Tribological behaviors of Ag-graphite composites reinforced with spherical graphite
(1. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China;
2. Institute of Mechanical and Electrical Engineering, Zhengzhou University of Light Industry, Zhengzhou 450002, China)
2. Institute of Mechanical and Electrical Engineering, Zhengzhou University of Light Industry, Zhengzhou 450002, China)
Abstract: Two kinds of Ag-graphite composites reinforced with spherical graphite (SG) and conventional flake graphite (FG) were prepared by powder metallurgy technology. The effect of graphite morphology on the tribological behavior for the Ag-SG and Ag-FG under the dry sliding wear was investigated with a pin-on-disk tribometer at a load of 3.0 N in atmosphere condition. The results indicated that the minimum wear rate of 3.5×10-5 mm3/(N·m) for Ag-FG was achieved and it reduced by nearly an order of magnitude, reaching 1.6×10-6 mm3/(N·m) for the Ag-SG. The obviously different tribological behaviors between the Ag-SG and Ag-FG were closely related to the formation of cracks in the sub-surface. The stress concentration tended to generate at the edges of flake graphite during sliding process, which resulted in the cracks and severe delamination wear of Ag-FG. However, no cracks were found around the spherical graphite in Ag-SG. The spherical graphite can effectively inhibit the initiation and propagation of cracks, achieving high wear resistance.
Key words: Ag-graphite composite; graphite morphology; wear resistance; microstructure; wear mechanism