SCC growth rate measurements and surface oxide film characterization on high SFE austenitic stainless steels in a simulated BWR water environment

2014 ◽  
Vol 1715 ◽  
Author(s):  
S. Ooki ◽  
T. Yonezawa ◽  
M. Watanabe ◽  
H. Kokawa
Keyword(s):  
Growth Rate ◽  
Stainless Steel ◽  
Chemical Composition ◽  
Oxide Film ◽  
Stainless Steels ◽  
Growth Rates ◽  
Oxidation Behavior ◽  
Water Environment ◽  
Austenitic Stainless Steels ◽  
Composition Control

ABSTRACTStress Corrosion Cracking (SCC) has been detected in Boiling Water Reactors (BWRs) on core shrouds and primary water re-circulation piping made of low carbon stainless steels. Material hardening strongly affects SCC propagation behavior, and SCC growth rates increase with increasing hardness of austenitic stainless steels caused by cold work or neutron irradiation.Research work has been conducted in the authors’ laboratories with the aim of improving SCC resistance using chemical composition control of stainless steels. It has been previously reported that high stacking fault energy (SFE) materials showed better SCC resistance than low SFE materials due to hardening being suppressed in high SFE materials. In the present study, SCC growth rate (CGR) tests were performed using 15% cold worked Types 316L and 25Cr-20Ni stainless steels in a simulated BWR water environment. The 25Cr-20Ni stainless steel used has high SFE value due to chemical composition control and measured SCC growth rates were lower than those of low SFE stainless steels.However, oxidation behavior is one of the more important factors influencing SCC of austenitic stainless steels in addition to material hardening behavior, and the influence of the chemical composition control necessary to increase SFE on oxidation behavior in BWR primary coolants is still unclear. In this study, therefore, immersion tests using Types 316L and 25Cr-20Ni stainless steel specimens were also conducted in the simulated BWR water environment. The surface oxide films on the specimens were then analyzed with micro-Raman spectroscopy and glow discharge optical emission spectroscopy in order to help clarify the oxidation behavior.The results of these tests and analyses showed that the NiFe2O4 content of the outer oxide layers on the high SFE stainless steels was higher than that on the low SFE stainless steels. The inner oxide film on the 25Cr-20Ni stainless steel also had a high chromium content.Based on the above results, SCC resistance and oxidation behavior of high SFE austenitic stainless steels in a simulated BWR water environment will be discussed.

Delta Ferrite Formation in Austenitic Stainless Steel Castings

2012 ◽  
Vol 730-732 ◽  
pp. 733-738 ◽  
Author(s):  
Angelo Fernando Padilha ◽  
Caio Fazzioli Tavares ◽  
Marcelo Aquino Martorano
Keyword(s):  
Stainless Steel ◽  
Chemical Composition ◽  
Cooling Rate ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Magnetic Method ◽  
Empirical Formulas ◽  
Delta Ferrite ◽  
Ferrite Formation ◽  
Steel Castings

The effects of chemical composition and cooling rate on the delta ferrite formation in austenitic stainless steels have been investigated. Ferrite fractions measured by a magnetic method were in the range of 0 to 12% and were compared with those calculated by empirical formulas available in the literature. The delta ferrite formation (amount and distribution) was strongly affected by the steel chemical composition, but less affected by the cooling rate. Among several formulas used to calculate the amount of delta ferrite, the best agreement was obtained with those proposed independently by Schneider and Schoefer, the latter being recommended in the ASTM 800 standard.

Crack Growth Rates of Irradiated Austenitic Stainless Steels in BWR Environments at 289°C

2007 ◽  
Author(s):  
O. K. Chopra ◽  
E. E. Gruber ◽  
B. Alexandreanu ◽  
Y. Chen ◽  
W. J. Shack
Keyword(s):  
Growth Rate ◽  
Crack Growth ◽  
Stainless Steels ◽  
Growth Rates ◽  
Austenitic Stainless Steels ◽  
Compact Tension ◽  
Constant Load ◽  
Specimen Size ◽  
Crack Growth Rates ◽  
Sawtooth Waveform

Crack growth rate (CGR) data have been obtained in boiling water reactor environments on several grades of austenitic stainless steels, including weld heat-affected-zone and cast materials, that were irradiated up to 2.0 × 1021 n/cm2 (E > 1 MeV) (≈3 dpa). Crack growth tests were conducted on 1/4-T compact tension specimens subjected to either a sawtooth waveform with load ratios up to 0.7 and rise times up to 1000 s, or a constant load with or without periodic partial unloading. The results indicate significant enhancement of crack growth rates in the irradiated steels. The results are compared with data obtained from other studies. The existing CGR data are also reviewed to evaluate the effects of material composition, irradiation, and water chemistry on the CGRs in austenitic SSs. The significance of specimen size criteria is discussed.

