聚四氟乙烯工程材料的摩擦磨损性能研究

用MPV-200型摩擦磨损试验机研究了干摩擦条件下磨损时间、滑动速度、载荷、填料等对聚四氟乙烯(PTFE)工程塑料摩擦磨损性能的影响，结果表明：PTFE材料的摩擦因数和磨损率先随速度的增大而减小，然后又随着速度的增大而增大；随磨损时间的增长而降低，最后趋于稳定值；另外，摩擦因数大体上随载荷的增大而减小，磨损量则随载荷的增大而增加；填料可将PTFE的磨损量降低2个数量级，其中石墨使PTFE的摩擦因数降低，玻璃纤维和碳纤维则增大了PTFE的摩擦因数，而MoS2对PTFE摩擦因数的影响较小。对PTFE工程塑料的摩擦磨损特性进行系统分析，为优化设计提供理论基础。     

纳米碳酸钙颗粒作为钛基脂添加剂的摩擦学性能

采用四球摩擦磨损试验机研究纳米碳酸钙作为复合钛基脂添加剂的摩擦磨损性能,利用X射线光电子能谱仪分析试验后钢球磨斑表面主要元素的化学状态,用扫描电子显微镜观察钢球的磨斑表面形貌。结果表明：纳米碳酸钙作为复合钛基脂添加剂具有明显的减摩抗磨效果;其中纳米碳酸钙质量分数为时3%复合钛基脂具有佳的减摩抗磨效果,与纯钛基脂相比,可使平均摩擦因数降低14.9 %,磨斑直径降低35.1%。在添加纳米碳酸钙的复合钛基脂润滑下,钢球磨斑表面形成了由纳米碳酸钙分解生成的CaO、钛基脂分解生成的TiO2,以及Fe2O3、FeO等无机化合物成分组成的多孔状保护膜,这层保护膜阻止了摩擦表面的直接接触,起到了有效的减摩抗磨效果。     

聚酰亚胺对聚四氟乙烯基自润滑复合材料摩擦磨损性能的影响

研究了不同聚酰亚胺(PI)含量的聚四氟乙烯(PTFE)基自润滑复合材料的摩擦磨损性能,并分析了干摩擦和预浸油润滑两种条件下的磨损表面形貌和磨损机理.研究表明:PI的加入在于摩擦状态下能显著提高复合材料的减摩性能,并且随着含量的增加效果更加明显;但其抗磨损作用并不明显,其磨损量取决于复合材料的协同作用,而玻璃纤维和MoS2减磨作用明显;在预浸油润滑条件下,由于油润滑占主导地位,复合材料基体减摩效果不能充分体现.     

聚氨酯和聚四氟乙烯的摩擦磨损性能试验研究

为提高现代密封行业中广泛应用的新型聚氨酯(PU)和聚四氟乙烯(PTFE)的密封性能,对其润湿性和摩擦磨损性能进行对比实验,并分析不同摩擦状态下的磨损性能,讨论接触压力和转速的影响。研究表明,聚氨酯的润湿性比聚四氟乙烯好;聚氨酯的耐磨性明显高于聚四氟乙烯,在干摩擦、滴油润滑和浸油润滑的试验条件下,聚氨酯都无明显磨损。干摩擦条件下,聚四氟乙烯的磨损主要受摩擦环转速的影响;滴油润滑条件下,摩擦环转速和接触压力对聚四氟乙烯的磨损都有一定影响;浸油润滑条件下,聚四氟乙烯的磨损主要受接触压力的影响。     

颗粒增强铝基复合材料摩擦磨损性能研究

对颗粒增强铝基复合材料及其基体与 4 0Cr钢摩擦材料组成的摩擦副的摩擦磨损特性进行了对比试验研究 ,并采用SEM对颗粒增强铝基复合材料及其基体磨损表面进行了观察 ,探讨了其磨损机理。试验表明 :复合材料具有较稳定的摩擦系数、低的磨损率 ;复合材料的主要磨损形式是磨粒磨损 ,基体材料的主要磨损形式是粘着磨损。     

