Experimental Investigations on the Tribological Performance of Electric Discharge Alloyed Ti–6Al–4V at 200–600 °C

Abstract

Nowadays, the titanium alloys observe broad applicability in aerospace, marine, automobile, and bio-medical industries due to their lightweight, bio-compatibility, good fatigue strength, and corrosion resistance. However, it possesses poor tribological behavior characterized by a high coefficient of friction (CoF) and the specific wear rate (SWR). In this paper, the impact of the electrical discharge machining on the tribological properties of Ti6Al4V (Ti64) was compared before and after electrical discharge machining (EDM) using a pin-on-disk tribometer under un-lubricated and ambient temperature. Besides, ex-situ analysis was performed on the distinct pin surfaces using (i) scanning electron microscopy (SEM), (ii) energy-dispersive X-ray spectroscopy (EDX), and (iii) X-ray diffraction spectroscopy (XRD) techniques to elucidate the associated wear mechanisms. The mechanical properties such as nano-hardness and elastic modulus of the test surfaces were also determined using a nano-indenter. Significant improvement in SWR (65.44% reduction) with a passable compromise for CoF (22.5% increment) occurred during experimentation (before and after EDM) at 100 N. Besides, the wear behavior of the electrical discharge alloyed Ti64 (ETi64) was evaluated at 200 °C, 400 °C, and 600 °C under the applied loads of 50–150 N. At 400 °C and 600 °C, the SWR initially decreased and then increased with variation in load from 50–100 N and 100–150 N, respectively. The enhanced tribo-behavior at 100 N was due to the protective influence of tribo-oxides, viz., TiO2 and Ti8O15 assisted by the hard Ti24C15 carbides in the recast layer (RL).