Study of the effect of normal load on friction coefficient and wear properties of CNx thin films

Abstract

The present study reports on the systematic analysis of the friction and the wear behaviors of carbon nitride (CNx) thin films deposited by direct current unbalanced magnetron sputtering. We focus on the normal load dependence on the friction coefficient and wear rate for the sliding friction of the SUJ2 ball with the CNx thin film. The friction coefficient was monitored using a ball-on-disc apparatus with various loads in ambient air. The friction coefficient (μ) increases linearly from ∼0.05 to 0.28 with increasing normal load, while the specific wear rate decreases with an increase in load. The wear rates of the SUJ2 ball ∼1.5 × 10−7 mm3/Nm for μ = 0.05 and ∼5.5 × 10−8 mm3/Nm for μ = 0.28 were observed in the deposited CNx films with the minimum and maximum normal load. The friction and wear mechanisms are discussed in relation to the surface morphology and microstructure of the CNx coatings.