The effect of random surface topography height on fretting in dry gross slip conditions

This paper describes the tribological effect of surface topography on friction and wear under dry fretting regime of a point contact. Experiments were made using SRV4 ball-on-disc tribotester. 100Cr6 sphere of 64 HRC (Rockwell method, scale C) hardness co-acted with a disc made of 42CrMo4 steel with hardness of 40 HRC. Fretting tests were carried out under dry gross slip conditions. The diameter of ball was 10 mm. During tests, normal load was kept constant at P = 50 N within the contact. Duration of each test was 15 min. Tests were performed in 26 ℃ temperature in the chamber at 39–43% of relative humidity. Displacement amplitude was 0.1 mm (stroke was 0.2 mm) with frequency of 20 Hz. The disc samples had different textures obtained after one process (grinding, vapor blasting, or polishing) and two process (grinding or vapor blasting followed by lapping). During tests, the friction force was monitored as a function of time. Wear of disks and balls was measured after the test using white light interferometer. Surface roughness height of discs, determined by the Sq parameter was in the range: 0.01–4.5 µm. It was found that initial surface roughness height had a significant influence on friction and wear in dry gross slip conditions. For rougher disc surfaces, the friction force in initial test stage and wear of co-acting parts were higher.