Austenitic stainless steel weld inspection

International Nuclear Information System (INIS)

Mech, S.J.; Emmons, J.S.; Michaels, T.E.

1978-01-01

Analytical techniques applied to ultrasonic waveforms obtained from inspection of austenitic stainless steel welds are described. Experimental results obtained from a variety of geometric and defect reflectors are presented. Specifically, frequency analyses parameters, such as simple moments of the power spectrum, cross-correlation techniques, and adaptive learning network analysis, all represent improvements over conventional time domain analysis of ultrasonic waveforms. Results for each of these methods are presented, and the overall inspection difficulties of austenitic stainless steel welds are discussed

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

International Nuclear Information System (INIS)

Vilpas, M.; Haenninen, H.

1999-01-01

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

Analysis of the influence of the anisotropy induced by cold rolling on duplex and super-austenitic stainless steels

Directory of Open Access Journals (Sweden)

Martino Labanti

2010-07-01

Full Text Available This report contains the results obtained from the mechanical characterization tests carried out on two different stainless steel (duplex 6%Ni, 22%Cr and super-austenitic 31%Ni, 28%Cr used for the manufacturing of pipes which are employed in the oil production. The activity has been performed in order to evaluate the effects of anisotropy, induced by cold rolling, on the mechanical characteristics of the investigated steels, measured in the three main directions. Considering the small size of the component, the method and the specimens used for the tests were not the standard one. The procedure carried out provided the strain measurement of the specimen during testing by means of resistive strain gages, bonded on the specimens.

Low temperature tensile properties and stress corrosion cracking resistance in the super duplex stainless steels weldments

International Nuclear Information System (INIS)

Lee, Jeung Woo; Sung, Jang Hyun; Lee, Sung Keun

1998-01-01

Low temperature tensile properties and SCC resistances of super duplex stainless steels and their weldments are investigated. Tensile strengths increase remarkably with decreasing test temperature, while elongations decrease steeply at -196 .deg. C after showing peak or constant value down to -100 .deg. C. Owing to the low tensile deformation of weld region, elongations of welded specimen decrease in comparison to those of unwelded specimen. The welded tensile specimen is fractured through weld region at -196 .deg. C due to the fact that the finely dispersed ferrite phase in the austenite matrix increases an opportunity to supply the crack propagation path through the brittle ferrite phase at low temperature. The stress corrosion cracking initiates preferentially at the surface ferrite phase of base metal region and propagates through ferrite phase. When the corrosion crack meets with the fibrously aligned austenite phase to the tensile direction, the ferrite phase around austenite continues to corrode. Eventually, fracture of the austenite phase begins without enduring the tensile load. The addition of Cu+W to the super duplex stainless steel deteriorates the SCC resistance in boiling MgCl 2 solution, possibly due to the increment of pits in the ferrite phase and reduction of N content in the austenite phase

Low-temperature creep of austenitic stainless steels

Science.gov (United States)

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

2017-09-01

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

Damping Capacity of High Manganese Austenitic Stainless Steel with a Two Phase Mixed Structure of Martensite and Austenite

International Nuclear Information System (INIS)

Hwang, Tae Hyun; Kang, Chang-Yong

2013-01-01

The damping capacity of high manganese austenitic stainless steel with a two phase mixed structure of deformation-induced martensite and reversed austenite was studied. Reversed austenite with an ultra-fine grain size of less than 0.2 μm was obtained by reversion treatment. The two phase structure of deformation-induced martensite and reversed austenite was obtained by annealing treatment at a range of 500-700 °C and various times in cold rolled high manganese austenitic stainless steel. The damping capacity increased with an increasing annealing temperature and time. In high manganese stainless steel with the two phase mixed structure of martensite and austenite, the damping capacity decreased with an increasing volume fraction of deformation-induced martensite. Thus, the damping capacity was strongly affected by deformation-induced martensite. The results confirmed that austenitic stainless steel with a good combination of strength and damping capacity was obtained from the two phase mixed structure of austenite and martensite.

Intergranular corrosion behavior associated with delta-ferrite transformation of Ti-modified Super304H austenitic stainless steel

International Nuclear Information System (INIS)

Bai, Guanshun; Lu, Shanping; Li, Dianzhong; Li, Yiyi

2015-01-01

Highlights: • Relationship between delta-ferrite transformation and IGC behavior was evaluated by DL-EPR test quantitatively. • The IGC site at austenite/ferrite grain boundary changes with aging time at 650 °C. • A higher fraction of delta-ferrite with poor stability increases the IGC sensitisation. • Self-healing of IGC was mainly induced by the Cr diffusion from primary austenite rather than the delta-ferrite. - Abstract: A double loop electrochemical potentiokinetic reactivation (DL-EPR) test was conducted to investigate the relationship between the evolution of delta-ferrite and the intergranular corrosion (IGC) of Ti-modified Super304H, which was aged at 650 °C for 4–500 h. Scanning electron microscopy and transmission electron microscopy were adopted to analyze the evolution of delta-ferrite. The results indicated that a higher fraction of delta-ferrite with poor stability increased the IGC sensitisation of Ti-modified Super304H. Moreover, the self-healing of the sensitisation of Ti-modified Super304H occurred after 48 h due to the diffusion of chromium atoms mainly from the adjacent primary austenite rather than the delta-ferrite

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

Science.gov (United States)

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

2016-05-01

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

Phase transformation by fatigue in austenitic stainless steel

International Nuclear Information System (INIS)

Jo, Y.S.; Kwun, S.I.

1988-01-01

The effect of strain induced martensite on the fatigue behavior of AISI 304 austenitic stainless steel was investigated. During low cycle fatigue, the austenitic stainless steel showed a continuous cyclic hardening until fracture. The extent of cyclic hardening increased with decreasing austenite stability. The austenite stability was controlled by different aging time and temperature, which resulted in different carbide morphologies. The fatigue crack propagation rate near ΔK th varied also with the austenite stability inside the plastic zone at the crack up. Especially, the near-threshold fatigue crack propagation rate of the grain boundary carbide precipitated condition was the lowest. This was considered to be due to the roughness induced closure caused by intergranular facet. A new model for the intergranular facet formation and the fatigue crack propagation of grain boundary carbide precipitated condition was proposed. (Author)

Effect of nitrogen and boron on weldability of austenitic stainless steels

International Nuclear Information System (INIS)

Bhaduri, A.K.; Albert, S.K.; Srinivasan, G.; Divya, M.; Das, C.R.

2012-01-01

Hot cracking is a major problem in the welding of austenitic stainless steels, particularly the fully austenitic grades. A group of alloys of enhanced-nitrogen 316LN austenitic stainless steel is being developed for structural components of the Indian Fast Reactor programme. Studying the hot cracking behaviour of this nitrogen-enhanced austenitic stainless steel is an important consideration during welding, as this material solidifies without any residual delta ferrite in the primary austenitic mode. Nitrogen has potent effects on the solidification microstructure, and hence has a strong influence on the hot cracking behaviour. Different heats of this material were investigated, which included fully austenitic stainless steels containing 0.070.22 wt% nitrogen. Also, borated austenitic stainless steels, such as type 304B4, have been widely used in the nuclear applications primarily due to its higher neutron absorption efficiency. Weldability is a major concern for this alloy due to the formation of low melting eutectic phase that is enriched with iron, chromium, molybdenum and boron. Fully austenitic stainless steels are prone to hot cracking during welding in the absence of a small amount of delta ferrite, especially for compositions rich in elements like boron that increases the tendency to form low melting eutectics. Detailed weldability investigations were carried out on a grade 304B4 stainless steel containing 1.3 wt% boron. Among the many approaches that have been used to determine the hot cracking susceptibility of different alloys, Variable-Restraint (Varestraint) weld test and Hot Ductility (Gleeble) tests are commonly used to evaluate the weldability of austenitic alloys. Hence, investigations on these materials consisted of detailed metallurgical characterization and weldability studies that included studying both the fusion zone and liquation cracking susceptibility, using Varestraint tests at 0.254.0%, strain levels and Gleeble (thermo

Effect of Nb Addition to Ti-Bearing Super Martensitic Stainless Steel on Control of Austenite Grain Size and Strengthening

Science.gov (United States)

Ma, Xiaoping; Langelier, Brian; Gault, Baptiste; Subramanian, Sundaresa

2017-05-01

The role of Nb in normalized and tempered Ti-bearing 13Cr5Ni2Mo super martensitic stainless steel is investigated through in-depth characterization of the bimodal chemistry and size of Nb-rich precipitates/atomic clusters and Nb in solid solution. Transmission electron microscopy and atom probe tomography are used to analyze the samples and clarify precipitates/atom cluster interactions with dislocations and austenite grain boundaries. The effect of 0.1 wt pct Nb addition on the promotion of (Ti, Nb)N-Nb(C,N) composite precipitates, as well as the retention of Nb in solution after cooling to room temperature, are analyzed quantitatively. (Ti, Nb)N-Nb(C,N) composite precipitates with average diameters of approximately 24 ± 8 nm resulting from epitaxial growth of Nb(C,N) on pre-existing (Ti,Nb)N particles, with inter-particle spacing on the order of 205 ± 68 nm, are found to be associated with mean austenite grain size of 28 ± 10 µm in the sample normalized at 1323 K (1050 °C). The calculated Zener limiting austenite grain size of 38 ± 13 µm is in agreement with the experimentally observed austenite grain size distribution. 0.08 wt pct Nb is retained in the as-normalized condition, which is able to promote Nb(C, N) atomic clusters at dislocations during tempering at 873 K (600 °C) for 2 hours, and increases the yield strength by 160 MPa, which is predicted to be close to maximum increase in strengthening effect. Retention of solute Nb before tempering also leads to it preferentially combing with C and N to form Nb(C, N) atom clusters, which suppresses the occurrence of Cr- and Mo-rich carbides during tempering.

Stress corrosion cracking of austenitic stainless steels in high temperature water and alternative stainless steel

International Nuclear Information System (INIS)

Yonezawa, T.

2015-01-01

In order to clarify the effect of SFE on SCC resistance of austenitic stainless steels and to develop the alternative material of Type 316LN stainless steel for BWR application, the effect of chemical composition and heat treatment on SFE value and SCCGR in oxygenated high temperature water were studied. The correlation factors between SFE values for 54 heats of materials and their chemical compositions for nickel, molybdenum, chromium, manganese, nitrogen, silicon and carbon were obtained. From these correlation factors, original formulae for SFE values calculation of austenitic stainless steels in the SHTWC, SHTFC and AGG conditions were established. The maximum crack length, average crack length and cracked area of the IGSCC for 33 heats were evaluated as IGSCC resistance in oxygenated high temperature water. The IGSCC resistance of strain hardened nonsensitized austenitic stainless steels in oxygenated high temperature water increases with increasing of nickel contents and SFE values. From this study, it is suggested that the SFE value is a key parameter for the IGSCC resistance of non-sensitized strain hardened austenitic stainless steels. As an alternative material of Type 316LN stainless steel, increased SFE value material, which is high nickel, high chromium, low silicon and low nitrogen material, is recommendable. (author)

Nondestructive characterization of austenitic stainless steels

International Nuclear Information System (INIS)

Jayakumar, T.; Kumar, Anish

2010-01-01

The paper presents an overview of the non-destructive methodologies developed at the authors' laboratory for characterization of various microstructural features, residual stresses and corrosion in austenitic stainless steels. Various non-destructive evaluation (NDE) parameters such as ultrasonic velocity, ultrasonic attenuation, spectral analysis of the ultrasonic signals, magnetic hysteresis parameters and eddy current amplitude have been used for characterization of grain size, precipitation behaviour, texture, recrystallization, thermomechanical processing, degree of sensitization, formation of martensite from metastable austenite, assessment of residual stresses, degree of sensitization and propensity for intergranular corrosion in different austenitic steels. (author)

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

Science.gov (United States)

Chai, Guocai; Kangas, Pasi

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

Lifespan estimation of seal welded super stainless steels for water condenser of nuclear power plants

Science.gov (United States)

Kim, Young Sik; Park, Sujin; Chang, Hyun Young

2014-01-01

When sea water was used as cooling water for water condenser of nuclear power plants, commercial stainless steels can not be applied because chloride concentration exceeds 20,000 ppm. There are many opinions for the materials selection of tube and tube sheets of a condenser. This work reviewed the application guide line of stainless steels for sea-water facilities and the estimation equations of lifespan were proposed from the analyses of both field data for sea water condenser and experimental results of corrosion. Empirical equations for lifespan estimation were derived from the pit initiation time and re-tubing time of stainless steel tubing in sea water condenser of nuclear power plants. The lifespan of seal-welded super austenitic stainless steel tube/tube sheet was calculated from these equations. Critical pitting temperature of seal-welded PRE 50 grade super stainless steel was evaluated as 60 °C. Using the proposed equation in engineering aspect, tube pitting corrosion time of seal-welded tube/tube sheet was calculated as 69.8 years and re-tubing time was estimated as 82.0 years.

Heat treatment temperature influence on ASTM A890 GR 6A super duplex stainless steel microstructure

International Nuclear Information System (INIS)

Martins, Marcelo; Casteletti, Luiz Carlos

2005-01-01

Duplex and super duplex stainless steels are ferrous alloys with up to 26% chromium, 8% nickel, 5% molybdenum and 0.3% nitrogen, which are largely used in applications in media containing ions from the halogen family, mainly the chloride ion (Cl - ). The emergence of this material aimed at substituting Copper-Nickel alloys (Cupro-Nickel) that despite presenting good corrosion resistance, has mechanical properties quite inferior to steel properties. The metallurgy of duplex and super duplex stainless steel is complex due to high sensitiveness to sigma phase precipitation that becomes apparent, due to the temperatures they are exposed on cooling from solidification as well as from heat treatment processes. The objective of this study was to verify the influence of heat treating temperatures on the microstructure and hardness of ASTM A890/A890M Gr 6A super duplex stainless steel type. Microstructure control is of extreme importance for castings, as the chemical composition and cooling during solidification inevitably provide conditions for precipitation of sigma phase. Higher hardness in these materials is directly associated to high sigma phase concentration in the microstructure, precipitated in the ferrite/austenite interface. While heat treatment temperature during solution treatment increases, the sigma phase content in the microstructure decreases and consequently, the material hardness diminishes. When the sigma phase was completely dissolved by the heat treatment, the material hardness was influenced only due to ferrite and austenite contents in the microstructure

A study on the effect of solution heat treatment on the corrosion resistance of super duplex stainless steels

International Nuclear Information System (INIS)

Park, Jee Yong; Park, Yong Soo; Kim, Soon Tae

2001-01-01

High temperature solution heat treatment(typically higher than 1100 .deg. C) is known generally to reduces the resistance to localized corrosion on super duplex stainless. This is attributed to the formation of zone depleted of alloying elements. In this study, the corrosion properties were investigated on super duplex stainless steels with various solution heat treatments. The corrosion resistance of these steels was evaluated in terms of critical pitting temperature and cyclic potentiodynamic polarization test. Chemical composition of the austenite and ferrite phases were analyzed by SEM-EDS. The following results were obtained. (1) By conducting furnace cooling, critical pitting temperature and repassivation potential increased. (2) By omitting furnace cooling, solution heat treatment produced Cr and Mo depleted zone in the phase boundary. (3) During furnace cooling, Cr and Mo rediffused through the phase boundary. This increased the corrosion resistance of super duplex stainless steels

Precipitation Mechanism of Sigma Phase in Super Duplex Stainless Steels

Science.gov (United States)

Nakade, Katsuyuki; Kuroda, Toshio

The influence of alloying elements on the precipitation behavior of sigma (σ) phase was investigated for conventional SAF2205 and SAF2507 super duplex stainless steel. Time-Temperature-Precipitation (T-T-P) diagram of sigma phase of SAF2507 were shifted toward to shorter times compared to SAF2205. The precipitation of sigma phase was accelerated with increasing Cr and Mo concentration. According to the microstructure observation, the sigma phase began to precipitate at ferrite (α) ⁄ austenite (γ) phase boundaries and grew into ferrite for SAF2507 and SAF2205 steel. In the as-received condition, Cr and Mo concentration in ferrite was clearly higher than that in austenite. Especially, it was found that Mo concentration in ferrite of SAF2507 was higher than that in ferrite of SAF2205. The result of EPMA-measurement showed that sigma phase was mainly Fe-Cr-Mo intermetallic compound and Mo was significantly enriched into sigma phase. The difference of Mo concentration in ferrite significantly affected to the sigma phase precipitation. The secondary austenite formation was also induced by sigma phase precipitation. Cr and Mo were ejected to the remained ferrite ⁄ austenite phase boundaries by secondary austenite formation. Consequently, sigma phase precipitation was more accelerated by the reheating.

Strain hardening of cold-rolled lean-alloyed metastable ferritic-austenitic stainless steels

Energy Technology Data Exchange (ETDEWEB)

Papula, Suvi [Aalto University School of Engineering, Department of Mechanical Engineering, P.O. Box 14200, FI-00076 Aalto (Finland); Anttila, Severi [Centre for Advanced Steels Research, University of Oulu, P.O. Box 4200, 90014 Oulu (Finland); Talonen, Juho [Outokumpu Oyj, P.O. Box 245, FI-00181 Helsinki (Finland); Sarikka, Teemu; Virkkunen, Iikka; Hänninen, Hannu [Aalto University School of Engineering, Department of Mechanical Engineering, P.O. Box 14200, FI-00076 Aalto (Finland)

2016-11-20

Mechanical properties and strain hardening of two pilot-scale lean-alloyed ferritic-austenitic stainless steels having metastable austenite phase, present at 0.50 and 0.30 volume fractions, have been studied by means of tensile testing and nanoindentation. These ferritic-austenitic stainless steels have high strain-hardening capacity, due to the metastable austenite phase, which leads to an improved uniform elongation and higher tensile strength in comparison with most commercial lean duplex stainless steels. According to the results, even as low as 0.30 volume fraction of austenite seems efficient for achieving nearly 40% elongation. The austenite phase is initially the harder phase, and exhibits more strain hardening than the ferrite phase. The rate of strain hardening and the evolution of the martensite phase were found to depend on the loading direction: both are higher when strained in the rolling direction as compared to the transverse direction. Based on the mechanical testing, characterization of the microstructure by optical/electron microscopy, magnetic balance measurements and EBSD texture analysis, this anisotropy in mechanical properties of the cold-rolled metastable ferritic-austenitic stainless steels can be explained by the elongated dual-phase microstructure, fiber reinforcement effect of the harder austenite phase and the presence and interplay of rolling textures in the two phases.

Phase transformation system of austenitic stainless steels obtained by permanent compressive strain

Energy Technology Data Exchange (ETDEWEB)

Okayasu, Mitsuhiro, E-mail: mitsuhiro.okayasu@utoronto.ca; Tomida, Sai

2017-01-27

In order to understand more completely the formation of strain-induced martensite, phase structures were investigated both before and after plastic deformation, using austenitic stainless steels of various chemical compositions (carbon C=0.007–0.04 mass% and molybdenum Mo=0–2.10 mass%) and varying pre-strain levels (0–30%). Although the stainless steels consisted mainly of γ austenite, two martensite structures were generated following plastic deformation, comprising ε and α′ martensite. The martensitic structures were obtained in the twin deformation and slip bands. The severity of martensite formation (ε and α′) increased with increasing C content. It was found that α′ martensite was formed mainly in austenitic stainless steel lacking Mo, whereas a high Mo content led to a strong ε martensite structure, i.e. a weak α′ martensite. The formation of α′ martensite occurred from γ austenite via ε martensite, and was related to the slip deformation. Molybdenum in austenitic stainless steel had high slip resistance (or weak stress-induced martensite transformation), because of the stacking fault energy of the stainless steel affecting the austenite stability. This resulted in the creation of weak α′ martensite. Models of the martensitic transformations γ (fcc)→ε (hcp)→α′ (bcc) were proposed on both the microscopic and nanoscopic scales. The α′ martensite content of austenitic stainless steel led to high tensile strength; conversely, ε martensite had a weak effect on the mechanical strength. The influence of martensitic formation on the mechanical properties was evaluated quantitatively by statistical analysis.

Anelastic mechanical loss spectrometry of hydrogen in austenitic stainless steels

International Nuclear Information System (INIS)

Yagodzinskyy, Y.; Andronova, E.; Ivanchenko, M.; Haenninen, H.

2009-01-01

Atomic distribution of hydrogen, its elemental diffusion jumps and its interaction with dislocations in a number of austenitic stainless steels are studied with anelastic mechanical loss (AML) spectrometry in combination with the hydrogen thermal desorption method. Austenitic stainless steels of different chemical composition, namely, AISI 310, AISI 201, and AISI 301LN, as well as LDX 2101 duplex stainless steel are studied to clarify the role of different alloying elements on the hydrogen behavior. Activation analyses of the hydrogen Snoek-like peaks are performed with their decomposition to sets of Gaussian components. Fine structure of the composite hydrogen peaks is analyzed under the assumption that each component corresponds to diffusion transfer of hydrogen between octahedral positions with certain atomic compositions of the nearest neighbouring lattice sites. An additional component originating from hydrogen-dislocation interaction is considered. Binding energies for hydrogen-dislocation interaction are also estimated for the studied austenitic stainless steels.

Effect of Multipass Friction Stir Processing on Mechanical and Corrosion Behavior of 2507 Super Duplex Stainless Steel

Science.gov (United States)

Mishra, M. K.; Gunasekaran, G.; Rao, A. G.; Kashyap, B. P.; Prabhu, N.

2017-02-01

The microstructure, mechanical properties, and corrosion behavior of 2507 super duplex stainless steel after multipass friction stir processing (FSP) were examined. A significant refinement in grain size of both ferrite and austenite was observed in stir zone resulting in improved yield and tensile strength. Electrochemical impedance spectroscopy and anodic polarization studies in 3.5 wt.% NaCl solution showed nobler corrosion characteristics with increasing number of FSP passes. This was evident from the decrease in corrosion current density, decrease in passive current density, and increase in polarization resistance. Also, the decrease in density of defects, based on Mott-Schottky analysis, further confirms the improvement in corrosion resistance of 2507 super duplex stainless steel after multipass FSP.

Transformation in austenitic stainless steel sheet under different loading directions

NARCIS (Netherlands)

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

2011-01-01

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

Transformation in Austenitic Stainless Steel Sheet under Different Loading Directions

NARCIS (Netherlands)

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

2011-01-01

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

Characterization of weld strength and impact toughness in the multi-pass welding of super-duplex stainless steel UNS 32750

International Nuclear Information System (INIS)

Devendranath Ramkumar, K.; Thiruvengatam, G.; Sudharsan, S.P.; Mishra, Debidutta; Arivazhagan, N.; Sridhar, R.

2014-01-01

Highlights: • Effect of filler metals on the weldability of super-duplex stainless steel plates. • Contemplative explanations on the metallurgical and mechanical properties of the weldments. • Enhanced mechanical properties of the welds at ambient room temperature. - Abstract: This paper investigates the weldability, metallurgical and mechanical properties of the UNS 32750 super-duplex stainless steels joints by Gas Tungsten Arc Welding (GTAW) employing ER2553 and ERNiCrMo-4 filler metals. Impact and tensile studies envisaged that the weldments employing ER2553 exhibited superior mechanical properties compared to ERNiCrMo-4 weldments. Microstructure studies performed using optical and SEM analysis clearly exhibited the different forms of austenite including widmanstatten austenite on the weld zone employing ER2553 filler. Also the presented results clearly reported the effect of filler metals on strength and toughness during the multi-pass welding. This research article addressed the improvement of tensile and impact strength using appropriate filler wire without obtaining any deleterious phases

Role of Nb in low interstitial 13Cr super martensitic stainless steel

Energy Technology Data Exchange (ETDEWEB)

Ma, X.P.; Wang, L.J. [Key Laboratory for Anisotropy and Texture of Materials, Northeastern University, Shenyang 110004 (China); Liu, C.M., E-mail: cmliu@mail.neu.edu.cn [Key Laboratory for Anisotropy and Texture of Materials, Northeastern University, Shenyang 110004 (China); Subramanian, S.V. [Department of Materials Science and Engineering, McMaster University, Hamilton, L8S-4L7 (Canada)

2011-08-25

Highlights: {yields} Nb retards the kinetics of reversed austenite formation. {yields} Nb suppresses the occurrence of Cr rich precipitates. {yields} Nano-scale precipitates contribute to the significant increase in strength. - Abstract: The effect of adding 0.1 wt% Nb to low interstitial (N 0.01 wt%, C 0.01 wt%) 13Cr super martensitic stainless steel (SMSS) on solid phase transformation and microstructures achieved by normalizing and tempering was investigated using dilatometer, electron backscattered diffraction (EBSD), transmission electron microscope (TEM), X-ray diffraction (XRD), and its consequence on mechanical properties was examined to clarify the role of Nb in low interstitial martensitic stainless steel. Nb was found to retard kinetics of reversed austenite formation during tempering and to suppress the occurrence of Cr rich precipitates. The measurement of mechanical properties shows that while the strength properties were significantly increased by nano-scale precipitates enriched in Nb in the steel with 0.10 wt% Nb, the ductility and toughness properties were restored by optimum volume fraction of retained austenite. Excellent strength and adequate toughness properties were obtained by tempering the steel with 0.10 wt% Nb and low interstitial (N 0.01 wt%, C 0.01 wt%) steel at 600 deg. C.

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

Science.gov (United States)

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

2013-10-01

The field of biomaterials has become a vital area, as these materials can enhance the quality and longevity of human life. Metallic materials are often used as biomaterials to replace structural components of the human body. Stainless steels, cobalt-chromium alloys, commercially pure titanium and its alloys are typical metallic biomaterials that are being used for implant devices. Stainless steels have been widely used as biomaterials because of their very low cost as compared to other metallic materials, good mechanical and corrosion resistant properties and adequate biocompatibility. However, the adverse effects of nickel ions being released into the human body have promoted the development of "nickel-free nitrogen containing austenitic stainless steels" for medical applications. Nitrogen not only replaces nickel for austenitic structure stability but also much improves steel properties. Here we review the harmful effects associated with nickel and emphatically the advantages of nitrogen in stainless steel, as well as the development of nickel-free nitrogen containing stainless steels for medical applications. By combining the benefits of stable austenitic structure, high strength, better corrosion and wear resistance and superior biocompatibility in comparison to the currently used austenitic stainless steel (e.g. 316L), the newly developed nickel-free high nitrogen austenitic stainless steel is a reliable substitute for the conventionally used medical stainless steels. Copyright © 2013 Elsevier B.V. All rights reserved.

Simulation of radiation induced segregation and PWSCC susceptibility for austenitic stainless steels

Energy Technology Data Exchange (ETDEWEB)

Fujimoto Koji; Yonezawa, Toshio; Iwamura, Toshihiko [Mitsubishi Heavy Industries Ltd., Takasago, Hyogo (Japan). Takasago R and D Center; Ajiki, Kazuhide [Mitsubishi Heavy Industries Ltd., Kobe (Japan). Kobe Shipyard and Machinery Works; Urata, Sigeru [General Office of Nuclear and Fossil Power Production, Kansai Electric Power Co., Inc., Osaka (Japan)

2000-08-01

Recently, irradiation assisted stress corrosion cracking (IASCC) of austenitic stainless steels for core internal components materials become a subject of discussion in light water reactors (LWRs). IASCC has not been found in Pressurized Water Reactors (PWRs). However, the authors have investigated on the possibility of IASCC of austenitic stainless steels for core internal materials so as to be able to estimate the degradation of PWR plants up to the end of their lifetime. In this study, in order to verify the hypothetical that the IASCC in PWRs shall be caused by the primary water stress corrosion cracking (PWSCC) as a result of radiation induced segregation (RIS) at grain boundaries, the authors simulated RIS at grain boundaries of austenitic stainless steels based on previous study and estimated RIS tendency after long time operation. And the authors melted the test alloys whose bulk compositions simulated the grain boundary compositions of irradiated austenitic stainless steels and made clear chromium-nickel-silicon compositions for PWSCC susceptibility area in austenitic alloys by slow strain rate tensile (SSRT) test. (author)

Simulation of radiation induced segregation and PWSCC susceptibility for austenitic stainless steels

International Nuclear Information System (INIS)

Fujimoto Koji; Yonezawa, Toshio; Iwamura, Toshihiko

2000-01-01

Recently, irradiation assisted stress corrosion cracking (IASCC) of austenitic stainless steels for core internal components materials become a subject of discussion in light water reactors (LWRs). IASCC has not been found in Pressurized Water Reactors (PWRs). However, the authors have investigated on the possibility of IASCC of austenitic stainless steels for core internal materials so as to be able to estimate the degradation of PWR plants up to the end of their lifetime. In this study, in order to verify the hypothetical that the IASCC in PWRs shall be caused by the primary water stress corrosion cracking (PWSCC) as a result of radiation induced segregation (RIS) at grain boundaries, the authors simulated RIS at grain boundaries of austenitic stainless steels based on previous study and estimated RIS tendency after long time operation. And the authors melted the test alloys whose bulk compositions simulated the grain boundary compositions of irradiated austenitic stainless steels and made clear chromium-nickel-silicon compositions for PWSCC susceptibility area in austenitic alloys by slow strain rate tensile (SSRT) test. (author)

Low temperature plasma carburizing of AISI 316L austenitic stainless steel and AISI F51 duplex stainless steel

OpenAIRE

Pinedo,Carlos Eduardo; Tschiptschin,André Paulo

2013-01-01

In this work an austenitic AISI 316L and a duplex AISI F51 (EN 1.4462) stainless steel were DC-Plasma carburized at 480ºC, using CH4 as carbon carrier gas. For the austenitic AISI 316L stainless steel, low temperature plasma carburizing induced a strong carbon supersaturation in the austenitic lattice and the formation of carbon expanded austenite (γC) without any precipitation of carbides. The hardness of the carburized AISI 316L steel reached a maximum of 1000 HV due to ∼13 at% c...

On the S-phase formation and the balanced plasma nitriding of austenitic-ferritic super duplex stainless steel

Science.gov (United States)

de Oliveira, Willian R.; Kurelo, Bruna C. E. S.; Ditzel, Dair G.; Serbena, Francisco C.; Foerster, Carlos E.; de Souza, Gelson B.

2018-03-01

The different physical responses of austenite (γ) and ferrite (α) iron structures upon nitriding result in technical challenges to the uniform modification of α-γ materials, as the super duplex stainless steel (SDSS). The effects of voltage (7-10 kV), frequency and pulse width on the nitrogen plasma immersion ion implantation of SDSS (α ∼ 56%, γ ∼ 44%) were investigated, correlated with structural, morphological and mechanical analyses. By controlling the treatment power, temperatures ranged from 292 °C to 401 °C. Despite the overall increase in hardness for any of the employed parameters (from ∼6 GPa to ∼15 GPa), the structure of individual grains was strikingly dissimilar at the same temperatures, depending on the energetic conditions of implantation. Modified-α grains containing iron nitrides (ε-Fe2-3N, γ‧ -Fe4N) presented intense brittleness, whereas the expanded phase γN (S-phase) laid principally in modified-γ grains, exhibiting ductile-like deformation features and thicker layers. The γN was the dominant phase in both α-γ grains at ∼401 °C, providing them with balanced structure and mechanical behavior. These phenomena corroborate with γN as mediator of the process, through a mechanism involving the nitrogen-promoted ferrite to austenite conversion and nitrides dissolution at high temperatures. An approximately linear correlation of the γN content with respect to the ion energy per pulse was demonstrated, which properly embodies limiting effects to the treatment. This can be a parameter for the α-γ steel surface modification, consisting in a better adjustment to obtain more precise control along with temperature.

Corrosion of austenitic stainless steel

Energy Technology Data Exchange (ETDEWEB)

Silva, M C.M. [Instituto Nacional de Tecnologia, Rio de Janeiro (Brazil)

1977-01-01

Types of corrosion observed in a heat exchanger pipe and on a support of still of molasses fermented wort, both in austenitic stainless steel, are focused. Not only are the causes which might have had any kind of influence on them examined, but also the measures adopted in order to avoid and lessen its occurence.

Development of new high-performance stainless steels

International Nuclear Information System (INIS)

Park, Yong Soo

2002-01-01

This paper focused on high-performance stainless steels and their development status. Effect of nitrogen addition on super-stainless steel was discussed. Research activities at Yonsei University, on austenitic and martensitic high-performance stainless, steels, and the next-generation duplex stainless steels were introduced

Study of irradiation damage structures in austenitic stainless steels

Energy Technology Data Exchange (ETDEWEB)

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

1997-08-01

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

Study of irradiation damage structures in austenitic stainless steels

International Nuclear Information System (INIS)

Hamada, Shozo

1997-08-01

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

Consitutive modeling of metastable austenitic stainless steel

NARCIS (Netherlands)

Perdahcioglu, Emin Semih; Perdahcioglu, Emin Semih

2008-01-01

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

Influences of passivating elements on the corrosion and biocompatibility of super stainless steels.

Science.gov (United States)

Yoo, Young-Ran; Jang, Soon-Geun; Oh, Keun-Taek; Kim, Jung-Gu; Kim, Young-Sik

2008-08-01

Biometals need high corrosion resistance since metallic implants in the body should be biocompatible and metal ion release should be minimized. In this work, we designed three kinds of super stainless steel and adjusted the alloying elements to obtain different microstructures. Super stainless steels contain larger amounts of Cr, Mo, W, and N than commercial alloys. These elements play a very important role in localized corrosion and, thus, their effects can be represented by the "pitting resistance equivalent number (PREN)." This work focused on the behavior which can arise when the bare surface of an implant in the body is exposed during walking, heavy exercise, and so on. Among the experimental alloys examined herein, Alloy Al and 316L stainless steels were mildly cytotoxic, whereas the other super austenitic, duplex, and ferritic stainless steels were noncytotoxic. This behavior is primarily related to the passive current and pitting resistance of the alloys. When the PREN value was increased, the passivation behavior in simulated body solution was totally different from that in acidic chloride solution and, thus, the Cr(2)O(3)/Cr(OH)(3) and [Metal oxide]/[Metal + Metal oxide] ratios of the passive film in the simulated body solution were larger than those in acidic chloride solution. Also, the critical current density in simulated body solution increased and, thus, active dissolution may induce metal ion release into the body when the PREN value and Ni content are increased. This behavior was closely related to the presence of EDTA in the simulated body solution. (c) 2007 Wiley Periodicals, Inc.

Constitutive modeling of metastable austenitic stainless steel

NARCIS (Netherlands)

Perdahcioglu, Emin Semih; Geijselaers, Hubertus J.M.; Huetink, Han; Khan, A.

2010-01-01

A physically based, macroscale constitutive model has been developed that can describe the complex mechanical behavior of metastable austenitic stainless steels. In the developed model a generalized model for the mechanically induced martensitic transformation is introduced. Mechanical tests have

Hot-Dip Aluminizing on AISI F55–UNS S32760 Super Duplex Stainless Steel Properties: Effect of Thermal Treatments

Directory of Open Access Journals (Sweden)

Andrea Francesco Ciuffini

2017-11-01

Full Text Available The behavior of super duplex stainless steels AISI F55-UNS S32760 in hot-dip aluminizing process has been studied, investigating the influence of cold working and of different initial microstructures obtained through a preliminary thermal treatment. The microstructural features examined are the secondary austenite precipitation, the static recovery of ferrite and the thermal dissolution of austenite within ferritic matrix. The hot-dip aluminizing temperature has been optimized through sessile drop tests. The treatment has been performed at 1100 °C for 300 s, 900 s and 2700 s. A strong chemical interaction occurs, generating intermetallic compounds at the interface. Molten aluminum interacts exclusively with the ferritic phase due to its much higher diffusivity in this phase coupled with its marked ferrite-stabilizer behavior. Thus, the influence of cold working is not remarkable, since the strains are mainly allocated by austenitic phase. The diffusivity of aluminum increases due to lattice defects thermally generated and, mainly, to influence given by grain boundaries, multiplied by secondary austenite precipitation, which act as short-circuit diffusion paths. Ni and Cr contents in the ferritic matrix have an influence but not highly relevant. Then, the best starting condition of the super duplex stainless steel substrates, to obtain a thick interfacial layer, are the thermal annealing at 1080 °C for 360 s/mm after a solution thermal treatment at 1300 °C for 60 s/mm.

Welding metallurgy of austenitic stainless steels

International Nuclear Information System (INIS)

Ibrahim, A.N.

1983-01-01

Austenitic stainless steels welds are commonly found in nuclear reactor systems. The macrostructure and the transformation of delta -phase into γ - phase which occur during rapid solidification of such welds are discussed. Finally, several types of defects which are derived from the welding operation, particularly defects of crack type, are also discussed in brief. (author)

Production and several properties of single crystal austenitic stainless steels

International Nuclear Information System (INIS)

Okamoto, Kazutaka; Yoshinari, Akira; Kaneda, Junya; Aono, Yasuhisa; Kato, Takahiko

1998-01-01

The single crystal austenitic stainless steels Type 316L and 304L were grown in order to improve the resistance to stress corrosion cracking (SCC) using a unidirectional solidification method which can provide the large size single crystals. The mechanical properties and the chemical properties were examined. The orientation and temperature dependence of tensile properties of the single crystals were measured. The yield stress of the single crystal steels are lower than those of the conventional polycrystal steels because of the grain boundary strength cannot be expected in the single crystal steels. The tensile properties of the single crystal austenitic stainless steel Type 316L depend strongly on the orientation. The tensile strength in orientation are about 200 MPa higher than those in the and orientations. The microstructure of the single crystal consists of a mixture of the continuous γ-austenitic single crystal matrix and the δ-ferrite phase so that the effects of the γ/δ boundaries on the chemical properties were studied. The effects of the δ-ferrite phases and the γ/δ boundaries on the resistance to SCC were examined by the creviced bent beam test (CBB test). No crack is observed in all the CBB test specimens of the single crystals, even at the γ/δ boundaries. The behavior of the radiation induced segregation (RIS) at the γ/δ boundaries in the single crystal austenitic stainless steel Type 316L was evaluated by the electron irradiation test in the high voltage electron microscope (HVEM). The depletion of oversized solute chromium at the γ/δ boundary in the single crystal austenitic stainless steel Type 316L is remarkably lower than that at the grain boundary in the polycrystalline-type 316L. (author)

Austenitic stainless steels for cryogenic service

International Nuclear Information System (INIS)

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

1985-01-01

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

Austenitic stainless steels for cryogenic service

Energy Technology Data Exchange (ETDEWEB)

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

1985-09-19

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

Fatigue crack propagation of super duplex stainless steel and time-frequency analysis of acoustic emission

International Nuclear Information System (INIS)

Lee, Sang Kee; Nam, Ki Woo; Kang, Chang Yong; Do, Jae Yoon

2000-01-01

On this study, the fatigue crack propagation of super duplex stainless steel is investigated in conditions of various volume fraction of austenite phase by changing heat treatment temperature. And we analysed acoustic emission signals during the fatigue test by time-frequency analysis methods. As the temperature of heat treatment increased, volume fraction of austenite decreased and coarse grain was obtained. The specimen heat treated at 1200 deg. C had longer fatigue life and slower rate of crack growth. As a result of time-frequency analyze of acoustic emission signals during fatigue test, main frequency was 200∼300 kHz having no correlation with heat treatment and crack length, and 500 kHz was obtained by dimple and separate of inclusion

Effect of Dynamic Reheating Induced by Weaving on the Microstructure of GTAW Weld Metal of 25% Cr Super Duplex Stainless Steel Weld Metal

Directory of Open Access Journals (Sweden)

Hee-Joon Sung

2017-11-01

Full Text Available The importance of the additional growth and/or transformation of the austenite phase that occurs in weld metals of super duplex stainless steel upon reheating is known. However, the effects have not been fully investigated, especially with respect to reheating induced by weaving during single-pass welding. In this work, bead-on-pipe gas tungsten arc welding (GTAW was conducted on super duplex stainless steel to understand the effect of weaving on the microstructure of weld metal. Microstructural analysis, electron backscatter diffraction (EBSD, and focused ion beam transmission electron microscopy (FIB-TEM were carried out to investigate the relationship between weaving and microstructural change. The weaving of GTAW produced a dynamic reheated area just before the weld bead during welding. It was revealed that extensive reheated weld existed even after one welding pass, and that the content of the austenite phase in the reheated area was higher than that in the non-reheated area, indicating the existence of a large quantity of intragranular austenite phase. In addition, the Cr2N content in the reheated area was lower than that in the non-reheated area. This reduction of Cr2N was closely related to the reheating resulting from weaving. TEM analysis revealed that Cr2N in the non-reheated area was dispersed following heating and transformed to secondary austenite.

High Cycle Fatigue of Metastable Austenitic Stainless Steels

OpenAIRE

Fargas Ribas, Gemma; Zapata Dederle, Ana Cristina; Anglada Gomila, Marcos Juan; Mateo García, Antonio Manuel

2009-01-01

Metastable austenitic stainless steels are currently used in applications where severe forming operations are required, such as automotive bodies, due to its excellent ductility. They are also gaining interest for its combination of high strength and formability after forming. The biggest disadvantage is the difficulty to predict the mechanical response, which depends heavily on the amount of martensite formed. The martensitic transformation in metastable stainless steels can b...

Characterization of the austenitic stability of metastable austenitic stainless steel with regard to its formability

Science.gov (United States)

Schneider, Matthias; Liewald, Mathias

2018-05-01

During the last decade, the stainless steel market showed a growing volume of 3-5% p.a.. The austenitic grades are losing market shares to ferritic or 200-series grades due to the high nickel price, but still playing the most important role within the stainless steel market. Austenitic stainless steel is characterized by the strain-induced martensite formation, causing the TRIP-effect (Transformation Induced Plasticity) which is responsible for good formability and high strength. The TRIP-effect itself is highly dependent on the forming temperature, the strain as well as the chemical composition which has a direct influence on the stability of the austenite. Today the austenitic stability is usually characterized by the so called Md30-temperature, which was introduced by Angel and enhanced by several researches, particularly Nohara. It is an empirical formula based on the chemical composition and the grain size of a given material, calculating the temperature which is necessary to gain a 50 % martensite formation after 30 % of elongation in a tensile test. A higher Md30-temperature indicates a lower stability and therefore a higher tendency towards martensite formation. The main disadvantage of Md30 -temperature is the fact that it is not based on forming parameters and only describes a single point instead of the whole forming process. In this paper, an experimental set up for measuring martensite and temperature evolution in a non-isothermal tensile test is presented, which is based on works of Hänsel and Schmid. With this set up, the martensite formation rate for different steels of the steel grade EN 1.4301 and EN 1.4310 is measured. Based on these results a new austenitic stability criterion is defined. This criterion and the determined Md30-temperatures are related to the stretch formability of the materials. The results show that the new IFU criterion is with regard to the formability a much more useful characteristic number for metastable austenitic steels

Optimal design for laser beam butt welding process parameter using artificial neural networks and genetic algorithm for super austenitic stainless steel

Science.gov (United States)

Sathiya, P.; Panneerselvam, K.; Soundararajan, R.

