Tribological stability of particle reinforced aluminum matrix composites in braking

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铝基复合材料的摩擦磨损性能

在制动试验条件下,研究铝基复合材料的摩擦磨损性能,研究结果表明：与铸铁材料相比,铝基复合材料能大大地降低摩擦表面温度,其摩擦系数可在较大载荷,较高转速下保持稳定,有利于制动性能的提高,复合材料在不同摩擦试验后的磨损量与ＳｉＣ含量和基体种类有关。在相同摩擦条件下,磨损量随颗粒含量增加而减少,与铸铁材料相比,它具有重量轻,导热快,摩擦系数稳定,不产生热裂,是较适宜的制动盘材料。     

Wear resistance of WCp/Duplex Stainless Steel metal matrix composite layers prepared by laser melt injection

Laser Melt Injection (LMI) was used to prepare metal matrix composite layers with a thickness of about 0.7 mm and approximately 10% volume fraction of WC particles in three kinds of Cast Duplex Stainless Steels (CDSSs). WC particles were injected into the molten surface layer using Nd:YAG high power laser beam. As a result the microstructure characterized by hard ceramic particles distributed in a metal matrix with the strong bonding to substrate is formed in the surface layer of the treated metal.Dry sliding wear properties of these metal matrix composites layers were measured and compared with the wear properties of the substrate and with surfaces simply remelted by the laser beam. The observed wear mechanisms are summarized and related to detailed microstructural observations. The layers have been found to show excellent interfacial bonding, coupled with substantially improved tribological properties expressed through the wear resistance increase of 8 times. The amount of WC particles was sufficient to reinforce the matrix and the particles have shown a good bonding to the matrix to support the contact stress in the layer.     

石墨烯/高密度聚乙烯在水润滑条件下的摩擦学性能研究

目的 探究石墨烯/高密度聚乙烯高分子材料在水润滑条件下的摩擦学性能,提高高密度聚乙烯的自润滑和耐磨损性能.方法 采用石墨烯纳米片填充高密度聚乙烯材料,利用RTEC摩擦磨损试验机,开展新型复合材料在水润滑条件下的摩擦学性能研究.通过分析新型复合材料的典型机械性能、摩擦系数、磨损形貌以及摩擦副接触表面的元素成分及分布情况,揭示石墨烯/高密度聚乙烯在水润滑条件下的摩擦磨损机理.结果 新型复合材料的拉伸强度、撕裂强度和肖氏硬度均随着石墨烯纳米片含量的增加而先增高后降低,1.5％石墨烯纳米片改性高密度聚乙烯表现出最高的强度,分别为19.81 MPa、31.34 MPa和92.6HSA.新型复合材料的平均摩擦系数和体积行程磨损率总体随着石墨烯含量的增加而减小,1.5％石墨烯纳米片改性的高密度聚乙烯平均摩擦系数和体积行程磨损率比纯高密度聚乙烯分别降低了53.6％和73.9％.Si3N4陶瓷球与1.5％、0.6％石墨烯纳米片改性高密度聚乙烯进行3600 s对磨试验,其磨损区域的碳元素质量分数分别约为3.5％和0.3％,表明含量较高的石墨烯纳米片有利于在微观界面形成石墨烯润滑层,从而降低摩擦系数.结论 石墨烯纳米片显著影响高密度聚乙烯的自润滑性能和耐磨损性能,适量的石墨烯纳米片促进了高密度聚乙烯磨损界面石墨烯润滑层的形成,降低摩擦系数和磨损量.该研究可为设计低摩擦、耐磨损的水润滑轴承复合材料提供参考.     

Tribological behavior of Ni/Sn metallic multilayer composites

The tribological behavior of Ni/Sn multilayer composites was studied. Composites with varied layer thickness and tin volume fraction were prepared by electrodeposition. The coefficient of friction and wear rate of these composites were characterized by pin-on-disk and block-on-ring tests. Both results suggested that soft tin acted as a solid lubricant between the contacting surfaces. Tin-rich films were detected on both the specimen and the steel wear pair surfaces, and wear resistance greatly depended on the thickness, area coverage, composition, and stability of this interfacial film. Specimens with a lower tin content and/or a thinner layer spacing exhibited enhanced wear resistance compared to those with a higher tin content and/or thicker layers. This was attributed to both the solid-lubricating effect of the tin and the enhanced mechanical properties of the multilayered composites.     

