Abstract:Taking an Inconel 718 (GH4169) turbine disk with an accumulated service time of approximately 60 000 h from a specific model of aircraft as the research object, the microstructure evolution of various regions of the service turbine disk was investigated. Detailed characterization of the microstructure was conducted using research methods such as optical microscopy, scanning electron microscopy, electron probe, extraction phase analysis, inclusion scanner, and nano-indentation. The results show that after long-term service, there is no significant change in the strengthening phases γ' and γ' of the turbine disk. However, the quantity, size, and morphology of primary MC carbides from the center to the edge have noticeable changes. The content decreases from 0.166wt% to 0.106wt%, and the morphology gradually changes from sharp and regular blocky at the interface to irregular near-circular ones. The nano-hardness decreases, and there is a significant redistribution of elements, with elements Nb, Ti, and C released and diffused into the matrix. The primary MC carbides are prone to dissolution and decomposition during long-term service, leading to a decrease in concentration and hardness of the carbide elements. The diffusion of carbide-forming elements into the matrix may cause a disturbance to the comprehensive mechanical properties of the alloy during the long-term service performance.