Numerical investigation of thermal behavior and melt pool morphology in multi-track multi-layer selective laser melting of the 316L steel

Abstract

Rapid melting and solidification of powder particles through a high-power laser is the characteristic feature of selective laser melting (SLM), which controls the material and physical properties of fabricated components. Considering the multi-track multi-layer nature of an actual SLM process, an investigation of thermal behavior and melt pool morphology in multi-track multi-layer SLM of the 316L steel is presented in this paper. The SLM process of a four-layer component with multiple tracks was modeled. Element birth and death technique was used to simulate the layer built-up process. The established FEM model was used to investigate the variations in thermal variables and melt pool morphology with increasing number of layers. Moreover, the influence of various processing parameters in a multi-track multi-layer SLM was also studied. The results show that maximum melt pool temperature, melt pool width, and melt pool depth increase with increasing number of layers, whereas heating rates and cooling rates decrease with increasing number of layers. Compared with the previous layer, melt pool lifetime was observed to have a decreasing trend for layer 2 and increasing trend for layers 3 and 4. An increase in melt pool depth and decrease in melt pool width was observed by increasing hatch spacing. Furthermore, it was found that increasing laser power and scanning speeds both increase the heating and cooling rates.