纳米和微米La2O3颗粒增强镍基复合镀层的摩擦磨损性能

用复合电沉积工艺制备了纳米和微米La2O3颗粒增强镍基复合镀层，在销盘式滑动磨损试验机上考察了复合镀层在干摩擦条件下的摩擦磨损性能，用扫描电子显微镜分析了其磨损机理。结果表明：在干摩擦条件下，纳米La2O3颗粒增强复合镀层的摩擦磨损性能明显优于微米La2O3颗粒增强复合镀层；纳米La2O3增强镍基复合镀层的磨损主要表现为轻微磨粒磨损特征，而微米La2O3增强镍基复合镀层的磨损机制为剥层磨损和磨粒磨损。     

钛基脂皂分子结构对其摩擦学性能的影响

采用实验室制脂釜制备出苯甲酸和癸二酸组分钛基脂,考察钛基脂的摩擦磨损性能及承载能力,分析皂分子结构和钛基脂摩擦学性能的关系。利用扫描电子显微镜(SEM)观察钢球的磨斑表面形貌,并用X射线光电子能谱(XPS)分析钢球磨斑表面元素含量,利用红外光谱分析表征钛基脂皂分子结构。结果表明:钛基脂摩擦学性能主要取决于钛基脂皂分子结构;含苯环结构苯甲酸组分钛基脂的抗磨特性优于癸二酸组分钛基脂,而他们的减摩特性和极压性能相同;2种钛基脂润滑下钢球主要的摩擦特征为黏着磨损。含苯环结构的苯甲酸组分钛基脂具有较好抗磨性能主要原因为在摩擦表面上生成了较厚含钛元素的化学沉积膜。     

SiC颗粒增强ZA27基复合材料的摩擦磨损性能

用环－块式磨损试验机研究了同一体积分数（１０ｖｏｌ％）、５￣８０μｍ粒径ＳｉＣ颗粒增强ＺＡ２７基复合材料的摩擦磨损特性。发现复合材料的耐磨性为未增强基体的１５倍以上;中等尺寸（１０,２０μｍ）的颗粒对耐磨性具有最佳增强效果。     

纳米Fe_3O_4磁性材料填充聚四氟乙烯的摩擦磨损性能

利用机械共混、冷压成型和烧结工艺制备不同含量的磁性纳米Fe3O4填充聚四氟乙烯(PTFE)复合密封材料,采用MM-200型摩擦磨损试验机考察其在干摩擦下与45#钢对磨时的摩擦磨损性能,借助扫描电子显微镜(SEM)对磨损表面形貌进行观察并分析磨损机制。结果表明:随磁性纳米Fe3O4含量的增加,复合材料的硬度显著提高,摩擦因数呈现先增大后减小再增大的变化趋势,耐磨性能得到明显改善;当Fe3O4质量分数为15%时,复合密封材料的摩擦因数较小,体积磨损率与纯PTFE相比降低两个数量级;随着Fe3O4含量的增加,磨损机制由纯PTFE的黏着磨损转变为黏着磨损与磨粒磨损共同作用。     

Tribological properties of nano‐calcium borate as lithium grease additive

Nano‐calcium borate (NCB) with an average particle size of about 70 nm was synthesised via ethanol supercritical fluid drying technique, and the morphology and microstructures of as‐prepared particles were characterised by means of scanning electron microscope (SEM, JEOL LTD., Tokyo, Japan) and X‐ray powder diffraction. The friction and wear behaviour of the NCB as additive in lithium grease were evaluated with an Optimol‐SRV IV (Optimol Instruments Prüftechnik GmbH, Munich, Germany) oscillating friction and wear tester (SRV tester). The morphology and surface composition of the worn surfaces of lower discs after SRV test were analysed by SEM and X‐ray photoelectron spectroscopy (XPS, Physical Electronics, Inc., USA). The result demonstrated that the anti‐wear and load‐carrying capacities of the lithium grease were significantly improved, and the friction coefficient of the lithium grease decreased with the addition of NCB additive. The analytical results of XPS indicate that the good tribological performance of NCB is attributable to the formation of a boundary lubrication film composed of deposited NCB and the tribochemical reaction products such as B₂O₃, CaO and iron oxides on the rubbing surface. Copyright © 2013 John Wiley & Sons, Ltd.     

