Friction and wear studies of polyimide composites filled with short carbon fibers and graphite and micro SiO2

Polyimide (PI) composites filled with short carbon fibers (SCFs), micro SiO₂, and graphite (Gr) particles were prepared by means of hot press molding technique. The friction and wear properties of the resulting composites sliding against GCr15 steel were investigated on a model ring-on-block test rig. Experimental results revealed that single incorporation of graphite and SCF significantly improve the tribological properties of the PI composites, but micro SiO₂ was harmful to the improvement of the friction and wear behavior of the PI composite. It is found that a combinative addition of Gr, SCF and micro SiO₂ was the most effective in improving the friction-reducing and anti-wear abilities of the PI composites. Research results also show that the filled PI composites exhibited better tribological properties under higher PV-product.     

Self-lubricating properties of PTFE/serpentine nanocomposite against steel at different loads and sliding velocities

The influences of normal contact pressure and sliding velocity on self-lubricating property of PTFE-based composite filled with nano-serpentine particles were mainly studied in the range of 0.12–0.96 m/s and 1.43–8.55 MPa. For comparison, the friction and wear experiments of pure PTFE also were carried out under the same conditions. A scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) were employed to examine the worn surfaces of PTFE/serpentine nanocomposite and transfer films. The experimental results showed that normal contact pressure and sliding velocity had significant effects on the tribological performances of PTFE/serpentine composite. Under different loads, the nanocomposite suffered from abrasive wear, fatigue wear and adhesive wear successively. And at different sliding velocity, the main wear mechanisms were abrasive wear and adhesive wear. SEM and EDS analyses indicated that the continuous and uniform transfer film generated on counterfaces acted as a solid lubricant, which was important to improve the self-lubricating property of PTFE/serpentine nanocomposite.     

Study on the synergistic effect of carbon fiber and graphite and nanoparticle on the friction and wear behavior of polyimide composites

In this paper, the effect of short carbon fiber (SCF), graphite (Gr) and nano-Si₃N₄ on the friction and wear behavior of polyimide (PI) composites were studied using a block-on-ring arrangement. Experimental results revealed that single incorporation of SCF and Gr can improve the friction-reducing and anti-wear abilities of the PI composites significantly. However, nano-Si₃N₄ deteriorated the wear resistance of the PI composite drastically as single filler. A synergistic effect was found for the combination of nano-Si₃N₄ and SCF and Gr, which lead to the best tribological properties. It also can be found that the filled PI composites exhibited better tribological properties under higher PV product (the product of load and sliding speed). Moreover, the filled PI composites showed better tribological properties under oil lubrication and worse tribological properties under water lubrication compared with that under dry sliding condition.     

金属硫化物及石墨填充PTFE 复合材料的摩擦磨损性能研究

利用MHK-500 型环-块磨损试验机, 对MoS₂、CuS、PbS 及石墨(添加量均为30 vo l% )填充的聚四氟乙烯(PTFE) 复合材料在干摩擦条件下与GCr15 轴承钢对摩时的摩擦磨损性能进行了较为系统的研究, 并利用扫描电子显微镜(SEM ) 和光学显微镜对PTFE 复合材料的磨屑和摩擦磨损表面进行了观察。结果表明, 添加石墨降低了PTFE 的摩擦系数, 而添加MoS₂、CuS 及PbS则增大了PTFE 的摩擦系数; 同时, 添加MoS₂、CuS、PbS 及石墨均可将PTFE 的磨损量降低2 个数量级, 其中以PbS 的减磨效果为最好, 而MoS₂ 的减磨效果则最差。      

Role of micro/nano fillers on mechanical and tribological properties of polyamide66/polypropylene composites

