Friction and wear behaviors of C/C-SiC composites containing Ti3SiC2

In the present paper, friction and wear behaviors of a carbon fiber reinforced carbon–silicon carbide–titanium silicon carbide (C-SiC–Ti₃SiC₂) hybrid matrix composites fabricated by slurry infiltration and liquid silicon infiltration were studied for potential application as brake materials. The properties were compared with those of C/C-SiC composites. The composites containing Ti₃SiC₂ had not only higher friction stability coefficient but also much higher wear resistance than C/C-SiC composites. At an initial braking speed of 28 m/s under 0.8 MPa pressure, the weight wear rate of the composites containing 5 vol% Ti₃SiC₂ was 5.55 mg/cycle, which was only one-third of C/C-SiC composites. Self-lubricious film-like debris was formed on the composites containing Ti₃SiC₂, leading to the improvement of friction and wear properties. The effect of braking speed and braking pressure on the tribological properties of modified composites were investigated. The average friction coefficient was significantly affected by braking speed and braking pressure, but the wear rate was less affected by braking pressure.     

Tribological properties of carbon nanotube-doped carbon/carbon composites

Carbon nanotube (CNT)-doped carbon/carbon (C/C) composites were fabricated by the chemical vapor infiltration (CVI) method to investigate the effect of CNTs on tribological properties of C/C composites. CNTs, which had been synthesized by catalytic pyrolysis of hydrocarbons, were added to carbon fiber formed preforms before CVI process. Ring-on-block-type wear tests were performed to evaluate the frictional properties of CNT-doped C/C composites. Results show that CNTs can not only increase wear resistance of C/C composites but also maintain stable friction coefficients under different loads. Polarized light microscopy, X-ray diffraction, scanning electron microscopy and Raman spectroscopy analyses demonstrate that favorable effects of CNTs on tribological properties of C/C composites have been achieved indirectly by altering microstructure of pyrocarbons and directly by serving as high-strength lubricative frictional media at the same time. Electron dispersive spectroscopy (EDS) analyses verify the existence of adhesive wear mechanism in both pure C/C composites and CNT-doped C/C composites albeit the two-body abrasive mechanism dominates in pure C/C composites.     

Arc Erosion Wear Characteristics and Mechanisms of Pure Carbon Strip Against Copper Under Arcing Conditions

The wear behavior of pure carbon strip against copper (carbon/copper pair) under continuous arcing condition was investigated. To simulate the extreme condition of continuous arc discharge at high current, sliding wear tests were conducted on a home-made wear tester. The arc erosion wear characteristics and mechanisms of carbon/copper pair were studied by analyzing the wear scars and wear debris of the carbon strip in detail. Therefore, various analytical techniques, including Raman spectroscopy, transmission and scanning electron microscopy, and focused ion beam systems, were utilized to characterize the wear scars and wear debris of the carbon strip. The results show that the wear rate and the degree of arc erosion of the carbon strip increase with increasing electric current density. Typical entwined turbostratic carbon nanospheres (ETCNs) exhibited sphere-like stacking structure that were observed in the microstructure of the wear debris of the carbon strip produced during the friction process with current, which is the characteristic of the textural changes in carbon materials under combined arcing and sliding friction conditions. Moreover, the number and size of ETCNs increase with the electric current density increase. The arc erosion wear mechanisms of the carbon/copper pair are mainly due to the synergetic action of oxidation ablation, local electric arc impact and high-temperature graphitization under continuous arcing.     

Influence of matrix carbon texture on the temperature field of carbon/carbon composites during braking

The friction, wear and thermal properties and temperature fields of three C/C composites with different matrix carbon textures were investigated in simulations of normal landing condition for aircraft brake disks. Temperature fields were also simulated using a finite element method. The matrix carbon textures had important influence on temperature fields. The sample with rough laminar pyrolytic carbon is the best choice for airplane brake disk due to its excellent friction, wear and thermal properties and lower temperature at the friction interface and thermal gradient by contrast with the samples with resin-derived carbon and smooth laminar pyrolytic carbon.     

