The effects of hydrogenated carbon films with different film thickness and nitrogen content on specimen mechanical properties, scratch critical load, adhesion work and tribological behavior

摘要

The contact mechanics developed for a sphere in contact with a flat plane is employed in this study to obtain the stress functions distributing in the elastic and plastic-deformation regions formed in a specimen with a hydrogenated carbon film. These stress functions are then used in the evaluation of the adhesion work of the specimen. All coating films using a silicon wafer as the substrate were prepared by differing the firm thickness and the volume fraction of nitrogen in the gas mixture of (N_2 + C_2H_2) during the deposition process. The critical load of a specimen with a coating film can be determined from a scratch test on a nanotester. The proportional relationship of the adhesion work and the critical load is found to be valid only for the specimens having the same film thickness and the same nitrogen content in the coating film. Nanoindentation tests have been earned out on a nanotester to obtain the Young's modulus of all specimens. The wear volumes of all specimens were also obtained from the nanoscratch tests under various operating conditions. The wear volume results are then tried to establish their connection with the parameters including adhesion work, Young's modulus and operating conditions. The behavior analysis indicates that the adhesion work of a specimen is not the unique factor to the wear volume; the mechanical properties of a specimen and the operating conditions are also involved as dominant factors. The elevation in either the adhesion work or the Young's modulus is helpful for the reduction of the wear volume.