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Sample records for austenitic steels approche

  1. Behaviour and damage of aged austenitic-ferritic steels: a micro-mechanical approach; Comportement et endommagement des aciers austeno-ferritiques vieillis: une approche micromecanique

    Energy Technology Data Exchange (ETDEWEB)

    Bugat, St

    2000-12-15

    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 {mu}m 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

  2. Developments in austenitic steels containing manganese

    International Nuclear Information System (INIS)

    Two broad categories of austenitic steels are considered in this review: (a) alloys based on the Fe-Mn-C system, typified by austenitic wear resistant (Hadfield) steels and (b) alloys based on the Fe-Mn-Cr system, typified by austenitic corrosion resistant steels. Advances made in recent years in understanding and improving the relevant properties and manufacturing methods of these steels are critically appraised. The development of austenitic manganese bearing high technology steels for fusion reactor and other non-magnetic applications, as well as those that can be used in cryogenic structures, is also considered. (author)

  3. High Mn austenitic stainless steel

    Science.gov (United States)

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

    2010-07-13

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

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

    International Nuclear Information System (INIS)

    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)

  5. Recycle of radiologically contaminated austenitic stainless steels

    International Nuclear Information System (INIS)

    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

  6. 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; alumina, and a stable essentially single phase FCC austenitic matrix microstructure, the austenitic matrix being essentially delta-ferrite free and essentially BCC-phase-free. A method of making austenitic stainless steel alloys is also disclosed.

  7. Explosive Surface Hardening of Austenitic Stainless Steel

    Science.gov (United States)

    Kovacs-Coskun, T.

    2016-04-01

    In this study, the effects of explosion hardening on the microstructure and the hardness of austenitic stainless steel have been studied. The optimum explosion hardening technology of austenitic stainless steel was researched. In case of the explosive hardening used new idea mean indirect hardening setup. Austenitic stainless steels have high plasticity and can be easily cold formed. However, during cold processing the hardening phenomena always occurs. Upon the explosion impact, the deformation mechanism indicates a plastic deformation and this deformation induces a phase transformation (martensite). The explosion hardening enhances the mechanical properties of the material, includes the wear resistance and hardness. In case of indirect hardening as function of the setup parameters specifically the flayer plate position the hardening increased differently. It was find a relationship between the explosion hardening setup and the hardening level.

  8. Austenitic stainless steels with cryogenic resistance

    International Nuclear Information System (INIS)

    The most used austenitic stainless steels are alloyed with chromium and nickel and have a reduced carbon content, usually lower than 0.1 % what ensures corresponding properties for processing by plastic deformation at welding, corrosion resistance in aggressive environment and toughness at low temperatures. Steels of this kind alloyed with manganese are also used to reduce the nickel content. By alloying with manganese which is a gammageneous element one ensures the stability of austenites. Being cheaper these steels may be used extensively for components and equipment used in cryogenics field. The best results were obtained with steels of second group, AMnNi, in which the designed chemical composition was achieved, i.e. the partial replacement of nickel by manganese ensured the toughness at cryogenic temperatures. If these steels are supplementary alloyed, their strength properties may increase to the detriment of plasticity and toughness, although the cryogenic character is preserved

  9. 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.

  10. Grain growth in heat resisting austenitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Denisova, I.K.; Zakharov, V.N.; Karpova, N.M.; Farber, V.M.

    1985-01-01

    A study was made on kinetics of grain growth in steels of 37Kh12N8G8 type alloyed by V, Nb, Ti, Mo, W. It was concluded that the nature of carbide phase and kinetics of its dissolution in heat resisting austenitic steels dictate steel tendency to grain growth. At the same time decrease of diffusion mobility of atoms in steel matrix during its alloying by titanium aid tungsten results in sufficient decrease of the tendency to grain growth and variation in grain size.

  11. Tritium in austenitic stainless steel vessels

    International Nuclear Information System (INIS)

    Austenitic stainless steels are normally recommended for components of hydrogen-handling equipment in applications where high in-service reliability is required. The literature leading to this recommendation is reviewed, and it is shown that AISI Type 316L stainless is particularly suitable for use in tritium-handling and storage systems. When made of this steel, the storage vessels will be extremely resistant to any degradation from tritium in both routine and accident conditions. (author)

  12. Austenitic stainless steels for cryogenic service

    Energy Technology Data Exchange (ETDEWEB)

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

    1985-09-19

    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.

  13. Corrosion of plasma nitrided austenitic stainless steels

    International Nuclear Information System (INIS)

    The corrosion behaviour of plasma nitrided austenitic stainless steel grades AISI 304, 316 and 321 was studied at various temperatures. Certain plasma nitriding cycles included a post-oxidation treatment. The corrosion rates were measured using linear polarisation technique. Results showed that corrosion rate increased with the plasma nitriding temperature. Minimum deterioration occurred at 653K. (author). 2 tabs., 4 figs., 10 refs

  14. Austenitic stainless steels for cryogenic service

    International Nuclear Information System (INIS)

    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

  15. 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.

  16. 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.

  17. Corrosion of austenitic steel in sodium loops

    International Nuclear Information System (INIS)

    The possibility of predicting corrosion effects for austenitic steel exposed to liquid sodium with an analytical diffusion model is presented. The analytically predicated corrosion effects are compared with experimental measurements of corrosion effects achieved in an accurately controlled sodium loop. The diffusion model is described with figures showing disc sample weight loss and sodium flow guidance tube chromium and nickel profiles. Finally, the concentration profile in the fuel rod wall (diffusion model) is presented for iron, chromium and nickel

  18. Electropolishing and chemical passivation of austenitic steel

    Directory of Open Access Journals (Sweden)

    A. Baron

    2008-12-01

    Full Text Available Purpose: The aim of the paper is investigations a dependence between the parameters of the electrochemical treatment of austenitic steel and their electrochemical behavior in Tyrod solution.Design/methodology/approach: Specimens (rode 30 mm × ø1 mm were to give in to the surface treatment – mechanically polishing, electrolytic polishing and passivation with various parameter. Electrochemical investigations concerning the corrosion resistance of austenitic steel samples were carried out by means of the potentiodynamic and electrochemical impedance spectroscopy method.Findings: The analysis of the obtained results leads to the conclusion that chemical passivation affects also the chemical composition of the passive layer of steel and changes its resistance to corrosion. Electrolytic polishing improves corrosion resistance, as can be proved by the shift of the value of the corrosion potential and break-down potential of the passive layer and the initiation of pittings.Research limitations/implications: The obtained results are the basis for the optimization of anodic passivation parameters of the austenitic steel as a metallic biomaterial. The future research should be focused on selected more suitable parameters of the electrochemical impedance spectroscopy test to better describe process on the solid/ liquid interface.Practical implications: In result of the presented investigations it has been found that the best corrosion resistance can be achieved thanks to the application of electrolytic polishing of the steel in a special bath and chemical passivation in nitric (V acid with an addition of chromic (VI acid temperature t = 60°C for one hour.Originality/value: The enormous demand for metal implants has given rise to a search for cheap materials with a good biotolerance and resistance to corrosion. Most commonly used are steel implants assigned to remain in the organism for some limited time only. It was compare two electrochemical methods

  19. Electron beam welding of austenitic stainless steel

    International Nuclear Information System (INIS)

    Austenitic stainless steel is used for liquid metal-cooled fast breeder reactors with operating temperature of about 550 deg C, because its elevated temperature properties are excellent and the results of use are abundant. The welded joints in LMFBRs require high degree of safety, and the application of electron beam welding is studied to make welding joints of high quality. When the inelastic deformation in a certain limit is allowed as prescribed in the ASME Code, Case 1592, the elevated temperature properties of the welded joints of structures are particularly important. The materials tested were 10 mm thick plates of SUS 304, SUS 316 and SUS 321 steels, and 150 kV - 40 mA electron beam welder was employed. The method of welding was one side, one pass Uranami welding, and first, the appropriate welding conditions were decided. Elevated temperature tensile test was carried out on the parent materials and welded joints by electron beam welding and coated arc welding. Creep rupture test and elevated temperature fatigue test were also carried out. In EB-welded austenitic stainless steel, delta ferrite is scattered finely in austenite, and its quantity is very small and less than 1.5%. The tensile strength and 0.2% proof stress of EB-welded joints are almost same as those of parent materials. The creep rupture and fatigue properties of the joints are also close to those of parent materials. (Kako, I.)

  20. Embrittlement of austenitic stainless steel welds

    International Nuclear Information System (INIS)

    To prevent hot-cracking, austenitic stainless steel welds generally contain a small percent of delta ferrite. Although ferrite has been found to effectively prevent hot-cracking, it can lead to embrittlement of welds when exposed to elevated temperatures. The aging behavior of type-308 stainless steel weld has been examined over a range of temperatures 475--850 C for times up to 10,000 hrs. Upon aging, and depending on the temperature range, the unstable ferrite may undergo a variety of solid state transformations. These phase changes creep-rupture and Charpy impact properties

  1. Fabrication and ageing of cast austenitic steels

    International Nuclear Information System (INIS)

    An investigation has been undertaken to determine the magnitude of any reduction in properties which may occur in cast duplex stainless steels and weldments during long term exposure to reactor operating conditions. Test panels were fabricated in CF3 stainless steel by a manual metal arc (MMA) process using 19.9.L (Type 308L) consumables. The mechanical properties and intergranular corrosion resistance of parent material and weldments were measured following accelerated ageing at 3750 and 4000C for up to 10,000 hours. Both the impact energy and J/sub R/ fracture toughness properties of the cast austenitic/ferritic stainless steel were reduced following aging at 4000C for 10,000 hours, whereas austenitic stainless steel MMA weld metals exhibited a reduction in J/sub R/ fracture toughness but no change in impact energy. Even in the unaged state, MMA weld metals were shown to have a much lower resistance to stable crack growth than the parent cast steel, and, following aging, there is a further reduction in the ductile tearing resistance of such weld metals. Therefore, in any assessment of the structural integrity of the reactor coolant pump bowl for a pressurized water reactor (PWR), the weld metal fracture properties during service are likely to be of considerable importance

  2. Ultrasonic testing of austenitic stainless steel welds

    International Nuclear Information System (INIS)

    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: 550 from SUS side, 450 from CS side) and in cast stainless steel welds (refraction angle: 450, 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 450 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)

  3. Grain boundary strengthening in austenitic nitrogen steels

    International Nuclear Information System (INIS)

    The effect of nitrogen and carbon on the strengthening of the austenitic steel Cr18Ni16Mn10 by grain boundaries is studied. It is established in accordance with previous results that contrary to carbon nitrogen increases the coefficient k in the Hall-Petch equation markedly. Because of a pronounced planar slip induced by nitrogen and the absence of any noticeable segregation of nitrogen atoms at the grain boundaries, nitrogen austenite presents an excellent object for testing different existing models of grain boundary strengthening (pile-up, grain boundary dislocation sources, work hardening theories). Based on the analysis of available data and measurements of interaction between nitrogen (carbon) atoms and dislocations it is shown that the nitrogen effect can be attributed to a strong blocking of dislocation sources in grains adjacent to those where the slip started. (orig.)

  4. Nickel-free austenitic stainless steels for medical applications

    OpenAIRE

    Ke Yang and Yibin Ren

    2010-01-01

    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 stainl...

  5. Ion-nitriding of austenitic stainless steels

    International Nuclear Information System (INIS)

    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

  6. Flow lines and microscopic elemental inhomogeneities in austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Mosley, Jr, W C

    1982-01-01

    Flow lines in mechanically formed austenitic stainless steels are known to influence fracture behavior. Enhancement of flow lines by chemical etching is evidence of elemental inhomogeneity. This paper presents the results of electron microprobe analyses to determine the nature of flow lines in three austenitic stainless steels: 21Cr-6Ni-9Mn, 304L, and 19Ni-18Cr.

  7. Wear behavior of austenite containing plate steels

    Science.gov (United States)

    Hensley, Christina E.

    As a follow up to Wolfram's Master of Science thesis, samples from the prior work were further investigated. Samples from four steel alloys were selected for investigation, namely AR400F, 9260, Hadfield, and 301 Stainless steels. AR400F is martensitic while the Hadfield and 301 stainless steels are austenitic. The 9260 exhibited a variety of hardness levels and retained austenite contents, achieved by heat treatments, including quench and tempering (Q&T) and quench and partitioning (Q&P). Samples worn by three wear tests, namely Dry Sand/Rubber Wheel (DSRW), impeller tumbler impact abrasion, and Bond abrasion, were examined by optical profilometry. The wear behaviors observed in topography maps were compared to the same in scanning electron microscopy micrographs and both were used to characterize the wear surfaces. Optical profilometry showed that the scratching abrasion present on the wear surface transitioned to gouging abrasion as impact conditions increased (i.e. from DSRW to impeller to Bond abrasion). Optical profilometry roughness measurements were also compared to sample hardness as well as normalized volume loss (NVL) results for each of the three wear tests. The steels displayed a relationship between roughness measurements and observed wear rates for all three categories of wear testing. Nanoindentation was used to investigate local hardness changes adjacent to the wear surface. DSRW samples generally did not exhibit significant work hardening. The austenitic materials exhibited significant hardening under the high impact conditions of the Bond abrasion wear test. Hardening in the Q&P materials was less pronounced. The Q&T microstructures also demonstrated some hardening. Scratch testing was performed on samples at three different loads, as a more systematic approach to determining the scratching abrasion behavior. Wear rates and scratch hardness were calculated from scratch testing results. Certain similarities between wear behavior in scratch testing

  8. Nickel-free austenitic stainless steels for medical applications

    Directory of Open Access Journals (Sweden)

    Ke Yang and Yibin Ren

    2010-01-01

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

  9. The effect of retained austenite on steel fracture toughness

    International Nuclear Information System (INIS)

    This paper is an attempt of reviewing the outlooks about the favourable influence of retained austenite on fracture toughness of tool steels. The tests were performed on the samples made of the new 70HG2MF steel in which the fraction of retained austenite was changed by subquenching or by changing the austenitizing temperature. It was revealed that in the subquenched samples retained austenite affects strongly the increase of fracture toughness. On the other hand, however, in the samples austenitized at growing temperatures, the effect of this phase on fracture toughness is not so univocal since not only the volume fraction of retained austenite is subjected to changes but also the character of fractures and the grain size. (author)

  10. Austenite Recrystallization and Controlled Rolling of Low Carbon Steels

    Institute of Scientific and Technical Information of China (English)

    DU Lin-xiu; ZHANG Zhong-ping; SHE Guang-fu; LIU Xiang-hua; WANG Guo-dong

    2006-01-01

    The dynamic recrystallization and static recrystallization in a low carbon steel were investigated through single-pass and double-pass experiments. The results indicate that as the deformation temperature increases and the strain rate decreases, the shape of the stress-strain curve is changed from dynamic recovery shape to dynamic recrystallization shape. The austenite could not recrystallize within a few seconds after deformation at temperature below 900 ℃. According to the change in microstructure during deformation, the controlled rolling of low carbon steel can be divided into four stages: dynamic recrystallization, dynamic recovery, strain-induced ferrite transformation, and rolling in two-phase region. According to the microstructure after deformation, the controlled rolling of low carbon steel can be divided into five regions: non-recrystallized austenite, partly-recrystallized austenite, fully-recrystallized austenite, austenite to ferrite transformation, and dual phase.

  11. X-ray fractography studies on austenitic stainless steels

    NARCIS (Netherlands)

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

    1996-01-01

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

  12. Effects of austenitizing temperature in quenched niobium steels

    International Nuclear Information System (INIS)

    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)

  13. Austenitic steels for boiler elements in USC power plants

    OpenAIRE

    A. Zieliński

    2013-01-01

    Purpose: Characteristics of functional properties of austenitic-based steels used for construction of boilers with supercritical and ultra-supercritical steam parameters.Design/methodology/approach: For selected austenitic steels in as-received state and after long-term annealing microstructural investigations were carried out with scanning and transmission electron microscope.Findings: Selected characteristics of structure and functional properties of materials to be used for critical elemen...

  14. Hydrogen Effects on Austenitic Stainless Steels and High-Strength Carbon Steels

    OpenAIRE

    Todoshchenko, Olga

    2015-01-01

    The resistance to hydrogen embrittlement is an important factor in the development of new steel grades for a variety of applications. The thesis describes investigations on hydrogen effects on two classes of steels - austenitic stainless steels and advanced high-strength carbon steels. Hydrogen solubility and diffusion in metastable austenitic stainless steels are studied with thermal desorption spectroscopy (TDS). This method, together with the mathematical modeling of the processes of hy...

  15. Friction Stir Welding of austenitic stainless steels

    Directory of Open Access Journals (Sweden)

    C. Meran

    2010-11-01

    Full Text Available Purpose: Friction Stir Welding (FSW was applied austenitic stainless steels that is difficult to weld using FSW technique. Proper weld can be obtained by using appropriate welding parameter. In this paper, the effect of different tool rotational speeds, traverse speeds, compressive tool forces, and tool angles was investigated.Design/methodology/approach: The dimension of 3 mm x 75 mm x 150 mm two stainless steel plates were used and butt welded by FSW method using 7.5 kW vertical head milling machine. All welded test specimens were prepared perpendicular to the weld line in order to determine the mechanical properties and tested with 12 MPa/sec stress rate under stress control using a servo-hydraulic Instron 8801. Microstructure of the welding zone and macrograph of the heat affected zone was investigated by SEM.Findings: The average grain size in the SZ was between 3 and 7 μm, which is smaller than that in the BM. The average grain size in the HAZ was about 20 μm, which is half of that in the BM.Fine-grained microstructures are present the welded area. The dark bands observed in the weld zone were also detected the microstructure of the transition zone. Dark and narrow bands do not consist of pores or cavities. It was determined that these bands do not process an ultra fine-grained microstructure. They are Cr2O3 oxide layers which over the surface of stainless steels may have been ruptured during friction stir welding and may form bands inside the welding bead due to stirring.Research limitations/implications: The proper cooling system helps to prevent the stirrer tool from the deformation.Practical implications: The strength of the welded zone of AISI 304 stainless steel can be easily found by implementing welding design parameters and high quality joints can be obtained.Originality/value: This study was performed in the frame of the TUBITAK project no 106M504, „Friction Stir Weldability of Stainless Steels and Investigation of the

  16. MODULATED STRUCTURES AND ORDERING STRUCTURES IN ALLOYING AUSTENITIC MANGANESE STEEL

    Institute of Scientific and Technical Information of China (English)

    L. He; Z.H. Jin; J.D. Lu

    2001-01-01

    The microstructure of Fe-10Mn-2Cr-1.5C alloy has been investigated with transmission electron microscopy and X-ray diffractometer. The superlattice diffraction spots and satellite reflection pattrens have been observed in the present alloy, which means the appearence of the ordering structure and modulated structure in the alloy. It is also proved by X-ray diffraction analysis that the austenite in the alloy is more stable than that in traditional austenitic manganese steel. On the basis of this investigation,it is suggested that the C-Mn ordering clusters exist in austenitic manganese steel and the chromium can strengthen this effect by linking the weaker C-Mn couples together,which may play an important role in work hardening of austenitic manganese steel.

  17. Austenite grain growth calculation of 0.028% Nb steel

    Directory of Open Access Journals (Sweden)

    Priadi D.

    2011-01-01

    Full Text Available Modeling of microstructural evolution has become a powerful tool for materials and process design by providing quantitative relationships for microstructure, composition and processing. Insufficient attention has been paid to predicting the austenite grain growth of microalloyed steel and the effect of undissolved microalloys. In this research, we attempted to calculate a mathematical model for austenite grain growth of 0.028% Nb steel, which can account for abnormal grain growth. The quantitative calculation of austenite grain growth generated from this model fit well with the experimental grain growth data obtained during reheating of niobium steels. The results of this study showed that increasing the temperature increases the austenite grain size, with a sharp gradient observed at higher temperatures.

  18. The influence of fabricating conditions and stability of austenite on forming behaviour of austenitic stainless steels

    International Nuclear Information System (INIS)

    The object of the investigation is the effect of various conditions of cold rolling austenitic stainless steels on the mechanical and technological properties and on the behaviour during forming with requirements in stretching and deep drawing. Fabricating 3 coils of various stability of austenite the degree of cold forming between the annealing processes is varied by cold rolling from the thickness of hot rolled coil to final thickness without or with one or two intermediate annealings. The most important results for cold forming sheets are: most favourable stretch forming behaviour is gained with instable austenitic steels, becomes better with increasing sheet thickness most favourable deep drawing behaviour is gained with highest degrees of cold rolling before final annealing, is undependent from the stability of austenite. Favourable is cold rolling to the highest degree before intermediate annealing, whilst the deformation before final annealing is of greater importance. According to the results conditions can be given for cold rolling to get best forming behaviour. (orig.)

  19. He blisters on welded austenitic stainless steel

    International Nuclear Information System (INIS)

    Surface blisters of single-crystal and polycrystalline metals induced by He-ion irradiation have been investigated by many researchers and several blister-formation mechanisms have been proposed. But there is no report on what blister densities and blister sizes are to be expected on a welded 316 austenitic stainless steel in use as a fusion reactor material. An experiment was carried out, and details are given. The exfoliation of blisters was almost not observed until the total dose of 2 x 1022 ions m-2 was reached. A figure shows the blister densities for every increment in blister diameter of 0.5 μm on the base and weld metals. A second figure shows the corresponding blister densities on the base and weld metals annealed at 653 K for 4.5 ksec after He-ion irradiation. The total blister densities of the base metals decrease to 4.3 to 5.5 x 1010 blisters m-2 and the average blister sizes increase to 2.8 to 3.2 μm. This phenomenon indicates that the implanted He ions diffuse in the weld and base metals. The blister sizes on the weld metals are smaller than those on the base metals and the densities on the weld metals are greater than those on the base metals. (author)

  20. X-ray stress measurement of high manganese austenitic steels

    International Nuclear Information System (INIS)

    By using psi0 oscillation method with CrKβ γ(311) diffraction, the X-ray stress measurement was made on five specimens, which were obtained by water toughening and various plastic working treatments (tensile pre-strain, hammered and explosive hardening) from Hadfield's high manganese austenitic steel, and their mechanical elastic constants, X-ray elastic constants and the accuracy of measurement were examined. The results obtained are as follows: (1) The mechanical elastic constant for 13% Mn austenitic steel after water toughening was 18900 kg/mm2. This value gradually decreased with increasing tensile pre-strain. But it changed little when the specimen was treated by hammered or explosive hardening. (2) The K-value (K sub(X) = -37.26 kg/mm2/deg) of austenitic steel adopted in the standard method of X-ray stress measurement is considered suitable for the X-ray stress measurement of 13% Mn austenitic steel which has not been subjected to severe plastic deformation. (3) The error in stress measurement Δσ in the X-ray stress measurement of high manganese austenitic steel becomes larger, depending more on the statistical fluctuation parameter, than that of ferritic steel. (author)

  1. Magnetic State of Deformed Austenite Before and After Martensite Nucleation in Austenitic Stainless Steels

    Institute of Scientific and Technical Information of China (English)

    GennadiiVSnizhnoi; MariyaSRasshchupkyna’

    2012-01-01

    The effect of the increase in the paramagnetic susceptibility of austenite up to the true value of the deformation-induced martensite transition point es has been experimentally established in steels X6CrNiTil8-10 (correspon& ing to AISI 321 steels). At this point nucleation and accumulation of martensite with the increase in the extent of de- formation but at a constant magnetic state of austenite takes place.

  2. Breakdown of protective oxide films on ferritic and austenitic steels

    International Nuclear Information System (INIS)

    The kinetics and morphology of scale formation on a 9% Cr ferritic and an 18% Cr austenitic steel in high pressure CO2 are discussed. For the ferritic steel, the normal protective oxidation mode is growth of a duplex scale with an Fe3O4 outer layer and an (Fe, Cr) spinel inner layer. After long times at elevated temperatures, the protective scale may break down. The more rapid attack that follows requires conjoint oxidation and carbon deposition. The austenitic steel is not susceptible to this kind of breakaway attack, but a 'breakaway' transition from M2O3 to duplex spinel growth can be induced by temperature cycling. (author)

  3. Effect of Geobacter sulfurreducens on the microbial corrosion of mild steel, ferritic and austenitic stainless steels

    OpenAIRE

    Mehanna, Maha; Basséguy, Régine; Délia, Marie-Line; Bergel, Alain

    2009-01-01

    The influence of Geobacter sulfurreducens was tested on the anaerobic corrosion of four different steels: mild steel 1145, ferritic steel 403 and austenitic steels 304L and 316L. Within a few hours, the presence of cells induced a free potential (Eoc) ennoblement around +0.3 V on 1145 mild steel, 403 ferritic steel and 304L austenitic steels and slightly less on 316L. The kinetics of Eoc ennoblement depended on the amount of bacteria in the inoculum, but the final potential value depended ess...

  4. EFFECT OF CHEMICAL COMPOSITION ON RETAINED AUSTENITE IN TRIP STEEL

    Institute of Scientific and Technical Information of China (English)

    Y. Chen; X. Chen; Q.F. Wang; G.L. Yuan; C.Y. Li; X.Y. Li; Y.X. Wang

    2002-01-01

    The systematic chemical compositions including common C, Si, Mn, Al, and micro- alloying elements of Ti and Nb were designed for high volume fraction of retained austenite as much as possible. The thermo-cycle experiments were conducted by using Gleeble 2000 thermo-dynamic test machine for finding the appropriate composition. The experimental results showed that chemical composition had a significant effect on retained austenite, and the appropriate compositions were determined for commercial production of TRIP steels.

  5. Hot-working behaviour of high-manganese austenitic steels

    OpenAIRE

    L.A. Dobrzański; A. Grajcar; W. Borek

    2008-01-01

    Purpose: The work consisted in investigation of newly elaborated high-manganese austenitic steels with Nb and Ti microadditions in variable conditions of hot-working.Design/methodology/approach: Determination of processes controlling strain hardening was carried out in continuous compression test using Gleeble 3800 thermo-mechanical simulator.Findings: It was found that they have austenite microstructure with numerous annealing twins in the initial state. Continuous compression tests ...

  6. Propagation of fissures by fatigue in metastable austenitic steels

    International Nuclear Information System (INIS)

    Many works discuss martensitic transformation in austenitic stainless steels, and especially transformations induced by temperature or monotonic charges. Some studies have focused on the propagation of fissures by fatigue in metastable austenitic test pieces, which display reduced propagation speed of fissures when martensite is induced at the end of the fissure. However, controversy still persists with regard to the role of different parameters in the fatigue behavior of these steels. This work presents preliminary analysis results of fissure propagation by fatigue using test pieces obtained from 1 mm thick sheets of austenitic steel EN 1.4318 (AISI 301LN) with 17% Cr, 7% Ni, low C and alloyed with N. The tests were performed at R charge relations (relation between minimum and maximum charge) of 0.1, 0.3, 0.5 and 0.7. The results were analyzed applying the concepts of the two driving forces concept (cw)

  7. Microstructural characterisation of carbon implanted austenitic stainless steel

    International Nuclear Information System (INIS)

    Low carbon (316L) austenitic stainless steel has been implanted with carbon ions with a fluence of 5 x 1017 C ions/cm2 using an ion energy of 75 keV. The effect of carbon ion implantation on the microstructure of the austenitic steel has been examined in cross-section using transmission electron microscopy (TEM) both before and after implantation, and the implantation data correlated with a computer based simulation, TRIM (Transport and Range of Ions in Matter). It has been found that the high-fluence carbon ion implantation modified the microstructure of the steel, as demonstrated by the presence of two amorphous layers separated by a layer of expanded austenite

  8. Microstructural characterisation of carbon implanted austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, M.E. [Scientific Affairs Research Group, Stryker Orthopaedics, Raheen Business Park, Limerick (Ireland)]. E-mail: matthew.murphy@stryker.com; Insley, G.M. [Scientific Affairs Research Group, Stryker Orthopaedics, Raheen Business Park, Limerick (Ireland); Laugier, M.T. [Department of Physics, University of Limerick, Limerick (Ireland); Newcomb, S.B. [Sonsam Ltd., Glebe Laboratories, Newport, Tipperary (Ireland)

    2005-06-01

    Low carbon (316L) austenitic stainless steel has been implanted with carbon ions with a fluence of 5 x 10{sup 17} C ions/cm{sup 2} using an ion energy of 75 keV. The effect of carbon ion implantation on the microstructure of the austenitic steel has been examined in cross-section using transmission electron microscopy (TEM) both before and after implantation, and the implantation data correlated with a computer based simulation, TRIM (Transport and Range of Ions in Matter). It has been found that the high-fluence carbon ion implantation modified the microstructure of the steel, as demonstrated by the presence of two amorphous layers separated by a layer of expanded austenite.

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

    Science.gov (United States)

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

    2016-05-01

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

  10. Structure and mechanical properties of austenitic steel after cold rolling

    Directory of Open Access Journals (Sweden)

    A. Kurc-Lisiecka

    2011-02-01

    Full Text Available Purpose: The aim of the paper is to determine the influence of the cold plastic deformation within the range 18-79% and heat treatment in a temperature range of 500 to 700°C on the microstructure and mechanical properties of austenitic stainless steel grade X5CrNi18-8.Design/methodology/approach: The investigations included observations of the microstructure on a light microscope, researches of mechanical properties in a static tensile test and hardness measurements made by Vickers’s method. The analysis of the phase composition was carried out on the basis of X-ray researches. Whereas, X-ray quantitative phase analysis was carried out by the Averbach Cohen method.Findings: Heat treatment of X5CrNi18-8 stainless steel in the range 500-700°C causes a significant decrease of the mechanical properties (Rm, Rp0.2 and increase of elongation (A. Hardness of investigated steel drops with decrease of cold working degree and increase of heat treatment temperature.Research limitations/implications: The analysis of the obtained results permits to state that the heat treatment causes an essential changes of the microstructure connected with fading of cold deformation. Heating of cold rolled austenitic stainless steels can cause a reverse transformation α’ → γ.Practical implications: Two-phase structure α’+γ of austenitic Cr-Ni steel in deformed state working at elevated temperature undergo a transformation. It significantly influences mechanical properties of steel. Austenite phase undergoes a recrystallization, while martensite α’ phase undergoes reverse transformation.Originality/value: The analytic dependence of the yield point of the investigated steel on the cold working degree in cold rolling process has been confirmed. Revealing this relation is of essential practical importance for the technology of sheetmetal forming of austenitic steel.

  11. 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...

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

    Directory of Open Access Journals (Sweden)

    M. Głowacka

    2012-12-01

    Full Text Available 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 withdrawal of the generator from the operation was leaks in the coil tube caused by corrosion damage. The metallographic investigations were performed with the use of light microscope and scanning electron microscope equipped with the EDX analysis attachment.Findings: Examinations of coil tubes indicated severe corrosion damages as pitting corrosion, stress corrosion cracking, and intergranular corrosion within base material and welded joints. Causes of corrosion was defined as wrong choice of austenitic steel grade, improper welding technology, lack of quality control of water supply and lack of surface treatment of stainless steel pipes.Research limitations/implications: It was not known the quality of water supply of steam generator and this was the reason for some problems in the identification of corrosion processes.Practical implications: Based on the obtained research results and literature studies some recommendations were formulated in order to avoid failures in the application of austenitic steels in the steam generators. These recommendations relate to the selection of materials, processing technology and working environment.Originality/value: Article clearly shows that attempts to increase the life time of evaporator tubes and steam coils by replacing non-alloy or low alloy structural steel by austenitic steel, without regard to restrictions on its use, in practice often fail.

  13. Austenite decomposition in carbon steel under dynamic deformation conditions

    Directory of Open Access Journals (Sweden)

    A. Nowotnik

    2007-01-01

    Full Text Available Purpose: The main purpose of this paper was to estimate the effect of the dynamic conditions resulting fromdeformation process on the austenite decomposition into ferrite and pearlite (A→F+P in the commercial carbon steel.Design/methodology/approach: In the paper flow stress curves and microstructure of deformed steel within therange of discontinuous (austenite to pearlite and austenite to ferrite transformation at different strain rates andcooling rates were presented. The microstructure of hot deformed samples was tested by means of an opticaland electron microscopy.Findings: It was shown that the flow localization during hot deformation and preferred growth of the pearlitecolonies at shear bands was very limited. The most characteristic feature of the microstructure observed for hotdeformed samples was the development of carbides that nucleated along elongated ferrite grains.Research limitations/implications: In spite of intense strain hardening due to deformation and phasetransformation overlapping, microstructural observation of deformed samples did not reveal significant flowlocalization effects or heterogeneous distribution of the eutectoid components. Therefore, complementary testsshould be carried out on the steel with higher strain above the 0.5 value.Originality/value: There was no data referred to particular features of the dynamic processes, such as dynamicrecrystallization and recovery, dynamic precipitation, that can occur during austenite decomposition into ferrite,and especially during discontinuous transformation of austenite to pearlite.

  14. Austenitic stainless steel patterning by plasma assisted diffusion treatments

    International Nuclear Information System (INIS)

    The new concept of surface texturing or surface patterning on austenitic stainless steel by plasma assisted diffusion treatment is presented in this paper. It allows the creation of uniform micro or nano relief with regularly shaped asperities or depressions. Plasma assisted diffusion treatments are based on the diffusion of nitrogen and/or carbon in a metallic material at moderate to elevated temperatures. Below 420 deg. C, a plasma assisted nitriding treatment of austenitic stainless steel produces a phase usually called expanded austenite. Expanded austenite is a metastable nitrogen supersaturated solid solution with a disordered fcc structure and a distorted lattice. The nitrided layer with the expanded austenite is highly enriched in nitrogen (from 10 to 35 at%) and submitted to high compressive residual stresses. From mechanical consideration, it is shown that the only possible deformation occurs in the direction perpendicular to the surface. Such an expansion of the layer from the initial surface of the substrate to the gas phase is used here for surface patterning of stainless steel parts. The surface patterning is performed by using masks (TEM grid) and multi-dipolar plasmas.

  15. Welding technology trend of austenitic stainless steels for cryogenic services

    International Nuclear Information System (INIS)

    At present, the large use of stainless steel in cryogenic field is the storage and transport system for liquefied gas represented by LNG and the nuclear fusion reactors utilizing superconductivity. Most of the stainless steel used for the LNG system is austenitic stainless steel SUS 304. The main use of stainless steel for fusion reactors is the support structures for superconductive magnets, and the thick plates over 150 mm are used. In the experiment, SUS 304L and 316L were used, but the development of a new high strength stainless steel is actively advanced. The target specification of the cryogenic structural material for the fusion experimental reactor (FER) was proposed in 1982. The proof stress is not lower than 1200 MPa, and the fracture toughness value is not lower than 200 MPa √m at 4 K. Six kinds of nitrogen-strengthened austenitic stainless steels and high manganese austenitic steels are developed. As the problems of the welded parts, the toughness and strength at extremely low temperature, the susceptibility to high temperature cracking, the material quality design of the welded metals and so on are examined. The welding methods are GTAW and GMAW. (K.I.)

  16. Residual stress studies of austenitic and ferritic steels

    International Nuclear Information System (INIS)

    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)

  17. Plastic localization phenomena in a Mn-alloyed austenitic steel

    OpenAIRE

    Matteis, Paolo; Firrao, Donato; Scavino, Giorgio; Russo Spena, Pasquale

    2010-01-01

    A 0.5 wt pct C, 22 wt pct Mn austenitic steel, recently proposed for fabricating automotive body structures by cold sheet forming, exhibits plastic localizations (PLs) during uniaxial tensile tests, yet showing a favorable overall strength and ductility. No localization happens during biaxial Erichsen cupping tests. Full-thickness tensile and Erichsen specimens, cut from as-produced steel sheets, were polished and tested at different strain rates. During the tensile tests, the PL phenomena co...

  18. Thermal fatigue of austenitic and duplex stainless steels

    OpenAIRE

    Virkkunen, Iikka

    2001-01-01

    Thermal fatigue behavior of AISI 304L, AISI 316, AISI 321, and AISI 347 austenitic stainless steels as well as 3RE60 and ACX-100 duplex stainless steels was studied. Test samples were subjected to cyclic thermal transients in the temperature range 20 - 600°C. The resulting thermal strains were analyzed with measurements and numerical calculations. The evolution of thermal fatigue damage was monitored with periodic residual stress measurements and replica-assisted microscopy. The elastic strai...

  19. To the corrosion of austenitic steels in sodium loops

    International Nuclear Information System (INIS)

    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.)

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

    NARCIS (Netherlands)

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

    2016-01-01

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

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

    International Nuclear Information System (INIS)

    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 0C) 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

  2. Nanostructured nickel-free austenitic stainless steel/hydroxyapatite composites.

    Science.gov (United States)

    Tulinski, Maciej; Jurczyk, Mieczyslaw

    2012-11-01

    In this work Ni-free austenitic stainless steels with nanostructure and their nanocomposites with hydroxyapatite are presented and characterized by means of X-ray diffraction and optical profiling. The samples were synthesized by mechanical alloying, heat treatment and nitriding of elemental microcrystalline powders with addition of hydroxyapatite (HA). In our work we wanted to introduce into stainless steel hydroxyapatite ceramics that have been intensively studied for bone repair and replacement applications. Such applications were chosen because of their high biocompatibility and ability to bond to bone. Since nickel-free austenitic stainless steels seem to have better mechanical properties, corrosion resistance and biocompatibility compared to 316L stainless steels, it is possible that composite made of this steel and HA could improve properties, as well. Mechanical alloying and nitriding are very effective technologies to improve the corrosion resistance of stainless steel. Similar process in case of nanocomposites of stainless steel with hydroxyapatite helps achieve even better mechanical properties and corrosion resistance. Hence nanocrystalline nickel-free stainless steels and nickel-free stainless steel/hydroxyapatite nanocomposites could be promising bionanomaterials for use as a hard tissue replacement implants, e.g., orthopedic implants. In such application, the surface roughness and more specifically the surface topography influences the proliferation of cells (e.g., osteoblasts). PMID:23421285

  3. Ferrite stability in duplex austenitic stainless steel welds

    International Nuclear Information System (INIS)

    The presence of ferrite in austenitic stainless steel welds is known to be beneficial in avoiding hot cracking problems. In particular, the primary delta ferrite mode of solidification is important. For alloy compositions in which primary ferrite forms, it has been shown that up to approximately 40% ferrite may exist in the as-solidified structures. With further cooling, the ferrite becomes unstable, transforming to austenite. However, under typical welding conditions, the cooling rate is sufficiently high to suppress the complete transformation of ferrite and some residual ferrite is retained. For example, for Type 308 austenitic stainless steel filler metal, gas-tungsten arc welds contain 6 to 10% ferrite, although under equilibrium conditions at elevated temperatures, this same alloy can be homogenized into a fully austenitic structure. Thus, it is clear the retained ferrite in such duplex structure welds is unstable and transforms during elevated temperature applications. The stability of ferrite was investigated by measuring its composition after several different thermal treatments. The composition was measured by means of analytical electron microscopy of thinned foils, and only the major constituents, iron, chromium, and nickel, were analyzed. The composition of ferrite was measured as a function of aging time and temperature. It was found that, during aging, the ferrite composition changes and approaches a metastable equilibrium limit before eventually transforming to sigma phase or austenite. This limiting composition was determined as a function of temperature

  4. Thermal fatigue cracking of austenitic stainless steels

    International Nuclear Information System (INIS)

    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 Ni 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 >> Ni, 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 usual

  5. Changes of structure of austenitic steel caused by hot deformation

    International Nuclear Information System (INIS)

    The phenomena taking place during hot deformation and reconstruction of the microstructure of chromium-manganese and chromium-nickel austenitic steels of low SFE were analyzed. In particular, the problems of recovery of dynamic recrystallization as well as changes of the microstructure after deformation were analyzed. The research of hot deformation carried out by means of the torsion test on a torsional plastometer allowed to determine the impact of the deformation conditions (ε, ε', T) on austenitic steel workability and to capture basic differences in strengthening and softening of manganese in relation to the austenite more extensively tested austenite in Cr-Ni steel. The differences in deformation of both materials up to maximal yield stress εm result from various dislocation splitting and association ability during deformation process. Manganese austenite is generally susceptible to splitting of dislocation in initial phases of deformation - that is why the strengthening intensity is so high. Carbon is additional factor strongly strengthening solid solution. The process of dynamic recrystallization of Cr-Mn steel (SFE approx. 50 mJ/m2) deformed at 900oC takes place through dislocation climbing within boundaries of adjacent subgrains and their coalescence. Nucleation of new grains and growth in the process of dynamic recrystallization of Cr-Ni steel (SFE approx. 20 mJ/m2) takes place through migration of high-angle grain boundaries as well as through the mechanism of subgrain coalescence. In the whole range of the steady plastic flow of samples of both steel grades, the size of grain formed in the result of dynamic recrystallization practically does not depend on the ε deformation size, but only on deformation conditions (T, ε'). Regardless the initial grain size of the tested austenitic steel grades practically the same grain sizes were obtained during dynamic recrystallization at the temperature of 1000-1100oC. No considerable influence of other

  6. Austenitic steels for boiler elements in USC power plants

    Directory of Open Access Journals (Sweden)

    A. Zieliński

    2013-04-01

    Full Text Available Purpose: Characteristics of functional properties of austenitic-based steels used for construction of boilers with supercritical and ultra-supercritical steam parameters.Design/methodology/approach: For selected austenitic steels in as-received state and after long-term annealing microstructural investigations were carried out with scanning and transmission electron microscope.Findings: Selected characteristics of structure and functional properties of materials to be used for critical elements in the pressure section of power boilers were summarised in a single paperPractical implications: The steel characteristics presented in this paper are used for assessment of structural changes and changes in strength properties of material of elements after long-term service under creep conditions.Originality/value: The presented results of the mechanical properties, structure and in the precipitation processes are applied to evaluation the condition of the elements in further industrial service.

  7. An alternative to the crystallographic reconstruction of austenite in steels

    International Nuclear Information System (INIS)

    An alternative crystallographic austenite reconstruction programme written in Matlab is developed by combining the best features of the existing models: the orientation relationship refinement, the local pixel-by-pixel analysis and the nuclei identification and spreading strategy. This programme can be directly applied to experimental electron backscatter diffraction mappings. Its applicability is demonstrated on both quenching and partitioning and as-quenched lath-martensite steels. - Highlights: • An alternative crystallographic austenite reconstruction program is developed. • The method combines a local analysis and a nuclei identification/spreading strategy. • The validity of the calculated orientation relationship is verified on a Q and P steel. • The accuracy of the reconstructed microtexture is investigated on a martensite steel

  8. Oxidation resistant high creep strength austenitic stainless steel

    Science.gov (United States)

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

    2010-06-29

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

  9. Phase control of austenitic chrome-nickel steel

    Energy Technology Data Exchange (ETDEWEB)

    Korkh, M. K., E-mail: KorkhMK@imp.uran.ru; Davidov, D. I., E-mail: davidov@imp.uran.ru; Korkh, J. V., E-mail: Korkh@imp.uran.ru; Rigmant, M. B., E-mail: Rigmant@imp.uran.ru; Nichipuruk, A. P., E-mail: Nichip@imp.uran.ru; Kazantseva, N. V., E-mail: kazantseva@imp.uran.ru [Institute of Metal Physics UrB RAS, Yekaterinburg (Russian Federation)

    2015-10-27

    The paper presents the results of the comparative study of the possibilities of different structural and magnetic methods for detection and visualization of the strain-induced martensitic phase in low carbon austenitic chromium-nickel steel. Results of TEM, SEM, optical microscopy, atomic and magnetic force microscopy, and magnetic measurements are presented. Amount of the magnetic strain-induced martensite was estimated. We pioneered magnetic force microscopic images of the single domain cluster distribution of the strain-induced martensite in austenite-ferrite materials.

