ROLE OF THIRD BODIES IN FRICTION AND WEAR OF Cu-GRAPHITE COMPOSITES
Department of Material Science and Engineering, Dalian Jiaotong University, Dalian, China
Abstract. Copper-graphite composites were fabricated through powder metallurgy technique. The performance of the composites in friction and wear was tested on a friction tester. The formation and development of third bodies during the friction were observed step by step. The results demonstrate that the morphological features of the third bodies affect the friction coefficient and wear rate. In pure copper, the third bodies are strongly adhesive, resulting in drastic oscillation in friction coefficient. As the content of graphite in the composite increases, the third bodies made of graphite become predominant. The presence of graphite prevents the adhesion of the materials, and hence lowers and stabilizes the friction coefficient and wear rate. Microstructural observations of the composite friction surfaces reveal that the third bodies undergo a particle formation and accumulation process and exist as particulates and compact zones. The compact zones are also the result of nucleation and growth processes.
Keywords: third body, friction and wear, Cu-matrix composite, graphite