Effects of a Binary Argon-Helium Shielding Gas Mixture on Ultra-Thin Features Produced by Laser-Powder Bed Fusion Additive Manufacturing
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Date
2021-05
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The Ohio State University
Abstract
The practice of Additive Manufacturing (AM) is currently the subject of extreme research interest as it
becomes increasingly available and feasible across multiple industries. Key characteristics of AM
processes include accelerated prototyping and increased design possibilities, with metal-based
processes such as Laser Powder Bed Fusion (L-PBF) proposing functional part production. However, the
current state of technology lacks the validation necessary to fully implement AM in place of traditional
manufacturing for established materials in industry. Through the implementation of fundamental
Materials Science and Welding Engineering concepts, an intersection between manufacturing process
and material properties informs the gap in information needed for further validation. The study of ultra thin features is accomplished through the manipulation of a Concept Laser Mlab Cusing LPBF machine
within the Welding Engineering department at The Ohio State University, to produce a series of fins
each produced by the single pass of the process laser composed of 316L stainless steel. Such fins allow
metallographic analysis to study and report the microstructural evolution of an AM part at the finest
resolution the process is capable of. Similarly, by only allowing single passes of a laser, remelting, and
reheating of material during printing is effectively studied without experiencing interference of
subsequent exposure to the process laser. Having successfully isolated this aspect of the printing
process, effects of adjusting shielding gas composition are studied by alternating argon and argon helium gas mixtures during the building process. Explained by differences in thermal conductivity of the
gasses, the effective thickness of each fin is shown to be larger when printing under the pure argon
condition, supported by metallographic evidence. However, fins printed under an equal mix of argon
and helium produce more consistent fins, with those designed to be overhanging proven to be produced
at an angle more near that of design than those produced under the pure argon condition. Under the
current state of research, fin deformation by thermal stresses is being studied, as such deformation is
detrimental to the accuracy of practical part manufacturing. Furthermore, the capabilities of the LPBF machine are being expanded to handle higher concentrations of helium to develop a wider range of data
to study. As the effect of shielding gas is better understood, its manipulation and effects on the resultant
part will be validated, further allowing the manipulation of this key parameter of the LPBF process in
industry.
Description
Keywords
Additive Manufacturing, Shielding Gas, Welding, Argon Helium