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Abstract
The first part of this paper describes an ultrahigh vacuum friction apparatus (tribometer). The tribometer can be used in a ball-on-disk configuration and is specifically designed to measure the friction and endurance life of solid lubricating films such as MoSx in vacuum at a pressure of 10−7 Pa, 10−9 torr. The sliding mode is typically unidirectional at a constant rotating speed. The second part of this paper presents some representative friction and endurance life data for magnetron sputtered MoSx films, 110 nm thick, deposited on sputter-cleaned 440C stainless-steel disk substrates, which were slid against a 6-mm-diameter 440C stainless-steel bearing ball. All experiments were conducted with loads of 0.49 to 3.6 N, average Hertzian contact pressure, 0.33 to 0.69 GPa, at a constant rotating speed of 120 rpm, sliding velocity ranging from 31 to 107 mm/s due to the range of wear track radii involved in the experiments, in a vacuum of 7×10−7 Pa, 5× 10−9 torr, and at room temperature. The results indicate that there are similarities in friction behavior of MoSx films over their life cycles regardless of load applied. The coefficient of friction μ decreases as load W increases according to μ = kW−1/3 , which is in agreement with the Hertzian contact model. The endurance life E of MoSx films decreases as the load W increases according to E = KW−1.4 for the load range. The load- (contact pressure-) dependent endurance life allows a reduction in the time needed for wear experiments and an acceleration of endurance life testing of MoSx films. For the magnetron-sputtered MoSx films deposited on 440C stainless-steel disks, the specific wear rate normalized to the load and the number of revolutions was 3 × 10−8 mm3/N -revolution; the specific wear rate normalized to the load and the total sliding distance was 8 × 10−7 mm3/N·m; and the nondimensional wear coefficient was approximately 5 × 10−6. The values are almost independent of load in the range 0.49 to 3.6 N, average Hertzian contact pressures of 0.33 to 0.69 GPa.
Presented at the 47th Annual Meeting in Philadelphia, Pennsylvania May 4–7, 1992
Notes
Presented at the 47th Annual Meeting in Philadelphia, Pennsylvania May 4–7, 1992
