for the fabrication of DMW joint.

  18. Evaluation of radiation-induced sensitization using electrochemical potentiokinetic reactivation technique for austenitic stainless steels

    International Nuclear Information System (INIS)

    Inazumi, T.; Bell, G.E.C.; Hishinuma, A.

    1990-01-01

    The electrochemical potentiokinetic reactivation (EPR) test technique was applied to the determination of sensitization in a neutron-irradiated (420 degree C, 10 dpa) titanium-modified austenitic stainless steel. Miniaturized specimens (3 mm diam by 0.25 mm thick) in solution-annealed and 25% cold-worked conditions were tested. The degree of sensitization (DOS) was calculated in terms of the reactivation charge (Pa). Results indicated the occurrence of radiation-induced sensitization when compared to control specimens thermally aged at the irradiation temperature. Post-EPR examination of the specimen surfaces showed etching across the face of each grain as well as at grain boundaries. This indicates that the Pa value normalized by the total grain boundary area, which is an accepted EPR-DOS criterion, cannot be directly used as an indicator of the DOS to determine the susceptibility of this irradiated material to intergranular stress corrosion cracking (IGSCC). Further investigations are necessary to correlate the results in this study to the IGSCC susceptibility of the irradiated stainless steel. 26 refs., 7 figs., 3 tabs

  19. The natural aging of austenitic stainless steels irradiated with fast neutrons

    Science.gov (United States)

    Rofman, O. V.; Maksimkin, O. P.; Tsay, K. V.; Koyanbayev, Ye. T.; Short, M. P.

    2018-02-01

    Much of today's research in nuclear materials relies heavily on archived, historical specimens, as neutron irradiation facilities become ever more scarce. These materials are subject to many processes of stress- and irradiation-induced microstructural evolution, including those during and after irradiation. The latter of these, referring to specimens "naturally aged" in ambient laboratory conditions, receives far less attention. The long and slow set of rare defect migration and interaction events during natural aging can significantly change material properties over decadal timescales. This paper presents the results of natural aging carried out over 15 years on austenitic stainless steels from a BN-350 fast breeder reactor, each with its own irradiation, stress state, and natural aging history. Natural aging is shown to significantly reduce hardness in these steels by 10-25% and partially alleviate stress-induced hardening over this timescale, showing that materials evolve back towards equilibrium even at such a low temperature. The results in this study have significant implications to any nuclear materials research program which uses historical specimens from previous irradiations, challenging the commonly held assumption that materials "on the shelf" do not evolve.

  20. Analysis of the strain induced martensitic transformation in austenitic steel subjected to dynamic perforation

    Directory of Open Access Journals (Sweden)

    Zaera R.

    2012-08-01

    Full Text Available An experimental and numerical analysis on the martensitic transformation in AISI 304 steel sheets subjected to perforation by conical and hemispherical projectiles is reported. Two target thicknesses are considered, 0.5 and 1.0 mm, and impact velocities range from 35 to 200 m/s. The perforation mechanisms are identified and the effect of the projectile nose-shape on the ability of the target for energy absorption is evaluated. Martensite has been detected in all the impacted samples and the role played by the projectile nose-shape on the transformation is highlighted. A 3D model implemented in ABAQUS/Explicit allowed to simulate the perforation tests. The material is defined through a constitutive description developed by the authors to describe the strain induced martensitic transformation taking place in metastable austenitic steels at high strain rates. The numerical results are compared with the experimental evidence and satisfactory matching is obtained. The numerical model succeeds in describing the perforation mechanisms associated to each projectile-target configuration analysed.

  1. Behaviour and damage of aged austenitic-ferritic steels: a micro-mechanical approach

    International Nuclear Information System (INIS)

    Bugat, St.

    2000-12-01

    The austenitic-ferritic steels are used in the PWR primary cooling system. At the running temperature (320 C), they are submitted to a slow aging, which leads to the embrittlement of the ferritic phase. This embrittlement leads to a decrease of the mechanical properties, in particular of the crack resistance of the austenitic-ferritic steels. The damage and rupture of the austenitic-ferritic steels have been approached at the ENSMP by the works of P. Joly (1992) and of L. Devilliers-Guerville (1998). These works have allowed to reveal a damage heterogeneity which induces a strong dispersion on the ductilities and the toughnesses as well as on the scale effects. Modeling including the damage growth kinetics measured experimentally, have allowed to verify these effects. Nevertheless, they do not consider the two-phase character of the material and do not include a physical model of the cleavage cracks growth which appear in the embrittled ferrite. In this study, is proposed a description of the material allowing to treat these aspects while authorizing the structure calculation. In a first part, the material is studied. The use of the ESBD allows to specify the complex morphology of these steels and crystal orientation relations between the two phases. Moreover, it is shown that the two phases keep the same crystal orientation in the zones, called bicrystals, whose size varies between 500 μm and 1 mm. The study of the sliding lines, coupled to the ESBD, allows to specify too the deformation modes of the two phases. At last, tensile and tensile-compression tests at various deformation range are carried out to characterize the macroscopic mechanical behaviour of these materials. Then, a micro-mechanical modeling of the material behaviour is proposed. This one takes into account the three scales identified at the preceding chapter. The first scale, corresponding to the laths is described as a monocrystal whose behaviour includes both an isotropic and a kinematic strain

  2. Hydrogen-Induced Delayed Cracking in TRIP-Aided Lean-Alloyed Ferritic-Austenitic Stainless Steels.

    Science.gov (United States)

    Papula, Suvi; Sarikka, Teemu; Anttila, Severi; Talonen, Juho; Virkkunen, Iikka; Hänninen, Hannu

    2017-06-03

    Susceptibility of three lean-alloyed ferritic-austenitic stainless steels to hydrogen-induced delayed cracking was examined, concentrating on internal hydrogen contained in the materials after production operations. The aim was to study the role of strain-induced austenite to martensite transformation in the delayed cracking susceptibility. According to the conducted deep drawing tests and constant load tensile testing, the studied materials seem not to be particularly susceptible to delayed cracking. Delayed cracks were only occasionally initiated in two of the materials at high local stress levels. However, if a delayed crack initiated in a highly stressed location, strain-induced martensite transformation decreased the crack arrest tendency of the austenite phase in a duplex microstructure. According to electron microscopy examination and electron backscattering diffraction analysis, the fracture mode was predominantly cleavage, and cracks propagated along the body-centered cubic (BCC) phases ferrite and α'-martensite. The BCC crystal structure enables fast diffusion of hydrogen to the crack tip area. No delayed cracking was observed in the stainless steel that had high austenite stability. Thus, it can be concluded that the presence of α'-martensite increases the hydrogen-induced cracking susceptibility.

  3. Hydrogen-Induced Delayed Cracking in TRIP-Aided Lean-Alloyed Ferritic-Austenitic Stainless Steels

    Directory of Open Access Journals (Sweden)

    Suvi Papula

    2017-06-01

    Full Text Available Susceptibility of three lean-alloyed ferritic-austenitic stainless steels to hydrogen-induced delayed cracking was examined, concentrating on internal hydrogen contained in the materials after production operations. The aim was to study the role of strain-induced austenite to martensite transformation in the delayed cracking susceptibility. According to the conducted deep drawing tests and constant load tensile testing, the studied materials seem not to be particularly susceptible to delayed cracking. Delayed cracks were only occasionally initiated in two of the materials at high local stress levels. However, if a delayed crack initiated in a highly stressed location, strain-induced martensite transformation decreased the crack arrest tendency of the austenite phase in a duplex microstructure. According to electron microscopy examination and electron backscattering diffraction analysis, the fracture mode was predominantly cleavage, and cracks propagated along the body-centered cubic (BCC phases ferrite and α’-martensite. The BCC crystal structure enables fast diffusion of hydrogen to the crack tip area. No delayed cracking was observed in the stainless steel that had high austenite stability. Thus, it can be concluded that the presence of α’-martensite increases the hydrogen-induced cracking susceptibility.

  4. 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.

