Control of dimensional accuracy of hollow turbine blades during investment casting

Abstract

Because of their variable airfoil cross sections and internal hollow cavities with complex serpentine shapes, hollow turbine blades are prone to sectional deformation during investment casting, resulting in dimensional errors. To control the deformation of turbine blades, a novel one-step reverse compensation method based on a variable shrinkage factor is proposed in this study. First, the directional solidification process was simulated to predict the deformation distribution of the turbine blades. The deformation of the airfoil and platform increases further after constraints removal, with the trailing edge of up to 0.4192 mm. Subsequently, the shrinkage rate of each finite element node of the turbine blades was calculated to guide the mold design. Finally, three cross sections of the blade were validated using a coordinate measuring machine. The experimental results show that the optimized deformation using the proposed method is within the design requirement of 0.15 mm, and the maximum deformation of the blade has lowered by 68.2 %, which indicates that the dimensional accuracy of the hollow turbine blades is effectively controlled.