Comparison of different multi-laser powder bed fusion exposure strategies and their influence on the part quality of IN718

Multi-laser powder bed fusion (M-LPBF) systems, characterized by large building envelopes and multiple lasers, have become increasingly prevalent in industrial additive manufacturing. The increased build rate of these machines relative to single laser systems offers the potential to drastically reduce the cost per part. However, one major challenge with M-LPBF is that often multiple lasers are needed to build a single part. Therefore, the exposure area must be divided, and the segments must be assigned to different lasers. Various strategies for splitting the exposure area are available, but their influence on part quality remains yet to be determined. This study aims to investigate the impact of the fixed exposure border, variable exposure border, and segmented stripes M-LPBF exposure strategy on the part quality of samples built with two lasers compared to samples built with one laser. Therefore, the porosity, microstructure, and mechanical properties of IN718 samples were evaluated. The research shows that the fixed exposure border strategy resulted in a localized increase in porosity at the border or within the overlap area between segmented exposure areas, as well as grain coarsening and increased texture within the remelted areas. The variable exposure strategy also resulted in a higher porosity level, but the microstructure was more like the single laser reference sample. These changes resulted in a minor decrease in mechanical properties. The segmented stripes strategy exhibited a similar microstructure and mechanical properties to the single laser reference, making it the most suitable approach for M-LPBF in industrial applications.