Microstructure and Mechanical Properties of Multi-Phase Reinforced MoFeCrTiWNb2.5(Al2O3)x High-Entropy Alloy Laser Cladding Coatings

In this study, high-entropy alloy coatings, based on MoFeCrTiWNb2.5(Al2O3)x (x = 0.4, 0.45, 0.5, 0.55, 0.6), were successfully fabricated on the surface of an M2 high-speed steel by laser cladding. The addition of Al2O3 promoted the formation of a eutectic microstructure. When x < 0.5, the coatings had a hypoeutectic structure with a proeutectic BCC phase. When x > 0.5, the coatings formed hypereutectic alloys with a proeutectic Laves phase. When x = 0.5, the coating had a typical eutectic lamellar microstructure with a hardness of 775 HV0.2. The microstructure and property evolution of MoFeCrTiWNb2.5(Al2O3)0.5 coatings treated for 6 h at different annealing temperatures of 750-1050 °C were investigated. The phase structure remained unchanged after annealing. The MoFeCrTiWNb2.5(Al2O3)0.5 coating is a typical lamellar eutectic microstructure, exhibiting excellent microstructural stability at 750 °C. When the annealing temperature exceeded 850 °C, the hardness and wear resistance of the coating decreased. The hardness of the coating remained 582 HV0.2 after annealing at 1050 °C for 6 h, indicating that the coating had excellent high-temperature softening resistance.