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.     

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.     

弹性金属塑料复合材料的摩擦磨损特性研究

在MPX-2000摩擦磨损试验机上，用环盘摩擦副，结合扫描电镜分别评价了弹性金属塑料（EMP）复合材料与钢在油润滑和干摩擦条件下的摩擦磨损特性。结果表明：两种试验条件下，相同滑动速度的摩擦系数随载荷的升高而减小，当载荷为2000N，滑动速度小于3.52m/s时，摩擦系数基于趋于稳定，EMP磨损率随滑动速度和载荷的升高耐增加，但不同试验条件的增幅不高，油润滑下滑动速度小于3.52m/s和干摩擦条件下滑动速度小于1.96m/s时，EMP以微切削，塑性变形和梨沟磨损为主，并在摩擦副两表面形成转移物。     

Effect of rubber on tribological behaviors of polyamide 66 under dry and water lubricated sliding

The friction and wear behaviors of polyamide 66 (PA 66) and rubber-filled PA 66 (PA 66/SEBS-g-MA) composites were investigated on a block-on-wheel model friction and wear tester under dry sliding and water lubricating conditions. In order to further understand the wear mechanisms, the worn surfaces and scraps of samples were analyzed by scanning electron microscopy (SEM) and differential scanning calorimeter (DSC). The experimental results indicated that the wear mass loss and the friction coefficient of PA 66 decreased with the addition of rubber particles. The friction coefficients of PA 66 and PA 66/SEBS-g-MA composites under water lubricating condition are lower than those under dry sliding condition, but the wear mass losses are higher than those under dry sliding condition. The main wear mechanisms under dry sliding condition are the plastic deformation and mechanical microploughing. Whereas the main wear mechanisms under water lubricating condition are the mechanical microploughing and abrasive wear.     

Friction and wear properties of bronze–graphite composite under water lubrication

Bronze–graphite composite was prepared using powder metallurgy. The friction and wear behaviors of the resulting composites in dry- and water-lubricated sliding against a stainless steel were comparatively investigated on an MM-200 friction and wear tester in a ring-on-block contact configuration. The wear mechanisms of the bronze–graphite composite were discussed based on examination of the worn surface morphologies of both the composite block and the stainless steel ring by means of scanning electron microscopy equipped with an energy dispersion spectrometry and on determination of some typical elements on the worn surfaces by means of X-ray photoelectron spectroscopy. It was found that the friction coefficient was higher under water lubrication than that under dry sliding and it showed margined change with increasing load under the both sliding conditions. A considerably decreased wear rate of the bronze–graphite composite was registered under water-lubricated sliding than under dry sliding, though it rose significantly at a relatively higher load. This was attributed to the hindered transfer of the composite onto the counterpart steel surface under water-lubricated sliding and the cooling effect of the water as a lubricant, while its stronger transfer onto the steel surface accounted for its higher wear rate under dry sliding. Thus, the bronze–graphite composite with much better wear-resistance under water-lubricated sliding than under dry sliding against the stainless steel could be a potential candidate as the tribo-material in aqueous environment.     

润滑油添加剂对聚合物及其复合材料摩擦磨损性能的影响

利用MHK-500型环-块磨损试验机研究了二烷基二硫代磷酸锌(ZDDP)对几种聚合物及其复合材料-金属摩擦副油润滑摩擦磨损性能的影响。结果表明,液体石蜡中的ZDDP对尼龙66(PA66)及聚酰亚胺(PI)-GCr15轴承钢摩擦副的摩擦系数影响不大,但却使聚四氟乙烯(PTEE)及其复合材料-GCr15轴承钢摩擦副的摩擦系数略有降低。PTEE及其复合材料-GCr15轴承钢摩擦副表面的ZDDP吸附膜具有一定的抗磨作用,它大幅度降低了Pb、PbO及MoS     

