Friction and Wear Behaviors of Several Polymers Sliding Against GCr15 and 316 Steel Under the Lubrication of Sea Water

Ocean tribology, a new research field of tribology, is currently being established and developed. The tribological behaviors of polyether ether ketone (PEEK), poly(phenyl p-hydroxybenzoate) (PHBA), polyimide (PI), and perfluoroethylene propylene copolymer (FEP) sliding against GCr15 and 316 steel rings under the lubrication of sea water were studied and compared with that under the lubrication of pure water. The results show that the friction and wear behaviors of a polymer under the lubrication of aqueous medium are not only related to the properties of polymer itself, but also to the corrosive effect and lubricating effect of the medium. When a polymer slid against GCr15 steel under sea water lubrication, the friction coefficient and wear rate of polymer were much larger than that under pure water lubrication because of indirect corrosive wear. However, when sliding against corrosion-resistant 316 steel, polymers PEEK, FEP, and PI exhibited lower coefficients of friction and wear rates under sea water lubrication, this was attributed to better lubricating effect of sea water as a result of the deposition of CaCO₃ and Mg(OH)₂ on the counterface. On the contrary, the friction coefficient and wear rate of PHBA sliding against 316 steel under sea water lubrication were larger than that under pure water lubrication, which may be related to the properties of PHBA itself.     

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。     

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.     

Microstructure of PTFE-Based Polymer Blends and Their Tribological Behaviors Under Aqueous Environment

Four polytetrafluoroethylene-based polymer blends (PTFE blends) with polyimide (PI), polyether ether ketone (PEEK), poly(phenyl p-hydroxybenzoate) (PHBA), and perfluoroethylene propylene copolymer (FEP) were prepared by compression molding and follow-up sintering. Their microstructure was observed by scanning electron microscope. And the tribological behaviors of PTFE blends sliding against 316 steel under pure water and sea water lubrication were comparatively evaluated using block-on-ring tribology test rig. The worn surface of counterpart was examined by X-ray photoelectron spectroscopy. The results showed that by blending with the four polymers, PTFE exhibited the transformed microstructure and improved wear resistance. Compared with FEP, rigid polymers PI, PHBA, and PEEK can enhance the wear resistance of PTFE greatly because they can effectively improve the load-carrying capacity of PTFE matrix and can more efficiently prevent the crystalline bands of PTFE from being pulled out. However, because of the weak inhibition on the pulling out of PTFE crystalline bands, FEP cannot enhance the wear resistance of PTFE as significantly as other polymers. In addition, the friction coefficients and wear rates of PTFE and its blends were lower under the lubrication of sea water than under the lubrication of pure water, which was ascribed to more excellent lubricating effect of sea water originating from the deposition of CaCO₃ and Mg(OH)₂ onto the sliding surfaces.     

极端工况下不同水润滑轴承材料摩擦磨损性能对比研究

在干摩擦工况下模拟水润滑膜严重破坏的极端情况,研究未经改性聚四氟乙烯(PTFE)、超高分子量聚乙烯(UHMWPE)和聚醚醚酮(PEEK)3种材料在不同转速和载荷下的摩擦磨损性能。结果表明:干摩擦工况下UHMWPE材料具有优异的耐磨性和良好的自润滑性能,压力对摩擦因数影响比转速大;PTFE材料具有稳定的摩擦因数,压力和转速对摩擦因数影响明显,耐磨性较差;PEEK材料摩擦因数较大,且相对容易受转速和压力变化的影响,但具有良好的耐磨性能。综合分析,在极端工况下UHMWPE的适应能力最好,PEEK次之, PTFE最差。     

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。     

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。     

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.     

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.     

