Influence of Changes in Pressure and Temperature of Supercritical Water on the Susceptibility to Stress Corrosion Cracking of 316L Austenitic Stainless Steel

2016 ◽  
Vol 3 (1) ◽  
Author(s):  
Alberto Sáez-Maderuelo ◽  
Dolores Gómez-Briceño ◽  
César Maffiotte
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Stress Corrosion ◽  
Supercritical Water ◽  
Stress Corrosion Cracking ◽  
High Efficiency ◽  
Austenitic Stainless Steels ◽  
Corrosion Cracking ◽  
General Corrosion ◽  
316L Austenitic Stainless Steel

The supercritical water reactor (SCWR) is one of the Generation IV designs. The SCWR is characterized by its high efficiency, low waste production, and simple design. Despite the suitable properties of supercritical water as a coolant, its physicochemical properties change sharply with pressure and temperature in the supercritical region. For this reason, there are many doubts about how changes in these variables affect the behavior of the materials to general corrosion or to specific types of corrosion such as stress corrosion cracking (SCC). Austenitic stainless steels are candidate materials to build the SCWR due to their optimum behavior in the light water reactors (LWRs). Nevertheless, their behavior under the SCWR conditions is not well known. First, the objective of this work was to study the SCC behavior of austenitic stainless steel 316 type L in deaerated supercritical water at 400°C/25  MPa and 30 MPa and 500°C/25  MPa to determine how variations in pressure and temperature influence its behavior with regard to SCC and to make progress in the understanding of mechanisms involved in SCC processes in this environment. Second, the oxide layer formed at 400°C/30  MPa/<10  ppb O2 was analyzed to gain some insight into these processes.

Corrosion and Stress Corrosion Cracking Susceptibility of Type 347H Stainless Steel in Supercritical Water

CORROSION ◽  
10.5006/2459 ◽  
2017 ◽  
Vol 74 (1) ◽  
pp. 83-95 ◽  
Author(s):  
Xianglong Guo ◽  
Wenhua Gao ◽  
Kai Chen ◽  
Zhao Shen ◽  
Lefu Zhang
Keyword(s):  
Stainless Steel ◽  
Stress Corrosion ◽  
Oxygen Content ◽  
Supercritical Water ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
General Corrosion ◽  
Scattered Electron ◽  
Intergranular Cracking ◽  
Exposure Test

The corrosion resistance and stress corrosion cracking (SCC) susceptibility of Type 347H stainless steel (SS) in supercritical water (SCW) were investigated. The general corrosion behavior was investigated by exposure test and the specimens after testing were characterized utilizing scanning electron microscopy (SEM), Auger and x-ray diffraction analysis, optical microscopy, and energy dispersive spectroscopy (EDS). The results show that with the increase of testing temperature, the corrosion rate of the materials is greatly enhanced. The corrosion process is analyzed and the formation of oxide islands on the surface of the corroded sample is attributed to the higher diffusion rate of Cr along the grain boundary. The effects of temperature and dissolved oxygen on SCC susceptibility were investigated by slow strain rate tensile test. The fractographs were characterized by SEM and the cross-section morphologies were characterized with back-scattered electron imaging, SEM, and EDS. The results indicate that, as temperature is increased, the tensile strength and strain of materials is greatly reduced, while the oxygen content in SCW has a limited effect on the mechanical properties. Intergranular cracking and ductile fracture are the main fracture modes for Type 347H SS tested in SCW, independent of temperature and oxygen content. The implications of the results to the mechanisms of SCC are discussed.

scholarly journals Stress Corrosion Cracking Probability of Selective Laser Melted 316L Austenitic Stainless Steel under the Effect of Grinding Induced Residual Stresses

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 327
Author(s):  
Arshad Yazdanpanah ◽  
Mattia Lago ◽  
Claudio Gennari ◽  
Manuele Dabalà
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Corrosion Cracking ◽  
Surface Residual Stress ◽  
Near Surface ◽  
Melt Pool ◽  
316L Austenitic Stainless Steel ◽  
Pit Initiation

Surface quality and dimensional tolerances of the selective laser melting (SLM) process are not good enough for many industrial applications and grinding as a common finishing process introduces many surface modifications. Investigation on the effect of grinding induced surface residual stress (RS) on early stages of stress corrosion cracking (SCC) of SLM manufactured 316L austenitic stainless steel was conducted. Potentiodynamic and galvanostatic tests in a 3.5% NaCl aqueous solution, XRD, SEM and energy-dispersive X-ray spectroscopy (EDX) analysis were performed. For annealed and specimens with a low RS magnitude, the dominant observation was pit initiation from existing pores and growth in the build direction. For specimens with medium RS level, SCC initiation from pore sites and propagation along melt pool boundaries and for specimens with the highest detected RS, crack initiation from melt pool boundaries, grains, machining marks, and pore sites were observed. Cracks propagated in different directions, i.e., along melt pool boundaries, near-surface transgranular, and transgranular through columnar microstructure. Galvanostatic tests showed three distinctive regions that corresponded to crack and pit initiation and growth. The synergistic effect of high dislocation density along melt pool boundaries, stress concentration in pore sites, molybdenum segregation, and surface RS was the cause of SCC susceptibility of specimens with high RS magnitude.

Wedging Action of Solid Corrosion Product During Stress Corrosion of Austenitic Stainless Steels

CORROSION ◽  
1962 ◽  
Vol 18 (6) ◽  
pp. 230t-239t ◽  
Author(s):  
H. W. PICKERING ◽  
F. H. BECK ◽  
M. G. FONTANA
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Yield Strength ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Corrosion Cracking ◽  
Corrosion Products ◽  
Order Of Magnitude

Abstract A study was made of corrosion products and their effects on stress corrosion cracking of austenitic stainless steel. Wedging action by solid corrosion products in notches or cracks induces high stresses and eventual failure of specimens by stress corrosion cracking. Data were obtained from stress-relieved and unloaded (externally) specimens so that wedging by corrosion products provided the only source of stress in the specimen. Pressures were measured in excess of 7000 psi due to wedging action of corrosion products. At the base of a notch these pressures developed stresses of the order of magnitude of the yield strength of the metal. Wedging action can provide all the energy required for stress corrosion cracking. A mechanism is proposed which involves a discontinuous type of propagation, with fluctuations occurring over one or a few atomic distances. A running or mechanical type of crack propagation for more than a few atomic distances is ruled out on the basis of the mechanics of the system. 3.4.3, 3.5.8, 6.2.5

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