Influence of process parameters on heat transfer of molten pool for selective laser melting

The stainless steel 316L metal powder is layered on the substrate and then directly heated by a laser beam on the surface of the powder, forming a molten pool. A three-dimensional numerical model is established to investigate the heat transfer in the molten pool. The influence of the thermal evaporation, Marangoni effect, laser beam radius, and surface tension gradient on the molten pool are discussed based on the dimensions, temperature distribution, and Marangoni number. In this study, the energy density is introduced as the laser condition in the simulation settings. The results indicate that the thermal evaporation effect obviously affects the dimensions of the molten pool. The fluid flow caused by the Marangoni effect results in the molten pool forming into a deep and narrow shape. The dimensions, including the depth and width of the molten pool, are expanded as laser beam radius increases. The large surface tension gradient leads to a high Marangoni number and aspect ratio of the molten pool. The shape and dimension of the molten pool obtained from the experimental micrograph are close to the predictions with a surface tension gradient of 0.45 × 10⁻³N/m-K.