SiC wear resistance coating with added Ni, for carbon/carbon composites

To improve the tribological performance of carbon/carbon (C/C) composites at high temperature, a SiC coating with added Ni (SiC-Ni coating) was prepared by pack cementation. Dry sliding tests were conducted at different temperatures, and related microstructure and mechanical characteristics were investigated by scanning electron microscopy, X-ray diffraction, nano-indention, and scratch tester. The SiC-Ni coating is mainly composed of SiC and NiSi₂, and the adhesion between coating and substrate is reliable. The friction coefficient of SiC-Ni coating is about 0.35 at 25°C, and the predominant wear mechanisms are micro-cutting and plastic deforming. Severe adhesion wear occurs at 600°C which results in high friction coefficient. However, the SiC-Ni coating exhibits self-lubricating properties at 800°C. A dense film (consisting of silica and nickel oxide) spreads on the wear track of SiC-Ni coating at 800°C. This film reduces the friction coefficient effectively and enhances the wear resistance of the coating.