【作者】 王新平；

【导师】 黄伯云； 周科朝；

【作者基本信息】 中南大学 ， 材料科学与工程， 2013， 博士

【摘要】 论文以卫星用银基固体自润滑电刷材料为研究对象,以实现该材料空间应用寿命的增长。通过对银基固体自润滑材料性能的测试分析,全面了解材料的基本力学性能及其摩擦磨损性能的基础上,分别研究了固溶强化和碳纤维增强两种方式在提高银基固体自润滑材料抗磨损性能方面的作用规律及实施效果,并与现役材料进行对比,揭示了材料寿命增长机理；对AuNi9、AgCu10丝式电刷材料进行了载流摩擦磨损性能的研究,掌握了该类材料的滑动电接触特性,通过与银基固体自润滑材料的性能对比,清晰而全面地掌握了主流国产空间滑动电接触材料的综合性能及应用特点；采用所得固溶强化银基固体自润滑材料作为环体材料,开展了空间导电环工程样机制备工作,对样机的各项电器性能进行测试,评估了所得样机的使用性能,为开发新一代大功率、长寿命空间导电环产品提供了有力的支撑。论文获得如下结论：1)采用化学法掺铜工艺制备了Ag-Cu复合粉末,然后采用气氛保护热压方法制备了Ag-2.5Cu-8MoS2复合材料,所得材料的组织结构均匀、稳定,各功能层界面清晰,结合良好；所得材料的相对密度大于96.5%,自润滑功能层的抗弯强度为167.2MPa,硬度大于HB50,摩擦系数0.12～0.20,磨损率<2×10-13m3/N·m,静态接触电阻<0.54mΩ；摩擦磨损性能测试结果表明,该材料在3A电流下其稳态摩擦系数在0.2左右,稳态工作寿命在10km以上,上述性能全面满足某型号卫星对滑动电接触材料所提出的工艺技术指标要求。2)采用粒度细小、分布合理的气雾化AgCu合金粉末取代原有化学法制备的Ag-Cu复合粉末制备了新型Ag-2.5Cu-8MoS2材料,实现了对该材料的固溶强化,所得材料的磨损率由前期的50x10-14m3/N·m降低到5-8×10-14m3/N·m,材料磨损率降低程度达一个数量级,表明气雾化粉末电刷材料具有较好的耐磨性,延长了电刷的使用寿命。3)研究发现粉末粒度及级配效果对Ag-2.5Cu-8MoS2复合材料的力学性能和MoS2分布状态的作用影响显著。气雾化Ag-2.5Cu-8MoS2复合材料的硬度和抗弯强度随着合金粉末粒度的减小而提高,当粉末粒度从-300+400目减小至-500目时,复合材料的硬度和抗弯强度分别从HB45.9、88.08MPa提高至HB56.8、179.08MPa;随着银铜合金粉末粒度的减小,MoS2团聚体在Ag-2.5Cu-8MoS2复合材料基体中的分布均匀性得到提高,材料的摩擦系数波动和稳定摩擦系数都随着减小,显著改善了材料服役的稳定性。4)采用经石墨化处理的碳纤维对Ag-2.5Cu-8MoS2复合材料进行磨损强化,获得了多种组分的Ag-2.5Cu-8MoS2-xCf材料。结果表明,随着碳纤维含量的增加,复合材料的摩擦系数略有上升,但材料的磨损率获得了有效的改善,当碳纤维体积分数从0%增加到15%时,复合材料的磨损率从6.31×10-14m3/N-m降低到2.07×10-14m3/N-m,即材料的磨损率获得了三倍的提升,磨损强化作用显著。5)对Ag-2.5Cu-8MoS2-xCf材料的载流摩擦磨损性能的研究表明,电流的加载对各材料磨损率的影响较小,但碳纤维的加入对材料的接触压降影响显著。结果表明,所制备的各组分材料的接触压降基本在0.03-0.09V范围内动态变化,但材料的接触压降值及波动幅度明显随碳纤维含量增加而升高,即接触状态变差。因此认为对于Ag-2.5Cu-8MoS2-xCf材料来说,在保障材料获得良好接触压降水平的同时还要有较好的耐磨性,碳纤维的添加量控制在6vo1%左右为宜(Ag-2.5Cu-8MoS2-6vol%Cf的磨损率为3.02×10-14m3/N·m)。6)通过对单丝／多丝AuNi9、AgCu10电刷材料常规摩擦磨损性能及载流摩擦磨损性能的测试,发现了该类材料的配对特点,其中AuNi9适于同具有的Au、Ni复合镀层进行配对,而AgCu10适于与黄铜镀金层配对；AuNi9与Au、Ni复合镀层配对获得了最佳的载流摩擦磨损性能,平均摩擦系数0.9,平均接触电压0.5mV/A,其平均接触电压值较采用AgCu10所得数据低3倍。7)采用银基固体自润滑电刷材料作为导电环环体,制造了一款新式的导电滑环样机,在导电环结构设计上获得的了创新。导电环样机性能测试指标完全符合设计要求,样机10.5万转(1s/r)跑合实验表明,长时间跑合后,各环的静态接触电阻经历了先升高再降低并趋于稳定的过程,整个跑合阶段接触电阻波动范围约为3-5mΩ,表明环刷材料接触性能稳定可靠。更多还原

