Centrifugal investment casting of a TiAl-based turbine blade

Vertical centrifugal casting of TiAl-alloy blade casting in an investment shell was investigated. The Ti-Al-alloy melt was produced by induction skull melting. At first, the shrinkage of TiAl alloy was measured and found to vary from 1.35% to 1.89% corresponding to cast temperatures of 1 595degreesC 1 685degreesC. The filling process of molten metal under a vertical centrifugal force was mimicked with wax. The results shown that before the melt touched the end of the mold, its flow adhered the counter-face, and then it counter flowed toward the vertical axis. Based on the filling process, a method analogous to bottom injection was adoped for the centrifugal casting process. Misrun of the blade edges is the main defect in blade castings produced by the method. It can be eliminated by increasing the melt temperature and that rate of rotation of the centrifugal plate. However, the potential problems such as contamination of casting surface and safety must be carefully addressed.