Ti/Al共掺杂类金刚石薄膜的表/界面结构设计与固液复合润滑机理

Compositing diamond-like carbon (DLC) films with lubricating oils and additives has been proved to be one of the effective methods to improve wear-resistance and friction properties of mechanical moving components in order to realize the long-time and reliability service. The tribological behavior is strongly related with the surface/interface structure of DLC films. However, due to the limitation of experimental characterization, the effect of surface/interface structure evolution on lubricating oils and additives and the composite lubrication mechanism are still unclear. In this project, Ti/Al co-doped DLC films are selected as representative case, the hybrid ion beam deposition system consisting of a DC magnetron sputtering and an anode-layer linear ion beam source will be used, and the composition and structure of the films will be optimized by modifying the process parameters to obtain the controllable preparation of Ti/Al co-doped DLC films with high performance; the surface/interface structure of Ti/Al co-doped films will be modulated by the multiple layers addition and the micro-nano fabrication such as plasma etching. The tribological behavior and surface/interface structure evolution of the films under the lubricating oil and additives conditions will be studied systematically. By combining the experiment and ab-initio calculations, the relation between the microstructure and mechanical and tribological properties will be clarified, the effect of surface/interface structure evolution on lubricating oils and additives will be revealed, and the synergistic mechanism of solid-liquid composite lubrication for tribological properties will be mainly clarified. This work will not only guide the structure design of carbon-based lubricating films, but also provide theoretic and technical basis for the development and application of solid–liquid composite lubrication systems with high performance.

类金刚石薄膜（DLC）和润滑油、添加剂的复合润滑材料与技术是减小关键部件摩擦磨损、实现长寿命和可靠运行的有效途径。因摩擦磨损与DLC薄膜表/界面结构密切相关，但受实验方法表征尺度限制，表/界面微结构演变与润滑油、添加剂的影响及固液复合润滑机理仍阐释不明。本项目优选Ti/Al共掺杂DLC薄膜为研究对象，采用线性离子束复合PVD沉积技术，通过深入细化工艺参数，实现薄膜的高质量可控制备；通过多层结构设计与等离子体刻蚀等微纳加工，构筑不同表/界面结构。研究薄膜在润滑油、添加剂下的摩擦学特性及表/界面微结构演变，结合第一性原理计算，阐明Ti/Al共掺杂DLC薄膜微结构与力学、摩擦学性能之间的构效关系，揭示表/界面结构演变对润滑油、添加剂的作用规律和固液复合润滑协同机理。相关结果有助于指导碳基润滑薄膜组分结构的选择和构建，为发展高性能的固液复合润滑体系和工程应用提供理论和技术基础。

摩擦磨损与类金刚石（DLC或a-C）薄膜表/界面结构密切相关，但受实验表征限制，表/界面结构演变对润滑油的影响及固液复合润滑机理阐释不明。本项目采用理论计算和实验相结合，开展了Ti/Al共掺杂DLC（Ti/Al-DLC）薄膜的表/界面结构设计与固液复合润滑机理的系统研究，良好完成任务要求的各项指标。所取得的成果主要体现在以下几方面：.1）实现了Ti/Al-DLC薄膜的高通量可控制备，其中Al主要以氧化态而Ti主要以氧化态和碳化态存在；随Al/Ti掺杂比从8.0减小至3.0，残余应力、硬度和韧性均增加，归因于薄膜中碳化钛纳米晶增多和软质Al含量的减少；当Al/Ti比为3.0时，摩擦性能最佳，摩擦系数和磨损率分别为0.06、4.7×10-7 mm3/Nm，而摩擦机制也随Al/Ti掺杂比的减小从界面石墨化转变为悬挂键钝化占主导。.2）揭示了本征DLC薄膜的低摩擦行为和界面结构演变，发现：摩擦性能强烈依赖接触压强和转速的比值；低摩擦机理主要归因于界面钝化，但随石墨化结构出现及其尺寸增加，摩擦机理由钝化行为转变为石墨化占主导。特别地，钝化机理主要通过同时减小界面接触面积和剪切强度而减小摩擦力，而石墨化导致的低摩擦力主要归因于单一剪切强度的降低。.3）开展了DLC薄膜的表/界面结构设计，以表面凹坑织构Ti/Al-DLC薄膜为例，表面织构对掺杂金属化学态和薄膜微结构、力学性能无明显影响；当织构化密度为5％时，薄膜摩擦性能最佳，归因于界面石墨化和凹坑织构对磨损颗粒捕获的协同作用。此外，表面氢化改性可有效减少表面悬挂键，结合氢原子的排斥作用，干摩擦下摩擦系数降低可达98.8%，而在固液复合下摩擦系统甚至可实现超滑。.4）薄膜界面添加润滑油可显著改善摩擦性能，但其有效性强烈依赖于接触压强和基础油、添加剂的种类、含量。对于基础油，接触压强增加导致油分子C-C骨架经特定断裂而解离，导致摩擦机理从流体润滑转变为界面钝化；对于添加剂，石墨烯锚接在薄膜表面，作为保护膜减小DLC悬挂键对油分子的吸附，与基础油协同改善摩擦性能，但过量石墨烯引起团聚和界面交联，导致摩擦系数增大。