The Solid Particle Erosion Behavior of Carbon/Carbon and Carbon/Phenolic Composite Used in Re-entry Vehicles

Several engineering components made of carbon-based heat-resistant composites are subjected to severe erosive wear. In view of the above, the solid particle erosion behavior of two and four dimensionally reinforced carbon/carbon (C/C) composites as well as that of carbon/phenolic (C/P) composite has been characterized at the ambient temperature. The investigated C/C composites have been produced through a liquid-phase infiltration method followed by hot isostatic pressing, while the C/P composite prepegs have been cured inside an autoclave. The erosion rates of these composites have been determined for two different impact angles and two different impact velocities using silica sand with average particle diameter of 200 μm. The morphologies of as-received and eroded surfaces of test specimens have been examined with the help of scanning electron microscopy to understand the mechanism of material removal. The erosion response, erosion efficiency, and erosion micromechanisms of these composites have been studied in detail. While the erosion resistance of the C/P composite is found to be superior to that of the investigated C/C composites, the four dimensionally reinforced C/C composite have shown the highest erosion efficiency. All the composites have exhibited a semi-ductile erosion response. Their mechanical properties have little correlation with the erosion rates.     

防冻液环境下PPS复合材料与不同配副材料的摩擦学行为

采用热压成型法制备短切碳纤维增强聚苯硫醚(PPS)复合材料,研究汽车专用防冻液环境中复合材料与4Cr13不锈钢、SiC陶瓷和Al2O3 陶瓷配副在不同载荷下的摩擦磨损性能;考察摩擦副在防冻液中的润湿性与耐腐蚀性;利用激光共聚焦显微镜和扫描电子显微镜对复合材料及对偶件磨损面进行观察,结合磨损面EDS和XRD分析探究材料的摩擦磨损机制。结果表明：防冻液环境中,SiC陶瓷耐腐蚀性能最强,Al2O3 陶瓷润湿性最好;在相同载荷下与4Cr13配副时复合材料的磨损率最低,但摩擦因数随载荷的增大上升最快,对偶件磨损率最大且磨粒磨损严重;与SiC或Al2O3配副时复合材料摩擦面呈现研磨特征;在相同载荷下与Al2O3 配副时复合材料磨损率最大,磨屑向对偶件表面沉积,与SiC配副时复合材料摩擦因数最小且对偶件磨损率最小。因此PPS复合材料与SiC配副宜作为防冻液环境下长耐久滑动轴承的优选材料。     

高速摆动下PTFE编织复合材料干摩擦研究

利用高速摩擦试验机对PTFE编织复合材料进行干摩擦试验,研究不同条件(载荷、速度和湿度)下PTFE编织复合材料干摩擦磨损性能;并利用扫描电子显微镜对不同条件下的磨屑形貌进行分析。结果表明:单因素变化条件下,摩擦因数随载荷和相对湿度的增大而减小,随摩擦速度的增大而增大;磨损量随载荷和速度的增大而增大,但相对湿度的增加可降低磨损;载荷及速度的增加显著影响材料磨损状况。     

Wear and friction behavior of sand cast brake rotor made of A359-20 vol% SiC particle composites sliding against automobile friction material

The effect of load range of 30-100 N and speed range of 3-12 m/s on the wear and friction behavior of sand cast brake rotor made of A359-20 vol% SiC particle composites sliding against automobile friction material was investigated. Dry sliding frictional and wear behavior were investigated in a pin-on-disc type apparatus. Automobile friction material was used as pin, while the A359-20 vol% SiC particle composites formed the rotating disc. For comparison, the wear and friction behavior of commercially used cast iron brake rotor were studied. The results showed that the wear rate of the composite disc decreased with increasing the applied load from 30 to 50 N and increased with increasing the load from 50 to100 N. However, the wear rate of the composite disc decreased with increasing the sliding speed at all levels of load applied in the present work. For all sliding speeds, the friction coefficient of the composite disc decreased with applied load. The worn surfaces as well as wear debris were studied using scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analyzer and X-ray diffraction (XRD) technique. At load of 50 N and speed range of 3-12 m/s, the worn surface of the composite disc showed a dark adherent layer, which mostly consisted of constituents of the friction material. This layer acted as a protective coating and lubricant, resulting in an improvement in the wear resistance of the composite.     