  5. In-Situ Measurements of Load Partitioning in a Metastable Austenitic Stainless Steel: Neutron and Magnetomechanical Measurements

    Science.gov (United States)

    Maréchal, David; Sinclair, Chad W.; Dufour, Philippe; Jacques, Pascal J.; Mithieux, Jean-Denis

    2012-12-01

    In order to construct physically based models of the mechanical response of metastable austenitic steels, one must know the load partitioning between the austenite and the strain-induced martensitic phases. While diffraction-based techniques have become common for such measurements, they often require access to large facilities. In this work, we have explored a simple magnetic technique capable of providing a measure of the stresses in an embedded ferromagnetic phase. This technique makes use of the coupling between the elastic strain and the magnetic response of the α^'-martensite in an austenitic stainless steel undergoing straining. The magnetic technique proposed here is compared to neutron diffraction measurements made on the same material and is shown to give nearly identical results. The resulting predictions of the load partitioning to the α^'-martensite phase suggest that α^' deforms in a complex fashion, reflecting the fact that the microstructure is progressively transformed from austenite to martensite with straining. In particular, it is shown that the apparent hardening of the α^'-martensite suggests elastic deformation as an important source of high macroscopic work-hardening rate in this material.

  6. Residual Stress Formation Relating to Peak Temperature- and Austenite Grain Size-based Phase Transformation of S355 Steel

    Science.gov (United States)

    Klaproth, Fabian; Vollertsen, Frank

    Nowadays thermal forming processes of steel are state of the art in industrial applications. Nevertheless, the influences of thermal induced phase-transformation on residual stresses and strength have not been fully observed. Times needed for transformation are affected by the initial austenite grain size, while the prevailing peak temperature influences austenite grain growth. Higher temperatures lead to larger austenite grains, leading to increased times for transformation. In order to get an embraced understanding of such effects numerical simulations of phase-transformations are mandatory. In this paper simulations of thermal forming processes, using S355 steel, are presented. Different continuous-cooling-transformation-diagrams (cct-diagrams) of specific austenite grain sizes for temperatures between transformation point AC3 and melting temperature are implemented in the model. It is shown that resulting magnitudes of residual stresses vary between 248 N/mm2 and 550 N/mm2. Finally an approach for the impact on relevant peak temperatures in the heat affected zone is outlined.

  7. Ageing of the welds of pipes in austenitic stainless steels of the sodium fast reactors

    International Nuclear Information System (INIS)

    Dubuisson, Ph.; Monnet, I.; Bougault, A.

    2006-01-01

    Full text of publication follows: The austenitic stainless steels are largely employed for the industrial components which operate at temperatures ranging between 300 deg. C and 600 deg. C. In the Sodium Fast Reactors (SFR), these steels and in particular the steels stabilized with titanium are employed for pipes of the secondary circuit and the exchangers. The whole of these components, and more particularly those in Ti-stabilized steel (AISI 321), have been the subject of an attention supported for more than ten years. The non destructive examinations carried out on these pipes showed indications on the heat affected zones (HAZ) of some circular welds. The first metallographic expertises carried out on the welds confirm the presence of real defects, intergranular cracks which appear on the intern surface at the weld toes and parallel with the fusion line. These defects were attributed to the stress relief cracking. The expertises made it possible to highlight a certain number of significant parameters for this mechanism. Temperature. No case of cracking was observed on the circuits working at 350 deg. C, whereas some cases were revealed on the circuits at 475 deg. C, the percentage of affected welds increasing for the circuit at 550 deg. C. The presence of a defect at the weld root. Each cracked weld shows that intergranular crack was propagated from a shrinkage or a defect of rolling. Initial work hardening in weld root generally observed on the cracked welds. Local loadings, and in particular the residual stresses of welding. Geometrical discontinuities or difference in materials also constitute factors worsening with respect to the mechanism. Microstructural examinations carried out by transmission electron microscopy on different welds affected or not by the stress relief cracking mechanism made it possible to establish a grid of risk of appearance of this type of cracking based on four microstructural features: Dislocations density close to the interface

  8. Optimization of the cold processing of 15-15Ti AIM1 austenitic steel cladding tubes

    International Nuclear Information System (INIS)

    Courtin, Laurine

    2015-01-01

    In order to face the next century energy demand growth, the worldwide development of the 4. generation of nuclear reactors is considered. The construction of a sodium-cooled fast reactor prototype (ASTRID) is currently envisaged at the CEA. The reference material selected for the fuel cladding of its first core is the 15-15Ti-AIM1 austenitic steel (Austenitic Improved Material). The goal of this PhD thesis work is to investigate the different ways of optimization for the cold working steps undergone by the claddings during their manufacture in order to improve their swelling resistance. The main investigations are focused on the conditions of the cold-working steps and the thermal treatments applied throughout the shaping of the claddings, especially of the last solution annealing treatment. The effects of these parameters on the microstructure are investigated (structural refinement, precipitation and the additive elements dissolution and arrangement of the dislocations). This study is divided into three main steps: An analysis of the fabrication routes applied in the past along with the study of the 'cold-work' and the thermal treatments conditions; An assessment of new shaping processes, such as the 'cold-pilgering' and the hammering, in order to verify the conformity of the manufactured tubes with respect to the required specifications; An attempt of optimization of the cold-work routes and the microstructure of the final material. The results of microstructure characterization and the mechanical behavior allow envisaging favorably the use of an alternative process such as the cold pilgering to manufacture claddings. (author) [fr

  9. 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.

  10. 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.

  11. Residual stress evaluation of austenitic stainless steel with a finished surface by polychromatic X-ray method

    Energy Technology Data Exchange (ETDEWEB)

    Shibano, Jun-ichi; Ukai, Takayoshi; Tadano, Shigeru [Hokkaido Univ., Sapporo (Japan). Faculty of Engineering; Todoh, Masahiro

    1995-11-01

    The residual stress in a subsurface layer of austenitic stainless steel with a finished surface was evaluated by the polychromatic X-ray method. A surface of austenitic stainless steel SUS316 plate was ground and lapped as the specimen. In this method, the relation between strain and depth was approximated with a linear function or an exponential function, and it was assumed that the plane stress state existed in each subsurface layer in the depth direction of the specimen. As a result, the residual strain which was estimated under the assumption of the exponential function showed more reasonable distribution than that of the linear function. In addition, the residual stress which was calculated from the strain distribution was maximum tension at the surface of the specimen, and maximum compression at a position 3 {mu}m below the surface. Therefore, the steep gradient of residual stress could be confirmed in a subsurface layer of the SUS316 with a finished surface. (author).

  12. Structure, properties, and resistance to stress-corrosion cracking of a nitrogen-containing austenitic steel strengthened by thermomechanical treatment

    Science.gov (United States)

    Mushnikova, S. Yu.; Kostin, S. K.; Sagaradze, V. V.; Kataeva, N. V.

    2017-11-01

    The results of comparative studies of the structure, mechanical properties, and resistance to stresscorrosion cracking (SCC) in the chloride solutions of a Cr-Mn-Ni austenitic nitrogen-containing steel (20Cr-6Ni-11Mn-1.5Mo-N-V-Nb) produced with the use of different regimes of the high-temperature thermomechanical treatment (HTTMT) have been presented. An unfavorable effect of the grain-boundary precipitates of the nitride phase on the impact toughness and resistance to SCC has been found. It has been shown that the strengthening of nitrogen-containing steel upon HTTMT, which ensures an increase in the yield stress by 1.8 times compared to the austenitized state, does not decrease the resistance to SCC.

  13. The influence of fire exposure on austenitic stainless steel for pressure vessel fitness-for-service assessment: Experimental research

    Science.gov (United States)

    Li, Bo; Shu, Wenhua; Zuo, Yantian

    2017-04-01

    The austenitic stainless steels are widely applied to pressure vessel manufacturing. The fire accident risk exists in almost all the industrial chemical plants. It is necessary to make safety evaluation on the chemical equipment including pressure vessels after fire. Therefore, the present research was conducted on the influences of fire exposure testing under different thermal conditions on the mechanical performance evolution of S30408 austenitic stainless steel for pressure vessel equipment. The metallurgical analysis described typical appearances in micro-structure observed in the material suffered by fire exposure. Moreover, the quantitative degradation of mechanical properties was investigated. The material thermal degradation mechanism and fitness-for-service assessment process of fire damage were further discussed.

