Damages on steel surface at the incubation stage of the vibration cavitation erosion in water

To investigate the damage mechanism of the cavitation erosion at the incubation stage, a kind of polished 40Cr steel was used as the sample in the vibration cavitation erosion experiment. After 1-min experiment, three kinds of erosion pits were found on the sample surface, they are complete pits, incomplete pits and thermal pits in this paper. Numerical simulation of a bubble collapse process in Fluent environment explains the formations of the three kinds of erosion pits. The micro-jet with a strong radius flow around is the main reason for the complete pits and their step-like openings, the shock wave generated outside the jet function domain is the main reason for the incomplete pit, and the high temperature in the compressed bubble at the moment of collapse is considered as the reason for the formation of the thermal pits.