Influence of Mo and Ru additions on the creep behavior of Ni-based single crystal superalloys at 1100 °C

In order to obtain more knowledge to replace or lower the content of expensive and heavy elements Re and Ru in advanced Ni-based single crystal superalloys, the role of Ru playing in the microstructure and creep performance at 1100 °C and 140 MPa was evaluated in this study by considering its individual effect and also synergizing it with Mo to maximize the beneficial effect from each element. A series of single crystal superalloys with varying alloying elements were investigated and their initial microstructure and microstructural evolution during the creep deformation were characterized. It was shown that both Mo and Ru could increase the γ/γ' lattice misfit and density of interfacial dislocations, that contributed to improve the creep resistance at high temperature and low stress condition. The inferior microstructural stability regarding to the TCP phase formation in alloys with more Mo addition lowered creep performance to some extent, however, that could be restrained by the addition of Ru. The high temperature and low stress creep performance could be enhanced by the co-addition of Mo and Ru since their synergistic effect could be able to enhance the γ/γ' interfacial strengthening and retain the microstructural stability.