Tribological behavior of short carbon fiber reinforced polyetherimide composite under water lubrication conditions

Short-carbon-fiber-reinforced polyetherimide (SCF/PEI) composites have good mechanical properties and are expected to have wide applications including components serving under water lubrication conditions. However, no work has been reported on the tribological behaviors of SCF/PEI composites under water lubrication conditions. This work attempts to explore the practicality of the SCF/PEI composite from a tribological point of view under water lubrication conditions. SCFs are coated by polydopamine (PDA) to enhance the interfacial interaction between fibers and matrix. The tribological performances of SCF/PEI composite are systematically investigated by sliding wear tests under tap and sea water lubrication conditions. Experimental results show that the SCF/PEI composite has a better friction performance in water lubrications than that under dry sliding because of the separation effects formed by a water molecule film and a transfer film. However, no remarkable differences of wear resistance are found between water lubrication and dry contact conditions, and the magnitude of specific wear rate under these conditions is around 1 x 10(-6) mm(3)/N.m. It is found that contact surface hardness of the SCF/PEI composite is reduced after a sliding test in water due to the plasticization phenomenon, especially sea water can accelerate the diffusion of water molecules into matrix, making the specific wear rate in sea water is ten times of that in tap water for highly-loaded conditions. Meanwhile, the abrasive wear is observed to be the dominated wear mode in boundary lubrication regime, and the adhesion wear occurs around the transition position from the boundary to mixed lubrication regime. It is also found that pressure has a significant effect on the temperature rise within the contact surface than the speed does. Finally, the tribological performance of the SCF/PEI composite under water is exhibited to be better than that of most of polymers and composites reported previously.