润滑油添加剂对聚合物材料摩擦磨损性能的影响研究

利用MM－200型磨损试验机考察了ZDDP对聚合物材料（PTFE、PI及MCPA）－GCr15轴承钢摩擦副摩擦磨损性能的影响。研究发现，液体石蜡及含ZDDP的液体石蜡润滑均可大幅度改善聚合物材料的摩擦磨损性能，且使其摩擦系数比干摩擦时降低一个数量级，摩擦副表面的ZDDP吸附膜均在不同程度上提高聚合物材料的耐磨性，但其对聚合物材料的摩擦性能影响不大。     

Investigation of wear mechanism of SiC particulate-reinforced Al-20Si-3Cu-1Mg aluminium matrix composites under dry sliding and water lubrication

Unreinforced Al-20Si-3Cu-1Mg (ASCM) aluminium alloy and SiC particle reinforced Al-20Si-3Cu-1Mg (ASCM-SiC) aluminium matrix composites were fabricated by powder metallurgy (). The samples were slid against 4Cr13 stainless steel in a reciprocal friction tester under a load of 25 N to 175 N and sliding velocity of 0.3 to 1.2 m s⁻¹ at ambient conditions. The results show that SiC particulate-reinforced aluminium matrix composites possess good wear resistance at dry sliding and less wear resistance under water lubrication. Ploughing wear is the dominant wear mechanism at dry sliding and tribochemical wear is dominant under water lubrication. SEM, AES and XPS were used to examine the wear morphology and surface chemistry.     

Effect of Blowing Air and Floating Sand-dust Particles on the Friction and Wear Behavior of PTFE, UHMWPE and PI

The friction and wear behaviors of polytetrafluoroethylene (PTFE), ultra-high molecular weight polyethylene (UHMWPE), and polyimide (PI) have been comparatively evaluated under dry sliding, blowing air, and simulated sand-dust conditions. The tribological tests were conducted on an improved block-on-ring test rig equipped with an attachment for simulating the sand-dust environment. The reason for the difference in the tribological behavior of these polymers under the three test conditions was also comparatively discussed, based on scanning electron microscopic examination of the worn polymer specimens and counterfaces. Under blowing air conditions, the decrease of the contact temperature produced by blowing air led to the increase in the shearing strength of the sliding surface when compared with dry sliding conditions and hence to cause an increase in the friction coefficient and a remarkable decrease in the wear rate of PTFE and UHMWPE. On the contrary, blowing air produced a decrease in the friction coefficient of PI because of the formation of transfer film on the counterfaces, and an increase in the wear rate, because the blowing air considerably promoted the transfer of PI onto the counterfaces when compared with dry sliding conditions. Both PTFE and UHMWPE registered the lowest wear rate under sand-dust conditions, owing to the tribolayer formation on the worn surfaces, while PI exhibited the highest wear rate because no tribolayer was formed during the abrasive wear process.     

Effect of MWCNTs-COOH Reinforcement on Tribological Behaviors of PI/MWCNTs-COOH Nanocomposites Under Seawater Lubrication

The carboxyl-functionalized multiwalled carbon nanotube (MWCNT-COOH) was achieved by grafting carboxyl (COOH) groups onto surfaces of MWCNTs. Then polyimide (PI)-based nanocomposites reinforced with MWCNTs-COOH and MWCNTs were prepared by in situ polymerization and the tribological behaviors of PI/MWCNTs-COOH and PI/MWCNT nanocomposites were studied under dry friction and seawater lubrication. The results showed that the incorporation of MWCNTs-COOH and MWCNTs could greatly improve the wear resistance of PI because of the lubricating effect of MWCNTs-COOH and MWCNTs. In additon, the PI/MWCNTs-COOH exhibited better tribological performance than the PI/MWCNTs under dry friction due to functionalization of MWCNTs. In addition, PI/MWCNTs-COOH nanocomposites presented better tribological properties under seawater lubrication than other conditions because of the excellent lubricating effect of seawater, especially when the content of MWCNTs-COOH was 0.7 wt%. Furthermore, the effects of applied load and sliding speed on the tribological behaviors of PI/MWCNTs-COOH nanocomposites were studied under seawater lubrication. It was found that 0.7 wt% PI/MWCNTs-COOH nanocomposites had the best friction reduction and antiwear properties when the applied load and sliding speed were 3 N and 0.26 m/s, respectively, under seawater lubrication.     

