WorldWideScience

Sample records for 304l stainless steel

  1. Forging evaluaion of 304L stainless steel

    The objective of this project was to evaluate and characterize the effects of various forging parameters on the metallographic structure and mechanical properties of 304L stainless steel forgings. Upset and die forgings were produced by hammer and Dynapak forging with forging temperatures ranging from 760 to 11450C, upset reductions ranging from 20 to 60%, and annealing times ranging from 0 to 25 minutes at 8430C. The carbide precipitation behavior observed was found to be a function of forging temperature and annealing time. Higher forging temperatures were beneficial in avoiding continuous carbide precipitation and annealing at 8430C promoted increased carbide precipitation. The yield strength of the unannealed forgings decreased with increasing forging temperature and, with the exception of the 11450C upset forgings, was significantly lowered by annealing

  2. Weld solidification cracking in 304 to 304L stainless steel

    Hochanadel, Patrick W [Los Alamos National Laboratory; Lienert, Thomas J [Los Alamos National Laboratory; Martinez, Jesse N [Los Alamos National Laboratory; Martinez, Raymond J [Los Alamos National Laboratory; Johnson, Matthew Q [Los Alamos National Laboratory

    2010-01-01

    A series of annulus welds were made between 304 and 304L stainless steel coaxial tubes using both pulsed laser beam welding (LBW) and pulsed gas tungsten arc welding (GTAW). In this application, a change in process from pulsed LBW to pulsed gas tungsten arc welding was proposed to limit the possibility of weld solidification cracking since weldability diagrams developed for GTAW display a greater range of compositions that are not crack susceptible relative to those developed for pulsed LBW. Contrary to the predictions of the GTAW weldability diagram, cracking was found. This result was rationalized in terms of the more rapid solidification rate of the pulsed gas tungsten arc welds. In addition, for the pulsed LBW conditions, the material compositions were predicted to be, by themselves, 'weldable' according to the pulsed LBW weldability diagram. However, the composition range along the tie line connecting the two compositions passed through the crack susceptible range. Microstructurally, the primary solidification mode (PSM) of the material processed with higher power LBW was determined to be austenite (A), while solidification mode of the materials processed with lower power LBW apparently exhibited a dual PSM of both austenite (A) and ferrite-austenite (FA) within the same weld. The materials processed by pulsed GT A W showed mostly primary austenite solidification, with some regions of either primary austenite-second phase ferrite (AF) solidification or primary ferrite-second phase austenite (FA) solidification. This work demonstrates that variations in crack susceptibility may be realized when welding different heats of 'weldable' materials together, and that slight variations in processing can also contribute to crack susceptibility.

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

    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.

  4. Martensitic transformation in 304L and 316L types stainless steels cathodically hydrogen charged

    This paper reports a TEM study on the role of phase transitions at the crack tip in 304L and 316L types stainless steels cathodically hydrogen charged in the absence of any eternally applied forces. The possible role of α prime and epsilon martensite phases in the fracture mechanism is discussed

  5. Dynamic compressive response of wrought and additive manufactured 304L stainless steels

    Nishida Erik

    2015-01-01

    Full Text Available Additive manufacturing (AM technology has been developed to fabricate metal components that include complex prototype fabrication, small lot production, precision repair or feature addition, and tooling. However, the mechanical response of the AM materials is a concern to meet requirements for specific applications. Differences between AM materials as compared to wrought materials might be expected, due to possible differences in porosity (voids, grain size, and residual stress levels. When the AM materials are designed for impact applications, the dynamic mechanical properties in both compression and tension need to be fully characterized and understood for reliable designs. In this study, a 304L stainless steel was manufactured with AM technology. For comparison purposes, both the AM and wrought 304L stainless steels were dynamically characterized in compression Kolsky bar techniques. They dynamic compressive stress-strain curves were obtained and the strain rate effects were determined for both the AM and wrought 304L stainless steels. A comprehensive comparison of dynamic compressive response between the AM and wrought 304L stainless steels was performed. SAND2015-0993 C.

  6. Dynamic Strength of 304L stainless steel under impact

    Werdiger, Meir; Bakshi, Lior; Glam, Benny; Pistinner, Shlomi

    2011-06-01

    We use the Asay self consistent technique to analyze the effects of pressure hardening and strain hardening on SS304L. Previously unloading experiment has been used to infer the strength of this material at high pressure, and recently the Johnson-Cook (JC) model has been calibrated at low strain rate. Release and reshock experiments with impact velocity range of 300-1700 m/s were preformed. We used VISAR to extract the particle velocity of the SS304L- LiF window interface. The velocity profile compared to hydrodynamic simulation using JC model. Our unloading experiments have clearly demonstrate that the material yield but does not fail. Thus infer substantial effect of pressure hardening.

  7. Optimization of process parameters in explosive cladding of titanium/stainless steel 304L plates

    Explosive cladding is a solid state welding process best suited for joining incompatible metals. The selection of process parameters viz., explosive mass ratio, stand off distance and initial angle of inclination dictate the nature of the cladding. Optimization of process parameters in explosive cladding of titanium-stainless steel 304L plates, based on two level three factorial design, is attempted to establish the influencing parameters. Analysis of variance was employed to find the linear, regression and interaction values. Mathematical models to estimate the responses-amplitude and wavelength were developed. The microstructure of the Ti-SS304L explosive clad interface reveals characteristic undulations concurrent with design expectations. (orig.)

  8. TESTING OF 304L STAINLESS STEEL IN NITRIC ACID ENVIRONMENTS WITH FLUORIDES AND CHLORIDES

    Mickalonis, J.

    2010-10-04

    Impure radioactive material processed in nitric acid solutions resulted in the presence of chlorides in a dissolver fabricated from 304L stainless steel. An experimental program was conducted to study the effects of chloride in nitric acid/fluoride solutions on the corrosion of 304L stainless steel. The test variables included temperature (80, 95, and 110 C) and the concentrations of nitric acid (6, 12, and 14 M), fluoride (0.01, 0.1, and 0.2 M) and chloride (100, 350, 1000, and 2000 ppm). The impact of welding was also investigated. Results showed that the chloride concentration alone was not a dominant variable affecting the corrosion, but rather the interaction of chloride with fluoride significantly affected corrosion.

  9. Passivity and passivity breakdown of 304L stainless steel in hot and concentrated nitric acid

    The objective of this study is to characterize the oxidation behavior of 304L stainless steel (SS) in representative conditions of spent nuclear fuel reprocessing, i.e. in hot and concentrated nitric acid. In these conditions the SS electrochemical potential is in the passive domain and its corrosion rate is low. However when the media becomes more aggressive, the potential may be shifted towards the trans-passive domain characterized with a high corrosion rate. Passivity and passivity breakdown in the trans-passive domain are of a major interest for the industry. So as to characterize these phenomenons, this work was undertaken with the following representative conditions: a 304L SS from an industrial sheet was studied, the media was hot and concentrated HNO3, long term tests were performed. First, the surface of an immersed 304L SS was characterized with several complementary techniques from the micro to the nanometer scale. Then oxidation kinetics was studied in the passive and in the trans-passive domain. The oxidation behavior was studied thanks to weight loss determination and surface analysis. Finally, oxidation evolution as a function of the potential was studied from the passive to the trans-passive domain. In particular, this allowed us to obtain the anodic curve of 304L SS in hot and concentrated and to define precisely the 304L SS limits of in such conditions. (author)

  10. Development of Nanocrystalline 304L Stainless Steel by Large Strain Cold Working

    Marina Odnobokova; Andrey Belyakov; Rustam Kaibyshev

    2015-01-01

    The microstructural changes leading to nanocrystalline structure development and the respective tensile properties were studied in a 304L stainless steel subjected to large strain cold rolling at ambient temperature. The cold rolling was accompanied by the development of deformation twinning and martensitic transformation. The latter readily occurred at deformation microshear bands, leading the martensite fraction to approach 0.75 at a total strain of 3. The deformation twinning followed by m...

  11. Comparison of Stress Corrosion Cracking Susceptibility of Laser Machined and Milled 304 L Stainless Steel

    Gupta, R. K.; Kumar, Aniruddha; Nagpure, D. C.; Rai, S. K.; Singh, M. K.; Khooha, Ajay; Singh, A. K.; Singh, Amrendra; Tiwari, M. K.; Ganesh, P.; Kaul, R.; Singh, B.

    2016-07-01

    Machining of austenitic stainless steel components is known to introduce significant enhancement in their susceptibility to stress corrosion cracking. The paper compares stress corrosion cracking susceptibility of laser machined 304 L stainless steel specimens with conventionally milled counterpart in chloride environment. With respect to conventionally milled specimens, laser machined specimens displayed more than 12 times longer crack initiation time in accelerated stress corrosion cracking test in boiling magnesium chloride as per ASTM G36. Reduced stress corrosion cracking susceptibility of laser machined surface is attributed to its predominantly ferritic duplex microstructure in which anodic ferrite phase was under compressive stress with respect to cathodic austenite.

  12. Corrosion of type 304L stainless steel in boiling dilute neptunium nitrate solution

    Corrosion of type 304L stainless steel in nitric acid solution containing neptunium was studied under immersion and heat-transfer condition. Corrosion rates of stainless steel were obtained by the weight loss measurement and the quantitative analysis of metallic ions dissolved in solution. The surface morphology was observed by scanning electron microscopy. The corrosion acceleration mechanism was investigated by polarization measurement and spectrophotometry. The corrosion rate in boiling 9M nitric acid was accelerated by addition of neptunium. The corrosion of stainless steel was promoted under heat-transfer condition compared to immersion condition. In polarization measurements, the cathodic current was increased by addition of neptunium. Spectrophotometric measurements showed the oxidization of neptunium in boiling nitric acid. It was suggested that the accelerated corrosion in nitric acid solution containing neptunium was caused by re-oxidation of neptunium. (author)

  13. Constant extension rate tensile tests on 304L stainless steel in simulated hazardous low-level waste

    New waste tanks which handle hazardous low-level waste were proposed to be constructed in H-area. The candidate material for the tanks is AISI Type 304L (304L) stainless steel. Constant extension rate tensile (CERT) tests were conducted to assess the susceptibility of 304L to stress-corrosion cracking (SCC) in these waste solutions. The tests demonstrated that 304L was not susceptible to SCC in simulated wastes. Based on these tests and previous pitting corrosion studies 304L is a suitable material of construction for the new tanks. Comparison tests in the same simulants were performed on A537 carbon steel (A537), a material that is similar to material of construction for the current tanks. Stress-corrosion cracking was indicated in two of the simulants. If carbon steel tanks are utilized to handle the hazardous low-level wastes, inhibitors such as nitrite or hydroxide will be necessary to prevent corrosion

  14. Corrosion and microstructural aspects of dissimilar joints of titanium and type 304L stainless steel

    Mudali, U. Kamachi. E-mail: kamachi@igcar.ernet.in; Ananda Rao, B.M.; Shanmugam, K.; Natarajan, R.; Raj, Baldev

    2003-09-01

    To link titanium and zirconium metal based (Ti, Zr-2, Ti-5%Ta, Ti-5%Ta-1.8Nb) dissolver vessels containing highly radioactive and concentrated corrosive nitric acid solution to other nuclear fuel reprocessing plant components made of AISI type 304L stainless steel (SS), high integrity and corrosion resistant dissimilar joints between them are necessary. Fusion welding processes produce secondary precipitates which dissolve in nitric acid, and hence solid-state processes are proposed. In this work, various dissimilar joining processes available for producing titanium-304L SS joints with adequate strength, ductility and corrosion resistance for this critical application are highlighted. Developmental efforts made at IGCAR, Kalpakkam are outlined. The possible methods and the microstructural-metallurgical properties of the joints along with corrosion results obtained with three phase (liquid, vapour, condensate) corrosion testing are discussed. Based on the results, dissimilar joint produced by the explosive joining process was adopted for plant application.

  15. Corrosion and microstructural aspects of dissimilar joints of titanium and type 304L stainless steel

    To link titanium and zirconium metal based (Ti, Zr-2, Ti-5%Ta, Ti-5%Ta-1.8Nb) dissolver vessels containing highly radioactive and concentrated corrosive nitric acid solution to other nuclear fuel reprocessing plant components made of AISI type 304L stainless steel (SS), high integrity and corrosion resistant dissimilar joints between them are necessary. Fusion welding processes produce secondary precipitates which dissolve in nitric acid, and hence solid-state processes are proposed. In this work, various dissimilar joining processes available for producing titanium-304L SS joints with adequate strength, ductility and corrosion resistance for this critical application are highlighted. Developmental efforts made at IGCAR, Kalpakkam are outlined. The possible methods and the microstructural-metallurgical properties of the joints along with corrosion results obtained with three phase (liquid, vapour, condensate) corrosion testing are discussed. Based on the results, dissimilar joint produced by the explosive joining process was adopted for plant application

  16. Microstructure and corrosion behavior of multipass gas tungsten arc welded 304L stainless steel

    Highlights: • Multipass gas tungsten arc welding of 304L stainless steel was successfully done. • All welds were austenitic with the presence of a small amount of δ-ferrite. • The morphology of δ-ferrite showed the lathy and skeletal δ-ferrite in the welds. • Hardness and corrosion resistance were improved by multipass welding. • The best joint properties were obtained after three passes welding. - Abstract: The purpose of this study was to discuss the effect of single pass and multipass (double and triple pass) gas tungsten arc welding (GTAW) on microstructure, hardness and corrosion behavior of 304L stainless steel. In this investigation, 308 stainless steel filler metal was used. Microstructures and hardness of the weldments were investigated using optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction analysis (XRD) and Vickers microhardness (HV0.5). A ferritescope was also used in the non-destructive evaluation to observe the ferrite content on the weldments. Corrosion behavior of weldments in 1 M H2SO4 solution at 25 ± 1 °C was investigated using potentiodynamic polarization and immersion tests. Results indicated that the microstructure of fusion zones exhibited dendritic structure contained lathy and skeletal δ-ferrite. The contents of δ-ferrite in the weld zone increased by increasing the number of passes. Therefore, as the number of passes increased, the hardness and corrosion resistance increased

  17. Corrosion testing of type 304L stainless steel in tuff groundwater environments

    The stress-corrosion cracking (SCC) resistance of Type 304L stainless steel (SS) to elevated temperatures in tuff rock and tuff groundwater environments was determined under irradiated and nonirradiated conditions using U-bend specimens and slow-strain-rate tests. The steel was tested both in the solution-annealed condition and after sensitization heat treatments. The material was found to be susceptible to SCC in both the solution-annealed and solution-annealed-and-sensitized conditions when exposed to an irradiated crushed tuff rock environment containing air and water vapor at 900C. A similar exposure at 500C did not result in failure after a 25-month test duration. Specimens of sensitized 304 SS conditioned with a variety of sensitization heat treatments resisted failure during a test of 1-year duration in which a nonirradiated environment of tuff rock and groundwater held at 2000C was allowed to boil to dryness on a cyclical basis. All specimens of sensitized 304 SS exposed to this environment failed. Slow-strain-rate studies were performed on 304L, 304, and 316L SS specimens. The 304L SS was tested in J-13 well water at 1500C, and the 316L SS at 950C. Neither material showed evidence of SCC in these tests. Sensitized 304 SS did exhibit SCC in J-13 well water in tests conducted at 1500C. 12 refs., 27 figs., 13 tabs

  18. Fatigue of welded joint in a stainless steel AISI 304 L

    The flexion fatigue behavior for the base metal and welded joint of an AISI 304 L stainless steel type, used in the Angra-1 reactor, was determined. An automatic welding process was used with improved procedures in order to assure better welding metallurgy. Fatigue tests samples reinforcements were done to allow the evaluation of metallurgical variables, specially the role played by delta ferrite. The resulting welded joint showed better fatigue life than the base metal. Delta ferrite was found to play an important role on the initiation and propagation processes of the fatigue cracks. (Author)

  19. Comparative Shock Response of Additively Manufactured Versus Conventionally Wrought 304L Stainless Steel*

    Wise, J. L.; Adams, D. P.; Nishida, E. E.; Song, B.; Maguire, M. C.; Carroll, J.; Reedlunn, B.; Bishop, J. E.

    2015-06-01

    Gas-gun experiments have probed the compression and release behavior of impact-loaded 304L stainless steel specimens machined from additively manufactured (AM) blocks as well as baseline ingot-derived bar stock. The AM technology allows direct fabrication of metal parts. For the present study, a velocity interferometer (VISAR) measured the time-resolved motion of samples subjected to one-dimensional (i.e., uniaxial strain) shock compression to peak stresses ranging from 0.2 to 7.5 GPa. The acquired wave-profile data have been analyzed to determine the comparative Hugoniot Elastic Limit (HEL), Hugoniot equation of state, spall strength, and high-pressure yield strength of the AM and conventional materials. Observed differences in shock loading and unloading characteristics for the two 304L source variants have been correlated to complementary Kolsky bar results for compressive and tensile testing at lower strain rates. The effects of composition, porosity, microstructure (e.g., grain size and morphology), residual stress, and sample axis orientation relative to the additive manufacturing deposition trajectory have been assessed to explain differences between the AM and baseline 304L dynamic mechanical properties. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  20. Effect of rare earth oxide additions on oxidation behavior of AISI 304L stainless steel

    Marina Fuser Pillis

    2006-12-01

    Full Text Available AISI 304L stainless steel powder compacts containing 2 vol% high purity rare earth oxides were prepared by mixing the different powders in a vibratory mill followed by pressing. The compacts thus obtained were sintered in a vacuum furnace and isothermal oxidation measurements were carried out in a muffle furnace, in air, up to 200 hours at 900 °C. The oxidized surfaces were examined in a scanning electron microscope and micro regions of the reaction products were studied using energy dispersive analysis. The addition of rare earth oxides decreased the oxidation rate of the stainless steel. Further evidence of predominant oxygen ion diffusion controlling the overall oxidation process in rare earth containing chromium oxide forming alloys has been observed.

  1. Modeling Periodic Adiabatic Shear Bands Evolution in a 304L Stainless Steel Thick-Walled Cylinder

    Liu, Mingtao; Hu, Haibo; Fan, Cheng; Tang, Tiegang

    2015-06-01

    The self-organization of multiple shear bands in a 304L stainless steel thick-walled cylinder (TWC) was numerically studied. The microstructures of material lead to the non-uniform distribution of local yield stress, which plays a key role in the formation of spontaneous shear localization. We introduced a probability factor satisfied Gauss distribution into the macroscopic constitutive relationship to describe the non-uniformity of local yield stress. Using the probability factor, the initiation and propagation of multiple shear bands in TWC were numerically replicated in our 2D FEM simulation. Experimental results in the literature indicate that the machined surface at the internal boundary of a 304L stainless steel cylinder provides a work-hardened layer (about 20 μm) which has significantly different microstructures from base material. The work-hardened layer leads to the phenomenon that most shear bands are in clockwise or counterclockwise direction. In our simulation, periodic oriented perturbations were applied to describe the grain orientation in the work-hardened layer, and the spiral pattern of shear bands was successfully replicated.

  2. Effect of H2O2 on the corrosion behavior of 304L stainless steel

    In connection with the safe storage of high level nuclear waste, effect of H2O2 on the corrosion behavior of 304L stainless steel was examined. Open circuit potentials and polarization curves were measured with and without H2O2. The experimental results show that H2O2 increased corrosion potential and decreased pitting potential. The passive range, therefore, decreased as H2O2 concentration increased, indicating that pitting resistance was decreased by the existence of H2O2 in the electrolyte. These effects of H2O2 on corrosion of 304L stainless steel are considered to be similar to those of γ-irradiation. To compare the effects of H2O2 with those of O2, cathodic and anodic polarization curves were made in three types of electrolyte such as aerated, deaerated, and stirred electrolyte. The experimental results show that the effects of H2O2 on the corrosion behavior were very similar to those of O2 such as increase of corrosion potential, decrease of pitting resistance, and increase of repassivation potential. Further, H2O2 played much greater role in controlling cathodic reaction rate in neutral water environment. In acid and alkaline media, potential shifts by H2O2 were restricted by the large current density of proton reduction and by the le Chatelier's principle respectively

  3. Repetitive Thermomechanical Processing towards Ultra Fine Grain Structure in 301, 304 and 304L Stainless Steels

    A. Momeni; S.M. Abbasi

    2011-01-01

    Thermomechanical processing as a combination of cold rolling and annealing was performed on austenitic stainless steels 301,304 and 304L. Two cold rolling steps each one up to a reduction of 75% were combined with an intermediate annealing at 800℃ for 20 min. The final annealing was performed at.the same temperature and time. Cold rolling contributed to martensite formation at the expense of metastable austenite in the studied materials. Austenite in 301 was found to be less stable than that in 304 and 304L. Hence, higher strength characteristics in the as-quenched 301 stainless steels were attributed to the higher volume fraction of martensite. Both α'-martensite and ε-martensite were found to form as induced by deformation. However, the intensity of ε-martensite increased as the stability of austenite decreased. Annealing after cold rolling led to the reversion of austenite with an ultra fine grained structure in the order of 0.5-1 μm from the strain induced martensite. The final grain size was found to be an inverse function of the amount of strain induced martensite. The thermomechanical processing considerably improved the strength characteristics while the simultaneous decrease of elongation was rather low.

  4. Chemical interaction between granular B4C and 304L-type stainless steel materials used in BWRs in Japan

    Chemical reactions between stainless steel and boron carbide were investigated using the materials applied for control rods in BWRs in Japan, specifically 304L-type stainless steel and granular boron carbide. The reaction region consisted of 2–4 layers, in which the significant composition variation of each element was detected, especially for B and C. Assuming that the reaction layer growth obeys the parabolic law, the effective rate constant between 304L-type stainless steel and granular boron carbide was evaluated to be approximately one order of magnitude smaller than the previously reported values for boron carbide pellets or powers. This difference might originate from the loose contact between the stainless steel and the granular boron carbide in the present study. Regarding liquefaction progress, the stainless steel components were selectively dissolved in the melt; consequently, the unreacted boron carbide tended to remain. (author)

  5. Comparison of SCC Behavior of 304L Stainless Steels With and Without Boron Addition in Acidic Chloride Environment

    Sivai Bharasi, N.; Pujar, M. G.; Nirmal, S.; Mallika, C.; Kamachi Mudali, U.; Angelo, P. C.

    2016-07-01

    The stress corrosion cracking (SCC) behavior of 304L B4 grade borated stainless steel (SS) as well as 304L SS was investigated by constant load and slow strain rate testing (SSRT) techniques. The microstructure, pitting, and SCC behavior of borated SS in the as-received, sensitized, and solution-annealed conditions were analyzed. Potentiodynamic anodic polarization and double loop electrochemical potentiokinetic reactivation (DLEPR) experiments were carried out to find out pitting corrosion resistance and degree of sensitization (DOS). The number of boride particles (composed of Cr, Fe, and B) were highest for the specimen solution annealed at 1423 K/2 h. Solution-annealing treatment at 1423 K/4 h was found to be beneficial in improving the corrosion resistance of borated 304L SS. Although the borated 304L SS exhibited a higher DOS, it showed improved pitting corrosion resistance compared to 304L SS. Constant load experiments revealed the time to failure to be the highest for the specimen solution annealed at 1423 K/4 h. SCC susceptibility index (Iscc) values obtained from SSRT tests were lower for solution-annealed borated 304L SS compared to the as-received and sensitized conditions. The improved SCC resistance of borated 304L SS was attributed not only to the solution-annealing treatment but also the higher stacking fault energy (SFE) value compared to 304L SS.

  6. Nitrogen interstitial diffusion induced decomposition in AISI 304L austenitic stainless steel

    The nature of the near-surface γN phase produced by low-temperature (∼400 °C) plasma-assisted nitriding of an austenitic stainless steel 304L is studied. A combination of global probes (X-ray diffraction, nuclear reaction analysis, glow discharge optical emission spectroscopy) and local probes (field ion microscopy, conversion electron Mössbauer, X-ray absorption near edge structure and extended X-ray absorption fine structure spectroscopies) is employed to reveal the morphology, phase structure, atomic ordering and chemical state of the obtained γN phase. The results consistently reveal the heterogeneous nature of the nitrided layer consisting of nanometric CrN precipitates embedded in a Fe4N-like matrix. The size of the precipitates is found to be larger at the surface than at the nitrided layer–steel interface. The precipitates have irregular, sphere-like shapes. Moreover, X-ray spectroscopic investigation revealed three different intermetallic distances and different chemical environments for Fe, Cr and Ni, accompanied by a large static disorder. These findings suggest that the presence of the interstitial N destabilizes the homogeneous element distribution in 304L even at such low temperatures. This leads to the segregation into Cr-rich zones that are coherent with the Fe4N matrix. Possible atomistic decomposition mechanisms are discussed. Based on the heterogeneous nature of the γN phase revealed in 304L, an alternative view of its remarkable combination of properties such as large hardness, induced ferromagnetism and preserved corrosion resistance is considered.

  7. Production of nano/submicron grained AISI 304L stainless steel through the martensite reversion process

    Research highlights: → At least 50% reduction is necessary to complete the transformation of austenite to martensite at 0 deg. C. → The parameters of Olsen-Cohen model were found as n = 4.5, α = 3.257 and β = 3.573. → The appropriate grain refining zone for annealing treatment was determined. → A diagram showing different zones for each level of grain sizes via annealing conditions is presented. → The hardness improves 2.5 times higher after the thermo-mechanical process. → Final structure exhibits not only high strength (above 1 GPa) but also good elongation (∼40%). - Abstract: Production of nano/submicron grained AISI 304L austenitic stainless steel through formation of strain-induced martensite and its reversion to austenite are studied in this paper. The effects of annealing parameters on the microstructural development and mechanical properties are also investigated. Heavily cold rolling at 0 deg. C is employed to induce the formation of martensite in the metastable austenitic material, followed by reversion treatment at the temperature range of 700-900 deg. C for 0.5-300 min. Microstructural evolutions are analyzed using Feritscope, X-ray diffraction, and scanning electron microscopy, whereas the mechanical properties are determined by hardness and tensile tests. The smallest grain size (about 135 nm) is obtained in the specimen annealed at 700 deg. C for 20 min. The resultant nano/submicron grained steel not only exhibits a high strength level (about 1010 MPa) but also a desirable elongation of about 40%. Moreover, an annealing map is developed which indicates the appropriate range of annealing parameters for grain refinement of AISI 304L stainless steel through the martensite reversion process.

  8. Production of nano/submicron grained AISI 304L stainless steel through the martensite reversion process

    Forouzan, Farnoosh, E-mail: forouzan.iut@gmail.com [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Najafizadeh, Abbas; Kermanpur, Ahmad; Hedayati, Ali; Surkialiabad, Roohallah [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of)

    2010-10-25

    Research highlights: {yields} At least 50% reduction is necessary to complete the transformation of austenite to martensite at 0 deg. C. {yields} The parameters of Olsen-Cohen model were found as n = 4.5, {alpha} = 3.257 and {beta} = 3.573. {yields} The appropriate grain refining zone for annealing treatment was determined. {yields} A diagram showing different zones for each level of grain sizes via annealing conditions is presented. {yields} The hardness improves 2.5 times higher after the thermo-mechanical process. {yields} Final structure exhibits not only high strength (above 1 GPa) but also good elongation ({approx}40%). - Abstract: Production of nano/submicron grained AISI 304L austenitic stainless steel through formation of strain-induced martensite and its reversion to austenite are studied in this paper. The effects of annealing parameters on the microstructural development and mechanical properties are also investigated. Heavily cold rolling at 0 deg. C is employed to induce the formation of martensite in the metastable austenitic material, followed by reversion treatment at the temperature range of 700-900 deg. C for 0.5-300 min. Microstructural evolutions are analyzed using Feritscope, X-ray diffraction, and scanning electron microscopy, whereas the mechanical properties are determined by hardness and tensile tests. The smallest grain size (about 135 nm) is obtained in the specimen annealed at 700 deg. C for 20 min. The resultant nano/submicron grained steel not only exhibits a high strength level (about 1010 MPa) but also a desirable elongation of about 40%. Moreover, an annealing map is developed which indicates the appropriate range of annealing parameters for grain refinement of AISI 304L stainless steel through the martensite reversion process.

  9. Microstructural features of hot pressure bonding between stainless steel type AISI-304 L and ziracloy-2

    The diffusion zone formed after reaching quasi-equilibrium in hot pressure bonding between stainless steel type AISI-304 L and Zircaloy-2 under particular thermal and compressive conditions (1000-11000C and 2-3 atm) contains two distinct layers, each separately localized in the modified stainless steel and Zircaloy matrices. SEM, TEM, X-ray diffraction and microanalysis were used to identify the phase structure and composition of the two diffusion layers. The nature and distribution of phases found in the diffusion layers can be explained in connection with the diffusion mechanisms operating after the initial stages of bond formation and interface disappearance: (a) The strog zirconium diffusion promotes ferrite and ZrCr2 formation in a narrow zone located near the stainless steel matrix. (b) Iron and nickel diffusion over large distances in the Zircaloy matrix leads to the occurrence of a larger zone having a two-phase structure. The light grey phase consists of untransformed α-Zr and a small precentage of high-temperature β-Zr phase. The darker grey phase contains essentially a very high amount of intermetallic bct compounds Zr-Fe-Ni, Zr2Fe and Zr2Ni dispersed in the small residue of Zircaloy matrix. (orig.)

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

    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.

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

    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.

  12. Electronic structures and nitride formation on ion-implanted AISI 304L austenitic stainless steel

    Chang, G.S.; Son, J.H.; Kim, S.H.; Chae, K.H.; Whang, C.N. (Yonsei Univ., Seoul (Korea, Republic of). Dept. of Physics); Menthe, E.; Rie, K.-T.; Lee, Y.P.

    1999-02-01

    A N[sub 2][sup +] implantation technique was employed to improve the surface hardness of stainless steel, and the electronic structures and nitride formation of the ion-implanted layer were investigated and compared with those produced using other techniques, including plasma nitriding. AISI 304L austenite stainless steel was irradiated by 80 keV N[sub 2][sup +] with a dosage ranging from 1.0 x 10[sup 16] to 1.0 x 10[sup 18] ions cm[sup -2] at room temperature. The formation of various nitrides was confirmed by X-ray diffraction. The quantitative hardness of the samples was measured by using a Knoop microhardness tester. X-ray photoelectron spectroscopy was also carried out to elucidate the chemical states and electronic structures of the ion-implanted layers. The measurements were repeated after post-annealing at 400 C for 1 h in a high vacuum. Changes in phase, chemical state and electronic structures were observed according to the ion dose and heat treatment. (orig.) 12 refs.

