Experiment on electric discharge machining of cooling holes in superalloy IN718

Processing methods of electrical discharge machining (EDM) using inner jet liquid rotating electrodes under the kerosene liquid about ■0.5 mm small holes on superalloy IN718 was proposed. The effects of process parameters of EDM, such as peak current, pulse on time, duty cycle and hydraulic pressure, on the material removal rate and the electrode relative-wear were studied using orthogonal design. Comprehensive formula about the material removal rate and the electrode relative-wear based on orthogonal experiment was established to choose the best processing parameters. The analysis of the results shows that the influence of peak current on the material removal is most obvious followed by the hydraulic pressure and duty cycle. The influence of pulse on time on the material removal rate is not significant; the influence of peak current on the electrode relative-wear is most obvious, followed by the hydraulic pressure. The influences of the pulse on time and the duty cycle on the electrode relative-wear are not significant; the optimization parameter group is the peak current 8 A, pulse on time 130 μs, duty cycle 0.35, and hydraulic pressure 5 MPa. This is the optimum parameter group obtained by experimental study.