带式输送机树脂基摩擦片干式制动条件下摩擦学行为

采用热压烧结技术制备桐油改性酚醛树脂和腰果壳油改性酚醛树脂基摩擦片,通过CFT环块摩擦磨损试验机研究其在不同的制动速度、制动正压力下以及在瞬时制动时的摩擦因数以及磨损率的变化规律,采用扫描电镜(SEM)对试样摩擦后的表面形貌进行观察分析。结果表明,2种树脂基摩擦片摩擦因数以及磨损率变化规律具有一致性:摩擦因数均随着制动正压力与制动速度的增加而减小;磨损率随着制动速度的增加而减小,随着制动正压力的增加而增加。以桐油改性酚醛树脂为基体,碳纤维为增强纤维的摩擦片在瞬时制动时具有较稳定的摩擦因数,而且在不同制动正压力与制动速度下磨损率较低。     

炭黑/双马来酰亚胺复合材料的性能研究

采用浇铸成型法制备了炭黑填充双马来酰亚胺(BM I-BA)复合材料,研究了炭黑的填充量对复合材料力学性能和摩擦学性能的影响。在M-200型磨损机上测试该复合材料的摩擦学性能,利用扫描电镜(SEM)观察了摩擦副的表面形貌。结果表明:炭黑能够有效提高复合材料的力学性能和摩擦学性能。当炭黑的添加量为4.0wt%时,复合材料的综合力学性能最好;当炭黑的的添加量为6.0wt%时,复合材料的耐磨性能最好。SEM显示复合材料主要是粘着磨损,能在对磨环上形成薄而连续均匀的转移膜,而BM-BA树脂主要发生的是疲劳磨损,并伴有塑性变形。     

Structural and chemical study of C/C composites before and after braking tests

The oxygen, nitrogen, and hydrogen contents of three kinds of C/C composites used for brake discs, before and after braking tests, have been measured by a combustion-infrared method. The morphologies of wear debris have been observed by SEM, and the relationships between their oxygen, nitrogen, and hydrogen contents and crystal structures and friction properties have been established. The results have shown that the oxygen, nitrogen, and hydrogen contents of the C/C composites are mainly determined by structural defects, and are independent of the degree of anisotropy; the greater the number of lattice defects, the higher the contents of oxygen, nitrogen, and hydrogen. Oxygen, nitrogen, and hydrogen were desorbed during the braking tests, but they were re-adsorbed on the friction surface and wear debris in greater amounts after braking. The oxygen content directly affects the friction behavior; the greater the amount of oxygen desorbed, the greater the increase in friction coefficient, that is, the worse the stability of friction.     

Dry wear studies on glass-fibre-reinforced epoxy composites

Continuous glass-fibre-reinforced epoxy composites were fabricated and their wear behaviour was studied. A rapid drop in the wear loss occurred with an increase in the sliding speed for the pure epoxy resin while the reinforced sample exhibited a mild decrease, a flat region and then a rise. Optical microscopy examination indicates that the higher wear loss for the composite at higher speeds could be due to loss of glass fibres. The variation in the coefficient of friction, μ, with load and sliding speed was studied. Both the epoxy resin and the composite show a marked dependence of μ on load, which includes a peak. The pure epoxy resin showed no significant dependence of the coefficient of friction on sliding speed whereas the composite shows a peak value, thereby emphasizing the important role of the reinforcing fibres.     

