Dependence of molybdenum content on the cavitation corrosion synergy and wear failure of laser cladded CoCrFeNiMnMo high entropy alloy coatings.

• Novel CoCrFeNiMnMo x HEA coatings were prepared by laser cladding. • Strengthening mechanisms of Mo solid solution in HEA coating were investigated. • Mo 1.0 coating with fine grains presented the excellent wear resistance. • Mo 0.5 retarded Mo and Cr enriching at grain boundaries, avoiding coupling corrosion. • Passive film formed at Mo 0.5 coating surface, proving corrosion-cavitation synergism. The CoCrFeNiMnMo high entropy alloy (HEA) coatings with various Mo contents (0.1, 0.5, 0.8, 1.0 in atomic ratio) were prepared by laser cladding, aiming at determining the optimum Mo content and the effect of Mo on the microstructure and properties of CoCrFeNiMnMo x HEA. The synergistic cavitation failure-corrosion impact of the coatings was also studied in 3.5 wt% NaCl solution. Experimental results showed that HEA coatings were only composed of FCC matrix and the grains were refined gradually with the increase of Mo contents. Meanwhile, the corrosion resistance of the coatings increased first and then decreased. The CoCrFeNiMnMo 05 possessed the highest corrosion resistance as indicated by the highest polarization resistance, strongest passivation tendency and lowest carrier concentration. The wear resistance of the coatings was significantly higher than that of the substract. The enhanced wear resistance was contributed to the grain refinement and solid solution strengthening. After 8h cavitation failure, the CoCrFeNiMnMo 05 showed the lowest mean depth failure of 0.05 μm as it maintains the highest self-healing ability and integrity of passive film during the synergistic effect of cavitation failure and corrosion. In this study, the optimum Mo content was determined and the effect of Mo on the microstructure and properties of CoCrFeNiMnMo x HEA was described. [ABSTRACT FROM AUTHOR]