铝/石墨复合材料高速高温下的摩擦磨损特性

本文研究了用中间法新工艺制造的铝石墨复合材料在高速高温下的摩擦磨损特性。试验在销盘式试验机上进行。滑动线速度最高达9.4米/秒。在2米/秒干摩擦时,所有测试的复合材料磨损量均小于基体合金。200℃时,含石墨2～5%的复合材料磨损量也此基体合金小。在9.4米/秒干摩擦时,含石墨2%的复合材料耐磨性能最好。以前曾有报导:滑动线速度大于1米/秒,铝石墨复合材料的磨损量大于基体合金[12,13]。本文认为新工艺制造的复合材料在9.4米/秒的高速摩擦时摩擦系数和磨损量下降是由于石墨与基体界面结合良好。      

MoS2与石墨对聚四氟蜡粘接涂层摩擦学性能的影响

利用MHK-500型环块摩擦磨损试验机分别考察了M oS2与石墨对聚四氟蜡/聚氨酯复合涂层摩擦磨损性能的影响,采用扫描电子显微镜和光学显微镜观察分析了涂层磨损表面和偶件上转移膜的分布情况。研究表明,M oS2与石墨的加入使聚四氟蜡/聚氨酯复合涂层的耐磨性提高,但对摩擦系数影响较小,并且添加M oS2的聚四氟蜡粘接涂层的耐磨性要优于添加石墨的聚四氟蜡粘接涂层。同时,负荷和速度对添加M oS2与石墨的聚四氟蜡/聚氨酯复合涂层的摩擦磨损性能有很大影响。在高负荷中速条件下复合涂层具有较好的耐磨性能。     

Enhanced wear resistance of hybrid PTFE/Kevlar fabric/phenolic composite by cryogenic treatment

Hybrid PTFE/Kevlar fabric was treated by cryogenic approach. The untreated or cryo-treated fabric was incorporated into fabric/phenolic composite for friction and wear tests. It was found that the wear resistance of the fabric/phenolic composite was improved after cryo-treatment, although the friction coefficient increased to a certain extent. SEM observations showed that the roughness of hybrid fabric increased by cryo-treatment, which may enhance the mechanical interlocking of the phenolic resin on the fiber surface. Enhanced fiber/resin adhesion was considered to contribute to the improved wear resistance of cryo-treated fabric/phenolic composite.     

Effect of sliding speed on friction and wear of uni-directional aramid fibre-phenolic resin composite

A previous study on the tribological performance of a compression-moulded aramid fibre-phenolic resin composite, containing 30% continuous fibre, showed that this composite provides a reasonable combination of the friction coefficient and wear rate to be used as a friction component, such as a brake shoe. In the present work, the effect of sliding speed on the friction and wear behaviour of this composite has been investigated. The sliding experiments were conducted in a speed range of 0.1–6 m s^–1 at two normal pressure levels of 1.0 and 4.9 MPa. The coefficient of friction was found to be stable over a wide range of sliding speeds and normal pressures. The wear of the composite was found to be insensitive to changes in the speed in the higher speed range. The results have been supplemented with scanning electron micrographs to help understand possible friction and wear mechanisms.     

石墨的添加对NiCr-W-Ti自润滑复合材料高温摩擦学性能的影响

本文以Ni20Cr合金为基体添加稀有金属Ti、W粉末及石墨后,充分混合,采用机械合金化及热压烧结工艺制备了NiCr金属基复合材料,研究了石墨含量对NiCr金属基复合材料的组织结构和摩擦学性能的影响。在UMT-3高温摩擦试验机上进行了该复合材料同Al_2O_3陶瓷球的滑动摩擦磨损实验,利用扫描电子显微镜(SEM)、X射线衍射仪(XRD)对复合材料及其摩擦测试后的形貌与结构进行观察分析,结果表明:当所添加石墨的质量分数为3wt.%时,复合材料具有相对较好的力学性能和摩擦学性能;当测试温度低于300℃时,摩擦表面未形成有效的摩擦膜,故磨损率较高;当温度高于500℃时,摩擦层中含有摩擦氧化物,摩擦表面被光滑氧化物所组成的润滑膜覆盖,对磨面具有很好的保护作用,因而磨损率降低。     

The influence of pressure on the electrical tribology of carbon nanotube–silver–graphite composite

The effect of pressure on the friction and wear properties of carbon nanotube–silver–graphite composite with 10 A/cm² and without electrical current has been investigated. The results show that the wear of composite increase with the increase of pressure under mechanical wear, but the wear of composite varies with the pressure in the shape of U under electrical wear. Pressure is a factor related to both the electrical heating, friction heating and abrasive wear. At a reasonable load without much increase in the frictional heating and mechanical wear, the electrical heating could be reduced which will result in lower total thermal effect, and the resultant wear rate could arrive at a minimum. The electrical wear is higher than mechanical wear by 6–20 times. The differences between the no-current and with-current wear is Joule heat released in the friction zone which leads to breakdown of the lubricating film, roughening of the brush surface, and intensification of the adhesive interaction at the contact spots. The wear of positive brush is higher than that of negative brush. The friction coefficient of composite with current is greater than that without current.     

