Microstructure, Hardness and Wear Behavior of Al_xCoCrFe₂Ni (x = 0.3, 0.7, 1.0) High Entropy Alloy Coatings Prepared by Laser Cladding

To develop inexpensive high-strength high entropy alloy (HEA) coatings, microstructure, hardness and wear behavior of Al_xCoCrFe₂Ni (with x = 0.3, 0.7, 1.0) high-entropy alloy coatings prepared by laser cladding were investigated in this work. It was found that the phase composition and microstructure of coatings with high Fe content could be tailored by adjusting Al content. Addition of Al could cause the phase to evolve from FCC to a mixture of FCC, ordered BCC (B2) and disordered BCC (A2) and finally to a mixture of A2 and B2. The hardness increased with the change of phase composition, resulting in a higher hardness (621HV) and better wear resistance at x = 1.0. The microstructure of AlCoCrFe₂Ni coating consisted of spherical nano-scale B2 particles and A2 matrix. The strengthening effects of A2/B2 morphology were estimated and strengthening of order was the most important strengthening factor. In addition, the main wear mechanism was abrasive wear with decreasing fraction of oxidation wear as Al content increased.