碳化硅表面碳基水润滑涂层的多元复合设计与摩擦学性能研究

Poor lubrication restricts the service life and reliability of the friction pairs badly under the conditions of frequent start-stop, low speed or high speed and boundary lubrication or near-dry friction in water environment. The silicon carbide (SiC) is an ideal friction material in water because of its excellent properties of high hardness, wear resistance , chemical corrosion resistance and high strength. This project puts forward to the lubrication modification and design of the SiC in water environment. The design ideals for the project contain the situ-carbonation of the SiC surface and following infiltration strengthening. Carbon-based multi-composite coating with high load-bearing, low friction and high wear resistance is prepared by using carbide-derived carbon technique combined with subsequent impregnation process. Furthermore, the friction and wear properties of the composite coating in water is investigated systematically. The effect of the composition on the water lubrication performance should be paid attention especially and the mechanism of the friction and wear should be analyzed. At last, the guideline for the water lubrication design of the carbide derived carbon would be deduced. The researches of the project can supply a new approach for designing and synthesizing water-lubricated coating on silicon carbide and expand the application in the field of sliding bearing and dynamic seal.

在变工况（频繁启停、低速/高速、边界润滑/近-干摩擦等）下，润滑不良严重地制约水环境摩擦部件使用寿命与可靠性。碳化硅（SiC）陶瓷具有高硬度、耐磨损、耐化学腐蚀、强度高等优良特性, 是水环境摩擦材料的理想选择。本项目拟深入开展SiC陶瓷在水环境中的润滑改性与设计工作。项目将从SiC表面原位碳化与浸渍强化设计思想出发，利用碳化物衍生碳技术结合浸渍强化工艺进行多元复合构筑，制备出具有高承载、低摩擦、耐磨损的碳基多元复合涂层，进而系统地考察复合涂层在水环境下的摩擦磨损特性，尤其关注涂层组成设计对其水润滑效应的影响，重点分析其摩擦机理与磨损损伤机制，最终提出碳化物衍生碳涂层的水润滑复合设计原则，为SiC表面高性能水润滑涂层的设计与制备提供新途径，拓宽SiC陶瓷在滑动轴承、动密封领域的应用。

碳化硅（SiC）具有高硬度、耐磨损、耐化学腐蚀、强度高等优良特性, 是水环境摩擦副材料的理想选择。SiC的水润滑性能优异，原因在于SiC表面容易发生摩擦化学反应生成SiO2纳米薄膜。然而在润滑不良情况下，高摩擦系数与磨损将会严重影响SiC摩擦部件的使用寿命和可靠性。因此，本项目的主要工作即是通过构筑多元复合涂层对SiC陶瓷进行水润滑改性设计，并考察多元复合涂层在各种工况下的摩擦磨损性能。多元复合涂层的制备主要包括两个过程：1、在900-1000oC下氯化处理SiC制得具有多孔结构的碳化物衍生碳（CDC)涂层；2、选用无机添加剂、润滑油和聚四氟乙烯（PTFE）乳液等对CDC样品进行真空浸渍处理制备多元复合涂层。在低于1000oC下, CDC涂层的生长速度随温度增加而增加，涂层结构以非晶碳为主。CDC涂层孔隙率非常高，内部吸附并储存了大量空气，形成较高的孔压。干摩擦过程中，内部高压气体在应力作用下逸出产生支撑力，有助于降低摩擦副之间的摩擦系数和提高涂层的承载能力。当CDC涂层被PAO润滑油浸渍后，孔洞中的液体润滑油在法向载荷作用下，不能通过涂层内部的贯穿孔洞释放，由此形成较大的液压造成涂层破裂。其润滑与承载性能相较CDC明显降低。然而当CDC涂层被聚四氟乙烯（PTFE）浸渍后，以不锈钢钢球为对偶，其摩擦系数在0.08-0.11区间，相较于CDC涂层降低了30-50%。PTFE-CDC涂层表现为典型的塑性变形磨损特征。在水润滑条件下，CDC的摩擦系数在0.14-0.16之间，磨损特征为典型的磨粒磨损；而PTFE-CDC涂层的摩擦系数在0.06-0.10之间，摩擦系数平稳。磨痕宽度约为CDC的1/3, 表面光滑平整。PTFE-SiO2-CDC涂层的润滑性能与PTFE-CDC涂层相当，但是其耐磨性能明显提高，非常适用于解决SiC的润滑与耐磨防护问题。