  14. Effect of additional minor elements on accumulation behavior of point defects under electron irradiation in austenitic stainless steels

    International Nuclear Information System (INIS)

    Sekio, Yoshihiro; Yamashita, Shinichiro; Takahashi, Heishichiro; Sakaguchi, Norihito

    2014-01-01

    Addition of minor elements to a base alloy is often applied with the aim of mitigating void swelling by decreasing the vacancy diffusivity and flux which influence vacancy accumulation behavior. However, the comparative evaluations of parameters, such as the diffusivity and flux, between a base alloy and modified alloys with specific additives have not been studied in detail. In this study, type 316 austenitic stainless steel as a base alloy and type 316 austenitic stainless steels modified with vanadium (V) or zirconium (Zr) additions were used to perform evaluations from the changes of widths of the void denuded zone (VDZ) formed near a random grain boundary during electron irradiation because these widths depend on vacancy diffusivity and flux. The formations of VDZs were observed in in-situ observations during electron irradiation at 723 K and the formed VDZ widths were measured from the transmission electron microscopic images after electron irradiation. As a result, the VDZs were formed in both steels without and with V, and respective widths were ∼119 and ∼100 nm. On the other hand, the VDZ formation was not observed clearly in the steel with Zr. From the measured VDZ widths in the steels without and with V addition, the estimated ratio of the vacancy diffusivity in the steel with V to that in the steel without V was about 0.50 and the estimated ratio of the vacancy flux in the steel with V to that in the steel without V was about 0.71. This result suggests that the effect of additional minor elements on vacancy accumulation behaviors under electron irradiation could be estimated from evaluations of the VDZ width changes among steels with and without minor elements. Especially, because void swelling is closely related with the vacancy diffusion process, the VDZ width changes would also be reflected on void swelling behavior. (author)

  15. Stability of grain-refined reversed structures in a 301LN austenitic stainless steel under cyclic loading

    Czech Academy of Sciences Publication Activity Database

    Järvenpää, A.; Jaskari, M.; Man, Jiří; Karjalalinen, L.P.

    2017-01-01

    Roč. 703, č. 4 (2017), s. 280-292 ISSN 0921-5093 R&D Projects: GA ČR GA13-32665S Institutional support: RVO:68081723 Keywords : austenitic stainless steel * reversion treatment * grain size * deformation induced martensite * strain-controlled fatigue Subject RIV: JL - Materials Fatigue, Friction Mechanics OBOR OECD: Audio engineering, reliability analysis Impact factor: 3.094, year: 2016

  16. The effects of adding molybdenum and niobium on the creep strength of 18Cr-10Ni-20Co austenitic steel

    International Nuclear Information System (INIS)

    Tomono, Yutaka

    1987-01-01

    The decrease in the creep strength of structural materials during service at elevated temperatures is a very important problem that affects the security of plants and machinery. The improvement in the creep strength of 18Cr-10Ni-20Co austenitic steel achieved through the addition of molybdenum and niobium was studied in tests carried out at 973K and 1,073K. The creep strengthening mechanism was examined using transmission electron micrographs, X-ray diffraction, etc. The results obtained are summarized as follows: (1) The creep strength of low C-18Cr-10Ni-20Co austenitic steel with molybdenum was greatly improved by the addition of niobium up to 1% by weight. In the case of long-term creep, no trend toward decreasing creep strength was observed. (2) The creep strength of austenitic steel possessing a matrix strengthened with molybdenum can be improved through the addition of niobium combined with precipitation hardening with fine carbides precipitated in the grains. (author)

  17. The Investigation on Strain Strengthening Induced Martensitic Phase Transformation of Austenitic Stainless Steel: A Fundamental Research for the Quality Evaluation of Strain Strengthened Pressure Vessel

    Science.gov (United States)

    Li, Bo; Cai Ren, Fa; Tang, Xiao Ying

    2018-03-01

    The manufacture of pressure vessels with austenitic stainless steel strain strengthening technology has become an important technical means for the light weight of cryogenic pressure vessels. In the process of increasing the strength of austenitic stainless steel, strain can induce the martensitic phase transformation in austenite phase. There is a quantitative relationship between the transformation quantity of martensitic phase and the basic mechanical properties. Then, the martensitic phase variables can be obtained by means of detection, and the mechanical properties and safety performance are evaluated and calculated. Based on this, the quantitative relationship between strain hardening and deformation induced martensite phase content is studied in this paper, and the mechanism of deformation induced martensitic transformation of austenitic stainless steel is detailed.

  18. 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

    The main objective of the EU-project CRETE (Contract No.: FIS5-1999-00280) was to assess the capability and the reliability of innovative NDT-inspection techniques for the detection of material degradation, induced by thermal fatigue and neutron irradiation, of metastable austenitic and ferritic low-alloy steel. Several project partners tested aged or irradiated samples, using various techniques (acoustic, magnetic and thermoelectric). However, these indirect methods require a careful interpretation of the measured signal in terms of micro-structural evolutions due to ageing of the material. Therefore the material had to be characterized in its undamaged, as well as in its damaged state. The present report summarises only the material characterization of the fatigue specimens. It is issued simultaneously as an PSI Bericht and the CRETE work package 3 (WP3) report. Each partner according to their own specifications purchased three materials under investigation, namely AISI 347, AISI 321 and AISI 304L. After sending the material to PSI, all fatigue specimens were manufactured by the same Swiss company. Each partner was responsible for his fatigue tests which are documented in the report WP1, written by FANP. In order to characterize the material in its unfatigued as well as in its fatigued state and to consider microstructural changes related to fatigue damage the methods listed below were employed either by PSI or by INSA de Lyon: (1) Inductive Coupled Plasma Emission Photometry (ICP-OES) was applied to determine the chemical composition, (2) Scanning electron microscopy (SEM) for observing cracks, slip bands between grain and twin boundaries, - Ferromaster for measuring the magnetic permeability, (3) Physical Properties Measuring System (PPMS) for measuring magnetization characteristics, (4) Neutron- and advanced X-ray diffraction methods for the quantitative determination of martensite, - Transmission electron microscopy (TEM) for the observation of crystalline

  19. Effect of microfissures on corrosion performance and mechanical properties of austenitic stainless steel weld metals

    Science.gov (United States)

    Cui, Yan

    It is generally recognized that hot cracking or microfissuring is one of the main concerns in austenitic stainless steel welding. In this study, eight kinds of commercial and modified electrodes provided by Lincoln Electric Company, ESAB and Hobart were used to produce fissure-containing and fissure-free welded coupons for extracting the samples for this investigation. The modified electrodes, E308L, E316L, E308H and E316H, are those electrodes which Ferrite Numbers are around zero to produce microfissures for the investigation. The corrosion performance of these weld deposits with different microfissure densities was evaluated by pitting and crevice corrosion testing in ferrite chloride solutions. Critical Pitting Temperature (CPT) and Critical Crevice Corrosion Temperature (CCT) were used to detect corrosion behavior of these weld deposits. In addition, cyclic polarization testing in 3.5% sodium chloride solution was also conducted to evaluate the corrosion behavior in terms of Epit and Eprot. The corrosion testing results showed that microfissures provided the pitting corrosion sites and degraded pitting and crevice corrosion resistance of austenitic stainless steel weld metals. CCT and CPT are a function of the microfissure level. With an increase in microfissure level a decrease in CPT and CCT is noted and microfissures have a more significant effect on CPT than CCT. Pits preferentially initiated at the tips of microfissures for fissure-containing samples and in overlapped region for fissure-free samples. When 308L is compared to 316L, the 316L deposits are superior with regard to CPT and CCT at the same microfissure level. The ferrite content does not appear to influence CPT and CCT at the same microfissure level. E316H deposits have the highest Epit, Eprot, followed by E308H, E316L, and E308L. The corrosion behavior obtained from cyclic polarization testing follows in the same order and is consistent with the immersion CPT and CCT results. Based on the

  20. A preliminary investigation of the initiation of pitting corrosion in austenitic stainless steels and nickel-based alloys

    International Nuclear Information System (INIS)

    Higginson, A.