  10. Phase control of austenitic chrome-nickel steel

    International Nuclear Information System (INIS)

    The paper presents the results of the comparative study of the possibilities of different structural and magnetic methods for detection and visualization of the strain-induced martensitic phase in low carbon austenitic chromium-nickel steel. Results of TEM, SEM, optical microscopy, atomic and magnetic force microscopy, and magnetic measurements are presented. Amount of the magnetic strain-induced martensite was estimated. We pioneered magnetic force microscopic images of the single domain cluster distribution of the strain-induced martensite in austenite-ferrite materials

  11. Hot-working of advanced high-manganese austenitic steels

    Directory of Open Access Journals (Sweden)

    L.A. Dobrzański

    2010-12-01

    Full Text Available Purpose: The work consisted in investigation of newly elaborated high-manganese austenitic steels with Nb and Ti microadditions in variable conditions of hot-working.Design/methodology/approach: The force-energetic parameters of hot-working were determined in continuous and multi-stage compression test performed in temperature range of 850 to 1100°C using the Gleeble 3800 thermomechanical simulator. Evaluation of processes controlling work-hardening were identified by microstructure observations of the specimens compresses to the various amount of deformation (4x0.29, 4x0.23 and 4x0.19. The microstructure evolution in successive stages of deformation was determined in metallographic investigations using light, scanning and electron microscopy as well as X-ray diffraction.Findings: The investigated steels are characterized by high values of flow stresses from 230 to 450 MPa. The flow stresses are much higher in comparison with austenitic Cr-Ni and Cr-Mn steels and slightly higher compared to Fe-(15-25Mn alloys. Increase of flow stress along with decrease of compression temperature is accompanied by translation of εmax strain in the direction of higher deformation. Results of the multi-stage compression proved that applying the true strain 4x0.29 gives the possibility to refine the austenite microstructure as a result of dynamic recrystallization. In case of applying the lower deformations 4x0.23 and 4x0.19, the process controlling work hardening is dynamic recovery and a deciding influence on a gradual microstructure refinement has statical recrystallization. The steel 27Mn-4Si-2Al-Nb-Ti has austenite microstructure with annealing twins and some fraction of ε martensite plates in the initial state. After the grain refinement due to recrystallization, the steel is characterized by uniform structure of γ phase without ε martensite plates.Research limitations/implications: To determine in detail the microstructure evolution during industrial

  12. 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...

  13. Nitrogen bearing austenitic stainless steels for surgical implants

    Energy Technology Data Exchange (ETDEWEB)

    Tschiptschin, A.P.; Aidar, C.H.; Alonso-Falleiros, N. [Sao Paulo Univ. (Brazil). Escola Politecnica; Neto, F.B. [Instituto de Pesquisas Tecnologicas, Sao Paulo (Brazil)

    1999-07-01

    Nitrogen addition promotes substantial improvements on general and localized corrosion performance of stainless steels. In recent times high nitrogen (up to 0.6 wt%) and Mn bearing super austenitic stainless steel has been studied for medical applications due to its low Ni content, the so called body friendly alloys. 18%Cr, 0.4%N and 15%Mn stainless steels were cast either from electrolytic or commercial master alloys in induction furnace, forged, solubilized at 1423K for 3 hours and water quenched. Delta ferrite and carbide precipitate free structures were observed. (orig.)

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

    OpenAIRE

    Ayo Samuel AFOLABI; Alaneme, K.K.; Samson Oluwaseyi BADA

    2009-01-01

    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 th...

  15. 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

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

    International Nuclear Information System (INIS)

    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

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

    International Nuclear Information System (INIS)

    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

  18. Study of irradiation damage structures in austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Hamada, Shozo [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1997-08-01

    The irradiation damage microstructures in austenitic stainless steels, which have been proposed to be a candidate of structural materials of a fusion reactor, under ions and neutrons irradiation have been studied. In ion irradiation experiments, cross-sectional observation of the depth distribution of damage formed due to ion irradiation became available. Comparison and discussion between experimental results with TEM and the calculated ones in the depth profiles of irradiation damage microstructures. Further, dual-phase stainless steels, consisted of ferritic/austenitic phases, showed irradiation-induced/enhanced precipitation during ion irradiation. High Flux Isotope Reactor with high neutron fluxes was employed in neutron-irradiation experiments. Swelling of 316 steel showed irradiation temperature dependence and this had strong correlation with phase instability under heavy damage level. Swelling resistance of Ti-modified austenitic stainless steel, which has good swelling resistance, decreased during high damage level. This might be caused by the instability of Ti-carbide particles. The preparation method to reduce higher radioactivity of neutron-irradiated TEM specimen was developed. (author). 176 refs.

  19. Solidification cracking in austenitic stainless steel welds

    Indian Academy of Sciences (India)

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

    2003-06-01

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

  20. Effect of shot peening on metastable austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-08-12

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

  1. Effect of shot peening on metastable austenitic stainless steels

    International Nuclear Information System (INIS)

    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

  2. Thermal stability of ultrafine-grained austenitic stainless steels

    International Nuclear Information System (INIS)

    Ultrafine-grained 316 and 304 austenitic stainless steel samples have been produced by high pressure torsion. Their microstructure, after deformation and annealing at a temperature in the 350-900 deg. C range, has been characterized using several techniques (transmission electron microscopy, X-ray diffraction, Moessbauer spectroscopy). The average grain size in the ultrafine-grained 316 is about 40 nm while it is larger in the ultrafine-grained 304 due to a smaller deformation. Results show the formation of α'-martensite during deformation in both steels while ε-martensite is formed only in the 304 steel. Annealing at 350 deg. C induces the decrease of α'-martensite content in the 316 steel. The trend is different in the 304 steel, in which the α'-martensite content increases. Recrystallization of grains is observed from 700 deg. C. Moessbauer spectroscopy shows a reduction of the level of solute atoms in α'-martensite during annealing.

  3. Manifestations of DSA in austenitic stainless steels and inconel alloys

    International Nuclear Information System (INIS)

    The aim of the investigation was to examine and compare different types of DSA (Dynamic Strain Aging) manifestations in AISI 316 austenitic stainless steel (SS) and Inconel 600 and Inconel 690 alloys by means of slow strain rate tensile testing, mechanical loss spectrometry (internal friction) and transmission electron microscopy (TEM). Another aim was to determine differences in the resulting dislocation structures and internal friction response of materials showing and not showing DSA behaviour

  4. Hot-working of advanced high-manganese austenitic steels

    OpenAIRE

    L.A. Dobrzański; W. Borek

    2010-01-01

    Purpose: The work consisted in investigation of newly elaborated high-manganese austenitic steels with Nb and Ti microadditions in variable conditions of hot-working.Design/methodology/approach: The force-energetic parameters of hot-working were determined in continuous and multi-stage compression test performed in temperature range of 850 to 1100°C using the Gleeble 3800 thermomechanical simulator. Evaluation of processes controlling work-hardening were identified by microstructure observati...

  5. Creep embrittlement of austenitic stainless steels with titanium addition

    International Nuclear Information System (INIS)

    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 5500C to 7500C 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

  6. 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.

  7. Producing nanostructured super-austenitic steels by friction stir processing

    International Nuclear Information System (INIS)

    Research highlights: → FSP was successfully used to produce nanostructured super-austenitic steel. → FSP led to breaking down the coarse sigma precipitates into the nanosize ones. → Determinable effect of sigma can be minimized by its fragmentation to nanoparticles. → FSP is a unique approach to break coarse particles to attain a uniform microstructure. - Abstract: In the present work, friction stir processing (FSP) was used to produce the nanostructured super-austenitic steel. After preheating, the specimens were subjected to FSP using the rotation and traverse speed of 2600 rpm and 30 mm min-1, respectively. The specimen temperature during FSP was about 950 ± 2 deg. C. The results show that a nanostructured layer of about 91 μm thick was produced on the specimen surface. The formed nanograins ranged from 50 to 90 nm. Besides, the hot severe deformation applied during FSP led to significant fragmentation of the coarse sigma particles to nanosize ones. The produced nanostructured layer was then characterized using field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), and scanning electron microscopy (SEM). The formed nanostructure led to a twofold increase in the hardness. The formation of nanostructure resulted in an increase in hardness up to 350 Hv, comparing to 185 Hv pertaining to base structure of super austenitic steel.

  8. Researches upon the cavitation erosion behaviour of austenite steels

    Science.gov (United States)

    Bordeasu, I.; Popoviciu, M. O.; Mitelea, I.; Salcianu, L. C.; Bordeasu, D.; Duma, S. T.; Iosif, A.

    2016-02-01

    Paper analyzes the cavitation erosion behavior of two stainless steels with 100% austenitic structure but differing by the chemical composition and the values of mechanical properties. The research is based on the MDE(t) and MDER(t) characteristic curves. We studied supplementary the aspect of the eroded areas by other to different means: observations with performing optical microscopes and roughness measurements. The tests were done in the T2 vibratory facility in the Cavitation Laboratory of the Timisoara Polytechnic University. The principal purpose of the study is the identification of the elements influencing significantly the cavitation erosion resistance. It was established the effect of the principal chemical components (determining the proportion of the structural components in conformity the Schaffler diagram) upon the cavitation erosion resistance. The results of the researches present the influence of the proportion of unstable austenite upon cavitation erosion resistance. The stainless steel with the great proportion of unstable austenite has the best behavior. The obtained conclusion are important for the metallurgists which realizes the stainless steels used for manufacturing the runners of hydraulic machineries (turbines and pumps) with increased resistance to cavitation attack.

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

    OpenAIRE

    D. S. Yawas; S.Y. Aku; S.O. Aluko

    2014-01-01

    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...

  10. Microstructural change during isothermal aging in high manganese austenitic steels

    International Nuclear Information System (INIS)

    Microstructural change during isothermal aging has been investigated in 13%Mn-0.9%C and 22%Mn-0.6%C steels by means of optical and electron microscopy and X-ray diffractometry. High manganese austenitic steels undergo three kinds of reactions during isothermal aging; (1) grain boundary precipitation of carbide, (2) precipitation of platelet carbide within austenite (γ) grains and (3) formation of lamellar structure through eutectoid transformation (γ → ferrite (α + carbide). In 13%Mn-0.9%C steel, all of the reactions occur and the carbide concerning the reactions is M3C in any case. On the other hand, in 22%Mn-0.6%C steel, only two of them occur; grain boundary precipitation of M23C6 carbide (not M3C) and the eutectoid transformation (γ → α + M3C). Besides, both of the two reactions in 22%Mn-0.6%C steel were effectively suppressed due to the chemical composition; high Mn and low C content. Eutectoid transformation proceeds by being supplied carbon from untransformed γ, so that this results in the shortage of carbon in untransformed γ during isothermal aging and the γ phase undergoes γ → ε (hcp) martensitic transformation on the following cooling. (author)

  11. 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)

  12. Tritium in austenitic stainless steel vessels

    International Nuclear Information System (INIS)

    The vessel used for the long-term storage of tritium (titanium tritide) will be of welded 316L stainless steel construction. The 316L stainless is chosen partially because of its excellent resistance, in the wrought condition, to any degradation of mechanical properties from contact with hydrogen isotopes. The work reported here was undertaken to check that the welds in the vessel would have a satisfactory response to the hydrogen isotopes. A satisfactory response has been demonstrated, leading to a general conclusion that the titanium tritide/316L stainless steel vessel combination provides an extremely reliable storage facility for the tritium

  13. Austenite Static Recrystallization Kinetics in Microalloyed B Steels

    Science.gov (United States)

    Larrañaga-Otegui, Ane; Pereda, Beatriz; Jorge-Badiola, Denis; Gutiérrez, Isabel

    2016-04-01

    Boron is added to steels to increase hardenability, substituting of more expensive elements. Moreover, B acts as a recrystallization delaying element when it is in solid solution. However, B can interact with N and/or C to form nitrides and carbides at high temperatures, limiting its effect on both phase transformation and recrystallization. On the other hand, other elements like Nb and Ti are added due to the retarding effect that they exert on the austenite softening processes, which results in pancaked austenite grains and refined room microstructures. In B steels, Nb and Ti are also used to prevent B precipitation. However, the complex interaction between these elements and its effect on the austenite microstructure evolution during hot working has not been investigated in detail. The present work is focused on the effect the B exerts on recrystallization when added to microalloyed steels. Although B on its own leads to retarded static recrystallization kinetics, when Nb is added a large delay in the static recrystallization times is observed in the 1273 K to 1373 K (1000 °C to 1100 °C) temperature range. The effect is larger than that predicted by a model developed for Nb-microalloyed steels, which is attributed to a synergistic effect of both elements. However, this effect is not so prominent for Nb-Ti-B steels. The complex effect of the composition on recrystallization kinetics is explained as a competition between the solute drag and precipitation pinning phenomena. The effect of the microalloying elements is quantified, and a new model for the predictions of recrystallization kinetics that accounts for the B and Nb+B synergetic effects is proposed.

  14. 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.

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

    International Nuclear Information System (INIS)

    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

  16. Effect of Geobacter sulfurreducens on the microbial corrosion of mild steel, ferritic and austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Mehanna, Maha [Laboratoire de Genie Chimique, CNRS - Universite de Toulouse, 5 rue Paulin Talabot, BP1301, 31029 Toulouse (France)], E-mail: mum34@psu.edu; Basseguy, Regine; Delia, Marie-Line; Bergel, Alain [Laboratoire de Genie Chimique, CNRS - Universite de Toulouse, 5 rue Paulin Talabot, BP1301, 31029 Toulouse (France)

    2009-11-15

    The influence of Geobacter sulfurreducens was tested on the anaerobic corrosion of four different steels: mild steel 1145, ferritic steel 403 and austenitic steels 304L and 316L. Within a few hours, the presence of cells induced a free potential (E{sub oc}) ennoblement around +0.3 V on 1145 mild steel, 403 ferritic steel and 304L austenitic steels and slightly less on 316L. The kinetics of E{sub oc} ennoblement depended on the amount of bacteria in the inoculum, but the final potential value depended essentially on the nature of the material. This effect was due to the capacity of G. sulfurreducens to create a direct cathodic reaction on steel surfaces, extracting the electrons directly from material. The presence of bacterial cells modified the corrosion features of mild steel and ferritic steel, so that corrosion attacks were gathered in determined zones of the surface. Local corrosion was significantly enhanced on ferritic steel. Potential ennoblement was not sufficient to induce corrosion on austenitic steels. In contrast G. sulfurreducens delayed the occurrence of pitting on 304L steel because of its capability to oxidize acetate at high potential values. The electrochemical behaviour of 304L steel was not affected by the concentration of soluble electron donor (acetate, 1-10 mM) or the amount of planktonic cells; it was directly linked to the biofilm coverage. After polarization pitting curves had been recorded, microscopic observations showed that pits propagated only in the surface zones where cell settlement was the densest. The study evidenced that Geobacter sulfurreducens can control the electrochemical behaviour of steels in complex ways that can lead to severe corrosion. As Geobacteraceae are ubiquitous species in sediments and soils they should now be considered as possible crucial actors in the microbial corrosion of buried equipment.

  17. Effect of Geobacter sulfurreducens on the microbial corrosion of mild steel, ferritic and austenitic stainless steels

    International Nuclear Information System (INIS)

    The influence of Geobacter sulfurreducens was tested on the anaerobic corrosion of four different steels: mild steel 1145, ferritic steel 403 and austenitic steels 304L and 316L. Within a few hours, the presence of cells induced a free potential (Eoc) ennoblement around +0.3 V on 1145 mild steel, 403 ferritic steel and 304L austenitic steels and slightly less on 316L. The kinetics of Eoc ennoblement depended on the amount of bacteria in the inoculum, but the final potential value depended essentially on the nature of the material. This effect was due to the capacity of G. sulfurreducens to create a direct cathodic reaction on steel surfaces, extracting the electrons directly from material. The presence of bacterial cells modified the corrosion features of mild steel and ferritic steel, so that corrosion attacks were gathered in determined zones of the surface. Local corrosion was significantly enhanced on ferritic steel. Potential ennoblement was not sufficient to induce corrosion on austenitic steels. In contrast G. sulfurreducens delayed the occurrence of pitting on 304L steel because of its capability to oxidize acetate at high potential values. The electrochemical behaviour of 304L steel was not affected by the concentration of soluble electron donor (acetate, 1-10 mM) or the amount of planktonic cells; it was directly linked to the biofilm coverage. After polarization pitting curves had been recorded, microscopic observations showed that pits propagated only in the surface zones where cell settlement was the densest. The study evidenced that Geobacter sulfurreducens can control the electrochemical behaviour of steels in complex ways that can lead to severe corrosion. As Geobacteraceae are ubiquitous species in sediments and soils they should now be considered as possible crucial actors in the microbial corrosion of buried equipment.

  18. The study of retained austenite morphology in low-carbon silico manganese steels

    International Nuclear Information System (INIS)

    The experimental results of a retained austenite morphology in low-carbon steels of a chemical composition of 0.2% C, 1.5% Mn, and 1.5% Si are presented. The microstructure of retained austenite after martensitic transformation in samples quenched from austenite region, dual phase region and suggested isothermal bainitic transformation were analysed. (author)

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

    International Nuclear Information System (INIS)

    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)

  20. 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...

  1. 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.

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

    International Nuclear Information System (INIS)

    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

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

    OpenAIRE

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

    2016-01-01

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

  4. Reaction of uranium and plutonium carbides with austenitic steels

    International Nuclear Information System (INIS)

    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) Fe2 + Cr23C6. 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)

  5. Interaction of deuterium with SS316 austenitic stainless steel

    International Nuclear Information System (INIS)

    Accumulation and desorption of deuterium implanted in SS316 austenitic stainless steel to concentrations ∼1 at.%, the influence of helium and radiation-induced defects on the process of mass transfer of deuterium and the mechanical properties of steel at different levels of damage were studied. The samples were irradiated with 15 keV/D, 30 keV/He and 1.4 MeV/Ar ions. For modeling of the defect structure formed in the materials of nuclear power plants, the irradiation with high-energy argon ions was performed. Studies were carried out by means of ion implantation, nuclear reactions D(3He,p)4He with analyzing beam of 3He (E = 0.3...1.4 MeV), thermal desorption spectroscopy, transmission electron microscopy and nanoindentation. It was found that the retention of deuterium in steel is increased significantly in the presence of radiation damage created by helium and argon pre-implantation

  6. Austenitic steel piping testing exercises in PISC

    International Nuclear Information System (INIS)

    In this paper capability and reliability studies of NDT procedures for the inspection of wrought and cast stainless steel piping used in nuclear power plants will be presented. The capability study was designed to identify procedures that have the potential to detect and size defects and to discriminate between flawed and unflawed material. The reliability study was undertaken to quantify on real and realistic flaws in-service inspection performance (detection and false call capability) under realistic field conditions. Furthermore parametric studes were performed to complement the capability and reliability studies by evaluating the effect of important material and flaw variables.The specimens used in these studies were cast-to-cast, cast-to-wrought, and wrought-to-wrought pipework welds. The evaluation methods used to quantify the inspection performance were selected to be as comparable as possible to the PISC II methods. These were adapted to allow also the evaluation of the effect of false calls. During the PISC II screening exercise for the cast-to-cast stainless steel round robin test and other piping round robin studies, it was indeed found that false call probabilities were large and could not be ignored in the evaluation of the inspection performance. The matrix of samples has also been designed to allow the implementation of specific statistical analysis procedures for the evaluation of results such as for example the relative operative characteristics analysis. (orig.)

  7. High temperature irradiation creep in austenitic steels

    International Nuclear Information System (INIS)

    An analysis has been made of the in-reactor and ex-reactor creep at 700 - 7500C of various Ti - and Nb - stabilised steels. Above a critical transition stress that depended on steel composition and thermomechanical treatment, the stress dependence of the creep rate was high but there was little influence of irradiation on the kinetics. At lower stresses the stress dependence was small and the creep rate varied as the inverse cube of the grain size. In-reactor creep rates were about ten times faster than those ex-reactor, the in-reactor rates approaching the magnitude of the Coble grain boundary diffusion creep process. A mechanism is proposed to explain the enhanced creep rates in-reactor based on the idea that SIPA irradiation creep of carbide particles occurs at the grain boundary vacancy sinks during diffusion creep. This limits the stress redistribution at the grain boundary and the generation of high stresses at the particles which, in the ex-reactor tests, can markedly inhibit the diffusion creep process. (author)

  8. Hot-working behaviour of high-manganese austenitic steels

    Directory of Open Access Journals (Sweden)

    L.A. Dobrzański

    2008-11-01

    Full Text Available Purpose: The work consisted in investigation of newly elaborated high-manganese austenitic steels with Nb and Ti microadditions in variable conditions of hot-working.Design/methodology/approach: Determination of processes controlling strain hardening was carried out in continuous compression test using Gleeble 3800 thermo-mechanical simulator.Findings: It was found that they have austenite microstructure with numerous annealing twins in the initial state. Continuous compression tests realized in the temperature range from 850 to 1050°C with the strain rate of 10s-1 enabled determination of yield stress values and values of εmax deformations – corresponding to maximum flow stress. It was found that initiation of dynamic recrystallization requires true strain equal at least 0.29. Holding of steel after plastic deformation allowed determining the progress of recrystallization in the function of isothermal holding time. Determined half-times of recrystallization at 900°C after deformation with 25% of reduction are equal 32 and 17s for 27Mn-4Si-2Al-Nb-Ti and 26Mn-3Si-3Al-Nb-Ti steel, respectively. Several-stage compression tests with true strain of 0.29 permit to use dynamic recrystallization for shaping fine-grained microstructure of steel in the whole range of deformation temperature. Decreasing true strain to 0.23 limits the course of dynamic recrystallization to two first deformation cycles. In two final cycles of deformation, as well as in the whole range of hot-working realized with true strain of 0.19 – dynamic recovery is the process controlling strain hardening.Practical implications: The obtained microstructure – hot-working conditions relationships and stress-strain curves can be useful in determination of power-force parameters of hot-rolling for sheets with fine-grained austenitic structures.Originality/value: The hot-working behaviour and microstructure evolution in various conditions of plastic deformation for new

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

    Institute of Scientific and Technical Information of China (English)

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

    2009-01-01

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

  10. The model of prediction of the microstructure austenite C-Mn steel

    OpenAIRE

    B. Koczurkiewicz

    2007-01-01

    Purpose: The subject of the work is analysis of author’s model for prediction of austenite microstructure of C-Mn steel based on Sellar’s solution.Design/methodology/approach: The present study adopts the Sellar’s solution for C-Mn steel to the prediction of phenomena occurring in the steel and the grain size of austeniteFindings: The developed model for the evolution of the austenite microstructure enables the correct determination of the grain size of austenite formed by multi-stage hot de...

  11. Kinetics of austenite grain growth in medium-carbon niobium-bearing steel

    Institute of Scientific and Technical Information of China (English)

    Ying-li ZHAO; Jie SHI; Wen-quan CAO; Mao-qiu WANG; Gang XIE

    2011-01-01

    In order to locate a reasonable heating system, the austenite grain growth behavior of Nb microalloyed medium carbon steel has been experimentally studied at various austenitizing temperatures and for different holding times. It is indicated that austenite grain growth increases with increasing austenitizing temperatures and holding times. Particularly when the austenitizing temperature was above 1100 ℃, austenite grains grew rapidly, and an abnormal austenite grain growth was observed. When the austenitizing temperature was lower than 1100 ℃, austenite grain size and growth rate were small. The activation energy of grain growth in the tested steel is 397 679.5 J/mol. To ensure an absence of coarse grains in microstructures, the heating technology of the tested steel should be controlled for 1 h at 1100 ℃. The relationships of austenite average grain size with soaking temperature and time of tested steel were obtained by mathematical calculation, and austenite average grain size was found to be in agreement with the measured size for different holding times.

  12. Defect microstructures and deformation mechanisms in irradiated austenitic stainless steels

    International Nuclear Information System (INIS)

    Microstructural evolution and deformation behavior of austenitic stainless steels are evaluated for neutron, heavy-ion and proton irradiated materials. Radiation hardening in austenitic stainless steels is shown to result from the evolution of small interstitial dislocation loops during light-water-reactor (LWR) irradiation. Available data on stainless steels irradiated under LWR conditions have been analyzed and microstructural characteristics assessed for the critical fluence range (0.5 too 10 dpa) where irradiation-assisted stress corrosion cracking susceptibility is observed. Heavy-ion and proton irradiations are used to produce similar defect microstructures enabling the investigation of hardening and deformation mechanisms. Scanning electron, atomic force and transmission electron microscopies are employed to examine tensile test strain rate and temperature effects on deformation characteristics. Dislocation loop microstructures are found to promote inhomogeneous planar deformation within the matrix and regularly spaced steps at the surface during plastic deformation. Twinning is the dominant deformation mechanism at rapid strain rates and at low temperatures, while dislocation channeling is favored at slower strain rates and at higher temperatures. Both mechanisms produce highly localized deformation and large surface slip steps. Channeling, in particular, is capable of creating extensive dislocation pileups and high stresses at internal grain boundaries which may promote intergranular cracking

  13. On the Development of the Brass-Type Texture in Austenitic Stainless Steel

    OpenAIRE

    Singh, C. D.

    1993-01-01

    It has been clarified and demonstrated that the conclusions drawn by Singh, Ramaswamy and Suryanarayana (1992) in an investigation of development of rolling textures in an austenitic stainless steel are correct. The observations and reinterpretations drawn by Leffers (1993) are without any proper scientific basis and do not hold good at least in austenitic stainless steel.

  14. Creep properties and microstructure of the new wrought austenitic steel

    Energy Technology Data Exchange (ETDEWEB)

    Vlasak, T.; Hakl, J.; Novak, P. [SVUM a.s., Prague (Czech Republic); Vyrostkova, A. [Slovak Academy of Sciences, Kosice (Slovakia). Inst. of Materials Research

    2010-07-01

    The contribution is oriented on the new wrought austenitic steel BGA4 (Cr23Ni15Mn6Cu3W1.5NbVMo) developed by the British Corus Company. Our main aim is to present creep properties studied in SVUM a.s. Prague during COST 536 programme. The dependencies of the creep strength, strength for specific creep strain and minimum creep strain rate were evaluated on the basis of long term creep tests carried out at temperature interval (625; 725) C. Important part of a paper is metallographic analysis. (orig.)

  15. Residual stresses associated with welds in austenitic steel

    International Nuclear Information System (INIS)

    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 8500 and 7500C 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)

  16. Fatigue crack growth of a metastable austenitic stainless steel

    OpenAIRE

    Martelo, D.F.; Mateo García, Antonio Manuel; Chapetti, M.D.

    2015-01-01

    The fatigue crack growth behavior of an austenitic metastable stainless steel AISI 301LN in the Paris region is investigated in this work. The fatigue crack growth rate curves are evaluated in terms of different parameters such as the range of stress intensity factor Delta K, the effective stress intensity factor Delta K-eff, and the two driving force parameter proposed by Kujawski K*.; The finite element method is used to calculate the stress intensity factor of the specimens used in this in...

  17. Laser Welding Of Finned Tubes Made Of Austenitic Steels

    OpenAIRE

    Stolecki M.; Bijok H.; Kowal Ł.; Adamiec J.

    2015-01-01

    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, ...

  18. Thermodynamic modeling of the stacking fault energy of austenitic steels

    Energy Technology Data Exchange (ETDEWEB)

    Curtze, S., E-mail: sven.curtze@oxinst.com [Tampere University of Technology, Department of Materials Science, P.O. Box 589, FI-33101 Tampere (Finland); Kuokkala, V.-T. [Tampere University of Technology, Department of Materials Science, P.O. Box 589, FI-33101 Tampere (Finland); Oikari, A. [Aalto University School of Science and Technology, Department of Engineering Design and Production, P.O. Box 14200, FI-00076 Aalto (Finland); Talonen, J. [Outokumpu Oyj, P.O. Box 140, FI-02201 Espoo (Finland); Haenninen, H. [Aalto University School of Science and Technology, Department of Engineering Design and Production, P.O. Box 14200, FI-00076 Aalto (Finland)

    2011-02-15

    The stacking fault energies (SFE) of 10 austenitic steels were determined in the temperature range 50 {<=} T {<=} 600 K by thermodynamic modeling of the Fe-Cr-Ni-Mn-Al-Si-Cu-C-N system using a modified Olson and Cohen modeling approach (Olson GB, Cohen M. Metall Trans 1976;7A:1897 ). The applied model accounts for each element's contribution to the Gibbs energy, the first-order excess free energies, magnetic contributions and the effect of interstitial nitrogen. Experimental SFE values from X-ray diffraction measurements were used for comparison. The effect of SFE on deformation mechanisms was also studied by electron backscatter diffraction.

  19. Hydrogen gas embrittlement of stainless steels mainly austenitic steels. Volumes 1 and 2

    International Nuclear Information System (INIS)

    Steel behavior in regard to hydrogen is examined especially austenitic steels. Gamma steels are studied particularly the series 300 with various stabilities and gamma steels with improved elasticity limit for intermetallic phase precipitation and nitrogen additions. A two-phase structure γ + α' is also studied. All the samples are tested for mechanical behavior in gaseous hydrogen. Influence of metallurgical effects and of testing conditions on hydrogen embrittlement are evidenced. Microstructure resulting from mechanical or heat treatments, dislocation motion during plastic deformation and influence of deformation rate are studied in detail

  20. Retained austenite thermal stability in a nanostructured bainitic steel

    International Nuclear Information System (INIS)

    The unique microstructure of nanostructured bainite consists of very slender bainitic ferrite plates and high carbon retained austenite films. As a consequence, the reported properties are opening a wide range of different commercial uses. However, bainitic transformation follows the T0 criteria, i.e. the incomplete reaction phenomena, which means that the microstructure is not thermodynamically stable because the bainitic transformation stops well before austenite reaches an equilibrium carbon level. This article aims to study the different microstructural changes taking place when nanostructured bainite is destabilized by austempering for times well in excess of that strictly necessary to end the transformation. Results indicate that while bainitic ferrite seems unaware of the extended heat treatment, retained austenite exhibits a more receptive behavior to it. - Highlights: • Nanostructured bainitic steel is not thermodynamically stable. • Extensive austempering in these microstructures has not been reported before. • Precipitation of cementite particles is unavoidable at longer austempering times. • TEM, FEG-SEM and XRD analysis were used for microstructural characterization

  1. Corrosion resistance of kolsterised austenitic 304 stainless steel

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-03-30

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

  2. Influence of austenitizing temperature on apparent morphologies of as-quenched microstructures of steels

    Institute of Scientific and Technical Information of China (English)

    LIU Yue-jun; LI Yi-min; HUANG Bai-yun

    2006-01-01

    The effects of austenitizing temperature on the morphologies and substructures of as-quenched microstructure were investigated by using 13 medium and high carbon steels. The formation reasons of various morphologies of martensite quenched at different austenitizing temperatures were also studied. The results show that the packet martensite in medium and high carbon steels quenched at higher austenitizing temperature is entirely different from that in as-quenched low carbon steels, which is still plate martensite, and not lath martensite. All the change laws of as-quenched microstructures in medium and high carbon steels are identical with an increase in austenitizing temperature, and the austenitizing temperature can merely change the combined morphology of martensitic platelets,but cannot alter the type of product of martensitic transformation in commercial steels.

  3. Amorphous stainless steel coatings prepared by reactive magnetron-sputtering from austenitic stainless steel targets

    OpenAIRE

    Cusenza, Salvatore; Schaaf, Peter

    2009-01-01

    Stainless steel films were reactively magnetron sputtered in argon/methane gas flow onto oxidized silicon wafers using austenitic stainless-steel targets. The deposited films of about 200 nm thickness were characterized by conversion electron Mössbauer spectroscopy, magnetooptical Kerr-effect, X-ray diffraction, scanning electron microscopy, Rutherford backscattering spectrometry, atomic force microscopy, corrosion resistance tests, and Raman spectroscopy. These complementary methods were us...

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

    International Nuclear Information System (INIS)

    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 900oC, Cr2N 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 WL= %Cr + 3.3 %Mo + 30 %N. (author) figs., tabs., refs

  5. Development of highest strength nitrogen alloyed austenitic steels

    International Nuclear Information System (INIS)

    This work deals with different possibilities to increase the strength of austenitic stainless steels. It may be interesting to the steel producer and to the steel user, because it shows ways to increase the strength of such steels. It may also be of interest to the metallurgist, because it analyzes the achieved results on the basis of physical metallurgy. It is shown that the increase of the nitrogen content in solid solution has a positive effect on the different hardening mechanisms. The investigation, therefore, focus on nitrogen alloyed steels. Grain boundary hardening, the increase of strength with decreasing strain size, is strongly pronounced in nitrogen alloyed steels. By means of an ultra rapid recrystallization heat treatment it is possible to produce a grain size as small as 2-3 microns. The yield strength reaches an unusually high value of 1030 MPa with an elongation of 48% and an area reduction of 63%. This completely recrystallized steel is free of any precipitation. From the Hall-Petch relation the yield strength may only be extrapolated down to a grain size of about 10 microns. The slope of the Hall-Petch plot, ky, decreases with decreasing grain size. This behavior may be explained by the different distribution of dislocation glide in fine and in coarse grained material. Strain hardening, the increase of strength due to deformation, was thoroughly investigated as a second hardening mechanism. The most important results for room temperature deformation are presented. Deformation at an increased temperature of about 300-400 oC was investigated as an alternative to room temperature deformation. The potentially useful results are also presented. Strain aging may further increase the strength of cold worked nitrogen alloys steels. A heat treatment between 300 and 500oC for a few minutes may lead to an increase in strength of more than 300 MPa. (author) 73 figs., refs

  6. Thermal stability of ultrafine-grained austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Etienne, A.; Radiguet, B.; Genevois, C.; Le Breton, J.-M. [Groupe de Physique des Materiaux, Universite et INSA de Rouen, UMR CNRS 6634, BP 12, 76 801 Saint Etienne du Rouvray Cedex (France); Valiev, R. [Institute of Physics of Advanced Materials, Ufa State Aviation Technical University, 12K. Marx Street, 450000 Ufa (Russian Federation); Pareige, P., E-mail: philippe.pareige@univ-rouen.fr [Groupe de Physique des Materiaux, Universite et INSA de Rouen, UMR CNRS 6634, BP 12, 76 801 Saint Etienne du Rouvray Cedex (France)

    2010-08-20

    Ultrafine-grained 316 and 304 austenitic stainless steel samples have been produced by high pressure torsion. Their microstructure, after deformation and annealing at a temperature in the 350-900 deg. C range, has been characterized using several techniques (transmission electron microscopy, X-ray diffraction, Moessbauer spectroscopy). The average grain size in the ultrafine-grained 316 is about 40 nm while it is larger in the ultrafine-grained 304 due to a smaller deformation. Results show the formation of {alpha}'-martensite during deformation in both steels while {epsilon}-martensite is formed only in the 304 steel. Annealing at 350 deg. C induces the decrease of {alpha}'-martensite content in the 316 steel. The trend is different in the 304 steel, in which the {alpha}'-martensite content increases. Recrystallization of grains is observed from 700 deg. C. Moessbauer spectroscopy shows a reduction of the level of solute atoms in {alpha}'-martensite during annealing.

  7. Manufacture and characterization of austenitic steel welded joints

    International Nuclear Information System (INIS)

    This paper describes the results of the first phase of the project, i.e. manufacturing and characterization of welded austenitic steel and the test matrix adopted to test the mechanical resistance of the welding. Five different welding methods have been tested and characterized in comparison to the parent material. The reference material was an AISI 316 L type steel close to the French Superphenix composition. The results of the mechanical testing and the relative comparison of the five welding methods are described in separate papers of the same session. As a general conclusion, the vacuum electron-beam welding proved to have better properties than the other weld methods and to attain in most cases the properties of the parent material. (author)

  8. Lattice dynamics of high-pressure hydrogenated austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Hoelzel, M [Darmstadt University of Technology, Institute for Materials Science, Petersenstrasse 23, 64287 Darmstadt (Germany); Rajevac, V [Darmstadt University of Technology, Institute for Materials Science, Petersenstrasse 23, 64287 Darmstadt (Germany); Danilkin, S A [Bragg Institute, ANSTO, New Illawarra Road, Lucas Heights, NSW 2234PMB 1, Menai (Australia); Udovic, T J [National Institute of Standards and Technology, NIST Center for Neutron Research, 100 Bureau Drive, MS 8562, Gaithersburg, MD 20899-8562 (United States); Wipf, H [Darmstadt University of Technology, Institute for Solid State Physics, Hochschulstrasse 6, 64289 Darmstadt (Germany); Fuess, H [Darmstadt University of Technology, Institute for Materials Science, Petersenstrasse 23, 64287 Darmstadt (Germany)

    2005-06-15

    The vibrational spectra of hydrogenated austenitic stainless steels AISI 304 (Fe/Cr18/Ni10) and AISI 310 (Fe/Cr25/Ni20) were investigated by inelastic neutron scattering. Based on the results of previous neutron diffraction studies, the data have been analysed by model calculations. The peaks corresponding to the optical modes show a significant broadening because of the variation of vibrational energies from one hydrogen site to another in the alloys. At high hydrogen contents (hydrogen-to-metal atomic ratios H/Me {approx}1) the peak profile is dominated by hydrogen-hydrogen interactions. Correspondingly, the optical peaks show a splitting into longitudinal and transverse modes for H/Me {approx}1. A continuous lowering of the vibrational energies with increasing hydrogen content was observed for both steels, reflecting a weakening of the hydrogen-metal interactions with increasing hydrogen-metal atomic distance.

  9. Lattice dynamics of high-pressure hydrogenated austenitic stainless steels

    International Nuclear Information System (INIS)

    The vibrational spectra of hydrogenated austenitic stainless steels AISI 304 (Fe/Cr18/Ni10) and AISI 310 (Fe/Cr25/Ni20) were investigated by inelastic neutron scattering. Based on the results of previous neutron diffraction studies, the data have been analysed by model calculations. The peaks corresponding to the optical modes show a significant broadening because of the variation of vibrational energies from one hydrogen site to another in the alloys. At high hydrogen contents (hydrogen-to-metal atomic ratios H/Me ∼1) the peak profile is dominated by hydrogen-hydrogen interactions. Correspondingly, the optical peaks show a splitting into longitudinal and transverse modes for H/Me ∼1. A continuous lowering of the vibrational energies with increasing hydrogen content was observed for both steels, reflecting a weakening of the hydrogen-metal interactions with increasing hydrogen-metal atomic distance

  10. Precipitation and cavity formation in austenitic stainless steels during irradiation

    International Nuclear Information System (INIS)

    Microstructural evolution in austenitic stainless steels subjected to displacement damage at high temperature is strongly influenced by the interactions between helium atoms and second phase particles. Cavity nucleation occurs by the trapping of helium at partially coherent particle-matrix interfaces. The recent precipitate point defect collector theory describes the more rapid growth of precipitate-attached cavities compared to matrix cavities where the precipitate-matrix interface collects point defects to augment the normal point deflect flux to the cavitry. Data are presented which support these ideas. It is shown that during nickel ion irradiation of a titanium-modified stainless steel at 6750C the rate of injection of helium has a strong effect on the total swelling and also on the nature and distribution of precipitate phases

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-03-30

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

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

    International Nuclear Information System (INIS)

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

  13. Hydrogen embrittlement of SUS 316 austenitic stainless steel weldments

    International Nuclear Information System (INIS)

    In order to understand the degrading behavior of hydrogen embrittlement of SUS 316 austenitic stainless steel weldment, base metal and welded joints which were welded with EBW and SMAW and heat-treated at 650 0C - 24 hr for carbide and 850 0C - 6 hr for Sigma-phase precipitation after welding were evaluated in tensile test at room temperature with and without hydrogen charging in the autoclave at 450 0C - 220 atm - 48 hr treatment. As a result the drastic degrading to 40 % in reduction in area of the welded joint was observed when hydrogen of 41 ppm was contained in the welded joint of SUS 316 stainless steel. (author)

  14. Ion beam nitriding of single and polycrystalline austenitic stainless steel

    International Nuclear Information System (INIS)

    Polycrystalline and single crystalline [orientations (001) and (011)] AISI 316L austenitic stainless steel was implanted at 400 deg. C with 1.2 keV nitrogen ions using a high current density of 0.5 mA cm-2. The nitrogen distribution profiles were determined using nuclear reaction analysis (NRA). The structure of nitrided polycrystalline stainless steel samples was analyzed using glancing incidence and symmetric x-ray diffraction (XRD) while the structure of the nitrided single crystalline stainless steel samples was analyzed using x-ray diffraction mapping of the reciprocal space. For identical treatment conditions, it is observed that the nitrogen penetration depth is larger for the polycrystalline samples than for the single crystalline ones. The nitrogen penetration depth depends on the orientation, the being more preferential for nitrogen diffusion than . In both type of samples, XRD analysis shows the presence of the phase usually called 'expanded' austenite or γN phase. The lattice expansion depends on the crystallographic plane family, the (001) planes showing an anomalously large expansion. The reciprocal lattice maps of the nitrided single crystalline stainless steel demonstrate that during nitriding lattice rotation takes place simultaneously with lattice expansion. The analysis of the results based on the presence of stacking faults, residual compressive stress induced by the lattice expansion, and nitrogen concentration gradient indicates that the average lattice parameter increases with the nitrided layer depth. A possible explanation of the anomalous expansion of the (001) planes is presented, which is based on the combination of faster nitriding rate in the (001) oriented grains and the role of stacking faults and compressive stress

  15. Research on Retained Austenite for Advanced Aluminum-containing Hot-rolled TRIP Steel

    Institute of Scientific and Technical Information of China (English)

    Guoyi TANG; Fangyu CHEN; Pinghe LI; Sunbing ZHOU

    2005-01-01

    A new type of hot-rolled transformation induced plasticity (TRIP) steel with 2.3%Al was developed to replace conventional Si-bearing TRIP steel to improve surface quality of the steel sheet. The relationship between retained austenite volume fraction and hot-rolling processing was researched by Gleeble-2000 thermo-dynamic test for the Al-bearing steel. The experimental result showed that aluminum played an important role on retaining austenite and the volume fraction increased from 4.4% to 7.5% as coiling temperature increased from 350℃ to 450℃, while coiling temperature had a stronger effect on retaining austenite than finishing rolling temperature.

  16. Corrosion of an austenite and ferrite stainless steel weld

    Directory of Open Access Journals (Sweden)

    BRANIMIR N. GRGUR

    2011-07-01

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

  17. In situ observations of austenite grain growth in Fe-C-Mn-Si super bainitic steel

    Institute of Scientific and Technical Information of China (English)

    Feng Liu; Guang Xu; Yu-long Zhang; Hai-jiang Hu; Lin-xin Zhou; Zheng-liang Xue

    2013-01-01

    In situ observations of austenite grain growth in Fe-C-Mn-Si super bainitic steel were conducted on a high-temperature laser scanning confocal microscope during continuous heating and subsequent isothermal holding at 850, 1000, and 1100◦C for 30 min. A grain growth model was proposed based on experimental results. It is indicated that the austenite grain size increases with austenitizing temperature and holding time. When the austenitizing temperature is above 1100◦C, the austenite grains grow rapidly, and abnormal austenite grains occur. In addition, the eff ect of heating rate on austenite grain growth was investigated, and the relation between austenite grains and bainite morphology after bainitic transformations was also discussed.

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

    DEFF Research Database (Denmark)

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

    2015-01-01

    A precipitation hardenable semi-austenitic stainless steel AISI 632 grade was austenitized according to industrial specifications and thereafter subjected to isothermal treatment at sub-zero Celsius temperatures. During treatment, austenite transformed to martensite. The isothermal austenite......-to-martensite transformation was monitored in situ by magnetometry and data was used to sketch a TTT diagram for transformation. As an alternative treatment, after austenitization the material was immersed in boiling nitrogen and up-quenched to room temperature by immersion in water prior to be subjected to isothermal...

  19. Hydrogen-related phase transformations in austenitic stainless steels

    Science.gov (United States)

    Narita, N.; Altstetter, C. J.; Birnbaum, H. K.

    1982-08-01

    The effect of hydrogen and stress (strain) on the stability of the austenite phase in stainless steels was investigated. Hydrogen was introduced by severe cathodic charging and by elevated temperature equilibration with high pressure H2 gas. Using X-ray diffraction and magnetic techniques, the behavior of two “stable” type AISI310 steels and an “unstable” type AISI304 steel was studied during charging and during the outgassing period following charging. Transformation from the fcc γ phase to an expanded fcc phase, γ*, and to the hcp ɛ phase occurred during cathodic charging. Reversion of the γ* and e phases to the original γ structure and formation of the bcc α structure were examined, and the kinetics of these processes was studied. The γ* phase was shown to be ferromagnetic with a subambient Curie temperature. The γ⇆ɛ phase transition was studied after hydrogen charging in high pressure gas, as was the formation of a during outgassing. These results are interpreted as effects of hydrogen and stress (strain) on the stability of the various phases. A proposed psuedo-binary phase diagram for the metal-hydrogen system was proposed to account for the formation of the γ* phase. The relation of these phase changes to hydrogen embrittlement and stress corrosion cracking of stainless steel is discussed.

