石墨含量对石墨/铜复合材料载流摩擦磨损性能的影响

以石墨/铜复合材料和QCr0.5铜合金为摩擦副,在自制的销盘摩擦磨损试验机上进行不同电流密度下的摩擦磨损试验,考察石墨含量对石墨/铜复合材料载流摩擦磨损性能的影响。结果表明:随着石墨含量的增加,石墨/铜复合材料的摩擦因数下降,载流效率和磨损率先下降后升高,石墨质量分数为10%时,载流效率最高,为12.5%时磨损率最低;随着电流密度的增加,石墨/铜复合材料的摩擦因数和载流效率下降,磨损率逐渐增加;石墨/铜复合材料在载流摩擦过程中存在黏着磨损、磨粒磨损和电弧烧蚀,电流密度较大时,电弧烧蚀比较严重。     

载流条件下银基复合材料-黄铜滑环摩擦副的摩擦学性能

采用粉末冶金方法制备一种银-铜-石墨-碳纤维复合材料,利用环块式摩擦磨损试验机对该复合材料和黄铜滑环组成的摩擦副在大气条件下进行载流摩擦磨损试验,分析不同速度下载流大小对摩擦因数、接触表面电阻、接触表面电噪声、磨损量的影响。研究结果表明,摩擦因数、接触电阻、磨损量随载流的增大而增大,接触表面电噪声与电流呈非线性关系;该银基复合材料与黄铜滑环摩擦副的磨损机制在纯机械摩擦磨损条件下主要为黏着磨损,在载流条件下为磨粒磨损,电弧产生的电蚀促进了磨粒磨损的发生。该银基复合材料与黄铜滑环摩擦副的电噪声符合相关标准,具有较高的可靠性。     

铜-10%石墨合金的载流摩擦磨损性能

为提高铜基合金的载流摩擦磨损性能,采用粉末冶金方法制备了含10%石墨的铜基合金,并在自制的销盘式载流摩擦磨损试验机上进行了不同电流和滑动速度下的摩擦磨损试验.结果表明:与不含石墨的铜合金相比较,在不同电流和滑动速度下,加入10%石墨铜合金的摩擦因数和磨损率均降低,耐磨性能明显提高,摩擦因数稳定.     

两种受电靴材料与不锈钢带电接触摩擦磨损特性的试验研究

在销-盘式摩擦磨损试验机上分别进行了不锈钢／铜基烧结合金材料和不锈钢／铜石墨烧结材料接触的载流摩擦磨损行为的试验研究。在试验中记录了摩擦因数和磨损量的变化，并对磨痕形貌进行了光学显微镜观察。结果显示，电流对2种摩擦副带电接触的摩擦磨损行为有重要的影响。2种材料的摩擦因数随电流的增大而呈现截然相反的变化趋势，但两者的磨损量却随电流的增加而增大。不锈钢／铜基烧结合金材料的磨损机制主要是粘着磨损及氧化磨损。不锈钢／铜石墨烧结材料磨损机制包括磨粒、粘着磨损和电弧烧蚀，其中电弧烧蚀对磨损量的影响随电流的增大而增加。     

20%C/Cu复合材料的载流摩擦磨损性能

采用冷压成型和热等静压烧结技术制备了20%C/Cu复合材料,研究了它在干摩擦条件下的载流摩擦磨损性能,并分析了它的磨损机理。结果表明:随着载荷增加,载流和非载流条件下的磨损率均逐渐增大,第三体的形成使摩擦因数不断降低;随着滑动速度增大,载流和非载流条件下的摩擦因数呈微小的上升趋势,磨损率则先增大后降低;载流条件下复合材料的摩擦因数和磨损率比非载流时的均有所下降,载流条件下第三体的润滑作用加强,提高了材料的耐磨性;复合材料的磨损过程中存在黏着磨损、磨粒磨损和剥层磨损,且在磨损表面上并未发现电弧烧蚀的痕迹。     

