The evolution of γ′ precipitates and hardness response of a novel PM Ni-based superalloy during thermal exposure

The effects of elemental repartitioning on the evolution of gamma ' precipitates and the hardness of the phase of a novel PM nickel-based superalloy after long-term thermal exposure at 750 degrees C were investigated in this study. The results showed that the splitting of gamma ' particles during exposure was related to the gamma '/gamma lattice mismatch caused by the partition changes in the elements. The increase in the concentrations of Ta, Hf, and W in the gamma ' particles and the decrease in the concentrations of W and Mo in the gamma matrix were the main reasons for the increase in the gamma '/gamma mismatch and the promotion of secondary gamma ' splitting. A hardness contribution model of the nanoindentation hardness was established, and the hardness changes in gamma ' and gamma during thermal exposure were obtained. In addition, the dominant roles of Ta, W, Hf, and Mo on the hardness of the gamma ' phase and the gamma matrix after long-term exposure were revealed.(c) 2023 Published by Elsevier B.V.