Computational investigation of thermal behavior and molten metal flow with moving laser heat source for selective laser melting process

Selective laser melting (SLM) process, which is one type of additive manufacturing (AM) processes, involves numerous complex physical phenomena such as heat transfer, molten metal flow, phase transformation, and Marangoni effect. These phenomena have significant effect on the final products quality. The aims of this research are to investigate the thermal behavior and molten metal flow characteristics, and to analyze the influence of the process parameters on scanning track formation. An integrated numerical modelling of discrete element method (DEM) and computational fluid dynamics (CFD) are applied. The results reveal that the molten metal backward flowed from the laser hot spot to the rear of the melt pool due to the surface tension gradient. The uniform tear-drop shape and high penetration scanning track occurred with laser power and scanning speed of 200 W and 1000 mm/s, 250 W and 1000 mm/s, and 250 W and 1200 mm/s. Moreover, the scanning track width and depth of all scanning speed levels, 1000 mm/s, 1200 mm/s, and 1500 mm/s, increased around 4-10 mu m and 14-22 mu m, respectively, with the increase in laser power of 50 W and reduced around 1-4 mu m and 3-6 mu m, respectively, per increasing in scanning speed of 100 mm/s.