含石墨转移层对铜－二氧化硅／ 钢摩擦磨损行为的影响

为探讨干摩擦磨损条件下含石墨转移层对摩擦磨损性能的影响,在45#钢表面覆盖含石墨润滑层,通过干滑动磨损试验,研究含石墨润滑层对钢/铜-二氧化硅摩擦副摩擦因数、磨损量及摩擦损（亚）表面的影响。结果表明：与无石墨润滑层的45#钢相比,含石墨润滑层的45#钢的摩擦因数、磨损率明显下降,且干滑动试验后磨损表面相对光滑平整,表明含石墨摩擦层起到了减摩降磨作用,抑制了金属的直接接触。     

SiC粒径对铜基复合材料载流磨损性能影响

采用粉末冶金法制备不同SiC粒径改性的SiC/C/Cu复合材料,研究SiC颗粒大小对材料组织结构和物理性能的影响;在载流摩擦磨损试验机上进行载流磨损试验,研究不同滑动速度下,SiC粒径对材料磨损率的影响。结果表明：在SiC/C/Cu复合材料中小颗粒SiC偏聚于C/Cu界面处,而大颗粒SiC均卡嵌在铜基体内,并且随着SiC颗粒的增大,复合材料硬度和密度稍有增加,孔隙率迅速降低,导电率增加;在较低滑动速度下,复合材料的磨损量随SiC粒径增大不断降低;在较高滑动速度下,随SiC粒径增大,复合材料的磨损率先降低后升高,25 μm SiC改性的复合材料具有最低的磨损率。     

SiC粒径对铜基复合材料载流磨损性能的影响

采用粉末冶金法制备不同SiC粒径改性的SiC/C/Cu复合材料,研究SiC颗粒大小对材料组织结构和物理性能的影响;在载流摩擦磨损试验机上进行载流磨损试验,研究不同滑动速度下,SiC粒径对材料磨损率的影响。结果表明:在SiC/C/Cu复合材料中小颗粒SiC偏聚于C/Cu界面处,而大颗粒SiC均卡嵌在铜基体内,并且随着SiC颗粒的增大,复合材料硬度和密度稍有增加,孔隙率迅速降低,导电率增加;在较低滑动速度下,复合材料的磨损量随SiC粒径增大不断降低;在较高滑动速度下,随SiC粒径增大,复合材料的磨损率先降低后升高,25μmSiC改性的复合材料具有最低的磨损率。     

双辉光离子渗铜对缸套-活塞环摩擦学性能的影响*

为研究铜元素对缸套-活塞环摩擦学性能的影响,通过双辉光离子渗透技术在缸套材料表面加工出不同厚度的渗铜改性层,使用RTEC多功能摩擦磨损试验机开展不同负载、不同润滑条件下的模拟试验,采集并分析试验过程中的摩擦因数以及试验后体积磨损量和磨损表面形貌,研究渗铜改性层对缸套材料摩擦学性能的影响规律及作用机制。结果表明：渗铜处理可有效降低缸套-活塞环摩擦副的摩擦因数,减少磨损量;高载荷和干摩擦条件下渗铜改性层的减摩抗磨作用效果尤为显著,最高可使摩擦因数分别降低13.15%和30.86%,磨损量分别降低30.70%和38.57%;渗铜后缸套-活塞环磨损表面形貌平整,摩擦表面形成了铜含量较高的润滑膜层,该表面膜起到了减摩、耐磨的作用。     

载流条件下铬青铜/3D碳/碳复合材料摩擦副的摩擦磨损性能

以3D碳/碳复合材料为销试样、铬青铜QCr0.5为盘试样进行了载流条件下的干滑动摩擦磨损试验。通过对有、无电流条件下销试样磨损量大小和摩擦因数影响度的比较,以及对销试样摩擦表面进行的微观形貌分析,结果表明,电流对铬青铜/3D碳/碳复合材料摩擦副的干摩擦行为具有显著的影响,并且由于电场、摩擦热、电弧热的共同作用,在销试样表层发生了磨粒磨损和氧化磨损。     

