The role of Re in improving the oxidation-resistance of a Re modified PtAl coating on Mo-rich single crystal superalloy

Abstract A novel Re modified β-(Ni,Pt)Al coating was prepared on a Mo-rich Ni3Al-based single crystal (SC) superalloy by electro-deposition of Re/Pt dual films and low-activity aluminizing. The isothermal oxidation behavior of the Re modified β-(Ni,Pt)Al coating and traditional β-(Ni,Pt)Al coating was comparatively studied at 1100 °C. Apparent spallation of oxide scale was found on the surface of traditional β-(Ni,Pt)Al coating after 300 h isothermal exposure, which mainly resulted from the evaporation of Mo-containing oxides. It is further found that the outward diffusion of Mo from the SC substrate was effectively inhibited in the Re modified β-(Ni,Pt)Al coating by forming the σ-MoRe phase both at the coating/superalloy interface and grain boundaries. It is also revealed that the addition of Re can stabilise Mo to form the σ-MoRe phase, allowing the improved oxidation resistance of the Re modified β-(Ni,Pt)Al coating.