900 °C oxidation resistance of Ni-base superalloys alloyed with different refractory elements

• 900 °C isothermal oxidation behavior of the Ni-base polycrystalline superalloys at were studied. • Al2O3 layer and Ta-W-Hf rich oxide layer are beneficial to antioxidation. • Adding proper contents of Ta, W, and Mo enhanced oxidation resistance. • 4 wt% Nb or 2 wt% Hf deteriorated the oxidation resistance. Refractory elements are added to strengthen the Ni-based superalloys for turbine disks, while the effects of these elements on the oxidation resistance remain to be investigated systematically to continually improve the working temperature. In this work, the effects of typical strengthening elements, including Ta, W, Mo, Hf and Nb, on the isothermal oxidation behavior of Ni-based superalloys at 900 °C were studied. The results indicated that increasing concentrations of Ta, W, and Mo enhanced the oxidation resistance, while adding 4 wt% Nb and 2 wt% Hf accelerated the oxidation rates in different degrees, which was explained in terms of diffusion and phase precipitation.