Improving high temperature properties of alumina based ceramic cores containing yttria by vacuum impregnating

Ceramic cores used in investment casting for directional solidification and single crystal blades must have excellent high temperature properties. A strengthening process was developed to improve high temperature properties of alumina based ceramic cores containing yttria. Besides, different parameters, including reinforcing agent, the number of times of vacuum impregnating, were investigated. The experimental results showed that aqueous yttria sol can improve the high temperature properties of ceramic cores through multiple impregnating, which made it a suitable reinforcing agent. Considering the effects of the strengthening process on the apparent porosity and sintered shrinkage of ceramic cores, the optimal vacuum impregnating process was determined. Furthermore, the strengthening mechanism was revealed by using X-ray diffraction and electron spectroscopy analysis. The high temperature properties of the strengthened ceramic cores can meet the requirements of directional solidification and single crystal casting, which benefits the production of turbine blades.