Near-weld creep crack growth behaviour in Type 316H steel ex-service components

Creep crack growth is known to be the dominant failure mechanism in high-temperature components. Particularly in welded structures operating at elevated temperatures, cracks are often found to initiate and propagate in the vicinity of the weld region which can eventually penetrate into the base material after a long period of operation. In this study, creep crack growth tests have been performed on specimens extracted from an ex-service 316 H welded component to examine the crack initiation and growth behaviour in near-weld regions. The results show that the cracking behaviour of the base metal in near-weld specimens is similar to the as-received 316 H data set, suggesting that the material inhomogeneity would not influence the crack propagation behaviour in service-exposed components. Moreover, the test results show that the crack initiation and growth behaviour of the HAZ specimens can be estimated in much shorter time scales by performing tests on pre-compressed material.