2018 Volume 4 Pages 18-00089
Carbonaceous coatings such as Diamond-Like Carbon (DLC) are attractive candidates for reducing friction under boundary lubrication. However, the wear particles generated from the DLC are believed to form hard slurries that scratch surfaces like an abrasive, and they can shorten the lifetime of the DLC itself. Generally, in conventional automobiles, these wear particles are collected by oil filters. Modern engine bearings are required to reduce the friction coefficient to low levels so that low-viscosity lubricants are used to reduce resistance to flow. However, using a low-viscosity lubricant result in direct solid contact between surfaces, which disrupts the hydrodynamic lubrication and generates numerous wear particles. In this study, we carried out friction tests between DLC/DLC surfaces with kerosene as a boundary lubricant at room temperature. The friction tests were conducted over 12,000 cycles, and we replaced the lubricant after every 2000 cycles without changing the contact pair. Wear particles were collected from the lubricant using an electric field with the electrophoresis effect. The wear particles gathered near the positive electrode and fell onto a glass plate. Finally, after the kerosene evaporated, scanning electron microscope and laser optical microscope observations showed the relations between particle size and shape, the number of wear particles, and the friction coefficient.
