Residual Stress and Precipitation Evolution of Bulk Nickel-Based Superalloy During Heat Treatment

The heat treatment process plays a significant role in enhancing the performance of turbine disks made from nickel-based superalloys. However, the residual stress that emerges during quenching can lead to distortion or even cracking in turbine disks made of nickel-based superalloys. The stress evolution in bulk nickel-based superalloy, together with the strengthening of precipitation, was investigated in the current research, aiming to reveal the evolution quantitatively and to support the process design. The residual stress was predicted using finite element (FE) simulation and the contour method was employed to validate the simulation. The simulated results agreed well with the experimental findings and the validity of the simulation was thus proved. The simulation demonstrates that the quenching-induced residual stress is compressive at the surface while tensile at the center. Maximum tensile stress of 1029 MPa emerged at the center after the bulk was quenched in oil at 160 °C and the stress reduced to 628 MPa during the subsequent aging. The classical precipitation-strengthening models are utilized to calculate the optimal size of γ′ precipitates (r_w) in nickel-based superalloys. After aging treatment, the size of the γ′ precipitates in the bulk sample falls within the optimal precipitate size range. Minimized residual stress and optimized mechanical properties were achieved synergistically via the process optimization.