    1984-01-01

    Pitting corrosion in a number of austenitic stainless steels and nickel-based alloys that differ widely in their resistance to corrosion was studed by electrochemical and electron-optical techniques. The effect of contamination of the sulphuric acid electrolyte by chloride ions was also investigated. Preliminary results for the surface analysis of samples of 316 stainless steel by Auger electron spectroscopy are presented, and suggestions are included for further application of this technique to the examination of pitting corrosion. A comprehensive review of the literature concerning the initiation of pitting corrosion is included

  1. Study of a particular type of intercrystalline cracking under stress at 7000C in austenitic stainless steels

    International Nuclear Information System (INIS)

    Bonnet, F.; Biscondi, M.

    1977-01-01

    Rupture under internal stresses at about 700 0 C, by propagation of an intergranular crack of great length, was first observed by Hodierne on extruded tubes made of stabilized austenitic steels. This phenomenon occurs in very particular thermomechanical conditions. It was reproduced by hot tension on various grades of industrial or synthetic steels, stabilized or not. Precipitation does not play the main role. A general interpretation is given which lies on concentration of stresses at the triple nodes due to intergranular slipping. Then, these observations can be explained, specially the existence of a critical tension velocity. The presence of some oligoelements in very low quantities clearly increases this type of brittleness [fr

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

    Directory of Open Access Journals (Sweden)

    A.K. Lakshminarayanan

    2014-12-01

    Full Text Available 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 reinforcement 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.

  3. Effects of Heat Input on Microstructure, Corrosion and Mechanical Characteristics of Welded Austenitic and Duplex Stainless Steels: A Review

    Directory of Open Access Journals (Sweden)

    Ghusoon Ridha Mohammed

    2017-01-01

    Full Text Available The effects of input heat of different welding processes on the microstructure, corrosion, and mechanical characteristics of welded duplex stainless steel (DSS are reviewed. Austenitic stainless steel (ASS is welded using low-heat inputs. However, owing to differences in the physical metallurgy between ASS and DSS, low-heat inputs should be avoided for DSS. This review highlights the differences in solidification mode and transformation characteristics between ASS and DSS with regard to the heat input in welding processes. Specifically, many studies about the effects of heat energy input in welding process on the pitting corrosion, intergranular stress, stresscorrosion cracking, and mechanical properties of weldments of DSS are reviewed.

  4. Electrochemical corrosion investigations on austenitic CrNi-steels in nitric acid with and without additions of metal ions

    International Nuclear Information System (INIS)

    Simon, R.

    1988-04-01

    The aim of the present work was to develop an electrochemical short-time test procedure for detecting intergranular corrosion (IGC) susceptibility of austenitic CrNi-steels in strongly oxidizing media, as e.g. concentrated nitric acid. This procedure should cover the test parameters of the usually applied ASTM Standard Huey Test, which is performed in boiling 14.4 n nitric acid. The described electrochemical test procedure - a potentiostatic polarisation of steel specimens in the transpassive range - is presented as an alternative to the Huey Test with equivalent results, but with a reduced testing time. (orig./IHOE) [de

  5. Effect of large strain warm rolling and subsequent annealing on the microstructure and mechanical properties of austenitic stainless steels

    Science.gov (United States)

    Odnobokova, M.; Yanushkevich, Z.; Belyakov, A.; Kaibyshev, R.

    2017-12-01

    The microstructural evolution of 304L and 316L steels during warm plate rolling to a strain of 3 and subsequent annealing as well as the structural effect on the mechanical properties were investigated. The warm rolled microstructures consisted of flattened wavy austenitic grains with transverse grain sizes of about 220 and 160 nm in 304L and 316L steels, respectively. The formation of the wavy austenite structures was facilitated by high density of microshear bands. The subsequent annealing was accompanied by the development of static recrystallization and grain growth. The 304L steel specimens were characterized by a lower stability against recrystallization and grain growth as compared to the 316L ones. The grain coarsening during annealing was accompanied by gradual softening. The hardness decreased by 50% in both steels after annealing at 800°C. The grain coarsening was accompanied by strength degradation, although the tensile strength above 900 and 1000 MPa remained in the 304L and 316L steel specimens, respectively, after annealing at 700°C.

  6. Effect of Welding Current on the Structure and Properties of Resistance Spot Welded Dissimilar (Austenitic Stainless Steel and Low Carbon Steel) Metal Joints

    Science.gov (United States)

    Shawon, M. R. A.; Gulshan, F.; Kurny, A. S. W.

    2015-04-01

    1.5 mm thick sheet metal coupons of austenitic stainless steel and plain low carbon steel were welded by resistance spot welding technique. The effects of welding current in the range 3-9 kA on the structure and mechanical properties of welded joint were investigated. The structure was studied by macroscopic, microscopic and scanning electron microscopy techniques. Mechanical properties were determined by tensile testing and microhardness measurements. Asymmetrical shape weld nugget was found to have formed in the welded joint which increased in size with an increase in welding current. The fusion zone showed cast structure with coarse columnar grain and dendritic with excess delta ferrite in austenitic matrix. Microhardness of the weld nugget was maximum because of martensite formation. An increase in welding current also increased tensile strength of the weld coupon. An attempt has also been made to relate the mode of fracture with the welding current.

  7. 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.

  8. Austenitic and duplex stainless steels in simulated physiological solution characterized by electrochemical and X-ray photoelectron spectroscopy studies.

    Science.gov (United States)

    Kocijan, Aleksandra; Conradi, Marjetka; Schön, Peter M

    2012-04-01

    A study of oxide layers grown on 2205 duplex stainless steel (DSS) and AISI 316L austenitic stainless steel in simulated physiological solution is presented here in order to establish the possibility of replacement of AISI 316 L with 2205 DSS in biomedical applications. The results of the potentiodynamic measurements show that the extent of the passive range significantly increased for DSS 2205 compared to AISI 316L stainless steel. Cyclic voltammetry was used to investigate electrochemical processes taking place on the steel surfaces. Oxide layers formed by electrochemical oxidation at different oxidation potentials were studied by X-ray photoelectron spectroscopy, and their compositions were analyzed as a function of depth. The main constituents on both the investigated materials were Cr- and Fe-oxides. Atomic force microscopy topography studies revealed the higher corrosion resistance of the DSS 2205 compared to the AISI 316L under the chosen experimental conditions. Copyright © 2012 Wiley Periodicals, Inc.

  9. 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.

  10. 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.

  11. New developments for the ultrasonic inspection of austenitic stainless steel welds

    International Nuclear Information System (INIS)

    Chassignole, Bertrand; Doudet, Loic; Dupond, Olivier; Fouquet, Thierry; Richard, Benoit

    2006-01-01

    EDF R and D undertakes studies in non destructive testing (NDT) for better understanding the influence of various parameters (material, type of defect, geometry) on the 'controllability' of the critical components for nuclear safety. In the field of ultrasonic testing, one of the principal research orientations is devoted to the study of the austenitic stainless steel welds of the primary cooling system. Indeed, the structure of these welds present characteristics making difficult their examination, for example: - a strong anisotropy of the properties of elasticity which, coupled with the heterogeneity of the grain orientations, can involve phenomena of skewing, division and distortion of the beam; - a significant scattering of the waves by the grains involving an high attenuation and sometimes backscattered signals. For several years, actions have been launched to improve comprehension of these disturbing phenomena and to evaluate the controllability of those welds. This work is based on the one hand on experimental analyses on representative mock-ups and on the other hand on the developments of modelling codes taking into account the characteristics of the materials. We present in this document a synthesis of this work by developing the following points in particular: - a description of the phenomena of propagation; - the works undertaken to characterize the structure of the welds; - an example of study coupling experimental and modelling analyses for a butt weld achieved by manual arc welding with coated electrodes. The paper has the following contents: 1. Context; 2. Presentation of the problem; 3. Characterization of austenitic welds; 4. From comprehension to industrial application; 5. Conclusion and perspectives; 5. Conclusion and perspectives. This synthesis shows that each austenitic stainless steel weld is a particular case for the ultrasonic testing. This work allowed to better apprehend the disturbances of the ultrasonic propagation in the welds and thus

  12. Depth distribution analysis of martensitic transformations in Xe implanted austenitic stainless steel

    International Nuclear Information System (INIS)

    Johnson, E.; Johansen, A.; Sarholt-Kristensen, L.; Chechenin, N.G.; Grabaek, L.; Bohr, J.

