The influence of sulphide on the ultrasonic cavitation erosion-corrosion behaviors of HVOF-sprayed WC-CrC-Ni coating.

The present study emphasizes the role of sulphide on ultrasonic cavitation erosion-corrosion (UCE-C) behaviors of HVOF-sprayed WC-CrC-Ni coating in 3.5 wt% NaCl solution with different sulphide concentrations. The results indicated that the ultrasonic cavitation erosion (UCE) resistance of the coating decreased significantly with increasing sulphide concentration. The coating reacted with oxygen and anion those transferred by UCE, and the cavitation impact force led to the lack of support for tungsten carbide particles, which resulted in the reduction in the mass of the coating. There were two main factors those affected the UCE-C mechanism, in which the passivation film helped to reduce the mass loss of the coating, while the impact force caused by cavitation destroyed the passivation film, led to the accelerated anion diffusion and ultimately accelerated the mass loss of the coating. Mechanical erosion dominated the UCE-C of the coating in all tested solutions.