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Microstructure and properties of FeCoNiCrAl high-entropy alloy coating by directed laser deposition

In order to improve the hardness and wear resistance of TC4 alloy under extreme service conditions in aerospace, FeCoNiCrAl high-entropy alloy(HEA) coatings are prepared on the surface of TC4 alloy using direct laser deposition technology. The result shows that the direct laser deposited FeCoNiCrAl HEA coating formed a good metallurgical bond with the TC4 alloy substrate, and the FeCoNiCrAl HEA is deposited in a single-phase body-centred cubic daisy-like equiaxed grains structure with an average grain size of 8.49 μm, and the grains were randomly distributed in (001), (101) and (111) and without obvious preferential growth direction. Elemental segregation was observed in the coating, with Al, Co and Ni elements segregating into the daisy-like equiaxed grains and Fe and Cr elements segregating between the dendrites, while Co, Cr and Ni elements are find to diffuse into the transition region(TR). The average microhardness of the direct laser-deposited FeCoNiCrAl HEA coating is 611.8 HV0.5, which is 1.6 times of that in TC4 alloy (374.9 HV0.5), and the average microhardness of the TR is 699.1 HV0.5 due to the significantly finer dendritic structure and the solid solution strengthening effect of Co, Cr and Ni elements, which is approximately 1.8 times that of the TC4 alloy substrate