| Fracture resistance is one of the most important properties of TiN coatings for the wear application. Therefore, this study was focused on improving the fracture resistance of TiN films and a new structure TiN film with Ti/TiN/Ti buffer layer/TiN were made. These new type TiN films were synthesized by cathodic arc ion plating with various thicknesses of the Ti buffer layer. The structure and phase compositions of the films were examined by scanning electron microscopy(SEM), X-ray diffraction(XRD) and Auger electron spectroscopy(AES) and the mechanical properties were studied by a micro knoop hardness tester and an impact wear tester. The results from XRD analysis showed that the Ti interlayer between the substrate and the TiN layer has a preferred growth orientation of (111) but the internal Ti buffer layer within TiN film showed a preferred orientation of (002) plane, which matches with TiN (111) plane coherently, resulting in reduced possibility of failure between the Ti buffer layer and TiN layer. Microhardness of TiN film without the Ti butter layer was approximately Hk=2850 but in case of TiN films with the Ti butter layer, microhardness decreased slightly to approximately Hk=2300∼2800, depending upon the thickness of the Ti buffer layer. Results from the impact wear test showed that impact wear volume of the TiN film with Ti buffer layer decreased approximately three times than that of the TiN film without Ti buffer layer. This tendency could be attributed to the stress accumulation and relaxation at the soft Ti buffer layer. |
|
