Microstructural evolution and properties of dual-layer CoCrFeMnTi0.2 high-entropy alloy coating fabricated by laser cladding

Abstract The dual-layer CoCrFeMnTi0.2 HEA coating was prepared on 15CrMn steel by laser cladding technology, to investigate the precipitation behavior and the surface properties. The microstructure of the coating is mainly composed of equiaxed crystals of FCC solid solution and intergranular precipitates of Laves phase in the first layer and evolves to the FCC solid solution/Laves lamellar eutectic structure surrounded by martensite and residual FCC solid solution phase in the second layer. The microstructural evolution and the phase transformation are believed to be associated with the dilution effect in the dual-layer deposition and the quenching effect of the multi-track overlapping process. The microhardness of the coating is (428.26 HV0.3) about 3.5 times higher than that of CoCrFeMnNi HEA. It is found that the coating is strengthened by the effect of solid solution strengthening, precipitation strengthening, and martensitic transformation. The values of wear rate show that the wear resistance of the coating is better than that of CoCrFeMnNi HEA. The wear mechanism of the coating is abrasive wear and slight oxidation wear. The coating with the corrosion rate of 0.131 μm/year, exhibits poorer corrosion resistance than CoCrFeMnNi HEA, on account of the formation of corrosion microcells. However, the coating possesses a wider passivation region due to refined grains and high content of passivation elements.