Design and Validation of a Novel Process Solution for Electrically Assisted Superalloy Capillary Microforming

Ultrathin-walled superalloy capillaries, with an outer diameter of 0.9 mm and a wall thickness of 50 to 60 μm, are indispensable components of the heat exchange system in hypersonic precooled aeroengines. To meet rigorous standards for dimensional accuracy and mechanical properties under extreme conditions, this study proposes a process solution design methodology for a novel and green electrically assisted (EA) capillary microforming technology. The methodology systematically addresses three key aspects: critical components, process route, and process parameters. Innovative designs for critical components, including the charging method, charging device, and drawing die, ensured stable excitation of capillaries by pulsed current during the EA drawing process. Given the variations in superalloy elongation under room temperature and EA tension, the EA capillary microforming process route was derived from the conventional capillary microforming process route, which was designed through theoretical calculations and validated by finite element simulation. The temperature and stress field distributions within capillaries during the EA drawing process were analyzed to calculate the drawing safety factor for various passes and temperatures, determining the optimal temperature in the drawn region that maximizes the electroplastic effect while ensuring safety. Additionally, optimal temperature and duration ranges for intermediate EA capillary annealing treatments were established based on the mechanical properties of pre-strained superalloy plates after EA annealing. The effectiveness of the designed process solution was preliminarily validated through process experiments.