Effect of carbon fibers surface treatment on tribological performance of polyurethane (PU) composite coating

The carbon fibers (CF) were pre-treated in two different ways: no pre-treatment, and activation in HNO3 plus application of toluene-2,4-diisocyanate (TDI). Carbon fibers have been introduced into polyurethane (PU) composite coatings. The tribological behaviors of the polyurethane composite coating filled with CF or TDI-modified CF (TDI-CF) were studied using a ring-on-block wear tester under dry sliding, and the worn surfaces of the filled PU coatings and transfer films formed on the surface of the counterpart ring sliding against the PU coating were investigated by SEM and optical microscope (OM), respectively. Owing to the effective improvement of the interfacial adhesion between the CF and polyurethane matrix, compared with the cases of untreated CF, the employment of low content TDI-CF provided the PU coating with much higher tribological performance enhancement efficiency. The investigations of the frictional surfaces showed that low content TDI-CF was able to enhance the adhesion of the transfer films of the PU coating to the surface of counterpart ring, so they significantly reduced the wear of the PU coating.