Performance of plastic gear made of carbon fiber reinforced poly-ether-ether-ketone: Part 2

Five kinds of PEEK/CF composites, made by blending poly-ether-ether-ketone (PEEK) with three kinds of PAN type carbon fibers (CFs) and two kinds of pitch type CFs respectively, were injection-molded into gears. Their gear performance such as the load capability and the wear of tooth were evaluated. The wear properties of PEEK/CF gears extremely varied depending on the kinds of CFs, when the same type gears were combined and grease was initially applied. Also, the load capabilities were significantly influenced by the affinity between PEEK and CF. A composite gear reinforced with CF of the highest density indicated the highest load capability irrespective of the test conditions, due to the lowest abrasive property of the CF as well as the excellent affinity between PEEK and CF. Its load capability under a high temperature running condition was found to be superior to that of polyamideimide (PAI) composite gear or polyphenylenesulphide (PPS) composite gear.     

Synergetic Effect of Lubricant Additive and Reinforcement Additive on the Tribological Behaviors of PEEK-Based Composites under Seawater Lubrication

Polyetheretherketone (PEEK)-based composites reinforced with lubricant additive (polytetrafluoroethylene, PTFE) and reinforcement additives including carbon fiber (CF), glass fiber (GF), and bronze powder were prepared using a hot-press molding technique. The synergetic effects of different additives on the tribological behaviors of PEEK-based composites sliding against 316 steel under seawater lubrication were investigated systematically using a ring-on-block test rig. The results showed that lubricant additive PTFE can decrease the friction coefficient and consequently improved the wear resistance of PEEK under seawater lubrication, especially when the volume fraction of PTFE was about 20%. It was also found that the incorporation of CF can further improve the wear resistance of PEEK blended with 20% PTFE, especially under high load and high sliding speed. This suggested that a synergistic effect on improving the wear resistance of PEEK existed between PTFE and CF, which originated from good lubrication of PTFE, good reinforcement of CF, and good interfacial combination between CF and PEEK-20%PTFE. However, two other reinforcement additives of GF and bronze powder had an antagonistic effect but not a synergetic effect with PTFE; that is, the incorporation of the two additives greatly deteriorated the wear resistance of PEEK blended with 20% PTFE.     

Comparative investigation on the tribological behaviors of CF/PEEK composites under sea water lubrication

Carbon fiber (CF) reinforced polyetheretherketone (PEEK) composites were prepared and their tribological behaviors under sea water lubrication were comparatively investigated. The results showed that the incorporation of CF can greatly improve the wear resistance of PEEK under sea water lubrication, especially when the volume fraction of CF was about 10%, because exposed CF can effectively share the main load between the contact surfaces and consequently protect the matrix from severe wear. In addition, CF/PEEK had better friction and wear properties under sea water lubrication than under dry friction and pure water lubrication due to better lubricating effect of sea water.     

On the Effect of Counterface Material and Aqueous Environment on the Sliding Wear of Carbon Fibre Reinforced Polyetheretherketone (PEEK)

Carbon fibre reinforced Polyetheretherketone (PEEK/CF) was exposed to unidirectional sliding at a speed of 28 mm/s against various counterparts. Some of these tests were repeated in water. The bearing steel produced the worst results. In this case, the carbon fibre reinforcement even increased the wear compared to unreinforced PEEK. Most other counterparts led to wear rates almost a factor 100 lower. Chemically inert hard counterparts performed best. The lowest wear rates were found against DLC. An aqueous environment usually accelerated the wear process. Only in case of alumina and DLC counterparts, the water lubrication reduced the wear rate. The addition of graphite plus Polytetraflourethylene (PTFE) to PEEK/CF reduced the sensitivity to the operation conditions.     

