Performance Analysis of Cavitation Erosion Resistance and Corrosion Behavior of HVOF-Sprayed WC-10Co-4Cr, WC-12Co, and Cr 3 C 2 -NiCr Coatings

Cavitation erosion is a major damage phenomenon in hydraulic turbine components that is caused by the bubble collapse. Protective coatings are widely applied as a form of surface modification to resist cavitation erosion. In this work, the WC and Cr3C2 cermet coatings were prepared by using HVOF, and their resistances to cavitation erosion in deionized water and 3.5 wt.% NaCl solution were evaluated. The corrosion behavior was investigated by potentiodynamic polarization in 3.5 wt.% NaCl solution, to examine the damaged surface morphologies and the corrosion products. Results indicated that higher hardness and fracture toughness, and lower porosity could enhance cavitation erosion resistance of the coatings in deionized water. In 3.5 wt.% NaCl solution, the cobalt matrix phase of the WC-12Co coating was dissolved in the corrosive solution, which accentuated the cavitation erosion damage. On the contrary, the oxidation product formed on the WC-10Co-4Cr and Cr3C2-NiCr coatings surface in 3.5 wt.% NaCl solution could mitigate delamination, seal surface pores, and protect from cavitation erosion damage. The WC-10Co-4Cr coating with higher hardness, higher toughness, and lower porosity, which exhibited the ability to form surface oxides in the corrosive solution, showed the best cavitation erosion resistance in both deionized water and 3.5 wt.% NaCl solution.