Friction and wear behaviour of stainless steel rubbing against copper-impregnated metallized carbon

A series of experimental tests were carried out using stainless steel rubbing against copper-impregnated metallized carbon under electrical current on a pin-on-disc test rig. The test parameters include the sliding speed of 60-100 km/h, normal force of 40-80 N and electrical current of 0-50 A. During testing, the friction coefficient and wear volume were recorded. The topography of worn surfaces was also observed with SEM. The cross sectional profiles of worn surfaces of stainless steel were measured with Ambios profiler. The result displays that electrical current, normal load and sliding speed have a distinct effect on the friction and wear behaviour of stainless steel rubbing against copper-impregnated metallized carbon. Without electric current, the friction coefficient is largest but the wear volume of copper-impregnated metallized carbon is lowest. With increasing electric current, the friction coefficient decreases while the wear volume of copper-impregnated metallized carbon increases. Through the whole test, it is found that the wear loss of stainless steel was light. The wear of copper-impregnated metallized carbon becomes severe when electrical current or sliding speed is high. When the electrical current or sliding speed is high, arc ablation is a dominant wear mechanism of copper-impregnated metallized carbon.     

Wear and tribocorrosion behaviour of 304L stainless steel welds

The influence of the microstructures of the base metal and weld metals on the wear and tribocorrosion properties of 304L stainless steel (SS) welds prepared by Manual Gas Tungsten Arc Welding (M-GTAW) and Activated Flux Gas Tungsten Arc Welding (A-GTAW) processes are reported. Increase in sliding speed increased both friction forces as well as wear rate. Higher hardness in M-GTAW weld metal resulted in increased wear resistance than A-GTAW weld metal and base metal. The inferior wear resistance of the base metal was due to the strain hardening behaviour under sliding condition. The polarization curves showed increase in passive current density under sliding condition. The applied potential was found to influence the tribocorrosion resistance of the material. Under tribocorrosion condition, the total material loss was higher in base metal followed by A-GTAW weld metal and M-GTAW weld metal. Characterization of worn surface by SEM indicated a mixed wear mechanism of abrasive and adhesive wear. The worn surface appeared relatively smoother in nitric acid medium than in dry condition. The influence of microstructure affecting the hardness, wear and tribocorrosion resistance of the base metal and weld metals of 304L SS is discussed.     

铜基粉末冶金/Q235B摩擦副载流摩擦磨损性能*

磁浮列车中部分制动闸片在服役时一直处于受流状态,导致材料磨损加剧,影响闸片的服役寿命。为研究中低速磁悬浮列车制动闸片在受流工况下的摩擦磨损性能,以制动闸片使用的铜基粉末冶金材料和刹车盘使用的Q235B材料为摩擦副,研究不同制动速度下铜基粉末冶金/Q235B摩擦副的载流摩擦磨损行为。结果表明：无电流时随着滑动速度的增大,摩擦因数及磨损率整体呈现下降的趋势,载流时随着滑动速度的增大,摩擦因数整体呈现下降的趋势,而磨损率则整体呈现上升的趋势;无电流时磨损后的铜基粉末冶金材料表面覆盖着一层靛色的第三体层,该第三体层低速时主要以颗粒状为主,随着速度的增加逐渐被压实成连续致密状,高速时因黏着磨损加剧使得连续致密状第三体被破环,导致材料的摩擦因数和磨损率呈现反向增长的趋势;载流下磨损后的铜基粉末冶金材料表面出现了以机械磨损为主和以电弧烧蚀为主的2个区域,其中以机械磨损为主的区域依然是由靛色的第三体层组成,而以电弧烧蚀为主的区域表面则覆盖了一层金色熔融状物质,并且随着速度的增大,烧蚀区面积也逐渐增大。     

有无电流工况下钢铝复合轨/受电靴的摩擦磨损特性

利用改进设计的销盘摩擦磨损试验机,研究了用于地铁供电的钢铝复合轨与受电靴在有无电工况下的滑动摩擦磨损性能,对比了磨损量与摩擦因数的变化,观察和分析了微观磨损形貌,分析了其摩擦磨损机制。试验表明:电流对摩擦副的干摩擦滑动行为具有显著的影响,随着电流的增加,钢铝复合轨和受电靴的磨损质量增加,摩擦因数减小,摩擦表面出现粘着磨损、电弧烧蚀、磨粒磨损、疲劳剥落特性。     

