The Influence of Creep-Fatigue Interaction on High Temperature Crack Growth in 316 Steel Weldments

High temperature crack growth in weldments is of great concern and generally occurs along the boundary between the heat affected zone (HAZ) and parent material (PM) of welded components in high temperature plants. Static creep and low frequency cyclic crack growth tests have been performed on compact tension, C(T), specimens manufactured from sections taken from a 316 steel weldment at 550 °C, where the crack tip was located along the fusion line within the HAZ. The data has been analyzed in terms of both the creep-brittle and creep-ductile crack tip parameters, K and C*, respectively. The cyclic test results have been compared to static creep crack growth tests on 316 steel weldments and homogeneous parent material specimens, and to crack growth models. The cracking rates of the cyclic crack growth tests are found to be higher than that of the of the static load creep crack growth tests on weldments. The data may be bounded by the high frequency fatigue and the static load creep crack growth predictions. However, further work is required to establish the fatigue and subsequently the creep component of the cyclic load crack growth tests on weldments.