含不同固体润滑剂矿用树脂基制动材料的制备及摩擦学性能

采用热压烧结技术制备含4种不同固体润滑剂(MoS_2、h-BN、石墨和Sb_2S_3)的矿用树脂基制动材料。采用环-块式摩擦磨损试验机研究制动材料在不同载荷和速度下的摩擦磨损特性。采用扫描电镜和能谱仪分析材料物相和摩擦表面形貌,探讨其磨损机制。结果表明:含不同固体润滑剂的制动材料具有相似的硬度值,其维氏硬度约为0.60 GPa;在所有试验条件下,随着载荷和速度的增加,四种样品的摩擦因数与磨损率均有所升高,且4种样品均表现出不同程度的黏着磨损、塑性变形与转移膜的形成,其中含固体润滑剂Sb_2S_3的样品存在轻微的犁削和磨粒磨损;4种样品中,含10%(体积分数)石墨的样品表现出最低的摩擦因数与磨损率。     

车轮材料对轮轨系统匹配性能的影响

利用MMS-2A型微机控制摩擦磨损试验机研究4种含碳量不同的车轮材料分别与PD3热轧钢轨进行匹配的磨损与疲劳性能。结果表明：随着车轮材料的含碳量增加,硬度增大、耐磨性增强,导致磨损量降低,轮轨系统的磨损量呈现先减小后增大的趋势;车轮试样的塑性变形层厚度随含碳量的增加而减小,抗疲劳性能加强;车轮试样表面由严重剥落损伤向轻微剥落转变,伴随有一定的黏着磨损;钢轨试样表面以剥落磨损为主。     

表面织构在脂润滑条件下的摩擦性能研究

采用声光调Q二极管泵浦Nd:YAG激光加工系统在H13钢表面加工出不同密度的织构,以润滑脂作为润滑剂,利用MMW-1A型微机控制万能摩擦磨损试验机考察表面织构在不同载荷、不同转速条件下的摩擦磨损特性。实验结果表明:在脂润滑条件下表面织构能有效改善摩擦副表面的摩擦性能;与光滑无织构试样相比,表面织构试样的摩擦因数显著降低;一定范围内,随着织构密度的增加,平均摩擦因数呈现出先减小后增大的趋势,且织构密度为10%时的平均摩擦因数最小,最小平均摩擦因数为0.18,较光滑无织构试样减小32.23%;摩擦因数随着试验载荷的增大而减小,但随着转速的增加呈现出先减小后增大的变化趋势。     

硬度对钢蜗轮副用材料微动磨损特性的影响

通过调整40CrNiMoA钢的热处理工艺参数获得了4种不同硬度的试样,在无润滑、室温条件下,在SRV Ⅳ微动磨损试验机上研究了硬度对40CrNiMoA钢-18Cr2Ni4WA钢摩擦副微动磨损量和摩擦因数的影响.结果表明:试验条件下,随着40CrNiMoA钢硬度的增加,其微动磨损体积减小,而较硬的18Cr2Ni4WA钢的微动磨损量变化趋势则与试样的位置等有关,但总存在一个硬度配对使得两摩擦副微动磨损体积相等;摩擦因数在40CrNiMoA钢为上试样时,随时间变化较平稳,波动较小;当40CrNiMoA钢为上试样时,其微动磨损机制主要为黏着磨损,而18Cr2Ni4WA钢的磨损机制以磨粒磨损和黏着磨损为主.     

石墨填充聚醚酰亚胺摩擦学性能分析

在M-200摩擦试验机上进行不同含量石墨填充PEI基复合材料的摩擦磨损试验,利用扫描电子显微镜分析了断口和磨损表面的显微结构,并分析了磨损机制。考察了表面硬度随含量填充量的变化规律。试验结果表明:石墨在复合材料基体中呈片状结构,磨损过程中易形成转移膜,从而改善了摩擦磨损情况,其中填充质量分数10%石墨的PEI基复合材料摩擦因数最低,填充30%石墨的复合材料磨损率最低,材料表面硬度随着填充石墨含量的增加而降低,石墨填充量在5%～30%之间表面硬度下降平缓,当填充量超过30%时,材料表面硬度下降剧烈。     

石墨润滑下人字闸门底枢摩擦副摩擦学性能*

为研究石墨润滑条件下各参数对人字闸门底枢摩擦副摩擦磨损性能的影响，采用UMT-2多功能摩擦磨损试验机进行销-盘摩擦副试验，模拟闸门底枢低速重载工况条件，研究不同摩擦速度、石墨粒径下不同表面粗糙度人字闸门底枢摩擦副的摩擦磨损性能。试验结果表明：在不同转速工况下，表面粗糙度为0.8 μm的摩擦副采用粒径10 μm石墨颗粒润滑时润滑性能最优，表面粗糙度为2.0 μm的摩擦副采用粒径21 μm石墨颗粒润滑时润滑性能最优；随着转速增加，摩擦副摩擦因数与磨损量均增加。研究表明，石墨粒径大小和摩擦副表面粗糙度共同影响摩擦副摩擦学性能，这为闸门底枢的固体润滑剂选择和摩擦参数设计提供理论依据。     

