Effect of Surface Machining on Stress Corrosion Cracking Sensitivity of 304L and 316L Austenite Stainless Steel

304L/316L austenitic stainless steels (SSs) often used for main pipe of PWR nuclear power plant. Surface machining has a significant effect on microstructure and residual stress of SS, which further affects its stress corrosion cracking (SCC) sensitivity. The present study results show that, the SCC sensitivity of machined specimens increases significantly tested in 300 °C high temperature and high pressure water environment by the slow strain rate tensile test (SSRT). It increased from less than 10% of polished specimens to 20–30% of machined specimen for SCC sensitivity. It was found that the machined specimen showed as cleavage cracking, while the polished specimen was shown as ductile cracking with obviously fracture necking phenomenon. The mechanism of SCC of two kinds of SSs materials focused on the deformation layer of machined specimen was analysed, and the model of SCC initiation caused by nanocrystalline layer was established.