2012-09-01

Laser welding input parameters play a very significant role in determining the quality of a weld joint. The joint quality can be defined in terms of properties such as weld bead geometry, mechanical properties and distortion. Therefore, mechanical properties should be controlled to obtain good welded joints. In this study, the weld bead geometry such as depth of penetration (DP), bead width (BW) and tensile strength (TS) of the laser welded butt joints made of AISI 904L super austenitic stainless steel were investigated. Full factorial design was used to carry out the experimental design. Artificial Neural networks (ANN) program was developed in MatLab software to establish the relationships between the laser welding input parameters like beam power, travel speed and focal position and the three responses DP, BW and TS in three different shielding gases (Argon, Helium and Nitrogen). The established models were used for optimizing the process parameters using Genetic Algorithm (GA). Optimum solutions for the three different gases and their respective responses were obtained. Confirmation experiment has also been conducted to validate the optimized parameters obtained from GA.

A Review on the Potential Use of Austenitic Stainless Steels in Nuclear Fusion Reactors

Science.gov (United States)

Şahin, Sümer; Übeyli, Mustafa

2008-12-01

Various engineering materials; austenitic stainless steels, ferritic/martensitic steels, vanadium alloys, refractory metals and composites have been suggested as candidate structural materials for nuclear fusion reactors. Among these structural materials, austenitic steels have an advantage of extensive technological database and lower cost compared to other non-ferrous candidates. Furthermore, they have also advantages of very good mechanical properties and fission operation experience. Moreover, modified austenitic stainless (Ni and Mo free) have relatively low residual radioactivity. Nevertheless, they can't withstand high neutron wall load which is required to get high power density in fusion reactors. On the other hand, a protective flowing liquid wall between plasma and solid first wall in these reactors can eliminate this restriction. This study presents an overview of austenitic stainless steels considered to be used in fusion reactors.

Ion-nitriding of austenitic stainless steels

International Nuclear Information System (INIS)

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

1995-01-01

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

Precipitation phases at different processes and heat treat ments as well as their effects on the mechanical properties of super-austenitic stainless steel

Science.gov (United States)

Sun, Hunying; Zhou, Zhangjian; Wang, Man; Li, Shaofu; Zhang, Liwei; Zou, Lei

2013-03-01

A new type lCr30Ni30Mo2TiZr super-austenitic stainless steel has been developed. The microstructures, precipitation phases and mechanical properties of the steel under different deformation processes and heat treatment (solution, stabilized treatment) were investigated using X-ray Diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) as well as mechanical tests. The results indicate that coarse carbides such as Cr-rich M23C6, sigma (σ), and little chi (χ) phases were formed in the steel, and large α' -Cr phases were also detected at three joint grain boundaries, and they were promoted by large strain. The precipitate phases were dissolved or transformed to intermetallic phase even at higher elevated temperature, and influenced the mechanical property obviously. These intermetallic compounds seriously reduced elongation of the rolled steel at room temperature and 700 °C, but increased the forged one at 700 °C. Impact absorbed energies of the stabilized specimens were lower than half of that solution status.

Structure and microstructure evolution of a ternary Fe–Cr–Ni alloy akin to super martensitic stainless steel

International Nuclear Information System (INIS)

Ravi Kumar, B.; Sharma, Sailaja; Munda, Parikshit; Minz, R.K.

2013-01-01

Highlights: • Reaustenisation by recrystallisation rather by a diffusion controlled process. • Ultrafine grained austenite formation in martensite matrix by recrystallisation. • In situ high temperature austenite transformation studies by X-ray diffraction. • Microstructure tailoring to achieve tensile strength (∼1 GPa) with good ductility. - Abstract: A ternary Fe–Cr–Ni alloy, akin to super martensitic stainless steels was prepared in vacuum induction furnace. The as cast ingot was solution treated at 1200 °C for 25 h and then hot forged and rolled to reduce into plate form. The hot rolled plate of martensitic microstructure was then cold rolled to 80% of thickness reduction. The phase transformation studies by X-ray diffraction analysis of hot and cold rolled specimens showed presence of retained austenite in air cooled as well as in water quenched state after annealing/austenising temperature of 1060 °C. The reaustenisation behaviour of the cold rolled alloy in water quenched state was studied by high temperature X-ray diffraction analysis. It showed very stable martensitic phase and the completion of reaustenisation process were observed to occur at about 950 °C. The recrystallisation behaviour of cold rolled material under isothermal and repeated annealing treatment was studied in detail by electron microscope. The tensile properties of the material were evaluated after various annealing treatments. The study revealed that by a suitable sequence of repetitive annealing process microstructure could be tailored to achieve tensile strength above 1 GPa with good ductility in a super martensitic stainless steel

Laser cladding crack repair of austenitic stainless steel

CSIR Research Space (South Africa)

Van Rooyen, C

2009-06-01

Full Text Available Laser cladding crack repair of austenitic stainless steel vessels subjected to internal water pressure was evaluated. The purpose of this investigation was to develop process parameters for in-situ repair of through-wall cracks in components...

Case histories of microbiologically influenced corrosion of austenitic stainless steel weldments

International Nuclear Information System (INIS)

Borenstein, S.W.; Buchanan, R.A.; Dowling, N.J.E.

1990-01-01

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

Kinetics analysis of two-stage austenitization in supermartensitic stainless steel

DEFF Research Database (Denmark)

Nießen, Frank; Villa, Matteo; Hald, John

2017-01-01

The martensite-to-austenite transformation in X4CrNiMo16-5-1 supermartensitic stainless steel was followed in-situ during isochronal heating at 2, 6 and 18 K min−1 applying energy-dispersive synchrotron X-ray diffraction at the BESSY II facility. Austenitization occurred in two stages, separated...... that the austenitization kinetics is governed by Ni-diffusion and that slow transformation kinetics separating the two stages is caused by soft impingement in the martensite phase. Increasing the lath width in the kinetics model had a similar effect on the austenitization kinetics as increasing the heating-rate....

Influence of delta ferrite on corrosion susceptibility of AISI 304 austenitic stainless steel

Directory of Open Access Journals (Sweden)

Lawrence O. Osoba

2016-12-01

Full Text Available In the current study, the influence of delta (δ ferrite on the corrosion susceptibility of AISI 304 austenitic stainless steel was evaluated in 1Molar concentration of sulphuric acid (H2SO4 and 1Molar concentration of sodium chloride (NaCl. The study was performed at ambient temperature using electrochemical technique—Tafel plots to evaluate the corrosive tendencies of the austenitic stainless steel sample. The as-received (stainless steel specimen and 60% cold-worked (stainless steel specimens were isothermally annealed at 1,100°C for 2 h and 1 h, respectively, and quenched in water. The results obtained show that the heat-treated specimen and the 60% cold-worked plus heat-treated specimen exhibited higher corrosion susceptibility than the as-received specimen, which invariably contained the highest fraction of δ ferrite particles. The finding shows that the presence of δ ferrite, in which chromium (Cr, the main corrosion inhibitor segregates, does not degrade and or reduces the resistance to aqueous corrosion of the austenitic stainless steel material.

On the High Temperature Deformation Behaviour of 2507 Super Duplex Stainless Steel

Science.gov (United States)

Mishra, M. K.; Balasundar, I.; Rao, A. G.; Kashyap, B. P.; Prabhu, N.

2017-02-01

High temperature deformation behaviour of 2507 super duplex stainless steel was investigated by conducting isothermal hot compression tests. The dominant restoration processes in ferrite and austenite phases present in the material were found to be distinct. The possible causes for these differences are discussed. Based on the dynamic materials model, processing map was developed to identify the optimum processing parameters. The microstructural mechanisms operating in the material were identified. A unified strain-compensated constitutive equation was established to describe the high temperature deformation behaviour of the material under the identified processing conditions. Standard statistical parameter such as correlation coefficient has been used to validate the established equation.

Cryogenic properties of austenitic stainless steels for superconducting magnet

International Nuclear Information System (INIS)

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

1983-01-01

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

Effect of Si and Mn additions on ferrite and austenite phase fractions in 25Cr-7Ni-1.5Mo-3W base super duplex stainless steels

International Nuclear Information System (INIS)

Jeong, S.W.; Lee, Z.-H.; Lee, H.M.

2000-01-01

The effect of heat treatment and Si and Mn additions on the ferrite and austenite phase fractions of the super duplex stainless steel (SDSS), Fe-25Cr-7Ni-1.5Mo-3W-Si-Mn-0.25N (numbers are all in wt.% unless specified otherwise), was investigated. The thermodynamic calculations of phase equilibria and phase fractions were performed using the Thermo-Calc program. Based on the calculated results, specific compositions of Si and Mn were selected and alloys with these compositions were analysed by Feritscope, X-ray diffractometry and scanning electron microscopy. The calculated phase fractions and experimentally analysed ones were compared and there was a good agreement between calculations and measurements. The optimum heat treatment condition for Fe-25Cr-7Ni-1.5Mo-3W-0.5Si-0.5Mn-0.25N is to hold at 1050 to 1100 C for 2 h in considering the ferrite to austenite ratio of 50:50 and to avoid second phase precipitation such as the σ phase. It was suggested that an excessive addition of more than 0.8Si and 1.0Mn may induce the σ phase precipitation. (orig.)

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

Directory of Open Access Journals (Sweden)

ZHOU Shu-cai

2007-08-01

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

Sandblasting induced stress release and enhanced adhesion strength of diamond films deposited on austenite stainless steel

Science.gov (United States)

Li, Xiao; Ye, Jiansong; Zhang, Hangcheng; Feng, Tao; Chen, Jianqing; Hu, Xiaojun

2017-08-01

We firstly used sandblasting to treat austenite stainless steel and then deposited a Cr/CrN interlayer by close field unbalanced magnetron sputtering on it. After that, diamond films were prepared on the interlayer. It is found that the sandblasting process induces phase transition from austenite to martensite in the surface region of the stainless steel, which decreases thermal stress in diamond films due to lower thermal expansion coefficient of martensite phase compared with that of austenite phase. The sandblasting also makes stainless steel's surface rough and the Cr/CrN interlayer film inherits the rough surface. This decreases the carburization extent of the interlayer, increases nucleation density and modifies the stress distribution. Due to lower residual stress and small extent of the interlayer's carburization, the diamond film on sandblast treated austenite stainless steel shows enhanced adhesion strength.

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

International Nuclear Information System (INIS)

Chung, H.M.

1989-02-01

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

Fatigue behavior of welded austenitic stainless steel in different environments

Directory of Open Access Journals (Sweden)

D.S. Yawas

2014-01-01

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

Microstructural Evolutions During Reversion Annealing of Cold-Rolled AISI 316 Austenitic Stainless Steel

Science.gov (United States)

Naghizadeh, Meysam; Mirzadeh, Hamed

2018-06-01

Microstructural evolutions during reversion annealing of a plastically deformed AISI 316 stainless steel were investigated and three distinct stages were identified: the reversion of strain-induced martensite to austenite, the primary recrystallization of the retained austenite, and the grain growth process. It was found that the slow kinetics of recrystallization at lower annealing temperatures inhibit the formation of an equiaxed microstructure and might effectively impair the usefulness of this thermomechanical treatment for the objective of grain refinement. By comparing the behavior of AISI 316 and 304 alloys, it was found that the mentioned slow kinetics is related to the retardation effect of solute Mo in the former alloy. At high reversion annealing temperature, however, an equiaxed austenitic microstructure was achieved quickly in AISI 316 stainless steel due to the temperature dependency of retardation effect of molybdenum, which allowed the process of recrystallization to happen easily. Conclusively, this work can shed some light on the issues of this efficient grain refining approach for microstructural control of austenitic stainless steels.

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

International Nuclear Information System (INIS)

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

2004-01-01

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

Response of cast austenitic stainless steel to low temperature plasma carburizing.

OpenAIRE

Sun, Yong

2008-01-01

The response of a cast 316 type austenitic stainless steel to the novel low temperature plasma carburizing process has been investigated in this work. The cast steel has a dendritic structure with a mix of austenite, ferrite and carbide phases. The results show that such a complex structure responds well to the carburizing process, and the inter-dendrite regions containing ferrite and carbides can be transformed to expanded austenite to form a continuous and uniform layer supersat...

The irradiation performance of austenitic stainless steel clade PWR fuel rods

International Nuclear Information System (INIS)

Teixeira e Silva, A.; Esteves, A.M.

1988-01-01

The steady state irradiation performance of austenitic stainless steel clad pressurized water reactor fuel rods is modeled with fuel performance codes of the FRAP series. These codes, originally developed to model the thermal-mechanical behavior of zircaloy clad fuel rods, are modified to model stainless steel clad fuel rods. The irradiation thermal-mechanical behavior of type 348 stainless steel and zircaloy fuel rods is compared. (author) [pt

Zinc Addition Effects on General Corrosion of Austenitic Stainless Steels in PWR Primary Conditions

International Nuclear Information System (INIS)

Qiao Peipeng; Zhang Lefu; Liu Ruiqin; Jiang Suqing; Zhu Fawen

2010-01-01

Zinc addition effects on general corrosion of austenitic stainless steel 316 and 304 were investigated in simulated PWR primary coolant without zinc or with 50 ppb zinc addition at 315 degree C for 500 h. The results show that with the addition of zinc, the corrosion rate of austenitic stainless steel is effectively reduced, the surface oxide film is thinner, the morphology and chemical composition of surface oxide scales are evidently different from those without zinc. There are needle-like corrosion products on the surface of stainless steel 304. (authors)

Studies on analytical method and nondestructive measuring method on the sensitization of austenitic stainless steels

International Nuclear Information System (INIS)

Onimura, Kichiro; Arioka, Koji; Horai, Manabu; Noguchi, Shigeru.

1982-03-01

Austenitic stainless steels are widely used as structural materials for the machine and equipment of various kinds of plants, such as thermal power, nuclear power, and chemical plants. The machines and equipment using this kind of material, however, have the possibility of suffering corrosion damage while in service, and these damages are considered to be largely due to the sensitization of the material in sometimes. So, it is necessary to develop an analytical method for grasping the sensitization of the material more in detail and a quantitative nondestructive measuring method which is applicable to various kinds of structures in order to prevent the corrosion damage. From the above viewpoint, studies have been made on the analytical method based on the theory of diffusion of chromium in austenitic stainless steels and on Electro-Potentiokinetics Reactivation Method (EPR Method) as a nondestructive measuring method, using 304 and 316 austenitic stainless steels having different carbon contents in base metals. This paper introduces the results of EPR test on the sensitization of austenitic stainless steels and the correlation between analytical and experimental results. (author)

On Necking, Fracture and Localization of Plastic Flow in Austenitic Stainless Steel Sheets

International Nuclear Information System (INIS)

Korhonen, A. S.; Manninen, T.; Kanervo, K.

2007-01-01

The forming limits of austenitic stainless steel sheets were studied in this work. It was found that the observed limit of straining in stretch forming, when both of the principal stresses are positive, is not set by localized necking, but instead by inclined shearing fracture in the through thickness direction. It appears that the forming limits of austenitic stainless steels may be predicted fairly well by using the classical localized and diffuse necking criteria developed by Hill. The strain path-dependence may be accounted for by integrating the effective strain along the strain path. The fracture criteria of Rice and Tracey and Cockcroft, Latham and Oh were also studied. The results were in qualitative agreement with the experimental observations. Recent experiments with high-velocity electrohydraulic forming of austenitic stainless steels revealed localized necks in stretch formed parts, which are not commonly observed in conventionally formed sheet metal parts

The Influence of Porosity on Corrosion Attack of Austenitic Stainless Steel

Science.gov (United States)

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

2017-10-01

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

Pitting corrosion resistant austenite stainless steel

Science.gov (United States)

van Rooyen, D.; Bandy, R.

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

Effect of annealing treatment on microstructure evolution and the associated corrosion behavior of a super-duplex stainless steel

International Nuclear Information System (INIS)

Deng, B.; Jiang, Y.M.; Gao, J.; Li, J.

2010-01-01

The influence of annealing temperature on the pitting corrosion of a super-duplex stainless steel (SDSS) with mischmetal addition was investigated in chloride solution by critical pitting temperature (CPT) measurement. The corrosion behavior is strongly dependent on the microstructure, namely the presence of secondary phases, elemental partitioning behavior and volume fractions of ferrite and austenite. Based on CPT results and alloying rules, the optimal annealing temperature is determined as 1070 o C and a guideline for further development of improved SDSS is formulated.

Austenite Formation from Martensite in a 13Cr6Ni2Mo Supermartensitic Stainless Steel

NARCIS (Netherlands)

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

2016-01-01

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

Determination of delta ferrite volumetric fraction in austenitic stainless steel

International Nuclear Information System (INIS)

Almeida Macedo, W.A. de.

1983-01-01

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

Determination of delta ferrite volumetric fraction in austenitic stainless steels

International Nuclear Information System (INIS)

Almeida Macedo, W.A. de.

1983-01-01

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

The Effects of Alloy Chemistry on Localized Corrosion of Austenitic Stainless Steels

Science.gov (United States)

Sapiro, David O.

This study investigated localized corrosion behavior of austenitic stainless steels under stressed and unstressed conditions, as well as corrosion of metallic thin films. While austenitic stainless steels are widely used in corrosive environments, they are vulnerable to pitting and stress corrosion cracking (SCC), particularly in chloride-containing environments. The corrosion resistance of austenitic stainless steels is closely tied to the alloying elements chromium, nickel, and molybdenum. Polarization curves were measured for five commercially available austenitic stainless steels of varying chromium, nickel, and molybdenum content in 3.5 wt.% and 25 wt.% NaCl solutions. The alloys were also tested in tension at slow strain rates in air and in a chloride environment under different polarization conditions to explore the relationship between the extent of pitting corrosion and SCC over a range of alloy content and environment. The influence of alloy composition on corrosion resistance was found to be consistent with the pitting resistance equivalent number (PREN) under some conditions, but there were also conditions under which the model did not hold for certain commercial alloy compositions. Monotonic loading was used to generate SCC in in 300 series stainless steels, and it was possible to control the failure mode through adjusting environmental and polarization conditions. Metallic thin film systems of thickness 10-200 nm are being investigated for use as corrosion sensors and protective coatings, however the corrosion properties of ferrous thin films have not been widely studied. The effects of film thickness and substrate conductivity were examined using potentiodynamic polarization and scanning vibrating electrode technique (SVET) on iron thin films. Thicker films undergo more corrosion than thinner films in the same environment, though the corrosion mechanism is the same. Conductive substrates encourage general corrosion, similar to that of bulk iron

Reformed austenite transformation during fatigue crack propagation of 13%Cr-4%Ni stainless steel

Energy Technology Data Exchange (ETDEWEB)

Thibault, Denis, E-mail: thibault.denis@ireq.ca [Institut de recherche d' Hydro-Quebec (IREQ), 1800, boul. Lionel-Boulet, Varennes, Quebec, J3X 1S1 (Canada); Bocher, Philippe, E-mail: philippe.bocher@etsmtl.ca [Ecole de technologie superieure, 1100, rue Notre-Dame Ouest, Montreal, Quebec, H3C 1K3 (Canada); Thomas, Marc, E-mail: marc.thomas@etsmtl.ca [Ecole de technologie superieure, 1100, rue Notre-Dame Ouest, Montreal, Quebec, H3C 1K3 (Canada); Lanteigne, Jacques, E-mail: lanteigne.jacques@ireq.ca [Institut de recherche d' Hydro-Quebec (IREQ), 1800, boul. Lionel-Boulet, Varennes, Quebec, J3X 1S1 (Canada); Hovington, Pierre, E-mail: hovington.pierre@ireq.ca [Institut de recherche d' Hydro-Quebec (IREQ), 1800, boul. Lionel-Boulet, Varennes, Quebec, J3X 1S1 (Canada); Robichaud, Patrice, E-mail: patrice.robichaud@riotinto.com [Centre de recherche et de developpement Arvida (CRDA), 1955, boul. Mellon, Jonquiere, Quebec, G7S 4K8 (Canada)

2011-08-15

Highlights: {yields} Reformed austenite in 13%Cr-4%Ni stainless steel transforms during fatigue crack growth. {yields} Low cycle fatigue tests showed that this transformation to martensite is gradual. {yields} XRD spectrums obtained on the fracture surface and have been correlated to LCF results. - Abstract: In the as-quenched state, 13%Cr-4%Ni martensitic stainless steels are essentially 100% martensitic. However, a certain amount of austenite is formed during the tempering of this alloy. This reformed austenite is thermally stable at room temperature but can transform to martensite under stress. This transformation is known to happen during impact testing but it has never been established if it occurs during fatigue crack propagation. This study presents the results of X-ray diffraction measurements of reformed austenite before and after crack growth testing. It has been found that reformed austenite does transform to martensite at the crack tip and that this transformation occurs even at a low stress intensity factor. Low-cycle fatigue tests were conducted to verify austenite transformation under cyclic straining. It was found that reformed austenite transforms only partially during the first strain reversal but that essentially all austenite has disappeared after 100 cycles. The relation between austenite transformation under low-cycle fatigue and its transformation during crack growth is also discussed.

Reformed austenite transformation during fatigue crack propagation of 13%Cr-4%Ni stainless steel

International Nuclear Information System (INIS)

Thibault, Denis; Bocher, Philippe; Thomas, Marc; Lanteigne, Jacques; Hovington, Pierre; Robichaud, Patrice

2011-01-01

Highlights: → Reformed austenite in 13%Cr-4%Ni stainless steel transforms during fatigue crack growth. → Low cycle fatigue tests showed that this transformation to martensite is gradual. → XRD spectrums obtained on the fracture surface and have been correlated to LCF results. - Abstract: In the as-quenched state, 13%Cr-4%Ni martensitic stainless steels are essentially 100% martensitic. However, a certain amount of austenite is formed during the tempering of this alloy. This reformed austenite is thermally stable at room temperature but can transform to martensite under stress. This transformation is known to happen during impact testing but it has never been established if it occurs during fatigue crack propagation. This study presents the results of X-ray diffraction measurements of reformed austenite before and after crack growth testing. It has been found that reformed austenite does transform to martensite at the crack tip and that this transformation occurs even at a low stress intensity factor. Low-cycle fatigue tests were conducted to verify austenite transformation under cyclic straining. It was found that reformed austenite transforms only partially during the first strain reversal but that essentially all austenite has disappeared after 100 cycles. The relation between austenite transformation under low-cycle fatigue and its transformation during crack growth is also discussed.

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

Energy Technology Data Exchange (ETDEWEB)

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

2015-01-15

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

Reduced-activation austenitic stainless steels: The Fe--Mn--Cr--C system

International Nuclear Information System (INIS)

Klueh, R.L.; Maziasz, P.J.

1988-01-01

Nickel-free manganese-stabilized steels are being developed for fusion-reactor applications. As the first part of this effort, the austenite-stable region in the Fe--Mn--Cr--C system was determined. Results indicated that the Schaeffler diagram developed for Fe--Ni--Cr--C alloys cannot be used to predict the constituents expected for high-manganese steels. This is true because manganese is not as strong an austenite stabilizer relative to δ-ferrite formation as predicted by the diagram, but it is a stronger austenite stabilizer relative to martensite than predicted. Therefore, the austenite-stable region for Ne--Mn--Cr--C alloys occurs at lower chromium and hugher combinations of manganese and carbon than predicted by the Schaeffler diagram. Development of a manganese-stabilized stainless steel should be possible in the composition range of 20 to 25% Mn, 10 to 15% Cr, and 0.01 to 0.25%C. Tensile behavior of an Fe--20%Mn--12%Cr--0.25%C alloy was determined. The strength and ductility of this possible base composition was comparable to type 316 stainless steel in both the solution-annealed and cold-worked condition

Constitutive Relationship Modeling and Characterization of Flow Behavior under Hot Working for Fe–Cr–Ni–W–Cu–Co Super-Austenitic Stainless Steel

Directory of Open Access Journals (Sweden)

Li-Chih Yang

2015-09-01

Full Text Available The hot deformation behavior of a Fe–22Cr–25Ni–3.5W–3Cu–1.5Co super-austenitic stainless steel was investigated using isothermal compression tests with a wide range of temperatures (1173–1373 K and strain rates (0.1–10 s−1. The results showed that all the flow curves gradually turned to balanced stress state without notable peak stress characteristics during the entire deformation, which indicated that the dynamic recovery behavior played a main restoration mechanism in the steel. Modeling constitutive equations relating to the temperature, strain rate and flow stress were proposed to determine the materials constants and activation energy necessary for deformation. In order to give the precise predicted values of the flow behavior, the influence of strain was identified using polynomial functions. The relationship of flow stress, temperature and strain rate was represented by the Zener-Hollomon parameter including the Arrhenius term. The predicted results validated that the developed constitutive equations can describe high temperature flow behavior well. Furthermore, a modified Zener-Hollomon parameter map of the studied steel was developed to clarify the restoration mechanism based on the constitutive modeling data and microstructural observation.

Monitoring of Fatigue Degradation in Austenitic Stainless Steels

International Nuclear Information System (INIS)

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

2004-01-01

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

Oxidation resistant high creep strength austenitic stainless steel

Science.gov (United States)

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

2010-06-29

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

Austenitic stainless steels with cryogenic resistance

International Nuclear Information System (INIS)

Tarata, Daniela Florentina

1999-01-01

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

Ultrasonic testing of austenitic stainless steel welds

International Nuclear Information System (INIS)

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

1982-05-01

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

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

DEFF Research Database (Denmark)

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

2015-01-01

A precipitation hardenable semi-austenitic stainless steel AISI 632 grade was austenitized according to industrial specifications and thereafter subjected to isothermal treatment at sub-zero Celsius temperatures. During treatment, austenite transformed to martensite. The isothermal austenite-to-martensite...... treatment. Magnetometry showed that the additional thermal step in boiling nitrogen yields a minor increment of the fraction of martensite, but has a noteworthy accelerating effect on the transformation kinetics, which more pronounced when the isothermal holding is performed at a higher temperature. Data...... is interpreted in terms of instantaneous nucleation of martensite during cooling followed by time dependent growth during isothermal holding....

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

Science.gov (United States)

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

2017-06-01

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

Fatigue crack propagation of super duplex stainless steel with dispersed structure and time-frequency analysis of acoustic emission

Science.gov (United States)

Nam, Ki-Woo; Kang, Chang-Yong; Do, Jae-Yoon; Ahn, Seok-Hwan; Lee, Sang-Kee

2001-06-01

The fatigue crack propagation of super duplex stainless steel was investigated for the effect of various volume fractions of the austenite phase by changing the heat treatment temperature. We also analyzed acoustic emission signals obtained during the fatigue crack propagation by the time-frequency analysis method. As the temperature of the heat treatment increased, the volume fraction of austenite decreased and coarse grain was obtained. The specimen treated at 1200 had a longer fatigue life and slower rate of crack growth. Results of time-frequency analysis of acoustic emission signals during the fatigue test showed the main frequency of 200-300 kHz to have no correlation with heat treatment and crack length, and the 500 kHz signal to be due to dimples and separation of inclusion.

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

Energy Technology Data Exchange (ETDEWEB)

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

2017-07-15

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

STRUCTURAL STABILITY OF HIGH NITROGEN AUSTENITIC STAINLESS STEELS

Directory of Open Access Journals (Sweden)

Jana Bakajová

2011-05-01

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

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

Science.gov (United States)

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

2018-02-01

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

Formation and stabilization of reversed austenite in supermartensitic stainless steel

DEFF Research Database (Denmark)

Nießen, Frank; Grumsen, Flemming Bjerg; Hald, John

2017-01-01

of the reversed austenite phase fraction. Annealing at higher temperatures led to a gradual increase in hardness which was caused by formation of fresh martensite from reversed austenite. It was demonstrated that stabilization of reversed austenite is primarily based on chemical stabilization by partitioning......The formation and stabilization of reversed austenite upon inter-critical annealing was investigated in a X4CrNiMo16-5-1 (EN 1.4418) supermartensitic stainless steel by means of scanning electron microscopy, electron backscatter-diffraction, transmission electron microscopy, energy-dispersive X......-ray spectroscopy and dilatometry. The results were supported by thermodynamics and kinetics models, and hardness measurements. Isothermal annealing for 2 h in the temperature range of 475 to 650 °C led to gradual softening of the material which was related to tempering of martensite and the steady increase...

Corrosion behaviour of dissimilar welds between ferritic-martensitic stainless steel and austenitic stainless steel from secondary circuit of CANDU NPP

International Nuclear Information System (INIS)

Popa, L.; Fulger, M.; Tunaru, M.; Velciu, L.; Lazar, M.

2016-01-01

Corrosion damages of welds occur in spite of the fact that the proper base metal and filler metal have been correctly selected, industry codes and standards have been followed and welds have been realized with full weld penetration and have proper shape and contour. In secondary circuit of a Nuclear Power Station there are some components which have dissimilar welds. The principal criteria for selecting a stainless steel usually is resistance to corrosion, and white most consideration is given to the corrosion resistance of the base metal, additional consideration should be given to the weld metal and to the base metal immediately adjacent to the weld zone. Our experiments were performed in chloride environmental on two types of samples: non-welded (410 or W 1.4006 ferritic-martensitic steel and 304L or W 1.4307 austenitic stainless steel) and dissimilar welds (dissimilar metal welds: joints between 410 ferritic-martensitic and 304L austenitic stainless steel). To evaluate corrosion susceptibility of dissimilar welds was used electrochemical method (potentiodynamic method) and optic microscopy (microstructural analysis). The present paper follows the localized corrosion behaviour of dissimilar welds between austenitic stainless steel and ferritic-martensitic steel in solutions containing chloride ions. It was evaluated the corrosion rates of samples (welded and non-welded) by electrochemical methods. (authors)

Microstructure of super-austenitic steels after long-term annealing

Czech Academy of Sciences Publication Activity Database

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

2010-01-01

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

Reversed austenite for enhancing ductility of martensitic stainless steel

Science.gov (United States)

Dieck, S.; Rosemann, P.; Kromm, A.; Halle, T.

2017-03-01

The novel heat treatment concept, “quenching and partitioning” (Q&P) has been developed for high strength steels with enhanced formability. This heat treatment involves quenching of austenite to a temperature between martensite start and finish, to receive a several amount of retained austenite. During the subsequent annealing treatment, the so called partitioning, the retained austenite is stabilized due to carbon diffusion, which results in enhanced formability and strength regarding strain induced austenite to martensite transformation. In this study a Q&P heat treatment was applied to a Fe-0.45C-0.65Mn-0.34Si-13.95Cr stainless martensite. Thereby the initial quench end temperature and the partitioning time were varied to characterize their influence on microstructural evolution. The microstructural changes were analysed by dilatometer measurements, X-ray diffraction and scanning electron microscopy, including electron back-scatter diffraction. Compression testing was made to examine the mechanical behaviour. It was found that an increasing partitioning time up to 30 min leads to an enhanced formability without loss in strength due to a higher amount of stabilized retained and reversed austenite as well as precipitation hardening.

Study of irradiation effects in austenitic stainless steels

Energy Technology Data Exchange (ETDEWEB)

Etienne, A. [GPM UMR CNRS 6634, Universite et INSA de Rouen (France); Material Department, University of California, Santa Barbara (United States); Pareige, P.; Radiguet, B. [GPM UMR CNRS 6634, Universite et INSA de Rouen (France); Cunningham, N.J.; Odette, G.O. [Material Department, University of California, Santa Barbara (United States); Pokor, C. [EDF RD, departement MMC, site des Renardieres, Moret-sur-Loing (France)

2011-07-01

Chemical analyses using Atom Probe Tomography were performed on a bolt made of cold worked 316 austenitic stainless steel, extracted from the internal structures of a pressurized water reactor after seventeen years of reactor service. The irradiation temperature of these samples was 633 K and the irradiation dose was estimated to 12 dpa. These analyses have shown that neutron irradiation has a strong effect on the intragranular distribution of solute atoms. A very high number density (6.10{sup 23} m{sup -3}) of Ni-Si enriched and Cr-Fe depleted clusters was detected after irradiation. In order to bring complementary experimental results and to determine the mechanism of formation of these Ni-Si nano-clusters, Fe{sup 5+} ion irradiations have been performed on a 316 austenitic stainless steel. As after neutron irradiation, the formation of solute enriched features is observed. Linear features and two kinds of clusters, rounded and torus shaped, are present. Considering that solute enriched features are probably formed by radiation induced segregation on point defect sinks, these different shapes are due to the nature of the sinks where segregation occurs. (authors)

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

Science.gov (United States)

Mohammadzadeh, Roghayeh; Akbari, Alireza; Grumsen, Flemming B.; Somers, Marcel A. J.

2017-10-01

Chromium-rich nitride precipitates in production of nickel-free austenitic stainless steel plates via pressurised solution nitriding of Fe-22.7Cr-2.4Mo ferritic stainless steel at 1473 K (1200 °C) under a nitrogen gas atmosphere was investigated. The microstructure, chemical and phase composition, morphology and crystallographic orientation between the resulted austenite and precipitates were investigated using optical microscopy, X-ray Diffraction (XRD), Scanning and Transmission Electron Microscopy (TEM) and Electron Back Scatter Diffraction (EBSD). On prolonged nitriding, Chromium-rich nitride precipitates were formed firstly close to the surface and later throughout the sample with austenitic structure. Chromium-rich nitride precipitates with a rod or strip-like morphology was developed by a discontinuous cellular precipitation mechanism. STEM-EDS analysis demonstrated partitioning of metallic elements between austenite and nitrides, with chromium contents of about 80 wt.% in the precipitates. XRD analysis indicated that the Chromium-rich nitride precipitates are hexagonal (Cr, Mo)2N. Based on the TEM studies, (Cr, Mo)2N precipitates presented a (1 1 1)γ//(0 0 2)(Cr, Mo)2N, ?γ//?(Cr, Mo)2N orientation relationship with respect to the austenite matrix. EBSD studies revealed that the austenite in the regions that have transformed into austenite and (Cr, Mo)2N have no orientation relation to the untransformed austenite.

Investigation of the applicability of some pre expressions for austenitic stainless steels

International Nuclear Information System (INIS)

Alfonsson, E.; Qvarfort, R.

1992-01-01

The alloying elements known to be most important for the pitting resistance of austenitic stainless steels are chromium, molybdenum and nitrogen. Several authors have tried to quantify the influence of these elements by expressions giving the relative influence of each element. By such an expression a ''pitting resistance equivalent, PRE'', can be calculated for a certain alloy. Recently it has become rather common among both producers and users of stainless steels to discuss pitting resistance in terms of PRE. In the present work, critical pitting temperatures, CPT, was determined in 1 M NaCl for a wide spectrum of austenitic stainless steels. With a newly developed electrochemical cell, the CPT can be determined with high accuracy as crevice corrosion in the specimen mount can be completely eliminated during test. The correlation between the experimental results and some PRE expressions from the literature is discussed

Precipitation of Chromium Nitrides in the Super Duplex Stainless Steel 2507

Science.gov (United States)

Pettersson, Niklas; Pettersson, Rachel F. A.; Wessman, Sten

2015-03-01

Precipitation of chromium nitrides during cooling from temperatures in the range 1373 K to 1523 K (1100 °C to 1250 °C) has been studied for the super duplex stainless steel 2507 (UNS S32750). Characterization with optical, scanning and transmission electron microscopy was combined to quantify the precipitation process. Primarily Cr2N nitrides were found to precipitate with a high density in the interior of ferrite grains. An increased cooling rate and/or an increased austenite spacing clearly promoted nitride formation, resulting in precipitation within a higher fraction of the ferrite grains, and lager nitride particles. Furthermore, formation of the meta-stable CrN was induced by higher cooling rates. The toughness seemed unaffected by nitrides. A slight decrease in pitting resistance was, however, noticed for quenched samples with large amounts of precipitates. The limited adverse effect on pitting resistance is attributed to the small size (~200 nm) of most nitrides. Slower cooling of duplex stainless steels to allow nitrogen partitioning is suggested in order to avoid large nitrides, and thereby produce a size distribution with a smaller detrimental effect on pitting resistance.

Defining the Post-Machined Sub-surface in Austenitic Stainless Steels

Science.gov (United States)

Srinivasan, N.; Sunil Kumar, B.; Kain, V.; Birbilis, N.; Joshi, S. S.; Sivaprasad, P. V.; Chai, G.; Durgaprasad, A.; Bhattacharya, S.; Samajdar, I.

2018-06-01

Austenitic stainless steels grades, with differences in chemistry, stacking fault energy, and thermal conductivity, were subjected to vertical milling. Anodic potentiodynamic polarization was able to differentiate (with machining speed/strain rate) between different post-machined sub-surfaces in SS 316L and Alloy A (a Cu containing austenitic stainless steel: Sanicroe 28™), but not in SS 304L. However, such differences (in the post-machined sub-surfaces) were revealed in surface roughness, sub-surface residual stresses and misorientations, and in the relative presence of sub-surface Cr2O3 films. It was shown, quantitatively, that higher machining speed reduced surface roughness and also reduced the effective depths of the affected sub-surface layers. A qualitative explanation on the sub-surface microstructural developments was provided based on the temperature-dependent thermal conductivity values. The results herein represent a mechanistic understanding to rationalize the corrosion performance of widely adopted engineering alloys.

Defining the Post-Machined Sub-surface in Austenitic Stainless Steels

Science.gov (United States)

Srinivasan, N.; Sunil Kumar, B.; Kain, V.; Birbilis, N.; Joshi, S. S.; Sivaprasad, P. V.; Chai, G.; Durgaprasad, A.; Bhattacharya, S.; Samajdar, I.

2018-04-01

Austenitic stainless steels grades, with differences in chemistry, stacking fault energy, and thermal conductivity, were subjected to vertical milling. Anodic potentiodynamic polarization was able to differentiate (with machining speed/strain rate) between different post-machined sub-surfaces in SS 316L and Alloy A (a Cu containing austenitic stainless steel: Sanicroe 28™), but not in SS 304L. However, such differences (in the post-machined sub-surfaces) were revealed in surface roughness, sub-surface residual stresses and misorientations, and in the relative presence of sub-surface Cr2O3 films. It was shown, quantitatively, that higher machining speed reduced surface roughness and also reduced the effective depths of the affected sub-surface layers. A qualitative explanation on the sub-surface microstructural developments was provided based on the temperature-dependent thermal conductivity values. The results herein represent a mechanistic understanding to rationalize the corrosion performance of widely adopted engineering alloys.

V and Nb Influence on the Austenitic Stainless Steel Corrosion in 0.1 M HCl

Directory of Open Access Journals (Sweden)

Amel GHARBI

2014-05-01

Full Text Available Vanadium and niobium were added in AISI309 austenitic stainless steel composition to modify their structure and pitting corrosion resistance in 0.1 M HCl. The structural characterization was carried out by X-rays diffraction and optical microscopy. Corrosion behavior was investigated using potentiodynamic tests and electrochemical impedance measurements (EIS .Results showed that vanadium and niobium addition precipitated stable carbides (VC, NbC to chromium carbides’ detriment and improved austenitic stainless steel corrosion resistance.

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

Science.gov (United States)

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

2017-09-01

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

Studies of microstructure-property relationships in austenitic stainless steels. Final report

International Nuclear Information System (INIS)

Spruiell, J.E.

1977-01-01

A final review is presented of the research carried out to provide better understanding of elevated temperature service of austenitic stainless steels, and especially the microstructural stability of both wrought-annealed steels and welded joints

Enhancing the capabilities of eddy current techniques for non-destructive evaluation of austenitic stainless steels

International Nuclear Information System (INIS)

Rao, B.P.C.; Thirunavukkarasu, S.; Sasi, B.; Jayakumar, T.; Baldev Raj

2010-01-01

Eddy current non-destructive evaluation (NDE) techniques find many applications during fabrication and in-service inspection of components made of stainless steel. In recent years, concurrent developments in electromagnetic field detection sensors such as giant magneto-resistive (GMR), giant-magneto impedance (GMI) and SQUIDs sensors, computers, microelectronics, and incorporating advanced signal and image processing techniques, have paved the way for enhancing the capabilities of existing eddy current (EC) techniques for examination of austenitic stainless steel (SS) plates, tubes and other geometries and several innovative methodologies have been developed. This paper highlights a few such applications in EC testing to austenitic stainless steel components used in fast reactors. (author)

Effect of shot peening on metastable austenitic stainless steels

Energy Technology Data Exchange (ETDEWEB)

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

2015-08-12

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

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

DEFF Research Database (Denmark)

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

2016-01-01

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

A review of hot cracking in austenitic stainless steel weldments

International Nuclear Information System (INIS)

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

1991-01-01

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

Austenite reversion in low-carbon martensitic stainless steels – a CALPHAD-assisted review

DEFF Research Database (Denmark)

Niessen, Frank

2018-01-01

Low-carbon martensitic stainless steels with 11.5–16 wt-% Cr and martensite upon inter-critical annealing. The review treats...... the mechanisms governing the formation and stabilisation of reverted austenite and is assisted by the computation of phase equilibria. Literature data on Cr and Ni concentrations of the reverted austenite/martensite dual-phase microstructure are assessed with respect to predicted concentrations. Reasonable...... agreement was found for concentrations in martensite. Systematic excess of Cr in austenite of approx. 2 wt-% relative to calculations was suspected to originate from the growth of M23C6 with a coherent interface to austenite. Within large scatter, measured values of Ni in austenite were on average 2 wt...

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

DEFF Research Database (Denmark)

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

2017-01-01

Chromium-rich nitride precipitates in production of nickel-free austenitic stainless steel plates via pressurised solution nitriding of Fe–22.7Cr–2.4Mo ferritic stainless steel at 1473 K (1200 °C) under a nitrogen gas atmosphere was investigated. The microstructure, chemical and phase composition......, morphology and crystallographic orientation between the resulted austenite and precipitates were investigated using optical microscopy, X-ray Diffraction (XRD), Scanning and Transmission Electron Microscopy (TEM) and Electron Back Scatter Diffraction (EBSD). On prolonged nitriding, Chromium-rich nitride...... precipitates were formed firstly close to the surface and later throughout the sample with austenitic structure. Chromium-rich nitride precipitates with a rod or strip-like morphology was developed by a discontinuous cellular precipitation mechanism. STEM-EDS analysis demonstrated partitioning of metallic...

Effects of rare earth metals addition on the resistance to pitting corrosion of super duplex stainless steel - Part 1

International Nuclear Information System (INIS)

Kim, Soon-Tae; Jeon, Soon-Hyeok; Lee, In-Sung; Park, Yong-Soo

2010-01-01

To elucidate the effects of rare earth metals addition on the resistance to pitting corrosion of super duplex stainless steel, a metallographic examination, potentiodynamic and potentiostatic polarization tests, a SEM-EDS and a SAM analysis of inclusion, austenite phase and ferrite phase were conducted. The addition of rare earth metals to the base alloy led to the formation of (Mn, Cr, Si, Al, Ce) oxides and (Mn, Cr, Si, Ce) oxides, which improved the resistance to pitting corrosion and caused a decrease in the preferential interface areas for the initiation of the pitting corrosion.

The improvement of ultrasonic characteristics in weld metal of austenitic stainless steel using magnetic stirring method

International Nuclear Information System (INIS)

Arakawa, T.; Tomisawa, Y.

1988-01-01

The magnetic stirring welding process was tested to save the difficulty of ultrasonic testing of austenitic stainless steel overlayed welds, due to grain refinement of weld solidification structure. The testing involved stirring the molten pool with Lorenz force induced by the interaction of welding current and alternative magnetic field applied from the outside magnetic coil. This report summarizes improvement of ultrasonic characteristic in austenitic stainless steel overlayed welds caused by magnetic stirring welding process

A review of compatibility of IFR fuel and austenitic stainless steel

International Nuclear Information System (INIS)

Keiser, D.D. Jr.

