Effect of heat treatment on grain boundary carbides and primary water stress corrosion cracking resistance of Alloy 182 weld

Highlights: • PWSCC resistance of Alloy 182 weld was improved after heat-treatment at 620 and 650 °C. • GB carbides were Cr₂₃C₆ for as-welded specimen, but M₇C₃ type after heat treatment. • Depth of oxidized GB ahead of crack decreased due to less Cr supply from Cr₇C₃ carbides. • Improvement in PWSCC resistance was, in part, caused by the formation of Cr₇C₃ carbides. Alloy 182 welds were heat-treated at 600, 620, and 650 °C for 10 h. The primary water stress corrosion cracking initiation test showed significant improvement in the cracking resistance of the heat-treated specimens over the as-welded specimens. Microstructure analysis demonstrated that Cr₂₃C₆ grain boundary carbides dominated in the as-welded specimen, while Cr₇C₃ carbides were dominant after heat treatment. The depth of grain boundary oxidation ahead of the crack tip was large for the as-welded specimen, but less for the heat-treated specimens. Therefore, the presence of Cr₇C₃ carbides, in part, contributed to the improved cracking resistance of the Alloy 182 weld.