Fretting and Electrical Contact Resistance Characteristics of Carbon Nanoparticle-Coated Cu Electrical Contacts

Abstract

Fretting wear is a phenomenon that can severely affect the duty life and efficiency of electrical contacts. To reduce its effect, the contacting sites are lubricated; however, these are usually detrimental to the electrical characteristics of the system. Therefore, in this work we propose carbon nanoparticle coatings. Carbon black, graphite flakes, graphene oxide, and carbon nanotube coatings were produced via electrophoretic deposition over copper surfaces. These coatings have the potential to act as solid lubricants – thus minimizing the damage incurred on the connector by fretting – while also having a minor effect on the conductivity of the substrate. To evaluate the lubricity of the coatings and their impact on the electrical conductivity of the system, fretting tests and electrical contact resistance measurements were carried out. The coatings and the fretting marks were morphologically and chemically characterized by electron microscopy and spectroscopy. Furthermore, the worn area of the fretting marks was evaluated using confocal laser scanning microscopy. The worn and oxidized areas of the coated samples were smaller than those of the copper reference after 50,000 fretting cycles – excluding the graphite coatings. For prolonged fretting cycles the resistance of all coated samples fell below that of the uncoated reference, highlighting their advantage.