Particle Scale Modelling of Selective Laser Melting-Based Additive Manufacturing Process Using Open-Source CFD Code OpenFOAM

摘要

Selective laser melting (SLM), the most advanced metal additive manufacturing process, produces parts directly from a CAD file. Currently, the main bottlenecks preventing the SLM parts from competing with traditionally manufactured metal parts include the defects, such as porosity, low surface finish quality, high residual stresses and anisotropy. Though post-build mechanical and microstructural characterization of the SLM-fabricated specimen provides an ample amount of information regarding the build quality, getting real-time information from experiments about temperature, porosity generation mechanism, melt pool formation and its flow behaviour is very challenging. Also, real-time monitoring by thermo-couples, infrared cameras or pyrometric techniques is highly challenging as the SLM process is highly confined (of the order of 60–200?μm melt pool size), rapid (cooling rate of the order of 10_(5)K?s_(?1)) and transient (of the order of 1–5?m?s_(?1)traversal velocity). Therefore, alternative strategies, such as computational modelling is becoming an effective tool to gain deeper insights of the SLM process. In this work, a three-dimensional multi-phase thermo-fluidic solver is developed in an open-source C++ CFD code OpenFOAM to study the transport phenomena (convection, melting/solidification phase change) and inert gas entrapment–ejection mechanism in the SLM process. The volume of fluid approach using the FVM method is used to identify and track the interface of the powder particles undergoing phase transition. The developed CFD platform helps to understand about laser/matter interaction, melting of particles, formation of the fusion zone and inert gas entrapment–ejection phenomenon.