The Impact of Organic Bentonite Content on the Properties of Stereolithographic 3D-Printed Silicon-Based Ceramic Core Paste

With the advancement of aero-engine thrust-to-weight ratios, turbine blades now incorporate complex hollow structures fabricated using ceramic cores. The emergence of light-curing 3D printing technology for ceramic cores offers a viable solution to producing such complex structural components. To avoid the breakage of the core when removing the support after the printing of the general paste, we used a rheological additive, organic bentonite, to prepare a light-curing 3D-printed silicon-based ceramic core paste that can allow for unsupported printing. This study pursues two primary research objectives: Firstly, the effect of organic bentonite on the rheological behavior and stability properties of silicon-based ceramic was investigated. Secondly, we conducted a comprehensive analysis of how organic bentonite modification influences the performance of silicon-based ceramics. The results show that, firstly, the addition of organic bentonite dramatically improves the rheology and stability of silicon-based ceramic paste, and that the optimal content is between 1 and 2 wt.% for the best effect. Second, after the primary sintering process (1250 °C), partial bentonite can produce a small amount of cordierite phase and promote the generation of cristobalite. The room-temperature performance of the ceramic core can be improved. However, organic bentonite, after secondary sintering at 1550 °C, completely forms cordierite and reduces the amount of square quartz produced. Then, it negatively affects the high-temperature performance of the ceramic core. Therefore, when the content of organic bentonite is 1 wt.%, the ceramic paste has superior rheology and stability, making unsupported printing possible. Our study revealed an apparent porosity of 32.43%, a bulk density of 1.64 g/cm³, a sintering shrinkage value of 2.94%, a room-temperature flexural strength of 24.7 MPa, a high-temperature (1550 °C) flexural strength of 10.1 MPa and a high-temperature deflection of 1.24 mm, which meet the requirements of core printing.