    1988-01-01

    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 electron microscopy (XTEM) of the implanted surface. It is found that the martensitic transformation of the surface layer occurs for fluences above 1x10 20 m -2 . The thickness of the transformed layer increases with fluence to ≅ 150 nm at 1x10 21 m -2 , which far exceeds the range plus straggling of the implanted Xe as calculated by the TRIM computer simulation code. Simulations using the MARLOWE code indicate that the thickness of the transformed layer coincides with the range of the small fraction of ions channeled under random implantation conditions. Using cross sectional TEM on the Xe implanted crystals, the depth distribution of gas inclusions and defects can be directly observed. Using X-ray diffraction on implanted single crystals, the solid epitaxial nature of the Xe inclusions, induced prior to the martensitic transformation, was established. The lattice constant obtained from the broad diffraction peak indicates that the pressure in the inclusions is ≅ 5 GPa. (orig./BHO)

  13. Microstructure of Al-Si Slurry Coatings on Austenitic High-Temperature Creep Resisting Cast Steel

    Directory of Open Access Journals (Sweden)

    Agnieszka E. Kochmańska

    2018-01-01

    Full Text Available This paper presents the results of microstructural examinations on slurry aluminide coatings using scanning electron microscopy, X-ray microanalysis, and X-ray diffraction. Aluminide coatings were produced in air atmosphere on austenitic high-temperature creep resisting cast steel. The function of aluminide coatings is the protection of the equipment components against the high-temperature corrosion in a carburising atmosphere under thermal shock conditions. The obtained coatings had a multilayered structure composed of intermetallic compounds. The composition of newly developed slurry was powders of aluminium and silicon; NaCl, KCl, and NaF halide salts; and a water solution of a soluble glass as an inorganic binder. The application of the inorganic binder in the slurry allowed to produce the coatings in one single step without additional annealing at an intermediate temperature as it is when applied organic binder. The coatings were formed on both: the ground surface and on the raw cast surface. The main technological parameters were temperature (732–1068°C and time of annealing (3.3–11.7 h and the Al/Si ratio (4–14 in the slurry. The rotatable design was used to evaluate the effect of the production parameters on the coatings thickness. The correlation between the technological parameters and the coating structure was determined.

  14. 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.

  15. Modeling of cavity swelling-induced embrittlement in irradiated austenitic stainless steels

    International Nuclear Information System (INIS)

    Han, X.

    2012-01-01

    During long-time neutron irradiation occurred in Pressurized Water Reactors (PWRs), significant changes of the mechanical behavior of materials used in reactor core internals (made of 300 series austenitic stainless steels) are observed, including irradiation induced hardening and softening, loss of ductility and toughness. So far, much effect has been made to identify radiation effects on material microstructure evolution (dislocations, Frank loops, cavities, segregation, etc.). The irradiation-induced cavity swelling, considered as a potential factor limiting the reactor lifetime, could change the mechanical properties of materials (plasticity, toughness, etc.), even lead to a structure distortion because of the dimensional modifications between different components. The principal aim of the present PhD work is to study qualitatively the influence of cavity swelling on the mechanical behaviors of irradiated materials. A micromechanical constitutive model based on dislocation and irradiation defect (Frank loops) density evolution has been developed and implemented into ZeBuLoN and Cast3M finite element codes to adapt the large deformation framework. 3D FE analysis is performed to compute the mechanical properties of a polycrystalline aggregate. Furthermore, homogenization technique is applied to develop a Gurson-type model. Unit cell simulations are used to study the mechanical behavior of porous single crystals, by accounting for various effects of stress triaxiality, of void volume fraction and of crystallographic orientation, in order to study void effect on the irradiated material plasticity and roughness at polycrystalline scale. (author) [fr

  16. Improved austenitic stainless steel for high temperature applications. [Improved stress-rupture properties

    Science.gov (United States)

    Not Available

    This invention describes a composition for an austenitic stainless steel which has been found to exhibit improved high temperature stress rupture properties. The composition of this alloy is about (in wt. %): 12.5 to 14.5 Cr; 14.5 to 16.5 Ni; 1.5 to 2.5 Mo; 1.5 to 2.5 Mn; 0.1 to 0.4 Ti; 0.02 to 0.08 C; 0.5 to 1.0 Si; 0.01 maximum, N; 0.02 to 0.08 P; 0.002 to 0.008 B; 0.004-0.010 S; 0.02-0.05 Nb; .01-.05 V; 0.005-0.02 Ta; 0.02-0.05 Al; 0.01-0.04 Cu; 0.02-0.05 Co; .03 maximum, As; 0.01 maximum, 0; 0.01 maximum, Zr; and with the balance of the alloy being essentially iron. The carbon content of the alloy is adjusted such that wt. % Ti/(wt. % C+wt. % N) is between 4 and 6, and most preferably about 5. In addition the sum of the wt. % P + wt. % B + wt. % S is at least 0.03 wt. %. This alloy is believed to be particularly well suited for use as fast breeder reactor fuel element cladding.

  17. Welding-induced microstructure in austenitic stainless steels before and after neutron irradiation

    International Nuclear Information System (INIS)

    Stoenescu, R.; Schaeublin, R.; Gavillet, D.; Baluc, N.

    2007-01-01

    The effects of neutron irradiation on the microstructure of welded joints made of austenitic stainless steels have been investigated. The materials were welded AISI 304 and AISI 347, so-called test weld materials, and irradiated with neutrons at 300 deg. C to 0.3 and 1.0 dpa. In addition, an AISI 304 type from a decommissioned pressurised water reactor, so-called in-service material, which had accumulated a maximum dose of 0.35 dpa at about 300 deg. C, was investigated. The microstructure of heat-affected zones and base materials was analysed before and after irradiation, using transmission electron microscopy. Neutron diffraction was performed for internal stress measurements. It was found that the heat-affected zone contains, relative to the base material, a higher dislocation density, which relates well to a higher residual stress level and, after irradiation, a higher irradiation-induced defect density. In both materials, the irradiation-induced defects are of the same type, consisting in black dots and Frank dislocation loops. Careful analysis of the irradiation-induced defect contrast was performed and it is explained why no stacking fault tetrahedra could be identified

  18. Welding-induced microstructure in austenitic stainless steels before and after neutron irradiation

    Science.gov (United States)

    Stoenescu, R.; Schäublin, R.; Gavillet, D.; Baluc, N.

    2007-02-01

    The effects of neutron irradiation on the microstructure of welded joints made of austenitic stainless steels have been investigated. The materials were welded AISI 304 and AISI 347, so-called test weld materials, and irradiated with neutrons at 300 °C to 0.3 and 1.0 dpa. In addition, an AISI 304 type from a decommissioned pressurised water reactor, so-called in-service material, which had accumulated a maximum dose of 0.35 dpa at about 300 °C, was investigated. The microstructure of heat-affected zones and base materials was analysed before and after irradiation, using transmission electron microscopy. Neutron diffraction was performed for internal stress measurements. It was found that the heat-affected zone contains, relative to the base material, a higher dislocation density, which relates well to a higher residual stress level and, after irradiation, a higher irradiation-induced defect density. In both materials, the irradiation-induced defects are of the same type, consisting in black dots and Frank dislocation loops. Careful analysis of the irradiation-induced defect contrast was performed and it is explained why no stacking fault tetrahedra could be identified.

