Developing stages of ultrasonically produced cavitation erosion and corresponding surface roughness

Vibratory-erosion tests on a typical erosion-resistant material made of 304 stainless steel were carried out. We carefully observed the erosion patterns and the surface roughness aspects with respect to test time, under a specified condition of uniform nuclei-size distribution, by a scanning electron microscope and a profilometer. The eroded surface is classified into three stages from surface topography and roughness profile. In the first stage, the surface is plastically deformed and its roughness rapidly increases. In the second stage, the surface becomes more hardened, so that cracks initiate and propagate; after that, local removal of material occurs. In addition, the roughness doubles and then increases slightly.