Effect of Zr content on friction and wear behavior of Cr-Zr-N coating system

Nanostructured Cr-Zr-N thin film with different Zr content (0 to 48.8 at.%) was deposited, using an RF magnetron-sputtering technique. The structural evolution and morphological changes were performed. The tribological performances were evaluated, using a ball-on-disk type Oscillating tribometer. The tests were carried out under normal loads of 2, 4 and 6N, respectively, with an alumina ball (Al2O3) as a counter face. The results showed that the crystallite size of the Cr-Zr-N system was reduced to 10.8nm at 31.8 at.% Zr content. Morphological studies of the films showed that the roughness continuously decreased with increasing Zr content, exhibiting a value of 11.2nm at 31.8 at.% Zr. The wear rate tends to decrease with the increasing of Zr content to reach a lowest value of 1.95x10-2m3.N.m-1 at 31.8 at.% Zr. The wear rate and friction coefficient were lower in the samples with 31.8 at.% Zr content. The improved friction and wear resistance were attributed to the grain refinement strengthening mechanism at 31.8 at.% of Zr.