  13. In situ study by atomic force microscopy of localised corrosion on a 304L stainless steel

    At this time, the understanding of the initiation of localized corrosion on stainless steels (SS) is still limited. In this context, the present work aimed at observing in situ by Atomic Force Microscopy (AFM) the initiation of corrosion pits and stress corrosion cracking (SCC) cracks. In order to complete the project, a new technique associating an AFM, an electrochemical cell and a traction platform as been developed. It allows in situ imaging of the surface evolutions of a 304L SS at the nano-scale. under controlled potential and/or under stress conditions. We show that corrosion pits initiate preferentially in relation with nano-metric defects of the surface. For the first time, a real-time kinetic study of the first steps of nano-metric pits growth has been performed. This study corroborates the 'point-defect' model (vertical pit growth speed of 0.18 angstrom.s-1, current densities inside pits evaluated to 73 μjA.cm-2. Combined with the EBSD technique (Electron Backscattered Diffraction), the AFM allows a total indexing of the activated slip systems during deformation and give information about the number of emerged dislocations (few units). The effect of strain hardening at the nano-scale on pitting susceptibility has been investigated: 70% of the pits set up at strain hardened areas. To explain this phenomenon, we propose a simple model based on the modification of the local work function of the surface due to local stress gradients. Concerning SCC, the first in situ observations seem to validate Magnin's mechanism: crack initiation appears at strain concentration spots. Observed after anodization of our 304L surface, organized arrays of nano-cavities (period of 50-100 nm) have been analyzed. In collaboration with an INSERM team, we showed that such nano-structured surfaces increase the adhesion and differentiation of bone cells. (author)

  14. Microstructure and Mechanical Properties of Plasma Arc Brazed AISI 304L Stainless Steel and Galvanized Steel Plates

    Jin, Yajuan; Li, Ruifeng; Yu, Zhishui; Wang, Yu

    2016-04-01

    Plasma arc brazing is used to join the AISI 304L stainless steel and galvanized steel plate butt joints with the CuSi3Mn1 filler wire. The effect of parameters on weld surface appearance, interfacial microstructure, and composition distribution in the joint was studied. The microhardness and mechanical tests were conducted to determine the mechanical properties of the welded specimens. The results indicated that good appearance, bead shape, and sufficient metallurgical bonding could be obtained when the brazing process was performed with a wire feeding speed of 0.8 m/min, plasma gas flow rate of 3.0 l/min, welding current of 100 A, and welding speed of 27 cm/min. During plasma arc brazing process, the top corner of the stainless steel and galvanized steel plate were heated and melted, and the melted quantity of stainless steel was much more than that of the galvanized steel due to the thermal conductivity coefficient difference between the dissimilar materials. The microhardness test results shows that the microhardness value gradually increased from the side of the galvanized steel to the stainless steel in the joint, and it is good for improving the mechanical properties of joint. The tensile strength was a little higher than that of the brazing filler, and the fracture position of weld joint was at the base metal of galvanized steel plate.

  15. Investigation of high temperature corrosion behavior on 304L austenite stainless steel in corrosive environments

    In this work, 304L stainless steel samples were exposed at 700 °C for 10hrs in different corrosive environments; dry oxygen, molten salt, and molten salt + dry oxygen. The corrosion behavior of samples was analyzed using weight change measurement technique, optical microscope (OM) and Scanning Electron Microscope (SEM) equipped with Energy Dispersive X-ray (EDX). The existence phases of corroded sample were determined using X-ray Diffraction (XRD). The lowest corrosion rate was recorded in dry oxygen while the highest was in molten salt + dry oxygen environments with the value of 0.0062 mg/cm2 and −13.5225 mg/cm2 respectively. The surface morphology of sample in presence of salt mixture showed scale spallation. Oxide scales of Fe3O4, Fe2O3 were the main phases developed and detected by XRD technique. Cr2O3 was not developed in every sample as protective layers but chromate-rich oxide was developed. The cross-section analysis found the oxide scales were in porous, thick and non-adherent that would not an effective barrier to prevent from further degradation of alloy. EDX analysis also showed the Cr-element was low compared to Fe-element at the oxide scale region

  16. Crack propagation in stainless steel AISI 304L in Hydrogen Chemistry conditions (HWC)

    Velocities of crack growth in samples type CT pre cracking of stainless steel AISI 304l solder and sensitized thermally its were obtained by the Rising Displacement method or of growing displacement. It was used a recirculation circuit that simulates the operation conditions of a BWR type reactor (temperature of 280 C and a pressure of 8 MPa) with the chemistry modified by the addition of hydrogen with and without the addition of impurities of a powerful oxidizer like the Cu+ ion. In each essay stayed a displacement velocity was constant of 1x10-9 m/s, making a continuous pursuit of the advance of the crack by the electric potential drop technique. Contrary to the idea of mitigation of the crack propagation velocity by effect of the addition of the hydrogen in the system, the values of the growth velocities obtained by this methodology went similar to the opposing ones under normal operation conditions. To the finish of the rehearsal one carries out the fractographic analysis of the propagation surfaces, which showed cracks growth in trans and intergranular way, evidencing the complexity of the regulator mechanisms of the IGSCC like in mitigation conditions as the alternative Hydrogen Chemistry. (Author)

  17. Cracking of 304L stainless steel observed within CANDU nuclear power plants under cyclic moist environments

    The stress corrosion cracking (SCC) of stainless steel Type 304L has been observed recently in a CANDU nuclear station. The cracking occurred on the inside surface of a piping structure and was transgranular in nature. It was mainly present in sections adjacent to welds, at pipe bends, and straight pipe sections. Such cracking mechanisms are governed by specific intrinsic parameters associated with stress, environment, and material factors. In this case, environmental factors not typical, and, presumably, the stresses at the affected locations are low. This paper discusses the results of the failure analysis conducted on affected component materials. The assessment of the observed mechanism includes the investigation of the affected piping (e.g., undamaged test welds, bends, and around the crack locations) using Orientation Imaging Microscopy (OIM) to evaluate the relative degree of residual plastic strain present in the crack locations and in the general pipe microstructure. Advance surface analysis (ToF-SIMS) was used to examine metal surface oxides buried beneath deposits and at strained regions of the pipe in order to elucidate the chemical species likely involved in the cracking/degradation process. (author)

  18. Mechanical properties of Austenitic Stainless Steel 304L and 316L at elevated temperatures

    Raghuram Karthik Desu

    2016-01-01

    Full Text Available Austenitic Stainless Steel grade 304L and 316L are very important alloys used in various high temperature applications, which make it important to study their mechanical properties at elevated temperatures. In this work, the mechanical properties such as ultimate tensile strength (UTS, yield strength (YS, % elongation, strain hardening exponent (n and strength coefficient (K are evaluated based on the experimental data obtained from the uniaxial isothermal tensile tests performed at an interval of 50 °C from 50 °C to 650 °C and at three different strain rates (0.0001, 0.001 and 0.01 s−1. Artificial Neural Networks (ANN are trained to predict these mechanical properties. The trained ANN model gives an excellent correlation coefficient and the error values are also significantly low, which represents a good accuracy of the model. The accuracy of the developed ANN model also conforms to the results of mean paired t-test, F-test and Levene's test.

  19. Propagation of crevices in stainless steel AISI304L in conditions of hydrogen chemistry (HWC)

    Crevice growth velocities in samples of AISI 304L stainless steel thermally welded and sensitized were obtained by the Rising displacement method or of growing displacement. It was used a recirculation circuit in where the operation conditions of a BWR type reactor were simulated (temperature of 288 C and a pressure of 8 MPa) with the chemistry modified by the addition of hydrogen with and without the addition of impurities of a powerful oxidizer like the Cu++ ion. CT pre cracked specimens were used and each rehearsal stayed to one constant displacement velocity of 1 x 10-9 m/s (3.6 μm/hr), making a continuous pursuit of the advance of the crack by the electric potential drop technique. To the end of the rehearsal it was carried out the fractographic analysis of the propagation surfaces. The values of the growth velocities obtained by this methodology went similar to the opposing ones under normal conditions of operation; while the fractographic analysis show the cracks propagation in trans and intergranular ways, evidencing the complexity of the regulator mechanisms of the one IGSCC even under controlled ambient conditions or with mitigation methodologies like the alternative hydrogen chemistry. (Author)

  20. Low cycle fatigue: high cycle fatigue damage accumulation in a 304L austenitic stainless steel

    The aim of this study was to evaluate the consequences of a Low Cycle Fatigue pre-damage on the subsequent fatigue limit of a 304L stainless steel. The effects of hardening and severe roughness (grinding) have also been investigated. In a first set of tests, the evolution of the surface damage induced by the different LCF pre-cycling was characterized. This has permitted to identify mechanisms and kinetics of damage in the plastic domain for different surface conditions. Then, pre-damaged samples were tested in the High Cycle Fatigue domain in order to establish the fatigue limits associated with each level of pre-damage. Results evidence that, in the case of polished samples, an important number of cycles is required to initiate surface cracks ant then to affect the fatigue limit of the material but, in the case of ground samples, a few number of cycles is sufficient to initiate cracks and to critically decrease the fatigue limit. The fatigue limit of pre-damaged samples can be estimated using the stress intensity factor threshold. Moreover, this detrimental effect of severe surface conditions is enhanced when fatigue tests are performed under a positive mean stress (author)

  1. Development of Nanocrystalline 304L Stainless Steel by Large Strain Cold Working

    Marina Odnobokova

    2015-04-01

    Full Text Available The microstructural changes leading to nanocrystalline structure development and the respective tensile properties were studied in a 304L stainless steel subjected to large strain cold rolling at ambient temperature. The cold rolling was accompanied by the development of deformation twinning and martensitic transformation. The latter readily occurred at deformation microshear bands, leading the martensite fraction to approach 0.75 at a total strain of 3. The deformation twinning followed by microshear banding and martensitic transformation promoted the development of nanocrystalline structure consisting of a uniform mixture of austenite and martensite grains with their transverse sizes of 120–150 nm. The developed nanocrystallites were characterized by high dislocation density in their interiors of about 3 × 1015 m−2 and 2 × 1015 m−2 in austenite and martensite, respectively. The development of nanocrystalline structures with high internal stresses led to significant strengthening. The yield strength increased from 220 MPa in the original hot forged state to 1600 MPa after cold rolling to a strain of 3.

  2. Thermomechanical history measurements on Type 304L stainless steel pipe girth welds

    Thermal and strain histories were recorded for three 40-cm-diameter (16 inch), Type 304L stainless steel (SS), schedule 40 (1.27 cm thickness) pipe girth welds. Two weld groove preparations were standard V grooves while the third was a narrow groove configuration. The welding parameters for the three pipe welds simulated expected field practice as closely as possible. The narrow gap weld was completed in four continuous passes while the other two welds required six and nine (discontinuous) passes, due to the use of different weld wire diameters. Thermomechanical history measurements were taken on the inner counterbore surface, encompassing the weld centerline and heat-affected zone (HAZ), as well as 10 cm of inner counterbore surface on either side of the weld centerline; a total of 47 data acquisition instruments were used for each weld. These instruments monitored: (1) weld shrinkages parallel to the pipe axis; (2) surface temperatures; (3) surface strains parallel to weld centerline; and (4) radial deformations. Results show that the weld and HAZ experienced cyclic deformation in the radial direction during welding, indicating that the final residual stress distribution in multi-pass pipe weldments is not axisymmetric. Measured radial and axial deformations were smaller for the narrow gap groove than for the standard V grooves, suggesting that the narrow gap groove weldment may have lower residual stress levels than the standard V groove weldments. This study provides the experimental database and a guideline for further computational modeling work

  3. Effect of thermal cycles on heavily cold deformed AISI 304L austenitic stainless steel

    The solution treated commercial grade AISI 304L austenitic stainless steel plate was heavily cold rolled to 90% of thickness reduction. Cold rolled specimens were annealed at various temperatures by thermal cycles and isothermal annealing. Strain-induced phase transformations and microstructure studies were carried out both in the cold rolled and annealed conditions. The X-ray diffraction and magnetic measurements were used for phase transformation studies. The transmission electron microscope characterisation revealed that the cyclic thermal process resulted in ultrafine grain austenite formation whereas, the isothermal annealing developed coarser grain size microstructure. The different microstructural evolutions by the above two processes largely influenced the development of the recrystallisation texture. The thermal cycling produced a distinct γ-fibre texture while the isothermal annealing resulted in a cube texture component along with the γ-fibre. The γ-fibre texture evolution was attributed to the over critical subgrains or nuclei and {1 0 0} cube texture to the coarser grains of micrometer size.

  4. Effect of pre-hardening on the lifetime of type 304L austenitic stainless steels

    This study deals with the effect of the loading history on the cyclic behavior and the fatigue life of two kinds (THYSSEN and CLI) of 304L stainless steel at room temperature. The experiments have been performed using two specimens' categories. The first one (virgin) has been submitted to only classical fatigue tests while in the second category, prior to the fatigue test, the specimen is subjected to a pre-hardening process under either monotonic or cyclic strain control. Cyclic softening followed by cyclic hardening are observed for the virgin specimens while only cyclic softening is exhibited by the pre-hardened specimens. The obtained results show that fatigue life is strongly influenced by the pre-hardening: it seems beneficial under stress control but detrimental under strain control, even in the presence of a compressive mean stress. The results are discussed regarding the cyclic evolution of the elastic modulus as well as the isotropic and kinematic parts of the strain hardening, and strain energy density per cycle, in different configurations: with or without prehardening,stress or strain control. (author)

  5. Superior radiation-resistant nanoengineered austenitic 304L stainless steel for applications in extreme radiation environments

    Sun, C.; Zheng, S.; Wei, C. C.; Wu, Y.; Shao, L.; Yang, Y.; Hartwig, K. T.; Maloy, S. A.; Zinkle, S. J.; Allen, T. R.; Wang, H.; Zhang, X.

    2015-01-01

    Nuclear energy provides more than 10% of electrical power internationally, and the increasing engagement of nuclear energy is essential to meet the rapid worldwide increase in energy demand. A paramount challenge in the development of advanced nuclear reactors is the discovery of advanced structural materials that can endure extreme environments, such as severe neutron irradiation damage at high temperatures. It has been known for decades that high dose radiation can introduce significant void swelling accompanied by precipitation in austenitic stainless steel (SS). Here we report, however, that through nanoengineering, ultra-fine grained (UFG) 304L SS with an average grain size of ~100 nm, can withstand Fe ion irradiation at 500°C to 80 displacements-per-atom (dpa) with moderate grain coarsening. Compared to coarse grained (CG) counterparts, swelling resistance of UFG SS is improved by nearly an order of magnitude and swelling rate is reduced by a factor of 5. M23C6 precipitates, abundant in irradiated CG SS, are largely absent in UFG SS. This study provides a nanoengineering approach to design and discover radiation tolerant metallic materials for applications in extreme radiation environments.

  6. Corrosion and slow-strain-rate testing of Type 304L stainless steel in tuff groundwater environments

    Type 304L stainless steel (SS) is the nuclear waste package reference material by the Nevada Nuclear Waste Storage Investigations (NNWSI) Project. The stress-corrosion cracking (SCC) resistance of this material to elevated-temperature tuff groundwater environments was determined under irradiated and unirradiated conditions. The material was found to be susceptible to SCC (in both the solution-annealed and solution-annealed-and-sensitized conditions) when exposed to an irradiated (3 x 105 rad/h) air/water vapor/crushed tuff rock environment at 900C. A similar exposure at 500C did not result in failure after a 25-month test duration. Specimens of sensitized Type 304 SS failed in both the 900C and 500C environments. U-bend specimens of Type 304L SS conditioned with a variety of sensitization heat treatments resisted failure during a test of 1-year duration in which an environment of tuff rock and groundwater held at 2000C was allowed to boil to dryness on a cyclical (weekly) basis. All specimens of sensitized Type 304 SS exposed to this environment failed. Slow-strain-rate studies were performed on 304L, 304, and 316L SS specimens. The Type 304L steel was tested in J-13 well water at 1500C; the Type 316L steel at 950C. Neither material showed evidence of SCC in these tests. Sensitized Type 304 SS, on the other hand, did exhibit SCC in J-13 well water in tests conducted at 1500C

  7. Martensitic Transformation in Ultrafine-Grained Stainless Steel AISI 304L Under Monotonic and Cyclic Loading

    Heinz Werner Höppel

    2012-02-01

    Full Text Available The monotonic and cyclic deformation behavior of ultrafine-grained metastable austenitic steel AISI 304L, produced by severe plastic deformation, was investigated. Under monotonic loading, the martensitic phase transformation in the ultrafine-grained state is strongly favored. Under cyclic loading, the martensitic transformation behavior is similar to the coarse-grained condition, but the cyclic stress response is three times larger for the ultrafine-grained condition.

  8. XPS Analysis of AISI 304L Stainless Steel Surface after Electropolishing

    Rokosz K.

    2015-03-01

    Full Text Available In the paper, the passive surface layers of AISI 304L after standard (EP50 and very-high-current density electropolishing (EP1000 in a mixture of orthophosphoric and sulfuric acids in a 1:4 ratio, are presented. The main finding of the presented studies is enrichment of the steel surface film in chromium: total chromium to total iron ratio was equal to 6.6 after EP50 and to 2.8 after EP1000; on the other hand, chromium compounds to iron compounds ratio was equal to 10.1 after EP50, and 3.9 after EP1000.

  9. The effect of electrode vertex angle on automatic tungsten-inert-gas welds for stainless steel 304L plates

    The effect of electrode vertex angle on penetration depth and weld bead width, in automatic tungsten-inert-gas (TIG) dcsp bead-on-plate welding with different currents, has been studied for stainless steel 304L plates 1.5 mm and 8 mm thick. It has been found that for thin plates, wider and deeper welds are obtained when using sharper electrodes while, for thick plates, narrower and deeper welds are produced when blunt electrodes (vertex angle 180 deg) are used. An explanation of the results, based on a literature survey, is included

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

    Nineteen alloys were evaluated as possible materials of construction for steam heating coils, the dissolver vessel, and the off-gas system of proposed facilities to process thorium and uranium fuels. Commercially available alloys were found that are satisfactory for all applications. With thorium fuel, which requires HNO3-HF for dissolution, the best alloy for service at 1300C when complexing agents for fluoride are used is Inconel 690; with no complexing agents at 1300C, Inconel 671 is best. At 950C, six other alloys tested would be adequate: Haynes 25, Ferralium, Inconel 625, Type 304L stainless steel, Incoloy 825, and Haynes 20 (in order of decreasing preference); based on composition, six untested alloys would also be adequate. The ions most effective in reducing fluoride corrosion were the complexing agents Zr4+ and Th4+; Al3+ was less effective. With uranium fuel, modestly priced Type 304L stainless steel is adequate. Corrosion will be most severe in HNO3-HF used occasionally for flushing and in solutions of HNO3 and corrosion products (ferric and dichromate ions). HF corrosion can be minimized by complexing the fluoride ion and by passivation of the steel with strong nitric acid. Corrosion caused by corrosion products can be minimized by operating at lower temperatures

  11. The role of martensitic transformation on bimodal grain structure in ultrafine grained AISI 304L stainless steel

    Sabooni, S., E-mail: s.sabooni@ma.iut.ac.ir [Department of Materials Engineering, Isfahan University of Technology, 84156-83111 Isfahan (Iran, Islamic Republic of); Karimzadeh, F.; Enayati, M.H. [Department of Materials Engineering, Isfahan University of Technology, 84156-83111 Isfahan (Iran, Islamic Republic of); Ngan, A.H.W. [Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong (China)

    2015-06-11

    In the present study, metastable AISI 304L austenitic stainless steel samples were subjected to different cold rolling reductions from 70% to 93%, followed by annealing at 700 °C for 300 min to form ultrafine grained (UFG) austenite with different grain structures. Transmission electron microscopy (TEM) and nanoindentation were used to characterize the martensitic transformation, in order to relate it to the bimodal distribution of the austenite grain size after subsequent annealing. The results showed that the martensite morphology changed from lath type in the 60% rolled sample to a mixture of lath and dislocation-cell types in the higher rolling reductions. Calculation of the Gibbs free energy change during the reversion treatment showed that the reversion mechanism is shear controlled at the annealing temperature and so the morphology of the reverted austenite is completely dependent on the morphology of the deformation induced martensite. It was found that the austenite had a bimodal grain size distribution in the 80% rolled and annealed state and this is related to the existence of different types of martensite. Increasing the rolling reduction to 93% followed by annealing caused changing of the grain structure to a monomodal like structure, which was mostly covered with small grains of around 300 nm. The existence of bimodal austenite grain size in the 80% rolled and annealed 304L stainless steel led to the improvement of ductility while maintaining a high tensile strength in comparison with the 93% rolled and annealed sample.

  12. Effect of sensitization on the mechanical properties of type 304 L stainless steel

    The sensitization is a corrosion cause that it has studied broadly in the austenitic steels; however its relations don't knowed very well, into the sensitization and the steel's mechanical properties. Wherefore, the objectives of this work was to study the mechanical properties, in tension of austenitic steel with different levels of sensitization. The material utilized was a 304 L steel of standard composition AISI. The samples were sensitized at 450, 650 and 850 Centigrade degree, by short expositions, following by a temper in water. After this treatment, the tension test tubes were carried to rupture at low deformation velocity. The sensitization was evaluated by the method of Akashi EPR cyclic polarization. The sensitization distribution was analyzed by optical metallography in color and the fracture surface were studied by sweeping electronic microscopy. The distribution and length of the carbides were the factor that control the mechanic behavior of materials. At 450 Centigrade, the border of the grain its founded free of carbides, also for the longest times of exposition, but the particles are presented as fine precipitates in the grain interior, with this is increased the mechanical properties by the internal interactions of hardness or oldness types. At 650 Centigrade the frontiers show a dense distribution of fine carbides. These precipitates are interacting with the borders grain, increasing lightly the mechanical properties of steel. At 850 Centigrade, were formed discontinued carbides that not affect the mechanical behavior, but whether the fracture; the resistance is reduced and the ductility is increased although to impose the thermic effect of treatment. (Author)

  13. Deposition and characterization of noble metal onto surfaces of 304l stainless steel

    Noble metal chemical addition (NMCA) plus hydrogen water chemistry is an industry-wide accepted approach for potential intergranular stress corrosion cracking mitigation of BWR internals components. NMCA is a method of applying noble metal onto BWR internals surfaces using reactor water as the transport medium that causes the deposition of noble metal from the liquid onto surfaces. In this work different platinum concentration solutions were deposited onto pre-oxidized surfaces of 304l steel at 180 C during 48 hr in an autoclave. In order to simulate the zinc water conditions, deposits of Zn and Pt-Zn were also carried out. The solutions used to obtain the deposits were: sodium hexahydroxyplatinate (IV), zinc nitrate hydrate and zinc oxide. The deposits obtained were characterized by scanning electron microscopy and X-ray diffraction. Finally, the electrochemical corrosion potential of pre-oxidized samples with Pt deposit were obtained and compared with the electrochemical corrosion potential of only pre-oxidized samples. (Author)

  14. Nanosecond laser surface modification of AISI 304L stainless steel: Influence the beam overlap on pitting corrosion resistance

    Pacquentin, Wilfried, E-mail: wilfried.pacquentin@cea.fr [CEA, DEN/DANS/DPC/SEARS/LISL, F-91191 Gif-sur-Yvette (France); Caron, Nadège [CEA, DEN/DANS/DPC/SEARS/LISL, F-91191 Gif-sur-Yvette (France); Oltra, Roland [Laboratoire Interdisciplinaire Carnot de Bourgogne, Université de Bourgogne, UMR CNRS 5209, 21078 Dijon Cedex (France)

    2014-01-01

    Surface modifications of AISI 304L stainless steel by laser surface melting (LSM) were investigated using a nanosecond pulsed laser-fibre doped by ytterbium at different overlaps. The objective was to study the change in the corrosion properties induced by the treatment of the outer-surface of the stainless steel without modification of the bulk material. Different analytical techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD), and glow discharge optical emission spectrometry (GDOES) were used to characterize the laser-melted surface. The corrosion resistance was evaluated in a chloride solution at room temperature by electrochemical tests. The results showed that the crystallographic structure, the chemical composition, the properties of the induced oxide layer and consequently the pitting corrosion resistance strongly depend on the overlap rate. The most efficient laser parameters led to an increase of the pitting potential by more than 300 mV, corresponding to a quite important improvement of the corrosion resistance. This latter was correlated to chromium enrichment (47 wt.%) at the surface of the stainless steel and the induced absence of martensite and ferrite phases. However, these structural and chemical modifications were not sufficient to explain the change in corrosion behaviour: defects and adhesion of the surface oxide layer must have been taken into consideration.

  15. Corrosion study of stainless steel SS304L in molten molybdates

    Usami, T.; Uruga, K.; Tsukada, T.; Miura, Y.; Komamine, S.; Ochi, E.

    2016-04-01

    Depending on operating conditions of the vitrification process of high-level liquid waste, molten salt mainly composed of sodium and molybdenum can be generated, and poured into stainless steel canisters. In this work, the possible reaction between the molten molybdate and stainless steel was investigated using multi-component molybdate and simple Na2MoO4 - MoO3 molybdate. In the experiments using multi-component molybdates, no significant reaction is observed between the mixed molybdates and the stainless steel specimens at 700 °C in 4 h. The reaction rate of the stainless steel with the multi-component molybdate increases in proportion to exp(-1/T). The depth of the most reacted area is about 300 μm even at 1000 °C, and was much smaller than the 6 mm thickness of the canister. In the simple Na2MoO4 - MoO3 molybdate, the reaction rate was proportional to the MoO3 concentration. The essence of the reaction is oxidation of metals by Mo6+ - > Mo4+. Part of the reaction product mainly composed of Fe is dissolved into the molybdate, while the other part mainly composed of Cr sloughs and forms a banded layer.

  16. Effects of Low Temperature on Hydrogen-Assisted Crack Growth in Forged 304L Austenitic Stainless Steel

    Jackson, Heather; San Marchi, Chris; Balch, Dorian; Somerday, Brian; Michael, Joseph

    2016-08-01

    The objective of this study was to evaluate effects of low temperature on hydrogen-assisted crack propagation in forged 304L austenitic stainless steel. Fracture initiation toughness and crack-growth resistance curves were measured using fracture mechanics specimens that were thermally precharged with 140 wppm hydrogen and tested at 293 K or 223 K (20 °C or -50 °C). Fracture initiation toughness for hydrogen-precharged forgings decreased by at least 50 to 80 pct relative to non-charged forgings. With hydrogen, low-temperature fracture initiation toughness decreased by 35 to 50 pct relative to room-temperature toughness. Crack growth without hydrogen at both temperatures was microstructure-independent and indistinguishable from blunting, while with hydrogen microcracks formed by growth and coalescence of microvoids. Initiation of microvoids in the presence of hydrogen occurred where localized deformation bands intersected grain boundaries and other deformation bands. Low temperature additionally promoted fracture initiation at annealing twin boundaries in the presence of hydrogen, which competed with deformation band intersections and grain boundaries as sites of microvoid formation and fracture initiation. A common ingredient for fracture initiation was stress concentration that arose from the intersection of deformation bands with these microstructural obstacles. The localized deformation responsible for producing stress concentrations at obstacles was intensified by low temperature and hydrogen. Crack orientation and forging strength were found to have a minor effect on fracture initiation toughness of hydrogen-supersaturated 304L forgings.

  17. Corrosion fatigue behavior of cold-worked 304L stainless steel in a simulated BWR coolant environment

    Fatigue crack growth tests were performed to evaluate the effect of cold work on the fatigue behavior of 304L stainless steel in the ambient air at room temperature and 300degC and in a simulated BWR coolant environment, respectively. The fatigue crack growth rates (FCGRs) for the as-received (AR) and cold-rolled specimens as room temperature were in the same range and the FCGRs obtained at 300degC in air were higher than at room temperature. In addition, the FCGRs for the AR specimens were higher at 300degC in air compared with those for the cold-rolled. The specimens tested in the water environment at 300degC showed higher corrosion fatigue crack growth rates (CFCGRs) relative to those measured in air at room temperature and 300degC. Local quasi-cleavages could account for the observation that the FCGRs in air at 300degC were faster than at room temperature. The dominant fracture features of quasi-cleavages, along with corrosion products, were observed with all the 304L specimens tested in the simulated BWR water environment, which could be related to the higher crack growth rates in the corrosive environment. (author)

  18. Examination of irradiated 304L stainless steel to 6061-T6 aluminum inertia welded transition joints after irradiation in a spallation neutron

    The Savannah River Technology Center (SRTC) designed and fabricated tritium target/blanket assemblies which were irradiated for six months at the Los Alamos Neutron Science Center (LANSCE). Cooling water was supplied to the assemblies through 1 inch diameter 304L Stainless Steel (SS) tubing. To attach the 304L SS tubing to the modules a 304L SS to 6061-T6 Aluminum (Al) inertia welded transition joint was used. These SS/Al inertia weld transition joints simulate expected transition joints in the Accelerator Production of Tritium (APT) Target/Blanket where as many as a thousand SS/Al weld transition joints will be used. Materials compatibility between the 304L SS and the 6061-T6 Al in the spallation neutron environment is a major concern as well as the corrosion associated with the cooling water flowing through the piping. The irradiated inertia weld examination will be discussed

  19. Effect of welding process, type of electrode and electrode core diameter on the tensile property of 304L austenitic stainless steel

    Akinlabi OYETUNJI

    2014-11-01

    Full Text Available The effect of welding process, type of electrode and electrode core diameter on the tensile property of AISI 304L Austenitic Stainless Steel (ASS was studied. The tensile strength property of ASS welded samples was evaluated. Prepared samples of the ASS were welded under these three various variables. Tensile test was then carried out on the welded samples. It was found that the reduction in ultimate tensile strength (UTS of the butt joint samples increases with increase in core diameter of the electrode. Also, the best electrode for welding 304L ASS is 308L stainless steel-core electrode of 3.2 mm core diameter. It is recommended that the findings of this work can be applied in the chemical, food and oil industries where 304L ASS are predominantly used.

  20. Influence of the temperature and the time of sensitization heat treatment on the rupture energy of notched specimen of 304 L austenitic stainless steel

    This study allowed us to show that the measurement of rupture energy on notched specimen, at low temperature (-180+-50C) is a sensitive method for evaluating the importance of carbide precipitation at grain boundaries when austenitic stainless steel 304 L is sensitized. This process had been studied between 500 and 9000C, and during 3 to 100 hrs

  1. Standard test method for electrochemical reactivation (EPR) for detecting sensitization of AISI type 304 and 304L stainless steels

    American Society for Testing and Materials. Philadelphia

    1994-01-01

    1.1 This test method covers a laboratory procedure for conducting an electrochemical reactivation (EPR) test on AISI Type 304 and 304L (UNS No. S30400 and S30403, respectively) stainless steels. This test method can provide a nondestructive means of quantifying the degree of sensitization in these steels (1, 2, 3). This test method has found wide acceptance in studies of the effects of sensitization on intergranular corrosion and intergranular stress corrosion cracking behavior (see Terminology G15). The EPR technique has been successfully used to evaluate other stainless steels and nickel base alloys (4), but the test conditions and evaluation criteria used were modified in each case from those cited in this test method. 1.2 The values stated in SI units are to be regarded as the standard. The inch-pound units given in parentheses are for information only. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this...

