Effects of Re on microstructure evolution of nickel-based single crystal superalloys

Abstract

The high temperature creep and long-term aging tests of the second-generation (DD6) and the third-generation (DD9) single crystal superalloys with different Re contents were carried out. The effects of Re, dislocations, TCP phases and their interaction on creep properties and microstructure evolution were researched. The third-generation single crystal superalloy has the more compact and uniform two-phase structure and the better creep properties. The rafting rate in dendrite is higher than that in interdendrite. The γ' phases connect into a stripline, the γ phases on the strip line are truncated, and the TCP phase is precipitated along the stripline. The element Re carries out the pipe diffusion and the vacancy diffusion at the high temperature. The TCP phase precipitates in the region with many dislocations and vacancies. Re hinders the movement of dislocations and promote the precipitation of TCP phases. The movement of dislocations promotes the diffusion of Re and the precipitation of TCP phases. TCP phases promote the diffusion of elements and accelerate the rafting of γ' phases.