Multiphysics simulation and microstructure prediction of coaxial wire-laser additive manufacturing process

The paper addresses the numerical modeling of heat transfer, fluid flow and microstructure formation in the wire-laser additive manufacturing (WLAM) process. The three-beam WLAM configuration is studied, where the primary laser light is divided into equivalent beams which coaxially converge to heat the feeder wire just prior its plunging and melting into the melt pool. The numerical modeling is conducted in a level set framework, using unstructured finite elements with periodic adaptative remeshing. An original method is proposed to avoid an explicit description of the feeding wire. Instead, a volume source domain is defined within the melt pool, where a specific velocity field is imposed. This velocity field accounts for the impingement effect of the incoming wire, and has a positive divergence derived from the mass feeding rate. At the same time, the right-hand side of the heat equation is modified to account for the input of energy due to the plunging of the heated wire. In addition, a cellular automaton method is coupled within the finite element analysis to predict grain structure development, by epitaxial growth from the substrate, based on the temperature field evolution during the solidification stage. The developed coupled methodology is applied to single-track deposition of IN718 on a substrate made of the same alloy. The influence of process parameters on bead morphology, microstructure evolution and texture formation are presented and discussed.