Effect of alloy elements on the precipitation behavior of thermodynamic equilibrium phases in new type nickel-based P/M superalloys

The effects of alloy elements on the precipitation behaviors of equilibrium phases in new type nickel-based powder metallurgy (P/M) superalloys at aging temperature were studied systematically by a thermodynamic calculation method. The calculation results show that the equilibrium precipitation phases of René 104 are γ', MC, M₂₃C₆, M₃B₂ and TCP phases. Cr and Co contents mainly influence the precipitation behaviors of TCP phases and the precipitation temperature of γ' phase. Cr content also plays a role in the precipitation behaviors of M₂₃C₆ and M₃B₂. The suggested content of Cr is 13%. Mo and W contents influence the precipitation behaviors of TCP phases and M₃B₂. The mass ratios of Al/Ti and Nb/Ta affect the precipitation behaviors of γ' phase. It suggests controlling the values of Al/Ti and Nb/Ta to be unity in order to make γ' phase having desire strengthen effect. C and B contents significantly influence the precipitation volumes of carbides and borides; they can restrain the precipitation of TCP phases indirectly. Zr content influences the precipitation behaviors of MC and M₂₃C₆. Besides, it is revealed that the composition optimization and design trend of the 3rd generation P/M turbine disc superalloys is with more Co, less Cr and to obtain a smaller lattice mismatch by adjusting the contents of alloy elements.