The development of new composite materials for polymer powder bed fusion (PBF/P) is seen as one of the main drivers for further growth of the technology and its industrial application. This study compares two different methods for producing filled polymer powders. The first method is dry blending a commercially available polymer powder with a filler. The second method is to compound polymer and filler and prepare a powder afterward by cryogenically milling the granulate. The thermal and rheological properties of the powders, as well as their particle size and powder flowability, were compared, and the impact of these properties during laser powder bed fusion (PBF-LB/P) processing was analyzed. Dry blending proved effective only with spherical fillers with a particle size above 13 μm, as smaller particles significantly impaired powder flowability and reduced the tensile strength of the specimens produced by PBF-LB/P. Dry blended fibers aligned with the recoating direction and caused a significant anisotropy. Cryogenic milling was found to be an effective method for incorporating spherical fillers that are at least one order of magnitude smaller than the powder particles typically used in PBF/P. The tensile strength could be increased by up to 50% by compounding and milling the powder with fine glass beads compared to an equivalent dry blend.
Kletetzka et al. (Sat,) studied this question.