Multivortex convection of metal in molten pool with dispersed impurity induced by laser radiation

Results of the numerical solution of an adjoint problem of thermocapillary microconvection induced by laser radiation in a molten pool on a metal substrate are presented. Problems of modeling various processes of laser-induced surface modification of materials (laser-induced hardening, alloying and cladding) are discussed. Distributions of temperature, velocity, and streamlines in the liquid dimple are presented, which demonstrate specific features of existence of three-dimensional multivortex flows responsible for thermohydrodynamics of the melt, formation of the bottom relief of the liquid dimple, and mixing of refractory alloying disperse components. Alloying additives are inserted into the molten pool by means of gas-jet transportation through a coaxial nozzle or by preliminary (before laser beam passage) application of these additives onto the surface of the processed material. A physicomathematical model for calculating the convection of the fine-grain impurity is proposed, and the calculated dynamics of tungsten and titanium carbide particles in a molten pool on a steel substrate is described. Distributions of their number concentrations in the melted zone after crystallization are obtained.