Comparative study on microstructure, bio-tribological behavior and cytocompatibility of Cr-doped amorphous carbon films for Co–Cr–Mo artificial lumbar disc

Abstract

Cr-doped amorphous carbon (a-C:Cr) film is a promising protective coating to extend the lifetime of Co–Cr–Mo implants. Here, a-C:Cr films with the same doping concentration of Cr and thickness are deposited on Co–Cr–Mo substrates using the closed-field unbalanced magnetron sputtering (UBMS) and the plasma-enhanced chemical vapor deposition (PECVD) methods. A comparative study on the microstructure, bio-tribological behavior, and cytocompatibility of two kinds of a-C:Cr films in the air and different simulated body fluids is conducted. Microstructural analysis results show that the a-C:Cr films prepared by UBMS and PECVD methods belong to graphite-like carbon (GLC) and diamond-like carbon (DLC) films, respectively. Nanohardness of the UBMS a-C:Cr film is found to be lower than that of the PECVD counterpart. However, the UBMS a-C:Cr film exhibits better lubrication, lower wear depth and lower wear volume under all the three simulated body fluids, because of the slight polishing wear and boundary lubrication mechanisms. Moreover, both kinds of a-C:Cr films significantly improve the cytocompatibility of Co–Cr–Mo substrate alloy.