Influence of Metallic Powder Characteristics On Extruded Feedstock Performance For Indirect Additive Manufacturing

Abstract Material Extrusion (MEX) of metallic powder-based filaments has been showing great potential as an additive manufacturing technology. MEX provides an easy solution, as an alternative to direct additive manufacturing technologies (e.g. SLM, EBM, DED) for problematic metallic powder, like copper powder, due to its reflectivity and thermal conductivity. MEX, an indirect technology, consists of 5 steps – optimising metal powder, mixing (feedstock), filament production, shaping, debinding and sintering. The great challenge in MEX is, undoubtedly, filament manufacturing for optimal green density, and consequently the sintered properties. The filament, to be extrudable, must accomplish at optimal powder volume concentration (CPVC) with good rheological performance, flexibility, and stiffness. These have a main role in the quality of the 3D objects after debinding and sintering. In this study, a feedstock composition (similar binder, additives and CPVC - 61% vol.) of copper with three different particle powder characteristics was selected, in order to highlight their role. The quality of the filaments, strands and 3D objects was analyzed by micro-CT highlighting the influence of the different powder characteristics on the homogeneity and defects of the greens. Sintered filaments were also analysed, regarding hardness, microstructure and a comparison between green and sintered defects, using micro-CT. The filament based on particles powder with D50 close to 11 µm and straight distribution of particles size shows the best homogeneity and lower defects.