High-efficient compound sinking machining of Ti6Al4V with the assistance of oxygen

Arc machining is suitable for efficiently processing typical difficult-to-cut material Ti6Al4V. Traditional arc sinking machining commonly uses water-based dielectric because of its safety and good cooling capacity. However, water-based dielectric generally has high conductivity that causes frequent short circuits and strong electrolytic reactions during machining, thereby reducing machining stability and deteriorating machining performance. This paper proposes a novel high-efficient compound sinking machining that combines arc machining with electrical discharge machining (EDM). The dielectric is formed by dispersing oxygen into deionized water, thus reducing the shortcomings of traditional water-based dielectric and introducing the advantages of gas-based one. The feasibility of the proposed method is systematically studied compared to the method that uses deionized water. Influences of oxygen pressure, pulse duration, and peak current are investigated. Characteristics of surface topography and recast layer are also studied. Results suggest that the properties of dielectric improve, and the machining stability and machining intensity increase with the assistance of oxygen. Therefore, compared with using deionized water, the proposed method shows better processing characteristics, including larger material removal rate (MRR), smaller relative electrode wear rate (REWR), and thinner recast layers. The proposed method is promising to process Ti6Al4V due to its high efficiency and environment-friendly properties.