The objectives of this research article is to evaluate the mechanical and tribological properties of polyamide66/polypropylene (PA66/PP) blend, graphite (Gr) filled PA66/PP, nanoclay (NC) filled PA66/PP and NC plus short carbon fiber (NC + SCF) filled PA66/PP composites. All composites were fabricated using a twin screw extruder followed by injection molding. The mechanical properties such as tensile, flexure, and impact strengths were investigated in accordance with ASTM standards. The friction and sliding wear behaviour was studied under dry sliding conditions against hard steel on a pin-on-disc apparatus. Scanning electron micrographs were used to analyze the fracture morphologies. From the experimental investigation, it was found that the presence of NC and SCF fillers improved the hardness of PA66/PP blend. Further, the study reveals that the tensile and flexural strength of NC + SCF filled PA66/PP was higher than that of PA66/PP blend. Inclusion of micro and nanofillers reduced the wear rate of PA66/PP blend. The wear loss of the composites increased with increasing sliding velocity. The lowest wear rate was observed for the blend with nanoclay and SCF fillers. The wear rates of the blends with micro/nanofillers vary from 30–81% and lower than that of PA66/PP blend. The wear resistance of the PA66/PP composites was found to be related to the stability of the transfer film on the counterface. The results have been supplemented with scanning electron micrographs to help understand the possible wear mechanisms.     

Tribological behavior of PTFE nanocomposite films reinforced with carbon nanoparticles

Carbon-based nanoparticles synthesized by heat treatment of nanodiamond in the temperature range of 1000–1900 °C were added to PTFE film to investigate the structural effect of the carbon particles on the tribological properties of PTFE composite film. Carbon-based nanoparticles were prepared by milling with micron sized beads in chemically treated water before their addition to PTFE film. The wear and frictional properties of PTFE nanocomposite film were measured by the ball on plate type wear test. The wear resistance of PTFE film was found to be enhanced by the addition of 2 wt% of carbon nanoparticles. The wear coefficient of PTFE film was decreased from 16.2 to 3.5 × 10⁻⁶ mm³/N m by the addition of carbon-based nanoparticles heat-treated at 1000 °C. Increasing the heating temperature of the nanodiamonds caused the extent of aggregation and particle size to increase. The wear resistance of PTFE nanocomposite film was enhanced by the addition of nanodiamonds heat-treated at 1000 °C, but decreased when the heat treatment temperature of carbon nanoparticles was further increased. Tribological behavior of PTFE nanocomposite films depending on the types of carbon nanoparticles were explained based on the structural, physical and chemical modification of carbon nanoparticles.     

Wear behaviour of an Al–12% Si alloy reinforced with a low volume fraction of SiC particles

Aluminium–silicon alloys reinforced with low volume fractions of SiC particles were prepared by the compocasting process. The wear behaviour of the unreinforced Al–12Si alloy and metal-matrix composites (MMCs) was investigated by using a block-on-ring test at room temperature under dry conditions. The results showed that the addition of a low volume fraction of SiC particles (2–8 vol%) is a very effective way of increasing the wear resistance of the matrix alloy. Metallographic examinations revealed that the wear zone of the Al–12Si alloy consists of both hardened and deformation layers. The depth of the hardened layer depended on the applied load and was in the vicinity of 10–50 μm. The formation of the hardened layer was related to the alignment and redistribution of fragmented eutectic phase to the surface region during sliding wear. Furthermore, the delamination of debris from the hardened layer was responsible for a higher wear loss observed in the Al–12Si alloy. The thickness of the hardened layer formed on the MMC specimens was reduced considerably by the incorporation of fragmented SiC particles. This layer exhibited higher hardness and wear resistance than that developed in the unreinforced alloy.     

纳米陶瓷颗粒填充PTFE基复合材料的干摩擦磨损性能

利用MM-200型环-块摩擦磨损试验机研究了纳米陶瓷颗粒SiC、Si3N4、AlN和TiN对聚四氟乙烯(PTFE)复合材料在干摩擦条件下与45#钢对磨时的摩擦磨损性能的影响,借助于扫描电子显微镜观察分析了试样磨损表面形貌,并探讨了磨损机理。结果表明:添加纳米TiN减少了PTFE的摩擦系数,而添加纳米SiC、Si3N4增大了PTFE的摩擦系数。与纯PTFE相比,PTFE复合材料的耐磨性能显著提高,其中以纳米AlN的减磨效果最好,纳米Si3N4的减磨效果最差。纯PTFE的磨损机制主要表现为粘着磨损和疲劳磨损,而纳米粒子填充PTFE基复合材料的磨损机制主要表现为不同程度的粘着磨损、犁沟效应和塑性变形特征。     

Impact of lubrication on the tribological behaviour of PTFE composites for guide rings application