磷酸酯对Ti6Al4V/钢摩擦副摩擦磨损性能的影响

采用SRV型微动摩擦磨损实验机分别考察了Ti6Al4V/钢摩擦副在3种磷酸酯润滑下的摩擦磨损性能,并利用扫描电子显微镜和X射线光电子能谱仪分析了Ti6Al4V磨斑表面形貌和典型元素的化学状态.结果表明,磷酸三甲苯酯作为Ti6Al4V/钢摩擦副的润滑剂,其摩擦学性能明显好于磷酸二(2-乙基己基)酯和磷酸三丁酯.载荷和频率对磷酸三甲苯酯摩擦因数和磨损率的影响不同,摩擦因数随载荷和频率的增加变化不显著,磨损率随载荷的增加逐渐增加,随频率的增加先急剧下降,然后缓慢降低并趋于稳定;其磨损机制为在磨损表面形成牢固的边界膜,保护底材不受磨损.     

高载荷条件下石墨-石墨摩擦副的摩擦学特性研究

利用研制的高载荷条件下摩擦因数测试装置,研究了石墨/石墨摩擦副在空气、水和油介质中的摩擦学特性。结果表明在4~15MPa范围内,随着载荷的增加,摩擦副在空气、水和油介质中的摩擦因数都逐渐降低;在油介质中摩擦副的摩擦因数最小,在水介质中摩擦因数变化最平稳,在空气中摩擦因数最大,且随载荷的增加变化幅度最大。磨损表面原始形貌对比分析表明,在空气中,摩擦副表面处于边界润滑状态,主要磨损机制是粘着磨损和犁削;水润滑条件下为轻微犁削;油润滑条件下,摩擦副表面处于为边界润滑和流体润滑状态,油中的减摩剂对试样表面有抛光作用。     

Ni+注入参数对Ti6Al4V表面改性层生物摩擦学性能的影响

为改善Ti6Al4V表面的生物摩擦学性能,把不同能量与剂量的Ni~+注入到Ti6Al4V表面以形成表面改性层。用Nano IndenterⅡ型纳米显微力学探针测定表面改性层的纳米硬度,在MRTR多功能摩擦磨损试验机上以Zr O2球/改性层为摩擦副,以透明质酸钠溶液润滑剂在室温下进行生物摩擦学实验,使用S-3000N扫描电子显微镜观察生物摩擦学试验后试样的磨痕形貌并分析磨损机制。结果表明:Ni~+注入Ti6Al4V表面的形成相为Ti2Ni;随着注入能量和剂量增加,改性层中Ti2Ni的质量分数增加,改性层的纳米硬度增加,摩擦因数下降,且磨损出现不同程度的减轻;注入能量增加比剂量增加更有利于提高改性层的生物摩擦学性能。     

铜合金镶嵌石墨材料的摩擦磨损性能

将硬度和强度不同的2种石墨分别镶嵌于Cu-15Ni-8Sn合金基体上,然后将Cu-15Ni-8Sn合金镶嵌石墨材料与05Cr17Ni4Cu4Nb沉淀硬化不锈钢组成摩擦副,研究了不同载荷(490,980,1470N)和润滑条件(干摩擦与湿摩擦)下该材料的摩擦磨损性能.结果表明:干摩擦条件下该材料的摩擦因数随载荷的增大基本呈增大趋势,且镶嵌较高硬度和强度石墨时材料的干摩擦因数小于镶嵌较低硬度和强度石墨时材料的;湿摩擦条件下,镶嵌较高硬度和强度时石墨材料的摩擦因数随载荷的增大而增大,且与干摩擦条件下的相当;随着载荷的增大,在干摩擦和湿摩擦条件下的磨损量均呈增大趋势;干摩擦条件下石墨的磨损机制以磨粒磨损为主,并伴有疲劳磨损,而湿摩擦条件下的磨损机制以磨粒磨损和冲刷磨损为主.     

