Study on the machining characteristics of high-efficiency mixed gas atomized discharge ablation process of titanium alloy

Abstract

Titanium alloy is widely used in aerospace and other industry fields because of its excellent physical and chemical properties. However, the fabrication process is still a challenge for the traditional machining processes due to the ultra hardness and chemical reactivity properties of titanium alloy. Electrical discharge machining (EDM) is a significant processing approach to machine titanium alloy regardless of hardness, while accompanied by disadvantages such as electrode wear and low machining efficiency. This paper proposed a novel mixed-gas atomization discharge ablation process (MA-DAP) method for high-efficiency machining titanium alloy with low tool wear. An atomized dielectric formed by a mixed gas, which mainly composed of oxygen and supplemented by nitrogen, and water medium was used in the machining process. The exothermic oxidation between the oxygen component in the atomized dielectric and high-temperature molten material activated by spark discharges could multiply accelerate material removal of workpiece. The explosive effect generated by the vaporization expansion of the water component in the dielectric would improve the machining quality and the processing capability of large depth-to-diameter ratio holes. To investigate the machining characteristics of the new approach, comparative experiments were conducted in terms of material removal rate, electrode relative wear rate, machining accuracy, surface morphology, and recast layer. The experimental results showed that, compared with traditional EDM, the material removal rate of MA-DAP was dramatically increased by more than an order of magnitude, and other technological indexes are greatly improved simultaneously. A deep-shaped blind hole with a depth-to-diameter ratio greater than 12 was obtained by the MA-DAP.