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

摘要

Derived from laser cladding, the Direct MetalrnDeposition (DMD) laser process is based upon a laserrnbeam – powder – melt pool interaction, and enablesrnthe manufacturing of complex 3D shapes much fasterrnthan conventional processes. However, the surfacernfinish remains critical, and DMD parts usuallyrnnecessitate post-machining steps. Within this context,rnthe focus of our work is to improve the understandingrnof the phenomenon responsible for deleteriousrnsurface finish by using numerical simulation. Mass,rnmomentum, and energy conservation equations arernsolved using COMSOL Multiphysics? in a 2Drntransient model including filler material with surfacerntension and thermocapillary effects at the freernsurface. The dynamic shape of the molten zone isrnexplicitly described by a moving mesh based on anrnArbitrary Lagrangian Eulerian method (ALE). Thisrnmodel is used to analyze the influence of the processrnparameters, such as laser power, scanning speed, andrnpowder feed rate, on the melt pool behavior. Thernsimulations of a single layer and multilayer claddingsrnare presented. The numerical results are comparedrnwith experimental data, in terms of layer height, meltrnpool length, and depth of penetration, obtained fromrnhigh speed camera. The experiments are carried outrnon a widely-used aeronautical alloy (Ti-6Al-4V)rnusing a Nd:YAG laser.