In this study, the friction and wear behaviours of polytetrafluoroethylene (PTFE)-based composites were comparatively evaluated under dry sliding and oil-lubricated conditions. Two PTFE composites filled with bronze and bronze + molybdenum disulfide (MoS₂) were considered. These composites were used as guide rings for hydraulic actuating cylinder. Friction and wear tests of the composite specimens sliding against high chromium steel ball were conducted using reciprocating linear tribometer. The wear mechanisms of the composites under the two different sliding conditions were analysed and discussed based on scanning electron microscopic (SEM) examinations of the worn surface and optical micrographs of the steel counterface. Under the oil-lubricated condition, the friction and wear behaviours of the composites were considerably improved if compared to that under the dry sliding. The oil adsorbed layer limited the transfer of the composite to the steel counterface and avoided the oxidation of the MoS₂ during the sliding test.     

The effect of silane coupling agent on the sliding wear behavior of nanometer ZrO<Subscript>2</Subscript>/bismaleimide composites

The polymer composites filled with nanoparticles have good friction and wear properties and widely used in many fields. The performances of nanocomposites are influenced extensively by the nanoparticles morphology, size, volume fraction and dispersion. Nanometer ZrO₂ particles have good properties, lower prices and shows good foreground in resist-materials of polymer composites. In this paper, the nanometer ZrO₂ particles are treated by silane coupling agent of N-(2-aminoethyl)-γ-aminopropylmethyl dimethoxy silane. The effect of nanometer ZrO₂ content and silane coupling agent on the friction and wear properties of BMI copmposites filled with nanometer ZrO₂ are investigated. The composites filled with untreated ZrO₂ and treated ZrO₂ are prepared by the same way of mechanical high shear dispersion process and casting method. The sliding wear performance of the nanocomposites is studied on an M-200 friction and wear tester. The experimental results indicate that the frictional coefficient and the wear rate of the composites can be reduced by filled with nanometer ZrO₂. The composites containing treated nanometer ZrO₂ have the better tribological performance than that containing untreated nanometer ZrO₂. The results are explained from the SEM morphologies of the worn surface of matrix resin and the composites containing nanometer ZrO₂ and the TEM photographs of the nanometer ZrO₂ dispersion in the matrix.     

稀土处理玻璃纤维填充PTFE复合材料的滑动磨损性能

研究了不同玻璃纤维表面处理对PTFE复合材料在干摩擦条件下滑动磨损性能的影响,并借助扫描电子显微镜(SEM)分析了磨损机理。结果表明:在干摩擦条件下,经表面处理玻璃纤维填充的PTFE复合材料的摩擦系数和摩擦表面温度比未经处理玻璃纤维填充的PTFE复合材料的低,且减磨性能优于未经处理的;而稀土处理玻璃纤维填充的PTFE复合材料的摩擦系数和摩擦表面温度最低,减磨性能最好;未经处理玻璃纤维填充的PTFE复合材料和偶联剂处理玻璃纤维填充的PTFE复合材料都发生了剧烈的粘着转移;偶联剂与稀土处理玻璃纤维填充的PTFE复合材料的磨损机理主要是明显的磨粒磨损;稀土处理玻璃纤维填充PTFE复合材料的磨损形式主要是粘着转移和轻微的磨粒磨损。     

Enhancement of the wear resistance of epoxy: short carbon fibre, graphite, PTFE and nano-TiO2

Enhancements of the wear resistance of epoxy using various fillers, e.g. short carbon fibre (CF), graphite, polytetrafluoroethylene (PTFE) and nano-TiO₂, have been systematically investigated in the present study. Wear properties were carried out on a block-on-ring apparatus. The best wear resistant composition was achieved by a combination of nano-TiO₂ with conventional fillers; as an example, epoxy+15 vol% graphite+5 vol% nano-TiO₂+15 vol% short-CF exhibits a specific wear rate of 3.2×10⁻⁷ mm³/Nm, which is about 100 times lower when compared to the neat epoxy. Worn surfaces were investigated using a scanning electron microscope and an atomic force microscope, from which it is assumed that a mechanism of nanoscale rolling governs this positive effect of the nanoparticles. The main concept of this paper is to strength the importance of integrating various functional fillers in the design of wear resistant polymer composites.     