铁路轮轨润滑脂的研制

采用IR、XRD、SEM-EDS等手段,对常用铁路轮轨润滑脂进行剖析,得到润滑脂的基础油种类和添加剂组成。研制一种新型铁路轮轨润滑脂,并与常用铁路轮轨润滑脂的性能进行比较。结果表明:研制的润滑脂的最大无卡咬负荷为863 N,比常用铁路轮轨润滑脂的大一倍多,其摩擦因数为0.008～0.032,明显小于常用铁路轮轨润滑脂的0.039～0.051,但烧结负荷小于常用铁路轮轨润滑脂;研制的润滑脂具有更好的胶体稳定性和耐热性。     

轮轨接触界面摩擦管理研究进展

列车向着高速与重载方向迅速发展,显著加剧了轮轨接触界面间的损伤。通过在轮轨接触界面进行摩擦管理能够有效地降低轮轨之间的磨损、显著提高列车的运行安全性以及降低运营成本。对轮轨接触界面摩擦管理研究现状进行综述,并介绍轮轨界面摩擦控制对轮轨作用力、黏着、磨耗、滚动接触疲劳以及振动与噪声影响的研究进展;展望了轮轨接触界面摩擦管理未来研究方向,即应针对不同应用环境和接触部位,研发合理的摩擦控制材料,以克服摩擦管理过程中对轮轨损伤及使用局限性等问题;应探究车轮踏面/轨顶面和轮缘/轨距面摩擦控制方式,严格控制摩擦材料喷涂量使两接触面不相互干扰,优化改进轮轨接触界面摩擦管理的最佳应用参数;应研发环境友好型的轮缘/轨距面润滑剂与车轮踏面/轨顶面摩擦控制剂,稳定调控轮轨接触界面的黏着特性。     

Pin-on-disc study of the effects of railway friction modifiers on airborne wear particles from wheel–rail contacts

Knowledge of wheel–rail interaction is crucial to wheel and rail maintenance. In this interaction, some of the worn-off material is transformed into airborne particles. Although such wear is well understood, few studies treat the particles generated. We investigated friction modifiers' effects on airborne particle characteristics generated in wheel–rail contacts in laboratory conditions. Pin-on-disc machine testing with a round-head pin loaded by a dead weight load 40 N simulated maximum contact pressure over 550 MPa. Airborne particle characteristics were investigated in dry contacts and in ones lubricated with biodegradable rail grease and water- and oil-based friction modifiers. The number of particles declined with the grease; the number of ultrafine particles increased with the water-based friction modifier, mainly due to water vaporization.     

分散剂对有机粘土润滑油摩擦学性能的影响

以30#机械油为基础油,以0.4%季铵盐修饰有机粘土为添加剂,5%低碱值合成磺酸钙和5%聚异丁烯双丁二酰亚胺为分散剂,制备了几种分散剂优化的有机粘土润滑油。采用OPTIEN2120型紫外/可见分光光度计对分散剂的分散效果进行了检测;在M-200和MS-800型摩擦磨损试验机上,分别对不同分散剂作用下的有机粘土润滑油的减摩抗磨性能和承载能力进行了测试。分散效果检测表明分散剂可有效控制粘土微粒的粒径,阻止粘土微粒的团聚,使得粘土微粒在基础油中有良好的分散稳定性。摩擦磨损试验表明:分散剂能改进有机粘土润滑油的摩擦学性能,其中2.5%低碱值合成磺酸钙与2.5%聚异丁烯双丁二酰亚胺分散剂复配使用时有机粘土润滑油的摩擦学性能最佳;分散剂的加入在一定程度上能够提高有机粘土润滑油的承载能力。     

Synthesis,Characterization, and Tribological Behavior of Neopentyl Polyol Ester-Based and Mixed Oil-Based Titanium Complex Grease

Four types of titanium complex grease were synthesized using a 3-l reaction vessel, and their friction and wear behavior were evaluated using a four-ball tester in the presence of two base oils: neopentyl polyol ester and a mixture oil of neopentyl polyol ester, 650SN, and epoxidized soy bean oil (4.5:2.5:1), with two compositions: benzoic acid/stearic acid and sebacic acid/stearic acid. The results indicate that mixed oil-based titanium complex grease has excellent tribological properties. Moreover, compositions affect the physical characteristics of titanium complex grease but have little effect on the friction-reduction, antiwear, and load-carrying capability of the same types of oil-based titanium complex grease. In addition, base oils also affect the tribological property of titanium complex grease. Based on scanning electron microscopy and x-ray photoelectron spectrometer of the worn surfaces of steel balls lubricated with the different types of grease, synergistic boundary lubrication was proposed to illustrate the friction-reduction and antiwear properties of titanium complex grease.     

