Global local modeling of melt pool dynamics and bead formation in laser bed powder fusion additive manufacturing using a multi-physics thermo-fluid simulation

Understanding the physical mechanism of laser–powder bed fusion (LPBF) additive manufacturing can benefit significantly through computational modeling. LPBF uses a laser heat source to melt a number of layer of powder particles and manufactures a part based on the CAD design. This work aims to assess the impact of Marangoni flow, buoyancy and recoil pressure to simulate the fluid flow around melt pool with a non-Gaussian laser beam to simulate the interaction between laser and powder bed. It was observed that velocity profile shows two peaks on either side of the highest temperature point owing to Marangoni convection on both sides due to gradient in surface tension. Dimensional analysis was also conducted based on Peclet number, Nusselt number and Marangoni number to determine the mode of heat transport at various laser power/scan speed combinations. Convective heat flow is the dominant form of heat transfer at higher energy input due to violent flow of the fluid and recoil pressure around the molten region, which can also create keyhole effect associated with defects such as porosities. The computational model was also validated by comparing solidified bead geometry with experimental data.