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Refractory high entropy alloys (RHEAs), which comprise high-melting-point refractory elements, have been regarded as potential candidates that can substitute nickel-based superalloys used in high-temperature applications. This study investigated the microstructure, hardness, corrosion, and oxidation behavior of the TiNbTaVW RHEA compared with commercial-grade IN718 alloy. The equiatomic TiNbTaVW RHEA was produced using an arc melting furnace. The microstructure of the as-cast RHEA consisted of a body-centered cubic solid-solution phase with a dendritic structure corresponding to the empirical phase prediction. The RHEA exhibited a higher hardness of 522±10 HV than the IN718 alloy with 301±14 HV. The higher hardness is due to solid-solution strengthening and grain refinement. The RHEA had a lower corrosion rate in 3.5 wt% NaCl (0.0003 mm/yr) and 1 M H2SO4 (0.0009 mm/yr) than the commercial IN718 alloy (0.054 mm/yr and 1.12 mm/yr, respectively). At 850°C after 15 hours and 1050°C after 15 hours, the IN718 alloy exhibited a mass gain of 4.41 mg/cm2 and 10.84 mg/cm2, respectively, while the TiNbTaVW RHEA exhibited a mass loss of −23.58 mg/cm2 and −45.92 mg/cm2, respectively, indicating that the IN718 alloy exhibited the best oxidation resistance. Thermal and growth stresses contributed to the pores, voids, cracks, and oxide layer spallation observed in the TiNbTaVW RHEA.
Bamisaye et al. (Sat,) studied this question.