Wear Characteristic Evaluation of Electrical Discharge Machined Ti6Al4V Surfaces at Dry Sliding Conditions

Abstract

The low tribo-characteristics of Ti6Al4V (Ti64) have delimited its range of applicability. To elucidate the underlying mechanism, the friction and wear behavior of Ti64 at elevated pin speeds (200 rpm, 300 rpm and 400 rpm), constant load (50 N) and temperature (ambient) conditions were initially evaluated. The wear, coefficient of friction and frictional force characteristics of the material were identified to follow incessant unsteady transitions, during test run. The pin speed of 300 rpm marked the highest wear, governed by the frictional heating, asperity flattening, centrifugal forced clearance (of the wear track) and third-body abrasion-assisted delamination. The reduced wear trend at 200 rpm and 400 rpm could be attributed to the protective coatings formed by tribo-oxidation and mechanically mixed layer, respectively. Further, the electrical discharge machined Ti64 samples were developed and subjected to friction and wear analyses at varying loads of 50 N and 100 N. In contrast, at similar testing conditions (load 50 N, speed 200 rpm, temperature ambient, sliding distance 1000 m), the electrical discharge machined Ti64 (with a peak wear value of 220 μm) showed enhanced tribo-characteristics compared to that of bare Ti64 (with a peak wear value of 370 μm). The improved tribo-behavior of the former was due to the presence of hard, fine-grained and non-etchable recast layer, which got spalled off at an increased load of 100 N.