Surface Treatment By Laser Generated Shock Waves

Abstract

A study of surface treatment by laser generated shock waves was carried out on various materials. A plasma trapping device enabled intense shock waves to be obtained with attenuated thermal effects. A hardening of 50 % over 1 mm of thickness was obtained on aluminium samples. Amongst the different surface treatment techniques which seem the most promising is that using a high power pulse laser. With the new technique it is possible to obtain intense shock waves over large surfaces of whatever form at the same time as attenuated thermal effects without creating bulk deformation. An experimental study of surface treatment by shock waves generated by an Nd-YAG pulse laser (30 J, 25 ns) was carried out on metals (aluminium, titanium, steel). To obtain high pressures (40 Kbar) with moderate energies and not very high laser intensities (109 W/cm2), a containment device for the plasma resulting from the interaction and the easily vaporizable materials was used. A analysis showed a hardening of more than 50 % over a surface of 0.6 cm2 throughout the thickness of an aluminium sample (1 mm). No hardening effect was observed for the other metals. These results were obtained without optimization of the trapping technique. Better control of this will enable a hardening effect to be obtained on other metals.