Stacking fault strengthening via Mo-Ru synergism in Mo-rich Ni-based single crystal superalloys for superior ultra-high-temperature creep properties

Stacking faults are critical planar defects in high temperature alloys, exhibiting pronounced strengthening effects via self interactions through the L-C lock mechanism and interactions with other dislocation structures. However, under ultra-high temperature and low stress conditions, the activation of stacking faults becomes difficult, thereby limiting their contribution to high temperature creep resistance. In this study, it is demonstrated that through optimized alloy composition, particularly by substantially increasing the Mo content to promote the formation of stacking faults and introducing Ru to enhance their thermal stability, the strengthening effect associated with stacking fault interactions can be effectively realized at 1200°C. At this temperature, a high volume fraction of the γ′ phase, the formation of dense dislocation networks induced by a designed negative lattice misfit, and the synergistic strengthening effect of K-W lock structure within the γ′ phase collectively suppress dislocation shearing from the γ matrix into the γ′ phase as well as their glide within the γ′ phase. This integrated mechanism effectively reduces the creep rate at 1200°C. • For the first time, a creep life of 324 hours at 1200 °C/80 MPa has been achieved in a nickel-based single crystal superalloy, representing a globally leading performance benchmark. • This work confirms that the thermally stable presence of stacking faults within the γ matrix at 1200 °C, along with the associated element segregation behavior, extends the known temperature boundary for stacking fault-related deformation mechanisms in superalloys.