Dynamics of the egress of gas microbubbles from a melt under laser irradiation of a metal surface

The results of a theoretical investigation of the efficiency of degassing of the near-surface region of a material exposed to laser radiation are presented. The case of a low volume concentration of the monodispersed gas phase representing microbubbles of size no greater than 10 μm is considered. The principal parameters are revealed which determine the regimes of the egress of gas bubbles from a laser-produced melt, and analytical formulas are obtained for estimating the process rate. The analytical results are compared with the results of two-dimensional numerical simulations which include the laser heating of a solid sample, its melting, the development of thermocapillary melt convection, and the escape of gas bubbles from the melt. The analytical and numerical results are found to be in good agreement.