Effects of ambient pressure on fretting friction and wear behavior between SUS 304 steels

Effects of ambient pressure on fretting friction and wear behavior between SUS 304 steels were investigated. The ambient pressure varied from 105 to 10−4 Pa. The experiments were conducted at normal loads of 0.6, 1.0 and 1.8 N, slip amplitudes of 50 and 100 μm, frequency of 10 Hz and 105 cycles. It was found that there was a critical pressure below which coefficient of friction was increased. The peak wear volume occurred at pressure of 103 Pa, not at atmospheric pressure (105 Pa), it was revealed that the wear volume depends on the formation of metallic particle or oxide particle and the effects of these particles on the contact surface. In order to examine the formation and removal of the oxide debris particles on the wear scar, another experiments were carried out in which ambient pressure was changed alternately from 105 to 10−3 Pa and from 10−3 to 105 Pa for every 103 cycles. Oxidized particle volumes were measured by subtracting the disk wear volumes before and after 3% HCl solution treatment which was used to remove oxidized particles. Oxide particle volume was proved to be larger after fretting wear at 105 Pa. These particle remains in the roughs of wear scar were difficult to be removed during the consequent fretting wear in 10−3 Pa even up to 106 cycles which results in coefficient of friction not increasing at 10−3 Pa as expected.