| This thesis is aimed at studying the tribology of sliding contacts subject to high current densities. A flat-ended Copper tip sliding on a flat Copper plate was the test configuration and current densities of the order of 10, 500 and 1000 A/mm2 were used. The friction coefficient, contact resistance and material transfer were studied for clean metal-to-metal contacts and compared with those for the case where a solid lubricant interface conditioner (SLIC) was used. Three types of tests were carried out. Static tests were done with and without pre-application of conditioner to evaluate the repeatability of contact resistance measurement and to study the effect of applied load and conditioner on the conductivity of the interface. It was found that pre-application of a thick layer of SLIC increases the contact resistance by 20%. Circular tests, with the pin repeatedly traversing a circle, were done to evaluate the effect of sliding distance on the frictional coefficient and contact resistance with and without pre-application of solid conditioner. It was found that the conditioner reduces the friction coefficient in half and increases the time to failure many-fold. However, there was a small increase in contact resistance with conditioner. The wear rate of the tip increased with increase in contact pressure and current density. Spiral tests, where the tip was moved outward from the center of the plate, were done to study the transfer of material between the pin and the plate and the effect of change in surface velocity. |
