Identification of a suitable volumetric heat source for modelling of selective laser melting of Ti6Al4V powder using numerical and experimental validation approach

Abstract

Using a suitable heat source is crucial to correctly simulate the selective laser melting (SLM) process as the heat source represents the absorbed heat energy, which governs the thermal and fluid flow phenomena associated with SLM. The discontinuous mass distribution in the powder bed causes absorption of incident laser energy over a substantial depth in the powder bed. Therefore, the conventional way of including laser beam energy as a surface heat flux in the modelling of SLM process is likely to provide inaccurate results. This draws attention towards the use of a volumetric heat source in SLM modelling. A number of models for the volumetric heat sources are present that make a selection very difficult. Therefore, several heat sources are investigated in this study using numerical modelling. A three-dimensional model of SLM of Ti6Al4V powder has been developed. The model comprises of a mathematical description of the SLM process along with models for thermal, physical and optical properties of the powder bed. The temperature field, melt pool dimensions, temperature gradient and cooling rate are discussed in detail. The simulation results are compared with the published experimental results to identify a suitable heat source for SLM modelling. Among different heat sources considered, the Gaussian exponential volumetric heat source is found to provide the best matching results with the experiments. Hence, it is identified as the suitable heat source for use in modelling of SLM.