Friction and surface behavior of selected titanium alloys during reciprocating-sliding motion

The frictional behavior of selected orthopaedic titanium alloys during reciprocating-sliding against hardened steel was found to be function of cyclic count, sliding velocity, contact stress, and alloy phase structure (metastable-β versus α+β). Surface observations have shown that the evolution of the frictional response involves localized asperity deformation and fracture, surface plowing with formation of small debris, adhesive wear with formation of larger surface debris, and transfer between titanium and the steel counterpart. Surfaces of the metastable-β alloys exhibited greater surface deformation and transfer than did Ti–6Al–4V pins, plowing being representative of surface damage for the two-phase α+β. The amount of titanium transfer increased with increasing contact stress, transfer being always greater for the metastable-β alloys. Additionally wear debris collected at the end of the tests were a mixture of titanium and steel alloy constituents. The extensive plastic deformation, plowing and galling, transfer, and mechanical alloying observed all indicate that the dynamic friction behavior of titanium alloys is controlled by their surface deformation behavior and transfer characteristics.