Offline powder-gas nozzle jet characterization for coaxial laser-based Directed Energy Deposition

One of the major challenges faced by laser-based Directed Energy Deposition (DED) is the process efficiency. This efficiency is significantly affected by the percentage of blown powder that effectively reaches the spherical metal melt pool. Increasing the powder efficiency would allow to reduce the overall costs of the DED process and consequently reduce the printed part cost. The present work focuses on the experimental characterization of the powder-gas jet in terms of powder stream shape, stand-off distance and powder-jet focus diameter by using 3 different high speed image-based approaches. The powder jet parameters are linked to the blown powder settings (carrier gas, shielding gas, powder feed rate, particle diameter) and optimized to minimize the powder waste. The different approaches give equivalent results and the reduction of the particle diameter turns out to be the most relevant parameter to decrease the powder-jet focus diameter and therefore increase the powder efficiency.

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