NiAlHf/Ru: Promising bond coat materials in thermal barrier coatings for advanced single crystal superalloys

• A novel Ru/NiAlHf coating was produced on Ni-based single crystal superalloy.
• The Ru/NiAlHf coating effectively constrained secondary reaction zone in the alloy.
• The Ru/NiAlHf coating revealed excellent cyclic oxidation resistance at 1100 °C.
• The roles of Ru/Hf in affecting the oxidation and interdiffusion were investigated.

NiAl and NiAlHf/Ru coatings were produced onto nickel-based single crystal superalloy to investigate the interdiffusion behaviour and cyclic oxidation resistance at 1100 °C. A ∼30 μm thick layer, mainly consisting of needle-like topologically close-packed phases (TCP) and secondary reaction zone (SRZ), was formed in the NiAl coated superalloy after annealing at 1100 °C for 100 h, whereas the precipitates of TCP and SRZ were effectively constrained in the NiAlHf/Ru coated alloy. The NiAlHf/Ru coating exhibited superior cyclic oxidation resistance as compared to the NiAl coating. The roles of Ru and Hf in affecting interdiffusion and cyclic oxidation were discussed.