  20. Rules of decomposition of austenite of low-pearlite steels in continuous cooling

    International Nuclear Information System (INIS)

    The kinetics of the transformation of the austenite of 12G2FR steel and, for comparison, of 09G2FB steel in continuous cooling were investigated. The chemical analyses of these steels are presented. The thermokinetic curves were constructed on an AD-73 dilatometer. Alloying of steel with up to 0.005% boron increases the stability of the austenite and provides higher hardenability of the steel. Heat treatment of plates of the steels after controlled rolling provides an increase in the strength properties from 560 to 610-640 MPa with satisfactory plasticity and impact strength

  1. Austenite Grain Growth and the Surface Quality of Continuously Cast Steel

    Science.gov (United States)

    Dippenaar, Rian; Bernhard, Christian; Schider, Siegfried; Wieser, Gerhard

    2014-04-01

    Austenite grain growth does not only play an important role in determining the mechanical properties of steel, but certain surface defects encountered in the continuous casting industry have also been attributed to the formation of large austenite grains. Earlier research has seen innovative experimentation, the development of metallographic techniques to determine austenite grain size and the building of mathematical models to simulate the conditions pertaining to austenite grain growth during the continuous casting of steel. Oscillation marks and depressions in the meniscus region of the continuously casting mold lead to retarded cooling of the strand surface, which in turn results in the formation of coarse austenite grains, but little is known about the mechanism and rate of formation of these large austenite grains. Relevant earlier research will be briefly reviewed to put into context our recent in situ observations of the delta-ferrite to austenite phase transition. We have confirmed earlier evidence that very large delta-ferrite grains are formed very quickly in the single-phase region and that these large delta-ferrite grains are transformed to large austenite grains at low cooling rates. At the higher cooling rates relevant to the early stages of the solidification of steel in a continuously cast mold, delta-ferrite transforms to austenite by an apparently massive type of transformation mechanism. Large austenite grains then form very quickly from this massive type of microstructure and on further cooling, austenite transforms to thin ferrite allotriomorphs on austenite grain boundaries, followed by Widmanstätten plate growth, with almost no regard to the cooling rate. This observation is important because it is now well established that the presence of a thin ferrite film on austenite grain boundaries is the main cause of reduction in hot ductility. Moreover, this reduction in ductility is exacerbated by the presence of large austenite grains.

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

    International Nuclear Information System (INIS)

    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

  3. A new effect of retained austenite on ductility enhancement in high strength bainitic steel

    International Nuclear Information System (INIS)

    Highlights: ► A new DARA effect in the bainitic steel is proposed. ► The conditions of DARA effect are proposed. ► The mechanism of retained austenite on ductility enhancement is clarified. - Abstract: A designed high strength bainitic steel with considerable amount of retained austenite is presented in order to study the effect of retained austenite on the ductility enhancement in bainitic steels. Transformation induced plasticity (TRIP) effect is verified by both X-ray diffraction (XRD) measurement of retained austenite fraction in various deformation stages and transmission electron microscopy observation of the deformed twin-type martensite. Results from XRD line profile analysis reveal that the average dislocation density in bainite during the deformation is lower than that before deformation, and such a phenomenon can be explained by a new effect, dislocations absorption by retained austenite (DARA) effect, based on our previous investigation of martensitic steels. DARA effect availably enhances the compatibility of deformation ability of bainite with retained austenite. In view of microstructure similarity of bainitic steels with martensitic steels, the conditions of DARA effect are proposed. The effects of retained austenite on the ductility enhancement in bainitic steels are clarified.

  4. 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.

  5. 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.

  6. Austenitization Behaviors of X80 Pipeline Steel With High Nb and Trace Ti Treatment

    Institute of Scientific and Technical Information of China (English)

    LIU Qing-you; SUN Xin-jun; JIA Shu-jun; ZHANG Lu-lin; HUANG Guo-jian; REN Yi

    2009-01-01

    The austenitization behaviors of two high niobium-containing X80 pipeline steels with different titanium contents, including the dissolution of microalloying precipitates and the austenite grain growth, were investigated by using physical-chemical phase analysis method and microstructural observation. The results illustrated that most niobium could be dissolved into austenite during soaking at 1180℃, whereas little amount of titanium could be dissolved. It was found that during soaking, the austenite grain growth rate was initially high, and then decreased after soaking for 1 h; moreover, the austenite grains grew up more rapidly at temperatures above 1180℃ than below 1180℃. The results show that the steel with titanium content of 0.016% has a larger austenite grain size than that with titanium content of 0.012% under the same soaking conditions, which is explained by considering the particle size distribution.

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

    Institute of Scientific and Technical Information of China (English)

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

    2009-01-01

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

  8. Influence of austenite grain size on overaging treatment of continuous annealed dual phase steels

    OpenAIRE

    García-Junceda, A; García Caballero, Francisca; Iung, T; Capdevila, Carlos; García de Andrés, Carlos

    2007-01-01

    A dual phase steel with an initial coarse microstructure was refined, by means of a thermal treatment, to study the influence of the austenite grain size reached during an intercritical annealing treatment on the martensite start temperature. Thus, the effect of the austenite grain size on a subsequent overaging treatment was also investigated. It was found that a coarser austenite grain size leads to a higher martensite start temperature and a lower amount of nontempered marte...

  9. 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

  10. Heat treatment of high manganese type X57MnAl27-5 austenitic steel

    International Nuclear Information System (INIS)

    In the paper, the influence of heat treatment parameters on microstructure and mechanical properties of high manganese type X57MnAl27-5 austenitic steel was investigated. The as-forged bar with diameter of 15 mm were underwent a saturation process at six different temperatures. The microstructural changes of austenite and the influence of heat treatment on the mechanical properties were considered. The quantitative analysis of austenite phase of the examined steel indicated that the parameters of saturation process resulted in changes of morphology and grain size of austenite. It was revealed that treatment temperature in the range of 950 deg. C - 1100 deg. C slightly influenced grain size, stress limit and hardness of the investigated steel. Treatment at temperature higher than 1150 deg. C resulted in the growth of austenite grain size and the decrease of mechanical properties.

  11. Fracture formation in austenitic cast steel during thermal fatigue

    Directory of Open Access Journals (Sweden)

    J. Tuleja

    2008-04-01

    Full Text Available In the paper are presented the results of numerical analyses of carburisation and thermal shock effect on fracture formation in stable austenitic cast steel of Fe–Ni–Cr–C type used in the charge–carrying elements of carburising furnaces. Using the method of finite element method, the distribution of stresses developing in carbides and their surrounding matrix were determined during rapid temperature changes. It was showed that very large tensile stresses developed in the carbides “out–coming” onto the alloy surface, regardless of the volume, type and anisotropy of properties, which could have led to their cracking as early as in the first cycles of heating and rapid cooling.

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

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

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

  13. Low temperature sensitization of austenitic stainless steel weldments

    International Nuclear Information System (INIS)

    The effect of long heat treatments on the structure and degree of sensitization of the HAZ in an austenitic stainless steel weld joint were studied. In the literature review sensitization as a phenomenon and the various metallurgical factors that affect sensitization are presented. Sensitization that occurs at temperatures well below the normal sensitization range, the so called low temperature sensitization (LTS), is described and the various variables affecting the susceptibility to LTS are considered. Transmission electron microscopy revealed that M23C6 carbides precipitate on rain boundaries in the HAZ. After welding the carbides are small and the degree of sensitization is low, but aging at temperatures below the precipitation range caused the growth of previously nucleated carbides. At the same time the degree of sensitization increased considerably. The degree of sensitization was evaluated with various intergranular corrosion tests. The electrochemical EPR-test proved to be suitable for measuring small changes in the degree of sensitization. (author)

  14. Formability analysis of austenitic stainless steel-304 under warm conditions

    Science.gov (United States)

    Lade, Jayahari; Singh, Swadesh Kumar; Banoth, Balu Naik; Gupta, Amit Kumar

    2013-12-01

    A warm deep drawing process of austenitic stainless steel-304 (ASS-304) of circular blanks with coupled ther mal analysis is studied in this article. 65 mm blanks were deep drawn at different temperatures and thickness distribution is experimentally measured after cutting the drawn component into two halves. The process is simulated using explicit fin ite element code LS-DYNA. A Barlat 3 parameter model is used in the simulation, as the material is anisotropic up to 30 0°C. Material properties for the simulation are determined at different temperatures using a 5 T UTM coupled with a furn ace. In this analysis constant punch speed and variable blank holder force (BHF) is applied to draw cups without wrinkle.

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

    International Nuclear Information System (INIS)

    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)

  16. Fatigue crack growth in metastable austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    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.

  17. Mechanized welding of austenitic precision stainless steel tubes

    International Nuclear Information System (INIS)

    Austenitic stainless steel tubes of material no. 1,4541 and 1,4550 are used for the tube systems to transport active and inactive gases in reactor experiments. A fully mechanical method was developed for the joining of these tubes by welding which makes use of an electrode holder with surrounding W electrode. This method, whose application is described here, enables the joining of the tubes in all welding positions. A pulsating direct current is used as welding current. Breaking tests on the welded samples gave values corresponding to the strength of the materials mentioned. The welded seams are subjected to the helium leak test and to the X-ray test. (GSCH/LH)

  18. 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.

  19. Steam generator local water chemistry and SCC of austenitic steel

    International Nuclear Information System (INIS)

    The titanium stabilized austenitic steel similar to the type of 321 is sensitive to the stress corrosion cracking under horizontal steam generator operating condition. SCC was observed under crevice corrosion parameters and has resulted in the transgranular or intergranular cracking at the both, components primary collectors and heat exchange tubes. The crevice environment is characterized by aggressive impurities and 'non aggressive' compounds. Sulfates and chlorides as aggressive species and silicates and alumino-silicates as 'non aggressive' species on the other hand are present in significant amount in the crevice environment under operating condition. Local water chemistry parameters were evaluated with MULTEQ Code. As input data the measured operational values of local and bulk environments have been used. The determined parameters were compared with the results of thread hole environment analyses and tube surface investigations respectively. Results of the hideout return profiles measurement showed an increase of sulfate concentration by one order of magnitude. Increase of the chloride content was not been observed, its value remains at operation levels. Examination of surface layers showed the preferential accumulation of sulfates, silicates and alumino-silicates in the deposit at tube support plates and in thread holes comparing relative to free span surfaces. The content of species in the water and deposits and the crystallographic structure of deposits correspond to MULTEQ results. Rising displacement tests were carried out with 0.5T CT specimens at a temperature 275 degrees C in the model water environment which simulated the crevice conditions. The experimental values are presented for crack growth rate versus stress intensity factor. Corrosion damage of the titanium stabilized austenitic steel is likely to be determined by the presence of sulfates and chlorides and other aggressive agents, as Cu. It is supposed that other decisive factor is the

  20. Features of phase composition of stainless austenitic steels and possibility of selection tubes of these steels in accordance with their steel grades by means of eddy current method

    International Nuclear Information System (INIS)

    Studies on mechanical, magnetic and electric characteristics of some types of chromium-nickel and chromium-nickel-molybdenum austenitic steels used for manufacturing hot-rolled tubes are carried out. A possibility of nondestructive control of stainless austenitic steel by grades is disclosed. A mock-up of an eddy device with a superposed transformer for measurements on samples of tubes is described

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

    International Nuclear Information System (INIS)

    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

  2. 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

  3. 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.

  4. Magnetic properties of single crystalline expanded austenite obtained by plasma nitriding of austenitic stainless steel single crystals.

    Science.gov (United States)

    Menéndez, Enric; Templier, Claude; Garcia-Ramirez, Pablo; Santiso, José; Vantomme, André; Temst, Kristiaan; Nogués, Josep

    2013-10-23

    Ferromagnetic single crystalline [100], [110], and [111]-oriented expanded austenite is obtained by plasma nitriding of paramagnetic 316L austenitic stainless steel single crystals at either 300 or 400 °C. After nitriding at 400 °C, the [100] direction appears to constitute the magnetic easy axis due to the interplay between a large lattice expansion and the expected decomposition of the expanded austenite, which results in Fe- and Ni-enriched areas. However, a complex combination of uniaxial (i.e., twofold) and biaxial (i.e., fourfold) in-plane magnetic anisotropies is encountered. It is suggested that the former is related to residual stress-induced effects while the latter is associated to the in-plane projections of the cubic lattice symmetry. Increasing the processing temperature strengthens the biaxial in-plane anisotropy in detriment of the uniaxial contribution, in agreement with a more homogeneous structure of expanded austenite with lower residual stresses. In contrast to polycrystalline expanded austenite, single crystalline expanded austenite exhibits its magnetic easy axes along basic directions. PMID:24028676

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

    NARCIS (Netherlands)

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

    2004-01-01

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

  6. The influence of titanium additions on the swelling of austenitic steels and nickel alloys irradiated with electrons

    International Nuclear Information System (INIS)

    It is shown that the addition of titanium is beneficial to the swelling behaviour of austenitic steels. The magnitude of the observed effects depends greatly on the nature and concentration of the other minor elements in the austenite matrix. (author)

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

    Science.gov (United States)

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

    2016-05-01

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

  8. Effect of initial microstructure on austenite formation kinetics in high-strength experimental microalloyed steels

    Science.gov (United States)

    López-Martínez, Edgar; Vázquez-Gómez, Octavio; Vergara-Hernández, Héctor Javier; Campillo, Bernardo

    2015-12-01

    Austenite formation kinetics in two high-strength experimental microalloyed steels with different initial microstructures comprising bainite-martensite and ferrite-martensite/austenite microconstituents was studied during continuous heating by dilatometric analysis. Austenite formation occurred in two steps: (1) carbide dissolution and precipitation and (2) transformation of residual ferrite to austenite. Dilatometric analysis was used to determine the critical temperatures of austenite formation and continuous heating transformation diagrams for heating rates ranging from 0.03°C•s-1 to 0.67°C•s-1. The austenite volume fraction was fitted using the Johnson-Mehl-Avrami-Kolmogorov equation to determine the kinetic parameters k and n as functions of the heating rate. Both n and k parameters increased with increasing heating rate, which suggests an increase in the nucleation and growth rates of austenite. The activation energy of austenite formation was determined by the Kissinger method. Two activation energies were associated with each of the two austenite formation steps. In the first step, the austenite growth rate was controlled by carbon diffusion from carbide dissolution and precipitation; in the second step, it was controlled by the dissolution of residual ferrite to austenite.

  9. Effect of initial microstructure on austenite formation kinetics in high-strength experimental microalloyed steels

    Institute of Scientific and Technical Information of China (English)

    Edgar Lpez-Martnez; Octavio Vzquez-Gmez; Hctor Javier Vergara-Hernndez; Bernardo Campillo

    2015-01-01

    Austenite formation kinetics in two high-strength experimental microalloyed steels with different initial microstructures compris-ing bainite–martensite and ferrite–martensite/austenite microconstituents was studied during continuous heating by dilatometric analysis. Austenite formation occurred in two steps:(1) carbide dissolution and precipitation and (2) transformation of residual ferrite to austenite. Di-latometric analysis was used to determine the critical temperatures of austenite formation and continuous heating transformation diagrams for heating rates ranging from 0.03°C×s−1 to 0.67°C×s−1. The austenite volume fraction was fitted using the Johnson–Mehl–Avrami–Kolmogorov equation to determine the kinetic parameters k and n as functions of the heating rate. Both n and k parameters increased with increasing heat-ing rate, which suggests an increase in the nucleation and growth rates of austenite. The activation energy of austenite formation was deter-mined by the Kissinger method. Two activation energies were associated with each of the two austenite formation steps. In the first step, the austenite growth rate was controlled by carbon diffusion from carbide dissolution and precipitation;in the second step, it was controlled by the dissolution of residual ferrite to austenite.

  10. 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. PMID:23910251

  11. Static Recrystallization Behavior of Hot Deformed Austenite for Micro-Alloyed Steel

    Institute of Scientific and Technical Information of China (English)

    Jie HUANG; Zhou XU; Xin XING

    2003-01-01

    Static recrystallization behavior of austenite for micro-alloyed steel during hot rolling was studied and the influence (τ-ε diagram) of holding time and deformation at different deformations and isothermal temperatures on microstructuralstate of austen

  12. 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.

  13. A study of the microstructural distribution of cathodic hydrogen in austenitic stainless steels by hydrogen microprint

    International Nuclear Information System (INIS)

    The cathodic hydrogen distribution in austenitic stainless steel (304L; 316L) microstructure is shwon, at electron microscope scale, using the hydrogen microprint technique. Cathodic hydrogen induced cracking is analysed

  14. Fractographic studies of hydrogen embrittlement of AISI 316L austenitic stainless steel

    International Nuclear Information System (INIS)

    This paper concerns a fractographic examination of hydrogen embrittlement of a stable AISI 316L type austenitic stainless steel. The objective is a better understanding of the possible role of hydrogen in stress corrosion cracking processes. (author)

  15. Characteristics of the Austenitic Steels Used in the LHC Main Dipoles

    CERN Document Server

    Lanza, C

    2002-01-01

    The LHC dipole structure is assembled using austenitic steel collars and austenitic steel end-laminations. The collars will be fine-blanked starting from 11'000 tonnes of steel; the end-laminations require 1'700 tonnes of steel. The procurement of the austenitic steels was divided in two phases: first we qualified different grades from different producers then we made the call for tender, adjudicated the contract and started the series production. The first part of this paper summarises the results of the first qualification phase when extensive checks and measurements were carried out on five different grades. The second part describes the approach used to control the series production and the results obtained. At the time of writing about 19% of the steel for collars and end-laminations has been manufactured and delivered.

  16. Effect of retained austenite on the fracture toughness of tempered tool steel

    OpenAIRE

    A. Kokosza; J. Pacyna

    2008-01-01

    Purpose: This paper is an attempt of reviewing the outlooks about the favourable influence of retained austeniteon fracture toughness of tool steels according to results of investigation concerning relations between temperingtemperature, hardness, fraction of retained austenite and fracture toughness.Design/methodology/approach: The tests were performed on the samples made of the 70MnCrMoV9-2-4-2steel in which the fraction of retained austenite was changed by cold treatment and by changing th...

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

    OpenAIRE

    W.S. Lin

    2008-01-01

    Purpose: The purpose of this research paper is focused on the surface roughness variation in high speed fine turning of the austenitic stainless steel.Design/methodology/approach: A series of experimental tests have been done to evaluate the possibility of high speed fine turning of the austenitic stainless steel from the surface roughness variation and machining stability.Findings: It was found that, the smaller the feed rate, the smaller the surface roughness value. But when the feed rate s...

  18. Microstructure and properties of laser surface alloyed PM austenitic stainless steel

    OpenAIRE

    Z. Brytan; M. Bonek; L.A. Dobrzański

    2010-01-01

    Purpose: The purpose of this paper is to analyse the effect of laser surface alloying with chromium on the microstructural changes and properties of vacuum sintered austenitic stainless steel type AISI 316L (EN 1.4404).Design/methodology/approach: Surface modification of AISI 316L sintered austenitic stainless steel was carried out by laser surface alloying with chromium powder using high power diode laser (HPDL). The influence of laser alloying conditions, both laser beam power (between 0.7 ...

  19. Stress corrosion cracking behaviour of gas tungsten arc welded super austenitic stainless steel joints

    OpenAIRE

    M. Vinoth Kumar; Balasubramanian, V.; S. RAJAKUMAR; Shaju K. Albert

    2015-01-01

    Super 304H austenitic stainless steel with 3% of copper posses excellent creep strength and corrosion resistance, which is mainly used in heat exchanger tubing of the boiler. Heat exchangers are used in nuclear power plants and marine vehicles which are intended to operate in chloride rich offshore environment. Chloride stress corrosion cracking is the most likely life limiting failure with austenitic stainless steel tubing. Welding may worsen the stress corrosion cracking susceptibility of t...

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

    Institute of Scientific and Technical Information of China (English)

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

    2004-01-01

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

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

    OpenAIRE

    Li Xiaoyun; Wu Wei; Zu Fangqiu

    2012-01-01

    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 disloca...

  2. Microstructure of 316L austenite stainless steel after charging with deuterium and tritium

    International Nuclear Information System (INIS)

    The microstructure of 316L austenite stainless steel after charging with deuterium and tritium for 6 years at room temperature is studied. The results indicate that the morphology of fracture surface after blasting is ductile rupture with dimple, stress produced by blasting of high pressure leads to the martensite transformation. The deuterium and tritium improve the ε martensite transformation of austenite and reduce the fault energy, which reduce the hydrogen-resistant properties of 316L stainless steel

  3. Effect of Austenite Deformation on Continuous Cooling Transformation Microstructures for 22CrSH Gear Steel

    Institute of Scientific and Technical Information of China (English)

    WANG Bing-xin; JIANG Ying-tian; XU Xu-dong; LIU Xiang-hua; WANG Guo-dong

    2007-01-01

    The effect of compressive deformation of austenite on continuous cooling transformation microstructures for 22CrSH gear steel has been investigated using a Gleeble 1500 thermal simulator. The experimental results show that the deformation of austenite promotes the formation of proeutectoid ferrite and pearlite, and leads to the increase of critical cooling rate of proeutectoid ferrite plus pearlite microstructure. The grain boundary allotriomorphic ferrite occupies the austenite grain surfaces when the prior deformation takes place or the cooling rate is decreased, which causes a transition from bainite to acicular ferrite. The deformation enhances the stability of transformation from austenite to acicular ferrite, which results in an increase of M/A constituent.

  4. Stress corrosion cracking of austenitic stainless steel core internal weld

    International Nuclear Information System (INIS)

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

  5. Mechanical Properties of Thermally Aged Austenitic Stainless Steel Welds and Cast Austenitic Stainless Steel

    International Nuclear Information System (INIS)

    Conventional test methods for tensile and J-R properties of such weld require large size specimens. Meanwhile, small punch (SP) test has advantages of using small size samples at specific location. In this study, the mechanical property changes caused by the thermal aging were evaluated for the stainless steel welds and CASSs using tensile, J-R, and SP test. Based on the results, correlations were developed to estimate the fracture toughness using the load-displacement curve of SP tests. Finally, the fracture surfaces of compact tension (CT) and SP test specimens are compared and discussed in view of the effect of thermal aging on microstructure. Stainless steel welds of ER316L and ER347 as well as CASS (CF8M) were thermally aged at 400 .deg. C for 5,000 h. So far, tensile properties and fracture toughness of un-aged materials were carried out at room temperature and 320 .deg. C as a reference data. In order to evaluate the effect of thermal aging on mechanical properties, aged specimens are being tested and the changes in these properties will be discussed. In addition, correlations will be developed to estimate the fracture toughness in between J-R curve and SP curve

  6. EFFECTS OF CARBON CONTENT AND ROLLING PROCESSING ON RETAINED AUSTENITE FOR HOT-ROLLED TRIP STEELS

    Institute of Scientific and Technical Information of China (English)

    Y. Chen; X. Chen; Z.X. Yuan; B.F. Xu; A.M. Guo; P.H. Li; S.K. Pu

    2002-01-01

    The effects of finishing rolling temperature and coiling temperature on retained austen-ire were studied for hot-rolled transformation induced plasticity (TRIP) steels withdifferent carbon content. The experimental results showed that an appropriate volumefraction of retained austenite from 6% to 11% could be obtained according to the dif-ferent carbon content less than 0.20% by controlled finishing rolling and coiling forthe hot-rolled TRIP steels. It can be concluded that carbon content has a significanteffect on the fraction of retained austenite and coiling processing plays stronger roleon retaining austenite than fishing rolling processing.

  7. Niobium effects on the austenitic grain growth and hardenability of steels for mechanical construction

    International Nuclear Information System (INIS)

    The austenitic grain growth and hardenability of SAE 86XX and 5120 steels modified with 0,001 to 0,20 per-cent niobium content were studied when submitted to case hardening and quenching heat treatments. The results show that niobium controlS the austenite grain size better than molybdenum up to 9500C austenitization temperature. The hardenability, evaluated by the Jominy test which the modified SAE 8640 steels, is more strongly inflencied by the grain refining resulting from niobium addition than by any other supposed effect. (Author)

  8. Influence of kinetics of supercooled austenite decomposition on structure formation in sparingly-alloyed tool steel

    Science.gov (United States)

    Krylova, S. E.; Yakovleva, I. L.; Tereshchenko, N. A.; Priimak, E. Yu.; Kletsova, O. A.

    2013-10-01

    The decomposition of supercooled austenite in 70Kh3G2VTB steel under isothermal conditions and continuous cooling have been studied. The isothermal and continuous cooling tranformation curves of the decomposition of austenite in the experimental steel have been constructed. The effect of alloying elements on phase transformations in the steel under heating and cooling have been established. The features of the formation of a microstructure in the 70Kh3G2VTB steel after different regimes of heat treatment have been described. The optimal parameters of hardening heat treatment have been developed.

  9. Influence of phase transformation on the hardening of austenitic stainless steels

    International Nuclear Information System (INIS)

    The influence of phase transformation on the true stress-true strain curves of austenitic stainless steels was studied. This investigation was carried on one type of AISI 302 steel and one AISI 316 steel. The temperature range varied from -1960C to room temperature. A model for the workhardening of metaestable austenitic stainless steel is proposed. It was concluded that stress induced martensite epsilon may be responsible for the lowering of yield strength as well as the initial plateau on workhardening in these materials. (Author)

  10. Influence of reverted austenite on the texture and magnetic properties of 350 maraging steel

    Energy Technology Data Exchange (ETDEWEB)

    Abreu, Hamilton F.G., E-mail: hamilton@ufc.br [Universidade Federal do Ceará, Campus do Pici-Bloco 729, CEP 60440-554 Fortaleza, CE (Brazil); Silva, Jean J. [Universidade Federal do Ceará, Campus do Pici-Bloco 729, CEP 60440-554 Fortaleza, CE (Brazil); Silva, Manoel R. [Universidade Federal de Itajubá, Campus Sede Itajubá/IFQ- Instituto de Física e Química, Itajubá, MG (Brazil); Gomes da Silva, Marcelo J., E-mail: mgsilva@ufc.br [Universidade Federal do Ceará, Campus do Pici-Bloco 729, CEP 60440-554 Fortaleza, CE (Brazil)

    2015-11-01

    The aging temperature to improve magnetic properties in Maraging-350 steel (Mar-350) is limited by the onset of austenite reversion. The traditional process of cooling after aging is to remove the piece from the oven and then to air cool it. The purpose of this research was to characterize the reverted austenite and to investigate the effect of cooling below the martensite start temperature (M{sub s}) on the magnetic properties. The Mar350 samples aged at temperatures above 550 °C, and subsequently cooled in liquid nitrogen presented less austenite than samples cooled in air, resulting in higher magnetization saturation and a lower coercive force. A combination of optical microscopy (OM), X-ray diffraction (XRD) and electron backscatter diffraction (EBSD) techniques were used to characterize the presence of reverted austenite. The crystallographic texture of both martensite and reverted austenite were analyzed. The texture of the reverted austenite coincides with the texture of the parent austenite indicating that a phenomenon of texture memory is present. - Highlights: • Cooling maraging samples in liquid nitrogen reduces reverted austenite fraction. • Retained austenite increases coercive force and decreases saturation magnetization. • Reverted and parent austenites have the same crystallographic texture. • Memory effect found during reversion transformation.

  11. Influence of reverted austenite on the texture and magnetic properties of 350 maraging steel

    International Nuclear Information System (INIS)

    The aging temperature to improve magnetic properties in Maraging-350 steel (Mar-350) is limited by the onset of austenite reversion. The traditional process of cooling after aging is to remove the piece from the oven and then to air cool it. The purpose of this research was to characterize the reverted austenite and to investigate the effect of cooling below the martensite start temperature (Ms) on the magnetic properties. The Mar350 samples aged at temperatures above 550 °C, and subsequently cooled in liquid nitrogen presented less austenite than samples cooled in air, resulting in higher magnetization saturation and a lower coercive force. A combination of optical microscopy (OM), X-ray diffraction (XRD) and electron backscatter diffraction (EBSD) techniques were used to characterize the presence of reverted austenite. The crystallographic texture of both martensite and reverted austenite were analyzed. The texture of the reverted austenite coincides with the texture of the parent austenite indicating that a phenomenon of texture memory is present. - Highlights: • Cooling maraging samples in liquid nitrogen reduces reverted austenite fraction. • Retained austenite increases coercive force and decreases saturation magnetization. • Reverted and parent austenites have the same crystallographic texture. • Memory effect found during reversion transformation

  12. Transformation of austenite to duplex austenite-ferrite assembly in annealed stainless steel 316L consolidated by laser melting

    Energy Technology Data Exchange (ETDEWEB)

    Saeidi, K.; Gao, X. [Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm (Sweden); Lofaj, F. [Institute of Materials Research of the Slovak Academy of Sciences, Watsonova 47, Košice (Slovakia); Faculty of Materials Science and Technology in Trnava, Slovak University of Technology in Bratislava, 916 24 Trnava (Slovakia); Kvetková, L. [Institute of Materials Research of the Slovak Academy of Sciences, Watsonova 47, Košice (Slovakia); Shen, Z.J. [Department of Materials and Environmental Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm (Sweden)

    2015-06-05

    Highlights: • Mechanical properties, phase and microstructure stability of laser melted steel was studied. • Duplex austenite-ferrite assembly with improved mechanical properties was formed. • Dissolution of Mo in the steel matrix resulted in ferrite stabilization and stress relief. • Enhanced mechanical properties were achieved compared to conventionally casted and annealed steel. - Abstract: Laser melting (LM), with a focused Nd:YAG laser beam, was used to form solid bodies from 316L austenite stainless steel powder and the laser melted samples were heat treated at various temperatures. The phase changes in heat treated samples were characterized using X-ray diffraction (XRD). Samples heat treated at 800 °C and 900 °C remained single austenite while in samples heat treated at 1100 °C and 1400 °C a dual austenite-ferrite phase assembly was formed. The ferrite formation was further verified by electron back scattering diffraction (EBSD) and selective area diffraction (SAD). Microstructural changes were studied by scanning and transmission electron microscopy (SEM, TEM). In samples heat treated up to 900 °C, coalescence of the cellular-sub grains was noticed, whereas in sample heat treated at and above 1100 °C the formation of ferrite phase was observed. The correlation between the microstructure/phase assembly and the measured strength/microhardness were investigated, which indicated that the tensile strength of the laser melted material was significantly higher than that of the conventional 316L steel even after heat treatment whereas caution has to be taken when laser melted material will be exposed to an application temperature above 900 °C.

  13. Transformation of austenite to duplex austenite-ferrite assembly in annealed stainless steel 316L consolidated by laser melting

    International Nuclear Information System (INIS)

    Highlights: • Mechanical properties, phase and microstructure stability of laser melted steel was studied. • Duplex austenite-ferrite assembly with improved mechanical properties was formed. • Dissolution of Mo in the steel matrix resulted in ferrite stabilization and stress relief. • Enhanced mechanical properties were achieved compared to conventionally casted and annealed steel. - Abstract: Laser melting (LM), with a focused Nd:YAG laser beam, was used to form solid bodies from 316L austenite stainless steel powder and the laser melted samples were heat treated at various temperatures. The phase changes in heat treated samples were characterized using X-ray diffraction (XRD). Samples heat treated at 800 °C and 900 °C remained single austenite while in samples heat treated at 1100 °C and 1400 °C a dual austenite-ferrite phase assembly was formed. The ferrite formation was further verified by electron back scattering diffraction (EBSD) and selective area diffraction (SAD). Microstructural changes were studied by scanning and transmission electron microscopy (SEM, TEM). In samples heat treated up to 900 °C, coalescence of the cellular-sub grains was noticed, whereas in sample heat treated at and above 1100 °C the formation of ferrite phase was observed. The correlation between the microstructure/phase assembly and the measured strength/microhardness were investigated, which indicated that the tensile strength of the laser melted material was significantly higher than that of the conventional 316L steel even after heat treatment whereas caution has to be taken when laser melted material will be exposed to an application temperature above 900 °C

  14. The model of prediction of the microstructure austenite C-Mn steel

    Directory of Open Access Journals (Sweden)

    B. Koczurkiewicz

    2007-07-01

    Full Text Available Purpose: The subject of the work is analysis of author’s model for prediction of austenite microstructure of C-Mn steel based on Sellar’s solution.Design/methodology/approach: The present study adopts the Sellar’s solution for C-Mn steel to the prediction of phenomena occurring in the steel and the grain size of austeniteFindings: The developed model for the evolution of the austenite microstructure enables the correct determination of the grain size of austenite formed by multi-stage hot deformation.Research limitations/implications: The model is limitated only for selected steel groupPractical implications: The results obtained on the basis of this model will be utilized in the study for the determination of the distribution and state of microstructure in sections with complicated shapes after the rolling process.Originality/value: The modelling of microstructure is very importante problem. There are a lot of general models in literature, which can be used for predicting evolution of microstructure after rolling proces of steel, but the results obtained from them are different. There is a need for adapting the general model for a selected steel group to the prediction of phenomena occurring in the steel and the grain size of austenite formed by means of multi-stage deformation.

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

    Institute of Scientific and Technical Information of China (English)

    Ke YANG; Manqi L(U)

    2007-01-01

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

  16. 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.

  17. The mechanical stability of retained austenite in low-alloyed TRIP steel under shear loading

    International Nuclear Information System (INIS)

    The microstructure evolution during shear loading of a low-alloyed TRIP steel with different amounts of the metastable austenite phase and its equivalent DP grade has been studied by in-situ high-energy X-ray diffraction. A detailed powder diffraction analysis has been performed to probe the austenite-to-martensite transformation by characterizing simultaneously the evolution of the austenite phase fraction and its carbon concentration, the load partitioning between the austenite and the ferritic matrix and the texture evolution of the constituent phases. Our results show that for shear deformation the TRIP effect extends over a significantly wider deformation range than for simple uniaxial loading. A clear increase in average carbon content during the mechanically-induced transformation indicates that austenite grains with a low carbon concentration are least stable during shear loading. The observed texture evolution indicates that under shear loading the orientation dependence of the austenite stability is relatively weak, while it has previously been found that under tensile load the {110}〈001〉 component transforms preferentially. The mechanical stability of retained austenite in TRIP steel is found to be a complex interplay between the interstitial carbon concentration in the austenite, the grain orientation and the load partitioning

  18. Effect of fresh martensite on the stability of retained austenite in quenching and partitioning steel

    International Nuclear Information System (INIS)

    Restrictions on fuel consumption and safety in the automotive industry have stimulated the development of quenching and partitioning (Q and P) steel. This steel is expected to have very high strength in combination with acceptable ductility owing to its microstructure consisting of martensite with a considerable amount of retained austenite. The effect of retained austenite on the mechanical properties and its transformation stability were determined by stepwise uniaxial micro-tensile testing and subsequent electron backscatter diffraction (EBSD) study of a pre-selected region. The austenite fraction evolution with increasing plastic deformation and the influence of fresh martensite on the local strain distribution were quantified based on the orientation data. The decrease of the retained austenite as a function of the applied strain was described by an exponential function with the pre-exponential and exponential factors related to the starting austenite fraction and its transformation stability respectively. It was proven that the presence of fresh martensite has a negative influence on this austenite transformation stability due to its constraining effect on the strain distribution. This effects the mechanical properties manifested by changes in the strain hardening behavior and total elongation. The results suggest that the ductility of the Q and P steels can be improved by an appropriate design of the heat treatment schedule in order to ensure high retained austenite fractions without the presence of fresh martensite in the final microstructure

  19. Dislocation loop evolution under ion irradiation in austenitic stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Etienne, A., E-mail: auriane.etienne@etu.univ-rouen.f [Groupe de Physique des Materiaux, Universite et INSA de Rouen, UMR CNRS 6634, BP 12, 76 801 Saint Etienne du Rouvray Cedex (France); Hernandez-Mayoral, M. [Division of Materials, CIEMAT, Avenida Complutense 22, 28040 Madrid (Spain); Genevois, C.; Radiguet, B.; Pareige, P. [Groupe de Physique des Materiaux, Universite et INSA de Rouen, UMR CNRS 6634, BP 12, 76 801 Saint Etienne du Rouvray Cedex (France)

    2010-05-01

    A solution annealed 304 and a cold worked 316 austenitic stainless steels were irradiated from 0.36 to 5 dpa at 350 deg. C using 160 keV Fe ions. Irradiated microstructures were characterized by transmission electron microscopy (TEM). Observations after irradiation revealed the presence of a high number density of Frank loops. Size and number density of Frank loops have been measured. Results are in good agreement with those observed in the literature and show that ion irradiation is able to simulate dislocation loop microstructure obtained after neutron irradiation. Experimental results and data from literature were compared with predictions from the cluster dynamic model, MFVIC (Mean Field Vacancy and Interstitial Clustering). It is able to reproduce dislocation loop population for neutron irradiation. Effects of dose rate and temperature on the loop number density are simulated by the model. Calculations for ion irradiations show that simulation results are consistent with experimental observations. However, results also show the model limitations due to the lack of accurate parameters.

  20. Dislocation loop evolution under ion irradiation in austenitic stainless steels

    Science.gov (United States)

    Etienne, A.; Hernández-Mayoral, M.; Genevois, C.; Radiguet, B.; Pareige, P.

    2010-05-01

    A solution annealed 304 and a cold worked 316 austenitic stainless steels were irradiated from 0.36 to 5 dpa at 350 °C using 160 keV Fe ions. Irradiated microstructures were characterized by transmission electron microscopy (TEM). Observations after irradiation revealed the presence of a high number density of Frank loops. Size and number density of Frank loops have been measured. Results are in good agreement with those observed in the literature and show that ion irradiation is able to simulate dislocation loop microstructure obtained after neutron irradiation. Experimental results and data from literature were compared with predictions from the cluster dynamic model, MFVIC (Mean Field Vacancy and Interstitial Clustering). It is able to reproduce dislocation loop population for neutron irradiation. Effects of dose rate and temperature on the loop number density are simulated by the model. Calculations for ion irradiations show that simulation results are consistent with experimental observations. However, results also show the model limitations due to the lack of accurate parameters.

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

    International Nuclear Information System (INIS)

    The wear properties of AISI 316 austenitic stainless steel implanted with Ti were investigated for ion doses in the range (2.3-5.4)x1016ionscm-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 5.1x1016ionscm-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.))

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

    Institute of Scientific and Technical Information of China (English)

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

    2009-01-01

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

  3. Dislocation loop evolution under ion irradiation in austenitic stainless steels

    International Nuclear Information System (INIS)

    A solution annealed 304 and a cold worked 316 austenitic stainless steels were irradiated from 0.36 to 5 dpa at 350 deg. C using 160 keV Fe ions. Irradiated microstructures were characterized by transmission electron microscopy (TEM). Observations after irradiation revealed the presence of a high number density of Frank loops. Size and number density of Frank loops have been measured. Results are in good agreement with those observed in the literature and show that ion irradiation is able to simulate dislocation loop microstructure obtained after neutron irradiation. Experimental results and data from literature were compared with predictions from the cluster dynamic model, MFVIC (Mean Field Vacancy and Interstitial Clustering). It is able to reproduce dislocation loop population for neutron irradiation. Effects of dose rate and temperature on the loop number density are simulated by the model. Calculations for ion irradiations show that simulation results are consistent with experimental observations. However, results also show the model limitations due to the lack of accurate parameters.

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

    Science.gov (United States)

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

    2015-02-01

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

  5. Lean-alloyed austenitic stainless steel with high resistance against hydrogen environment embrittlement

    International Nuclear Information System (INIS)

    Highlights: · Hydrogen environment embrittlement of austenitic steel. · Novel alloying concept for austenitic stainless steel with improved HEE resistance. · Influence of austenite stability and strain-induced α-martensite on HEE. · Cost efficiency by reduced amounts of nickel and molybdenum. · Influence of silicon on HEE. - Abstract: To address the upcoming austenitic stainless steel market for automotive applications involving hydrogen technology, a novel lean - alloyed material was developed and characterized. It comprises lower contents of nickel and molybdenum compared to existing steels for high - pressure hydrogen uses, for instance 1.4435 (AISI 316L). Alloying with manganese and carbon ensures a sufficient stability of the austenite at 8 wt.% of nickel while silicon is added to improve resistance against embrittlement by dissolved hydrogen. Investigations were performed by tensile testing in air and 400 bar hydrogen at 25 deg. C, respectively. In comparison to a standard 1.4307 (AISI 304L) material, a significant improvement of ductility was found. The materials concept is presented in general and discussed with regard to austenite stability and microstructure.

  6. 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...

  7. Compatibility of Austenitic Steel With Molten Lead-Bismuth-Tin Alloy

    Institute of Scientific and Technical Information of China (English)

    ZHANG Rui-qian; LI Yan; WANG Xiao-min

    2011-01-01

    The compatibility of the austenitic AISI 304 steel with Pb-Bi-Sn alloy was analyzed. The AISI 304 steels were immersed in stagnant molten Pb-33.3Bi-33. 3Sn alloy at 400, 500 and 600℃ for different exposure times (100-2 000 h) respectively. XRay diffractio

  8. Thermal Stability of Retained Austenite in TRIP Steel After Different Treatments

    Institute of Scientific and Technical Information of China (English)

    SHI Wen; LI Lin; Bruno C De Cooman; Patrick Wollants; YANG Chun-xia

    2008-01-01

    Thermal decomposition of retained austenite in TRIP steel was investigated by means of differential scanning calorimetry (DSC). The decomposition curve was abnormal, and the decomposition temperature and the activation energy were measured by the Kissinger method, which were all higher than those in quenched steel. The thermal decomposition data of samples soaked in liquid nitrogen after TRIP treatment were all similar to those without additional low temperature treatment. It indicated that there is a high thermal stability in retained austenite of the TRIP steel at low temperature, which was also proved by XRD analysis.

  9. Stages of austenitization of cold-worked low-carbon steel in intercritical temperature range

    Science.gov (United States)

    Panov, D. O.; Simonov, Y. N.; Spivak, L. V.; Smirnov, A. I.

    2015-08-01

    Austenization processes in 10Kh3G3MF low-carbon steel in the initially cold-worked state are investigated during its continuous heating in an intercritical temperature range. The austenization of this steel has three stages, which is shown by dilatometry, differential scanning calorimetry, and transmission electron microscopy. The thermokinetic diagram of the austenite formation in 10Kh3G3MF steel is constructed. Critical points A c1 and A c2 and temperature ranges of austenite formation at every stage of the α → γ transformation at heating rates of 0.6-400 K/s are determined.

  10. 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 of...... industrial tool used for high volume production of pump components, to compare forming of LDX 2101 and austenitic stainless steel with equal thickness. The forming forces, the geometry and the strains in the sheet material were compared for the same component. It was found that LDX steels can be formed to...... high strain levels in tools normally applied for forming of austenitic steels, but tool adaptations are needed to comply with the higher strength and springback of the material....

  11. The structure and corrosion behavior of electron beam treated austenitic stainless steels

    International Nuclear Information System (INIS)

    The influence of electron beam surface melting of austenitic AISI 304 stainless steel on its microstructure and anodic potentiostatic behavior in 1N sulphuric acid at 25 C has been studied. Delta ferrite formed in the surface melted layer and was found to vary with electron beam current and stainless steel plate thickness. The structure and anodic behavior of AISI 304 specimens conventionally heat treated to provoke ferrite formation were also studied. The length of active region in the anodic potentiostatic curves for both the surface melted and heat treated specimens decreased with increasing ferrite in the austenitic steel. Overall, surface melting using high energy sources has been found to significantly improve the aqueous corrosion resistance of austenitic stainless steel by provoking the formation of duplex microstructures. (author)

  12. Regularities of structure formation during hot deformation of austenite in alloy steels

    International Nuclear Information System (INIS)

    Regularities of substructure formation during hot working of austenite in 110Kh6 and 40Kh8G8 alloy steels, structural peculiarities and relations between structure development and a hot deformation curve were investigated. The possibility of structure formation modeling is also evaluated for deformation under commercial procedure conditions. Hot deformation during high temperatue thermomechanical treatment was carried out by rolling and compression. It is found that in alloy steel austenite during hot deformation up to 7-10% the processes of intensive strain hardening develop which result in formation of substructure with high density of dislocations either distributed uniformly or forming a cellular type substructure. Strain softening processes (dynamic polygonization) arise with a deformation degree increase. The relationship found between a hot deformation curve and structural changes during hot working of alloy steel austenite provides the option for conditions of high temperature thermomechanical treatment of commerical alloy steels softening according to a dynamic polygonization mechanism

  13. Effect of retained austenite on the fracture toughness of tempered tool steel

    Directory of Open Access Journals (Sweden)

    A. Kokosza

    2008-06-01

    Full Text Available Purpose: This paper is an attempt of reviewing the outlooks about the favourable influence of retained austeniteon fracture toughness of tool steels according to results of investigation concerning relations between temperingtemperature, hardness, fraction of retained austenite and fracture toughness.Design/methodology/approach: The tests were performed on the samples made of the 70MnCrMoV9-2-4-2steel in which the fraction of retained austenite was changed by cold treatment and by changing the temperingtemperature. On the ground of analysis of dependencies between fraction of retained austenite, hardness, fracturetoughness and tempering temperature of hardened 70MnCrMoV9-2-4-2 steel the influence of retained austenite onfracture toughness of tested steel was investigated.Findings: was found that retained austenite remaining in the structure of tested steel after quenching increased itsfracture toughness on directly proportional way to its volume fraction. Advantageous influence of this phase wasalso found after tempering tested steel.Research limitations/implications: It was pointed out that most beneficial influence of retained austeniteexists when tested steel after hardening is low-tempered. At that moment the highest stabilization of the phaseoccurs. While at tempering temperatures above 220°C it was indicated that it is possible to combine retainedaustenite transition and irreversible tempering brittleness.Originality/value: On the basis of own research, the authors present their own, original point of view on theissue of presence of retained austenite in the structure, its stability and the influence on fracture toughness of lowtemperedtools steel.

