Studies on wear mechanism of ultrathin protective carbon overcoat by micro-wear scan technique

Abstract

By combining the micro-wear and microscratch techniques in a microindenter, a new methodology to investigate the mechanical properties of ultrathin coatings has been developed. With a 0.18 μm/sec scratch speed along a Y-direction while oscillating the indenter tip along the X-direction at a 6.55 Hz frequency, uniform wear tracks of approximately 20 μm × 90 μm in dimension can be created under either a constant or a gradually increased applied normal load. The wear-scan methodology has rendered several immediate advantages over the conventional microscratch technique, offering features such as a much larger testing area thus facilitating the failure and morphology analyses afterwards, the possibility of studying the wear debris generation and the flexibility in testing characteristics. Two thin film disks with different hydrogenated carbon overcoats have been tested by using the micro-wear scan technique. The results in the mechanical measurements, the wear processes and the morphology evolution are illustrated and discussed.