The mechanism of stress corrosion cracking of alloy 600 in high temperature water

The different mechanisms proposed to explain the stress corrosion cracking (SCC) of alloy 600 are briefly reviewed and their validity to explain the influence of the variables and to predict the crack growth rate (CGR) is assessed. It is concluded that several of the proposed models seem to give a fair estimate of the CGR values under certain conditions; it appears that a single mechanism cannot explain in detail the complex alloy 600 SCC. There is a total absence of explanation in the literature of the events leading to the nucleation of cracking. It is suggested that processes controlled by diffusion such as internal oxidation or environmentally assisted creep may establish the length of induction time observed in plants. (author)