Model Development in OpenFOAM for Laser Metal Deposition-based Additive Manufacturing Process

Laser metal deposition (LMD) process is an additive manufacturing process that uses a high-power laser to melt the metal powder supplied coaxially to the focus of the laser beam through a deposition head. The LMD process involves various interconnected physical phenomenon that are challenging to model numerically. It includes laser-material interaction, fall of molten droplets in a melt pool and the associated heat, momentum and mass transfer, free surface flow, bubble formation and air entrapment, and rapid solidification. A numerical solver in open-source platform OpenFOAM((R)) using the VOF approach is developed for the spot LMD process. Flows due to natural and Marangoni convection are modelled by adding source terms in momentum equation. Energy addition in the substrate due to laser irradiation is added as a source term in energy equation. Enthalpy-porosity technique is used to model the melting and solidification phase change. Mass and energy addition due to falling droplets are modelled by adding molten droplets in the melt pool. The role of melt pool convection on heat transfer and melt pool geometry is established by an analysis using relevant dimensionless numbers. Ratio of Marangoni number and Grashof number suggest that the fluid flow within the melt pool during laser heating stage is mainly driven by Marangoni force.