Estimation of the effect of hafnium on equilibrium phases in FGH97 PM superalloy

The stable phases and composition of FGH97 powder metallurgy(P/M) superalloy with different contents of hafnium were calculated by JMatPro software.The effects of hafnium content on the equilibrium phases and composition were studied.Meanwhile,the stable phases were analyzed and checked by physical and chemical phase analyses and microstructure observations.Then,the behaviors of phase precipitation and the character of hafnium partition in different phases were revealed and the effects of hafnium on FGH97 P/M superalloy were summarized.It is shown that the stable phases at 750℃ include γ matrix,γ' phase,MC carbide,M₂₃C₆ carbide,M₃B₂ boride,and μ phase.Hafnium mainly exists in γ' phase and MC carbide,and increasing the hafnium content causes the different distribution of hafnium between γ' phase and MC carbide.