对偶表面粗糙度对Nano-SiO2改性PTFE复合材料摩擦学性能的影响

为了研究干摩擦条件下对偶表面粗糙度对纳米粒子填充改性聚四氟乙烯（PTFE）复合材料摩擦磨损及转移膜特性的影响规律，本文采用冷压成型、热烧结的工艺方法制备nano-SiO2填充改性PTFE复合材料；采用LSR-2M型往复摩擦磨损试验机评价了nano-SiO2改性PTFE复合材料与具有三种不同表面粗糙度的对偶钢块（GCr15）之间的摩擦磨损性能；利用光学显微镜（OM）、扫描电子显微镜（SEM）和能谱仪（EDS）分别表征了转移膜及磨屑的形貌、微观结构以及化学成分，从微观角度揭示nano-SiO2改性PTFE复合材料的摩擦转移机理。试验结果表明，纯PTFE及不同含量nano-SiO2填充改性PTFE复合材料的摩擦系数均随对偶钢块表面粗糙度的增大整体呈增大趋势，在粗糙度为Ra0.1的对偶表面上复合材料的摩擦系数随着nano-SiO2含量的增加变化相对较小；在三种不同粗糙度对偶表面上，nano-SiO2的加入均有效降低了PTFE的磨损体积，当填充比例为0.5wt%时复合材料在粗糙度为Ra1.2的对偶面上摩擦学性能最佳，磨合时间约为纯PTFE的1/3（缩短了近10min），耐磨性较纯PTFE提高了34.1%。由此可见，复合材料中nano-SiO2的含量与对偶表面粗糙度存在一定的协同效应，即nano-SiO2的含量与对偶表面粗糙度具有匹配性，合理的摩擦配副能有效促进复合材料的摩擦转移，并能在对偶表面形成覆盖率高、均匀、连续、表面较粗糙且与摩擦方向趋向一致的转移膜，有利于降低材料的磨损。

Effect of Counterpart Surface Roughness on the Tribological Properties of Nano-SiO2 Modified PTFE Composites

In order to study the influence of counterpart surface roughness on friction, wear and transfer film of PTFE composites filled with na-noparticles under dry friction condition, nano-SiO2 filled PTFE composites were prepared by cold pressing and hot sintering in this paper. The tribological properties of nano-SiO2 filled PTFE composites sliding on three kinds of counterpart (GCr15) surface with dif-ferent surface roughness were evaluated by LSR-2M reciprocating friction and wear tester. The morphologies, microstructures and chemical compositions of the transfer films and debris were characterized by Optical Microscopy (OM), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectrometer (EDS), respectively , in order to reveal the friction transfer mechanism of nano-SiO2 filled PTFE composites from the microscopic perspective. The experimental results showed that the friction coefficients of pure PTFE and different content of nano-SiO2 filled PTFE composites increased with the increase of the surface roughness of the steel counterpart, while the friction coefficients of the composites on the counterpart surface with roughness of Ra0.1 changes relatively little with the increase of nano-SiO2 content. The addition of nano-SiO2 effectively reduced the wear volume of PTFE on three different counterpart surface roughness. When the filling ratio was 0.5wt%, the best tribological property was obtained on the counterpart surface with roughness Ra1.2, the running-in time was about 1/3 of that of pure PTFE (shortened by nearly 10 minutes), and the wear resistance was 34.1% higher than that of pure PTFE. Therefore, we could conclude that the content of nano-SiO2 in the composites had a certain syner-gistic effect with the counterpart surface roughness. Namely, the content of nano-SiO2 matched with the roughness of the counterpart surface. Reasonable friction pairs could promote the friction transfer of the composite materials effectively, and then the transfer films with high coverage, uniformity, continuity, rough surface and consistent with the direction of friction on the counterpart surface were formed, which was conducive to reducing the wear of materials.