Evaluation of Crack Growth Rate of Neutron Irradiated Austenitic Stainless Steels at High Stress Intensity Factor Levels

2020 ◽  
Author(s):  
Hitoshi Seto ◽  
Masato Koshiishi ◽  
Shigeaki Tanaka ◽  
Ryoji Obata
Keyword(s):  
Growth Rate ◽  
Stress Intensity Factor ◽  
Stainless Steel ◽  
Crack Growth ◽  
Stainless Steels ◽  
High Stress ◽  
Austenitic Stainless Steels ◽  
High K ◽  
Normal Water ◽  
Crack Growth Rates

Abstract Crack growth rates (CGRs) at high K levels (more than 30 MPa·m0.5) were obtained in simulated boiling water reactor normal water chemistry under constant K conditions for Type 316NG stainless steel irradiated up to 2.0 dpa. Valid CGRs were obtained even at high K conditions such as K ≈ 40 MPa·m0.5 although branching was observed on the fracture surface of the specimen after CGR testing. CGRs were compared with predictions by a theoretical model and a disposition curve and it was found that these predictions are applicable even to high K levels around K ≈ 40 MPa·m0.5.

Improvement of Oxidation Behavior at 1,073 and 1,173K of Austenitic Stainless Steels by Addition of Ni

2014 ◽  
Vol 931-932 ◽  
pp. 338-343 ◽  
Author(s):  
Ornin Srihakulung ◽  
Panyawat Wangyao ◽  
Gobboon Lothongkum ◽  
Prasonk Sricharoenchai
Keyword(s):  
Growth Rate ◽  
Weight Gain ◽  
Oxide Scale ◽  
Oxidation Resistance ◽  
Rate Constant ◽  
Stainless Steels ◽  
Oxidation Behavior ◽  
Austenitic Stainless Steels ◽  
Exponential Rate ◽  
Nickel Addition

This work studied the effect of Nickel addition to improve the oxidation behavior of austenitic stainless steels at 1,073 K and 1,173 K. The results show that Nickel increases the oxidation resistance of the austenitic stainless steels. The compositions of oxide scale also change form only Cr2O3 to be Cr2O3, Fe2O3, NiFe2O4 and Ni (Cr2O4). The oxidation behavior follows the parabolic rate law; W = ktn, where W = weight gain (g/cm2), t = time (s), k is the exponential rate constant and n is the exponent of growth rate. The n values are between 0.47-0.88.

Oxidation behavior of 26Cr-16Ni and AISI 309 austenitic stainless steels in air flow at 1,173 K

2015 ◽  
Vol 57 (7-8) ◽  
pp. 597-601 ◽  
Author(s):  
Peeraya Pipatnukun ◽  
Panyawat Wangyao ◽  
Gobboon Lothongkum
Keyword(s):  
Stainless Steels ◽  
Oxidation Behavior ◽  
Air Flow ◽  
Austenitic Stainless Steels

ALZ 316

Alloy Digest ◽  
1999 ◽  
Vol 48 (8) ◽  
Keyword(s):  
Mechanical Properties ◽  
Stainless Steel ◽  
Corrosion Resistance ◽  
Austenitic Stainless Steel ◽  
Physical Properties ◽  
Tensile Properties ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Heat Treating

Abstract ALZ 316 is an austenitic stainless steel with good formability, corrosion resistance, toughness, and mechanical properties. It is the basic grade of the stainless steels, containing 2 to 3% molybdenum. After the 304 series, the molybdenum-containing stainless steels are the most widely used austenitic stainless steels. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, and joining. Filing Code: SS-756. Producer or source: ALZ nv.

ALLOY 0Cr25Ni6Mo3CuN

Alloy Digest ◽  
1998 ◽  
Vol 47 (2) ◽  
Keyword(s):  
Fracture Toughness ◽  
Stainless Steel ◽  
Corrosion Resistance ◽  
High Temperature ◽  
Physical Properties ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Temperature Performance ◽  
Steel Research ◽  
Oil Refinement

Abstract ALLOY 0Cr25Ni6Mo3CuN is one of four grades of duplex stainless steel that were developed and have found wide applications in China since 1980. In oil refinement and the petrochemical processing industries, they have substituted for austenitic stainless steels in many types of equipment, valves, and pump parts. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on low and high temperature performance, and corrosion resistance as well as forming and joining. Filing Code: SS-706. Producer or source: Central Iron & Steel Research Institute.