  2. Reactor Materials Program: Mechanical properties of irradiated Types 304 and 304L stainless steel weldment components

    The vessels (reactor tanks) of the Savannah River Site nuclear production reactors constructed in the 1950's are comprised of Type 304 stainless steel with Type 308 stainless steel weld filler. Irradiation exposure to the reactor tank sidewalls through reactor operation has caused a change in the mechanical properties of these materials. A database of as-irradiated mechanical properties for site-specific materials and irradiation conditions has been produced for reactor tank structural analyses and to quantify the effects of radiation-induced materials degradation for evaluating reactor service life. The data has been collected from the SRL Reactor Materials Program (RMP) irradiations and testing of archival stainless steel weldment components and from previous SRL programs to measure properties of irradiated reactor Thermal Shield weldments and reactor tank (R-tank) sidewall material. Irradiation programs of the RMP are designed to quantify mechanical properties at tank operating temperatures following irradiation to present and future tank wall maximum exposure conditions. The exposure conditions are characterized in terms of fast neutron fluence (En > 0.1 MeV) and displacements per atom (dpa)3. Tensile properties, Charpy-V notch toughness, and elastic-plastic fracture toughness were measured for base, weld, and weld heat-affected zone (HAZ) weldment components from archival piping specimens following a Screening Irradiation in the University of Buffalo Reactor (UBR) and following a Full-Term Irradiation in the High Flux Isotope Reactor (HFIR)

  3. Reactor Materials Program: Mechanical properties of irradiated Types 304 and 304L stainless steel weldment components

    Sindelar, R.L.; Caskey, G.R. Jr.

    1991-12-01

    The vessels (reactor tanks) of the Savannah River Site nuclear production reactors constructed in the 1950`s are comprised of Type 304 stainless steel with Type 308 stainless steel weld filler. Irradiation exposure to the reactor tank sidewalls through reactor operation has caused a change in the mechanical properties of these materials. A database of as-irradiated mechanical properties for site-specific materials and irradiation conditions has been produced for reactor tank structural analyses and to quantify the effects of radiation-induced materials degradation for evaluating reactor service life. The data has been collected from the SRL Reactor Materials Program (RMP) irradiations and testing of archival stainless steel weldment components and from previous SRL programs to measure properties of irradiated reactor Thermal Shield weldments and reactor tank (R-tank) sidewall material. Irradiation programs of the RMP are designed to quantify mechanical properties at tank operating temperatures following irradiation to present and future tank wall maximum exposure conditions. The exposure conditions are characterized in terms of fast neutron fluence (E{sub n} > 0.1 MeV) and displacements per atom (dpa){sup 3}. Tensile properties, Charpy-V notch toughness, and elastic-plastic fracture toughness were measured for base, weld, and weld heat-affected zone (HAZ) weldment components from archival piping specimens following a Screening Irradiation in the University of Buffalo Reactor (UBR) and following a Full-Term Irradiation in the High Flux Isotope Reactor (HFIR).

  4. Reactor Materials Program: Mechanical properties of irradiated Types 304 and 304L stainless steel weldment components

    Sindelar, R.L.; Caskey, G.R. Jr.

    1991-12-01

    The vessels (reactor tanks) of the Savannah River Site nuclear production reactors constructed in the 1950's are comprised of Type 304 stainless steel with Type 308 stainless steel weld filler. Irradiation exposure to the reactor tank sidewalls through reactor operation has caused a change in the mechanical properties of these materials. A database of as-irradiated mechanical properties for site-specific materials and irradiation conditions has been produced for reactor tank structural analyses and to quantify the effects of radiation-induced materials degradation for evaluating reactor service life. The data has been collected from the SRL Reactor Materials Program (RMP) irradiations and testing of archival stainless steel weldment components and from previous SRL programs to measure properties of irradiated reactor Thermal Shield weldments and reactor tank (R-tank) sidewall material. Irradiation programs of the RMP are designed to quantify mechanical properties at tank operating temperatures following irradiation to present and future tank wall maximum exposure conditions. The exposure conditions are characterized in terms of fast neutron fluence (E{sub n} > 0.1 MeV) and displacements per atom (dpa){sup 3}. Tensile properties, Charpy-V notch toughness, and elastic-plastic fracture toughness were measured for base, weld, and weld heat-affected zone (HAZ) weldment components from archival piping specimens following a Screening Irradiation in the University of Buffalo Reactor (UBR) and following a Full-Term Irradiation in the High Flux Isotope Reactor (HFIR).

  5. Microelectrochemical investigation of the effect of cathodic polarisation on the corrosion resistance of 304L stainless steel in a 1 M NaCl solution

    Arjmand Gholenji, Farzin; Adriaens, Annemie

    2012-01-01

    304L stainless steel was cathodically polarised in a 1 M sodium chloride solution using a microcapillary electrochemical droplet cell. During the cathodic polarisation the produced hydrogen atoms penetrate into the sample and accumulate at sites of the steel surface. We observed that the pitting potential (E-pit), the anodic current density (I-corr) and the corrosion potential (E-corr) of the polarised steel are strongly influenced by the applied cathodic potential and therefore by the amount...

  6. Study on prevention of chloride induced stress corrosion cracking for type 304L, 316L stainless steel canister

    For the practical application of multi-purpose canisters (MPCs), there are technical issues for containment function to prevent the initiation of chloride induced stress corrosion cracking (SCC). Therefore, the SCC test were conducted to clarify the critical salt density to initiate SCC and the effect which the reduction treatment of weld residual stress influents to prevent SCC. (1) The minimum threshold of salt for SCC initiation could be 4 g/cm2 as Cl under the condition of the temperatures of 50degC and the relative humidity of 35% with the 316 type L-grade austenite stainless steel used over 5000 hr. However, the threshold could be reduced to 2 g/m2 as Cl under the actual equipment surface condition corresponding to the conventional stainless steel MPC. (2) An accelerated corrosion test was performed using mock-up MPC made of Type 304L, in which the salt concentration on the surface of weld lines was kept to 4 g/cm2 as Cl. As the result of the test, SCC on the surface-treated weld line by ZSP didn't occur because of the compressed stress induced appropriately, therefore the validity of surface treatment techniques was confirmed. (author)

  7. Corrosion behaviour of single (Ti) and duplex (Ti-TiO2) coating on 304L stainless steel in nitric acid medium

    Highlights: → Ti coated 304L SS showed moderate to marginal corrosion resistance in 1 M and 8 M HNO3. → Duplex Ti-TiO2 coated 304L SS showed minimization of structural heterogeneities. → Passive film property improves by minimizing structural heterogeneities. → Protection efficiency for 304L SS increases with duplex Ti-TiO2 coating in HNO3. - Abstract: Sputter deposited single titanium (Ti) layer, and duplex Ti-TiO2 coating on austenitic type 304L stainless steel (SS) was prepared, and the corrosion performance was evaluated in nitric acid medium using surface morphological and electrochemical techniques. Morphological analysis using atomic force microscope of the duplex Ti-TiO2 coated surface showed minimization of structural heterogeneities as compared to single Ti layer coating. The electrochemical corrosion results revealed that, titanium coated 304L SS showed moderate to marginal improvement in corrosion resistance in 1 M, and 8 M nitric acid, respectively. Duplex Ti-TiO2 coated 304L SS specimens showed improved corrosion resistance as compared to Ti coating from dilute (1 M) to concentrated medium (8 M). The percentage of protection efficiency for base material increases significantly for duplex Ti-TiO2 coating as compared to single Ti layer coating. The oxidizing ability of nitric acid on both the coatings as well as factors responsible for improvement in protection efficiency are discussed and highlighted in this paper.

  8. Chloride induced localized corrosion in simulated concrete pore solution: effect of a phosphate-based inhibitor on the behavior of 304L stainless steel compared to carbon steel

    In this paper, the acoustic emission technique coupled with electrochemical measurements was used to determine, in simulated concrete pore solution (Ca(OH)2), the critical value [Cl-] / [OH-], which prevents the pitting corrosion initiation of AISI 304L austenitic stainless steel, and to compare this critical value with that of the carbon steel in the same medium with and without inhibitor Na3PO4. The results show that for the austenitic stainless steel, the critical threshold of pitting corrosion initiation is around 5, while for carbon steel without inhibitor in Ca(OH)2 solution, it has a low value of about 0.6. However, the presence of the inhibitor Na3PO4 in this solution leads to the formation of a protective phosphate layer on the steel surface, increasing the critical ratio [Cl-] / [OH-] from 0.6 to 15. Under these conditions, the corrosion behavior of carbon steel is improved and, thanks to the blocking of pitting sites by the Na3PO4 inhibitor, it becomes much more resistant to localized corrosion than AISI 304L austenitic steel. (authors)

  9. In situ AFM study of pitting corrosion and corrosion under strain on a 304L stainless steel

    Our study is centred on surface localised corrosion under strain of a standard stainless steel (304L). The interest we take in these corrosion phenomena is led by the general misunderstanding of its primary initiation steps. The goal of this study is to determine precisely the relationships between local geometrical defects (grain boundaries, dislocation lines, etc) or chemical defects (inclusions) with the preferential sites of corrosion on the strained material. By combining three techniques at the same time: Atomic Force Microscopy, an electrochemical cell and a traction plate, we can observe in situ the effect of localised stress and deformation on the sample surface exposed to a corrosive solution. We managed to build an original set-up compatible with all the requirements of these three different techniques. Furthermore, we prepared the surface of our sample as flat as possible to decrease at maximum the topographical noise in order to observe the smallest defect on the surface. By using a colloidal suspension of SiO2, we obtained surfaces with a typical corrugation (RMS) of about 1 A for areas of at least 1 μm2. Our experimental study has been organised in two primary investigations: - In situ study of the morphology evolution of the surface under a corrosive chloride solution (borate buffer with NaCl salt). The influence of time, NaCl concentration, and potential was investigated; - In situ exploration of a 304L strained surface. It revealed the first stages of the surface plastic evolutions like activation of sliding dislocations, materialized by parallel steps of about 2 nm high in the same grain. The secondary sliding plane systems were also noticeable for higher deformation rates. Recent results concerning in situ AFM observation of corroded surfaces under strain in a chloride media will be presented. (authors)

  10. On the dynamic strength of 304l stainless steel under impact

    Werdiger, Meir; Glam, Benny; Bakshi, Lior; Moshe, Ella; Horovitz, Yossef; Pistinner, Shlomi Levi

    2012-03-01

    Uniaxial strain plane impact (300-1700 m/s), loading and reloading experiments carried out on SS304L are reported. The aim of these experiments was to measure the material strength properties under shock compression. Most of the experiments reported here show a viscous type elastic precursor. The experimental results are compared to numerical simulations performed using a 1D code. The input physics to the simulations are the Steinberg equation of state and Johnson-Cook strength model. This model has been previously calibrated under uniaxial stress conditions in the rangee ɛ =1-5×103 s-1. Our experiments extended the data into the regione ɛ =105 -106 s-1. In spite of this extrapolation, there is a general agreement between simulations and experiments. However, differences in some details still exist.

  11. Four nondestructive electrochemical tests for detecting sensitization in type 304 and 304L stainless steels

    Three different electrochemical reactivation tests are compared with etch structures produced in the electrolytic oxalic acid etch test. These nondestructive tests are needed to evaluate welded stainless steel pipes and other plant equipment for susceptibility to intergranular attack. Sensitization associated with precipitates of chromium carbides at grain boundaries can make these materials subject to intergranular attack in acids and, in particular, to intergranular stress corrosion cracking in high-temperature (2890C) water on boiling water nuclear reactor power plants. In the first of the two older reactivation tests, sensitization is detected by the electrical charge generated during reactivation. In the second, it is measured by the ratio of maximum currents generated by a prior anodic loop and the reactivation loop. A third, simpler reactivation method based on a measurement of the maximum current generated during reactivation is proposed. If the objective of the field tests, which are to be carried out with portable equipment, is to distinguish between nonsensitized and sensitized material, this can be accomplished most simply, most rapidly, and at lowest cost by an evaluation of oxalic acid etch structures

  12. Effect of low temperature on hydrogen-assisted crack propagation in 304L/308L austenitic stainless steel fusion welds

    Highlights: •Measured crack growth resistance of welds at 223 K with 140 wppm H (gas charged). •H reduced fracture initiation toughness by >59% and altered fracture mode. •223 K altered fracture mode but had no effect on JIC of precharged welds. •At 293 K, microcracks initiate at δ-ferrite, and ferrite governed crack path. •At 223 K, microvoids form at γ deformation band intersections near phase boundaries. -- Abstract: Effects of low temperature on hydrogen-assisted cracking in 304L/308L austenitic stainless steel welds were investigated using elastic–plastic fracture mechanics methods. Thermally precharged hydrogen (140 wppm) decreased fracture toughness and altered fracture mechanisms at 293 and 223 K relative to hydrogen-free welds. At 293 K, hydrogen increased planar deformation in austenite, and microcracking of δ-ferrite governed crack paths. At 223 K, low temperature enabled hydrogen to exacerbate localized deformation, and microvoid formation, at austenite deformation band intersections near phase boundaries, dominated damage initiation; microcracking of ferrite did not contribute to crack growth

  13. Evaluation of stress corrosion cracking of irradiated 304L stainless steel in PWR environment using heavy ion irradiation

    Gupta, J.; Hure, J.; Tanguy, B.; Laffont, L.; Lafont, M.-C.; Andrieu, E.

    2016-08-01

    IASCC has been a major concern regarding the structural and functional integrity of core internals of PWR's, especially baffle-to-former bolts. Despite numerous studies over the past few decades, additional evaluation of the parameters influencing IASCC is still needed for an accurate understanding and modeling of this phenomenon. In this study, Fe irradiation at 450 °C was used to study the cracking susceptibility of 304 L austenitic stainless steel. After 10 MeV Fe irradiation to 5 dpa, irradiation-induced damage in the microstructure was characterized and quantified along with nano-hardness measurements. After 4% plastic strain in a PWR environment, quantitative information on the degree of strain localization, as determined by slip-line spacing, was obtained using SEM. Fe-irradiated material strained to 4% in a PWR environment exhibited crack initiation sites that were similar to those that occur in neutron- and proton-irradiated materials, which suggests that Fe irradiation may be a representative means for studying IASCC susceptibility. Fe-irradiated material subjected to 4% plastic strain in an inert argon environment did not exhibit any cracking, which suggests that localized deformation is not in itself sufficient for initiating cracking for the irradiation conditions used in this study.

  14. High temperature microstructural evolution of 304L stainless steel as function of pre-strain and strain rate

    304L stainless steel specimens are pre-strained to 0.15 or 0.5 and are then deformed at strain rates ranging from 2000 s-1 to 6000 s-1 at temperatures of 300 deg. C, 500 deg. C and 800 deg. C using a compressive split-Hopkinson pressure bar. The results show that for both values of the pre-strain, the flow stress increases with increasing strain rate, but reduces with increasing temperature. At deformation temperatures of 300 deg. C or 500 deg. C, the flow stress in the 0.5 pre-strained specimen is higher than that in the specimen pre-strained to 0.15. However, at a temperature of 800 deg. C, the two specimens exhibit a similar level of flow stress. Transmission electron microscopy (TEM) observations reveal that the strengthening effect observed in the specimens deformed at 300 deg. C or 500 deg. C is the combined result of dislocations, mechanical twins and martensite transformation. However, at a deformation temperature of 800 deg. C, the strengthening effect is the result primarily of dislocation multiplication. The volume fraction of martensite transformation decreases with increasing strain rate and temperature. In addition, both the dislocation density and the twin density increase with increasing strain rate, but decrease with increasing temperature. Finally, the quantitative analysis results indicate that the flow stress varies with the square root of the dislocation density, the twin density and the volume fraction of martensite, respectively.

  15. Plasma nitriding of AISI 304L and AISI 316L stainless steels: effect of time in the formation of S phase and the chromium nitrides

    Plasma nitriding can improve hardness and wear resistance of austenitic stainless steels without losses in corrosion resistance. This fact relies on a nitrided layer constituted only by S phase, without chromium nitrides precipitation. In this work, the effect of nitriding time on phases formed on nitrided layer was investigated in two austenitic stainless steels: AISI 304L e AISI 316L. The samples were nitrided at 420 deg C, using a mixture of 60 % N2 and 40% H2, during 5, 7 and 9 hours. It was noted that chromium nitrides were formed on samples of AISI 304L, nitrided for 7 e 9 hours, while all nitrided samples of AISI 316L showed only formation of S phase. The nitrided layers were characterized using optical microscope and x-ray diffraction. (author)

  16. Effect of strain-path on stress corrosion cracking of AISI 304L stainless steel in PWR primary environment at 360 deg. C

    Austenitic stainless steels (ASS) are widespread in primary and auxiliary circuits of PWR. Moreover, some components suffer stress corrosion cracking (SCC) under neutron irradiation. This degradation could be the result of the increase of hardness or the modification of chemical composition at the grain boundary by irradiation. In order to avoid complex and costly corrosion facilities, the effects of irradiation on the material are commonly simulated by applying a cold work on non-irradiated material prior to stress corrosion cracking tests. Slow strain rate tests were conducted on an austenitic stainless steel (SS) AISI 304L in PWR environment (360 deg. C). Particular attention was directed towards pre-straining effects on crack growth rate (CGR) and crack growth path (CGP). Results have demonstrated that the susceptibility of 304L to SCC in high-temperature hydrogenated water was enhanced by pre-straining. It seemed that IGSCC was enhanced by complex strain paths. (authors)

  17. Numerical Simulation and Artificial Neural Network Modeling for Predicting Welding-Induced Distortion in Butt-Welded 304L Stainless Steel Plates

    Narayanareddy, V. V.; Chandrasekhar, N.; Vasudevan, M.; Muthukumaran, S.; Vasantharaja, P.

    2016-02-01

    In the present study, artificial neural network modeling has been employed for predicting welding-induced angular distortions in autogenous butt-welded 304L stainless steel plates. The input data for the neural network have been obtained from a series of three-dimensional finite element simulations of TIG welding for a wide range of plate dimensions. Thermo-elasto-plastic analysis was carried out for 304L stainless steel plates during autogenous TIG welding employing double ellipsoidal heat source. The simulated thermal cycles were validated by measuring thermal cycles using thermocouples at predetermined positions, and the simulated distortion values were validated by measuring distortion using vertical height gauge for three cases. There was a good agreement between the model predictions and the measured values. Then, a multilayer feed-forward back propagation neural network has been developed using the numerically simulated data. Artificial neural network model developed in the present study predicted the angular distortion accurately.

  18. Effect of welding process, type of electrode and electrode core diameter on the tensile property of 304L austenitic stainless steel

    Akinlabi OYETUNJI; Nwafagu NWIGBOJI

    2014-01-01

    The effect of welding process, type of electrode and electrode core diameter on the tensile property of AISI 304L Austenitic Stainless Steel (ASS) was studied. The tensile strength property of ASS welded samples was evaluated. Prepared samples of the ASS were welded under these three various variables. Tensile test was then carried out on the welded samples. It was found that the reduction in ultimate tensile strength (UTS) of the butt joint samples increases with increase in core diameter of...

  19. Establishing precursor events for stress corrosion cracking initiation in type 304L stainless steel

    The present study attempts to establish slip band emergence, due to localized deformation, as a precursor event for SCC initiation in type 304L SS. The unidirectional tensile loading was used for straining flat tensile specimen, less than 10% strain, in air, 0.5 M NaCl + 0.5 M H2SO4 and boiling water reactor (BWR) simulated environment (288 C. degrees, 10 MPa). The surface features were characterized using optical microscopy, scanning electron microscopy (including electron backscattered diffraction-EBSD) and atomic force microscopy. The study shows that with increase in strain level, during unidirectional slow strain rate test (SSRT), average slip band height increases in air and the attack on slip lines occurs in acidified chloride environment. In BWR simulated environment, preferential oxidation on slip lines and initiation of a few cracks on some of the slip lines are observed. Based on the observation, the study suggests slip bands, formed due to localized deformation, to act as a precursor for SCC initiation. (authors)

  20. Investigation of micro-structure and micro-hardness properties of 304L stainless steel treated in a hot cathode arc discharge plasma

    Malik, Hitendra K., E-mail: hkmalik@physics.iitd.ac.in [Department of Physics, Indian Institute of Technology Delhi, New Delhi – 110016 (India); Singh, Omveer [Centre for Energy Studies, Indian Institute of Technology Delhi, New Delhi – 110016 (India); Dahiya, Raj P. [Centre for Energy Studies, Indian Institute of Technology Delhi, New Delhi – 110016 (India); Deenbandhu Chhotu Ram University of Science and Technology, Murthal–131039 (India)

    2015-08-28

    We have established a hot cathode arc discharge plasma system, where different stainless steel samples can be treated by monitoring the plasma parameters and nitriding parameters independently. In the present work, a mixture of 70% N{sub 2} and 30% H{sub 2} gases was fed into the plasma chamber and the treatment time and substrate temperature were optimized for treating 304L Stainless Steel samples. Various physical techniques such as x-ray diffraction, energy dispersive x-ray spectroscopy and micro-vickers hardness tester were employed to determine the structural, surface composition and surface hardness of the treated samples.

  1. Optimisation of CO2 laser welding of thin sheets made of stainless steel 304 L. Fabrication of prototype detection modules for a large size electromagnetic calorimeter

    For the new calorimeter detector, to be used in UA1 experiment at CERN proton-antiproton collider, about 35'000 stainless steel boxes with a volume of the order of 500 x 400 x 3 mm3, containing immerged electrodes in Tetramethylpentane (TMP) are required. The first hundred prototype boxes were built at CERN using CO2 laser welding technique. The results of a systematic experimental investigation and optimization of the welding parameters for 0.1 mm thick 304 L stainless steel sheets are presented

  2. Investigation of micro-structure and micro-hardness properties of 304L stainless steel treated in a hot cathode arc discharge plasma

    We have established a hot cathode arc discharge plasma system, where different stainless steel samples can be treated by monitoring the plasma parameters and nitriding parameters independently. In the present work, a mixture of 70% N2 and 30% H2 gases was fed into the plasma chamber and the treatment time and substrate temperature were optimized for treating 304L Stainless Steel samples. Various physical techniques such as x-ray diffraction, energy dispersive x-ray spectroscopy and micro-vickers hardness tester were employed to determine the structural, surface composition and surface hardness of the treated samples

  3. Environmental effect on cracking of an 304L austenitic stainless steels in PWR primary environment under cyclic loading

    The present study was undertaken in order to get further insights on cracking mechanisms in a 304L stainless steel. More precisely, a first objective of this study was to evaluate the effect of various cold working conditions on the cyclic stress-strain behavior and the fatigue life in air and in PWR primary environment. In air a prior hardening was found to reduce the fatigue life in the LCF regime but not in primary environment. In both environments, the fatigue limit of the hardened materials was increased after cold working.The second objective addresses the effect of the air and the PWR primary environments on the cracking mechanisms (initiation and propagation) in the annealed material in the LCF regime. More precisely, the kinetics of crack initiation and micro crack propagation were evaluated with a multi scale microscopic approach in air and in primary environment. In PWR primary environment, during the first cycles, preferential oxidation occurs along emerging dissociated dislocation and each cycle generates a new C-rich/Fe-rich oxide layer. Then, during cycling, the microstructure evolves from stacking fault into micro twinning and preferential oxidation occurs by continuous shearing and dissolution of the passive film. Beyond a certain crack depth (≤3 μm), the crack starts to propagate with a direction close to a 90 degrees angle from the surface. The crack continues its propagation by successive generation of shear bands and fatigue striations at each cycle up to failure. The role of corrosion hydrogen on these processes is finally discussed. (author)

  4. The role of atomic hydrogen and hydrogen-induced martensites in hydrogen embrittlement of type 304L stainless steel

    潘川; 褚武扬; 李正邦; 梁东图; 宿彦京; 乔利杰

    2002-01-01

    The role of atomic hydrogen and hydrogen-induced martensites in hydrogen embrittlement in slow strain rate tensile tests and hydrogen-induced delayed cracking (HIC) in sustained load tests for type 304 L stainless steel was quantitatively studied.The results indicated that hydrogen-induced martensites formed when hydrogen concentration C0 exceeded 30 ppm,and increased with an increase in C0,i.e.M(vol%)=62-82.5exp(-C0/102).The relative plasticity loss caused by the martensites increased linearly with increasing amount of the martensites,i.e.Iδ(M),%=0.45M(vol %)=27.9-37.1 exp(-C0/102).The plasticity loss caused by atomic hydrogen Iδ(H) increased with an increase in C0 and reached a saturation value Iδ(H)max=40% when C0>100 ppm.Iδ(H) decreased with an increase in strain rate ,i.e.Iδ(H),%=-21.9-9.9,and was zero when ≥c=0.032/s.HIC under sustained load was due to atomic hydrogen,and the threshold stress intensity for HIC decreased linearly with lnC0,i.e.KIH(Mpam1/2)=91.7-10.1 lnC0(ppm).The fracture surface of HIC was dimple if KI was high or/and C0 was low,otherwise it was quasi-cleavage.The boundary line between ductile and brittle fracture surface was KI-54+25exp(-C0/153)=0.``

  5. A 3D finite element analysis of temperature and stress fields in girth welded 304L stainless steel pipe

    A 3D finite element analysis model was developed to simulate a multipass, narrow gap pipe girth welding process. The pipe simulated was a Type 304L stainless steel pipe with a diameter of 406 mm, a thickness of 12.7 mm, and a narrow groove configuration. This pipe was finished in four continuous welding passes with one start-stop position. Temperatures, deformations and strains were recorded in real time during pipe welding. The thermal results from this model were tuned to match the calculated temperature histories with the comparable experimental thermal cycles. The calculated temperature histories were found to be axisymmetrically distributed around the pipe except in locations close to the welding start-stop position. This is in good agreement with what was observed from the experimental data. The calculated stress results show that the tensile residual stress zone on the pipe inner surface is about 30 mm from the weld centerline on each side and the tensile residual stress zone in the pipe wall thickness is about 5 mm from the pipe inner surface for up to 19 mm from the weld centerline (WCL). The calculated residual stresses are, in general, axisymmetrically distributed around the pipe except in locations near the welding start-stop position. This is not in agreement with what was noted from the experimental results. The comparison between the calculated stress results with the limited neutron diffraction residual stress measurements on the pipe inner surface demonstrates reasonable agreement between them. This 3D model is the first attempt at simulation of a full multipass girth pipe welding process. Much improvement could be realized, but more experimental residual stress measurements on pipe weldments are needed to verify this model

  6. Comparative study in the induced corrosion by sulfate reducing microorganisms, in a stainless steel 304L sensitized and a carbon steel API X65

    In spite of the operational experience related with the presence of the phenomenon of microbiological corrosion (MIC) in industrial components, it was not but until the decade of the 80 s when the nuclear industry recognized its influence in some systems of Nuclear Generating Power plants. At the moment, diverse studies that have tried to explain the generation mechanism of this phenomenon exist; however, they are even important queries that to solve, especially those related with the particularities of the affected metallic substrates. Presently work, the electrochemical behavior of samples of stainless steel AISI 304L sensitized is evaluated and the carbon steel APIX65, before the action of sulfate reducing microorganisms low the same experimental conditions; found that for the APIX65 the presence of this type of bacteria promoted the formation of a stable biofilm that allowed the maintenance of the microorganisms that damaged the material in isolated places where stings were generated; while in the AISI 304L, it was not detected damage associated to the inoculated media. The techniques of Resistance to the Polarization and Tafel Extrapolation, allowed the calculation of the speed of uniform corrosion, parameter that doesn't seem to be influenced by the presence of the microorganisms; while that noise electrochemical it distinguished in real time, the effect of the sulfate reducing in the steel APIX65. (Author)

  7. Effect of prior deformation on the 76-K fracture toughness of AISI 304L and AWS 308L stainless steels

    AISI 304L and its weld metal, AWS 308L, may undergo a partial transformation to martensite during cryogenic service owing to thermal and mechanical stresses. In this study, the effect of service-induced deformation on the toughness of these materials were determined. Low temperature compressive loading in the laboratory produced larger deformations. Crack initiation toughness, K/sub Ic/(J), and tearing resistance, dJ/da, at 76 K were evaluated as a function of martensite content, a measure of the deformation in these steels. The results showed that the toughness properties of the 304L decrease gradually as the martensite content increases from the 5 to 8% level found in the service condition to the 45% level obtained by compressive loading. The decrease was less than that expected on the basis of the increased flow stress. The toughness properties of the 308L weld metal decreased more sharply with increased martensite content than those of the 304L. The sharp decrease is associated with a degradation of the properties of the delta ferrite rather than that of the austenite

  8. Correlation between Corrosion Potential and Pitting Potential for AISI 304L Austenitic Stainless Steel in 3.5% NaCl Aqueous Solution

    Neusa Alonso-Falleiros; Stephan Wolynec

    2002-01-01

    We investigated the effect of surface finish of two AISI 304L (UNS S30403) stainless steels on the corrosion potential (Ecorr) in 3.5% NaCl aqueous solution and its value was compared with the pitting potential (Ep) value and the type of anodic potentiodynamic curve obtained for determination of Ep in this solution. Five different surface finishes were examined. Ecorr and its standard deviation are strongly affected by the type of surface finish. Moreover, there are evidences of a linear corr...

