EFFECT OF FRICTIONAL HEATING ON MECHANICALLY MIXED LAYERS DURING DRY SLIDING CONTACT OF Ti-6Al-4V ALLOYS AT HIGH TEMPERATURE IN VACUUM CONDITION

Ti-6Al-4V (an α+β titanium alloy) pins were slid against the SS316L disc in a pin-on-disc apparatus at different temperatures under vacuum and ambient conditions. Tribological characterization was performed using a field emission scanning electron microscope (FESEM) equipped with energy dispersive X-ray (EDAX) analysis and X-ray diffraction. The worn pin surfaces of Ti-6Al-4V were investigated in order to identify the effect of frictional heating at the interface of tribo-pair. To investigate the effects of frictional heating on mechanically mixed layer (MML), experiments were performed under vacuum conditions (2×10−4 Torr) by varying the temperature from 25°C to 400°C at a constant sliding speed of 0.01ms−1 and at constant normal load of 137N. The material was found to transfer from the counter-face to the worn pin surface of alloy where an MML and tribo-oxide (TO) layer were observed to developed on the worn pin surfaces under both the experimental environments. Moreover, a new mechanism, called the “debris burial mechanism†during the formation of the MML at different temperatures was obtained at the interface. The rate of wear was observed to decreased with the increase in frictional heating at the interface resulting to the progressive formation of thicker MML over the worn pin surface. The wear resistances in Ti–6Al–4V alloy decrease rapidly due to loosening the generated MML on the sliding surface.