New approach to preparing near zero shrinkage alumina ceramic cores with excellent properties by vat photopolymerization

Abstract

Vat photopolymerization (VPP) 3D printing technology has broken through mold limitations and shown great potential to manufacture complex-structured ceramic cores for turbine blades. However, improving dimensional accuracy is difficult for the VPP 3D printed parts due to the high contraction deformation. Reducing shrinkage is a key challenge for developing 3D-printed ceramic cores. In this study, 3D-printed alumina ceramic cores with near-zero shrinkage in the X direction were achieved for the first time using a novel approach that was called atmosphere-controlled in-situ oxidation of aluminum powder. The in-situ oxidation reaction of the aluminum powder was creatively tuned by changing the atmosphere transition temperature from argon to air. Then, the microstructure and properties of the ceramic core could be controlled by the liquid-phase sintering with the participation of atmosphere-protected molten aluminum. As a result, the pore size of the ceramic cores was significantly increased by almost ten times, but the bonding strength of the grains was also increased. In addition, the powder consolidation generated by the action of molten aluminum was considered to be an important reason for reducing the linear shrinkage of ceramic cores. Under the optimized parameters, the linear shrinkage of the ceramic cores was as low as 0.3% in the X direction. The high apparent porosity (45.02%) and flexural strength (72.7 MPa) of the alumina ceramic cores were realized at the same time. The in-situ control of sintering by changing the atmosphere will be a creative method for regulating the properties of ceramic materials.