Mechanism of friction and wear of carbon fiber reinforced metals : Effect of environment

The effect of the atmosphere on the friction and wear properties in the combination of a nodular cast iron (FCD60) disk and pins of carbon fiber reinforced metal (CFRM) and matrix metal was investigated by the wear test under atmospheres of oxygen, nitrogen, argon, and vacuum. No lubrication was used, temperature was held at 20 ± 1°C, sliding velocity was 0.135-0.160 m/s, and normal load was 5.0 N. The following conclusions were drawn on the basis of an analysis of the worn surface topography, observations with a differential interference microscope, and EPMA analysis of the surface. (1) The wear rate of a CFRM pin is lowest in vacuum due to the thin but even lubricating film developed and is successively larger under atmospheres of argon, nitrogen, and oxygen. The coefficient of friction is low in nitrogen and argon and successively higher in vacuum and oxygen. (2) Wear rate of pin varies with mean depth of grooves, leveling depth, and mean radii of curvature at asperity tips. The results show that a rough quantitative estimate of wear rate can be made using two criteria: the ratio of volume removed as a debris to apparent groove volume and wear index.