1996-01-01

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

On qualification of TOFD technique for austenitic stainless steel welds inspection

Energy Technology Data Exchange (ETDEWEB)

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

2006-07-01

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

Influence of ageing time on hardness, microstructure and wear behaviour of AISI2507 super duplex stainless steel

Science.gov (United States)

Davanageri, Mahesh; Narendranath, S.; Kadoli, Ravikiran

2017-08-01

The effect of ageing time on hardness, microstructure and wear behaviour of super duplex stainless AISI 2507 is examined. The material was solution treated at 1050 °C and water quenched, further the ageing has been carried out at 850 °C for 30 min, 60 min and 90 min. The chromium (Cr) and molybdenum (Mo) enriched intermetallic sigma phase (σ) were found to precipitate at the ferrite/austenite interface and within the ferrite region. The concentration of intermetallic sigma phase (σ), which was quantified by a combination of scanning electron microscopy and image analysis, increases with increasing ageing time, leading to significant increase in the hardness. The x-ray diffraction (XRD) and energy dispersive x-ray (EDX) was employed to investigate the element distribution and phase identification. Wear characterstics of the aged super duplex stainless steel were measured by varying normal loads, sliding speeds, sliding distance and compared with solution treated (as-cast) specimens. Scanning electron microscopy was used to assist in analysis of worn out surfaces. The outcomes suggested that the increase in percentage of sigma phase increases hardness and wear resistance in heat-treated specimens compared to solution treated specimens (as-cast).

Martensitic transformation of austenitic stainless steel orthodontic wires during intraoral exposure.

Science.gov (United States)

Izquierdo, Paula P; de Biasi, Ronaldo S; Elias, Carlos N; Nojima, Lincoln I

2010-12-01

Our purpose was to study the mechanical properties and phase transformations of orthodontic wires submitted to in-vivo exposure in the mouth for different periods of time. Stainless steel wires were tied to fixed orthodontic appliances of 30 patients from the orthodontics clinic of Universidade Federal do Rio de Janeiro School of Dentistry in Brazil. According to the duration of the clinical treatment, the patients were divided into 3 groups. After in-vivo exposure, the samples were studied by mechanical testing (torsion) and ferromagnetic resonance. Statistical analyses were carried out to evaluate the correlation between time of exposure, mechanical properties, and austenite-to-martensite transformation among the groups. The results were compared with as-received control samples. The torque values increased as time in the mouth increased. The increase in torque resistance showed high correlations with time of exposure (P = 0.005) and austenite-martensite phase transformation. The resistance of stainless steel orthodontic wires increases as the time in the mouth increases; this effect is attributed to the austenite-to-martensite transformation. Copyright © 2010 American Association of Orthodontists. Published by Mosby, Inc. All rights reserved.

Effects of irradiation on the fracture behavior of austenitic stainless steels

International Nuclear Information System (INIS)

Grossbeck, M.L.; Stiegler, J.O.; Holmes, J.J.

1977-01-01

Fracture in irradiated materials occurs by mechanisms which occur in unirradiated materials in addition to mechanisms related to irradiation phenomena. The paper examines radiation effects in austenitic stainless steels for use as core structural materials in fast breeder reactors

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

Energy Technology Data Exchange (ETDEWEB)

Lu, Qiaofeng [Department of Mechanical & Materials Engineering, University of Nebraska–Lincoln, Lincoln, NE 68588 (United States); Su, Qing [Nebraska Center for Energy Sciences Research, University of Nebraska–Lincoln, Lincoln, NE 68588 (United States); Wang, Fei [Department of Mechanical & Materials Engineering, University of Nebraska–Lincoln, Lincoln, NE 68588 (United States); Zhang, Chenfei; Lu, Yongfeng [Department of Electrical Engineering, University of Nebraska–Lincoln, Lincoln, NE 68588 (United States); Nastasi, Michael [Department of Mechanical & Materials Engineering, University of Nebraska–Lincoln, Lincoln, NE 68588 (United States); Nebraska Center for Energy Sciences Research, University of Nebraska–Lincoln, Lincoln, NE 68588 (United States); Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE 68588 (United States); Cui, Bai, E-mail: bcui3@unl.edu [Department of Mechanical & Materials Engineering, University of Nebraska–Lincoln, Lincoln, NE 68588 (United States); Nebraska Center for Materials and Nanoscience, University of Nebraska-Lincoln, Lincoln, NE 68588 (United States)

2017-06-15

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

Strain direction dependency of martensitic transformation in austenitic stainless steels: The effect of gamma-texture

NARCIS (Netherlands)

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

2013-01-01

Uniaxial tensile tests on both a non-textured and a highly textured, fully austenitic stainless steel were performed in both the rolling and the transverse directions. Both materials show mechanically induced phase transformation from the austenitic FCC to the martensitic BCC phase. Differences in

The Microstructure and Properties of Super Martensitic Stainless Steel Microalloyed with Tungsten and Copper

Science.gov (United States)

Ye, Dong; Li, Jun; Liu, Yu-Rong; Yong, Qi-Long; Su, Jie; Cao, Jian-Chun; Tao, Jing-Mei; Zhao, Kun-Yu

2011-06-01

The microstructure and properties of super martensitic stainless steel (SMSS) microalloyed with tungsten and copper were studied by means of optical microscopy, dilatometer, X-ray diffraction, and tensile tests. The results showed that the microstructure of SMSS, after quenching and tempering, was a typical biphase structure with tempered martensite and reversed austenite dispersedly distributed in the martensite matrix. W and Cu were added into the SMSS to reduce the transformation temperature (Ms) and improve the strength and hardness of the matrix by grain refining and solid solution strengthening. Thermocalc calculations confirmed that M23C6 compound and Laves phase were precipitated during tempering in the investigated steel. Compared with the traditional SMSS, the steel microalloyed with W and Cu performed better mechanical properties.

Low-activation Mn-Cr austenitic stainless steel with further reduced content of long-lived radioactive elements

Energy Technology Data Exchange (ETDEWEB)

Onozuka, M.; Saida, T.; Hirai, S. [Mitsubishi Heavy Ind. Ltd., Yokohama (Japan); Kusuhashi, M.; Sato, I.; Hatakeyama, T. [The Japan Steel Works Ltd., Chatsu-machi 4, Muroran 051-8505 (Japan)

1998-06-01

Low-activation austenitic stainless steel based on Mn-Cr non-magnetic steels has been developed. The alloying elements of long-life activation, such as Ni, Mo and Co, were eliminated and substituted with Mn along with an addition of N. A Mn-Cr austenitic stainless steel, 24.5Mn-13.5Cr-0.02C-0.2N, has been developed successfully. Examined material properties, including mechanical, thermal and magnetic properties, as well as weldability and characteristics of corrosion resistance, are presented. It was found that the alloy has excellent material properties virtually equivalent to those of 316SS. In this study, the applicability of the Schaeffler, DeLong and Hull constitution diagrams for the stainless steels with low Ni and high Mn contents was also examined. The boundary conditions distinguishing the single austenite phase from the others have been identified for the Mn-Cr steels. (orig.) 22 refs.

Low-activation Mn Cr austenitic stainless steel with further reduced content of long-lived radioactive elements

Science.gov (United States)

Onozuka, Masanori; Saida, Tomikane; Hirai, Shouzou; Kusuhashi, Mikio; Sato, Ikuo; Hatakeyama, Tsuyoshi

1998-06-01

Low-activation austenitic stainless steel based on Mn-Cr non-magnetic steels has been developed. The alloying elements of long-life activation, such as Ni, Mo and Co, were eliminated and substituted with Mn along with an addition of N. A Mn-Cr austenitic stainless steel, 24.5Mn-13.5Cr-0.02C-0.2N, has been developed successfully. Examined material properties, including mechanical, thermal and magnetic properties, as well as weldability and characteristics of corrosion resistance, are presented. It was found that the alloy has excellent material properties virtually equivalent to those of 316SS. In this study, the applicability of the Schaeffler, DeLong and Hull constitution diagrams for the stainless steels with low Ni and high Mn contents was also examined. The boundary conditions distinguishing the single austenite phase from the others have been identified for the Mn-Cr steels.

Eddy current techniques for super duplex stainless steel characterization

Science.gov (United States)

Camerini, C.; Sacramento, R.; Areiza, M. C.; Rocha, A.; Santos, R.; Rebello, J. M.; Pereira, G.

2015-08-01

Super duplex stainless steel (SDSS) is a two-phase material where the microstructure consists of grains of ferrite (δ) and austenite (γ). SDSS exhibit an attractive combination of properties, such as: strength, toughness and stress corrosion cracking resistance. Nevertheless, SDSS attain these properties after a controlled solution heat treatment, leading to a similar volumetric fraction of δ and γ. Any further heat treatment, welding operation for example, can change the balance of the original phases, or may also lead to precipitation of a deleterious phase, such as sigma (σ). For these situations, the material corrosion resistance is severely impaired. In the present study, several SDSS samples with low σ phase content and non-balanced microstructure were intentionally obtained by thermally treating SDSS specimens. Electromagnetic techniques, conventional Eddy Current Testing (ECT) and Saturated Low Frequency Eddy Current (SLOFEC), were employed to characterize the SDSS samples. The results showed that ECT and SLOFEC are reliable techniques to evaluate σ phase presence in SDSS and can provide an estimation of the δ content.

Hydrogen-Induced Delayed Cracking in TRIP-Aided Lean-Alloyed Ferritic-Austenitic Stainless Steels

Directory of Open Access Journals (Sweden)

Suvi Papula

2017-06-01

Full Text Available Susceptibility of three lean-alloyed ferritic-austenitic stainless steels to hydrogen-induced delayed cracking was examined, concentrating on internal hydrogen contained in the materials after production operations. The aim was to study the role of strain-induced austenite to martensite transformation in the delayed cracking susceptibility. According to the conducted deep drawing tests and constant load tensile testing, the studied materials seem not to be particularly susceptible to delayed cracking. Delayed cracks were only occasionally initiated in two of the materials at high local stress levels. However, if a delayed crack initiated in a highly stressed location, strain-induced martensite transformation decreased the crack arrest tendency of the austenite phase in a duplex microstructure. According to electron microscopy examination and electron backscattering diffraction analysis, the fracture mode was predominantly cleavage, and cracks propagated along the body-centered cubic (BCC phases ferrite and α’-martensite. The BCC crystal structure enables fast diffusion of hydrogen to the crack tip area. No delayed cracking was observed in the stainless steel that had high austenite stability. Thus, it can be concluded that the presence of α’-martensite increases the hydrogen-induced cracking susceptibility.

Microstructural evolution and strain hardening behavior of the cold-drawn austenitic stainless steels

International Nuclear Information System (INIS)

Choi, Jeom Yong; Jin, Won

1998-01-01

The strain induced α ' -martensite formation and the strain hardening behavior of metastable austenitic stainless steel during cold drawing have been investigated. The strain induced α ' -martensite nucleates mainly at the intersection of the mechanical twins rather than ε-martensite. It could be explained by the increase of stacking fault energy which arises from the heat generated during high speed drawing and, for AISI 304/Cu, the additional effect of Cu additions. The strain hardening behavior of austenitic stainless steel is strongly related to the microstructural evolution accompanied by strain induced α ' -martensite. The work hardening rates of cold-drawn 304 increased with increasing interstitial element(C,N) contents which affect the strength of the strain induced α ' -martensite

Resistance Element Welding of Magnesium Alloy/austenitic Stainless Steel

Science.gov (United States)

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

2017-09-01

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

Reversed austenite in 0Cr13Ni4Mo martensitic stainless steels

Energy Technology Data Exchange (ETDEWEB)

Song, Y.Y., E-mail: songyuanyuan@imr.ac.cn [Institute of Metal Research, Chinese Academy of Science, Shenyang 110016 (China); Li, X.Y.; Rong, L.J.; Li, Y.Y. [Institute of Metal Research, Chinese Academy of Science, Shenyang 110016 (China); Nagai, T. [National Institute for Materials Science, Sengen 1-2-1, Tsukuba 305-0047 (Japan)

2014-01-15

The austenite reversion process and the distribution of carbon and other alloying elements during tempering in 0Cr13Ni4Mo martensitic stainless steel have been investigated by in-situ high temperature X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM). The microstructure of the reversed austenite was characterized using transmission electron microscopy (TEM). The results revealed that the amount of the reversed austenite formed at high temperature increased with the holding time. Direct experimental evidence supported carbon partitioning to carbides and Ni to the reversed austenite. The reversed austenite almost always nucleated in contact with lath boundary M{sub 23}C{sub 6} carbides during tempering and the diffusion of Ni promoted its growth. The Ni enrichment and the ultrafine size of the reversed austenite were considered to be the main factors that accounted for the stability of the reversed austenite. - Highlights: • The amount of the reversed austenite formed at high temperature increases with the holding time. • STEM results directly show that carbon is mainly partitioned into the carbides and Ni into the reversed austenite. • The Ni enrichment and the ultrafine size are the main factors leading to the stabilization of the reversed austenite.

Microstructure and properties of 13Cr5Ni1Mo0.025Nb0.09V0.06N super martensitic stainless steel

International Nuclear Information System (INIS)

Ma, X.P.; Wang, L.J.; Liu, C.M.; Subramanian, S.V.

2012-01-01

Highlights: ► Characterization of the microstructures of a commercial martenistic stainless steel. ► Excess N content causes the occurrence of coarse carbo-nitride and Cr 2 N. ► Correlation of microstructures with mechanical and corrosion properties. ► The poor pitting resistance is due to Cr rich precipitates. - Abstract: The morphological microstructure, the density and dispersion of high angle boundaries, morphology and micro chemical composition of precipitates and the volume fraction of retained austenite of a commercial super martensitic stainless steel (SMSS) normalized and tempered at various temperatures were characterized by optical microscope, scanning electron microscope (SEM), electron backscattered diffraction (EBSD), transmission electron microscope (TEM) and X-ray diffraction (XRD) in the light of equilibrium phase diagram of the alloy calculated using Thermo-Calc software. The mechanical properties and pitting corrosion resistance were determined to correlate with microstructures. Two kinds of morphology of precipitate were observed in tempered commercial super martensitic stainless. Besides the globular Nb and V rich carbo-nitride precipitates, rod-like Cr rich nitrides were formed due to excess N content. While high density of high angle boundaries and precipitates contribute to strength properties, the dislocation softening of the matrix and retained austenite from tempering restore the ductility and impact toughness properties. The poor resistance to pitting corrosion is attributed to the occurrence of Cr rich precipitates. It is demonstrated that by lowering the nitrogen content and adding niobium, the Cr rich precipitates can be suppressed and the mechanical properties and resistance to pitting corrosion can be significantly improved.

Influence of helium embrittlement on post-irradiation creep rupture behaviour of austenitic and martensitic stainless steels

International Nuclear Information System (INIS)

Wassilew, C.

1982-01-01

The author has investigated the influence of helium embrittlement on the creep rupture properties of the austenitic stainless steels 1.4970 and 1.4962 and the martensitic stainless steel 1.4914 after irradiation in the BR-2 reactor in Mol, Belgium. The results show that austenitic steels react much more strongly to the embrittlement effect of the helium than do martensitic steels. The causes of the lower embrittlement tendency of the martensitic than of both austenitic stainless steels were analysed carefully. A new embrittlement model was developed on the basis of data derived from the creep rupture experiments, and reinforced by a simple metallographic investigation of the fracture zone and its immediate environment. This model pays specific attention to the role of the twin planes as the most efficient area of increased vacancy production, and takes into account the ability of the twin boundaries to transport these vacancies with reduced energy and low loss into the high-angle grain boundaries. (author)

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

Directory of Open Access Journals (Sweden)

D. PHILIP SELVARAJ

2010-09-01

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

Ultrasonic velocity measurements- a potential sensor for intelligent processing of austenitic stainless steels

International Nuclear Information System (INIS)

Venkadesan, S.; Palanichamy, P.; Vasudevan, M.; Baldev Raj

1996-01-01

Development of sensors based on Non-Destructive Evaluation (NDE) techniques for on-line sensing of microstructure and properties requires a thorough knowledge on the relation between the sensing mechanism/measurement of an NDE technique and the microstructure. As a first step towards developing an on-line sensor for studying the dynamic microstructural changes during processing of austenitic stainless steels, ultrasonic velocity measurements have been carried out to study the microstructural changes after processing. Velocity measurements could follow the progress of annealing starting from recovery, onset and completion of recrystallization, sense the differences in the microstructure obtained after hot deformation and estimate the grain size. This paper brings out the relation between the sensing method based on ultrasonic velocity measurements and the microstructure in austenitic stainless steel. (author)

Evolution behavior of nanohardness after thermal-aging and hydrogen-charging on austenite and strain-induced martensite in pre-strained austenitic stainless steel

Science.gov (United States)

Zheng, Yuanyuan; Zhou, Chengshuang; Hong, Yuanjian; Zheng, Jinyang; Zhang, Lin

2018-05-01

Nanoindentation has been used to study the effects of thermal-aging and hydrogen on the mechanical property of the metastable austenitic stainless steel. Thermal-aging at 473 K decreases the nanohardness of austenite, while it increases the nanohardness of strain-induced ɑ‧ martensite. Hydrogen-charging at 473 K increases the nanohardness of austenite, while it decreases the nanohardness of strain-induced ɑ‧ martensite. The opposite effect on austenite and ɑ‧ martensite is first found in the same pre-strained sample. This abnormal evolution behavior of hardness can be attributed to the interaction between dislocation and solute atoms (carbon and hydrogen). Carbon atoms are difficult to move and redistribute in austenite compared with ɑ‧ martensite. Therefore, the difference in the diffusivity of solute atoms between austenite and ɑ‧ martensite may result in the change of hardness.

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

NARCIS (Netherlands)

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

2008-01-01

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

Attenuation capability of low activation-modified high manganese austenitic stainless steel for fusion reactor system

Energy Technology Data Exchange (ETDEWEB)

Eissa, M.M. [Steel Technology Department, Central Metallurgical Research and Development Institute (CMRDI), Helwan (Egypt); El-kameesy, S.U.; El-Fiki, S.A. [Physics Department, Faculty of Science, Ain Shams University, Cairo (Egypt); Ghali, S.N. [Steel Technology Department, Central Metallurgical Research and Development Institute (CMRDI), Helwan (Egypt); El Shazly, R.M. [Physics Department, Faculty of Science, Al-Azhar University, Cairo (Egypt); Saeed, Aly, E-mail: aly_8h@yahoo.com [Nuclear Power station Department, Faculty of Engineering, Egyptian-Russian University, Cairo (Egypt)

2016-11-15

Highlights: • Improvement stainless steel alloys to be used in fusion reactors. • Structural, mechanical, attenuation properties of investigated alloys were studied. • Good agreement between experimental and calculated results has been achieved. • The developed alloys could be considered as candidate materials for fusion reactors. - Abstract: Low nickel-high manganese austenitic stainless steel alloys, SSMn9Ni and SSMn10Ni, were developed to use as a shielding material in fusion reactor system. A standard austenitic stainless steel SS316L was prepared and studied as a reference sample. The microstructure properties of the present stainless steel alloys were investigated using Schaeffler diagram, optical microscopy, and X-ray diffraction pattern. Mainly, an austenite phase was observed for the prepared stainless steel alloys. Additionally, a small ferrite phase was observed in SS316L and SSMn10Ni samples. The mechanical properties of the prepared alloys were studied using Vickers hardness and tensile tests at room temperature. The studied manganese stainless steel alloys showed higher hardness, yield strength, and ultimate tensile strength than SS316L. On the other hand, the manganese stainless steel elongation had relatively lower values than the standard SS316L. The removal cross section for both slow and total slow (primary and those slowed down in sample) neutrons were carried out using {sup 241}Am-Be neutron source. Gamma ray attenuation parameters were carried out for different gamma ray energy lines which emitted from {sup 60}Co and {sup 232}Th radioactive sources. The developed manganese stainless steel alloys had a higher total slow removal cross section than SS316L. While the slow neutron and gamma rays were nearly the same for all studied stainless steel alloys. From the obtained results, the developed manganese stainless steel alloys could be considered as candidate materials for fusion reactor system with low activation based on the short life

Study of problems associated with the ultrasonic examination of repeatedly repaired austenitic stainless steel welds

International Nuclear Information System (INIS)

Subbaratnam, R.; Palaniappan, M.; Baskaran, A.; Chandramohan, R.

1994-01-01

In recent years the ultrasonic examination of austenitic stainless steel weldments has gained increased importance as an NDE technique for the volumetric examination in the nuclear power plant construction and other industries. A study has been undertaken to evaluate the effects of multiple repairs on austenitic stainless steel weldments, for the successful ultrasonic examination. The test welds have been subjected to repeated welding cycles and the ultrasonic parameters including the defect characterization have been evaluated for analysis. The paper discusses the approach followed, analysis, results obtained and the recommendations based on the above. 1 fig., 2 tabs

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

Directory of Open Access Journals (Sweden)

Sinclair C.W.

2013-11-01

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

Assessment of precipitates of isothermal aged austenitic stainless steel using measurement techniques of ultrasonic attenuation

International Nuclear Information System (INIS)

Kim, Hun Hee; Kim, Hak Joon; Song, Sung Jin; Lim, Byeong Soo; Kim, Kyung Cho

2014-01-01

AISI 316L stainless steel is widely used as a structural material of high temperature thermoelectric power plants, since austenitic stainless steel has excellent mechanical properties. However, creep damage is generated in these components, which are operated under a high temperature and high pressure environment. Several researches have been done on how microstructural changes of precipitates affect to the macroscopic mechanical properties. And they investigate the relation between ultrasonic parameters and metallurgical results. But, these studies are limited by experiment results only. In this paper, attenuations of ultrasonic with isothermal damaged AISI 316L stainless steel were measured. Also, simulation of ultrasonic attenuation with variation of area fraction and size of precipitates were performed. And, from the measured attenuations, metallographic data and simulation results, we investigate the relations between the ultrasonic attenuations and the material properties which is area fraction of precipitates for the isothermal damaged austenitic stainless steel specimens. And, we studied parametric study for investigation of the relation between ultrasonic parameters and metallurgical results of the isothermal damaged AISI 316L stainless steel specimens using numerical methods.

Corrosion resistance of stainless steel pipes in soil

Energy Technology Data Exchange (ETDEWEB)

Sjoegren, L.; Camitz, G. [Swerea KIMAB AB, Box 55970, SE-102 16 Stockholm (Sweden); Peultier, J.; Jacques, S.; Baudu, V.; Barrau, F.; Chareyre, B. [Industeel and ArcelorMittal R and D, 56 rue Clemenceau, BP19, FR-71201 le Creusot, Cedex (France); Bergquist, A. [Outokumpu Stainless AB, P.O. Box 74, SE-774 22 Avesta (Sweden); Pourbaix, A.; Carpentiers, P. [Belgian Centre for Corrosion Study, Avenue des Petits-Champs 4A, BE 1410 Waterloo (Belgium)

2011-04-15

To be able to give safe recommendations concerning the choice of suitable stainless steel grades for pipelines to be buried in various soil environments, a large research programme, including field exposures of test specimens buried in soil in Sweden and in France, has been performed. Resistance against external corrosion of austenitic, super austenitic, lean duplex, duplex and super duplex steel grades in soil has been investigated by laboratory tests and field exposures. The grades included have been screened according to their critical pitting-corrosion temperature and according to their time-to-re-passivation after the passive layer has been destroyed locally by scratching. The field exposures programme, being the core of the investigation, uses large specimens: 2 m pipes and plates, of different grades. The exposure has been performed to reveal effects of aeration cells, deposits or confined areas, welds and burial depth. Additionally, investigations of the tendency of stainless steel to corrode under the influence of alternating current (AC) have been performed, both in the laboratory and in the field. Recommendations for use of stainless steels under different soil conditions are given based on experimental results and on operating experiences of existing stainless steel pipelines in soil. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

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

International Nuclear Information System (INIS)

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

2007-01-01

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

Austenitic stainless steel alloys having improved resistance to fast neutron-induced swelling

International Nuclear Information System (INIS)

1976-01-01

A specification is provided for an austenitic stainless steel consisting of Fe, Cr and Ni, with small amounts of Mo, Mn, Si and Ti. The specification includes a fuel element and a method for cladding a reactor fuel. (U.K.)

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

Science.gov (United States)

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

2018-02-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2015-07-31

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

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

Science.gov (United States)

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

2016-09-01

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

Internal hydrogen-induced subcritical crack growth in austenitic stainless steels

Science.gov (United States)

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

1991-11-01

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

Microstructural features of dissimilar welds between 316LN austenitic stainless steel and alloy 800

International Nuclear Information System (INIS)

Sireesha, M.; Sundaresan, S.

2000-01-01

For joining type 316LN austenitic stainless steel to modified 9Cr-1Mo steel for power plant application, a trimetallic configuration using an insert piece (such as alloy 800) of intermediate thermal coefficient of expansion (CTE) has been sometimes suggested for bridging the wide gap in CTE between the two steels. Two joints are thus involved and this paper is concerned with the weld between 316LN and alloy 800. These welds were produced using three types of filler materials: austenitic stainless steels corresponding to 316,16Cr-8Ni-2Mo, and the nickel-base Inconel 182 1 . The weld fusion zones and the interfaces with the base materials were characterised in detail using light and transmission electron microscopy. The 316 and Inconel 182 weld metals solidified dendritically, while the 16-8-2(16%Cr-8%Ni-2%Mo) weld metal showed a predominantly cellular substructure. The Inconel weld metal contained a large number of inclusions when deposited from flux-coated electrodes, but was relatively inclusion-free under inert gas-shielded welding. Long-term elevated-temperature aging of the weld metals resulted in embrittling sigma phase precipitation in the austenitic stainless steel weld metals, but the nickel-base welds showed no visible precipitation, demonstrating their superior metallurgical stability for high-temperature service. (orig.)

A study on corrosion resistance of dissimilar welds between Monel 400 and 316L austenitic stainless steel

Science.gov (United States)

Mani, Cherish; Karthikeyan, R.; Vincent, S.

2018-04-01

An attempt has been made to study the corrosion resistance of bi-metal weld joints of Monel 400 tube to stainless steel 316 tube by GTAW process. The present research paper contributes to the ongoing research work on the use of Monel400 and 316L austenitic stainless steel in industrial environments. Potentiodynamic method is used to investigate the corrosion behavior of Monel 400 and 316L austenitic stainless steel welded joints. The analysis has been performed on the base metal, heat affected zone and weld zone after post weld heat treatment. Optical microscopy was also performed to correlate the results. The heat affected zone of Monel 400 alloy seems to have the lowest corrosion resistance whereas 316L stainless steel base metal has the highest corrosion resistance.

Electron microscopy and plastic deformation of industrial austenitic stainless steels

International Nuclear Information System (INIS)

Thomas, Barry

1976-01-01

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

Microstructure and properties of 13Cr5Ni1Mo0.025Nb0.09V0.06N super martensitic stainless steel

Energy Technology Data Exchange (ETDEWEB)

Ma, X.P.; Wang, L.J. [Key Laboratory for Anisotropy and Texture of Materials, Northeastern University, Shenyang 110819 (China); Liu, C.M., E-mail: cmliu@mail.neu.edu.cn [Key Laboratory for Anisotropy and Texture of Materials, Northeastern University, Shenyang 110819 (China); Subramanian, S.V. [Department of Materials Science and Engineering, McMaster University, Hamilton, L8S-4L7 (Canada)

2012-03-30

Highlights: Black-Right-Pointing-Pointer Characterization of the microstructures of a commercial martenistic stainless steel. Black-Right-Pointing-Pointer Excess N content causes the occurrence of coarse carbo-nitride and Cr{sub 2}N. Black-Right-Pointing-Pointer Correlation of microstructures with mechanical and corrosion properties. Black-Right-Pointing-Pointer The poor pitting resistance is due to Cr rich precipitates. - Abstract: The morphological microstructure, the density and dispersion of high angle boundaries, morphology and micro chemical composition of precipitates and the volume fraction of retained austenite of a commercial super martensitic stainless steel (SMSS) normalized and tempered at various temperatures were characterized by optical microscope, scanning electron microscope (SEM), electron backscattered diffraction (EBSD), transmission electron microscope (TEM) and X-ray diffraction (XRD) in the light of equilibrium phase diagram of the alloy calculated using Thermo-Calc software. The mechanical properties and pitting corrosion resistance were determined to correlate with microstructures. Two kinds of morphology of precipitate were observed in tempered commercial super martensitic stainless. Besides the globular Nb and V rich carbo-nitride precipitates, rod-like Cr rich nitrides were formed due to excess N content. While high density of high angle boundaries and precipitates contribute to strength properties, the dislocation softening of the matrix and retained austenite from tempering restore the ductility and impact toughness properties. The poor resistance to pitting corrosion is attributed to the occurrence of Cr rich precipitates. It is demonstrated that by lowering the nitrogen content and adding niobium, the Cr rich precipitates can be suppressed and the mechanical properties and resistance to pitting corrosion can be significantly improved.

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

Directory of Open Access Journals (Sweden)

Torchane Lazhar

2014-04-01

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

Effect of Aging on Precipitation Behavior and Pitting Corrosion Resistance of SAF2906 Super Duplex Stainless Steel

Science.gov (United States)

Li, Jianchun; Li, Guoping; Liang, Wei; Han, Peide; Wang, Hongxia

2017-09-01

The effect of aging temperature and holding time on the precipitation of secondary phases and pitting corrosion resistance of SAF2906 super duplex stainless steel was examined. Chromium nitride and σ phase were observed to preferentially precipitate at the ferrite/austenite interface. An amount of nitrides was also observed within the ferrite grain. The precipitation of chromium nitride occurred before the σ phase. The increase in aging temperature and holding time did not affect the concentration of the nitrides but increased the area fraction of the σ phase at a faster rate. The Cr2N precipitation in SAF2906 is more evident than that of the other duplex stainless steels. The variation tendency of the precipitation concentrations is primarily consistent with the prediction results of Thermo-Calc software. The electrochemical results showed that Cr2N and σ phase significantly reduced the pitting potential. Scanning electron microscope observations revealed that pits appear mainly in regions adjacent to sigma phase and Cr2N.

Mechanical Properties of Super Duplex Stainless Steel 2507 after Gas Phase Thermal Precharging with Hydrogen

Science.gov (United States)

San Marchi, C.; Somerday, B. P.; Zelinski, J.; Tang, X.; Schiroky, G. H.

2007-11-01

Thermal precharging of super duplex stainless steel 2507 with 125 wppm hydrogen significantly reduced tensile ductility and fracture toughness. Strain-hardened 2507 exhibited more severe ductility loss compared to the annealed microstructure. The reduction of area (RA) was between 80 and 85 pct for both microstructures in the noncharged condition, while reductions of area were 25 and 46 pct for the strain-hardened and annealed microstructures, respectively, after hydrogen precharging. Similar to the effect of internal hydrogen on tensile ductility, fracture toughness of strain-hardened 2507 was lowered from nearly 300 MPa m1/2 in the noncharged condition to less than 60 MPa m1/2 in the hydrogen-precharged condition. While precharging 2507 with hydrogen results in a considerable reduction in ductility and toughness, the absolute values are similar to high-strength austenitic steels that have been tested under the same conditions, and which are generally considered acceptable for high-pressure hydrogen gas systems. The fracture mode in hydrogen-precharged 2507 involved cleavage cracking of the ferrite phase and ductile fracture along oblique planes in the austenite phase, compared to 100 pct microvoid coalescence in the absence of hydrogen. Predictions from a strain-based micromechanical fracture toughness model were in good agreement with the measured fracture toughness of hydrogen-precharged 2507, implying a governing role of austenite for resistance to hydrogen-assisted fracture.

High Nitrogen Austenitic Stainless Steel Precipitation During Isothermal Annealing

OpenAIRE

Maria Domankova; Katarína Bártová; Ivan Slatkovský; Peter Pinke

2016-01-01

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

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

International Nuclear Information System (INIS)

Zinkle, S.J.; Maziasz, P.J.; Stoller, R.E.

1993-01-01

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

Chemically Induced Phase Transformation in Austenite by Focused Ion Beam

Science.gov (United States)

Basa, Adina; Thaulow, Christian; Barnoush, Afrooz

2014-03-01

A highly stable austenite phase in a super duplex stainless steel was subjected to a combination of different gallium ion doses at different acceleration voltages. It was shown that contrary to what is expected, an austenite to ferrite phase transformation occurred within the focused ion beam (FIB) milled regions. Chemical analysis of the FIB milled region proved that the gallium implantation preceded the FIB milling. High resolution electron backscatter diffraction analysis also showed that the phase transformation was not followed by the typical shear and plastic deformation expected from the martensitic transformation. On the basis of these observations, it was concluded that the change in the chemical composition of the austenite and the local increase in gallium, which is a ferrite stabilizer, results in the local selective transformation of austenite to ferrite.

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

International Nuclear Information System (INIS)

Kohyama, Akira; Donomae, Takako

1999-03-01

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

Grain boundary precipitation in an austenitic stainless steel

International Nuclear Information System (INIS)

Jones, A.R.; Howell, P.R.; Ralph, B.

The precipitation of second phase particles of niobium carbide in an austenitic stainless steel is shown to be considerably influenced by the degree of deformation introduced prior to the ageing treatment. Sites for the nucleation of second phase particles are identified and the importance of one type of nucleation site, extrinsic dislocations, to the evolution of the final boundary precipitate distributions is emphasized. Further, it is shown that the presence of a grain boundary can effect precipitation processes for some considerable distance into the matrix on either side of the boundary. (author)

Plastic deformation and fracture behaviors of nitrogen-alloyed austenitic stainless steels

International Nuclear Information System (INIS)

Wang Songtao; Yang Ke; Shan Yiyin; Li Laifeng

2008-01-01

The plastic deformation and fracture behaviors of two nitrogen-alloyed austenitic stainless steels, 316LN and a high nitrogen steel (Fe-Cr-Mn-0.66% N), were investigated by tensile test and Charpy impact test in a temperature range from 77 to 293 K. The Fe-Cr-Mn-N steel showed ductile-to-brittle transition (DBT) behavior, but not for the 316LN steel. X-ray diffraction (XRD) confirmed that the strain-induced martensite occurred in the 316LN steel, but no such transformation in the Fe-Cr-Mn-N steel. Tensile tests showed that the temperature dependences of the yield strength for the two steels were almost the same. The ultimate tensile strength of the Fe-Cr-Mn-N steel displayed less significant temperature dependence than that of the 316LN steel. The strain-hardening exponent increased for the 316LN steel, but decreased for the Fe-Cr-Mn-N steel, with decreasing temperature. Based on the experimental results and the analyses, a modified scheme was proposed to explain the fracture behaviors of austenitic stainless steels

Mechanical Properties of High Manganese Austenitic Stainless Steel JK2LB for ITER Central Solenoid Jacket Material

Science.gov (United States)

Saito, Toru; Kawano, Katsumi; Yamazaki, Toru; Ozeki, Hidemasa; Isono, Takaaki; Hamada, Kazuya; Devred, Arnaud; Vostner, Alexander

A suite of advanced austenitic stainless steels are used for the ITER TF, CS and PF coil systems.These materials will be exposed to cyclic-stress at cryogenic temperature. Therefore, high manganese austenitic stainless steel JK2LB, which has high tensile strength, high ductility and high resistance to fatigue at 4 K has been chosen for the CS conductor. The cryogenic temperature mechanical property data of this material are very important for the ITER magnet design. This study is focused on mechanical characteristics of JK2LB and its weld joint.

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

International Nuclear Information System (INIS)

Chandra, K.; Kain, Vivekanand; Raja, V.S.; Tewari, R.; Dey, G.K.

2012-01-01

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

Heat treatment giving a stable high temperature micro-structure in cast austenitic stainless steel

Science.gov (United States)

Anton, Donald L.; Lemkey, Franklin D.

1988-01-01

A novel micro-structure developed in a cast austenitic stainless steel alloy and a heat treatment thereof are disclosed. The alloy is based on a multicomponent Fe-Cr-Mn-Mo-Si-Nb-C system consisting of an austenitic iron solid solution (.gamma.) matrix reinforced by finely dispersed carbide phases and a heat treatment to produce the micro-structure. The heat treatment includes a prebraze heat treatment followed by a three stage braze cycle heat treatment.

Effect of both sulphur content and deoxidation degree on the hot ductility of resulphurized austenitic stainless steels in the solidified state

International Nuclear Information System (INIS)

Botella, J.; Sanchez, R.

1998-01-01

The manufacture of free machining austenitic stainless steels features a specific drawback derived from their high sulphur content, which is needed for generating, into the austenitic matrix inclusions to optimize the different machining operations. However, sulphur has ahamfull effect on hot workability. This paper deals with assessing the effect of sulphur content and deoxidation level on the hot ductility of resulphurized austenitic stainless steels in as cast condition. Hot tensile tests were conducted on a Gleeble machine, at temperatures between 1,150 and 1,250 degree celsius, studying a suctility factor as a function of sulphur content, deoxidation degree, as well as type, size and distribution of sulfides. Results point out the harmful effect of increasing sulphur and oxygen contents on the hot workability of resulphurized austenitic stainless steels, and the need to control carefully the level of oxides of these steels. (Author) 5 refs

Austenitic stainless steel alloys having improved resistance to fast neutron-induced swelling

International Nuclear Information System (INIS)

Bloom, E.E.; Stiegler, J.O.; Rowcliffe, A.F.; Leitnaker, J.M.

1979-01-01

The present invention is based on the discovery that radiation-induced voids which occur during fast neutron irradiation can be controlled by small but effective additions of titanium and silicon. The void-suppressing effect of these metals in combination is demonstrated and particularly apparent in austenitic stainless steels

Irradiation Assisted Stress Corrosion Cracking of austenitic stainless steels

Energy Technology Data Exchange (ETDEWEB)

Tsukada, Takashi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

1998-03-01

Irradiation Assisted Stress Corrosion Cracking (IASCC) of austenitic stainless steels in oxygenated high temperature water was studied. The IASCC failure has been considered as a degradation phenomenon potential not only in the present light water reactors but rather common in systems where the materials are exposed simultaneously to radiation and water environments. In this study, effects of the material and environmental factors on the IASCC of austenitic stainless steels were investigated in order to understand the underlying mechanism. The following three types of materials were examined: a series of model alloys irradiated at normal water-cooled research reactors (JRR-3M and JMTR), the material irradiated at a spectrally tailored mixed-spectrum research reactor (ORR), and the material sampled from a duct tube of a fuel assembly used in the experimental LMFBR (JOYO). Post-irradiation stress corrosion cracking tests in a high-temperature water, electrochemical corrosion tests, etc., were performed at hot laboratories. Based on the results obtained, analyses were made on the effects of alloying/impurity elements, irradiation/testing temperatures and material processing, (i.e., post-irradiation annealing and cold working) on the cracking behavior. On the basis of the analyses, possible remedies against IASCC in the core internals were discussed from viewpoints of complex combined effects among materials, environment and processing factors. (author). 156 refs.

Cryogenic properties of V-bearing austenitic stainless steel

International Nuclear Information System (INIS)

Nohara, Kiyohiko

1985-01-01

A new type austenitic stainless steel which is expected as the cryogenic structural material for superconducting magnets has been developed. This steel is that vanadium was added to SUS 316 stainless steel of low carbon and high nitrogen, which has the sufficient strength and toughness at 4 K, and maintains the stable nonmagnetic state. This is applicable both to the solution state and the state of carrying out age hardening heat treatment for precipitating Nb 3 Sn subsequent to it. Accordingly, this material can be applied to the sheath material for nuclear fusion and the manufacture of superconducting magnets by Wind and React process besides the candidate material of superconducting magnets for nuclear fusion. This phenomenon is due to the fact that vanadium carbide precipitates in crystal grains before chrome carbide precipitates at grain boundaries, thus the precipitation of chrome carbide is suppressed. In this experiment, the effect of vanadium addition on the cryogenic properties of SUS 316 stainless steel was examined. The experimental method and the results of the effects of vanadium and nitrogen, solution treatment and precipitation aging, and the measurement of magnetism are reported. (Kako, I.)

On the cryogenic magnetic transition and martensitic transformation of the austenite phase of 7MoPLUS duplex stainless steel

Energy Technology Data Exchange (ETDEWEB)

Lo, K.H., E-mail: KHLO@umac.m [Department of Electromechanical Engineering, University of Macau, Macau (China); Department of Physics and Materials Science, City University of Hong Kong (Hong Kong); Lai, J.K.L. [Department of Physics and Materials Science, City University of Hong Kong (Hong Kong)

2010-08-15

The magnetic behaviour and martensitic transformation at cryogenic temperatures (down to 4 K) of the austenite phase of the duplex stainless steel (DSS), 7MoPLUS, were studied. As regards the prediction of Neel temperature, the empirical expressions for austenitic stainless steels are not applicable to the austenite phase of 7MoPLUS, although the composition of the austenite phase falls within the composition ranges within which the expressions were developed. Regarding the prediction of martensitic point Ms, the applicability of 'old' and recently developed expressions has been examined. The recently developed expressions, which take into account more alloying elements and their interactions, are not suitable for the austenite phase of 7MoPLUS. But for the 'old', simpler expressions, they seem to be valid in the sense that they all predict high stability of the austenite phase. Results obtained from 7MoPLUS were qualitatively the same as those obtained from another DSS, designated as 2205. Reasons for the applicability and inapplicability of these empirical expressions are suggested.

High Nitrogen Austenitic Stainless Steel Precipitation During Isothermal Annealing

Directory of Open Access Journals (Sweden)

Maria Domankova

2016-07-01

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

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

NARCIS (Netherlands)

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

2017-01-01

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

Repair welding of cracked steam turbine blades using austenitic and martensitic stainless-steel consumables

International Nuclear Information System (INIS)

Bhaduri, A.K.; Gill, T.P.S.; Albert, S.K.; Shanmugam, K.; Iyer, D.R.

2001-01-01

The procedure for repair welding of cracked steam turbine blades made of martensitic stainless steels has been developed using the gas tungsten arc welding process. Weld repair procedures were developed using both ER 316L austenitic and ER 410 martensitic stainless-steel filler wire. The overall development of the repair welding procedure included selection of welding consumables (for austenitic filler metal), optimisation of post-weld heat treatment parameters, selection of suitable method for local pre-heating and post-weld heat treatment (PWHT) of the blades, determination of mechanical properties of weldments in as-welded and PWHT conditions, and microsturctural examination. After various trials using different procedures, the procedure of local PWHT (and preheating when using martensitic stainless-steel filler wire) using electrical resistance heating on the top surface of the weldment and monitoring the temperature by placing a thermocouple at the bottom of the weld was found to give the most satisfactory results. These procedures have been developed and/or applied for repair welding of cracked blades in steam turbines

The Formation of Martensitic Austenite During Nitridation of Martensitic and Duplex Stainless Steels

Science.gov (United States)

Zangiabadi, Amirali; Dalton, John C.; Wang, Danqi; Ernst, Frank; Heuer, Arthur H.

