复杂形状表面金刚石薄膜加热辅助化学机械复合磨料流抛光机理及工艺研究

Polishing can significantly enhance the performance of diamond films deposited on complicated surfaces, owing to the effect on reducing the surface roughness. The present project is proposed based on hot filament chemical vapor deposition (HFCVD) and abrasive flow machining (AFM) technologies. A novel method to finish diamond films on complicated surfaces is probed, namely heat-assisted chemical-mechanical AFM polishing adopting the specially-designed abrasive flow containing oxidizing agents and diamond abrasives. Based on the power law fluid governing equation, the flow model of the abrasive flow is established, and influences of the oxidizing agent, diamond abrasives and the temperature on the flow condition of the abrasive flow are studied. Effects of the type and concentration of the oxidizing agent, along with the temperature on the diamond oxidation in the closed environment of the abrasive flow are investigated. Force and motion equations of a single abrasive are determined, and the model of the material removal rate related to the mechanical effect is established. The material removal mechanism under the combined actions of the chemical and mechanical effects is analyzed. Special fixtures are designed according to simulation results on the static pressure distributions and the flow lines of the abrasive flow on complicated surfaces, and polishing parameters are optimized. Besides, combined with deposition methods of nano-sized and composite diamond films, controllable and high-efficiency AFM polishing of diamond films on complicated surfaces can be accomplished. On the basis of all above researches, a complete set of technique is fixed, including the selection of the diamond film type, the optimization of deposition parameters, and the controllable and high-efficiency polishing. The application of such the technique can significantly improve the comprehensive performance of diamond coated complicated components.

抛光加工可降低复杂形状表面金刚石薄膜的表面粗糙度，有效改善其性能。本项目以热丝化学气相沉积及磨料流抛光技术为基础，开发含有氧化剂及金刚石磨粒的新型磨料流，提出针对复杂形状表面金刚石薄膜抛光的加热辅助化学机械复合磨料流抛光方法；基于幂律流体控制方程建立磨料流流动模型，研究氧化剂、磨粒及温度对磨料流流动状态的影响；分析磨料流封闭环境下氧化剂种类、浓度及温度对于金刚石氧化的影响规律；构建单颗磨粒的受力及运动方程，建立纯机械作用下金刚石薄膜的材料去除率模型；深入分析化学和机械复合作用下的材料去除机理，确定磨料流配比方案；根据复杂表面磨料流静压力分布及流线仿真结果，设计专用夹具，优化抛光工艺，并结合金刚石薄膜晶粒纳米化及复合技术，实现复杂形状表面金刚石薄膜的可控高效复合抛光；在此基础上，开发“薄膜类型优选——沉积工艺优化——可控高效抛光”整套工艺，提升复杂形状金刚石薄膜涂层制品的整体性能。

本项目针对复杂形状表面金刚石薄膜的表面抛光问题，提出了新型化学机械复合磨料流抛光方法。完成了金刚石氧化化学热力学及动力学分析；采用密度泛函理论计算方法对金刚石表面氧吸附进行了理论计算，阐明了掺杂元素位置对金刚石表面氧吸附的影响规律；提出了适用于掺杂金刚石抗氧化性能预测的理论方法（可推广应用于含各类杂质元素的其他典型材料的抗氧化性能预测），通过吸附能、表面重构、电子密度及键布居综合分析，并结合相关实验表征，阐明了典型掺杂元素（硼、氮、硅）对金刚石材料抗氧化性能的影响规律，实现了金刚石材料抗氧化性能的精确定量调控(-36%~54.3%)，在此基础上进一步实现了对金刚石进行反应离子刻蚀及机械化学抛光加工效率的定量调控（反应离子刻蚀效率-26.4%~16.5%，机械化学抛光效率-12%~45.2%）；开发了基于尿素的高效、安全氮掺杂工艺，并系统对比了氮气和尿素掺杂源及掺杂比对金刚石薄膜生长特性、基础性能及机械性能的影响规律；选用考虑壁面滑移的Oldroyd-B粘弹性模型，分析了典型通孔及模具内孔磨料流流动状态，重点研究了不同流量、磨料粘度和壁面滑移系数下壁面滑移速度的变化规律；分析了机械-化学复合磨料流加工过程中磨料流载体及工件表面对单颗磨粒的作用力、工件加工表面位置单颗磨粒的运动方程、切削力及比能，建立了纯机械作用及复合加工过程的材料去除率模型；综合上述研究结果，开发了适用于金刚石及其他超硬材料复杂形状表面高效抛光的机械化学复合磨料流抛光原型装置及夹具（分别适用于金刚石薄膜涂层拉拔模具及复杂形状刀具），对关键工艺参数（主要包括温度、氧化剂单次注入量及注入频率）的影响性进行了系统分析，完成了抛光参数优化及初步的应用测试。基于本项目研究成果，针对不同应用需求对金刚石特性的影响，可选用特定类型的金刚石薄膜，并完成其沉积参数优化，进而确定配套的抛光工艺实现高质量高效抛光加工。