Influence of linear energy on side surface roughness in powder bed fusion electron beam melting process: Coupled experimental and simulation study

The optimization of the side surface roughness of the as-built part is one of great interest in the additive manufacturing field because of the post-processing difficulty. In this study, the generation mechanism of the side surface in the powder bed fusion electron beam melting process was investigated using modified René80 alloy under different linear energies. The dimensional inaccuracy of the as-built part mainly attributes to part diameter variation rather than part height variation. The side surface roughness of the as-built part was increased with linear energy owing to the formation of wavy bulges. The multi-physics model was developed to investigate the side surface generation in the electron beam melting process. The right-angled stair edge was relaxed at high linear energy owing to the increased molten pool dimension. The molten pool convection via the Marangoni effect was increased at high linear energy because of the large difference in temperature and low viscosity. The formation of wavy bulges on the side surface originated from the severe heat accumulation at the last solidified region in each melting path under high linear energy. Therefore, it was confirmed that the side surface roughness in the powder bed fusion electron beam melting process can be improved by optimizing the linear energy to restrict the formation of wavy bulges and coarse particles.