Tribological behavior of carbon-fiber-reinforced polyimide composites under water lubrication

Polyimide-based composites filled with various solid lubricants and reinforced with carbon fiber were prepared by compression molding. The tribological behavior of the composite sliding against steel (1Cr18Ni9Ti) under water lubrication was investigated and compared with that under dry sliding. The wear mechanism under water lubrication and that under dry sliding comparatively were examined as well. As a result, the PI-based filled composites sliding against stainless steel register lower friction coefficients and wear rates in water than in air. The lowest wear rate is recorded as 0.99 ×10-6 mm3/N&middotm for the PTFE filled PI composite. The lowest wear rate of PI-based composites could depend on the polar imide radicals in the composite molecules. In other words, the polar imide radicals could link with water molecules by hydrogen bond. Consequently an adsorbed film of water could form to keep off the direct contact between two sliding surfaces of the frictional pair. Therefore a decreased wear rate of the composite would be observed.