Controlled anisotropy in 3D printing of silica-based ceramic cores through oxidization reaction of aluminum powders

Ceramic cores are key components to form inner hollow structures in aero-engine blades, and 3D printing is an ideal molding technology for ceramic cores. In this work, silica-based ceramic cores are fabricate via 3D printing of digital light processing (DLP) stereolithography, and the anisotropy in microstructure and property are controlled by aluminum powders. The ceramic cores without aluminum powders exhibit anisotropic microstructure with interlayer gaps, which get narrower and disappear with doping of 7.5–10 wt% of aluminum powders, due to the volume expansion during oxidization reaction of aluminum powders filling the interlayer gaps. The anisotropy in mechanical property is rely on the printing direction, and the ratio of strength in different directions (σV/σH) is put forward to value the mechanical anisotropy; the ratios rise from 0.40 to 0.92 at room temperature and 0.51 to 0.97 at 1540 °C, as 7.5 wt% of aluminum is doped, and the optimized ceramic cores show high-temperature strengths of 16.6 MPa and 16.1 MPa in different printing directions. Even though ceramic cores with 10 wt% of aluminum show uniform microstructure and higher σV/σH ratio, the weak particle bonding within printing layers limits their mechanical property, and the strengths decrease to 13.8 MPa and 13.4 MPa at 1540 °C. This work inspires a new technique to excellent high-temperature mechanical properties with anisotropy control in 3D printing of ceramic cores.