Single crystal casting of gas turbine blades using superior ceramic core

Abstract A ceramic core employed in a single-crystal casting process should endure for a long time at casting temperatures above 1500 °C. Therefore, in this work, an inorganic binder was applied to a conventional injection-molding method to produce a core having enough strength during the casting process. The starting powders for the ceramic core used a mixture of three kinds of fused silica with particle sizes of 117 μm, 33 μm, and 17 μm, zircon flour of 10 μm, and silicon carbide of 16 μm. The mixed ceramic powder was coated with a silica precursor and then dried at 80 °C for 1 h. The dried powder was mixed with wax and injection molded. The injected ceramic core was heat-treated at 1200 and 1500 °C for 1 h,and then reheated at 1550 °C for 3 h. The heat treatment at 1550 °C was conducted to investigate the applicability of the core coated with the inorganic binder in the casting process. The inorganic binder-coated core with a superior firing strength had no cracks or surface defects after the heat treatment, compared with the core without the inorganic binder. In addition, the turbine blade of 150 mm length was well cast as a single crystal and the internal core was completely eluted.