Influence of Environmental Humidity on the Electrical and Mechanical Tribological Behavior of Metal-Immersed Carbon Sliders

To investigate the influence of ambient humidity on the tribological behavior of pantograph carbon slider and contact wire friction, using a metal-immersed carbon slider and a copper-silver alloy contact wire as the friction pair, a circular block-type pantograph-catenary system current-carrying friction and wear testing bench was employed to study the variation patterns of carbon slider wear, temperature rise, arcing rate, as well as surface topography and roughness under different ambient humidities with and without current loading. The results showed that without current loading, an increase in environmental humidity was beneficial to the improvement of the self-lubricating performance of the carbon slide plate surface. Characteristics such as the wear quantity of the carbon slider plate decreased with the increase of relative humidity, and the trend gradually slowed down. The wear quantity and temperature rise of the carbon slider plate at 60% RH were approximately half of those at 30% RH. Under current-carrying conditions, relevant wear characteristics increased with the increase of current. The influence of environmental humidity on the current-carrying tribological behavior of the pantograph-catenary system showed a "U" - shaped distribution. There was a strong correlation among the temperature rise at the contact point of the friction pair, the arcing rate, and the wear quantity of the metal-immersed carbon slider plate. Electrical wear was the main wear form of the pantograph-catenary friction pair. The low-humidity and dry environment had the most prominent effect on the wear behavior of the friction pair, and abnormal wear was likely to occur. While the high-humidity environment would also exacerbate the wear of the friction pair. A humidity value with the optimal wear performance was obtained near a relative humidity of 50%, and the wear quantity decreases by 1/3 and 1/4 respectively compared with the conditions of 30% and 60% relative humidity.