Tribological Property of Selective Laser Melting–Processed 316L Stainless Steel against Filled PEEK under Water Lubrication

Abstract

As a 3D printing technology, selective laser melting has remarkable advantages such as high processing flexibility, high material utilization, and short production cycle. The applications of selective laser melting technology in industry have become quite extensive. There are many tribological studies on selective laser melting materials, but few based on water lubrication (Zhu, et al., Journal of Zhejiang University-Science A, 19(2), pp 95–110). In this article, the tribological properties of 316L stainless steel processed by selective laser melting and traditional methods have been studied under water lubrication. Polyether ether ketone (PEEK) filled with carbon fiber (CF)/polytetrafluoroethylene (PTFE)/graphite was selected as the counterpart. 316L stainless steel and PEEK are a tribopair commonly used in water hydraulics. This study is of great significance to the application of selective laser melting material of tribopairs in water hydraulics. Friction and wear tests were carried out on a pin-on-disc contact test apparatus under different operating conditions. The friction coefficient, specific wear coefficient, scanning electron microscopy (SEM) of the worn surface, and energy-dispersive spectroscopy (EDS) of the surface adhesions of the three tribopairs were measured and compared. The results revealed that the friction coefficient of the selective laser melting (SLM) 316L stainless steel was significantly higher than that of traditionally processed (TP) 316L stainless steel, which might be caused by the pores on the surface of SLM 316L stainless steel. Adhesion and cutting on the surface of SLM 316L stainless steel were also more serious, resulting in a higher specific wear coefficient of its counterpart PEEK composite compared to PEEK composite against TP 316L stainless steel.     

On the effect of counterface material and aqueous environment on the sliding wear of various PEEK compounds

Polyetheretherketone (PEEK) compounds containing carbon fibres (CF), glass fibres (GF), PTFE, and graphite, respectively, were exposed to unidirectional sliding against various counterparts (100Cr6, X5CrNi18-10, alumina, and bronze). Some of these tests were repeated in water. The stainless steel revealed the best results under dry conditions, whereas alumina was the best counterpart in water. The compound containing GF plus PTFE performed best under dry conditions. Under wet conditions, CF were superior to GF, which react very susceptibly to water. The aqueous environment usually accelerated the compound wear. Only in case of CF containing compounds sliding against alumina, the water lubrication reduced the wear rate.     

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.     

Right Way of Using Graphene Oxide Additives for Water-Lubricated PEEK: Adding in Polymer or Water?

Water-lubricated polymer is attracting more and more interest from the industry. Adding nanoparticles is considered to be an effective way to improve the tribological performance. In this work, water-lubricated Polyetheretherketone (PEEK)-steel contacts were employed as the objects of study. A careful comparative study was made by investigating the effect of adding graphene oxide (GO) into water or into PEEK. Results show that adding GO into water can significantly reduce the wear and friction coefficient of pure PEEK, which is much more effective than adding GO into PEEK. Under the lubrication of GO aqueous dispersion, the wear of PEEK remains very low even under a harsh condition where the pressure reaches 50 MPa and the linear sliding speed is 0.7 m/s. Neat PEEK and GO/PEEK composites in pure water exhibit serious wear under this harsh condition. The excellent lubricating properties of GO aqueous dispersion are attributed to GO nanosheets entering into solid contacts, which can not only form a protective layer on steel counterpart repairing the worn surface, but also strongly adhere to the PEEK matrix resulting in an in situ-formed GO coating and prevent the scratch by steel counterpart.     

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。     

FDM 3D打印聚醚醚酮零件摩擦磨损特性研究

为研究3D打印各向异性对摩擦性能的影响,通过熔融沉积成型(FDM)制备了0°、45°、90°3种打印角度的聚醚醚酮(PEEK)试样,研究3种不同打印角度及载荷变化对PEEK试样摩擦学性能及磨损机制的影响。利用MFT-5000摩擦磨损试验机对PEEK材料进行室温水润滑下的往复滑动摩擦试验,用超景深显微镜观察磨损后表面形貌。试验结果表明：不同载荷下3种打印角度试样的摩擦因数由大到小依次为0°试样、90°试样、45°试样,磨损率由大到小依次为90°试样、45°试样、0°试样;随着载荷的增大,3种不同打印角度试样的摩擦因数均呈现下降趋势,磨损率则呈现上升趋势;PEEK磨损机制是黏着磨损以及疲劳磨损引起的表层脱落。     

