Effect of Si₃N₄ on the Wear Resistance of SiC Coatings on Surface of Carbon/Carbon Composites

Abstract

Aiming at improving the wear resistance of SiC coatings on surface of carbon/carbon composites, SiC/Si3N4 coating was synthesized by pack cementation and nitriding treatment. The surface morphology, phase composition, worn surface, and friction and wear properties of SiC coating and SiC/Si3N4 coating were analyzed by X - ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X - ray spectroscopy (EDS) and friction and wear test, respectively. Furthermore, the relationship between microstructure of the coating and wear mechanisms was investigated. Results showed that the SiC/Si3N4 coating consisited of the Si3N4 phase, SiC phase and C phases. The SiC/Si3N4 coating surface was flat and dense. Additionally, SiC/Si3N4 coating had lower frictional coefficient (<0.05) and exhibited more stable property. The main wear mechanisms of the high friction coefficient value of SiC coating were adhesive wear and abrasive wear. A thinner lubricating film was formed in the SiC/Si3N4 coating and reduced the friction coefficient in the subsequent friction and wear stages. Moreover, the addition of the Si3N4 phase could effectively improve the surface structure of the SiC coating, making the friction coefficient of the SiC coating smaller and more stable, thereby improving the wear resistance of the coating.

Keywords

• carbon/carbon composites|sic/si₃n₄&#x00a0;coating|microstructure|wear mechanism