高温自补偿润滑的热力耦合驱动模型及成膜机理研究

发布时间：2018-10-08 10:14

【摘要】：微孔高温自补偿润滑复合材料是将熔融复合固体润滑剂真空压力下熔浸到微孔基体中而制备的一种新型的自润滑复合材料。在高温环境下工作时,储存于其孔隙内的固体润滑剂因摩擦热-应力作用析出到摩擦界面形成润滑膜,从而实现自润滑功能。其摩擦学特性取决于复合固体润滑剂的析出量及组分组成。因此,建立热-力耦合驱动模型,研究固体润滑剂析出机制及成膜机理,对于微孔高温自补偿润滑复合材料的设计制备具有重要意义。基于多孔介质球粒装填理论和高温自补偿润滑材料微孔结构特征,建立胞体结构模型;针对摩擦过程中的热力耦合问题,对胞体模型温度场和应力场计算;针对润滑剂析出的驱动力,利用热弹性力学理论建立热力耦合驱动模型,并对环境温度、摩擦热、摩擦力等影响因素分析。利用ANSYS Workbench完成熔渗型高温自补偿润滑材料的瞬态热分析和热力耦合分析,得到摩擦过程中温度场、应力场分布变化规律及相关原因,分析润滑剂和基体的温度、应力、应变的变化趋势,探讨不同影响因素(加热温度、摩擦热、孔变形挤压力)对润滑剂驱动力的影响。仿真结果表明:加热温度对驱动力具有增益效果,持续加热后需考虑摩擦热的影响;相对加热温度,摩擦热对润滑剂的驱动力具有显著的促进作用,而孔变形产生的挤压应力影响较小;润滑剂在加热温度、摩擦热-应力及变形挤压的共同作用下析出到摩擦界面。基于润滑体与基体材料的匹配性和互溶性,通过润湿试验,结合经验公式分析,对固体润滑剂进行了组分设计,其最佳配比为:Pb65Sn35+12~18%Ag+0.2~0.3%RE(Y2O3);采用高频电磁感应熔浸工艺实现了基体与润滑剂的熔渗复合,制备出了熔渗型M3/2/TiC系高温自润滑复合材料。在销盘式高温摩擦磨损试验机上考察了其摩擦磨损性能,利用扫描电子显微镜(SEM)、光电子能谱(EDXA)和X射线衍射仪(XRD)分析磨损表面成分、形貌和结构。结果表明:熔渗型高温自润滑复合材料在高温摩擦磨损过程中,润滑剂通过微孔通道析出至摩擦表面形成了一层含有Pb、Sn、Ag、RE等元素的固体润滑膜;在Pb65Sn35-12Ag润滑剂基础上添加0.25%RE,润滑性能相对提高;基于SEM表面形貌分析,探讨了高温自补偿润滑复合材料的成膜机理。
[Abstract]:Microporous high temperature self-compensation lubricating composite is a new type of self-lubricating composite material, which is prepared by melting melt composite solid lubricant into microporous matrix under vacuum pressure. At high temperature, the solid lubricant stored in the pore of the lubricant can form a lubricating film at the friction interface due to the effect of friction heat and stress, so that the self-lubricating function can be realized. Its tribological properties depend on the amount of precipitation and composition of the composite solid lubricant. Therefore, it is of great significance to establish a thermal-mechanical coupling drive model and study the precipitation mechanism and film formation mechanism of solid lubricant for the design and preparation of microporous high-temperature self-compensation lubricating composites. Based on the theory of spherical filling in porous media and the characteristics of micropore structure of high temperature self-compensating lubricating materials, the cell body structure model is established, and the temperature field and stress field of the cell body model are calculated according to the thermo-mechanical coupling problem in the friction process. According to the driving force of lubricant precipitation, the thermoelastic theory is used to establish the thermo-mechanical coupling driving model, and the influence factors such as ambient temperature, friction heat and friction force are analyzed. The transient thermal analysis and thermo-mechanical coupling analysis of infiltrated high-temperature self-compensation lubricating materials were completed by ANSYS Workbench. The temperature field, stress field distribution and related reasons were obtained during friction process. The temperature and stress of lubricant and matrix were analyzed, and the temperature and stress of lubricant and matrix were analyzed. The influence of different factors (heating temperature, friction heat, hole deformation extrusion pressure) on the driving force of lubricant is discussed. The simulation results show that the heating temperature has gain effect on the driving force, the effect of friction heat should be taken into account after continuous heating, and the friction heat has a significant promoting effect on the driving force of lubricant compared with the heating temperature. However, the effect of pore deformation on extrusion stress is relatively small, and lubricant precipitates to the friction interface under the combined action of heating temperature, frictional thermal-stress and deformation extrusion. Based on the matching and mutual solubility of lubricant and matrix material, the composition design of solid lubricant was carried out by wetting test and empirical formula analysis. The optimum ratio is: 1 / Pb65Sn35 12~18%Ag 0.2~0.3%RE (Y2O3), and the infiltrating composite of matrix and lubricant is realized by high frequency electromagnetic induction infiltration process, and the infiltrated M3/2/TiC system high temperature self-lubricating composite is prepared. The friction and wear properties were investigated on a pin disk high temperature friction and wear tester. The wear surface composition, morphology and structure were analyzed by scanning electron microscope (SEM),) photoelectron spectroscopy (EDXA) and X-ray diffractometer (XRD). The results show that during high temperature friction and wear of the infiltrated high temperature self-lubricating composite, the lubricant precipitates to the friction surface through the micropore channel to form a layer of solid lubricating film containing Pb,Sn,Ag,RE and other elements. On the basis of Pb65Sn35-12Ag lubricant, the lubricating property is improved by adding 0.25 RE.The film forming mechanism of high temperature self-compensation lubricating composite is discussed based on SEM surface morphology analysis.
【学位授予单位】：济南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB33

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