Wear-resistant single-phase high-entropy alloy coatings prepared on Ti6Al4V with laser cladding

Abstract

Excellent wear-resistant high-entropy alloy (HEA) coatings were successfully synthesized on Ti6Al4V with laser cladding using FeCrCoNiAlMox (x = 0.5, 1.0, 1.5) as the cladding materials. Investigations into the effect of Mo on the microstructures and mechanical properties (microhardness and wear resistance) of the coatings were carried out. The results showed that all the coatings exhibited good metallurgical bonding with the substrate where no clear defects were found. The dilution rate of the coatings increased with an increase in the content of Mo (60.39 % for x = 0.5, 64.09 % for x = 1.0, 72.68 % for x = 1.5). The coating for x = 1.0 was mainly composed of a single solid solution (BCC). Besides the solid solution, traces of TiC dendrites were also synthesized in the other two coatings (x = 0.5 and x = 1.5). The solid solution exhibited two different morphologies, corresponding to fine rod-like particles and coarse equiaxial grains. Due to the solution-and dispersion-strengthening effects, the hardness of the coatings (759.4 HV0.2 for x = 0.5, 857.2 HV0.2 for x = 1.0, 844.3 HV0.2 for x = 1.5) was significantly superior to that of the substrate (330 HV0.2). The friction coefficient of the coatings (0.80 for x = 0.5, 0.61 for x = 1.0 and 0.78 for x = 1.5) was obviously reduced when compared with that of the substrate (1.04). The wear volumes of the coatings were decreased by 51 %, 65 % and 48 % (1.145 ± 0.021 mm3 for x = 0.5, 0.823 ± 0.012 mm3 for x = 1.0, 1.219 ± 0.018 mm3 for x = 1.5) when compared with that of the substrate (2.329 ± 0.025 mm3). It can be confirmed that the coating with x = 1.0 exhibited the optimum wear resistance.