Development of lubricious DLC coatings for microdevices.

DLC (Diamond-like Carbon) coatings have remarkable tribological properties due mainly to their good frictional behaviour. These coatings can be applied in many industrial and biomedical applications where sliding or contact generates wear and high frictional forces on the components. This work reports on the development and tribological characterisation of functionally gradient DLC coatings. A PVD-Magnetron Sputtering technique has been used as the deposition method, using a metal interlayer in order to improve the adhesion of the coating to the substrate. Furthermore, the coatings have been deposited with a gradual change in composition to decrease internal stress and to avoid delamination. The quality of the films has been examined by scanning electron microscopy and the tribological characterisation of the DLC coatings has included frictional tests using a ball-on-disc geometry, resulting in friction coefficient values below 0.2 with no measurable wear on the surface. In addition, microhardness and elastic properties have been measured by a dynamic microindentation technique and adhesion of the coatings to the substrate has been evaluated by the scratch test method.