Resolving the effects of local convective heat transfer via adjustment of thermo-physical properties in pure heat conduction simulation of Laser Powder Bed Fusion (L-PBF): Paper

Numerical models, especially when validated against experimental findings, are valuable tools that can be used as a cheap and reliable alternative to the expensive and time-consuming experimental investigations. In the current work, a multiphysics model of laser powder bed fusion (L-PBF) has been developed for stainless steel SS 316-L and validated against experimental findings. By configuring the model, the effects of the inverse Marangoni flow on the melt pool morphology and the heat and fluid flow conditions were analysed. It was shown that for high surface tension sensitivities, the total heat flux through the melt pool boundaries increases. The enhanced cooling will lead to a smaller melt pool size with larger depth to width ratio and causes a relatively uniform temperature field, which reduces the role of the conduction heat transfer. Furthermore, a Nusselt number was derived to quantify the role of the Marangoni effect on the convection heat transfer from the melt pool. This expression was used to calculate an effective thermal conductivity required for a modified pure conduction heat transfer calculation. It was shown that, via using a combination of the derived Nusselt number and the concept of the effective thermal conductivity, the average melt pool temperature determined from the modified pure conduction model gets very close to that of the more advanced CFD model.