Thermal behavior of integral Al₂O₃-based ceramic molds for fabricating gas turbine blades

Integrating ceramic shell and ceramic core for the fabrication of gas turbine blade is a promising method based on stereolithography and gelcasting technologies. But the cracking in the integral Al₂O₃-based ceramic mold takes place readily during casting process. The effect of hydrostatic pressure and thermal shock resulting from high-temperature liquid metal on the stress in Al₂O₃-based ceramic mold was respectively investigated, and the thickness of ceramic shell was also studied. The results show that the thermal stress is the main reason for the cracking in Al₂O₃-based ceramic mold, and the thickness of ceramic shell has a significant effect on thermal shock of liquid metal. The optimal value of Al₂O₃-based ceramic shell thickness is 9 mm so as to decrease its thermal stress effectively. Compared with micronsized Y2O3 powders, nano-Y2O3 powders are more beneficial to improve high-temperature fracture strength of Al₂O₃ ceramic mold. Finally, a gas turbine blade is successfully fabricated.