Effect of Surface Roughness on Tribological Characteristics of Chromium Nitride Films Deposited by Arc Ion Plating

Tribological properties of chromium nitride films deposited by arc ion plating were investigated as a function of surface roughness caused by droplets adhering to the surface, which decreased with an increase in substrate bias voltage during deposition. In a reciprocating type tribological testing of the chromium nitride films with alumina balls in air with no lubrication, a sudden or gradual shift to the low friction coefficient was observed, depending on the surface roughness of the film; the transition to the low friction coefficient was delayed with an increase in the surface roughness of the films. The low friction coefficient was attributed to the Cr2O3: wear debris of chromium nitride films, which is formed on the friction surface of alumina balls. Undulation or protrusions on the films would prevent the Cr2O3 from depositing on alumina balls, resulting in delaying transitions.