Tribological properties of SS 304 and Ti6Al4V using four reciprocating geometries

An automated bio-tribometer with four reciprocating geometries – linear, circle, square and eight/butterfly – was used to study the tribological properties of stainless steel (SS) 304 and the titanium–6 wt.% aluminium (Al)–4 wt.% vanadium (V) (Ti6Al4V) alloy under dry conditions and when lubricated with simulated body fluid (SBF) against a zirconia pin as the counterbody. The sliding speed, distance and normal load were kept constant, and the effect of the various geometries on the coefficient of friction (CoF) and wear was studied. Theoretical calculations showed a variation of CoF as linear < circle < eight/butterfly < square, and the experimental data also showed similar CoF in all the geometries except for the linear profile. The CoF was primarily controlled by the shear forces exhibited by each geometry. The CoF, as well as wear, decreased in magnitude (∼20%) under SBF due to the formation of a lubricant film on the contact surface. The developed shear stresses, simulated by finite-element analysis, showed an increase with the increased complexity of traverse geometries due to the concomitant actions of rapid changes in the direction of motion and dynamic friction. However, the trend in variation remained intact and was controlled by the shear forces exhibited by each geometry.