Thermal behavior of integral Al_2O_3-based ceramic molds for fabricating gas turbine blades

摘要

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 Al_2O_3-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 Al_2O_3-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 Al_2O_3-based ceramic mold, and the thickness of ceramic shell has a significant effect on thermal shock of liquid metal. The optimal value of Al_2O_3-based ceramic shell thickness is 9 mm so as to decrease its thermal stress effectively. Compared with micronsized Y_2O_3 powders, nano-Y_2O_3 powders are more beneficial to improve high-temperature fracture strength of Al_2O_3 ceramic mold. Finally, a gas turbine blade is successfully fabricated.