Predicting crack growth rate vs. temperature behaviour of type 304 stainless steel in dilute sulphuric acid solutions

The coupled-environment fracture model for intergranular stress corrosion cracking of Type 304 stainless steel in boiling water reactor primary (water) heat transport circuits containing relatively pure water has been extended to incorporate the effects of sulphuric acid additions to the coolant and to include thermal activation of the crack tip strain rate. These extensions allow comparisons to be made between theoretically estimated and experimentally determined crack growth rates (CGRs) over a considerable temperature range after calibration at a single temperature. The model predicts, in agreement with experiment, that the CGR passes through a maximum with increasing temperature at a temperature of about 180°C. The temperature dependence of the CGR is attributed to the competing effects of temperature on the thermally activated processes that occur at the crack tip and the properties (including ECP and conductivity) of the external environment.