Relationship Between Powder Size, Prior Particle Boundaries and Properties of FGH4096M Nickel-Based Superalloy

Failure of nickel-based powder metallurgy (PM) components usually originates from prior particle boundaries (PPBs), which act as cracking initiators and provide accessible channels for cracking propagation. In this study, the effect of the PPBs number and size on the microstructure and mechanical properties of the nickel-based superalloy FGH4096M was investigated. Fine (HIP-F) and coarse (HIP-C) FGH4096M powder with average particle sizes of 38.1 μm and 114.1 μm, respectively were selected to conduct HIP (hot isostatic pressing) experiments. The results revealed that the tensile strength and ductility of HIP-F are 14.1% and 88.7%, respectively, higher than those of HIP-C. This is supposed to be because refined particles make the crack expansion paths more tortuous, and result in more work hardening of HIP-F, since the cracking deflections in HIP-F are ~ 3 times those in HIP-C. Furthermore, the primary reason is that the denser PPBs of HIP-F caused higher volume fractions of carbides (~ 1.9%) in the PPBs than those of HIP-C (~ 0.8%), which leads to an average grain size of HIP-C being about 2 times that of HIP-F. Therefore, refining the size of PPBs may be a strategy to reduce their impact on the mechanical properties of PM superalloys.