SCC Initiation Model and Its Implementation for Probabilistic Assessment

An engineering model was recently developed to account for the inter-dependent influence of applied plus residual stress, material strength, strain-hardening, and cold work on stress corrosion cracking (SCC) susceptibility and time to initiation. Both the experimental observations and the model response suggest that a careful and combined consideration of these factors is essential in a quantitative or predictive assessment of SCC. These findings and the basic model are presented in this paper. Also, the proposed modeling framework of SCC susceptibility distinguishes, in the engineering sense, the influence of prior or additional cold work on the residual macro-stress and the microstructure, in addition to the role of (raised) strength properties. The model presented in this paper was evaluated for typical Alloy 600 and Type 304 stainless steel in high purity water environment. Additional objective of this paper is to demonstrate the utility and implementation of the model in a probabilistic assessment of the initiation of a short crack of engineering significance. It is shown that the basis and framework of the model provide a simple approach to quantify the key uncertainties in SCC initiation leading to results of interest in a probabilistic or risk-based methodology for SCC evaluation. Application of the results and possible implementation of the model are discussed with reference to the SCC of materials in the light water reactor environments.