Sulphide stress cracking behaviour of the dissimilar metal welded joint of X60 pipeline steel and Inconel 625 alloy

•The closer to the fusion boundary, the lower hardness in the dilution zone.•Dissimilar welding joint shows a high SSC susceptibility.•Crack initiation is caused by the asymmetric stress concentration.•Hydrogen-enhanced localised plasticity affects the crack propagation direction.•Anodic dissolution prevents crack blunting.

The sulphide stress cracking (SSC) behaviour of the dissimilar metal welded joint of X60 pipeline steel and Inconel 625 alloy in H2S environment was investigated using constant load testing, weight loss testing and finite element analysis. The dissimilar welded joint shows high SSC susceptibility, and the asymmetric stress concentration after corrosion is the prerequisite for crack initiation. Anodic dissolution prevents crack blunting, whereas hydrogen embrittlement increases the crack propagation rate and affects SSC to propagate along the fusion boundary.