Directed energy deposition of metal matrix composites: Computational and experimental comparison of powder particle flow behavior

Abstract

Directed energy deposition (DED) additive manufacturing of metal matrix composites (MMC) involves a mixture of metal and ceramic particles with a range of sizes, morphologies, and densities. Such a heterogeneous mixture of physical characteristics makes it difficult to establish optimum deposition conditions, and hence extensive parametric experiments are often needed to optimize the microstructure and performance of a final component. To provide insight into the behavior of metal and ceramic powders during DED, we report on a study that uses two complementary approaches. First, we formulate a 3-dimensional COMSOL numerical model to simulate the particle trajectories under the influence of gas flow, particle-gas interactions and particle-wall collisions. Second, we implement high-speed photography to examine and compare the powder flow behavior of metallic particles (Inconel 718) and ceramic particles (TiC). Our results reveal that there are distinct differences in particle velocity and spatial distribution between the Inconel 718 and TiC particles, due to the dissimilar particle sizes, morphologies, material densities, and particle collision behavior. By understanding these differences, as presented here, targeted compositions and homogeneous reinforcement distribution can be attained in DED components through proper material and process parameter selection; furthermore, the custom design of tailored microstructures for heterogenous functionality can also be achieved.