What are the Progresses and Challenges, from the Electrical Properties of Current-Carrying Friction System to Tribological Performance, for a Stable Current-Carrying Interface?

Despite many years of research, the current-carrying friction interface still strongly depends on the lubricating film between the friction pairs, because this film can reduce the probability of arc occurrence. However, this film has poor conductivity, cannot self-heal, and is prone to be greasy, which reduces the efficiency of current conduction, which seriously affects the contact status. In order to solve this problem, graphite materials with excellent lubricating properties and electrical conductivity are used to make current-carrying friction materials. Graphite and graphite-based composite materials are the most widely used current-carrying friction materials in various industries. Graphite has excellent lubricity, conductivity, and high temperature resistance to steel and many other metal materials. However, with the passage of time, due to the continuous deterioration of the application conditions and the environment, such as arc under high current density, spark phenomenon, severe mechanical wear under high load, etc., the lubricating film is destroyed, which greatly weakened the performance of protecting friction pairs. Therefore, improving the working stability of the current-carrying friction pair is the key to ensuring that the contact pair does not spark. In this review, we mainly discuss how to improve the stability of the current-carrying friction system, reduce the wear of the current-carrying friction system, and thereby extend the service life of the current-carrying friction material. At first, we discussed the latest research progress of current-carrying friction from the electrical properties, contact resistance, thermal effect, and arc of current-carrying friction materials to tribological characteristics. Secondly, the influence of contact resistance parameters and structural function parameters on the wear life of current-carrying friction pairs is discussed. The current research status of current-carrying performance and tribological performance of current-carrying friction pairs under the coupled effects of temperature field and current field is discussed. It is necessary to combine experiment, theory, and simulation to study the temperature field of the current-carrying friction pair, especially the influence of complicated conditions such as oil and dust on the friction performance of the current-carrying. Thirdly, the influence of arcing, sparking, and dynamic characteristics on the friction performance of the current-carrying friction system is reviewed. At the same time, the prediction model of current-carrying friction and wear should be studied systematically to detect current-carrying friction and wear online. Finally, it introduces in detail that new current-carrying friction materials are developing in the direction of tissue functionalization and structural composite.