Wear of alumina-PTFE against non-ferrous substrates

PTFE matrix composites reinforced with Į-Al₂O₃ fillers are a viable solid lubricant which exhibit ultra-low wear rates (k ~ 10-⁸ mm³/Nm) when sliding against steel. Low wear in these composites is facilitated by robust tribological films that develop on both sides of the sliding interface. These interfacial films form due to mechanochemical reactions that involve breaking of PTFE chains due to shear stresses developed at the sliding interface, and subsequent passivation by ambient moisture. However, nearly all prior research that reports on ultra-low wear of Į-Al₂O₃ PTFE involves sliding against steel substrates. In contrast, some preliminary recent work has shown that alumina-PTFE exhibits high wear against a brass countersurface. These results suggest that ultra-low wear of alumina-PTFE is dependent on counter surface chemistry, however mechanisms for these differences remain unclear. In the present work, the mechanochemical mechanisms that result in differing wear of alumina-PTFE composites on brass and aluminum countersurfaces are examined.