Using a dual-laser system to create periodic coalescence in laser powder bed fusion

Conventional laser-based powder bed fusion of metals (PBF-LB/M) currently faces technological challenges in scalability due to its low building rate and manufacturing throughput. One approach to address this issue is to parallelize multiple laser beams to increase processing flexibility. Recent research has studied, for instance, the improvements to mechanical properties of final products when using two or more laser beams in PBF-LB/M. However, some obstacles still need to be addressed involving the proximity of molten pools and their interaction mechanism. In particular, interactions between two close, parallel molten pools have not been fully understood yet. In this study, two lasers create two parallel-running molten pools with a small spatial offset in between. With different spatial offsets, experimental results reveal that besides the completely merged and completely separated regimes, there exists a new regime which yields periodic coalescence between the two molten pools. High-speed imaging shows two different mechanisms for the formation of such coalescence, what we denote as head-to-head and head-to-tail coalescence. By changing processing parameters including laser power and spatial offset, periodic structures with various wavelengths can be engineered using this dual-laser approach.