Vacancy defects in a stress-corrosion-cracked Type 304 stainless steel investigated by positron annihilation spectroscopy

Yabuuchi, Atsushi; Maekawa, Masaki; Kawasuso, Atsuo

To reveal vacancy formation during the stress corrosion cracking (SCC), three factors influencing SCC in Type 304 stainless steels - sensitization heat treatment, corrosion treatment and tensile plastic deformation - were investigated by means of positron annihilation spectroscopy. Vacancy defects induced by the sensitization heat treatment and by tensile deformation were identified as monovacancies. These monovacancies were annealed within the same temperature range in which light water reactors are operated (280-320 C). The above results allow us to conclude that such vacancy defects play an important role in high-temperature-water SCC crack propagation.