Abstract
Oxidative wear is significant in fretting wear when sufficient oxygen is supplied. In vacuum, however, oxide does not form readily. In this paper friction and wear behaviours were studied at various atmospheric pressures in order to clarify the effect of ambient pressure on them. Experiments were conducted with 0.45% C steel at ambient pressures from 1.0 × 10 5 to 1.3 × 10 −3 Pa. The load was 14 N, the peak-to-peak slip amplitudes were 35 and 110 μm and the frequency was usually 8.3 Hz. Friction behaviours are characterized into three types according to the ambient pressure: 1.0 × 10 5 − 10 Pa, 10 − 10 −1 Pa and below 10 −1 Pa. The coefficient of friction increases with a decrease in ambient pressure below 1 Pa. The critical pressure in fretting is found to be 10 Pa, above which the oxidation rate is independent of the ambient pressure and α-Fe 2O 3 is formed. Wear decreases with ambient pressure below the critical pressure where Fe 3O 4 is formed. Adhesive transfer of metallic debris occurs below 10 −1 Pa. The relationship between the coefficient of friction and oxide thickness is obtained analytically, and the effect of frequency on the oxidation rate is considered.
Published Version
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