Debinding and Sintering of Dense Ceramic Structures Made with Fused Deposition Modeling

Abstract

Shaping and thermal processing of ceramic structures with fused deposition modeling (FDM) is promising, but still a challenging technique. Achieving an optimal compromise between the thermoplastic feedstock properties in terms of 3D printing and debinding behavior is not trivial. In this paper aluminum oxide (Al2O3), zirconium oxide toughened aluminum oxide (ZTA) and ZrO2 (zirconium oxide) thermoplastic filaments were developed for multi-material printing of 2-2 and 3-3 composites using a Bowden extruder with 2.8 mm filament thickness. For all filaments, a thermoplastic binder based on Ethylene Vinyl Acetate (EVA) and stearic acid (SA) with a ceramic filler content of 45 vol.% were used. Increasing the SA content, it was possible to use the solvent debinding process and therefore the thickness of the printed structures could be increased up to 10 mm. After 2 h in acetone solvent, more than 40 wt% could be removed. With additional thermal partial debinding process at 240 °C for 8 h, up to 82 wt% of the thermoplastic binder could be removed successfully. The monolithic printed discs achieved a relative density of 98.2 and 99.1% for the ZTA and the ZrO2 samples, respectively. Finally, the mechanical properties were investigated by ring-on-ring bending test method based on ASTM standard. For ZrO2 discs a mechanical strength of 429 MPa could be achieved. By mixing 5% yttrium stabilized ZrO2 with Al2O3, the mechanical strength could be increased from 220 (pure Alumina) to 297 MPa (ZTA). For the 2-2 composite, a mechanical bending strength of 214 MPa could be achieved.