  14. MODELING OF AUSTENITE GRAIN SIZE IN LOW-ALLOY STEEL WELD METAL

    Institute of Scientific and Technical Information of China (English)

    A.G.Huang; Y.S.Wang; Z.Y.Li; J.G.Xiong; Q.Hu

    2004-01-01

    The size of austenite grain hassignificant effects on components and proportions of various ferrites in low-alloy steel weld metal.Therefore,it is important to determine the size of austenite grain in the weld metal.In this paper,a model based upon the carbon diffusion rate is developed for computing austenite grain size in low-alloy steel weld metal during continuous cooling.The model takes into account the effects of the weld thermal cycles,inclusion particles and various alloy elements on the austenite grain growth.The calculating results agree reasonably with those reported experimental observations.The model demonstrates a significant promise to understand the weld microstructure and properties based on the welding science.

  15. The effect of cooling rate and austenite grain size on the austenite to ferrite transformation temperature and different ferrite morphologies in microalloyed steels

    International Nuclear Information System (INIS)

    The effect of different austenite grain size and different cooling rates on the austenite to ferrite transformation temperature and different ferrite morphologies in one Nb-microalloyed high strength low alloy steel has been investigated. Three different austenite grain sizes were selected and cooled at two different cooling rates for obtaining austenite to ferrite transformation temperature. Moreover, samples with specific austenite grain size have been quenched, partially, for investigation on the microstructural evolution. In order to assess the influence of austenite grain size on the ferrite transformation temperature, a temperature differences method is established and found to be a good way for detection of austenite to ferrite, pearlite and sometimes other ferrite morphologies transformation temperatures. The results obtained in this way show that increasing of austenite grain size and cooling rate has a significant influence on decreasing of the ferrite transformation temperature. Micrographs of different ferrite morphologies show that at high temperatures, where diffusion rates are higher, grain boundary ferrite nucleates. As the temperature is lowered and the driving force for ferrite formation increases, intragranular sites inside the austenite grains become operative as nucleation sites and suppress the grain boundary ferrite growth. The results indicate that increasing the austenite grain size increases the rate and volume fraction of intragranular ferrite in two different cooling rates. Moreover, by increasing of cooling rate, the austenite to ferrite transformation temperature decreases and volume fraction of intragranular ferrite increases.

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

    International Nuclear Information System (INIS)

    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

  17. Mechanical properties and damage behavior of non-magnetic high manganese austenitic steels

    International Nuclear Information System (INIS)

    Fe-Cr-Mn steels have been considered as materials of structural components for fusion reactor because of their low induced-radio-activity compared with SUS316 stainless steels. It has been expected to develop a non-magnetic steel with a high stability of the austenitic phase and a strong resistance to irradiation environments. For these objectives, a series of the Fe-Cr-Mn steels have been examined by tensile tests and simulation irradiation by electrons. The main alloying compositions of the steels developed are: C:0.02-0.2 wt%, Mn: 15 wt%, Cr: 15-16 wt%, N: 0.2 wt%. These steels were heat-treated at 1323 K for 1 h. The structure of the steels after the heat-treatment was austenite single phase. The yield stress of the steels was 350-450 MPa and the elongation were 55-60%. When the steels of high C and N was electron-irradiated at below 673 K, no voids were nucleated and only small dislocation loops were formed with high density. The austenite phase was also stable during irradiation below 673 K. Thus, newly developed high manganese steels have excellent mechanical proprieties and high irradiation resistance at relatively low temperature. (orig.)

  18. The influence of chemical composition on structure and mechanical properties of austenitic Cr-Ni steels

    Directory of Open Access Journals (Sweden)

    A. Kurc-Lisiecka

    2013-12-01

    Full Text Available Purpose: The aim of the paper is to investigated the influence of the chemical composition on the structure and mechanical properties of austenitic Cr-Ni steels. Special attention was put on the effect of solution heat treatment on mechanical properties of examined steels. Design/methodology/approach: The examinations of static tensile tests were conducted on ZWICK 100N5A. Hardness measurements were made by Vickers method. The X-ray analyzes were realized with the use of Dron 2.0 diffractometer equipped with the lamp of the cobalt anode. The metallographic observations were carried out on LEICA MEF 4A light microscope. Findings: Results shown that after solution heat treatment the values of strength properties (UTS, YS0.2 and hardness (HV of both investigated steels decrease and their elongation (EL increases. The X5CrNi18-8 steel in delivery state shown austenitic microstructure with twins and numerous non-metallic inclusions, while in steel X10CrNi18-8 revealed a austenitic microstructure with numerous slip bands in areas with deformation martensite α’. The examined steels after solution heat treatment followed by water-cooling has the structure of austenite. Research limitations/implications: To investigate in more detail the influence of chemical composition on structure and mechanical properties the examinations of substructure by TEM should be conducted. Originality/value: The relationship between the solution heat treatment, structure and mechanical properties of investigated steels was specified.

  19. Deformation-induced austenite grain rotation and transformation in TRIP-assisted steel

    OpenAIRE

    Tirumalasetty, G.K.; van Huis, M.A.; Kwakernaak, C.; Sietsma, J.; Sloof, W.G.; Zandbergen, H. W.

    2012-01-01

    Uniaxial straining experiments were performed on a rolled and annealed Si-alloyed TRIP (transformation-induced plasticity) steel sheet in order to assess the role of its microstructure on the mechanical stability of austenite grains with respect to martensitic transformation. The transformation behavior of individual metastable austenite grains was studied both at the surface and inside the bulk of the material using electron back-scattered diffraction (EBSD) and X-ray diffraction (XRD) by de...

  20. Effect of Silicon Content on Thermodynamics of Austenite Decomposition in C-Si-Mn TRIP Steels

    Institute of Scientific and Technical Information of China (English)

    ZHU Li-juan; WU Di; ZHAO Xian-ming

    2006-01-01

    Some numerical models such as central atoms model (CAM) and superelement model were used to simulate the thermodynamics of austenite decomposition in the Fe-C-Mn-Si TRIP (transformation induced plasticity) steels. Thermodynamic calculations were carried out under a para-equilibrium (PE) condition. The results show that certain silicon content can accelerate the polygonal ferritic transformation and increase the volume fraction and stability of retained austenite by retarding the precipitation of carbides during the bainitic transformation.

  1. 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...... demonstrate that a case of expanded austenite develops and that, in particular, strain-induced martensite has a large influence on the nitrided zone....

  2. Austenite reconstruction via EBSD measurements: a tool to understand low Carbon martensite steel properties

    OpenAIRE

    Bracke Lieven; Sanchez Laura Moli; Bernier Nicolas

    2015-01-01

    The basic characterization of the austenite grain size and shape prior to quenching to martensite was already used in the past to optimize the mechanical properties and impact toughness of low Carbon martensitic steel. This basic characterization can typically be done by optical microscopy. To better understand the mechanisms that generate the different properties, however, a more detailed analysis is required. An algorithm has been developed to calculate the austenite orientation starting fr...

  3. Hot ductility of austenitic and duplex stainless steels under hot rolling conditions

    OpenAIRE

    Kömi, J. (Jenni)

    2001-01-01

    Abstract The effects of restoration and certain elements, nitrogen, sulphur, calcium and Misch metal, on the hot ductility of austenitic, high-alloyed austenitic and duplex stainless steels have been investigated by means of hot rolling, hot tensile, hot bending and stress relaxation tests. The results of these different testing methods indicated that hot rolling experiments using stepped specimens is the most effective way to investigate the relationship between the s...

  4. Dependence of nanoindentation hardness with crystallographic orientation of austenite grains in metastable stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Roa, J.J., E-mail: joan.josep.roa@upc.edu [CIEFMA – Departament de Ciència dels Materials i Engineria Metallúrgica, ETSEIB, Universitat Politècnica de Catalunya, Avda. Diagonal 647, 08028 Barcelona (Spain); CRnE, Campus Diagonal Sud, Edifici C’, Universitat Politècnica de Catalunya, C/ Pascual i Vila 15, 08028 Barcelona (Spain); Fargas, G.; Mateo, A.; Jiménez-Piqué, E. [CIEFMA – Departament de Ciència dels Materials i Engineria Metallurgica, ETSEIB, Universitat Politècnica de Catalunya, Avda. Diagonal 647, 08028 Barcelona (Spain); CRnE, Campus Diagonal Sud, Edifici C’, Universitat Politècnica de Catalunya, C/ Pascual i Vila 15, 08028 Barcelona (Spain)

    2015-10-01

    The mechanical behaviour of a metastable austenitic stainless steel has been studied by means of nanoindentation of individual grains. Hardness, elastic modulus and estimation of wear resistance were determined as a function of crystallographic orientation. Electron backscattered diffraction, atomic force microscopy and focused ion beam analysis was performed at the residual imprints. Results show that austenitic grains display an anisotropic behaviour as regard as hardness in contrast with the elastic modulus which remained constant and equal to 200 GPa.

  5. Dependence of nanoindentation hardness with crystallographic orientation of austenite grains in metastable stainless steels

    International Nuclear Information System (INIS)

    The mechanical behaviour of a metastable austenitic stainless steel has been studied by means of nanoindentation of individual grains. Hardness, elastic modulus and estimation of wear resistance were determined as a function of crystallographic orientation. Electron backscattered diffraction, atomic force microscopy and focused ion beam analysis was performed at the residual imprints. Results show that austenitic grains display an anisotropic behaviour as regard as hardness in contrast with the elastic modulus which remained constant and equal to 200 GPa

  6. Grain refinement of a nickel and manganese free austenitic stainless steel produced by pressurized solution nitriding

    International Nuclear Information System (INIS)

    Prolonged exposure at high temperatures during solution nitriding induces grain coarsening which deteriorates the mechanical properties of high nitrogen austenitic stainless steels. In this study, grain refinement of nickel and manganese free Fe–22.75Cr–2.42Mo–1.17N high nitrogen austenitic stainless steel plates was investigated via a two-stage heat treatment procedure. Initially, the coarse-grained austenitic stainless steel samples were subjected to an isothermal heating at 700 °C to be decomposed into the ferrite + Cr2N eutectoid structure and then re-austenitized at 1200 °C followed by water quenching. Microstructure and hardness of samples were characterized using X-ray diffraction, optical and scanning electron microscopy, and micro-hardness testing. The results showed that the as-solution-nitrided steel decomposes non-uniformly to the colonies of ferrite and Cr2N nitrides with strip like morphology after isothermal heat treatment at 700 °C. Additionally, the complete dissolution of the Cr2N precipitates located in the sample edges during re-austenitizing requires longer times than 1 h. In order to avoid this problem an intermediate nitrogen homogenizing heat treatment cycle at 1200 °C for 10 h was applied before grain refinement process. As a result, the initial austenite was uniformly decomposed during the first stage, and a fine grained austenitic structure with average grain size of about 20 μm was successfully obtained by re-austenitizing for 10 min. - Highlights: • Successful grain refinement of Fe–22.75Cr–2.42Mo–1.17N steel by heat treatment • Using the γ → α + Cr2N reaction for grain refinement of a Ni and Mn free HNASS • Obtaining a single phase austenitic structure with average grain size of ∼ 20 μm • Incomplete dissolution of Cr2N during re-austenitizing at 1200 °C for long times • Reducing re-austenitizing time by homogenizing treatment before grain refinement

  7. Grain refinement of a nickel and manganese free austenitic stainless steel produced by pressurized solution nitriding

    Energy Technology Data Exchange (ETDEWEB)

    Mohammadzadeh, Roghayeh, E-mail: r_mohammadzadeh@sut.ac.ir; Akbari, Alireza, E-mail: akbari@sut.ac.ir

    2014-07-01

    Prolonged exposure at high temperatures during solution nitriding induces grain coarsening which deteriorates the mechanical properties of high nitrogen austenitic stainless steels. In this study, grain refinement of nickel and manganese free Fe–22.75Cr–2.42Mo–1.17N high nitrogen austenitic stainless steel plates was investigated via a two-stage heat treatment procedure. Initially, the coarse-grained austenitic stainless steel samples were subjected to an isothermal heating at 700 °C to be decomposed into the ferrite + Cr{sub 2}N eutectoid structure and then re-austenitized at 1200 °C followed by water quenching. Microstructure and hardness of samples were characterized using X-ray diffraction, optical and scanning electron microscopy, and micro-hardness testing. The results showed that the as-solution-nitrided steel decomposes non-uniformly to the colonies of ferrite and Cr{sub 2}N nitrides with strip like morphology after isothermal heat treatment at 700 °C. Additionally, the complete dissolution of the Cr{sub 2}N precipitates located in the sample edges during re-austenitizing requires longer times than 1 h. In order to avoid this problem an intermediate nitrogen homogenizing heat treatment cycle at 1200 °C for 10 h was applied before grain refinement process. As a result, the initial austenite was uniformly decomposed during the first stage, and a fine grained austenitic structure with average grain size of about 20 μm was successfully obtained by re-austenitizing for 10 min. - Highlights: • Successful grain refinement of Fe–22.75Cr–2.42Mo–1.17N steel by heat treatment • Using the γ → α + Cr{sub 2}N reaction for grain refinement of a Ni and Mn free HNASS • Obtaining a single phase austenitic structure with average grain size of ∼ 20 μm • Incomplete dissolution of Cr{sub 2}N during re-austenitizing at 1200 °C for long times • Reducing re-austenitizing time by homogenizing treatment before grain refinement.

  8. Study by factorial analysis of the influence of chemical composition on the stress corrosion cracking of austenitic stainless steels

    International Nuclear Information System (INIS)

    The stress corrosion cracking of austenitic stainless steels has been treated by factorial correspondence analysis. This statistical method gives a relationship between chemical characteristics and the susceptibility of the steels to the phenomenon

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

    International Nuclear Information System (INIS)

    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

  10. TEM studies of plasma nitrided austenitic stainless steel.

    Science.gov (United States)

    Stróz, D; Psoda, M

    2010-03-01

    Cross-sectional transmission electron microscopy and X-ray phase analysis were used to study the structure of a layer formed during nitriding the AISI 316L stainless steel at temperature 440 degrees C. It was found that the applied treatment led to the formation of 6-microm-thick layer of the S-phase. There is no evidence of CrN precipitation. The X-ray diffraction experiments proved that the occurred austenite lattice expansion - due to nitrogen atoms - depended on the crystallographic direction. The cross-sectional transmission electron microscopy studies showed that the layer consisted of a single cubic phase that contained a lot of defects such as dislocations, stacking faults, slip bands and twins. The high-resolution electron microscopy observations were applied to study the defect formation due to the nitriding process. It was shown that the presence of great number of stacking faults leads to formation of nanotwins. Weak, forbidden {100} reflections were still another characteristic feature of the S-phase. These were not detected in the X-ray spectra of the phase. Basing on the high-resolution electron microscopy studies it can be suggested that the short-range ordering of the nitrogen atoms in the octahedral sites inside the f.c.c. matrix lattice takes place and gives rise to appearance of these spots. It is suggested that the cubic lattice undergoes not only expansion but also slight rombohedral distortion that explains differences in the lattice expansion for different crystallographic directions. PMID:20500370

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

    International Nuclear Information System (INIS)

    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. Austenite formation during intercritical annealing in C-Mn cold-rolled dual phase steel

    Institute of Scientific and Technical Information of China (English)

    李声慈; 康永林; 朱国明; 邝霜

    2015-01-01

    Two different kinds of experimental techniques were used to in-situ study the austenite formation during intercritical annealing in C-Mn dual phase steel. The microstructure evolution was observed by confocal laser scanning microscope, and the austenite isothermal and non-isothermal transformation kinetics were studied by dilatometry. The results indicate that banded structure is produced for the reason of composition segregation and the competition between recrystallization and phase transformation. Austenite prefers to nucleate not only at ferrite/ferrite grain boundaries, but also inside the grains of ferrite. Furthermore, the austenitizing process is accomplished mainly via migration of the existing austenite/ferrite interface rather than nucleation of new grains. The incubation process can be divided into two stages which are controlled by carbon and manganese diffusion, respectively. During the incubation process, the nucleation rate of austenite decreases, and austenite growth changes from two-dimensional to one-dimensional. The partitioning coefficient, defined as the ratio of manganese content in the austenite to that in the adjacent ferrite, increases with increasing soaking time.

  13. Evaluation of the retained austenite mechanical stability in the medium-carbon TRIP steel

    Directory of Open Access Journals (Sweden)

    A. Kokosza

    2012-12-01

    Full Text Available Purpose: The aim of this study was to evaluate the inclination to mechanical destabilization of retained austenite in the microstructure of the TRIP steel containing 0.4% C, 1.5% Mn and 1.2% Si.Design/methodology/approach: The new, simple method for evaluating the mechanical stability of retained austenite was proposed, which is based on the bending test and the measurement of volume fraction of retained austenite by X-ray quantitative phase analysis. The relationship between stress and local strain as well as local volume fraction of this phase in selected locations on the surface of the bending sample were revealed.Findings: The applied heat treatment, modified with respect to the classic one, allowed remain approximately 25 vol.% of the retained austenite in the microstructure of the investigated TRIP steel. It was pointed that retained austenite has high mechanical stability if stress is low. Under influence of the higher stress a partial destabilization this phase occurred. It was found that in the examined steel such mechanical destabilization of retained austenite has two - or three-stage nature.Research limitations/implications: Results of this study indicate a significant stability of retained austenite in the investigated TRIP steel. It is advisable to check how will change the stability of this phase when the stress or strain will be higher than those that occurred in this research.Practical implications: The new method of the evaluation of the retained austenite mechanical stability provides the possibility of an easy and effective estimation of this phase tendency to mechanical destabilisation and to martensite transformation in the steel. In addition, this method allows analysing the influence of the stress as well as the strain on changes in this phase volume fraction, which occur during three-point bending.Originality/value: The proposed method may be used for evaluation of susceptibility of retained austenite on transformation

  14. Fracture toughness of austenitic stainless steels after BWR irradiation

    International Nuclear Information System (INIS)

    Austenitic stainless steels used for the core internal materials in BWRs are hardened by exposure to fast neutrons, and the fracture toughness is reduced by neutron fluence. It is important for integrity estimation of aged core internals to understand the reduction behavior of fracture toughness by neutron irradiation. In this study, core shroud materials (Type 304 SS) with 38 mm thickness and top guide materials (Type 316 SS) with 9.1 mm thickness, actually used for over twenty years in BWRs, were transported to PIE facility. Neutron fluence of type 304 SS was 1-6*1024 (n/m2, E > 1 MeV) and that of type 316 SS was 3-17*1024 (n/m2, E > 1 MeV). Fracture toughness tests for base metal were performed at 288 C in air using the CT specimen with real thickness of core shroud and top guide to obtain valid fracture toughness. And fracture toughness tests for heat affected zone (HAZ) were conducted using 0.7 TCT by the restriction of weld line direction. JIC and JQ of irradiated type 304 and type 316 base metals decreased with neutron fluence. JIC values of type 304 SS base metal and HAZ were obtained over 140 kJ/m2 at 5*1024 n/m2. JIC values of type 316 SS base metal were obtained over 240 kJ/m2 at 1.7*1025 n/m2. JIC values of type 304 HAZ were similar to those of base metal. JQ values of type 316 SS base metal had a higher value than JIC of type 304 SS base metal at similar neutron fluence. The difference between type 304 SS and type 316 SS is considered to be caused by the orientation effect of microstructure in CT specimen. From the SEM observation of crack surfaces, a linear relationship between JIC and the critical stretched zone width (SZWC) was found to exist in irradiated stainless steel materials. (authors)

  15. Effects of Nitrogen Content and Austenitization Temperature on Precipitation in Niobium Micro-alloyed Steels

    Institute of Scientific and Technical Information of China (English)

    Lei CAO; Zhong-min YANG; Ying CHEN; Hui-min WANG; Xiao-li ZHAO

    2015-01-01

    The influences of nitrogen content and austenitization temperature on Nb(C,N)precipitation in niobium micro-alloyed steels were studied by different methods:optical microscopy,tensile tests,scanning electron mi-croscopy,transmission electron microscopy,physicochemical phase analysis,and small-angle X-ray scattering. The results show that the strength of the steel with high nitrogen content is slightly higher than that of the steel with low nitrogen content.The increase in the nitrogen content does not result in the increase in the amount of Nb(C,N) precipitates,which mainly depends on the niobium content in the steel.The mass fraction of small-sized Nb(C,N) precipitates (1-10 nm)in the steel with high nitrogen content is less than that in the steel with low nitrogen con-tent.After austenitized at 1 150 ℃,a number of large cuboidal and needle-shaped particles are detected in the steel with high nitrogen content,whereas they dissolve after austenitized at 1 200 ℃ and the Nb(C,N)precipitates become finer in both steels.Furthermore,the results also show that part of the nitrogen in steel involves the formation of al-loyed cementite.

  16. Modifying microstructure and property of 30CrMnSi steel by subcritical austenite reverse transformation quenching

    OpenAIRE

    Li, Anming

    2015-01-01

    Subcritical austenite reverse transformation quenching was used to improve the mechanical properties of 30CrMnSi steel, and the microstructure and mechanical properties of the samples were analyzed by subcritical austenite reverse transformation quenching. Experimental results show that subcritical reverse transformation quenching can refine the austenite grains of the 30CrMnSi steel. Lath-shaped martensite can be obtained after quenching. Ferrite is exited in the martensite lath when quenchi...

  17. Laser Shock Processing of an Austenitic Stainless Steel and a Nickel-base Superalloy

    Institute of Scientific and Technical Information of China (English)

    Huaming WANG; Xijun SUN; Xiaoxuan LI

    2003-01-01

    An austenitic stainless steel 1Cr18Ni9Ti and a solid solution-strengthened Ni-base superalloy GH30 were shock processed usinga Q-switched pulsed Nd-glass laser. Microstructure, hardness and residual stress of the laser shock processed surface wereinvestigated as functions of laser processing parameters. Results show that high density of dislocations and fine deformationtwins are produced in the laser shock processed surface layers in both the austenitic stainless steel and the nickel-base superalloy.Extensive strain-induced martensite was also observed in the laser shock processed zone of the austenitic steel. The hardnessof the laser shock processed surface was significantly enhanced and compressive stress as high as 400 MPa was produced inthe laser shock processed surface.

  18. Thermal stability of metastable austenite in rapidly solidified chromium-molybdenum-vanadium tool steel powder

    International Nuclear Information System (INIS)

    Thermal stability of metastable austenite in a Cr-Mo-V tool steel of ledeburite type was investigated by tempering rapidly solidified (RS) particles at temperatures from 100 up to 700 deg. C and by continuous heating during differential thermal analysis. A rapid increase in microhardness was observed after the tempering at temperatures over 400 deg. C. According to Moessbauer effect measurements, only non-magnetic phases were observed in the RS particles after atomization, as well as after the tempering at temperatures below 540 deg. C. Above this temperature, the metastable austenite gradually transformed into martensite during cooling from the tempering temperature. The secondary hardening peak corresponding to 1220 HV appears at 600 deg. C. This temperature is higher than the temperature of the secondary hardening peak for this steel after conventional heat treatment. The thermal stability of austenite was determined and the mechanisms of phase transformations responsible for the achievement of secondary hardness in this steel following rapid solidification are described

  19. Thermal stability of metastable austenite in rapidly solidified chromium-molybdenum-vanadium tool steel powder

    Energy Technology Data Exchange (ETDEWEB)

    Grgac, P.; Moravcik, R.; Kusy, M.; Toth, I.; Miglierini, M.; Illekova, E

    2004-07-15

    Thermal stability of metastable austenite in a Cr-Mo-V tool steel of ledeburite type was investigated by tempering rapidly solidified (RS) particles at temperatures from 100 up to 700 deg. C and by continuous heating during differential thermal analysis. A rapid increase in microhardness was observed after the tempering at temperatures over 400 deg. C. According to Moessbauer effect measurements, only non-magnetic phases were observed in the RS particles after atomization, as well as after the tempering at temperatures below 540 deg. C. Above this temperature, the metastable austenite gradually transformed into martensite during cooling from the tempering temperature. The secondary hardening peak corresponding to 1220 HV appears at 600 deg. C. This temperature is higher than the temperature of the secondary hardening peak for this steel after conventional heat treatment. The thermal stability of austenite was determined and the mechanisms of phase transformations responsible for the achievement of secondary hardness in this steel following rapid solidification are described.

  20. Effects of milling process and alloying additions on oxide particle dispersion in austenitic stainless steel

    International Nuclear Information System (INIS)

    An oxide dispersion strengthened (ODS) austenitic stainless steel was developed by mechanical alloying (MA) of advanced SUS316 stainless steel. A nano-characterization was performed to understand details of the effect of minor alloying elements in the distribution of dispersoids. It is shown that Y2O3 particles dissolve into the austenitic matrix after the MA for 6 h. Annealing at 1073 K or higher temperatures result in a distribution of fine oxide particles in the recrystallized grains in the ODS austenitic stainless steel. Additions of Hafnium or Zirconium led to the distribution of finer oxide particles than in samples without these elements, resulting in an increase in the hardness of the samples. The most effective concentration of Hf and Zr to increase the hardness was 0.6 and 0.2–0.3 wt%, respectively

  1. Long term corrosion resistance of alumina forming austenitic stainless steels in liquid lead

    International Nuclear Information System (INIS)

    Highlights: • Alumina forming austenitic stainless steels (AFA) were exposed to lead at 550 °C. • The influence of Al addition and Ni content was evaluated. • The low Ni (14 wt.%) AFA formed a thin protective Al rich oxide on its surfaces. • 17% ferrite was formed in the 14Ni AFA alloy as a result of the one year exposure. - Abstract: Alumina forming austenitic steels (AFA) and commercial stainless steels have been exposed in liquid lead with 10−7 wt.% oxygen at 550 °C for up to one year. It is known that chromia forming austenitic stainless steels, such as 316L and 15–15 Ti, have difficulties forming protective oxides in liquid lead at temperatures above 500 °C, which is confirmed in this study. By adding Al to austenitic steels, it is in general terms possible to increase the corrosion resistance. However this study shows that the high Ni containing AFA alloys are attacked by the liquid lead, i.e. dissolution attack occurs. By lowering the Ni content in AFA alloys, it is possible to achieve excellent oxidation properties in liquid lead. Following further optimization of the microstructural properties, low Ni AFA alloys may represent a promising future structural steel for lead cooled reactors

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

    Energy Technology Data Exchange (ETDEWEB)

    Porollo, S.I.; Shulepin, S.V.; Konobeev, Y.V.; Garner, F. [Pacific Northwest National Laboratory, P.o. Box 999, Richland WA, AK 99352 (United States)

    2007-07-01

    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 {approx} 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)

  3. Diagrams of supercooled austenite transformations of low-carbon and medium-carbon TRIP-steels

    Directory of Open Access Journals (Sweden)

    A. Grajcar

    2008-07-01

    Full Text Available Purpose: The aim of the paper is to determine the influence of cooling conditions on a structure and a shape of CCT-diagrams of TRIP-aided steels.Design/methodology/approach: The diagrams of undeformed supercooled austenite transformations for low-carbon and medium-carbon steels were determined. The specimens were austenitized at a temperature of 1100°C and cooled from a temperature of 900°C with a rate in a range from 1 to 300°Cs-1. The dilatometric tests were carried out by the use of the DIL805A/D dilatometer with a LVDT-type measuring head.Findings: It was found that obtained CCT-diagrams of low-carbon and medium-carbon steels are favourable for manufacturing TRIP-type steels with multiphase structures. The steels are characterized by large ferritic and bainitic fields and a right-displaced pearlitic range. However, a ferrite fraction obtained after cooling with an optimum rate from a temperature of 900°C is low. Increasing the fraction of the α phase requires two-stage cooling after austenitizing.Research limitations/implications: To obtain the optimum ferrite fraction, it is necessary to modify a cooling course in a range of γ→α transformation. It should result in an effective utilization of the time for the transformation of austenite into the fine-grained ferrite.Practical implications: The obtained diagrams of supercooled austenite transformations can be useful in a determination of a cooling course from a finishing rolling temperature for sheets with a multiphase structure.Originality/value: The diagrams of the undeformed supercooled austenite for the low-carbon and medium-carbon steels containing Nb and Ti microadditions were obtained.

  4. Influence of austenitic orientation on martensitic transformations in a compressed high manganese steel

    International Nuclear Information System (INIS)

    Highlights: → Parent orientation affects product kinetics, variant, size and orientation. → Martensite, like austenite twinning, forms fastest in compressed austenite. → The only one martensite variant formed in austenite leads to grain coarsening. → Both transformation and deformation contribute to final texture in martensite. - Abstract: High manganese TRIP/TWIP steels contain two types of martensite and the morphology, size, variant selection and texture of both types of martensite are influenced by the parent austenite grain orientation. In the present paper the TRIP effect was investigated in a compressed high manganese steel, focusing on the crystallographic behavior by means of X-ray diffraction and the electron back scatter diffraction (EBSD) technique. It is observed that γ austenite oriented with close to the compression axis (CA) transformed more easily into α'-martensite with only one variant, whereas the transformation in CA// and -oriented austenite was sluggish and often yielded several variants. This orientation dependency was ascribed to the ease of either deformation twinning or Shockley dislocation movement. Similarly, ε-M was also observed to transform smoothly into α'-M in nearly -oriented austenite and more sluggishly in other austenite grains of other orientations. However, the number of ε-M variants detected by EBSD was higher than direct observation. In contrast to thermally induced martensitic transformations, the TRIP effect during compression failed to cause grain refinement in the transformed α'-M. The rapid formation of α'-M in -oriented γ promoted the formation of a texture of the α'-M, whereas the texture developed in the austenite at high level of compression led to a restricted transformation into martensite. The reasons for the occurrence of a texture in the α'-M and for the behavior of the ε-M are discussed.

  5. The influence of nitrogen alloying on the pitting and crevice corrosion of austenitic and duplex stainless steels

    International Nuclear Information System (INIS)

    The effect of nitrogen alloying on the pitting corrosion resistance of duplex and austenitic stainless steels has been examined. In order to avoid alteration of the phase ratio as a result of nitrogen alloying of the duplex steels, a simultaneous decrease has been made in the nickel content. Austenitic alloys of compositions corresponding to the austenite phase of the duplex steels have been investigated and compared to the behaviour of austenitic steels in which the nitrogen content or the nickel content alone has been varied. Nitrogen has a beneficial effect on pitting and crevice corrosion resistance in all cases but the duplex stainless steel exhibit a lower resistance to pitting and a higher resistance to crevice corrosion than predicted from the austenite nitrogen content. (orig.)

  6. Investigations into radiation swelling and mechanical properties of irradiated austenitic chromium-manganese steel

    International Nuclear Information System (INIS)

    Presented are the results of investigations of material with fast-dropping radioactivity-austenitic Cr-Mn steel (04Kh12G14N4YuM), damage dose dependence of swelling and mechanical properties of steel. It is shown that 04Kh12G14N4YuM steel has high radiation swelling resistance up to a damage dose of 60 dpa at temperature ranging from 340 to 530 deg C. Mechanical properties of steel are as good as those of austenitic Cr-Ni steels up to 30 dpa and 40 deg C. Ductility does not decrease lower than 2-5 %. Dose and temperature increase leads to instability of γ-solid solution, that is confirmed by the results of TEM and X-ray examinations. 4 refs.; 6 figs.; 2 tabs

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

    Institute of Scientific and Technical Information of China (English)

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

    2004-01-01

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

  8. Structure Evolution and Solidification Behavior of Austenitic Stainless Steel in Pulsed Magnetic Field

    Institute of Scientific and Technical Information of China (English)

    LI Qiu-shu; LI Hai-bin; ZHAI Qi-jie

    2006-01-01

    To understand the solidification behavior of austenitic stainless steel in pulsed magnetic field, the solidification process is investigated by means of the self-made high voltage pulse power source and the solidification tester. The results show that the solidification structure of austenitic stainless steel can be remarkably refined in pulsed magnetic field, yet the grains become coarse again when the magnetic intensity is exceedingly large, indicating that an optimal intensity range existed for structure refinement. The solidification temperature can be enhanced with an increase in the magnetic intensity. The solidification time is shortened obviously, but the shortening degree is reduced with the increase of the magnetic intensity.

  9. Advances in development of refractory austenitic steels and nickel alloys for power engineering

    International Nuclear Information System (INIS)

    An evaluation is presented of the current state of knowledge of the properties and technologies of refractory austenitic steels and Ni alloys, this mainly of materials used in the temperature range of 600 to 1100 degC where the main causes of damage are creep, fatigue and high temperature corrosion. Attention is mainly devoted to the results of applied research. The problems of concrete applications in nuclear engineering were dealt with in the paper ''Assessment of long-term refractory properties of selected types of austenitic steels''. (J.B.)

  10. Microstructure and mechanical properties of low carbon silicon manganese steel sheets containing retained austenite

    International Nuclear Information System (INIS)

    The effect of bainite transformation temperature and of plastic deformation on the microstructure and mechanical properties of a 0.2%C, 1.5%Si, 1.5%Mn triple-phase steel as well as on the stability and morphology of retained austenite is reported. Carefully designed control-rolling, control-cooling and isothermal bainite transformation allowed to obtain a multiphase steel containing retained austenite susceptible to transformation-induced plasticity (TRIP effect). Mechanical properties are discussed in terms of the obtained dependence of instantaneous strain hardening exponent on true strain. (author)

  11. Short-term low-temperature glow discharge nitriding of 316L austenitic steel

    Directory of Open Access Journals (Sweden)

    T. Frączek

    2011-07-01

    Full Text Available The AISI 316L austenitic steel after glow discharge nitriding at temperature of T = 673 K and duration of τ=14,4 ks, for two different variants of specimen arrangement in the glow-discharge chamber was investigated. In order to assess the effectiveness of nitriding process, the surface layers profile analysis examination, surface hardness and hardness profile examination, the analysis of surface layer structures and corrosion resistance tests were performed. It has been found that application of a booster screen effects in a nitrogen diffusion depth increment into the 316L austenitic steel surface, what results in the surface layer thickness escalation.

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

    Directory of Open Access Journals (Sweden)

    Sinclair C.W.

    2013-11-01

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

  13. Ferrite and austenite phase identification in duplex stainless steel using SPM techniques

    Science.gov (United States)

    Guo, L. Q.; Lin, M. C.; Qiao, L. J.; Volinsky, Alex A.

    2013-12-01

    It can be challenging to properly identify the phases in electro-polished duplex stainless steel using optical microscopy or other characterization techniques. This letter describes magnetic force microscopy to properly identify the phases in electropolished duplex stainless steel. The results are also confirmed with the current sensing atomic force and scanning Kelvin probe force microscopy. The difference in topography heights between the ferrite and austenite phases is attributed to the different etching rates during electropolishing, although these phases have different mechanical properties. The current in the austenite is much higher compared with the ferrite, thus current sensing atomic force microscopy can also be used to properly identify the phases.

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

    International Nuclear Information System (INIS)

    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)

  15. Damage mechanism of piping welded joints made from austenitic Steel for the type RBMK reactor

    International Nuclear Information System (INIS)

    In the process of operation of RBMK reactors the damages were taking place on welded piping, produced from austenitic stainless steel of the type 08X18H10T. The inspection of damaged sections in piping has shown that in most cases crack-like defects are of corrosion and mechanical character. The paper considers in details the reasons of damages appearance and their development for this type of welded joints of downcomers 325xl6 mm, which were fabricated from austenitic stainless steel using TlG and MAW welding methods. (author)

  16. 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.

  17. Stress-corrosion and fatigue cracking behaviour of nitrogen-alloyed austenitic and ferritic-austenitic chrome-nickel-(molybdenum)steels

    International Nuclear Information System (INIS)

    Under unfavorable heat-exchanger conditions simulated with 3 % sodium chloride solutions of different rhoH-values and redox potentials there excists a close connection between the stress-corrosion and fatigue behavior and the results of electrochemical measurements for nitrogen-alloyed austenitic and ferritic-austenitic high-alloy stells. Elevated contents of chromium and molybdenum have a positive effect. With free corrosion the materials no. 1.4311 and 1.4406 as well as partly also 1.4439 and the corresponding weldings are not suited if there is a hazard of stress corrosion. For 1.4439 and 1.4462 and their weldings of the same type a lower-bound stress may be given for the hazard of stress corrosion. It is within the order of magnitude of the garanteed elevated temperature yield strength and is therefore distinctly higher for the ferritic-austenitic steel 1.4462 than for nitrogenous austenitic steels. For the nitrogenous austenitic steels mentioned the dynamic loading capacity with and without the action of corrosive media is marked by lower than for the steel 1.4462 with ferritic-austenitic structure and its welding of the same type. As the notch sensitivity for both groups of material can be taken as equal the steel 1.4462 appears suitable for being used under unfavorable heat-exchanger conditions if high resistance against stress-corrosion and fatigue cracking is taken into account. (orig.)

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-01-15

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

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

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

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

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

    Directory of Open Access Journals (Sweden)

    ZHOU Shu-cai

    2007-08-01

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

  2. Improvement of austenitic Hadfield Mn-steel properties by thermomechanical processing

    International Nuclear Information System (INIS)

    A thermomechanical processing technique is used to improve austenitic Hadfield Mn-steel wear properties. ASTM A128 grade C steel billets were sized and multi-pass hot rolled. Rolling has been successfully carried out up to an 80% reduction in thickness on four passes in the temperature range 1200 to 800 oC. The inter-pass time ranged between 9 to 13 seconds. The steel was then solution treated at 900, 1000 and 1100 oC for 30 min. at temperature. Austenite grain size was measured and the carbide volume fraction was evaluated. The austenitic grains of the as-cast structure are surrounded by a network of carbides. The carbides have a lamellar structure and are richer in Cr and Mn than the austenitic grains. Austenitizing at 1100 oC was the optimum to dissolve the network of carbides. However, solution treatment at the higher temperature coarsens the austenite grains while decreasing the carbide volume fraction. By contrast, hot rolling creates finer grains and significantly reduces the carbide content. Furthermore, hot rolling followed by solution treatment further decreases the carbide content and distributes them homogeneously. This process has a positive effect on both the mechanical and wear properties. High reductions by hot rolling of the Hadfield steel creates both deformation bands and a twinned structure. These twinning boundaries are considered as slip obstacles to provide strengthening. A thick sheet martensitic structure is created accompanying twinning. Moreover, solution treatment of the hot deformed steel leads to the formation of a thin martensitic structure. (author)

  3. Hot deformation behavior of austenite in HSLA-100 microalloyed steel

    Energy Technology Data Exchange (ETDEWEB)

    Momeni, A., E-mail: ammomeni@aut.ac.ir [Mining and Metallurgical Engineering Department, Amir Kabir University of Technology, Tehran (Iran, Islamic Republic of); Arabi, H. [Tarbiat Modarres University, Tehran (Iran, Islamic Republic of); Rezaei, A.; Badri, H.; Abbasi, S.M. [KNT University of Technology, Tehran (Iran, Islamic Republic of)

    2011-02-25

    Research highlights: {yields} The flow stress is well fitted by the exponential constitutive equation. {yields} The average value of apparent activation energy for hot deformation is 377 kJ mol{sup -1}. {yields} A yield point phenomenon is observed on flow curves at high temperatures. {yields} The Avrami exponent is determined around unity for dynamic recrystallization. - Abstract: Dynamic recrystallization of austenite in the Cu-bearing HSLA-100 steel was investigated by hot compression testing at a temperature range of 850-1150 deg. C and a strain rate of 0.001-1 s{sup -1}. The obtained flow curves at temperatures higher than 950 deg. C were typical of DRX while at lower temperatures the flow curves were associated with work hardening without any indication of DRX. At high temperatures, flow stress exhibited a linear relation with temperature while at temperatures below 950 deg. C the behavior changed to non-linear. Hence, the temperature of 950 deg. C was introduced as the T{sub nr} of the alloy. All the flow curves showed a yield point elongation like phenomenon which was attributed to the interaction of solute atoms, notably carbon, and moving dislocations. The maximum elongation associated with the yield point phenomenon was observed at about 950 deg. C. Since the maximum yield point elongation was observed about the calculated T{sub nr}, it was concluded that carbon atoms were responsible for it. It was also concluded that the temperature at which the yield point elongation reaches the maximum value increases as strain rate rises. The stress and strain of the characteristic points of DRX flow curves were successfully correlated to the Zener-Hollomon parameter, Z, by power-law equations. The constitutive exponential equation was found more precise than the hyperbolic sine equation for modeling the dependence of flow stress on Z. The apparent activation energy for DRX was determined as 377 kJ mol{sup -1}. The kinetics of DRX was modeled by an Avrami

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

    International Nuclear Information System (INIS)

    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

  5. Interaction of Hydrogen and Retained Austenite in Bainite/Martensite Dual-Phase High Strength Steel

    Institute of Scientific and Technical Information of China (English)

    GU Jia-lin; CHANG Kai-di; FANG Hong-sheng; YANG Zhi-gang; BAI Bing-zhe

    2004-01-01

    The hydrogen trapping phenomena in two bainite/martensite dual-phase high strength steels (U20Si and U20DSi) were investigated by electrochemical permeation technique. The hydrogen diffusivity was calculated from data of permeation delay time, and the diffusion coefficient in U20Si is far less than that in U20DSi. Moreover, the hydrogen diffusivity decreases as the volume percent of retained austenite increases. The experiment results show that there are different hydrogen trappings and different volume percents of retained austenite in U20Si and U20DSi. The retained austenite is precipitated as films. The trap binding energy for the retained austenite and hydrogen is calculated to be 40.4 kJ·mol-1.

  6. 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.

  7. Solidification crack susceptibility in weld metals of fully austenitic stainless steels, (1)

    International Nuclear Information System (INIS)

    It has been well known that weld metals of fully austenitic stainless steels exhibit greater susceptibility to hot cracking and austenitic weld metals containing a small amount (in the order of 5%) of delta ferrite are much more resistant during welding. However, it has not been clarified completely why the presence of some delta-ferrite prevents hot cracking in Cr-Ni weld metals. Therefore, the authors have investigated the structural change during solidification from a metallographic standpoint for the both weld metals of fully austenitic stainless steel AISI 310S (25Cr-20Ni; Japanese Industrial Standards: SUS 310S) and austenitic stainless steel AISI 304 (18Cr-8Ni; JIS: SUS 304) containing a small amount of delta-ferrite to which sulphur and phosphorus were added as harmful impurities. Each specimen was rapidly quenched in water during TIG arc bead-on-plate, so that each bead showed the instantaneous structures from solidification front to room temperature along welding direction. Solidification behaviors of the fully austenitic and the duplex microstructures, microsegregation (especially S and P) during solidification and distribution of alloying elements between delta- and γ-phases at high temperature were investigated. (auth.)

