A closer look at shielding gas in laser powder bed fusion: a review

Abstract The ongoing advancement of additive manufacturing (AM) techniques, particularly in laser powder bed fusion (LPBF), is effectively bridging the knowledge gap between AM and conventional manufacturing methods. At present, most of the research is focused on optimizing key process parameters such as laser power, laser speed, hatch spacing, layer thickness, scan pattern, powder size distribution, and so on. These studies help improve the part density and refine the microstructure of LPBF components, thereby enhancing the mechanical properties. Despite these advancements, an area in LPBF that is receiving comparatively less attention is the shielding gas: its flow during the printing process, and its relationships to the underlying structures and properties of AM materials. Shielding gas plays an important role during the printing process by creating an inert medium so the printed parts do not react with the atmosphere while also facilitating the removal of any process by-products that develop during the printing. Within the scientific community, there is an absence of review articles that summarize current research on shielding gas flow. This work addresses this gap by reviewing the current literature on different shielding gases used, how the printer gas inlet design configurations help in the uniform flow of the gas, the role of the gas in the elimination of by-products, and their influence on the melt pool, part quality, and repeatability. All aspects discussed in this review article are crucial to the advancement of metal AM processes that require the use of a shielding gas, specifically LPBF, and the qualification of materials produced for a variety of industrial applications.