Effect of hot isostatic pressing quenching and post-hot isostatic pressing heat treatments on the microstructure and properties of a high-temperature Ni-based superalloy

Astroloy is a nickel-based alloy with a high-volume fraction of γ ′ phase, which is widely used in high-temperature applications due to its excellent strength, corrosion, and oxidation resistance. However, traditional manufacturing methods are not suitable for this alloy, and powder Near Net Shape Hot Isostatic Pressing (NNS-HIP) has emerged as the optimal manufacturing process. Despite this, uncertainties remain regarding the effect of process parameters on microstructural evolution and properties. Previous studies established correlations between microstructural features like γ / γ ′, carbides type, and volume fraction and prior particle boundaries and mechanical properties for conventionally HIPed and heat-treated (HTed) samples. This study compares those findings with quenched HIPed and HTed samples. Thermo-Calc calculations, related to the stability and composition of phases, were also correlated with experimental results. The HIP-quenched microstructures exhibited higher material strength compared to conventionally HIPed and HTed samples. Besides, an increase in the HIP temperature by 30°C significantly influenced the elimination of primary γ ′ at the grain boundaries and the dissolution of carbides.