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.

这项研究使用X射线衍射（XRD）和电子背散射衍射（EBSD），基于微观结构评估，研究了敏化奥氏体不锈钢在应力腐蚀开裂（SCC）早期的成核行为。进行SCC实验时，在四硫酸盐溶液中施加相当于2％初始应变的恒定载荷。在测试之前和之后，通过EBSD确定热敏样品光滑表面上的晶体取向，并使用XRD间歇检查衍射点。由于腐蚀溶液中的恒定拉伸载荷，发现一些具有较高Schmid因子的晶粒在晶界（GBs）附近局部变形，从而在这些GBs上出现了晶间应力腐蚀裂纹。这项工作的结果表明，金属上的钝化膜首先由于局部变形而破裂，然后在GBs附近新产生的表面暴露在腐蚀性溶液中。随后在GBs附近的贫铬区域进行局部裂纹状腐蚀，生成晶间SCC。