Enhanced Cavitation Resistance of HVOF-Sprayed NiCr/10WC Coatings in Deionized Water and 3.5 mass% NaCl Solution

NiCr and NiCr/10WC coatings were fabricated by high-velocity oxy-fuel (HVOF) spraying to investigate the effect of WC incorporation on cavitation and cavitation–corrosion behavior in deionized water and 3.5 mass% NaCl solution. The NiCr/10WC coating exhibited a significantly lower cavitation erosion rate than the NiCr coating in both media. The improvement was attributed to a pronounced reduction in porosity (from 5.7% to 0.5%) and a 46% increase in the microhardness of the Ni(Cr) solid-solution. Microstructural observations revealed that semi-molten WC particles exerted a peening effect during spraying, suppressing the formation of pores and oxide films and enhancing coating densification and strain hardening. In deionized water, the NiCr/10WC coating primarily failed by localized WC spallation, while the Ni(Cr) solid-solution remained largely intact. In 3.5 mass% NaCl solution, electrochemical analysis showed that NiCr/10WC coating exhibited a more noble corrosion potential (−0.352 V) and a lower corrosion current density (1.68 × 10−6 A cm−2) than NiCr, confirming its superior corrosion resistance. The improved cavitation–corrosion resistance originated from a synergistic effect between the enhanced impact resistance and the chemical stability of WC and the Ni(Cr) solid-solution. The incorporation of WC thus transforms the failure mode from defect-driven large-area degradation to localized, WC-controlled damage, establishing a beneficial coupling between mechanical robustness and corrosion resistance.