Tribological properties and insulation effect of nanometer TiO2 and nanometer SiO2 as additives in grease

New greases were synthesized using oleophilic nanometer-TiO₂ and nanometer-SiO₂ as additives. When the additives in naphthenic oil is 0.1 wt%, the alternating current (AC) breakdown strength is enhanced by 10.4% and 8.2% at power frequency, respectively. Also the grease volume resistivities are improved by 23% and 30% compared with base grease, which use naphthenic oil as base oil. The greases tribological behaviors were explored. Scanning electron microscope linked with energy dispersive X-ray spectroscope was utilized in order to analyze these scratches. The good tribological characteristics of nanometer-TiO₂ greases and the good friction-reducing characteristic of nanometer-SiO₂ greases are ascribed to the nanoparticles mechanical effect, and are also ascribed to the protect film generated by Ti and Si deposited or metallic oxide.     

Remarks on the wear of a journal bearing lubricated by a grease containing a powdered PTFE additive

This paper presents the results of tests on wear of a journal bearing lubricated by a grease containing a powdered polytetrafluorethylene (PTFE) additive. The wear of the bearing lubricated by such a grease is initially greater than the wear of the bearing lubricated by the grease without the PTFE additive, but the total wear of the bearing lubricated by the PTFE loaded grease is almost 2.8 times less than the wear on a similar bearing lubricated by the unloaded grease. An explanation of this phenomenon is suggested.     

Tribological properties of molybdenum disulfide nanosheets by monolayer restacking process as additive in liquid paraffin

Molybdenum disulfide nanosheets were prepared by monolayer restacking process. Results of transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and scanning electron microscopy (SEM) showed that the obtained MoS₂ nanosheets had a thickness about 30-70 nm. The tribological properties of the so-prepared MoS₂ nanosheets were investigated on a MQ-800 four-ball tribometer. The results showed the base oil with MoS₂ nanosheets had better friction reduction, wear resistance and extreme pressure than those with commercial micro-MoS₂. The good tribological properties of MoS₂ nanosheets were mainly ascribed to the surface effect and the dimension effect of nanoparticles. Moreover, the formation of MoO₃ and FeSO₄ complex film on the rubbed surface also played an important role in friction reduction and wear resistance.     

Experimental study of tribological properties of lithium-based grease with Cu nanoparticle additive

The tribological properties of lithium-based grease with nanometer Cu additive are studied in this paper. The feasibility of Cu nanoparticle as grease additive is evaluated by four ball friction tester. Both the bearing temperature rise and the vibration acceleration at different lubrication states are investigated using the bearing test machine. Results show that when the adding amount of nanometer Cu is 0.25% in grease, the friction coefficient and the wear scar diameter of the steel ball are the smallest. Moreover, the vibration acceleration and temperature rise of bearing in 1171-0.25 lithium-based grease are decreased and the bearing speed limit is improved because of the self-repair role of Cu nanoparticles on bearing rolling surfaces.     

Tribological investigation of CaF2 nanocrystals as grease additives

Calcium fluoride (CaF₂) nanocrystals with average grain size of 60 nm were synthesized via a precipitation method. The morphology and structure of nanocrystals were characterized by means of transmission electron microscopy (TEM) and X-ray powder diffraction (XRD). TEM and XRD showed that CaF₂ nanocrystals are cubic particles in submicron scale. The tribological properties of the prepared CaF₂ nanocrystals as an additive in lithium grease were evaluated with a four-ball tester. The results indicated that these nanocrystals exhibit excellent antiwear, friction reduction and extreme pressure (EP) properties. It was also found that the EP and antiwear capabilities of the grease are not proportional to the content of CaF₂ nanocrystals but there existed a certain value. The rubbed surface after friction test was investigated with X-ray photoelectron spectroscopy and scanning electron microscopy to understand the action mechanism. The results show that a boundary film mainly composed of CaF₂, CaO, iron oxide and some organic compounds was formed on the rubbed surface after friction test and the thickness of boundary film was about 12 nm. The disproportion of stoichiometric ratio of Ca and F in boundary lubrication film indicates that tribochemical reaction of CaF₂ nanocrystals occurred on the worn steel surface at severe tribological conditions.     

