[en] Graphite powders were introduced in aqueous alumina paste to prepare alumina cores with high porosity using layered extrusion forming, which was a type of additive manufacturing methods. Rheological behaviours of pastes with different solid loading were tested. Paste composed of 50vol.% alumina loading and 5g graphite powders generated specimens with highest shape retention and finest surface quality. During formation and sintering process, basic shapes of rectangular specimens could be well maintained. With the increase of graphite addition, open porosity increased and flexural strength decreased of sintered specimens. Specimens prepared from paste with 50vol.% alumina loading and 10g graphite powders possessed best comprehensive performance, which was promising for application in alloys casting. (paper)

[en] Highlights: • A water soluble slurry was used as an easily removed support material. • Support material is suitable for different sinter temperatures (from 900 to1300 °C). • The salt-based support material can be removed easily after sintering. -- Abstract: The support material is necessary to prevent the collapse of the suspended structure when forming complex ceramic parts via layered extrusion forming (LEF, a type of additive manufacturing) method, and needs to be removed easily after sintering. In this work, salt-based slurries were prepared with magnesium sulfate monohydrate (MSM) and polyvinyl pyrrolidone (PVP) in order to solve the problem of extrusion and removal of the support material. The effect of the solid content on the rheological performance of slurries and the printing quality of specimens was studied. The results showed that the salt-based slurry containing 60 wt% MSM and 10 wt% PVP powder possessed shear-thinning behavior and the corresponding samples held sufficient bending strength and superior surface quality, which satisfied the requirements for the support structures in LEF method. After calcination at different temperature, the salt-based support structure could be easily removed, which offers an alternative support material choice for the LEF method.