随着临床医学的快速发展，人们对医疗水平的期望值越来越高，这就要求钛合金用人工关节在人体体液的复杂环境下使用时具有更久的服役寿命和更高的运转稳定性。另一方面，在汽车向轻量化、环保、节能方向发展的今天，钛合金无疑是最具有潜质的汽车发动机关键零部件用材料。然而，不得不指出的是，目前钛合金在工业中多以结构性材料使用，除了本身价格较为昂贵、成形性不好及焊接性能差等缺点外，另一个不容忽视的原因在于钛合金表现出较差的摩擦学性能，严重限制了钛合金作为机器关键运动部件的应用。对钛合金进行表面改性处理能够有效改善其在人体体液及油润滑下的摩擦学性能，延长使用寿命，提高钛合金用零部件运行的可靠性。基于此，本文在钛合金表面制备了热氧化层和类金刚石(DLC)膜，并将两者有机结合构筑双层复合薄膜，研究了薄膜的耐腐蚀磨损性能和润滑性能，探讨了减摩、抗磨机理。论文得到以下主要结论： (1)表面沉积的Cr／CrC／DLC梯度过渡薄膜体系能够明显改善TC4钛合金在模拟人工体液中的耐腐蚀磨损性能，其中高C₂H₂流量制备的Cr／CrC(40)／DLC薄膜体系，其CrC过渡层由柱状晶结构转变为非晶／纳米晶结构，提高了过渡层的硬度，降低了薄膜的内应力，增强了膜基结合强度。同时，CrC的非晶／纳米晶结构具有更多的晶界，可以有效抑制摩擦过程中裂纹的萌生与扩散，延迟腐蚀介质对TC4钛合金基底的侵蚀，因此表现出优异的耐腐蚀磨损性能。 (2)研究了热氧化处理温度及时间两个参数对TC4钛合金样品表面氧化膜的结构及耐腐蚀磨损性能的影响。实验发现，在模拟人工体液中，热氧化后样品的耐腐蚀和耐腐蚀磨损性能并不随着热氧化温度的升高及热氧化时间的延长而增强，在本研究所涉及的温度及时间范围内，经700℃和5h热氧化处理得到的样品具有更优的表面硬度、更致密的膜结构和更好的膜基结合性能，在模拟人工体液中呈现最优的耐腐蚀和耐腐蚀磨损性能。 (3)分别采用浸渍涂覆和化学气相沉积技术在热氧化处理后TC4钛合金氧化层表面沉积了聚四氟乙烯(PTFE)和DLC薄膜，得到了双层复合薄膜体系。涂覆的表层薄膜一方面封闭了氧化物薄膜的缺陷，有效提高了涂层的致密度，其本身良好的疏水性阻止了腐蚀性离子与基底的接触，提高了耐腐蚀性能；另一方面，表层薄膜具有良好的润滑性能。因此，相比于单纯热氧化处理样品，双层复合薄膜在模拟人工体液中耐腐蚀和耐腐蚀磨损性能得到了显著的提高。 (4)在全合成机油润滑条件下，热氧化处理的TC4钛合金样品表面形成的TiO₂层提高了表面硬度，减小了粘着磨损，改善了表面润湿性，同时促进了润滑油中抗磨添加剂在表面发生摩擦化学反应生成具有减摩耐磨性能的磷酸盐边界膜，因此表现出良好的摩擦学性能。 (5)率先提出一种利用热氧化处理的TC4钛合金表面TiO₂层本身的光催化性能在摩擦过程中催化降解润滑油分子在接触区原位构筑DLC薄膜而起到减摩、耐磨性能的润滑设计思想，系统考察了聚α烯烃(PAO6)分子在TiO₂表面降解生成DLC的减摩、耐磨机理。 关键词：TC4钛合金；热氧化；DLC；腐蚀磨损；摩擦催化；润滑

 With the rapid development of clinical medicine, people's expectations for medical level are getting higher and higher, which requires artificial joints made by titanium alloy to have longer service life and higher running stability when used in the complex environment of human body fluids. On the other hand, in today's automobile development towards light weight, environmental protection and energy conservation, titanium alloy is undoubtedly the most potential material for key automotive engine components. However, it must be pointed out that titanium alloys are mostly used in structural materials in the industry at present. In addition to their disadvantages such as high price, poor formability and poor welding performance, another reason that can not be ignored is that titanium alloys exhibit poor tribological properties which severely limit the use of titanium alloys as key moving parts in machines. The surface modification treatment of titanium alloy can effectively improve the tribological properties under human body fluid and oil lubrication, prolonging the service life and improving the reliability of the operation of components made by titanium alloy. Based on this, a thermal oxide film and a DLC film were prepared on the surface of titanium alloy, and the two layers were organically combined to construct a two-layer composite film. The corrosion resistance and lubrication properties of the film were studied, and the antifriction and antiwear mechanism was discussed. The paper has the following main conclusions: (1)The surface deposited Cr/CrC/DLC gradient transition film system can significantly improve the corrosion and wear resistance of TC4 titanium alloy in simulated artificial body fluids. The Cr/CrC(40)/DLC film system prepared by high C₂H₂ flow has a CrC transition layer which is transformed from a columnar crystal structure to an amorphous/nanocrystalline