Simultaneous enhancement of hardness and fracture resistance in aged AlCoCrFeNi high-entropy alloy coatings via mixed-powder laser cladding

A complete columnar-to-equiaxed transition was achieved in an AlCoCrFeNi high-entropy alloy (HEA) coating by employing mechanically blended elemental powders during laser cladding. To assess the influence of microstructure on aging behavior, coatings produced from mixed powder (MP-HEA) and gas-atomized pre-alloyed powder (GP-HEA) were subsequently investigated after aging at 550 °C. While both conditions exhibited a BCC + B2 dual-phase structure with spinodal decomposition features, the MP-HEA showed a fully equiaxed and significantly refined grain structure. The refined microstructure was accompanied by a much finer spinodal modulation (∼7.5 nm vs. ∼30 nm), resulting in superior mechanical performance. The MP-HEA reached a hardness of 747 HV, 18.6% higher than the GP-HEA, and exhibited increased compressive yield strength (1013 MPa) together with improved fracture resistance. The results demonstrate that powder feedstock design provides an effective strategy to tailor microstructure and achieve simultaneous enhancement of hardness and fracture resistance in HEA coatings. • Fully equiaxed grains achieved via powder feedstock design in laser cladding. • Mixed elemental powders enabled a complete columnar-to-equiaxed transition. • Grain refinement and fine spinodal structure enhanced hardness and fracture resistance.