Study on Microstructure and Wear and Corrosion Resistance of CoCrMnNiMox High Entropy Alloy Coatings

In order to increase the wear and corrosion resistance of the surface of the steel structures, four kinds of CoCrMnNiMox (x=0.1, 0.2, 0.3, 0.4) high entropy alloy (HEA) coatings with different compositions were prepared on N80 steel substrate by laser cladding. The effect of Mo content on microstructure, wear resistance and corrosion resistance of HEA coating was studied. Results showed that the CoCrMnNiMox coating structure was a single FCC phase. With the increase of Mo content, the coating hardness increased. The average Vickers hardness of the CoCrMnNiMo0.4 HEA coating was up to 628 HV, which was 3.8 times higher than that of N80 steel substrate (165 HV). The friction coefficient decreased first and then increased, reaching the lowest (0.38) at Mo content of 0.3, which reduced by 0.40 compared to that of N80 substrate. The wear mechanism of clad layer changed from adhesive wear to abrasive wear and the wear resistance increased. The dynamic corrosion and static corrosion of clad layer reached the optimum at Mo content of 0.3. Compared with the substrate, the dynamic corrosion potential increased by 0.2 V at Mo content of 0.3, and the corrosion current density decreased by one order of magnitude. However, the corrosion resistance of the clad layer was greatly reduced compared with the static corrosion due to the promoting effect of wear on corrosion. The corrosion wear coupling test results showed that with the increase of Mo content, the potential first gradually increased and then decreased. The potential reached the highest (-0.28 V) at Mo content of 0.3. The corrosion resistance under friction condition was the best, which was 0.22 V higher than that of N80 substrate (-0.50 V). The wear and corrosion resistance of the substrate surface were well improved. The friction coefficient of the sample under corrosion increased first and then decreased. Except for the high friction coefficient at Mo content of 0.2, the friction coefficient of the other samples was low in the stable run-in stage, and the wear resistance under corrosion condition was relatively good.