Tribological Behaviors of Carbon Fiber–Reinforced PEEK Sliding on Ion-Nitrided 2Cr13 Steel Lubricated with Tap Water

Selecting the proper material and surface treatment methods for elements is one of the essential problems when designing water hydraulic components due to the corrosiveness and poor lubricity of water. Experimental investigation was performed to study the tribological properties of ion-nitrided 2Cr13, a kind of martensitic stainless steel, sliding on carbon fiber–reinforced polyetheretherketone (CFRPEEK). The influence of factors such as sliding velocity, load, and lubrication condition were studied through experiments mainly under tap water lubrication. It was found that the friction coefficients are influenced by both the pressure and the sliding velocity. In contrast, the friction coefficients between quenched 2Cr13 and CFRPEEK are much higher. Compared to water lubrication, both the wear rate and friction coefficients increase in the case of dry friction. Wear mainly occurred on the CFRPEEK. By examining the worn surfaces of the specimens, it was found that adhesion was the main form of wear of the PEEK composite.     

Friction and Wear Behavior of CF/PTFE Composites Lubricated by Choline Chloride Ionic Liquids

The use of ionic liquids (ILs) as lubricants has received increasing attention in recent years. The use of ILs, however, is limited by the corrosion problem and their potential toxic property. Here we present the results of our initial study on the tribological properties of carbon fiber (CF)-filled polytetrafluoroethylene (PTFE) composites, which have an excellent chemical resistance property, lubricated by choline chloride ILs. The difference between choline chloride ILs and water and hydraulic oil as lubricants was studied at the same time, as was the effect of the anion on the lubricating property of choline chloride ILs. The worn surface and transfer film of CF/PTFE composites were studied by scanning electron microscopy. Our results indicate that the lubricating property of choline chloride ILs is much better than that of water and hydraulic oil. The friction coefficient and wear rate of CF/PTFE composites lubricated with ILs were approximately 60 and 50 % lower than those under the dry friction condition. Among the three kinds of ILs tested, the best tribological properties of the CF/PTFE composites were found for those sliding in the mixture of 1,2-propanediol and choline chloride. The worn surface and transfer film of CF/PTFE composites were also much smoother than those under the dry friction, water lubrication, and hydraulic oil lubrication conditions.     

聚合物填充聚四氟乙烯复合材料的摩擦磨损性能

采用机械共混-冷压成型-烧结的工艺制备了PEEK、PPS填充PTFE基粘弹．摩擦型阻尼材料，用环-块式磨损试验机研究了在干摩擦条件下的摩擦磨损性能；用扫描电子显微镜观察磨损表面形貌和内部组织结构。结果表明：混合填充PEEK和PPS时，2种填充物的比例对材料的摩擦因数影响不大，当二者含量相近时，摩擦因数最大；填充物对磨损性能的影响与对摩擦因数的相同；随着PEEK含量的增加和PPS含量的减少，材料的磨损方式由疲劳剥落磨损为主转变为犁削、粘着磨损；PTFE含量的增加，使得复合材料的摩擦因数减小，而磨损有所增大。综合考虑认为，PTFE与适当比例的PEEK／PPS混合填充，具有合适的摩擦因数和较好的耐磨性，能够满足特殊工况下阻尼材料的需要。     

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.     

润滑条件对纳米SiO2填充尼龙复合材料摩擦学性能的影响

利用MM-200磨损实验机在干摩擦、水润滑和油润滑等条件下，研究了润滑条件对含量为10％的纳米SiO2填充尼龙1010复合材料与45^#钢对磨时的摩擦学性能的影响，并利用扫描电子显微镜对纳米SiO2-PA1010复合材料的磨损表面和磨损机理进行了观察和分析。结果表明水润滑时，纳米SiO2-PA1010复合材料的摩擦因数比在干摩擦时有一定程度的降低，但磨损量却比干摩擦时增加了很多；而在油润滑时，摩擦因数和磨损量均比干摩擦和水润滑时降低了许多；复合材料的磨损机制也随着润滑条件的不同发生了相应的变化。