  19. Melt expulsion during ultrasonic vibration-assisted laser surface processing of austenitic stainless steel.

    Science.gov (United States)

    Alavi, S Habib; Harimkar, Sandip P

    2015-05-01

    Simultaneous application of ultrasonic vibrations during conventional materials processing (casting, welding) and material removal processes (machining) has recently been gaining widespread attention due to improvement in metallurgical quality and efficient material removal, respectively. In this paper, ultrasonic vibration-assisted laser surface melting of austenitic stainless steel (AISI 316) is reported. While the application of ultrasonic vibrations during laser processing delays the laser interaction with material due to enhancement of surface convection, it resulted in expulsion of melt from the irradiated region (forming craters) and transition from columnar to equiaxed dendritic grain structure in the resolidified melt films. Systematic investigations on the effect of ultrasonic vibrations (with vibrations frequency of 20 kHz and power output in the range of 20-40%) on the development of microstructure during laser surface melting (with laser power of 900 W and irradiation time in the range of 0.30-0.45 s) are reported. The results indicate that the proposed ultrasonic vibration-assisted laser processing can be designed for efficient material removal (laser machining) and improved equiaxed microstructure (laser surface modifications) during materials processing. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. 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)

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

    International Nuclear Information System (INIS)

    Ernst, Frank

    2016-01-01

    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. We intended to demonstrate that SECIS can be adapted for post-processing of clad tubing to significantly enhance mechanical properties (hardness, wear resistance, and fatigue life), corrosion resistance, resistance to stress-corrosion cracking (hydrogen-induced embrittlement), and - potentially - radiation resistance (against electron-, neutron-, or ion-radiation damage). To test this hypothesis, we measured various relevant properties of the surface-engineered alloys and compared them with corresponding properties of the non-treated, as-received alloys. In particular, we studied the impact of heat exposure corresponding to BWR (boiling-water reactor) working and accident (loss-of-coolant) conditions and the effect of ion irradiation.

  2. Pitting and stress corrosion cracking behavior in welded austenitic stainless steel

    International Nuclear Information System (INIS)

    Lu, B.T.; Chen, Z.K.; Luo, J.L.; Patchett, B.M.; Xu, Z.H.

    2005-01-01

    The effect of microstructural changes in 304 austenitic stainless steel induced by the processes of gas tungsten arc welding (GTAW) and laser-beam welding (LBW) on the pitting and stress corrosion cracking (SCC) behaviors was investigated. According to the in situ observations with scanning reference electrode technique (SRET) and the breakdown potentials of the test material with various microstructures, the GTAW process made the weld metal (WM) and heat-affected zone (HAZ) more sensitive to pitting corrosion than base metal (BM), but the LBW process improved the pitting resistance of the WM. In the initiation stage of SCC, the cracks in the BM and HAZ propagated in a transgranular mode. Then, the crack growth mechanism changed gradually into a mixed transgranular + intergranular mode. The cracks in the WM were likely to propagate along the dendritic boundaries. The crack initiation rate, crack initiation lifetime and crack propagation rate indicated that the high-to-low order of SCC resistance is almost the same as that for pitting resistance. High heat-input (and low cooling rate) was likely to induce the segregation of alloying elements and formation of Cr-depleted zones, resulting in the degradation in the corrosion resistance

  3. Evaluation of Alumina-Forming Austenitic Stainless Steel Alloys in Microturbines

    Energy Technology Data Exchange (ETDEWEB)

    Brady, M.P.; Matthews, W.J. (Capstone Turbine Corp.)

    2010-09-15

    Oak Ridge National Laboratory (ORNL) and Capstone Turbine Corporation (CTC) 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 microturbine recuperator components. ORNL delivered test coupons of three different AFA compositions to CTC. The coupons were exposed in steady-state elevated turbine exit temperature (TET) engine testing, with coupons removed for analysis after accumulating ~1,500, 3,000, 4,500, and 6,000 hours of operation. Companion test coupons were also exposed in oxidation testing at ORNL at 700-800°C in air with 10% H2O. Post test assessment of the coupons was performed at ORNL by light microscopy and electron probe microanalysis. The higher Al and Nb containing AFA alloys exhibited excellent resistance to oxidation/corrosion, and thus show good promise for recuperator applications.

  4. Effect of martensitic transformation on springback behavior of 304L austenitic stainless steel

    Science.gov (United States)

    Fathi, H.; Mohammadian Semnani, H. R.; Emadoddin, E.; Sadeghi, B. Mohammad

    2017-09-01

    The present paper studies the effect of martensitic transformation on the springback behavior of 304L austenitic stainless steel. Martensite volume fraction was determined at the bent portion under various strain rates after bending test. Martensitic transformation has a significant effect on the springback behavior of this material. The findings of this study indicated that the amount of springback was reduced under a situation of low strain rate, while a higher amount of springback was obtained with a higher strain rate. The reason for this phenomenon is that higher work hardening occurs during the forming process with the low strain rate due to the higher martensite volume fraction, therefore the formability of the sheet is enhanced and it leads to a decreased amount of springback after the bending test. Dependency of the springback on the martensite volume fraction and strain rate was expressed as formulas from the results of the experimental tests and simulation method. Bending tests were simulated using LS-DYNA software and utilizing MAT_TRIP to determine the martensite volume fraction and strain under various strain rates. Experimental result reveals good agreement with the simulation method.

  5. Study on Characteristics of Corrosion Fatigue Crack Propagation for Austenitic Stainless Steel

    International Nuclear Information System (INIS)

    Lim, Uh Joh; Kim, Bu Ahn

    1988-01-01

    The characteristics of the corrosion fatigue cracking of both TIG weld heat affected zone and base metal for austenitic stainless steel were investigated under the environments of various specific resistance and the air. The corrosion fatigue crack initiation sensitivity was quantitatively investigated for SUS 304 weldments in the various specific resistances. Also, the characteristics of corrosion fatigue cracking for the weldments were investigated from mechanical, electrochemical, and microstructural point of view. Main results obtained are as follows: (1) The corrosion fatigue crack initiation sensitivity on the base metal and weld hea affected zone increases as the specific resistance of corrosion environment decreases, and the sensitivity of the weld heat affected zone appears increasing more than that of the base metal. (2) The corrosion potentials of various specific resistances are almost constant in initial corrosion fatigue cracking, but the corrosion potential becomes less noble promptly with the corrosion fatigue crack growth as the specific resistances decrease. (3) The corrosion fatigue crack growth of the weld heat affected zone rapid than that of the base metal, because of the softening and the less noble potential caused by welding heat cycle

  6. Thermal stability of the structural features in the superhydrophobic boehmite films on austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Xiaoxue [Department of Materials Science, Tampere University of Technology, P.O. Box 589, FI-33101 Tampere (Finland)], E-mail: xiaoxue.zhang@tut.fi; Honkanen, Mari [Department of Materials Science, Tampere University of Technology, P.O. Box 589, FI-33101 Tampere (Finland); Jaern, Mikael; Peltonen, Jouko [Department of Physical Chemistry, Abo Akademi University, Porthaninkatu 3-5, FI-20500 Turku (Finland); Pore, Viljami [Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki (Finland); Levaenen, Erkki; Maentylae, Tapio [Department of Materials Science, Tampere University of Technology, P.O. Box 589, FI-33101 Tampere (Finland)

    2008-06-15

    Boehmite thin film with 50-100 nm surface flake structure has been synthesized on AISI 316 type austenitic stainless steel by immersing boehmite gel film into boiling water. When further coated with hydrolyzed (heptadecafluoro-1,1,2,2-tetrahydrodecyl) trimethoxysilane (FAS), the boehmite film becomes superhydrophobic with a contact angle for water of 152 deg. The superhydrophobic property results from both the nanoscale surface flake structure and the low surface energy of the FAS top layer. The topography of such film was revealed by atomic force microscope (AFM) and a set of roughness parameters of such film was discussed. The degradation of superhydrophobicity of the surface was studied as a function of the heat-treatment temperatures. Below 600 deg. C, the surface remained to be superhydrophobic with the FAS top layer. Above 700 deg. C, the surface was not superhydrophobic anymore due to a gradual loss in surface roughness which was revealed by field emission scanning electron microscope (FESEM). A phase change from boehmite to {gamma}-Al{sub 2}O{sub 3} occurred during the heat-treatments from 700 to 900 deg. C which was studied by the selected area electron diffraction (SAED) patterns from the transmission electron microscope (TEM) measurement.

