Fluorinated FeF3 catalyst interactions in three different oil formulations using design of experiment optimization and chemistry characterization of tribofilms

The influence of fluorinated FeF₃ catalyst on the formation and properties of tribofilms was examined using design of experiment (DOE) under extreme boundary lubrication (385 N or maximum Hertzian contact pressure of 2.72 GPa). A closed loop boundary condition test was developed to examine the behaviour of lubricants under boundary conditions. The reduction of phosphorus in engine oil was examined using two different plain oils and one fully formulated oil. Results indicate the formation of a thicker tribofilm in plain fluorinated oil when compared with fluorinated fully formulated oils. Several chemistry combinations were prepared and tested. Wear and frictional properties were evaluated using DOE, and the interactions of fluorinated FeF₃ catalyst with minimum phosphorus were studied and compared with respect to fully formulated and plain zinc dialkyl dithiophosphate oils. Tribofilms with thickness ranging from 150 to 350 nm were developed during wear tests and were analysed for fluorinated plain and fully formulated oils that target reducing phosphorus. Three specific tests with optimised 0.6% FeF₃ catalyst concentrations were used with 0.05% phosphorus in plain and fully formulated oil to verify the model optimised conditions with respect to wear and time to full break down. Scanning electron microscopy, hardness of the tribofilms and Auger spectroscopy confirm the presence of fluorine and phosphorus. These tests confirm the optimised prediction of the DOE model. Copyright © 2011 John Wiley & Sons, Ltd.     

Direct visualization of sliding-induced tribofilm on Au/MoS<Subscript>2</Subscript> nanocomposite coatings by c-AFM

The nanoscale lubrication mechanism of nanocomposite Au/MoS₂ solid lubricant coatings has been studied by conductive atomic force microscopy (c-AFM). A direct visualization of the lubricating process suggests tribomechanical formation of a MoS₂ tribofilm to be a key mechanism. The sliding-induced tribofilm formation was visualized by a reduction in local friction and conductivity in nanoscale AFM images. The tribofilm was found to possess considerable crystallinity and orientation, which was not observed in the as-deposited coatings. The observed mechanism is broadly applicable to a range of nanocomposite metal/MoS₂ coatings.     

摩擦表面重构的研究

在干摩擦或边界润滑条件下,摩擦副材料的组成与摩擦学特性都会在摩擦接触过程中发生改变。分析了多种摩擦系统中表面重构对于材料和机械摩擦学性能的重要影响。提出了从改善材料表面重构入手,设计新型材料和润滑剂的研究思路。     

宽温域环境下不同纤维织物/聚酰亚胺复合材料的摩擦学性能研究

目的 研究高温条件下聚合物织物复合材料的摩擦学性能。方法 分别制备碳纤维织物及芳纶纤维织物/聚酰亚胺复合材料及纯聚酰亚胺(CF-PI、AF-PI及PI),对比研究2种织物复合材料与聚酰亚胺的热力学性能,以及在25、50、100、150、200 ℃下的摩擦学性能。结果 AF-PI的热稳定性低于CF-PI,其中CF-PI热失质量稳定在800 ℃左右,AF-PI的热失质量稳定在700 ℃左右。同时,2种织物复合材料的拉伸强度均高于纯PI,且CF-PI的拉伸强度要高于AF-PI。断面形貌分析发现,CF-PI为脆性断裂,AF-PI为韧性断裂。摩擦实验结果表明,25 ℃时,AF-PI的摩擦系数和磨损率较低,更适用于室温环境,而CF-PI在200 ℃时具有较好的耐磨性,其磨损率为1.48´10^–4 mm³/(N×m)。结论 转移膜结构和化学状态分析证实,由于CF-PI与GCr15之间较强的界面作用,室温条件下对摩后,轴承钢表面更易发生摩擦氧化。高温条件下,由于金属–有机螯合物的形成,提高了转移膜的结构稳定性,CF-PI表现出优异的摩擦学性能,然而200 ℃时,由于AF-PI的力学性能降低,材料被磨穿,转移膜的结构被破坏,导致了金属之间的摩擦,发生了严重的摩擦氧化。     

In Situ Raman Observations of the Formation of MoDTC-Derived Tribofilms at Steel/Steel Contact Under Boundary Lubrication

ABSTRACT

In this study, the time-dependent formation process of molybdenum dithiocarbamate (MoDTC)-derived tribofilms at steel/steel contact under boundary lubrication was investigated by using an in situ Raman tribometer. Especially, we focused on the effects of zinc dialkyldithiophosphate (ZDDP) concentration in MoDTC solution on MoDTC tribofilm formation process. A laboratory-built in situ Raman tribometer was used to evaluate friction and the formation process of MoDTC-derived tribofilms. All our results clearly suggest that there is an optimum ZDDP concentration in MoDTC solution for promoting the formation of MoS₂ tribofilms on the sliding surfaces, and there is also a threshold value for the formation rate of MoS₂ on the sliding surface for achieving low friction under lubrication with MoDTC-containing lubricants.     

