【作者】 刘元；

【导师】 李长生；

【作者基本信息】 江苏大学 ， 机械设计及理论， 2010， 硕士

【摘要】 在无油或少油润滑状态下,自润滑材料显示了独特的优越性。铜基自润滑复合材料是金属基自润滑复合材料的重要组成部分,具有优良的摩擦学特性,以及具有导电、导热、抗氧化、耐腐蚀等性能而得到了广泛的应用。铜-石墨-MoS₂是典型的滑动电接触材料,广泛用于电机的固定部件和旋转部件（换向器或集电环）之间传导电流。对于滑动电接触材料,要求其具有低接触电阻,以减少电功率损耗;同时又希望其具有低的摩擦磨损。铜-石墨-MoS₂主要依靠Cu改善材料的导电导热能力,依靠石墨和MoS₂的减摩和自润滑来改善材料的摩擦学特性。但铜-石墨-MoS₂存在如下问题:MoS₂的电阻率高,导电性能差;石墨虽然导电性能好,但在真空环境中摩擦磨损严重。随各类电机仪表朝小型化,大电流,高速度方向发展,要求电接触材料的允许线速度大,接触电压低,摩擦系数小,磨损率低,载流能力大,而铜-石墨-MoS₂电接触材料在性能上难以满足这些要求。纳米NbSe₂具有和MoS₂类似的晶体结构和摩擦学特性,而电阻率仅为10^-4Ω.cm比MoS₂低六个数量级,比石墨低一个数量级。用片状NbSe₂-Ag制备的复合材料在航天飞机的导电滑环上有成功的应用,而NbSe₂纳米纤维既有减摩耐磨的作用,又可以提高复合材料的力学性能。同时利用NbSe₂纳米纤维的各向异性的特点,可以在提高其导电性的同时,改善其换向能力。以往对于NbSe₂-Cu（Ag）的研究多是片层状的,对于纤维状的NbSe₂的摩擦特性的研究还未见报道。本文选用铜基体,选用合适大小和含量的纳米NbSe₂材料充当固体润滑组元。采用粉末冶金方法,制得纳米NbSe₂铜基固体润滑复合材料。结果表明,在一定温度下,烧结工艺对改善纳米NbSe₂和铜基体界面结合的效果有一定影响。通过不同条件下的摩擦磨损试验,以及运用扫描电镜、X-射线衍射仪、光电子能谱仪等微观分析手段,对复合材料显微组织、磨痕表面形貌、磨损颗粒的成分组成进行分析,探讨了在室温下铜基自润滑复合材料的摩擦磨损行为及机理。主要内容包括以下:（1）采用固相反应法:在不同的温度和保温时间下,硒单质和金属Nb在密封的石英管内加热进行反应,分别生成了大量纳米NbSe₂纤维和片状材料。对所合成的纳米材料分别用TEM、SEM、XRD等测试手段进行表面形貌和结构成分的表征。（2）将制备出的纤维状和片层状纳米NbSe₂材料作为润滑添加剂与铜粉相混合,通过粉末冶金法制备出含纳米NbSe₂的铜基复合材料。用INT-2型微观摩擦磨损试验机对它们的摩擦学性能进行了初步研究。结果表明:发现纳米NbSe₂的加入能较大程度的改善铜基复合材料的减摩性能,且纤维状纳米NbSe₂较片层状纳米NbSe₂更能改善铜基复合材料的摩擦学性能。通过对摩擦数据和两种NbSe₂微观结构的分析,对摩擦机理进行了初步推测,认为纳米NbSe₂材料对复合材料的摩擦学性能改善是由其独特的闭合结构、润滑膜的形成、纳米材料的填充自修复共同作用的结果。更多还原

【Abstract】 Self-lubricating（SL） materials exhibit superior performances especially in many cases with a little oil or without oil.Copper（Cu） matrix SL composite,as one of the most important metal matrix SL composites,is widely used owing to its excellent tribological properties,oxidization resistance and corrosion resistance etc.Recently,the graphite/MoS₂/Cu composites are the typical sliding electric contact materials,applied in conducting the electric currents between the fixed parts of electric generator and the rotating components widely.But these composites have the following problems:the MoS₂ had the high electrical resistivity and inferior electrical conductivity;the graphite and MoS₂ were more ductile,which decreased the load capacity,wear resistance properties and welding resistance of the electric contact materials.With the development of all kinds of electrical instruments into miniaturization,large voltage and current,high speed,the electric contact materials were required to have large critical linear velocity,large carrying capacity,low contact voltage,low friction coefficient,low wear loss,but these properties of the graphite/MoS₂/Cu composites were difficult to meet the above requirements.However,NbSe₂ with the similar crystalline structure and tribological properties of MoS₂,but the electrical resistivity is only 10^-4Ω.cm that six amount levels less than that of MoS₂,one less than the graphite.NbSe₂ had not only anti-friction and wear resistance,but also improved the mechanical properties of the composites.Meanwhile, the anisotropy of NbSe₂ improved the electrical conductivity and commutating capability.So far the research into NbSe₂-copper（Ag） composites has much focused on the layered structure（such as sheets）,the tribological properties of the NbSe₂ nanofiber has not been reported.In the thesis,the bronze was selected as the matrix,and nano-NbSe₂ materials with appropriate size and quantity was added as the solid self-lubricant.The copper matrix composites with NbSe₂ nanofiber of low electrical resistivity and excellent anti-friction and wear resistance properties were successfully fabricated by powder metallurgy.The results showed that the combination of the interfaces between matrix and nano-NbSe₂ materials was affected by the high temperature sintering process. After the wear and friction tests,the micro-structures,fracture morphologies,worm surfaces,composition and morphology of debris of the composite samples were analyzed by SEM（scanning electron microscope）,XRD（X-ray diffraction）, EDS（energy dispersion spectrometer）,respectively.The wear behaviors and mechanisms were investigated in detail in the room temperature.During the wear tests,nano-NbSe₂ materials were pressed and moved to surface,and then gradually deformed into continuous thin solid lubricating film.The so-formed film was tightly adhered on the friction surfaces and caused good anti-friction.The main contents are following:（1） NbSe₂ nanofibers or sheets were obtained by heating sealed quartz ampoules by mixed Se and Nb in high temperature boxed furnace.Besides,the mixture of Se and Nb powders were milling in high energy ball-milling machine,the mixture after milling were heat in tubular furnace,a lot of NbSe₂ nanoparticles produced.The component and microstructure of NbSe₂ were investigated by means of X-ray diffraction（XRD）,scanning electronic microscope（SEM） and transmission electronic microscope（TEM）.（2） NbSe₂ nanofibers or sheets were mixed with bronze power uniformity,then copper composites sintered materials with NbSe₂ nanoparticles were prepared by a process of powder metallurgy.The friction and wear performance of composites were investigated by UMT-2 Multi-specimen test system.It was found that the incorporation of NbSe₂ nanoparticles contributed to effectively steady the friction coefficients under all kinds of loads and improve the antifriction performance of the composites,which was attributed to the self-lubricity of the NbSe₂ nanoparticles lubricating film formed on the worn composite surface,and NbSe₂ nanofibers as solid lubricants is improving the tribological properties better than NbSe₂ sheets in the copper-base composites.The friction mechanism of lubrication was discussed preliminary based on the analysis of experiment data and microstructure of NbSe₂ nanoparticles.The lubrication has excellent tribological properties may be due to the following factors:unique closed structures,lubrication films and fill up-repair.更多还原