Analysis of the early stage of stress corrosion cracking in austenitic stainless steel by EBSD and XRD

This study examined nucleation behavior during the early stage of stress corrosion cracking (SCC) in sensitized austenitic stainless steel based on microstructural assessments, using X-ray diffraction (XRD) and electron back-scattered diffraction (EBSD). The SCC experiment was conducted while applying a constant load corresponding to an initial strain of 2% in a tetrathionate solution. The crystal orientations on the smooth surface of a thermally sensitized specimen were determined via EBSD before and after testing, and diffraction spots were intermittently examined using XRD. Some grains having a high Schmid factor were found to be locally deformed near grain boundaries (GBs) due to constant tensile loading in the corrosive solution, such that intergranular stress corrosion cracks occurred at these GBs. The results of this work demonstrate that the passivation film on the metal first fractures due to localized deformation, after which newly created surfaces near GBs are exposed to the corrosive solution. Localized crack-like corrosion subsequently proceeds in chromium-depleted zones near GBs to generate intergranular SCC.