Laser beam shape optimization: Exploring alternative profiles to Gaussian-shaped laser beams in powder bed fusion of metals

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Date

2023

Authors

Holla, Vijaya
Kopp, Philipp
Grundewald, Jonas
Praegla, Patrick M.
Meier, Christoph
Wudy, Katrin
Kollmannsberger, Stefan

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University of Texas at Austin

Abstract

Laser-based powder bed fusion of metals (PBF-LB/M) commonly utilizes Gaussian-shaped laser beams characterized by a high intensity at the center. However, this type of profile leads to localized high temperatures and temperature gradients. When the laser power is increased beyond a certain threshold, the temperature inside the melt pool can reach the boiling point, causing excessive metal evaporation, hydrodynamic instabilities, and undesired effects such as keyholing. On the other hand, ring-shaped laser beams generate a more uniform temperature distribution but tend to produce shallower, wider, and shorter melt pools with reduced resolution compared to the Gaussian profiles. The deep, narrow, and elongated melt pools generated by the Gaussian shapes still have advantages for increased precision in the PBF-LB/M processes. This contribution uses numerical optimization to generate a new laser beam shape that also leads to a deep, narrow, and elongated melt pool, similar to a Gaussian-shaped beam, while maintaining a lower and more uniform temperature distribution inside the melt pool. The resulting optimized laser profile lowers the maximum laser intensity by 40 % without decreasing the total laser power compared to the Gaussian profile. The more uniform distribution of temperature with a peak value of just above 3 000 ◦C indicates a conduction dominated process with less hydrodynamic and minimal evaporative effects. This is expected to reduce the associated defects and improve the process stability

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