Graphitization-enhanced mechanical polishing of nanocrystalline diamond

HX Yuan and JJ Zhang, DIAMOND AND RELATED MATERIALS, 158, 112720 (2025).

DOI: 10.1016/j.diamond.2025.112720

While both ultrahigh hardness and anisotropic properties of individual grains strongly affect the deformation behavior of nanocrystalline diamond (NCD), achieving the high machinability of NCD is challenging. In the present work, we demonstrate the effectiveness of applying surface graphitization treatment in promoting the mechanical polishing performance of NCD by experiments and atomistic simulations. The stress transmission modes, thermodynamic evolution and phase transformation during mechanical polishing of graphitized NCD are analyzed at the atomic scale, which demonstrate that both the alleviated local stress concentration and promoted uniform release of strain energy within subsurface layer are largely dependent on grain boundary characteristics. Consequently, the coordination and controllability of subsurface phase transformation is achieved through modifications of subsurface stress and temperature fields, which are verified by experimental results with crosssectional characterization of subsurface layer. While the presence of graphite layer significantly improves the polishing efficiency of NCD, optimized parameters are subsequently obtained to achieve both low surface roughness and high polishing efficiency of graphitized NCD. These findings not only deepen the understanding of the material removal mechanisms during NCD polishing, but also provide theoretical foundation and technological support for graphitization-assisted high performance mechanical polishing of NCD.

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