Hard amorphous carbon films exhibit excellent wear resistance and low friction. The hard carbon films are brittle and have a high internal stress. Also the abrupt change of elastic modulus at the interface of the film and metallic substrate results in low adhesion and reduces load carrying capacity. Composite film structures with alternating layers of hard carbon and metallic films has been shown to possess unique mechanical properties such as enhanced fracture toughness and high hardness. Elastic mismatch may also be avoided by careful control of composition. The stress relaxation, when possible, enables the growth of thicker films. Multilayer films with alternating layers of hard carbon and TiNx have been deposited by using an arc discharge deposition apparatus. The carbon plasma is generated with a pulsed plasma source. The titanium and TiN films are deposited by using a d.c. arc source equipped with a particle filtering. Films with a thickness of about 0.5 μm were deposited with 10 layers of carbon and TiNx. The substrate materials were AISI440B stainless steel and (100) silicon. The film composition was determined by nuclear resonance analysis, Rutherford backscattering, scanning electron microscopy and scanning force microscopy. The wear resistance and load carrying capacity was tested by using a pin-on-disc test. The friction coefficient of the multilayer films was observed to be lower than for the pure diamond-like carbon films, while the wear rate of the multilayer film slightly increased and the wear rate of the counter surface was increased about ten fold.
- Diamond-like carbon
- Interfacial layers