Al2O3短纤维/SiC颗粒混杂增强铝合金复合材料

研究了Ａｌ２Ｏ３ 短纤维和ＳｉＣ 颗粒混杂增强铝合金复合材料在制动过程中的摩擦磨损性能。结果表明复合材料在制动过程中的摩擦系数较稳定, 磨损量较小, 与传统的制动材料铸铁相比, 复合材料的表面温升较低, 铸铁由于表面温升较高而产生了大量的裂纹。复合材料由于增强体的存在, 制动过程中表面易形成致密连续的转移膜, 该转移膜的出现保证了复合材料在制动过程中摩擦系数的稳定, 降低了复合材料的磨损量。与铸铁相比, 复合材料的密度较低, 更适用于作制动材料     

Tribological characteristics of C/C-SiC braking composites under dry and wet conditions

C/C-SiC braking composites, based on reinforcement of carbon fibers and matrices of carbon and silicon carbide, were fabricated by warm compaction and in situ reaction process. The tribological characteristics of C/C-SiC braking composites under dry and wet conditions were investigated by means of MM-1000 type of friction testing machine. The influence of dry and wet conditions on the tribological characteristics of the C/C-SiC composites was ascertained. Under dry condition, C/C-SiC braking composites show superior tribological characteristics, including high coefficient of friction （0.38）, good abrasive resistance （thickness loss is 1.10 μm per cycle） and steady breaking. The main wear mechanism is plastic deformation and abrasion caused by plough. Under wet condition, frictional films form on the worn surface. The coefficient of friction （0.35） could maintain mostly, and the thickness loss （0.70 μm per cycle） reduces to a certain extent. Furthermore, braking curves are steady and adhesion and oxidation are the main wear mechanisms.     

球墨铸铁轧辊表面镍基激光合金化层及其磨损性能

采用激光合金化技术在球墨铸铁QT600-3表面制备镍基合金强化层,通过XRD、SEM和摩擦磨损试验等研究了不同激光扫描速率对合金化层物相、微观结构、力学性能、常温和高温摩擦学性能的影响,并使用Raman光谱仪对磨痕进行分析。结果表明:Ni合金化层与基体冶金结合好、显微硬度高(高达720 HV0.1)、高温摩擦因数低至0.305、高温磨损率低至7.55×10^-6 g·N^-1·m^-1。随着扫描速率的增加,显微组织更加致密,显微硬度先升高后降低,700 ℃耐磨性能提高,但合金化层裂纹率增加。高温摩擦磨损过程中,合金化层的磨损机制以磨粒磨损为主,同时还存在疲劳磨损和氧化磨损。同时,扫描速率的增加可细化晶粒和提高显微硬度。而Ni合金化层表面在高温摩擦过程中形成的氧化产物和碳化物在高温下会对提高其耐磨性能产生积极作用。     

Wear properties of potassium titanate whiskers-reinforced Al-12Si alloy composites

Potassium titanate(K2O·6TiO2) whiskers-reinforced Al-12Si alloy composites were prepared by the squeeze casting technique.Wear properties of the composites were investigated by pin-on-disc tests under dry conditions.The experimental results showed that K2O·6TiO2 whiskers can effectively reinforce the matrix alloy and improve the wear resistance of the composite when the volume fraction of whiskers is low at 10 vol%.However,the composites with a high volume fraction of whiskers showed lower wear resistance than the Al-12Si alloy.The main wear mechanism of the composites is clarified as de-lamination and abrasive wear.     

SiCp/Mahle142铝基复合材料的油润滑摩擦磨损性能研究

用液态搅拌法制备了SiCp/Mahle142铝基复合材料,研究了2%-15%SiC/Mahle142铝基复合材料和基体合金Mahle142与球墨铸铁对磨时的油润滑摩擦磨损性能.结果表明,SiCp/Mahle142复合材料的油润滑耐磨性随SiCp体积分数的增加而显著提高,在本研究条件下,980N载荷时,15%SiCp/Mahle142铝基复合材料的耐磨性优良,磨损率仅为基体合金的10.3%,而摩擦系数相当;扫描电镜对磨损表面形貌的观察分析表明,SiCp/Mahle142铝基复合材料磨损机制主要表现为磨粒磨损和粘着磨损.     