Erosive wear properties of unidirectional carbon fiber reinforced PEEK composites

The erosive wear properties of unidirectional carbon fiber (CF) reinforced polyetheretherketone (PEEK) composites were studied. A semi-ductile erosive wear manner was found regardless of the CF orientation. Wear mechanism analysis revealed that both cutting and deformation mechanisms existed in the erosion of the composites, although different damaging forms were involved depending on the impingement angles and CF orientation. To give further support on the erosion mechanisms, a special procedure was designed to observe the cross-sectional surface of the eroded composites, and the surface temperature variation was registered. It increased with increasing impingement angle, indicating higher energy dissipation by deformation, which is consistent with the revealed shift of the main erosive wear mechanism from cutting to deformation and “wholesale” fiber fracture.     

Tribo‐investigation of PEEK‐short carbon fibre composites in severe testing conditions

A series of composites of polyetheretherketone (PEEK) containing short carbon fibre (CF) in the range of 0–30% (w/w) was developed. Their wear behaviour in low amplitude oscillating wear (LAOW) mode was studied under various operating parameters such as load and temperature. The LAOW mode was studied in ball‐on‐plate configuration against steel (100 Cr 6) at ambient temperature and at 100°C. In this mode, the coefficient of friction (µ), specific wear rate (Ko) and limiting loading pressure‐sliding speed (PV) values were investigated. It was observed that with increase in %CF, the wear performance and utility of PEEK (limiting PV value) improved significantly. Thirty percent CF was best performing composite in all aspects. The µ, however, was hardly influenced with the inclusion of CF or variation in operating parameters. The same composites were also evaluated in abrasive wear mode to study the influence of severe operating conditions on wear and friction performance. In this wear mode, the CF‐filled composites showed poorer wear resistance than did neat PEEK. The specific wear rate was correlated with strength properties and it was observed that these composites closely followed the predictions of the Ratner–Lancaster plot. Scanning electron microscopy was used to examine the microstructural features of worn surfaces. Copyright © 2007 John Wiley & Sons, Ltd.     

Fretting Wear Study of PEEK-Based Composites for Bio-implant Application

The failure caused by fretting wear is a key issue in orthopedic applications as well as other engineering applications. In this study, fretting wear tests were conducted on poly (ether ether ketone) (PEEK), glass fiber reinforced PEEK (GFRPEEK) and carbon fiber reinforced PEEK (CFRPEEK), respectively. Surface characterizations of tested specimens were performed using XRD, microhardness tester, 3D white-light interfering profilometry, SEM and optical microscopy to analyze their wear features. The obtained results showed that the fibers increased the microhardness values and reduced the friction coefficients and wear rates of PEEK-based composites. The fretting regimes of PEEK, GFRPEEK and CFRPEEK were gross slip. The fretting wear mechanisms of those PEEK composites were dominated by abrasive wear, adhesive wear and delamination. CFRPEEK has demonstrated superior fretting wear characteristics, and hence, is a potential bio-implant material for applications such as artificial joints.     

碳纤维/聚醚醚酮(CF/PEEK)复合材料摩擦磨损性能及抗摩擦静电特性研究

利用真空热压烧结技术制备了不同碳纤含量的碳纤维/聚醚醚酮(CF/PEEK)复合材料,采用热导率分析仪和热重测试仪对材料的热学性能进行表征,并利用多功能摩擦磨损试验机、三维形貌轮廓仪、扫描电子显微镜和摩擦静电计对材料的摩擦磨损性能和抗摩擦静电性能进行分析。分析结果表明：随着CF添加量的增加,复合材料摩擦因数、磨损率和摩擦静电电压先降低后升高,当CF添加量(质量分数)为20%时,摩擦因数、磨损率和摩擦静电电压达到最低,分别为0.247、5.6×10^-6 mm/(N·m)和3.3 V,证明此种方法制备的20%CF/PEEK材料具有优异的摩擦磨损性能和抗静电性能。CF/PEEK复合材料磨损机理以黏着磨损为主,并且伴随着轻微的磨粒磨损。     

Microfriction of various phases in a carbon fiber, polytetrafluoroethylene, graphite and polyetheretherketone composite blend as measured by atomic force microscopy