【Abstract】 Silver matrix solid self-lubricating brush materials used for satellites were investigated in this paper, and the duration of this kind of materials in space application was increased. The physical and mechanical properties, along with friction and wear behaviors, of silver matrix brush materials were known after tests and analysis, so the mechanism and effect of the wear-resistance improvement of this material was investigated by two strength methods such as solid solution and carbon fiber reinforced. The improved materials were also compared with the application material, so as to find the mechanism of lifetime growth. The sliding electrical contact performance of AuNi9and AgCu10wire brushes were researched by friction and wear tests under electrical current. Comparing the silver matrix composite brushes with noble metal wire brushes, we clearly and completely know the properties and application characteristics of sliding electrical contact materials for space application. A model slip ring was made and its electrical properties were tested, the ring of this slip ring was made using solid solution strengthen silver matrix composite material. The application behavior of this slip ring was assessed, and this will be an important support for the development of new generation slip ring with high power and long duration in space.The main conclusions and results are summarized as follows:1) Ag-Cu composite powder was prepared by chemical adding copper method, and then it was used to prepare the Ag-2.5Cu-8MoS2composite by hot-pressing. The structure of the prepared composite is uniform and stable, and the interfaces of each function layer are clear and well combined. The relative density of prepared composite is above96.5%, and the bending strength of self-lubricating function layer is167.2MPa, and the hardness, friction coefficient, wear rate and static contact resistance are HB50,0.12-0.20,<2×10-13m3/N·m, and<0.54mΩ, respectively. The results of friction and wear test under3A current indicate that the stable friction coefficient of the material is about0.2and the stable operation life is above10km. The properties of the prepared Ag-2.5Cu-8MoS2composite satisfy the technology demand of some type of satellite.2) A new kind of Ag-2.5Cu-8MoS2composites was prepared with small size atomized AgCu alloy powder instead of Ag-Cu composite powder. The prepared material was strengthened by solid solution, and the wear rate of the composite was reduced from former50×10-14m3/N-m to5-8×10-14m3/N-m. The reduction degree of wear rate is almost a magnitude. The result turned out that the brush material prepared with atomized powder has high wear resistance, and the duration of the brush is increased.3) It was found that the influence of powder size and distribution to the mechanical properties and MoS2distribution of Ag-2.5Cu-8MoS2composite is significant. The hardness and bending strength of the composite increase with decreasing the size of alloy powder. As the size of alloy powder decreasing from-300+400mesh to-500mesh, the hardness and bending strength of composites increase from HB45.9,88.08MPa to HB56.8,179.08MPa. The distribution of MoS2particle in Ag-2.5Cu-8MoS2composites was improved when small size alloy powder was used, which caused the reduction of friction coefficient and its fluctuation. The operation stability of the material is significant improved.4) The Ag-2.5Cu-8MoS2composite was reinforced by graphitized carbon fiber, and Ag-2.5Cu-8MoS2-xCf composites with different volume fraction of carbon fiber were prepared. It is found that the friction coefficient of the composites increase slightly and the wear rate is improved a lot with increasing the amount of carbon fiber. The wear rate of the composite decreases from6.31×10-14m3/N-m to2.07×10-14m3/N·m when the volume fraction of carbon fiber increases from0%to15%. There is three times of increase with the wear rate the composite, and the strength effect to wear is remarkable.5) The friction and wear behaviors of Ag-2.5Cu-8MoS2-xCf composites were investigated under current. It is found that the influence of current on the wear rate of composites is insignificant. However, the influence of carbon fiber addition on contact voltage drop is apparent. The contact voltage drop values of all prepared composites are in the range of0.03-0.09V, but the value and fluctuation of contact voltage drop increase with the increase of carbon fiber content. Therefore, it is believed that the carbon fiber content in composite should be around6vol%, so that it has low contact voltage drop and good wear resistance (the wear rate of Ag-2.5Cu-8MoS2-6vol%Cf is3.02×10-14m3/N-m).6) The friction and wear behavior of AuNi9and AgCu10brush of one wire type and fiber type were investigated with or without current, and the match characteristic of this kind brush was found. AuNi9fiber brush matches well with gold plated Ni coating, and AgCu10fiber brush matches well with gold plated brass. The sliding electrical contact behavior of AuNi9brush sliding on the gold plated Ni coating is best among them. The friction coefficient of it is0.9, and the average contact voltage drop is0.5mV/A, which is three times lower than that of AgCu10.7) A new type of model slip ring was made using the silver matrix solid self-lubricating brush material as the ring material, and this is an innovation to the structure of slip ring. The test properties of the slip ring fit well with the design demand. The running test with one hundred thousand revolutions (1s/r) turned out that the static contact resistance increases at first, then decrease and finally maintain stable. The variation of contact resistance is about3-5mΩ during the running process, which shows that the contact between brush and ring is reliable.更多还原