Prediction of stress corrosion crack growth rate of irradiated alloy X-750 with different crack tip strain rate models

Abstract

This study developed a prediction method for the crack growth rates (CGRs) of irradiated X-750 using the crack tip strain rate. First, the optimum input parameters for the Hashimoto-Koshiishi model, which is a mechanistic crack growth model of stress corrosion cracking (SCC), were obtained for unirradiated X-750. Second, the methodology to incorporate the effect of neutron irradiation on SCC CGRs was developed to fit the experimental data. The strain rate equation for elastic-ideally plastic materials was employed for evaluating the crack tip strain rate since irradiated X-750 showed no strain hardening in its stress–strain curve. Calculated CGRs agreed well with experimental CGRs at 0.3 dpa and 1.4 dpa not only for normal water chemistry but also for hydrogen water chemistry. Finally, the CGR dependency on irradiation dose was evaluated with the developed model. The model prediction showed that the CGRs increased slowly with irradiation dose and became almost constant above 1 dpa.