High-temperature oxidation of TiNbTaVW RHEA: Oxide layer formation under parabolic behaviour

The potential of refractory high entropy alloys (RHEAs) as high-temperature structural materials depends on optimising their oxidation resistance. This study examines the surface and cross-sectional oxide layers of TiNbTaVW RHEA after five hours of oxidation, comparing them to previously studied layers formed after 15 h. At 850°C, the surface and cross-sectional oxide layers remained crack-free after 5 h, in contrast to the cracked layers observed after 15 h. A crack-free oxide layer effectively slows oxidation by limiting oxygen diffusion. However, at 1050°C, cracks were present in the surface and cross-sectional oxide layers after 5 h, similar to those observed after 15 h. Understanding short-term oxidation mechanisms provides valuable insights for developing strategies to enhance the high-temperature oxidation resistance of RHEAs. • No cracks were observed on the surface layer of TiNbTaVW at 850 °C after 5 h. • Cross-sectional layer of TiNbTaVW at 850 °C is 139 μm and free of cracks. • Cross-sectional layer of TiNbTaVW at 1050 °C is 227 μm and contains cracks. • Surface oxide structure at 850 °C and 1050 °C comprises rod-shaped oxides.