Precision Casting of Titanium Alloy Closed Impeller via Stereolithography 3D Printing

Abstract:

To address the challenges of integrated shell molding in precision investment casting of titanium alloy closed impellers and the prolonged cycle time of conventional methods, a fabrication process for titanium alloy closed impellers based on stereolithography 3D printing has been developed. By optimizing powder bulk density by multilevel particle gradation and using ammonium citrate dispersants of 1.5wt% combined with alkaline environment of pH=10.0, a stable aqueous slurry with 62vol% solid content and 394 mPa·s viscosity was achieved, effectively suppressing Y₂O₃ hydration-induced slurry instability. The effect of key process parameters on molding performance was systematically investigated: the green body exhibits 18.9 MPa flexural strength at 62vol% solid content, which increases to 25.4 MPa after two vacuum impregnations with 20wt% nano-Y₂O₃ dispersion. Stereolithography 3D-printed resin prototypes combined with gel casting enable one-step fabrication of yttria molds with complex flow channels. Vacuum gravity casting successfully produces fully formed titanium alloy closed impellers, with no chemical sand adhesion observed after mold removal, and the microstructure characteristics and α layer thickness of the casting are essentially identical to those of ZTC4 casting produced by traditional investment casting process. Experimental results demonstrated that this process significantly shortens the lead time compared to traditional investment casting, providing a novel approach for cost-effective precision casting of high-performance titanium alloy components with complex geometries.