MoFeCrTiWAlNb refractory high-entropy alloy coating fabricated by rectangular-spot laser cladding

In order to improve the wear resistance of M2 tool steel, a MoFeCrTiWAlNb high-entropy alloy (HEA) coating has been successfully fabricated by the rectangular-spot laser-cladding technique. The phase structures, microstructure, hardness, and wear resistance of HEA coatings were carefully investigated. The final laser-cladding process parameters are P = 3.0 kW, v = 4 mm/s, and a rectangular spot of 10 × 2 mm. The phase composition of the coating consists of body-centered-cubic solid solution and (Nb,Ti)C carbides plus small amounts of hexagonal-close-packed Fe2Nb phases. The coating metallurgically bonds to the substrate. Al2O3 formed by oxidization of Al atoms was a heterogenous nuclear center for (Nb,Ti)C. The highest average microhardness value of HEA coatings reached 1050 HV0.2, which is far higher than that of the substrate (approximately 330 HV0.2). Furthermore, compared with the substrate, the HEA coating exhibits prominent wear resistance with lower friction coefficient, fewer wear volumes, and smoother worn surface under the same conditions.