  9. Oligo-cyclic damage and behaviour of a 304 L austenitic stainless steel according to environment (vacuum, air, PWR primary water) at 300 C

    Nowadays, for nuclear power plants licensing or operating life extensions, various safety authorities require the consideration of the primary water environment effect on the fatigue life of Pressurized Water Reactor (PWR) components. Thus, this work focused on the study of low cycle fatigue damage kinetics and mechanisms, of a type 304L austenitic stainless steel. Several parameters effects such as temperature, strain rate or strain amplitude were investigated in air as in PWR water. Thanks to targeted in-vacuum tests, the intrinsic influence of these parameters and environments on the fatigue behaviour of the material was studied. It appears that compared with vacuum, air is already an active environment which is responsible for a strong decrease in fatigue lifetime of this steel, especially at 300 C and low strain amplitude. The PWR water coolant environment is more active than air and leads to increased damage kinetics, without any modifications of the initiation sites or propagation modes. Moreover, the decreased fatigue life in PWR water is essentially attributed to an enhancement of both initiation and micropropagation of 'short cracks'. Finally, the deleterious influence of low strain rates on the 304L austenitic stainless steel fatigue lifetime was observed in PWR water environment, in air and also in vacuum without any environmental effects. This intrinsic strain rate effect is attributed to the occurrence of the Dynamic Strain Aging phenomenon which is responsible for a change in deformation modes and for an enhancement of cracks initiation. (author)

  10. Dependence of the cyclic stress–strain curve on loading history and its interaction with fatigue of 304L stainless steel

    Highlights: ► Contrary to low deformation, cyclic curve is not unique at high strain amplitude. ► However, as the loading was continued cyclic hardening tends to stabilize. ► Cyclic hardening is mainly kinematic type, isotropic component remains quasi-linear. ► Increasing in pre-hardening strain amplitude has almost no effect on fatigue damage. ► Fatigue life decreasing is associated with formation of walls, cells and defect bands. - Abstract: This study investigates the effects of loading history on the cyclic stress–strain curve and fatigue behavior of 304L stainless steel at room temperature. Tension–compression tests were performed on the same specimen under controlled strain, using several loading sequences of increasing or decreasing amplitude. The results show that the cyclic curve is not unique, as it depends on the loading sequence. The same predeformed specimens were subjected to fatigue tests. The results showed that fatigue life is significantly reduced by the previous loading history. A previously developed method for determining the effect of prehardening was evaluated. Microstructural analyses were also performed; the microstructures after preloading and their evolution during the fatigue cycles were characterized by transmission electron microscopy (TEM). The results of these analyses improve our understanding of the macroscopic properties of 304L stainless steel and can help us identify the causes of failure and lifetime reduction.

  11. The mechanical properties of 316L/304L stainless steels, Alloy 718 and Mod 9Cr-1Mo after irradiation in a spallation environment

    Maloy, S. A.; James, M. R.; Willcutt, G.; Sommer, W. F.; Sokolov, M.; Snead, L. L.; Hamilton, M. L.; Garner, F.

    2001-07-01

    The Accelerator Production of Tritium (APT) project proposes to use a 1.0 GeV, 100 mA proton beam to produce neutrons via spallation reactions in a tungsten target. The neutrons are multiplied and moderated in a lead/aluminum/water blanket and then captured in 3He to form tritium. The materials in the target and blanket region are exposed to protons and neutrons with energies into the GeV range. The effect of irradiation on the tensile and fracture toughness properties of candidate APT materials, 316L and 304L stainless steel (annealed), modified (Mod) 9Cr-1Mo steel, and Alloy 718 (precipitation hardened), was measured on tensile and fracture toughness specimens irradiated at the Los Alamos Neutron Science Center accelerator, which operates at an energy of 800 MeV and a current of 1 mA. The irradiation temperatures ranged from 50°C to 164°C, prototypic of those expected in the APT target/blanket. The maximum achieved proton fluence was 4.5×10 21 p/ cm2 for the materials in the center of the beam. This maximum exposure translates to a dpa of 12 and the generation of 10 000 appm H and 1000 appm He for the Type 304L stainless steel tensile specimens. Specimens were tested at the irradiation temperature of 50-164°C. Less than 1 dpa of exposure reduced the uniform elongation of the Alloy 718 (precipitation hardened) and Mod 9Cr-1Mo to less than 2%. This same dose reduced the fracture toughness by 50%. Approximately 4 dpa of exposure was required to reduce the uniform elongation of the austenitic stainless steels (304L and 316L) to less than 2%. The yield stress of the austenitic steels increased to more than twice its non-irradiated value after less than 1 dpa. The fracture toughness reduced significantly by 4 dpa to ˜100 MPa m 1/2. These results are discussed and compared with results of similar materials irradiated in fission reactor environments.

  12. Influence of low-temperature nitriding on the strain-induced martensite and laser-quenched austenite in a magnetic encoder made from 304L stainless steel

    Leskovšek, Vojteh; Godec, Matjaž; Kogej, Peter

    2016-08-01

    We have investigated the possibility of producing a magnetic encoder by an innovative process. Instead of turning grooves in the encoder bar for precise positioning, we incorporated the information in 304L stainless steel by transforming the austenite to martensite after bar extrusion in liquid nitrogen and marking it with a laser, which caused a local transformation of martensite back into austenite. 304L has an excellent corrosion resistance, but a low hardness and poor wear resistance, which limits its range of applications. However, nitriding is a very promising way to enhance the mechanical and magnetic properties. After low-temperature nitriding at 400 °C it is clear that both ε- and α‧-martensite are present in the deformed microstructure, indicating the simultaneous stress-induced and strain-induced transformations of the austenite. The effects of a laser surface treatment and the consequent appearance of a non-magnetic phase due to the α‧ → γ transformation were investigated. The EDS maps show a high concentration of nitrogen in the alternating hard surface layers of γN and α‧N (expanded austenite and martensite), but no significantly higher concentration of chromium or iron was detected. The high surface hardness of this nitride layer will lead to steels and encoders with better wear and corrosion resistance.

  13. Characterization of welding of AISI 304l stainless steel similar to the core encircling of a BWR reactor; Caracterizacion de soldaduras de acero inoxidable AISI 304L similares a las de la envolvente del nucleo de un reactor BWR

    Gachuz M, M.E.; Palacios P, F.; Robles P, E.F. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico)

    2003-07-01

    Plates of austenitic stainless steel AISI 304l of 0.0381 m thickness were welded by means of the SMAW process according to that recommended in the Section 9 of the ASME Code, so that it was reproduced the welding process used to assemble the encircling of the core of a BWR/5 reactor similar to that of the Laguna Verde Nucleo electric plant, there being generated the necessary documentation for the qualification of the one welding procedure and of the welder. They were characterized so much the one base metal, as the welding cord by means of metallographic techniques, scanning electron microscopy, X-ray diffraction, mechanical essays and fracture mechanics. From the obtained results it highlights the presence of an area affected by the heat of up to 1.5 mm of wide and a value of fracture tenacity (J{sub IC}) to ambient temperature for the base metal of 528 KJ/m{sup 2}, which is diminished by the presence of the welding and by the increment in the temperature of the one essay. Also it was carried out an fractographic analysis of the fracture zone generated by the tenacity essays, what evidence a ductile fracture. The experimental values of resistance and tenacity are important for the study of the structural integrity of the encircling one of the core. (Author)

  14. Crack propagation in stainless steel AISI 304L in Hydrogen Chemistry conditions (HWC); Propagacion de Grietas en Acero Inoxidable AISI 304L en Condiciones de Quimica de Hidrogeno (HWC)

    Diaz S, A.; Fuentes C, P.; Merino C, F. [ININ, Carretera Mexico -Toluca s/n, La Marquesa, Ocoyoacac, Mexico (Mexico); Castano M, V. [Instituto de Fisica Aplicada, UNAM, Km 15.5 Carretera Queretaro-San Luis Potosi, Juriquilla, Queretaro (Mexico)]. e-mail: ads@nuclear.inin.mx

    2006-07-01

    Velocities of crack growth in samples type CT pre cracking of stainless steel AISI 304l solder and sensitized thermally its were obtained by the Rising Displacement method or of growing displacement. It was used a recirculation circuit that simulates the operation conditions of a BWR type reactor (temperature of 280 C and a pressure of 8 MPa) with the chemistry modified by the addition of hydrogen with and without the addition of impurities of a powerful oxidizer like the Cu{sup +} ion. In each essay stayed a displacement velocity was constant of 1x10{sup -9} m/s, making a continuous pursuit of the advance of the crack by the electric potential drop technique. Contrary to the idea of mitigation of the crack propagation velocity by effect of the addition of the hydrogen in the system, the values of the growth velocities obtained by this methodology went similar to the opposing ones under normal operation conditions. To the finish of the rehearsal one carries out the fractographic analysis of the propagation surfaces, which showed cracks growth in trans and intergranular way, evidencing the complexity of the regulator mechanisms of the IGSCC like in mitigation conditions as the alternative Hydrogen Chemistry. (Author)

  15. Propagation of crevices in stainless steel AISI304L in conditions of hydrogen chemistry (HWC); Propagacion de grietas en acero inoxidable AISI304L en condiciones de quimica de hidrogeno (HWC)

    Diaz S, A.; Fuentes C, P.; Merino C, F. [ININ, 52750 Ocoyoacac, Estado de Mexico (Mexico); Castano M, V. [IFA-UNAM, Juriquilla, Queretaro (Mexico)]. e-mail: ads@nuclear.inin.mx

    2006-07-01

    Crevice growth velocities in samples of AISI 304L stainless steel thermally welded and sensitized were obtained by the Rising displacement method or of growing displacement. It was used a recirculation circuit in where the operation conditions of a BWR type reactor were simulated (temperature of 288 C and a pressure of 8 MPa) with the chemistry modified by the addition of hydrogen with and without the addition of impurities of a powerful oxidizer like the Cu{sup ++} ion. CT pre cracked specimens were used and each rehearsal stayed to one constant displacement velocity of 1 x 10{sup -9} m/s (3.6 {mu}m/hr), making a continuous pursuit of the advance of the crack by the electric potential drop technique. To the end of the rehearsal it was carried out the fractographic analysis of the propagation surfaces. The values of the growth velocities obtained by this methodology went similar to the opposing ones under normal conditions of operation; while the fractographic analysis show the cracks propagation in trans and intergranular ways, evidencing the complexity of the regulator mechanisms of the one IGSCC even under controlled ambient conditions or with mitigation methodologies like the alternative hydrogen chemistry. (Author)

  16. Low cycle fatigue: high cycle fatigue damage accumulation in a 304L austenitic stainless steel; Endommagement et cumul de dommage en fatigue dans le domaine de l'endurance limitee d'un acier inoxydable austenitique 304L

    Lehericy, Y

    2007-05-15

    The aim of this study was to evaluate the consequences of a Low Cycle Fatigue pre-damage on the subsequent fatigue limit of a 304L stainless steel. The effects of hardening and severe roughness (grinding) have also been investigated. In a first set of tests, the evolution of the surface damage induced by the different LCF pre-cycling was characterized. This has permitted to identify mechanisms and kinetics of damage in the plastic domain for different surface conditions. Then, pre-damaged samples were tested in the High Cycle Fatigue domain in order to establish the fatigue limits associated with each level of pre-damage. Results evidence that, in the case of polished samples, an important number of cycles is required to initiate surface cracks ant then to affect the fatigue limit of the material but, in the case of ground samples, a few number of cycles is sufficient to initiate cracks and to critically decrease the fatigue limit. The fatigue limit of pre-damaged samples can be estimated using the stress intensity factor threshold. Moreover, this detrimental effect of severe surface conditions is enhanced when fatigue tests are performed under a positive mean stress (author)

  17. Correlation between Corrosion Potential and Pitting Potential for AISI 304L Austenitic Stainless Steel in 3.5% NaCl Aqueous Solution

    Alonso-Falleiros Neusa

    2002-01-01

    Full Text Available We investigated the effect of surface finish of two AISI 304L (UNS S30403 stainless steels on the corrosion potential (Ecorr in 3.5% NaCl aqueous solution and its value was compared with the pitting potential (Ep value and the type of anodic potentiodynamic curve obtained for determination of Ep in this solution. Five different surface finishes were examined. Ecorr and its standard deviation are strongly affected by the type of surface finish. Moreover, there are evidences of a linear correlation between Ecorr and Ep, as well as between the percentage of anodic curves with a well-defined pitting potential and the uncertainty in the determination of Ecorr.

  18. Thermal fatigue of a 304L austenitic stainless steel: simulation of the initiation and of the propagation of the short cracks in isothermal and aniso-thermal fatigue

    The elbow pipes of thermal plants cooling systems are submitted to thermal variations of short range and of variable frequency. These variations bound to temperature changes of the fluids present a risk of cracks and leakages. In order to solve this problem, EDF has started the 'CRECO RNE 808' plan: 'thermal fatigue of 304L austenitic stainless steels' to study experimentally on a volume part, the initiation and the beginning of the propagation of cracks in thermal fatigue on austenitic stainless steels. The aim of this study is more particularly to compare the behaviour and the damage of the material in mechanic-thermal fatigue (cycling in temperature and cycling in deformation) and in isothermal fatigue (the utmost conditions have been determined by EDF for the metal: Tmax = 165 degrees C and Tmin = 90 degrees C; the frequency of the thermal variations can reach a Hertz). A lot of experimental results are given. A model of lifetime is introduced and validated. (O.M.)

  19. Effects of concentration of sodium chloride solution on the pitting corrosion behavior of AISI 304L austenitic stainless steel

    Asaduzzaman M.D.

    2011-01-01

    Full Text Available The pitting corrosion behavior of the austenitic stainless steel in aqueous chloride solution was investigated using electrochemical technique. Corrosion potential (Ecorr measurement, potentiodynamic experiments, potential-hold experiments in the passive range, and microscopic examination were used for the evaluation of corrosion characteristics. The experimental parameters were chloride ion concentration, immersion time and anodic-hold potential. Ecorr measurements along with microscopic examinations suggest that in or above 3.5 % NaCl at pH 2 pitting took place on the surface in absence of applied potential after 6 hour immersion. The potentiodynamic experiment reveals that Ecorr and pitting potential (Epit decreased and current density in the passive region increased with the increase of chloride ion concentrations. A linear relationship between Epit and chloride ion concentrations was found in this investigation. The analysis of the results suggests that six chloride ions are involved for the dissolution of iron ion in the pitting corrosion process of austenitic stainless steel.

  20. Experimental investigation of Tie6Ale4V titanium alloy and 304L stainless steel friction welded with copper interlayer

    R. KUMAR; M. BALASUBRAMANIAN

    2015-01-01

    The basic principle of friction welding is intermetallic bonding at the stage of super plasticity attained with self-generating heat due to friction and finishing at upset pressure. Now the dissimilar metal joints are especially popular in defense, aerospace, automobile, bio-medical, refinery and nuclear engineerings. In friction welding, some special alloys with dual phase are not joined successfully due to poor bonding strength. The alloy surfaces after bonding also have metallurgical changes in the line of interfacing. The reported research work in this area is scanty. Although the sound weld zone of direct bonding between Tie6Ale4V and SS304L was obtained though many trials, the joint was not successful. In this paper, the friction welding characteristics between Tie6Ale4V and SS304L into which pure oxygen free copper (OFC) was introduced as interlayer were investigated. BoxeBehnken design was used to minimize the number of experiments to be performed. The weld joint was analyzed for its mechanical strength. The highest tensile strength between Tie6Ale4V and SS304L between which pure copper was used as insert metal was acquired. Micro-structural analysis and elemental analysis were carried out by EDS, and the formation of intermetallic compound at the interface was identified by XRD analysis.

  1. Analyses of oxide films grown on AISI 304L stainless steel and Incoloy 800HT exposed to supercritical water environment

    Fulger, Manuela; Mihalache, Maria; Ohai, Dumitru; Fulger, Stefan; Valeca, Serban Constantin

    2011-08-01

    Supercritical water (SCW) is being considered as a cooling medium for the next generation nuclear reactors because it provides high thermal efficiency and plant simplification. However, materials corrosion has been identified as a critical problem due to the oxidative nature of supercritical water. Thus, for safety using of these nuclear reactor systems a systematic study of candidate materials corrosion is needed. As in other high temperature environments, corrosion in SCW occurs by the growth of an oxide layer on the materials surface. The current work aims to evaluate oxidation behavior of AISI 304L SS and Incoloy 800HT in water at supercritical temperatures in the range 723-873 K under a pressure of 25 MPa for up to 1680 h. After exposure to deaerated supercritical water, the samples were investigated using gravimetry, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS). Oxide films grown on these materials have a layered structure with an outer layer consisting of a mixture of iron oxide/iron-nickel spinel oxides and an inner layer consisting of chromium oxide in the case of Incoloy 800HT and nickel-chromium spinel oxide in the case of AISI 304L SS. The mass gains for Incoloy 800HT at all temperatures were small, while comparatively with AISI 304L SS which exhibited higher oxidation rates. In the same time the results obtained by EIS indicate the best corrosion resistance of oxides grown on Incoloy 800HT surface.

  2. Analyses of oxide films grown on AISI 304L stainless steel and Incoloy 800HT exposed to supercritical water environment

    Fulger, Manuela, E-mail: manuela.fulger@nuclear.ro [Institute for Nuclear Research Pitesti, POB 78, Campului Street, No. 1, 115400 Mioveni (Romania); Mihalache, Maria; Ohai, Dumitru [Institute for Nuclear Research Pitesti, POB 78, Campului Street, No. 1, 115400 Mioveni (Romania); Fulger, Stefan [University Politechnica Bucharest, Splaiul Independentei Street, No. 313, Bucharest 060042 (Romania); Valeca, Serban Constantin [University of Pitesti, Targul din Vale Street, No. 1, 110040 Pitesti (Romania)

    2011-08-15

    Supercritical water (SCW) is being considered as a cooling medium for the next generation nuclear reactors because it provides high thermal efficiency and plant simplification. However, materials corrosion has been identified as a critical problem due to the oxidative nature of supercritical water. Thus, for safety using of these nuclear reactor systems a systematic study of candidate materials corrosion is needed. As in other high temperature environments, corrosion in SCW occurs by the growth of an oxide layer on the materials surface. The current work aims to evaluate oxidation behavior of AISI 304L SS and Incoloy 800HT in water at supercritical temperatures in the range 723-873 K under a pressure of 25 MPa for up to 1680 h. After exposure to deaerated supercritical water, the samples were investigated using gravimetry, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and electrochemical impedance spectroscopy (EIS). Oxide films grown on these materials have a layered structure with an outer layer consisting of a mixture of iron oxide/iron-nickel spinel oxides and an inner layer consisting of chromium oxide in the case of Incoloy 800HT and nickel-chromium spinel oxide in the case of AISI 304L SS. The mass gains for Incoloy 800HT at all temperatures were small, while comparatively with AISI 304L SS which exhibited higher oxidation rates. In the same time the results obtained by EIS indicate the best corrosion resistance of oxides grown on Incoloy 800HT surface.

  3. Influence of surface finish on the high cycle fatigue behavior of a 304L austenitic stainless steel

    This work has dealt with the influence of surface finish on the high cycle fatigue behavior of a 304L. The role played by roughness, surface hardening and residual stresses has been particularly described. First part of this study has consisted of the production of several surface finishes. These latter were obtained by turning, grinding, mechanical polishing and sandblasting. The obtained surfaces were then characterised in terms of roughness, hardening, microstructure and residual stresses. Fatigue tests were finally conducted under various stress ratios or mean stresses at two temperatures (25 C and 300 C). Results clearly evidenced an effect of the surface integrity on the fatigue resistance of the 304L. This influence is nevertheless more pronounced at ambient temperature and for a positive mean stress. For all explored testing conditions, the lowest endurance limit was obtained for ground specimens whereas polished samples exhibited the best fatigue strength. Results also cleared out a detrimental influence of a positive mean stress in the case of specimens having surface defaults of a great acuity. The study of the relative effect of each of the surface parameter, under a positive stress ratio and at the ambient temperature, showed that roughness profile and surface hardening are the two more influential factors. The role of the residual stresses remains negligible due to their rapid relaxation during the application of the first cycles of fatigue. The estimation of the initiation and propagation periods showed that mechanisms differed as a function of the applied stress ratio. Crack propagation is governed by the parameter DK at a positive stress ratio and by Dep/2 in the case of tension-compression tests. (author)

  4. The initiation and propagation of chloride-induced transgranular stress-corrosion cracking (TGSCC) of 304L austenitic stainless steel under atmospheric conditions

    Highlights: • Cracking consistent with corrosion enhanced plasticity model of Magnin. • Cracking stress threshold is 10 MPa, substantially lower than current guidance. • Humidity threshold for cracking is 30%. • Measured length of cracks very dependent on polishing practice. • Cracking could occur at 290–300 K, based on measured activation energy. - Abstract: Bending tests were used to investigate the stress-corrosion cracking of 304L stainless steel in a corrosive atmosphere containing magnesium chloride. Initially smooth specimens showed multiple closely spaced cracks after exposures of up to 500 h. These showed threshold stresses of 10 MPa and a threshold humidity of 30%. Cracking rates increased with stress but were a maximum at plastic strains of 2%. Examination of cracks using focussed ion beam milling and electron diffraction indicated a multi-stage mechanism of propagation via preferential oxidation of slip planes. The apparent activation energy was 34 kJ mol−1 in the temperature range 333–363 K

  5. Effect of surface machining and cold working on the ambient temperature chloride stress corrosion cracking susceptibility of AISI 304L stainless steel

    Effect of plastic deformation induced by cold rolling or surface machining on the susceptibility to chloride-induced stress corrosion cracking at ambient temperature of 304L austenitic stainless steel was investigated in this study. The test material was subjected to three treatments: (a) solution annealed, (b) cold rolled and (c) surface machined to induce different levels of strain/stresses in the material. Subsequently constant strained samples were produced as per ASTM G30 for each condition and these were exposed to 1 M HCl at ambient temperature until cracking occurred. Subsequently the cracked samples were characterized using stereo microscopy, optical microscopy and atomic force microscopy to understand the effect of microstructural changes produced by straining on the susceptibility to stress corrosion cracking at ambient temperature. Strained surface produced by machining accelerated the process of crack initiation resulting in densely distributed shallow surface cracks in a very short period of time as compared to solution annealed and cold worked sample. Crack propagation in cold worked sample was along the slip lines and cracking occurred much earlier than in the solution annealed sample.

  6. Heat transfer and fluid flow during keyhole mode laser welding of tantalum, Ti-6Al-4V, 304L stainless steel and vanadium

    Because of the complexity of several simultaneous physical processes, most heat transfer models of keyhole mode laser welding require some simplifications to make the calculations tractable. The simplifications often limit the applicability of each model to the specific materials systems for which the model is developed. In this work, a rigorous, yet computationally efficient, keyhole model is developed and tested on tantalum, Ti-6Al-4V, 304L stainless steel and vanadium. Unlike previous models, this one combines an existing model to calculate keyhole shape and size with numerical fluid flow and heat transfer calculations in the weld pool. The calculations of the keyhole profile involved a point-by-point heat balance at the keyhole walls considering multiple reflections of the laser beam in the vapour cavity. The equations of conservation of mass, momentum and energy are then solved in three dimensions assuming that the temperatures at the keyhole wall reach the boiling point of the different metals or alloys. A turbulence model based on Prandtl's mixing length hypothesis was used to estimate the effective viscosity and thermal conductivity in the liquid region. The calculated weld cross-sections agreed well with the experimental results for each metal and alloy system examined here. In each case, the weld pool geometry was affected by the thermal diffusivity, absorption coefficient, and the melting and boiling points, among the various physical properties of the alloy. The model was also used to better understand solidification phenomena and calculate the solidification parameters at the trailing edge of the weld pool. These calculations indicate that the solidification structure became less dendritic and coarser with decreasing weld velocities over the range of speeds investigated in this study. Overall, the keyhole weld model provides satisfactory simulations of the weld geometries and solidification sub-structures for diverse engineering metals and alloys

  7. Comparative study in the induced corrosion by sulfate reducing microorganisms, in a stainless steel 304L sensitized and a carbon steel API X65; Estudio comparativo de la corrosion inducida por microorganismos sulfatorreductores, en un acero inoxidable 304L sensibilizado y un acero al carbono API X65

    Diaz S, A.; Gonzalez F, E.; Arganis J, C.; Luna C, P.; Carapia M, L. [ININ, Carretera Mexico-Toluca Km. 36.5, 52045 Estado de Mexico (Mexico)]. e-mail: ads@nuclear.inin.mx

    2004-07-01

    In spite of the operational experience related with the presence of the phenomenon of microbiological corrosion (MIC) in industrial components, it was not but until the decade of the 80 s when the nuclear industry recognized its influence in some systems of Nuclear Generating Power plants. At the moment, diverse studies that have tried to explain the generation mechanism of this phenomenon exist; however, they are even important queries that to solve, especially those related with the particularities of the affected metallic substrates. Presently work, the electrochemical behavior of samples of stainless steel AISI 304L sensitized is evaluated and the carbon steel APIX65, before the action of sulfate reducing microorganisms low the same experimental conditions; found that for the APIX65 the presence of this type of bacteria promoted the formation of a stable biofilm that allowed the maintenance of the microorganisms that damaged the material in isolated places where stings were generated; while in the AISI 304L, it was not detected damage associated to the inoculated media. The techniques of Resistance to the Polarization and Tafel Extrapolation, allowed the calculation of the speed of uniform corrosion, parameter that doesn't seem to be influenced by the presence of the microorganisms; while that noise electrochemical it distinguished in real time, the effect of the sulfate reducing in the steel APIX65. (Author)

  8. THE EFFECT OF SMALL AMOUNTS OF ELEMENTS ON SHAPES OF POTENTIODYNAMIC AND POTENTIOSTATIC CURVES OF AISI 304L AND AISI 316L STAINLESS STEELS IN CHLORIDE MEDIA

    D. Pulino-Sagradi

    1997-06-01

    Full Text Available Abstract - Samples of high purity grade and commercial purity grade type AISI 304L and AISI 316L steels were studied by the potentiodynamic and potentiostatic techniques in a naturally aerated 3.5% NaCl aqueous solution at a controlled temperature of (23±2°C. The anodic polarization curves of the potentiodynamic technique showed that not always is it possible to determine pitting potential: most of the curves of commercial purity grade steels displayed a smooth curvature in the region where the current density should increase sharply. The density current versus time potentiostatic curves also showed different shapes according to the purity grade steels: for the commercial purity grade steels, the current density showed large oscillations with time (related to unstable pits, whereas for the high purity grade steels, a regular behavior of current density as a function of time was found (related to stable pits

  9. Initiation and growth of thermal fatigue crack networks in an AISI 304 L type austenitic stainless steel (X2 CrNi18-09)

    We studied the behaviour of a 304 L type austenitic stainless steel submitted to thermal fatigue. Using the SPLASH equipment of CEA/SRMA we tested parallelepipedal specimens on two sides: the specimens are continuously heated by Joule effect, while two opposites faces are cyclically. cooled by a mixed spray of distilled water and compressed air. This device allows the reproduction and the study of crack networks similar to those observed in nuclear power plants, on the inner side of circuits fatigued by mixed pressurized water flows at different temperatures. The crack initiation and the network constitution at the surface were observed under different thermal conditions (Tmax = 320 deg C, ΔT between 125 and 200 deg C). The experiment produced a stress gradient in the specimen, and due to this gradient, the in-depth growth of the cracks finally stopped. The obtained crack networks were studied quantitatively by image analysis, and different parameters were studied: at the surface during the cycling, and post mortem by step-by-step layer removal by grinding. The maximal depth obtained experimentally, 2.5 mm, is relatively coherent with the finite element modelling of the SPLASH test, in which compressive stresses appear at a depth of 2 mm. Some of the crack networks obtained by thermal fatigue were also tested in isothermal fatigue crack growth under 4-point bending, at imposed load. The mechanisms of the crack selection, and the appearance of the dominating crack are described. Compared to the propagation of a single crack, the crack networks delay the propagation, depending on the severity of the crack competition for domination. The dominating crack can be at the network periphery, in that case it is not as shielded by its neighbours as a crack located in the center of the network. It can also be a straight crack surrounded by more sinuous neighbours. Indeed, on sinuous cracks, the loading is not the same all along the crack path, leading to some morphological

  10. Correlation of radiation-induced changes in microstructure/microchemistry, density and thermo-electric power of type 304L and 316 stainless steels irradiated in the Phénix reactor

    Annealed specimens of type 304L and 316 stainless steel and cold-worked 316 specimens were irradiated in the Phénix reactor in the temperature range 381–394 °C and to different damage doses up to 39 dpa. The microstructure and microchemistry of both 304L and 316 have been examined using the combination of the different techniques of TEM to establish the void swelling and precipitation behavior under neutron irradiation. TEM observations are compared with results of measurements of immersion density and thermo-electric power obtained on the same irradiated stainless steels. The similarities and differences in their behavior on different scales are used to understand the factors in terms of the chemical composition and metallurgical state of steels, affecting the precipitation under irradiation and the swelling behavior. Irradiation induces the formation of some precipitate phases (e.g., M6C and M23C6-type carbides, and γ’- and G-phases), Frank loops and cavities. According to the metallurgical state and chemical composition of the steel, the amount of each type of radiation-induced defects is not the same, affecting their density and thermo-electric power

  11. AES depth profiles in Mo-coated 304L stainless steel achieved by RF-magnetron sputtering and influence of Mo on the corrosion in 3.5% NaCl solution

    Saidi, D. [Département de métallurgie, Division de Technologie du Combustible, Centre de Recherche Nucléaire de Draria CRND, BP. 43 Draria, Alger (Algeria); Zaid, B., E-mail: zaidbachir@yahoo.com [Département de métallurgie, Division de Technologie du Combustible, Centre de Recherche Nucléaire de Draria CRND, BP. 43 Draria, Alger (Algeria); Souami, N. [Centre de Recherche Nucléaire d’Alger CRNA, 2 Bd. Frantz Fanon, Alger (Algeria); Saoula, N. [Division des Milieux Ionisés et Lasers, Centre de Développement des Technologies Avancées CDTA, Cité du 20 août 1956, Baba Hassan, BP n 17, Alger (Algeria); Siad, M. [Centre de Recherche Nucléaire d’Alger CRNA, 2 Bd. Frantz Fanon, Alger (Algeria); Si Ahmed, A. [Im2np, UMR 7334 CNRS, Aix-Marseille Université, 13397 Marseille Cedex 20 (France); Biberian, J.P. [CINaM, UMR 7525 CNRS, Aix Marseille Université, 13288 Marseille Cedex 9 (France)

    2015-10-05

    Highlights: • Mo coating of 304L stainless steel is achieved via RF-magnetron sputtering. • The AES depth profiles before and after annealing in air (at 973 K) are analyzed. • The corrosions in NaCl solution of bare and Mo-coated samples are compared. • Mo-coated steels exhibit better corrosion behaviors. • The positive action of Mo oxide via its semi-conducting properties is deduced. - Abstract: Molybdenum-coated 304L stainless steel samples, fabricated by RF-magnetron sputtering, are characterized by Auger Electron Spectroscopy (AES) before and after annealing in air at 973 K. The electrochemical parameters of bare and coated materials, in NaCl 3.5% water solution at 298 K, are derived from the potentiodynamic polarization curves. The corrosion current of Mo-coated samples (before and after annealing) is significantly lower than that of its bare counterpart. The information gained from the AES depth profiles leads us to infer that the positive action of molybdenum on the corrosion behavior may be attributed to the changes induced by the semi-conducting properties of Mo oxide in the passive film.