2017-01-01

Isothermal martensite/ferrite-to-austenite phase transformations have been observed after low-temperature nitridation in the martensite and δ-ferrite phases in 15-5 PH (precipitation hardening), 17-7 PH, and 2205 (duplex) stainless steels. These transformations, in the region with nitrogen concentrations of 8 to 16 at. pct, are consistent with the notion that nitrogen is a strong austenite stabilizer and substitutional diffusion is effectively frozen at the paraequilibrium temperatures of our experiments. Our microstructural and diffraction analyses provide conclusive evidence for the martensitic nature of these phase transformations.

Austenitic stainless steel alloys having improved resistance to fast neutron-induced swelling

International Nuclear Information System (INIS)

Bloom, E.E.; Stiegler, J.O.; Rowcliffe, A.F.; Leitnaker, J.M.

1977-01-01

The present invention is based on the discovery that radiation-induced voids which occur during fast neutron irradiation can be controlled by small but effective additions of titanium and silicon. The void-suppressing effect of these metals in combination is demonstrated and particularly apparent in austenitic stainless steels. 3 figures, 3 tables

Development of neural network models for the prediction of solidification mode, weld bead geometry and sensitisation in austenitic stainless steels

International Nuclear Information System (INIS)

Vasudevan, M.; Raj, B.; Prasad Rao, K.

2005-01-01

Quantitative models describing the effect of weld composition on the solidification mode, ferrite content and process parameters on the weld bead geometry are necessary in order to design composition of the welding consumable to ensure primary ferritic solidification mode, proper ferrite content and to ensure right choice of process parameters to achieve good bead geometry. A quantitative model on sensitisation behaviour of austenitic stainless steels is also necessary to optimise the composition of the austenitic stainless steel and to limit the strain on the material in order to enhance the resistance to sensitisation. The present paper discuss the development of quantitative models using artificial neural networks to correlate weld metal composition with solidification mode, process parameter with weld bead geometry and time for sensitisation with composition, strain in the material before welding and the temperature of exposure in austenitic stainless steels. (author)

Effect of χ Phase Formation on the Mechanical Properties of 25Cr-7Ni-4Mo-0.2N Super Duplex Stainless Steel

International Nuclear Information System (INIS)

Kang, Chang Yong; Kim, Jae Hwan

2011-01-01

This study was carried out to investigate the precipitation behavior of χ phase and effect of χ-phase which precipitated at the initial stage of aging on mechanical properties of 25%Cr-7%Ni-4%Mo-0.2%N super duplex stainless steel. χ-phase was precipitated mainly at the interface of ferrite / austenite phases and inside of the ferrite phase at the initial stage of aging, and it was transformed into σ-phase with an increase of aging time. The ferrite phase was decomposed into new austenite(γ 2 )phase and σ-phase by aging treatment. The hardness and tensile strength of the initial stage of aging when χ-phase was precipitated did not changed considerably, while elongation rapidly decreased. Accordingly, it is considered that χ-phase didn't affect the hardness and strength significantly, but it affected the elongation.

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

Directory of Open Access Journals (Sweden)

A. Almubarak

2013-01-01

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

Weldability and microstructural analysis of nuclear-grade austenitic stainless steels

International Nuclear Information System (INIS)

Lee, C.H.

1988-01-01

This study evaluated the hot-ductility response, and hot-cracking susceptibility (fusion-zone solidification cracking and HAZ liquation cracking) of modified nuclear-grade and standard austenitic stainless steels. Extensive microstructural characterization using state-of-the-art analytical electron microscopy (TEM and STEM) as well as SEM (EDAX) and OLM was performed to correlate the material behavior with metallurgical characteristics. In addition, studies of the effect of Si, N, and rare earth elements on hot-cracking susceptibility, significance of the ductility dip phenomena and backfilled solidification cracks were also performed. Furthermore, based on the metallurgical evaluation, the possible mechanisms involved in solidification cracking and HAZ liquation cracking of the modified alloys are proposed. Finally, the optimized chemical specifications and requirements for nuclear-grade stainless steels are also suggested

On the grain boundary hardening in a B-bearing 304 austenitic stainless steel

International Nuclear Information System (INIS)

Yao, X.X.

1999-01-01

The precipitates, (Cr,Fe) 23 (C,B) 6 carbides and (Cr,Fe) 2 B borides, formed along the grain boundaries in a 304 austenitic stainless steel containing boron of 33 ppm after solution treatment at 1100 C for 1 h followed by isothermal ageing for 0.5 h at temperatures ranging from 750 to 1050 C have been identified. The influence of these precipitates on the grain boundary hardening has been investigated by means of micro-Vickers hardness measurements. It is found that the degree of grain boundary hardening below 900 C decreases, while it increases above 900 C with increasing ageing temperature. The dissolution of (Cr,Fe) 23 (C,B) 6 carbides and the precipitation of (Cr,Fe) 2 B borides are associated with the changes of grain boundary hardening in this B-bearing 304 austenitic stainless steel between 750 and 1100 C. The non-equilibrium boron segregation enhances the grain boundary hardening when the ageing temperature is above 900 C. (orig.)

Fracture analysis procedure for cast austenitic stainless steel pipe with an axial crack

International Nuclear Information System (INIS)

Kamaya, Masayuki

2012-01-01

Since the ductility of cast austenitic stainless steel pipes decreases due to thermal aging embrittlement after long term operation, not only plastic collapse failure but also unstable ductile crack propagation (elastic-plastic failure) should be taken into account for the structural integrity assessment of cracked pipes. In the fitness-for-service code of the Japan Society of Mechanical Engineers (JSME), Z-factor is used to incorporate the reduction in failure load due to elastic-plastic failure. However, the JSME code does not provide the Z-factor for axial cracks. In this study, Z-factor for axial cracks in aged cast austenitic stainless steel pipes was derived. Then, a comparison was made for the elastic-plastic failure load obtained from different analysis procedures. It was shown that the obtained Z-factor could derive reasonable elastic-plastic failure loads, although the failure loads were more conservative than those obtained by the two-parameter method. (author)

Laser cladding of Colmonoy 6 powder on AISI316L austenitic stainless steel

International Nuclear Information System (INIS)

Zhang, H.; Shi, Y.; Kutsuna, M.; Xu, G.J.

2010-01-01

Stainless steels are widely used in nuclear power plant due to their good corrosion resistance, but their wear resistance is relatively low. Therefore, it is very important to improve this property by surface treatment. This paper investigates cladding Colmonoy 6 powder on AISI316L austenitic stainless steel by CO 2 laser. It is found that preheating is necessary for preventing cracking in the laser cladding procedure and 450 o C is the proper preheating temperature. The effects of laser power, traveling speed, defocusing distance, powder feed rate on the bead height, bead width, penetration depth and dilution are investigated. The friction and wear test results show that the friction coefficient of specimens with laser cladding is lower than that of specimens without laser cladding, and the wear resistance of specimens has been increased 53 times after laser cladding, which reveals that laser cladding layer plays roles on wear resistance. The microstructures of laser cladding layer are composed of Ni-rich austenitic, boride and carbide.

Eddy current techniques for super duplex stainless steel characterization

Energy Technology Data Exchange (ETDEWEB)

Camerini, C., E-mail: cgcamerini@metalmat.ufrj.br [Laboratory of Non-Destructive Testing, Corrosion and Welding, Department of Metallurgical and Materials Engineering, Federal University of Rio de Janeiro (Brazil); Sacramento, R.; Areiza, M.C.; Rocha, A. [Laboratory of Non-Destructive Testing, Corrosion and Welding, Department of Metallurgical and Materials Engineering, Federal University of Rio de Janeiro (Brazil); Santos, R. [PETROBRAS R& D Center, Rio de Janeiro (Brazil); Rebello, J.M.; Pereira, G. [Laboratory of Non-Destructive Testing, Corrosion and Welding, Department of Metallurgical and Materials Engineering, Federal University of Rio de Janeiro (Brazil)

2015-08-15

Super duplex stainless steel (SDSS) is a two-phase material where the microstructure consists of grains of ferrite (δ) and austenite (γ). SDSS exhibit an attractive combination of properties, such as: strength, toughness and stress corrosion cracking resistance. Nevertheless, SDSS attain these properties after a controlled solution heat treatment, leading to a similar volumetric fraction of δ and γ. Any further heat treatment, welding operation for example, can change the balance of the original phases, or may also lead to precipitation of a deleterious phase, such as sigma (σ). For these situations, the material corrosion resistance is severely impaired. In the present study, several SDSS samples with low σ phase content and non-balanced microstructure were intentionally obtained by thermally treating SDSS specimens. Electromagnetic techniques, conventional Eddy Current Testing (ECT) and Saturated Low Frequency Eddy Current (SLOFEC), were employed to characterize the SDSS samples. The results showed that ECT and SLOFEC are reliable techniques to evaluate σ phase presence in SDSS and can provide an estimation of the δ content. - Highlights: • Sigma phase precipitation, even for low amounts, dramatically affects SDSS properties. • SDSS samples were thermally treated and carefully characterized by X-Ray Diffraction. • NDT techniques detected low amounts of sigma phase in SDSS microstructure.

Eddy current techniques for super duplex stainless steel characterization

International Nuclear Information System (INIS)

Camerini, C.; Sacramento, R.; Areiza, M.C.; Rocha, A.; Santos, R.; Rebello, J.M.; Pereira, G.

2015-01-01

Super duplex stainless steel (SDSS) is a two-phase material where the microstructure consists of grains of ferrite (δ) and austenite (γ). SDSS exhibit an attractive combination of properties, such as: strength, toughness and stress corrosion cracking resistance. Nevertheless, SDSS attain these properties after a controlled solution heat treatment, leading to a similar volumetric fraction of δ and γ. Any further heat treatment, welding operation for example, can change the balance of the original phases, or may also lead to precipitation of a deleterious phase, such as sigma (σ). For these situations, the material corrosion resistance is severely impaired. In the present study, several SDSS samples with low σ phase content and non-balanced microstructure were intentionally obtained by thermally treating SDSS specimens. Electromagnetic techniques, conventional Eddy Current Testing (ECT) and Saturated Low Frequency Eddy Current (SLOFEC), were employed to characterize the SDSS samples. The results showed that ECT and SLOFEC are reliable techniques to evaluate σ phase presence in SDSS and can provide an estimation of the δ content. - Highlights: • Sigma phase precipitation, even for low amounts, dramatically affects SDSS properties. • SDSS samples were thermally treated and carefully characterized by X-Ray Diffraction. • NDT techniques detected low amounts of sigma phase in SDSS microstructure

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

DEFF Research Database (Denmark)

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

2015-01-01

This article addresses an investigation of the influence of plastic deformation on low temperature surface hardening by gaseous nitriding of two commercial austenitic stainless steels: AISI 304 and EN 1.4369. The materials were plastically deformed to different equivalent strains by uniaxial...... demonstrate that a case of expanded austenite develops and that, in particular, strain-induced martensite has a large influence on the nitrided zone....

Hardness analysis of welded joints of austenitic and duplex stainless steels

Science.gov (United States)

Topolska, S.

2016-08-01

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

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

DEFF Research Database (Denmark)

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

2015-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

Dau, G; Behravesh, M; Amirato, P; Stone, R [Electric Power Research Inst., Charlotte, NC (United States). Nondestructive Evaluation Center

1988-12-31

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

Stress and Composition of Carbon Stabilized Expanded Austenite on Stainless Steel

DEFF Research Database (Denmark)

Christiansen, Thomas; Somers, Marcel A. J.

2009-01-01

Low-temperature gaseous carburizing of stainless steel is associated with a colossal supersaturation of the fcc lattice with carbon, without the development of carbides. This article addresses the simultaneous determination of stress and composition profiles in layers of carbon xpanded austenite...... obtained by low-temperature gaseous carburizing of AISI 316. X-ray diffraction was applied for the determination of lattice spacing depth profiles by destructive depth profiling and reconstruction of the original lattice spacing profiles from the measured, diffracted intensity weighted, values....... The compressive stress depth distributions correlate with the depth distribution of the strain-free lattice parameter, the latter being a measure for the depth distribution of carbon in expanded austenite. Elastically accommodated compressive stress values as high as -2.7 GPa were obtained, which exceeds...

Integrity of austenitic stainless steel piping welds for nuclear service

International Nuclear Information System (INIS)

Canalini, A.; Lopes, L.R.

1983-01-01

A criterion applying K 1d concept was developed to determine the fracture mechanics properties of austenitic stainless steel nuclear piping welds. The critical dimensions, lenght and depth, for crack initiation were established and plotted in a chart. This study enables the dimensions of a discontinuity detected in an in-service inspection to be compared to the critical dimensions for crack initiation, and the indication can be judged critical or non-critical for the component. (author) [pt

Nanostructure evolution and mechanical property changes during aging of a super duplex stainless steel at 300 °C

Energy Technology Data Exchange (ETDEWEB)

Pettersson, Niklas, E-mail: niklas.pettersson@swerea.se [Swerea KIMAB AB, P.O. Box 7047, SE-164 07 Kista (Sweden); Wessman, Sten [Swerea KIMAB AB, P.O. Box 7047, SE-164 07 Kista (Sweden); Thuvander, Mattias [Department of Applied Physics Chalmers University of Technology, SE-412 96 Göteborg (Sweden); Hedström, Peter; Odqvist, Joakim [Department of Material Science and Engineering, KTH Royal Institute of Technology, SE-100 44 Stockholm (Sweden); Pettersson, Rachel F.A. [The Swedish Steel Producers' Association, Box 1721, SE-111 87 Stockholm (Sweden); Hertzman, Staffan [Outokumpu Stainless Research Foundation, Brinellvägen 23, SE-100 44 Stockholm (Sweden)

2015-10-28

The nanostructure evolution and the corresponding changes in mechanical properties of a super duplex stainless steel 2507 (UNS S32750) during aging at 300 °C up to 12,000 h have been investigated. Microstructural studies using transmission electron microscopy and atom probe tomography show that subtle Cr concentration fluctuations develop during aging. The amplitude of the concentration fluctuations is proportional to the hardness of the ferrite phase, and it is also proportional to the decrease in room temperature impact toughness during aging. The fracture behaviour of the alloy changes gradually from ductile to cleavage fracture, upon aging. The cracks were found to propagate through the ferrite phase, partly along deformation twin interfaces, and delamination between the austenite and ferrite phases was observed.

The Investigation on Strain Strengthening Induced Martensitic Phase Transformation of Austenitic Stainless Steel: A Fundamental Research for the Quality Evaluation of Strain Strengthened Pressure Vessel

Science.gov (United States)

Li, Bo; Cai Ren, Fa; Tang, Xiao Ying

2018-03-01

The manufacture of pressure vessels with austenitic stainless steel strain strengthening technology has become an important technical means for the light weight of cryogenic pressure vessels. In the process of increasing the strength of austenitic stainless steel, strain can induce the martensitic phase transformation in austenite phase. There is a quantitative relationship between the transformation quantity of martensitic phase and the basic mechanical properties. Then, the martensitic phase variables can be obtained by means of detection, and the mechanical properties and safety performance are evaluated and calculated. Based on this, the quantitative relationship between strain hardening and deformation induced martensite phase content is studied in this paper, and the mechanism of deformation induced martensitic transformation of austenitic stainless steel is detailed.

Sensitivity of the magnetization curves of different austenitic stainless tube and pipe steels to mechanical fatigue

International Nuclear Information System (INIS)

Niffenegger, M.; Leber, H.J.

2008-01-01

In meta-stable austenitic stainless steels, fatigue is accompanied by a partial strain-induced transformation of paramagnetic austenite to ferromagnetic martensite [G.B. Olsen, M. Cohen, Kinetics of strain induced martensite nucleation, Metall. Trans. 6 (1975) 791-795]. The associated changes of magnetic properties as the eddy current impedance, magnetic permeability or the remanence field may serve as an indication for the degree of fatigue and therefore the remaining lifetime of a component, even though the exact causal relationship between martensite formation and fatigue is not fully understood. However, measuring these properties by magnetic methods may be limited by the low affinity for strain-induced martensite formation. Thus other methods have to be found which are able to detect very small changes of ferromagnetic contents. With this aim the influence of cyclic strain loading on the magnetization curves of the austenitic stainless tube and pipe steels TP 321, 347, 304L and 316L is analysed in the present paper. The measured characteristic magnetic properties, which are the saturation magnetization, residual magnetization, coercive field and the field dependent permeability (AC-magnetization), are sensitive to fatigue and the corresponding material changes (martensitic transformation). In particular, the AC-magnetization was found to be very sensitive to small changes of the amount of strain induced martensite and therefore also to the degree of fatigue. Hence we conclude that applying magnetic minor loops are promising for the non-destructive evaluation of fatigue in austenitic stainless steel, even if a very small amount of strain induced martensite is formed

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

DEFF Research Database (Denmark)

Nießen, Frank; Villa, Matteo; Apel, Daniel

2016-01-01

The austenitization and inter-critical annealing of X4CrNiMo16-5-1 (1.4418) supermartensitic stainless steel were investigated in-situ with synchrotron X-ray diffraction (XRD), dilatometry and differential scanning calorimetry (DSC) under isochronal heating conditions. Austenitization occurred...... of surface martensite formation on the XRD measurement. The applicable temperature range for DSC as well as the close proximity of the Ac1- and the Curietemperature limited the usage of the technique in the present case....

The characteristics creep fracture of austenitic stainless steels

International Nuclear Information System (INIS)

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

1977-05-01

The characteristics of fracture on creep of two AISI type 316 austenitic stainless steels tested at constant load from 600 to 800 0 C were studied by scanning electron microscopy. The morphological aspects of the fracture were analysed and correllated to the ductility level attained in creep. A marked change from intergranular to transgranular type of fracture was observed in going from 600 to 800 0 C. At 800 0 C on the other hand, the condition for crack nucleation at sigma phase as well as the special conditions of oxidation, are apparently responsible for that same change with the applied stress. (Author) [pt

Mechanical properties of austenitic stainless steels in sodium

International Nuclear Information System (INIS)

Lloyd, G.J.

1978-03-01

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

Study of the Sensitization on the Grain Boundary in Austenitic Stainless Steel Aisi 316

Directory of Open Access Journals (Sweden)

Kocsisová Edina

2014-12-01

Full Text Available Intergranular corrosion (IGC is one of the major problems in austenitic stainless steels. This type of corrosion is caused by precipitation of secondary phases on grain boundaries (GB. Precipitation of the secondary phases can lead to formation of chromium depleted zones in the vicinity of grain boundaries. Mount of the sensitization of material is characterized by the degree of sensitization (DOS. Austenitic stainless steel AISI 316 as experimental material had been chosen. The samples for the study of sensitization were solution annealed on 1100 °C for 60 min followed by water quenching and then sensitization by isothermal annealing on 700 °C and 650 °C with holding time from 15 to 600 min. Transmission electron microscopy (TEM was used for identification of secondary phases. Electron backscattered diffraction (EBSD was applied for characterization of grain boundary structure as one of the factors which influences on DOS.

Equi-biaxial loading effect on austenitic stainless steel fatigue life

Directory of Open Access Journals (Sweden)

C. Gourdin

2016-10-01

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

Overview of microstructural evolution in neutron-irradiated austenitic stainless steels

International Nuclear Information System (INIS)

Maziasz, P.J.

1993-01-01

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

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

Science.gov (United States)

Maziasz, Philip J.

2018-01-01

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

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

International Nuclear Information System (INIS)

Prajitno, Djoko Hadi; Syarif, Dani Gustaman

2014-01-01

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

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

NARCIS (Netherlands)

Perdahcioglu, Emin Semih; Geijselaers, Hubertus J.M.

2012-01-01

Mechanically induced martensitic transformation and the associated transformation plasticity phenomena in austenitic stainless steels are studied. The mechanisms responsible for the transformation are investigated and put into perspective based on experimental evidence. The stress and strain

Precipitation and cavity formation in austenitic stainless steels during irradiation

International Nuclear Information System (INIS)

Lee, E.H.; Rowcliffe, A.F.; Mansur, L.K.

1982-01-01

Microstructural evolution in austenitic stainless steels subjected to displacement damage at high temperature is strongly influenced by the interaction between helium atoms and second phase particles. Cavity nucleation occurs by the trapping of helium at partially coherent particle-matrix interfaces. The recent precipitate point defect collector theory describes the more rapid growth of precipitate-attached cavities compared to matrix cavities where the precipitate-matrix interface collects point defects to augment the normal point deflect flux to the cavity. Data are presented which support these ideas. It is shown that during nickel ion irradiation of a titanium-modified stainless steel at 675 0 C the rate of injection of helium has a strong effect on the total swelling and also on the nature and distribution of precipitate phases. (orig.)

G-phase precipitation in austenitic stainless steel deformed by high pressure torsion

International Nuclear Information System (INIS)

Shuro, I.; Kuo, H.H.; Sasaki, T.; Hono, K.; Todaka, Y.; Umemoto, M.

2012-01-01

Highlights: ► Using TEM and APT analyses, G-phase precipitation was observed in HPTed SUS304 with no trace of spinodal decomposition. ► G-phase precipitation occurred much shorter time than previous studies probably due to the elimination of prior SD and enhanced diffusion by severe plastic deformation. ► G-phase composition is a function of aging time. ► Tensile tests showed that in SUS304 embrittlement occurs solely due to G-phase precipitation. - Abstract: G phase an intermetallic silicide has been observed in martensite of precipitation hardened stainless steels and in the ferrite of dual (austenite and ferrite) phase stainless steels. In both cases, before G-phase precipitates, the matrix composition changes due to spinodal decomposition and solute partitioning between ferrite and austenite. Thus in the present study, single bcc phase and high Ni content stainless steel, was selected to study G-phase precipitation expecting elimination of the interference from spinodal decomposition and solute partitioning. Fe–18Cr–8Ni (SUS304) austenitic stainless steel samples were deformed at room temperature by high pressure torsion to obtain 100% volume fraction of deformation induced martensite (α′). HPT deformation was chosen due to its ability to induce high strength by grain refinement and also attain 100% α′ at room temperature. After annealing at 400 °C for 500 h, G-phase precipitation was observed in the fully martensitic matrix without spinodal decomposition. Crystallographic analysis of annealed samples using high resolution transmission electron microscopy (HRTEM) and energy dispersive spectroscopy (EDS) detected a Mn–Ni–Si rich G-phase with fcc crystal structure with lattice parameter of 1.16 nm. The value of lattice parameter corresponds well with previously reported values. Chemical analysis by atom probe tomography (APT) showed G-phase of composition Mn 21 Ni 50 Si 24 Fe 4 Cr. Tensile tests showed that G-phase precipitation leads to

G-phase precipitation in austenitic stainless steel deformed by high pressure torsion

Energy Technology Data Exchange (ETDEWEB)

Shuro, I., E-mail: innoshuro@martens.me.tut.ac.jp [Functional Materials Engineering, Toyohashi University of Technology, 1-1, Toyohashi, Aichi 441-8580 (Japan); Kuo, H.H. [Functional Materials Engineering, Toyohashi University of Technology, 1-1, Toyohashi, Aichi 441-8580 (Japan); Sasaki, T.; Hono, K. [National Institute for Materials Sciences, Sengen 1-2-1, Tsukuba 305-0047 (Japan); Todaka, Y.; Umemoto, M. [Functional Materials Engineering, Toyohashi University of Technology, 1-1, Toyohashi, Aichi 441-8580 (Japan)

2012-08-30

Highlights: Black-Right-Pointing-Pointer Using TEM and APT analyses, G-phase precipitation was observed in HPTed SUS304 with no trace of spinodal decomposition. Black-Right-Pointing-Pointer G-phase precipitation occurred much shorter time than previous studies probably due to the elimination of prior SD and enhanced diffusion by severe plastic deformation. Black-Right-Pointing-Pointer G-phase composition is a function of aging time. Black-Right-Pointing-Pointer Tensile tests showed that in SUS304 embrittlement occurs solely due to G-phase precipitation. - Abstract: G phase an intermetallic silicide has been observed in martensite of precipitation hardened stainless steels and in the ferrite of dual (austenite and ferrite) phase stainless steels. In both cases, before G-phase precipitates, the matrix composition changes due to spinodal decomposition and solute partitioning between ferrite and austenite. Thus in the present study, single bcc phase and high Ni content stainless steel, was selected to study G-phase precipitation expecting elimination of the interference from spinodal decomposition and solute partitioning. Fe-18Cr-8Ni (SUS304) austenitic stainless steel samples were deformed at room temperature by high pressure torsion to obtain 100% volume fraction of deformation induced martensite ({alpha} Prime ). HPT deformation was chosen due to its ability to induce high strength by grain refinement and also attain 100% {alpha} Prime at room temperature. After annealing at 400 Degree-Sign C for 500 h, G-phase precipitation was observed in the fully martensitic matrix without spinodal decomposition. Crystallographic analysis of annealed samples using high resolution transmission electron microscopy (HRTEM) and energy dispersive spectroscopy (EDS) detected a Mn-Ni-Si rich G-phase with fcc crystal structure with lattice parameter of 1.16 nm. The value of lattice parameter corresponds well with previously reported values. Chemical analysis by atom probe tomography

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

Science.gov (United States)

Verma, Jagesvar; Taiwade, Ravindra V.

2016-11-01

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

Corrosion Study of Super Ferritic Stainless Steel UNS S44660 (26Cr-3Ni-3Mo) and Several Other Stainless Steel Grades (UNS S31603, S32101, and S32205) in Caustic Solution Containing Sodium Sulfide

Science.gov (United States)

Chasse, Kevin R.; Singh, Preet M.

2013-11-01

Electrochemical techniques, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) were used in this study to show how the corrosion mechanism of several commercial grades of stainless steel in hot caustic solution is strongly influenced by the presence of sodium sulfide. Experimental results from super ferritic stainless steel UNS S44660 (26Cr-3Ni-3Mo) were compared to austenitic stainless steel UNS S31603, lean duplex stainless steel (DSS) UNS S32101, and standard DSS UNS S32205 in caustic solution, with and without sodium sulfide, at 443 K (170 °C). Weight loss measurements indicated that corrosion rates of UNS44660 were much lower than the other grades of stainless steel in the presence of the sodium sulfide. Potentiodynamic polarization and linear polarization resistance measurements showed that the electrochemical behavior was altered by the adhesion of sulfur species, which reduced the polarization resistances and increased the anodic current densities. SEM and XPS results imply that the surface films that formed in caustic solution containing sodium sulfide were defective due to the adsorption of sulfide, which destabilized the passive film and led to the formation of insoluble metal sulfide compounds.

Characterization of the martensite phase formed during hydrogen ion irradiation in austenitic stainless steel

Science.gov (United States)

Jin, Hyung-Ha; Lim, Sangyeob; Kwon, Junhyun

2017-10-01

Microstructural changes in austenitic stainless steel caused by hydrogen ion irradiation were investigated using transmission electron microscopy (TEM). It has been confirmed that the irradiation induced the formation of martensite along the grain boundary; the martensite phase exhibited a crystal orientation relationship with the adjacent austenite phase. The results of this study also indicate that the concentration of Cr in the martensite phase is lower compared to that in the austenite matrix. The TEM results showed the development of asymmetric radiation-induced segregation (RIS) near the grain boundary, which leads to local changes in the chemical composition such as reduction of Cr near the grain boundary. The asymmetric RIS serves as a prerequisite for the formation of the martensite under hydrogen irradiation.

Sigma phase morphologies in cast and aged super duplex stainless steel

International Nuclear Information System (INIS)

Martins, Marcelo; Casteletti, Luiz Carlos

2009-01-01

Solution annealed and water quenched duplex and super duplex stainless steels are thermodynamically metastable systems at room temperature. These systems do not migrate spontaneously to a thermodynamically stable condition because an energy barrier separates the metastable and stable states. However, any heat input they receive, for example through isothermal treatment or through prolonged exposure to a voltaic arc in the welding process, cause them to reach a condition of stable equilibrium which, for super duplex stainless steels, means precipitation of intermetallic and carbide phases. These phases include the sigma phase, which is easily identified from its morphology, and its influence on the material's impact strength. The purpose of this work was to ascertain how 2-hour isothermal heat treatments at 920 deg. C and 980 deg. C affect the microstructure of ASTM A890/A890M GR 6A super duplex stainless steel. The sigma phase morphologies were found to be influenced by these two aging temperatures, with the material showing a predominantly lacy microstructure when heat treated at 920 deg. C and block-shaped when heat treated at 980 deg. C.

Hydrogen embrittlement of austenitic stainless steels revealed by deformation microstructures and strain-induced creation of vacancies

International Nuclear Information System (INIS)

Hatano, M.; Fujinami, M.; Arai, K.; Fujii, H.; Nagumo, M.

2014-01-01

Hydrogen embrittlement of austenitic stainless steels has been examined with respect to deformation microstructures and lattice defects created during plastic deformation. Two types of austenitic stainless steels, SUS 304 and SUS 316L, uniformly hydrogen-precharged to 30 mass ppm in a high-pressure hydrogen environment, are subjected to tensile straining at room temperature. A substantial reduction of tensile ductility appears in hydrogen-charged SUS 304 and the onset of fracture is likely due to plastic instability. Fractographic features show involvement of plasticity throughout the crack path, implying the degradation of the austenitic phase. Electron backscatter diffraction analyses revealed prominent strain localization enhanced by hydrogen in SUS 304. Deformation microstructures of hydrogen-charged SUS 304 were characterized by the formation of high densities of fine stacking faults and ε-martensite, while tangled dislocations prevailed in SUS 316L. Positron lifetime measurements have revealed for the first time hydrogen-enhanced creation of strain-induced vacancies rather than dislocations in the austenitic phase and more clustering of vacancies in SUS 304 than in SUS 316L. Embrittlement and its mechanism are ascribed to the decrease in stacking fault energies resulting in strain localization and hydrogen-enhanced creation of strain-induced vacancies, leading to premature fracture in a similar way to that proposed for ferritic steels

Effects of sulfur addition on pitting corrosion and machinability behavior of super duplex stainless steel containing rare earth metals: Part 2

International Nuclear Information System (INIS)

Jeon, Soon-Hyeok; Kim, Soon-Tae; Lee, In-Sung; Park, Yong-Soo

2010-01-01

Research highlights: → The mechanisms on the effects of rare earth metals (REM) and sulfur (S) additions on the initiation and propagation of pitting corrosion and machinabillity of a super duplex stainless steel (SDSS) were elucidated → It was found that, in consideration of the ratio of lifetime (the resistance to pitting corrosion) to cost (machining and raw material), a costly austenitic stainless steel with high Ni , medium Mo and low N can be replaced by the high S and REM added SDSS with 7 wt.% Ni-4 wt% Mo-0.3 wt.% N → The resistance to pitting corrosion of the tested super duplex stainless steel was affected by the type of inclusions, the preferential interface areas between inclusions and the substrate, and the PREN difference between the γ-phase and the α-phase for the initiation and propagation of the pitting corrosion. - Abstract: To elucidate the effects of sulfur addition on pitting corrosion and machinability behavior of alloys containing rare earth metals, a potentiostatic polarization test, a critical pitting temperature test, a SEM-EDS analysis of inclusions, and a tool life test were conducted. As sulfur content increased, the resistance to pitting corrosion decreased due to the formation of numerous manganese sulfides deteriorating the corrosion resistance and an increase in the preferential interface areas for the initiation of the pitting corrosion. With an increase in sulfur content, the tool life increased due to the lubricating films of manganese sulfides adhering to tool surface.

Mass transfer behavior of a modified austenitic stainless steel in lithium

International Nuclear Information System (INIS)

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

1983-01-01

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

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

DEFF Research Database (Denmark)

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

2016-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

Sen, Indrani [Department of Materials Engineering, Indian Institute of Science, Bangalore 560012 (India); Amankwah, E. [Department of Materials Engineering, Indian Institute of Science, Bangalore 560012 (India); Department of Materials Science, African University of Science and Technology, Abuja (Nigeria); Kumar, N.S. [Department of Materials Engineering, Indian Institute of Science, Bangalore 560012 (India); Fleury, E. [Center for High Temperature Energy Materials, Korea Institute of Science and Technology, Seoul 136-791 (Korea, Republic of); Oh-ishi, K.; Hono, K. [National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan); Ramamurty, U., E-mail: ramu@materials.iisc.ernet.in [Department of Materials Engineering, Indian Institute of Science, Bangalore 560012 (India)

2011-05-25

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

Overview of Strategies for High-Temperature Creep and Oxidation Resistance of Alumina-Forming Austenitic Stainless Steels

Science.gov (United States)

Yamamoto, Y.; Brady, M. P.; Santella, M. L.; Bei, H.; Maziasz, P. J.; Pint, B. A.

2011-04-01

A family of creep-resistant, alumina-forming austenitic (AFA) stainless steel alloys is under development for structural use in fossil energy conversion and combustion system applications. The AFA alloys developed to date exhibit comparable creep-rupture lives to state-of-the-art advanced austenitic alloys, and superior oxidation resistance in the ~923 K to 1173 K (650 °C to 900 °C) temperature range due to the formation of a protective Al2O3 scale rather than the Cr2O3 scales that form on conventional stainless steel alloys. This article overviews the alloy design approaches used to obtain high-temperature creep strength in AFA alloys via considerations of phase equilibrium from thermodynamic calculations as well as microstructure characterization. Strengthening precipitates under evaluation include MC-type carbides or intermetallic phases such as NiAl-B2, Fe2(Mo,Nb)-Laves, Ni3Al-L12, etc. in the austenitic single-phase matrix. Creep, tensile, and oxidation properties of the AFA alloys are discussed relative to compositional and microstructural factors.

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

Science.gov (United States)

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

2016-07-01

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

Low temperature sensitization of austenitic stainless steel: an ageing effect during BWR service

International Nuclear Information System (INIS)

Shah, B.K.; Sinha, A.K.; Rastogi, P.K.; Kulkarni, P.G.

1994-01-01

Sensitization in austenitic stainless steel refers to chromium carbide precipitation at the grain boundaries with concomitant depletion of chromium below 12% near grain boundaries. This makes the material susceptible to either intergranular corrosion (IGC) or intergranular stress corrosion cracking (IGSCC). This effect is predominant whenever austenitic stainless steel is subjected to thermal exposure in the temperature range 723-1073K either during welding or during heat treatment. Low temperature sensitization (LTS) refers to sensitization at temperature below the typical range of sensitization i.e. 723-1073K. A prerequisite for LTS phenomenon is reported to be the presence of chromium carbide nuclei at the grain boundaries which can grow during boiling water reactor service even at a relatively lower temperature of around 560K. LTS can lead to failure of BWR pipe due to IGSCC. The paper reviews the phenomenological and mechanistic aspects of LTS. Studies carried out regarding effect of prior cold work on LTS are reported. Summary of the studies reported in literature to examine the occurrence of LTS during BWR service has also been included. (author). 10 refs., 3 figs

SCC of cold-worked austenitic stainless steels exposed to PWR primary water conditions: susceptibility to initiation

International Nuclear Information System (INIS)

Herms, E.; Raquet, O.; Sejourne, L.; Vaillant, F.

2009-01-01

Heavily cold-worked austenitic stainless steels (AISI 304L and 316L types) could be significantly susceptible to Stress Corrosion Cracking (SCC) when exposed to PWR nominal primary water conditions even in absence of any pollutants. Susceptibility to SCC was shown to be related with some conditions such as initial hardness, procedure of cold-work or dynamic straining. A dedicated program devoted to better understand the initiation stage on CW austenitic stainless steels in PWR water is presented. Initiation is studied thanks to SCC test conditions leading to an intergranular cracking propagation mode on a CW austenitic stainless steel which is the mode generally reported after field experience. SCC tests are carried out in typical primary water conditions (composition 1000 ppm B and 2 ppm Li) and for temperature in the range 290 - 340 C. Material selected is 316L cold-worked essentially by rolling (reduction in thickness of 40%). Initiation tests are carried out under various stress levels with the aim to investigate the evolution of the initiation period versus the value of applied stress. SCC tests are performed on cylindrical notched specimens in order to increase the applied stress and allow accelerated testing without modify the exposure conditions to strictly nominal hydrogenated PWR water. Respective influences of cyclic/dynamic conditions on SCC initiation are presented and discussed. Dedicated interrupted tests help to investigate the behaviour of the crack initiation process. These SCC tests have shown that crack initiation could be obtained after a very short time under dynamic loading conditions on heavily pre-strained austenitic stainless steels. Actual results show that the most limiting stage of the cracking process on CW 316L seems to be the transition from slow transgranular propagation of surface initiated cracks to intergranular fast propagation through the thickness of the sample. The duration of this stage during crack initiation tests is

Stress distributions due to hydrogen concentrations in electrochemically charged and aged austenitic stainless steel

International Nuclear Information System (INIS)

Rozenak, P.; Loew, A.

2008-01-01

As a result of hydrogen concentration gradients in type austenitic stainless steels, formed during electrochemical charging and followed by hydrogen loss during aging, at room temperature, surface stresses were developed. These stresses were measured by X-ray technique and the crack formation thus induced could be studied using equilibrium stress equations. After various electrochemical charging and aging times, X-ray diffraction patterns obtained from samples indicated that the reflected and broadened diffraction peaks are the result of the formation of a non-uniform but continuous solid solution in the austenitic matrix. Since both hydrogen penetrations during charging and hydrogen release during aging are diffusion controlled processes and huge hydrogen concentration gradients in the thin surface layer, at depths comparable with the depth of X-ray penetration, are observed. The non-uniform hydrogen concentration in the austenitic matrix, results to the non-uniform expansion of the atomic microstructure and latter inevitably leads to the development of internal stresses. The internal stresses development formulae's are very similar to those relating to non-uniform heating of the materials, where thermal stresses appear due to non-uniform expansion or contraction. The relevant well developed theory is applicable in our case of non-uniform hydrogen concentrations in a solid solution of electrochemically charged and aged austenitic matrix. A few cracks were present on the surface after some minutes of electrochemical charging and the severity of cracking increased as hydrogen was lost during subsequent aging. This is consistent with the expectation of high compressive stresses in the bulk of the specimen during charging and high tensile surface stresses (at the level of 1 x 10 11 Pa) during the aging process. These stresses can induce the formation of surface cracks during the aging process after electrochemical charging in the AISI 316 stainless steel

Deformation mechanisms induced under high cycle fatigue tests in a metastable austenitic stainless steel

Energy Technology Data Exchange (ETDEWEB)

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

2014-03-01

Advanced techniques were used to study the deformation mechanisms induced by fatigue tests in a metastable austenitic stainless steel AISI 301LN. Observations by Atomic Force Microscopy were carried out to study the evolution of a pre-existing martensite platelet at increasing number of cycles. The sub-superficial deformation mechanisms of the austenitic grains were studied considering the cross-section microstructure obtained by Focused Ion Beam and analysed by Scanning Electron Microscopy and Transmission Electron Microscopy. The results revealed no deformation surrounding the pre-existing martensitic platelet during fatigue tests, only the growth on height was observed. Martensite formation was associated with shear bands on austenite, mainly in the {111} plane, and with the activation of the other intersecting austenite {111}〈110〉 slip system. Furthermore, transmission electron microscopy results showed that the nucleation of ε-martensite follows a two stages phase transformation (γ{sub fcc}→ε{sub hcp}→α'{sub bcc})

Optimized chemical composition, working and heat treatment condition for resistance to irradiation assisted stress corrosion cracking of cold worked 316 and high-chromium austenitic stainless steel

International Nuclear Information System (INIS)

Yonezawa, Toshio; Iwamura, Toshihiko; Fujimoto, Koji; Ajiki, Kazuhide

2000-01-01

The authors have reported that the primary water stress corrosion cracking (PWSCC) in baffle former bolts made of austenitic stainless steels for PWR after long-term operation is caused by irradiation-induced grain boundary segregation. The resistance to PWSCC of simulated austenitic stainless steels whose chemical compositions are simulated to the grain boundary chemical composition of 316 stainless steel after irradiation increased with decrease of the silicon content, increases of the chromium content, and precipitation of M 23 C 6 carbides at the grain boundaries. In order to develop resistance to irradiation assisted stress corrosion cracking in austenitic stainless steels, optimized chemical compositions and heat treatment conditions for 316CW and high-chromium austenitic stainless steels for PWR baffle former bolts were investigated. For 316CW stainless steel, ultra-low-impurities and high-chromium content are beneficial. About 20% cold working before aging and after solution treatment has also been recommended to recover sensitization and make M 23 C 6 carbides coherent with the matrix at the grain boundaries. Heating at 700 to 725degC for 20 to 50 h was selected as a suitable aging procedure. Cold working of 5 to 10% after aging produced the required mechanical properties. The optimized composition of the high-chromium austenitic stainless steel contents 30% chromium, 30% nickel, and ultra-low impurity levels. This composition also reduces the difference between its thermal expansion coefficient and that of 304 stainless steel for baffle plates. Aging at 700 to 725degC for longer than 40 h and cold working of 10 to 15% after aging were selected to meet mechanical property specifications. (author)

Magnetic properties of the austenitic stainless steels at cryogenic temperatures

International Nuclear Information System (INIS)

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

2002-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2014-03-24

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

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

DEFF Research Database (Denmark)

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

1979-01-01

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

Fatigue behaviour of friction welded medium carbon steel and austenitic stainless steel dissimilar joints

International Nuclear Information System (INIS)

Paventhan, R.; Lakshminarayanan, P.R.; Balasubramanian, V.

2011-01-01

Research highlights: → Fusion welding of dissimilar metals is a problem due to difference in properties. → Solid state welding process such as friction welding is a solution for the above problem. → Fatigue life of friction welded carbon steel and stainless steel joints are evaluated. → Effect of notch on the fatigue life of friction welded dissimilar joints is reported. → Formation of intermetallic is responsible for reduction in fatigue life of dissimilar joints. -- Abstract: This paper reports the fatigue behaviour of friction welded medium carbon steel-austenitic stainless steel (MCS-ASS) dissimilar joints. Commercial grade medium carbon steel rods of 12 mm diameter and AISI 304 grade austenitic stainless steel rods of 12 mm diameter were used to fabricate the joints. A constant speed, continuous drive friction welding machine was used to fabricate the joints. Fatigue life of the joints was evaluated conducting the experiments using rotary bending fatigue testing machine (R = -1). Applied stress vs. number of cycles to failure (S-N) curve was plotted for unnotched and notched specimens. Basquin constants, fatigue strength, fatigue notch factor and notch sensitivity factor were evaluated for the dissimilar joints. Fatigue strength of the joints is correlated with microstructure, microhardness and tensile properties of the joints.

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

DEFF Research Database (Denmark)

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

2015-01-01

This article addresses an investigation of the influence of plastic deformation on low temperature surface hardening by gaseous nitriding of three commercial austenitic stainless steels: AISI 304, EN 1.4369 and Sandvik Nanoflex® with various degrees of austenite stability. The materials were...... case included X-ray diffraction analysis, reflected light microscopy and microhardness. The results demonstrate that a case of expanded austenite develops and that, in particular, strain-induced martensite has a large influence on the nitrided zone....

Experimental Analysis of Residual Stresses in Samples of Austenitic Stainless Steel Welded on Martensitic Stainless Steel Used for Kaplan Blades Repairs

Directory of Open Access Journals (Sweden)

Vasile Cojocaru

2011-01-01

Full Text Available Residual stresses occur in materials as a result of mechanical processes: welding, machining, grinding etc. If residual stresses reach high values they can accelerate the occurrence of cracks and erosion of material. An experimental research was made in order to study the occurrence of residual stresses in the repaired areas of hydraulic turbine components damaged by cavitation erosion. An austenitic stainless steel was welded in various layer thicknesses on a martensitic stainless steel base. The residual stresses were determined using the hole drilling strain gage method.

