Nanoscratch Studies of Uncoated and Coated Ceramic Matrix Composite Materials

Ceramics and cermets (ceramic matrix composites) are commonly used for various structural and tribological applications. Pullout of phases at high loads in a composite can be an issue and can be alleviated using a hard overcoat. In this study, nanoscratch and nanoindentation experiments on a SiC composite impregnated with graphite were carried out using a depth‐sensing nanoindenter. Additional indentation studies on the graphite phase were carried out to examine whether it becomes fractured or dislodges readily. Additionally, experiments were carried out to study scratch performance and nanohardness of a hard overcoat and its ability to protect SiC composite phases underneath. We find that a hard overcoat adequately protects the substrate underneath. Finally, nanoscratch and nanoindentation experiments were performed on pure SiC as well as commonly used manufactured carbon–carbon graphite. It is found that SiC exhibits the highest scratch resistance and carbon graphite the least.