Experimental study on wire electric discharge machining of nimonic 90 using coated electrode

WEDM machine is an unconventional machine that got accepted in the industries because of its skill to machine any material precisely in the required shape and size. Wire electric discharge machine uses electrical energy to cut hard conductive materials. In the present study, Nimonic 90 a nickel-based superalloy is machined in WEDM using a zinc-coated brass wire electrode to study its surface characteristics and its machinability. Experiments were carried out with a central composite design with controllable WEDM factors such as Pulse duration, Servo-voltage, and wire-tension were used to investigate machining performance such as material transfer rate (MRR) and average surface roughness (Ra). The second-order quadratic models are developed between WEDM parameters and responses by regression analysis. Analysis of Variance was employed to validate the accuracy of the established statistical models and the impact of the process variables. The RSM-based optimization was used to find the optimal process parameter of Wire Tension 11.962 N, Pulse on Time 79.785 mu s and Servo Voltage 100 V to achieve a maximum MRR of 5.3574 (mm3 min-1) and minimal Ra of 2.6513 (mu m). The validity of the response surface model is further verified by conducting confirmation experiments and found that errors are within the permissible limit. Further, the surface morphology of the WEDMed specimen was carried out through SEM to ascertain the mechanisms of material removal under the different settings of WEDM.