Wear mechanisms in reciprocal scratching of polycarbonate, studied by atomic force microscopy

An atomic force microscopic (AFM) was used to study the microwear process of polycarbonate (PC). Testing included multiple scratching (scan-scratching) and line-scratching using a microfabricated Si 3N 4 AFM tip of 10–20 nm radius. Interfacial adhesion, friction, the effect of number of cycles, scratching speed and the interaction of scratches were studied. Unlike previous reports, projections as a result of polycarbonate volume increase were observed after reciprocal scratching on the same track (without AFM tip lateral feed). In spite of analytically predicted elastic/plastic contact, no plastic deformation was found during the tests. A model, based on the cracks formation and growth process was suggested to explain these phenomena. The importance of lateral feed in the process of wear particles formation was shown. No scratching speed effect on friction or microwear was found.