Effect mechanism of water as liquid medium on mixed-gas atomization discharge ablation process on titanium alloy

The use of a liquid medium in near-dry electrical discharge machining (EDM) with a two-phase gas‒liquid medium endows it with desirable characteristics such as a stable discharge process and high material removal rate. However, the effect mechanism of the liquid medium in near-dry EDM is not well understood, which limits its development. In this present, a variant of the near-dry EDM technology, namely, mixed-gas atomization discharge ablation processing (MA-DAP) of titanium alloy, is used to reveal the effect mechanism of a liquid medium in the process of near-dry EDM. This technology uses a mixed gas containing oxygen and a liquid medium to form the dielectric medium, so as to obtain a higher effective material erosion ability than near-dry EDM. Through the combination of experimental and theoretical modeling and analysis, it can be concluded that liquid dielectric water has the functions of endothermic cooling, inducing an intermittent gas supply environment between electrodes, efficient etching product removal, improving oxygen utilization efficiency, controlling oxygen diffusion speed, and increasing the discharge gap between electrodes, which can significantly improve the inter-electrode discharge state and material removal rate. Compared with conventional EDM, the material removal rate associated with MA-DAP technology increases by 16 times, and the relative wear rate of the electrode is reduced by more than 93%.