Development of innovative machine elements using electron, atom, ion and molecule (synthesis of thin film with super-high wear resistance)

C-N thin films were prepared on several engineering material substrates with evaporation of C by electron beam and simultaneous bombardment of N and Ar ion beam. Synthesis condition of the CN film obtained consisted of numerous carbon nanotube-like structural elements grown vertical to the substrate was clarified by use of cross sectional high-resolution transmission electron microscopy. The optimum condition was found to be ion acceleration energy of 200 eV, C/N transport ratio of 2 and ion beam gas ratio (Ar/N₂) of 1 below 373 K for substrate temperature during deposition. X-ray photoelectron spectroscopy indicated the mixture bonding state of both sp² and sp³ in the film obtained. This bonding state showed a unique nanotube-like structure with existence of strong bonds of C and N between the carbon nanotube-like sheets. Nano-indentation studies showed excellent hardness of the films up to 21 GPa. The friction coefficients against SiC and steel balls were 0.2 irrespective of substrate materials in both laboratory air and vacuum of 1.3 × 10^-4 Pa. Significant improvement of wear resistance was verified by forming C-N film on engineering substrate materials. Especially, CN films prepared on the TiN substrate with [200] preferred orientation showed much less wear rate than that of DLC films commercial a-C:H (DLC) films even in a vacuum. These results show that CN films have a superior ability for wear resistance to a conventional DLC.