Tribological behavior of SiC coating on C/C composites against SiC and WC under unlubricated sliding

In this work, SiC coatings were prepared by chemical vapor deposition on carbon/carbon (C/C) composites. The microstructure and mechanical characteristics of the as-prepared SiC coatings were investigated by scanning electron microscopy, X-ray diffraction and nano-indention. The tribological behavior of SiC coating was evaluated by a tribometer with a ball-on-disk configuration, applying SiC and WC balls as counterparts with normal contact loads of 2 N, 10 N and 20 N under unlubricated condition. The results of tribological tests show that the friction coefficient of the SiC coating against the SiC ball (SiC/SiC coupling) is lower than that of the SiC coating against the WC ball (SiC/WC coupling) at all tested loads, and the wear volume of SiC coating for the SiC/SiC coupling is lower than that for the SiC/WC coupling by an order of magnitude. A silica film was formed between the contact surfaces for SiC/SiC coupling at 10 and 20 N, which could act as lubrication layer. However, the dominant wear mechanisms of SiC/WC coupling were a mixture of abrasive and fatigue wear.