High-temperature performance of silica ceramic cores with additives prepared by stereolithography 3D printing

Ceramic cores are key to forming a cooling structure within the hollow blade cavities. The use of stereolithography (SL) 3D printing technology eliminates the need for moulds, facilitating the preparation of complex-shaped ceramic cores. In this study, silica-based ceramic cores incorporating nano-3YSZ (3mol.% yttria stabilised zirconia) and micron-sized Y 2 O 3 were prepared via SL 3D printing ceramic technology to promote the formation of cristobalite and ZrSiO 4 , thereby improving the high-temperature properties. The flexural strength at 25 °C and 1,500 °C, deflection at 1,500 °C, shrinkage rate, and porosity of the core samples sintered at different temperatures (1,170 °C, 1,185 °C, 1,200 °C, 1,215 °C, and 1,230 °C) were tested and investigated. The mechanism underlying the high temperature performance of the cores was elucidated through analysis of cross-sectional morphology, element distribution, and phase constitution of the samples. As the sintering temperature increases, the shrinkage and flexural strength at 25 °C of the core rise, while the open porosity and deflection at 1,500 °C decrease. When the sintering temperature reaches 1,200 °C or higher, the 1,500 °C flexural strength can be measured, which increases as the sintering temperature rises. The core exhibits excellent creep resistance when sintered at temperatures of 1,200 °C and above. Considering the comprehensive performance requirements for the core, the sintering temperature of 1,200 °C was selected. At the sintering temperature of 1,200 °C, the core exhibits shrinkage rates of 3.76% ( X ), 3.38% ( Y ), and 3.95% ( Z ), alongside a flexural strength of 9.01 MPa at 25 °C and 32.15 MPa at 1,500 °C, and an open porosity of 26.39%. The deflection of the core at 1,500 °C is 0.15 mm, which helps to maintain the dimensional stability of the ceramic core during casting. XRD results indicate that samples fractured after 25 °C flexural strength test still contain amorphous quartz glass, alongside substantial quantities of yttria stabilized zirconia and Y 2 O 3 . Samples fractured after 1,500 °C flexural strength test exhibit significant crystallisation of amorphous quartz glass into cristobalite, with silica and 3YSZ combining to form ZrSiO 4 . Y 2 O 3 as a network modifier of the glass network destroys the bridging oxygen in the silica-oxygen bond, thereby reducing the energy required for glass crystallisation and promoting the crystallisation reaction of quartz glass to form cristobalite. In addition, nano-3YSZ combines with SiO 2 at high temperatures to form ZrSiO 4 . Since cristobalite and ZrSiO 4 are crystals, both of them have strong creep resistance, thus improving the high temperature flexural strength and deformation resistance of the ceramic cores.