Mechanisms of Lubrication and Wear of a Bonded Solid-Lubricant Film

Abstract

To obtain a better understanding of how bonded solid-lubricant film lubricate and wear (in general), the tribological properties of polyimide-bonded graphite fluoride films were studied (in specific). A pin-on-disk type of testing apparatus was used; but in addition to sliding a hemispherically tipped rider, a rider with a 0.95-mm-diameter flat area was slid against the film. This was done so that a lower, less variable contact stress could be achieved. Two stages (regimes) of lubrication were found to occur. In the first, the film supported the load and the lubricating mechanism consisted of the shear of a thin surface layer (of the film) between the rider and the bulk of the film. The second occurred after the bonded film had worn to the substrate, and consisted of the shear of very thin lubricant film between the rider and flat plateaus generated on the metallic substrate asperities. The film wear mechanism was found to be strongly dependent on contact stress.