2种改性聚四氟乙烯固体润滑剂的摩擦学二次转移行为

为改善聚四氟乙烯(PTFE)复合材料的性能,将青铜粉(Bronze)、聚酰亚胺(PI)填充PTFE材料对其进行改性,采用冷压成型、自由烧结工艺分别制备了2种固体润滑剂,在改装的M-2000型摩擦磨损试验机上考察了2种固体润滑剂的二次转移性能;用扫描电子显微镜对上试样的磨损表面进行观察和分析。结果表明:PTFE复合材料作固体润滑剂所形成的二次转移能够改善体系的摩擦学性能,填料的加入增强了PTFE复合材料转移膜与底材的结合强度,起到了保护金属表面的作用;PTFE/Bronze比PTFE/PI的复合材料更适宜作润滑源使用。     

Tribological behavior of poly (phenyl p-hydroxybenzoate)/polytetrafluoroethylene composites filled with hexagonal boron nitride under dry sliding condition

The sliding friction and wear behavior of polytetrafluoroethylene (PTFE) composites filled with poly (phenyl p-hydroxybenzoate) (PHBA) and hexagonal boron nitride (h-BN) was investigated with a pin-on-disc tester. The tensile properties, ball indentation hardness, impact strength and thermal diffusivity were measured. The test results in this paper indicate that the tensile strength, elongation at break, and impact strength decreased, however, the ball indentation hardness and thermal diffusivity were increased when the content of h-BN was increased. PTFE composites filled with 20 wt% PHBA and 20 wt% h-BN exhibited a comparative friction coefficient to pure PTFE. Meantime, the wear rate of the composite decreased about 15 times compared to pure PTFE. The synergistic effect of h-BN with low friction and PHBA with high bearing ability promoted the low friction coefficient and wear rate of h-BN/PHBA/PTFE composites.     

Hybrid effect of nanoparticles with carbon fibers on the mechanical and wear properties of polymer composites

Polyetheretherketone (PEEK) composites reinforced with carbon fibers (CFs) and nano-ZrO₂ particles were prepared by incorporating nanoparticles into PEEK/CF composites via twin-screw extrusion. The effects of nanoparticles on the mechanical and wear properties of the PEEK/CF composites were studied. The results showed that the incorporation of nano-ZrO₂ particles with carbon fiber could effectively enhance the tensile properties of the composites. The tensile strength and Young’s modulus of the composites increased with the increasing nano-ZrO₂ content. The enhancement effect of the particle was more significant in the hybrid reinforced composites. The compounding of the two fillers also remarkably improved the wear resistance of the composites under water condition especially under high pressures. It was revealed that the excellent wear resistance of the PEEK/CF/ZrO₂ composites was due to a synergy effect between the nano-ZrO₂ particles and CF. CF carried the majority of load during sliding process and prevented severe wear to the matrix. The incorporation of nano-ZrO₂ effectively inhibited the CF failures through reducing the stress concentration on the carbon fibers interface and the shear stress between two sliding surfaces. It was also indicated that the wear rates of the hybrid composites decreased with the increasing applied load and sliding distance under water lubrication. And low friction coefficient and low wear rate could be achieved at high sliding velocity.     

Dry wear properties of A356-SiC particle reinforced MMCs produced by two melting routes

SiC particle reinforced metal matrix composites (MMCs) were produced by a common liquid phase technique in two melting routes. In the first route, 5, 10, 15 and 20 vol% SiC reinforced A356-based MMCs were produced. In the second route, an Alcan A356 + 20 vol% SiC composite was diluted to obtain 5, 10, 15 and 20 vol% SiC MMCs. In both cases the average particle size was 12 μm. The composites that produced by two different routes were aimed to compare the dry wear resistance properties. A dry ball-on disk wear test was carried out for both groups of MMCs and their matrix materials. The tests were performed against a WC ball, 4.6 mm in diameter, at room temperature and in laboratory air conditions with a relative humidity of 40–60%. Sliding speed was chosen as 0.4 m/s and normal loads of 1, 2, 3 and 5 N were employed. The sliding distance was kept at 1000 m. The wear damage on the specimens was evaluated via measurement of wear depth and diameter. A complete wear microstructural characterization was carried out via scanning electron microscopy. The wear behaviors were recorded nearly similar for both groups of composites. Diluted samples showed lower friction coefficient values compared with the friction coefficient values of the vortex-produced composites. This was attributed poor bonding between matrix and particles in the vortex-produced composites associated with high porosities. But, in general, diluted Alcan composites showed slightly lower wear rate relationship with the particle volume percent and applied load when compared with vortex produced materials.     