载流条件下的1Cr18Ni9Ti/浸金属碳摩擦磨损性能研究

在销-盘摩擦磨损试验机上试验了载荷、速度、电流对1Cr18Ni9Ti/浸金属碳对磨时的摩擦因数、磨损量及磨损形貌的影响。试验结果表明,载荷对1Cr18Ni9Ti/浸金属碳摩擦副的摩擦因数和销试样的磨损率有显著影响:载荷越大,摩擦因数越大,磨损率越低;摩擦因数、磨损率与速度的关系受载荷的制约。当低载时,以电流影响为主。销试样的磨损表面出现了粘着磨损,氧化磨损和电弧烧蚀。     

紫铜/铬青铜摩擦副在干摩擦和水雾条件下的载流摩擦磨损性能研究

在HST-100载流高速摩擦磨损试验机上,对比考察了紫铜/铬青铜摩擦副在干摩擦和水雾2种状态下的载流摩擦磨损性能,采用扫描电镜(SEM)对磨损表面形貌进行了观测。结果表明:水雾条件下销试样载流摩擦磨损时,其摩擦因数及磨损率均低于纯载流状态下;该试样在纯载流条件下的磨损机制主要为粘着磨损和电气磨损,在水雾条件下主要为电弧侵蚀、塑性变形和轻微的粘着磨损。这是因为水有利于降低摩擦副接触表面的温度,有效地抑制了铜的转移,阻止了粘着磨损的发生。水因素的介入也导致了电弧发生频率的增多,但在综合影响下,水可以有效地改善该试样的磨损性能。     

Effect of arc discharge on the wear rate and wear mode transition of a copper-impregnated metallized carbon contact strip sliding against a copper disk

Wear of the contact strip on the pantograph of electric railway vehicles is governed mainly by arc discharge occurring simultaneously with break of contact between the strip and trolley wire. As a step to clarify the wear mechanism of metallized carbon contact strips under the occurrence of contact break arc discharge, a detailed sliding wear test of 30 min duration was carried out for the combination of a copper-impregnated carbon strip and a copper disk at a sliding speed of 100 km/h. The worn surfaces of the strip and disk were observed every 5 min. The voltage drop and electric current were measured throughout the test, and the occurrence and energy of the arc discharge were evaluated for each revolution of the disk. The wear process is considered in terms of the wear mode transition, and the effect of arc discharge on the mode transition and wear rate of the strip is discussed.     

Arc Erosion Wear Characteristics and Mechanisms of Pure Carbon Strip Against Copper Under Arcing Conditions

The wear behavior of pure carbon strip against copper (carbon/copper pair) under continuous arcing condition was investigated. To simulate the extreme condition of continuous arc discharge at high current, sliding wear tests were conducted on a home-made wear tester. The arc erosion wear characteristics and mechanisms of carbon/copper pair were studied by analyzing the wear scars and wear debris of the carbon strip in detail. Therefore, various analytical techniques, including Raman spectroscopy, transmission and scanning electron microscopy, and focused ion beam systems, were utilized to characterize the wear scars and wear debris of the carbon strip. The results show that the wear rate and the degree of arc erosion of the carbon strip increase with increasing electric current density. Typical entwined turbostratic carbon nanospheres (ETCNs) exhibited sphere-like stacking structure that were observed in the microstructure of the wear debris of the carbon strip produced during the friction process with current, which is the characteristic of the textural changes in carbon materials under combined arcing and sliding friction conditions. Moreover, the number and size of ETCNs increase with the electric current density increase. The arc erosion wear mechanisms of the carbon/copper pair are mainly due to the synergetic action of oxidation ablation, local electric arc impact and high-temperature graphitization under continuous arcing.     

地铁刚性弓网系统接触线磨损特性试验研究

为研究地铁刚性接触网系统接触线磨损的规律,以地铁刚性接触网系统常用的浸金属碳滑板/铜银合金接触线作为摩擦副,通过模拟地铁弓网系统运行参数,使用载流摩擦磨损试验机研究有、无电火花放电情况下,浸金属碳滑板与铜银合金接触线直流电滑动过程中磨损量、摩擦因数、载流效率随滑动距离的变化。试验结果表明：电火花放电会使得接触线与浸金属碳滑板磨损量显著上升,出现电火花放电时摩擦因数较小,弓网系统载流效率会明显降低同时出现大幅波动。试验后对碳滑板和接触线表面形貌的观察可知：电火花放电会使得浸金属碳滑板表面烧蚀坑数量和尺寸大小增加,同时会出现滑板材料大面积剥落和表面裂纹增多的问题,接触线表面形貌变得更加粗糙。     