Corrosion of silicon-containing austenitic stainless steels under trans-passive conditions

International Nuclear Information System (INIS)

Stolarz, Jacek

1989-01-01

This research thesis addresses austenitic stainless steels which are used in installations for the chemical treatment of nuclear fuels, and are there in contact with nitric acid solutions the oxidising character of which generally promotes metal passivity. However, if this nitric environment becomes too oxidising, these steels may face severe corrosion problems. More particularly, this thesis addresses the study of intergranular corrosion, and aims at analysing various aspects of the corrosion of these austenitic stainless steels in trans-passive conditions. The author aims at determining and distinguishing the contributions due to silicon and those related to the presence of other impurities and addition elements by comparing the behaviours of industrial grade steels and high purity alloys in rigorously controlled electrochemical conditions. Another objective is to study the influence of the intergranular structure on silicon segregation by means of an attack technique in trans-passive conditions. After a report of a bibliographical study on the addressed topics and a presentation of the studied materials and implemented experimental techniques, the author reports the study of steel behaviour with respect to generalised dissolution in trans-passive conditions, as well in the nitric environment as in a sulphuric acid solution at imposed potential. Localised intragranular corrosion phenomena are discussed. A trans-passive intragranular corrosion model is proposed, and its possibilities in the analysis of intergranular segregation analysis are discussed. Experimental results of trans-passive intergranular corrosion of stainless steels are presented and interpreted by using the McLean segregation model. The influence of steel composition and of experimental conditions is discussed, as well as the role of grain boundary structure in the corrosion process [fr

Failures of austenitic stainless steel components during storage: Case studies

International Nuclear Information System (INIS)

Shah, B.K.; Rastogi, P.K.; Sinha, A.K.; Kulkarni, P.G.

1993-01-01

Three studies of failures of austenitic stainless steel components during storage are described. In all cases, stress corrosion cracking was the failure mode by the action of residual stress alone. However, the source of residual stress was different for each case. Case 1 was the failure of a sample tube header for a pressurized heavy water reactor (PHWR). In Case 2, a heat exchanger shell failed during a hydrotest in a fertilizer plant. Cases concerned the cracking of type 304L plates used for spent fuel pool lining of a nuclear power station

Dilution and Ferrite Number Prediction in Pulsed Current Cladding of Super-Duplex Stainless Steel Using RSM

Science.gov (United States)

Eghlimi, Abbas; Shamanian, Morteza; Raeissi, Keyvan

2013-12-01

Super-duplex stainless steels have an excellent combination of mechanical properties and corrosion resistance at relatively low temperatures and can be used as a coating to improve the corrosion and wear resistance of low carbon and low alloy steels. Such coatings can be produced using weld cladding. In this study, pulsed current gas tungsten arc cladding process was utilized to deposit super-duplex stainless steel on high strength low alloy steel substrates. In such claddings, it is essential to understand how the dilution affects the composition and ferrite number of super-duplex stainless steel layer in order to be able to estimate its corrosion resistance and mechanical properties. In the current study, the effect of pulsed current gas tungsten arc cladding process parameters on the dilution and ferrite number of super-duplex stainless steel clad layer was investigated by applying response surface methodology. The validity of the proposed models was investigated by using quadratic regression models and analysis of variance. The results showed an inverse relationship between dilution and ferrite number. They also showed that increasing the heat input decreases the ferrite number. The proposed mathematical models are useful for predicting and controlling the ferrite number within an acceptable range for super-duplex stainless steel cladding.

Effects of heat input on pitting corrosion in super duplex stainless steel weld metals

Science.gov (United States)

Shin, Yong taek; Shin, Hak soo; Lee, Hae woo

2012-12-01

Due to the difference in reheating effects depending on the heat input of subsequent weld passes, the microstructure of the weld metal varies between acicular type austenite and a mixture of polygonal type and grain boundary mixed austenite. These microstructural changes may affect the corrosion properties of duplex stainless steel welds. This result indicates that the pitting resistance of the weld can be strongly influenced by the morphology of the secondary austenite phase. In particular, the ferrite phase adjacent to the acicular type austenite phase shows a lower Pitting Resistance Equivalent (PRE) value of 25.3, due to its lower chromium and molybdenum contents, whereas the secondary austenite phase maintains a higher PRE value of more than 38. Therefore, it can be inferred that the pitting corrosion is mainly due to the formation of ferrite phase with a much lower PRE value.

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

Science.gov (United States)

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

2015-03-01

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

Genetic algorithm based optimization of the process parameters for gas metal arc welding of AISI 904 L stainless steel

International Nuclear Information System (INIS)

Sathiya, P.; Ajith, P. M.; Soundararajan, R.

2013-01-01

The present study is focused on welding of super austenitic stainless steel sheet using gas metal arc welding process with AISI 904 L super austenitic stainless steel with solid wire of 1.2 mm diameter. Based on the Box - Behnken design technique, the experiments are carried out. The input parameters (gas flow rate, voltage, travel speed and wire feed rate) ranges are selected based on the filler wire thickness and base material thickness and the corresponding output variables such as bead width (BW), bead height (BH) and depth of penetration (DP) are measured using optical microscopy. Based on the experimental data, the mathematical models are developed as per regression analysis using Design Expert 7.1 software. An attempt is made to minimize the bead width and bead height and maximize the depth of penetration using genetic algorithm.

Genetic algorithm based optimization of the process parameters for gas metal arc welding of AISI 904 L stainless steel

Energy Technology Data Exchange (ETDEWEB)

Sathiya, P. [National Institute of Technology Tiruchirappalli (India); Ajith, P. M. [Department of Mechanical Engineering Rajiv Gandhi Institute of Technology, Kottayam (India); Soundararajan, R. [Sri Krishna College of Engineering and Technology, Coimbatore (India)

2013-08-15

The present study is focused on welding of super austenitic stainless steel sheet using gas metal arc welding process with AISI 904 L super austenitic stainless steel with solid wire of 1.2 mm diameter. Based on the Box - Behnken design technique, the experiments are carried out. The input parameters (gas flow rate, voltage, travel speed and wire feed rate) ranges are selected based on the filler wire thickness and base material thickness and the corresponding output variables such as bead width (BW), bead height (BH) and depth of penetration (DP) are measured using optical microscopy. Based on the experimental data, the mathematical models are developed as per regression analysis using Design Expert 7.1 software. An attempt is made to minimize the bead width and bead height and maximize the depth of penetration using genetic algorithm.

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

Directory of Open Access Journals (Sweden)

Ronnie Rusli

2011-05-01

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

Effect of Aging Treatment on Impact Toughness and Corrosion Resistance of Super Duplex Stainless Steel

Science.gov (United States)

Kim, Jae-Hwan; Oh, Eun-Ji; Lee, Byung-Chan; Kang, Chang-Yong

2016-01-01

The effect of aging time on impact toughness and corrosion resistance of 25%Cr-7%Ni-2%Mo-4%W-0.2%N super duplex stainless steel from the viewpoint of intermetallic secondary phase variation was investigated with scanning electron microscopic observation with energy-dispersive x-ray spectroscopic analysis and transmission electron microscopy. The results clarified that R-phase is precipitated not only at the interface of ferrite and austenite but inside the ferrite at an initial stage of aging and then transformed into σ-phase from an aging time of 1 h, while the ferrite phase decomposed into γ2 and σ-phase with increase of aging time. This variation of the phases led to decrease of its impact toughness, and specifically, the R-phase was proved to be predominant in the degradation of the impact toughness at the initial stage of the aging. Additionally, these secondary phases led to deterioration of corrosion resistance because of Cr depletion.

The influence of fire exposure on austenitic stainless steel for pressure vessel fitness-for-service assessment: Experimental research

Science.gov (United States)

Li, Bo; Shu, Wenhua; Zuo, Yantian

2017-04-01

The austenitic stainless steels are widely applied to pressure vessel manufacturing. The fire accident risk exists in almost all the industrial chemical plants. It is necessary to make safety evaluation on the chemical equipment including pressure vessels after fire. Therefore, the present research was conducted on the influences of fire exposure testing under different thermal conditions on the mechanical performance evolution of S30408 austenitic stainless steel for pressure vessel equipment. The metallurgical analysis described typical appearances in micro-structure observed in the material suffered by fire exposure. Moreover, the quantitative degradation of mechanical properties was investigated. The material thermal degradation mechanism and fitness-for-service assessment process of fire damage were further discussed.

Effects of fluoride and other halogen ions on the external stress corrosion cracking of Type 304 austenitic stainless steel

International Nuclear Information System (INIS)

Whorlow, K.M.; Hutto, F.B. Jr.

1997-07-01

The drip procedure from the Standard Test Method for Evaluating the Influence of Thermal Insulation on External Stress Corrosion Cracking Tendency of Austenitic Stainless Steel (ASTM C 692-95a) was used to research the effect of halogens and inhibitors on the External Stress Corrosion Cracking (ESCC) of Type 304 stainless steel as it applies to Nuclear Regulatory Commission Regulatory Guide 1.36, Nonmetallic Thermal Insulation for Austenitic Stainless Steel. The solutions used in this research were prepared using pure chemical reagents to simulate the halogens and inhibitors found in insulation extraction solutions. The results indicated that sodium silicate compounds that were higher in sodium were more effective for preventing chloride-induced ESCC in Type 304 austenitic stainless steel. Potassium silicate (all-silicate inhibitor) was not as effective as sodium silicate. Limited testing with sodium hydroxide (all-sodium inhibitor) indicated that it may be effective as an inhibitor. Fluoride, bromide, and iodide caused minimal ESCC which could be effectively inhibited by sodium silicate. The addition of fluoride to the chloride/sodium silicate systems at the threshold of ESCC appeared to have no synergistic effect on ESCC. The mass ratio of sodium + silicate (mg/kg) to chloride (mg/kg) at the lower end of the NRC RG 1.36 Acceptability Curve was not sufficient to prevent ESCC using the methods of this research

Interface segregation behavior in thermal aged austenitic precipitation strengthened stainless steel

Energy Technology Data Exchange (ETDEWEB)

Li, Hui [Key Laboratory for Microstructures, Shanghai University, Shanghai 200444 (China); Technical Department, Jiuli Hi-Tech Metals Co., Ltd., Huzhou 313008 (China); Song, Hui [Key Laboratory for Microstructures, Shanghai University, Shanghai 200444 (China); Liu, Wenqing, E-mail: wqliu@staff.shu.edu.cn [Key Laboratory for Microstructures, Shanghai University, Shanghai 200444 (China); Institute of Materials, Shanghai University, Shanghai 200072 (China); Xia, Shuang; Zhou, Bangxin [Institute of Materials, Shanghai University, Shanghai 200072 (China); Su, Cheng; Ding, Wenyan [Technical Department, Jiuli Hi-Tech Metals Co., Ltd., Huzhou 313008 (China)

2015-12-15

The segregation of various elements at grain boundaries, precipitate/matrix interfaces were analyzed using atom probe tomography in an austenitic precipitation strengthened stainless steel aged at 750 °C for different time. Segregation of P, B and C at all types of interfaces in all the specimens were observed. However, Si segregated at all types of interfaces only in the specimen aged for 16 h. Enrichment of Ti at grain boundaries was evident in the specimen aged for 16 h, while Ti did not segregate at other interfaces. Mo varied considerably among interface types, e.g. from segregated at grain boundaries in the specimens after all the aging time to never segregate at γ′/γ phase interfaces. Cr co-segregated with C at grain boundaries, although carbides still did not nucleate at grain boundaries yet. Despite segregation tendency variations in different interface types, the segregation tendency evolution variation of different elements depending aging time were analyzed among all types of interfaces. Based on the experimental results, the enrichment factors, Gibbs interface excess and segregation free energies of segregated elements were calculated and discussed. - Highlights: • Solute atoms segregated at interfaces were analyzed in an austenitic stainless steel. • The comparison of segregation in different interfaces was studied by APT. • The evolution of interface segregation during aging treatment was discussed.

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

NARCIS (Netherlands)

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

2009-01-01

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

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

NARCIS (Netherlands)

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

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

Microstructural investigations of fast reactor irradiated austenitic and ferritic-martensitic stainless steel fuel cladding

International Nuclear Information System (INIS)

Agueev, V.S.; Medvedeva, E.A.; Mitrofanova, N.M.; Romanueev, V.V.; Tselishev, A.V.

1992-01-01

Electron microscopy has been used to characterize the microstructural changes induced in advanced fast reactor fuel claddings fabricated from Cr16Ni15Mo3NbB and Cr16Ni15Mo2Mn2TiVB austenitic stainless steels in the cold worked condition and Cr13Mo2NbVB ferritic -martensitic steel following irradiation in the BOR-60, BN-350 and BN-600 fast reactors. The data are compared with the results obtained from a typical austenitic commercial cladding material, Cr16Ni15Mo3Nb, in the cold worked condition. The results reveal a beneficial effect of boron and other alloying elements in reducing void swelling in 16Cr-15Ni type austenitic steels. The high resistance of ferritic-martensitic steels to void swelling has been confirmed in the Cr13Mo2NbVB steel. (author)

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

Science.gov (United States)

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

2010-07-13

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

Study of copper precipitation behavior in a Cu-bearing austenitic antibacterial stainless steel

International Nuclear Information System (INIS)

Ren, Ling; Nan, Li; Yang, Ke

2011-01-01

Copper (Cu) precipitation behavior in a type 304 Cu-bearing austenitic antibacterial stainless steel was studied by analyses of variations in micro-hardness, electrical resistivity, electrochemical impedance and lattice constant of the steel, complemented with transmission electron microscopy (TEM) observation, showing more or less changes on these properties of the steel with different aging time. It was found that both micro-hardness and electrical resistivity measurements were relatively sensitive and accurate to reflect the Cu precipitation behavior in the experimental steel, indicating the beginning and finishing points of the precipitation, which are more simple and effective to be used for development of the new type of antibacterial stainless steels.

Strain hardening and plastic instability properties of austenitic stainless steels after proton and neutron irradiation

International Nuclear Information System (INIS)

Byun, T.S.; Farrell, K.; Lee, E.H.; Hunn, J.D.; Mansur, L.K.

2001-01-01

Strain hardening and plastic instability properties were analyzed for EC316LN, HTUPS316, and AL6XN austenitic stainless steels after combined 800 MeV proton and spallation neutron irradiation to doses up to 10.7 dpa. The steels retained good strain-hardening rates after irradiation, which resulted in significant uniform strains. It was found that the instability stress, the stress at the onset of necking, had little dependence on the irradiation dose. Tensile fracture stress and strain were calculated from the stress-strain curve data and were used to estimate fracture toughness using an existing model. The doses to plastic instability and fracture, the accumulated doses at which the yield stress reaches instability stress or fracture stress, were predicted by extrapolation of the yield stress, instability stress, and fracture stress to higher dose. The EC316LN alloy required the highest doses for plastic instability and fracture. Plastic deformation mechanisms are discussed in relation to the strain-hardening properties of the austenitic stainless steels

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

Energy Technology Data Exchange (ETDEWEB)

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

1996-04-01

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

Carburization behavior of AISI 316LN austenitic stainless steel - Experimental studies and modeling

Energy Technology Data Exchange (ETDEWEB)

Sudha, C. [Physical Metallurgy Division, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, Tamilnadu (India); Sivai Bharasi, N. [Corrosion Science and Technology Division, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, Tamilnadu (India); Anand, R. [Physical Metallurgy Division, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, Tamilnadu (India); Shaikh, H., E-mail: hasan@igcar.gov.i [Corrosion Science and Technology Division, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, Tamilnadu (India); Dayal, R.K. [Corrosion Science and Technology Division, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, Tamilnadu (India); Vijayalakshmi, M. [Physical Metallurgy Division, Metallurgy and Materials Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, Tamilnadu (India)

2010-07-31

AISI type 316LN austenitic stainless steel was exposed to flowing sodium at 798 K for 16,000 h in the bi-metallic (BIM) sodium loop. A modified surface layer of 10 {mu}m width having a ferrite structure was detected from X-ray diffraction and electron micro probe based analysis. Beneath the modified surface layer a carburized zone of 60 {mu}m width was identified which was found to consist of M{sub 23}C{sub 6} carbides. A mathematical model based on finite difference technique was developed to predict the carburization profiles in sodium exposed austenitic stainless steel. In the computation, effect of only chromium on carbon diffusion was considered. Amount of carbon remaining in solution was determined from the solubility parameter. The predicted profile showed a reasonably good match with the experimental profile. Calculations were extended to simulate the thickness of the carburized layer after exposure to sodium for a period of 40 years. Attempt was also made to predict the carburization profiles based on equilibrium calculations using Dictra and Thermocalc which contain both thermodynamic and kinetic databases for the system under consideration.

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

International Nuclear Information System (INIS)

Horii, Kiyomasa; Ishibashi, Tetsu; Toriyama, Tamotsu; Wakabayashi, Hidehiko; Iijima, Hiroshi; Kawasaki, Katsunori; Hayashi, Nobuyuki; Sakamoto, Isao.

1996-01-01

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

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

Directory of Open Access Journals (Sweden)

Topolska S.

2017-12-01

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

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

International Nuclear Information System (INIS)

Bandy, R.; Cahoon, J.R.

1977-01-01

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

The Use of Austenitic Stainless Steel versus Monel (Ni-Cu) Alloy in Pressurized Gaseous Oxygen (GOX) Life Support Systems.

Science.gov (United States)

1985-03-01

Carbon Steel AISI 1025 2. AISI 4140 3. Ductile Iron 4. 304 Stainless Steel 5. 17-4 PH Stainless Steel 6. 410 Stainless Steel 7. Lead Babbit 8. Tin Babbit...9. Inconel 718 i0. Aluminum 1100 30 6- AISI 4140 steel, all the results were negative (no ignitions). The single exception was with a sample of 4140 ...rates for austenitic stainless steel ( AISI 316), Monel (63% Ni - 34% Cu) and carbon steel (AMS 5050) tubing in this environment. 12 - 14-660 A 7

Fatigue crack propagation behavior and acoustic emission characteristics of the heat affected zone of super duplex stainless steel

International Nuclear Information System (INIS)

Do, Jae Yoon; Kim, Jin Hwan; Ahn, Seok Hwan; Park, In Duck; Kang, Chang Yong; Nam, Ki Woo

2002-01-01

Because duplex stainless steel shows the good strength and corrosion resistance properties, the necessity of duplex stainless steel, which has long life in severe environments, has been increased with industrial development. The fatigue crack propagation behavior of Heat Affected Zone(HAZ) has been investigated in super duplex stainless steel. The fatigue crack propagation rate of HAZ of super duplex stainless steel was faster than that of base metal of super duplex stainless steel. We also analysed acoustic emission signals during the fatigue test with time-frequency analysis method. According to the results of time-frequency analysis, the frequency ranges of 200-400 kHz were obtained by striation and the frequency range of 500 kHz was obtained due to dimple and separate of inclusion

Numerical and experimental study of long term creep damage in austenitic stainless steels

International Nuclear Information System (INIS)

Cui, Yiting

2015-01-01

The creep fracture of 316L(N) austenitic stainless steels has been studied both experimentally and theoretically for temperatures from 525 C up to 700 C and lifetimes up to nineteen years. For short term creep, failure is due to necking. Experimental lifetimes are bounded by the lower and upper bound predictions provided by a necking model and taking into account scatter in input parameters. This model leads to fair predictions of lifetimes up to a few thousand hours at very high temperature. Based on FEG-SEM observations, the transition observed in the failure curves is due to intergranular cavitation. The Riedel modeling of cavity growth by vacancy diffusion along grain boundaries coupled with continuous nucleation is carried out. Lifetimes are predicted fairly well using this model for long term creep failure whatever the considered austenitic stainless steel (316L(N), 304H, 316H, 321H) and the applied temperature (525 C - 700 C). Taking into account low and high stress regimes of Norton-power law, the Riedel model allows us to predict the creep lifetimes up to 25 years which differ from experimental data by less than a factor 3. The effect of the heterogeneity of the microstructure on grain boundary stress concentrations and cavity nucleation is simulated by the finite element method (Cast3M software). It aims to determine the distribution of grain boundary normal stress fields around precipitates depending on time and temperature. The features of the precipitates and the creep behavior of the austenitic matrix are both taking into account. (author) [fr

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

International Nuclear Information System (INIS)

Pereira, Silvio Andre de Lima

2012-01-01

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

Biofouling on austenitic stainless steels in spent nuclear fuel pools

Energy Technology Data Exchange (ETDEWEB)

Sarro, M I; Moreno, D A; Chicote, E; Lorenzo, P I; Garcia, A M [Universidad Politecnica de Madrid, Departamento de Ingenieria y Ciencia de los Materiales, Escuela Tecnica Superior de Ingenieros Industriales, Jose Gutierrez Abascal, 2, E-28006 Madrid (Spain); Montero, F [Iberdrola Generacion, S.A., y C.M.D.S., Centro de Tecnologia de Materiales, Paseo de la Virgen del Puerto, 53, E-28005 Madrid (Spain)

2003-07-01

The objective of this study was to investigate the biofilm formation on three different types of austenitic stainless steel (UNS S30400, S30466 and S31600) submerged in a spent nuclear fuel pool. The presence of microorganisms in coupons was characterised using standard culture microbiological methods, microscopic techniques (epifluorescence microscopy and scanning electron microscopy), and molecular biology techniques (denaturing gradient gel electrophoresis and sequencing fragments of 16S rDNA). The microscopy techniques showed signs of colonisation of stainless steels in spite of these extreme conditions. Based on sequencing of cultured microorganisms, different bacteria belonging to {alpha}, {beta}, {gamma}-Proteobacteria, Bacilli, and Actinobacteria classes have been identified. The biofilm radioactivity was measured using gamma-ray spectrometry and, according to the data gathered, the radionuclides present in the water pool were entrapped in the biofilm increasing the amount of radiation at the surface of the different materials. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

Biofouling on austenitic stainless steels in spent nuclear fuel pools

International Nuclear Information System (INIS)

Sarro, M.I.; Moreno, D.A.; Chicote, E.; Lorenzo, P.I.; Garcia, A.M.; Montero, F.

2003-01-01

The objective of this study was to investigate the biofilm formation on three different types of austenitic stainless steel (UNS S30400, S30466 and S31600) submerged in a spent nuclear fuel pool. The presence of microorganisms in coupons was characterised using standard culture microbiological methods, microscopic techniques (epifluorescence microscopy and scanning electron microscopy), and molecular biology techniques (denaturing gradient gel electrophoresis and sequencing fragments of 16S rDNA). The microscopy techniques showed signs of colonisation of stainless steels in spite of these extreme conditions. Based on sequencing of cultured microorganisms, different bacteria belonging to α, β, γ-Proteobacteria, Bacilli, and Actinobacteria classes have been identified. The biofilm radioactivity was measured using gamma-ray spectrometry and, according to the data gathered, the radionuclides present in the water pool were entrapped in the biofilm increasing the amount of radiation at the surface of the different materials. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

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

Energy Technology Data Exchange (ETDEWEB)

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

2010-03-15

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

Effect of Plastic Deformation on the Corrosion Behavior of a Super-Duplex Stainless Steel

Science.gov (United States)

Renton, Neill C.; Elhoud, Abdu M.; Deans, William F.

2011-04-01

The role of plastic deformation on the corrosion behavior of a 25Cr-7Ni super-duplex stainless steel (SDSS) in a 3.5 wt.% sodium chloride solution at 90 °C was investigated. Different levels of plastic strain between 4 and 16% were applied to solution annealed tensile specimens and the effect on the pitting potential measured using potentiodynamic electrochemical techniques. A nonlinear relationship between the pitting potential and the plastic strain was recorded, with 8 and 16% causing a significant reduction in average E p, but 4 and 12% causing no significant change when compared with the solution-annealed specimens. The corrosion morphology revealed galvanic interaction between the anodic ferrite and the cathodic austenite causing preferential dissolution of the ferrite. Mixed potential theory and the changing surface areas of the two phases caused by the plastic deformation structures explain the reductions in pitting potential at certain critical plastic strain levels. End-users and manufacturers should evaluate the corrosion behavior of specific cold-worked duplex and SDSSs using their as-produced surface finishes assessing in-service corrosion performance.

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

DEFF Research Database (Denmark)

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

2010-01-01

Two simulative test methods were used to study galling in sheet forming of two types of stainless steel sheet: austenitic (EN 1.4301) and lean duplex LDX 2101 (EN 1.4162) in different surface conditions. The pin-on-disc test was used to analyse the galling resistance of different combinations of ...

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

Energy Technology Data Exchange (ETDEWEB)

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

2016-07-15

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

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

International Nuclear Information System (INIS)

Starkman, T.

1984-07-01

Austenitic stainless steels were oxidized in static autoclaves in light water reactor conditions. After the autoclave treatments the specimens were decontaminated with the aid of alkaline potassium permanganate (AP) and oxalic and citric acid (CITROX) as well as electrochemically in H 3 PO 4 . Alternating oxidation and decontamination tests were performed. An elemental analysis of the surfaces of the specimens was carried out by electron spectroscopy. Changes in structures and thicknesses of the oxide layers were observed. (author)

Five-parameter crystallographic characteristics of the interfaces formed during ferrite to austenite transformation in a duplex stainless steel

Science.gov (United States)

Haghdadi, N.; Cizek, P.; Hodgson, P. D.; Tari, V.; Rohrer, G. S.; Beladi, H.

2018-05-01

The crystallography of interfaces in a duplex stainless steel having an equiaxed microstructure produced through the ferrite to austenite diffusive phase transformation has been studied. The five-parameter interface character distribution revealed a high anisotropy in habit planes for the austenite-ferrite and austenite-austenite interfaces for different lattice misorientations. The austenite and ferrite habit planes largely terminated on (1 1 1) and (1 1 0) planes, respectively, for the austenite-ferrite interfaces associated with Kurdjumov-Sachs (K-S) and Nishiyama-Wasserman (N-W) orientation relationships. This was mostly attributed to the crystallographic preference associated with the phase transformation. For the austenite-ferrite interfaces with orientation relationships which are neither K-S nor N-W, both austenite and ferrite habit planes had (1 1 1) orientations. Σ3 twin boundaries comprised the majority of austenite-austenite interfaces, mostly showing a pure twist character and terminating on (1 1 1) planes due to the minimum energy configuration. The second highest populated austenite-austenite boundary was Σ9, which tended to have grain boundary planes in the tilt zone due to the geometrical constraints. Furthermore, the intervariant crystallographic plane distribution associated with the K-S orientation relationship displayed a general tendency for the austenite habit planes to terminate with the (1 1 1) orientation, mainly due to the crystallographic preference associated with the phase transformation.

Resonant creep enhancement in austenitic stainless steels due to pulsed irradiation at low doses

International Nuclear Information System (INIS)

Kishimoto, N.; Amekura, H.; Saito, T.

1994-01-01

Steady-state irradiation creep of austenitic stainless steels has been extensively studied as one of the most important design parameters in fusion reactors. The steady-state irradiation creep has been evaluated using in-pile and light-ion experiments. Those creep compliances of various austenitic steels range in the vicinity of ε/Gσ = 10 -6 ∼10 -5 (dpa sm-bullet MPa) -1 , depending on chemical composition etc. The mechanism of steady-state irradiation creep has been elucidated, essentially in terms of stress-induced preferential absorption of point defects into dislocations, and their climb motion. From this standpoint, low doses such as 10 -3 ∼10 -1 dpa would not give rise to any serious creep, and the irradiation creep may not be a critical issue for the low-dose fusion devices including ITER. It is, however, possible that pulsed irradiation causes different creep behaviors from the steady-state one due to dynamic unbalance of interstitials and vacancies. The authors have actually observed anomalous creep enhancement due to pulsed irradiation in austenitic stainless steels. The resonant behavior of creep indicates that pulsed irradiation may cause significant deformation in austenitic steels even at such low doses and slow pulsing rates, especially for the SA-materials. The first-wall materials in plasma operation of ∼10 2 s may suffer from unexpected transient creep, even in the near-term fusion deices, such as ITER. Though this effect might be a transient effect for a relatively short period, it should be taken into account that the pulsed irradiation makes influences on stress relaxation of the fusion components and on the irradiation fatigue. The mechanism and the relevant behaviors of pulse-induced creep will be discussed in terms of a point-defect model based on the resonant interstitial enrichment

Updating of actual technique for ultrasonic testing of austenitic stainless materials and welds

International Nuclear Information System (INIS)

Lindholm, P.O.; Pers-Anderson, E.B.

1982-01-01

The technique for ultrasonic testing of stainless austenitic steels and weldings has been studied and it has been brought to the latest standard. Many problems exist when testing, the most serious being the occurence of false indications and the damping of energy. Laboratory tests show that the detectors with transversal sound waves should be used for plane defects. Best results were achieved with a 45 degrees detector. (GB)

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

International Nuclear Information System (INIS)

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

1978-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2015-06-05

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

Hydrogen Embrittlement Mechanism in Fatigue Behaviour of Austenitic and Martensitic Stainless Steels

Directory of Open Access Journals (Sweden)

Brück Sven

2018-01-01

Full Text Available In the present study, the influence of hydrogen on the fatigue behaviour of the high strength martensitic stainless steel X3CrNiMo13-4 and the metastable austenitic stainless steels X2Crni19-11 with various nickel contents was examined in the low and high cycle fatigue regime. The focus of the investigations was the changes in the mechanisms of short crack propagation. The aim of the ongoing investigation is to determine and quantitatively describe the predominant processes of hydrogen embrittlement and their influence on the short fatigue crack morphology and crack growth rate. In addition, simulations were carried out on the short fatigue crack growth, in order to develop a detailed insight into the hydrogen embrittlement mechanisms relevant for cyclic loading conditions.

Development of austenitic stainless steel PC wire and strand

International Nuclear Information System (INIS)

Tsubono, Hideyoshi; Kawabata, Yoshinori; Yamaoka, Yukio

1986-01-01

The effects of aging and stress-aging (called hot stretching) at the temperatures from 120 deg C to 700 deg C on the mechanical properties, relaxation values, Charpy impact values and SCC behavior of hard drawn SUS 304, SUS 316 stainless steel wires have been studied. The main results obtained are as follows: (1) Yield and tensile strength of the wires increased by aging at 230 deg C and 530 deg C as well as by hot stretching. The strengthening after 230 deg C treatment may be due to the strain aging by C and the increase of strength after 530 deg C treatment results from precipitation of Cr 23 C 6 on dislocations. (2) Stress relaxation values up to 250 deg C are low due to precipitation of Cr 23 C 6 . Almost no difference can be observed between aging and hot stretching. (3) Impact value at -196 deg C of SUS 304 stainless steel wire which was measured with 1 mm V-notched specimen was found to be about the same as that of 9 % Ni steel. (4) It is considered that in comparison with high carbon PC wire SUS 304 stainless steel showing high tensile strength is insensitive to SCC in NH 4 SCN and NH 4 NO 3 solutions. (5) In practice, tension member of the austenitic stainless steel wire and strand which were produced by aging at 500 deg C may be useful in special industrial field, for example, (a) SUS 304, in cryogenic field use (b) SUS 316, in intensive magnetic field use as a nonmagnetic material. (author)

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

CERN Document Server

Sgobba, Stefano; Liimatainen, J; Kumpula, M

2000-01-01

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

Corrosion of an austenite and ferrite stainless steel weld

Directory of Open Access Journals (Sweden)

BRANIMIR N. GRGUR

2011-07-01

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

Radiation damage of austenitic stainless steels and zirconium alloys; Pregled radijacionog ostecenja austenitnih nerdjajucih celika i legura cirkonijuma

Energy Technology Data Exchange (ETDEWEB)

Stefanovic, V [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Yugoslavia)

1965-11-15

This review contains analyses of available data concerning texture deformations and radiation damage of zirconium and zircaloy-2; radiation damage, influence of neutron radiation on the mechanical properties of austenitic, ferritic and other types of stainless steels.

Static strain aging type AISI-304 austenitic stainless steel

International Nuclear Information System (INIS)

Trindade, M.B.

1981-03-01

Static strain aging of type AISI-304 austenitic stainless steel was studied from room temperature up to 623K by conducting tests in which the load was held approximately constant, continuously relaxing and unloaded. The aging times varied between 10s and 100h, using a plastic pre deformation of 9% in most of the cases. The static strain aging of 304 steel furnished an activation energy of 23,800 cal/mol. This implies that vacancies play an important role on the aging process. The curve of the variation of the discontinuous yielding with aging time presented different stages, to which specific mathematical expressions were developed. These facts permited the conclusion that Snoek type mechanisms are responsible for the aging in such conditions. (Author) [pt

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

International Nuclear Information System (INIS)

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

2015-01-01

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

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

International Nuclear Information System (INIS)

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

2012-01-01

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

Concurrent microstructural evolution of ferrite and austenite in a duplex stainless steel processed by high-pressure torsion

International Nuclear Information System (INIS)

Cao, Y.; Wang, Y.B.; An, X.H.; Liao, X.Z.; Kawasaki, M.; Ringer, S.P.; Langdon, T.G.; Zhu, Y.T.

2014-01-01

A duplex stainless steel with approximately equal volume fractions of ferrite and austenite was processed by high-pressure torsion. Nano-indentation, electron backscatter diffraction and transmission electron microscopy were used to investigate the hardness and microstructure evolutions of the steel. Despite the different strain-hardening rates of individual ferrite and austenite, the microstructures of the two phases evolved concurrently in such a way that the neighbouring two phases always maintained similar hardness. While the plastic deformation and grain refinement of ferrite occurred mainly via dislocation activities, the plastic deformation and grain refinement process of austenite were more complicated and included deformation twinning and de-twinning in coarse grains, grain refinement by twinning and dislocation–twin interactions, de-twinning in ultrafine grains and twin boundary subdivision

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

International Nuclear Information System (INIS)

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

2012-01-01

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

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

Science.gov (United States)

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

2016-05-01

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

Magnetic susceptibility and magnetization studies of some commercial austenitic stainless steels

International Nuclear Information System (INIS)

Collings, E.W.

1979-01-01

Results of magnetic susceptibility measurements using the Curie magnetic force technique are reported for six AISI 300-series alloys 310S, 304, 304L, 304N, 316, 316L as well as AWS 330 weld metal and Inconel 625. The temperature ranged from 5 to 416 0 K. Magnetization measurements over the temperature range 3 to 297 0 K, performed using a vibrating-sample magnetometer, are also reported. Alloy compositions and sample preparation procedures are discussed and numerical results of the study are presented. Magnetic characteristics of the four principal types of austenitic stainless steels studied are summarized

Pitting corrosion in austenitic stainless steel water tanks of hotel trains

International Nuclear Information System (INIS)

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

2011-01-01

The water storage tanks of hotel trains suffered pitting corrosion. To identify the cause, the tanks were subjected to a detailed metallographic study and the chemical composition of the austenitic stainless steels used in their construction was determined. Both the tank water and the corrosion products were further examined by physicochemical and microbiological testing. Corrosion was shown to be related to an incompatibility between the chloride content of the water and the base and filler metals of the tanks. These findings formed the basis of recommendations aimed at the prevention and control of corrosion in such tanks. (Author) 18 refs.

Metallographic screening of grain boundary engineered type 304 austenitic stainless steel

Energy Technology Data Exchange (ETDEWEB)

Hanning, F., E-mail: Fabian.Hanning@googlemail.com; Engelberg, D.L., E-mail: Dirk.engelberg@manchester.ac.uk

2014-08-15

An electrochemical etching method for the identification of grain boundary engineered type 304 austenitic stainless steel microstructures is described. The method can be applied for rapid microstructure screening to complement electron backscatter diffraction analysis. A threshold parameter to identify grain boundary engineered microstructure is proposed, and the application of metallographic etching for characterising the degree of grain boundary engineering discussed. - Highlights: • As-received (annealed) and grain boundary engineered microstructures were compared. • Electro-chemical polarisation in nitric acid solutions was carried out. • A metallographic screening method has been developed. • The screening method complements EBSD analysis for microstructure identification.

Compatibility of different stainless steels in molten Pb-Bi eutectic at high temperatures

International Nuclear Information System (INIS)

Chandra, K.; Kain, Vivekanand; Laik, A.; Sharma, B.P.; Bhattacharya, S.; Debnath, A.K.

2005-10-01

Advanced nuclear reactors and the accelerator driven subcritical (ADS) system require the structural materials to be in contact with the molten metals/lead-bismuth eutectic at 400 degC and higher temperatures. One of the primary concerns in using the molten lead-bismuth eutectic (LBE) as a coolant in the primary circuit of these systems is the degradation of structural materials in contact with LBE. An experimental setup has been fabricated to expose the materials in the molten LBE at high temperatures in stagnant condition under inert atmosphere. Samples from five different stainless steels (types 304L, 316L, 403, duplex SS SAF 2205 and super austenitic SS 2RK65) were exposed in this setup at 450 degC for 200h and at 500 degC for 600 and 2100 h under argon atmosphere. A different setup was prepared in which type 316L SS tube in the as-welded condition was exposed in molten LBE at 500 degC for 1200 h in rotating condition. All the samples showed formation of oxide on their surfaces. The thickness and compositional profiles of these oxides analyzed by EPMA confirmed formation of a double layer oxide on type 316L SS. The oxide thickness was highest on SS 403, while it was lowest on 304L and 316L SS. SEM results showed dissolution of materials at the surface in Sandvik 2RK65 and preferential dissolution of austenite phase in duplex SS. None of the stainless steels, except the duplex and the super austenitic stainless steels, showed any localized or selective corrosion. The composition of LBE before and after the exposure tests was analyzed by XRF technique. The result showed presence of Fe, Cr and Ni in the used LBE but these elements were not present in the virgin Pb-Ei alloy. This showed that the corrosion of stainless steels in LBE at temperatures upto 500 degC is due to oxidation and dissolution of alloying elements through the oxide on stainless steels. (author)

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

Energy Technology Data Exchange (ETDEWEB)

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

2015-07-15

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

The carbide M7C3 in low-temperature-carburized austenitic stainless steel

International Nuclear Information System (INIS)

Ernst, Frank; Li, Dingqiang; Kahn, Harold; Michal, Gary M.; Heuer, Arthur H.

2011-01-01

Prolonged low-temperature gas-phase carburization of AISI 316L-type austenitic stainless steel can cause intragranular precipitation of the carbide M 7 C 3 (M: randomly dispersed Fe, Cr, Ni). Transmission electron microscopy revealed that the carbide particles have the shape of needles. They grow by a ledge-migration mechanism and in a crystallographic orientation relationship to the austenite matrix that enables highly coherent interphase interfaces. A small solubility limit of Ni in the carbide and restricted Ni diffusivity at the processing temperature leads to Ni pileup around the particles and may explain the extreme aspect ratio of the particle shape. These characteristics closely resemble what has been observed earlier for precipitates of M 5 C 2 under slightly different processing conditions and can be rationalized by considering the particular constraints imposed by carburization at low temperature.

Influence of deformation on SCC susceptibility of austenitic stainless steel in PWR primary water

Energy Technology Data Exchange (ETDEWEB)

Kaneshima, Yoshiari; Totsuka, Nobuo; Nakajima, Nobuo [Institute of Nuclear Safety System Inc., Mihama, Fukui (Japan)

2001-09-01

Slow strain rate tests (SSRT) were carried out to evaluate the SCC susceptibility of four types of austenitic stainless steels (SUS304, SUS316, SUS304L and SUS316L) in PWR primary water. The influence of deformation on SCC susceptibility of SUS316 was studied. All types of stainless steel were susceptible to SCC, and the SCC susceptibility varied depending on the steel type. The comparison of the SSRT results and tensile test in air based on the reduction of area measurement showed that the SCC susceptibility increased with increasing the degree of deformation. For explaining the influence of deformation on SCC susceptibility, it is necessary to evaluate both intergranular and transgranular fractures. (author)

Mechanical Properties of Austenitic Stainless Steel Made by Additive Manufacturing.

Science.gov (United States)

Luecke, William E; Slotwinski, John A

2014-01-01

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

Corrosion fatigue initiation and short crack growth behaviour of austenitic stainless steels under light water reactor conditions

International Nuclear Information System (INIS)

Seifert, H.P.; Ritter, S.; Leber, H.J.

2012-01-01

Highlights: ► Corrosion fatigue in austenitic stainless steels under light water reactor conditions. ► Identification of major parameters of influence on initiation and short crack growth. ► Critical system conditions for environmental reduction of fatigue initiation life. ► Comparison with the environmental factor (F env ) approach. - Abstract: The corrosion fatigue initiation and short crack growth behaviour of different wrought low-carbon and stabilised austenitic stainless steels was characterised under simulated boiling water reactor and pressurised water reactor primary water conditions by cyclic fatigue tests with sharply notched fracture mechanics specimens. The special emphasis was placed to the behaviour at low corrosion potentials and, in particular, to hydrogen water chemistry conditions. The major parameter effects and critical conjoint threshold conditions, which result in relevant environmental reduction and acceleration of fatigue initiation life and subsequent short crack growth, respectively, are discussed and summarised. The observed corrosion fatigue behaviour is compared with the fatigue evaluation procedures in codes and regulatory guidelines.

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

OpenAIRE

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

2015-01-01

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

Detection of secondary phases in duplex stainless steel by magnetic force microscopy and scanning Kelvin probe force microscopy

Energy Technology Data Exchange (ETDEWEB)

Ramírez-Salgado, J. [Instituto Mexicano del Petróleo, Dirección de Investigación y Posgrado, Eje Central Norte Lázaro Cárdenas, No. 152, 07730 D.F., México (Mexico); Domínguez-Aguilar, M.A., E-mail: madoming@imp.mx [Instituto Mexicano del Petróleo, Dirección de Investigación y Posgrado, Eje Central Norte Lázaro Cárdenas, No. 152, 07730 D.F., México (Mexico); Castro-Domínguez, B. [University of Tokyo, Department of Chemical System Engineering, Faculty of Engineering Bldg. 5, 7F 722, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113–8656 (Japan); Hernández-Hernández, P. [Instituto Mexicano del Petróleo, Dirección de Investigación y Posgrado, Eje Central Norte Lázaro Cárdenas, No. 152, 07730 D.F., México (Mexico); Newman, R.C. [University of Toronto, Department of Chemical Engineering and Applied Chemistry, 200 College Street, Toronto M5S 3E5 (Canada)

2013-12-15

The secondary phase transformations in a commercial super duplex stainless steel were investigated by micro-chemical analyses and high resolution scanning probe microscopy. Energy dispersive X-ray and electron probe detected ferrite and austenite as well as secondary phases in unetched aged duplex stainless steel type 25Cr-7Ni-3Mo. Volta potential indicated that nitride and sigma appeared more active than ferrite, while secondary austenite and austenite presented a nobler potential. Reversal order in nobility is thought to be attributable to the potential ranking provided by oxide nature diversity as a result of secondary phase surface compositions on steel. After eutectoid transformation, secondary austenite was detected by electron probe microanalysis, whereas atomic force microscopy distinguished this phase from former austenite by image contrast. Magnetic force microscopy revealed a “ghosted” effect on the latter microstructure probably derived from metal memory reminiscence of mechanical polishing at passivity and long range magnetic forces of ferrite phase. - Highlights: • Nobility detection of secondary phases by SKPFM in DSS particles is not a straightforward procedure. • As Volta potential and contrast are not always consistent SKPFM surface oxides is thought played an important role in detection. • AFM distinguished secondary austenite from former austenite by image contrast though SEM required EPMA.

