Ultrasonic cavitation erosion of high-velocity oxygen-fuel (HVOF) sprayed near-nanostructured WC–10Co–4Cr coating in NaCl solution

• A near-nanostructured WC–10Co–4Cr coating was prepared by HVOF spraying process.
• Cavitation erosion characteristics of the coating were studied in NaCl solution.
• Continuous cavitation erosion damage in the microstructure was revealed.
• The coating possessed higher cavitation erosion resistance than steel 1Cr18Ni9Ti.

The high-velocity oxygen-fuel (HVOF) spraying process was used to prepare near-nanostructured WC–10Co–4Cr coating. The cavitation erosion behavior and mechanism of the coating in 3.5 wt.% NaCl solution were analyzed in detail. The results showed that the amorphous phase and WC grain were present in the coating. The cavitation erosion resistance of the coating was about 1.27 times that of the stainless steel 1Cr18Ni9Ti under the same testing conditions. The effects of erosion time on the microstructural evolution were discussed. It was revealed that cracks initiated at the edge of pre-existing pores and propagated along the carbide–binder interface, leading to the pull-out of carbide particle and the formation of pits and craters on the surface. The main failure mechanism of the coating was erosion of the binder phases, brittle detachment of hard phases and formation of pitting corrosion products.