Coating thickness effect on initial wear of nitrogen-doped amorphous carbon in nano-scale sliding contact: Part II—theoretical modeling

This is the second paper of a two-part report. In the first paper, empirical data on the wear particle generation in carbon nitride coatings subjected to repeated sliding contact with a spherical diamond counter-face is reported. The effect of coating thickness on the wear particle generation is also discussed in the first paper. In this paper, a simplified theoretical expression, combining the Coffin-Manson equation with the analytical solution of a proposed elastic perfectly-plastic indentation model, is introduced. The expression successfully correlates critical number of friction cycles for wear particle generation Nc to coating thickness h, contact pressure P and radius of spherical asperity on the tip of the diamond pin R. With this expression, the lifespan of sliding components can be predicted. eoretical results computed for diamond pin with a specific asperity radius value of 250 nm were compared with the experimental results reported in the first paper. The theoretical model successfully predicts the maximum lifespan of a component, Nc, in repeated sliding applications. The influences of various contact pressures and asperity radii on the maximum lifespan were also assessed using the model.