structure. This improves the hardness of the transition layer, reduces the internal stress of the film and improve film base bonding strength. At the same time, the amorphous/nanocrystalline structure of CrC has more grain boundaries, which can effectively inhibit the initiation and diffusion of cracks in the friction process, delay the corrosion of the TC4 titanium alloy substrate in the corrosive medium, and thus exhibit excellent corrosion and wear resistance. (2)The effects of temperature and time of thermal oxidation treatment on the structure and corrosion resistance of oxidized film on the surface of TC4 titanium alloy samples were investigated. In the experiment, it was found that in the simulated artificial body fluid, the corrosion resistance and corrosion wear resistance of the sample after thermal oxidation did not increase with the increase of the thermal oxidation temperature or the prolongation of the thermal oxidation time. In the temperature and time range of the study, the samples, obtained by thermal oxidation treatment at 700℃ for 5h, have better surface hardness, more dense membrane structure, better membrane-based bonding performance, exhibiting optimal corrosion and corrosion resistance resistance in simulated artificial body fluids.. (3)Polytetrafluoroethylene (PTFE) and DLC films were deposited on the surface of TC4 titanium alloy oxide film after thermal oxidation treatment by dip coating and chemical vapor deposition, respectively. The double-layer composite film system was obtained. On the one hand, the surface film closes the defects of the oxide film, effectively increases the density of the coating, prevents the contact of corrosive ions with the substrate and improves the corrosion resistance by their good hydrophobicity. On the other hand, the surface film has good lubrication properties. Therefore, the corrosion resistance and corrosion resistance of the two-layer composite film in the simulated artificial body fluid is significantly improved, as compared to the pure thermal oxidation sample. (4)Under the lubrication condition by a fully formulated oil, the TiO₂ layer formed on the surface of the thermally oxidized TC4 titanium alloy sample improves the surface hardness, reduces the adhesive wear, improves the surface wettability, and promotes the anti-wear in the lubricating oil. The additive undergoes a tribochemical reaction on the surface to form a phosphate boundary film which has antifriction and wear resistance, and thus exhibits excellent tribological properties. (5)Based on the photocatalytic performance of TiO₂ layer on the surface of TC4 titanium alloy by thermal oxidation, the in situ catalytic degradation of lubricating oil molecules in the friction process during the friction process, which builds DLC film in the contact zone to reduce the friction and wear, is firstly proposed. The design idea is systematically investigated to study the anti-friction and wear-resisting mechanism of polyalphaolefin (PAO6) molecules which are degraded on TiO₂ surface to form DLC coating. Key words: TC4 titanium alloy; thermal oxidation; DLC; corrosion wear; friction catalysis; lubrication