Microstructure Characterization of Ni-Based Superalloys During Thermal Exposure

Ni-based superalloys are critical materials of aero-engine turbine disks and blades. Microstructure characterization of Ni-based superalloys during thermal exposure have been investigated in present research. The evolution characteristics of grains, γ′ phase and twin boundaries of Ni-based superalloys during thermal exposure at 650 ℃ for 10–5000 h were analyzed based on OM, SEM and EBSD. The results show that crystal boundaries bending when thermal exposure time reaches 5000 h, the grains size un-occurred significantly variation, Σ3 twin boundaries first increase and then decrease. The morphology of secondary γ′ phases changed from initial near spherical / square to spherical, the size increase and content decrease with thermal exposure time prolongation. Tertiary spherical γ′ precipitates priority growth and precipitate as spheroids and ellipses, and content decreased significantly during thermal exposure for 2000 h. Microstructure characterization of Ni-based superalloys during near-service status have been revealed in present research, which provides theoretical reference for service conditions of Ni-based superalloys.