Possibility and stabilizing effect of Mo clusters in the Ni-based single-crystal superalloy

Nickel-based single-crystal superalloys are crucial materials for the preparation of aero-engine turbine blades. Many solute elements are added to superalloys for strengthening. However, the relationship between the clustering behavior of solute atoms and the properties of nickel-based single-crystal superalloys is still unclear. Herein, we conduct first-principles calculations onγ phases with Mo-Mo and Mo-Mo-Ru clusters to reveal the possibility and stabilizing mechanism of solute clusters. Introducing Mo lowers the total energy, binding energy, and formation energy of the γ phase due to the replacement of weak Ni-Ni interaction with strong Mo-Ni bonding. Note that the γ phase containing the Mo-Mo cluster is more stable than that containing a Mo single atom, possibly owing to a wide affecting range. The Ru atom added to the γ phase can further boost system stability, and it tends to form a Mo-Mo-Ru cluster. The stabilizing impact of the Mo-Mo-Ru cluster is demonstrated to be the replacement of weak Ni-Mo interaction by the strong Ru-Mo interaction, which may be derived from the enhanced d-orbital hybridization.