Developed Stages of Ultrasonically Produced Cavitation Erosion and Corresponding Surface Roughness

The vibratory-erosion-tests on a typical material of 304 stainless steel were carried out. We carefully observed the erosion patterns and the surface-roughness-aspects with respect to test times, under a specified condition of a uniform nuclei-size-distribution, by a scanning electron microscope and by a profilometer. Both surface topography and surface profile divided the eroded surfaces into three stages. In the first one, the surface was plastically deformed and the roughness rapidly increaseed. In the second stage, the surface became more hardened, so the crack initiated and propagated, and after that, local removal of material occured. Also, the roughness doubled and slightly increaseed. In the third stage, almost all the virgin surface was removed and the surface roughness doubled, again. Both the skewness and the kurtosis was calculated. It was found that the skewness has a positive and a negative value before and after the material removal, respectively. The kurtosis had a positive value for all test times.