Tribological properties of the film formed by borated dioctyl dithiocarbamate as an additive in liquid paraffin

This paper discusses the preparation of borated dioctyl dithiocarbamate as an oil-soluble antiwear and extreme pressure additive for lubricants. Its tribological performance when added to liquid paraffin was evaluated on a four-ball tester and a ring-on-block machine. The relationships between its performances and the concentrations are also given, and are compared with these of zinc dialkyldithiophospate (ZDDP). The results show that the novel compound possesses an excellent load-carrying capacity and friction reduction property similar to ZDDP, and exhibits better antiwear property than ZDDP above 392 N. In addition, the novel compound has good anticorrosive property and high thermal stability. The rubbed surface was investigated using X-ray photoelectron spectroscopy, and the antiwear mechanism was discussed.     

Tribological Properties of PTFE and PTFE Composites at Different Temperatures

The friction and wear properties of polytetrafluoroethylene (PTFE) and its composites with fillers such as bronze, glass fiber, carbon fiber, carbon, graphite, and polymer were studied at ambient temperature and high temperature. The wear resistance and hardness were enhanced by the fillers. Results showed that the wear resistance of all composites was much higher than that of pure PTFE. Pure PTFE has the lowest friction coefficient at ambient temperature (temperature: 23 ± 2°C, humidity: 50 ± 10%) but highest friction coefficient at high temperature (above 100°C). The PTFE composite filled with bronze showed the best wear resistance at ambient temperature but the poorest wear resistance at high temperature. The carbon-graphite- or polymer-filled PTFE composite showed a lower friction coefficient and moderate wear resistance at both ambient and high temperature.     

Tribological Behavior of Carbon-Nanotube-Filled PTFE Composites

Carbon nanotube/polytetrafluoroethylene (CNT/PTFE) composites with different volume fractions were prepared and their friction and wear properties were investigated using a ring-on-block under dry conditions. It was found that CNTs signifi-cantly increased the wear resistance of PTFE composites and decreased their coefficient of friction. PTFE composites with 15–20 vol.% CNTs exhibited very high wear resistance. The significant improvements in the tribological properties of CNT/PTFE composites are attributed to the super-strong mechanical properties and the very high aspect ratio of CNTs. The CNTs greatly reinforce the structure of the PTFE-based composites and thereby greatly reduce the adhesive and plough wear of CNT/PTFE composites. The CNTs are released from the composite during sliding and transferred to the interface of the friction couples. They thus serve as spacers, preventing direct contact between the mating surfaces and thereby reducing both wear rate and friction coefficient.     

Tribological behaviors of surfactant-functionalized carbon nanotubes as lubricant additive in water

The multi-walled carbon nanotubes (MWCNTs) are functionalized by self-assembled surfactant layers after sonication in anionic surfactant sodium dodecyl sulfate (SDS) aqueous solution. The tribological properties of the SDS-functionalized MWCNTs as additive in water-based lubricants were evaluated with a four-ball tester. The results show that the SDS-functionalized MWCNTs exhibit good anti-wear and friction reduction properties as well as enhanced load-carrying capacity. The maximum non-seizure load (PB value) can be raised about 3–7 times when SDS-functionalized MWCNTs were added into water. The mechanism of SDS-functionalized MWCNT additive was investigated with scanning electron microscopy (SEM), Auger electron spectroscopy (AES), and Raman spectroscopy. These preliminary results show a promise in applications of surfactant functional carbon nanotubes as an additive in water.