Performance and wear mechanisms of polycrystalline diamond tools with different diamond grains in milling Cf/SiC composites

Carbon fiber-reinforced ceramic matrix composites (Cf/SiC) are widely used in the aerospace industry, but severe tool wear and premature tool failure exist during the machining process. Polycrystalline diamond (PCD) tools have promising applications in machining composites due to their excellent mechanical properties. This paper compares the performance of three PCD tools with different grain sizes and analyzes the wear mechanisms in depth using scanning electron microscopy and transmission electron microscopy techniques. The results show that the performance of the PCD tool improves with the increase in grain size, but the tool with excessive large grains has the worst performance. The main wear morphologies are pits-bumps on the flank face and micro-voids on the rake face. Pit-bumps are caused by intergranular fracture, supplemented by cleavage fracture. Micro-voids are caused by thermal expansion and oxidation of the binder protruding from the surface and then removed by mechanical scraping. The tools with small grain size are more prone to cleavage fracture, while the tools with large grain size are more prone to intergranular fracture.