添加纳米磁性微粒的润滑油摩擦学行为研究

用化学方法制备纳米MnZnFe2O4磁性微粒,在四球摩擦磨损试验机和立式万能摩擦磨损试验机上考察了MnZnFe2O4纳米磁性微粒作为润滑油添加剂的抗磨减摩性能及对磨损表面的修复作用,并用扫描电子显微镜观察分析了磨斑表面形貌。实验表明,MnZnFe2O4纳米微粒添加剂可以显著提高基础油的承载能力,减小磨斑直径;磁性颗粒有利于加强吸附在摩擦副表面上形成物理吸附膜,并在摩擦表面形成自修复膜,对磨损表面具有一定的修复作用。     

热喷涂A1_2O_3-TiO_2复合陶瓷涂层滑动磨损特性研究

本文利用环块磨损试验机在不同载荷下对热喷涂Al_2O_3-TiO_2复合陶瓷涂层的滑动磨损特性进行了研究,结果表明热喷涂Al_2O_3-TiO_2复合陶瓷涂层干摩擦和水润滑时的磨损量均随载荷的增加而增大.利用扫描电镜观察了磨损表面形貌并用能谱分析了磨损表面成分,结果表明干摩擦情况下在低载和高载时其磨损机理有所不同:低载时主要为钢轮对涂层的涂抹及陶瓷涂层的剥落,高载时主要为陶瓷涂层的断裂剥落;水润滑情况下的磨损机理与低载干摩擦时相类似,主要为涂抹及剥落.     

电场对WC-Co/Ti6Al4V摩擦磨损性能的影响

为了研究电场对摩擦副摩擦磨损性能的影响,在自行设计的高速摩擦磨损试验装置上,进行了WC-Co/Ti6Al4V摩擦副的摩擦磨损试验。结果表明：断开摩擦副热电回路可以有效地减小热电流对WC-Co/Ti6Al4V摩擦副摩擦磨损的影响,静电冷却环境下形成的强电场的效果更加明显,在抑制摩擦副磨损的同时还可以改善
Ti6Al4V磨损表面质量。通过扫描电镜及EDS能谱分析可知,静电冷却条件下的列宾捷尔效应削弱了钛合金的黏着能力,从而有效地减小了WC-Co的黏着磨损;WC-Co在高速摩擦时主要以黏着磨损、氧化磨损为主,同时伴有微裂纹的产生。
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Determination of load carrying ability of chemical films developed in sliding point contact

It has already been known for many years that the use of some extreme-pressure (EP), antiwear or friction modifier (FM) additives in mineral oils can produce different kind of boundary or chemical reaction films on sliding contact surfaces of some kinds of steel in boundary lubrication conditions. Using a sliding ball-on-disc configuration lubricated with some kinds of EP or FM, the wear scars on the balls can always reach the same limit size at a specified applied load and sliding velocity. From the fact that the limit sizes of wear scars decrease as sliding speed is increased or applied load is decreased, the load carrying ability of a chemical film can be obtained by extrapolating the data to the condition of zero sliding speed and is so defined that if the contact pressure is greater than this load carrying ability, the contact surfaces will continuously be worn; if the contact pressure is smaller than it, no more wear will occur on the surfaces. Based on this load carrying ability, the hydrodynamic effect of sliding pairs can also be identified. Therefore, the limit size of wear scar at specified sliding speed and applied load can also be predicted in a mixed lubrication condition.     

Performance and anti-wear mechanism of CaCO3 nanoparticles as a green additive in poly-alpha-olefin

This paper reports the tribological behavior of CaCO₃ nanoparticles as a green additive in poly-alpha-olefin (PAO) base oil under variable applied load, sliding speed, sliding duration, and temperature. The tribological properties and the electrical contact resistance between the tribo-pairs lubricated with PAO alone, and PAO containing CaCO₃ nanoparticles, were determined using an Optimol-SRV 4 oscillating friction and wear tester (SRV). The morphology and wear volume of the worn scar were measured simultaneously using a surface profilometer. The results showed that CaCO₃ nanoparticles can dramatically improve the load-carrying capacity, as well as the anti-wear and friction-reduction properties of a PAO base oil. In addition, higher applied load, moderate frequency, longer duration time, and lower temperatures are beneficial to the deposition of CaCO₃ nanoparticles accumulating on rubbing surfaces. X-ray photoelectron spectroscopy (XPS) reveals a boundary film composed of CaCO₃, CaO, iron oxide, and some organic compounds on the worn surfaces.     

平底直动盘形凸轮耐磨损分析

平底直动盘形凸轮主要的失效形式为滑动磨损,导致凸轮的传动精度降低,使用寿命减少.本文结合弹流润滑理论和滑动磨损计算公式,对平底直动盘形凸轮机构的润滑特性以及磨损规律进行探讨,预测凸轮危险磨损表面和磨损寿命,为凸轮的耐磨损设计提供依据.     

