Effect of metallic-coating properties on the tribology of coated and oil-lubricated ceramics

Friction and wear behavior xvas determined for zirconia ceramics lubricated with solid coatings (Ag, Au, and Nb) deposited by ion- beam-assisled-deposilion (IBAD) techniques, and a polyol-ester-based synthetic oil. Although the use of soft Ag and A u coatings as solid lubricants in conjunction with the synthetic oil significantly reduced the friction and wear under boundary lubrication at temperatures up to 250°C, these films had poor durability. In contrast, the Nb coating was more durable in terms of chemical reactivity and adhesion during the tribo-lests than were the Ag or Au films. However, the friction and wear behavior of the Nb-coated zirconia was poorer than that of the ceramics coated with Ag or Au.