Friction and wear properties of metal powder filled PTFE composites under oil lubricated conditions

Four kinds of polytetrafluoroethylene (PTFE)-based composite, pure PTFE, PTFE+30vol.%Cu, PTFE+30vol.%Pb and PTFE+30vol.%Ni composite, were prepared. The friction and wear properties of these metal powder filled PTFE composites sliding against GCr15 bearing steel under both dry and lubricated conditions were studied using an MHK-500 ring-block wear tester. The worn surfaces of the PTFE composites and the transfer films formed on the surface of GCr15 bearing steel were examined using scanning electron microscopy (SEM) and optical microscopy respectively. Experimental results show that the friction and wear properties of the PTFE composites can be greatly improved by liquid paraffin lubrication. The wear of these PTFE composites can be decreased by at least 1 to 2 orders of magnitude compared with that under dry friction conditions, while the friction coefficients can be decreased by 1 order of magnitude, SEM and optical microscopy investigations of the rubbing surfaces show that metal fillers of Cu, Pb and Ni not only raise the load carrying capacity of the PTFE composites, but also promote transfer of the PTFE composites onto the counterfaces, so they greatly reduce the wear of the PTFE composites. However, the transfer of these PTFE composites onto the counterfaces can be greatly reduced by liquid paraffin lubrication, but transfer still takes place.     

Dry sliding friction and casing wear behavior of PCD reinforced WC matrix composites

The friction and casing wear properties of PCD reinforced WC matrix composites were investigated using a cylinder-on-ring wear-testing machine against N80 casing steel counterface under dry sliding conditions. The results indicate that the friction and casing wear rate of PCD reinforced WC matrix composites are the lowest among the materials. As the applied load and sliding speed steadily increase, the friction coefficients of PCD reinforced WC matrix composites decrease. In addition, the casing wear rates increase with increasing load, but decline with sliding velocity. The dominant wear mechanism of the PCD composite is the micro-cutting wear, accompanied by adhesive wear.     

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。     

干摩擦和水润滑条件下单晶硅的摩擦磨损性能研究

在UMT-2微摩擦试验机上,对单晶硅片进行了干摩擦和水润滑两种状态下的摩擦磨损试验,分析讨论了载荷和滑动速度对单晶硅片的摩擦因数和磨损率的影响规律;运用扫描电子显微镜,观察和分析了其磨损表面形貌。结果表明:干摩擦条件下的磨损机理主要表现为黏着磨损,水润滑条件下的磨损机理主要表现为机械控制化学作用下的原子/分子去除过程;水润滑条件下的摩擦因数和磨损量均较小,最小磨损率仅为10μm3/s;在水润滑条件下,载荷和滑动速度达到一定值时,硅片表面将发生摩擦化学反应,生成具有润滑作用的Si(OH)4膜,即机械作用在一定条件下对化学反应具有促进作用。     

Effect of the degree of crystallinity on the friction and wear of poly(ethylene terephthalate) under water lubrication

By means of a pin-on-disk type of wear-testing apparatus, coefficients of friction and wear depths of various poly(ethylene terephthalate) (PET) specimens with different degrees of crystallinity were measured at sliding speeds of 0.01 and 0.1 m s⁻¹ under a constant load of 10 N with water lubrication. The coefficients of friction with lubrication were lower than those for unlubricated conditions and there was little dependence on the degree of crystallinity. However, the wear rates with lubrication were higher than those obtained under dry conditions and decreased with increasing degree of crystallinity, in contrast with the unlubricated wear rates. These results are discussed on the basis of the plasticization of worn polymer surfaces by water.The worn surfaces and frictional tracks were observed by optical and electron microscopy. The frictional tracks for low crystallinity PET were smooth with many fine scratches and characteristic of transfer wear. For high crystallinity, frictional tracks were somewhat different from those for low crystallinity PET.     

