Effect of Heat Treatment on the Microstructure and Fracture Behaviors of a Ni–Cr–Fe Superalloy

Abstract

The influences of the size and shape of the γ′ phase and the type and distribution of carbides on the fracture behavior of a new Ni–Cr–Fe superalloy subjected to four different solution aging treatments are examined. The γ′ phase and γ matrix of the L12‐ordered structure maintain a coherent orientation relationship on the {100} and {110} atomic planes according to transmission electron microscopy observations. The material becomes stronger because the movement of dislocations is hindered by the γ′ phase and MC (Nb‐rich, Ti‐rich) and M23C6 (Cr‐rich, Mo‐rich) carbides. The two‐stage aging system (850 °C × 4 h + 730 °C × 4 h) substantially increases the size of the γ′ phase. The solid solution sample shows a microporous‐aggregated ductile fracture, and the solution‐aged samples show a microporous‐aggregated crystalline fracture according to scanning electron microscopy observations. The fracture mechanism is also discussed.