Atomic force microscopy and friction force microscopy have been used to conduct microfriction studies on short carbon fiber reinforced PEEK/PTFE composite blends. The relative micro-scale coefficients of friction of different filler particles (PTFE, CF in normal and anti-plane orientation, and graphite) have been compared with the matrix PEEK. The order of the nanoscopic coefficients of friction was: carbon fiber in normal orientation>carbon fiber in plane orientation>PEEK matrix>graphite flake>carbon fiber in parallel orientation>PTFE particle. Additional microhardness studies resulted in qualitative hardness comparisons of the various phases. Their order of the form: carbon fibers PEEK and graphite>PTFE also reflects the contribution of the various phases to the wear resistance of the composite blend. The latter can be estimated from the AFM-topography traces of the polished composite surfaces.     

CF/PEEK复合材料自阻电热-原位膜混合加热固化方法

碳纤维增强聚醚醚酮树脂基(CF/PEEK)复合材料密度小、韧性强、疲劳强度高,且可循环使用,但PEEK树脂熔融温度高(>340℃)、熔融黏度大(>1000 Pa·s)、熔融-烧蚀工艺温度窗口小,零件固化难度大。提出一种CF/PEEK树脂基复合材料自阻电热-原位膜混合加热固化方法,结合有限元仿真,引入组合原位膜自适应地辅助加热制件。有限元仿真和实验研究结果证明了该方法的有效性：加热过程中相较纯自阻电热加热方法,制件温度均匀性提高了75%,结晶度提高了16.2%,实现了CF/PEEK树脂基复合材料的高效、均匀加热固化。     

Elevated pitting wear of injection molded polyetheretherketone (PEEK) rolls

The increased pitting wear of PEEK rolls applied as bearing elements in drawer guide rails was investigated. Similar to findings for PEEK gear wheels the increased pitting occurred only in the presence of lubricants. Simple assumptions found in literature to explain this effect for PEEK gear wheels could be disproved within this research. Moreover, high irreversible deformations during the rolling process of PEEK rolls which were observed in a previous study were shown to not influence the mechanical properties of the surface material significantly. Additionally, the chemical analysis of the tribological system with Raman spectroscopy excluded a chemical reason for the intensified pitting. A detailed microscopic analysis of unstressed PEEK rolls combined with microtome cuts of the surfaces showed distinct pre-cracks in the outermost surface region which were not visible to the naked eye. Assuming a crack growth mechanism that was strongly supported by the fluid pressure of grease enclosed in the surface pre-cracks the injection molding process was adapted in order to improve the surface quality of the PEEK rolls. By this way the fatigue lifetime of the latter was increased by a factor of 2–3 which was crucial for the practical application.     

A technique for calculating tribotechnical characteristics of tractive cylindrical gear of VL-10 locomotive

A technique for the design calculations of the local strength, wear, and durability of tractive cylindrical double gear of VL-10 locomotive with angular tooth correction has been suggested. The technique allows for realistic engagement conditions (parity and wear-induced changes in the tooth profile curvature). The regularities of the effect that structural (angular engagement correction) and operational (linear tooth wear) factors have on these parameters for triple–double–triple tooth engagement in this gear have been revealed. It has been established that, when considering tooth correction, there are certain optimum displacement coefficients that maximize the durability compared to the uncorrected gear. It has been shown that, if one allows for changes in the tooth-profile due to wear are allowed for, the actual durability and bearing capacity of the gear is higher. The results have been presented graphically in order to help establish regularities of the effect of engagement conditions on the tribotechnical characteristics.     

模拟矿井环境下的PEEK/SiO2/CF-MoS2复合材料摩擦行为研究*

为改善聚醚醚酮（PEEK）在矿井工况下的摩擦性能,选用纳米二氧化硅（SiO2）、二硫化钼（MoS2）和短切碳纤维（CF）为增强填料制备PEEK/SiO2/CF-MoS2复合材料,并探究PEEK/SiO2/CF-MoS2复合材料在不同工况条件下的滑动与滚动摩擦学性能;通过模拟滚轮罐耳在矿井环境下的运行方式,分析其磨损形貌和磨损机制。结果表明：PEEK/SiO2/CF-MoS2复合材料在不同载荷条件下均具有良好的减摩和耐磨特性;滑动摩擦在水介质工况下及滚动摩擦在干摩擦工况下,复合材料的摩擦因数和磨损率最低,其磨损机制均以磨粒磨损为主。与矿井常用的聚氨酯材料的对比,PEEK/SiO2/CF-MoS2复合材料的摩擦学性能更为优异。     

