Effect of Breakdown Behavior of Passive Films on the Electrochemical Jet Milling of Titanium Alloy TC4 in Sodium Nitrate Solution

摘要

Electrochemical jet milling (EJM) has broad prospects in engineering applications, its flexibility andversatility offering distinct advantages over traditional electrochemical machining (ECM). In the EJMprocess, the breakdown time of the passive film plays an important role in the selection of processingparameters. The Ti-6Al-4V (TC4), has been the most widely used titanium alloy in EJM in recent years.However, little research has been conducted on the breakdown time of the passive film on TC4. In thisstudy, experiments concerning the breakdown behavior of the passive film on TC4 were conducted toinvestigate the influence of breakdown time on machining process in NaNO3 solution. Results showedthat the breakdown time of the passive film stabilized at 0.58 s when the current density at the breakdownpoint exceeded 70 A/cm2. For any point on the anode surface, the breakdown of the film occurred whenthe quantity of electric charge reached the point needed for breakdown. The effect of cathode feed rateon the EJM process was also investigated by simulation and experimentation. It was found that anincrease of cathode feed rate could improve the machining quality. However, when the feed rate wasincreased to 50 mm/min, a large area of unbroken passive film remained on the anode surface. Based onsystematic studies, a feed rate of between 3 and 12 mm/min was judged to be optimal for the EJMprocess.