Coatings with different porosities were prepared by controlling high velocity oxy-fuel process parameters.
Pores were distributed homogeneously along the thickness of the coatings. Cavitation erosion rate of the coating
was obtained by a vibratory cavitation equipment following ASTM G32 standard. As porosity of the coating
increases, the cavitation erosion rate increases. Significantly high cavitation erosion rate was obtained in the early
stage of the test for the coating with high porosity. As cavitation erosion test proceeds, the cavitation erosion
rate tends to decrease. Cracks initiated in the surface pore area propagate along powder boundaries and merge
to pores near surface. Due to the cracks, large coating parts consisting of a bunch of powders with good bonding
were detached from the coating increasing the cavitation erosion rate. Corrosion products were preferentially
formed on the pore areas enhancing the cavitation erosion rate. Consequently, pores near coating surface significantly
accelerate the cavitation erosion rate through mechanical as well as chemical manners.