A Fluid-Dynamic Numerical Model for the Selective Laser Melting of High-Thickness Metallic Layers

Abstract

Productivity in the Selective Laser Melting Process (SLM) is directly related with the thickness of the powder bed that is repeatedly applied, at every increment, in the growing of consolidated material in the additive manufacturing process. Although most of the relevant phenomena (limited diffusivity associated to particles contact, phase changes, gradients of surface tension associated with Marangoni convection, or even recoil pressure) are considered in the models with small bed thicknesses (roughly 20 µm ? 40 µm), in the case of larger thicknesses (between 100 µm and 200 µm) these factors strongly influence the size and shape of the fusion bath leading to a non trivial geometry of the final consolidated material. The present work proposes the use of the Arbitrary Lagrangean-Eulerian method (ALE method) to solve the thermal and Navier-Stokes equations in the frame of a free-moving discretization to predict simultaneously the space-time temperature evolution and the associated fusion bath dynamics. It allows for using a continuous domain to represent the powder bed, which, instead of a particle model approach, is advantageously compatible with realistic process parameters, where long paths are covered by the laser. The model was validated with experimental data using Inconel as working material, showing a good degree of agreement.