  8. Effect of Niobium on Isothermal Transformation of Austenite to Ferrite in HSLA Low-Carbon Steel

    Institute of Scientific and Technical Information of China (English)

    CAO Jian-chun; LIU Qing-you; YONG Qi-long; SUN Xin-jun

    2007-01-01

    Using thermomechanical simulation experiment, the kinetics of the isothermal transformation of austenite to ferrite in two HSLA low-carbon steels containing different amounts of niobium was investigated under the conditions of both deformation and undeformation. The results of optical microstructure observation and quantitative metallography analysis showed that the kinetics of the isothermal transformation of austenite to ferrite in lower niobium steel with and without deformation suggests a stage mechanism, wherein there exists a linear relationship between the logarithms of holding time and ferrite volume fraction according to Avrami equation, whereas the isothermal transformation of austenite to ferrite in high niobium steel proceeds via a two stage mechanism according to micrographs, wherein, the nucleation rate of ferrite in the initial stage of transformation is low, and in the second stage,the rate of transformation is high and the transformation of residual austenite to ferrite is rapidly complete. Using carbon extraction replica TEM, niobium carbide precipitation for different holding time was investigated and the results suggested that NbC precipitation and the presence of solute niobium would influence the transformation of austenite to ferrite. The mechanism of the effect of niobium on the isothermal transformation was discussed.

  9. Dynamic Recrystallization Behavior of a Fe-Cr-Ni Super-Austenitic Stainless Steel

    Institute of Scientific and Technical Information of China (English)

    A. Hoseini Asli; A. Zarei-Hanzaki

    2009-01-01

    The super-austenitic stainless steels are extensively utilized in the seamless tubes production for oil extraction industries. Due to the importance of thermo-mechanical processing in the production of these tubes, the dynamic recrystallization (DRX) characteristics of a Cr-Ni super austenitic stainless steel (1.4563) were investigated in the present study. This was performed using the hot compression testing method in the temperature range of 950-1150℃ and the strain rate of 10~(-3)-10~(-1)s~(-1). The initiation and evolution of DRX were examined through microstructural analysis. The results indicated that the recrystallized grain formed a necklace type structure at the prior austenite grain boundaries at higher strain rates. In addition, DRX nucleation occurs by bulging and successive strain induced boundary migration (SIBM).

  10. Reheating Austenitizing Temperature of Spring Steel 60Si2MnA for Railway

    Institute of Scientific and Technical Information of China (English)

    CUI Juan; LIU Ya-zheng; PAN Hui; GAO Li-feng

    2008-01-01

    The microsturctural transformation of austenite grain,pearlite interlamellar spacing,and lamellar cementite thickness of spring steel 60Si2MnA for railway were studied in the hot-rolled and reheated states.Furthermore,the effect of microstructural characterization on its final mechanical properties was discussed.The results showed that as far as 60Si2MnA,the pearlite interlamellar spacing determined the hardness,whereas,the austenite grain determined the toughness.Compared with microstructure and mechanical properties in the hot-rolled state,after reheating treatment at 950℃,its average grain sizes are apparently fine and the pearlite interlamellar spacing and lamellar cementite thickness coarsen to some extent,but both hardness and impact toughness increase to HRC 48 and 8.5 J.respectively.In the course of making spring,the optimum reheating austenitizing temperature for the 60Si2MnA steel is 950℃.

  11. Analytical Investigation of Prior Austenite Grain Size Dependence of Low Temperature Toughness in Steel Weld Metal

    Institute of Scientific and Technical Information of China (English)

    X.F. Zhang; P. Hall; H. Terasak; M. Sato; Y. Komizo

    2012-01-01

    Prior austenite grain size dependence of the low temperature impact toughness has been addressed in the bainitic weld metals by in situ observations.Usually,decreasing the grain size is the only approach by which both the strength and the toughness of a steel are increased.However,low carbon bainitic steel with small grain size shows a weakening of the low temperature impact toughness in this study.By direct tracking of the morphological evolution during phase transformation,it is found that large austenite grain size dominates the nucleation of intragranular acicular ferrite,whereas small austenite grain size leads to grain boundary nucleation of bainite.This kinetics information will contribute to meet the increasing low temperature toughness requirement of weld metals for the storage tanks and offshore structures.

  12. Degradation of superheater tubes made of austenitic T321H steel after long term service

    Energy Technology Data Exchange (ETDEWEB)

    Hernas, Adam [Silesian Technical Univ., Katowice (Poland). Faculty of Material Science; Augustyniak, Boleslaw; Chmielewski, Marek [Gdansk Univ. of Technology (Poland). Mechanical Dept.; Sablik, M.J. [Applied Magnetic and Physical Modeling, LLC, San Antonio, TX (United States)

    2010-07-01

    There are presented results of complementary tests performed for the evaluation of creep damage in austenitic steel grade T321H exploited over 200,000 hours in the secondary superheater part of a power plant boiler. The following techniques have been applied: SEM microscopy, X-ray diffraction, tensile tests, hardness measurements and novel eddy current inspection. The novel eddy current inspection is proposed as a non-destructive method of estimating the creep damage stage of austenite steel boiler tubes after long-term service in power plants. We compare the results provided by the different techniques and discuss the correlations and also point out the problems which need to be addressed in order to elaborate the remaining life assessment of austenitic boiler tubes. (orig.)

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

    International Nuclear Information System (INIS)

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

  14. Effects of Cr - Ni 18/9 Austenitic Cast Steel Modification by Mischmetal

    OpenAIRE

    Gajewski, M; J. Kasińska

    2012-01-01

    This paper presents the results of Cr - Ni 18/9 austenitic cast steel modifications by mischmetal. The study was conducted on industrial melts. Cast steel was melted in an electric induction furnace with a capacity of 2000 kg and a basic lining crucible. .The mischmetal was introduced into the ladle during tapping of the cast steel from the furnace. The effectiveness of modification was examined with the carbon content of 0.1% and the presence of δ ferrite in the structure of cast steel stabi...

  15. Assessment of molybdenum influence on long-term heat resistance of selected austenitic steel grades

    International Nuclear Information System (INIS)

    Analysis gave evidence that an increase in the long-term heat resistance by addition of approximately 2.5% molybdenum is, in the long run, more efficient in unstabilized austenitic CrNiMo(N) steels of the AISI 316 type than in stabilized X 6 CrNiMoTi 17 12 steel. The effect of molybdenum can be intensified or reduced by factors such as the stabilization ratio and grain size in stabilized CrNiMoTi steels, and the boron, nitrogen and carbon contents in unstabilized CrNiMo(N) steels. (Z.S.). 6 tabs., 6 figs., 62 refs

  16. Corrosion resistance of modern austenitic-ferritic (duplex) stainless steel. Corrosion of special types. (Review)

    International Nuclear Information System (INIS)

    Recent data on resistance of modern corrosion-resistant austenitic-ferritic steels to different types of corrosion are generalized. It is shown that these steels are characterized by high resistance to general corrosion in acid, alkali, chloride and other solutions, are not inclined to intercrystalline, pitting and crevice corrosion and are noted for high resistance to corrosion cracking and corrosion fatigue. All this is combined with technological and economical effectiveness. It is advisible to use these steels instead of highly-alloyed and expensive steels and alloys in chemical, power and other industries. 59 refs.; 2 tabs

  17. High temperature strength of simple and solute-modified 10Cr-30Mn austenitic steels

    International Nuclear Information System (INIS)

    In order to develop potential reduced activation manganese-stabilized austenitic steels for use in the first wall component of a fusion reactor, tensile and high temperature creep properties have been investigated for simple and solute-modified 10% Cr-30% Mn austenitic steels. The yield stress increased linearly with carbon concentration over the range from room temperature to 873 K. The creep-rupture strength at 873 K increased linearly with carbon concentration at short times, below 360 ks (100 h). The contribution of carbon to the increase in creep rupture strength decreased at high carbon concentration, above 0.2%, and at long times, above 3600 ks (1000 h). A solute-modified 10Cr-30Mn-2W-0.2Ti-0.008B-0.04P-0.15C(wt%) steel exhibited very high tensile and creep rupture strength that were superior to those of type 316 steel. (orig.)

  18. The effect of hydrogen on strain hardening and fracture mechanism of high-nitrogen austenitic steel

    Science.gov (United States)

    Maier, G. G.; Astafurova, E. G.; Melnikov, E. V.; Moskvina, V. A.; Vojtsik, V. F.; Galchenko, N. K.; Zakharov, G. N.

    2016-07-01

    High-nitrogen austenitic steels are perspective materials for an electron-beam welding and for producing of wear-resistant coatings, which can be used for application in aggressive atmospheres. The tensile behavior and fracture mechanism of high-nitrogen austenitic steel Fe-20Cr-22Mn-1.5V-0.2C-0.6N (in wt.%) after electrochemical hydrogen charging for 2, 10 and 40 hours have been investigated. Hydrogenation of steel provides a loss of yield strength, uniform elongation and tensile strength. The degradation of tensile properties becomes stronger with increase in charging duration - it occurs more intensive in specimens hydrogenated for 40 hours as compared to ones charged for 2-10 hours. Fracture analysis reveals a hydrogen-induced formation of brittle surface layers up to 6 μm thick after 40 hours of saturation. Hydrogenation changes fracture mode of steel from mixed intergranular-transgranular to mainly transgranular one.

  19. The Synthesis and Electrochemical Behavior of High-Nitrogen Nickel-Free Austenitic Stainless Steel

    Science.gov (United States)

    Sun, Shicheng; Wei, Sufeng; Wang, Guoyong; Jiang, Zhonghao; Lian, Jianshe; Ji, Changtao

    2014-11-01

    A new smelting method to synthesize high-nitrogen nickel-free austenitic stainless steel was suggested. The synthesized steel completely consists of austenite and represents more brilliant anti-corrosion ability both in salt solution and sulfuric acid solution. The brilliant anti-corrosion ability is retained even after severe cold-rolling deformation, which ensures its workability in practice. The potentiodynamic polarization curves, electrochemical impedance spectroscopy, and passivating treatment were used to characterize its corrosion properties and uncover its corrosion mechanism in salt solution. X-ray photoelectron spectroscopy was used to clarify the mechanism of passivation. The results demonstrate that the steel has a more uniform and thicker passive film than traditional stainless steel due to the cooperation of nitrogen and chromium.

  20. Laser welding of butt joints of austenitic stainless steel AISI 321

    Directory of Open Access Journals (Sweden)

    A. Klimpel

    2007-11-01

    Full Text Available Purpose: of this paper: A study of an automated laser autogenous welding process of butt joints of austenitic stainless steel AISI 321 sheets 0.5 [mm] and 1.0 [mm] thick using a high power diode laser HPDL has been carried out.Design/methodology/approach: Influence of basic parameters of laser welding on shape and quality of the butt joints and the range of optimal parameters of welding were determined.Findings: It was showed that there is a wide range of laser autogenous welding parameters which ensures high quality joints of mechanical strength not lower than the strength of the base material (BM. The butt joints of austenitic steel AISI 321 sheets welded by the HPDL diode laser at optimal parameters are very high quality, without any internal imperfections and the structure and grain size of weld metal and HAZ is very small and also the HAZ is very narrow and the fusion zone is very regular.Research limitations/implications: Studies of the weldability of stainless steels indicate that the basic influence on the quality of welded joints and reduction of thermal distortions has the heat input of welding, moreover the highest quality of welded joints of austenitic stainless steel sheets are ensured only by laser welding.Practical implications: The technology of laser welding can be directly applied for welding of butt joints of austenitic steel AISI 321 sheets 0.5 and 1.0 [mm] thick.Originality/value: Application of high power diode laser for welding of austenitic stainless steel AISI 321.

  1. Cast heat-resistant austenitic steel with improved temperature creep properties and balanced alloying element additions and methodology for development of the same

    Science.gov (United States)

    Pankiw, Roman I; Muralidharan, Govindrarajan; Sikka, Vinod Kumar; Maziasz, Philip J

    2012-11-27

    The present invention addresses the need for new austenitic steel compositions with higher creep strength and higher upper temperatures. The new austenitic steel compositions retain desirable phases, such as austenite, M.sub.23C.sub.6, and MC in its microstructure to higher temperatures. The present invention also discloses a methodology for the development of new austenitic steel compositions with higher creep strength and higher upper temperatures.

  2. 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.

  3. The influence of chemical composition on structure and mechanical properties of austenitic Cr-Ni steels

    OpenAIRE

    A. Kurc-Lisiecka; M. Kciuk

    2013-01-01

    Purpose: The aim of the paper is to investigated the influence of the chemical composition on the structure and mechanical properties of austenitic Cr-Ni steels. Special attention was put on the effect of solution heat treatment on mechanical properties of examined steels. Design/methodology/approach: The examinations of static tensile tests were conducted on ZWICK 100N5A. Hardness measurements were made by Vickers method. The X-ray analyzes were realized with the use of Dron ...

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

    OpenAIRE

    Kochanowski K.; Oliferuk W.; Płochocki Z.; Adamowicz A.

    2014-01-01

    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 complic...

  5. Out-of-plane magnetic patterning on austenitic stainless steels using plasma nitriding

    OpenAIRE

    Menéndez, E.; Nogués, Josep

    2010-01-01

    A correlation between the grain orientation and the out-of-plane magnetic properties of nitrogen-enriched polycrystalline austenitic stainless steel surface is performed. Due to the competition between the magnetocrystalline anisotropy, the exchange and dipolar interactions, and the residual stresses induced by nitriding, the resulting effective magnetic easy-axis can lay along unusual directions. It is also demonstrated that, by choosing an appropriate stainless steel texturing, arrays of fe...

  6. Niobium-containing quenching and partitioning processed ultrahigh strength martensite–austenite dual phase steels

    International Nuclear Information System (INIS)

    Given the strong recent interest in quenching and partitioning processed steels, we present here a study concerning niobium bearing steel with medium carbon content. The quenching and partitioning process leads to an extremely high product of tensile strength and percentage elongation approaching 38 GPa%. The contribution is a cumulative effect of martensite with tempered randomly-oriented laths, small fraction of lower bainite, and a high fraction of retained austenite

  7. Acoustic Emission Technique for Characterizing Deformation and Fatigue Crack Growth in Austenitic Stainless Steels

    Science.gov (United States)

    Raj, Baldev; Mukhopadhyay, C. K.; Jayakumar, T.

    2003-03-01

    Acoustic emission (AE) during tensile deformation and fatigue crack growth (FCG) of austenitic stainless steels has been studied. In AISI type 316 stainless steel (SS), AE has been used to detect micro plastic yielding occurring during macroscopic plastic deformation. In AISI type 304 SS, relation of AE with stress intensity factor and plastic zone size has been studied. In AISI type 316 SS, fatigue crack growth has been characterised using acoustic emission.

  8. The welding of austenitic-ferritic Mo-alloyed Cr-Ni-Steel

    International Nuclear Information System (INIS)

    This paper provides general information and guidance on the welding of austenitic-ferritic Mo-alloyed Cr-Ni stainless steel. Information is given on the various chemical compositions and on resistance to corrosion and on the mechanical and physical properties of commercially available steels. The effect of welding on the base metal and the selection of welding processes and welding consumables are described

  9. Progress in EPRI-programs on the inspection of cast austenitic stainless steel

    International Nuclear Information System (INIS)

    This document presents the progress in EPRI programs on in-service inspection of Cast austenitic Stainless Steel (CSS). The CSS examination strategy is presented, together with results concerning thermal fatigue cracks and mechanical fatigue cracks. A statistical analysis method is provided, in order to estimate the crack detectability and the false call (a non-crack called crack). (TEC)

  10. The structure of austenitic steel AISI 316 after ECAP and low-cycle fatigue

    Directory of Open Access Journals (Sweden)

    L. Kander

    2008-06-01

    Full Text Available Purpose: The article presents results of investigation of structure and properties of austenitic steel grade AISI 316 after application of Equal Channel Angular Pressing (ECAP at the temperature of approx. 290ºC.Design/methodology/approach: The ECAP method led to significant improvement of strength of investigated material. Experiments were planned and realised at the temperature ranging from room temperature up to above mentioned temperature.Findings: It was established with use of the EBSD technique that after 8 passes through the ECAP die the sub-grains with an angle of disorientation smaller than 10º formed less than 20% of resulting structure. Average size of austenitic grains with high angle boundary after 8 passes was approx. 0.32 µm. It was proven that the ECAP method enables obtaining of ultra fine-grained austenitic structure formed by recrystallised grains with very low density of dislocations.Practical implications: The Technology ECAP was applied on austenitic steel AISI 316. It was verification of ECAP application possibility on steel AISI 316 importantly for following applying on similar kinds of steel, because ECAP technology influence on fatigue properties was confirmed.Originality/value: It can be predicted on the basis of obtained results that, contrary to low-cycle fatigue the ultra-fine grained material will manifest at fatigue load in the mode of constant amplitude of stress higher fatigue characteristics, particularly fatigue limit.

  11. 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 in...

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

    DEFF Research Database (Denmark)

    Belluco, Walter; De Chiffre, Leonardo

    2004-01-01

    The efficiency of six cutting oils was evaluated in drilling AISI 316L austenitic stainless steel using conventional HSS-Co tools by measurements of tool life, tool wear, cutting forces and chip formation. Seven tools were tested with each fluid to catastrophic failure. Cutting forces and chip...

  13. Void Volume Swelling Dependent on Grain Size in Austenitic Stainless Steel

    DEFF Research Database (Denmark)

    Singh, Bachu Narain

    1973-01-01

    Describes some of the main findings of a systematic study of the effect of grain size on the void volume swelling. In this study a powder-produced 20 Ni/20 Cr austenitic stainless steel, with 0.02% carbon and without carbide-forming elements was used. Some specimens containing dispersions of...

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

    NARCIS (Netherlands)

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

    2013-01-01

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

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

    OpenAIRE

    Ogórek, M.; Skuza, Z.; 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.

  16. 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.

  17. Welding of super austenitic stainless steels with very high nitrogen contents

    International Nuclear Information System (INIS)

    Results of studies performed on the weld of different super austenitic stainless steels show that nitrogen additions as high as 0.5% does not deteriorate the weldability but on the contrary improves the mechanical and corrosion properties of the weld. (A.B.). 5 refs., 5 figs., 6 tabs

  18. Hardened austenite steel with columnar sub-grain structure formed by laser melting

    International Nuclear Information System (INIS)

    Laser melting (LM), with a focused Nd: YAG laser beam, was used to form solid bodies from a 316L austenite stainless steel powder. The microstructure, phase content and texture of the LM stainless steel were characterized and compared with conventional 316L stainless steel. The crack-free LM samples achieved a relative density of 98.6±0.1%. The XRD pattern revealed a single phase Austenite with preferential crystallite growth along the (100) plane and an orientation degree of 0.84 on the building surface. A fine columnar sub-grain structure of size 0.5 μm was observed inside each individual large grain of single-crystal nature and with grain sizes in the range of 10–100 μm. Molybdenum was found to be enriched at the sub-grain boundaries accompanied with high dislocation concentrations. It was proposed that such a sub-grain structure is formed by the compositional fluctuation due to the slow kinetics of homogeneous alloying of large Mo atoms during rapid solidification. The local enrichment of misplaced Mo in the Austenite lattice induced a network of dislocation tangling, which would retard or even block the migration of newly formed dislocations under indentation force, turning otherwise a soft Austenite to hardened steel. In addition, local formation of spherical nano-inclusions of an amorphous chromium-containing silicate was observed. The origin and the implications of the formation of such oxide nano-inclusions were discussed

  19. 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

  20. On the comparison of microstructural characteristics and mechanical properties of high-vanadium austenitic manganese steels with the Hadfield steel

    International Nuclear Information System (INIS)

    Highlights: ► Mechanical properties of HV-AMS are affected by the type and distribution of VCs. ► Solution treatment of Hadfield steels has no significant effect on HV-AMS alloys. ► HV-AMS alloys have superior wear resistance compared with Hadfield steels. - Abstract: In this study, high-vanadium austenitic manganese steel (HV-AMS) alloys and the standard Hadfield steel were investigated. The microstructure of these high-vanadium alloyed Hadfield steels was studied thoroughly using optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD) and was compared to the Hadfield steel. The hardness and unnotched Charpy impact strength of HV-AMS alloys and Hadfield steel were examined at ambient temperature in the as-cast and heat-treated conditions. A pin-on-disk wear test at linear speed of 10 m/min and a 55 N normal load was employed to evaluate the wear behavior of both steel samples. Microstructural results showed that varying the carbon content in HV-AMS alloys can affect the vanadium carbide morphology and its distribution in the austenite matrix which leads to considerable changes of the mechanical properties. Abrasion test revealed that HV-AMS alloys have superior wear resistance, about 5 times of the standard Hadfield steel.

  1. Enhancement of mechanical properties of a TRIP-aided austenitic stainless steel by controlled reversion annealing

    Energy Technology Data Exchange (ETDEWEB)

    Hamada, A.S., E-mail: atef.hamada@suezuniv.edu.eg [Centre for Advanced Steels Research, Box 4200, University of Oulu, 90014 Oulu (Finland); Metallurgical and Materials Engineering Department, Faculty of Petroleum & Mining Engineering, Suez University, Box 43721, Suez (Egypt); Kisko, A.P. [Centre for Advanced Steels Research, Box 4200, University of Oulu, 90014 Oulu (Finland); Sahu, P. [Department of Physics, Jadavpur University, Kolkata 700032 (India); Karjalainen, L.P. [Centre for Advanced Steels Research, Box 4200, University of Oulu, 90014 Oulu (Finland)

    2015-03-25

    Controlled martensitic reversion annealing was applied to a heavily cold-worked metastable austenitic low-Ni Cr–Mn austenitic stainless steel (Type 201) to obtain different ultrafine austenite grain sizes to enhance the mechanical properties, which were then compared with the conventional coarse-grained steel. Characterization of the deformed and reversion annealed microstructures was performed by electron back scattered diffraction (EBSD), X-ray diffraction (XRD) and light and transmission electron microscopy (TEM). The steel with a reverted grain size ~1.5 μm due to annealing at 800 °C for 10 s showed significant improvements in the mechanical properties with yield stress ~800 MPa and tensile strength ~1100 MPa, while the corresponding properties of its coarse grained counterpart were ~450 MPa and ~900 MPa, respectively. However, the fracture elongation of the reversion annealed steel was ~50% as compared to ~70% in the coarse grained steel. A further advantage is that the anisotropy of mechanical properties present in work-hardened steels also disappears during reversion annealing.

  2. Enhancement of mechanical properties of a TRIP-aided austenitic stainless steel by controlled reversion annealing

    International Nuclear Information System (INIS)

    Controlled martensitic reversion annealing was applied to a heavily cold-worked metastable austenitic low-Ni Cr–Mn austenitic stainless steel (Type 201) to obtain different ultrafine austenite grain sizes to enhance the mechanical properties, which were then compared with the conventional coarse-grained steel. Characterization of the deformed and reversion annealed microstructures was performed by electron back scattered diffraction (EBSD), X-ray diffraction (XRD) and light and transmission electron microscopy (TEM). The steel with a reverted grain size ~1.5 μm due to annealing at 800 °C for 10 s showed significant improvements in the mechanical properties with yield stress ~800 MPa and tensile strength ~1100 MPa, while the corresponding properties of its coarse grained counterpart were ~450 MPa and ~900 MPa, respectively. However, the fracture elongation of the reversion annealed steel was ~50% as compared to ~70% in the coarse grained steel. A further advantage is that the anisotropy of mechanical properties present in work-hardened steels also disappears during reversion annealing

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2011-01-15

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

  4. Spinodal decomposition of austenite in long-term-aged duplex stainless steel

    International Nuclear Information System (INIS)

    Spinodal decomposition of austenite phase in the cast duplex stainless steels CF-8 and -8M grades has been observed after long- term thermal aging at 400 and 350/degree/C for 30,000 h (3.4 yr). At 320/degree/C, the reaction was observed only at the limited region near the austenite grain boundaries. Ni segregation and ''worm-holes'' corresponding to the spatial microchemical fluctuations have been confirmed. The decomposition was observed only for heats containing relatively high overall Ni content (9.6--12.0 wt %) but not in low-Ni (8.0--9.4 wt %) heats. In some specimens showing a relatively advanced stage of decomposition, localized regions of austenite with a Vickers hardness of 340--430 were observed. However, the effect of austenite decomposition on the overall material toughness appears secondary for aging up to 3--5 yr in comparison with the effect of the faster spinodal decomposition in ferrite phase. The observation of the thermally driven spinodal decomposition of the austenite phase in cast duplex stainless steels validates the proposition that a miscibility gap occurs in Fe-Ni and ancillary systems. 16 refs., 7 figs., 1 tab

  5. Ultrahigh strength martensite–austenite dual-phase steels with ultrafine structure: The response to indentation experiments

    International Nuclear Information System (INIS)

    In medium to high carbon steels, characterized by martensite–austenite microstructure processed by quenching and partitioning process, martensite potentially provides high strength, while austenite provides work hardening [Fu, Wu, and Misra, DOI: 10.1179/1743284712/068]. Given the significant interest in these steels in the steel community, the paper reports for the first time the nanoscale deformation experiments and accompanying microstructural evolution to obtain micromechanical insights into the deformation behavior of ultrahigh strength-high ductility dual-phase steels with significant retained austenite fraction of ∼0.35. During deformation experiments with nanoindenter, dislocations were distributed on several slip systems, whereas strain-induced twinned martensite and twinning were the deformation mechanisms in carbon-enriched and thermally stabilized retained austenite. Furthermore, ultrafine dual-phase steels exhibited high strain rate sensitivity.

  6. 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.

  7. Austenite Grain Growth and Precipitate Evolution in a Carburizing Steel with Combined Niobium and Molybdenum Additions

    Science.gov (United States)

    Enloe, Charles M.; Findley, Kip O.; Speer, John G.

    2015-11-01

    Austenite grain growth and microalloy precipitate size and composition evolution during thermal processing were investigated in a carburizing steel containing various additions of niobium and molybdenum. Molybdenum delayed the onset of abnormal austenite grain growth and reduced the coarsening of niobium-rich precipitates during isothermal soaking at 1323 K, 1373 K, and 1423 K (1050 °C, 1100 °C, and 1150 °C). Possible mechanisms for the retardation of niobium-rich precipitate coarsening in austenite due to molybdenum are considered. The amount of Nb in solution and in precipitates at 1373 K (1100 °C) did not vary over the holding times evaluated. In contrast, the amount of molybdenum in (Nb,Mo)C precipitates decreased with time, due to rejection of Mo into austenite and/or dissolution of fine Mo-rich precipitates. In hot-rolled alloys, soaking in the austenite regime resulted in coarsening of the niobium-rich precipitates at a rate that exceeded that predicted by the Lifshitz-Slyozov-Wagner relation for volume-diffusion-controlled coarsening. This behavior is attributed to an initial bimodal precipitate size distribution in hot-rolled alloys that results in accelerated coarsening rates during soaking. Modification of the initial precipitate size distribution by thermal processing significantly lowered precipitate coarsening rates during soaking and delayed the associated onset of abnormal austenite grain growth.

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

    International Nuclear Information System (INIS)

    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)

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

    International Nuclear Information System (INIS)

    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)

  10. 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.

  11. 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...... case included X-ray diffraction analysis, reflected light microscopy and microhardness. The results demonstrate that a case of expanded austenite develops and that, in particular, strain-induced martensite has a large influence on the nitrided zone....

  12. Study of interactions between liquid lead-lithium alloy and austenitic and martensitic steels

    International Nuclear Information System (INIS)

    In the framework of Fusion Technology, the behaviour of structural materials in presence of liquid alloy Pb17Li is investigated. First, the diffusion coefficients of Fe and Cr have been determined at 500 deg C. Then mass transfer experiments in Pb17Li have been conducted in an anisothermal container with pure metals (Fe, Cr, Ni), Fe-Cr steels and austenitic steels. These experiments showed a very high loss of Nickel, which is an accordance with its high solubility, and Cr showed mass-losses one order of magnitude higher than for pure iron, as the diffusion coefficient of Cr is three orders of magnitude higher than for pure Fe. The corrosion rate of binary Fe-Cr and pure Fe are identical. In austenitic steels, the gamma lattice allows a higher mass-transfer of Cr than the alpha lattice, the presence of Cr slows downs the dissolution of Ni, and the porosity of corrosion layers results of losses of Cr and Ni. Finally, a review of our results and those of other laboratories allowed an identification of the corrosion limiting step. In the case of 1.4914 martensitic steel it is the diffusion of Fe in Pb17Li, while in the case of 316L austenitic steel it is the diffusion of Cr in Pb17Li

  13. Nanostructured nickel-free austenitic stainless steel composites with different content of hydroxyapatite

    International Nuclear Information System (INIS)

    Highlights: ► Ni-free austenitic stainless steel/hydroxyapatite composites were produced. ► Nanocrystalline structure was confirmed by three different techniques. ► Nitriding of the surface slightly increases crystallite size. ► The mean grain size of the obtained materials do not exceed 100 nm. - Abstract: The aim of this work is to show that Ni-free austenitic stainless steels with nanostructure and their nanocomposites with hydroxyapatite can be synthesized by mechanical alloying, heat treatment and nitriding of elemental microcrystalline powders with addition of hydroxyapatite (HA). Hydroxyapatite was introduced into stainless steel because it is intensively studied for bone repair and replacement applications. Nickel-free austenitic stainless steels seem to have better mechanical properties, corrosion resistance and biocompatibility compared to 316L stainless steels. Therefore it's combination with hydroxyapatite that has high biocompatibility and ability to bond to bone could have improved properties, as well. To confirm nanocrystalline structure of obtained material and reveal topographical features of the surface, small-angle X-ray analysis (SAXS) and atomic force microscopy (AFM) were used. Results are consistent and the mean grain size of the obtained materials do not exceed 100 nm.

  14. Effect of Austenite Recrystallization on Microstructure and Properties of Q345 Steel

    Institute of Scientific and Technical Information of China (English)

    ZHU Fu-xian; LI Yan-mei; LIU Yan-chun; WANG Guo-dong

    2005-01-01

    The Q345 plate steel austenite recrystallization behavior and strain accumulation during rolling were investigated through thermal simulation and rolling. The effect of the recrystallization behavior on the microstructure and properties of the steel was discussed and analyzed. The control principles of the pass reduction in the austenite recrystallization region and partial recrystallization region were established. It is found that to increase the thickness of intermediate billet in the finish temperature interval of 880-820 ℃ is favorable to grain refinement.The result has been applied to the industrial production of the 3 500 mm plate mill of Shougang Group. The average grain size of the steel plate conforms to ASTM No. 10-12, and the grade of band structure has been reduced to below 1.5.

  15. Hydrogen embrittlement of martensitic and austenitic stainless steels for fusion applications

    International Nuclear Information System (INIS)

    In this study the Disk Pressure Method was employed to investigate the mechanical behaviour of several stainless steels with potential application in fusion reactors. Tests were carried out on as-received material and on specimens charged with different hydrogen concentrations. The DPT tests were performed at hydrogen concentrations ranging from 1 to 15 wt ppm for martensitic materials and at a maximum concentration of 30 wt ppm for austenitic steel. The mechanical properties of martensitic steels were greatly affected by the presence of hydrogen only above well defined concentrations. The critical concentration values measured are reported and discussed in terms of hydrogen diffusion and trapping, as well as microstructural parameters such as prior austenitic grain size. No significant mechanical effects were found in the case of 316L at the hydrogen concentrations indicated. (orig.)

  16. Modelling of Nb influence on phase transformation behaviours from austenite to ferrite in low carbon steels

    Science.gov (United States)

    Wang, L.; Parker, S. V.; Rose, A. J.; West, G. D.; Thomson, R. C.

    2016-03-01

    In this paper, a new model has been developed to predict the phase transformation behaviours from austenite to ferrite in Nb-containing low carbon steels. The new model is based on some previous work and incorporates the effects of Nb on phase transformation behaviours, in order to make it applicable for Nb-containing steels. Dissolved Nb atoms segregated at prior austenite grain boundaries increase the critical energy for ferrite nucleation, and thus the ferrite nucleation rate is decreased. Dissolved Nb atoms also apply a solute drag effect to the moving transformation interface, and the ferrite grain growth rate is also decreased. The overall transformation kinetics is then calculated according to the classic Johnson-Mehl-Avrami-Kolmogorov (JMAK) theory. The new model predictions are quite consistent with experimental results for various steels during isothermal transformations or continuous cooling.

  17. 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.

  18. The effect of porosity on the austenite to ferrite transformation in powder metallurgy steels

    International Nuclear Information System (INIS)

    Research highlights: → Presence of porosity in samples reduces overall stability of austenite phase. → Nucleation rate of ferrite increases with increase in porosity in the samples. → Measurements showed reduction in incubation time with increasing porosity. → Avrami exponent, n, found to be independent of temperature and pore fraction. → Avrami constant, b(T), found to be dependent on porosity. - Abstract: The effect of porosity on the kinetics of the austenite to ferrite isothermal transformation in powder metallurgy steels was characterized using high-speed quench dilatometery. The measurements reveal that the presence of porosity in these steels reduces the stability of austenite and hence shortens the incubation time of the transformation. An Avrami-type equation was fitted to the measured data in order to quantify the effect of porosity on the Avrami constants. In addition, samples with varying levels of porosity were interruptedly quenched after holding them at 650 deg. C for 900 s. Quantitative microscopic measurements performed on these samples showed an increase in the number and a decrease in the average diameter of the ferrite grains with increasing porosity. It is hypothesized that pores in powder metallurgy steels increase the rate of nucleation of ferrite from austenite by providing high diffusivity paths for carbon atoms that help accelerate their partitioning during the transformation.

  19. Corrosion behaviour of Fe-Mn-Si-Al austenitic steel in chloride solution

    Directory of Open Access Journals (Sweden)

    W. Krukiewicz

    2009-04-01

    Full Text Available Purpose: The aim of the paper is to investigate the corrosion behaviour of the new-developed high-manganese austenitic steel in 0.5n NaCl solution.Design/methodology/approach: The steel used for the investigation was thermomechanically rolled and solution heat-treated from a temperature of 850°C. Corrosion resistance of investigated steel was examined using weight and potentiodynamic methods. In the weight method, the specimens were immersed in the prepared solution for 24h. In the potentiodynamic method, anodic polarization curves with a rate of potential changes of 1 mV/s in the anodic direction were registered. After the current density being equal 1 mA/cm2 was achieved, the direction of polarization has been changed. Basing on the registered curves, the pitting potential, repassivation potential, polarization resistance and corrosion current were determined.Findings: It was found that the steel is characterized by a partially recrystallized austenitic microstructure with numerous annealing twins and slip bands. According to the results of potentiodynamic analyses it was found that the samples of examined steel show poor corrosion resistance in the NaCl solution. The observed corrosion pits are related to the chemical composition. It is connected with the high dissolution rate of Mn and Fe atoms in NaCl solution. Fractographic analyses of samples revealed corrosion products on their surface in a form of pits with diversified size.Research limitations/implications: To investigate in more detail the corrosion behaviour of high-manganese steel, the investigations should include steels with a wider Al concentration.Practical implications: The obtained results can be used for searching the appropriate way of improving the corrosion resistance of a modern group of high-manganese austenitic steels.Originality/value: The corrosion behaviour in chloride solution of a new-developed Fe-Mn-Si-Al steel was investigated.

  20. Modeling of Austenite Decomposition in Low Si-Mn TRIP Steel During Cooling

    Institute of Scientific and Technical Information of China (English)

    ZHU Li-juan; WU Di; ZHAO Xian-ming

    2008-01-01

    Transformation behavior in low carbon Si-Mn TRIP steel was investigated by means of microstructural observation and computer modelling. A transformation model in which transformation is controlled by carbon diffusion was suggested,which well described the volume fractional change of ferrite,pearlite,and bainite during continuous cooling.The influence of Si content and austenite grain size was thoroughly investigated.The calculated results indicated that Si retards pearlite transformation,accelerates polygonal ferrite transformation,refines the austenite grain,and increases the ferrite transformation rate.

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

    Science.gov (United States)

    Wang, Qingchuan; Zhang, Bingchun; Yang, Ke

    2016-05-01

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

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

    Science.gov (United States)

    Wang, Qingchuan; Zhang, Bingchun; Yang, Ke

    2016-07-01

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

  3. Influence of hot-working conditions on a structure of high-manganese austenitic steels

    Directory of Open Access Journals (Sweden)

    A. Grajcar

    2008-08-01

    Full Text Available Purpose: The aim of the paper is to determine the influence of hot deformation conditions on σ-ε curves and structure changes of new-developed high-manganese austenitic steels.Design/methodology/approach: The force-energetic parameters of hot-working were determined in hot-compression tests performed in a temperature range of 850 to 1050°C by the use of the Gleeble 3800 thermomechanical simulator. Evaluation of processes controlling work hardening at 850°C were identified by microstructure observations of the specimens water-quenched after plastic deformation to a true strain equal 0.22, 0.51 and 0.92.Findings: At initial state the steel containing 3% of Si and Al possesses homogeneous austenite structure with many annealing twins. Increased up to 4% Si concentration and decreased to 2% Al concentration result in a presence of some fraction of ε martensite plates. For applied deformation conditions, the values of flow stress vary from 250 to 450MPa – increasing with decreasing deformation temperature. A relatively small values ofε max deformation at temperatures of 1050 and 950°C allow to suppose that in this range of temperature, to form a fine-grained microstructure of steels, dynamic recrystallization can be used. At a temperature of 850°C, the dynamic recrystallization leads to structure refinement after true strain of about 0.51.Research limitations/implications: To determine in detail the hot-working behaviour of developed steels, a progress of recrystallization as a function of time at deformation temperature should be investigated.Practical implications: The obtained stress-strain curves can be useful in determination of power-force parameters of hot-rolling of high-manganese austenitic steels.Originality/value: The hot-working behaviour of new-devoloped high-manganese austenitic steels containing Nb and Ti microadditions was investigated.

  4. Case histories of microbiologically influenced corrosion of austenitic stainless steel weldments

    International Nuclear Information System (INIS)

    Microbiologically influenced corrosion (MIC) is initiated or accelerated by microorganisms and is currently recognized as a serious problem affecting the construction and operation of many industrial facilities, including nuclear power plants. The purpose of this paper is to review how biofouling and MIC can occur and discuss current mechanistic theories. A case history of MIC attack in power plants is examined with emphasis on the role of welding and heat treatment variables using laboratory electrochemical analyses. Although MIC can occur on a variety of alloys, pitting corrosion failures of austenitic stainless steels are often associated with weldments. MIC occurs as the result of a consortium of microorganisms colonizing on the metal surface and their variety (fungi, bacteria, algae, mold, and slimes) enables them to form support systems for cross feeding to enhance survival. The metabolic processes influence corrosion behaviour of materials by destroying protective coatings, producing a localized acid environment, creating corrosive deposits, or altering anodic and cathodic reactions. On stainless steels, biofilms destroy the passive oxide film on the surface of the steels and subject them to localized forms of corrosion. Many of the MIC failures in industry result in pitting to austenitic stainless steel weldments. Pitting primarily occurs in the weld metal, heat affected zones, and adjacent to the weld in the base metal. Depending on the conditions of the concentration cell created by the biofilm, either phase of the two-phase duplex stainless steel, austenite or delta ferrite, may be selectively attacked. Theories have been proposed about the mechanism of MIC on austenitic stainless steel and and a general understanding is that some function associated with the biofilm formation directly affects the electrochemical process

  5. Corrosion behaviour of Fe-Mn-Si-Al austenitic steel in chloride solution

    OpenAIRE

    W. Krukiewicz; A. Grajcar; M. Opiela

    2009-01-01

    Purpose: The aim of the paper is to investigate the corrosion behaviour of the new-developed high-manganese austenitic steel in 0.5n NaCl solution.Design/methodology/approach: The steel used for the investigation was thermomechanically rolled and solution heat-treated from a temperature of 850°C. Corrosion resistance of investigated steel was examined using weight and potentiodynamic methods. In the weight method, the specimens were immersed in the prepared solution for 24h. In the potentiody...

  6. Anodic polarization curves of austenitic steel Super304H in sulphuric acid solution

    OpenAIRE

    Chmela T.

    2016-01-01

    Polarization curves measured in a sufficiently aggressive environment (e.g. 0.5 mol dm−3 of H2SO4) may help to assess corrosion resistance of stainless steels. New phases precipitate in steel exposed long-term to high temperatures, which may affect the corrosion resistance. Potentiostatic polarization curves were measured on austenitic steel Super304H in a solution annealed state (from the producer) and in a state aged for 15 000 hours at temperatures of 650, 675 and 700 °C. The higher level ...

  7. Thermo-mechanical processing and microstructure evolution of highmanganese austenitic TRIP-type steels

    Directory of Open Access Journals (Sweden)

    M. Ondrula

    2012-08-01

    Full Text Available Purpose: The aim of the paper is to determine the influence of hot-working conditions on microstructure evolution and phase composition of new-developed high-manganese austenitic TRIP-type steels.Design/methodology/approach: The hot-working behaviour was determined in continuous and multistage compression tests performed in a temperature range of 850 to 1100°C by the use of the Gleeble 3800 thermo-mechanical simulator. The processes controlling work hardening and removing it were identified by microstructure evolution observations in different stages of compression with the amount of true strain 4x0.23. Phase composition of steels was confirmed by X-ray diffraction analysis.Findings: It was found that they have austenite microstructure with numerous annealing twins in the initial state. Continuous compression tests realized in the temperature range from 850 to 1050°C with the strain rate of 0.1, 1 and 10 s-1 enabled determination of yield stress values and values of εmax deformations - corresponding to maximum flow stress. The investigated steels are characterized by high values of flow stress from 120 to 380 MPa. Results of the multi-stage compression proved that applying the true strain 4x0.23 gives the possibility to refine the austenite microstructure.Research limitations/implications: To determine in detail the microstructure evolution during industrial rolling, the hot-working schedule should take into account real number of passes and higher strain rates.Practical implications: The obtained microstructure - hot-working conditions relationships and stress-strain curves can be useful in determination of power-force parameters of hot-rolling for sheets with fine-grained austenitic structures.Originality/value: The hot-working behaviour and microstructure evolution in various conditions of plastic deformation for new-developed high-manganese austenitic TRIP-type steels with Nb and Ti microadditions were investigated.

  8. Microstructure evolution and phase composition of high-manganese austenitic steels

    Directory of Open Access Journals (Sweden)

    L.A. Dobrzański

    2008-12-01

    Full Text Available Purpose: The aim of the paper is to determine the influence of hot-working conditions on microstructure evolution and phase composition of new-developed high-manganese austenitic steels.Design/methodology/approach: Determination of processes controlling strain hardening was carried out in continuous compression test using Gleeble 3800 thermo-mechanical simulator. Evaluation of processes controlling work hardening and occurring after deformation at 900°C were identified by microstructure observations of the specimens solution heat-treated after plastic deformation to a true strain equal 0.23, 0.50 and 0.91. Phase composition of steels was confirmed by X-ray diffraction analysis.Findings: The steels have a fine-grained austenite microstructure with many annealing twins to a temperature of about 1000°C. The initiation of dynamic recrystallization occurs already after true deformation equal 0.29. Participation of fine grains arranged in a matrix of dynamically recovered grains essentially increases after increasing true strain to 0.5. Fully dynamically recrystallized microstructure of steel can be obtained after the true strain equal 0.9. The conditions of hot-working influence phase state of investigated steels. Steel no. 1 keeps stable austenite microstructure independently from conditions of plastic deformation. Steel with initial bi-phase microstructure keeps a certain portion of εmartensite, yet dependant on conditions of hot-working.Research limitations/implications: To determine in detail the hot-working behaviour of developed steels, a progress of microstructure evolution in subsequent stages of multi-stage compression test should be investigated.Practical implications: The obtained microstructure – hot-working conditions relationships and stress-strain curves can be useful in determination of power-force parameters of hot-rolling for sheets with fine-grained austenitic structures.Originality/value: The hot-working behaviour and

  9. Hot deformation and recrystallization of advanced high-manganese austenitic TWIP steels

    Directory of Open Access Journals (Sweden)

    L.A. Dobrzański

    2011-05-01

    Full Text Available Purpose: The aim of the paper is to determine the influence of hot-rolling conditions on structure of new-developed high-manganese austenitic steels.Design/methodology/approach: Flow stresses during continuous and multi-stage compression tests were measured using the Gleeble 3800 thermo-mechanical simulator. To describe the hot-working behaviour, the steels were compressed to the various amount of deformation (4x0.29, 4x0.23 and 4x0.19. The microstructure evolution in different stages of hot-rolling was determined in metallographic investigations using light microscopy as well as X-ray diffraction.Findings: The steels are characterized by different microstructure in the initial state. Steel with higher Al concentration has stable microstructure of austenite with annealing twins, while steel with higher Si concentration consists of certain portion of ε martensite in form of plates. The flow stresses are in the range of 200-430 MPa for the applied conditions of hot-working and are up to 40 MPa lower compared to continuous compressions. Results of the multi-stage compression proved that applying the true strain 4x0.29 gives the possibility to refine the austenite microstructure as a result of dynamic recrystallization. In case of applying the lower deformations 4x0.23 and 4x0.19, the process controlling work hardening is dynamic recovery. On the basis of analysis of thermo-mechanical treatment carried out in continuous axisymetrical compression test and multi-stage compression test using the Gleeble 3800 simulator allowed to work out a schedule of three different variants of hot-rolling for each of investigated steels 26Mn-3Si-3Al-Nb-Ti and 27Mn-4Si-2Al-Nb-Ti.Research limitations/implications: To fully describe the hot-rolling behaviour of the new-developed steels, further investigations in wider temperature and strain rate ranges are required.Practical implications: Various conditions of hot-rolling for advanced high-manganese austenitic steels

  10. 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...

