Experimental study on microscopic wear mechanism of copper/carbon/rice bran ceramics composites

This paper reports on the analysis of microscopic wear mechanisms of copper/carbon/rice bran ceramics (Cu/C/RBC) composites, which were developed as a new pantograph contact strip material for the current collector of electric trains, and the proposal of the wear equation of those composites. Low friction coefficients, of less than 0.15, and relatively low specific wear rates, of less than 10(-4) mm(2)/N, were obtained for the Cu/C/RBC composites, when both the mean diameter and the mass fraction of the rice bran ceramics (RBC) particulate were small. At the opposite compounding ratios, the contrary results were obtained. According to SEM observation on wear particles and worn surfaces at low and high wear conditions, different wear modes were observed as follows: ploughing with no typical wear particle; small cracks and small plastic flow with fine wear particles; large brittle fracture and severe plastic flow with flake-like-shaped wear particles. On the basis of the wear mode map of ceramics proposed by Hokkirigawa, the wear mode transition of the Cu/C/RBC composites is discussed. The wear equation which showed the exponential relationship between the specific wear rates and the parameter S-w is proposed. As indicated by this equation, the Cu/C/RBC composites have low S-w values due to their high fracture toughness and low friction coefficient resulting in low specific wear rates. (C) 2012 Elsevier B.V. All rights reserved.