Investigation of the removal mechanism of unidirectional C/SiC under scratching by single diamond grain

This study investigated the design and fabrication of a unidirectional ceramic matrix composite (C/SiC) and its machining process using single-grit diamond scratching. Results showed significant anisotropy in friction performance, with longitudinal friction approximately 1.3 times higher than normal. Scratch depth and surface crack width follow the pattern: normal < longitudinal < transverse, with transverse scratches penetrating about 1.5 times deeper and surface widths approximately 2.8 times wider than normal scratches. Increasing scratching velocity (1–50 μm/s) led to larger material removal scales, attributed to reduced material fracture energy. Low-speed scratching exhibited similar material removal patterns to high-speed grinding. A material removal model for single abrasive grain machining was proposed; the study revealed a comprehensive mode of matrix cracking, interface failure, and fiber fracture interaction, primarily through brittle fracture. These findings deepen understanding of ceramic matrix composites in machining applications, with implications for process optimization and material property enhancement.