The role of Mo on the creep deformation of a 4th generation Ni-based single crystal superalloy at 1100 °C

Abstract

The effects of Mo content on the creep property of a 4th generation Ni-based single crystal superalloy were investigated systematically at high temperature and low stress. Under the condition of 1100 °C and 137 MPa, the performance of SC containing 2 wt% Mo and 3 wt% Mo was close, revealing that low Mo addition could meet the requirements of creep properties at 1100 °C and 137 MPa. However, the massive precipitation of TCP phases significantly degraded the creep performance when Mo content was more than 3 wt%. Mo addition also accelerated the broadening of the γ channel, decreasing the resistance of the dislocation slip. With regard to the positive impacts, Mo addition increased the magnitude of lattice misfit, leading to dense interfacial dislocation networks with high creep resistance. Mo also retarded the diffusion of alloying elements, thereby suppressing the formation of creep pores and the elemental inhomogeneity during creep. The comprehensive Mo-effect was summarized. Moreover, the optimum Mo content in the 4th generation single crystal superalloys was determined for the guidance of alloy design based on the creep results and comparison with other alloys.