Microstructure evolution and properties of laser cladding AlFeCrMoNbx refractory high entropy alloy coatings

Refractory high-entropy alloy (RHEA) has superior mechanical properties but low room-temperature ductility. However, eutectic heterostructure alloy has strength-ductility trade-off. In this study, the AlFeCrMoNbx (x = 1, 1.2, 1.4, 1.6, 1.8, and 2.0) RHEA coatings were successfully prepared on the surface of an M2 high-speed steel (HSS) by laser cladding. The increase of Nb content promoted the formation of eutectic microstructure, the coating changed from hypoeutectic structure to hypereutectic structure. When x = 1.8, the coating exhibited a near-eutectic structure consisting of BCC and Laves phases with high hardness and wear resistance. After annealed at 750 degrees C for 8 h, the phases and microstructure of Nb1.8 REHEA coating did not change, contributing to a high microhardness and wear resistance. With annealing temperature rising, the microhardness and wear resistance decreased. After annealing at 1050 degrees C, the hardness of the coating still remained 549 HV0.2, indicating a good high-temperature softening resistance of REHEA coating.