Wear Resistant Behavior of Amorphous Carbon and Carbon Nitride Films Prepared by Shielded Arc Ion Plating

Amorphous carbon (a-C) and carbon nitride (a-CNx) films are promising for many industrial applications owing to their high hardness, wear resistance and solid lubricity. Nowadays, the films attract much attention as biomedical, since the films have chemical and mechanical durabilities in vivo. A CNx frequently shows excellent wear resistance, even though its hardness is not so high in comparison with a-C. Tribological properties of such films have been intensively studied in relation to chemical structures of the films. However, those are not sufficiently elucidated. In this study, a-C and a-CNx films are deposited by shielded arc ion plating (SAIP) with arc current of 60 A, bias voltage in the range from 0 to 500 V and gas pressure of 1 Pa. Mechanical properties of the films including hardness, elastic modulus, recovery, contact stiffness and plastic and elastic deformation energies were measured by a nanoindenter interfaced with an atomic force microscopy (AFM) using a diamond tip (Berkovich type: 65.3 of half angle). Wear resistant behavior of the films was studied by a ball-on-disc tribotester with a load of 5 N and a sliding speed of 100 mm/s. The nanoindenter was also applied to evaluate wear resistant behavior of the films in nm scale. To study chemical structures, the films were analyzed by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. We will mainly discuss on the wear resistant behavior in relation to other mechanical properties of a-C and a-CNx films measured based on nanoindentation, as well as the relation of the chemical structures to the tribological properties of the films.