Experimental investigation on the effects of green dielectric medium air and argon on the near-dry electrical discharge machining of titanium alloy

Near-dry electrical discharge machining (EDM) is an environmentally friendly method that uses a two-phase atomized medium composed of gas and water as the discharge dielectric. The relevant research literature shows that the material removal rate (MRR) of steel materials processed by near-dry EDM with air medium (Air-NEDM) is higher than that of near-dry EDM with inert gas medium. However, the results of this present show that when argon is used as the gas medium for near-dry EDM (Ar-NEDM) to process titanium alloy, the MRR is more than 80% higher than that of Air-NEDM. Therefore, the material removal mechanism of near-dry EDM in air medium and argon medium is studied by single-pulse discharge experiment. Then, the effects of processing parameters such as current, pulse width, and gas pressure on MRR, relative electric wear rate (REWR), surface roughness (SR), and recast layer thickness (RLT) were studied through a one-factor-at-a-time approach. The results of single-pulse discharge experiment show that the discharge gap of Ar-NEDM is larger than that of Air-NEDM, and the discharge crater is also larger. The experimental results show that compared to Air-EDM, Ar-NEDM cannot only obtain higher MRR, but also can obtain a micro-surface without obvious microcracks and micropores, smaller SR, and thinner RLT, but its REWR is relatively high.