Effect of hatch spacing in selective laser melting process of Ti-6Al-4V alloy on finished surface roughness: A computational study

The Selective Laser Melting (SLM) process is a promising additive manufacturing technology for producing complex metal parts. However, this process has certain limitations, including lack of fusion and defects, which can hinder its industrial applications. These challenges can be addressed by determining the appropriate overlap percentage parameters. This study used numerical simulation to explore the effect of overlap percentage on multi-track melting in the SLM process for Ti-6Al-4V. The simulation results categorize the multi-track melting morphologies into two distinct groups. The first group, (0% to 40% overlap), displays consistent surface roughness with an average Ra value of 7 µm. In contrast, the second group (50% to 60% overlap), shows non-uniform shapes. Specifically, the three central tracks in this group present an Ra value of approximately 4 µm. However, when all five tracks of this group are taken into account, the average Ra rises to 14 µm. These differences in surface roughness can be attributed to factors like energy density and the Marangoni effect. Both melt pool depth and shrinkage depth in the overlap area are significant as they might contribute to the risk of the lack of fusion defects. The insights from this research hold potential in shaping scanning pattern strategy design.