Surface and sub surface evaluation in coated-wire electrical discharge machining (WEDM) of INCONEL® alloy 718

Wire Electncal Discharge Machining (WEDM) is one of the most versatile and useflil technological processes for cuttmg complex shapes made of conductive matenals such as those typical of aerospace applications. With the aim to optimize process parameters, this paper studies the surface and subsurface modifications of INCONEL® alloy 718 (UNS N077 18) machined by WEDM using a Zinc coated brass wire. Machining was perfomwd under roughing and finishing conditions by setting different values of discharge energy and wire feed rate. Surface roughness of the cut surfaces was measured as well as the micro-hardness profile on polished sections. WED-machined surfaces and their cross sections were also observed by Scannmg Electron Microscope (SEM) and analyzed by Energy Dispersive X-ray Spectroscopy (EDS) to evaluate possible vanations of the surface chemical composition. In this investigation, results are discussed as a ifinction of the feed rate and of the smgle pulse discharge energy, which is determined by duration, peak current and discharge voltage of the discharge pulse. The research demonstrates that the required surface roughness can be achieved by properly settmg the feed rate and the smgle pulse discharge energy on the WEDM machme. Expenmental results also show that under the re-melted layer thickness no significant white layer formation or thermal modification occur, indicatmg that the chosen set of operatmg parameters minimizes secondary and unwanted chemical reactions.