Ceramic cutting tools play a pivotal role in high-speed machining of difficult-to-cut materials owing to their exceptional hardness and unique thermomechanical properties. Al₂O₃-based ceramics, in particular, are widely adopted due to their excellent chemical inertness and cost-effectiveness. In recent years, high-entropy carbides such as (HfNbTaTiZr)C, characterized by superior hardness, have been incorporated into the Al₂O₃ matrix as hardening phases to further enhance tool performance. However, the inherent brittleness of Al₂O₃-(HfNbTaTiZr)C ceramic often leads to premature tool failure, severely limiting service life. Therefore, identifying an optimal toughening strategy to address this issue is of paramount importance. Graphene, a two-dimensional (2D) nanoscale reinforcement phase, offers a novel approach for toughening ceramic cutting tools due to its ultrahigh strength, large specific surface area, and exceptional crack-bridging capabilities.

Despite the emerging potential of graphene as a toughening phase for ceramics, existing studies lack systematic optimization of its microstructural parameters (layer number, flake size, and orientation) and interfacial bonding strength with the ceramic matrix. In this study, we developed a three-dimensional (3D) finite element model to comprehensively investigate the effects of graphene’s microstructural architecture (layer number and flake dimensions) and interfacial bonding strength (ceramic grain boundary-to-grain interior strength ratio and graphene–ceramic interface strength ratio) on the mechanical properties of graphene-toughened Al₂O₃-(HfNbTaTiZr)C ceramic tools, thereby identifying multiscale-optimized parameters. Building on this foundation, the influence of graphene orientation on tool lifespan during high-speed machining of 20CrMnTi steel was further evaluated, revealing the optimal orientations for maximizing tool longevity and minimizing cutting temperature.