PEEK450 FC30与SiC陶瓷在海水润滑下的摩擦磨损特性研究

碳纤维增强聚醚醚酮PEEK450 FC30与工程陶瓷SiC软硬组合作为海水柱塞泵关键摩擦副备选材料,利用MCF 10摩擦磨损试验机对其在海水润滑下的摩擦磨损特性进行试验研究,探讨接触压力、滑动转速对材料磨损率和摩擦系数的影响规律。试验结果表明：在一定范围内的滑动速度、接触压力下,该摩擦副呈现出较小的磨损率和摩擦系数。当滑动速度在0.5~1.5 m/s之间,接触压力为1.33 MPa时,磨损率最小。通过扫描电子显微镜观察摩擦副磨损表层发现,在海水润滑下,SiC磨损并不明显,而PEEK450 FC30的磨损主要是以塑性涂抹为特征的粘着和SiC表面粗糙峰引起的机械犁耕。研究结果对水液压元件的选材具有十分重要的指导作用。     

水润滑下316L不锈钢与聚醚醚酮摩擦磨损性能研究

为了寻找适合于水液压泵/马达的摩擦副材料,以316 L不锈钢与纯聚醚醚酮树脂、30%玻璃纤维增强PEEK(PEEKGF30)、30%碳纤维增强PEEK(PEEKCA30),PTFE和石墨及碳纤维填充PEEK(PEEKHPV)组成的摩擦副为研究对象,利用MMW-1立式万能摩擦磨损试验机测量摩擦副在水润滑下接触表面的摩擦因数和温度以及试样的磨损量,并通过激光共聚焦显微镜对试件表面磨损形貌进行分析。结果表明:316 L-PEEKHPV摩擦副的摩擦因数、摩擦温升、磨损量均小于其余3组摩擦副,适合作为水液压泵/马达的关键摩擦副材料。316 L不锈钢与PEEKGF30配对时,摩擦机制为涂抹和擦伤,磨损较为严重;与PEEKCA30配对时,摩擦机制为擦伤;与PEEKHPV配对时摩擦机制主要为划伤,磨损较为轻微。     

不同方法表面改性碳纤维增强热塑性聚酰亚胺复合材料的摩擦磨损性能

采用硝酸氧化改性和涂层复合改性法分别对碳纤维(CF)进行了表面处理,并制备了CF增强热塑性聚酰亚胺(TPI)复合材料;对CF的表面形貌进行了观察,研究了表面改性方法对复合材料摩擦磨损性能的影响,并利用扫描电子显微镜观察了磨损表面形貌。结果表明:硝酸氧化改性增大了CF的表面粗糙度,随处理时间的延长粗糙度增大;经涂层复合改性后,CF表面包覆了一层聚酰亚胺(PI),保护了CF并提高了其与基体界面的结合强度;经表面改性后的CF增强TPI复合材料的摩擦磨损性能均得到提高,以涂层复合改性的效果最好;硝酸氧化改性后的CF在摩擦过程中易断裂,复合材料的磨损形貌以磨粒磨损为主,而涂层复合改性后的CF断裂得到抑制,与基体结合更为牢固,磨损表面较为平整。     

The Effect of Applied Load on Tribological Behaviors of Potassium Titanate Whiskers Reinforced PEEK Composites Under Water Lubricated Condition