聚四氟乙烯碳纤维增强双马来酰亚胺复合材料的摩擦学性能

研究了不同含量PTFE碳纤维增强双马来酰亚胺复合材料的力学和摩擦学性能,并分析了在干摩擦和水润滑条件下的磨损表面形貌和磨损机制。结果表明:添加质量分数10%~15%PTFE的复合材料体系机械性能最佳,随PTFE含量的增加,复合材料的摩擦因数下降,而磨损率呈上升趋势。水润滑下,摩擦因数和磨损率比干摩擦下都有相应的降低。干摩擦下,材料的磨损主要以塑性变形、微观破裂及破碎为主;水润滑下,这一机制明显减弱,主要表现为微切削形态。     

Tribological Properties of Short Fiber C/SiC Brake Materials and 30CrSiMoVA Mate

In this study, the short fiber C/SiC brake materials were prepared by a combined process of the fibers dipped with resin, chopping, warm pressing, pyrolyzing, and the liquid silicon infiltration process. The tribological properties of short fiber C/SiC brake materials and 30CrSiMoVA mate were investigated. The results indicated that the average friction coefficient decreased with the increase of braking speed (initial braking speed), and the friction coefficient tended to be constant when the braking speed was higher than 20 m/s. The braking was stable when the braking speed was 5 m/s, and the braking was unstable when the braking speed was higher than 10 m/s. The wear rate of the C/SiC increased with the increase of braking speed when the braking speed was less than 10 m/s, decreased with the increase of braking speed when the braking speed was less than 20 m/s, and then increased afterward with the increase of braking speed. When the braking speed was higher than 20 m/s, an oxidation-abrasion mechanism could occur. With braking speed increasing, the number of the ribbon debris increased, and the ribbon debris got long and thick, and the number of big granular debris increased.     

碳管分散程度对环氧树脂复合材料的摩擦磨损性能影响

采用浇铸法,制备多壁碳纳米管(MWNTs)/环氧树脂(EP)复合材料,利用M-200摩擦磨损试验机研究了MWNTs含量、分散时间及方式对环氧复合材料摩擦磨损性能影响,通过SEM、TEM分析试样磨损形貌表面、MWNTs分散程度。结果表明:碳纳米管添加量1.5%(质量分数)时,MWNTs/EP复合材料比环氧树脂摩擦因数降低17.8%,磨耗率降低91.7%;加入碳纳米管降低了复合材料粘着磨损与疲劳剥落;延长超声波时间及采用高功率超声波仪器能够有效提高碳纳米管分散程度,提高复合材料摩擦磨损性能。     

The friction and wear properties of nanometre SiO2 filled polyetheretherketone

Nanometre SiO₂ filled-polyetheretherketone (PEEK) composite blocks with different filler proportions were prepared by compression moulding. Their friction and wear properties were investigated on a block-on-ring machine by running a plain carbon steel (AISI 1045 steel) ring against the composite block. The morphologies of the wear traces and the transfer film were observed by scanning electron microscopy (SEM). It was found that nanometre SiO₂ filled-PEEK exhibited considerably lower friction coefficient and wear rate in comparison with pure PEEK. The lowest wear rate was obtained with the composite containing 7.5 wt.% SiO₂. The SEM pictures of the wear traces indicated that with the frictional couple of carbon steel ring/composite block (fillec with 7.5 wt.% filler), a thin, uniform, and tenacious transfer film was formed on the ring surface. It was inferred that the transfer film contributed largely to the decreased friction coefficient and wear rate of the filled PEEK composites.     

