Effect of Cr content on synergistic effect of Cr-Al during oxidation of high-entropy AlCoCrxNiTi alloys

AlCoCrxNiTi high-entropy alloy coatings, mainly composed of the BCC and B2 phases, were synthesized on Ti-6Al-4V substrates by laser cladding. The incorporation of Cr-refined grains enhanced the hardness of the alloy. Oxidation kinetic curves of the alloys at 800 °C in the air followed the parabolic law, and AlCoCr0.5NiTi alloy exhibited excellent oxidation resistance. The incorporation of an appropriate amount of Cr provided a structural template for the formation of Al2O3 and increased the diffusion rate of Al in the stable oxidation stage, leading to a reduction in the concentration required to form a continuous Al2O3 oxide film.