2D FINITE ELEMENT MODELING OF HEAT TRANSFER AND FLUID FLOW DURING MULTILAYERED DMD LASER PROCESS

摘要

Derived from laser cladding, the Direct Metal Deposition (DMD) laser process is based upon a laser beam - powder - melt pool interaction, and enables the manufacturing of complex 3D shapes much faster than conventional processes. However, the surface finish remains critical, and DMD parts usually necessitate post-machining steps. Within this context, the focus of our work is to improve the understanding of the phenomenon responsible for deleterious surface finish by using numerical simulation. Mass, momentum, and energy conservation equations are solved using COMSOL Multiphysics in a 2D transient model including filler material with surface tension and thermocapillary effects at the free surface. The dynamic shape of the molten zone is explicitly described by a moving mesh based on an Arbitrary Lagrangian Eulerian method (ALE). This model is used to analyze the influence of the process parameters, such as laser power, scanning speed, and powder feed rate, on the melt pool behavior. The simulations of a single layer and multilayer claddings are presented. The numerical results are compared with experimental data, in terms of layer height, melt pool length, and depth of penetration, obtained from high speed camera. The experiments are carried out on a widely-used aeronautical alloy (Ti-6Al-4V) using a Nd:YAG laser.