  11. Super austenitic stainless steels - a promising replacement for the currently used type 316L stainless steel as the construction material for flue-gas desulphurization plant

    Energy Technology Data Exchange (ETDEWEB)

    Rajendran, N.; Rajeswari, S. [University of Madras, Madras (India). Dept. of Analytical Chemistry

    1996-12-15

    Potentiodynamic anodic cyclic polarization experiments on type 316L stainless steel and 6Mo super austenitic stainless steels were carried out in simulated flue-gas desulphurization (FGD) environment in order to assess the localized corrosion resistance. The pitting corrosion resistance was higher in the case of the super austenitic stainless steel containing 6Mo and a higher amount of nitrogen. The accelerated leaching study conducted for the alloys showed that the super austenitic stainless steels have a little tendency for leaching of metal ions such as iron, chromium and nickel at different impressed potentials. This may be due to surface segregation of nitrogen as CrN, which would, in turn, enrich a chromium and molybdenum mixed oxide film and thus impede the release of metal ions. The present study indicates that the 6Mo super austenitics can be adopted as a promising replacement for the currently used type 316L stainless steel as the construction material for FGD plants.

  12. Effect of composition on the electrochemical behavior of austenitic stainless steel in Ringer's solution

    International Nuclear Information System (INIS)

    Potentiodynamic cyclic polarization tests on Type 316L stainless steel, a common orthopedic implant alloy, in Ringer's solution show considerable hysteresis and a protection potential more active than the open circuit corrosion potential. This implies that chances of repassivation of actively growing pits in this alloy are limited. Tests in Ringer's solution containing hydrochloric acid show that the open circuit potential of Type 316L steel in this solution may exceed in the noble direction the critical pitting potential in the same solution. This signifies that spontaneous breakdown of passivity may occur in a bulk environment which grossly simulates the electrochemical environment within a crevice. Alloying elements such as Mo, Ni, Cr, all improve the corrosion resistance of Type 316L stainless steel in that the critical pitting potential shifts in the noble direction in the alloys having any of the three alloying elements in a higher proportion than in Type 316L steel. Polarization tests in Ringer's solution on a 20% Cr, 25% Ni, 4.5% Mo, 1.5% Cu austenitic stainless steel, having Mo, Cr, and Ni--all in higher proportions than in Type 316L steel, does not show any critical pitting potential or hysteresis at potentials below that for dissociation of water. However, test in 4% NaCl solution at 60 C, a more aggressive chloride environment than Ringer'ssolution, reveals considerable hysteresis and a very active protection potential, indicating that this behavior is a common feature of austenitic stainless steel in sufficiently aggressive, chloride media

  13. Effect of cryorolling on the microstructure and tensile properties of bulk nano-austenitic stainless steel

    International Nuclear Information System (INIS)

    We report the synthesis of nanostructured austenitic AISI 304L stainless steel (SS) through cryorolling (CR) and reversion annealing in the temperature range of 700–800 °C. Severe CR at sub-zero temperature promotes twinning in γ-austenite, which transform into α'-martensite with lath thickness of 50–100 nm. Whereas, 50–300 nm size γ-grains recrystallize in nano-twinned α' through reversion annealing as confirmed by transmission electron microscopy (TEM) and electron back scattered diffraction (EBSD) imaging. The evolution of highly processable bulk nano-austenitic SS with bimodal grain size distribution on achieving high strength (~1295 MPa), large tensile ductility (~0.47), and true necking strain of 0.59, have been discussed

  14. A comparison of the iraddiated tensile properties of a high-manganese austenitic steel and type 316 stainless steel

    International Nuclear Information System (INIS)

    The USSR steel EP-838 is a high-manganese, low-nickel steel that also has lower chromium and molybdenum than type 316 stainless steel. Tensile specimens of 20%-cold-worked EP-838 and type 316 stainless steel were irradiated in the High Flux Isotope Reactor (HFIR) at the coolant temperature (approx.=500C). A displacement damage level of 5.2 dpa was reached for the EP-838 and up to 9.5 dpa for the type 316 stainless steel. Tensile tests at room temperature and 3000C on the two steels indicated that the irradiation led to increased strength and decreased ductility compared to the unirradiated steels. Although the 0.2% yield stress of the type 316 stainless steel in the unirradiated condition was greater than that for the EP-838, after irradiation there was essentially no difference between the strength or ductility of the two steels. The results indicate that the replacement of the majority of the nickel by manganese and a reduction of chromium and molybdenum in an austenitic stainless steel of composition near that for type 316 stainless steel has little effect on the irradiated and unirradiated tensile properties at low temperatures. (orig.)

  15. Comparison of the irradiated tensile properties of a high-manganese austenitic steel and type 16 stainless steel

    International Nuclear Information System (INIS)

    The USSR steel EP-838 is a high-manganese (13.5%), low-nickel (4.2%) steel that also has lower chromium and molybdenum than type 316 stainless steel. Tensile specimens of 20%-cold-worked EP-838 and type 316 stainless steel were irradiated in the High Flux Isotope Reactor (HFIR) at the coolant temperature (approx. 500C). A displacement damage level of 5.2 dpa was reached for the EP-838 and up to 9.5 dpa for the type 316 stainless steel. Tensile tests at room temperature and 3000C on the two steels indicated that the irradiation led to increased strength and decreased ductility compared to the unirradiated steels. Although the 0.2% yield stress of the type 316 stainless steel in the unirradiated condition was greater than that for the EP-838, after irradiation there was essentially no difference between the strength or ductility of the two steels. The results indicate that the replacement of the majority of the nickel by manganese and a reduction of chromium and molybdenum in an austenitic stainless steel of composition near that for type 316 stainless steel has little effect on the irradiated and unirradiated tensile properties at low temperatures

  16. Development of high strength austenitic stainless steel for conduit of Nb3Al conductor

    International Nuclear Information System (INIS)

    Japan Atomic Energy Research Institute (JAERI) started developing new austenitic stainless steel for a conduit (1 - 2 mm) of a Nb3Al conductor in collaboration with Nippon Steel Corporation (NSC). A high strength austenitic stainless steel is required for a conduit of a Nb3Al conductor to make the best use of superconducting properties of a Nb3Al conductor. JAERI and NSC successfully developed the high strength austenitic stainless steel, JN1 (YS ≥ 1,300 MPa, KIc ≥ 200 MPa√m at 4K) for magnet structures having thick section. However, JN1 is not suitable for a conduit material because elongation of JN1 decreases to less than 10 % due to sensitization during reaction heat treatment for Nb3Al. Therefore, modification of JN1 was performed as a first step to develop a new conduit material which withstands Nb3Al reaction heating. Small trial lots heat-treated at 973 - 1173 K for 2 - 200 hours were prepared and evaluated by Charpy impact test and tensile test at 77 K and 4K. A material having yield strength of 1,390 MPa and elongation of 34 % after aging at 973 K x 200 h are developed up to now. This paper describes requirements on the mechanical properties and status of the development work. In addition, empirical equations to predict 4K yield strength, elongation, and Charpy absorbed energy from 77K data are proposed in this paper

  17. Application Feasibility of PRE 50 grade Super Austenitic Stainless Steel as a Steam Generator Tubing

    Energy Technology Data Exchange (ETDEWEB)

    Park, Yong Soo [Yonsei University, Seoul (Korea, Republic of); Kim, Young sik [Andong National University, Andong (Korea, Republic of); Kim, Taek Jun; Kim, Sun Tae; Park, Hui Sang [Yonsei University, Seoul (Korea, Republic of)

    1997-07-01

    The aim of this study is to evaluate the properties of the super austenitic stainless steel, SR-50A for application as steam generator tubing material. The microstructure, mechanical properties, corrosion properties, were analyzed and the results were compared between super austenitic stainless steel and Alloy 600 and Alloy 690. Super austenitic stainless steel, SR-50A is superior to Alloy 600, Alloy 690 and Alloy 800 in the mechanical properties(tensile strength, yield strength, and elongation). It was investigated that thermal conductivity of SR-50A was higher than Alloy 600. As a result of thermal treatment on super stainless steel, SR-50A, caustic SCC resistance was increased and its resistance was as much as Alloy 600TT and Alloy 690TT. In this study, optimum thermal treatment condition to improve the caustic corrosion properties was considered as 650 deg C or 550 deg C 15 hours. However, it is necessary to verify the corrosion mechanism and to prove the above results in the various corrosive environments. 27 refs., 6 tabs., 59 figs. (author)

  18. Self-consistent modeling of rolling textures in an austenitic-ferritic duplex steel

    International Nuclear Information System (INIS)

    Research highlights: → The selection of slip systems is linked to the grain-boundary-mediated activities. → In the duplex steel interactions between phases play a big role on the texture. → For austenite, a reliable prediction of texture is achieved at small deformations. → A model incorporating micro-scale shear banding in f.c.c. phases was developed. - Abstract: Rolling textures of the constituent phases in an austenitic-ferritic duplex stainless steel are measured by X-ray diffraction experiments, showing that the brass-type texture, typical of f.c.c. materials with low SFE, is developed in the austenitic phase, and the rotated-cube and brass-R textures are developed in the ferritic phase. On the basis of the experimental texture components and fibers at different reductions, rolling textures of the respective phases in the duplex steel are simulated using a self-consistent model. After considering various micromechanical interactions within the steel, a reliable prediction of the evolution of grain orientation distributions for the phases at small reductions is achieved. An attempt in modeling the brass-type texture for the f.c.c. metallic phase is also performed by incorporating the shear banding mechanism into the presented model.

  19. Microstructure and tensile properties of friction welded SUS 304HCu austenitic stainless steel tubes

    International Nuclear Information System (INIS)

    Austenitic stainless steels are used in superheater/reheater tubing for their oxidation resistance and fireside corrosion resistance, in addition to their creep strength. The addition of 3 wt. % Cu to SUS 304HCu austenitic stainless steel to reduce the corrosion, has found to increase the creep performance in temperature range of 650°–750 °C. The addition of Cu to steels can have adverse effects on the mechanical properties of the fusion welded joints. During fusion welding, Cu can form low temperature eutectic phases that preferentially segregate to the grain boundaries and embrittle the alloy. There is a need for a better welding procedure/technique to fabricate this alloy. Friction welding is a solid state welding process which nullifies the adverse effects of low temperature eutectics segregation. Hence, in this investigation an attempt has been made to study the microstructural and tensile properties of the friction welded SUS 304HCu austenitic stainless steel tube joints fabricated using optimized parameters. -- Highlights: • Friction welding of SUS 304HCu tubes is reported. • Microstructures of friction welded SUS 304HCu tubes were reported. • Fracture surface of the tensile samples is characterized using SEM. • XRD analysis of the SUS 304HCu tube is reported

  20. 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 transfo

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-11-15

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

  3. Considerations on ultrasonic testing of austenitic steel weld joints

    International Nuclear Information System (INIS)

    Starting from concrete examples, the Working Group describes the difficulties encountered when ultrasonic testing of welds is carried out on austenitic alloys. It indicates particularly the technique used for the detection of defects such as lack of fusion and cracks and also where inspection has to be carried out on welds between dissimilar metals or between strongly attenuated parent metals. It concludes on the necessity of carrying out a case study for each testing problem encountered, taking into account the testability of a component from the stage of manufacturing

  4. Wear of plasma nitrided and nitrocarburized AISI 316L austenitic stainless steel

    Directory of Open Access Journals (Sweden)

    F.A.P. Fernandes

    2010-06-01

    Full Text Available Purpose: the purpose of the work is to compare the wear resistance, in dry and lubricated conditions, of AISI 316L austenitic stainless steel samples that were plasma nitrided or nitrocarburized at 450°C for 5 and 10 h, respectively.Design/methodology/approach: Hardness and wear resistance of austenitic stainless steel can be increased substantially, without losing corrosion resistance, by plasma nitriding or nitrocarburizing surface treatments. In this work, AISI 316L austenitic stainless steel was plasma nitrided and nitrocarburized at 450°C, for 5 and 10 h respectively.Findings: The obtained layers were characterized by optical microscopy, X-ray diffraction, microhardness and micro-wear tests in dry and lubricated conditions. Optical microscopy and X-ray diffraction analysis demonstrated that the nitrided layer is homogeneous and primarily composed of nitrogen rich expanded austenite with a thickness of about 15 µm. Nitrocarburized samples exhibited an external layer of chromium and iron compounds and a sub-layer of expanded austenite with a total thickness of 45 µm. Microhardness profiles showed that the hardness near to the surface was close to 1100 HV for nitriding and 1300 HV for nitrocarburizing. Plasma nitrided and nitrocarburized layers exhibited substantial wear reduction in dry and lubricated test conditions. The use of a lubricant oil reduces wear by a factor of approximately 200 compared to the dry test results.Research limitations/implications: The plasma nitrided layer yielded the best wear performance in both dry and lubricated conditions.Originality/value: Plasma nitriding resulted in the best wear performance when compared with nitrocarburizing in dry and lubricated sliding which is probably due to reduced layer fragility.

  5. Study of structural modifications induced by ion implantation in austenitic stainless steel

    International Nuclear Information System (INIS)

    Ion implantation in steels, although largely used to improve the properties of use, involves structural modifications of the surface layer, which remain still prone to controversies. Within this context, various elements (N, Ar, Cr, Mo, Ag, Xe and Pb) were implanted (with energies varying from 28 to 280 keV) in a 316LVM austenitic stainless steel. The implanted layer has a thickness limited to 80 nm and a maximum implanted element concentration lower than 10 % at. The analysis of the implanted layer by grazing incidence X ray diffraction highlights deformations of austenite lines, appearance of ferrite and amorphization of the layer. Ferritic phase which appears at the grain boundaries, whatever the implanted element, is formed above a given 'threshold' of energy (produced of fluency by the energy of an ion). The formation of ferrite as well as the amorphization of the implanted layer depends only on energy. In order to understand the deformations of austenite diffraction lines, a simulation model of these lines was elaborated. The model correctly describes the observed deformations (broadening, shift, splitting) with the assumption that the expansion of the austenitic lattice is due to the presence of implanted element and is proportional to the element concentration through a coefficient k'. This coefficient only depends on the element and varies linearly with its radius. (author)

  6. Quality of austenite chrome-nickel steel made by gas-oxygen refining

    International Nuclear Information System (INIS)

    Properties and structure were investigated of austenitic 03Kh18N11 and 08KhN10T steels melted at gas oxygen refining aggregates. It was established that mechanical and corrosion properties of rolling of such steels were in agreement with standard properties of metal of open melting. Sheet 08Kh18N10T steel has the level of strength and plasticity regulated for 12Kh18N10T steel. As steel of 08Kh18N10T holds the complex of high mechanical and corrosion properties, 08Kh18N10T is recommended to be replace by 12Kh18N10T with the aim of decrease of titanium usage and increase of process efficiency

  7. Effects of austenite grain size and cooling rate on Widmanstaetten ferrite formation in low-alloy steels

    Energy Technology Data Exchange (ETDEWEB)

    Bodnar, R.L.; Hansen, S.S. (Bethlehem Steel Corp., PA (United States). Hot Rolled Products Div.)

    1994-04-01

    Deformation dilatometry is used to simulate the hot rolling of 0.20 pct C-1.10 pct Mn steels over a product thickness range of 6 to 170 mm. In addition to a base steel, steels with additions of 0.02 pct Ti, 0.06 pct V, or 0.02 pct Nb are included in the study. The transformation behavior of each steel is explored for three different austenite grain sizes, nominally 30, 55, and 100 [mu]m. In general, the volume fraction of Widmanstaetten ferrite increases in all four steels with increasing austenite grain size and cooling rate, with austenite grain size having the more significant effect. The Nb steel has the lowest transformation temperature range and the greatest propensity for Widmanstaetten ferrite formation, while the amount of Widmanstaetten ferrite is minimized in the Ti steel (as a result of intragranular nucleation of polygonal ferrite on coarse TiN particles). The data emphasize the importance of a refined austenite grain size in minimizing the formation of a coarse Widmanstaetten structure. With a sufficiently fine prior austenite grain size (e.g., [le]30 [mu]m), significant amounts of Widmanstaetten structure can be avoided, even in a Nb-alloyed steel.

  8. Hydrogen-induced defects in austenite and ferrite of a duplex steel.

    Science.gov (United States)

    Głowacka, A; Swiatnicki, W A; Jezierska, E

    2006-09-01

    The influence of hydrogen on the microstructure of two types of austeno-ferritic duplex stainless steel (Cr26-Ni6 model steel and Cr22-Ni5-Mo3 commercial steel), each of them after two thermo-mechanical treatments, was investigated. The aim of this study was to reveal microstructural changes appearing during the hydrogen charging and particularly to clarify the occurrence of phase transformations induced by hydrogen. The specific microstructural changes in the ferrite (alpha) and austenite (gamma) of both types of steel were observed. A strong increase of dislocation density was noticed in the alpha phase. In the case of model steel, longer hydrogen charging times led to significant ferrite grain refinement. In the commercial steel, the strips and twin plates appeared in the ferrite after hydrogenation. The appearance of stacking faults was revealed in the gamma phase. The martensite laths appeared in austenite after longer hydrogenation times. It seems that the microstructural changes gave rise to the formation of microcracks in the alpha and gamma phases as well as on the alpha/gamma interphase boundaries. PMID:17059551

  9. Processing of a new high strength high toughness steel with duplex microstructure (Ferrite + Austenite)

    International Nuclear Information System (INIS)

    Highlights: ► This new steel has exceptional combination of high strength and fracture toughness. ► Austempering treatment resulted in a very fine scale bainitic ferrite microstructure. ► As the austempering temperature increases yield strength and toughness decreases. ► Maximum fracture toughness of 105 MPa √m is obtained after austempering at 371 °C. ► A relationship between fracture toughness and the parameter σy(XγCγ)1/2 was observed. - Abstract: In this investigation a new third generation advanced high strength steel (AHSS) has been developed. This steel was synthesized by austempering of a low carbon and low alloy steel with high silicon content. The influence of austempering temperature on the microstructure and the mechanical properties including the fracture toughness of this steel was also examined. Compact tension and cylindrical tensile specimens were prepared from a low carbon low alloy steel and were initially austenitized at 927 °C for 2 h and then austempered in the temperature range between 371 °C and 399 °C to produce different microstructures. The microstructures were characterized by X-ray diffraction, scanning electron microscopy and optical metallography. Test results show that the austempering heat treatment has resulted in a microstructure consisting of very fine scale bainitic ferrite and austenite. A combination of very high tensile strength of 1388 MPa and fracture toughness of 105 MPa √m was obtained after austempering at 371 °C

  10. Mechanism and estimation of fatigue crack initiation in austenitic stainless steels in LWR environments.

    Energy Technology Data Exchange (ETDEWEB)

    Chopra, O. K.; Energy Technology

    2002-08-01

    The ASME Boiler and Pressure Vessel Code provides rules for the construction of nuclear power plant components. Figures I-9.1 through I-9.6 of Appendix I to Section III of the Code specify fatigue design curves for structural materials. However, the effects of light water reactor (LWR) coolant environments are not explicitly addressed by the Code design curves. Existing fatigue strain-vs.-life ({var_epsilon}-N) data illustrate potentially significant effects of LWR coolant environments on the fatigue resistance of pressure vessel and piping steels. This report provides an overview of fatigue crack initiation in austenitic stainless steels in LWR coolant environments. The existing fatigue {var_epsilon}-N data have been evaluated to establish the effects of key material, loading, and environmental parameters (such as steel type, strain range, strain rate, temperature, dissolved-oxygen level in water, and flow rate) on the fatigue lives of these steels. Statistical models are presented for estimating the fatigue {var_epsilon}-N curves for austenitic stainless steels as a function of the material, loading, and environmental parameters. Two methods for incorporating environmental effects into the ASME Code fatigue evaluations are presented. The influence of reactor environments on the mechanism of fatigue crack initiation in these steels is also discussed.

  11. Stacking fault energy and plastic deformation of fully austenitic high manganese steels: Effect of Al addition

    International Nuclear Information System (INIS)

    Dependence of the dislocation glide mode and mechanical twinning on the stacking fault energy (SFE) in fully austenitic high manganese steels was investigated. Fully austenitic Fe-22Mn-xAl-0.6C (x = 0, 3, and 6) steels with the SFE in the range of 20-50 mJ/m2 were tensile tested at room temperature, and their deformed microstructures were examined at the different strain levels by optical microscopy and transmission electron microscopy. Deformation of all steels was dominated by planar glide before occurrence of mechanical twinning, and its tendency became more evident with increasing the SFE. No dislocation cell formation associated with wavy glide was observed in any steels up to failure. Dominance of planar glide regardless of the SFE is to be attributed to the glide plane softening phenomenon associated with short range ordering in the solid solution state of the present steels. Regarding mechanical twinning, the higher the SFE is, the higher the stress for mechanical twinning becomes. However, in the present steels, mechanical twinning was observed at the stresses lower than those predicted by the previous model in which the partial dislocation separation is considered to be a function of not only the SFE but also the applied stress. An analysis revealed that, of the various dislocation-defect interactions in the solid solution alloy, the Fisher interaction tied to short range ordering is qualitatively shown to lower the critical stress for mechanical twinning.

  12. Chemical gradients across phase boundaries between martensite and austenite in steel studied by atom probe tomography and simulation

    Energy Technology Data Exchange (ETDEWEB)

    Dmitrieva, O.; Ponge, D.; Inden, G.; Millan, J.; Choi, P. [Max-Planck-Institut fuer Eisenforschung, Max-Planck-Str. 1, 40237 Duesseldorf (Germany); Sietsma, J. [Delft University of Technology, Faculty 3mE, Dept. MSE, 2628 CD Delft (Netherlands); Raabe, D., E-mail: d.raabe@mpie.de [Max-Planck-Institut fuer Eisenforschung, Max-Planck-Str. 1, 40237 Duesseldorf (Germany)

    2011-01-15

    Partitioning at phase boundaries of complex steels is important for their properties. We present atom probe tomography results across martensite/austenite interfaces in a precipitation-hardened maraging-TRIP steel (12.2 Mn, 1.9 Ni, 0.6 Mo, 1.2 Ti, 0.3 Al; at.%). The system reveals compositional changes at the phase boundaries: Mn and Ni are enriched while Ti, Al, Mo and Fe are depleted. More specific, we observe up to 27 at.% Mn in a 20 nm layer at the phase boundary. This is explained by the large difference in diffusivity between martensite and austenite. The high diffusivity in martensite leads to a Mn flux towards the retained austenite. The low diffusivity in the austenite does not allow accommodation of this flux. Consequently, the austenite grows with a Mn composition given by local equilibrium. The interpretation is based on DICTRA and mixed-mode diffusion calculations (using a finite interface mobility).

  13. Chemical gradients across phase boundaries between martensite and austenite in steel studied by atom probe tomography and simulation

    International Nuclear Information System (INIS)

    Partitioning at phase boundaries of complex steels is important for their properties. We present atom probe tomography results across martensite/austenite interfaces in a precipitation-hardened maraging-TRIP steel (12.2 Mn, 1.9 Ni, 0.6 Mo, 1.2 Ti, 0.3 Al; at.%). The system reveals compositional changes at the phase boundaries: Mn and Ni are enriched while Ti, Al, Mo and Fe are depleted. More specific, we observe up to 27 at.% Mn in a 20 nm layer at the phase boundary. This is explained by the large difference in diffusivity between martensite and austenite. The high diffusivity in martensite leads to a Mn flux towards the retained austenite. The low diffusivity in the austenite does not allow accommodation of this flux. Consequently, the austenite grows with a Mn composition given by local equilibrium. The interpretation is based on DICTRA and mixed-mode diffusion calculations (using a finite interface mobility).

  14. An integrated computer model with applications for austenite-to-ferrite transformation during hot deformation of Nb-microalloyed steels

    Science.gov (United States)

    Majta, Janusz; Pietrzyk, Maciej; Zurek, Anna K.; Cola, Mark; Hochanadel, Pat

    2002-05-01

    This work presents an austenite decomposition model, based on the thermodynamics of the system and diffusion-controlled nucleation theory, to predict the evolution of microstructure during hot working of niobium-microalloyed steels. The differences in microstructural development of hotdeformed microalloyed steel in the single-phase austenite and two-phase (austenite + ferrite) regions have been effectively described using an integrated computer modeling process. The complete model presented here takes into account the kinetics of recrystallization, recrystallized austenite grain size, precipitation, phase transformation, and the resulting ferrite structure. After considering existing austenite decomposition models, we decided that the method adopted in the present work relies on isothermal transformation kinetics and the principle-of-additivity rule. The thermomechanical part of the modeling process was carried out using the finite-element method. Experimental results at different temperatures, strain rates, and strain levels were obtained using a Gleeble thermomechanical simulator. A comparison of results of the model with experiments shows good agreement.

  15. Effect of the delta ferrite solidification morphology of austenitic steels weld metal on the joint properties

    International Nuclear Information System (INIS)

    The properties of austenitic stainless steel weld metals are largely influenced by the appearance in the microstructure of delta ferrite of a given morphology. The susceptibility to hot cracks and low temperature toughness are deeply conditioned by the mixed complex austenitic-ferritic structures which depending on the steel chemical composition and on the cooling rate may be developed. The latest research on this issue points out the importance of the sodification mode as regards to the influence in the appearance of delta ferrite of a certain morphology. In fact, it is very important to understand the solidification sequences, the primary solidification modes which are possible and the subsequent solid state transformations to correlate the structural elements of the weld metal with the parameters of the welding process on the one had, and the weld joint properties on the other. (Author) 19 refs

  16. Effect of silicon and prior deformation of austenite on isothermal transformation in low carbon steels

    Institute of Scientific and Technical Information of China (English)

    Minghui CAI; Hun DING; Jiansu ZHANG; Long LI

    2009-01-01

    Isothermal transformation (TTT) behavior of the low carbon steels with two Si con-tents (0.50 wt pct and 1.35 wt pct) was investigated with and without the prior deformation. The results show that Si and the prior deformation of the austenite have significant effects on the transformation of the ferrite and bainite. The addition of Si refines the ferrite grains, accelerates the polygonal ferrite transformation and the formation of M/A constituents, leading to the improvement of the strength. The ferrite grains formed under the prior deformation of the austenite become more ho-mogeneous and refined. However, the influence of deformation on the tensile strength of both steels is dependent on the isothermal temperatures. Thermodynamic calcu-lation indicates that Si and prior deformation reduce the incubation time of both ferrite and bainite transformation, but the effect is weakened by the decrease of the isothermal temperatures.

  17. 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.

  18. Improvement of high temperature strength and low temperature toughness of high manganese-chromium austenitic steels

    International Nuclear Information System (INIS)

    High Mn-Cr austenitic steels are still considered to be an important high temperature structural material from the point of view of fast-induced radioactivity decay (FIRD) and non-magneticity. The objective of the present study is to investigate the mechanical properties of 12% Cr-15% Mn austenitic stainless steels and to compare these properties with those of the reference materials of JPCAs and JFMS, which are being investigated for the development of fusion reactor structural materials in Japan. The effects of the alloying elements V, Ti, Ta, etc. were investigated to determine the improvement of mechanical properties. Tiny precipitates of VN and Ti(C, N) raised the high-temperature strength considerably. Content of 0.1 to 0.2% C, however, formed very coarse precipitates of M23C6 type carbide on the grain boundaries, which deteriorated low temperature toughness inducing intergranular fracture. Microstructural evolution during long-term aging was also investigated. ((orig.))

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

    Directory of Open Access Journals (Sweden)

    Torchane Lazhar

    2014-04-01

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

  20. Mechanical properties of 15%Mn steel with fine lamellar structure consisting of ferrite and austenite phases

    International Nuclear Information System (INIS)

    New steel with fine lamellar structure consisting of austenite and ferrite was developed. 15mass%Mn-3%Al-3%Si steel sheet was used in this study. First of all, the effect of the cooling rate on the microstructure was examined. The cooling at the slower speed of 100 deg/hour created the dual phase structure consisting of both austenite and ferrite. The additional rolling developed the fine lamellar duplex structure. Improvement of both the tensile strength and elongation was achieved by rolling. The strength increases furthermore by the rolling up to larger reduction. The 90% rolled sheet shows high tensile strength around 1000MPa with large elongation (15%-20%). These results indicate that the multi-phased structure with controlled lamellar morphology is beneficial for the management of both high strength and large ductility.

  1. Material for hot rolling of high boron content austenite stainless steel, and hot rolling method

    International Nuclear Information System (INIS)

    A hot rolling material made of a high boron content austenite stainless steel of the present invention comprises a slab made of an austenite stainless steel containing from 0.6 to 2.0% by weight of B and a pad-welded metal layer formed on the side surface of the slab. The pad-welded metal layer has δ ferrite amount of from 3 to 12% by volume, B content up to 0.3% by weight, a thickness of 3mm or greater, and is subjected to hot rolling after heated to a temperature of from 1100 to 1200degC. This can prevent occurrence of peripheral cracking and the material can be industrially manufactured stably at a low cost. (T.M.)

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

    International Nuclear Information System (INIS)

    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)

  3. Hydrogen Environment Embrittlement on Austenitic Stainless Steels from Room Temperature to Low Temperatures

    Science.gov (United States)

    Ogata, Toshio

    2015-12-01

    Hydrogen environment embrittlement (HEE) on austenitic stainless steels SUS304, 304L, and 316L in the high pressure hydrogen gas was evaluated from ambient temperature to 20 K using a very simple mechanical properties testing procedure. In the method, the high- pressure hydrogen environment is produced just inside the hole in the specimen and the specimen is cooled in a cooled-alcohol dewar and a cryostat with a GM refrigerator. The effect of HEE was observed in tensile properties, especially at lower temperatures, and fatigue properties at higher stress level but almost no effect around the stress level of yield strength where almost no strain-induced martensite was produced. So, no effect of HEE on austenitic stainless steels unless the amount of the ferrite phase is small.

  4. Embrittlement and strain hardining of the hydrogenated AISI 304 austenitic stainless steel

    International Nuclear Information System (INIS)

    The influence of hydrogen the mechanical properties of type AISI 304 austenitic stainless steel was analysed. Hydrogenation was performed cathodically, at room temperature, in a 1N H2SO4 solution. The variables controlled for analysis were current density and time. Uniaxial tensile tests were conducted with constant nominal strain rate. Fracture morphology was analysed by scanning electron microscopy and the kinetics of strain hardening by applying Ludwick's equation to the resulting stress-strain curves. It was verified that hydrogen embrittles markedly, the austenitic AISI 304 steel, leading to a significant loss of ductility and modifying the fracture made, from essentially ductile to a transgrannular fragile fracture, containing small regions of intergranular fracture. With increasing amounts of hydrogen there was also a decrease in the maximum uniform stress, the strength coefficient, the strain hardening exponent and in the range the deformation stages II and III extended. (Author)

  5. Prevision of in-service aging of molded austenitic-ferritic stainless steels components

    International Nuclear Information System (INIS)

    After having recalled the service conditions of the nuclear PWR boilers, the austenitic-ferritic molded stainless steels and their uses in the primary coolant circuit are described. The main consequences of the thermal aging on the rupture mechanisms and the mechanical properties are recalled too. Then are described the laboratory studies carried out in France and abroad which have allowed the development of an extensive knowledge of the aging reaction kinetics and then of embrittlement anticipation formulae. Measures and sampling carried out on down-rated components or even on in service components are used to verify the quality of the in-service aging anticipation. At last are identified the subjects on which it will be important to advance to improve our knowledge of the behaviour of the austenitic-ferritic stainless steels components. (O.M.)

  6. Effect of Austenitizing Temperature on Microstructure and Mechanical Properties of Semi-High-Speed Steel Cold-Forged Rolls

    Science.gov (United States)

    Wu, Qiong; Sun, Da-Le; Liu, Chang-Sheng

    2009-10-01

    The effect of austenitizing temperature on the microstructure and mechanical properties of semi-high-speed steel (S-HSS) cold-forged rolls was investigated. Low-temperature austenitizing below 1313 K induced carbide coarsening during subsequent tempering at 973 K due to the nucleation effect of undissolved M7C3. On the other hand, the heavy dissolution of M7C3 above 1353 K caused the fine carbide formation on lath and plate boundaries, which retarded the subgrain growth during tempering. The increase in strength with increasing austenitizing temperature was attributed to the fine carbide distribution and the high dislocation density. Furthermore, as the austenitizing temperature increased, the impact energy markedly reduced, due to the large prior austenite grain size and the high strength. Finally, based on the microstructure and mechanical properties, an optimal austenitizing temperature range between 1313 and 1333 K was determined.

  7. Effect of Structural Heterogeneity on In Situ Deformation of Dissimilar Weld Between Ferritic and Austenitic Steel

    Science.gov (United States)

    Ghosh, M.; Santosh, R.; Das, S. K.; Das, G.; Mahato, B.; Korody, J.; Kumar, S.; Singh, P. K.

    2015-08-01

    Low-alloy steel and 304LN austenitic stainless steel were welded using two types of buttering material, namely 309L stainless steel and IN 182. Weld metals were 308L stainless steel and IN 182, respectively, for two different joints. Cross-sectional microstructure of welded assemblies was investigated. Microhardness profile was determined perpendicular to fusion boundary. In situ tensile test was performed in scanning electron microscope keeping low-alloy steel-buttering material interface at the center of gage length. Adjacent to fusion boundary, low-alloy steel exhibited carbon-depleted region and coarsening of matrix grains. Between coarse grain and base material structure, low-alloy steel contained fine grain ferrite-pearlite aggregate. Adjacent to fusion boundary, buttering material consisted of Type-I and Type-II boundaries. Within buttering material close to fusion boundary, thin cluster of martensite was formed. Fusion boundary between buttering material-weld metal and weld metal-304LN stainless steel revealed unmixed zone. All joints failed within buttering material during in situ tensile testing. The fracture location was different for various joints with respect to fusion boundary, depending on variation in local microstructure. Highest bond strength with adequate ductility was obtained for the joint produced with 309L stainless steel-buttering material. High strength of this weld might be attributed to better extent of solid solution strengthening by alloying elements, diffused from low-alloy steel to buttering material.

  8. 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. PMID:17122924

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

    International Nuclear Information System (INIS)

    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

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

    OpenAIRE

    J. U. Anaele; O. O. ONYEMAOBI; Nwobodo, C. S.; C. C. Ugwuegbu

    2015-01-01

    The effect of electrode types on the solidification cracking susceptibility of austenitic stainless steel weld metal was studied. Manual metal arc welding method was used to produce the joints with the tungsten inert gas welding serving as the control. Metallographic and chemical analyses of the fusion zones of the joints were conducted. Results indicate that weldments produced from E 308-16 (rutile coated), E 308-16(lime-titania coated) electrodes, and TIG welded joints fall within the range...

  11. Variation of carbon concentration in proeutectoid ferrite during austenitization in hypoeutectoid steel

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Minsu; Cho, Wontae; Park, Jihye; Jung, Jae-Gil; Lee, Young-Kook, E-mail: yklee@yonsei.ac.kr

    2014-08-15

    The variation of the C concentration in proeutectoid ferrite (α{sub PF}) during austenitization in hypoeutectoid steels was quantitatively investigated using the massive transformation start temperature (T{sub m}) of α{sub PF} to austenite (γ) measured by high-temperature confocal laser scanning microscopy and hardness of α{sub PF}. The C concentration in α{sub PF} at T{sub m} in hypoeutectoid steels increased with increasing total C concentration up to approximately 0.2 wt.% during heating. The hardness of α{sub PF} with isothermal holding time at 775 °C in S20C steel revealed C enrichment in α{sub PF} at the early stage of isothermal holding and its reduction with further holding. These results explain the redistribution of the C in α{sub PF} during austenitization as follows: free C atoms released from cementite during pearlite decomposition diffuse excessively into neighboring α{sub PF} as well as pearlitic ferrite. The supersaturated C concentration in α{sub PF} is reduced during the long-range diffusive transformation of α{sub PF} to γ. However, some of the excess C atoms still remain in α{sub PF} until α{sub PF} starts to massively transform to γ. - Highlights: • Massive transformation of αPF to γ in hypoeutectoid steels was observed using CLSM. • C content in αPF during austenitization was analyzed by measured Tm and hardness. • Tm decreases and C content in αPF at Tm increases with increasing total C. • C atoms released from θ during formation of P to γ diffuse excessively into αPF. • Supersaturated C content in αPF is reduced during transformation of αPF to γ.

  12. Variation of carbon concentration in proeutectoid ferrite during austenitization in hypoeutectoid steel

    International Nuclear Information System (INIS)

    The variation of the C concentration in proeutectoid ferrite (αPF) during austenitization in hypoeutectoid steels was quantitatively investigated using the massive transformation start temperature (Tm) of αPF to austenite (γ) measured by high-temperature confocal laser scanning microscopy and hardness of αPF. The C concentration in αPF at Tm in hypoeutectoid steels increased with increasing total C concentration up to approximately 0.2 wt.% during heating. The hardness of αPF with isothermal holding time at 775 °C in S20C steel revealed C enrichment in αPF at the early stage of isothermal holding and its reduction with further holding. These results explain the redistribution of the C in αPF during austenitization as follows: free C atoms released from cementite during pearlite decomposition diffuse excessively into neighboring αPF as well as pearlitic ferrite. The supersaturated C concentration in αPF is reduced during the long-range diffusive transformation of αPF to γ. However, some of the excess C atoms still remain in αPF until αPF starts to massively transform to γ. - Highlights: • Massive transformation of αPF to γ in hypoeutectoid steels was observed using CLSM. • C content in αPF during austenitization was analyzed by measured Tm and hardness. • Tm decreases and C content in αPF at Tm increases with increasing total C. • C atoms released from θ during formation of P to γ diffuse excessively into αPF. • Supersaturated C content in αPF is reduced during transformation of αPF to γ

  13. 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. 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

  14. Experimental Investigation of Ultrasonic Vibration Assisted Turning of 304 Austenitic Stainless Steel

    OpenAIRE

    Zou, Ping; Xu, Yingshuai; He, Yu; Chen, Mingfang; Wu, Hao

    2015-01-01

    This research study focuses on the experimental analysis of the three-dimensional (3D) surface topography and surface roughness of the workpiece machined with ultrasonic vibration assisted turning (UAT) in comparison to conventional turning (CT). For the challenge that machining difficulties of 304 austenitic stainless steel (ASS 304) and high demands for the machined surface quality and machining precision represent, starting with cutting principle and processing technology, the ultrasonic v...

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

    OpenAIRE

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

    2015-01-01

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

  16. Solid solution strengthening effect on creep strength of austenitic stainless steel

    OpenAIRE

    Abouzari, Sara

    2012-01-01

    Sanicro 25 is a newly developed austenitic stainless steel, designed for the next generation of Ultrasupercritical coal-fired boilers in electrical power plants. This material is applicable in reheater and superheater tubes, where the material temperature is up to 700 °C. One of the main strengthening mechanisms in high temperature materials is solid solution strengthening. A combination of this mechanism and precipitation hardening, promotes creep strength of heat resistance materials. The a...

  17. Formation of a submicrocrystalline structure in metastable austenitic steels during severe plastic deformation and subsequent heating

    Science.gov (United States)

    Mal'tseva, L. A.; Mal'tseva, T. V.; Yurovskikh, A. S.; Raab, G. I.; Sharapova, V. A.; Vakhonina, K. D.

    2016-03-01

    The structure and the mechanical properties of metastable austenitic steels after severe plastic deformation by four or six passes of equal-channel angular pressing (ECAP) at a temperature of 400°C are studied. It is shown that ECAP results in strain hardening mainly due to the formation of a submicrocrystalline structure, which is retained after subsequent heating to 500°C.

  18. DIFFUSIONAL PROPERTIES OF INTERPHASE BOUNDARIES IN TWO-PHASE FERRITIC-AUSTENITIC STEEL

    OpenAIRE

    Światnicki, W.; Świderski, J.; Grabski, M.

    1990-01-01

    Thermal stability of trapped lattice dislocations in ferritic austenitic steel have been studied in order to determine the diffusional properties of internal interfaces. It was found that interphase boundaries with low diffusivity are characterised by the ordered semicoherent structure, formed in Kurdjumov-Sachs or Nishiyama-Wassermann orientation relationship. The fraction of these "special" interfaces varies considerably with the thermomechanical treatment employed as it acts on the process...

  19. Preparation and characterization of electrolytic alumina deposit on austenitic stainless steel

    OpenAIRE

    El Hajjaji, Souad; El Alaoui, Sidi Mohammed; Simon, Patrice; Guenbour, Abdellah; Ben Bachir, Ali; Puech-Costes, Edith; Maurette, Marie-Thérèse; Aries, Lucien

    2005-01-01

    Conversion coating modified by alumina has been studied as a way for improving the resistance to thermal oxidation of an austenitic stainless steel. Conversion coating, characterized by a particular morphology and strong interfacial adhesion with the substrate, facilitate the electrochemical deposition of ceramic layers and enhance their adhesion to the substrate. The influence of the current density and treatment time on alumina deposit was studied using statistical experimental designs like...

  20. 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...

  1. Weld bead center line shift during laser welding of austenitic stainless steels with different sulfur content

    International Nuclear Information System (INIS)

    The magnitude of the shift in position of the maximum depth of penetration, the center line shift (CLS), for a laser weld produced between two heats of austenitic stainless steels with large differences in S content was smaller relative to gas tungsten arc (GTA) welds made with both higher and lower heat inputs. The results of this study suggest that both surface tension driven fluid (Marangoni) flow effects and arc shift effects may contribute to the CLS in GTA welding

  2. Multi-response optimization of CO2 laser welding process of austenitic stainless steel

    OpenAIRE

    Benyounis, Khaled; Olabi, Abdul-Ghani; Hashmi, Saleem

    2008-01-01

    Recently, laser welding of austenitic stainless steel has received great attention in industry, due to its wide spread application in petroleum refinement stations, power plant, pharmaceutical industry and households. Therefore, mechanical properties should be controlled to obtain good welded joints. The welding process should be optimized by the proper mathematical models. In this research, the tensile strength and impact strength along with the joint operating cost of laser welded butt join...

  3. Microstructure and properties of laser surface alloyed PM austenitic stainless steel

    Directory of Open Access Journals (Sweden)

    Z. Brytan

    2010-05-01

    Full Text Available Purpose: The purpose of this paper is to analyse the effect of laser surface alloying with chromium on the microstructural changes and properties of vacuum sintered austenitic stainless steel type AISI 316L (EN 1.4404.Design/methodology/approach: Surface modification of AISI 316L sintered austenitic stainless steel was carried out by laser surface alloying with chromium powder using high power diode laser (HPDL. The influence of laser alloying conditions, both laser beam power (between 0.7 and 2.0 kW and powder feed rate (1.0-4.5 g/min at constant scanning rate of 0.5m/min on the width of alloyed surface layer, penetration depth, microstructure evaluated by LOM, SEM x-ray analysis, surface roughness and microhardness were presented.Findings: The microstructures of Cr laser alloyed surface consist of different zones, starting from the superficial zone rich in alloying powder particles embedded in the surface; these particles protrude from the surface and thus considerably increase the surface roughness. Next is alloyed zone enriched in alloying element where ferrite and austenite coexists. The following transient zone is located between properly alloyed material and the base metal and can be considered as a very narrow HAZ zone. The optimal microstructure homogeneity of Cr alloyed austenitic stainless steel was obtained for powder feed rate of 2.0 and 4.5 g/min and laser beam power of 1.4 kW and 2 kW.Practical implications: Laser surface alloying can be an efficient method of surface layer modification of sintered stainless steel and by this way the surface chromium enrichment can produce microstructural changes affecting mechanical properties.Originality/value: Application of high power diode laser can guarantee uniform heating of treated surface, thus uniform thermal cycle across treated area and uniform penetration depth of chromium alloyed surface layer.

