Effects of heat treatment on corrosion fatigue and stress corrosion crack growth of additive-manufactured Alloy 800H in high-temperature water

Crack growth behaviour of additively manufactured (AM) Alloy 800H were studied under cyclic and static load in high-temperature water, focusing on heat treatment effects. Under cyclic loading, heat treatment gently affected corrosion fatigue. The growth rate is comparable to wrought 800H. As the load cycle frequency reduced to below 0.001 Hz, AM 800H exhibited inconsistent stress corrosion cracking response as compared to wrought 800H. Depending on heat treatment, inhomogeneous crack propagation and localized pinning were observed in stress-relieved and recrystallized AM 800H, attributed to carbides, microstructural inhomogeneity, and twin boundaries. Grain boundary sensitization at (similar to)10 wt% Cr caused fast crack growth.

Automated summary

The crack growth behavior of additively manufactured Alloy 800H in high-temperature water was studied, with a focus on the effects of heat treatment. It was observed that heat treatment had a mild impact on corrosion fatigue under cyclic loading, and the growth rate was comparable to wrought 800H. However, at lower load cycle frequencies, inconsistent stress corrosion cracking responses were observed in AM 800H compared to wrought 800H. Additionally, inhomogeneous crack propagation and localized pinning were attributed to carbides, microstructural inhomogeneity, and twin boundaries in stress-relieved and recrystallized AM 800H, leading to fast crack growth caused by grain boundary sensitization at around 10 wt% Cr.