Evaluating gas-driven flow mechanics of non-spherical powders for directed energy deposition

The size and shape of metal powder particles play a central role in the performance and utility of directed energy deposition (DED) based metal additive manufacturing processes. Given their significant economic advantage, unconventional non-spherical metal powders have recently emerged as a potential, economically viable, alternative for use as DED feedstock. In this work, we investigate the mechanics of carrier-gas driven powder flows for non-spherical metal powders using coupled experiments and numerical simulations. The experiments are performed on a custom-built DED system that allows us to individually vary both gas and powder flows systematically. By suitably adjusting the flow conditions to ensure equal mass flow rates, we show that non-spherical powders compare favorably against gas atomized spherical particles vis-a-vis final concentration distribution and flow mechanics. The differences between these two types of powder particles are quantified with flat, angled and curved substrate geometries, allowing predictions for many practical deposition situations. The simulations use a two-way discrete phase model and predict best (perfectly elastic) and worst (perfectly inelastic) case concentrations on the substrate by varying the particle restitution coefficient. Our results suggest suitable process modifications (gas flow rate, feed rate, axis traverse speed) to facilitate the use of non-spherical powders alongside conventional spherical powders in DED processes.

Automated summary

The size and shape of metal powder particles are crucial for directed energy deposition (DED) based metal additive manufacturing processes. Unconventional non-spherical metal powders have emerged as a potential alternative feedstock for DED due to their economic advantage. This study investigates the mechanics of carrier-gas driven powder flows for non-spherical metal powders through experiments and numerical simulations, showing that non-spherical powders compare favorably to spherical particles in terms of final concentration distribution and flow mechanics. The results provide insights into suitable process modifications to facilitate the use of non-spherical powders in DED processes.