Crystallographic and mechanical investigation of intergranular stress corrosion crack initiation in austenitic stainless steel

This study used crystallographic and mechanical analyses to investigate the nucleation of intergranular stress corrosion cracking (IGSCC) on a smooth surface of type 304 austenitic stainless steel. Constant load testing was conducted on thermally sensitized austenitic stainless steel in a tetrathionate solution, and the nucleation behavior of IGSCC on a smooth surface was observed in situ. Then, grain boundaries (GBs) at which stress corrosion cracks occurred were characterized based on the coincidence site lattice model, GB length, and stress acting on GBs. It was found that GBs with the following characteristics exhibited high susceptibility to IGSCC: GBs with little resistance to intergranular corrosion (IGC), long GBs, and GBs subjected to high normal stress. Shear stress acting on GBs seemed to have little effect on the nucleation of IGSCC. Then, a criterion for intergranular stress corrosion crack initiation was developed using the susceptibility of GBs to IGC, GB length, and the stresses acting on GBs.