  12. Materials Reliability Program Environmental Fatigue Testing of Type 304L Stainless Steel U-Bends in Simulated PWR Primary Water (MRP-100), Phase A (Optimization of Test Procedures and Baseline Testing)

    OAK-B135 Laboratory data generated over the past two decades indicate the possibility of a significant reduction in component fatigue life when reactor water environmental effects are experimentally simulated. However, these laboratory data have not been confirmed by nuclear power plant component operating experience. In a recent comprehensive review of laboratory, component and structural test data performed through the EPRI Materials Reliability Program, flow rate was identified as a critical variable that was generally not considered in laboratory studies but is applicable in plant operating environments. Available corrosion fatigue data for carbon/low-alloy steel piping components suggest that high flow is beneficial regarding the effects of reactor water environments. Similar information is lacking for stainless steel piping materials. MRP-49 recommended that additional laboratory testing be performed to improve the applicability of laboratory test results under simulated reactor water environmental conditions for stainless steel materials. This report documents progress made in an extensive testing program underway to evaluate the effects of flow rate on fatigue of 304L stainless steel in simulated PWR primary water

  13. Microstructural origins of radiation-induced changes in mechanical properties of 316 L and 304 L austenitic stainless steels irradiated with mixed spectra of high-energy protons and spallation neutrons

    Sencer, B. H.; Bond, G. M.; Hamilton, M. L.; Garner, F. A.; Maloy, S. A.; Sommer, W. F.

    2001-07-01

    A number of candidate alloys were exposed to a particle flux and spectrum at Los Alamos Neutron Science Center (LANSCE) that closely match the mixed high-energy proton/neutron spectra expected in accelerator production of tritium (APT) window and blanket applications. Austenitic stainless steels 316 L and 304 L are two of these candidate alloys possessing attractive strength and corrosion resistance for APT applications. This paper describes the dose dependence of the irradiation-induced microstructural evolution of SS 316 L and 304 L in the temperature range 30-60°C and consequent changes in mechanical properties. It was observed that the microstructural evolution during irradiation was essentially identical in the two alloys, a behavior mirrored in their changes in mechanical properties. With one expection, it was possible to correlate all changes in mechanical properties with visible microstructural features. A late-term second abrupt decrease in uniform elongation was not associated with visible microstructure, but is postulated to be a consequence of large levels of retained hydrogen measured in the specimens. In spite of large amounts of both helium and hydrogen retained, approaching 1 at.% at the highest exposures, no visible cavities were formed, indicating that the gas atoms were either in solution or in subresolvable clusters.

  14. Microstructural features of a type 304L stainless steel deformed at 1473 K in the strain rate interval 10[sup [minus]3] s[sup [minus]1] to 10[sup 2] s[sup [minus]1

    Sundararaman, D.; Divakar, R.; Raghunathan, V.S. (Indira Gandhi Centre for Atomic Research, Kalpakkam (India))

    1993-05-01

    Deformation processing of materials in continuously being refined by dynamic materials modeling procedures to establish a safe window for the manufacture of engineering components. Microstructure development during the processing and its correlation with the mechanical properties is inevitable for better understanding of the materials. On this basis, microstructural examination of the dynamically processed type 304L austenitic stainless steels has been carried out. The samples that have been deformed at 1,473 K under various strain rates, ranging from 10[sup [minus]2]s[sup [minus]1] to 10[sup 2]s[sup [minus]1], were observed by transmission electron microscopy, to corroborate the energy efficiency of the process. The details of the energy efficiency contours and their implications are reported elsewhere. In this report the authors present some of the unusual microstructural features that, in general, are not desirable for the safe processing of materials.

  15. Thermal fatigue of a 304L austenitic stainless steel: simulation of the initiation and of the propagation of the short cracks in isothermal and aniso-thermal fatigue; Fatigue thermique d'un acier inoxydable austenitique 304L: simulation de l'amorcage et de la croissance des fissures courtes en fatigue isotherme et anisotherme

    Haddar, N

    2003-04-01

    The elbow pipes of thermal plants cooling systems are submitted to thermal variations of short range and of variable frequency. These variations bound to temperature changes of the fluids present a risk of cracks and leakages. In order to solve this problem, EDF has started the 'CRECO RNE 808' plan: 'thermal fatigue of 304L austenitic stainless steels' to study experimentally on a volume part, the initiation and the beginning of the propagation of cracks in thermal fatigue on austenitic stainless steels. The aim of this study is more particularly to compare the behaviour and the damage of the material in mechanic-thermal fatigue (cycling in temperature and cycling in deformation) and in isothermal fatigue (the utmost conditions have been determined by EDF for the metal: Tmax = 165 degrees C and Tmin = 90 degrees C; the frequency of the thermal variations can reach a Hertz). A lot of experimental results are given. A model of lifetime is introduced and validated. (O.M.)

  16. Superficial and electrochemical study of stainless steel 304l with an inhibitory protective coating (TiO{sub 2} and ZrO{sub 2}); Estudio superficial y electroquimico de acero inoxidable 304L con una capa protectora inhibidora (TiO{sub 2} y ZrO{sub 2})

    Davila N, M. L.; Contreras R, A.; Arganis J, C. R., E-mail: aida.contreras@inin.gob.mx [ININ, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico)

    2014-10-15

    The degradation mechanisms in the boiling water reactors (BWR) have been an alert focus for owners, especially the cracking by stress corrosion cracking (SCC), therefore different techniques have been studied to inhibit this problem inside which is the water injection of hydrogen feeding (HWC, Hydrogen Water Chemistry), together with the noble metals injection (NMCA, Nobel Metal Chemical Addition) and the ceramic materials injection that form an inhibitory protective coating (Ipc). In this work the Ipc was simulated, for which were carried out hydro-thermals deposits starting from suspensions of 1000 ppm of zirconium oxide in its crystalline phase baddeleyite and titanium oxides in its anatase and rutile phases, on test tubes of stainless steel 304l previously rusty under simulated conditions of pressure and temperature of a BWR (288 C and 8 MPa). The superficial characterization was realized by scanning electron microscopy, energy-dispersive of X-ray and X-ray diffraction. The capacity to mitigate the corrosion was studied with the electrochemical technique of Tafel polarization (288 C and 8 MPa). The steel presents the formation of two oxide coatings formed by magnetite and hematite. The baddeleyite presents a deposit more thick and homogeneous it also presents the most negative electrochemical potential of corrosion, what indicates that it has the bigger capacity to mitigate the SCC. (Author)

  17. Study of diffusion welding between the zirconium alloy Zy{sub 4} and the stainless steel 304L. Morphology of the interface and nature of the phases formed; Etude du soudage diffusion entre l'alliage de zirconium Zy{sub 4} et l'acier inoxydable 304L. Morphologie de l'interface et nature des phases formees

    Taouinet, M. [Centre de Recherche Nucleaire de Draria (CRNA), Alger (Algeria); Lebaili, S. [Universite des Sciences et de la Technologie Houari Boumediene, Lab. de Science et Genie des Materiaux, Faculte de Genie Mecanique et Genie des Procedes, Alger (Algeria); Souami, N. [Centre de Recherche Nucleaire d' Alger (CRNA), Alger (Algeria)

    2009-07-01

    We approach a study on the solid state diffusion bonding between zircaloy (Zy{sub 4}) and stainless steel (304L) for an application in the sector of the nuclear power. The diffusion couples prepared underwent treatments at the temperatures ranging between 850 and 1020 C in a controlled atmosphere and under dynamic pressures. We give a particular attention to the morphology of the interface, formed, and to the determination of the nature of the compounds formed. The observations and chemical analysis are realized by ESEM-EDX and XRD. The quantitative distribution as well as the detailed localization of the basic chemical elements are defined by chemical profiles, and series of images X. The junction of diffusion consists of three zones distinct, formed from a solid solution FeCr({alpha}), rich in Cr in the form of a homogeneous edge, localized in steel side. The two other zones of the center of the Zy{sub 4} side are two phase of type Zr{sub {alpha}}, (FeCr){sub {alpha}}-Zr(Fe, Cr){sub 2} and Zr{sub {alpha}}-Zr{sub 2}(Fe{sub 1-x}Ni{sub x}), 0.15{<=}x{<=}0.25. The detailed results obtained, are a regrouping, between those obtained from the observations and chemical analysis and radio crystallographic. The values of the measured micro-hardnesses give very heterogeneous filiations to the level of the interface. (authors)

  18. Assessment and comparison of oxides grown on 304l ods steel and 304l ss in water environment in supercritical conditions

    In order to fulfil superior cladding for new reactor generation G IV, the austenitic304L stainless steel was improved by oxide dispersion strengthening (ODS), using two nano-oxides: titanium and yttrium oxides. The behaviour of the new material resulted, 304 ODS, in water at supercritical temperature of about 550OC and 25 MPa pressure, was considered. The oxidation kinetics by weigh gain measurements for both materials have been estimated and compared. The weight gain of ODS samples is higher than basic austenitic steel up to 1320 hours. The oxides developed on the ODS samples in SCPW are layered and more uniform than in 304L SS. The protectively character of oxide films was estimated by different techniques. The morphology of oxide surface, the layering and chemical formula of oxides films were investigated by scanning electron microscopy (SEM), Energy Dispersion X-Ray Spectrometry (EDS), electrochemical impedance spectrometry (EIS) and by Small Angle X-ray Diffraction (SAXD). 1. (authors)

  19. THE EMPHASIS OF PHASE TRANSFORMATIONS AND ALLOYING CONSTITUENTS ON HOT CRACKING SUSCEPTIBILITY OF TYPE 304L AND 316L STAINLESS STEEL WELDS

    RATI SALUJA; K. M. MOEED

    2012-01-01

    Hot cracking is a significant problem due to transformation of retained ferrite into sigma phase, which results preferential corrosion of ferrite. The Hot Cracking Susceptibility is high for fully austenitic compositions but specimens with 5 to 30% ferrite were quite resistant to cracking. Hot cracking in 304L and 316L is amplified by low-melting eutectics containing impurities such as S, P, Si, N. It could be diminished by small increase in C, N, Cr, Ni, Si or by substantial increase in Mn c...

  20. Hydrogen-assisted crack propagation in 304L/308L and 21Cr–6Ni–9Mn/308L austenitic stainless steel fusion welds

    Highlights: ► Measured crack growth resistance of welds with 140 wppm H from gas charging. ► H reduced fracture initiation toughness by over 67% and altered fracture mode. ► With H, microcracks initiate at weld ferrite. Without H, fracture is uniformly ductile. ► With H, localized deformation in austenite creates stress concentrations at ferrite. ► In austenite/ferrite microstructures, JIC decreases with increasing vol.% ferrite. - Abstract: Elastic–plastic fracture mechanics methods were used to characterize hydrogen-assisted crack propagation in two austenitic stainless steel gas tungsten arc (GTA) welds. Thermally precharged hydrogen (140 wppm) degraded fracture initiation toughness and crack growth toughness and altered fracture mechanisms. Fracture initiation toughness in hydrogen-precharged welds represented a reduction of >67% from the estimated toughness of non-charged welds. In hydrogen-precharged welds, microcracks initiated at ferrite, and dendritic microstructure promoted crack propagation along ferrite. Deformation twinning in austenite interacts with ferrite, facilitating microcrack formation. While hydrogen altered fracture mechanisms similarly for both welds, the amount of ferrite governed the severity of hydrogen-assisted crack propagation.

  1. Multi-scale analysis of behavior and fatigue life of 304L stainless under cyclic loading with pre-hardening

    This study investigates the effects of loading history on the cyclic stress-strain curve and fatigue behavior of 304L stainless steel at room temperature. Tension-compression tests were performed on the same specimen under controlled strain, using several loading sequences of increasing or decreasing amplitude. The results showed that fatigue life is significantly reduced by the previous loading history. A previously developed method for determining the effect of prehardening was evaluated. Microstructural analyses were also performed; the microstructures after pre-loading and their evolution during the fatigue cycles were characterized by TEM. The results of these analyses improve our understanding of the macroscopic properties of 304L stainless steel and can help us identify the causes of failure and lifetime reduction. (author)

  2. Initiation and growth of thermal fatigue crack networks in an AISI 304 L type austenitic stainless steel (X2 CrNi18-09); Amorcage et propagation de reseaux de fissures de fatigue thermique dans un acier inoxydable austenitique de type X2 CrNi18-09 (AISI 304 L)

    Maillot, V

    2004-07-01

    We studied the behaviour of a 304 L type austenitic stainless steel submitted to thermal fatigue. Using the SPLASH equipment of CEA/SRMA we tested parallelepipedal specimens on two sides: the specimens are continuously heated by Joule effect, while two opposites faces are cyclically. cooled by a mixed spray of distilled water and compressed air. This device allows the reproduction and the study of crack networks similar to those observed in nuclear power plants, on the inner side of circuits fatigued by mixed pressurized water flows at different temperatures. The crack initiation and the network constitution at the surface were observed under different thermal conditions (Tmax = 320 deg C, {delta}T between 125 and 200 deg C). The experiment produced a stress gradient in the specimen, and due to this gradient, the in-depth growth of the cracks finally stopped. The obtained crack networks were studied quantitatively by image analysis, and different parameters were studied: at the surface during the cycling, and post mortem by step-by-step layer removal by grinding. The maximal depth obtained experimentally, 2.5 mm, is relatively coherent with the finite element modelling of the SPLASH test, in which compressive stresses appear at a depth of 2 mm. Some of the crack networks obtained by thermal fatigue were also tested in isothermal fatigue crack growth under 4-point bending, at imposed load. The mechanisms of the crack selection, and the appearance of the dominating crack are described. Compared to the propagation of a single crack, the crack networks delay the propagation, depending on the severity of the crack competition for domination. The dominating crack can be at the network periphery, in that case it is not as shielded by its neighbours as a crack located in the center of the network. It can also be a straight crack surrounded by more sinuous neighbours. Indeed, on sinuous cracks, the loading is not the same all along the crack path, leading to some

  3. Selection of suitable stainless steels for nuclear reprocessing plants: application of chemical and electrochemical testing methods to austenitic CrNi steel AISI type 304L in various chemical compositions

    DIN Standard Huey testing has been performed in boiling 14.4n nitric acid during 5-15 periods (240-720 h) for selection of appropriate nitric acid resistant materials for nuclear fuel reprocessing applications. The paper describes the testing process during which the intermediate and final results of metal loss by dissolution are directly transferred from the balance to the computer, stored and activated - besides material properties data - for documentation purposes. Further routine evaluation of these experiments includes metallography in cross-section and surface microscopy to look after uniform and local metal dissolution phenomena and their relationship to the bulk structure. A large variety of materials have been tested this way through the last years. It was shown how sensitively the chosen testing conditions are able to differ between materials of the same nominal composition AISI 304L/Material No. 1.4306 in different contents of residual elements. Especially, for the purest electroslag-molten steel (ESU) results of parameter studies concerning the influence of sensitization, cold deformation, grain size and sheet thickness (in respect to end grain attack) are given. Within an attempt to define faster methods of corrosion testing, e.g. to differ within a group of materials of similar composition, but different corrosion behaviour, electrochemical tests in heated nitric acid were performed under potentiostatic conditions. The necessary electrochemical equipment and the results of its application by potentiostatic tests on AISI 304L in above mentioned three chemical compositions at 1250 mV, 14n HNO3 are presented. The evaluation by light and electron microscopy of the corroded surfaces, supported by measurements of current density, weight change, metallography and surface roughness, proved that within one hour a remarkable differentiation of the corrosion behaviour took place which can serve as a basis of materials preselection and to diminish the extent of

  4. Fatigue behaviour of 304L steel welded structures: influence of residual stresses and surface mechanical finishing

    This study focuses on the influence of residual stresses and surface mechanical finishing on lifetime of stainless steel 304L welded structures. Residual stresses are determined on specific specimens of three types: base-metal, as-welded and ground-welded specimens. Each type is submitted to fatigue tests in order to assess the influence of these parameters on the lifetime, and to determine their evolution. The experiments show that an important surface stress concentration is located in the weld root of as-welded structures, which has a negative effect on the fatigue life. The grinding operation generates high-level surface residual stresses but the lifetime is higher thanks to the reduction of the notch effect. The fatigue test results are compared to the nuclear industry best-fit S-N curves. This enables the determination of correction factors related to fatigue test results of polished specimens, and to assess the lifetime of structures. (author)

  5. High temperature oxidation behavior of AISI 304L stainless steel—Effect of surface working operations

    Highlights: ► Surface working resulted in thinner oxide on the surface. ► Oxides on machined/ground surfaces richer in Cr, higher in specific resistivity. ► Additional ionic transport process at the metal-oxide for ground sample established. ► Presence of fragmented grains and martensite influenced oxide nature/morphology. - Abstract: The oxidation behavior of grade 304L stainless steel (SS) subjected to different surface finishing (machining and grinding) operations was followed in situ by contact electric resistance (CER) and electrochemical impedance spectroscopy (EIS) measurements using controlled distance electrochemistry (CDE) technique in high purity water (conductivity −1) at 300 °C and 10 MPa in an autoclave connected to a recirculation loop system. The results highlight the distinct differences in the oxidation behavior of surface worked material as compared to solution annealed material in terms of specific resistivity and low frequency Warburg impedance. The resultant oxide layer was characterized for (a) elemental analyses by glow discharge optical emission spectroscopy (GDOES) and (b) morphology by scanning electron microscopy (SEM). Oxide layers with higher specific resistivity and chromium content were formed in case of machined and ground conditions. Presence of an additional ionic transport process has also been identified for the ground condition at the metal/oxide interface. These differences in electrochemical properties and distinct morphological features of the oxide layer as a result of surface working were attributed to the prevalence of heavily fragmented grain structure and presence of martensite.

  6. Result of International Round Robin Test on Young's Modulus Measurement of 304L and 316L Steels at Cryogenic Temperatures

    Ogata et al. reported in 1996 results of international Round Robin tests on mechanical property measurement of several metals at cryogenic temperatures. Following the report, the standard deviation of Young's modulus of 316L steel is much larger than those of yield and tensile strengths, that is, 4.6 % of the mean value for Young's modulus, while 1.4 % and 1.6 % of the mean values for yield and for tensile strengths, respectively. Therefore, an international Round Robin test on Young's modulus of two austenitic stainless steels at cryogenic temperatures under the participation often institutes from four nations has been initiated within these two years. As a result, the ratios of standard deviation to the mean values are 4.2 % for 304L and 3.6 % for 316L. Such a drop in the standard deviation is attributable to the decrease in the number of institute owing to the application of single extensometer or direct strain gage technique

  7. Study on interim storage of spent nuclear fuel by concrete cask for practical use. Feasibility study on prevention of chloride induced stress corrosion cracking for type304L stainless steel canister

    For the practical use of the concrete cask storage method, remaining issues are preventive design (monitoring, inspection and countermeasures) and its demonstration of the Stress Corrosion Cracking (SCC) on the canister surface. Scenarios to maintain its confinement function of the canister made of the conventional SUS 304L materials during storage period were established by keeping the salt density on the canister surface not be exceed its critical salt density to initiate SCC or by controlling the crack propagation if the salt density exceeded the critical value. Furthermore the feasibility of the scenarios were demonstrated by tests defining the critical salt density for the SCC initiation and by tests of crack propagation based on metrological data of representative coastal sites in Japan. On top of that, methods of reduction of welding residual stress to prevent SCC were demonstrated by SCC tests using small scale test model made of SUS 304L simulating wall thickness of the real canister and welding methods. (author)

  8. Resistance Spot Weldability of Dissimilar Materials: BH180-AISI304L Steels and BH180-IFT123 Steels

    Fatih Hayat

    2011-01-01

    In this study, resistance spot weldability of 180 grade bake hardening steel (BH180), 7123 grade interstitial free steel (IF7123) and 304 grade austenitic stainless steel (AISI304L) with each other was investigated. In the joining process, electrode pressure and weld current were kept constant and six different weld time were chosen. Microstructure, microhardness, tensile-shear properties and fracture types of resistance spot welded joints were examined. In order to characterize the metallurgical structure of the welded joint, the microstructural profile was developed, and the relationship between mechanical properties and microstructure was determined. The change of weld time, nugget diameter, the HAZ (heat affected zone) width and the electrode immersion depth were also investigated. Welded joints were examined by SEM (scanning electron microscopy) images of fracture surface. As a result of the experiment, it was determined that with increasing weld time, tensile shear load bearing capacity (TLBC) increased with weld time up to 25 cycle and two types of tearing occurred. It was also determined that while the failure occurred from IF side at the BHIS0+IF7123 joint, it occurred from the BH180 side at the BHIS0+AISI304L joint.

  9. Influence of Size on the Microstructure and Mechanical Properties of an AISI 304L Stainless Steel—A Comparison between Bulk and Fibers

    Francisco J. Baldenebro-Lopez

    2015-01-01

    Full Text Available In this work, the mechanical properties and microstructural features of an AISI 304L stainless steel in two presentations, bulk and fibers, were systematically studied in order to establish the relationship among microstructure, mechanical properties, manufacturing process and effect on sample size. The microstructure was analyzed by XRD, SEM and TEM techniques. The strength, Young’s modulus and elongation of the samples were determined by tensile tests, while the hardness was measured by Vickers microhardness and nanoindentation tests. The materials have been observed to possess different mechanical and microstructural properties, which are compared and discussed.

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

    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.

  11. Comparison of Strength and Serration at Cryogenic Temperatures among 304L, 316L and 310S Steels

    Shibata, K.; Ogata, T.; Nyilas, A.; Yuri, T.; Fujii, H.; Ohmiya, S.; Onishi, T.; Weiss, K. P.

    2008-03-01

    Tensile tests of 310S steel were performed at temperatures below 300 K and the yield strength and deformation behavior were compared with those of 304L and 316L steels. Computer simulations were also carried out to graph stress-elongation curves in order to discuss the effects of martensitic transformations induced during deformation on their strengths and deformation behavior at low temperatures. Tensile tests showed that yield strength of 310S steel is highest and that of 304L is lowest. The differences in yield strengths between 316L and 310S steels and between 304L and 316L steels are larger than those expected from the differences in solid solution strengthening. This can be explained by the effect of the strain through γ to ɛ martensitic transformation induced by elastic stress in 304L and 316L steels. The strength level and the shape of stress-elongation curves at cryogenic temperatures excluding serration can be qualitatively revealed by simulation when higher strength of ɛ phase comparing to α' phase and the window effect of α' were considered simultaneously. In liquid hydrogen, the three steels exhibit large serrations on the stress-elongation curves after the deformation near to the ultimate stress, while the curves are smooth before the onset of the serration. Such serrations in liquid hydrogen could not be revealed by simulation.

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

    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

  13. Stainless Steel Permeability

    Buchenauer, Dean A. [Sandia National Laboratories (SNL-CA), Livermore, CA (United States); Karnesky, Richard A. [Sandia National Laboratories (SNL-CA), Livermore, CA (United States)

    2015-09-01

    An understanding of the behavior of hydrogen isotopes in materials is critical to predicting tritium transport in structural metals (at high pressure), estimating tritium losses during production (fission environment), and predicting in-vessel inventory for future fusion devices (plasma driven permeation). Current models often assume equilibrium diffusivity and solubility for a class of materials (e.g. stainless steels or aluminum alloys), neglecting trapping effects or, at best, considering a single population of trapping sites. Permeation and trapping studies of the particular castings and forgings enable greater confidence and reduced margins in the models. For FY15, we have continued our investigation of the role of ferrite in permeation for steels of interest to GTS, through measurements of the duplex steel 2507. We also initiated an investigation of the permeability in work hardened materials, to follow up on earlier observations of unusual permeability in a particular region of 304L forgings. Samples were prepared and characterized for ferrite content and coated with palladium to prevent oxidation. Issues with the poor reproducibility of measurements at low permeability were overcome, although the techniques in use are tedious. Funding through TPBAR and GTS were secured for a research grade quadrupole mass spectrometer (QMS) and replacement turbo pumps, which should improve the fidelity and throughput of measurements in FY16.

  14. Notch Effect on Tensile Deformation Behavior of 304L and 316L Steels in Liquid Helium and Hydrogen

    Tensile tests of type 304L and 316L steels were carried out using round bar specimens with a notch in liquid helium, hydrogen, liquid nitrogen and at ambient temperature. The obtained tensile strengths were compared with the tensile strengths of smooth specimens. For smooth specimens, tensile strength increased with a decrease in temperature and the strengths in liquid helium and hydrogen show similar values in both steels. For notched specimen of 304L steel, tensile strength (including fracture strength) increased noticeably from ambient to liquid nitrogen temperature but showed a large decrease in liquid helium and hydrogen. In liquid hydrogen and helium, the tensile strength is a little lower in liquid hydrogen than in liquid helium and both strengths are lower than tensile strengths of smooth specimens. For notched specimen of 316L steel, an increase in tensile strength from ambient to liquid nitrogen temperature was not so large and a decrease from liquid nitrogen to liquid hydrogen was small. The tensile strengths in liquid helium and hydrogen were nearly same and higher than those of smooth specimens. Different behavior of serration was observed between liquid helium and hydrogen, and between 304L and 316L steels. The reasons for these differences were discussed using computer simulation

  15. Notch Effect on Tensile Deformation Behavior of 304L and 316L Steels in Liquid Helium and Hydrogen

    Shibata, K.; Fujii, H.

    2004-06-01

    Tensile tests of type 304L and 316L steels were carried out using round bar specimens with a notch in liquid helium, hydrogen, liquid nitrogen and at ambient temperature. The obtained tensile strengths were compared with the tensile strengths of smooth specimens. For smooth specimens, tensile strength increased with a decrease in temperature and the strengths in liquid helium and hydrogen show similar values in both steels. For notched specimen of 304L steel, tensile strength (including fracture strength) increased noticeably from ambient to liquid nitrogen temperature but showed a large decrease in liquid helium and hydrogen. In liquid hydrogen and helium, the tensile strength is a little lower in liquid hydrogen than in liquid helium and both strengths are lower than tensile strengths of smooth specimens. For notched specimen of 316L steel, an increase in tensile strength from ambient to liquid nitrogen temperature was not so large and a decrease from liquid nitrogen to liquid hydrogen was small. The tensile strengths in liquid helium and hydrogen were nearly same and higher than those of smooth specimens. Different behavior of serration was observed between liquid helium and hydrogen, and between 304L and 316L steels. The reasons for these differences were discussed using computer simulation.

  16. Mechanisms-based viscoplasticity: Theoretical approach and experimental validation for steel 304L.

    Zubelewicz, Aleksander; Oliferuk, Wiera

    2016-01-01

    We propose a mechanisms-based viscoplasticity approach for metals and alloys. First, we derive a stochastic model for thermally-activated motion of dislocations and, then, introduce power-law flow rules. The overall plastic deformation includes local plastic slip events taken with an appropriate weight assigned to each angle of the plane misorientation from the direction of maximum shear stress. As deformation progresses, the material experiences successive reorganizations of the slip systems. The microstructural evolution causes that a portion of energy expended on plastic deformation is dissipated and the rest is stored in the defect structures. We show that the reorganizations are stable in a homogeneously deformed material. The concept is tested for steel 304L, where we reproduce experimentally obtained stress-strain responses, we construct the Frost-Ashby deformation map and predict the rate of the energy storage. The storage is assessed in terms of synchronized measurements of temperature and displacement distributions on the specimen surface during tensile loading. PMID:27026209

  17. Mechanisms-based viscoplasticity: Theoretical approach and experimental validation for steel 304L

    Zubelewicz, Aleksander; Oliferuk, Wiera

    2016-03-01

    We propose a mechanisms-based viscoplasticity approach for metals and alloys. First, we derive a stochastic model for thermally-activated motion of dislocations and, then, introduce power-law flow rules. The overall plastic deformation includes local plastic slip events taken with an appropriate weight assigned to each angle of the plane misorientation from the direction of maximum shear stress. As deformation progresses, the material experiences successive reorganizations of the slip systems. The microstructural evolution causes that a portion of energy expended on plastic deformation is dissipated and the rest is stored in the defect structures. We show that the reorganizations are stable in a homogeneously deformed material. The concept is tested for steel 304L, where we reproduce experimentally obtained stress-strain responses, we construct the Frost-Ashby deformation map and predict the rate of the energy storage. The storage is assessed in terms of synchronized measurements of temperature and displacement distributions on the specimen surface during tensile loading.

  18. Thermal fatigue of austenitic and duplex stainless steels

    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. Corrosion behavior of mild steel and SS 304L in presence of dissolved nickel under aerated and deaerated conditions

    Mohd Mobin

    2011-12-01

    Full Text Available In dual purpose water/power co-generation plants, the presence of high concentration of Cu and Ni in the re-circulating brine/condensate as a result of condenser tubes corrosion has been attributed as one of the several causes of corrosion damage of flash chamber materials and water touched parts of the boilers. The present investigation deals with the effect of dissolved nickel in the concentration range of 10 ppb to 100 ppm on the corrosion behavior of mild steel and SS 304L in two aqueous medium namely, distilled water and artificial seawater. The effect of pH, dissolved oxygen and flow condition of aqueous medium on the corrosion behavior was also monitored. The experimental techniques include immersion test and electrochemical tests which include free corrosion potential measurements and potentiodynamic polarization measurements. The corrosion rate of mild steel and SS 304L under different experimental conditions was determined by weight loss method and spectrophotometric determination of iron ion entered into the test solution during the period of immersion. The pH of the test solution was also monitored during the entire period of immersion. The left over nickel ions present in the test solution after completion of immersion was also estimated using Atomic Absorption Spectrophotometer. The surface morphology of the corroded steel surface was also examined using scanning electron microscopy (SEM. The results of the studies show that SS 304L largely remains unaffected in both distilled water and artificial seawater under different experimental conditions. However, the effect of nickel on the corrosion behavior of mild steel is quite pronounced and follows interesting trends.

  20. Corrosion behavior of mild steel and SS 304L in presence of dissolved nickel under aerated and deaerated conditions

    Mohd Mobin; Hina Shabnam

    2011-01-01

    In dual purpose water/power co-generation plants, the presence of high concentration of Cu and Ni in the re-circulating brine/condensate as a result of condenser tubes corrosion has been attributed as one of the several causes of corrosion damage of flash chamber materials and water touched parts of the boilers. The present investigation deals with the effect of dissolved nickel in the concentration range of 10 ppb to 100 ppm on the corrosion behavior of mild steel and SS 304L in two aqueous ...