High performance nanocomposites for tribological applications: Preparation and characterization

High performance nanocomposites were prepared by incorporating 0–12 vol.% nano-sized (39 nm) Al₂O₃ particles into PEEK matrix using compression molding. The microhardness and dynamic mechanical properties of the nanocomposites increase with increasing Al₂O₃ content. The wear resistance of the nanocomposites evaluated at a sliding speed of 1.0 m/s and nominal pressure from 0.5 MPa to 1.25 MPa under dry sliding conditions was improved more than threefold at 0.8 vol.% Al₂O₃ content. However, the wear resistance of the nanocomposites containing above 1.67 vol.% Al₂O₃ was deteriorated, despite their higher hardness and stiffness as compared to that of nanocomposites containing lower Al₂O₃ content. The surface roughness of the wear track formed over the countersurface increases with increasing Al₂O₃ content. The coefficient of friction of nanocomposites was higher than that of pure PEEK. SEM and optical microscopy have shown that wear of pure PEEK occurs by the mechanism of adhesion mainly, whereas of nanocomposites by microploughing and abrasion. Energy dispersive spectrometry (EDS) shows that Fe and alloying elements of countersurface transfer to the wear debris at higher Al₂O₃ content.     

The tribological behavior of nanometer and micrometer TiO2 particle-filled polytetrafluoroethylene/polyimide

The friction and wear properties of micrometer and nanometer TiO₂ particle-filled polytetrafluoroethylene (PTFE)/polyimide (PI) composites were studied in this paper. The effect of filler contents (0.5%, 1%, 1.5%, 2%, 3%, 5% and 7 vol.%) on the tribological properties was examined. The transfer films and the worn surfaces of the PTFE/PI composites filled with micrometer and nanometer TiO₂ particles were investigated by using a scanning electron microscope (SEM). Experimental results show that anti-wear properties of the PTFE/PI composites can be improved greatly by filling nanometer TiO₂ particles. The wear rate of 1.5% nanometer TiO₂ filled composite is the lowest, which is about 52% lower than that of PTFE/PI. In the case of micrometer TiO₂ filler, the friction coefficient and wear rates increase with increasing filler volume fractions under identical test conditions. It was also found that the wear mechanism of micrometer TiO₂ particle-filled PTFE/PI is mainly severe adhesion and abrasive wear, while that of nanometer TiO₂ particle-filled PTFE/PI is mainly slight abrasive wear.     

PTFE基复合材料摩擦磨损特性研究

用机械共混、冷压成型自由烧结的方法制备了PTFE基复合材料;用M-2000型磨损试验机测试了在干摩擦定载荷条件下各试样的磨损性能;用扫描电子显微镜(SEM)对磨损试样的表面形貌进行了观察和分析.结果表明:在实验条件下,复合材料的抗磨性能,随青铜粉用量的增大逐渐增强,当青铜粉的用量大于20vol.%后,抗磨损性能增强的趋势明显减缓,在干摩擦条件下复合材料主要发生粘着磨损和磨粒磨损,且随青铜粉用量的增加,磨粒磨损也越明显.研究发现,当青铜粉:氧化镉:二硫化钼为20:6:4(体积比)时,复合材料的摩擦磨损性能最佳.     

Role of zirconia filler on friction and dry sliding wear behaviour of bismaleimide nanocomposites

This paper discusses the friction and dry sliding wear behaviour of nano-zirconia (nano-ZrO₂) filled bismleimide (BMI) composites. Nano-ZrO₂ filled BMI composites, containing 0.5, 1, 5 and 10 wt.% were prepared using high shear mixer. The influence of these particles on the microhardness, friction and dry sliding wear behaviour were measured with microhardness tester and pin-on-disc wear apparatus. The experimental results indicated that the frictional coefficient and specific wear rate of BMI can be reduced at rather low concentration of nano-ZrO₂. The lowest specific wear rate of 4 × 10⁻⁶ mm³/Nm was observed for 5 wt.% nano-ZrO₂ filled composite which is decreased by 78% as compared to the neat BMI. The incorporation of nano-ZrO₂ particles leads to an increased hardness of BMI and wear performance of the composites shows good correlation with the hardness up to 5 wt.% of filler loading. The results have been supplemented with scanning electron micrographs to help understand the possible wear mechanisms.