载流条件下铬青铜/纯铜摩擦副摩擦磨损性能研究

在自制的销盘摩擦磨损试验机上,对铬青铜/纯铜摩擦副进行载流条件下的干滑动模拟试验,研究了电流、速度、载荷对铬青铜/纯铜摩擦磨损性能的影响规律。试验结果表明:电流是影响摩擦副摩擦磨损性能最显著的因素,摩擦因数和磨损率都随着电流的增大而增大;速度和载荷对摩擦因数和磨损率也有显著影响;电流的存在,摩擦副间产生了比无电流时更严重的粘着磨损和塑性变形,同时增加了电化学腐蚀,使磨损更加严重。     

Low wear metal sliding electrical contacts at high current density

Operation of a low wear (2 × 10^?5 mm³/(N-m)), low contact resistance copper sliding electrical contact was demonstrated. The wear rate of a lightly loaded copper–beryllium metal fiber sliding on a polished copper counterface was insensitive to (DC) current density values as great as 440 A/cm² (in a brush positive or anodic configuration). Low wear and relatively low friction (μ ～ 0.2 to 0.3) was achieved by operating the contact immersed in a liquid medium consisting of a hydrofluoroether with helium cover gas, inhibitingoxidationand providing cooling of the contact. Similar experiments performed in liquid mediums of ultrapure water and dilute (3%) hydrogen peroxide show an order of magnitude increase in wear rate and provide further insight on the role of electrochemically enhanced oxidation and the degraded contact resistance and tribological behavior of non-noble sliding electrical contacts in general. In contrast to high current density slidingin hydrofluoroether, an order of magnitude greater wear rate was observed for similar sliding conditionsin hydrogen peroxide or water without the aid of externally supplied electric potential. A conceptual model is proposed correlatingthe rate of brush wear to fatigue strength and electrochemically enhanced oxidation as a result of high current density transport through the contact. A mathematical expression was derived to calculate the approximate wear volume of a single fiber laterally contacting a slip-ring, based on direct measurement of the wear scar geometry.     

基于UHMWPE/纳米ZnO复合材料的滑动摩擦磨损机制

用热压成型法制备了超高分子量聚乙烯(UHMWPE)纳/米ZnO复合材料,采用销盘式摩擦磨损试验机考察了载荷和相对滑动线速度对复合材料摩擦学性能的影响;采用扫描电子显微镜观察了复合材料磨损表面形貌。结果表明:在低载荷试验条件下磨损机制为粘着磨损,在高载荷试验条件下磨损机制为粘着磨损和疲劳磨损。而在一定载荷试验条件下,无论相对滑动线速度高或低,复合材料的磨损机制主要表现为粘着磨损,只是在高速情况下粘着磨损程度加大,局部还出现了表面撕裂的痕迹。     

Wear behaviors of ceramics TIN,TIC and TICN with Arc ion plating

In order to determine the wear properties of AIP(Arc Ion Plating) deposition, wear process was evaluated by using a Falex test machine. Also, in order to determine the effects of coating material on the wear process, TiC, TiN, and TiCN coatings of thickness about 5 μrn — 6 μm coated by Arc ion plating deposition method were tested. The wear property was determined under a dry sliding condition as a function of the applied load, sliding distance, sliding velocity and temperature. The results show that when wear of the coating-layer occurred, specific wear amount increased with the wear rate. At initial state, the wear rate rapidly increased, but it gradually reduced as the velocity increased. Also, when raising the temperature, the wear rate increased in the order of TiCN, TiN and TiC due to the frictional heat.     

表面粗糙度对滑动电接触磨损率的影响

在电气化铁路弓网系统中,磨损率是衡量列车运行状态与接触导线使用状态的重要指标。为了充分模拟弓网系统中磨损率情况,利用自行搭建的滑动电接触摩擦磨损试验机对滑板和接触导线进行摩擦磨损试验,分析滑板表面粗糙度、法向压力、接触电流与运行速度对磨损率的影响。得出结论:滑板磨损率随滑板初始表面粗糙度、接触电流、法向压力、运行速度的增加而增加,而高载荷下粗糙度对于磨损率的影响降低;滑板摩擦从磨合期进入稳定摩擦期存在一个临界表面粗糙度,当滑板初始表面粗糙度值等于临界粗糙度值时,其磨损率最低;不同初始表面粗糙度的滑板在跑合期内磨损过程不同,在稳定摩擦期内磨损过程趋于一致,且摩擦试验后滑板表面粗糙度也接近。