2020 Volume 69 Issue 4 Pages 112-130
Author discusses a relationship between grain boundary characteristics and acoustic emission （AE） activity in the intergranular stress corrosion cracking （IG-SCC） of Type-304 and Type-316 austenitic stainless steels in chloride and acidic tetra-thionic solutions. The author also discusses source mechanism of the AE signals emitted during crack opening operation of the IG-SCC, based on the coincidence site lattice （CSL） data of the both steels. He found that the Type-316 steel showed a high resistance against both the chloride and acidic tetra-thionic IG-SCC and a much emission of AEs, while the Type-304 steel showed lower resistance and lower AE emission rate. He observed many projections on the fracture surface of the sensitized Type-316 steel, but quiet few projection for the Type-304 steel. The authors demonstrates that the projections are produced by mechanical fracture of the coincident grain boundaries which possess higher resistance against anodic dissolution and that this portion corresponds to the short edges of twin bands. The mechanical fracture of the short edges produces much AE signals, and then the higher emission rate of AE signals designates a higher resistance against the IG-SCC.
