Effect of minor chemistry variations on the structural and mechanical behaviour of a PM nickel base superalloy

Abstract

Addition of 0.7% Hf to a heavily alloyed low carbon Ni base PM superalloy has been found to significantly reduce the alloy solidus in contrast to another chemisty variant free of Hf but with increased alloying. The Hf-bearing alloy showed major microstructural changes with increase in HIPing temperature. Reduction in C to < 0.02% severely affected its elevated temperature strength. The Hf-free alloy containing 0.03% C offered a good combination of tensile and stress rupture properties after a suitable heat treatment.