Stress corrosion cracking of 304L stainless steel in water at 288°C

Stress corrosion cracking (SCC) of a sensitized 304L stainless steel was carried out under slow tension of a pre-cracked sample in water containing oxygen at 288°C. Thin foil samples were prepared along its cross-section containing the pre-cracks, and the tip region of SCC was studied by analytical TEM. The observations show that there are oxides with a size of several hundreds nanometers ahead of a crack tip of SCC and around the discontinuous microcracks. Fine-probe analysis was used to determine local compositions of the oxides, indicating the oxides were Cr₂O₃, Fe₃O₄ and their mixture. Many microcracks are distributed unevenly in the oxides. Microcracks initiated discontinuously in the oxides ahead of a main crack because of a large stress concentration. The growth and connection of the discontinuous microcracks in the oxides resulted in the propagation of SCC.