Melting and solidification processes in a moving graphite-covered titaniumsurface subjected to multi-pulse laser irradiation

Experimental results of surface melting by pulsed Nd-YAG laser irradiation of titanium covered with graphite powder were analysed in comparison with t he results of numerical simulations. The simulations of the thermal events, such as the maximum of temperature gradient at the surface and the duratio n of the liquid state after irradiation, were found due to a semi-analytic model of the space-time temperature distributions which were induced by the irradiation treatments. These simulations were required in order to calcul ate a series of integrals by Simpson's numerical method. They have allowed us to explain the experimental results such as the incorporation of carbon in melted zone, which produces titanium carbide and possible graphite inclu sions, as a function of the irradiation parameters. The perpetual absence i n the thickness and the exceptional presence at the surface of the solidifi cation structure resulting from the plane-front growth of titanium carbide have, moreover, been justified.