LAUSR

Abstract High-entropy superalloys (HESAs) can replace commercial Ni-based superalloys. For high-temperature applications, the oxidation resistance of HESAs must be considered. Herein, the oxidation mechanism of HESA with sufficient minor Nb addition was conducted at 900 °C under atmosphere. With 0.9 at% Nb added in the base metal, oxidation resistance was significantly improved, which was confirmed by a furnace test and thermogravimetry. The isothermal oxidation resistance was enhanced by approximately 66%, owing to the presence of the Nb-rich layer. This improvement was observed and analyzed by backscattering electron images through scanning electron microscopy and wavelength dispersive spectroscopy with a field-emission electron probe microanalyzer. The mechanism of oxide formation was elucidated by X-ray diffraction for various exposure time durations. With Nb minor addition, the microstructures of the present alloy were found to be composed of γ matrix and γ′ precipitates and the mechanical properties were slightly higher than those without Nb.