Heat transfer and phase transition in the selective laser melting process

This paper investigates the heat transfer and phase transition during the selective laser melting (SLM) process under a moving volumetric heat source. Specifically, our objective is to study the heating, melting, vaporization and cooling processes. The model initiatively incorporates a phase function to differentiate the powder phase, melting liquid phase, dense solid phase and vaporized gas phase. The dependence of material properties on temperature and phase is also accounted for. The model involves the volume shrinkage induced by the density change during the melting process. The problem is formulated using the heat transfer equation and solved by the finite difference method. The results show the detailed temperature evolution during the SLM process. The phase transition of the material can be tracked and the melting pool can be predicted according to the phase function. The process parameter study reveals that the melting pool with low scan velocity or high laser power has large width and length, and deep penetration. The unified model proves neglecting of vaporization or temperature dependence of material properties leads to results overestimating the shape and volume of the melting pool. (C) 2017 Elsevier Ltd. All rights reserved.