Structural, mechanical and tribological properties of nanostructured CN x/TiN multilayers

Abstract

Nanostructured CN x /TiN multilayers were deposited onto Si(1 0 0) and M42 high-speed steel substrates using closed-filed unbalanced magnetron sputtering. The deposition process was controlled by a closed-loop optical emission monitor (OEM) to regulate the flow of N 2 gas. Different carbon nitride Λ CN x layer thicknesses could be attained by varying the C target current (0.5–2.0 A). OEM settings and bilayer thickness periods (i.e. Λ CN x = 0.3 – 1.2 nm , while Λ TiN=3.0 nm) significantly affected the mechanical and tribological properties of CN x /TiN multilayer films. XPS analyses revealed that the chemical states, such as TiN, TiC, TiN x O y ???????????and TiO 2, existed in a TiN layer. The nanohardness of the film with bilayer thickness Λ TiN=3.0 nm and Λ CN x = 0.9 nm was ∼41.0 GPa. The residual compressive stress was found to be between 1.5 and 3.0 GPa. By the scratch test, the critical load value obtained was high ∼78 N. Rockwell-C adhesion tests exhibited the best adhesion and cohesive strength for multilayers with Λ TiN=3.0 nm, Λ CN x = 0.3 and 0.6 nm . The friction coefficient of a multilayer was found to be low 0.11. Lower frictional coefficients and wear rates were the consequences of the increase in Λ CN x , which provided a lubricating function in the multilayers.