Experimental Investigation on Surface Integrity and Wear Behavior of Ti-6Al-7Nb Alloy under Rough and Trim Cut Modes of Wire Electrical Discharge Machining

Abstract

Surface properties of metallic material significantly affect its fatigue, tribological and other functional properties. Titanium (Ti) alloys are hard to machine material, and therefore, wire electrical discharge machining (WEDM) is preferred over the conventional turning and milling process for machining of Ti-alloys. In the present work, surface integrity and wear behavior of Ti-6Al-7Nb have been evaluated under rough cut and trim cut modes of WEDM process. Rough cut mode resulted in high thermal damage with high surface roughness (Ra 2.34 μm), thick recast layer (Avg. 13.71 μm) and high crack density with large size micro-cracks. Significant improvement in surface properties of Ti-6Al-7Nb has obtained using trim cut mode with reduced surface roughness (0.94 μm), thin recast layer (3.51 μm), and the average crack length and average crack density reduced by 30% approximately. Energy-dispersive spectroscopy analysis showed that the trim cut mode yielded a high percentage of Ti and O elements in machined surface layers and reduced the contents of Al, Cu and C, thus favors the improved biocompatibility of Ti-alloy. Rough cut and trim cut modes of WEDM played the significant role in enhancing the surface hardness of Ti-6Al-7Nb, thus affected the coefficient of friction (c.o.f.) and wear rate. Trim cut mode resulted in lowest c.o.f. and wear rate as compared to rough cut machining and polishing. The results of the present work are highly motivated to promote the trim cut mode of WEDM as a promising manufacturing route for Ti-alloy.