Stochastic model for intergranular stress corrosion cracking of stainless steel

Intergranular stress corrosion cracking (IGSCC) occurs in polycrystalline alloys, and this process is inherently stochastic. This study proposed a new approach to predict the service life of a component subjected to IGSCC considering the scatter of its processes due to microstructural inhomogeneity. First, the crack initiation, growth, and coalescence in IGSCC were stochastically modeled considering the influence of microstructural inhomogeneity on cracking behavior. Then, a time-evolution simulation was developed based on the models. In this simulation, the time and crack length were described using probability density functions. Hence, once a crack length reaches a certain critical value, a cumulative distribution function of the time to failure is obtained, which reveals the service life due to IGSCC. The developed simulation was applied to IGSCC of type 304 stainless steel in a simulated boiling water reactor environment. The simulation successfully reproduced the crack initiation event after the incubation period followed by repeated crack growth and coalescence events, which were characteristic of the entire IGSCC process, and the results agreed with those of another simulation that well reproduced previous experimental results. Furthermore, the critical crack was set at 5 mm long, and the service life distribution was obtained from a single calculation. The developed simulation based on the stochastic models is a sophisticated approach to predict the service life of a component considering crack initiation, growth, and coalescence. Hence, it is expected that the simulation contributes to ensuring long-term structural integrity.