Abstract The gaseous atmosphere plays a major role in the quality of the manufactured parts in Laser Powder Bed Fusion (L-PBF) by protecting the metal from high temperature oxidation. If argon and nitrogen are the most commonly used gases, helium has almost never been considered as a possible candidate as a chemically inert shielding gas. To provide a better understanding of the influence of the gas atmosphere on the process stability, a comparative study of L-PBF manufacturing under argon and helium atmospheres has been carried out, considering a nickel-based alloy Inconel® 625 and a single bead configuration. To this end, in-situ process measurements were carried out on a dedicated experimental setup. The melt pool behaviour, the expansion of the vapour plume and the amount of spatters were evaluated with high-speed imaging for the two gases considered, together with the final L-PBF bead dimensions. Results were also compared to single fusion beads carried out in an industrial L-PBF machine for a comparable range of volume energy densities. The influence of the shielding atmosphere on L-PBF single beads was as follows: (1) dimensions of beads were shown to be constant whatever the gas; (2) fewer and smaller spatters were produced under helium atmosphere, especially for high volume energy densities. Physical mechanisms were then discussed to understand those specific effects.

中文翻译：

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气氛（Ar或He）对Ni基合金激光粉末床熔合的影响

摘要 气态气氛通过保护金属免受高温氧化对激光粉末床融合 (L-PBF) 制造的零件质量起着重要作用。如果氩气和氮气是最常用的气体，那么氦气几乎从未被认为是一种可能的化学惰性保护气体。为了更好地了解气体气氛对工艺稳定性的影响，我们对氩气和氦气气氛下的 L-PBF 制造进行了比较研究，考虑了镍基合金 Inconel® 625 和单珠配置。为此，在专用实验装置上进行了原位过程测量。熔池行为，蒸汽羽流的膨胀和飞溅物的数量是通过高速成像对所考虑的两种气体以及最终的 L-PBF 珠尺寸进行评估的。还将结果与在工业 L-PBF 机器中进行的单个融合珠进行比较，以获得可比较的体积能量密度范围。屏蔽气氛对 L-PBF 单珠的影响如下： (1) 无论气体如何，珠的尺寸都是恒定的；(2) 在氦气气氛下产生的飞溅更少和更小，特别是对于高体积能量密度。然后讨论物理机制以了解这些特定影响。屏蔽气氛对 L-PBF 单珠的影响如下： (1) 无论气体如何，珠的尺寸都是恒定的；(2) 在氦气气氛下产生的飞溅更少和更小，特别是对于高体积能量密度。然后讨论物理机制以了解这些特定影响。屏蔽气氛对 L-PBF 单珠的影响如下： (1) 无论气体如何，珠的尺寸都是恒定的；(2) 在氦气气氛下产生的飞溅更少和更小，特别是对于高体积能量密度。然后讨论物理机制以了解这些特定影响。