Comparative Capabilities of Conventional and Ultrasonic-Assisted-Electrical Discharge Machining of Nimonic Alloy 75.

Nimonic alloy 75, a high strength temperature resistant material, has widespread applications in gas turbine engines, industrial furnaces, nuclear engineering, etc. This paper presents a comparative study of capabilities evaluation between the conventional electrical discharge machining (EDM) and ultrasonic-assisted-electrical discharge machining (UAEDM) of Nimonic alloy 75 work material. During experimentation, input parameters namely tool material; discharge current; servo voltage and pulse on duration were varied to find their effects on material removal rate (MRR) and surface roughness (SR). Results indicated that UAEDM process leads to an increase of 53.57% in MRR over conventional EDM process, whereas SR of UAEDM process is 18.47% higher compared to conventional EDM process. Scanning electron microscope 'SEM' images shows that UAEDM process has fewer surface irregularities compared to conventional EDM process. Energy-dispersive x-ray (EDS) test has shown tool material migration and carbon enrichment of EDMed and UAEDMed surfaces. X-ray diffraction 'XRD' analysis has shown the formation of NiC phase on EDMed and UAEDMed surface when compared to unmachined surface. Further, a significant reduction in crystallite size was observed for EDMed and UAEDMed surface in comparison to unmachined surface. The surface microhardness increased after conventional EDM and UAEDM process as compared to unmachined surface. [ABSTRACT FROM AUTHOR]