  7. Welding-induced mechanical properties in austenitic stainless steels before and after neutron irradiation

    Science.gov (United States)

    Stoenescu, R.; Schäublin, R.; Gavillet, D.; Baluc, N.

    2007-03-01

    The effects of neutron irradiation on the mechanical properties of welded joints made of austenitic stainless steels have been investigated. The materials are welded AISI 304 and AISI 347, so-called test weld materials, irradiated with neutrons at 573 K to doses of 0.3 and 1.0 dpa. In addition, an AISI 304 from a decommissioned pressurised water reactor, so-called in-service material, which had accumulated a maximum dose of 0.35 dpa at about 573 K, was investigated. The mechanical properties of heat-affected zones and base materials were analysed before and after irradiation. Tensile parameters were determined at room temperature and at 573 K, for all materials and irradiation conditions. In the test weld materials it is found that radiation hardening is lower and loss of ductility is higher in the heat-affected zone than in the base material. In the in-service material radiation hardening is about the same in heat-affected zone and base material. After irradiation, deformation takes place by stacking faults and twins, at both room temperature and high temperature, contrary to unirradiated materials, where deformation takes place by twinning at room temperature and by dislocation cells at high temperature. No defect free channels are observed.

  8. Hydrogen emission in fatigue process of hydrogen-charged austenitic stainless steels

    Science.gov (United States)

    Hayashida, Katsuya; Matsunaga, Hisao; Endo, Masahiro

    2010-03-01

    The acceleration of hydrogen diffusion in the fatigue process of AISI type 304 and 316L meta-stable austenitic stainless steels was studied by paying attention to the relation between fatigue slip bands and hydrogen emission. Slip bands were formed in tension-compression fatigue tests of round specimens in ambient air, and then the specimens were cathodically charged with hydrogen. The location of hydrogen emission was microscopically visualized by means of the hydrogen microprint technique (HMT). Hydrogen was mainly emitted from slip bands on the surface of fatigued specimens. The depth of hydrogen diffusion into the specimens was also observed on the fatigue fracture surfaces by the HMT. The depth for a specimen hydrogen-charged before fatigue testing was about 50 μm at a maximum, whereas the depth for a specimen that was hydrogen-charged after slip bands had been formed in a preliminary fatigue test was about 300 μm. Those results suggested that slip bands act as a pathway where hydrogen will move preferentially.

  9. Variation behavior of residual stress distribution by manufacturing processes in welded pipes of austenitic stainless steel

    International Nuclear Information System (INIS)

    Ihara, Ryohei; Hashimoto, Tadafumi; Mochizuki, Masahito

    2012-01-01

    Stress corrosion cracking (SCC) has been observed near heat affected zone (HAZ) of primary loop recirculation pipes made of low-carbon austenitic stainless steel type 316L in the nuclear power plants. For the non-sensitization material, residual stress is the important factor of SCC, and it is generated by machining and welding. In the actual plants, welding is conducted after machining as manufacturing processes of welded pipes. It could be considered that residual stress generated by machining is varied by welding as a posterior process. This paper presents residual stress variation due to manufacturing processes of pipes using X-ray diffraction method. Residual stress distribution due to welding after machining had a local maximum stress in HAZ. Moreover, this value was higher than residual stress generated by welding or machining. Vickers hardness also had a local maximum hardness in HAZ. In order to clarify hardness variation, crystal orientation analysis with EBSD method was performed. Recovery and recrystallization were occurred by welding heat near the weld metal. These lead hardness decrease. The local maximum region showed no microstructure evolution. In this region, machined layer was remained. Therefore, the local maximum hardness was generated at machined layer. The local maximum stress was caused by the superposition effect of residual stress distributions due to machining and welding. Moreover, these local maximum residual stress and hardness are exceeded critical value of SCC initiation. In order to clarify the effect of residual stress on SCC initiation, evaluation including manufacturing processes is important. (author)

  10. High Temperature Tensile Properties of Unirradiated and Neutron Irradiated 20 Cr-35 Ni Austenitic Steel

    Energy Technology Data Exchange (ETDEWEB)

    Roy, R.B.; Solly, B.

    1966-12-15

    The tensile properties of an unirradiated and neutron irradiated (at 40 deg C) 20 % Cr, 35 % Ni austenitic steel have been studied at 650 deg C, 750 deg C and 820 deg C. The tensile elongation and mode of fracture (transgranular) of unirradiated specimens tested at room temperature and 650 deg C are almost identical. At 750 deg C and 820 deg C the elongation decreases considerably and a large part of the total elongation is non-uniform. Furthermore, the mode of fracture at these temperatures is intergranular and microscopic evidence suggests that fracture is caused by formation and linkup of grain boundary cavities. YS and UTS decrease monotonically with temperature. Irradiated specimens show a further decrease in ductility and an increase in the tendency to grain boundary cracking. Irradiation has no significant effect on the YS, but the UTS are reduced. The embrittlement of the irradiated specimens is attributed to the presence of He and Li atoms produced during irradiation and the possible mechanisms are discussed. Prolonged annealing of irradiated and unirradiated specimens at 650 deg C appears to have no significant effect on tensile properties.

  11. The Investigation of Strain-Induced Martensite Reverse Transformation in AISI 304 Austenitic Stainless Steel

    Science.gov (United States)

    Cios, G.; Tokarski, T.; Żywczak, A.; Dziurka, R.; Stępień, M.; Gondek, Ł.; Marciszko, M.; Pawłowski, B.; Wieczerzak, K.; Bała, P.

    2017-10-01

    This paper presents a comprehensive study on the strain-induced martensitic transformation and reversion transformation of the strain-induced martensite in AISI 304 stainless steel using a number of complementary techniques such as dilatometry, calorimetry, magnetometry, and in-situ X-ray diffraction, coupled with high-resolution microstructural transmission Kikuchi diffraction analysis. Tensile deformation was applied at temperatures between room temperature and 213 K (-60 °C) in order to obtain a different volume fraction of strain-induced martensite (up to 70 pct). The volume fraction of the strain-induced martensite, measured by the magnetometric method, was correlated with the total elongation, hardness, and linear thermal expansion coefficient. The thermal expansion coefficient, as well as the hardness of the strain-induced martensitic phase was evaluated. The in-situ thermal treatment experiments showed unusual changes in the kinetics of the reverse transformation (α' → γ). The X-ray diffraction analysis revealed that the reverse transformation may be stress assisted—strains inherited from the martensitic transformation may increase its kinetics at the lower annealing temperature range. More importantly, the transmission Kikuchi diffraction measurements showed that the reverse transformation of the strain-induced martensite proceeds through a displacive, diffusionless mechanism, maintaining the Kurdjumov-Sachs crystallographic relationship between the martensite and the reverted austenite. This finding is in contradiction to the results reported by other researchers for a similar alloy composition.

  12. 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. We intended to demonstrate that SECIS can be adapted for post-processing of clad tubing to significantly enhance mechanical properties (hardness, wear resistance, and fatigue life), corrosion resistance, resistance to stress–corrosion cracking (hydrogen-induced embrittlement), and – potentially – radiation resistance (against electron-, neutron-, or ion-radiation damage). To test this hypothesis, we measured various relevant properties of the surface-engineered alloys and compared them with corresponding properties of the non–treated, as-received alloys. In particular, we studied the impact of heat exposure corresponding to BWR (boiling-water reactor) working and accident (loss-of-coolant) conditions and the effect of ion irradiation.

  13. Creep rupture properties of indigenously developed 304 HCu austenitic stainless steel

    International Nuclear Information System (INIS)

    Ganesan, V.; Laha, K.; Bhaduri, A.K.

