Deep hole electrical discharge machining of nickel-based Inconel-718 alloy using response surface methodology

The blades in the high-pressure turbine section of engines of modern aerospace and defense industries need to be drilled for pressurization. The milling and drilling of nickel-base material Inconel-718 are likely to create tool wear and tear, so the drilling process of milling is extensively replaced by deep hole electrical discharge machining (EDM). However, EDM creates reaming or overcut phenomenon, so to reduce this, parameter optimization is important. This study used response surface methodology to establish the influencing factors of machining parameters in hole enlargement and machining speed. The experimental results show that the main influencing factor in the nickel-based alloy deep hole EDM is the discharge voltage; the second factor is the discharge current. The hole enlargement of the processed hole without optimization is 60 ~100 μm. The DOE is used for the measurement of hole enlargement and machining speed to design important parameters and to predict experiment data analysis. The half-normal probability graph, Pareto chart, and analysis of variance (ANOVA) are used to learn about the significant factors of parameters and the influence of interaction. The outlet value of optimized parameters was observed to be relatively uniform, and the hole morphology is relatively free of residue stacking. Finally, the inlet and outlet results improved by 17.9% compared with the original parameters. The optimization parameter value predicted by the fitted model was 0.0392 mm, and the optimized upper and lower holes validation experiment machining error was 0.0380 mm, and the values are quite close, proving that this prediction model is accurate. The model prediction of this DOE can enhance the applied technology of deep hole EDM for nickel-based alloy.