Microstructure and creep properties of Ni-based single-crystal superalloys with Mo/Al addition at 760 °C/850 MPa

The effect of Mo and Al addition on the microstructure as well as creep rupture properties at 760 °C/850 MPa was investigated by transmission electron microscopy (TEM) in a Ni-based single-crystal (SC) alloy with the composition of Ni–6.5Al–8.0Mo–2.4Cr–6.2Ta–4.9Co–1.5Re–(0.01–0.05)Y (wt%). The microstructure analysis shows that 0.5 wt% Al addition induces rapid decrease in creep rupture life, and this can be attributed to the formation of dense stacking faults cutting into γ′ precipitates, which can be explained by the increase in Orowan stress caused by the narrower γ channel width and the decrease in stacking faults energy. Besides, 1.5 wt% Mo addition increases the anti-phase boundary energy and decreases the stacking faults energy, resulting in fewer stacking faults and thus a slight decrease in the creep rupture life.