  1. Stainless steel recycle FY94 progress report

    The Materials Technology Section (MTS) of the Savannah River Technology Center (SRTC) was asked to demonstrate the practicality of recycling previously contaminated stainless steel components such as reactor heat exchanger heads, process water piping and slug buckets into 208 liters (55 gallon) drums and 2.8 cubic meter (100 ft3) storage boxes. Radioactively contaminated stainless steel scrap will be sent to several industrial partners where it will be melted, decontaminated/cast into ingots, and rolled into plate and sheet and fabricated into the drums and boxes. As part of this recycle initiative, MTS was requested to demonstrate that radioactively contaminated Type 304L stainless steel could be remelted and cast to meet the applicable ASTM specification for fabrication of drums and boxes. In addition, MTS was requested to develop the technical basis of melt decontamination and establish practicality of using this approach for value added products. The findings presented in this investigation lead to the following conclusions: recycle of 18 wt% Cr-8 wt% Ni alloy can be achieved by melting Type 304 stainless steel in a air vacuum induction furnace; limited melt decontamination of the contaminated stainless steel was achieved, surface contamination was removed by standard decontamination techniques; carbon uptake in the as-cast ingots resulted from the graphite susceptor used in this experiment and is unavoidable with this furnace configuration. A new furnace optimized for melting stainless steel has been installed and is currently being tested for use in this program

  2. Weldability of Stainless Steels

    It gives an outline of metallographic properties of welding zone of stainless steels, generation and mechanisms of welding crack and decreasing of corrosion resistance of welding zone. It consists of seven chapters such as introduction, some kinds of stainless steels and properties, metallographic properties of welding zone, weld crack, toughness of welding zone, corrosion resistance and summary. The solidification modes of stainless steels, each solidification mode on the cross section of Fe-Cr-Ni alloy phase diagram, each solidification mode of weld stainless steels metal by electron beam welding, segregation state of alloy elements at each solidification mode, Schaeffler diagram, Delong diagram, effects of (P + S) mass content in % and Cr/Ni equivalent on solidification cracking of weld stainless steels metal, solidification crack susceptibility of weld high purity stainless steels metal, effects of trace impurity elements on solidification crack susceptibility of weld high purity stainless steels metal, ductile fracture susceptibility of weld austenitic stainless steels metal, effects of H2 and ferrite content on generation of crack of weld 25Cr-5N duplex stainless steels, effects of O and N content on toughness of weld SUS 447J1 metals, effect of ferrite content on aging toughness of weld austenitic stainless steel metal, corrosion morphology of welding zone of stainless steels, generation mechanism of knife line attack phenomenon, and corrosion potential of some kinds of metals in seawater at room temperature are illustrated. (S.Y.)

  3. Effect of Cold-Rolling on Precipitation Phenomena in Sensitized Type 316L and 340L Austenitic Stainless Steels

    H.Tsubakino; A.Yamamoto; T. Yamada; L.Liu; M.Terasawa; S.Nakahigashi; H.Harada

    2004-01-01

    Precipitation phenomena in Type 316L and 304L stainless steels were studied mainly by transmission electron microscopic (TEM) observations after cold-rolling ranging from 0% (as solution annealed) to 80% reduction in thickness,and then by sensitization treatment. Precipitates were identified by electron diffraction analysis and EDS analysis.Precipitates observed in sensitized 316L stainless steel were sigma and chi phases, whereas carbide and sigma were observed in sensitized 304L stainless steel. Recrystallized grains were formed in 30% cold-rolled and sensitized 304L.However, the tendency toward recrystallization in sensitized 316L was much lower than in 304L. Precipitation of sigma and chi phases was accelerated by cold-rolling and they were observed at grain boundaries in lower cold-rolling; they were also seen, in grain interiors in higher cold-rolling. Higher deformation induced partially recrystallization combined with precipitation, resulting in the formation of heterogeneous microstructures.

  4. Phenomena of the coupling between steel 304L and platinum group metal particles in the environment of the dissolution of burned nuclear fuels

    This work describes the phenomena of the electrochemical coupling between stainless steel (304L) and platinum group metal particles in the environment of the recycling of burned nuclear fuels. The main goals of this work are to prove the acceleration of the corrosion by these deposits, the comprehension of the mechanisms and the development of a corrosion model. First the corrosion phenomena are evidenced for steel in contact with noble particles (RuO2,xH2O and Ru(0)). Their accelerating effect on the corrosion process is quantified in 8 mol.L-1 HNO3. Second a local approach on the reduction process is performed using Scanning Electrochemical Microscopy (SECM). The reduction reaction is investigated for microelectrodes and for different substrates (Ru, Pt, bare steel and steel with deposit). This approach clearly showed the catalytic effect of the noble particles on the reduction process of nitrate. Most probably the limiting step of the reduction process, the chemical formation of NO2, is catalyzed by these particles. Third a reduction scheme is developed for different materials which can describe the experimental results. Simulation results were in agreement with the experimental results. This demonstrates the validity of the assumptions for the model. Finally a model was developed for the bare steel as well as the covered steel, taking into account the dissolution step. It is shown that the most important parameter, that governs the whole corrosion process is the concentration of N(III) species. It can be concluded that, due to the presence of the deposits, the concentration of these species is higher in the vicinity of the steel substrate. (author)

  5. Ion-nitriding of austenitic stainless steels

    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. Warm compacting behavior of stainless steel powders

    肖志瑜; 柯美元; 陈维平; 召明; 李元元

    2004-01-01

    The warm compacting behaviors of four different kinds of stainless steel powders, 304L, 316L, 410L and 430L, were studied. The results show that warm compaction can be applied to stainless steel powders. The green densities and strengths of compacts obtained through warm compaction are generally higher than those obtained through cold compaction. The compacting behaviors in warm compaction and cold compaction are similar.Under the compacting pressure of 700 MPa, the warm compacted densities are 0. 10 - 0.22 g/cm3 higher than the cold compacted ones, and the green strengths are 11.5 %-50 % higher. The optimal warm compacting temperature is 100 - 110 ℃. In the die wall lubricated warm compaction, the optimum internal lubricant content is 0.2%.

  7. Welding irradiated stainless steel

    Conventional welding processes produced severe underbead cracking in irradiated stainless steel containing 1 to 33 appm helium from n,a reactions. A shallow penetration overlay technique was successfully demonstrated for welding irradiated stainless steel. The technique was applied to irradiated 304 stainless steel that contained 10 appm helium. Surface cracking, present in conventional welds made on the same steel at the same and lower helium concentrations, was eliminated. Underbead cracking was minimal compared to conventional welding methods. However, cracking in the irradiated material was greater than in tritium charged and aged material at the same helium concentrations. The overlay technique provides a potential method for repair or modification of irradiated reactor materials

  8. The Influence of Surface Processing on Outgassing Measurements of High-Mn Stainless Steel

    Fukaya, Masuhiro; Teraoka, Shin-Ichi; Sato, Yoshihiro; Uota, Masahiko; Saito, Yoshio

    An outgassing rate was measured for a stainless steel material of YUS130S, having a high-mangany content (Fe-18Cr-7Ni-11Mn-0.3N), and compared with that for a stainless steel of SUS304L. A surface processing of both electropolished and electrochemical buffing followed by an in-air oxidation was examined in order to investigate the outgas reduction effect in the case of with and without baking. Further, a depth profile of the surface composition was analyzed by glow-discharge emission spectroscopy (GDS). Based on the results, the outgassing rate of YUS130S was 35% lower than that of SUS304L, when electropolished and electrochemical buffing. The oxidation process in air at 723 K in the case of electrochemical buffing showed effect on the outgassing reduction in both YUS130S and SUS304L. The GDS observation shows that, by electropolishing, Cr-Mn-rich and Cr-rich passive films were formed on the YUS130S and SUS304L surface, respectively. By electrochemical buffing, passive films changed to more Fe-rich films. The further process of in-air-oxidation causes a change in oxide films to Fe-Mn-rich and Fe-rich characteristics for YUS130S and SUS304L respectively. The stainless steel with Mn-rich and Cr-poor passive films shows low outgassing rate.

  9. Self-organisation of nanoscaled pores in anodic oxide overlayer on stainless steels

    Martin, F. [CEA de Saclay, DEN, DPC, SCCME, Laboratoire d' Etude de la Corrosion Aqueuse, F-91191 Gif-sur-Yvette (France); Del Frari, D. [CEA de Saclay, DSM, IRAMIS, SPSCI, F-91191 Gif-sur-Yvette (France); Cousty, J. [CEA de Saclay, DSM, IRAMIS, SPSCI, F-91191 Gif-sur-Yvette (France)], E-mail: jacques.cousty@cea.fr; Bataillon, C. [CEA de Saclay, DEN, DPC, SCCME, Laboratoire d' Etude de la Corrosion Aqueuse, F-91191 Gif-sur-Yvette (France)

    2009-04-15

    The nanoscaled morphology of the overlayer covering stainless steels after electropolishing in perchloric acid-based electrolyte was explored mainly by AFM and SEM. Two kinds of stainless steels were tested. For the austenitic one (AISI 304L), a quasi-periodic arrangement of pores in this overlayer has been observed. Depending on the experimental conditions, the distance between neighbouring pores ranged from 20 nm up to 230 nm. This inter-pore distance varied either with the applied voltage or with the current density for a constant voltage. From XPS spectra performed on the nanostructured surfaces, analysis of the energy shifts of Cr and Fe 2p levels showed that the anodic overlayer was enriched in Cr atoms compared to the 304L steel bulk composition. For the austeno-ferritic duplex stainless steel, the electropolished surface exhibited nanoscaled pores, which had grown and self-organised on both phases but with different characteristic dimensions.

  10. Steam oxidation of boron carbide–stainless steel liquid mixtures

    In the framework of nuclear reactor core meltdown accidents studies, the oxidation kinetics of boron carbide–stainless steel liquid mixtures exposed to argon/steam atmospheres was investigated at temperatures up to 1527 °C. A B–Cr–Si–O liquid protective layer forms on the surface of the mixtures in contact with steam. This protective layer gradually transforms into a Cr2O3-rich slag. Important quantities of liquid can be projected from the melt during oxidation. These projections are favoured by high B4C contents in the melt, high steam partial pressures and low temperatures. In addition to stainless steel–boron carbide melts, simpler compositions (pure 304L stainless steel, iron–boron, iron–boron carbide and stainless steel–boron) were studied, in order to identify the basic oxidation mechanisms.

  11. Articles comprising ferritic stainless steels

    Rakowski, James M.

    2016-06-28

    An article of manufacture comprises a ferritic stainless steel that includes a near-surface region depleted of silicon relative to a remainder of the ferritic stainless steel. The article has a reduced tendency to form an electrically resistive silica layer including silicon derived from the steel when the article is subjected to high temperature oxidizing conditions. The ferritic stainless steel is selected from the group comprising AISI Type 430 stainless steel, AISI Type 439 stainless steel, AISI Type 441 stainless steel, AISI Type 444 stainless steel, and E-BRITE.RTM. alloy, also known as UNS 44627 stainless steel. In certain embodiments, the article of manufacture is a fuel cell interconnect for a solid oxide fuel cell.

  12. Contribution to analysis of fatigue crack propagation at room temperature in low carbon austenitic steels type 18-10(304L) and Mo 17-12(316L). Relation between macroscopic and microscopic phenomena

    Low cycle fatigue phenomenon on the structural components of reactors is one of the most important problem. In this paper were carried out some fatigue tests on stainless steels type Z2CN18-10 (AISI 304L) and Z2CND17-12 (AISI 316L) at room temperature in air and in a corrosive medium (NaCl solution at different pH values). Length of cracks and crack propagation under stresses were determined. Z2CND17-12 has a better behavior than Z2CN18-10 because of a better structural stability both in air and in a corrosive environment. Structure was examined by transmission electron microscopy and microhardness was measured in the perturbed zones

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

    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.)

  14. Stress corrosion cracking of L-grade stainless steel in high temperature water

    L-grade stainless steels such as 316NG, SUS316L and SUS304L are used for the BWR reactor internals and re-circulation pipes. The L-grade stainless steels are known as typical SCC resistant materials because they are hardly thermally sensitized in usual welding process due to its lower carbon contents. However SCC of the L-grade material components were recently reported. This paper summarizes the recent knowledge and reports about the SCC behavior of L-grade stainless steels and its mitigation and improvement methods in BWR primary water condition. (author)

  15. Evaluation of the austenitic alloys 304L, 316L, and alloy 825 under Tuff repository conditions

    Austenitic alloys 304L and 316L and stainless steel 825 were investigated as candidate materials for containers for waste disposal in the relatively benign conditions of the Yucca Mountain site. In this vault there will be very little water, and what there is will contain small amounts of chlorides, nitrates, sulphates and carbonates. The radiation fields will be 104 rad/h initially, but will decay to low levels by the end of the containment period. The initial temperature will be around 250 C, and it will remain above the boiling point of water for the containment period (approximately 300 years). There will be no lithostatic or hydrostatic pressure. Type 304L stainless steel is a base case material used in comparisons with other candidates. Type 316L stainless steel possesses enhanced resistance to sensitization and localized corrosion; alloy 825 is stabilized to have a much better resistance to sensitization and localized corrosion and performs better in chloride environments

  16. HYDROGEN ABSORPTION INDUCED SLOW CRACK GROWTH IN AUSTENITIC STAINLESS STEELS FOR PETROCHEMICAL PRESSURE VESSEL INDUSTRIES

    Ronnie Higuchi Rusli

    2010-01-01

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

  17. Characterisation of passive films on 300 series stainless steels

    The formation and breakdown of the passive films on stainless steels are mainly controlled by ionic and electronic transport processes. Both these processes are in part controlled by the electronic properties of the oxide film. Consequently, it is vital to gain a detailed perception of the electronic properties of the passive films together with structural and compositional information for a comprehensive understanding of mechanisms behind passivity and localised corrosion. As a step towards this goal the passive films formed on two main austenitic stainless steels AISI 316L and AISI 304L in borate solution were characterised by in situ Raman spectroscopy and photocurrent spectroscopy coupled with electrochemical measurements. This revealed the formation of an Fe-Cr spinel as the dominant constituent in the passive films with more Cr enrichment in the oxide film on 316L than that of 304L. Bandgap readings and semiconductivities of the two stainless steels suggested that three different applied potential regions existed; 800 mV(SCE) to 300 mV(SCE), 200 mV(SCE) to -300 mV(SCE) and below -500 mV(SCE)

  18. YAG laser welding of neutron irradiated stainless steels

    Type 304L stainless steel plates of 8 mm thickness irradiated in a boiling water reactor (BWR) to 1.2 x 025 n/m2 (E > 1.0 MeV) containing 9 appm helium from transmutation have been successfully welded using a high power Nd-YAG laser under conditions of both continuous wave (CW) and pulse modes. Unirradiated type 316L stainless steel plate was lap welded to the irradiated type 304L stainless steel plate under heat inputs ranging from 240 to 540 J/cm. Bead on plate welding was carried out under the same welding conditions as lap welding. Tensile tests of lap welded joints were conducted at room temperature. All joints fractured not in the irradiated materials but in the unirradiated materials and showed good mechanical properties. Based on these results it does not appear that helium affects the mechanical properties of joints. Small grain boundary cracks were observed in HAZ of the weld made by the CW YAG laser with heat inputs of 480 and 540 J/cm and crack length decreased with decreasing heat input. (orig.)

  19. The effects of tritium and decay helium on the fracture toughness properties of stainless steels

    J-integral fracture mechanics techniques and scanning electron microscopy observations were used to investigate the effects of tritium and its decay product, helium-3, on Types 304L, 316L, 21-6-9, A286, and JBK-75 (Modified A286) stainless steels. Tritium-exposed samples of each steel had lower fracture toughness values and less resistance to stable crack growth than control samples. Type 316L stainless steel was more resistant to the embrittling effects of tritium and decay helium than the other steels

  20. Non destructive testing by acoustic signature of damage level in 304L steel samples submitted to rolling, tensile test and thermal annealing treatments

    The aim of this work is to demonstrate the ability of acoustic signature technique to detect in a non-destructive way mechanical property variations due to damage of the internal material structure for 304L steel samples, provided by EDF company. For this purpose, the velocity and the attenuation of Rayleigh acoustic waves have been measured for rolled, drawn and thermally treated samples. Complementary information provided by echography have also been used to calculate the corresponding variations of the dynamic Young's modulus E

  1. Quantitative characterization of porosity in laser welds of stainless steel

    Standing-edge joints made by a continuous-wave Nd:YAG laser are examined in 304L stainless steel to advance understanding of the linkage between processing and microstructure in high-rate solidification events. Microcomputed tomography combined with traditional metallography has provided qualitative and quantitative characterization of welds in this material system of broad use and applicability. Pore presence and variability have been examined three-dimensionally for average values, spatial distributions and morphology, and related to processing parameters such as weld speed, delivered power and focal lens.

  2. Metal release reduction from stainless steel for LWR

    Reduction of metal release from structural materials is one of key subjects on reliability in nuclear power plants. This study describes the pre-filming technology to reduce Cr and Co release from TP304L feeder water tube. Reducing content of elements that have long half time from the structural materials is very important for reduction of radioactivity. Stainless steels contain slight amount of Co as contamination. Lower Co in TP304L is obtained during a steel making process using a raw material from a blast furnace to reduce scraps which contains Co contamination. So extra low Co (< 0.02%) is applied to the chemical controlled TP304L for the feeder water tubes. Furthermore, pre-filming was also studied. It was known that metal release increased during early term in operation and reduced with growing oxide film. In high temperature water, Cr2O3 is stable oxide. So Cr2O3 pre-filming for inner surface of the feeder water tube was investigated for the reduction of metal release. TP304L consists of mainly Fe, Cr and Ni. Cr has the lowest oxygen potential than those of them. Cr can be oxidized selectivity by controlling a dew point of atmosphere during a heat treatment. Pre-filming on inner surface of the feeder water tube was performed by the final heat treatment under the controlled dew points in flowing H2 gas. The amount of metal release was measured in water at 488 K by a refreshed type autoclave. The rate of Cr rerelease from the pre-filming tube was two third that from the bare tube without pre-filming. It was considered that pre-filming was effective for the reduction of the metal release from the tube. (author)

  3. Corrosion of stainless steels in lead-bismuth eutectic up to 600 deg. C

    An experimental program has been carried out to understand the differences in the corrosion behaviour between different stainless steels: the austenitic steels 304L and 316L, the martensitic steels F82Hmod, T91 and EM10, and the low alloy steel P22. The influence of oxygen level in Pb-Bi, temperature and exposure time is studied. At 600 deg. C, the martensitic steels and the P22 steel exhibit thick oxide scales that grow with time, following a linear law for the wet environment and a parabolic law for the dry one. The austenitic stainless steels show a better corrosion behaviour, especially AISI 304L. Under reducing conditions, the steels exhibit dissolution, more severe for the austenitic stainless steels. At 450 deg. C, all the materials show an acceptable behaviour provided a sufficient oxygen level in the Pb-Bi. At reducing conditions, the martensitic steels and the P22 steel have a good corrosion resistance, while the austenitic steels exhibit already dissolution at the longer exposures

  4. Corrosion of stainless steels in lead-bismuth eutectic up to 600 deg. C

    Soler, L. [Dpto. Fision Nuclear, CIEMAT, Edificio 30, Avda. Complutense 22, Madrid 28040 (Spain)]. E-mail: laura.soler@ciemat.es; Martin, F.J. [Dpto. Fision Nuclear, CIEMAT, Edificio 30, Avda. Complutense 22, Madrid 28040 (Spain); Hernandez, F. [Dpto. Fision Nuclear, CIEMAT, Edificio 30, Avda. Complutense 22, Madrid 28040 (Spain); Gomez-Briceno, D. [Dpto. Fision Nuclear, CIEMAT, Edificio 30, Avda. Complutense 22, Madrid 28040 (Spain)

    2004-11-01

    An experimental program has been carried out to understand the differences in the corrosion behaviour between different stainless steels: the austenitic steels 304L and 316L, the martensitic steels F82Hmod, T91 and EM10, and the low alloy steel P22. The influence of oxygen level in Pb-Bi, temperature and exposure time is studied. At 600 deg. C, the martensitic steels and the P22 steel exhibit thick oxide scales that grow with time, following a linear law for the wet environment and a parabolic law for the dry one. The austenitic stainless steels show a better corrosion behaviour, especially AISI 304L. Under reducing conditions, the steels exhibit dissolution, more severe for the austenitic stainless steels. At 450 deg. C, all the materials show an acceptable behaviour provided a sufficient oxygen level in the Pb-Bi. At reducing conditions, the martensitic steels and the P22 steel have a good corrosion resistance, while the austenitic steels exhibit already dissolution at the longer exposures.

  5. Optimization of tensile strength of friction welded AISI 1040 and AISI 304L steels according to statistics analysis (ANOVA)

    Kirik, Ihsan [Batman Univ. (Turkey); Ozdemir, Niyazi; Firat, Emrah Hanifi; Caligulu, Ugur [Firat Univ., Elazig (Turkey)

    2013-06-01

    Materials difficult to weld by fusion welding processes can be successfully welded by friction welding. The strength of the friction welded joints is extremely affected by process parameters (rotation speed, friction time, friction pressure, forging time, and forging pressure). In this study, statistical values of tensile strength were investigated in terms of rotation speed, friction time, and friction pressure on the strength behaviours of friction welded AISI 1040 and AISI 304L alloys. Then, the tensile test results were analyzed by analysis of variance (ANOVA) with a confidence level of 95 % to find out whether a statistically significant difference occurs. As a result of this study, the maximum tensile strength is very close, which that of AISI 1040 parent metal of 637 MPa to could be obtained for the joints fabricated under the welding conditions of rotation speed of 1700 rpm, friction pressure of 50 MPa, forging pressure of 100 MPa, friction time of 4 s, and forging time of 2 s. Rotation speed, friction time, and friction pressure on the friction welding of AISI 1040 and AISI 304L alloys were statistically significant regarding tensile strength test values. (orig.)

  6. Attenuation of shock waves in copper and stainless steel

    Harvey, W.B.

    1986-06-01

    By using shock pins, data were gathered on the trajectories of shock waves in stainless steel (SS-304L) and oxygen-free-high-conductivity copper (OFHC-Cu). Shock pressures were generated in these materials by impacting the appropriate target with thin (approx.1.5 mm) flying plates. The flying plates in these experiments were accelerated to high velocities (approx.4 km/s) by high explosives. Six experiments were conducted, three using SS-304L as the target material and three experiments using OFHC-Cu as the target material. Peak shock pressures generated in the steel experiments were approximately 109, 130, and 147 GPa and in the copper experiments, the peak shock pressures were approximately 111, 132, and 143 GPa. In each experiment, an attenuation of the shock wave by a following release wave was clearly observed. An extensive effort using two characteristic codes (described in this work) to theoretically calculate the attenuation of the shock waves was made. The efficacy of several different constitutive equations to successfully model the experiments was studied by comparing the calculated shock trajectories to the experimental data. Based on such comparisons, the conclusion can be drawn that OFHC-Cu enters a melt phase at about 130 GPa on the principal Hugoniot. There was no sign of phase changes in the stainless-steel experiments. In order to match the observed attenuation of the shock waves in the SS-304L experiments, it was necessary to include strength effects in the calculations. It was found that the values for the parameters in the strength equations were dependent on the equation of state used in the modeling of the experiments. 66 refs., 194 figs., 77 tabs.

  7. Attenuation of shock waves in copper and stainless steel

    By using shock pins, data were gathered on the trajectories of shock waves in stainless steel (SS-304L) and oxygen-free-high-conductivity copper (OFHC-Cu). Shock pressures were generated in these materials by impacting the appropriate target with thin (approx.1.5 mm) flying plates. The flying plates in these experiments were accelerated to high velocities (approx.4 km/s) by high explosives. Six experiments were conducted, three using SS-304L as the target material and three experiments using OFHC-Cu as the target material. Peak shock pressures generated in the steel experiments were approximately 109, 130, and 147 GPa and in the copper experiments, the peak shock pressures were approximately 111, 132, and 143 GPa. In each experiment, an attenuation of the shock wave by a following release wave was clearly observed. An extensive effort using two characteristic codes (described in this work) to theoretically calculate the attenuation of the shock waves was made. The efficacy of several different constitutive equations to successfully model the experiments was studied by comparing the calculated shock trajectories to the experimental data. Based on such comparisons, the conclusion can be drawn that OFHC-Cu enters a melt phase at about 130 GPa on the principal Hugoniot. There was no sign of phase changes in the stainless-steel experiments. In order to match the observed attenuation of the shock waves in the SS-304L experiments, it was necessary to include strength effects in the calculations. It was found that the values for the parameters in the strength equations were dependent on the equation of state used in the modeling of the experiments. 66 refs., 194 figs., 77 tabs

  8. Atom probe, AFM, and STM studies on vacuum-fired stainless steels.

    Stupnik, A; Frank, P; Leisch, M

    2009-04-01

    The surface morphology of grades 304L and 316LN stainless steels, after low-temperature bake-out process and vacuum annealing, has been studied by atomic force microscopy (AFM) and scanning tunnelling microscopy (STM). The local elemental composition on the surface before and after thermal treatment has been investigated by atom probe (AP) depth profiling measurements. After vacuum annealing, AFM and STM show significant changes in the surface structure and topology. Recrystallization and surface reconstruction is less pronounced on the 316LN stainless steel. AP depth profiling analyses result in noticeable nickel enrichment on the surface of grade 304L samples. Since hydrogen recombination is almost controlled by surface structure and composition, a strong influence on the outgassing behaviour by the particular surface microstructure can be deduced. PMID:19167824

  9. Stainless steels low temperature nitriding

    Nitrogen ions implantation of 316L stainless steel leads to monophasic diffusion layers, which are constituted of a solid solution (γN) fcc, metastable, nitrogen sur-saturated, and without order. This article shows that for 316L stainless steels,these layers improve the tribological properties without degradation of the corrosion resistance. (A.B.). 13 refs. 6 figs

  10. Effect of cold work and type of load in the SCC behaviour of austenitic stainless steels in PWR conditions

    Austenitic stainless steels are susceptible to SCC in high temperature water, even in reducing environment such as the PWR primary water. Both laboratory results and field evidences confirm that stainless steels are susceptible to SCC when these materials are in a cold work condition. CGR experiments have been performed in order to assess the factors influencing SCC propagation in stainless steels. Compact tension specimens were fabricated of 316 L, 304 L and 347 SS to evaluate the influence of degree of cold work and its way of application, water chemistry, temperature and loading conditions. (authors)

  11. Corrosion behavior of powder metallurgical stainless steels in urban and marine environments

    Bautista, A.; F. Velasco; S. Guzmán; Fuente, Daniel de la; Cayuela, F.; Morcillo, Manuel

    2006-01-01

    This work studies the development of corrosive attack on sintered components manufactured from AISI 316L and AISI 304L powders. The stainless steels were sintered in vacuum and in nitrogen-base atmosphere at 1,120 and 1,250ºC, and their corrosion resistance was then analyzed by electrochemical techniques and by atmospheric corrosion testing (two years) at urban and marine test sites. Images are shown of the morphology of the attack on the surface of the stainless steels and the development...

  12. Corrosion behavior of powder metallurgical stainless steels in urban and marine environments

    Bautista, A.; F. Velasco; S. Guzmán; de la Fuente, D.; Cayuela, F.; Morcillo, M.

    2006-01-01

    This work studies the development of corrosive attack on sintered components manufactured from AISI 316L and AISI 304L powders. The stainless steels were sintered in vacuum and in nitrogen-base atmosphere at 1,120 and 1,250 ºC, and their corrosion resistance was then analyzed by electrochemical techniques and by atmospheric corrosion testing (two years) at urban and marine test sites. Images are shown of the morphology of the attack on the surface of the stainless steels and the development o...

  13. Stress corrosion cracking susceptibilities of various stainless steels in high temperature water

    The intergranular stress corrosion cracking (IGSCC) behaviors of several austenitic stainless steels in high temperature water were evaluated using three types of SCC tests, i.e., single U-bend test in chloride containing water, uniaxial constant load and constant extension rate tests (CERT) in pure water. The steels used were SUS 304, 304L, 316, 316L, 321 and 347 and several heats of them to examine heat to heat variations. The three test methods gave the same relative ranking of the steels. The CERT is the most sensitive method to detect the relative IGSCC susceptibilities. The CERT result for relative ranking from poor to good is: SUS 304 - 0.07% C, 304 - 0.06% C, 304L - 0.028% C, 316 - 0.07% C. The IGSCC susceptibilities of SUS 304L - 0.020% C, 316L - 0.023% C, 321 and 347 were not detected. These test results suggest that the use of the low carbon, molybdenum bearing, or stabilized austenitic stainless steel is beneficial for eliminating the IGSCC problem in boiling water reactor environment. (author)

  14. Multi-cracking in uniaxial and biaxial fatigue of 304L stainless steel

    When a mechanical part is subjected to a repeated mechanical stress, it may be damaged after a number of cycles by several cracks initiation and propagation of a main crack. This is the phenomenon of fatigue damage. The thesis deals specifically with possible damage to some components of nuclear plants due to thermal fatigue. Unlike conventional mechanical fatigue damage where a main crack breaks the part, the thermal fatigue damage usually results in the appearance of a surface crack network. Two aspects are discussed in the thesis. The first is the experimental study of fatigue multiple cracking stage also called multi-cracking. Two mechanical test campaigns with multi-cracking detection by digital image correlation were conducted. These campaigns involve uniaxial and equi-biaxial mechanical loads in tension/compression without mean stress. This work allows to monitor and to observe the evolution of different networks of cracks through mechanical solicitations. The second is the numerical simulation of the phenomenon of fatigue damage. Several types of model are used (stochastic, probabilistic, cohesive finite elements). The experimental results have led to identify a multiple crack initiation law in fatigue which is faced with the numerical results. This comparison shows the relevance of the use of an analytical probabilistic model to find statistical results on the density of cracks that can be initiated with thermal and mechanical fatigue loadings. (author)

  15. Influence of surface states on the plasma-jet oxidation of 304 L stainless steel

    Many parameters related to the plasma spraying process and to the substrate surface properties control the quality of plasma sprayed coating; Current studies have pointed out the fact that a preliminary oxidation, in case of metallic surfaces, enhances really the adhesion of the deposits. This oxidation is achieved by the plume of the plasma jet during a time tp at the estimated surface temperature conditions and also for given initial surface preparations. In order to understand the influence of these different surface states to their plasma oxidation behaviour. Oxide layers, metallic bulk and oxide-metal interfaces have been investigated using different spectroscopic techniques, like XRD, CEMS and near ultraviolet-visible-near infrared spectroscopy. (authors)

  16. Influence of Water Pollution on MIC of Stainless Steel 304L

    2002-01-01

    The influence of water pollution and welding defects on MIC (microbiologically influenced corrosion) was studied. The open circuit potential (OCP) was measured during MIC test. It was found that OCP shifted to a higher level when the system was inoculated with bacteria while the OCP of those samples in water without bacteria was kept at a low level. The OCP decreased dramatically when MIC started in polluted water. Combination of weld defect-heat tint, polluted water and adding bacteria causes MIC happen at high rate. Some elements inside the tubercle were analyzed with EDXA. The pits and biofilm were observed with SEM. Microbiological analysis revealed the difference of bacteria between corroded and uncorroded samples.