Influence of graphite content on the dry sliding and oil impregnated sliding wear behavior of Al 2024–graphite composites produced by in situ powder metallurgy method

The influence of graphite content on the dry sliding and oil impregnated sliding wear characteristics of sintered aluminum 2024 alloy–graphite (Al/Gr) composite materials has been assessed using a pin-on-disc wear test. The composites with 5–20 wt.% flake graphite particles were processed by in situ powder metallurgy technique. For comparison, compacts of the base alloy were made under the same consolidation processing applied for Al/Gr composites. The hardness of the sintered materials was measured using Brinell hardness tester and their bending strength was measured by three-point bending tests. Scanning electron microscopy (SEM) was used to analyze the debris, wear surfaces and fracture surfaces of samples. It was found that an increase in graphite content reduced the coefficient of friction for both dry and oil impregnated sliding, but this effect was more pronounced in dry sliding. Hardness and fracture toughness of composites decreased with increasing graphite content. In dry sliding, a marked transition from mild to severe wear was identified for the base alloy and composites. The transition load increased with graphite content due to the increased amount of released graphite detected on the wear surfaces. The wear rates for both dry and oil impregnated sliding were dependent upon graphite content in the alloy. In both cases, Al/Gr composites containing 5 wt.% graphite exhibited superior wear properties over the base alloy, whereas at higher graphite addition levels a complete reversal in the wear behavior was observed. The wear rate of the oil impregnated Al/Gr composites containing 10 wt.% or more graphite particles were higher than that of the base alloy. These observations were rationalized in terms of the graphite content in the Al/Gr composites which resulted in the variations of the mechanical properties together with formation and retention of the solid lubricating film on the dry and/or oil impregnated sliding surfaces.     

Effect of carbon nanotube addition on the tribological behavior of carbon/carbon composites

Carbon nanotube composite coatings were applied onto carbon/carbon composites to improve wear properties. Carbon nanotubes have been prepared by catalytic pyrolysis of hydrocarbons. The nanotube slurry was prepared by addition of phenolic resin and solvent to infiltrate into C/C composites. The nanotube added composites were then carbonized in a nitrogen atmosphere. Ball-on-disc type wear tests were performed to evaluate the tribological properties of the carbon nanotube added carbon composites. The result showed that addition of nanotube has the potential to increase the wear resistance of carbon composites. Changes in Raman spectra, morphology and surface damage were studied to explain observed wear behavior.     

Effects of temperature on mechanical and tribological properties of dental restorative composite materials

The purpose of this study is to evaluate the effects of temperature on the mechanical and tribological properties of three commercial posterior direct filling resin based restorative composite materials, Synergy (Coltene/Whaledent, Altstätten, Switzerland), Surefil (Dentsply/Caulk, New York, USA) and Alert (Pentron Clinical, Wallingford, USA). The aim of this paper was to evaluate how temperature influences; the hardness, flexural modulus and strength, elastic modulus, and wear of the listed commercial restorative materials.Three commercial resin composites were tested at several temperatures. A closed control system was used to ensure constant test conditions that simulated the temperatures found in an oral environment. For each of the tests, the following mechanical and tribological properties were determined, microhardness (Vickers micro-indentation), elastic modulus (determined both by dynamical methods and by bending tests), flexural resistance and work of fracture parameter (bending tests), and wear (reciprocating tests).Following the tests, the evaluation of the mechanical and tribological properties of the resins suggests that their performance in an oral environment can be significantly affected by temperature, especially the wear resistance. Surefil is the resin least sensitive to temperature variation, while Synergy exhibited the best resistance to wear with respect to temperature variation.     

Unlubricated wear of Si/SiC and its composite with nickel Si/SiC-Ni

Using a pin-on-disk tribometer, dry friction and wear properties at different temperatures were investigated for reaction-sintered silicon carbide Si/SiC and its composites with nickel Si/SiC-Ni. The friction and wear properties of the composites are improved by the addition of nickel. The analysis on the worn surfaces and sub-surfaces by SEM suggest that shallow grooves are the main wear feature at 15°C. At 600°C, surface cracking and fracture is the predominating wear mechanism for Si/SiC, and the formation of flake pits on the surface due to crack propagation at subsurface is the main wear mechanism for Si/SiC-Ni. Finally the relationships between wear resistance and mechanical properties are discussed.     