  4. Microstructure evolution and phase composition of high-manganese austenitic steels

    OpenAIRE

    L.A. Dobrzański; A. Grajcar; W. Borek

    2008-01-01

    Purpose: The aim of the paper is to determine the influence of hot-working conditions on microstructure evolution and phase composition of new-developed high-manganese austenitic steels.Design/methodology/approach: Determination of processes controlling strain hardening was carried out in continuous compression test using Gleeble 3800 thermo-mechanical simulator. Evaluation of processes controlling work hardening and occurring after deformation at 900°C were identified by microstructure obser...

  5. Wear mechanisms in austenitic stainless steel drilling : A comprehensive wear study

    OpenAIRE

    Dahlström, Alexander

    2015-01-01

    This thesis is meant to serve as part of a competence platform for future product development projects at Sandvik Coromant AB, Solid Round Tools Department, Västberga, Sweden. The project objective is to gain generic knowledge of the wear mechanisms that restrict tool lifetime when drilling austenitic stainless steel. Thus, identifying if the weakest link of the tool is located within the coating, the coating adherence or in the strength of the substrate. A theoretical review of the work-pie...

  6. From micro to nano scales -recent progress in the characterization of nitrided austenitic stainless steels

    OpenAIRE

    Luo, Quanshun; Yang, Shicai

    2015-01-01

    In the frontier of materials science, understanding of materials has been in multiple scales from macro, micro, to atomic levels. This is attributed to the advanced instrumentations such as SEM, TEM, XPS, XRD, as well as several other spectroscopic and metallographic analyses. Fe-Cr-Ni based austenitic stainless steels have a diverse range of modern applications ranging from biomedical prostheses in human bodies, food processing, to chemical engineering and nuclear power generation. The outst...

  7. Short-term low-temperature glow discharge nitriding of 316L austenitic steel

    OpenAIRE

    T. Frączek; Olejnik, M.; Jasiñski, J.; Skuza, Z.

    2011-01-01

    The AISI 316L austenitic steel after glow discharge nitriding at temperature of T = 673 K and duration of τ=14,4 ks, for two different variants of specimen arrangement in the glow-discharge chamber was investigated. In order to assess the effectiveness of nitriding process, the surface layers profile analysis examination, surface hardness and hardness profile examination, the analysis of surface layer structures and corrosion resistance tests were performed. It has been found that application...

  8. Technique for ultrasonic testing of austenitic steel weldments of NPP components

    International Nuclear Information System (INIS)

    Special literature on ultrasonic testing of weldments of austenitic steel is analysed. Technique for ultrasonic testing of the ring and longitudinal butt welded joints of NPP components without reinforcing bead removal is described. Special converter design and fabrication practice are described. Results of experimental check of the developed testing technology and its application during NNPs' mounting and operation are presented. Results of ultrasonic and X-ray testing are compared

  9. A new high nitrogen super austenitic stainless steel with improved structure stability and corrosion resistance properties

    International Nuclear Information System (INIS)

    A new highly alloyed (Cr, Mo, W, N) super austenitic grade has been developed. This grade offers high mechanical properties combined with excellent corrosion resistance in chloride acid media. This grade is particularly designed for applications in chloride, oxidizing acid media encountered in the chemical, transportation, pollution control, offshore and pulp and paper industries. Mechanical properties, corrosion resistance and weldability of this grade are presented and compared to that of other stainless steels and nickel base alloys

  10. A new high nitrogen super austenitic stainless steel with improved structure stability and corrosion resistance properties

    Energy Technology Data Exchange (ETDEWEB)

    Gagnepain, J.C.; Charles, J.; Coudreuse, L.; Bonnefois, B. [Creusot-Loire Industrie, Le Creusot (France)

    1996-11-01

    A new highly alloyed (Cr, Mo, W, N) super austenitic grade has been developed. This grade offers high mechanical properties combined with excellent corrosion resistance in chloride acid media. This grade is particularly designed for applications in chloride, oxidizing acid media encountered in the chemical, transportation, pollution control, offshore and pulp and paper industries. Mechanical properties, corrosion resistance and weldability of this grade are presented and compared to that of other stainless steels and nickel base alloys.

  11. Grain refinement effect on fatigue properties of austenitic stainless steel with deformation induced martensite formation

    Czech Academy of Sciences Publication Activity Database

    Chlupová, Alice; Man, Jiří; Polák, Jaroslav; Škorík, Viktor; Karjalalinen, L.P.

    Ostrava : Tanger, 2014. ISBN 978-80-87294-55-0. [NANOCOM 2014. Internatinal Conference /6./. Brno (CZ), 05.11.2014-07.11.2014] R&D Projects: GA ČR GA13-32665S; GA MŠk(CZ) ED1.1.00/02.0068 Institutional support: RVO:68081723 Keywords : fatigue * 301LN austenitic stainless steel * grain refinement * reversion annealing * phase transformation Subject RIV: JL - Materials Fatigue, Friction Mechanics

  12. Effect of decontamination on oxidation of austenitic stainless steel in reactor conditions

    International Nuclear Information System (INIS)

    Austenitic stainless steels were oxidized in static autoclaves in light water reactor conditions. After the autoclave treatments the specimens were decontaminated with the aid of alkaline potassium permanganate (AP) and oxalic and citric acid (CITROX) as well as electrochemically in H3PO4. Alternating oxidation and decontamination tests were performed. An elemental analysis of the surfaces of the specimens was carried out by electron spectroscopy. Changes in structures and thicknesses of the oxide layers were observed. (author)

  13. Effects of a Hydrogen Gas Environment on Fatigue Crack Growth of a Stable Austenitic Stainless Steel

    Science.gov (United States)

    Kawamoto, Kyohei; Oda, Yasuji; Noguchi, Hiroshi; Higashida, Kenji

    In order to clarify the effects of a hydrogen gas environment on the fatigue crack growth characteristics of stable austenitic stainless steels, bending fatigue tests were carried out in a hydrogen gas, in a nitrogen gas at 1.0 MPa and in air on a SUS316L using the Japanese Industrial Standards (type 316L). Also, in order to discuss the difference in the hydrogen sensitivity between austenitic stainless steels, the fatigue tests were also carried out on a SUS304 using the Japanese Industrial Standards (type 304) metastable austenitic stainless steel as a material for comparison. The main results obtained are as follows. Hydrogen gas accelerates the fatigue crack growth rate of type 316L. The degree of the fatigue crack growth acceleration is low compared to that in type 304. The fracture surfaces of both the materials practically consist of two parts; the faceted area seemed to be brittle and the remaining area occupying a greater part of the fracture surface and seemed to be ductile. The faceted area does not significantly contribute to the fatigue crack growth rate in both austenitic stainless steels. The slip-off mechanism seems to be valid not only in air and in nitrogen, but also in hydrogen. Also, the main cause of the fatigue crack growth acceleration of both materials occurs by variation of the slip behaviour. The difference in the degree of the acceleration, which in type 316L is lower than in type 304, seems to be caused by the difference in the stability of the γ phase.

  14. 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.

  15. Investigation of shot-peened austenitic stainless steel 304L by means of magnetic Barkhausen noise

    International Nuclear Information System (INIS)

    Research highlights: The results and the conclusions drawn in this paper are important for the scientific community and especially for scientist who are looking for method to characterize phase transformations in metallic materials. We show that Barkhausen noise measurements can be successfully used to monitor strain-induced martensite in austenitic stainless steels. - Abstract: Different shot peening conditions were applied to an austenitic stainless steel AISI 304L in order to transform austenite to martensite α' at different depths. Magnetic Barkhausen noise measurements performed on this steel reveal a correlation between the strength of the signal and the depth of the treatment. The combined effect of the volume fraction of martensite and the residual stress in martensite determined using X-ray diffraction analysis were found to be responsible for the evolution of the Barkhausen noise response. Using tensile plastic deformation, the residual stress in martensite was changed, giving rise to a strong increase of the Barkhausen noise activity. This variation was correlated to a modification of the sign and amplitude of the residual stress in the martensite phase. Directional measurements of the Barkhausen noise revealed the anisotropy of the residual stresses induced by the tensile plastic deformation. It is concluded that the Barkhausen noise activity recording could lead to the determination of the residual stresses in martensite induced by shot peening processes.

  16. Investigation of shot-peened austenitic stainless steel 304L by means of magnetic Barkhausen noise

    Energy Technology Data Exchange (ETDEWEB)

    Kleber, X., E-mail: xavier.kleber@insa-lyon.fr [Universite de Lyon, INSA-Lyon, MATEIS CNRS UMR5510, 7 Avenue Jean Capelle, F-69621 Villeurbanne (France); Barroso, S. Pirfo [Universite de Lyon, INSA-Lyon, MATEIS CNRS UMR5510, 7 Avenue Jean Capelle, F-69621 Villeurbanne (France)

    2010-08-20

    Research highlights: The results and the conclusions drawn in this paper are important for the scientific community and especially for scientist who are looking for method to characterize phase transformations in metallic materials. We show that Barkhausen noise measurements can be successfully used to monitor strain-induced martensite in austenitic stainless steels. - Abstract: Different shot peening conditions were applied to an austenitic stainless steel AISI 304L in order to transform austenite to martensite {alpha}' at different depths. Magnetic Barkhausen noise measurements performed on this steel reveal a correlation between the strength of the signal and the depth of the treatment. The combined effect of the volume fraction of martensite and the residual stress in martensite determined using X-ray diffraction analysis were found to be responsible for the evolution of the Barkhausen noise response. Using tensile plastic deformation, the residual stress in martensite was changed, giving rise to a strong increase of the Barkhausen noise activity. This variation was correlated to a modification of the sign and amplitude of the residual stress in the martensite phase. Directional measurements of the Barkhausen noise revealed the anisotropy of the residual stresses induced by the tensile plastic deformation. It is concluded that the Barkhausen noise activity recording could lead to the determination of the residual stresses in martensite induced by shot peening processes.

  17. On-line model for control of hot rolling of austenitic steel strips

    International Nuclear Information System (INIS)

    The on-line model of strip rolling for austenitic steels is described in the paper. Three components are included in the model. The first is a new thermal model, which is based on an analytical solution of the Fourier equation. Thermophysical properties of the austenitic steels are introduced in the model. The numerical procedure, which designs a rolling schedule, is the second part of the model. The rolling velocities and the reductions in subsequent passes are determined by a solution of a set of non-linear equations, which compose continuity condition and energy balance for all stands. The problem is solved using optimisation techniques with constraints, that allows imposing of the technological limitations on the solution. The adaptive procedure is applied to adjust coefficient in the flow stress equation during the on-line work of the model. Microstructure evolution model is the third part of the system. This model is based on semi-empirical equations describing microstructural phenomena for austenitic steels. The microstructural model is included in the temperature calculations, but it does not take part in the control of the rolling process directly. Its task is to supply information regarding the microstructure and mechanical properties predicted for the current rolling technology, designed by the system. Description of all the developed models is given in the paper. Results of numerical experiments including calculations of rolling schedules are presented. (author)

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

    International Nuclear Information System (INIS)

    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

  19. 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.

  20. 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.

  1. Role of alloyed molybdenum in austenitic stainless steels in the inhibition of pitting in neutral halide solutions

    Energy Technology Data Exchange (ETDEWEB)

    Sugimoto, K.; Sawada, Y.

    1976-09-01

    In the passive region of austenitic stainless steels alloyed with Mo, the formation of MoO/sub 4//sup 2 -/ ions can be expected in neutral halide solutions by the transpassive dissolution of Mo. It has been shown that MoO/sub 4//sup 2 -/ ions added to neutral NaCl solutions act as an effective inhibitor against pitting of austenitic stainless steels with and without Mo. The interaction between alloyed Mo in the steels and added MoO/sub 4//sup 2 -/ ions in the solutions is appreciable. It is likely that the inhibition of pit growth by the adsorption of MoO/sub 4//sup 2 -/ ions which are thought to result from the dissolution of the steels at the initial stage of pitting leads to increased pitting resistance of austenitic stainless steels containing Mo.

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

    International Nuclear Information System (INIS)

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-01-01

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

  4. Austenite grain size control of a hot working tool steel by addition of niobium

    International Nuclear Information System (INIS)

    The substitution of vanadium by niobium for controlling the austenite grain size of a hot working tool steel was studied, using the addition of the same atomic percentage as a criterion. The austenitising temperatures ranged from 850 to 1.2000C. At low austenitising temperature, both vanadium and niobium are effective in producing small grain size. At high austenitising temperatures, niobium was more effective than vanadium. Possible causes of this difference and the occurrence of coarse niobium carbide in the niobium steel are discussed on the basis of the difference in solubility between niobium and vanadium carbides

  5. Cryogenic mechanical properties of heavy-section weldment in high-manganese austenitic steel

    International Nuclear Information System (INIS)

    Cryogenic mechanical properties of a heavy-section weldment of high-manganese austenitic steel for the structure of superconducting magnet were evaluated, The heavy-section weld joint with a 200 mm thickness was manufactured by gas tungsten arc welding (GTAW) process using 21Mn-13Cr-5Ni-0.2N-B steel weld material. No cracks were observed in the weld metal. Tensile property and fracture toughness were tested at 4 K. The yield strength and the fracture toughness value, KIc(J), were 1223 - 1278 MPa and 181∼ 201 MPam1/2 in the weld metal, respectively

  6. Hot deformation and recrystallization of advanced high-manganese austenitic TWIP steels

    OpenAIRE

    L.A. Dobrzański; W. Borek

    2011-01-01

    Purpose: The aim of the paper is to determine the influence of hot-rolling conditions on structure of new-developed high-manganese austenitic steels.Design/methodology/approach: Flow stresses during continuous and multi-stage compression tests were measured using the Gleeble 3800 thermo-mechanical simulator. To describe the hot-working behaviour, the steels were compressed to the various amount of deformation (4x0.29, 4x0.23 and 4x0.19). The microstructure evolution in different stages of hot...

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

    Institute of Scientific and Technical Information of China (English)

    TIAN Rujin; SUN Juncai; WANG Jianli

    2006-01-01

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

  8. Dynamic tensile tests on ferritic and austenitic steels with improved testing and measuring technique

    OpenAIRE

    Kussmaul, K.; Schuele, M.

    1994-01-01

    For analysing dynamically loaded structures by means of the finite element method a dynamic constitutive material model is necessary to obtain reliable results. For this purpose dynamic tensile tests were performed with the fine grained steel 20 MnMoNi 5 5 (A 508 Cl. 3) and the austenitic steel X 6 CrNi 18 11 at different velocities. Smooth round bar specimens of different geometries were used. Displacement at the lower end of the specimen as well as force and strain were measured. The whole ...

  9. Microscopic investigation of pitting corrosion in plasma nitrided austenitic stainless steel

    International Nuclear Information System (INIS)

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

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

    International Nuclear Information System (INIS)

    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 that the level of damage per atomic displacement may be larger in the pressurized water environment

  11. Effect of oxygen in sodium upon radionuclide release from austenitic stainless steel

    International Nuclear Information System (INIS)

    This paper deals with the effect of oxygen in sodium upon radionuclide release from austenitic stainless steel. The work described herein was conducted in Source Term Control Loop (STCL-1) with a specimen temperature of 604C, a loop minimum temperature of 427C, sodium velocity at the specimens of 6.7 to 7.6m/s. Weight losses of Fe, Cr, Mn and Ni from the steel specimen were analysed. Release data for 54Mn and 60Co are calculated. Future work is briefly described

  12. Utilization of Non-Destructive Thermoelectric Power Measurements for Determination of Interstitial Nitrogen Content in Nitrogen-Strengthened Austenitic Stainless Steel Welds

    International Nuclear Information System (INIS)

    Through utilization of modern physics concepts, a new non-destructive, portable thermoelectric power device has been designed for the use of rapid material characterization in nitrogen-strengthened austenitic stainless steel weldments. Nitrogen is used as an interstitial strengthener in austenitic stainless steel offering enhancement in mechanical properties and corrosion resistance. A direct correlation exists between the thermoelectric power coefficient as a function of interstitial nitrogen content, revealing microstructural characteristics of the austenitic stainless steel weldment

  13. Self-healing of creep cavities formed in austenitic stainless steel

    International Nuclear Information System (INIS)

    In austenitic stainless steels creep cavities nucleate at grain boundaries by long time use at high temperatures. These creep cavities grow along grain boundaries, form grain boundary cracks by linking up each other, and cause premature and low ductility fracture. Therefore long time creep rupture life and ductilities chiefly depend upon the behavior of nucleation and growth of creep cavities. If the growth of creep cavities could be suppressed, creep rupture life and ductilities should be improved remarkably. The present work is intended to propose a self-healing process for the cavitation by utilization of thin filmy precipitation at creep cavity surface and improve the creep rupture properties by the self-healing process. In ordinary austenitic stainless steels, sulfur is contained as impurity and segregates to creep cavity surface because of its high surface activity. It is thought that a stable compound can precipitate at creep cavity surface if the sulfur is completely removed. Therefore in order to remove sulfur completely and precipitate a stable compound at creep cavity surface, a modified 304 stainless steel added with cerium, titanium, boron and nitrogen was laboratory-melted. The modified steel showed high rupture strength and high rupture ductilities, and it was confirmed that boron nitride precipitates at creep cavity surface in the steel. It was thought that the boron nitride at creep cavity surface suppresses the creep cavity growth and improves creep rupture properties by the self-healing effect on creep cavities. (author)

  14. Dose dependence of the microstructural evolution in neutron-irradiated austenitic stainless steel

    International Nuclear Information System (INIS)

    Microstructural data on the evolution of the dislocation loop, cavity, and precipitate populations in neutron-irradiated austenitic stainless steels are reviewed in order to estimate the displacement damage levels needed to achieve the 'steady state' condition. The microstructural data can be conveniently divided into two temperature regimes. In the low temperature regime (below about 200 degrees C) the microstructure of austenitic stainless steel is dominated by 'black spot' defect clusters and faulted interstitial dislocation loops. The dose needed to approach saturation of the loop and defect cluster densities is generally on the order of 1 displacement per atom (dpa) in this regime. In the high temperature regime (∼300 to 700 degrees C), cavities, precipitates, loops and network dislocations are all produced during irradiation; doses in excess of 10 dpa are generally required to approach a 'steady state' microstructural condition. Due to complex interactions between the various microstructural components that form during irradiation, a secondary transient regime is typically observed in commercial stainless steels during irradiation at elevated temperatures. This slowly evolving secondary transient may extend to damage levels in excess of 50 dpa in typical 300-series stainless steels, and to >100 dpa in radiation-resistant developmental steels. The detailed evolution of any given microstructural component in the high-temperature regime is sensitive to slight variations in numerous experimental variables, including heat-to-heat composition changes and neutron spectrum

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

    International Nuclear Information System (INIS)

    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

  16. 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.

  17. Neutron irradiation creep experiments on austenitic stainless steel alloys

    International Nuclear Information System (INIS)

    Results of measurements of the neutron induced creep elongation on AMCR-steels (Mn-base), on 316 CE-reference steels, and on US 316 jand US PCA steels are reported. It was found that the stationary creep rate is not very sensitive to variations of the irradiation temperature between 300 and 400 degC and that the stress-exponent of plastically deformed and of annealed materials is n ≅ and n ≅ 1.59, respectively. A small primary creep stage is found in annealed materials. Deformed materials show a negative creep elongation at the beginning of the irradiation, which increases for decreasing stresses and decreases for increasing irradiation temperatures. (author). 7 refs.; 7 figs.; 1 tab

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

    International Nuclear Information System (INIS)

    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

  19. Influence of thermal treatment on the caustic SCC of super austenitic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Yoo, Y.R.; Park, Y.B.; Chung, T.J.; Kim, Y.S. [School of Advanced Materials Engineering, Andong National Univ. (Korea); Chang, H.Y. [Korea Power Engineering Co. (Korea); Park, Y.S. [Dept. of Metallurgical Engineering, Yonsei Univ. (Korea)

    2005-07-01

    In general, thermal treatment at 500 C {proportional_to} 900 C ranges depending upon alloy composition of stainless steels can sensitize the steels and promote the intergranular cracking, and their intergranular corrosion resistance is decreased. These behaviors seem to be related to the change of microstructures. So, heat treatment at that temperature range should be avoided in fabrication, especially welding of stainless steels. In this work, it is focused on the effect of thermal treatment on caustic stress corrosion cracking of super austenitic stainless steel - S32050 The low temperature thermal treatment increased greatly the resistance to caustic SCC than those of annealed specimen. This enhancement might be closely related to the reduction of residual stress and slightly large grain, but its resistance was not affected by the anodic polarization behavior. (orig.)

  20. Stochastic aspects of evolution of creep damage in austenitic stainless steel

    International Nuclear Information System (INIS)

    A stochastic model for the creep damage evolution and associated scatter in austenitic stainless steel has been developed in terms of a discontinuous Markov process. The magnitude of damage has been described in the form of a probability distribution function whose evolution in time characterizes the nondeterministic nature of the damage accumulation process. The long-term creep behavior on samples obtained from different locations of a thick walled SS304 LN steel pipe are studied under an identical stress and temperature condition so as to observe the scatter in creep deformation and failure data. Also the occurrences of damage and its accumulation due to creep deformation were evaluated through microstructural assessment using light optical microscope and scanning electron microscope. The validity of the model has been established by repeat data of SS304 LN steel and 316 stainless steel .

  1. Eddy current testing of longitudinal welds in austenitic steel pipes

    International Nuclear Information System (INIS)

    The existing steel-iron test sheet 1914 'Nondestructive Testing of Fusion Welded Joints in Tubes of Stainless Steels' (SEP 1914) had to be revised. The physical correlation between test frequency, phase position, amplitude and defect size for different pipe dimensions were pointed out and discussed on the basis of numerous measurement series. The influence of coil-specific parameters, filtration and electromagnetic magnetization on the eddy current signal were clarified. Additionally, the transferability of the amplitude and phase behaviour of simulated defects on naturally occurring defects was investigated in order to guarantee that the determined test parameters for the revision of existing test regulations are practice-oriented. As the most important result, it is stated that the definition of the test sensitivity in the steel-iron test sheet 1914 is too insensitive for a great number of pipe dimensions. Therefore, the existing steel-iron test sheet 1914 was revised with regard to the definition of the test sensitivity on the basis of the required detection sensitivity of a 20% internal groove. (orig./HP)

  2. Processes forming the microstructure evolution of high-manganese austenitic steel in hot-working conditions

    Directory of Open Access Journals (Sweden)

    L.A. Dobrzański

    2009-12-01

    Full Text Available Purpose: The aim of the paper is to characterise the microstructure evolution of new-developed 27Mn-4Si-2Al-Nb-Ti high-manganese steel in various conditions of hot-working.Design/methodology/approach: Flow stresses during the multistage compression test were measured usingthe Gleeble 3800 thermo-mechanical simulator. To describe the hot-working behaviour, the steelwas compressed to the various amount of deformation (4x0.29, 4x0.23 and 4x0.19. The microstructure evolution in successive stages of deformation was determined in metallographic investigations using light, scanning and electron microscopy as well as X-ray diffraction.Findings: The steel has austenite microstructure with annealing twins and some fraction of ε martensite plates in the initial state. The flow stresses are much higher in comparison with austenitic Cr-Ni and Cr-Mn steelsand slightly higher compared to Fe-(15-25 Mn alloys. The flow stresses are in the range of 200-400 MPafor the applied conditions of hot-working. Making use of dynamic and metadynamic recrystallization,it is possible to refine the microstructure and to decrease the flow stress to 350 MPa during the last deformation at 850°C. Applying the true strains of 0.23 and 0.19 requires the microstructure refinementby static recrystallization. After the grain refinement due to recrystallization, the steel is characterisedby uniform structure of γ phase without ε martensite plates.Research limitations/implications: To fully describe the hot-working behaviour of the new-developed steel, further investigations in wider temperature and strain rate ranges are required.Originality/value: The hot-deformation resistance and microstructure evolution in various conditionsof hot-working for the new-developed high-manganese 27Mn-4Si-2Al-Nb-Ti austenitic steel were investigated.

  3. 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. PMID:19627825

  4. The Effect of Welding Method on the Electrochemical Behavior of Austenitic Stainless Steel Sheet

    International Nuclear Information System (INIS)

    The corrosion of the flexible tube in the automobile exhaust system is caused by the ambient water and chloride ions. Since welding is one of the key processes of the flexible tube manufacturing, it is required to select a proper welding method to prevent the flexible tube corrosion and to increase its lifetime. There are many studies about the efficiency of the welding method, but no systematic study is performed for the effect of welding method on the corrosion property of the austenitic stainless weldment. The aim of the present study is to provide information on the effect of two different welding methods of TIGW (tungsten inert gas welding) and PAW (plasma arc welding) on the corrosion property of austenitic stainless steel weldment. Materials used in this study were two types of the commercial austenitic stainless steel, STS321 and XMI5JI, which were used for flexible tube material for the automotive exhaust system. Microstructure was observed by using optical microscopy (OM) and scanning electron microscopy (SEM). To evaluate the corrosion behavior, potentiodynamic and potentiostatic tests were performed. The chemical state of the passive film was analyzed in terms of XPS depth profile. Metallurgical analysis show that the ferrite content in fusion zone of both STS321 and XMI5JI is higher when welded by PAW than by TIGW. The potentiodynamic and potentiostatic test results show that both STS321 and XMI5JI have higher transpassive potential and lower passive current density when welded by PAW than by TIGW. XPS analysis indicates that the stable Cr2O3 layer at the outermost layer of the passive film is formed when welded by PAW. The result recommends that PAW is more desirable than TIGW to secure corrosion resistance of the flex tube which is usually made of austenitic stainless steel

  5. Effect of heavy ion irradiation on microstructural evolution in CF8 cast austenitic stainless steel

    Science.gov (United States)

    Chen, Wei-Ying; Li, Meimei; Kirk, Marquis A.; Baldo, Peter M.; Lian, Tiangan

    2016-04-01

    The microstructural evolution in ferrite and austenitic in cast austenitic stainless steel (CASS) CF8, as received or thermally aged at 400 °C for 10,000 h, was followed under TEM with in situ irradiation of 1 MeV Kr ions at 300 and 350 °C to a fluence of 1.9 × 1015 ions/cm2 (∼3 dpa) at the IVEM-Tandem Facility. For the unaged CF8, the irradiation-induced dislocation loops appeared at a much lower dose in the austenite than in the ferrite. At the end dose, the austenite formed a well-developed dislocation network microstructure, while the ferrite exhibited an extended dislocation structure as line segments. Compared to the unaged CF8, the aged specimen appeared to have lower rate of damage accumulation. The rate of microstructural evolution under irradiation in the ferrite was significantly lower in the aged specimen than in the unaged. This difference is attributed to the different initial microstructures in the unaged and aged specimens, which implies that thermal aging and irradiation are not independent but interconnected damage processes.

  6. Effect of Multi-Step Tempering on Retained Austenite and Mechanical Properties of Low Alloy Steel

    Institute of Scientific and Technical Information of China (English)

    Hamid Reza Bakhsheshi-Rad; Ahmad Monshi; Hossain Monajatizadeh; Mohd Hasbullah Idris; Mohammed Rafiq Abdul Kadir; Hassan Jafari

    2011-01-01

    The effect of multi-step tempering on retained austenite content and mechanical properties of low alloy steel used in the forged cold back-up roll was investigated.Microstructural evolutions were characterized by optical microscope,X-ray diffraction,scanning electron microscope and Feritscope,while the mechanical properties were determined by hardness and tensile tests.The results revealed that the content of retained austenite decreased by about 2% after multi-step tempering.However,the content of retained austenite increased from 3.6% to 5.1% by increasing multi-step tempering temperature.The hardness and tensile strength increased as the austenitization temperature changed from 800 to 920 ℃,while above 920 ℃,hardness and tensile strength decreased.In addition,the maximum values of hardness,ultimate and yield strength were obtained via triple tempering at 520 ℃,while beyond 520 ℃,the hardness,ultimate and yield strength decreased sharply.

  7. Modelling grain-scattered ultrasound in austenitic stainless-steel welds: A hybrid model

    Energy Technology Data Exchange (ETDEWEB)

    Nowers, O.; Duxbury, D. J. [NDE Research, Support and Development, Rolls-Royce Marine, Derby, PO BOX 2000, DE21 7XX (United Kingdom); Velichko, A.; Drinkwater, B. W. [Department of Mechanical Engineering, University Walk, University of Bristol, Bristol BS8 1TR (United Kingdom)

    2015-03-31

    The ultrasonic inspection of austenitic stainless steel welds can be challenging due to their coarse grain structure, charaterised by preferentially oriented, elongated grains. The anisotropy of the weld is manifested as both a ‘steering’ of the beam and the back-scatter of energy due to the macroscopic granular structure of the weld. However, the influence of weld properties, such as mean grain size and orientation distribution, on the magnitude of scattered ultrasound is not well understood. A hybrid model has been developed to allow the study of grain-scatter effects in austenitic welds. An efficient 2D Finite Element (FE) method is used to calculate the complete scattering response from a single elliptical austenitic grain of arbitrary length and width as a function of the specific inspection frequency. A grain allocation model of the weld is presented to approximate the characteristic structures observed in austenitic welds and the complete scattering behaviour of each grain calculated. This model is incorporated into a semi-analytical framework for a single-element inspection of a typical weld in immersion. Experimental validation evidence is demonstrated indicating excellent qualitative agreement of SNR as a function of frequency and a minimum SNR difference of 2 dB at a centre frequency of 2.25 MHz. Additionally, an example Monte-Carlo study is presented detailing the variation of SNR as a function of the anisotropy distribution of the weld, and the application of confidence analysis to inform inspection development.

  8. Improved superheater tubing material - Ti and Nb bearing austenitic steel

    International Nuclear Information System (INIS)

    A newly developed 18 Cr-8 Ni stainless steel modified with small amounts of Ti and Nb has considerably high stress-rupture strength and is considered to be suitable for superheater material for power boilers. Data for stress-rupture and creep for long times, the strength of welded joints, the changes of characteristics due to exposure to high temperatures, etc., are presented and discussed. Some investigations after trial services indicate that the experimental data are applicable to actual applications. (author)

  9. Corrosion of an austenite and ferrite stainless steel weld

    OpenAIRE

    BRANIMIR N. GRGUR; VLADANA N. RAJAKOVIĆ-OGNJANOVIĆ

    2011-01-01

    Dissimilar metal connections are prone to frequent failures. These failures are attributed to the difference in the mechanical properties across the weld, the coefficients of thermal expansion of the two types of steels and the resulting creep at the interface. For the weld analyzed in this research, it was shown that corrosion measurements can be used for a proper evaluation of the quality of weld material and for the prediction of whether or not the material, after the applied welding proce...

  10. Mechanical behaviour of an austenitic stainless steel under repeated impacts

    International Nuclear Information System (INIS)

    Cyclic indentation tests realised with an energy controlled spherical indenter allow a characterisation of the material behaviour under dynamic solicitations. This solicitation is, for example, able to show erosion and matting phenomenon. This test has been performed on AISI 316 stainless steels samples. Results have shown an increase of the hardness and the depth of the affected area versus the cycles number. With a micrographic optical analysis, we have detected a work hardening effect below the contact area. (authors)

  11. 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...

  12. Weldability of corrosion-resistant high-nitrogen austenitic Kh22AG16N8M-type steels

    Science.gov (United States)

    Bannykh, O. A.; Blinov, V. M.; Kostina, M. V.; Blinov, E. V.; Zvereva, T. N.

    2007-10-01

    The influence of thermal treatment on the structures and mechanical properties of welds of corrosion-resistant high-nitrogen austenitic 05Kh22AG16N8M-type steels is studied. In these steels, austenite is found to be highly resistant to discontinuous precipitation and the formation of σ phase and δ ferrite upon cooling regardless of the temperature of heating for quenching (from 900 to 1250°C) and the cooling conditions (water, air, furnace). Welding of these steels can produce high-strength welds with an enhanced impact toughness.

  13. Effect of nitrogen on the stabilization of austenite in a tungsten-molybdenum high-speed steel

    International Nuclear Information System (INIS)

    A study was made of the tendency of steels R6M5 and R6Am5 to austenite stabilization after subzero treatment and high-temperature tempering in hot-rolled bars. Data indicate that in steel R6AM5 during quenching there is almost instantaneous austenite stabilization. The data was derived from a study of phase composition (exposure from a microsection in DRON-2.0 equipment in iron K /SUB alpha/ radiation), microstructure, and hardness. The authors conclude that in view of serious difficulties in metallurgical and tool production, steel R6AM5 should be supplied only at the request of the customer

  14. Low temperature thermal ageing embrittlement of austenitic stainless steel welds and its electrochemical assessment

    International Nuclear Information System (INIS)

    Highlights: ► Embrittlement study of austenitic stainless steel welds after ageing up to 20,000 h. ► Spinodal decomposition and G-phase precipitation in ferrite at 400 °C. ► Spinodal decomposition of ferrite at 335 and 365 °C. ► Large decrease in corrosion resistance due to G-phase precipitation. ► Good correlation between electrochemical properties and the degree of embrittlement. - Abstract: The low temperature thermal ageing embrittlement of austenitic stainless steel welds is investigated after ageing up to 20,000 h at 335, 365 and 400 °C. Spinodal decomposition and G-phase precipitation after thermal ageing were identified by transmission electron microscopy. Ageing led to increase in hardness of the ferrite phase while there was no change in the hardness of austenite. The degree of embrittlement was evaluated by non-destructive methods, e.g., double-loop and single-loop electrochemical potentiokinetic reactivation tests. A good correlation was obtained between the electrochemical properties and hardening of the ferrite phase of the aged materials.

  15. Predicting the toughness of SMA austenitic stainless steel welds at 77 K

    International Nuclear Information System (INIS)

    Austenitic stainless steels often provide the best combination of strength and toughness for cryogenic applications: however, the weld toughness is frequently much lower than that of the base metal. This study proposes a more accurate and simpler model for developing improved filler metal compositions. Several previous studies of the weld toughness were analyzed separately and in combination using a stepwise regression method and an expanded variable list. The total data base consisted of chemical composition, ferrite number (FN), and the Charpy V-notch (CVN) toughness at 77 K of 79 austenitic stainless steel welds deposited by the shielded metal arc process. Analysis of the complete data base revealed that the FN calculated from the Schaeffler diagram was the most significant variable for predicting the CVN toughness. The predictive equation produced a better correlation between the measured and predicted values of weld toughness than the previously published predictive equations. The group of 36 fully austenitic welds and the group of 21 type 316 welds in the data base were analyzed by the same procedure. In both cases the ferrite number was found to be the most significant predictor of toughness

  16. Difference in transformation behavior between ferrite and austenite formations in medium manganese steel

    International Nuclear Information System (INIS)

    The difference in transformation behavior between the γ → α and α′ → γ transformations at the transition temperature T0 was investigated in 0.1%C–5%Mn steel. The γ → α transformation was very slow, and so little ferrite phase formed at T0, even after a lengthy annealing time of 50 h. However, the α′ → γ transformation was relatively fast and rapidly proceeded at T0. In the dual-phase structure formed by the α′ → γ transformation, thin film-shaped reversed austenite grains with sufficient thermal stability formed along the lath boundaries of the tempered martensite matrix. The simulation using diffusion-controlled transformations (DICTRA) software confirmed that the rapid austenite formation in medium manganese steel is attributed to: (1) the high density of austenite nucleation sites derived from the hierarchical lath martensitic structure; (2) the negligible-partitioning local equilibrium growth controlled by very fast carbon diffusion at the initial stage; and (3) the relatively higher diffusivity of Mn within the martensite matrix under the partitioning local equilibrium growth that occurred at a subsequent stage

  17. Determining Experimental Parameters for Thermal-Mechanical Forming Simulation considering Martensite Formation in Austenitic Stainless Steel

    Science.gov (United States)

    Schmid, Philipp; Liewald, Mathias

    2011-08-01

    The forming behavior of metastable austenitic stainless steel is mainly dominated by the temperature-dependent TRIP effect (transformation induced plasticity). Of course, the high dependency of material properties on the temperature level during forming means the temperature must be considered during the FE analysis. The strain-induced formation of α'-martensite from austenite can be represented by using finite element programs utilizing suitable models such as the Haensel-model. This paper discusses the determination of parameters for a completely thermal-mechanical forming simulation in LS-DYNA based on the material model of Haensel. The measurement of the martensite evolution in non-isothermal tensile tests was performed with metastable austenitic stainless steel EN 1.4301 at different rolling directions between 0° and 90 °. This allows an estimation of the influence of the rolling direction to the martensite formation. Of specific importance is the accuracy of the martensite content measured by magnetic induction methods (Feritscope). The observation of different factors, such as stress dependence of the magnetisation, blank thickness and numerous calibration curves discloses a substantial important influence on the parameter determination for the material models. The parameters obtained for use of Haensel model and temperature-dependent friction coefficients are used to simulate forming process of a real component and to validate its implementation in the commercial code LS-DYNA.

  18. Cyclic deformation behaviour of austenitic steels at ambient and elevated temperatures

    Indian Academy of Sciences (India)

    Th Nebel; D Eifler

    2003-02-01

    The aim of the present investigation is to characterise cyclic deformation behaviour and plasticity-induced martensite formation of metastable austenitic stainless steels at ambient and elevated temperatures, taking into account the influence of the alloying elements titanium and niobium. Titanium and niobium are ferrite-stabilising elements which influence the ferrite crystallisation. Furthermore, They form carbides and/or carbonitrides and thus limit the austenite-stabilising effect of carbon and nitrogen. Several specimen batches of titanium and niobium alloyed austenite and of a pure Cr-Ni-steel for comparison were tested under stress and total strain control at a frequency of 5 Hz and triangular load-time waveforms. Stress-strain-hysteresis and temperature measurements were used at ambient temperature to characterise cyclic deformation behaviour. Plasticity-induced martensite content was detected with non-destructive magnetic measuring techniques. The experiments yield characteristic cyclic deformation curves and corresponding magnetic signals according to the actual fatigue state and the amount of martensite. Fatigue behaviour of X6CrNiTi1810 (AISI 321), X10CrNiCb189 (AISI 348) and X5CrNi1810 (AISI 304) is characterised by cyclic hardening and softening effects which are strongly influenced by specific loading conditions. Martensite formation varies with the composition, loading conditions, temperature and number of cycles.

  19. Microstructure and mechanical properties of annealed SUS 304H austenitic stainless steel with copper

    International Nuclear Information System (INIS)

    Research highlights: → SUS 304H austenitic stainless steel containing 3 wt.% Cu was annealed at 700 deg. C for up to 100 h. → Microstructure and mechanical properties of annealed alloys are examined. → Nano-sized Cu-rich precipitation upon annealing. → Strength of the alloy remains invariant with annealing whereas ductility improves. → Fatigue crack growth threshold of 3 wt.% Cu added alloy increases with annealing. - Abstract: An experimental investigation into the effect of Cu on the mechanical properties of 0 and 3 wt.% Cu added SUS 304H austenitic stainless steel upon annealing at 700 deg. C for up to 100 h was conducted. Optical microscopy reveals grain coarsening in both the alloys upon annealing. Observations by transmission electron microscopy revealed the precipitation of nanometer-sized spherical Cu particles distributed within the austenitic grains and the presence of carbides at the dislocations. Both the yield and ultimate tensile strengths of the alloys were found to remain invariant with annealing. Tensile ductility and the threshold stress intensity factor range for fatigue crack growth for 3 wt.% Cu added alloy increase with annealing. These are attributed to the grain coarsening with annealing. In all, the addition of Cu to SUS 304H does not affect the mechanical performance adversely while improving creep resistance.

  20. Swelling of advanced austenitic stainless steels developed for the environment of heavy neutron exposure

    International Nuclear Information System (INIS)

    Modified Type-316 and higher-nickel advanced austenitic steels were irradiated in the FFTF and JOYO fast reactors to a neutron dose as high as 210 dpa. At temperatures greater than 500 C, P-, Si-, and Ti-bearing cold-worked austenitic steels showed significant swelling suppression even after 150 dpa. The dominant mechanism is associated with formation of stable phosphide precipitated by addition of Ti and/or increased Si. In the lower-temperature regime, where the phosphide precipitate is not present, silicon acts to suppress swelling at contents of about 0.8 wt%. Only at this higher silicon level, increased amounts of nickel reduced the swelling. At 0.5 wt% silicon, the swelling was insensitive to the alloying elements, such as Ni, Ti and P. The effect of Si and Ni could be explained by their influence on void nucleation through effects on effective vacancy diffusion coefficient. Further improvement in swelling was expected by increasing the nickel and possibly the phosphorus contents of the advanced austenitics. ((orig.))

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

    Directory of Open Access Journals (Sweden)

    A. Almubarak

    2013-01-01

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

  2. Residual and trace element effects on the high-temperature creep strength of austenitic stainless steels

    International Nuclear Information System (INIS)

    The heat-to-heat variation in the creep strength and ductility of austenitic stainless steels was reviewed from the viewpoint of residual and trace element effects. Based on data reported in the literature the creep strength of unstabilized alloys such as types 304 and 316 stainless steel increased with residual element and trace element content. Niobium appeared to be the most potent strengthener. There was no direct evidence that trace elements such as sulfur and phosphorus had a deleterious effect on either strength and ductility. It was assumed that the creep strength and ductility of the unstabilized grades of austenitic stainless steels are controlled by the precipitate characteristics. It follows from this that thermomechanical treatment or residual element additions that affect the precipitate characteristics influence subsequent time dependent mechanical properties. This view is consistant with most of the information in the literature. It was concluded that more systematic studies of trace and residual element effects would be beneficial to the improvement of steels. Incorporated into the studies should be quantitative characterization of evolving precipitate morphology and composition as they are in fluenced by residual elements. This information should be incorporated into modeling studies of nonequilibrium segregation. Ultimately, optimum elevated-temperature strength could be developed based on a materials science approach

  3. The Effect of Hydrogen on Plasma Nitriding of Austenitic Stainless Steel: Kinetic Modeling

    Science.gov (United States)

    Moskalioviene, Teresa; Galdikas, Arvaidas

    2015-12-01

    The kinetic model of adsorption and stress-induced diffusion of nitrogen in austenitic stainless steels taking place during plasma nitriding using various mixtures of nitrogen and hydrogen is proposed. On the basis of proposed model, a numerical study has been undertaken to analyze and describe the effect of hydrogen on plasma nitriding of austenitic stainless steel. It was shown that the addition of hydrogen with concentrations in the range ~(30 to 40) pct enhances nitrogen penetration into steel. This is due to two factors: (1) reduction of the surface oxide due to chemical etching of the oxygen by hydrogen and (2) increase of NH radicals which are converted to active nitrogen atoms on the steel surface, i.e., the amount of adsorbed and diffused nitrogen increases. As a result, the thicker nitrogen-containing layer is observed. Moreover, results of numerical prediction show that an excessive amount of hydrogen (more than ~70 pct) in the gas mixture retards the nitriding process in comparison with nitriding in pure nitrogen plasma.

