Strengthening Enhanced by Ru Partitioned to Γ' Phases in Advanced Nickel-based Single Crystal Superalloys

Two Nickel-based single crystal superalloys (one Ru-free and one containing 3 wt.% Ru) were comparatively investigated by the three-dimensional atom probe tomography and the nanoindentation atomic force microscope to reveal the effect of Ru addition on the microstructure and the mechanical properties of gamma' phases after standard heat treatment. The results showed that the Ru addition neither altered the morphology and the volume fraction of gamma' phases, nor changed the interface structure and the partition coefficients of alloying elements between gamma and gamma' phases, however, it enhanced the hardness and elastic modulus of gamma' phases. First-principles calculation indicated that no matter whether the Ni site or Al site was occupied by Ru, the elastic modulus of gamma' phases increased, which might be ascribed to the solution strengthening effect of Ru on gamma' phases.