Chemistry of ZDDP Tribofilm by ToF-SIMS

Time-of-flight secondary ion mass spectrometry (ToF-SIMS) (static and dynamic modes) has been applied to chemical characterization of zinc dithiophosphate additives tribofilm. Main result concerns insights in the spatial distribution of phosphate and sulphide species in the whole tribofilm thickness, at a sub-micrometer scale. The disappearance of oxide layer at the interface between steel and the tribofilm is also noticed.     

TEM-EELS study of low-friction superlattice TiAlN/VN coating: the wear mechanisms

A 20–50 nm thick tribofilm was generated on the worn surface of a multilayer coating TiAlN/VN after dry sliding test against an alumina counterpart. The tribofilm was characterized by applying analytical transmission electron microscopy techniques with emphasis on detailed electron energy loss spectrometry and energy loss near edge structure analysis. Pronounced oxygen in the tribofilm indicated a predominant tribo-oxidation wear. Structural changes in the inner-shell ionization edges of N, Ti and V suggested decomposition of nitride fragments.     

柴油碳烟对ZDDP摩擦反应膜的分布、成分及力学性能的影响

为研究柴油碳烟对ZDDP摩擦反应膜的分布、成分和力学性能的影响。采用HFRR摩擦磨损试验机进行了摩擦磨损试验。采用激光显微镜、SEM/EDS、拉曼光谱、XPS和纳米压痕仪对由ZDDP和碳烟摩擦磨损后的表面进行了分析。结果表明，碳烟会刮离ZDDP摩擦反应膜并嵌入磨损表面，导致膜厚减小和摩膜的不均匀分布。ZDDP摩擦膜中的磷酸盐结构由短链焦磷酸盐向长链偏磷酸盐转变，归于碳烟磨粒磨损引起的接触应力增加，促进了ZDDP的交联。磨损表面的硬度（H）和弹性模量（E）增加，而硬度与弹性模量的比值（H/E）降低，这表明碳烟导致耐磨性降低。     

摩擦过程中过碱水杨酸钙与ZDDP相互作用的研究

利用X射线吸收精细结构光谱（XANES）研究了过碱水杨酸钙与二烷基二硫代磷酸锌（ZDDP）复配使用时形成润滑膜的表面化学行为,并提出了其和ZDDP的相互作用机制.结果表明,在ZDDP中加入过碱水杨酸钙后完全改变了ZDDP单独使用时形成润滑膜的结构,润滑膜中含有一定数量的钙离子,其结构以磷酸钙为主;对超高碱值的水杨酸钙与ZDDP复配体系,在润滑膜中除发现磷酸钙外,同时观测到碳酸钙颗粒的沉积.润滑膜结构的改变是ZDDP和过碱水杨酸钙复配体系抗磨性能变差的主要原因.     

结晶器铜板Ni-Co电镀层的耐磨性

针对含Co质量分数不同的Ni-Co电镀层,通过扫描电子显微镜(SEM)、X射线衍射仪(XRD)和显微硬度表征其组织结构和硬度,采用高温销/盘磨损试验机评价其在室温和280℃时与35CrMo钢销或Si3N4陶瓷球配副时的耐磨性。结果表明:随Co质量分数增加,结晶取向变化、晶粒细化和固溶强化作用将镀层硬度从2.03GPa提高至3.96GPa,增强抵抗硬质点犁削的能力。280℃试验后,镀层的磨损量相比室温成倍增加,与钢销对摩后,1.5%Co镀层磨痕表面粘附钢销材料,其磨损量低于硬度较高的27%Co镀层;与陶瓷球对摩后,27%的Co质量分数促进磨损过程中生成Co的氧化物和形成耐磨的摩擦反应层,使镀层磨损量相比1.5%Co镀层下降65.4%。结合结晶器使用工况考虑,27%Co有利于提高Ni-Co电镀层的耐磨性。