Gelcasting of alumina based ceramic cores containing yttria for single crystal and directional solidification blades

Ceramic cores play an essential role in investment casting. In this paper, gelcasting process has been successfully employed to fabricate alumina based ceramic cores containing yttria for single crystal and directional solidification blades. Based on an investigation of the formability of different ceramic slurries, material compositions of ceramic cores are determined by experiments. A proper sintering process is developed to get low sintered shrinkage, high apparent porosity and high room temperature flexural strength. The high temperature properties of ceramic cores are improved by dipping in water based yttria sol and resintering. The test results show that comprehensive properties of alumina based ceramic cores containing yttria fabricated by gelcasting are better than those of AC-1 ceramic cores made by the Beijing Institute of Aeronautical Materials, China, and that the ceramic cores can be applied to single crystal and directional solidification blade casting.