Tribological behavior of aluminum alloy graphite particle composites
Focus was on the qualitative mechanism of arriving at the steady-state tribo-surface containing a thin film of solid lubricants as was observed in these composites. The coefficient of friction of the composites reduces with graphite content. However, around 25 vol% graphite, the coefficient of friction levels off at a value of 0.2-0.25 and becomes almost independent of graphite content at graphite contents higher than 25 vol%. Wear resistance increases with the volume fraction of graphite particles as reflected in the reduction of weight loss by a factor of 4-5 as a result of dispersion of graphite particles until a volume fraction of about 25 vol%. A sliding direction along the narrow transverse dimension of flake graphite (sliding angle 90{degree}) results in a covering of the graphite by the matrix as a result of plastic flow and consequently, the coefficient of friction increases. Sliding direction parallel to longitudinal direction of graphite is also not effective for transfer of graphite particles on the tribo-surface. On the other hand, a sliding angle of about 45{degree} results in the best wear resistance and relatively lower value of friction. XPS analysis shows that the lubricating film formed on the tribo-surface of the composites is composed of a mixture of various carbonaceous species, including carbon oxides, air-deposited, adventitious carbon, graphitic carbon, and some very fine aluminum particles (primarily Al{sub 2}O{sub 3}).
- Research Organization:
- Wisconsin Univ., Milwaukee, WI (United States)
- OSTI ID:
- 5470171
- Country of Publication:
- United States
- Language:
- English
Similar Records
Tribological properties of Al alloy particle composites
Tribological Performance of M50-Ag-TiC Self-Lubricating Composites at Elevated Temperature