Numerical simulation of multi-field coupling behavior and heat and mass transfer mechanism in laser additive manufacturing process

The serviceability of cladding layers manufactured by laser depends on the microstructure formed by the metallurgical solidification. The microstructure in the clad layer is influenced by several factors. Among them, the elemental distribution state of the molten powder in the molten pool plays a dominant role. The diffusion distribution of elements is closely related to the non-equilibrium metallurgical behavior in the additive manufacturing process. Therefore, it is important to conduct an in-depth study on the multi-field coupling behavior and the heat and mass transfer mechanism in laser additive manufacturing process. In this study, a coupled thermal-fluid–solid multi-physical field numerical model for the laser cladding of 316L stainless steel powder on 45 steels was developed. The transient change patterns of the temperature, flow and stress fields for the cladding process were quantitatively revealed. The diffusion process of the powder elements within the molten pool was considered to reveal the element distribution law in the clad layer. The effects of the surface tension, buoyancy for molten pool, and Marangoni convection on the flow field also were considered, and the validity of the numerical model was verified. This study provides a theoretical basis for optimizing the laser cladding process.