Characterizing cavitation erosion particles by analysis of SEM images

Wear particles produced by vibratory cavitation erosion on stationary-aluminum Al-99.999 were analyzed using scanning electron microscope (SEM), forming a database for further analysis. The particle morphology features were first clarified based on the characteristic stages of the vibratory erosion rate-time pattern. Next, size, area, perimeter and shape factors (elongation and roundness) were determined for eroded particles, using image analysis software. In incubation period, the particles have distinctive characteristics which differed from that for the subsequent periods. These characteristics include the value of longitudinal ratio and roundness factor, limit size range and morphological features such as lamella shape, folding, curving with one of the particle surfaces as the virgin surface. In acceleration, steady-state and attenuation periods, the particles have a wide size range and larger thickness compared with that for the incubation period. The maximum particle size reached about 360 μm in acceleration and steady-state period. For all the cavitation erosion rate periods, the particles were out of sphericity and they have a roundness factor larger than 2. Detailed surface characteristics of the particles produced during cavitation erosion is significant and can open ways for monitoring the cavitation erosion progress.