  17. Stainless steel display evaluation

    Hopper, Darrel G.; Meyer, Frederick M.; Longo, Sam J.; Trissell, Terry L.

    2007-04-01

    Active matrix organic light emitting diode (AMOLED) technology is one candidate to become a low power alternative in some applications to the currently dominant, active matrix liquid crystal display (AMLCD), technology. Furthermore, fabrication of the AMOLED on stainless steel (SS) foil rather than the traditional glass substrate, while presenting a set of severe technical challenges, opens up the potential for displays that are both lighter and less breakable. Also, transition to an SS foil substrate may enable rollable displays - large when used but small for stowage within gear already worn or carried or installed. Research has been initiated on AMOLED/SS technology and the first 320 x 240 color pixel 4-in. demonstration device has been evaluated in the AFRL Display Test and Evaluation Laboratory. Results of this evaluation are reported along with a research roadmap.

  18. Chromium-Makes stainless steel stainless

    Kropschot, S.J.; Doebrich, Jeff

    2010-01-01

    Chromium, a steely-gray, lustrous, hard metal that takes a high polish and has a high melting point, is a silvery white, hard, and bright metal plating on steel and other material. Commonly known as chrome, it is one of the most important and indispensable industrial metals because of its hardness and resistance to corrosion. But it is used for more than the production of stainless steel and nonferrous alloys; it is also used to create pigments and chemicals used to process leather.

  19. Threshold stress intensities and crack growth rates in tritium-exposed HERF stainless steels

    This paper reports on a falling-load compliance technique used to measure threshold stress intensities and crack growth rates in tritium-exposed-and- aged, high-energy-rate-forged (HERF) stainless steels. Triplicate 304L and 316 fracture toughness samples were exposed to high pressure tritium gas at 413 K, aged at 273 K for helium build-in from tritium decay, and then tested at room temperature. The samples contained about 740 appm tritium and 440 appm helium. The results showed that 304L had a lower threshold stress intensity (67.9 MPa-m1/2) than 316 (95.5 MPa-m1/2) and that the Stage II crack growth rates were, on average, more than an order of magnitude faster in 304L than in 316. During Stage II crack growth, each of the 304L samples showed periodic, order-of-magnitude changes in the crack velocities. These latter effects are apparently a result of the diffusion controlled process of concentrating tritium at the crack tip and/or the process of microcracks linking up to the main crack front. In both materials, the cracking was for the most part along grain- and-twin boundaries but glide-plane decohesion was also observed

  20. Overlay welding irradiated stainless steel

    An overlay technique developed for welding irradiated stainless steel may be important for repair or modification of fusion reactor materials. Helium, present due to n,α reactions, is known to cause cracking using conventional welding methods. Stainless steel impregnated with 3 to 220 appm helium by decay of tritium was used to develop a welding process that could be used for repair. The result was a gas metal arc weld overlay technique with low-heat input and low-penetration into the helium-containing material. Extensive metallurgical and mechanical testing of this technique demonstrated substantial reduction of helium embrittlement damage. The overlay technique was applied to irradiated 304 stainless steel containing 10 appm helium. Surface cracking, present in conventional welds made on the same steel at lower helium concentrations, was eliminated. Underbead cracking, although greater than for tritium charged and aged material, was minimal compared to conventional welding methods

  1. Strip casting of stainless steels

    Raabe, D.

    1997-01-01

    FLAT PRODUCTS OF STAINLESS STEELS ARE CONVENTIONALLY MANUFACTURED BY CONTINUOUS CASTING, HOT ROLLING, HOT BAND ANNEALING, PICKLING, COLD ROLLING AND RECRYSTALLISATION. IN THE LAST YEARS STRIP CASTING HAS INCREASINGLY ATTRACTED ATTENTION. IT OFFERS THREE IMPROVEMENTS IN COMPARISON TO THE CONVENTIONAL METHOD.1.) IT ALLOWS TO CAST STEEL SHEETS WITH THE SAME THICKNESS AND WIDTH AS THOSE PRODUCED BY HOT ROLLING. THIS MEANS THAT THE HOT ROLLING PROCESSIS BYPASSED. 2.) THE STRIP CAST STEEL REVEALS A...

  2. Hydrogen Embrittlement Evaluation in Tensile Properties of Stainless Steels at Cryogenic Temperatures

    Ogata, T.

    2008-03-01

    The advanced design of fuel-cell vehicles requires high-pressure low-temperature hydrogen systems, which in turn requires a high-pressure low-temperature mechanical properties database to address hydrogen embrittlement issues. A very simple and safe mechanical properties testing procedure to evaluate low temperature hydrogen embrittlement has been developed and is reported here. Tensile properties of stainless steel, SUS 304, 304L and 316L, obtained by this simple method are in good agreement with previous data obtained in a high pressure chamber. The effect of hydrogen changed also with the amount of strain-induced martensitic transformation in those steels at low temperatures.

  3. Cryogenic material properties of stainless steel tube-to-flange welds

    Siewert, T. A.; McCowan, C. N.; Vigliotti, D. P.

    The mechanical properties of stainless steel tube-to-flange welds for a cryogenic piping application were measured. A planar specimen was developed to duplicate the constraint, loading and heat-sink properties of the circular joint, while reducing preparation time and cost. Specimens were evaluated containing welds between the tube material (21 Cr-6Ni-9Mn) and the three stainless steels being considered for the flange materials: type 304L, type 316L and 21 Cr-6Ni-9Mn. The mechanical property tests consisted of three phases: simple tensile testing to failure, tensile testing of notched specimens (where the notch simulated fabrication flaws) and fatigue testing of notched specimens for the 4 × 10 4 cycle design life of the structure. The type 316L stainless steel flange produced welds with the best combination of strength and ductility at 295 and 4 K in all three phases of testing.

  4. Multitechnique characterisation of 304L surface states oxidised at high temperature in steam and air atmospheres

    Mamede, Anne-Sophie; Nuns, Nicolas; Cristol, Anne-Lise; Cantrel, Laurent; Souvi, Sidi; Cristol, Sylvain; Paul, Jean-François

    2016-04-01

    In case of a severe accident occurring in a nuclear reactor, surfaces of the reactor coolant system (RCS), made of stainless steel (304L) rich in Cr (>10%) and Ni (8-12%), are oxidised. Fission products (FPs) are released from melt fuel and flow through the RCS. A part of them is deposited onto surfaces either by vapour condensation or by aerosol deposition mechanisms. To be able to understand the nature of interactions between these FPs and the RCS surfaces, a preliminary step is to characterize the RSC surface states in steam and air atmosphere at high temperatures. Pieces of 304L stainless steel have been treated in a flow reactor at two different temperatures (750 °C and 950 °C) for two different exposition times (24 h and 72 h). After surfaces analysing by a unique combination of surface analysis techniques (XPS, ToF-SIMS and LEIS), for 304L, the results show a deep oxide scale with multi layers and the outer layer is composed of chromium and manganese oxides. Oxide profiles differ in air or steam atmosphere. Fe2O3 oxide is observed but in minor proportion and in all cases no nickel is detected near the surface. Results obtained are discussed and compared with the literature data.

  5. Welding of stainless steel clad fuel rods for nuclear reactors

    This work describes the obtainment of austenitic stainless steel clad fuel rods for nuclear reactors. Two aspects have been emphasized: (a) obtainment and qualification of AISI 304 and 304 L stainless steel tubes; b) the circumferential welding of pipe ends to end plugs of the same alloy followed by qualification of the welds. Tubes with special and characteristic dimensions were obtained by set mandrel drawing. Both, seamed and seamless tubes of 304 and 304 L were obtained.The dimensional accuracy, surface roughness, mechanical properties and microstructural characteristics of the tubes were found to be adequate. The differences in the properties of the tubes with and without seams were found to be insignificant. The TIG process of welding was used. The influence of various welding parameters were studied: shielding gas (argon and helium), welding current, tube rotation speed, arc length, electrode position and gas flow. An inert gas welding chamber was developed and constructed with the aim of reducing surface oxidation and the heat affected zone. The welds were evaluated with the aid of destructive tests (burst-test, microhardness profile determination and metallographic analysis) and non destructive tests (visual inspection, dimensional examination, radiography and helium leak detection). As a function of the results obtained, two different welding cycles have been suggested; one for argon and another for helium. The changes in the microstructure caused by welding have been studied in greater detail. The utilization of work hardened tubes, permitted the identification by optical microscopy and microhardness measurements, of the different zones: weld zone; heat affected zone (region of grain growth, region of total and partial recrystallization) and finally, the zone not affected by heat. Some correlations between the welding parameters and metallurgical phenomena such as: solidification, recovery, recrystallization, grain growth and precipitation that occurred

  6. Plating on stainless steel alloys

    Quantitative adhesion data are presented for a variety of electroplated stainless steel type alloys. Results show that excellent adhesion can be obtained by using a Wood's nickel strike or a sulfamate nickel strike prior to final plating. Specimens plated after Wood's nickel striking failed in the deposit rather than at the interface between the substrate and the coating. Flyer plate quantitative tests showed that use of anodic treatment in sulfuric acid prior to Wood's nickel striking even further improved adhesion. In contrast activation of stainless steels by immersion or cathodic treatment in hydrochloric acid resulted in very reduced bond strengths with failure always occurring at the interface between the coating and substrate

  7. Low-cycle fatigue properties of stainless steels and aluminum alloys at liquid helium temperature

    Axial-strain controlled fatigue tests of stainless steels (SUS 304 L, SUS 316 L and WM-X) and aluminum alloys (A 5083-O and A 5356) were conducted at 4 K with the strain rate of 0.4 %/s and the strain ratio of -1. The fatigue tests at 77 and 300 K were also conducted for comparison. The TIG weld metal of stainless steel (WM-X) showed cyclic strain-hardening at 4 and 77 K, and cyclic strain-softening at 300 K, although other materials showed cyclic strain-hardening at 4, 77 and 300 K. It seemed that the strain-induced martensitic transformation influenced the cyclic stress responce of stainless steel. In the fatigue life range of 1000 cycles or more, the fatigue resistance, that means the strain capability at given cycles of fatigue life, of SUS 304 L, SUS 316 L, WM-X and A 5083-O at 4 K were nearly equal to or a bit higher than that at 77 K. At 4 K, the fatigue resistance of SUS 316 L was higher than that of SUS 304 L, but lied in the middle of a scatter band by a factor of 2 among base metals of stainless steels in literatures. The fatigue resistance of A 5083-O was the lowest in a scatter band by a factor of 1.4 among base metals of aluminum alloys in literatures. At 4 K, the fatigue resistance of WM-X was almost equivalent to that of SUS 304 L and was lower than that of SUS 316 L by 20 %, being away below that of base metals of stainless steels at 300 K. However, the fatigue resistance of the MIG weld metal of aluminum alloy (A 5356) was lower than that of A 5083-O by 45 %, being closer to that of base metals of aluminum alloy at 300 K. One must be careful to use the weld metal A 5356 at 4 K. (author)

  8. Low temperature thermal aging of austenitic stainless steel welds: Kinetics and effects on mechanical properties

    Highlights: ► Embrittlement of 304L and 316L welds after aging up to 20,000 h. ► Spinodal decomposition and G-phase precipitation in ferrite at 400 °C. Only spinodal decomposition at 335 and 365 °C. ► Charpy impact, microhardness and tensile tests for evaluation of aging embrittlement and its kinetics determined. - Abstract: Austenitic stainless steel welds in components used in light water reactors are susceptible to thermal aging embrittlement at reactor operating temperature of around 300 °C after a long service life. In this study, low temperature aging embrittlement of types 304L and 316L stainless steel welds with 10% ferrite was investigated on the basis of changes in mechanical properties and microstructure after aging up to 20,000 h at 335, 365 and 400 °C. Spinodal decomposition and G-phase precipitation in the ferrite was observed after aging which lead to embrittlement in the material. In contrast to the small effect on tensile properties, the impact toughness was significantly degraded after aging. Charpy impact test of the aged samples showed decrease in upper-shelf and lower-shelf energy and increase in ductile brittle transition temperature. Large increase in the microhardness of ferrite phase was observed with no change in austenite hardness. The embrittlement in 316L weld was higher compared to 304L weld for similar aging condition. The kinetics of aging embrittlement was established based on Arrhenius relationship. A constant activation energy was determined for 304L weld in the temperature range 335–400 °C, however, 316L weld showed different activation energy values in each temperature range.

  9. Low temperature thermal aging of austenitic stainless steel welds: Kinetics and effects on mechanical properties

    Chandra, K., E-mail: kchandra@barc.gov.in [Materials Science Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Kain, Vivekanand [Materials Science Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Bhutani, Vikas [Punjab Engineering College, Chandigarh 160 012 (India); Raja, V.S. [Indian Institute of Technology, Mumbai 400 076 (India); Tewari, R.; Dey, G.K. [Materials Science Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Chakravartty, J.K. [Mechanical Metallurgy Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)

    2012-02-01

    Highlights: Black-Right-Pointing-Pointer Embrittlement of 304L and 316L welds after aging up to 20,000 h. Black-Right-Pointing-Pointer Spinodal decomposition and G-phase precipitation in ferrite at 400 Degree-Sign C. Only spinodal decomposition at 335 and 365 Degree-Sign C. Black-Right-Pointing-Pointer Charpy impact, microhardness and tensile tests for evaluation of aging embrittlement and its kinetics determined. - Abstract: Austenitic stainless steel welds in components used in light water reactors are susceptible to thermal aging embrittlement at reactor operating temperature of around 300 Degree-Sign C after a long service life. In this study, low temperature aging embrittlement of types 304L and 316L stainless steel welds with 10% ferrite was investigated on the basis of changes in mechanical properties and microstructure after aging up to 20,000 h at 335, 365 and 400 Degree-Sign C. Spinodal decomposition and G-phase precipitation in the ferrite was observed after aging which lead to embrittlement in the material. In contrast to the small effect on tensile properties, the impact toughness was significantly degraded after aging. Charpy impact test of the aged samples showed decrease in upper-shelf and lower-shelf energy and increase in ductile brittle transition temperature. Large increase in the microhardness of ferrite phase was observed with no change in austenite hardness. The embrittlement in 316L weld was higher compared to 304L weld for similar aging condition. The kinetics of aging embrittlement was established based on Arrhenius relationship. A constant activation energy was determined for 304L weld in the temperature range 335-400 Degree-Sign C, however, 316L weld showed different activation energy values in each temperature range.

  10. Effect of neptunium ions on corrosion of stainless steel in nitric acid solution

    We have studied corrosion of a stainless steel in nitric acid solution containing neptunium. Using type 304L stainless steel, corrosion tests in boiling neptunium nitrate solution were conducted under immersion and heat-transfer condition. By the weight loss measurement of stainless steel and the quantitative analysis of metallic ions dissolved in solution, the corrosion rates of stainless steel were obtained. The surface morphology was observed by scanning electron microscopy. The corrosion acceleration mechanism was investigated by polarization measurement and spectrophotometry. The corrosion rate of stainless steel was accelerated by addition of neptunium in nitric acid solution. Preferential intergranular corrosion was observed. The corrosion of stainless steel was promoted under heat-transfer condition compared to immersion condition. In polarization measurements, the cathodic over-voltage was decreased; the cathodic current was increased by addition of neptunium. Spectrophotometric measurements showed the oxidization of neptunium in boiling nitric acid. The corrosion mechanism in nitric acid solution containing neptunium suggested the re-oxidation of neptunium. (author)

  11. The deformation response of L-grade stainless steels relative to IGSCC in 288 C water

    Laboratory testing of L-grade stainless steels in representative boiling water nuclear reactor (BWR) core environments has shown that the intergranular (IG) cracking behavior is sensitive to the composition, corrosion potential and cold work. The objective of this study is to explore the deformation response of L-grade stainless steels to better understand its role on the IGSCC behavior. The deformation response was studied as a function of composition to evaluate the phase stability, susceptibility to sensitization and creep relaxation behaviors. The effect of deformation on 304, 304L, 316L and 316NG materials were evaluated metallographically and as a function of thermal treatment using the double loop electrochemical potentiokinetic reactivation (DL-EPR) technique. Metallographic results show that 304L is most likely to form deformation induced martensite, consistent with calculations. The DL-EPR response of 304L and 316L/NG materials increases significantly upon thermal treatment of cold worked material. These results are being used to determine the combinations of cold work and thermal treatment that promote IGSCC in 288 C high purity water at ∼ +200mVSHE of 304L weld material obtained from an unirradiated nuclear station core shroud. The creep relaxation response of 304, 304L, 316L and 316NG materials were evaluated as a function of the stress intensity in 288 C air using compact tension specimens. The preliminary results suggest that the lower alloyed 304L exhibits more creep strain in the same period of time than higher alloyed 316L/NG and Alloy 600 materials. These results have implications in terms of the slip-oxidation model for crack advance where higher creep rates are expected to promote a higher crack tip strain rate and faster crack growth rates. Future work will study the crack growth rates of 304W316L/316NG in various states of cold work and thermal treatment to evaluate the roles of phase stability, sensitization and creep relaxation on the

  12. AEM ANALYSIS OF STAINLESS STEEL

    Ogilvie, R.

    1984-01-01

    Quantitative AEM of thin films of stainless steel is presented. The X-ray data is corrected for absorption, secondary fluorescence and detector efficiency. A new form of the fluorescence correction has been derived. A modified form of the Cliff-Lorimer equations is also presented.

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

    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...

  14. Corrosion behavior of 2205 duplex stainless steel.

    Platt, J A; Guzman, A; Zuccari, A; Thornburg, D W; Rhodes, B F; Oshida, Y; Moore, B K

    1997-07-01

    The corrosion of 2205 duplex stainless steel was compared with that of AISI type 316L stainless steel. The 2205 stainless steel is a potential orthodontic bracket material with low nickel content (4 to 6 wt%), whereas the 316L stainless steel (nickel content: 10 to 14 wt%) is a currently used bracket material. Both stainless steels were subjected to electrochemical and immersion (crevice) corrosion tests in 37 degrees C, 0.9 wt% sodium chloride solution. Electrochemical testing indicates that 2205 has a longer passivation range than 316L. The corrosion rate of 2205 was 0.416 MPY (milli-inch per year), whereas 316L exhibited 0.647 MPY. When 2205 was coupled to 316L with equal surface area ratio, the corrosion rate of 2205 reduced to 0.260 MPY, indicating that 316L stainless steel behaved like a sacrificial anode. When 316L is coupled with NiTi, TMA, or stainless steel arch wire and was subjected to the immersion corrosion test, it was found that 316L suffered from crevice corrosion. On the other hand, 2205 stainless steel did not show any localized crevice corrosion, although the surface of 2205 was covered with corrosion products, formed when coupled to NiTi and stainless steel wires. This study indicates that considering corrosion resistance, 2205 duplex stainless steel is an improved alternative to 316L for orthodontic bracket fabrication when used in conjunction with titanium, its alloys, or stainless steel arch wires. PMID:9228844

  15. Stainless steel denitriding with slag

    Calculation and experimental methods were used to investigate the process of titanium nitride formation when alloying chromium nickel stainless steels with titanium. At common concentrations of titanium and nitrogen, titanium nitrides were observed to be precipitated from the melt into slag in amounts of 0.1% and more. The laboratory study of the slag influence of the process of steel refining from titanium nitrides showed that the slag containing calcium, aluminium and magnesium oxides is favourable to the denitriding of steel. In addition, the possibility of direct transition of dissolved nitrogen from the metal into the slag is revealed. 7 refs., 1 fig., 2 tabs

  16. Characteristics of vacuum sintered stainless steels

    Z. Brytan; L.A. Dobrzański; M. Actis Grande; Rosso, M.

    2009-01-01

    Purpose: In the present study duplex stainless steels were sintered in vacuum. using rapid cooling form the mixture of prealloyed and alloying element powders The purpose of this paper was to describe the obtained microstructures after sintering as well as the main mechanical properties of sintered stainless steels.Design/methodology/approach: In presented work duplex stainless steels were obtained through powder metallurgy starting from austenitic 316L or ferritic 410L prealloyed stainless s...

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

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

  18. Effect of heating rate on sintered series 300 stainless steel

    Ornmanee Coovattanachai

    2010-05-01

    Full Text Available Stainless steel powders (303L, 304L, 310L and 316L were formed into tensile test bars using the “press and sinter”process. Most processing parameters, except heating rate, were kept constant. During the heating of the experimental specimensfrom 700°C to the sintering temperature of 1300°C, heating rates were varied, e.g., 2.5, 5.0, and 10.0°C/min. Experimentalresults showed that a material heated with a low heating rate tended to have higher sintered density and tensile strength.However, the low heating rate caused grain growth in the sintered material. These results are in contradiction with the improved densification of some ceramics by ultra rapid heating. The reasons for contradiction are as follows. First, the heatingrates employed in this work are not very different. The second is attributed to small thermal gradients generated in thethin metal powder compacts. Because of these reasons, densification of the sintered stainless steels series 300 is controlled by an isothermal condition. The low heating rate allows longer time for atomic diffusion, which is an important sintering factor. This means more atoms move to points of contact between powder particles to form necking and to cause neckinggrowth. This results in better sintering. However, the low heating rate means that the materials are exposed to heat for longertime and thus their grains have a tendency to grow.

  19. Microbial corrosion of stainless steel.

    Ibars, J R; Moreno, D A; Ranninger, C

    1992-11-01

    Stainless steel, developed because of their greater resistance to corrosion in different aggressive environments, have proved to be affected, however, by various processes and types of corrosion. Some of these types of corrosion, mainly pitting, is activated and developed in the presence of microorganisms, which acting in an isolated or symbiotic way, according to their adaptation to the environment, create a favorable situation for the corrosion of these steel. The microorganisms that are involved, mainly bacteria of both the aerobic and anaerobic type, modify the environment where the stainless steel is found, creating crevices, differential aeration zones or a more aggressive environment with the presence of metabolites. In these circumstances, a local break of the passive and passivating layer is produced, which is proper to these types of steel and impedes the repassivation that is more favorable to corrosion. In the study and research of these types of microbiologically influenced corrosion are found electrochemical techniques, since corrosion is fundamentally an electrochemical process, and microbiological techniques for the identification, culture, and evaluation of the microorganisms involved in the process, as well as in the laboratory or field study of microorganism-metal pairs. Microstructural characterization studies of stainless steel have also been considered important, since it is known that the microstructure of steel can substantially modify their behavior when faced with corrosion. As for surface analysis studies, it is known that corrosion is a process that is generated on and progresses from the surface. The ways of dealing with microbiologically influenced corrosion must necessarily include biocides, which are not always usable or successful, the design of industrial equipment or components that do not favor the adherence of microorganisms, using microstructures in steel less sensitive to corrosion, or protecting the materials. PMID:1492953

  20. Effects of alloy and solution chemistry on the fracture of passive films on austenitic stainless steel

    The Taguchi analysis method was used to simultaneously study the effects of alloy chemistry, pH, and halide ion concentrations on the fracture of electrochemically grown passive films using a nanoindentation technique. Three austenitic stainless steels, 304L, 316L, and 904L were potentiostatically polarized in hydrochloric acid solutions. The fracture load was dominated primarily by alloy chemistry. Passive films mechanically weaken as the atomic iron concentration increases in the film. Prolonged anodic ageing time increases the fracture load of passive films

  1. Effects of alloy and solution chemistry on the fracture of passive films on austenitic stainless steel

    Alamr, A. [School of Mechanical and Materials Engineering, Washington State University, P.O. Box 642920, Pullman, WA 99164-2920 (United States)]. E-mail: alamrz@wsu.edu; Bahr, D.F. [School of Mechanical and Materials Engineering, Washington State University, P.O. Box 642920, Pullman, WA 99164-2920 (United States)]. E-mail: bahr@mail.wsu.edu; Jacroux, Michael [Department of Statistics, Washington State University, Pullman, WA 99164-3144 (United States) ]. E-mail: jacroux@wsu.edu

    2006-04-15

    The Taguchi analysis method was used to simultaneously study the effects of alloy chemistry, pH, and halide ion concentrations on the fracture of electrochemically grown passive films using a nanoindentation technique. Three austenitic stainless steels, 304L, 316L, and 904L were potentiostatically polarized in hydrochloric acid solutions. The fracture load was dominated primarily by alloy chemistry. Passive films mechanically weaken as the atomic iron concentration increases in the film. Prolonged anodic ageing time increases the fracture load of passive films.

  2. Porosity decrease in laser welds of stainless steel using plasma control

    High-energy laser welding incorporating plasma control has been studied and reported by numerous investigators. These investigators demonstrated significant increases in laser weld penetration by use of plasma control. This report shows, in addition to variations in weld penetration, drastic decrease in porosity and variation in weld bead shapes resulting from laser welds incorporating plasma control. In particular, deep laser welds (greater than 6 mm) have been produced in 304L stainless steel that show no root porosity and only very few, if any, detectable micropores

  3. Porosity in millimeter-scale welds of stainless steel : three-dimensional characterization.

    Aagesen, Larry K. (University of Michigan, Ann Arbor, MI); Madison, Jonathan D.

    2012-05-01

    A variety of edge joints utilizing a continuous wave Nd:YAG laser have been produced and examined in a 304-L stainless steel to advance fundamental understanding of the linkage between processing and resultant microstructure in high-rate solidification events. Acquisition of three-dimensional reconstructions via micro-computed tomography combined with traditional metallography has allowed for qualitative and quantitative characterization of weld joints in a material system of wide use and broad applicability. The presence, variability and distribution of porosity, has been examined for average values, spatial distributions and morphology and then related back to fundamental processing parameters such as weld speed, weld power and laser focal length.

  4. The comparison of frictional resistance in titanium, self-ligating stainless steel, and stainless steel brackets using stainless steel and TMA archwires: An in vitro study

    Syed Altaf Khalid; Vadivel Kumar; Prithviraj Jayaram

    2012-01-01

    Aim: The aim of the study was to compare the frictional resistance of titanium, self-ligating stainless steel, and conventional stainless steel brackets, using stainless steel and titanium molybdenum alloy (TMA) archwires. Materials and Methods: We compared the frictional resistance in 0.018 slot and 0.022 slot of the three brackets - titanium, self-ligating stainless steel, and conventional stainless steel - using stainless steel archwires and TMA archwires. An in vitro study of simulated ca...

  5. Effect of Specimen Diameter on Tensile Properties of Austenitic Stainless Steels in Liquid Hydrogen and Gaseous Helium at 20K

    Fujii, H.; Ohmiya, S.; Shibata, K.; Ogata, T.

    2006-03-01

    Tensile tests using round bar type specimens of 3, 5 and 7 mm in diameter were conducted at 20K in liquid hydrogen and also in gaseous helium at the same temperature for three major austenitic stainless steels, JIS SUS304L, 316L and 316LN, extensively used for cryogenic applications including liquid hydrogen transportation and storage vessels. Stress-strain curves were considerably different between circumstances and also specimen diameter, resulting in differences of strength and ductility. In liquid hydrogen, serrated deformation appeared after considerable work hardening and more active in specimens with larger diameter. Meanwhile serrated deformation was observed from the early stage of plastic deformation in gaseous helium at 20 K and serration was more frequent in specimens with smaller diameter. The serrated deformation behaviors were numerically simulated for 304L steel with taking thermal properties such as thermal conductivity, specific heat, heat transfer from specimens to cryogenic media into account, and some agreement with the experiments was obtained.

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

    2001-01-01

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

  7. The resistance of austenitic stainless steels to pitting corrosion in simulated BFS/OPC pore waters containing thiosulphate ions

    Current plans for the disposal of intermediate-level nuclear waste involve the use of austenitic stainless steel drums. The immediate environment seen by both the inner and outer surfaces of these drums will be alkaline, as a consequence of the encasement of both the drum and its contents in concrete. Normally there would be no risk of localized corrosion of the steel in this situation, but a possible complication is introduced by the use of blast-furnace slag (BFS) to decrease the permeability of the concrete. Metal sulphides in the BFS react with air and water to yield thiosulphate ions, which are known to be corrosive towards stainless steels in environments of near-neutral pH. This research was carried out to study the effects of thiosulphate at alkaline pH, simulating the concrete environment. Types 304L and 316L stainless steel have been tested for pitting corrosion resistance in simulated BFS/Ordinary Portland Cement pore waters of pH 10-13, at 20oC and 50oC. The results show that the 316L steel is essentially immune to pitting. The 304L steel shows some pitting at the higher temperature, especially at the higher chloride concentrations, but only at pH values of less than 12, which would require serious deterioration of the cement matrix. (author)

  8. Nano-composite stainless steel

    Dehoff, Ryan R.; Blue, Craig A.; Peter, William H.; Chen, Wei; Aprigliano, Louis F.

    2015-07-14

    A composite stainless steel composition is composed essentially of, in terms of wt. % ranges: 25 to 28 Cr; 11 to 13 Ni; 7 to 8 W; 3.5 to 4 Mo; 3 to 3.5 B; 2 to 2.5 Mn; 1 to 1.5 Si; 0.3 to 1.7 C; up to 2 O; balance Fe. The composition has an austenitic matrix phase and a particulate, crystalline dispersed phase.

  9. GFRP stainless steel hybrid cryostat

    As an instrument to measure superconducting properties (Jc,Tc,Hc) by the magnetization method, a cryostat containing the magnet that generated an external magnetic field has been developed. To ensure thermal insulation ability and structural durability, this cryostat consists of a GFRP inner vessel and a stainless steel outer vessel. Various tests were carried out to verify the sufficient performance of this cryostat. Results are presented

  10. Nickel: makes stainless steel strong

    Boland, Maeve A.

    2012-01-01

    Nickel is a silvery-white metal that is used mainly to make stainless steel and other alloys stronger and better able to withstand extreme temperatures and corrosive environments. Nickel was first identified as a unique element in 1751 by Baron Axel Fredrik Cronstedt, a Swedish mineralogist and chemist. He originally called the element kupfernickel because it was found in rock that looked like copper (kupfer) ore and because miners thought that "bad spirits" (nickel) in the rock were making it difficult for them to extract copper from it. Approximately 80 percent of the primary (not recycled) nickel consumed in the United States in 2011 was used in alloys, such as stainless steel and superalloys. Because nickel increases an alloy's resistance to corrosion and its ability to withstand extreme temperatures, equipment and parts made of nickel-bearing alloys are often used in harsh environments, such as those in chemical plants, petroleum refineries, jet engines, power generation facilities, and offshore installations. Medical equipment, cookware, and cutlery are often made of stainless steel because it is easy to clean and sterilize. All U.S. circulating coins except the penny are made of alloys that contain nickel. Nickel alloys are increasingly being used in making rechargeable batteries for portable computers, power tools, and hybrid and electric vehicles. Nickel is also plated onto such items as bathroom fixtures to reduce corrosion and provide an attractive finish.

