Effect of heat treatment on phase stability and wear behavior of laser clad AlCoCrFeNiTi0.8 high-entropy alloy coatings

To explore the effect of phase stability on the properties of high entropy alloy, the AlCoCrFeNiTi0.8 coatings are prepared by laser cladding, and then the microstructure evolution and wear resistance of the coatings after heat treatment at various temperatures are studied comprehensively. The coating is composed of BCC-FeCr solid solution matrix, B2-AlNi precipitated phase and in-situ TiC particle phase. The microstructure is stable below 700 °C. The coarsening behavior of AlNi precipitates can be observed after heat treatment at 900 °C, and the precipitates present an Ostwald ripening phenomenon after heat treatment at 1200 °C. There is a close relationship between the wear resistance and the microstructure evolution of the coating, that is, the coarsening and ripening of the precipitates could lead to the decrease of wear resistance. The coating shows a significant decrease in wear resistance after heat treatment at 1200 °C. The volume wear rate of the as-deposited coating is 1.36 × 10−6 mm3·N−1·m−1, while that of the coatings after heat treatment at 700 °C, 900 °C, and 1200 °C is 1.64 × 10−6 mm3·N−1·m−1, 1.96 × 10−6 mm3·N−1·m−1, and 6.96 × 10−6 mm3·N−1·m−1, respectively.