BOUNDARY LUBRICATION THIN FILM STUDY BY GRAZING-ANGLE-MICROSCOPE/FTIR SPECTROSCOPY

Abstract

Measurements of boundary lubrication thin film of less than 20 angstroms have been achieved using a grazing-angle-microscope/FTIR technique. The thin film was observed only in a wear scar area resulting from a boundary lubrication experiment performed on a Cameron-Plint tribometer. The experimental conditions were 250 N load, 6 Hz frequency, a maximum velocity of 0.17 m/sec, at $100^{\circ}$C and with a pin-on-disk configuration operating for 5 hours. The lubricant used was Fomblin-Z. The wear scar area has blue and yellow colors under the microscope. The colors are not from the residual lubricants, as they survive ultrasonic cleaning in Freon-113 for 30 minutes. The film thickness found in the blue area is about 25 times thicker than that in the yellow area. The most dramatic change in thickness occurs at the interface between these two different colors. Mapping studies were also carried out and reveal that the thickness distribution can be explained by the load and velocity variations used in the Cameron-Plint tribometer. The boundary lubrication thin film surface species were partially characterized. The thin film strength was estimated by a chemisorption study of $CF_{3}COF/FeF_{3}$ system. A model explaining the formation of the thin film is proposed.