An Economical Approach to Cold Gas Dynamic Spraying using In-Line Nitrogen-Helium Blending

The cold gas dynamic spraying process provides a solution in regards to the deposition and additive manufacturing of metals due to the reduced reactive environment, its simplicity of operation, and the high deposition rates it offers. It is known that the deposition efficiency of the cold spray process can be substantially increased by switching the process gas from nitrogen to helium. However, running pure helium can be cost prohibitive in many situations and commercially available helium recovery systems are large and constitutes a major capital investment on top of the spray system and ancillary equipment.

This work focuses on the development and use of a novel, in-line gas mixing system, designed to provide a blend of nitrogen and helium at any ratio. Deposits produced with different gas ratios were investigated through 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 costing model is proposed which when provided experimental values and user costs, will find the optimized nitrogen-helium ratio that will produce the lowest overall coating cost.