Chopped carbon fibers as pore-forming agent to fabricate the integral ceramic mold

Based on stereolithgraphy (SL) and gelcasting technologies, the integral fabrication technique of ceramic mold for hollow turbine blade was put forward. The casting process of blade requires that the ceramic mold should have a porous microstructure for gas permeability and deformability to prevent hot tearing of the alloy. In order to fabricate a mold with controlled porosity, chopped carbon fibers were introduced as pore-forming agent in this study. The result found that the drying shrinkage of green samples was reduced to 0.12% after carbon fibers (CFs) were added. Unlike traditional pore-forming agents, the mid-temperature strength (400 °C) was improved rather than decreased from 1.75 to 3.42 MPa. The porosity of the final mold increased from 26% to 39.7%, while hollow rod arrays (microtubes) could be observed by scanning electron microscopy (SEM). At last, a bulk ceramic mold for a gas turbine blade was fabricated successfully, which was validated by X-ray scan.