Achieving superior thermal stability in vat photopolymerized silica-based ceramic cores via kyanite-induced expansion compensation

Vat photopolymerization (VPP) 3D printing has emerged as a predominant technology for fabricating complex-shaped ceramic cores used in aero-engine hollow turbine blades. However, the inherent limitations of VPP 3D printing-fabricated silica-based cores, such as excessive sintering shrinkage and high high-temperature deflection, have severely restricted their application in high-performance investment casting. In this study, we proposed a novel strategy to overcome this challenge by introducing kyanite into the silica-based ceramic core. The influence of kyanite content on microstructural evolution and comprehensive properties was systematically explored, and a Ceramic Cores Quality Index (CQI) model was further established to evaluate the comprehensive performance. The results indicated that when kyanite content exceeded 15 wt.%, the volume expansion resulting from high-temperature decomposition effectively inhibited sintering shrinkage within the temperature range of 1300 °C to 1400 °C. Furthermore, the columnar mullite crystals generated from the decomposition acted as the key factor enhancing the high-temperature performance. Optimal comprehensive properties, corresponding to a maximum CQI score of 78.85, were achieved with a kyanite content of 15 wt.% and a sintering temperature of 1225 °C. Under this condition, the sintering shrinkage and casting shrinkage of ceramic cores were reduced to 3.06% and 0.86%, respectively. Additionally, the high-temperature deflection was significantly decreased to 0.82 mm, while the flexural strength and high-temperature flexural strength reached 10.06 MPa and 27.05 MPa, respectively. This study provides a novel strategy for fabricating silica-based ceramic cores with a lower sintering and casting shrinkage, while elucidating the regulatory mechanism of kyanite on the core properties.