Effect of Hot Isostatic Pressing on Microstructure and Mechanical Property of DZ417G Superalloy

Effect of HIP (hot isostatic pressing) with relatively fast cooling rate (≈100 °C/min) on the microstructure restoration for the service DZ417G blade, as well as on the tensile and stress rupture properties for the DZ417G alloy in SHT (standardization heat treatment, 1220 °C/4h/Air cooling (AC) + 980 °C/16h/AC) was studied in detail. The results show that HIP with relatively fast cooling rate can heal the injured microstructure in Service blade, which mainly includes that the coarsening phases evolve into finely cubic γ′ in dendritic core zone, the slim stripe γ′ in the easy rafting zone (ERZ) and creep pores adjacent to the eutectic phase disappear completely, C₂₃C₆ particles formed by the decomposition of the (Ti, Mo, V) C is eradicated. In addition, HIP triggers microstructure optimization and surface recrystallization simultaneously in this study. Surface recrystallization is formed because the accumulated strain by sample machining and HIP reaches the recrystallization critical strain at high HIP temperature. Compared to the SHT alloy, the surface recrystallization layer with 50μm in SHT-HIP-Age tensile sample causes the slight reduction in elongation and fracture surface shrinkage, while the tensile strength and stress rupture life are improved due to microstructure optimization.