Mathematical modeling of melting tungsten exposed to pulsed laser beam

Melting in a tungsten plate exposed to a pulsed thermal load is numerically simulated by solving the two-phase Stefan problem. The free boundary is ignored during the calculation, since the numerical model is based on Samarskii’s approach. Calculations in axially symmetric geometry show that about a quarter of the incident energy is consumed by evaporation in the center of the melt region. This is five times more than estimates based on the solution of the one-dimensional heat equation. When tungsten evaporation is taken into account, the calculated and experimental cooling surface temperatures and radii of the melt region are in good agreement. The results of the mathematical modeling confirm the existence of an evaporation cooling mode when the tungsten is heated by an electron beam to temperatures significantly higher than the melting point.