转向精密磨研下纳米孪晶金刚石的表面生成机理研究

纳米孪晶金刚石(Nt-D)的硬度和韧性均数倍于天然金刚石，是制造超精密切削刀具的理想选材。然而，Nt-D硬度极高，微结构类型多且分布复杂，已有金刚石材料的表面生成机理不适用，现有的刀具制造工艺难以对其进行有效加工。为克服Nt-D刀具制造难题，本项目提出转向精密磨研的工艺，依据磨研面晶粒的磨削率实时调整磨研方向，以保证晶界两侧的材料去除率一致。通过磨削模拟和转向精密磨研实验探究机械磨研下Nt-D的表面磨损规律，系统阐明表面生成、表面材料去除、晶界处应力集中等问题。结合磨削模拟与磨研实验结果，明确磨研后表面质量优异的微结构，澄清孪晶分布等内部微结构和磨研方向等外部加工参数对Nt-D表面宏观性能的影响规律，建立内部微结构-外部加工参数-表面宏观性能的理论描述；揭示Nt-D的表面生成机理，提出可有效对Nt-D进行刀具制造的工艺参数。项目研究成果有望为高性能Nt-D刀具的制造提供理论基础和技术支撑。

The hardness and toughness of artificial nanotwinned diamond (Nt-D) are times than that of natural diamond, and it is an ideal material for manufacturing ultra-precision cutting tools. However, due to extremely high hardness, complex microstructure types and distribution of Nt-D, the surface generation mechanism of existing diamond materials is not suitable for Nt-D, and it is difficult to effectively process Nt-D by the current manufacturing technology. To overcome the manufacturing difficulty of Nt-D cutting tools，it propose a steering precision grinding process in which the grinding direction is continuously adjusted according to the grinding efficiency of grain on the grinding surface. This method ensures the same materials removal rate on both sides of the grain boundary. The grinding simulation and steering precision grinding experiment are adopted to explore the surface wear law of Nt-D under mechanical grinding process, which systematically clarify the mechanism of surface formation, surface removal, and the concentration of stress at grain boundary. Combining grinding simulation and grinding experiment, the type of Nt-D microstructure with excellent surface quality after grinding will be clarified, and the effects of internal microstructure characteristics such as twinning distribution, and external processing parameters such as grinding direction on the macroscopic properties of Nt-D surface can be revealed. Based on the above results, the theoretical description between the internal microstructure characteristics, the external process parameters and the macroscopic surface properties will be established. Then, the surface formation mechanism of Nt-D can be revealed, and the process parameters that can effectively manufacture tools for Nt-D will be proposed. The research results are expected to provide theoretical basis and technical support for the manufacture of high-performance Nt-D cutting tools.