Microstructure, mechanical properties, and corrosion resistance of SiC reinforced AlxCoCrFeNiTi1-x high-entropy alloy coatings prepared by laser cladding

By introducing ceramic SiC particles, AlxCoCrFeNiTi1-x/SiC (x = 0.5,0.8 in molar ratio) high entropy alloy coatings (abbreviated as Al0.5, Al0.8, Al0.5/SiC, and Al0.8/SiC alloy coating respectively) were fabricated by laser cladding (LC) on the AISI1045 steel in this work. The microstructures, phase constitutions, mechanical and corrosion-resisting behaviors of the as-prepared coatings with and without SiC particles were investigated and compared intensively. It was found that the added SiC particles decomposed into the Si and C during the LC processing, which was verified to have a significant influence on constructing microstructures of the alloy coatings. The cuboidal L21 precipitates within the disordered BCC matrix in Al0.5 alloy coating transformed to the coarse lath-like microstructures composed by the L21 and FCC matrix in Al0.5/SiC. Simultaneously, the more refined braided network structures were obtained in Al0.8/SiC alloy coating, corresponding to the increased volume fraction of the B2 phase. The microhardness of the Al0.8/SiC alloy coating improved from 637 HV0.2 in Al0.8 to 718 HV0.2, and the coefficient of friction decreased from 0.40 to 0.31 with the SiC addition. In contrast, the SiC particles showed a negative effect on the microhardness of Al0.5/SiC alloy coating from 743 HV0.2 to 679 HV0.2, as a result of coarsened microstructure and increased fraction of the supple FCC solid solution. The friction coefficient reaches its lowest value of 0.29 in Al0.5 alloy coating, and there is a mixture wear mechanism of wear and delamination wear. Furthermore, the pitting potentials of both the Al0.5/SiC and Al0.8/SiC were lower than that of the SiC-free alloy coating. With the dissolution of SiC particles, the prompted spinodal decomposition and enlargement of lattice misfits between phases reduced the coatings' resistance to pitting corrosion.