The cold gas dynamic spraying process solves many issues with respect to the deposition and additive manufacturing of metals. Namely, it provides a reduced reactive environment, simplicity of operation, and high deposition rates. It is known that the deposition efficiency of the cold spray process can be substantially increased using helium instead of nitrogen as the process gas. However, the use of pure helium can be cost prohibitive in many situations and commercially available helium recovery systems constitute a major capital investment on top of the spray system and ancillary equipment. This work focuses on the development and use of a novel, inline gas mixing system, designed to provide a blend of nitrogen and helium at any ratio. Deposits produced with different gas ratios were investigated through particle velocity, deposition efficiency, porosity, and hardness. The experimental results show that helium, even in lower percentages, can have a significant effect on deposition efficiency and that helium percentage can be optimized to reduce the overall coating production costs. From the results, a cost model is presented which, when provided experimental values and user costs, can be used to identify the nitrogen-helium ratio that will produce the lowest overall coating cost.

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