    2016-01-01

    The 304HCu austenitic stainless steel tubes are being produced for the first time indigenously in India. Creep tests have been carried out at 923 K and 973 K on two heats with different solution annealed conditions. Stress levels ranged from 180 - 300 MPa at 923 K and 100-170 MPa at 973 K. The creep curves showed a small instantaneous strain followed by primary, secondary and tertiary creep stages. The rupture lives varied in the range of 50 to 8700 hours. Higher rupture life was observed in the heat with higher solutionising temperature. The variation of creep rupture life with applied stress at different temperatures is compared with internationally reported data and it is found that the indigenous 304HCu SS tube material has creep rupture strength comparable with internationally reported data. The variation of steady state creep rate with stress showed a power law relationship. Rupture ductility generally found to decrease with increase in rupture life. SEM fractography revealed mixed mode failure with predominance of intergranular creep cavitation. (author)

  14. 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.

  15. 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.

  16. Mechanism-Based Modeling for Low Cycle Fatigue of Cast Austenitic Steel

    Science.gov (United States)

    Wu, Xijia; Quan, Guangchun; Sloss, Clayton

    2017-09-01

    A mechanism-based approach—the integrated creep-fatigue theory (ICFT)—is used to model low cycle fatigue behavior of 1.4848 cast austenitic steel over the temperature range from room temperature (RT) to 1173 K (900 °C) and the strain rate range from of 2 × 10-4 to 2 × 10-2 s-1. The ICFT formulates the material's constitutive equation based on the physical strain decomposition into mechanism strains, and the associated damage accumulation consisting of crack nucleation and propagation in coalescence with internally distributed damage. At room temperature, the material behavior is controlled by plasticity, resulting in a rate-independent and cyclically stable behavior. The material exhibits significant cyclic hardening at intermediate temperatures, 673 K to 873 K (400 °C to 600 °C), with negative strain rate sensitivity, due to dynamic strain aging. At high temperatures >1073 K (800 °C), time-dependent deformation is manifested with positive rate sensitivity as commonly seen in metallic materials at high temperature. The ICFT quantitatively delineates the contribution of each mechanism in damage accumulation, and predicts the fatigue life as a result of synergistic interaction of the above identified mechanisms. The model descriptions agree well with the experimental and fractographic observations.

  17. Mechanism of Dynamic Strain Aging in a Niobium-Stabilized Austenitic Stainless Steel

    Science.gov (United States)

    Zhou, Hongwei; Bai, Fengmei; Yang, Lei; Wei, Hailian; Chen, Yan; Peng, Guosheng; He, Yizhu

    2018-04-01

    Dynamic strain aging (DSA) behavior of a niobium (Nb)-stabilized austenitic stainless steel (TP347H) was studied from room temperature (RT) to 973 K via tensile testing, transmission electron microscopy (TEM), and internal friction (IF) measurements. The DSA effect is nearly negligible from 573 K to 673 K, and it becomes significant at temperatures between 773 K and 873 K with strain rates of 3 × 10-3 s-1, 8 × 10-4 s-1, and 8 × 10-5 s-1, respectively. The results indicate that a dislocation planar slip is dominant in the strong DSA regime. The Snoek-like peak located at 625 K is highly sensitive to the diffusion of free carbon (C) atoms in solid solution. C-Nb octahedrons are formed by C chemical affinity to substitutional Nb solute atoms. Octahedron structure is very stable and captures most free C atoms and inhibits DSA at low tensile test temperatures of 573 K to 673 K. At high test temperatures in the range from 773 K to 873 K, C-Nb octahedrons break up and release free C and Nb atoms, resulting in the stronger Snoek-like peak. The interaction between C atoms and dislocations is responsible for DSA at low temperatures ranging from 573 K to 673 K. At higher temperature of 773 K to 873 K, the Cr and Nb atoms lock the dislocations, and this formation contributes to DSA.

  18. Effect of initial grain size on dynamic recrystallization in high purity austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    El Wahabi, M. [Centre SMS, CNRS UMR 5146, Ecole Nationale Superieure des Mines de Saint-Etienne, 158, cours Fauriel-42023, Saint-Etienne Cedex 2 (France); Departamento de Ciencia de los Materiales e Ingenieria Metalurgica, ETSEIB - Universidad Politecnica de Cataluna, Av. Diagonal 647, 08028-Barcelona (Spain); Gavard, L. [Centre SMS, CNRS UMR 5146, Ecole Nationale Superieure des Mines de Saint-Etienne, 158, cours Fauriel-42023, Saint-Etienne Cedex 2 (France); Montheillet, F. [Centre SMS, CNRS UMR 5146, Ecole Nationale Superieure des Mines de Saint-Etienne, 158, cours Fauriel-42023, Saint-Etienne Cedex 2 (France); Cabrera, J.M. [Departamento de Ciencia de los Materiales e Ingenieria Metalurgica, ETSEIB - Universidad Politecnica de Cataluna, Av. Diagonal 647, 08028-Barcelona (Spain)]. E-mail: jose.maria.cabrera@upc.edu; Prado, J.M. [Departamento de Ciencia de los Materiales e Ingenieria Metalurgica, ETSEIB - Universidad Politecnica de Cataluna, Av. Diagonal 647, 08028-Barcelona (Spain)

    2005-10-15

    The influence of initial microstructure on discontinuous dynamic recrystallization (DDRX) has been investigated by using high purity and ultra high purity austenitic stainless steels with various initial grain sizes. After uniaxial compression tests at constant strain rates and various temperatures, the steady state microstructure or the state corresponding to the maximum strain ({epsilon} = 1) attained in the test was analyzed by scanning electron microscopy aided with automated electron back scattering diffraction. Recrystallized grain size d {sub rec} and twin boundary fraction f {sub TB} measurements were carried out. The mechanical behavior was also investigated by comparing experimental stress-strain curves with various initial grain sizes. DDRX kinetics was described by the classical Avrami equation. It was concluded that larger initial grain sizes promoted a delay in the DDRX onset in the two alloys. It was also observed that the softening process progressed faster for smaller initial grain sizes. The effect of initial grain size is larger in the HP material and becomes more pronounced at low temperature.

  19. Residual Stresses Due to Circumferential Girth Welding of Austenitic Stainless Steel Pipes

    Science.gov (United States)

    Tarak, Farzan

    Welding, as a joining method in fabrication of engineering products and structural elements, has a direct influence on thermo-mechanical behavior of components in numerous structural applications. Since these thermo-mechanical behaviors have a major role in the life of welding components, predicting thermo-mechanical effects of welding is a major factor in designing of welding components. One of the major of these effects is generation of residual stresses due to welding. These residual stresses are not the causes of failure in the components solely, but they will add to external loads and stresses in operating time. Since, experimental methods are time consuming and expensive, computational simulation of welding process is an effective method to calculate these residual stresses. This investigation focuses on the evaluation of residual stresses and distortions due to circumferential girth welding of austenitic stainless steel pipes using the commercial finite element software ESI Visual-Environment and SYSWELDRTM to simulate welding process. Of particular importance is the comparison of results from three different types of mechanics models: 1) Axisymmetric, 2) Shell, and 3) Full 3-D.

  20. Experimental and numerical investigation of formability for austenitic stainless steel 316 at elevated temperatures

    Directory of Open Access Journals (Sweden)

    Syed Mujahed Hussaini

    2014-01-01

    Full Text Available Sheet metal forming at elevated temperature is not much used in industries but it is going to be a very important process in the future. The present work is aimed to investigate the formability of austenitic stainless steel 316 at elevated temperatures. Limiting drawing ratio and thickness of the drawn cup are the indicators of formability in deep drawing. In the present investigation circular blanks are deep drawn at room temperature, 150 °C and 300 °C using a 20 ton hydraulic press coupled with a furnace. Finite element simulations are carried out using Dynaform with LS-Dyna solver. Simulations and experimental results show an increase in the limiting drawing ration as the temperature increases and a decrease in the thickness of the drawn cup without any fracture. An artificial neural network model is developed for the prediction of the cup thickness at different locations. Based on the input variables, such as distance from the center of the cup, temperature and LDR, a back propagation neural network model to predict the thickness as output was develop. The comparison between these sets of results indicates the reliability of the predictions. It was found that there is a good agreement between the experimental and predicted values.