Optimizing mechanical performance and microstructural integrity in CaO-doped alumina ceramic cores by additive manufacturing

Alumina ceramics are crucial for high-performance applications, such as turbine blades, due to their excellent thermal stability and mechanical properties. However, existing fabrication methods often fail to balance strength, porosity, and dimensional precision. This study partially fills this research gap through a systematic investigation of calcium oxide (CaO) doping effects on alumina ceramic cores fabricated via ceramic stereolithography, with controlled doping ratios and sintering parameters. A ceramic paste was prepared using coarse and fine Al2O3 particles mixed with CaO as a sintering aid, followed by debinding and sintering to achieve optimal mechanical properties. The results show that CaO doping significantly enhances the flexural strength of alumina cores while maintaining porosity levels between 20% and 30% and controlling the sintering shrinkage rate to about 5%. Additionally, CaO doping alters the microstructure by inhibiting the transformation of spherical fine particles into flaky grains, improving sintering activity. However, as the CaO doping content increases, the bending strength increases, while the shrinkage rate of the material also tends to increase, resulting in a reduction in the overall porosity. This has a negative impact on the control of the manufacturing precision of turbine blades. Thus, although CaO doping improves strength and microstructure, achieving necessary dimensional control requires further optimization of doping content and sintering conditions.