High-temperature oxidation behavior of Y-doped CoAl_1.5NiCrFe high-entropy powder at 1000–1100 °C

To develop a novel high-temperature servicing material, CoAl_1.5NiCrFe high-entropy powder with Y-doping is prepared by gas atomization, and its high-temperature oxidation behavior at 1000 °C, 1050 °C, and 1100 °C is investigated. In this study, the establishment of thermally grown oxide (TGO), oxidation kinetics, phase components, and TGO stress evolution of this powder were investigated to evaluate its high-temperature oxidation resistance. Results indicate that the CoAlNiCrFeY high-entropy powder exhibits a dual-BCC structure with Y segregating at its grain boundaries. During the initial oxidation, a low temperature and Y³⁺ synergistically suppress the phase transition from θ-Al₂O₃ to α-Al₂O₃, triggering a high θ-Al₂O₃ fraction in TGO. After long-term oxidation, its TGO at all three temperatures mainly consists of α-Al₂O₃, without spinel. Furthermore, the TGO exhibits a low growth rate (only 3.02 ± 0.32 μm/200 h at 1100 °C) primarily because of the Y-doping and the sluggish diffusion of the high-entropy composition. TGO stress tests show that the sample at 1000 °C exhibits tensile stress, whereas those at 1050 °C and 1100 °C demonstrate compressive stress. Meanwhile, TGO at three temperatures display excellent spallation resistance. These results indicate that the CoAlNiCrFeY high-entropy powder has great application potential for high-temperature protection.