Tribological investigations of polyetherimide composite

Polyetherimide (PEI), commercially known as ULTEM and manufactured by GEC (USA), is one of the newest high-performance thermoplastics. Its graphite and short-glass-fibre (GF) filled composition was evaluated for friction and wear properties. Tribological studies of the material sliding against mild steel, under different loads, counterface roughnesses and sliding distances were performed on a pin and disc configuration. It was observed that this composite displayed very good wear resistance due to glass-fibre reinforcement and low friction due to the solid lubricant graphite. The wear mechanism was studied with scanning electron microscopy by observing the worn pin and disc surfaces. Fatigue was observed to be the main factor in wear, along with adhesive and abrasive modes.     

Tribological properties of powder metallurgy – Processed aluminium self lubricating hybrid composites with SiC additions

In this experimental study, aluminium (Al)-based graphite (Gr) and silicon carbide (SiC) particle-reinforced, self-lubricating hybrid composite materials were manufactured by powder metallurgy. The tribological and mechanical properties of these composite materials were investigated under dry sliding conditions. The results of the tests revealed that the SiC-reinforced hybrid composites exhibited a lower wear loss compared to the unreinforced alloy and Al–Gr composites. It was found that with an increase in the SiC content, the wear resistance increased monotonically with hardness. The hybridisation of the two reinforcements also improved the wear resistance of the composites, especially under high sliding speeds. Additionally, the wear loss of the hybrid composites decreased with increasing applied load and sliding distance, and a low friction coefficient and low wear loss were achieved at high sliding speeds. The composite with 5 wt.% Gr and 20 wt.% SiC showed the greatest improvement in tribological performance. The wear mechanism was studied through worn surface and wear debris analysis as well as microscopic examination of the wear tracks. This study revealed that the addition of both a hard reinforcement (e.g., SiC) and soft reinforcement (e.g., graphite) significantly improves the wear resistance of aluminium composites. On the whole, these results indicate that the hybrid aluminium composites can be considered as an outstanding material where high strength and wear-resistant components are of major importance, predominantly in the aerospace and automotive engineering sectors.     

感应熔覆原位自生TiC/Ni基复合涂层的组织与耐磨性研究

为了提高16Mn钢的干滑动磨损耐磨性能,以Ni60、钛粉和石墨粉为原料对16Mn钢表面进行感应熔敷处理,制备出以TiC颗粒为增强相的原位自生复合涂层,利用金相、SEM、XRD等技术分析了涂层的显微组织,在室温干滑动磨损试验条件下测试了涂层的耐磨性.结果表明:涂层中TiC颗粒均匀分布于共晶基体上,整个涂层组织均匀、无气孔、无裂纹;涂层与基材形成了良好的冶金结合,涂层具有很高的硬度,在室温干滑动磨损试验条件下具有优异的耐磨性能.     

Studies on mechanical and wear properties of alloyed hypereutectic gray cast irons in the as-cast pearlitic and austempered conditions

The mechanical and wear behavior of a series of as-cast gray iron alloys were compared with properties obtained after austempering at 360 °C. The austempered alloys showed equivalent or moderately enhanced mechanical strength than the as-cast pearlitic gray irons. The specific wear rates of all the austempered alloys decreased significantly by 7–15 times and friction coefficient reduced by 30–50% compared to pearlitic alloyed gray irons. The dry sliding wear studies of as-cast alloys against high carbon 1%Cr through-thickness hardened steel shows that the specific wear rate ranged from 5.6 to 19.1 (×10⁻⁷) g/Nm with friction coefficient from 0.55 to 0.7. While, the austempered alloys showed wear rates from 0.5 to 2.6 (×10⁻⁷) g/Nm with friction coefficient ranging from 0.23 to 0.4. The improved wear resistance was attributed to the layer wise surface phase transformation associated with strain induced martensite formation of the stabilized austenite in the austempered matrix, lubrication of the interface by the flake graphite and better heat conduction from the rubbing interface by higher volume fraction of the graphite. Cast iron alloyed with Ni shows enhanced mechanical properties and wear resistance. The tensile strength shows decreasing trend with increase in carbon equivalent and graphite volume. The specific wear rate and friction coefficient shows decreasing trend with increase in hardness and graphite flake volume.     

