TRIBOLOGICAL PROPERTIES OF AG/TI FILMS ON AL2O3 CERAMIC SUBSTRATES

Silver solid lubricant films with a thin titanium interlayer for enhanced adhesion, were sputter deposited on Al2O3 substrate disks to reduce friction and wear. The dual Ag/Ti films were tested at room temperature in a pin-on-disk tribometer sliding against bare, uncoated Al2O3 pins under a load of 4.9 N at a sliding velocity of 1 m s-1. The Ag/Ti films reduced the friction coefficient by 50% to about 0.42 compared to unlubricated baseline specimens. Pin wear was reduced by a factor of 140 and disk wear was reduced by a factor of 2.5 compared to the baseline. These films retain their good tribological properties, including adhesion, after heat treatment in argon at 850 C and thus may be able to lubricate over a wide temperature range. This lubrication technique is applicable to space lubrication, advanced heat engines and advanced transportation systems.