The surface integrity of metal micro-hole structures produced by electrochemical discharge machining is unsatisfactory owing to the insufficient reaction area and strength of electrolysis action. A novel ultrahigh-speed Rotary Electrochemical Discharge Machining (R-ECDM) using non-water-based electrolyte is proposed to improve surface integrity by changing the breakdown medium of spark discharge and increasing the reaction area and strength of electrolysis. A mathematical model was developed to establish the relationship between rotational speed and forces acting on the bubble. Based on the magnitude of forces, controlling rotational speed changed the behavior and departure radius of bubbles on the cathode surface. High-speed photographs validate that, in the mathematical model, the number and departure radius of bubbles on the cathode surface gradually decrease with the increase of rotational speed. The experimental results show that the roughness (R_a) of the micro-hole sidewall decreases from 2.54 μm to 0.20 μm when the rotational speed increases from 500 r/min to 40000 r/min. The length loss and wear ratio of the cathode are only 9.75 μm and 6.5%, respectively. Finally, the micro-holes array with recast-free and surface roughness of 0.20 μm is fabricated, demonstrating that the proposed approach contributes to improving surface integrity of metal micro-holes.

In aero-engines, mortise-tenon joint structures are often used to connect the blades to the turbine disk. The disadvantages associated with conventional manufacturing techniques mean that a low-cost, high-efficiency, and high-quality nickel-based mortise–tenon joint structure is an urgent requirement in the field of aviation engineering. Electrochemical cutting is a potential machining method for manufacturing these parts, as there is no tool degradation in the cutting process and high-quality surfaces can be obtained. To realize the electrochemical cutting of a mortise-tenon joint structure, a method using a tube electrode with helically distributed jet-flow holes on the side-wall is proposed. During feeding, the tube electrode rotates along its central axis. Flow field simulations show that the rotational speed of the tube electrode determines the direct spraying time of the high-speed electrolyte ejected from the jet-flow holes to the machining area, while the electrolyte pressure determines the flow rate of the electrolyte and the velocity of the electrolyte ejected from the jet-flow holes. The machining results using the proposed method are verified experimentally, and the machining parameters are optimized. Finally, mortise and tenon samples are successfully machined using 20 mm thick Inconel 718 alloy with a feeding rate of 5 μm/s.