Numerical Simulation and Analysis of Surface Evolution of Molten Pool in Selective Laser Melting of 316L Stainless Steel

Abstract

The molten pool characteristics play a crucial role in the quality of parts formed through selective laser melting (SLM). Therefore, comprehending the evolution mechanism and studying the features of the molten pool during the SLM process are vital for optimizing the forming process. This study developed a multiphysics finite element model to simulate the laser selective melting of 316L stainless steel powder, considering factors such as phase change, recoil pressure, surface tension, and the Marangoni effect. The simulation results illustrated the temperature evolution, flow field, and surface morphology changes over time during the single-melt channel SLM forming process. The agreement between simulated and experimental surface morphology results was observed. Notably, the Marangoni effect causes fluid in the molten pool to move opposite to the laser scanning direction, leading to ripple formation on the surface and the creation of protrusions and depressions at specific points. Furthermore, the thermal gradient and solidification speed of solid–liquid interface of molten pool were analyzed; it was found that the solidification speed decreased with the increase of the depth of the molten pool and approached to zero at the bottom of the molten pool. Variations in molten pool geometry and length-to-depth ratio under different powers and scanning speeds were also analyzed, revealing that the molten pool geometry is more sensitive to changes in laser parameters at lower powers or scanning speeds.