Experimental Study on Submerged High-Pressure Jet and Parameter Optimization for Cavitation Peening

To increase the performance of high pressure submerged cavitation jet that has been used for cavitation peening, the effect of stand-off distance and the nozzle geometry on the impact capacity is investigated and optimized. High speed photography of the cavitation bubble clouds taken to reveal the unsteady characteristics of the cavitating jet. The impact ability of the jet with different nozzles and standoff distance is tested using Al 1060 at first, and the optimized jet is used then for cavitation peening on 304 stainless steel. The surface profile as well as the grain structures before and after peening using different nozzles are observed from SEM images. It is found that, the divergent angle of the nozzle has a great effect on the impact capability of the submerged high-pressure jet, which is important for improving the peening efficiency. In the nozzles with divergent angle 40°, 60° and 80°, the 60° nozzle shows the best performance. After peening, grain cells under the metal surface are changed and a twin layer is formed. The current research reveals the transient characteristics of the submerged cavitation jet and main factors that affect its impact rate, which provides guide for the nozzle design and application for the high-pressure cavitation jet peening.