Determination of the Optimum Conditions for Machining NiTi Shape Memory Alloys by Electrical Discharge Machining

• Published in: Journal of the Institution of Engineers (India) Series C 2024, Vol.105 (5), p.1035-1046
• Main Authors: Güven, Sedat, Yilmaz, Metehan, Gökkaya, Hasan, Nas, Engin
• Format: Article
• Language: English
• Subjects: Aerospace Technology and Astronautics; Copper; EDM electrodes; Electric discharge machining; Electrode materials; Electrodes; Engineering; Industrial and Production Engineering; Intermetallic compounds; Machinability; Material removal rate (machining); Mechanical Engineering; Microcracks; Nickel base alloys; Nickel titanides; Original Contribution; Parameters; Production methods; Shape memory alloys; Surface roughness; Variance analysis; Workpieces
• ISSN: 2250-0545; 2250-0553
• DOI: 10.1007/s40032-024-01099-z

In this study, the machinability of nickel-titanium (NiTi) shape memory alloys (SMAs) was investigated via an unconventional manufacturing method. Experimental studies with electrical discharge machining (EDM) methods were carried out with three different electrodes (copper, graphite, and tungsten-copper) in a dielectric fluid (dielectricum 358). The experimental parameters were three different currents (6, 12, 18 A), pulse durations (200, 400, 600 µs), constant voltage (3 V) and pulse-off time (50 µs). The aim was to determine the most suitable cutting conditions in terms of the material removal rate (MRR) and average surface roughness (SR) from the experiments performed with these parameter values. After the machining operations, the experimental samples and electrode diameters were measured and compared. In addition, gaps and cracks were detected by scanning electron microscopy (SEM) images taken from the workpiece surface. Energy dispersive spectroscopy (EDX) analysis was carried out to determine the extent to which the electrode material broke during the machining process adhered to the sample surface. Analysis of variance (ANOVA) was applied to determine the influence of the experimental parameters on the variables. The use of different electrode materials did not significantly affect the MRR or SR, while the overcut was the most significant and most effective input parameter. In addition, the presence of blobs, debris, lumps, microcracks and pores was determined from the surface images. On the surfaces where high SRs were measured, it was determined that Cu and W residues, which were detached from the electrode material and could not be removed from the cutting zone with dielectric fluid, were adhered to the workpiece surface.