Powder grading for enhanced properties in DLP 3D printed silica ceramic cores

Silica ceramic cores are widely used for forming the inner cavity in hollow turbine blade casting. While the employment of 3D printing brings complex shapes and high production efficiency of ceramic cores, the clear downside of poor properties hinders their practical applications in comparison with traditional ones. This work aims to improve the comprehensive performance of 3D-printed silica ceramic cores, where the proposed powder gradation design leads to silica ceramic cores with high porosity, low shrinkage, and excellent high-temperature flexural strength. DLP-based 3D printing was utilized for ceramic core fabrication here. The studies on the powder shape and size reveal the merits of spherical particles on the flow and irregular particles on the stationarity of ceramic slurry. The sintering process suggests that coarse powder provides sufficient porosity for the core, while medium and fine powder enhance the densification degree of the core. As a result, when the mass ratio of coarse, medium, and fine powders was 1:1:2 and sintered at 1200 ℃, the comprehensive performance of the ceramic core was significantly improved, with a high open porosity of 30 %, reduced shrinkage rate to 1.2 %, surface roughness Ra reduced to 1.25 μm, and the high-temperature flexural strength increased to 39 MPa. This study will provide theoretical guidance and data support for 3D-printed silica ceramic cores.