INFLUENCE OF ENVIRONMENT AND TEMPERATURE ON DUSTING WEAR TRANSITIONS OF CARBON-CARBON COMPOSITES

This paper describes an investigation on the combined influence of env ironment and temperature on the tribological behaviour of a carbon-car bon (C/C) composite material with a particular reference to the intera ction between water vapour and oxygen in air and the carbon surface. E xperiments were conducted in nitrogen and air with a low-speed three-p ins-on-disc apparatus and a high-energy ring-on-ring apparatus. Like c onventional graphitic carbon materials, C/C composites exhibited a hig h friction and wear phenomenon, also known as ''dusting'', in dry nitr ogen from room temperature up to 700 degrees C owing to the lack of lu bricant gases and vapours in the environment. In ambient air, however, C/C composites exhibited three temperature-dependent tribological reg imes. Abrupt increases in the friction at 150-200 degrees C and 650-70 0 degrees C marked the transitions between different regimes. The tran sition phenomena were explained in terms of the desorption of physisor bed water vapour and chemisorbed oxygen from the rubbing surface.