Effect of stabilization annealing on fatigue crack propagation behavior of inconel 706 alloy at 25 and 650 °C

Stabilization annealing (SA) treatment is often performed on precipitation-hardened IN706 (Ni-37.7Fe-15.6Cr-3Nb-1.7Ti-0.23Al) before aging to improve the resistance to creep, while sacrificing the tensile properties. In this study, the effect of SA treatment on fatigue crack propagation (FCP) behavior of IN706 at 25 and 650oC was examined based on detailed fractographic and micrographic analyses. IN706 specimen with SA treatment at 845oC for 3 hours showed a considerable amount of η precipitates, that were located along grain boundaries and within grains. It was found that η precipitates, particularly those linearly aligned within grains, provided easy crack path, reducing the resistance to FCP of IN706 at both 25 and 650oC.