On modeling of heat transfer and molten pool behavior in multi-layer and multi-track laser additive manufacturing process

In this paper, the processes accompanying multitrack and multilayer selective laser melting of metal powder are studied by methods of multiscale numerical simulation. The model includes the coupled macro-scale balance equations of energy and momentum, describing heat transfer, fluid flow and phase transformations, while modeling the structure of the deposited layer by the discrete elements method. The features of the processes of heat transfer and the formation of the melt pool are studied, the surface profile and the relative density (porosity) of the synthesized sample of stainless steel 304 are determined. The calculated values of the final porosity coincide with the experimental data. On the micro-scale, a phase field method characterized by a self-consistent thermodynamic approach and universality is used to describe phase transitions and structure formation dynamics. The numerical implementation of the microstructure evolution micromodel is carried out, the dynamics of morphology and growth of columnar dendritic microstructures in the process of selective laser melting is analyzed. The influence of the governing parameters of the model and the process on the formation of stress fields in dendritic crystal structures is studied.