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

    International Nuclear Information System (INIS)

    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

  5. Metallurgical basis for the development of high nitrogen, high toughness, high strength austenitic steels

    International Nuclear Information System (INIS)

    Stainless steels containing 1 wt.-% of nitrogen are a new group of materials with interesting properties. They show a very good combination of high strength and high toughness and also a high corrosion resistance. The addition of 1 wt.-% nitrogen increases the yield strength by about 500 MPa. The fracture toughness remains at level of 500 MPa√m. The corrosion resistance of these steels is indicated by the pitting resistance equivalent PRE = %Cr + 3.3%Mo + 20%N. All these properties make the group of high nitrogen steels interesting for technical applications. Therefore it is necessary to find a way for their economical production. This has become possible through melting at atmospheric pressure, which does not need any sophisticated and expensive equipment. The limitation of the nitrogen pressure in the air, at a level of 0.8atm, requires the optimization of the alloy composition in order to reach very high nitrogen contents of 1% or even more in the melt. Strength, toughness and corrosion resistance depend on the chemical composition as well as on the stability of the microstructure. Thus the microstructure of this steels had to be newly examined because of the high contents of several elements like nitrogen, chromium, molybdenum and especially manganese. High contents of manganese and nitrogen increase the stability of the austenitic structure. Furthermore the influence of nitrogen on the formation of sigma-phase has been described. Increasing contents of nitrogen shift the formation of sigma-phase to higher temperatures. Sigma-phase has a detrimental influence on the workability of these steels like forging or hot extruding. High nitrogen contents change the fracture behavior of austenitic Cr-Mn stainless steels. They result in a low temperature embrittlement that has been described by an empirical equation. It is now possible to design new steels by giving attention to their properties such as strength, toughness, structure, corrosion resistance and

  6. Corrosion of silicon-containing austenitic stainless steels under trans-passive conditions

    International Nuclear Information System (INIS)

    This research thesis addresses austenitic stainless steels which are used in installations for the chemical treatment of nuclear fuels, and are there in contact with nitric acid solutions the oxidising character of which generally promotes metal passivity. However, if this nitric environment becomes too oxidising, these steels may face severe corrosion problems. More particularly, this thesis addresses the study of intergranular corrosion, and aims at analysing various aspects of the corrosion of these austenitic stainless steels in trans-passive conditions. The author aims at determining and distinguishing the contributions due to silicon and those related to the presence of other impurities and addition elements by comparing the behaviours of industrial grade steels and high purity alloys in rigorously controlled electrochemical conditions. Another objective is to study the influence of the intergranular structure on silicon segregation by means of an attack technique in trans-passive conditions. After a report of a bibliographical study on the addressed topics and a presentation of the studied materials and implemented experimental techniques, the author reports the study of steel behaviour with respect to generalised dissolution in trans-passive conditions, as well in the nitric environment as in a sulphuric acid solution at imposed potential. Localised intragranular corrosion phenomena are discussed. A trans-passive intragranular corrosion model is proposed, and its possibilities in the analysis of intergranular segregation analysis are discussed. Experimental results of trans-passive intergranular corrosion of stainless steels are presented and interpreted by using the McLean segregation model. The influence of steel composition and of experimental conditions is discussed, as well as the role of grain boundary structure in the corrosion process

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

    Energy Technology Data Exchange (ETDEWEB)

    Kostryzhev, Andrii G., E-mail: andrii@uow.edu.au [School of Mechanical, Materials and Mechatronic Engineering, The University of Wollongong, NSW 2522 (Australia); Al Shahrani, Abdullah, E-mail: amfa065@uowmail.edu.au [School of Mechanical, Materials and Mechatronic Engineering, The University of Wollongong, NSW 2522 (Australia); Zhu, Chen, E-mail: chen.zhu@sydney.edu.au [Australian Centre for Microscopy and Microanalysis, and School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Ringer, Simon P., E-mail: simon.ringer@sydney.edu.au [Australian Centre for Microscopy and Microanalysis, and School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Pereloma, Elena V., E-mail: elenap@uow.edu.au [School of Mechanical, Materials and Mechatronic Engineering, The University of Wollongong, NSW 2522 (Australia)

    2013-10-01

    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.

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

    International Nuclear Information System (INIS)

    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

  9. Characterization and understanding of ion irradiation effect on the microstructure of austenitic stainless steels

    International Nuclear Information System (INIS)

    Austenitic stainless steels are widely used in nuclear industry for internal structures. These structures are located close to the fuel assemblies, inside the pressure vessel. The exposure of these elements to high irradiation doses (the accumulated dose, after 40 years of operation, can reach 80 dpa), at temperature close to 350 C, modifies the macroscopic behavior of the steel: hardening, swelling, creep and corrosion are observed. Moreover, in-service inspections of some of the reactor internal structures have revealed the cracking of some baffle bolts. This cracking has been attributed to Irradiation Assisted Stress Corrosion Cracking (IASCC). In order to understand this complex phenomenon, a first step is to identify the microstructural changes occurring during irradiation, and to understand the mechanisms at the origin of this evolution. In this framework, a large part of the European project 'PERFORM 60' is dedicated to the study of the irradiation damage in austenitic stainless steels. The objective of this PhD work is to bring comprehensive data on the irradiation effects on microstructure. To reach this goal, two model alloys (FeNiCr and FeNiCrSi) and an industrial austenitic stainless steel (316 steel) are studied using Atom Probe Tomography (APT), Transmission Electron Microscope (TEM) and Positron Annihilation Spectroscopy (PAS). They are irradiated by Ni ions in CSNSM (Orsay) at two temperatures (200 and 450 C) and three doses (0.5, 1 and 5 dpa). TEM observations have shown the appearance of dislocation loops, cavities and staking fault tetrahedra. The dislocation loops in 316 steel were preferentially situated in the vicinity of dislocations, while they were randomly distributed in the FeNiCr alloy. APT study has shown the redistribution of Ni and Si under irradiation in FeNiCrSi model alloy and 316 steel, leading to the appearance of (a) Cottrell clouds along dislocation lines, dislocation loops and other non-identified crystalline defects and (b

  10. 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 ...

  11. Characterization of Austenite Dynamic Recrystallization under Different Z Parameters in a Microalloyed Steel

    Institute of Scientific and Technical Information of China (English)

    M. Shaban; B. Eghbali

    2011-01-01

    A low carbon Nb-Ti microalloyed steel was subjected to hot torsion testing over the temperature range 850-1100℃ and strain rates 0.01-1 s-1 to study the influence of deformation conditions on the dynamic recrystallization characteristics of austenite. The results show that dynamic recrystallization occurs more easily with the decrease of strain rate and the increase of deformation temperature. The complete dynamically recrystallized grain size as a function of Zener-Hollomon parameter was established. It was found that dynamically recrystallized grain sizes decrease with increasing strain rate and decreasing deformation temperature. The effect of microalloying elements on peak strain was investigated and the solute drag corrected peak strain was determined. Also, the dynamic recrystallization map of austenite was obtained by using recrystallization critical parameters.

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

    Institute of Scientific and Technical Information of China (English)

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

    2002-01-01

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

  13. Characteristics of low nickel ferritic-austenitic corrosion resistant cast steel

    Directory of Open Access Journals (Sweden)

    B. Kalandyk

    2014-10-01

    Full Text Available The article presents the results of microscopic examinations of corrosion resistant cast steel with reduced nickel content obtained in a test casting with varying wall thickness. Investigations were carried out in as-cast condition and after heat treatment. Regardless of the casting wall thickness, increasing the manganese and nitrogen content to about 5 % and 2 500 ppm, respectively, yields the material with a two-phase microstructure containing ferrite in an amount of 55,6 ÷ 57,2 % (magnetic method and 52,3 ÷ 55,2 % (analytical method. Based on the results of metallographic examinations, total elimination of the secondary austenite from the microstructure was observed. Microhardness measurements showed average values of 352,3 μHV20 and 267 μHV20 for the chromium ferrite and austenite, respectively.

  14. Thermal property characterization of a titanium modified austenitic stainless steel (alloy D9)

    Energy Technology Data Exchange (ETDEWEB)

    Banerjee, Aritra [Physical Metallurgy Section, Materials Characterisation Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Raju, S. [Physical Metallurgy Section, Materials Characterisation Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India)]. E-mail: sraju@igcar.ernet.in; Divakar, R. [Physical Metallurgy Section, Materials Characterisation Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Mohandas, E. [Physical Metallurgy Section, Materials Characterisation Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Panneerselvam, G. [Fuel Chemistry Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Antony, M.P. [Fuel Chemistry Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India)

    2005-12-01

    The temperature dependence of lattice parameter and enthalpy increment of alloy D9, a titanium modified nuclear grade austenitic stainless steel were studied using high temperature X-ray diffraction and inverse drop calorimetry techniques, respectively. A smooth variation of the lattice parameter of the austenite with temperature was found. The instantaneous and mean linear thermal expansion coefficients at 1350 K were estimated to be 2.12 x 10{sup -5} K{sup -1} and 1.72 x 10{sup -5} K{sup -1}, respectively. The measured enthalpy data were made use of in estimating heat capacity, entropy and Gibbs energy values. The estimated isobaric heat capacity C {sub p} at 298 K was found to be 406 J kg{sup -1} K{sup -1}. An integrated theoretical analysis of the thermal expansion and enthalpy data was performed to obtain approximate values of bulk modulus as a function of temperature.

  15. Measurement of thickness of austenitic overlays on carbon steel walls using a magnetic method

    International Nuclear Information System (INIS)

    Mechanical and magnetic methods are used for measuring the thickness of austenitic overlays on the walls of carbon steel pressure vessels. Specific problems pertaining to the magnetic methods are briefly discussed. A magnetic thickness gage has been developed for overlays using the principle of ferrite effect suppression. Thickness gaging is done by aligning the gage with the layer to be measured on the overlay side. Basic accuracy of the instrument is 7% for overlays containing 2 to 8% ferrite. For the ferrite content 0 to 2% or 8 to 10%, accuracy reduces to roughly 12%. The method is simple, reliable and versatile during the manufacture of a pressure vessel and after it is finished. The economic benefit is considerable because it allows overlaying of a thickness which practically is without reserve; each millimeter of the austenitic layer thickness on the pressure vessel costs more than a million Czechoslovak crowns. (Z.M.). 7 figs., 5 refs

  16. 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...... obtained by low-temperature gaseous carburizing of AISI 316. X-ray diffraction was applied for the determination of lattice spacing depth profiles by destructive depth profiling and reconstruction of the original lattice spacing profiles from the measured, diffracted intensity weighted, values. The...... compressive stress depth distributions correlate with the depth distribution of the strain-free lattice parameter, the latter being a measure for the depth distribution of carbon in expanded austenite. Elastically accommodated compressive stress values as high as -2.7 GPa were obtained, which exceeds the...

  17. 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)

  18. In-Situ Austenite Steel Matrix Composite Reinforced by Granular γ+(Fe,Mn)3C Eutectic

    Institute of Scientific and Technical Information of China (English)

    LIANG Gao-fei; XU Zhen-ming; JIANG Qi-chuan; LI Jian-guo

    2004-01-01

    A new in-situ austenite matrix composite reinforced by granular γ+(Fe, Mn)3C binary eutectics (abbreviated to in-situ AMGE) was prepared in as-cast state, in which the modifier, yttrium-based heavy rare earth alloy, was used to influence carbon segregation, manganese segregation and phase formation. The eutectics are formed in the molten pools among austenite dendrites at the later stage of non-equilibrium solidification because the modifier enhances carbon segregation and manganese segregation greatly. Pin-on-disc dry wear tests show that the wear resistance of in-situ AMGE is 1-3 times higher than that of austenite medium manganese steel under low and medium loads, and the loads under which serious wear of in-situ AMGE occurs are much higher than that of austenite medium manganese steel.

  19. 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.

  20. Development of a System to Measure Austenite Grain Size of Plate Steel Using Laser-Based Ultrasonics

    International Nuclear Information System (INIS)

    A measurement system for austenite grain size of plate steel using laser-based ultrasonics has been developed. At first, the relationship between the ultrasonic attenuation coefficients using longitudinal waves and austenite grain size of samples was investigated in the laboratory experiments. According to the experimental results, the ultrasonic attenuation coefficients showed a good correlation with actual austenite grain sizes. For the next step, the system was installed in a hot rolling pilot plant of plate steel, and it was verified that the austenite grain size could be measured even in the environment of a hot rolling pilot plant. In the experiments, it was also confirmed that the fiber delivery system could deliver Nd:YAG laser beam of 810 mJ/pulse and ultrasonic signals could be obtained successfully

  1. Effects of Cr - Ni 18/9 Austenitic Cast Steel Modification by Mischmetal

    Directory of Open Access Journals (Sweden)

    M. Gajewski

    2012-12-01

    Full Text Available This paper presents the results of Cr - Ni 18/9 austenitic cast steel modifications by mischmetal. The study was conducted on industrial melts. Cast steel was melted in an electric induction furnace with a capacity of 2000 kg and a basic lining crucible. .The mischmetal was introduced into the ladle during tapping of the cast steel from the furnace. The effectiveness of modification was examined with the carbon content of 0.1% and the presence of δ ferrite in the structure of cast steel stabilized with titanium. The changes in the structure of cast steel and their effect on mechanical properties and intergranular corrosion were studied. It was found that rare earth metals decrease the sulfurcontent in cast steel and above all, they cause a distinct change in morphology of the δ ferrite and non-metallic inclusions. These changes have improved mechanical properties. R02, Rm, and A5 and toughness increased significantly. There was a great increase of the resistance to intergranular corrosion in the Huey test. The study confirmed the high efficiency of cast steel modification by mischmetal in industrial environments. The final effect of modification depends on the form and manner of placing mischmetal into the liquid metal and the melting technology, ie the degree of deoxidation and desulfurization of the metal in the furnace.

  2. 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)

  3. Influence of localized deformation on A-286 austenitic stainless steel stress corrosion cracking in PWR primary water

    International Nuclear Information System (INIS)

    Irradiation-assisted stress corrosion cracking (IASCC) of austenitic stainless steels is known to be a critical issue for structural components of nuclear reactor cores. The deformation of irradiated austenitic stainless steels is extremely heterogeneous and localized in deformation bands that may play a significant role in IASCC. In this study, an original approach is proposed to determine the influence of localized deformation on austenitic stainless steels SCC in simulated PWR primary water. The approach consists in (i) performing low cycle fatigue tests on austenitic stainless steel A-286 strengthened by γ' precipitates Ni3(Ti,Al) in order to shear and dissolve the precipitates in intense slip bands, leading to a localization of the deformation within and in (ii) assessing the influence of these γ'-free localized deformation bands on A-286 SCC by means of comparative CERT tests performed on specimens with similar yield strength, containing or not γ'-free localized deformation bands. Results show that strain localization significantly promotes A-286 SCC in simulated PWR primary water at 320 and 360 C. Moreover, A-286 is a precipitation-hardening austenitic stainless steel used for applications in light water reactors. The second objective of this work is to gain insights into the influence of heat treatment and metallurgical structure on A-286 SCC susceptibility in PWR primary water. The results obtained demonstrate a strong correlation between yield strength and SCC susceptibility of A-286 in PWR primary water at 320 and 360 C. (author)

  4. Quantitative prediction of deformed austenite and transformed ferrite texture in hot-rolled steel sheet

    Science.gov (United States)

    Tanaka, Y.; Tomida, T.; Mohles, V.

    2015-04-01

    A model to quantitatively predict ferrite (α) textures in hot-rolled steel sheets has been developed. In this model, the crystal plasticity model, called “Grain Interaction model (GIA)”, and the transformation texture model, called “Double K-S relation (DKS)”, are linked together. The deformed austenite (γ) texture is predicted by GIA with taking not only the standard {111} slip system but also non-octahedral slip systems into account. Then the transformed a texture is calculated by DKS, in which a nucleated α prefers to have orientation relationship near the Kurdjumov-Sachs relation with both of two neighboring γ grains. For validation, single pass hot-rolling tests on a C-Si-Mn steel were carried out. The comparison between the predicted and the experimental textures shows that the linked model (GIA & DKS) can lead to a remarkable reproduction of the texture of hot-rolled steel sheets.

  5. Suggested solutions to improve the surface hardness of austenitic stainless steels without loosing their corrosion resistance

    International Nuclear Information System (INIS)

    Ionic nitridation is a process which is already used industrially. Indeed, by nitrogen diffusion, it is possible to harden the surfaces and then to improve the wear, seizure, and fatigue resistances. Nevertheless, the direct application to stainless steels induces a strong degradation of their un-oxidizable character. But this process can be optimized in order to maintain a good oxidation resistance. One way consists to work with a nitrogen plasma or with a carbon plasma. The materials properties obtained with a nitrogen plasma are discussed. Example of control elements of a PWR type reactor are given. This process is then compared with those whose plasma is a carbon plasma. According to the studied process, it is possible to increase the wear resistance of the austenitic stainless steel by a factor of 60 to 700 while entirely conserving the corrosion resistance of the untreated steel. (O.M.)

  6. ESD morphology deposition with WZr8 electrode on austenitic stainless steel support

    Science.gov (United States)

    Perju, M. C.; Ţugui, C. A.; Nejneru, C.; Axinte, M.; Vizureanu, P.

    2016-06-01

    Stainless steels are used to obtain mechanical parts, working in severe conditions with high dynamic loads in wet, chemically active environments. For this reason, these materials have good corrosion resistance in acidic or basic chemical agents. The main drawback is the relatively low wear and resistance to mechanical stress. This paper proposes a remedy by deposition of the hard thin films of tungsten electrode by spark electro-deposition method (ESD). Tungsten is an alfagen element and causes an increase for the mechanical properties at high and low temperatures for the austenitic stainless steels. Tungsten does not alter the corrosion resistance of stainless steels. The morphology for the obtained layers was analyzed using SEM, in 3D images, and profilographs.

  7. Study of austenitic stainless steel creep between 5500C and 6500C

    International Nuclear Information System (INIS)

    This work is a contribution to identification and analysis of microscopic mechanisms of creep damages in austenitic stainless steels used for steam generators of fast neutron reactors. Statistical analysis of slip at the grain boundaries and tests on polycrystalline of alloy 800 grade II indicate the role of structural parameters: matrix reinforcement and boundary slip. Microstructure analysis shows the deformation mechanisms and the differences between steel 316 and alloy 800. In situ tests on bicrystalline samples of steel ZCN17/13 show the event chronology. Characteristic data on damaging at the nanometer scale (cavity size, crack dimensions) are determined. From these results a beginning of simulation is attempted for the two types of damage. 67 refs

  8. Corrosion studies of austenitic and duplex stainless steels in aqueous lithium bromide solution at different temperatures

    International Nuclear Information System (INIS)

    The corrosion behavior of three stainless steels EN 14311, EN 14429 (austenitic stainless steels) and EN 14462 (duplex stainless steel) was studied in a commercial LiBr solution (850 g/l LiBr solution containing chromate as inhibitor) at different temperatures (25, 50, 75 and 85 deg C) by electrochemical methods. Open circuit potentials shifted towards more active values as temperature increased, while corrosion potentials presented the opposite tendency. The most resistant alloys to general corrosion were EN 14429 and EN 14462 because they had the lowest corrosion current for all temperatures. In all the cases corrosion current increases with temperature. Pitting corrosion resistance is improved by the EN 14462, which presented the highest pitting potential, and the lowest passivation current for the whole range of temperatures studied. The duplex alloy also presents the worst repassivation behavior (in terms of the narrowest difference between corrosion potential and pitting potential); it does not repassivate from 50 deg C

  9. On low temperature ion nitriding of austenitic stainless steel AISI 316

    Directory of Open Access Journals (Sweden)

    R. Russev

    2007-11-01

    Full Text Available Purpose: The purpose of this paper is to discuss some problems concerning the extremely high values of the nitride layer hardness and the features of so called S-phase which are formed after low-temperature ion nitriding of high-alloyed austenitic (austenitic-ferritic steels.Design/methodology/approach: The investigations are performed mainly by using of ray diffraction method after ion nitrided 316 (AISI steel.Findings: As a result of the work some data, concerning the structure and substructure, the phase composition of the S-phase, crystal lattice, the broadening of diffraction reflexes, mechanism of transformation of γ'- phase into S-phase, its high hardness etc. of the nitrided layer are obtained. It could be concluded that S-phase could be classified as a modified γ’-phase. The extremely high values of the hardness could be explained by the high nitrogen concentration in the solid solution and by the presence of increased density of the defects in the austenitic volume, which is transformed in the new S-phase.Research limitations/implications: The potencionstatic investigations of the electrochemical properties of the nitriding probes, performed by us, confirmed the data, obtained by the literature, but this problem will be discussed in some of the next publications.Originality/value: The high micro- and macro-deformations of the lattice of S-phase could be explained by the considerable registered expansions and the angle replacements of the slope (ψ on the ray diffraction maxima. The registered macro deformations could reach immense values, in the range of (1.4 – 2.1�10-2, which corresponds to macro deformations around 1900 – 2300 MPa (if we accept, for the austenite, the usual module of elasticity of 2.1�105 MPa. For such final decision it is necessary to obtain also some other confirmation facts.

  10. Tearing resistance of aged cast austenitic stainless steels

    International Nuclear Information System (INIS)

    CF8 and CF8M type cast stainless steels containing about 10 to 25 % ferrite are used in the primary piping of light water reactors (PWRs and BWRs). It is now recognized that these materials are embrittled by thermal aging at the operating temperature (between 2900C and 3300C), mainly due to precipitation hardening of the ferrite by α', and other phases. Extensive research programs are under way in several countries to better understand the mechanisms of embrittlement and to determine the mechanical properties of components as a function of aging time and temperature. In earlier studies thermal aging embrittlement was mainly characterized by the evolutions of the tensile and Charpy impact properties. However the evaluation of reactor coolant circuit integrity through mechanical analyses requires the knowledge of fracture toughness properties. The first measurements of the tearing resistance of a CF8M type severely aged material were presented in 1983 by SLAMA, PETREQUIN and MAGER. Other contributions to the knowledge of the fracture toughness of aged materials were published, but were relative to medium or high toughness materials. The objective of this paper is to present the results of tearing resistance measurements made on a large spectrum of severely embrittled materials, which allow to give lower bound properties for aged CF8 and CF8M type cast stainless steels

  11. 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

  12. Effect of Free Surface on the Stability of Individual Retained Austenite Grains in a Duplex Stainless Steel

    Science.gov (United States)

    He, B. B.; Huang, M. X.; Ngan, A. H. W.; van der Zwaag, S.

    2014-10-01

    The present work explored the effect of free surface on the stability of individual austenite grains in a duplex stainless steel. It was found that martensitic transformation took place automatically in the retained austenite grain when a free surface was introduced. This is due to the fact that the martensite nucleation energy barrier can be lowered to a thermally surmountable value as the strain energy induced by martensitic transformation is largely lowered when the matrix constraints were removed.

  13. Energy absorption behaviour of austenitic and duplex stainless steels in a crash box geometry

    Energy Technology Data Exchange (ETDEWEB)

    Ratte, E.; Bleck, W. [Dept. of Ferrous Metallurgy, RWTH Aachen Univ., Aachen (Germany); Leonhardt, S. [Honda R und D Europe (Deutschland), Offenbach/ Main (Germany); Franzen, M.; Urban, P. [Inst. fuer Kraftfahrwesen, RWTH Aachen Univ., Aachen (Germany)

    2006-09-15

    The improvement of the passive safety plays an important role in the development of new steels for automotive parts. At the same time aspects of weight reduction as well as the industrial feasibility have to be considered. Powered by these objectives, the development and application of new steel concepts for various purposes is promoted. For the present investigation especially weight reduction combined with an improvement of the passive safety are emphasised. As example one representative part of the body structure, the crash box, is considered. At the moment different steel grades (dual phase-, TRIP-and HSLA-steels) as well as fibre reinforced materials are applied. New materials for this special purpose have to exhibit outstanding formability, a high capacity to absorb energy during a possible crash and should be cost effective compared to already existing material concepts. During this project different grades of austenitic stainless steels with varying stability were compared to duplex stainless steels and a TRIP grade with regard to their possible application as crash-box material. The austenitic grades show excellent gradual formability according to their strength level. All of them exhibit an extraordinary strain hardening behaviour. The duplex grades show a lower formability but on a much higher yield level. Besides the determination of classical material data such as uni- and multi-axial flow curves, dynamic tensile tests and forming tests for the determination of forming limit curves were performed. The material data were used in the simulation of a drop tower test which is commonly used to evaluate the performance of different materials in car components. The results were then evaluated with regard to the absorbed energy, the folding behaviour and the resulting forces. (orig.)

  14. Assessment of Retained Austenite in AISI D2 Tool Steel Using Magnetic Hysteresis and Barkhausen Noise Parameters

    Science.gov (United States)

    Kahrobaee, Saeed; Kashefi, Mehrdad

    2015-03-01

    Inaccurate heat treatment process could result in excessive amount of retained austenite, which degrades the mechanical properties, like strength, wear resistance, and hardness of cold work tool steel parts. Thus, to control the mechanical properties, quantitative measurement of the retained austenite is a critical step in optimizing the heat-treating parameters. X-ray diffraction method is the most frequently used technique for this purpose. This technique is, however, destructive and time consuming. Furthermore, it is not applicable to 100% quality inspection of industrial parts. In the present paper, the influence of austenitizing temperature on the retained austenite content and hardness of AISI D2 tool steel has been studied. Additionally, nondestructive magnetic hysteresis parameters of the samples including coercivity, magnetic saturation, and maximum differential permeability as well as their magnetic Barkhausen noise features (RMS peak voltage and peak position) have been investigated. The results revealed direct relations between magnetic saturation, differential permeability, and MBN peak amplitude with increasing austenitizing temperature due to the retained austenite formation. Besides, both parameters of coercivity and peak position had an inverse correlation with the retained austenite fraction.

  15. Experimental study of behavior and functional capability of ferritic steel elbows and austenitic stainless steel thin-walled elbows

    International Nuclear Information System (INIS)

    The results are presented of two series of tests performed on 900 large-radius elbows. A first series of 10 tests was conducted on TU 42 C (equivalent to ASME SA 106 grade B) ferritic steel elbows with an outside diameter-to-wall thickness ratio of 6.7. A second series of 15 tests was conducted on Z2 CN 18-10 (equivalent to ASME TP 304 L) austenitic stainless steel elbows with an outside diameter-to-wall thickness ratio of 90. These elbows were subjected to in-plane (opening and closing) and out-of-plane bending moments. Changes in elbow angular deflection and ovalization of the mid-section were recorded as a function of applied moment. Measurements were made well into the plastic region. Influence of pressure, temperature and cyclic loading was also studied. The tests supplied extensive data on the behaviour of thin-walled austenitic stainless steel elbows when subjected to large displacements, including ability of the elbow to carry the flow under high loadings. Analysis in accordance with the requirements of the RCC-M1 was also performed to quantify flow area reduction at stress limits allowed by these rules, in addition to the displacement amplitude margin allowed by the level D service limit criteria with respect to the experimental limit moment. A criteria is proposed which aims to limit secondary stresses under faulted conditions. (author)

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

    International Nuclear Information System (INIS)

    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

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

    International Nuclear Information System (INIS)

    The stress relaxation behavior of 304 and 316 stainless steels during cyclic deformation at 538 and 6500C 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 6500C 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 5380C, the internal stress in 304 is nonzero and microstructural recovery appears minimal. In 316 tested at 6500C 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

  18. Fatigue crack growth in austenitic stainless steel piping

    International Nuclear Information System (INIS)

    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

  19. On the Stress Corrosion Cracking and Hydrogen Embrittlement Behavior of Austenitic Stainless Steels in Boiling Saturated Magnesium Chloride Solutions

    OpenAIRE

    Alyousif, Osama M.; Rokuro Nishimura

    2012-01-01

    The stress corrosion cracking (SCC) and hydrogen embrittlement (HE) behaviors for types 304, 310, and 316 austenitic stainless steels were investigated in boiling saturated magnesium chloride solutions using a constant load method under different conditions including test temperature, applied stress, and sensitization. Both of type 304 and type 316 stainless steels showed quite similar behavior characteristics, whereas type 310 stainless steel showed a different behavior. The time to failure ...

  20. Effect of Austenite Stability on Microstructural Evolution and Tensile Properties in Intercritically Annealed Medium-Mn Lightweight Steels

    Science.gov (United States)

    Song, Hyejin; Sohn, Seok Su; Kwak, Jai-Hyun; Lee, Byeong-Joo; Lee, Sunghak

    2016-06-01

    The microstructural evolution with varying intercritical-annealing temperatures of medium-Mn ( α + γ) duplex lightweight steels and its effects on tensile properties were investigated in relation to the stability of austenite. The size and volume fraction of austenite grains increased as the annealing temperature increased from 1123 K to 1173 K (850 °C to 900 °C), which corresponded with the thermodynamic calculation data. When the annealing temperature increased further to 1223 K (950 °C), the size and volume fraction were reduced by the formation of athermal α'-martensite during the cooling because the thermal stability of austenite deteriorated as a result of the decrease in C and Mn contents. In order to obtain the best combination of strength and ductility by a transformation-induced plasticity (TRIP) mechanism, an appropriate mechanical stability of austenite was needed and could be achieved when fine austenite grains (size: 1.4 μm, volume fraction: 0.26) were homogenously distributed in the ferrite matrix, as in the 1123 K (850 °C)—annealed steel. This best combination was attributed to the requirement of sufficient deformation for TRIP and the formation of many deformation bands at ferrite grains in both austenite and ferrite bands. Since this medium-Mn lightweight steel has excellent tensile properties as well as reduced alloying costs and weight savings, it holds promise for new automotive applications.

  1. Pearlite transformation in high carbon steels deformed in metastable austenite region; Jun`antei austenite iki de kakoshita kotansoko no pearlite hentai

    Energy Technology Data Exchange (ETDEWEB)

    Daito, Y.; Aihara, K.; Nishizawa, T. [Sumitomo Metal Industries, Ltd., Osaka (Japan)

    1997-09-01

    Pearlite structure was discussed noticing particularly on the state of nucleus composition, for the case when high carbon steels mainly structured by pearlite was processed in metastable austenite region below the point A1 which is thought a non-recrystallized region. When the processing amount is increased in the metastable austenite region, the size of pearlite colonies decreased. This is because of increase in nucleus producing site as a result of the processing. Even with a steel of eutectoid carbon concentration of an equilibrium diagram, proeuctoid ferrite is produced if the processing is given in the metastable austenite region. Furthermore, the production amount of the proeuctoid ferrite increased with increasing processing amount. If the processing is given in the metastable austenite region, the region that becomes a single pearlite structure shifted to hypereuctoid carbon concentration side as the transformation temperature has fallen. The result of an experiment performed in carbon concentration at which the single pearlite structure is obtained agreed well with drive force equilibrium line of ferrite and cementite as calculated based on the Gibbs energy. 18 refs., 11 figs., 1 tab.

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

    International Nuclear Information System (INIS)

    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

  3. Nitrogen segregation and blister formation of 316LN austenitic steels during electron beam welding

    International Nuclear Information System (INIS)

    Full text of publication follows: High nitrogen austenitic stainless steel (316LN) has been selected as the structure material in shield blanket and the gravity support system in ITER due to its excellent erosion/corrosion resistance, high strength and toughness. However, most of nitrogen in this steel exists in the form of solid solution. The nitrogen can segregate from the matrix material and form small blisters or defects in the welding area, resulting in mechanical property reduction, which should be considered in the design and manufacture processing. In this study, we have investigated the blister and defect formation processing during electron beam welding. Focused electron beam with 100-150 kV high voltage, 300-500 mA beam current has been applied to weld the 316LN austenitic stainless steel components under vacuum condition. The blister formation in the welding area has been observed by both SEM and TEM directly, and was further confirmed by the micro-area composition analysis. The size and density distribution of blisters and defects with the welding depth, the vacuum condition and electron beam parameters has been investigated. At the same time, the tensile strength of the welded components was examined and compared with that of the matrix material. In this report, the mechanism of nitrogen blisters formation and its effects on the mechanical property of the welding components has also been discussed. (authors)

  4. Development of nickel-free austenitic stainless steels for ambient and cryogenic applications

    Energy Technology Data Exchange (ETDEWEB)

    Haddick, G.T.; Thompson, L.D.; Parker, E.R.; Zackay, V.F.

    1978-02-01

    A series of alloys have been developed as possible replacements for some austenitic stainless steels. These alloys utilized a Mn substitution for Ni and a reduced Cr concentration from the 18% ordinarily found in the AISI 300 series stainless steels to a concentration of 13%. The base system studied was an alloy containing Fe-16%Mn-13%Cr while other elements added included small additions of N, Si and Mo. A range of microstructures was produced from the alloying additions. The base composition had a triplex (fcc, hcp, bcc) structure while the most highly modified compositions were fully austenitic. Mechanical testing included tensile testing and Charpy V-notch testing conducted at various temperatures between -196/sup 0/C to 23/sup 0/C. Excellent combinations of strength and ductility were obtained (40--65 ksi yield strength, 100--125 ksi ultimate strength, 45--75% elongation and 60--80% reduction of area) at room temperature. Upper shelf energies in Charpy V-notch testing were as high as 185 ft-lbs with a ductile-brittle transition temperature (DBTT) of -160/sup 0/C. Analysis of fracture surfaces determined that alloys without interstitials had no transition in the mode of failure between room temperature and liquid nitrogen temperature. Results of an ASTM sensitization corrosion test, where the experimental alloys were compared to 347 stainless steel, indicated that the alloys were not susceptible to intergranular attack.

  5. Stress corrosion cracking behaviour of gas tungsten arc welded super austenitic stainless steel joints

    Directory of Open Access Journals (Sweden)

    M. Vinoth Kumar

    2015-09-01

    Full Text Available Super 304H austenitic stainless steel with 3% of copper posses excellent creep strength and corrosion resistance, which is mainly used in heat exchanger tubing of the boiler. Heat exchangers are used in nuclear power plants and marine vehicles which are intended to operate in chloride rich offshore environment. Chloride stress corrosion cracking is the most likely life limiting failure with austenitic stainless steel tubing. Welding may worsen the stress corrosion cracking susceptibility of the material. Stress corrosion cracking susceptibility of Super 304H parent metal and gas tungsten arc (GTA welded joints were studied by constant load tests in 45% boiling MgCl2 solution. Stress corrosion cracking resistance of Super 304H stainless steel was deteriorated by GTA welding due to the formation of susceptible microstructure in the HAZ of the weld joint and the residual stresses. The mechanism of cracking was found to be anodic path cracking, with transgranular nature of crack propagation. Linear relationships were derived to predict the time to failure by extrapolating the rate of steady state elongation.

  6. Repair welding of cracked steam turbine blades using austenitic and martensitic stainless-steel consumables

    International Nuclear Information System (INIS)

    The procedure for repair welding of cracked steam turbine blades made of martensitic stainless steels has been developed using the gas tungsten arc welding process. Weld repair procedures were developed using both ER 316L austenitic and ER 410 martensitic stainless-steel filler wire. The overall development of the repair welding procedure included selection of welding consumables (for austenitic filler metal), optimisation of post-weld heat treatment parameters, selection of suitable method for local pre-heating and post-weld heat treatment (PWHT) of the blades, determination of mechanical properties of weldments in as-welded and PWHT conditions, and microsturctural examination. After various trials using different procedures, the procedure of local PWHT (and preheating when using martensitic stainless-steel filler wire) using electrical resistance heating on the top surface of the weldment and monitoring the temperature by placing a thermocouple at the bottom of the weld was found to give the most satisfactory results. These procedures have been developed and/or applied for repair welding of cracked blades in steam turbines

  7. Repair welding of cracked steam turbine blades using austenitic and martensitic stainless-steel consumables

    Energy Technology Data Exchange (ETDEWEB)

    Bhaduri, A.K. E-mail: bhaduri@igcar.ernet.in; Gill, T.P.S.; Albert, S.K.; Shanmugam, K.; Iyer, D.R

    2001-06-01

    The procedure for repair welding of cracked steam turbine blades made of martensitic stainless steels has been developed using the gas tungsten arc welding process. Weld repair procedures were developed using both ER 316L austenitic and ER 410 martensitic stainless-steel filler wire. The overall development of the repair welding procedure included selection of welding consumables (for austenitic filler metal), optimisation of post-weld heat treatment parameters, selection of suitable method for local pre-heating and post-weld heat treatment (PWHT) of the blades, determination of mechanical properties of weldments in as-welded and PWHT conditions, and microsturctural examination. After various trials using different procedures, the procedure of local PWHT (and preheating when using martensitic stainless-steel filler wire) using electrical resistance heating on the top surface of the weldment and monitoring the temperature by placing a thermocouple at the bottom of the weld was found to give the most satisfactory results. These procedures have been developed and/or applied for repair welding of cracked blades in steam turbines.

  8. Titanium diffusion coatings on austenitic steel obtained by the pack cementation method

    Directory of Open Access Journals (Sweden)

    MIRELA BRITCHI

    2009-02-01

    Full Text Available The surface of specimens made of 316L austenitic steel was modified by titanium diffusion. The diffusion coatings were obtained by packing in a powder mixture consisting of titanium powder, NH4Cl and Al2O3 powder. The procedure required high temperatures, over 900 °C, and long durations. Atomic titanium was formed in the muffle during the process. Titanium atoms from the metallic part surfaces diffuse towards the interior and a diffusion layer is formed as a function of the steel composition. Titanium diffusion into the surface of 316L austenitic steel determines the formation of a complex coating: a thin layer of TiN at the exterior and a layer consisting of compounds containing Ti, Ni and Fe in the interior of the coating. The obtained coatings were continuous, adherent and had a hardness higher than that of the substrate material. The diffusion coatings were investigated by optical and electron microscopy, X-ray diffraction and Vickers microhardness tests.

  9. 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 ||TA (tensile axis) and ||TA were twin free and grain with ||TA and grains oriented close to a Schmid factor maximum contained deformation twins.

  10. Notch tensile measurements and fracture toughness correlations for austenitic stainless steels

    International Nuclear Information System (INIS)

    Thirty-two alloys were included in a study of conventional notch tensile testing as a method of fracture toughness characterization for austenitic stainless steels at liquid helium temperature, 4 K. For the same austenitic stainless steels, tensile and J-integral fracture toughness (K/sub Ic/(J)) measurements have also been conducted. For these materials the notch tensile strength (sigma/sub NTS) generally increases with yield strength (sigma/sub y/), and the contains/sub NTS//sigma/sub y/ ratios are typically much greater than 1.0. Correlations between sigma/sub NTS/, K/sub Ic/(J), and sigma/sub y/ were assessed. The best data fit was found between the ratio, sigma/NTS/K/sub Ic/(J), and the toughness, K/sub Ic/(J). Unfortunately, from this relation there is not uniqueness of K/sub Ic/ from sigma/sub NTS/. Therefore at this time it is not considered practical to obtain estimates of K/sub Ic/ from notch tensile tests for austenitic steels at 4 K. However, one may compare the J-integral fracture toughness and cylindrical bar notch tensile measurements. There are three regions: (1) linear elastic (sigma/sub NTS/ increases as K/sub Ic/(J) increases); (2) elastic-plastic (sigma/sub NTS/ is essentially independent of K/sub Ic/(J); (3) plastic (sigma/sub NTS/ decreases as K/sub Ic/(J) increases. The elastic-plastic (transition) region is associated with a plastic zone that extends completely through the notched cross-sectional area

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

    Science.gov (United States)

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

    2015-06-01

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

  12. The effect of austenitizing temperature in C.O.D. initial values of Niocor 2 steel of two different niobium contents

    International Nuclear Information System (INIS)

    The effect of the austenitizing temperature on the fracture toughness of Niocar 2 steel of two different niobium contents (0,04 and 0,16%) was studied by means of C.O.D. testing. Except for very elevated austenitizing temperatures (12500C), C.O.D. values for initiation were shown to be higher for the high niobium steel. The decrease in toughness associated with elevated austenitizing temperatures is attributed to the presence of acicular phase transformation products. (Author)

  13. Effect of Silicon on the Microstructures and Tensile Properties of Austenitic ODS Stainless Steels for Fast Reactor Cladding

    International Nuclear Information System (INIS)

    Oxide dispersion strengthened (ODS) steels have excellent high temperature mechanical properties due to the presence of thermally stable nano-scale oxides distributed in their matrix. Therefore, ODS steels are being used for high temperature structural applications and ODS ferritic martensitic steels (FMS) have been considered as candidate cladding and. Generally, fabrication processes of ODS steels have incorporated a mechanical alloying (MA) process, in which repeated fracture and welding of mixed powders occur by a high energy impact of steel balls. Although MA has many advantages in forming a nano-scale microstructure, it is a very long-time expensive process and vulnerable to impurities contamination. High oxygen and carbon contents degrade the high temperature strength and creep strength of ODS steels. To overcome the problem of MA process, AISI 316Lbased austenitic ODS steels were fabricated by a wet mixing of metallic salts. This method dispersed oxide particles by thermal decomposition of metallic salt during fabrication process. Austenitic ODS steel could be fabricated successfully by a wet-mixing process of 316L stainless steel powder in yttrium containing salt solution. Wet-mixed ODS steel had lower carbon and oxygen contents than that of MAODs steel, because minimum inflow of carbon and oxygen during the manufacture process was kept in wet-mixed ODS steel. Ryu. et. al was reported that yttrium silicates were formed by reaction of silicon and yttrium oxide during the fabrication process. In this study, we made simulated 316 stainless steel powder without adding silicon by using MA and then fabricated ODS steel by using a wet process in order to analyze the effect of silicon on the microstructures and tensile properties of the austenitic ODS stainless steels

  14. Fracture behavior of neutron-irradiated high-manganese austenitic steels

    International Nuclear Information System (INIS)

    The instrumented Charpy impact test was applied to study the fracture behavior of high-manganese austenitic steels before and after neutron irradiations. Quarter-size specimens of a commercial high-manganese steel (18% Mn-5% Ni-16% Cr), three reference steels (21% Mn-1% Ni-9% Cr, 20% Mn-1% Ni-11% Cr, 15% Mn-1% Ni-14% Cr) and two model steels (17% Mn-4.5% Si-6.5% Cr, 22% Mn-4.5% Si-6.5% Cr-0.2% N) were used for the impact tests at temperatures between 77 and 523 K. The load-deflection curves showed typical features corresponding to characteristics of the fracture properties. The temperature dependences of fracture energy and failure deflection obtained from the curves clearly demonstrate only small effects up to 2x1023 n/m2 (E > 0.1 MeV) and brittleness at room temperature in 17% Mn-Si-Cr steel at 1.6x1025 n/m2 (E > 0.1 MeV), while ductility still remains in 22% Mn-Si-Cr steel. (orig.)

  15. The effect of phosphorus on the radiation induced microstructure of stabilized austenitic stainless steels

    International Nuclear Information System (INIS)

    This paper deals with the correlation of irradiation behavior and microstructural evolution of mono-(Ti) and multi-(Ti,Nb,V) stabilized type 316 stainless steels with different phosphorus levels. These steels, in the 20% cold worked condition, were irradiated between 400 and 5000C up to 100 dpa in Phenix reactor as stressed and unstressed samples. Phosphorus decreases strongly the swelling of stabilized austenitic steels. This effect is due to a large increase of the swelling incubation dose. The best swelling resistance is observed for the multistabilized (Nb, V, Ti) steel. Phosphorus decreases also the irradiation creep strain, but only because of the decrease in swelling. The transmission electron microscopy (TEM) examinations show that the improvement of swelling resistance by phosphorus addition comes from a decrease in void density, that occurs mainly when a uniform distribution of needle-shaped phosphides appears. In titanium stabilized steels, the phosphides are FeTiP whereas in the phosphides of the multistabilized steel, titanium is replaced by niobium, leaving the titanium in solution to play its role of swelling inhibitor for long irradiations

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

    International Nuclear Information System (INIS)

    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.)

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

    Energy Technology Data Exchange (ETDEWEB)

    Vilpas, M. [VTT Manuf. Technol. (Finland); Haenninen, H. [Helsinki Univ. of Technol., Espoo (Finland). Lab. of Eng. Mater.

    1999-07-01

    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.)

  18. Development of neural network models for the prediction of solidification mode, weld bead geometry and sensitisation in austenitic stainless steels

    International Nuclear Information System (INIS)

    Quantitative models describing the effect of weld composition on the solidification mode, ferrite content and process parameters on the weld bead geometry are necessary in order to design composition of the welding consumable to ensure primary ferritic solidification mode, proper ferrite content and to ensure right choice of process parameters to achieve good bead geometry. A quantitative model on sensitisation behaviour of austenitic stainless steels is also necessary to optimise the composition of the austenitic stainless steel and to limit the strain on the material in order to enhance the resistance to sensitisation. The present paper discuss the development of quantitative models using artificial neural networks to correlate weld metal composition with solidification mode, process parameter with weld bead geometry and time for sensitisation with composition, strain in the material before welding and the temperature of exposure in austenitic stainless steels. (author)

  19. Calculation of microsegregation and amount of retained δ-ferrite in Fe-Cr-Ni austenitic stainless steel

    International Nuclear Information System (INIS)

    In equilibrium, 304 stainless steel has only γ-austenite phase below about 1170 .deg. C and solutes are uniformly distributed in γ-austenite. Due to incomplete solid-state diffusion, it has retained δ-ferrite as well as γ-austenite and the solute distribution becomes inhomogeneous in each phase. To further understand the solidification behavior of 304 stainless steel, the variation of δ-ferrite amount with temperature and the solute concentration in each phase across the phase boundary are calculated in this study. The calculated solute contents at the interface are in good agreement with experimental data available. It is shown that the equilibrium calculation using 304 steel composition itself produces better results than using equivalent composition. The calculated amounts of retained δ-ferrite using 304 equivalent composition are somewhat higher than experimentally observed values. Much better agreement between calculation results and experimental data is expected if more reliable experimental data can be obtained

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

    Institute of Scientific and Technical Information of China (English)

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

    2015-01-01

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