Friction Surface Morphology and Tribological Property of Copper-Steel-Aluminum Lamellar Composite Materials

The mixture of multi-components and the existence of third-body on the friction surface of powder metallurgy materials make it difficult to clarify the contributions of each components to the tribological property. In this paper, copper-steel-aluminum lamellar friction materials were prepared through mechanical combination. Using a constant-speed tribometer under dry and wet conditions, the changes of friction surface microstructure with respect to friction speed of the three components were investigated, and the tribological property under different conditions was measured. It was found that, the excellent ductility and bondability of copper made it easy to form third body with good bonding to the matrix, resulting in increased surface roughness. The high strength of steel and the brittleness of its oxides led to good flowability of the third body and limited its bonding strength to the matrix, making it easy to crack and spall. The aluminum-oxide-rich third body formed by aluminum had relatively weak bonding between particles, thus it is easy to disperse on the surface, resulting in good surface smoothness. When the friction velocity was below 900 r/min, due to the lubrication of water, the friction coefficient under wet friction condition was lower than under dry condition, when the friction velocity was higher than 900 r/min, the water cooled and cleaned the tiny third body particles, which reduced the softening of the material and the flowability of third body, making the wet friction coefficient greater than dry friction coefficient.