Stress corrosion crack initiation in machined type 316L austenitic stainless steel in simulated pressurized water reactor primary water

The effect of machining on stress corrosion crack initiation of annealed Type 316L stainless steel was investigated through accelerated testing in high-temperature hydrogenated water. It was observed that stress corrosion cracks only initiated on machined surfaces with machining marks perpendicular to the loading direction and a porous inner oxide layer was identified as an important factor contributing to crack initiation. Furthermore, most cracks stopped within the machining-induced near-surface ultrafine-grained layer and the machining-induced residual stresses did not appear to have a significant effect on crack initiation. A correlation between crack initiation and the surface/near-surface features is identified and discussed.