CARTECH 347

Alloy Digest ◽  
2021 ◽  
Vol 70 (9) ◽  
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
Austenitic Stainless Steel ◽  
Stainless Steels ◽  
Intergranular Corrosion ◽  
Austenitic Stainless Steels ◽  
Heat Treating ◽  
Intermittent Heating ◽  
Technology Corporation ◽  
Carpenter Technology Corporation

Abstract CarTech 347 is a niobium+tantalum stabilized austenitic stainless steel. Like Type 321 austenitic stainless steel, it has superior intergranular corrosion resistance as compared to typical 18-8 austenitic stainless steels. Since niobium and tantalum have stronger affinity for carbon than chromium, carbides of those elements tend to precipitate randomly within the grains instead of forming continuous patterns at the grain boundaries. CarTech 347 should be considered for applications requiring intermittent heating between 425 and 900 °C (800 and 1650 °F). This datasheet provides information on composition, physical properties, hardness, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: SS-1339. Producer or source: Carpenter Technology Corporation.

scholarly journals Surface Modification of a Nickel-Free Austenitic Stainless Steel by Low-Temperature Nitriding

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1845
Author(s):  
Francesca Borgioli ◽  
Emanuele Galvanetto ◽  
Tiberio Bacci
Keyword(s):  
Stainless Steel ◽  
Corrosion Resistance ◽  
Austenitic Stainless Steel ◽  
Low Temperature ◽  
Stainless Steels ◽  
Volume Fraction ◽  
Surface Hardness ◽  
Austenitic Stainless Steels ◽  
Surface Layers ◽  
Modified Surface

Low-temperature nitriding allows to improve surface hardening of austenitic stainless steels, maintaining or even increasing their corrosion resistance. The treatment conditions to be used in order to avoid the precipitation of large amounts of nitrides are strictly related to alloy composition. When nickel is substituted by manganese as an austenite forming element, the production of nitride-free modified surface layers becomes a challenge, since manganese is a nitride forming element while nickel is not. In this study, the effects of nitriding conditions on the characteristics of the modified surface layers obtained on an austenitic stainless steel having a high manganese content and a negligible nickel one, a so-called nickel-free austenitic stainless steel, were investigated. Microstructure, phase composition, surface microhardness, and corrosion behavior in 5% NaCl were evaluated. The obtained results suggest that the precipitation of a large volume fraction of nitrides can be avoided using treatment temperatures lower than those usually employed for nickel-containing austenitic stainless steels. Nitriding at 360 and 380 °C for duration up to 5 h allows to produce modified surface layers, consisting mainly of the so-called expanded austenite or gN, which increase surface hardness in comparison with the untreated steel. Using selected conditions, corrosion resistance can also be significantly improved.

Developing New Cast Austenitic Stainless Steels With Improved High-Temperature Creep Resistance

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
Philip J. Maziasz ◽  
John P. Shingledecker ◽  
Neal D. Evans ◽  
Michael J. Pollard
Keyword(s):  
Stainless Steel ◽  
High Temperature ◽  
Creep Strength ◽  
Stainless Steels ◽  
Creep Resistance ◽  
Austenitic Stainless Steels ◽  
Creep Rupture ◽  
Particulate Filter ◽  
Alloy Development ◽  
Wide Range

Oak Ridge National Laboratory and Caterpillar (CAT) have recently developed a new cast austenitic stainless steel, CF8C-Plus, for a wide range of high-temperature applications, including diesel exhaust components and turbine casings. The creep-rupture life of the new CF8C-Plus is over ten times greater than that of the standard cast CF8C stainless steel, and the creep-rupture strength is about 50–70% greater. Another variant, CF8C-Plus Cu/W, has been developed with even more creep strength at 750–850°C. The creep strength of these new cast austenitic stainless steels is close to that of wrought Ni-based superalloys such as 617. CF8C-Plus steel was developed in about 1.5 years using an “engineered microstructure” alloy development approach, which produces creep resistance based on the formation of stable nanocarbides (NbC), and resistance to the formation of deleterious intermetallics (sigma, Laves) during aging or service. The first commercial trial heats (227.5 kg or 500 lb) of CF8C-Plus steel were produced in 2002, and to date, over 27,215 kg (300 tons) have been produced, including various commercial component trials, but mainly for the commercial production of the Caterpillar regeneration system (CRS). The CRS application is a burner housing for the on-highway heavy-duty diesel engines that begins the process to burn-off particulates trapped in the ceramic diesel particulate filter (DPF). The CRS/DPF technology was required to meet the new more stringent emissions regulations in January, 2007, and subjects the CRS to frequent and severe thermal cycling. To date, all CF8C-Plus steel CRS units have performed successfully. The status of testing for other commercial applications of CF8C-Plus steel is also summarized.

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