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

Energy Technology Data Exchange (ETDEWEB)

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

2015-03-25

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

Fracture toughness of irradiated wrought and cast austenitic stainless steels in BWR environment

International Nuclear Information System (INIS)

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

2007-01-01

Experimental data are presented on the fracture toughness of wrought and cast austenitic stainless steels (SSs) that were irradiated to a fluence of ∼ 1.5 x 10 21 n/cm 2 (E > 1 MeV) * (∼ 2.3 dpa) at 296-305 o C. To evaluate the possible effects of test environment and crack morphology on the fracture toughness of these steels, all tests were conducted in normal-water-chemistry boiling water reactor (BWR) environments at ∼ 289 o C. Companion tests were also conducted in air on the same material for comparison. The fracture toughness J-R curves for SS weld heat-affected-zone materials in BWR water were found to be comparable to those in air. However, the results of tests on sensitized Type 304 SS and thermally aged cast CF-8M steel suggested a possible effect of water environment. The available fracture toughness data on irradiated austenitic SSs were reviewed to assess the potential for radiation embrittlement of reactor-core internal components. The synergistic effects of thermal and radiation embrittlement of cast austenitic SS internal components are also discussed. (author)

Void swelling behaviour of austenitic stainless steel during electron irradiation

International Nuclear Information System (INIS)

Sheng Zhongqi; Xiao Hong; Peng Feng; Ti Zhongxin

1994-04-01

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

Characteristic of Low Temperature Carburized Austenitic Stainless Steel

Science.gov (United States)

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

2018-01-01

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

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

DEFF Research Database (Denmark)

Chen, Ming; Alimadadi, Hossein; Molin, Sebastian

2017-01-01

Ferritic stainless steel interconnect plates are widely used in planar solid oxide fuel cell and electrolysis cell stacks. During stack production and operation, nickel from the Ni/yttria stabilized zirconia fuel electrode or from the Ni contact component layer diffuses into the interconnect plate......, causing transformation of the ferritic phase into an austenitic phase in the interface region. This is accompanied with changes in volume, and in mechanical and corrosion properties of the interconnect plates. In this work, kinetic modeling of the inter-diffusion between Ni and FeCr based ferritic...

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

Institute of Scientific and Technical Information of China (English)

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

2007-01-01

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

The high temperature oxidation behaviour of austenitic stainless steels

International Nuclear Information System (INIS)

Hales, R.

1977-04-01

High temperature annealing in a dynamic vacuum has been utilised to induce the growth of duplex oxide over the whole surface of stainless steel specimens. It is found that duplex oxide grows at a rate which does not obey a simple power law. The oxidation kinetics and oxide morphology have also been studied for a series of ternary austenitic alloys which cover a range of composition between 5 and 20% chromium. A model has been developed to describe the formation of duplex oxide and the subsequent formation of a 'healing layer' which virtually causes the oxidation process to stop. This phase tends to form at grain boundaries and a relationship has been derived for the reaction kinetics which relates the reaction rate with grain size of the substrate. (author)

Characterization of the dissimilar welding - austenitic stainless steel with filler metal of the nickel alloy

International Nuclear Information System (INIS)

Soares, Bruno Amorim; Schvartzman, Monica Maria de Abreu Mendonca; Campos, Wagner Reis da Costa

2007-01-01

In elevated temperature environments, austenitic stainless steel and nickel alloy has a superior corrosion resistance due to its high Cr content. Consequently, this alloys is widely used in nuclear reactors components and others plants of energy generation that burn fossil fuel or gas, chemical and petrochemical industries. The object of the present work was to research the welding of AISI 304 austenitic stainless steel using the nickel alloy filler metals, Inconel 625. Gas tungsten arc welding, mechanical and metallographic tests, and compositional analysis of the joint were used. A fundamental investigation was undertaken to characterize fusion boundary microstructure and to better understand the nature and character of boundaries that are associated with cracking in dissimilar welds. The results indicate that the microstructure of the fusion zone has a dendritic structure, inclusions, and precipitated phases containing Ti and Nb are present in the inter-dendritic region. In some parts near to the fusion line it can be seen a band in the weld, probably a eutectic phase with lower melting point than the AISI 304, were the cracking may be beginning by stress corrosion. (author)

Austenitic stainless steels and high strength copper alloys for fusion components

International Nuclear Information System (INIS)

Rowcliffe, A.F.; Zinkle, S.J.; Alexander, D.J.; Stubbins, J.F.

1998-01-01

An austenitic stainless steel (316LN), an oxide-dispersion-strengthened copper alloy (GlidCop A125), and a precipitation-hardened copper alloy (Cu-Cr-Zr) are the primary structural materials for the ITER first wall/blanket and divertor systems. While there is a long experience of operating 316LN stainless steel in nuclear environments, there is no prior experience with the copper alloys in neutron environments. The ITER first wall (FW) consists of a stainless steel shield with a copper alloy heat sink bonded by hot isostatic pressing (HIP). The introduction of bi-layer structural material represents a new materials engineering challenge; the behavior of the bi-layer is determined by the properties of the individual components and by the nature of the bond interface. The development of the radiation damage microstructure in both classes of materials is summarized and the effects of radiation on deformation and fracture behavior are considered. The initial data on the mechanical testing of bi-layers indicate that the effectiveness of GlidCop A125 as a FW heat sink material is compromised by its strongly anisotropic fracture toughness and poor resistance to crack growth in a direction parallel to the bi-layer interface. (orig.)

EFFECT OF INTERMETALLIC PHASES ON CORROSION BEHAVIOR AND MECHANICAL PROPERTIES OF DUPLEX STAINLESS STEEL AND SUPER-DUPLEX STAINLESS STEEL

OpenAIRE

Prabhu Paulraj; Rajnish Garg

2015-01-01

Duplex Stainless Steels (DSS) and Super Duplex Stainless Steel (SDSS) have excellent integration of mechanical and corrosion properties. However, the formation of intermetallic phases is a major problem in their usage. The mechanical and corrosion properties are deteriorated due to the presence of intermetallic phases. These phases are induced during welding, prolonged exposure to high temperatures, and improper heat treatments. The main emphasis of this review article is on intermetallic pha...

Swelling and swelling resistance possibilities of austenitic stainless steels in fusion reactors

International Nuclear Information System (INIS)

Maziasz, P.J.

1983-01-01

Fusion reactor helium generation rates in stainless steels are intermediate to those found in EBR-II and HFIR, and swelling in fusion reactors may differ from the fission swelling behavior. Advanced titanium-modified austenitic stainless steels exhibit much better void swelling resistance than AISI 316 under EBR-II (up to approx. 120 dpa) and HFIR (up to approx. 44 dpa) irradiations. The stability of fine titanium carbide (MC) precipitates plays an important role in void swelling resistance for the cold-worked titanium-modified steels irradiated in EBR-II. Futhermore, increased helium generation in these steels can (a) suppress void conversion, (b) suppress radiation-induced solute segregation (RIS), and (c) stabilize fine MC particles, if sufficient bubble nucleation occurs early in the irradation. The combined effects of helium-enhanced MC stability and helium-suppressed RIS suggest better void swelling resistance in these steels for fusion service than under EBR-II irradiation

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

DEFF Research Database (Denmark)

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

1989-01-01

In recent years the implantation of noble gases in metals has been found to induce some exciting phenomena such as formation of inclusions containing solid gas at extremely high pressures. In stainless steels these inclusions are the origin of a stress-induced martensitic fcc → bcc phase...... transformation in the implanted layer. In this work we present results from a depth distribution analysis of the martensitic phase change occurring in Xe implanted single crystals of austenitic stainless steel. Analysis was done by in situ RBS/channeling analysis, X-ray diffraction and cross-section transmission...... electron microscopy (XTEM) of the implanted surface. It is found that the martensitic transformation of the surface layer occurs for fluences above 1 × 1020 m−2. The thickness of the transformed layer increases with fluence to ≈ 150 nm at 1 × 10 21 m−2, which far exceeds the range plus straggling...

Stability of grain-refined reversed structures in a 301LN austenitic stainless steel under cyclic loading

Czech Academy of Sciences Publication Activity Database

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

2017-01-01

Roč. 703, č. 4 (2017), s. 280-292 ISSN 0921-5093 R&D Projects: GA ČR GA13-32665S Institutional support: RVO:68081723 Keywords : austenitic stainless steel * reversion treatment * grain size * deformation induced martensite * strain-controlled fatigue Subject RIV: JL - Materials Fatigue, Friction Mechanics OBOR OECD: Audio engineering, reliability analysis Impact factor: 3.094, year: 2016

Creep-fatigue damage in austenitic stainless steels

International Nuclear Information System (INIS)

Rezgui, Brahim.

1980-06-01

This is a study of hold time effects on the low cycle fatigue (L.C.F.) properties of 316L austenitic stainless steel at 600 0 C in air. Results obtained for different plastic strain levels indicate that a tension hold time at peak strain lead to a reduction in fatigue life. The importance of this effect depend on the length of hold period, and also on the strain amplitude. No saturation had been observed. Metallographic and microstructural analysis of failed specimens indicates mechanisms by which failure is produced. For continuous cycling the fractures occurs by the initiation and the propagation of a trans-granular crack. Creep damage in the bulk of material is formed during periods of tensile stress relaxation; it causes a change in the failure mode which became intergranular. It is the interaction between this creep-damage and fatigue cracks which is partly responsable for the reduction in the fatigue life. Predictions based upon linear cumulative damage method indicate that virgin material properties may be irrelevant in creep-fatigue interactions [fr

Forecasting of mechanical - and structural behavior of 316 austenitic stainless steels by deformation charts

International Nuclear Information System (INIS)

Monteiro, S.N.

1980-01-01

The utilization of deformation charts applied to AISI 316 austenitic stainless steel with the purpose of foreseeing its behavior associated with structural and mechanical phenomena, is evaluated. The ocurrence of phenomena such as dynamic aging, martensite transformation, static aging, failure at creep curve, cells, subgrains and boundary slips is discussed in the different regions of the chart. A practical example of the charts' utilization for components of fast reactors is finally presented. (Author) [pt

The electrochemical corrosion behavior of austenitic alloys, cobalt or nickel based super alloys, structurally hardened martensitic, Inconel, zircaloy, super austenitic, duplex and of Ni-Cr or NTi deposits in tritiated water. 3 volumes

International Nuclear Information System (INIS)

Bellanger, G.

1994-01-01

The redox potential of 3 H 2 O, as well as the corrosion potentials in this medium are found, abnormally, in the trans-passive region. This is completely different from the behavior in the chemical industry or in the water in nuclear powers. With such behavior, there will be breakdowns of the protective oxide layers, and in the presence of chloride there will be immediate pitting. The steels that are most resistant to this behavior are the super austenitic and super Duplex. To avoid corrosion, another solution is to decompose the radiolytic products by imposing a slight reducing potential. Corrosion inhibitors, which are stable in tritiated water, can be used. (author). 69 refs., 421 figs., tabs

A preliminary investigation of the initiation of pitting corrosion in austenitic stainless steels and nickel-based alloys

International Nuclear Information System (INIS)

Higginson, A.

1984-01-01

Pitting corrosion in a number of austenitic stainless steels and nickel-based alloys that differ widely in their resistance to corrosion was studed by electrochemical and electron-optical techniques. The effect of contamination of the sulphuric acid electrolyte by chloride ions was also investigated. Preliminary results for the surface analysis of samples of 316 stainless steel by Auger electron spectroscopy are presented, and suggestions are included for further application of this technique to the examination of pitting corrosion. A comprehensive review of the literature concerning the initiation of pitting corrosion is included

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

International Nuclear Information System (INIS)

Kupka, I.; Mrkous, P.

1977-01-01

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

Prediction of Irradiation Damage by Artificial Neural Network for Austenitic Stainless Steels

International Nuclear Information System (INIS)

Kim, Won Sam; Kim, Dae Whan; Hwang, Seong Sik

2007-01-01

The internal structures of pressurized water reactors (PWR) located close to the reactor core are used to support the fuel assemblies, to maintain the alignment between assemblies and the control bars and to canalize the primary water. In general these internal structures consist of baffle plates in solution annealed (SA) 304 stainless steel and baffle bolts in cold worked (CW) 316 stainless steel. These components undergo a large neutron flux at temperatures between 280 and 380 .deg. C. Well-controlled irradiation-assisted stress corrosion cracking (IASCC) data from properly irradiated, and properly characterized, materials are sorely lacking due to the experimental difficulties and financial limitations related to working with highly activated materials. In this work, we tried to apply the artificial neural network (ANN) approach, predicted the susceptibility to an IASCC for an austenitic stainless steel SA 304 and CW 316. G.S. Was and J.-P. Massoud experimental data are used. Because there is fewer experimental data, we need to prediction for radiation damage under the internal structure of PWR. Besides, we compared experimental data with prediction data by the artificial neural network

Ultra-large size austenitic stainless steel forgings for fast breeder reactor 'Monju'

International Nuclear Information System (INIS)

Tsukada, Hisashi; Suzuki, Komei; Sato, Ikuo; Miura, Ritsu.

1988-01-01

The large SUS 304 austenitic stainless steel forgings for the reactor vessel of the prototype FBR 'Monju' of 280 MWe output were successfully manufactured. The reactor vessel contains the heart of the reactor and sodium coolant at 530 deg C, and its inside diameter is about 7 m, and height is about 18 m. It is composed of 12 large forgings, that is, very thick flanges and shalls made by ring forging and an end plate made by disk forging and hot forming, using a special press machine. The manufacture of these large forgings utilized the results of the basic test on the material properties in high temperature environment and the effect that the manufacturing factors exert on the material properties and the results of the development of manufacturing techniques for superlarge forgings. The problems were the manufacturing techniques for the large ingots of 250 t class of high purity, the hot working techniques for stainless steel of fine grain size, the forging techniques for superlarge rings and disks, and the machining techniques of high precision for particularly large diameter, thin wall rings. The manufacture of these large stainless steel forgings is reported. (Kako, I.)

Microstructure characterization in the weld joint of a high nickel austenitic alloy and Cr18-Ni8 stainless steel

Energy Technology Data Exchange (ETDEWEB)

Wu, Na; Li, Yajiang; Wang, Juan [Shandong Univ., Jinan (CN). Key Lab. for Liquid - Solid Structural Evolution and Processing of Materials (Ministry of Education)

2012-06-15

High nickel austenitic alloy, 6 mm thick, and Cr18-Ni8 stainless steel with a thickness of 0.6 mm were joined by pulsed current tungsten inert gas arc welding without filler metal in this work. Metallographic examination, microhardness measurement and electron microprobe analysis were used to reveal microstructural characteristics in the joint. The results indicated that the weld metal consisted of {gamma}-austenite, {delta}-ferrite and carbides without the appearance of martensite. There were dendrite crystals at the edge of the weld metal near the high nickel austenitic alloy and isometric crystals in the center of the weld metal. The microhardness of the weld metal was the highest due to the existence of carbides and its finer structure. Graphite flakes were still embedded in the austenite matrix of the heat-affected zone without the formation of martensite. (orig.)

Dynamical recrystallization of high purity austenitic stainless steels

International Nuclear Information System (INIS)

Gavard, L.

2001-01-01

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

Temperature dependent measurement of internal damping of austenitic stainless steels

Directory of Open Access Journals (Sweden)

Oravcová Monika

2018-01-01

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

Erosion-corrosion resistance properties of 316L austenitic stainless steels after low-temperature liquid nitriding

Science.gov (United States)

Zhang, Xiangfeng; Wang, Jun; Fan, Hongyuan; Pan, Dong

2018-05-01

The low-temperature liquid nitriding of stainless steels can result in the formation of a surface zone of so-called expanded austenite (S-phase) by the dissolution of large amounts of nitrogen in the solid solution and formation of a precipitate-free layer supersaturated with high hardness. Erosion-corrosion measurements were performed on low-temperature nitrided and non-nitrided 316L stainless steels. The total erosion-corrosion, erosion-only, and corrosion-only wastages were measured directly. As expected, it was shown that low-temperature nitriding dramatically reduces the degree of erosion-corrosion in stainless steels, caused by the impingement of particles in a corrosive medium. The nitrided 316L stainless steels exhibited an improvement of almost 84% in the erosion-corrosion resistance compared to their non-nitrided counterparts. The erosion-only rates and synergistic levels showed a general decline after low-temperature nitriding. Low-temperature liquid nitriding can not only reduce the weight loss due to erosion but also significantly reduce the weight loss rate of interactions, so that the total loss of material decreased evidently. Therefore, 316L stainless steels displayed excellent erosion-corrosion behaviors as a consequence of their highly favorable corrosion resistances and superior wear properties.

The difference in thermal and mechanical stabilities of austenite between carbon- and nitrogen-added metastable austenitic stainless steels

International Nuclear Information System (INIS)

Masumura, Takuro; Nakada, Nobuo; Tsuchiyama, Toshihiro; Takaki, Setsuo; Koyano, Tamotsu; Adachi, Kazuhiko

2015-01-01

In order to evaluate the effects of carbon and nitrogen addition on the stability of austenite, athermal and deformation-induced α′-martensitic transformation behaviors were investigated using type 304-metastable austenitic stainless steels containing 0.1 mass% carbon or nitrogen. The difference in the development of the deformation microstructure in particular is discussed in terms of the stacking-fault energy (SFE). Since carbon-added steel has a lower SFE than that of nitrogen-added steel, deformation twins and ε-martensite were preferentially formed in the carbon-added steel, whereas a dislocation cell structure developed in the nitrogen-added steel. Crystallographic analysis using the electron backscatter diffraction method revealed that the difference in the deformation microstructure has a significant influence on the growth behavior of deformation-induced α′-martensite, that is, the interface of the deformation twins and ε-martensite suppresses the growth of α′-martensite, whereas dislocation cell boundaries are not effective. As a result, the mechanical stability of carbon-added steel is slightly higher than that of nitrogen-added steel, although the thermal stabilization effect of carbon is much lower than that of nitrogen

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

International Nuclear Information System (INIS)

Dalton, J.H.

1978-01-01

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

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

International Nuclear Information System (INIS)

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

2003-01-01

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

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

International Nuclear Information System (INIS)

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

1979-01-01

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

Effects of Copper and Sulfur Additions on Corrosion Resistance and Machinability of Austenitic Stainless Steel

International Nuclear Information System (INIS)

Kim, Soon Tae; Park, Yong Soo; Kim, Hyung Joon

1999-01-01

Effects of Cu and S on corrosion resistance and machinability of austenitic stainless steel were investigated using immersion test, metallographic examination, Auger surface analysis and tool life test with single point turning tools. Corrosion resistance of the experimental Cu containing alloys in 18.4N H 2 SO 4 at 80 ∼ 120 .deg. C and 3N HCl at 40 .deg. C decreased as S content increased. However, one of the experimental alloys (Fe- 18%Cr- 21%Ni-3.2%Mo- 1.6%W- 0.2%N- 3.1%Cu- 0.091%S) showed general and pitting corrosion resistance equivalent to that of CW12MW in highly concentrated SO 4 2- environment. The alloy also showed pitting corrosion resistance superior to super stainless steel such as 654SMO in Cl - environment. The reasons why the increase in S content deteriorated the corrosion resistance were first, that the number and size of (Mn, Cr)S sulfides having corrosion resistance lower than that of matrix increased, leading to pitting corrosion and second, that rapid dissolution of the matrix around the pits was caused by adsorbed S. However, the alloy containing 3.1 %Cu and 0.091 % S maintained high general and pitting corrosion resistance due to heavily enriched noble Cu through selective dissolution of active Fe and Ni. The tool life for 3.1 % Cu + 0.091 % S added alloy was about four times that of 0.06%Cu + 0.005% S added alloy due to high shear strain rate generated by Cu addition giving easy cross slip of dislocation, lubrication of ductile (Mn, Cr)S sulfides adhering to tool crater surface and low cutting force resulting from thin continuous sulfides formed in chips during machining

Correlation between Fatigue Crack Growth Behavior and Fracture Surface Roughness on Cold-Rolled Austenitic Stainless Steels in Gaseous Hydrogen

Directory of Open Access Journals (Sweden)

Tai-Cheng Chen

2018-03-01

Full Text Available Austenitic stainless steels are often considered candidate materials for use in hydrogen-containing environments because of their low hydrogen embrittlement susceptibility. In this study, the fatigue crack growth behavior of the solution-annealed and cold-rolled 301, 304L, and 310S austenitic stainless steels was characterized in 0.2 MPa gaseous hydrogen to evaluate the hydrogen-assisted fatigue crack growth and correlate the fatigue crack growth rates with the fracture feature or fracture surface roughness. Regardless of the testing conditions, higher fracture surface roughness could be obtained in a higher stress intensity factor (∆K range and for the counterpart cold-rolled specimen in hydrogen. The accelerated fatigue crack growth of 301 and 304L in hydrogen was accompanied by high fracture surface roughness and was associated with strain-induced martensitic transformation in the plastic zone ahead of the fatigue crack tip.

Microstructure and local texture evolution by plasma nitriding in a 316L austenitic stainless steel and consequences on its fatigue durability

International Nuclear Information System (INIS)

Stinville, Jean-Charles

2010-01-01

The present study concerns the surface and mechanical properties induced by specific low temperature (∼400 C) plasma nitriding of an AISI 316L austenitic stainless steel largely used for structural component in nuclear and chemical industries. It focuses especially on its influence on the fatigue durability. The great advantages of this plasma nitriding process are to produce thick nitrided layers with a high concentration of nitrogen atoms in solid solution into the material and to preserve the stainless character of the substrate. As a consequence a new phase named expanded austenite or γ N phase is formed and the lattice expansion associated with the high supersaturation of interstitial nitrogen atoms results in residual compressive stresses at the surface that exceed 2 GPa. The surface is then strongly modified as a result of complex effects including some crystallographic plane rotation, plasticity and damage in some grains depending on their orientation. The considerable increase of hardness and wear resistance produced by plasma nitriding of austenitic stainless steels is now well documented but there are practically no data on the influence on fatigue properties. Series of fatigue tests in air at room temperature carried out in the low cycle fatigue range show a significant improvement of the fatigue life. The results are discussed especially taking into account the compressive residual stresses induced by the nitrided layer. (authors)

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

International Nuclear Information System (INIS)

Bertrand, C.; Ardellier, A.

1996-01-01

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

A new model for fatigue damage accumulation of austenitic stainless steel under variable amplitude loading

International Nuclear Information System (INIS)

Taheri, S.; Vincent, L.; Le-Roux, J.C.

2013-01-01

The application of Miner's rule using a loading issued from a mock-up of a RHR system (removal heat system) of PWR plant, made of 304 steel gives a very important non-conservative fatigue life in strain control when strain fatigue curve is used. This result is due to the absence of sequence effect in Miner's rule. Many non linear damage accumulation models have been proposed to get a sequence effect. Shortcomings of some non linear damage accumulation models are discussed. So Smith-Watson-Topper and Fatemi-Socie criterions with a linear damage accumulation rule are then applied to experimental data. A major issue is the need for an elastic-plastic constitutive law which is difficult to propose in the presence of high cycle secondary hardening observed in austenitic stainless steels. A conservative model for fatigue damage accumulation under variable amplitude loading is then proposed for austenitic stainless steels in strain control, which does not need a constitutive law, but takes into account plasticity through cyclic strain stress curve. The model uses a linear damage accumulation rule. This model is based on the fact that for stainless steels, pre-hardening is detrimental for fatigue life in strain control, while it is beneficial in stress control. In the presence of low mean stress, the model is approved based on a large number of tests. Moreover the model allows to explain the larger detrimental effect of a tension mean stress in strain control tests than in stress control tests. (authors)

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

International Nuclear Information System (INIS)

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

2011-01-01

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

Characterization of microstructures in austenitic stainless steels by ultrasonics

International Nuclear Information System (INIS)

Raj, Baldev; Palanichamy, P.; Jayakumar, T.; Kumar, Anish; Vasudevan, M.; Shankar, P.

2000-01-01

Recently, many nondestructive techniques have been considered for microstructural characterization of materials to enable in-situ component assessment for pre-service quality and in-service performance. Ultrasonic parameters have been used for estimation of average grain size, evaluation of recrystallization after cold working, and characterization of Cr2N precipitation during thermal aging in different grades of austenitic stainless steels. Ultrasonic first back wall echo signals were obtained from several specimens of AISI type 316 stainless steel with different grain sizes. Shift in the spectral peak frequency and the change in the full width at half maximum of the autopower spectrum of the first back wall echo are correlated with the grain size in the range 30-150 microns. The advantages of this method are: (i) independence of variation in couplant conditions (ii), applicable even to highly attenuating materials, (iii) direct correlation of the ultrasonic parameters with yield strength and (iv) suitability for shop-floor applications. Recrystallization behavior (temperature range 973-1173 K and time durations 0.5-1000 h) of cold worked titanium modified 316 stainless steel (D9) has been characterized using ultrasonic velocity measurements. A velocity parameter derived using a combination of shear and longitudinal wave velocities is correlated with the degree of recrystallization. These velocity measurement could also identify onset, progress and completion of recrystallization more accurately as compared to hardness and strength measurements. Ultrasonic velocity measurements were performed in thermally aged (at 1123 K for 10 to 2000 h) nuclear grade 316 LN stainless steel. Change in velocity due to thermal aging treatment could be used to reveal the formation of (i) Cr-N clusters associated with high lattice strains, (ii) coherent Cr2N precipitation, (iii) loss of coherency and (iv) growth of incoherent Cr2N precipitates. Microstructural characterization by

Ultrasonic inspectability of austenitic stainless steel and dissimilar metal weld joints

Energy Technology Data Exchange (ETDEWEB)

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

2008-07-01

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

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

DEFF Research Database (Denmark)

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

1981-01-01

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

Effect of martensitic phase transformation on the behavior of 304 austenitic stainless steel under tension

Energy Technology Data Exchange (ETDEWEB)

Wang, H., E-mail: wanghm@lanl.gov [Materials Science and Technology, Los Alamos National Laboratory, Los Alamos, NM (United States); Jeong, Y. [Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD (United States); Clausen, B.; Liu, Y.; McCabe, R.J. [Materials Science and Technology, Los Alamos National Laboratory, Los Alamos, NM (United States); Barlat, F. [Graduate Institute of Ferrous Technology, POSTECH (Korea, Republic of); Tomé, C.N. [Materials Science and Technology, Los Alamos National Laboratory, Los Alamos, NM (United States)

2016-01-01

The present work integrates in-situ neutron diffraction, electron backscatter diffraction and crystal plasticity modeling to investigate the effect of martensitic phase transformation on the behavior of 304 stainless steel under uniaxial tension. The macroscopic stress strain response, evolution of the martensitic phase fraction, texture evolution of each individual phase, and internal elastic strains were measured at room temperature and at 75 °C. Because no martensitic transformation was observed at 75 °C, the experimental results at 75 °C were used as a reference to quantify the effect of formed martensitic phase on the behavior of 304 stainless steel at room temperature. A crystallographic phase transformation model was implemented into an elastic–viscoplastic self-consistent framework. The phase transformation model captured the macroscopic stress strain response, plus the texture and volume fraction evolution of austenite and martensite. The model also predicts the internal elastic strain evolution with loading in the austenite, but not in the martensite. The results of this work highlight the mechanisms that control phase transformation and the sensitivity of modeling results to them, and point out to critical elements that still need to be incorporated into crystallographic phase transformation models to accurately describe the internal strain evolution during phase transformation.

UNS S32750 super duplex steel welding using pulsed Nd:YAG laser

International Nuclear Information System (INIS)

Francini, O.D.; Andrade, G.G.; Clemente, M.S.; Gallego, J.; Ventrella, V.A.

2016-01-01

Laser is a flexible and powerful tool with many relevant applications in industry, mainly in the welding area. Lasers today provide the welding industry technical solutions to many problems. This work studied the weld metal obtained by pulsed laser welding of Nd: YAG super duplex stainless steel UNS S32750 employed in the oil and natural gas, analyzing the influence of high cooling rate, due to the laser process, the swing phase ferrite / austenite. Were performed weld beads in butt joint with different repetition rates. The different microstructures were obtained by optical microscopy and scanning electron microscopy. The results showed that the effect of varying the welding energy of Nd: YAG laser on the volume fractions of the phases ferrite/austenite in the weld metal was its ferritization and low austenite amount on the grain boundary. (author)

Study of precipitation phenomena during the creep of austenitic stainless steels

International Nuclear Information System (INIS)

Le May, I.; Bassett, B.J.; White, W.E.

1975-01-01

Creep-rupture data for two austenitic stainless steels, AISI Types 310 and 316, are presented, together with observations of precipitation taking place during creep. While the effects of creep deformation on precipitation in the Type 310 were negligible, ferrite precipitation was considerably greater in the Type 316 undergoing creep than in unstressed material. Ferrite precipitation appears to promote grain boundary cavitation and internal cracking, thus reducing creep resistance and a correlation has been noted between increased ferrite precipitation and apparent further weakening of the Type 316 over the temperature range 730 to 800 0 C approximately, as evidenced by breaks in the isostress lines on a plot of log (time to rupture) versus temperature

Shallow-Land Buriable PCA-type austenitic stainless steel for fusion application

International Nuclear Information System (INIS)

Zucchetti, M.

1991-01-01

Neutron-induced activity in the PCA (Primary Candidate Alloy) austenitic stainless steel is examined, when used for first-wall components in a DEMO fusion reactor. Some low-activity definitions, based on different waste management and disposal concepts, are introduced. Activity in the PCA is so high that any recycling of the irradiated material can be excluded. Disposal of PCA radioactive wastes in Shallow-Land Buriable (SLB) is prevented as well. Mo, Nb and some impurity elements have to be removed or limited, in order to reduce the radioactivity of the PCA. Possible low-activity versions of the PCA are introduced (PCA-la); they meet the requirements for SLB and may also be recycled under certain conditions. (author)

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

International Nuclear Information System (INIS)

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

1992-01-01

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

Low temperature plasma carburizing of AISI 316L austenitic stainless steel and AISI F51 duplex stainless steel Cementação sob plasma à baixa temperatura do aço inoxidável austenítico AISI 316L e do aço inoxidável duplex AISI F51

OpenAIRE

Carlos Eduardo Pinedo; André Paulo Tschiptschin

2013-01-01

In this work an austenitic AISI 316L and a duplex AISI F51 (EN 1.4462) stainless steel were DC-Plasma carburized at 480ºC, using CH4 as carbon carrier gas. For the austenitic AISI 316L stainless steel, low temperature plasma carburizing induced a strong carbon supersaturation in the austenitic lattice and the formation of carbon expanded austenite (γC) without any precipitation of carbides. The hardness of the carburized AISI 316L steel reached a maximum of 1000 HV due to ∼13 at% c...

Effect of laser heat treatment on intergranular corrosion of austenitic stainless steel; Austenite kei stainless ko no ryukai fushoku kanjusei ni oyobosu laser netsushori no eikyo

Energy Technology Data Exchange (ETDEWEB)

Osawa, M.; Yoneyama, T. [Tokyo Denki University, Tokyo (Japan). Faculty of Engineering; Isshiki, Y. [Tokyo Metropolitan Industrial Technology Center, Tokyo (Japan)

1995-03-15

The laser heat treatment of SUS304 steel was studied to lower the intergranular corrosion sensitivity of austenitic stainless steel. By the short-time heating around 923K, the SUS304 steel is sensitized to the intergranular corrosion with the deposition of Cr carbide into the granular field of crystals. To recover it, it is necessary to solidly dissolve, and simultaneously, quickly cool the Cr carbide above 1273K. For such solution heat treatment, CO2 laser beams were used with the treatment condition that the power and beam diameter were 800 to 1200W and 0.3 to 0.64cm, respectively. Regardless of both power density and beam diameter, the desensitization was observed at heating temperatures above 1323K. As a result of calculation by simulation, the solid dissolution of Cr carbide and recovery of Cr`s depletion zone in the granular field of crystals took place in a very short time at heating temperatures above 1323K. It agreed well with the experimental result. The laser beams are effective in the solution heat treatment of stainless steel. 14 refs., 15 figs., 1 tab.

Thermal aging evaluation of cast austenitic stainless steel pipe

International Nuclear Information System (INIS)

Song, T. H.; Jung, I. S.

2002-01-01

24 years have been passed since Kori Unit 1 began its commercial operation, and 19 years have been passed since Kori Unit 2 began its commercial operation. As the end point of design life become closer, plant life extension and periodic safety assessment is paid more and more attention to by utility company. In this paper, the methodologies and results of cast austenitic stainless steel pipe thermal aging evaluations of both units have been presented in association with aging time of 10, 20, and 30 years and operating temperature, respectively. Life extension cases respectively. As a result of this, at the operating temperature of 280 .deg. C, thermal aging was not a problem as long as Charpy V-notch room temperature minimum impact energy is concerned. However, more than 300 .deg. C and 30 years of operating condition, we should perform detailed fracture mechanics analysis with CMTR of NPP pipe

Analysis of the non-isothermal austenite-martensite transformation in 13% Cr-type martensitic stainless steels

International Nuclear Information System (INIS)

Garcia-De-Andris, C.; Alvarez, L.F.

1996-01-01

In martensitic stainless steels, as in other alloyed containing carbide-forming elements, the carbide dissolution and precipitation processes that take place during heat treatment can cause modifications to the chemical composition of the austenite phase of these steels. The chemical composition of this phase is a fundamental factor for the evolution of the martensitic transformation. As a result of their influence on the dissolution and precipitation processes, the parameters of the quenching heat treatment exert a strong influence on the behavior of the martensitic transformation in these steels. In the present study, the effect of the heating temperature and the cooling rate on the martensitic transformation in two 13% Cr-type martensitic stainless steels with different carbon contents were properly evaluated. (author)

submitter Physical Properties of a High-Strength Austenitic Stainless Steel for the Precompression Structure of the ITER Central Solenoid

CERN Document Server

Sgobba, Stefano; Arauzo, Ana; Roussel, Pascal; Libeyre, Paul

2016-01-01

The ITER central solenoid (CS) consists of six independent coils kept together by a precompression support structure that must react vertical tensile loads and provide sufficient preload to maintain coil-to-coil contact when the solenoid is energized. The CS precompression system includes tie plates, lower and upper key blocks, load distribution and isolation plates and other attachment, support and insulating hardware. The tie plates operating at 4 K are manufactured starting from forgings in a high-strength austenitic stainless steel (FXM-19) with a stringent specification. Moreover, forged components for the lower and upper key blocks have to be provided in the same FXM-19 grade with comparably strict requirements. FXM-19 is a high-nitrogen austenitic stainless steel, featuring high strength and toughness, ready weldability, and forgeability. It features as well higher integral thermal contraction down to 4 K compared with the very high Mn steel grade selected for the CS coil jackets, hence providing an ad...

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

Science.gov (United States)

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

2018-03-01

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

Effect of light impurities on the early stage of swelling in austenitic stainless steel

International Nuclear Information System (INIS)

Igata, N.

1998-01-01

The objective of this study is to analyse the early stage of swelling and clarify the role of light impurities (nitrogen) in swelling of austenitic stainless steel. Recent results show that light impurities affect the swelling of 316 stainless steel under HVEM irradiation up to 10 dpa. At low concentration of light impurities the radiation swelling increases then decreases through the maximum as the concentration of light impurities increases. In the present paper the theoretical model is presented for the explanation of this effect. The model is based on the two factors: the influence of absorbed impurities on the voids caused by the production of an additional gas pressure in voids for their stabilization and the effect of impurities segregated around the surface of voids by the lowering of surface tension. These two affects are taken into account in the calculations of the critical size and the growth rate of cavities. The theoretical predictions on the radiation swelling rate dependent on the impurity concentration and temperature coincided with the experimental results on 316 stainless steel irradiated by HVEM. (orig.)

Effect of Dynamic Reheating Controlled by the Weaving Width on the Microstructure of GTA Bead-On-Pipe Weld Metal of 25% Cr Super Duplex Stainless Steel

Directory of Open Access Journals (Sweden)

Hee-Joon Sung

2018-05-01

Full Text Available Gas tungsten arc welding (GTAW with three different heat inputs controlled by the weaving width was performed to understand their effects on the microstructural changes during bead-on-pipe welding of super duplex stainless steel. The microstructure of the weld metals was categorized into three different types of zones: non-reheated, reheated type, and reheating-free zone. Even though single-pass welding with different weaving widths was employed, a reheated microstructure was detected, which has been previously observed with multiple pass welding. This phenomenon was called “dynamic reheating”, because it was produced by the weaving operation during welding regardless of the weaving width. The categorized area fraction varied with the weaving width change. Electron backscatter diffraction (EBSD results at the edge (the area near the fusion line of the low-heat-input condition indicated a higher austenite volume fraction and a lower Cr2N fraction than that of the medium heat input condition. Thus, it described an inverse relationship, because higher heat input provided a lower austenite fraction. In addition, it was observed clearly that the austenite fraction at the medium heat input condition was dramatically increased by reheating, while the Cr2N fraction was reduced. Regardless of the weaving width, reheating contributed to the increase of the austenite fraction, further reducing the Cr2N quantity. The edge areas in the map showed an inverse relationship in the reheated area fraction between low heat input and medium heat input. For this reason, the austenite fraction on the weld metal was determined not only by the heat input, but also by the amount of reheating.

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

Science.gov (United States)

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

2017-12-01

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

In-Situ Investigation of Strain-Induced Martensitic Transformation Kinetics in an Austenitic Stainless Steel by Inductive Measurements

Directory of Open Access Journals (Sweden)

Carola Celada-Casero

2017-07-01

Full Text Available An inductive sensor developed by Philips ATC has been used to study in-situ the austenite (γ to martensite (α′ phase transformation kinetics during tensile testing in an AISI 301 austenitic stainless steel. A correlation between the sensor output signal and the volume fraction of α′-martensite has been found by comparing the results to the ex-situ characterization by magnetization measurements, light optical microscopy, and X-ray diffraction. The sensor has allowed for the observation of the stepwise transformation behavior, a not-well-understood phenomena that takes place in large regions of the bulk material and that so far had only been observed by synchrotron X-ray diffraction.

Experimental study of fatigue crack propagation in type 316 austenitic stainless steel

International Nuclear Information System (INIS)

Mostafa, M.; Vessiere, G.; Hamel, A.; Boivin, M.

1983-01-01

In this work, are grouped and compared the crack propagation rates in type 316 austenitic stainless steel in two loading cases: plane strain and plane stress. Plane strain has been obtained on axisymmetric cracked specimens, plane stress on thin notched specimens, subjected to alternative bending. The results show that the crack propagation rate is greater for plane strain, i.e. in the case of the smallest plastic zone. The Elber concept was also used for explaining the different values of the crack propagation rate. It's noteworthy to find out that the Paris' law coefficients for different loading levels and those fo Elber's law are correlated [fr

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

DEFF Research Database (Denmark)

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

2017-01-01

A new metastable Ni-free duplex stainless steel has been designed with superior plasticity by optimizing austenite stability using thermodynamic calculations of stacking fault energy and with reference to literature findings. Several characterization methods comprising optical microscopy, magnetic......, including an ultimate tensile strength of ~900 MPa and elongation to fracture of ~94 pct due to the synergistic effects of transformation-induced plasticity and twinning-induced plasticity. The deformation mechanism of austenite is complex and includes deformation banding, strain-induced martensite...... formation, and deformation-induced twinning, while the ferrite phase mainly deforms by dislocation slip. Texture analysis indicates that the Copper and Rotated Brass textures in austenite (FCC phase) and {001}〈110〉 texture in ferrite and martensite (BCC phases) are the main active components during...

Mechanical behaviour of austenitic stainless steels in inert environment and in hot chloride environment: influence of molybdenum addition

International Nuclear Information System (INIS)

Daret, Jacques

1978-01-01

This research thesis reports the study of the influence of molybdenum addition. It is based on an experimental method which brings to the fore correlations between mechanical and electrochemical parameters of the phenomenon of stress corrosion cracking of austenitic stainless steels. After having recalled some characteristics of dry corrosion and electrochemical corrosion, presented austenitic stainless steels (mechanical properties such as elastic modulus, yield strength, tensile strength, ultimate elongation, creep behaviour, inter-crystalline and pitting corrosion, stress corrosion cracking behaviour), the author addresses the stress corrosion cracking behaviour of these steels in chloride environment (general characteristics, parameters, proposes theories to explain stress corrosion cracking), reports the study of the influence of molybdenum in these steels, notably on corrosion resistance and on stress corrosion cracking. Experimental method and results are described and discussed: tensile tests and creep tests in inert environment, stress corrosion cracking test in chloride environment with analysis based either on corrosion potential evolution or on sample elongation evolution. Results are notably discussed in terms of crack situation within metal lattice, crack growth rate, and scanning electronic microscopy observations [fr

The carbide M{sub 7}C{sub 3} in low-temperature-carburized austenitic stainless steel

Energy Technology Data Exchange (ETDEWEB)

Ernst, Frank, E-mail: frank.ernst@cwru.edu [Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, OH 44106-7204 (United States); Li, Dingqiang; Kahn, Harold; Michal, Gary M.; Heuer, Arthur H. [Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, OH 44106-7204 (United States)

2011-04-15

Prolonged low-temperature gas-phase carburization of AISI 316L-type austenitic stainless steel can cause intragranular precipitation of the carbide M{sub 7}C{sub 3} (M: randomly dispersed Fe, Cr, Ni). Transmission electron microscopy revealed that the carbide particles have the shape of needles. They grow by a ledge-migration mechanism and in a crystallographic orientation relationship to the austenite matrix that enables highly coherent interphase interfaces. A small solubility limit of Ni in the carbide and restricted Ni diffusivity at the processing temperature leads to Ni pileup around the particles and may explain the extreme aspect ratio of the particle shape. These characteristics closely resemble what has been observed earlier for precipitates of M{sub 5}C{sub 2} under slightly different processing conditions and can be rationalized by considering the particular constraints imposed by carburization at low temperature.

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

DEFF Research Database (Denmark)

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

2016-01-01

: - plastic deformation of metastable austenitic stainless steels leads to the development of strain-induced martensite, which compromises the uniformity and the homogeneity of the expanded austenite zone. - during low temperature surface engineering composition and stress profiles develop. On numerical......Thermochemical surface engineering by nitriding of austenitic stainless steel transforms the surface zone into expanded austenite, which improves the wear resistance of the stainless steel while preserving the stainless behavior. As a consequence of the thermochemical surface engineering, huge...