Experimental study on wear and spalling behaviors of railway wheel

The current researches of the wear and spalling behaviors of wheel/rail materials focus on the field investigation rather than the mechanism. However, it is necessary and significant for clarifying the mechanism and relationship between the wear and spalling damage of railway wheel to test and reproduce the wheel damages in laboratory. The objective of this paper is to investigate the wear and spalling damage behaviors of railway wheel using a JD-1 wheel/rail simulation facility, which consists of a small wheel serving as rolling stock wheel, and a larger wheel serving as rail. The damage process of wheel roller is explored in terms of the creep ratio, axle load, and carbon content by means of various microscopic examinations. The experimental results show that the wear volume growth of wheel roller is proved to be proportional to the increase of the creep ratio and normal load between simulating wheel and rail. The increase of carbon content of wheel material causes a linear reduction in the wear volume. The microscopic examinations indicate that the rolling wear mechanism transfers from abrasive wear to adhesive and fatigue wear with an increase of tangential friction force, which results in the initiation of fatigue crack, and then aggravates spalling damage on the wheel roller surface. The surface hardness of material depends strongly upon its carbon content. The decrease of the carbon content of wheel material may alleviate spalling damage, but can cause a significant growth in the wear volume of wheel roller. Therefore, there is a competitive relationship between the wear and spalling damage of wheel material. This research proposes an important measure for alleviating or preventing the wear and spalling damage of railway wheel material.     

Tribological behaviors of surface-coated serpentine ultrafine powders as lubricant additive

The effect of surface-coated ultrafine powders (UFPs) of serpentine suspended in lubricants on the tribological behaviors of a mated 1045 steel contact was investigated. Through the addition of serpentine UFPs to oil, the wear resistance ability was improved and the friction coefficient was decreased. The addition of 1.5 wt% serpentine to oil is found most efficient in reducing friction and wear. The nano-hardness and the ratio of hardness to modulus of friction surface are observably increased. Such effects can be attributed to the formation of a tribofilm of multi-apertured oxide layer, on which the micrometric alumina particles embedded and serpentine nano-particles adsorbed.     

曲线半径及轴重对轮轨摩擦功影响的研究

基于非Hertz滚动接触理论利用数值计算方法详细分析了静态接触情况下,轴重和曲线半径对轮轨接触质点间等效应力、接触斑粘滑区的分布、总滑动量和摩擦功的影响。分析计算表明,轴重增加引起轮轨接触质点间等效应力,接触质点间粘滑区的面积以及总滑动量的变化,同时对轮轨接触质点阍的摩擦功的变化有重要影响;小曲线半径处轮轨接触质点间的总滑动量,接触斑滑移区的面积以及摩擦功都明显增大,导致曲线上钢轨磨损加剧。因此曲线半径和轴重是影响轮轨滚动接触磨损的重要因素。     

Friction torque in grease lubricated thrust ball bearings

Thrust ball bearings lubricated with several different greases were tested on a modified Four-Ball Machine, where the Four-Ball arrangement was replaced by a bearing assembly. The friction torque and operating temperatures in a thrust ball bearing were measured during the tests. At the end of each test a grease sample was analyzed through ferrographic techniques in order to quantify and evaluate bearing wear.A rolling bearing friction torque model was used and the coefficient of friction in full film lubrication was determined for each grease, depending on the operating conditions.The experimental results obtained showed that grease formulation had a very significant influence on friction torque and operating temperature. The friction torque depends on the viscosity of the grease base oil, on its nature (mineral, ester, PAO, etc.), on the coefficient of friction in full film conditions, but also on the interaction between grease thickener and base oil, which affected contact replenishment and contact starvation, and thus influenced the friction torque.     

Tribological Performance of Lubricating Greases Based on Calcium Carbonate Polymorphs Under the Boundary Lubrication Condition

In this article, we synthesized the calcium sulphonate grease (CSG) based on the calcite using the bright stock (150BS) as the base oil. In order to investigate the tribological performance of lubricating grease containing different calcium carbonate polymorphs under boundary lubrication condition, a calcium sulphonate complex grease (CSCG) based on the vaterite was used as a reference. An oscillating reciprocating friction and wear tester set at a series of applied loads and frequencies was adopted to evaluate the tribological performance under boundary condition. Results showed that the lubricating grease that was composed of crystalline calcite as the partial thickener had excellent friction-reducing and antiwear (AW) properties, regardless of the applied loads and frequencies. The vaterite in CSCG easily experienced a polymorph transformation into calcite or aragonite characterized by Raman spectroscopy. This polymorph transformation was attributed to the highly local friction temperature and activated hydrogen from water or acids oxidated in the rubbing process at high load or frequency. The physical polymorph transformation corresponded to the fluctuations of the friction coefficients, then contributed to the severe wear. XPS analysis indicated that two calcium sulphonate lubricating greases occurred a tribochemical reaction and boundary tribofilms consisted of CaCO₃, CaO, iron oxide and FeSO₄ were formed on the rubbing surfaces. The tribofilm formed by the introduction of the CSG that mainly depended upon the thickeners of calcite structure contributed to an excellent AW protection. The possible boundary friction mechanism for greases based on various calcium carbonate polymorphs was also proposed. Effect of calcium carbonate polymorphs on the tribological performance was discussed.