Additive manufacturing (AM) has during years gained significant interest owing to its endless component design possibilities. One of the most popular AM techniques is laser powder bed fusion (LPBF), which selectively melts metal powder layer-by-layer in a chamber with protective argon atmosphere. This technique is attractive for realizing Cu-based products in which the high electrical conductivity of Cu is combined with component design possibilities. The successful use of Cu powder not only poses challenges owing to the high reflectivity and thermal conductivity of Cu but also involves the important concern of controlling the powder surface chemistry since the powder surface constitutes the main source of oxygen. It is of crucial importance to control the oxygen level in order to maintain good electrical conductivity and brazing ability of the AM-fabricated Cu-part. In LPBF, fine spherical powder with size of 10-60 mu m is used, providing significant specific surface area, and this powder is also usually recycled several times, and hence, the role of powder surface chemistry is evident. Two kinds of copper powder with purities 99.70 and 99.95 wt% were analysed in both virgin and in used conditions after numerous printing cycles using LPBF. The powder was analysed by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). A clear difference between the two powder grades in terms of surface chemistry was observed. The oxide thickness and bulk oxygen content increased for both powder grades after recycling. The surface oxides under different conditions are identified and the effect of powder purity on the oxide formed is discussed.

中文翻译：

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用于增材制造的铜粉的表面化学分析

多年来，增材制造 (AM) 因其无尽的组件设计可能性而引起了人们的极大兴趣。最受欢迎的 AM 技术之一是激光粉末床融合 (LPBF)，它在具有保护性氩气的腔室中选择性地逐层熔化金属粉末。该技术对于实现铜基产品具有吸引力，其中铜的高导电性与组件设计的可能性相结合。由于铜的高反射率和热导率，铜粉的成功使用不仅带来了挑战，而且还涉及控制粉末表面化学的重要问题，因为粉末表面构成了氧气的主要来源。为了保持 AM 制造的 Cu 部件的良好导电性和钎焊能力，控制氧含量至关重要。在LPBF中，使用尺寸为10-60μm的细球形粉末，提供了显着的比表面积，并且这种粉末通常也被回收多次，因此粉末表面化学的作用是明显的。在使用 LPBF 进行多次印刷循环后，在原始和使用条件下分析了纯度为 99.70 和 99.95 wt% 的两种铜粉。通过 X 射线光电子能谱 (XPS) 和扫描电子显微镜 (SEM) 分析粉末。观察到两种粉末等级在表面化学方面存在明显差异。回收后两种粉末等级的氧化物厚度和整体氧含量均增加。