Thermofluid field of molten pool and its effects during selective laser melting (SLM) of Inconel 718 alloy

A physical model coupled with heat transfer and fluid flow was developed to investigate the thermofluid field of molten pool and its effects on SLM process of Inconel 718 alloy, in which a heat source considering the porous properties of powder bed and its reflection to laser beam is used. The simulation results showed that surface tension caused by temperature gradient on the surface of molten pool drives to Marangoni convection, which makes fluid flow state mainly an outward convection during SLM process. Marangoni convection includes convective and conductive heat flux, both of them have effects of on molten pool shape, but the effect of convective heat flux is dominant because its magnitude is one order larger than that of conductive heat flux. The convective heat flux accelerates the flow rate of the molten metal, benefits to heat dissipation. The convective heat flux makes the molten pool wider, while the conductive heat flux makes comparably the molten pool deeper and wider. Furthermore, heat accumulation caused by multiple scanning increases convection and conduction heat flux resulting in the increase of the width and depth of the molten pool, but no change of dominant role of convective heat flux to the shape of the molten pool.