Rapid casting of hollow turbine blades with converging-expanding film cooling holes

In this paper, a novel indirect solid freeform fabrication process was developed by combining gelcasting with stereolithography (SL) technique to manufacture integral ceramic casting molds for hollow turbine blades with converging-expanding film cooling holes. Based on the model of hindered drying shrinkage, a calculation formula of critical drying shrinkage was derived. Through experimental research, freeze-drying characteristics of gelcasting green bodies were discovered. The freeze-drying shrinkage was increased with water lose degree. After losing about 50 percent of water, the green body stopped shrinking. With the decrease of pre-freezing temperature, the freeze-drying shrinkage reduced. A suitable lyophilization process was adopted to control the freeze-drying shrinkage, and the structural integrity of ceramic casting mold was maintained. A rapid casting case study was presented to verify the feasibility and effectiveness of the proposed process.