Indirect powder bed fusion of spray dried industrial porcelain powders

Directly processing ceramics with high energy output Laser-based technologies is difficult and currently leads to poor results, making indirect Powder Bed Fusion (iPBF) an attractive alternative to produce porcelain parts. Severe lack of knowledge of industrial powders behaviour in iPBF, makes it difficult for industrial scale up. Rotating drum rheology was used to predict powder flow of PA12/porcelain mixtures. Although 50%wt PA12 showed superior flowability (lower cohesive index) and better packing (higher Hausner ratio) than PA12 it was unsinterable. Even with 25%wt special care was needed during depowdering/sintering, due to poor mechanical strength and large retraction (63% in volume). The overall shape and details are maintained after glazing. The printing direction mainly affected the surface topography, with few differences found in the microstructures of the sintered materials for all conditions and printing directions. All sintered parts have marginally the same physical (density < 2.52 g/cm3) and mechanical properties (flexural strength < 17 MPa) which suggest that the microstructure and resulting properties were majorly driven from the debinding and sintering cycles, instead of the printing conditions and orientation. To establish optimal printing and post-processing conditions for iPBF of industrial powders, we propose a framework based on Design, Feedstock, Printing and Post-processing relations that are complemented by advanced materials characterization, such as rotating drum powder rheology that is poorly explored in PBF. This work highlights the usefulness of iPBF to produce complex porcelain parts, from industrial feedstocks, and its disruptive potential to produce ceramic unique parts at a scalable industrial level.