聚丙烯、炭黑和碳纤维共混填充超高分子量聚乙烯复合材料的力学和摩擦磨损性能

采用模压成型的方式制备超高分子量聚乙烯(UHMWPE)复合材料,通过AG-1型电子万能实验机和MM-200型摩擦磨损试验机分别研究填料对复合材料力学性能和摩擦磨损性能的影响,采用光学显微镜分析复合材料磨损表面的形貌。结果表明:聚丙烯(PP)和无机填料炭黑(CB)或CB与碳纤维(CF)混杂填料的加入使UHMWPE复合材料的拉伸强度降低,弯曲模量和硬度增加,其中UHMWPE/PP/CB/CF复合材料的弯曲模量和硬度增幅大于UHM-WPE/PP/CB复合材料。填料的加入可改善UHMWPE复合材料的摩擦磨损性能,当填料的质量分数为5%时,UHMWPE复合材料的摩擦磨损性能最好,且UHMWPE/PP/CB/CF复合材料的耐磨性能优于UHMWPE/PP/CB复合材料。与UHM-WPE相比,UHMWPE/PP/CB/CF复合材料的摩擦因数和磨痕宽度分别下降了10%和44%,UHMWPE/PP/CB复合材料则分别下降了12%和42%。光学显微镜观察表明填料的加入大大改善了UHMWPE的磨粒磨损,复合材料表面以较浅的犁沟磨损为主要特征。     

Comparative Study on Wear Behaviors of Metal-Impregnated Carbon Material and C/C Composite Under Electrical Sliding

In this article, the wear behavior of metal-impregnated carbon materials (MIC) and carbon–carbon composites(C-C) was investigated using a self-made current-carrying wear tester producing an electrical current of 40–160 A and a contact speed of 10–50 m/s. The worn surfaces were observed by means of scanning electron microscopy (SEM), and a new parameter for current-carrying stability that describes the stability of the current as a function of wear was proposed. The results indicate that the wear rate of both materials tested increased with either an increase in electrical current or contact sliding speed. Compared to the metal-impregnated carbon material, the C-C composite material not only displayed superior wear resistance but superior current-carrying stability as well. With increasing electrical current, the current-carrying stability of the two materials changed within a narrow range at a speed of 20 m/s and decreased at a speed of 50 m/s. Wear failure was mainly due to electrical erosion occurring at high speed and high current.     

Effect of humidity on the tribological behavior of carbon-carbon composites

The present work is a study of the effect of humidity on the tribological behavior of carbon-carbon composites, including two-dimensional PAN/pitch (designated TM), PAN/CVI (designated E), and pitch/resin/CVI (designated A) formulae. Results indicate that there exist close relationships among friction coefficient, wear rate, and worn surface morphology. Whenever a morphological transition has occurred, transitions in friction and wear also occur. Three different debris morphologies are identified. The smooth type I and type III debris films can lubricate, but not the powdery type II debris. The relative humidity level has a strong effect on the tribological behavior of all three composites. Low humidity and high sliding speed generally accelerate the occurrence of type I-to-type II transitions in friction, wear, and debris morphology, whereas high humidity and low speed enhance the formation of type III debris. At any humidity level, the type I morphology is always accompanied by low friction and wear. After the type I-to-type II transition, higher friction coefficient and wear rate are observed in the low humidity than in the high humidity. Under the present conditions, composite E appears to be the most sensitive to the humidity effect, while composite A appears the least sensitive.     

聚甲醛复合材料在不同载荷和转速下的摩擦学特性

为了考察外界条件对聚甲醛复合材料摩擦学特性的影响,用摩擦磨损实验对模压法制备的Ekonol/POM和Ekonol/G/MoS2/POM复合材料在不同载荷和转速下的摩擦学性能进行了研究,并用扫描电镜(SEM)对磨损表面进行了观察和分析,在此基础上探讨了复合材料在不同条件下的磨损机制。结果表明:随着载荷或转速的增加,聚甲醛(POM)及其复合材料的摩擦因数呈先增大后减小的趋势,而材料的磨损量则随着载荷或转速的增加而增大;随着载荷或转速的提高,ZOGM20的磨损机制发生了由粘着磨损到疲劳磨损再向塑性流动的转变。