  11. 24 h-corrosion tests combined with electrochemical potential measurements of CrNi-steel DIN W.Nr. 1.4306 (AISI Type 304 L) in 7 molar nitric acid containing oxidizing metal ions at 90deg C

    Corrosion experiments - combined with measurements of the free corrosion potential of the steels under test and the redox potential of the corrosive nitric acid media - have been performed. Three different versions of the austenitic CrNi steel DIN W.Nr. 1.4306 (AISI Type 304 L) in the solution annealed condition were tested at 90deg C during 24 h in nitric acid and nitric acid solutions containing single or combined additions of Fe(III)-, Cr(VI)- and Ce(IV)-ions. The relationship between the rate of metal loss and the free corrosion potential of the corroding steels was confirmed to be an exponential one. Furthermore, it was shown that these short-term tests could reveal within a narrow band of free corrosion potentials (1150-1250 mV) an extent of surface corrosion which is specific for small compositional or microstructural differences of these steels. (orig.)

  12. Irradiation embrittlement of ferritic stainless steels

    The characteristics of the irradiation embrittlement of some ferritic stainless steels were examined by tensile tests. Steels selected in this investigation were classified into three groups: chi phase, precipitation hardened Fe-13Cr steels; tempered martensitic Fe-12Cr steels; and low alloy steels. The latter steels were chosen in order to compare the irradiation embrittlement characteristics with those of stainless steels. The stainless steels were superior to the low alloy steels with regard to the irradiation embrittlement (the changes in both ductile-brittle transition temperature (DBTT) and unstable plastic flow transition temperature (UPFTT)), irrespective of whether these stainless steels had chi phase precipitated structures or tempered martensitic structures. The suppression of the DBTT increase owing to irradiation results from low yield stress increase Δσsub(y) and high |[dσsub(y)(u)/dT]|, where u denotes unirradiated, in the stainless steels. The suppression of the UPFTT results from the high work hardening rate or the high work exponent and the low Lueders strain in the stainless steels. These characteristics of irradiation embrittlement in the ferritic stainless steels are thought to be caused by the defect structure, which is modified by Cr atoms. (author)

  13. Hot workability of duplex stainless steels

    Martin, Guilhem

    2011-01-01

    The Duplex Stainless Steels (DSS) are defined as a family of stainless steels consisting of a two-phase microstructure involving δ-ferrite and γ-austenite. Exceptional combinations of strength and toughness together with good corrosion resistance under critical working conditions designate DSS a suitable alternative to conventional austenitic stainless steels. Unfortunately, the relatively poor hot workability of these alloys makes the industrial processing of flat products particularly criti...

  14. The role of microchemical and microstructural effects in the IASCC of high purity austenitic stainless steels

    The role of chromium depletion and radiation hardening on the irradiation assisted stress corrosion cracking in CERT tests in high purity 288 degrees C water following proton irradiation at either 400 degrees C or 200 degrees C has been examined using ultra high purity 304L stainless steel and austenitic Fe/xCr/24Ni (x=15, 20, 24) alloys. No intergranular cracking was found in any of the irradiated 254 wt% nickel alloys after CERT tests in 2 ppm O2 water at 288 degrees C, with 0.5, 1.0 or 3.2 μS/cm conductivity, while the UHP 304L alloy cracked extensively. Since the 24 wt% Ni alloys experienced severe grain boundary Cr depletion (from 6.3 at% to 13 at% below bulk), these results suggest that Ni improves the resistance of the irradiated alloys to cracking. Conversely, these results also show little correlation with grain boundary Cr depletion. Cracking of the UHP 304L alloy still occurred, although to a lesser extent, when the sample was irradiated at 200 degrees C where radiation induced segregation was expected to be significantly suppressed. This indicated that radiation hardening may play a role in IASCC in high temperature water

  15. Study of the Intercrystalline Corrosion in Pipes of Stainless Steel in a Combined Cycle

    Raúl Andrés Montejo Serrano

    2014-09-01

    Full Text Available The present work is carried out with the purpose of giving answer to the possible presence ofintercrystalline corrosion and its future consequences in the built tubes of stainless steel 304L anddedicated to the conduction from the water to the boilers of a combined cycle of electricity production.The plant is these in this moments in installation of process investor and assembly and this study wasrequested since during the trial of installation of the pipes of stainless steel that will drive the watertried to the steam generators, they were detected on the part of the operatives some imperfections inthe material, what generated the doubt about the possibility of presence of intercrystalline corrosion orof another type in the pipes. After the realized rehearsals according to international norms and alsousing rehearsals metallography you concludes that the material employee is not sensitive to this typeof corrosion.

  16. Effects of postweld treatments on corrosion of stainless steel weldments in microbial fresh-water systems

    Li, P.; Buchanan, R.A.; Lundin, C.D. [Univ. of Tennessee, Knoxville, TN (United States). Dept. of Materials Science and Engineering; Tuthill, A.H. [Tuthill Associates, Inc., Blacksburg, VA (United States); Avery, R.E. [Avery Consulting Associates, Inc., Londonderry, NH (United States); Angell, P. [Center for Environmental Biotechnology, Knoxville, TN (United States); Sachs, D.E. [Arizona Public Service Co., Phoenix, AZ (United States)

    1995-10-01

    Corrosion studies of 304L and 316L stainless steel weldments were conducted in natural and simulated fresh-water systems containing microorganisms. Experimental conditions were chosen to simulate microbiologically influenced corrosion (MIC) conditions in practical applications. Results showed that corrosion, with the formation of nodules, occurred at imposed crevice locations within weldment heat-tint areas. Upon removal of the heat tint, either chemically, electrochemically, or mechanically, corrosion nodules were not formed even under crevice conditions. Follow-up experiments indicated that the stainless steel weldments were less corrosion resistant in the bacterial environments. The results were correlated to the presence of the heat tint, the crevice geometry, the chloride concentration, and the bacterial activities.

  17. Stress corrosion cracking susceptibility of various austenitic stainless steel pipe welds in high temperature oxygenated water

    Stress corrosion cracking (SCC) susceptibility of various austenitic stainless steel pipe welds has been studied by means of constant load tensile tests and pipe tests in 2880C water containing 26 ppm dissolved oxygen. The results obtained are summarized as follows: (1) SCC susceptibility of SUS 304 pipe welds is comparatively low under the condition of as-welded. It becomes, however, high remarkably by grinder operation and/or low temperature sensitization heat treatment. The distribution of time of failure on SUS 304 pipe welds can be expressed as a log-normal or Weibull distribution. (2) SUS 304L, 304NG, 316NG, and 347 stainless steel pipe welds have a good SCC resistance and sensitization resistance. Furthermore, the life estimation on alternate pipe welds was conducted statistically. (author)

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

    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.

  19. Stainless steel for reinforcing bar concrete

    Where corrosion resisting reinforcing bar is required, stainless steel has been employed for many applications. The longest recorded use so far is over 75 years for a restoration project in the United Kingdom. Other areas are highway bridge decks, retaining walls, tunnels, pier and overpass structures all of which use stainless steel to prevent corrosion and extend structure life. Carbon steel rebar leads to premature failure via concrete spalling that results in excessive repair, high cost, traffic delay and commerce disruption. Selection of stainless steel is based on its corrosion resistance, strength and long life. Installed cost using stainless steel reinforcing barranges from one to fifteen percent depending on structure complexity. Life Cycle Cost calculations reveal when stainless steel reinforcing bar is factored into the design, with a life expectancy up to 125 years, the alloy is cost effective. Data will be exhibited relative to mechanical and physical properties of stainless steel compared to carbon steel rebar. Some stainless rebar applications around the World will be discussed in addition to laboratory and field test results with U-bent stainless steel specimens embedded in concrete. Comments will also be made relative to the environment, lengthened journeys, delivery delay, fuel burned as vehicles sit at idle, drilling, blasting, crushing and transport of aggregate, cement and the attendant power units to manufacture these items for reconstruction. (author)

  20. Electrochemical and corrosion behavior of passive film on stainless steels after gamma-ray irradiation

    The nature and structure of passive film on AISI 304L and AISI 446 stainless steels, after bare metal anodic oxidation and after the subsequent galvanostatic reduction or gamma-ray irradiation of the oxide film formed, were investigated by XPS and Electrochemical Impedance Spectroscopy (EIS). Atomic Absorption Spectroscopic (AAS) analysis of irradiated solution was also undertaken. Results obtained from XPS measurement indicated that gamma-ray irradiation can have significant effects on the stability of passive film due to the release of iron and corresponding enrichment in chromium oxides. The EIS technique was used to elucidate the physical structure of passive film after irradiation and galvanostatic reduction. The passive film formed on AISI 304L and AISI 446 stainless steels have a compact structure. The galvanostatic treatment leads to a film composed of two layers, the external one showing a spongy-like structure, while the gamma-ray irradiation treatment leads to a thinner compact film exhibiting higher capacitive behavior compared to that of unirradiated samples

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

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

    2004-11-01

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

  2. Corrosion behavior of powder metallurgical stainless steels in urban and marine environments

    Bautista, A.

    2006-06-01

    Full Text Available This work studies the development of corrosive attack on sintered components manufactured from AISI 316L and AISI 304L powders. The stainless steels were sintered in vacuum and in nitrogen-base atmosphere at 1,120 and 1,250 ºC, and their corrosion resistance was then analyzed by electrochemical techniques and by atmospheric corrosion testing (two years at urban and marine test sites. Images are shown of the morphology of the attack on the surface of the stainless steels and the development of this attack in the interior of the material.

    Este trabajo estudia el desarrollo del proceso corrosivo en componentes sinterizados fabricados a partir de polvos de AISI 316L y AISI 304L. Los aceros inoxidables fueron sinterizados en vacío y en atmósfera base nitrógeno a 1.120 y 1.250 ºC y, su resistencia a corrosión se ha analizado mediante técnicas electroquímicas y mediante ensayos de corrosión atmosférica (dos años en ambientes urbano y marino. Se muestran imágenes de la morfología del ataque en la superficie de los aceros inoxidables y del desarrollo de este ataque en el interior del material.

  3. A temperature dependent slip factor based thermal model for friction stir welding of stainless steel

    M Selvaraj

    2013-12-01

    This paper proposes a new slip factor based three-dimensional thermal model to predict the temperature distribution during friction stir welding of 304L stainless steel plates. The proposed model employs temperature and radius dependent heat source to study the thermal cycle, temperature distribution, power required, the effect of process parameters on heat generation per mm length of the weld and peak temperature during the friction stir welding process. Simulations of friction stir welding process were carried out on 304L stainless steel workpieces for various rotational and welding speeds. The predicted thermal cycle, power required and temperature distributions were found to be in good agreement with the experimental results. The heat generation per mm length of weld and peak temperature were found to be directly proportional to rotational speed and inversely proportional to welding speed. The rate of increase in heat generation per mm length of the weld and peak temperature are found to be higher at lower rotational speeds and lower at higher rotational speed. The heat generation during friction stir welding was found to be 80.8 % at shoulder, 16.1 % at pin side and 3.1 % at the bottom of the pin.

  4. Weld bonding of stainless steel

    Santos, I. O.; Zhang, Wenqi; Goncalves, V.M.;

    2004-01-01

    This paper presents a comprehensive theoretical and experimental investigation of the weld bonding process with the purpose of evaluating its relative performance in case of joining stainless steel parts, against alternative solutions based on structural adhesives or conventional spot-welding. The...... overall assessment of the weld bonding process is made using several commercial adhesives with varying working times under different surface conditions. The quality of the resulting joints is evaluated by means of macroetching observations, tension-shear tests and peel tests. The theoretical investigation...

  5. Spectrographic analysis of stainless steels

    Two spectrogaphyic solution techniques, 'Porous Cup' and 'Vacuum Cup', were investigated in order to determine the minor constituents (Cr, Ni, Mo, Mn, Cu and V) of stainless steels. Iron and cobalt were experimented as internal standards. The precision varied from 4 to 11% for both spectrographic techniques, in which cobalt was used as international standard. Certified standards from National Bureau of Standards and Instituto de Pesquisas Tecnologicas were analysed to verify the accuracy of both techniques. The best accuracy was obtained with the Vacuum Cup techniques. (Author)

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

    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

  7. Effects of Cold Rolling and Strain-Induced Martensite Formation in a SAF 2205 Duplex Stainless Steel

    Breda, Marco; Brunelli, Katya; Grazzi, Francesco; Scherillo, Antonella; Calliari, Irene

    2015-02-01

    Duplex stainless steels (DSSs) are biphasic steels having a ferritic-austenitic microstructure that allows them to combine good mechanical and corrosion-resistance properties. However, these steels are sensitive to microstructural modifications, such as ferrite decomposition at high temperatures and the possibility of strain-induced martensite (SIM) formation from cold-worked austenite, which can significantly alter their interesting features. In the present work, the effects of cold rolling on the developed microstructural features in a cold-rolled SAF 2205 DSS and the onset of martensitic transformation are discussed. The material was deformed at room temperature from 3 to 85 pct thickness reduction, and several characterization techniques (scanning and transmission electron microscopy, X-ray diffraction, hardness measurements, and time-of-flight-neutron diffraction) were employed in order to fully describe the microstructural behavior of the steel. Despite the low stacking fault energy of DSS austenite, which contributed to SIM formation, the steel was found to be more stable than other stainless steel grades, such as AISI 304L. Rolling textures were similar to those pertaining to single-phase materials, but the presence of the biphasic (Duplex) microstructure imposed deformation constraints that affected the developed microstructural features, owing to phases interactions. Moreover, even if an intensification of the strain field in austenite was revealed, retarded SIM transformation kinetics and lower martensite amounts with respect to AISI 304L were observed.

  8. Research on the mechanism of stainless steel decontamination

    The most important oxide appearing on structural materials in NPPs operating CANDU type reactors is the magnetite (Fe3O4), a mixed ferro-ferric oxide (FeO·Fe2O3) in which radionuclides are built up by adsorption. On the surface of austenitic stainless steels immersed in lithiated water, at high temperature, a duplex oxide occurs, formed of an inner layer of the type (Fe,Cr)2O3 and an outer, spinel one, rich in Fe, of the type NiFe2O4. To decontaminate such components solving of the oxide layer is necessary , avoiding as much as possible an attack against the basic material. Due to the high Cr concentration in this superficial oxides the chemical processes imply: a pre-treatment stage during which oxidation of Cr3+ into Cr6+ takes place and implicitly the solubilization of Cr2O3, followed by removal of solution and washing out with demineralized water; a second stage in which the remnant oxide is removed from the component by a usual procedure, specific to carbon steel decontamination (such as CAN-DECON procedure). Among the oxiding agents the most frequently used is potassium permanganate while in the second stage a mixture of oxalic and citric acids as well as Na-EDTA and corrosion inhibitors are added. The mechanism of solving the oxide film from samples of 304L stainless steels was studied by means of XPS technique while the structure of the oxide film was evidenced by ESCA. The results obtained are in good agreement with the theoretical studies

  9. Interaction between stainless steel and plutonium metal

    Dunwoody, John T [Los Alamos National Laboratory; Mason, Richard E [Los Alamos National Laboratory; Freibert, Franz J [Los Alamos National Laboratory; Willson, Stephen P [Los Alamos National Laboratory; Veirs, Douglas K [Los Alamos National Laboratory; Worl, Laura A [Los Alamos National Laboratory; Archuleta, Alonso [Los Alamos National Laboratory; Conger, Donald J [Los Alamos National Laboratory

    2010-01-01

    Long-term storage of excess plutonium is of great concern in the U.S. as well as abroad. The current accepted configuration involves intimate contact between the stored material and an iron-bearing container such as stainless steel. While many safety scenario studies have been conducted and used in the acceptance of stainless steel containers, little information is available on the physical interaction at elevated temperatures between certain forms of stored material and the container itself. The bulk of the safety studies has focused on the ability of a package to keep the primary stainless steel containment below the plutonium-iron eutectic temperature of approximately 410 C. However, the interactions of plutonium metal with stainless steel have been of continuing interest. This paper reports on a scoping study investigating the interaction between stainless steel and plutonium metal in a pseudo diffusion couple at temperatures above the eutectic melt-point.

  10. Statistical and regression analysis of Material Removal Rate for wire cut Electro Discharge Machining of SS 304L using design of experiments

    Vishal Parashar; Rehman, A.; J.L.Bhagoria,; Y.M.Puri

    2010-01-01

    In this paper, statistical and regression analysis of Material removal rate (MRR) using design of experiments is proposed for WEDM operations. Experimentation was planned as per Taguchi’s L’32 (21 X 44) mixed orthogonal array. Each experiment has been performed under different cutting conditions of gap voltage, pulse ON time, pulseOFF time, wire feed and dielectric flushing pressure. Stainless Steel grade 304L was selected as a work material to conduct the xperiments. From experimental resul...

  11. The comparison of frictional resistance in titanium, self-ligating stainless steel, and stainless steel brackets using stainless steel and TMA archwires: An in vitro study

    Syed Altaf Khalid

    2012-01-01

    Full Text Available Aim: The aim of the study was to compare the frictional resistance of titanium, self-ligating stainless steel, and conventional stainless steel brackets, using stainless steel and titanium molybdenum alloy (TMA archwires. Materials and Methods: We compared the frictional resistance in 0.018 slot and 0.022 slot of the three brackets - titanium, self-ligating stainless steel, and conventional stainless steel - using stainless steel archwires and TMA archwires. An in vitro study of simulated canine retraction was undertaken to evaluate the difference in frictional resistance between titanium, self-ligating stainless steel, and stainless steel brackets, using stainless steel and TMA archwires. Results and Conclusion: We compared the frictional resistance of titanium, self-ligating stainless steel, and conventional stainless steel brackets, using stainless steel and TMA archwires, with the help of Instron Universal Testing Machine. One-way analysis of variance (ANOVA, Student′s "t" test, and post hoc multiple range test at level of <0.05 showed statistically significant difference in the mean values of all groups. Results demonstrated that the titanium, self-ligating stainless steel, and stainless steel brackets of 0.018-inch and 0.022-inch slot had no significant variations in frictional résistance. The self-ligating bracket with TMA archwires showed relatively less frictional resistance compared with the other groups. The titanium bracket with TMA archwires showed relatively less frictional resistance compared with the stainless steel brackets.

  12. Behaviour of stainless steels immersed in natural waters: electrochemistry and bacterial adhesion

    The free corrosion potential of a stainless steel immersed in natural seawater rises quickly until it reaches values ranging between +100 and +350 mV/SCE, which increases the risk of initiation of pitting corrosion. According to literature this phenomenon also occurs in fresh waters. The aim of this study is to confirm or to invalidate this trend; the electrochemical behaviour of samples of stainless steels immersed in river water and the influence of the bio-film formed on the surface of the samples are studied. The free corrosion potentials of three different stainless steels (S30403 or AISI 304L, S31603 or AISI 316L, S31254 or 254SMO) have been measured continuously during their immersion in the Seine river. SEM observations of the samples surface show the presence of a bio-film on the three kinds of stainless steel. The free corrosion potentials increase and end up between +100 and +300 mV/SCE. This increase is not immediate, the latency time being around 20 days. This could be related to an effect of the low temperature of the water during the immersion (8-10 C) and/or to an effect of the Total Organic Carbon (TOC), which would limit the growth rate of the bio-film, hence its influence on the evolution of the free corrosion potential. (authors)

  13. Tensile and Fracture Properties of Circumferentially Notched Tensile Specimens of Stainless Steel Weldments

    The tensile and fracture properties of different types of austenitic stainless steel weldments were determined using round notched tensile specimens. These included 304L, 316L and 6%Mo super austenitic stainless steels and their weld metals. The triaxial state of stress, the plastic constraint and the plane strain conditions developed ahead of the notch root make notched specimens eligible for the evaluation of fracture toughness. This was achieved through the testing procedure: J-evaluation on tensile test (JETT) using circumferentially notched round bar specimens. The JETT index was taken as a measure of the relevant elastic-plastic fracture toughness of the tested materials. In the case of austenitic stainless steels being too ductile at room temperature the resulted JETT were of relatively higher values than the fracture toughness values determined from the standard fracture mechanics test methods. This could be related to the difference in the stress state ahead of the sharp crack of the standard fracture mechanics specimen and that of the blunt notch of the tensile specimen. The results showed that the 6% Mo weld metal ranked highest while the 316L weld metal ranked lowest regarding JETT fracture toughness values. The deformation mechanisms pertinent to austenitic stainless steels (generation of stacking faults and formation of strain induced martensite) were employed for the interpretation of the experimental results.

  14. Fire resistance of stainless steel structural elements

    Gomboši, Jana

    2015-01-01

    Graduation thesis represents behavior of structural elements made from stainless steel in case of fire. The general rules according to the European standard SIST EN 1993-1-2 to determine design resistance of the steel structural element for fire conditions are presented. The main focus was to determinate behavior of stainless steel column exposed to the standard fire. Buckling resistance of the column was calculated with a simplified method from the standard SIST EN 1993-1-2. Mech...

  15. Behaviour comparison of various flux cored wires in FCAW on austenitic stainless steel

    This study deals with the GMAW process evaluation for the orbital butt welding of strong thickness pipings, in order to increase the productivity of these operations (higher deposition rate than in GTAW, process currently used). The main goal of this project is to evaluate the operational feasibility of mechanized orbital welding under gas protection in narrow gap with stainless flux cored wire 308L on stainless steel 304L. The study was composed of two parts with firstly a bibliographical research which has allowed to underline this operation practice, as good with rutile flux cored wire in smooth mode as with metal cored wire in pulsed mode. In the second part, flat and in position welding tests, by unit cords and filling of narrow grooves, made possible to define preliminary welding parameters. (author)

  16. Duplex stainless steels for osteosynthesis devices.

    Cigada, A; Rondelli, G; Vicentini, B; Giacomazzi, M; Roos, A

    1989-09-01

    The austenitic stainless steels used today for the manufacture of osteosynthesis devices are sensitive to crevice corrosion. In this study the corrosion properties of some duplex stainless steels were evaluated and compared to traditional austenitic stainless steels. According to our results the following ranking was established: 23Cr-4Ni less than AISI 316L less than ASTM F138 less than 22Cr-5Ni-3Mo less than 27Cr-31Ni-3.5Mo less than 25Cr-7Ni-4Mo-N. In particular the results showed that the high-performance 25Cr-7Ni-4Mo-N duplex stainless steel, with high molybdenum and nitrogen contents, can be considered not susceptible to crevice corrosion in the human body. The duplex stainless steels have also better mechanical properties at the same degree of cold working compared with austenitic stainless steels. Hence the 25Cr-7Ni-4Mo-N duplex stainless steel can be considered a convenient substitute of ASTM F138 for orthopedic and osteosynthesis devices. PMID:2777835

  17. Preparation of precursor for stainless steel foam

    ZHOU Xiang-yang; LI Shan-ni; LI Jie; LIU Ye-xiang

    2008-01-01

    The effects of polyurethane sponge pretreatment and slurry compositions on the slurry loading in precursor were discussed, and the,performances of stainless steel foams prepared from precursors with different slurry loadings and different particle sizes of the stainless steel powder were also investigated. The experimental results show that the pretreatment of sponge with alkaline solution is effective to reduce the jam of cells in precursor and ensure the slurry to uniformly distribute in sponge, and it is also an effective method for increasing the slurry loading in precursor; the mass fraction of additive A and solid content in slurry greatly affect the slurry loading in precursor, when they are kept in 9%-13% and 52%-75%, respectively, the stainless steel foam may hold excellent 3D open-cell network structure and uniform muscles; the particle size of the stainless steel powder and the slurry loading in precursor have great effects on the bending strength, apparent density and open porosity of stainless steel foam; when the stainless steel powder with particle size of 44 tan and slurry loading of 0.5 g/cm3 in precursor are used, a stainless steel foam can be obtained, which has open porosity of 81.2%, bending strength of about 51.76 MPa and apparent density of about 1.0 g/cm3.

  18. Impact Tensile Testing of Stainless Steels at Various Temperatures

    D. K. Morton

    2008-03-01

    Stainless steels are used for the construction of numerous spent nuclear fuel or radioactive material containers that may be subjected to high strains and moderate strain rates during accidental drop events. Mechanical characteristics of these base materials and their welds under dynamic loads in the strain rate range of concern (1 to 300 per second) are not well documented. However, research is being performed at the Idaho National Laboratory to quantify these characteristics. The work presented herein discusses tensile impact testing of dual-marked 304/304L and 316/316L stainless steel material specimens. Both base material and welded material specimens were tested at -20 oF, room temperature, 300 oF, and 600 oF conditions. Utilizing a drop weight impact test machine and 1/4-inch and 1/2-inch thick dog bone-shaped test specimens, a strain rate range of approximately 4 to 40 per second (depending on initial temperature conditions) was achieved. Factors were determined that reflect the amount of increased strain energy the material can absorb due to strain rate effects. Using the factors, elevated true stress-strain curves for these materials at various strain rates and temperatures were generated. By incorporating the strain rate elevated true stress-strain material curves into an inelastic finite element computer program as the defined material input, significant improvement in the accuracy of the computer analyses was attained. However, additional impact testing is necessary to achieve higher strain rates (up to 300 per second) before complete definition of strain rate effects can be made for accidental drop events and other similar energy-limited impulsive loads. This research approach, using impact testing and a total energy analysis methodology to quantify strain rate effects, can be applied to many other materials used in government and industry.

  19. Tritiated Water Interaction with Stainless Steel

    Glen R. Longhurst

    2007-05-01

    Experiments conducted to study tritium permeation of stainless steel at ambient and elevated temperatures revealed that HT converts relatively quickly to HTO. Further, the HTO partial pressure contributes essentially equally with elemental tritium gas in driving permeation through the stainless steel. Such permeation appears to be due to dissociation of the water molecule on the hot stainless steel surface. There is an equilibrium concentration of HTO vapor above adsorbed gas on the walls of the experimental apparatus evident from freezing transients. The uptake process of tritium from the carrier gas involves both surface adsorption and isotopic exchange with surface bound water.

  20. Recycle of radiologically contaminated austenitic stainless steels

    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

  1. Experimental study of behavior of austenitic stainless steel thin-walled-elbows - functional capability

    Results of a series of 15 tests on 90 large radius elbows are presented. These elbows were made from Z2 CN 18 10 steel (corresponding to ASME TP 304 L) and had an outside diameter-to-wall thickness ratio of 89.5. They 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 were also studied. The tests therefore supplied extensive data on the behavior of an austenititc stainless steel thin-walled elbow when subjected to large displacements, including its ability to carry the required flow under high loadings. Analysis per the RCC-M (1983) was also performed to quantify flow area reductions at stress limits allowed by these rules. (orig.)

  2. Some properties of chromized stainless steels

    Materials used for constructions in food processing industry should meet mechanical specifications and sanitary requirements. The most often used steels AISI304 and 316L have similar mechanical characteristics but the corrosion resistance of 316L stainless steel is considerably better. On the other hand the price of 316L steel is twice higher. The advantageous solution with minimal investment cost is chemical modification of stainless steel surface layer. Main directions of chemical modifications of surface layers were characterized in this paper. In this paper there were also presented effects of chromizing of steel type AISI316L in order to increasing erosion - corrosion resistance. There were analysed structures; mechanical characteristics and durability of chromized stainless steel. (author)

  3. Stainless Steel to Titanium Bimetallic Transitions

    Kaluzny, J. A. [Fermilab; Grimm, C. [Fermilab; Passarelli, D. [Fermilab

    2015-01-01

    In order to use stainless steel piping in an LCLS-II (Linac Coherent Light Source Upgrade) cryomodule, stainless steel to titanium bimetallic transitions are needed to connect the stainless steel piping to the titanium cavity helium vessel. Explosion bonded stainless steel to titanium transition pieces and bimetallic transition material samples have been tested. A sample transition tube was subjected to tests and x-ray examinations between tests. Samples of the bonded joint material were impact and tensile tested at room temperature as well as liquid helium temperature. The joint has been used successfully in horizontal tests of LCLS-II cavity helium vessels and is planned to be used in LCLS-II cryomodules. Results of material sample and transition tube tests will be presented.

  4. Hydrogen compatibility handbook for stainless steels

    Caskey, G.R. Jr.

    1983-06-01

    This handbook compiles data on the effects of hydrogen on the mechanical properties of stainless steels and discusses this data within the context of current understanding of hydrogen compatibility of metals. All of the tabulated data derives from continuing studies of hydrogen effects on materials that have been conducted at the Savannah River Laboratory over the past fifteen years. Supplementary data from other sources are included in the discussion. Austenitic, ferritic, martensitic, and precipitation hardenable stainless steels have been studied. Damage caused by helium generated from decay of tritium is a distinctive effect that occurs in addition to the hydrogen isotopes protium and deuterium. The handbook defines the scope of our current knowledge of hydrogen effects in stainless steels and serves as a guide to selection of stainless steels for service in hydrogen.

  5. Horizontal electron beam welding for stainless steels

    Stainless steel samples have been realized by local vacuum apparatus for electron beam welding applications to reactor core shell realizations. The best welding parameters have been determined by a systematic study. The welds have been characterized by mechanical tests

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

    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.

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

    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.

  8. Tritium in austenitic stainless steel vessels

    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)

  9. Studies of stainless steel exposed to sandblasting

    Horodek Paweł; Eseev Marat K.; Kobets Andrey G.

    2015-01-01

    The influence of sandblasting on surface and subsurface of stainless steel is investigated using variable energy positron beam (VEP), positron annihilation spectroscopy (PAS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Samples of stainless steel were blasted using 110 μm particles of Al2O3 under different pressure and time duration. In the case of sandblasting for 90 s, the reduction of positron diffusion length depending on the applied pressure was observed. Sandb...

  10. A Duplex Stainless Steel for Chloride Environments

    Sridhar, N.; Kolts, J.; Flasche, L. H.

    1985-03-01

    This paper examines the effects of microstructural changes on the corrosion, stress corrosion cracking and corrosion fatigue resistance of a duplex stainless steel to chloride environments. The microstructural changes can be precipitation of phases such as sigma and carbides, or changes in the distribution of austenite and ferrite. The former can be important in hot forming operations while the latter is important in welding. The methods of minimizing these deleterious effects can sometimes be different from those used for austenitic stainless steel.