New approach for controlling sintering shrinkage and properties of additively manufactured silica-based ceramic cores

Silica-based ceramic cores are widely used in the manufacture of hollow aero-engine turbine blades due to their excellent leaching performance and mechanical properties. However, their application is limited by high sintering shrinkage and insufficient high-temperature strength, which adversely affect dimensional accuracy and service reliability. This study introduces aluminum powder, which undergoes in-situ oxidation to form Al2O3. In-situ oxidation of aluminum powder is accompanied by volume expansion, which effectively counteracts the sintering shrinkage of ceramic cores. Compared to samples without aluminum, those modified with 2 wt% aluminum powder exhibited significantly reduced anisotropic shrinkage of 53%, 76%, and 76% along the X, Y, and Z axes, respectively, and achieved an open porosity of 30 ± 3 vol%. Additionally, the aluminum powder addition provides higher surface energy, promoting sintering densification and leading to strengthened mechanical properties of the ceramic core. The ceramic core with 1.0% aluminum powder demonstrated satisfactory high-temperature mechanical performance, achieving a flexural strength as high as 17.13 ± 1 MPa at 1500 °C, compared to its room-temperature strength of 10.02 ± 0.8 MPa. This study provides a theoretical foundation for the precision and performance control of high-performance, geometrically complex ceramic cores in additive manufacturing.