Computational analysis of thermo-fluid dynamics with metallic powder in SLM

Abstract

Selective Laser Melting (SLM) is a powder bed additive manufacturing (AM) process. The metallic powder particles are subject to melting-solidifying along each line scanning which consequently results in intense thermo-capillary convection within the melt pool. Therefore, in order to accurately capture the fluid dynamics, discrete powder particles should be properly modelled. In this study, a 3D thermo-fluid model using the volume of fluid approach with powder particles incorporated was developed using ANSYS/FLUENT. A sequential powder adding algorithm was utilized to generate randomly dispersed particles of a given size distribution in a powder bed. As a result of continuous melting and solidification, the temperature distribution, the molten metal flow, and the free-surface formation can be numerically analyzed. The influence of sequential addition of powder particles to the transport phenomena can be studied and the mechanisms of different pore formation investigated. When the powder particles are melted, the formed melt pool would solidify to form the single track and its density depends on the process parameters. The high speed, 1600 mm/s, of laser would result in less dense tracks with numerous pores would further aggravate with increasing layers.