Stress-free reference for neutron diffraction measurement of residual stress in butt-welded joints of austenitic stainless steel pipes

International Nuclear Information System (INIS)

Maekawa, Akira; Takahashi, Tsuneo; Tsuji, Takashi; Suzuki, Hiroshi; Moriai, Atsushi

2012-01-01

Stress-free lattice spacing d_0 has the most influence on reliability of neutron stress measurements made using an angle dispersive method. However, it is hard to evaluate the lattice spacing of welded structures and ductile materials such as stainless steel accurately. In this study, suitable measurement conditions for d_0 of welded pipe joints of austenitic stainless steel were discussed. The d_0 values derived from {311} and {111} reflections, which are often used in austenitic stainless steel for residual stress measurement, were examined. Comparison of the residual strains and stresses evaluated using the obtained d_0 and the finite element analysis showed that the way the d_0 values were chosen affected the measurement accuracy significantly. The stress measurement accuracy was remarkably improved when the {311} reflection was used and the proper d_0 value was chosen in the respective neutron diffraction measurements. For instance, for the axial diffraction measurements using the {311} reflection, it was recommended that only the axial d_0 value of the {311} reflection be used; the measurements using the {111} reflection were less accurate due to the large Young's modulus. Additionally, a lower diffraction angle was judged to be one of the factors leading to a decrease of the strain measurement accuracy. (author)

Prediction of residual life of low-cycle fatigue in austenitic stainless steel based on indentation test

International Nuclear Information System (INIS)

Yonezu, Akio; Touda, Yuya; Kim, HakGui; Yoneda, Keishi; Sakihara, Masayuki; Minoshima; Kohji

2011-01-01

In this study, a method to predict residual life of low-cycle fatigue in austenitic stainless steel (SUS316NG) was proposed based on indentation test. Low-cycle fatigue tests for SUS316NG were first conducted based on uniaxial tensile-compressive loading under the control of true strain range. Applied strain ranges were varied from about 3 to 12%. Their hysteresis loops of stress and strain were monitored during the fatigue tests. Plastic deformation range in hysteresis loop at each cycle could be roughly expressed by bi-linear hardening rule, whose plastic properties involve yield stress and work-hardening coefficient. The cyclic plastic properties were found to be dependent on the number of cycles and applied strain range, due to work-hardening. We experimentally investigated the empirical relationship between the plastic properties and number of cycles for each applied strain range. It is found that the relationship quantitatively predicts the applied strain range and number of cycles, when the plastic properties, or yield stress and work-hardening coefficient were known. Indentation tests were applied to the samples subjected to low cycle fatigue test, in order to quantitatively determine the plastic properties. The estimated properties were assigned to the proposed relationship, yielding the applied strain range and the cycle numbers. The proposed method was applied to the several stainless steel samples subjected to low cycle fatigue tests, suggesting that their residual lives could be reasonably predicted. Our method is thus useful for predicting the residual life of low-cycle fatigue in austenitic stainless steel. (author)

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

Directory of Open Access Journals (Sweden)

Tatiana Oršulová

2017-04-01

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

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

International Nuclear Information System (INIS)

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

1993-08-01

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

Progress report on the influence of higher interpass temperatures on the integrity of austenitic stainless steel welded joints

Energy Technology Data Exchange (ETDEWEB)

Yarmuch, M.; Choi, L. [Alberta Research Council, Edmonton, AB (Canada); Armstrong, K.; Radu, I. [PCL Industrial Constructors Inc., Nisku, AB (Canada)

2008-07-01

This report discussed the progress of the Welding Productivity Group (TWPG) interpass temperature assessment project (ITAP). The project was initiated to evaluate the influence of interpass temperatures on the metallurgical, corrosive, and mechanical properties of austenitic stainless steel, carbon steel, and low-alloy pressure weldments. To date, the project has conducted experiments to determine if interpass temperatures in austenitic stainless steel weldments are higher than temperatures recommended by API requirements. Elevated interpass temperatures for various base materials have been evaluated. Preliminary metallurgical, mechanical, and laboratory corrosion data from 3 experiments with 304/304L and 316/316L stainless steel weldment test specimens has shown that no significant changes occur as a result of elevated interpass temperatures. Results from side bend specimens have demonstrated that elevated interpass temperatures produce acceptable weldment ductility. No intergranular cracking was observed during oxalic acid etch tests conducted for the 316/316L samples. Huey tests performed on the 304/304L specimens indicated that elevated interpass temperatures did not adversely affect the intergranular corrosion resistance of weldments with less than 3 weld passes. Huey tests performed on the 316 specimens showed a marked increase in corrosion rates and normalized weight losses. It was concluded that rates of attack correlate with the maximum interpass temperature and not the average weld metal ferrite number. 22 refs., 11 tabs., 12 figs.

Initiation of stress corrosion cracking in pre-stained austenitic stainless steels exposed to primary water

International Nuclear Information System (INIS)

Huguenin, P.

2012-01-01

Austenitic stainless steels are widely used in primary circuits of Pressurized Water Reactors (PWR) plants. However, a limited number of cases of Intergranular Stress Corrosion Cracking (IGSCC) has been detected in cold-worked (CW) areas of non-sensitized austenitic stainless steel components in French PWRs. A previous program launched in the early 2000's identified the required conditions for SCC of cold-worked stainless steels. It was found that a high strain hardening coupled with a cyclic loading favoured SCC. The present study aims at better understanding the role of pre-straining on crack initiation and at developing an engineering model for IGSCC initiation of 304L and 316L stainless steels in primary water. Such model will be based on SCC initiation tests on notched (not pre-cracked) specimens under 'trapezoidal' cyclic loading. The effects of pre-straining (tensile versus cold rolling), cold-work level and strain path on the SCC mechanisms are investigated. Experimental results demonstrate the dominating effect of strain path on SCC susceptibility for all pre-straining levels. Initiation can be understood as crack density and crack depth. A global criterion has been proposed to integrate both aspects of initiation. Maps of SCC initiation susceptibility have been proposed. A critical crack depth between 10 and 20 μm has been demonstrated to define transition between slow propagation and fast propagation for rolled materials. For tensile pre-straining, the critical crack depth is in the range 20 - 50 μm. Experimental evidences support the notion of a KISCC threshold, whose value depends on materials, pre-straining ant load applied. The initiation time has been found to depend on the applied loading as a function of (σ max max/YV) 11,5 . The effect of both strain path and surface hardening is indirectly taken into account via the yield stress. In this study, material differences rely on strain path effect on mechanical properties. As a result, a stress

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

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Thiago AmaroVicente

2018-03-01

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

Combining gradient structure and TRIP effect to produce austenite stainless steel with high strength and ductility

International Nuclear Information System (INIS)

Wu, X.L.; Yang, M.X.; Yuan, F.P.; Chen, L.; Zhu, Y.T.

2016-01-01

We report a design strategy to combine the benefits from both gradient structure and transformation-induced plasticity (TRIP). The resultant TRIP-gradient steel takes advantage of both mechanisms, allowing strain hardening to last to a larger plastic strain. 304 stainless steel sheets were treated by surface mechanical attrition to synthesize gradient structure with a central coarse-grained layer sandwiched between two grain-size gradient layers. The gradient layer is composed of submicron-sized parallelepiped austenite domains separated by intersecting ε-martensite plates, with increasing domain size along the depth. Significant microhardness heterogeneity exists not only macroscopically between the soft coarse-grained core and the hard gradient layers, but also microscopically between the austenite domain and ε-martensite walls. During tensile testing, the gradient structure causes strain partitioning, which evolves with applied strain, and lasts to large strains. The γ → α′ martensitic transformation is triggered successively with an increase of the applied strain and flow stress. Importantly, the gradient structure prolongs the TRIP effect to large plastic strains. As a result, the gradient structure in the 304 stainless steel provides a new route towards a good combination of high strength and ductility, via the co-operation of both the dynamic strain partitioning and TRIP effect.

Synergy between molybdenum and nitrogen on the pitting corrosion and passive film resistance of austenitic stainless steels as a pH-dependent effect

Energy Technology Data Exchange (ETDEWEB)

Loable, Carole, E-mail: carole.loable@lepmi.grenoble-inp.fr [Univ. Grenoble Alpes, LEPMI, F-38000 Grenoble (France); CNRS, LEPMI, F-38000 Grenoble (France); Dep. Eng. Quimica, Instituto Superior Técnico-Universidade de Lisboa, Av. Rovisco Pais, 1049 001 Lisbon (Portugal); Viçosa, Isadora N., E-mail: inogueira@poli.ufrj.br [Univ. Grenoble Alpes, LEPMI, F-38000 Grenoble (France); CNRS, LEPMI, F-38000 Grenoble (France); Mesquita, Thiago J., E-mail: Thiago.mesquita@total.com [CRU Ugitech, Avenue Paul Girod, 73403 Ugine Cedex (France); Mantel, Marc, E-mail: Marc.Mantel@ugitech.com [CRU Ugitech, Avenue Paul Girod, 73403 Ugine Cedex (France); Université Grenoble Alpes, SIMAP, F-38000 Grenoble (France); CNRS, SIMAP, F-38000 Grenoble (France); Nogueira, Ricardo P., E-mail: rnogueira@pi.ac.ae [Univ. Grenoble Alpes, LEPMI, F-38000 Grenoble (France); CNRS, LEPMI, F-38000 Grenoble (France); Department of Chemical Engineering, The Petroleum Institute, P.O. Box 2533, Abu Dhabi (United Arab Emirates); Berthomé, Gregory, E-mail: gregory.berthome@simap.grenoble-inp.fr [Université Grenoble Alpes, SIMAP, F-38000 Grenoble (France); CNRS, SIMAP, F-38000 Grenoble (France); Chauveau, Eric, E-mail: eric.chauveau@ugitech.fr [Department of Chemical Engineering, The Petroleum Institute, P.O. Box 2533, Abu Dhabi (United Arab Emirates); Roche, Virginie, E-mail: virginie.roche@lepmi.grenoble-inp.fr [Univ. Grenoble Alpes, LEPMI, F-38000 Grenoble (France); CNRS, LEPMI, F-38000 Grenoble (France)

2017-01-15

This paper brings up some insights upon the pH dependence of the synergistic effect of Mo and N on the localized corrosion resistance of austenitic stainless steels. The objective of this work is to study the synergetic effect of Mo and N additions on corrosion and passive film properties of austenitic grades. A comparison between Mo containing (3 wt% Mo); Mo and N containing (3 wt% Mo and 0.1% N) and free Mo or free Mo and N grades of highly controlled laboratory heats was done considering their localized corrosion resistance and oxide film formation in different aggressive conditions, from neutral to alkaline pH. The passive layer was characterized by EIS and XPS analyses. The combined effect of Mo and N on the pitting potential was confirmed to be synergistic, and not just the addition of their individual effects. Moreover, this effect was found to be pH-dependent, being very positive in acid to neutral conditions whereas it was almost inexistent in high pH. - Highlights: • Laboratory austenitic stainless steels with Mo and/or N were tested. • Mo and N acted synergistically to improve pitting resistance. • Synergistic effect is pH-dependent. • N clearly enhanced the repassivation of austenitic SS in presence of Mo.

Synergy between molybdenum and nitrogen on the pitting corrosion and passive film resistance of austenitic stainless steels as a pH-dependent effect

International Nuclear Information System (INIS)

Loable, Carole; Viçosa, Isadora N.; Mesquita, Thiago J.; Mantel, Marc; Nogueira, Ricardo P.; Berthomé, Gregory; Chauveau, Eric; Roche, Virginie

2017-01-01

This paper brings up some insights upon the pH dependence of the synergistic effect of Mo and N on the localized corrosion resistance of austenitic stainless steels. The objective of this work is to study the synergetic effect of Mo and N additions on corrosion and passive film properties of austenitic grades. A comparison between Mo containing (3 wt% Mo); Mo and N containing (3 wt% Mo and 0.1% N) and free Mo or free Mo and N grades of highly controlled laboratory heats was done considering their localized corrosion resistance and oxide film formation in different aggressive conditions, from neutral to alkaline pH. The passive layer was characterized by EIS and XPS analyses. The combined effect of Mo and N on the pitting potential was confirmed to be synergistic, and not just the addition of their individual effects. Moreover, this effect was found to be pH-dependent, being very positive in acid to neutral conditions whereas it was almost inexistent in high pH. - Highlights: • Laboratory austenitic stainless steels with Mo and/or N were tested. • Mo and N acted synergistically to improve pitting resistance. • Synergistic effect is pH-dependent. • N clearly enhanced the repassivation of austenitic SS in presence of Mo.

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

International Nuclear Information System (INIS)

Maziasz, P.J.

1984-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2015-06-11

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

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

International Nuclear Information System (INIS)

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

2014-01-01

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

Effect of reversion annealing on the formation of nano/ultrafine grained structure in 201 austenitic stainless steel

Energy Technology Data Exchange (ETDEWEB)

Moallemi, Mohammad; Najafizadeh, Abbas; Kermanpur, Ahmad [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Rezaee, Ahad, E-mail: a.rezaee@ma.iut.ac.ir [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of)

2011-12-15

Highlights: Black-Right-Pointing-Pointer The secondary increase in the martensite content after reversion annealing. Black-Right-Pointing-Pointer Formation of thermally induced martensite due to carbide precipitation. Black-Right-Pointing-Pointer The smallest average grain size of 70 nm is achieved by annealing at 850 Degree-Sign C for 15 s. Black-Right-Pointing-Pointer A fully austenitic structure with grain size of 100 nm and 1370 MPa yield strength. - Abstract: The formation of nano/ultrafine grain structure in a 201 austenitic stainless steel was investigated by the martensite thermomechanical treatment. Cast ingots were first homogenized, then hot-forged and solution-annealed to reduce the initial grain size. Cold rolling was then conducted down to 90% reduction in thickness, followed by reversion annealing at a temperature in the range of 1023-1173 K for 15-1800 s. The effect of reversion parameters on grain refinement was investigated. The resulting microstructures were characterized by a scanning electron microscopy equipped with X-ray energy-dispersive spectrometer, an X-ray diffractometer and a Feritscope. The hardness was measured by the Vickers method. The results show that a nano/ultrafine-grained structure formed in the initial stages of the reversion, but significant grain growth took place during the entire course of reversion. Initially lowered, the volume fraction of martensite increased again during the reversion treatment due to carbide precipitation. A fully austenitic nano grained 201 stainless steel with the average grain size of 100 nm was produced, possessing a yield strength of about 1370 MPa.

The influence of grain size on the strain-induced martensite formation in tensile straining of an austenitic 15Cr–9Mn–Ni–Cu stainless steel

International Nuclear Information System (INIS)

Kisko, A.; Misra, R.D.K.; Talonen, J.; Karjalainen, L.P.

2013-01-01

In order to improve understanding on the behavior of ultrafine-grained austenitic stainless steels during deformation, the influence of the austenite grain size and microstructure on the strain-induced martensite transformation was investigated in an austenitic 15Cr–9Mn–Ni–Cu (Type 204Cu) stainless steel. By different reversion treatments of the 60% cold-rolled sheet, varying grain sizes from ultrafine (0.5 μm), micron-scale (1.5 μm), fine (4 μm) to coarse (18 μm) were obtained. Some microstructures also contained a mixture of ultrafine or micron-scale and coarse initially cold-worked austenite grains. Samples were tested in tensile loading and deformation structures were analyzed after 2%, 10% and 20% engineering strains by means of martensite content measurements, scanning electron microscope together with a electron backscatter diffraction device and transmission electron microscope. The results showed that the martensite nucleation sites and the rate of transformation vary. In ultrafine grains strain-induced α′-martensite nucleates at grain boundaries and twins, whereas in coarser grains as well as in coarse-grained retained austenite, α′-martensite formation occurs at shear bands, sometimes via ε-martensite. The transformation rate of strain-induced α′-martensite decreases with decreasing grain size to 1.5 μm. However, the rate is fastest in the microstructure containing a mixture of ultrafine and retained cold-worked austenite grains. There the ultrafine grains transform quite readily to martensite similarly as the coarse retained austenite grains, where the previous cold-worked microstructure is still partly remaining

A Short review on wrought austenitic stainless steels at high temperatures: processing, microstructure, properties and performance

Directory of Open Access Journals (Sweden)

Ronald Lesley Plaut

2007-12-01

Full Text Available Wrought austenitic stainless steels are widely used in high temperature applications. This short review discusses initially the processing of this class of steels, with emphasis on solidification and hot working behavior. Following, a brief summary is made on the precipitation behavior and the numerous phases that may appear in their microstructures. Creep and oxidation resistance are, then, briefly discussed, and finalizing their performance is compared with other high temperature metallic materials.

Investigations into the fatigue behaviour of nuclear grades of austenitic stainless steel

International Nuclear Information System (INIS)

Mann, J.

2015-01-01

Full text of publication follows. Fatigue is an important problem within the nuclear industry due to the complex combination of thermal and mechanical loading that components experience during the operation of a nuclear reactor. Austenitic stainless steels are widely used within nuclear reactors for a number of applications including piping systems and pressure vessels. A number of studies have shown that austenitic stainless steel components operating within a light water reactor (LWR) environment may experience a significant reduction in fatigue life under certain circumstances, however the precise mechanisms responsible for the reduction are still not fully understood. The effects of environment are included in some fatigue assessment methods, however these are generally considered to be over-conservative and predicted fatigue lifetimes are not reflected well by service experience. This project aims to enhance the understanding of fatigue in both air and LWR environments through the synergistic use of a wide range of different microscopy techniques. It is expected that a better understanding of each of the different stages of fatigue will lead to more accurate fatigue predictions that ultimately result in better and safer lifetime predictions. This paper focuses on introducing the background behind the project, highlighting the current methods for assessing fatigue lifetimes and the motivations for the current research. The results of various initial microscopic investigations are presented, with a focus on a number of novel applications using laser scanning confocal microscopy to perform large scale analyses of fatigue fracture surfaces and test specimen gauge length surfaces. The use of surface replicas in conjunction with laser scanning confocal microscopy is discussed along with its potential applications for the assessment of fatigue damage in in-service components. Initial finite element modelling of crack growth within fatigue test specimens is discussed

Expanded austenite, crystallography and residual stress

DEFF Research Database (Denmark)

Christiansen, Thomas; Hummelshøj, Thomas Strabo; Somers, Marcel A. J.

2010-01-01

The identity of expanded austenite as developing during low temperature nitriding and/or carburising of austenitic stainless steel has been under debate since the very first observation of this phase. In the present article, recent results obtained with (a) homogeneous samples of various uniform ...

Expanded austenite; crystallography and residual stress

DEFF Research Database (Denmark)

Christiansen, Thomas; Hummelshøj, Thomas Strabo; Somers, Marcel A. J.

2009-01-01

The identity of expanded austenite as developing during low temperature nitriding and/or carburizing of austenitic stainless steel has been under debate since the very first observation of this phase. In the present article recent results obtained with i) homogeneous samples of various uniform co...

Applications of nitrogen-alloyed stainless steels

Energy Technology Data Exchange (ETDEWEB)

Sundvall, J.; Olsson, J. [Avesta Sheffield AB (Sweden); Holmberg, B. [Avesta Welding AB (Sweden)

1999-07-01

A selected number of applications for different types of nitrogen-alloyed stainless steels are described. The applications and grades are based on how nitrogen improves different properties. Conventional austenitic grades of type 304 and 316 can be alloyed with nitrogen to increase the strength and to maintain the austenite stability after cold deformation when exposed to cryogenic temperatures. Such examples are presented. The addition of nitrogen to duplex grades of stainless steel such as 2205 improves the pitting resistance, among other things, and also enables faster reformation of the austenite in the heat affected zone. This means that heavy plate can be welded without pre-heating or post-weld heating. Such applications are covered. Modern highly alloyed austenitic stainless steels almost always contain nitrogen and all reasons for this are covered, i.e. to stabilise the austenite, to increase the strength, and to improve the pitting resistance. The increased strength is the characteristic exemplified the least, since the higher strength of duplex grades is well known, but examples on austenite stability and improved pitting resistance are presented. (orig.)

Corrosion studies of austenitic and duplex stainless steels in aqueous lithium bromide solution at different temperatures

International Nuclear Information System (INIS)

Igual Munoz, A.; Garcia Anton, J.; Lopez Nuevalos, S.; Guinon, J.L.; Perez Herranz, V.

2004-01-01

The corrosion behavior of three stainless steels EN 14311, EN 14429 (austenitic stainless steels) and EN 14462 (duplex stainless steel) was studied in a commercial LiBr solution (850 g/l LiBr solution containing chromate as inhibitor) at different temperatures (25, 50, 75 and 85 deg C) by electrochemical methods. Open circuit potentials shifted towards more active values as temperature increased, while corrosion potentials presented the opposite tendency. The most resistant alloys to general corrosion were EN 14429 and EN 14462 because they had the lowest corrosion current for all temperatures. In all the cases corrosion current increases with temperature. Pitting corrosion resistance is improved by the EN 14462, which presented the highest pitting potential, and the lowest passivation current for the whole range of temperatures studied. The duplex alloy also presents the worst repassivation behavior (in terms of the narrowest difference between corrosion potential and pitting potential); it does not repassivate from 50 deg C

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

International Nuclear Information System (INIS)

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

1993-08-01

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

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

Directory of Open Access Journals (Sweden)

Bore V. Jegdic

2017-06-01

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

A study of precipitation phenomena during the creep of austenitic stainless steels

International Nuclear Information System (INIS)

Le May, I.; White, W.E.; Bassett, B.J.

1975-01-01

Creep-rupture data for two austenitic stainless steels, AISI Types 310 and 316, are presented, together with observations of precipitation taking place during creep. While the effects of creep deformation on precipitation in the Type 310 were negligible, ferrite precipitation was considerably greater in the Type 316 undergoing creep than in unstressed material. Ferrite precipitation appears to promote grain boundary cavitation and internal cracking, thus reducing creep resistance, and a correlation has been noted between increased ferrite precipitation and apparent further weakening of the Type 316 over the temperature range 730 0 C to 800 0 C approximately, as evidenced by breaks in the isostress lines on a plot of log (time to rupture) versus temperature. (author)

Microhardness technique for determination of radiation hardening in austenitic stainless steel using

International Nuclear Information System (INIS)

Hofman, A.

1995-01-01

The use of microhardness technique to determine the radiation hardening has been studied. Microhardness measurements have been conducted on austenitic stainless steel 0H18N10T irradiated up to 2·10 23 nm -2 . It was determined that the increase in microhardness varies directly with the measured increase in the 0,2% offret yield strength and has been found that microhardness technique may be an effective tool to measurements of radiation induced hardening. Based on the results and Cahoon's relation that σ 0,2 (MPa)=3,27HV(0,1) n method for evaluating the yield stress σ 0,2 by microhardness technique is analyzed. 14 refs., 3 figs., 3 tabs

Stainless austenitic steels strengthened due to reversible phase transformations and by ageing

International Nuclear Information System (INIS)

Sagaradze, V.V.; Kositsyna, I.I.; Ozhiganov, A.V.

1981-01-01

The effect of the reversible phase transformations, consisting in the conduction of the direct and reverse martensite transformations and aging, during which the intermetallide γ'-phase of the composition Ni 3 Ti is formed, on the streng-thening of alloys in the Fe-Cr-Ni-Ti system is considered. Stainless austenitic steels Kh12N12T3 and Kh12N14T3, which acquire high mechanical properties: σsub(0.2)=685-785 MPa, σsub(B)=1275 MPa, delta >= 20%, as a result of reversible phase transformations and aging, are suggested. After the reversible phase transformations and ageing the steels possess a high resistance to γ-α-transformation during cold treatment [ru

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

Energy Technology Data Exchange (ETDEWEB)

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

1999-07-01

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

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

Energy Technology Data Exchange (ETDEWEB)

Kasahara, Shigeki, E-mail: kasahara.shigeki@jaea.go.jp [Japan Atomic Energy Agency (JAEA), 2-4 Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Kitsunai, Yuji [Nippon Nuclear Fuel Development, 2163 Narita-cho, Oarai-machi, Higashi-ibaraki-gun, Ibaraki 311-1313 (Japan); Chimi, Yasuhiro [Japan Atomic Energy Agency (JAEA), 2-4 Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan); Chatani, Kazuhiro; Koshiishi, Masato [Nippon Nuclear Fuel Development, 2163 Narita-cho, Oarai-machi, Higashi-ibaraki-gun, Ibaraki 311-1313 (Japan); Nishiyama, Yutaka [Japan Atomic Energy Agency (JAEA), 2-4 Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1195 (Japan)

2016-11-15

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

Comparison of high temperature wear behaviour of plasma sprayed WC–Co coated and hard chromium plated AISI 304 austenitic stainless steel

International Nuclear Information System (INIS)

Balamurugan, G.M.; Duraiselvam, Muthukannan; Anandakrishnan, V.

2012-01-01

Highlights: ► WC–12wt.%Co powders were deposited to a thickness of 300 μm on to steel substrates. ► The micro hardness of the above coatings was lower than that of chromium plating. ► Wear resistance of chromium coating was increased up to five times of AISI 304 austenitic stainless steel. ► Wear resistance of chromium coat higher than plasma coat at different temperatures. -- Abstract: The wear behaviour of plasma sprayed coating and hard chrome plating on AISI 304 austenitic stainless steel substrate is experimentally investigated in unlubricated conditions. Experiments were conducted at different temperatures (room temp, 100 °C, 200 °C and 300 °C) with 50 N load and 1 m/s sliding velocity. Wear tests were carried out by dry sliding contact of EN-24 medium carbon steel pin as counterpart on a pin-on-disc wear testing machine. In both coatings, specimens were characterised by hardness, microstructure, coating density and sliding wear resistance. Wear studies showed that the hard chromium coating exhibited improved tribological performance than that of the plasma sprayed WC–Co coating. X-ray diffraction analysis (XRD) of the coatings showed that the better wear resistance at high temperature has been attributed to the formation of a protective oxide layer at the surface during sliding. The wear mechanisms were investigated through scanning electron microscopy (SEM) and XRD. It was observed that the chromium coating provided higher hardness, good adhesion with the substrate and nearly five times the wear resistance than that obtained by uncoated AISI 304 austenitic stainless steel.

Microstructural characterization of dissimilar welds between Incoloy 800H and 321 Austenitic Stainless Steel

Energy Technology Data Exchange (ETDEWEB)

Sayiram, G., E-mail: sayiram.g@vit.ac.in; Arivazhagan, N.

2015-04-15

In this work, the microstructural character of dissimilar welds between Incoloy 800H and 321 Stainless Steel has been discussed. The microscopic examination of the base metals, fusion zones and interfaces was characterized using an optical microscope and scanning electron microscopy. The results revealed precipitates of Ti (C, N) in the austenitic matrix along the grain boundaries of the base metals. Migration of grain boundaries in the Inconel 82 weld metal was very extensive when compared to Inconel 617 weldment. Epitaxial growth was observed in the 617 weldment which increases the strength and ductility of the weld metal. Unmixed zone near the fusion line between 321 Stainless Steel and Inconel 82 weld metal was identified. From the results, it has been concluded that Inconel 617 filler metal is a preferable choice for the joint between Incoloy 800H and 321 Stainless Steel. - Highlights: • Failure mechanisms produced by dissimilar welding of Incoloy 800H to AISI 321SS • Influence of filler wire on microstructure properties • Contemplative comparisons of metallurgical aspects of these weldments • Microstructure and chemical studies including metallography, SEM–EDS • EDS-line scan study at interface.

A morphological evaluation of a duplex stainless steel processed by high energy Ball Mill

International Nuclear Information System (INIS)

Yonekubo, Ariane Emi; Cintho, Osvaldo Mitsuyuki; Aguiar, Denilson Jose Marcolino de; Capocchi, Jose Deodoro Trani

2009-01-01

The duplex stainless steels are formed by a ferrite and austenite mixture, giving them a combination of properties. Commercially, these steels are hot rolled, developing an anisotropic, alternated ferrite and austenite elongated lamellae microstructure. In this work, a duplex stainless steel was produced by the mixture of elementary powders with the composition Fe-19.5Cr-5Ni processed in an ATTRITOR ball mill during periods up to 15 hours. The powders obtained were compressed in specimens and were heat treated in the temperatures of 900, 1050 and 1200 °C during 1 hour and analysed by x ray diffraction, optic microscopy, scanning electron microscopy and energy dispersion spectroscopy. An optimized microstructure with ultrafine, equiaxial and regular duplex microstructure was obtained in the 15 hour milling and 1200 °C heat treatment. Afterwards, a commercially super duplex stainless steel UNS S32520 was aged at 800 °C aiming the precipitation of σ phase in order to reduce its toughness and then, milled in SPEX mill. The resulting microstructure was a very fine duplex type with irregular grain boundary morphology duo to the grain growth barrier promoted by the renascent σ phase particles during sintering process. (author)

Microstructure Evolution During Creep of Cold Worked Austenitic Stainless Steel

Science.gov (United States)

Krishan Yadav, Hari; Ballal, A. R.; Thawre, M. M.; Vijayanand, V. D.

2018-04-01

The 14Cr–15Ni austenitic stainless steel (SS) with additions of Ti, Si, and P has been developed for their superior creep strength and better resistance to void swelling during service as nuclear fuel clad and wrapper material. Cold working induces defects such as dislocations that interact with point defects generated by neutron irradiation and facilitates recombination to make the material more resistant to void swelling. In present investigation, creep properties of the SS in mill annealed condition (CW0) and 40 % cold worked (CW4) condition were studied. D9I stainless steel was solution treated at 1333 K for 30 minutes followed by cold rolling. Uniaxial creep tests were performed at 973 K for various stress levels ranging from 175-225 MPa. CW4 samples exhibited better creep resistance as compared to CW0 samples. During creep exposure, cold worked material exhibited phenomena of recovery and recrystallization wherein new strain free grains were observed with lesser dislocation network. In contrast CW0 samples showed no signs of recovery and recrystallization after creep exposure. Partial recrystallization on creep exposure led to higher drop in hardness in cold worked sample as compared to that in mill annealed sample. Accelerated precipitation of carbides at the grain boundaries was observed during creep exposure and this phenomenon was more pronounced in cold worked sample.

Alumina-Forming Austenitic Stainless Steels Strengthened by Laves Phase and MC Carbide Precipitates

Science.gov (United States)

Yamamoto, Y.; Brady, M. P.; Lu, Z. P.; Liu, C. T.; Takeyama, M.; Maziasz, P. J.; Pint, B. A.

2007-11-01

Creep strengthening of Al-modified austenitic stainless steels by MC carbides or Fe2Nb Laves phase was explored. Fe-20Cr-15Ni-(0-8)Al and Fe-15Cr-20Ni-5Al base alloys (at. pct) with small additions of Nb, Mo, W, Ti, V, C, and B were cast, thermally-processed, and aged. On exposure from 650 °C to 800 °C in air and in air with 10 pct water vapor, the alloys exhibited continuous protective Al2O3 scale formation at an Al level of only 5 at. pct (2.4 wt pct). Matrices of the Fe-20Cr-15Ni-5Al base alloys consisted of γ (fcc) + α (bcc) dual phase due to the strong α-Fe stabilizing effect of the Al addition and exhibited poor creep resistance. However, adjustment of composition to the Fe-15Cr-20Ni-5Al base resulted in alloys that were single-phase γ-Fe and still capable of alumina scale formation. Alloys that relied solely on Fe2Nb Laves phase precipitates for strengthening exhibited relatively low creep resistance, while alloys that also contained MC carbide precipitates exhibited creep resistance comparable to that of commercially available heat-resistant austenitic stainless steels. Phase equilibria studies indicated that NbC precipitates in combination with Fe2Nb were of limited benefit to creep resistance due to the solution limit of NbC within the γ-Fe matrix of the alloys studied. However, when combined with other MC-type strengtheners, such as V4C3 or TiC, higher levels of creep resistance were obtained.

Non-destructive evaluation of austenite stainless steels using a scanning Hall-sensor microscope

International Nuclear Information System (INIS)

Oota, Akio

2004-01-01

Spontaneous magnetic field on the surface of austenite stainless steel SUS304 was measured under a static condition by using a scanning Hall-sensor microscope, which had magnetic sensitive area of 50μm x 50μm. The precursor of fatigue fracture was tentatively detected from the change of magnetic image observed by the microscope. Specimens used in this experiment were prepared by following procedures: Rolled SUS304 was cut into a piece of 110 mm length x 40 mm width by electric discharge processing, and then notches were carved at both centers of the length of the piece. A test of tensile strength of the piece was run at room temperature, and the change of spontaneous magnetization image was studied before and after the tensile strength test. After the test, spontaneous magnetic field was observed around the notches although it was not detected before the test. Many slip lines were found around the location where the spontaneous magnetic field was observed, and a significant increase of hardness was examined by Vickers hardness. These facts indicated that the spontaneous magnetic field observed after the test would be caused from stress-induced martensitic transformation in austenite stainless steel. The stress distribution after applying tensile stress was simulated and the result was compared with the distribution of the spontaneous magnetic field. After the comparison between the stress and the spontaneous magnetic field distribution, it was concluded that the distribution of spontaneous magnetic field resembled that of principal shear stress rather than of principal stress. Therefore, the principal shear stress would be suggested to be a driving force for the stress-induced martensitic transformation. (Y. Kazumata)

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

International Nuclear Information System (INIS)

Klueh, R.L.; Grossbeck, M.L.

1984-01-01

The USSR steel EP-838 is a high-manganese, low-nickel steel that also has lower chromium and molybdenum than type 316 stainless steel. Tensile specimens of 20%-cold-worked EP-838 and type 316 stainless steel were irradiated in the High Flux Isotope Reactor (HFIR) at the coolant temperature (approx.=50 0 C). A displacement damage level of 5.2 dpa was reached for the EP-838 and up to 9.5 dpa for the type 316 stainless steel. Tensile tests at room temperature and 300 0 C on the two steels indicated that the irradiation led to increased strength and decreased ductility compared to the unirradiated steels. Although the 0.2% yield stress of the type 316 stainless steel in the unirradiated condition was greater than that for the EP-838, after irradiation there was essentially no difference between the strength or ductility of the two steels. The results indicate that the replacement of the majority of the nickel by manganese and a reduction of chromium and molybdenum in an austenitic stainless steel of composition near that for type 316 stainless steel has little effect on the irradiated and unirradiated tensile properties at low temperatures. (orig.)

Characterization of phase properties and deformation in ferritic-austenitic duplex stainless steels by nanoindentation and finite element method

International Nuclear Information System (INIS)

Schwarm, Samuel C.; Mburu, Sarah; Ankem, Sreeramamurthy

2016-01-01

The phase properties and deformation behavior of the δ–ferrite and γ–austenite phases of CF–3 and CF–8 cast duplex stainless steels were characterized by nanoindentation and microstructure-based finite element method (FEM) models. We evaluated the elastic modulus of each phase and the results indicate that the mean elastic modulus of the δ–ferrite phase is greater than that of the γ–austenite phase, and the mean nanoindentation hardness values of each phase are approximately the same. Furthermore, the elastic FEM model results illustrate that greater von Mises stresses are located within the δ–ferrite phase, while greater von Mises strains are located in the γ–austenite phase in response to elastic deformation. The elastic moduli calculated by FEM agree closely with those measured by tensile testing. Finally, the plastically deformed specimens exhibit an increase in misorientation, deformed grains, and subgrain structure formation as measured by electron backscatter diffraction (EBSD).

Stress corrosion cracking of austenitic stainless steel in glycerol solution and chloride solution at elevated temperature

International Nuclear Information System (INIS)

Haftirman; Maruhum Tua Lubis

2009-01-01

Stress Corrosion Cracking (SCC) is an environmentally assisted failure caused by exposure to a corrodant while under a sustained tensile stress. SCC is most often rapid, unpredictable and catastrophic. Failure can occur in as little as a few hours or take years to happen. Most alloys are susceptible to SCC in one or more environments requiring careful consideration of alloy type in component design. In aqueous chloride environments austenitic stainless steels and many nickel based alloys are known to perform poorly. One of products Oleo chemical is glycerol solution. Glycerol solution contains chloride with concentration 50 ppm - 150 ppm. Austenitic stainless steel is usually used in distillation construction tank and pipe line of glycerol. Material AISI 304 will be failure in this glycerol solution with this concentration in 5 years. In production process, concentration of chloride in glycerol becomes more than 150 ppm at temperature 150 degree Celsius. The reason is that the experiment I conducted in high chloride with concentration such as 6000 ppm, 9000 ppm, and 12000 ppm. The stress corrosion cracking of the austenitic stainless steels of types AISI 304, 316 and 316L in glycerol solution at elevated temperature 150 degree Celsius is investigated as a function variation of chloride concentration, namely 50, 6000, 9000 and 12000 ppm using a constant load method with two kinds of initial tensile stress as 50 % and 70 % yield strength. The experiment uses a spring loaded fixture type and is based on ASTM G49 for experiment method, and E292 for geometry of specimen. Pitting corrosion occurs on the surface specimen until the stress level reaches the ultimate strength. Pitting corrosion attack and depletion occur on the surface as initiation of SCC failure as the stress reaches the ultimate strength. Failure has occurred in catastrophic brittle fracture type of transgranular. AISI 304 was more susceptible for all conditions. In chloride solution with concentration of

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

DEFF Research Database (Denmark)

Belluco, Walter; De Chiffre, Leonardo

2004-01-01

breaking were recorded for each bore, and tool wear was measured at constant intervals. A commercial mineral-based oil was taken as reference product, and five vegetable-based cutting fluids at different levels of additivation were tested. All measured parameters were in agreement, confirming......The efficiency of six cutting oils was evaluated in drilling AISI 316L austenitic stainless steel using conventional HSS-Co tools by measurements of tool life, tool wear, cutting forces and chip formation. Seven tools were tested with each fluid to catastrophic failure. Cutting forces and chip...... to tool life testing. All vegetable-based fluids performed better than the reference product. The best performance was obtained with a cutting fluid yielding 177% increases in tool life and 7% reduction in thrust force. (C) 2003 Elsevier B.V. All rights reserved....

Grain-to-grain variations in NbC particle size distributions in an austenitic stainless steel

International Nuclear Information System (INIS)

Barlow, C.Y.; Ralph, B.; Silverman, B.; Jones, A.R.

1979-01-01

Quantitative information has been obtained concerning the size distributions of NbC precipitate particles in different grains in a deformed and aged austenitic stainless steel specimen. The precipitate size distributions obtained differ from one grain to another. The average disparity measured between the mean precipitate sizes was a function of the distance between the grains compared. The results obtained are considered in terms of differences in precipitation behaviour due to variations in the levels of plastic strain in constituent grains of the deformed specimen. (author)

Corrosion properties of modified PNC1520 austenitic stainless steel in supercritical water as a fuel cladding candidate material for supercritical water reactor

International Nuclear Information System (INIS)

Nakazono, Yoshihisa; Iwai, Takeo; Abe, Hiroaki

2009-01-01

The supercritical water-cooled reactor (SCWR) has been designed and investigated because of its high thermal efficiency and plant simplification. There are some advantages including the use of a single phase coolant with high enthalpy. Supercritical Water (SCW) has never been used in nuclear power applications. There are numerous potential problems, particularly with materials. As the operating temperature of SCWR will be between 553 K and 893 K with a pressure of 25 MPa, the selection of materials is difficult and important. The PNC1520 austenitic stainless steel has been developed by Japan Atomic Energy Agency (JAEA) as a nuclear fuel cladding material for a Na-cooled fast breeder reactor. Austenitic Fe-base steels were selected for possible use in supercritical water systems because of their corrosion resistance and radiation resistance. The PNC1520 austenitic stainless steel was selected for possible use in supercritical water systems. The corrosion data of PNC1520 in SCW is required but does not exist. The purpose of the present study is to research the corrosion properties for PNC1520 austenitic stainless steel in SCW. The SCW corrosion test was performed for the standard PNC1520 (1520S) and the Ti-additional type of PNC1520 (1520T) by using a SCW autoclave. The 1520S and 1520T are the first trial production materials of SCWR cladding candidate material in our group. Corrosion and compatibility tests on the austenitic 1520S and 1520T steels in supercritical water were performed at 673, 773 and 600degC with exposures up to 1000 h. We have evaluated the amount of weight gain, weight loss and weight of scale after the corrosion test in SCW for 1520S and 1520T austenitic steels. After 1000 h corrosion test performed, the weight gains of both austenitic stainless steels were less than 2 g/m 2 at 400degC and 500degC. But 1520T weight increases more and weight loss than 1520S at 600degC. The SEM observation result of the surface after 1000 h corrosion of an test

Effect of Tempering Temperature and Time on the Corrosion Behaviour of 304 and 316 Austenitic Stainless Steels in Oxalic Acid

OpenAIRE

Ayo S. Afolabi; Johannes H. Potgieter; Ambali S. Abdulkareem; Nonhlanhla Fungura

2011-01-01

The effect of different tempering temperatures and heat treatment times on the corrosion resistance of austenitic stainless steels in oxalic acid was studied in this work using conventional weight loss and electrochemical measurements. Typical 304 and 316 stainless steel samples were tempered at 150oC, 250oC and 350oC after being austenized at 1050oC for 10 minutes. These samples were then immersed in 1.0M oxalic acid and their weight losses were measured at every five days for 30 days. The r...

Study on creep-fatigue life of irradiated austenitic stainless steel

International Nuclear Information System (INIS)

Ioka, Ikuo; Miwa, Yukio; Tsuji, Hirokazu; Yonekawa, Minoru; Takada, Fumiki; Hoshiya, Taiji

2001-01-01

The low cycle creep-fatigue test with tensile strain hold of the austenitic stainless steel irradiated to 2 dpa was carried out at 823K in vacuum. The applicability of creep-fatigue life prediction methods to the irradiated specimen was examined. The fatigue life on the irradiated specimen without tensile strain hold time was reduced by a factor of 2-5 in comparison with the unirradiated specimen. The decline in fatigue life of the irradiated specimen with tensile strain hold was almost equal to that of the unirradiated specimen. The creep damage of both unirradiated and irradiated specimens was underestimated by the time fraction rule or the ductility exhaustion rule. The creep damage calculated by the time fraction rule or the ductility exhaustion rule increased by the irradiation. The predictions derived from the linear damage rule are unsafe as compared with the experimental fatigue lives. (author)

Microstructural evolution in fast-neutron-irradiated austenitic stainless steels

International Nuclear Information System (INIS)

Stoller, R.E.

1987-12-01

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

Mechanical property degradation and microstructural evolution of cast austenitic stainless steels under short-term thermal aging

Science.gov (United States)

Lach, Timothy G.; Byun, Thak Sang; Leonard, Keith J.

2017-12-01

Mechanical testing and microstructural characterization were performed on short-term thermally aged cast austenitic stainless steels (CASS) to understand the severity and mechanisms of thermal-aging degradation experienced during extended operation of light water reactor (LWR) coolant systems. Four CASS materials-CF3, CF3M, CF8, and CF8M-were thermally aged for 1500 h at 290 °C, 330 °C, 360 °C, and 400 °C. All four alloys experienced insignificant change in strength and ductility properties but a significant reduction in absorbed impact energy. The primary microstructural and compositional changes during thermal aging were spinodal decomposition of the δ-ferrite into α/α‧, precipitation of G-phase in the δ-ferrite, segregation of solute to the austenite/ferrite interphase boundary, and growth of M23C6 carbides on the austenite/ferrite interphase boundary. These changes were shown to be highly dependent on chemical composition, particularly the concentration of C and Mo, and aging temperature. The low C, high Mo CF3M alloys experienced the most spinodal decomposition and G-phase precipitation coinciding the largest reduction in impact properties.

Influence of strain-induced martensitic transformation on fatigue short crack behaviour in an austenitic stainless steel

International Nuclear Information System (INIS)

Baffie, N.; Stolarz, J.; Magnin, Th.

