Laser-matter interaction in laser shock processing

Abstract

Laser shock processing (LSP) is an emerging industrial process in the field of surface treatment with particular application to the improvement of fatigue and corrosion properties. In the standard configuration, the metal sample is coated with a sacrificial layer in order to protect it from detrimental thermal effects, and a water overlay is used to improve the mechanical coupling by a confining like effect. Whereas the induced mechanical effects are now well understood, very few studies have been realized concerning the thermal effects. For this purpose, the knowledge of the confined plasma microscopic parameters has a great importance. A complete model describing the laser-liquid-metal interaction is presented. The model predicts the time evolution of the plasma parmmeters (temperature, density, ionization) and allows us to compute the induced pressure and temperature in the metal sample. By comparing the numerical results with various experimental measurements, predictions can be made concerning the best laser irradiation conditions for LSP.