Friction and wear properties of polyphenyl ester and graphite filler in the carbon fibre‐reinforced ultra‐high‐molecular‐weight polyethylene composites

Ultra‐high‐molecular‐weight polyethylene (UHMWPE) reinforced with carbon fibre (CF) underwent an enhancement of heat and wear resistant with the addition of polyphenyl ester (POB) and graphite, respectively. The effect of graphite content on the tribological properties of the composites was studied. The wear surface was examined using scanning electron microscope (SEM). The results of the sliding wear tests showed that with graphite loading, wear resistance increased and the coefficient of friction was much more stable. In addition, graphite improved the tribological properties of the composite. Hardness, impact strengths and thermal stability of the composites were enhanced. With increased load, the wear rate of the ultra‐high‐molecular‐weight polyethylene+carbon fibre+polyphenyl ester+10 % graphite composite tended to increase, whereas the coefficient of friction decreased. The adherence and plastic deformation were dominant wear mechanisms for the ultra‐high‐molecular‐weight polyethylene+carbon fibre+polyphenyl ester+graphite composites. The formation of a thin and uniform transfer film was observed.     

Effect of testing conditions and microstructure on the sliding wear of graphite fibre/PEEK matrix composites

The sliding friction and wear behaviour of unreinforced polyetheretherketone (PEEK) matrix and its unidirectional continuous and two-dimensional woven graphite fibre-reinforced composites were investigated. The operating wear mechanisms, as evinced by scanning electron microscopy of the worn surfaces, and the coefficients of friction and the wear rates changed considerably with the fibre reinforcement form and orientation. Sliding wear rates, on account of their extreme sensitivity to the microstructure of the interacting surfaces at the sliding interface, were found to be a function of not only the surface roughness, but also of the sliding time. Complex interactions arising due to the effects of the testing parameters such as fibre orientation, sliding velocity, contact pressure and interface temperature were characterized for the neat matrix and the two composite systems. The wear rates of the two-dimensional woven composites were almost an order of magnitude lower than those of the unidirectional fibre composite or the unreinforced matrix.     

Effect of different matrices on wear characteristics of glass woven roving/polymer composites

The influence of three thermosetting matrix resins — epoxy, polyester and poly(vinylbutyral)-modified phenolic — on the sliding wear of glass woven roving reinforced polymer composites under dry conditions has been investigated. Amongst the three composites, glass/phenolic composites exhibit the highest mechanical properties whereas the highest wear resistance (minimum specific wear rate) is offered by glass/epoxy composites. The critical velocity, at which the specific wear attains a minimum value, is higher for glass/polyester composite than for the other two composites. The lowest coefficient of friction has been observed in glass/phenolic composites at all sliding velocities.     

芳纶沉析纤维-多巴胺/聚酰亚胺-酚醛树脂复合膜的力学及摩擦磨损性能

以聚酰亚胺（PI）纤维和酚醛树脂（PF）为基体,通过对PI纤维表面进行多巴胺（PDA）修饰,并引入芳纶沉析纤维（AF）作为增强体,采用湿法成型和热压固化技术制备了15wt% AF和7.5wt% PDA的AF-PDA/PI-PF复合膜,重点研究了AF的添加和PDA改性修饰对PI-PF复合膜力学性能和摩擦磨损性能的影响,并探讨了其磨损机制。研究结果表明:当添加AF并对PI纤维进行PDA改性时,AF-PDA/PI-PF复合膜的应力为47.54 MPa,抗张指数为56.91 Nmg-1,层间结合强度为1 265.6 Jm-2,相比PI-PF复合膜分别提高了33.65%、41.67%和64.11%;磨损率为1.01×10-4 mm3J-1,约降低了34.84%,其磨损机制主要为黏着磨损。这是由于PI纤维与AF可形成"互穿网络"结构,此外,PDA对PI纤维的化学改性处理可增加PI纤维表面活性,AF和PDA对提高PI纤维与树脂间的界面结合力及AF-PDA/PI-PF复合膜的力学性能和摩擦磨损性能起到协同作用。      

Polymere Hochtemperatur-Verbundwerkstoffe für Anwendungen als Gleitelemente

High temperature polymer composites for applications as sliding elements Polymeric composites are nowadays frequently used for applications in which friction and wear are critical issues. Quite often, they also have to operate at elevated temperatures, so that the use of high temperature polymers is needed. This overview decribes on the example of sliding elements that can be used e.g in textile drying machines, how matrix, fiber and filler components of the composites can affect their friction and wear properties under sliding conditions against steel counterparts. As a good solution for a composite operating as a sliding element under extrem conditions, polyetheretherketone (PEEK) with 10 weight% of each, short carbon fibers, graphite filler, and polytetrafluoroethylene (PTFE) particles is suggested.     

