Simulation of unsteady-state thermocapillary mass transfer for laser doping of metals

Abstract

By imposing the approximation of a shallow melt bath, small reduced Reynolds number and of a plane free surface, unsteady-state thermocapillary flow of melt is considered for the case of melting a metallic solid body by a Gaussian surface heat source. Based on the velocity field obtained, convective mass transfer of the doping impurity is analysed by the method of model particles in the assumption of a small Schmidt number. The feasibility of producing both a relatively homogeneous and an essentially nonmonotonous (layered) structure of concentration fields in the remelted zone is shown. The analysis of the formation of such structures is made and their specific features are revealed in the case of laser doping of metals from the gas (plasma) phase and from previously deposited coatings. Comparison between the predicted concentration profiles and the results of experiments is made and their satisfactory qualitative agreement is obtained.