Research on discharge characteristics of working mediums of electric discharge machining

Abstract

Successful surface modification can be obtained by Electrical Discharge Machining (EDM). In this work the discharge characteristics in misted deionized water and near-dry powder-mixed medium was studied systematically, as well as the microstructure and properties of electrical discharge strengthened layers on TC4 alloy. It indicates that the breakdown voltage of EDM in misted deionized water medium has been reduced to about 1/3 than in air medium. In near-dry powder-mixed medium, it is reduced to about 1/9, because the discharge gap is much larger than that of other mediums. In other words, a stable discharge can be obtained by larger discharge gaps and lower pulse energy than traditional EDM surface strengthening method, which leads to more stable discharge process. Experimental researches show that dense and sound combination with matrix like, multiphase hybrid intensification and chrysanthemum petal-like microstructure of strengthened layers can be observed in the near-dry powder-mixed medium. Meanwhile, it is found that the microhardness of the strengthened layer is up to about 1200 HV, which is four times higher than the base material.

Effect of Mechanical Grinding on the Physicochemical, Structural, and Functional Properties of Foxtail Millet (Setaria italica (L.) P. Beauv) Bran Powder

“…Moreover, the M120 samples displayed a wider particle size distribution, which corresponded with the span value provided in Table 1 . This observation corresponded with the findings of Li et al [ 18 ] for chrysanthemum powder. In general, larger particles decreased the span value [ 19 ].…”

Numerical simulation and experimentation to investigate the performance of powder mixed dielectric in electrical discharge micromachining

“…The machining stability in terms of occurrence of normal discharges or prevention of abnormal discharges and efficient cleaning of the gap is possible with the effective removal of debris particles at higher IEG. 25,26 Electric field simulation using multiple powder particles in the gap Transient variation of electric field and its coupling with gap breakdown. Multiple powder particles (total 35 particles, including 6 bridging particles) are introduced in the IEG of 10 mm, whereas the voltage required for the breakdown of the gap and corresponding charging time is evaluated from the capacitor's charging characteristics (refer to Figure 2(c)).…”

“…The machining stability in terms of occurrence of normal discharges or prevention of abnormal discharges and efficient cleaning of the gap is possible with the effective removal of debris particles at higher IEG. 25,26…”

An insight on Powder Mixed Electric Discharge Machining: A state of the art review

“…In comparison with PM- EDM milling, PMEDM showed higher MRR by machining surface movement. 127 The addition of powder in medium and near dry EDM effects was explained with the Impurity breakdown theory. This theory stated that with the increase in powder concentration the breakdown voltage decreased which made the sparking mechanism easier.…”