2000-01-01

The influence of martensitic transformation induced by cyclic straining on the mechanisms of low cycle fatigue damage in a metastable austenitic stainless steel with different grain sizes has been investigated using macroscopic measurements and microscopic observations of short crack evolutions. The amount of martensite formed during cyclic straining increases with increasing plastic strain amplitude and cumulative plastic strain but the dominant parameter is the grain size of austenite. The fine microstructure (D = 10 μm) with maximum martensite fraction of about 20% is characterised by a better fatigue resistance than the coarse one (D 40μm and only 2% of martensite) for the same plastic strain amplitude. Martensitic transformation is found to radically modify the cyclic response of the alloy and consequently the damage mechanisms. Indeed, both short crack nucleation and growth take place exclusively in the transformed regions. A mechanism of short crack propagation based on the γ→ α' transformation assisted by stress concentration at the crack tip is proposed. The indirect influence of grain boundaries in the austenite on crack propagation in the martensite is demonstrated. The better fatigue resistance of metastable alloys with fine granular structure can thus be understood. (authors)

Influence of alloy elements on physical and mechanical properties of single crystalline austenitic stainless steels

International Nuclear Information System (INIS)

Okamoto, Kazutaka; Kaneda, Junya; Yoshinari, Akira; Aono, Yasuhisa

2000-01-01

The single crystalline austenitic stainless steels based on 316 L were developed to improve their resistance to intergranular corrosion and stress corrosion cracking. However the mechanical properties of the single crystals were lower than those of polycrystalline. The precipitation hardening methods were applied to the single crystal for the increase of their mechanical strength by addition of niobium and heat treatments. In this paper, the influences of niobium concentration on the several physical and mechanical properties of these single crystalline austenitic stainless steels were studied. The thermal conductivity, coefficients of thermal expansion and elastic constants of the single crystals were almost the same as those of polycrystalline independently of the niobium concentration. The mechanical properties of the single crystals strongly depended on the niobium concentration and the orientation. In the specimen which contains 1.0 mass% niobium, 0.2% proof stress were remarkably improved; 370 MPa, 337 MPa and 403 MPa were obtained in , and orientations at the room temperature. The creep rupture strength and the high cycle fatigue strength were also improved by addition of niobium. In the -orientated specimen which contains 1.0 mass% niobium, the creep rupture strength at 873 K for 103 hours, 245 MPa and the high cycle fatigue strength at 773 K for 107 cycles, 220 MPa were obtained. Furthermore, the single crystalline pipe, bolts and nuts were successfully manufactured for the application of these single crystals. (author)

Effect of irradiation temperature on microstructural changes in self-ion irradiated austenitic stainless steel

Science.gov (United States)

Jin, Hyung-Ha; Ko, Eunsol; Lim, Sangyeob; Kwon, Junhyun; Shin, Chansun

2017-09-01

We investigated the microstructural and hardness changes in austenitic stainless steel after Fe ion irradiation at 400, 300, and 200 °C using transmission electron microscopy (TEM) and nanoindentation. The size of the Frank loops increased and the density decreased with increasing irradiation temperature. Radiation-induced segregation (RIS) was detected across high-angle grain boundaries, and the degree of RIS increases with increasing irradiation temperature. Ni-Si clusters were observed using high-resolution TEM in the sample irradiated at 400 °C. The results of this work are compared with the literature data of self-ion and proton irradiation at comparable temperatures and damage levels on stainless steels with a similar material composition with this study. Despite the differences in dose rate, alloy composition and incident ion energy, the irradiation temperature dependence of RIS and the size and density of radiation defects followed the same trends, and were very comparable in magnitude.

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

International Nuclear Information System (INIS)

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

2013-01-01

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

Characterization and understanding of ion irradiation effect on the microstructure of austenitic stainless steels

International Nuclear Information System (INIS)

Volgin, Alexandre

2012-01-01

Austenitic stainless steels are widely used in nuclear industry for internal structures. These structures are located close to the fuel assemblies, inside the pressure vessel. The exposure of these elements to high irradiation doses (the accumulated dose, after 40 years of operation, can reach 80 dpa), at temperature close to 350 C, modifies the macroscopic behavior of the steel: hardening, swelling, creep and corrosion are observed. Moreover, in-service inspections of some of the reactor internal structures have revealed the cracking of some baffle bolts. This cracking has been attributed to Irradiation Assisted Stress Corrosion Cracking (IASCC). In order to understand this complex phenomenon, a first step is to identify the microstructural changes occurring during irradiation, and to understand the mechanisms at the origin of this evolution. In this framework, a large part of the European project 'PERFORM 60' is dedicated to the study of the irradiation damage in austenitic stainless steels. The objective of this PhD work is to bring comprehensive data on the irradiation effects on microstructure. To reach this goal, two model alloys (FeNiCr and FeNiCrSi) and an industrial austenitic stainless steel (316 steel) are studied using Atom Probe Tomography (APT), Transmission Electron Microscope (TEM) and Positron Annihilation Spectroscopy (PAS). They are irradiated by Ni ions in CSNSM (Orsay) at two temperatures (200 and 450 C) and three doses (0.5, 1 and 5 dpa). TEM observations have shown the appearance of dislocation loops, cavities and staking fault tetrahedra. The dislocation loops in 316 steel were preferentially situated in the vicinity of dislocations, while they were randomly distributed in the FeNiCr alloy. APT study has shown the redistribution of Ni and Si under irradiation in FeNiCrSi model alloy and 316 steel, leading to the appearance of (a) Cottrell clouds along dislocation lines, dislocation loops and other non-identified crystalline defects and (b

Hydrogen Embrittlement Mechanism in Fatigue Behavior of Austenitic and Martensitic Stainless Steels

Directory of Open Access Journals (Sweden)

Sven Brück

2018-05-01

Full Text Available In the present study, the influence of hydrogen on the fatigue behavior of the high strength martensitic stainless steel X3CrNiMo13-4 and the metastable austenitic stainless steels X2Crni19-11 with various nickel contents was examined in the low and high cycle fatigue regime. The focus of the investigations were the changes in the mechanisms of short crack propagation. Experiments in laboratory air with uncharged and precharged specimen and uncharged specimen in pressurized hydrogen were carried out. The aim of the ongoing investigation was to determine and quantitatively describe the predominant processes of hydrogen embrittlement and their influence on the short fatigue crack morphology and crack growth rate. In addition, simulations were carried out on the short fatigue crack growth, in order to develop a detailed insight into the hydrogen embrittlement mechanisms relevant for cyclic loading conditions. It was found that a lower nickel content and a higher martensite content of the samples led to a higher susceptibility to hydrogen embrittlement. In addition, crack propagation and crack path could be simulated well with the simulation model.

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

Energy Technology Data Exchange (ETDEWEB)

Krugers, Jan-Paul

1993-01-19

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

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

International Nuclear Information System (INIS)

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

1993-01-01

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

Effect of solution treatment conditions on the sensitization of austenitic stainless steel

Directory of Open Access Journals (Sweden)

XIAOFEI YU

2009-11-01

Full Text Available In this study, the impact of the conditions of solution treatment on the degree of sensitization (DOS of austenitic stainless steel (AISI 304 was investigated in detail. The results derived from the electrochemical potentiodynamic reactivation (EPR test indicated that the DOS decreased as the solution treatment temperature and time increased. The reason for this was studied via the SEM morphologies and EDS results, which indicated that the grain size influenced the DOS. Furthermore, cellular automaton (CA was utilized to simulate grain growth, the precipitation of Cr-rich carbides and the three dimensional distribution of the chromium concentration, which vividly illuminated the effect of the grain size on the DOS and was in accordance with the experiment results.

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

Directory of Open Access Journals (Sweden)

D. Klobčar

2016-10-01

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

Low-Temperature Mechanical Behavior of Super Duplex Stainless Steel with Sigma Precipitation

OpenAIRE

Kim, Seul-Kee; Kang, Ki-Yeob; Kim, Myung-Soo; Lee, Jae-Myung

2015-01-01

Experimental studies in various aspects have to be conducted to maintain stable applications of super duplex stainless steels (SDSS) because the occurrence rate of sigma phase, variable temperature and growth direction of sigma phase can influence mechanical performances of SDSS. Tensile tests of precipitated SDSS were performed under various temperatures to analyze mechanical and morphological behavior.

Low-Temperature Mechanical Behavior of Super Duplex Stainless Steel with Sigma Precipitation

Directory of Open Access Journals (Sweden)

Seul-Kee Kim

2015-09-01

Full Text Available Experimental studies in various aspects have to be conducted to maintain stable applications of super duplex stainless steels (SDSS because the occurrence rate of sigma phase, variable temperature and growth direction of sigma phase can influence mechanical performances of SDSS. Tensile tests of precipitated SDSS were performed under various temperatures to analyze mechanical and morphological behavior.

Lattice expansion of carbon-stabilized expanded austenite

DEFF Research Database (Denmark)

Hummelshøj, Thomas Strabo; Christiansen, Thomas; Somers, Marcel A. J.

2010-01-01

The lattice parameter of expanded austenite was determined as a function of the content of interstitially dissolved carbon in homogeneous, carburized thin stainless steel foils. For the first time this expansion of the face-centered cubic lattice is determined on unstrained austenite. It is found...

Modified Monkman–Grant relationship for austenitic stainless steel foils

Energy Technology Data Exchange (ETDEWEB)

Osman Ali, Hassan, E-mail: hassaninsan@gmail.com [Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor (Malaysia); Tamin, Mohd Nasir, E-mail: taminmn@fkm.utm.my [Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 UTM Skudai, Johor (Malaysia)

2013-02-15

Characteristics of creep deformation for austenitic stainless steel foils are examined using the modified Monkman–Grant equation. A series of creep tests are conducted on AISI 347 steel foils at 700 °C and different stress levels ranging from 54 to 221 MPa. Results showed that at lower stress levels below 110 MPa, the creep life parameters ε{sub min},ε{sub r},t{sub r} can be expressed using the modified Monkman–Grant equation with exponent m′= 0.513. This indicates significant deviation of the creep behavior from the first order reaction kinetics theory for creep (m′ = 1.0). The true tertiary creep damage in AISI 347 steel foil begins after 65.9% of the creep life of the foil has elapsed at stress levels above 150 MPa. At this high stress levels, Monkman–Grant ductility factor λ{sup ′} saturates to a value of 1.3 with dislocation-controlled deformation mechanisms operating. At low stress levels, λ{sup ′} increases drastically (λ{sup ′}=190 at 54 MPa) when slow diffusion-controlled creep is dominant.

Effect of protective gas on the properties of the pure support of super-martensitic stainless steel

International Nuclear Information System (INIS)

Zappa, Sebastian; Svoboda, Hernan G; Ramini de Rissone, N.Mabel; Surian, Estela S; De Vedia, Luis A

2006-01-01

This work studied the effect of protective gas on the operability, mechanical properties and microstructure of the super-martensitic stainless pure support metal, deposited with a metal-cored tubular wire, using the semi-automatic welding process under gaseous protection. Three pure support test tubes were welded following ANSI/AWS A5.22-95, with a 1.2 mm diameter tubular wire using three gaseous mixtures as protection: 70 % Ar-30 % He, 98 % Ar-2 % Co 2 and 82 % Ar-18 % Co 2 . The welding position was by hand with an average thermal support of 1.1 kJ/mm. Transverse cuts were extracted from each welded coupon for metallography and chemical composition, 1 'Minitrac' traction test piece and about 20 test pieces for a V-Charpy impact trial. The microstructure was defined with optic and scanning electronic microscopes and with X-ray diffraction. Micro hardness profiles were determined as well as the properties in traction and on impact. With reference to operability, the number of spatters increased noticeably with an increased content of Co 2 in the protective mixture. The content of Mn, Si and Mo dropped after increasing the gas oxidation potential. Regarding the mechanical properties small variations in the flow limit, the resistance to traction and the hardness for the different gaseous mixtures used were observed. A slight drop in the absorbed energy, with an increase in the Co2 content in the protective gas was noted in the V-Charpy impact tests carried out at 20, 0, -20, -40 and -60 o C. Expressions were obtained that correlated the measured properties with the oxidation potential of the gas for these materials. The microstructure consists of martensite, ferrite and retained austenite. Significant variations were not observed in the ferrite and austenite fractions for the different gases that were used (CW)

Verification of an optimized condition for low residual stress employed water-shower cooling during welding in austenitic stainless steel plates

International Nuclear Information System (INIS)

Yanagida, N.; Enomoto, K.; Anzai, H.

2004-01-01

To reduce tensile residual stress in a welded region, we have developed a new cooling method that uses a water-shower behind the welding torch. When this method is applied to the welding of austenitic stainless steel, the welding and cooling conditions mainly determine how much the residual stress can be reduced. To optimize these conditions, we first used a robust design method to determine the effects of the preheating temperature, the heat input quantity, and the water-shower area on the residual stress, and found that, to decrease the tensile residual stress, the preheating temperature should be high, the heat input low, and the water-shower area large. To confirm the effectiveness of these optimized conditions, the residual stresses under optimized or non-optimized conditions were measured experimentally. It was found that the residual stresses were tensile under the non-optimized conditions, but compressive under the optimized ones. These measurements agree well with the 3D-FEM analyses. It can therefore be concluded that the optimized conditions are valid and appropriate for reducing residual stress in an austenitic stainless-steel weld. (orig.)

Localized corrosion and stress corrosion cracking behavior of austenitic stainless steel weldments containing retained ferrite. Annual progress report, June 1, 1978--March 31, 1979

International Nuclear Information System (INIS)

Savage, W.F.; Duquette, D.J.

1979-03-01

Localized corrosion and stress corrosion cracking experiments have been performed on single phase 304 stainless steel alloys and autogeneous weldments containing retained delta ferrite as a second phase. The results of the pitting experiments show that the pressure of delta ferrite decreases localized corrosion resistance with pits initiating preferentially at delta ferrite--gamma austenite interphase boundaries. This increased susceptibility is reversible with elevated temperature heat treatments which revert the metastable ferrite phase to the equilibrium austenite phase

Fatigue crack growth threshold of austenitic stainless steels in simulated PWR primary water

International Nuclear Information System (INIS)

Tsutsumi, Kazuya; Yamamoto, Kenji; Nitta, Yoshikazu

2007-01-01

Many studies have revealed that fatigue crack growth (FCG) rate of austenitic stainless steels is accelerated in light water reactor environment compared to that in air at room temperature. Major driving factors in the acceleration of FCG rate are stress ratio, temperature and stress rise time. Based on this knowledge, FCG curves have been developed considering these factors as parameters. However, there are few data of FCG threshold ΔK th in light water reactor environment. Hence it is necessary to clarify FCG rate under near-threshold condition for more accurate evaluation of fatigue crack growth behavior under cyclic stress with relatively low ΔK. In the present study, therefore, ΔK th was determined for austenitic stainless steels in simulated PWR primary water, and FCG behavior under near-threshold condition was revealed by collecting fatigue crack propagation data. The results are summarized as follows: No propagation of fatigue crack was found in high temperature water, and there was a definite ΔK th . Average ΔK eff,th was 4.3 MPa·m 0.5 at 325degC, 3.3 MPa·m 0.5 at 100degC, and there was no considerable reduction compared to currently known ΔK eff,th in air. Thus, it was revealed tha ambient conditions had minimal effect, on ΔK eff,th , ΔK th increases with increasing temperature and decreasing frequency. As a result of fracture surface observation, oxide-induced-crack-closure was considered to be a cause of the dependency described above. In addition, it was suggested that changes in material properties also had influence on ΔK th, since ΔK eff,th itself increased at elevated temperature. (author)

Effects of laser shock processing on mechanical properties and micro-structure of ANSI 304 austenitic stainless steel

International Nuclear Information System (INIS)

Luo, K.Y.; Lu, J.Z.; Zhang, Y.K.; Zhou, J.Z.; Zhang, L.F.; Dai, F.Z.; Zhang, L.; Zhong, J.W.; Cui, C.Y.

2011-01-01

Highlights: → Effects of LSP on mechanical properties of stainless steel ANSI 304 are evaluated. → LSP can clearly enhance the values of mechanical properties in the shocked region. → Martensite transformation does not take place in the surface layer subjected to LSP. → Enhancement mechanisms of LSP on mechanical property of stainless steel are revealed. → The results can provide some insights on the surface modification of stainless steel. - Abstract: The aim of this article is to address the effects of a single laser shock processing (LSP) impact on the nano-hardness, elastic modulus, residual stress and phase transformation of ANSI 304 austenitic stainless steel. Residual stress distribution of the LSP-shocked region is determined by X-ray diffraction (XRD) with sin 2 ψ method, and the micro-structural features in the near-surface layer are characterized by using cross-sectional optical microscopy (OM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). By comparing with the untreated samples, LSP can clearly improve nano-hardness, elastic modulus, and residual stress in the LSP-shocked region. The underlying enhancement mechanisms of LSP on nano-hardness, elastic modulus and residual stress of stainless steel ANSI 304 are also revealed. These studies may provide some important insights into surface modification for metal materials.

Effect of Heat Input on Geometry of Austenitic Stainless Steel Weld Bead on Low Carbon Steel

Science.gov (United States)

Saha, Manas Kumar; Hazra, Ritesh; Mondal, Ajit; Das, Santanu

2018-05-01

Among different weld cladding processes, gas metal arc welding (GMAW) cladding becomes a cost effective, user friendly, versatile method for protecting the surface of relatively lower grade structural steels from corrosion and/or erosion wear by depositing high grade stainless steels onto them. The quality of cladding largely depends upon the bead geometry of the weldment deposited. Weld bead geometry parameters, like bead width, reinforcement height, depth of penetration, and ratios like reinforcement form factor (RFF) and penetration shape factor (PSF) determine the quality of the weld bead geometry. Various process parameters of gas metal arc welding like heat input, current, voltage, arc travel speed, mode of metal transfer, etc. influence formation of bead geometry. In the current experimental investigation, austenite stainless steel (316) weld beads are formed on low alloy structural steel (E350) by GMAW using 100% CO2 as the shielding gas. Different combinations of current, voltage and arc travel speed are chosen so that heat input increases from 0.35 to 0.75 kJ/mm. Nine number of weld beads are deposited and replicated twice. The observations show that weld bead width increases linearly with increase in heat input, whereas reinforcement height and depth of penetration do not increase with increase in heat input. Regression analysis is done to establish the relationship between heat input and different geometrical parameters of weld bead. The regression models developed agrees well with the experimental data. Within the domain of the present experiment, it is observed that at higher heat input, the weld bead gets wider having little change in penetration and reinforcement; therefore, higher heat input may be recommended for austenitic stainless steel cladding on low alloy steel.

Facile fabrication of superhydrophobic surfaces from austenitic stainless steel (AISI 304) by chemical etching

Science.gov (United States)

Kim, Jae-Hun; Mirzaei, Ali; Kim, Hyoun Woo; Kim, Sang Sub

2018-05-01

Stainless steels are among the most common engineering materials and are used extensively in humid areas. Therefore, it is important that these materials must be robust to humidity and corrosion. This paper reports the fabrication of superhydrophobic surfaces from austenitic stainless steel (type AISI 304) using a facile two-step chemical etching method. In the first step, the stainless steel plates were etched in a HF solution, followed by a fluorination process, where they showed a water contact angle (WCA) of 166° and a sliding angle of 5° under the optimal conditions. To further enhance the superhydrophobicity, in the second step, they were dipped in a 0.1 wt.% NaCl solution at 100 °C, where the WCA was increased to 168° and the sliding angle was decreased to ∼2°. The long-term durability of the fabricated superhydrophobic samples for 1 month storage in air and water was investigated. The potential applicability of the fabricated samples was demonstrated by the excellent superhydrophobicity after 1 month. In addition, the self-cleaning properties of the fabricated superhydrophobic surface were also demonstrated. This paper outlines a facile, low-cost and scalable chemical etching method that can be adopted easily for large-scale purposes.

Effects of Heat Input on Microstructure, Corrosion and Mechanical Characteristics of Welded Austenitic and Duplex Stainless Steels: A Review

Directory of Open Access Journals (Sweden)

Ghusoon Ridha Mohammed

2017-01-01

Full Text Available The effects of input heat of different welding processes on the microstructure, corrosion, and mechanical characteristics of welded duplex stainless steel (DSS are reviewed. Austenitic stainless steel (ASS is welded using low-heat inputs. However, owing to differences in the physical metallurgy between ASS and DSS, low-heat inputs should be avoided for DSS. This review highlights the differences in solidification mode and transformation characteristics between ASS and DSS with regard to the heat input in welding processes. Specifically, many studies about the effects of heat energy input in welding process on the pitting corrosion, intergranular stress, stresscorrosion cracking, and mechanical properties of weldments of DSS are reviewed.

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

International Nuclear Information System (INIS)

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

1981-01-01

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

Relationship between 0.2% proof stress and Vickers hardness of work-hardened low carbon austenitic stainless steel, 316SS

International Nuclear Information System (INIS)

Matsuoka, Saburo

2004-01-01

Stress corrosion cracking (SCC) occurs in shrouds and piping made of low carbon austenitic stainless steels at nuclear power plants. A work-hardened layer is considered to be one of the probable causes for this occurrence. The maximum Vickers hardness measured at the work-hardened layer is 400 HV. It is important to determine the yield strength and tensile strength of the work-hardened layer in the investigation on the causes of SCC. However, the tensile specimen cannot be obtained since the thickness of the work-hardened layer is as mall as several hundred μm, therefore, it is useful if we can estimate these strengths from its Vickers hardness. Consequently, we investigated the relationships between Vickers hardness versus yield strength and tensile strength using the results obtained on various steels in a series of Fatigue Data Sheets published by the National Institute for Materials Science and results newly obtained on a parent material and rolled materials (reduction of area: 10 - 50%, maximum hardness: 350 HV) for a low carbon stainless steel. The results showed that (1) the relationship between the 0.2% proof stress and the Vickers hardness can be described by a single straight line regardless of strength, structure, and rolling ratio, however, (2) the tensile strength is not correlated with the Vickers hardness, and the austenitic stainless steel in particular shows characteristics different from those of other steels. (author)

Fatigue life evaluation method of austenitic stainless steel in PWR water

International Nuclear Information System (INIS)

Sakaguchi, Katsumi; Nomura, Yuichiro; Suzuki, Shigeki; Kanasaki, Hiroshi; Higuchi, Makoto

2006-09-01

It is known that the fatigue life in elevated temperature water is substantially reduced compared with that in the air. The fatigue life reduction has been investigated experimentally in EFT project of Japan Nuclear Energy Safety Organization (JNES) to evaluate the environmental effect on fatigue life. Many tests have been done for carbon, low alloy, stainless steels and nickel-based alloy under the various conditions. In this paper, the results of the stainless steel in simulated PWR water environments were reported. Fatigue life tests in simulated PWR environments were carried out and the effect of key parameters on fatigue life reduction was examined. The materials used in this study were base and weld metal of austenitic stainless steel SS316, weld metal of SS304 and the base and aged metal of the duplex stainless steel SCS14A. In order to evaluate the effects of stain amplitude, strain rate, strain ratio, temperature, aging, water flow rate and strain holding time, many fatigue tests were examined. In transient condition in an actual plant, however, such parameters as temperature and strain rate are not constant. In order to evaluate fatigue damage in actual plant on the basis of experimental results under constant temperature and strain rate condition, the modified rate approach method was developed. Various kinds of transient have to be taken into account of in actual plant fatigue evaluation, and stress cycle of several ranges of amplitude has to be considered in assessing damage from fatigue. Generally, cumulative usage factor is applied in this type of evaluation. In this study, in order to confirm the applicability of modified rate approach method together with cumulative usage factor, fatigue tests were carried out by combining stress cycle blocks of different strain amplitude levels, in which strain rate changes in response to temperature in a simulated PWR water environment. Consequently, fatigue life could be evaluated with an accuracy of factor of 3

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

International Nuclear Information System (INIS)

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

1999-01-01

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

An assessment of microstructure, mechanical properties and corrosion resistance of dissimilar welds between Inconel 718 and 310S austenitic stainless steel

International Nuclear Information System (INIS)

Mortezaie, A.; Shamanian, M.

2014-01-01

In the present study, dissimilar welding between Inconel 718 nickel-base superalloy and 310S austenitic stainless steel using gas tungsten arc welding process was performed to determine the relationship between the microstructure of the welds and the resultant mechanical and corrosion properties. For this purpose, three filler metals including Inconel 625, Inconel 82 and 310 stainless steel were used. Microstructural observations showed that weld microstructures for all filler metals were fully austenitic. In tension tests, welds produced by Inconel 625 and 310 filler metals displayed the highest and the lowest ultimate tensile strength, respectively. The results of Charpy impact tests indicated that the maximum fracture energy was related to Inconel 82 weld metal. According to the potentiodynamic polarization test results, Inconel 82 exhibited the highest corrosion resistance among all tested filler metals. Finally, it was concluded that for the dissimilar welding between Inconel 718 and 310S, Inconel 82 filler metal offers the optimum properties at room temperature. - Highlights: • Three filler metals including Inconel 625, Inconel 82 and 310 SS were used. • A columnar to equiaxed dendritic structure was seen for IN-625 weld metal. • A granular austenitic microstructure obtained for Inconel 82 weld metal. • Microstructure of 310 weld metal includes solidification cracks along SSGB. • IN-82 weld metal showed the highest corrosion potential

Nano/ultrafine grained austenitic stainless steel through the formation and reversion of deformation-induced martensite: Mechanisms, microstructures, mechanical properties, and TRIP effect

Energy Technology Data Exchange (ETDEWEB)

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

2015-05-15

A comprehensive study was carried out on the strain-induced martensitic transformation, its reversion to austenite, the resultant grain refinement, and the enhancement of strength and strain-hardening ability through the transformation-induced plasticity (TRIP) effect in a commercial austenitic 304L stainless steel with emphasis on the mechanisms and the microstructural evolution. A straightforward magnetic measurement device, which is based on the measurement of the saturation magnetization, for evaluating the amount of strain-induced martensite after cold rolling and reversion annealing in metastable austenitic stainless steels was used, which its results were in good consistency with those of the X-ray diffraction (XRD) method. A new parameter called the effective reduction in thickness was introduced, which corresponds to the reasonable upper bound on the obtainable martensite fraction based on the saturation in the martensitic transformation. By means of thermodynamics calculations, the reversion mechanisms were estimated and subsequently validated by experimental results. The signs of thermal martensitic transformation at cooling stage after reversion at 850 °C were found, which was attributed to the rise in the martensite start temperature due to the carbide precipitation. After the reversion treatment, the average grain sizes were around 500 nm and the nanometric grains of the size of ~ 65 nm were also detected. The intense grain refinement led to the enhanced mechanical properties and observation of the change in the work-hardening capacity and TRIP effect behavior. A practical map as a guidance for grain refining and characterizing the stability against grain growth was proposed, which shows the limitation of the reversion mechanism for refinement of grain size. - Graphical abstract: Display Omitted - Highlights: • Nano/ultrafine grained austenitic stainless steel through martensite treatment • A parameter descriptive of a reasonable upper bound on

Nano/ultrafine grained austenitic stainless steel through the formation and reversion of deformation-induced martensite: Mechanisms, microstructures, mechanical properties, and TRIP effect

International Nuclear Information System (INIS)

Shirdel, M.; Mirzadeh, H.; Parsa, M.H.

2015-01-01

A comprehensive study was carried out on the strain-induced martensitic transformation, its reversion to austenite, the resultant grain refinement, and the enhancement of strength and strain-hardening ability through the transformation-induced plasticity (TRIP) effect in a commercial austenitic 304L stainless steel with emphasis on the mechanisms and the microstructural evolution. A straightforward magnetic measurement device, which is based on the measurement of the saturation magnetization, for evaluating the amount of strain-induced martensite after cold rolling and reversion annealing in metastable austenitic stainless steels was used, which its results were in good consistency with those of the X-ray diffraction (XRD) method. A new parameter called the effective reduction in thickness was introduced, which corresponds to the reasonable upper bound on the obtainable martensite fraction based on the saturation in the martensitic transformation. By means of thermodynamics calculations, the reversion mechanisms were estimated and subsequently validated by experimental results. The signs of thermal martensitic transformation at cooling stage after reversion at 850 °C were found, which was attributed to the rise in the martensite start temperature due to the carbide precipitation. After the reversion treatment, the average grain sizes were around 500 nm and the nanometric grains of the size of ~ 65 nm were also detected. The intense grain refinement led to the enhanced mechanical properties and observation of the change in the work-hardening capacity and TRIP effect behavior. A practical map as a guidance for grain refining and characterizing the stability against grain growth was proposed, which shows the limitation of the reversion mechanism for refinement of grain size. - Graphical abstract: Display Omitted - Highlights: • Nano/ultrafine grained austenitic stainless steel through martensite treatment • A parameter descriptive of a reasonable upper bound on

Evaluation of deformation behavior of in grains and grain boundaries of L-grade austenitic stainless steel 316L

International Nuclear Information System (INIS)

Nagashima, Nobuo; Hayakawa, Masao; Tsukada, Takashi; Kaji, Yoshiyuki; Miwa, Yukio; Ando, Masami; Nakata, Kiyotomo

2009-01-01

In this study, micro-hardness tests and AFM observations were performed on SUS 316L low-carbon austenitic stainless steel pre-strained by cold rolling to investigate its deformation behavior. The following results were obtained. Despite the fact that the same plastic strain was applied, post-tensile test AFM showed narrower slip-band spacing in a reduction in area of 30% cold-rolled specimen than the unrolled specimen. Concentrated slip bands were observed near grain boundaries. These were presumably due to slip blocking at grain boundaries. SCC sensitivity increased at a hardness of 300 or higher, the frequency occurrence of a hardness of 300 or higher in the micro-hardness measurements was compared. The micro-hardness did not exceed 300 both within grains and at grain boundaries in the unrolled and up to a reduction in area of 20% cold-rolled specimens of before and after the tensile tests. Micro-hardness exceeding 300 was found to occur frequently in after tensile test specimens with a reduction in area of 30% or more, particularly at grain boundaries. It is suggested that the nonuniformity of deformation at grain boundaries plays an important role of IGSCC crack propagation mechanism of low-carbon austenitic stainless steel. (author)

Dislocation concepts applied to fatigue properties of austenitic stainless steels including time-dependent modes

Energy Technology Data Exchange (ETDEWEB)

Tavassoli, A.A.

1986-10-01

Dislocation substructures formed in austenitic stainless steel 304L and 316L, fatigued at 673 K, 823 K and 873 K under total imposed strain ranges of 0.7 to 2.25%, and their correlation with mechanical properties have been investigated. In addition substructures formed at lower strain ranges have been examined using foils prepared from parts of the specimens with larger cross-sections. Investigation has also been extended to include the effect of intermittent hold-times up to 1.8 x 10/sup 4/s and sequential creep-fatigue and fatigue-creep. The experimental results obtained are analysed and their implications for current dislocation concepts and mechanical properties are discussed.

Structural transformations in austenitic stainless steel induced by deuterium implantation: irradiation at 100 K.

Science.gov (United States)

Morozov, Oleksandr; Zhurba, Volodymyr; Neklyudov, Ivan; Mats, Oleksandr; Rud, Aleksandr; Chernyak, Nikolay; Progolaieva, Viktoria

2015-01-01

Deuterium thermal desorption spectra were investigated on the samples of austenitic stainless steel 18Cr10NiTi preimplanted at 100 K with deuterium ions in the dose range from 3 × 10(15) to 5 × 10(18) D/cm(2). The kinetics of structural transformation development in the implantation steel layer was traced from deuterium thermodesorption spectra as a function of implanted deuterium concentration. At saturation of austenitic stainless steel 18Cr10NiTi with deuterium by means of ion implantation, structural-phase changes take place, depending on the dose of implanted deuterium. The maximum attainable concentration of deuterium in steel is C = 1 (at.D/at.met. = 1/1). The increase in the implanted dose of deuterium is accompanied by the increase in the retained deuterium content, and as soon as the deuterium concentration attains C ≈ 0.5 the process of shear martensitic structural transformation in steel takes place. It includes the formation of bands, body-centered cubic (bcc) crystal structure, and the ferromagnetic phase. Upon reaching the deuterium concentration C > 0.5, the presence of these molecules causes shear martensitic structural transformations in the steel, which include the formation of characteristic bands, bcc crystal structure, and the ferromagnetic phase. At C ≥ 0.5, two hydride phases are formed in the steel, the decay temperatures of which are 240 and 275 K. The hydride phases are formed in the bcc structure resulting from the martensitic structural transformation in steel.

Tensile properties of four types of austenitic stainless steel welded joints

International Nuclear Information System (INIS)

Balladon, P.

1990-01-01

In the field of an LMFBR research programme on austenitic stainless steel welds in a Shared Cost Action Safety, Research Area 8, coordinated by JRC-Ispra, four cooperating laboratories (ECN, IKE/MPA, the Welding Institute and UNIREC) have been involved in the fabrication and extensive characterization of welded joints made from one plate of ICL 167 stainless steel. The materials included parent metal, four vacuum electron beam welds, one non vacuum electron beam weld, one submerged arc weld, one gas metal arc weld and one manual metal arc weld. This report summarizes the 106 tensile tests performed at room temperature and 550 0 C, including the influence of strain rate, specimen orientation and welding procedure. Main results are that electron beam welds have tensile properties close to those of parent metal with higher values of yield strength in longitudinal orientation and lower values of total elongation in transverse orientation but with a similar reduction of area, that filler metal welds own the highest values of yield strength and lowest values of ductility. Most of the welds properties are higher than the minimum specified for parent metal, except for some values of total elongation, mainly in transverse orientation. In view of using electron beam welding for production of components used in LMFBR, results obtained show that tensile properties of electron beam welds compare well to those of classical welds. (author)

Effect of nitrogen ion dose on the corrosion resistance, the microstructure and the phase structure of the biomaterials austenitic stainless steel 316L

International Nuclear Information System (INIS)

Lely Susita RM; Bambang Siswanto; Ihwanul Aziz; Anjar Anggraini H

2016-01-01

The succeed of the use of biomaterials for orthopedic implant device is determined by its mechanical properties, chemical stability and biocompatibility in tissues and body fluids. The corrosion resistance is one of the main property of biomaterials to determine for successful orthopedic implant in body tissues. Surface modification is carried out to improve biomaterial surface properties of austenitic stainless steel 316L with nitrogen ion implantation technique and ion nitriding. Nitrogen ion implantation performed on 60 keV ion energy and ion dose variations 2 x 10"1"6 ions/cm"2- 2 x 10"1"7 ions/cm"2. The corrosion resistance of austenitic stainless steel 316L in Hanks solution is measured by using a potentiostat, and corrosion resistance optimum of a sample is obtained at an ion dose of 5 x 10"1"6 ions/cm"2 and increase by a factor of 2.1 if compared to the sample without the nitrogen ion implantation. Further the sample of austenitic stainless steel 316L with the optimum corrosion resistance is processed by ion nitriding technique at a nitriding temperature of 350 °C and nitriding time of 4 hours. Based on corrosion test of the sample produced by ion nitriding is obtained an increasing the corrosion resistance by a factor of 2.96 when compared to the sample before nitrogen ion implantation. The improvement of corrosion resistance of the sample is caused by the formation of iron nitride ξ-Fe2N and γ- Fe4N which has excellent corrosion resistance properties. (author)

Copper precipitation behavior and mechanical properties of Cu-bearing 316L austenitic stainless steel: A comprehensive cross-correlation study

International Nuclear Information System (INIS)

Xi, Tong; Babar Shahzad, M.; Xu, Dake; Zhao, Jinlong; Yang, Chunguang; Qi, Min; Yang, Ke

2016-01-01

The effect of precipitation hardening on mechanical properties and coarsening behavior of Cu-rich precipitates in a Cu-bearing 316L austenite stainless steel after aging at 700 °C for different time were systematically investigated. The variations of morphology and composition of Cu-rich precipitates as a function of aging time were respectively characterized by electrical resistivity, atom probe tomography (APT) and transmission electron microscopy (TEM). It was found that both hardness and mechanical strength increased to peak value within short aging time, and remained nearly unchanged with prolonged aging time. The TEM observation confirmed a coherent interface between Cu-rich precipitates and austenite matrix, while high number densities of spheroidal Cu-rich precipitates were observed in all aged samples. APT analyses confirmed virtually 100% Cu core composition of Cu-rich precipitates, whereas the average radius was slightly increased from 1.38±0.46 nm to 2.39±0.81 nm with increasing the aging time. The relatively slow growth and coarsening behavior of Cu-rich precipitates was largely attributed to the slower diffusion kinetics of Cu, low interfacial energy and high strain energy of Cu-rich precipitates in the austenite matrix, and was well predicted by the Lifshitz-Slyozov-Wagner theory. The slow increase in average radius of Cu-rich precipitates was consistent with the modest change in hardness and yield strength with extended aging. In addition, the precipitation strengthening effects of Cu-rich precipitates were quantitatively evaluated and analyzed. These cumulative results and analyses could provide a solid foundation for much wider applications of Cu-bearing stainless steels.

Copper precipitation behavior and mechanical properties of Cu-bearing 316L austenitic stainless steel: A comprehensive cross-correlation study

Energy Technology Data Exchange (ETDEWEB)

Xi, Tong [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China); Babar Shahzad, M.; Xu, Dake; Zhao, Jinlong [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Yang, Chunguang, E-mail: cgyang@imr.ac.cn [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Qi, Min [School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024 (China); Yang, Ke, E-mail: kyang@imr.ac.cn [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)

2016-10-15

The effect of precipitation hardening on mechanical properties and coarsening behavior of Cu-rich precipitates in a Cu-bearing 316L austenite stainless steel after aging at 700 °C for different time were systematically investigated. The variations of morphology and composition of Cu-rich precipitates as a function of aging time were respectively characterized by electrical resistivity, atom probe tomography (APT) and transmission electron microscopy (TEM). It was found that both hardness and mechanical strength increased to peak value within short aging time, and remained nearly unchanged with prolonged aging time. The TEM observation confirmed a coherent interface between Cu-rich precipitates and austenite matrix, while high number densities of spheroidal Cu-rich precipitates were observed in all aged samples. APT analyses confirmed virtually 100% Cu core composition of Cu-rich precipitates, whereas the average radius was slightly increased from 1.38±0.46 nm to 2.39±0.81 nm with increasing the aging time. The relatively slow growth and coarsening behavior of Cu-rich precipitates was largely attributed to the slower diffusion kinetics of Cu, low interfacial energy and high strain energy of Cu-rich precipitates in the austenite matrix, and was well predicted by the Lifshitz-Slyozov-Wagner theory. The slow increase in average radius of Cu-rich precipitates was consistent with the modest change in hardness and yield strength with extended aging. In addition, the precipitation strengthening effects of Cu-rich precipitates were quantitatively evaluated and analyzed. These cumulative results and analyses could provide a solid foundation for much wider applications of Cu-bearing stainless steels.

Experimental and field achievements in the ultrasonic examination of austenitic stainless steel

International Nuclear Information System (INIS)

Dombret, P.; Cermak, J.; Delaide, M.; Verspeelt, D.; Caussin, P.

1988-01-01

In spite of the many disturbances caused in the propagation of acoustic waves by the metallurgical structure of austenitic stainless steel, ultrasonic examination can provide in many cases key information in the process of assessing the structural integrity of industrial installations made from such materials. Indeed the steel structure variability makes every cases peculiar, with the consequence that the achievement of a dedicated feasibility study will often enhance drastically the examination performance. Such an exploratory exercise imposes to use a careful methodology regarding transducer and pulser selection, data analysis, performance evaluation, procedure qualification and field implementation. Through various examples from the nuclear industry field, the paper illustrates that kind of approach, as well as the extent to which it has been made possible to optimize the actual inspection capability and reliability. (author)

Experimental and field achievements in the ultrasonic examination of austenitic stainless steel

Energy Technology Data Exchange (ETDEWEB)

Dombret, P; Cermak, J; Delaide, M; Verspeelt, D; Caussin, P

1988-12-31

In spite of the many disturbances caused in the propagation of acoustic waves by the metallurgical structure of austenitic stainless steel, ultrasonic examination can provide in many cases key information in the process of assessing the structural integrity of industrial installations made from such materials. Indeed the steel structure variability makes every cases peculiar, with the consequence that the achievement of a dedicated feasibility study will often enhance drastically the examination performance. Such an exploratory exercise imposes to use a careful methodology regarding transducer and pulser selection, data analysis, performance evaluation, procedure qualification and field implementation. Through various examples from the nuclear industry field, the paper illustrates that kind of approach, as well as the extent to which it has been made possible to optimize the actual inspection capability and reliability. (author).

Stress corrosion cracking of austenitic stainless steels in NaCl-AlCl/sub 3/ at 175C

International Nuclear Information System (INIS)

Smyrl, W.H.

1987-01-01

Austenitic stainless steels are susceptible to stress corrosion cracking in chloride media. A test that is often used to determine the susceptibility of a new alloy involves boiling aqueous MgCl/sub 2/ solutions. The compositions of the solution is not controlled in the tests, and changes as water is evaporated. The pH may change as well. Such poorly defined conditions make any mechanistic interpretation very tenuous, and the results may be tabulated as purely empirical data. the choice of the molten salt in the present investigation was made for two reasons. First, the studies could be carried in the molten salt media with the exclusion of H/sub 2/O. Second, the crack propagation could be investigated under well controlled electrochemical conditions. Therefore, the results may help to identify the controlling processes that occur during stress corrosion cracking, and the comparison to results in boiling MgCl/sub 2/ may help to reveal the controlling processes in that medium as well. Crack propagation has been studied for several nitronic stainless steels in the molten salt medium under controlled electrochemical potential conditions. The alloys were studied under fully austenitic conditions. The material was studied in the annealed and work hardened condition, and both were susceptible to cracking in the molten salt. The velocity of cracking was studied as a function of applied stress at several electrochemical potentials

Martensitic transformation behaviour in sensitized SUS304 austenitic stainless steel during isothermal holding at low temperature

International Nuclear Information System (INIS)

Lee, Jae-hwa; Fukuda, Takashi; Kakeshita, Tomoyuki

2009-01-01

We investigated martensitic transformation behaviour in sensitized SUS304 austenitic stainless steel to determine the stability of the austenitic phase at low temperatures. We found that a specimen that was sensitized at 973 K for 100 h exhibits an isothermal martensitic transformation when the specimen is held in the temperature range between 60 and 260 K. We constructed a time-temperature-transformation (TTT) diagram corresponding to the formation of 0.5 vol. % α'-martensite. A magnetization measurement was used to evaluate the volume fraction of a'-martensite. The TTT diagram shows a double-C curve with two noses located at about 100 and 200 K. In-situ optical microscope observations reveal that the double C-curve is due to two different transformation sequences. That is, the upper part of the C-curve is due to a direct γ → α' martensitic transformation and the lower part of the C-curve is due to a successive γ → ψ → α' martensitic transformation. The direct γ → α' transformation occurs in the vicinity of grain boundaries while the successive γ → ψ' → α' transformation occurs near the centre of grains. A scanning electron microscope observation reveals that carbide particles of M 23 C 6 are formed in the grain boundaries. The concentration difference between the centre of the grains and regions near grain boundaries is the reason for the difference in the isothermal transformation sequence for the sensitized SUS304 stainless steel.