Enhanced Mechanical and Tribological Properties of Graphene-Reinforced TiAl Matrix Composites

This study investigated the mechanical properties and dry-sliding friction and wear behaviors of graphene-reinforced TiAl matrix composites in expectation of providing valuable information for the application of graphene. The results suggested that the incorporation of graphene apparently improved the microhardness, fracture toughness, and tribological properties of the composites. For the composite with 3?wt% graphene, the microhardness increased by 129%, the fracture toughness increased by 149%, the friction coefficient decreased by 37% and the wear rate decreased by 78%. Also, the microstructural analyses of the worn surfaces indicated that three types of graphene-rich films, with different percentages of coverage, were generated on the worn surfaces under various wear conditions. An evolution mechanism of the films as a function of wear conditions was proposed, and the corresponding variation of friction and wear behavior was also discussed.     

Effects of Resin Type and Fiber Length on the Mechanical and Tribological Properties of Brake Friction Materials

In this study, the effects of resin type and fiber length on mechanical properties and friction characteristics of automotive brake materials were studied. Three types of resin, viz. straight phenolic resin (SR), cashew nut shell liquid modified resin (CR), and melamine resin (MR) were used as matrix material. Lapinus with different lengths was used as inorganic fiber. Three series of friction composites composed of nine composites in the form of brake materials were manufactured. Physical, mechanical, and tribological properties of all composites were investigated. The friction tests were performed using a Chase type friction tester. The results showed that both resin type and fiber length played an important role on the mechanical and tribological properties of the friction materials. The highest and the lowest friction coefficient for resin types were recorded for SR and MR composites, respectively, while MR and CR composites showed the highest and the lowest wear resistance, respectively. For the fiber length considered, increasing the fiber length increased the wear resistance of the composites. The coefficient of friction, in general, showed a good correlation with the wear resistance of the composites. But, there was no clear correlation with the mechanical and tribological properties of the composites. The morphological features of worn surfaces and wear debris of the composites were analyzed in order to understand the friction and wear mechanisms of this tribosystem.     

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.     

磨粒对ADZ复合陶瓷材料磨损性能的影响

采用块 -块摩擦磨损试验机在不同磨粒的 5 %NaOH泥浆中 ,对氧化铝增强四方氧化锆多晶陶瓷材料 (ADZ)的磨损性能进行了研究。研究结果表明尖锐磨粒对ADZ复合陶瓷材料磨损的影响要比球形磨粒严重的多 ,磨料硬度是影响陶瓷材料磨损率的重要因素 ,磨损率随磨粒硬度的提高而增大。在不同形状的SiO2 磨粒的泥浆中ADZ陶瓷材料的主要磨损机理为塑性变形和微犁削。在高硬度Al2 O3磨料的泥浆中ADZ陶瓷材料磨损表面以断裂机制占主导地位。     

玻璃微珠增强PPS复合材料的摩擦性能研究

2种不同粒径的空心玻璃微珠与聚苯硫醚树脂通过熔融共混挤出制得复合材料,研究了这2种玻璃微珠对聚苯硫醚树脂摩擦磨损性能的影响。通过扫描电子显微镜(SEM)对摩擦表面、断面形貌进行了观察和分析。结果表明:经过偶联剂处理的玻璃微珠能够提高PPS的减摩抗磨性能,玻璃微珠粒径越小,所得复合材料的摩擦因数越小;聚合物材料在摩擦过程中形成结合牢固、薄而均匀的转移膜是其发挥摩擦学作用的重要保证,复合材料的磨损机制主要为粘着磨损和疲劳磨损;采用玻璃微珠提高聚苯硫醚树脂的减摩耐磨性能是可行的,而大小均匀、完全规则的球形玻璃微珠粒子将可以更有效地提高复合材料的摩擦性能。     

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.