Bubble dynamic evolution, material strengthening and chemical effect induced by laser cavitation peening.

The mechanism of laser cavitation peening (LCP) including laser shock wave, bubble collapse shock wave, and water-jet was investigated at various stand-off distances (γ) combined with experiment and simulation. The dynamic characteristics, pressure field, and temperature field of cavitation bubble were investigated. The Q235 steel was impacted by LCP and the strengthening mechanism was analyzed, and the chemical effect in LCP was discussed. The results found that the pressure intensity of shock wave and water-jet decreases with increasing the γ. At γ=0, the laser shock wave, bubble collapse shock wave, and water-jet are 989 Mpa, 763 Mpa, and 369 Mpa respectively. The pressure and temperature of the bubble decrease obviously in the second and third pulsations. The impact of LCP causes plastic deformation on the Q235 steel surface and refines the grains on the surface layer within a depth of 20-30 μm. The enhancement of microhardness and the residual stress increases with the increase of γ, and the optimal value for LCPwc is 0.4. The degradation rate of MB solution in the infinite domain, LCPwc, and LCP is 26.4%, 41.7%, and 34.5%.