Directed Energy Deposition Using Non-Spherical Metal Powders?

Metal additive manufacturing (AM) enables the production of non-trivial geometries and intricate internal structures. Directed energy deposition (DED) is one such AM process that has the inherent advantage of producing multi-material components on complex pre-existing geometries. Significant recent interest in DED processes has been driven by the need for inexpensive powders and potential material recycling. In this work, we explore the possibility of using non-standard arbitrary shaped metal powders within the DED process. A standard numerical model, comprising a three-dimensional viscous, compressible, turbulent solver with two-way discrete phase coupling is employed to understand the mechanics of gas-driven non-spherical powder flow. Spatial distributions of non-spherical powder on a set of pre-existing geometric features (e.g., corners, curved surfaces) are evaluateds and compared with standard spherical powders. The effect of particle collisions on the substrate is evaluated and corresponding density distributions are quantified. Non-spherical particles are generally found to exhibit higher velocities, and greater deposition track width, compared to spherical particles. Our simulations also reveal the effect of particle shape on their flow properties and final powder density. Using a custom-built DED configuration, we present preliminary experimental results of single-track depositions using both spherical and non-spherical powder particles. Based on our findings, we make a case for the use of non-spherical powders for DED applications.