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<p>Laser-directed energy deposition (L-DED) of maraging steels has focused on the effect of the four core parameters’ (i.e., laser power, scan speed, powder feed rate, and scan strategy) influence on part quality, generally leaving gas flow parameters constant. This study investigates the effect of powder carrier gas (CG) and melt pool shielding gas (SG) flow rates, in addition to considering the effect of changing the four core parameters, on the bead and clad surface quality and internal defects of L-DED produced maraging steel. It is shown that the ratio between CG and SG (CG/SG) results in different regimes of material quality without significantly changing the bead geometry. Generally, increasing the CG/SG ratio improves surface morphology, surface roughness, and reduces spatter. However, higher CG/SG ratios also exhibited increased oxide formation on the deposited surface and gas entrapment porosity within the deposited material. The findings highlight the importance of balancing CG and SG flows: a minimum threshold SG flow is necessary to minimize oxidation and higher CG flow values optimize surface quality, whereas lower CG values minimize porosity and oxidation. These results provide practical guidelines for gas flow rate adjustments for L-DED systems with diffuse melt pool shielding, relatively high powder velocities, and small laser spot sizes (LSSs).</p>

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Understanding the effects of shielding and carrier gas flows on the surface quality and defect formation during laser-directed energy deposition of 18Ni maraging steel

  • 期刊论文

  • 发表日期：

    2025年9月1日

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  • Christopher Paul,
  • Mikhail Malmyguine,
  • Lisa Tobber,
  • Milan Brandt,
  • Michael J. Benoit

摘要

Laser-directed energy deposition (L-DED) of maraging steels has focused on the effect of the four core parameters’ (i.e., laser power, scan speed, powder feed rate, and scan strategy) influence on part quality, generally leaving gas flow parameters constant. This study investigates the effect of powder carrier gas (CG) and melt pool shielding gas (SG) flow rates, in addition to considering the effect of changing the four core parameters, on the bead and clad surface quality and internal defects of L-DED produced maraging steel. It is shown that the ratio between CG and SG (CG/SG) results in different regimes of material quality without significantly changing the bead geometry. Generally, increasing the CG/SG ratio improves surface morphology, surface roughness, and reduces spatter. However, higher CG/SG ratios also exhibited increased oxide formation on the deposited surface and gas entrapment porosity within the deposited material. The findings highlight the importance of balancing CG and SG flows: a minimum threshold SG flow is necessary to minimize oxidation and higher CG flow values optimize surface quality, whereas lower CG values minimize porosity and oxidation. These results provide practical guidelines for gas flow rate adjustments for L-DED systems with diffuse melt pool shielding, relatively high powder velocities, and small laser spot sizes (LSSs).