聚四氟乙烯纤维基层压材料的摩擦学行为研究

以无碱玻璃纤维布作为基材,以浸渍有聚四氟乙烯的棉纤维布为表层,以环氧树脂为黏合剂,经热压制备聚四氟乙烯纤维基层压材料;采用 MRH-03型高速环－块摩擦磨损试验机研究其在空气、纯水、海水介质中的摩擦学行为,利用扫描电镜观察并分析磨损表面的形貌及摩擦形式。结果表明,与基底材料相比,增加聚四氟乙烯棉纤维布后,材料的摩擦性能有明显的改善;加入水作为润滑介质后,由于水膜边界润滑的作用,特别是由于海水作为润滑介质时摩擦产生的淤泥状的 Mg （OH）2和 CaCO3的自润滑作用,摩擦因数和磨损率进一步减小。     

Sliding wear behavior of planar random zinc-alloy matrix composites

The friction and wear behavior of planar random zinc-alloy matrix composites reinforced by discontinuous carbon fibres under dry sliding and lubricated sliding conditions has been investigated using a block-on-ring apparatus. The effects of fibre volume fractions and loads on the sliding wear resistance of the zinc-alloy matrix composites were studied. Experiments were performed within a load range of 50–300 N at a constant sliding velocity of 0.8 m s⁻¹. The composites with different volume fractions of carbon fibres (0–30%) were used as the block specimens, and a medium-carbon steel used as the ring specimen. Increasing the carbon fibre volume fraction significantly decreased the coefficient of friction and wear rates of both the composites and the medium-carbon steel under dry sliding conditions. Under lubricated sliding conditions, however, increasing the carbon fibre volume fraction substantially increased the coefficient of friction, and slightly increased the wear of the medium-carbon steel, while reducing the wear of the composite.Under dry sliding conditions, an increasing load increased not only the wear rates of both the composite and the unreinforced zinc alloy, but also those of their corresponding steel rings. However, the rate of increase of wear with increasing load for both the composite and its corresponding steel ring was much smaller than for the unreinforced zinc alloy and its corresponding steel ring. The coefficient of friction under dry sliding conditions appeared to be constant as load increased within a load range of 50–150 N for both the composite and the unreinforced zinc alloy, but increased at the higher loads. Under any load the coefficient of friction of the composite was lower than half that of the unreinforced zinc alloy under dry sliding conditions.     

滚动与滑动耦合作用下GCr15钢的磨损行为研究

选用GCr15钢在M2000磨损试验机上进行了干摩擦和油润滑的摩擦磨损试验，用表面粗糙度仪测量试件在不同磨损阶段的表面形貌，用称重法测量其磨损量，分析了滚动与滑动耦合作用下GCr15钢的磨损机理。研究表明，在滚动与滑动耦合作用下GCr15钢的磨损以滑动摩擦磨损为主，温度和润滑条件直接决定着GCr15钢的磨损情况。     

聚四氟乙烯复合材料的摩擦学二次转移行为研究

采用冷压成型、自由烧结工艺分别制备了青铜粉、聚酰亚胺、二硫化钼和石墨填充改性的聚四氟乙烯复合材料,在改装的M-2000型摩擦磨损试验机上考察了材料的二次转移摩擦学性能;用扫描电子显微镜对磨损表面进行观察和分析。结果表明:增加载荷有利于提高转移膜与基底的结合强度;填料种类对PTFE复合材料二次转移膜的摩擦学性能有影响,在本实验条件下(干摩擦、室温、滑动速度为0.42m/s、接触载荷为30N),以PTFE复合材料作为润滑剂提供源使用时,PTFE/MoS2、PTFE/Graphite复合材料形成的二次转移膜最好,PTFE/Bronze复合材料二次转移膜次之,PTFE/PI复合材料形成二次转移膜的能力最差。     

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.