Research On Superplastic Forming And Diffusion Bonding Technology Of Hollow Wide-chord Fan Blade

The hollow wide-chord titanium fan blade shows obvious advantages in weight control,efficiency promotion and impact resistance, which also improves thrust-to-weight ratio of the engine.They have been widely used in high-performance turbofan engines. Modern hollow fan blades are difficult to fabricate due to structural complexity along with strict integrative requirements. Combined forming processes based on superplastic forming and diffusion bonding(SPF/DB) have been widely adopted in production practice. However, the core technique has not been completely mastered by local manufacturers until now. With the rapid development of the domestic aviation industry, the demand for high-performance turbofan engine increases dramatically. The need for homemade hollow blade components becomes much more eager. This paper is concentrated on the critical technology in fabrication of the two-layer hollow wide-chord TC4 titanium fan blade based on SPF/DB technology,the corresponding research was conducted as follows.1. Technological difficulties in SPF/DB forming were analyzed according to the blade structural feature. Then a process using three times of heating cycle was proposed and specified. Quality test methods were determined according to the quality requirement.2. Based on the inverse approach of FEM, the blank shape optimization was performed in commercial software ABAQUS. The initial blank surfaces were rebuilt using geometry reconstruction technique, and 3-D model was prepared for the blank machining.3. The diffusion bonding process of ribbed blade blanks was studied. Important process details such as parameters selection, joint face pretreating, cavity dimension calculation and locative structure design were specified. Integral hollow blanks were fabricated successfully through experiment. Ultrasonic C scan and microstructure check shows that diffusion bonding quality can meet the requirement.4. The hot-twist preforming approach of hollow blanks was studied. The motion rule of twist clamps was analyzed based on the mechanism design. Through numerical simulation, the difference of single-axis twisting and double-axis twisting was investigated, and proper parameters were selected.The hollow blank was formed to the desired in-process shape as expected.5. The blade finishing process was studied based on the preformed shape. Mold pressing forming along with gas-load superplastic forming were used to correct the blade geometric profile and smooth the skin. The die and gas circuit were designed. Numerical simulation was carried out to investigatethe effect of speed, holding time and maximum value of gas pressure. Proper process parameters were selected to conduct the experiment. The hollow blade prototype with intact structure, uniform skin thickness and precise profile was made successfully.The research conquers several key technologies in two-layer hollow titanium fan blade fabrication. Smaller quantities of hollow wide-chord TC4 titanium fan blades have been successfully manufactured. Quality test results show that the obtained component can fully satisfy the technical requirement. The presented work provides an important reference for the development of homemade large-scale hollow wide-chord titanium fan blade.