Stress Corrosion Cracking of 316NG Stainless Steel Weld Joint in High-Temperature High-Pressure Water Containing Chloride

The effect of applied potential on stress corrosion cracking（SCC） behavior of stainless steel 316 NG weld joint was studied by slow strain rate tensile（SSRT） tests and high-temperature electrochemistry test in high-temperature high-pressure water containing high concentration chloride.The results revealed that the SCC susceptibility increases dramatically with the applied potential than the potential above a critical potential which exists between +50~+100mV（vs.SHE）.The SCC susceptibility is low and no obvious intergranular stress corrosion cracks but only a little transgranular stress corrosion cracks can be found when the applied potential below this critical potential which corresponds to oxygenated water chemistry.When electrode potential is more than this critical potential,the weld joint exhibits significant SCC appearing large area intergranular stress corrosion cracks.Besides,in Ar and low corrosion（electrode potential ≤50mV） environments,the weld joint cracking is plastic fracture determined by the mechanical properties,which related to the hardness distribution along the joint.In high corrosion（electrode potential ＞50mV） environments,the weld joint cracking is brittle fracture determined by the corrosion resistance and apparently the weld and heating affected zone exhibit higher SCC susceptibility than the base metal.