High-speed schlieren imaging of non-gaussian beam shapes in laser directed energy deposition

The objective of this work is to provide new insights into laser powder-blown directed energy deposition (DED-LB) when using non-Gaussian beam shapes by in situ gas flow visualization. This is motivated by the incomplete understanding of interaction between the laser and powder flow on melt pool formation. High-speed Schlieren imaging was implemented to visualize the effect of plume velocity on powder particle flow for seven beam distributions and demonstrates that 450 µm feature sizes can be achieved. The plume velocity ranged from 0.5 m/s to 16 m/s, and three regimes of behavior were identified as beams transitioned between Gaussian and annular distributions.