The effect of sliding time and speed on the wear of composite materials

Abstract

The friction and wear properties of an Al 201 alloy and a unidirectionally oriented graphite fiber-aluminum matrix composite (T50-Al 201) were investigated. The experiments were conducted on a pin-on-disc type friction machine. The diameter of the pin was 0.22 cm and the load 4.46 N. The sliding velocity varied between 0.17 and 0.43 m s −1. The disc counterface was of commercially pure iron. It has been found that the friction coefficient μ and the wear rate W L of the composite material decrease as the sliding time is increased until a steady state value is reached. The steady state wear rate is proportional to the reciprocal of the sliding speed in accord with a recently proposed model. Scanning electron microscopy and Auger electron spectroscopy observations indicate that the high initial values of μ and W L are due to a high degree of matrix adhesion to the counterface accompanied by fiber breaking and transfer. The low steady state values of μ and W L are due to the formation of a film that impedes adhesion and confers some degree of self-lubrication. It is suggested that the observed variation of W L with sliding speed is related to changes in the degree of subsurface damage as the velocity is varied.