Hot deformation behavior and microstructure evolution of a nickel-based powder metallurgy superalloy

Abstract

The hot deformation behavior and microstructure evolution of a HIP-treated FGH96 nickel-based powder metallurgy superalloy were investigated through isothermal compression tests under varying conditions of temperature and strain rate. Deformation temperatures ranged from 950°C to 1200°C, and strain rates from 0.1 s⁻¹ to 10 s⁻¹. Microstructural observations were conducted using optical microscopy (OM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD). The results indicated that dynamic recrystallization (DRX) was the main softening mechanism, with DRX grain size and volume fraction significantly influenced by both strain rate and temperature. At lower strain rates and higher temperatures, complete DRX occurred, with grain sizes increasing from 2.5 ± 0.3 µm at 1100°C to 8.2 ± 0.6 µm at 1150°C. The study highlights the critical role of γ’ phase evolution and its interaction with DRX during hot deformation, providing insights into optimizing the processing conditions for nickel-based superalloys in high-temperature applications.