Wear phenomena and tribofilm formation of copper/copper-graphite sliding electrical contact materials

• Copper-graphite composites of different compositions sliding against copper are investigated with regards to friction, wear and contact resistance. We find that comprehensive studies including the tribological as well as electrical aspects are rarely found in the literature. We combine friction, wear and contact resistance measurements with thorough surface analysis to complete the understanding. We find that including graphite in the composite greatly reduce the coefficient of friction. However, increasing the vol.% of graphite above 74 will not continue to reduce the friction. We conclude that the coefficient of friction is slightly lower when testing is performed without current than at 5 A current. A comparison of the specific wear rate for the tested composites shows that the one with 74 vol.% of graphite gives the lowest wear rate. In general, the wear rate is higher when tests are performed without current. Chemical analysis of the tribofilm that forms on the copper surface shows that it consists of graphite as well as Cu2O. It is also shown that the amount of graphite in the tribofilm correlates to the composition of the copper-graphite. Novel cross-section images of the tribofilm contribute to a deeper understanding of how sliding electrical contact surfaces are affected by current and sliding motion.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Materialteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Materials Engineering (hsv//eng)

Nyckelord

Tribofilm

electrical contact

copper-graphite

contact resistance

friction

Teknisk fysik med inriktning mot tribomaterial

Engineering Science with specialization in Tribo Materials

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)