Effect of Nb on δ phase precipitation and the tensile properties in cast alloy IN625

Abstract

Cast alloy IN625 is a candidate Ni-base alloy for advanced ultra-supercritical (A-USC) power plants. The aim of this study was to investigate the influences of Nb on δ phase precipitation and the tensile properties in this alloy. The results show that the δ phase is easy to precipitate after long-term aging at 700°C (the service temperature of A-USC power plants) and it is strongly affected by the content of Nb in the alloy. The strength of alloys after aging at 700°C for 10,000 h increases with the increasing Nb content and also increases sharply when compared to that of as-heat-treated alloys. The increase in strength is found to be primarily associated with the precipitation of the δ phase.