Compositional dependence of the microscopic frictional properties of single crystal metal carbides

Abstract

The frictional properties of TiC(100), Ti 0.3 V 0.6 C(100), and VC(100) surfaces in contact with a silicon nitride probe tip have been investigated by atomic force microscopy (AFM) under ambient pressures of dry nitrogen as well as environments of different relative humidities. Calibration of normal and lateral force has permitted the determination of the quantitative frictional properties of the three carbide samples on a nanometer length scale. In these studies, TiC(100) exhibits the lowest friction coefficient, ranging from $0.044 to $0.082 under the different environments. VC(100) and Ti 0.3 V 0.6 C(100) have similar friction coefficients ($0.07) under dry nitrogen conditions, yet VC exhibits a larger friction coefficient ($0.158) than Ti 0.3 V 0.6 C ($0.129) under conditions of higher relative humidity ($55%). Condensation of water vapor with increasing relative humidity results in an increase in the frictional response for all the three samples. The experimental results demonstrate that the frictional properties of the three carbide samples are correlated to their surface composition and surface free energy.

Deposition and Nanotribological Characterization of Sub-100-nm Thick Protective Ti-Based Coatings for Miniature Applications

“…In all cases studied, the wear depth is far from the film's thickness showing the wear resistance of these films. Chen et al [27] reported on the dependence of frictional properties on the composition for TiC (100), Ti 0.3 V 0.6 C (100), and VC (100) coatings. They found that TiC exhibits the lower COF value.…”

“…They proposed that surface oxidation and water vapor condensation at the asperities seems to regulate the frictional properties as they were evaluated using AFM. Chen et al [27] concluded that native oxides provide unique frictional properties on these coatings. Thus, they suggest that differences in surface free energy are the dominating factor for the different performance.…”