Tribological characterization of Al6061/alumina/graphite/redmud hybrid composite for brake rotor application

Dry sliding tribological characterization of redmud particle-reinforced Al6061/alumina/graphite hybrid metal matrix composite (RM-AlHMMC) was investigated as per ASTM G99-05 using pin on disc experimental setup. Initially, hybrid composites were fabricated through stir casting process by varying the wt.% of redmud particle as 3, 7, and 11, and then the wear tests were carried out based on L₂₇ orthogonal array. The experimental results revealed that 11?wt.% RM-AlHMMC showed maximum of 90% improved wear resistance than AlHMMC. For all the composites, the coefficient of friction (CoF) increases and saturates with the applied load and sliding distance, in which 11?wt.% RM-AlHMMC showed maximum of 48% increased CoF than AlHMMC. Metallographic investigation of worn-out AlHMMC composite showed that at maximum applied load, sliding velocity, and sliding distance, the wear mechanism changes from abrasive to adhesive, but adding of redmud particle showed combined adhesive and abrasive wear mechanisms. The optimized tribological parameters were obtained using grey relational analysis which revealed that 11?wt.% RM-AlHMMC has improved tribological properties.     

Improving the specific wear rate and coefficient of friction of polyamide 6 polymer and its composite by adding wax under self-operation conditions

Polyamide polymers are widely used in tribological areas in a wide range of industries. The purpose of this study is to extend the tribological life of this material. For this purpose, composite materials were produced by adding solid lubricants such as graphite and wax to the polyamide 6 (PA6) matrix at different rates, and the synergistic effect of these composites on tribological behavior was investigated. Tribological experiments were carried out under dry sliding conditions and on themselves. The polyamide 6/graphite/wax composites were first produced in the form of granules in a twin-screw extruder, and then test samples were molded using the injection molding technique. Wear tests were performed using a pin-on-disc wear device. Tribological tests were carried out at a sliding speed of 0.5 m s⁻¹ and under loads ranging from 10 N to 250 N. Following the experiments, the friction coefficient, specific wear rate, and surface wear were determined under the condition of the materials working on each other. The results showed that the lowest specific wear rate and friction coefficient were obtained for the polyamide 6 composites containing 6 % wax and 15 % glass fiber working on each other.     

碳纤维及石墨填充聚四氟乙烯复合材料的摩擦学性能研究

利用M-200型环-块摩擦磨损试验机对石墨(Gr.)及碳纤维(CF)填充聚四氟乙烯(PTFE)复合材料的摩擦磨损性能进行了研究,探讨了石墨及碳纤维的协同润滑效应.认为碳纤维的加入大大提高了复合材料的承载能力,石墨的加入减小了碳纤维表面与对偶的摩擦系数,从而降低了碳纤维的脱落趋势,提高了复合材料的耐磨性.利用扫描电子显微镜(SEM)对PTFE复合材料的摩擦面及对偶转移膜进行了观察.结果表明,本实验中20%的石墨和10%碳纤维填充PTFE复合材料的摩擦磨损性能最好,且在高载荷下的摩擦磨损性能尤为突出,具有一定的应用价值.     

C/C复合材料特性对其摩擦磨损性能的影响

在MM-2000环-块摩擦试验机上研究了制备工艺、石墨化度、密度、纤维取向等材料特性对其摩擦磨损性能的影响。研究结果表明，采用化学气相渗透(CVI) 浸渍工艺制备并经过多次浸渍增密且石墨化后的材料具有优良的摩擦磨损特性。石墨化后试样的密度越大，其摩擦磨损性能也越好。一般情况下在载荷适中时，垂直试样的摩擦系数要大于平行试样，而体积磨损量却小于平行试样。C／C复合材料比高强石墨材料更适宜用作航空发动机轴间密封材料。     

Studies on POM/graphite/Ekonol composites

POM/graphite/Ekonol composites were prepared by the Torque Rheometer mixing and compression molding, and their hardness, compressive and impact strengths have been tested. The tribology behaviour was also investigated by the friction and wear experiment. The worn surface of the composite was studied by SEM technique, and on its basis, the wear mechanism was analysed. Results show that it was possible to prepare POM/graphite/Ekonol composites of high tribology performance and good mechanical properties by the Torque Rheometer mixing and compression molding. With the rise of Ekonol content, the wear mechanism was changed from adhesion plus plough to fatigue wear plus abrasive wear.