The tribological behavior of potassium titanate whiskers (PTW) reinforced polyetheretherketone (PEEK) composite has been investigated using the pin-on-disk configuration at different applied loads under water lubricated condition. It was found that the incorporation of the PTW into PEEK would achieve high wear resistance and low friction coefficient at low load. When the applied load increased up to 4 MPa, only the composite filled with 5 wt% PTW showed a significant improvement in the frictional reduction and wear resistance; on the contrary, a rapid increasing of the friction coefficient was observed for the composites of high PTW content. In the meantime, the severe wear loss occurred along with the sharply increasing temperature. This sudden deterioration of the wear resistance should be attributed to the change of the wear mechanism. The main wear mechanism of mild fatigue for the neat PEEK and mild abrasive wear for the 5 wt% PTW filled composite did not alter with the rising of the load. In this case, no transfer film could be detected on the counterpart surface. However, for the high PTW filled composites, the wear mechanism changed from the mild abrasive wear at low applied load to the severe fatigue wear at high load. Large amounts of wear debris were generated by the fatigue-delamination of the composite surface. And then, the debris served as third-body abrasives during the subsequent sliding process and the wear mechanism changed to severe abrasive wear. And unexpectedly, a thick and lumpy transfer film was formed on the counterface.     

Comparative Study on Tribological Behaviors of Polyetheretherketone Composite Reinforced with Carbon Fiber and Polytetrafluoroethylene Under Water-Lubricated and Dry-Sliding Against Stainless Steel

The tribological behaviors of the composites of polyetheretherketone (PEEK) reinforced by carbon fiber and polytetrafluoroethylene (PTFE) under distilled-water-lubricated- and dry-sliding against stainless steel were investigated. It was found that the PEEK composite had much better wear-resistance under water-lubricated sliding against stainless steel than under dry-sliding. The transfer film had smaller effect on the tribological behavior of PEEK composite under water-lubricated condition than under dry-sliding, because under water-lubricated condition the cooling and boundary lubricating effects of the water medium dominated the tribological behavior. Moreover, the considerably hindered transfer of the PEEK composite under water lubrication might also account for the decreased wear rate under water lubrication. The PEEK composite was characterized by mild scuffing and fiber protruding under water lubrication, while the plastic deformation and adhesion was significantly abated than under dry-sliding.     

Self-Lubricating PTFE-Based Composites with Black Phosphorus Nanosheets

Black phosphorus (BP), a newly emerging two-dimensional material, has recently received considerable attention. Our recent work suggested that BP nanosheets exhibit extraordinary mechanical and lubrication properties. In the present work, the tribological properties of polyetheretherketone (PEEK)/polytetrafluoroethylene (PTFE) and carbon fiber (CF)/PTFE composites with BP nanosheets have been investigated. The morphologies and surface element distribution of the worn tracks of the tribopair surfaces were examined by different analytical techniques. The results show that the coefficients of friction (COFs) of both the PEEK/PTFE and CF/PTFE composites decreased dramatically after the addition of BP nanosheets, and the minimum COF of the composite was 0.04, which was a quarter of that of the PTFE composite without BP nanosheets. After BP nanosheets were added into the composites, the wear rate of the PTFE/PEEK composite decreased dramatically, while that of the CF/PTFE composite increased significantly with the increase in the filler concentration. The analysis of the lubrication mechanism of the PTFE composite with BP nanosheets suggested that BP nanosheets could be constantly supplied into the contact area and gradually formed a BP film composed of phosphorus oxide and phosphoric acid on the counterpart surface instead of the formation of PTFE transfer film. The formed BP transfer film promoted the friction reduction and the disappearance of the adhesive wear.     

碳纤维增强尼龙1010复合材料的摩擦磨损性能及磨损机理研究

以注塑成型法制备了尼龙1010及碳纤维(CF)增强尼龙1010复合材料，研究了CF含量和载荷对材料摩擦学性能和磨损机制的影响。结果表明，CF的加入可显著改善尼龙的摩擦学性能，以体积分数为20％的CF增强尼龙1010复合材料的耐磨性能最好。较低的CF含量下复合材料磨损表面主要受到对偶钢环上微凸峰的切削和犁沟作用，较高载荷时发生了热疲劳剥层磨损；随着CF含量增加，复合材料表面在较高载荷时产生明显疲劳断裂，并使对偶钢环产生较剧烈磨损。