High-performance 3D-printed Al2O3 cores for low-temperature sintering

Superalloy single-crystal blades are essential components of aviation engines. The increased thrust-to-weight ratio in aviation engines necessitates more stringent requirements on the complex ceramic core formation of the internal cooling channel of the hollow blade. The progress of traditional hot injection processes for ceramic cores has difficulty meeting the increasingly complex core production requirements. Vat photopolymerization 3D-printing technology for ceramic core fabrication has the advantages of not requiring mold manufacturing and flexible shaping, making it widely used in the production of complex structured ceramic cores. In addition, the industrial applicability of Al2O3 ceramic cores is limited by their low performance and high sintering temperature. In this work, high-performance Al2O3 cores with low-temperature sintering were successfully fabricated using DLP-3D-printing technology. The effects of Y2SiO5 addition and sintering temperature on the microstructure and properties of Al2O3 ceramic cores were investigated. The sintering mechanism of Al2O3 ceramic cores was investigated through analysis of phase composition, microstructure, and thermodynamic calculations. The results of the work show that, the flexural strength and sintering shrinkage of the Al2O3 ceramic cores progressively increased as the sintering temperature increased, while the open porosity rapidly dropped. The density of the Al2O3 ceramic cores increases significantly when the sintering temperature exceeds 1450 °C. The optimum sintering temperature for the ceramic core (15 wt% addition of Y2SiO5) is 1350 °C, at which point the strength is 20.282 MPa and the open porosity is 39.31%. This work provides a new process of the high-performance Al2O3 ceramic cores for low-temperature sintering, which reveals the mechanism of Y2SiO5's effect on the densification of Al2O3 ceramics during sintering.