不同热处理下滑动速度对SiCp/Al复合材料摩擦学性能影响研究

SiCp/Al复合材料非匀质性微观结构使其摩损机制较传统匀质材料更为复杂,不同工况及热处理工艺下复合材料的摩擦学性能也存在差异。以SiCp/2024Al复合材料为研究对象,进行球-面接触干滑动摩擦磨损实验,探究它在不同热处理状态及滑动速率下的摩擦磨损性能及磨损机制。结果表明:热处理对复合材料力学性能和摩擦学性能有显著影响,固溶+人工时效态复合材料具有更高的强度、硬度及耐磨性;滑动速度影响复合材料的表面接触性质及磨损程度,摩擦因数和磨损量随滑动速度提高逐渐增大;随滑动速度增加,复合材料主要磨损机制由剥层磨损向磨粒磨损转变,而磨损机制的转变明显加快了复合材料的磨损,在实际应用中应尽量避免此现象发生。     

等离子熔化沉积TiC增强Inconel 718基原位自生复合材料显微组织及高温耐磨性

为改善镍基高温合金Inconel 718的高温耐磨性,利用同轴送粉等离子熔化沉积快速成形技术原位合成了TiC增强Inconel 718高温合金基高温耐磨复合材料。分析了复合材料的显微组织结构和原位自生过程,探讨了增强相TiC的含量对复合材料的显微硬度及高温干滑动摩擦磨损性能的影响规律,研究了复合材料的高温磨损机理。结果表明:复合材料组织细小致密,显微硬度随TiC增强相体积分数增加而相应提高;在高温干滑动磨损实验条件下,复合材料表现出优异的耐磨性。     

Effect of Compaction Load and Sintering Temperature on Tribological and Mechanical Behavior of Ni/SiC/MoS<Subscript>2</Subscript> Composites

In the present investigation, the effects of compaction load and sintering temperature on the tribological and mechanical behavior of Ni/20%SiC/7%MoS₂ hybrid composites was studied. The density, compression strength, and hardness of the composites were evaluated and compared. The wear properties of the composites were evaluated for the test condition of 1 m/s speed and 10 N load using a pin-on-disk tribometer. The braking performance of the composites was evaluated in a subscale dynamometer for the 500 kJ energy condition. The microstructure and wear surface morphology of the composites were analyzed by stereo, optical, and scanning electron microscopes. From the results, the following important conclusions are drawn: (1) the compaction load of 1400 kN and sintering temperature of 900 °C are optimum to obtain the best combination of tribological and mechanical properties; (2) the properties such as density, compression strength, hardness, wear, and friction increase up to a critical sintering temperature, and then decrease later; (3) the composition and thickness of the interface reaction product phases (Ni₂Si, Ni₃Si, and graphite) play a key role in deciding the strength of Ni/SiC interface that consequently affects the mechanical and tribological properties of the composites; (4) the abrasive wear is found to be the main wear mechanism in the highly densified composites, whereas the delamination wear and the third-body wear are major wear mechanisms in the poorly densified composites; and (5) the better braking performance of the highly densified composites is attributed to the absence of third-body wear, controlled flow of solid lubricant, and lower porosity.     

石墨增强聚酰亚胺在海水中的摩擦学性能

目的为石墨增强聚酰亚胺复合材料在海水环境下的摩擦学应用提供实验依据。方法利用SST-ST销/盘摩擦试验机,研究了质量分数为15%石墨增强聚酰亚胺复合材料与17-4PH不锈钢组成的摩擦副在海水介质中的摩擦学性能,并与干摩擦和纯水润滑条件下的摩擦学性能进行比较。结果聚酰亚胺复合材料在干摩擦下的摩擦系数和磨损体积最大,分别为0.134、1.930 mm~3。干摩擦条件下,聚酰亚胺复合材料的磨损表面存在较深的犁沟,在犁沟周围出现了材料塑性流动及粘着剥落现象,对偶件表面有聚酰亚胺复合材料转移。磨损机理主要表现为磨粒磨损、材料塑性变形以及粘着和剥落。在纯水润滑下,聚酰亚胺复合材料表面存在较多材料粘着撕裂现象,同时存在宽浅不一的犁沟,磨损机理主要为粘着磨损和磨粒磨损。在海水润滑下,复合材料的摩擦系数和磨损体积最小,分别为0.086、1.235 mm~3,材料磨损表面十分光滑,只有沿运动方向存在少量轻微犁沟,磨损机理主要表现为磨粒磨损。结论石墨增强聚酰亚胺复合材料在海水中的摩擦学性能优于干摩擦和纯水环境下的摩擦学性能。     

离心铸造自生Zn—Al—Si表面复合材料的组织与性能

采用热膜金属型离心铸造Zn-27Al-5Si合金,获得了内层含大量初晶Si,外层有少量初晶Si,中层为细小共晶Si的表面复合材料,考察了复合材料的组织形貌和复合材料的,吧及模温和转速对组织的影响。结果,随着模温的提高,初晶Si、共晶Si和基体组织变得粗大;随着模转速的增加,初晶Si在内侧富集层厚度减小,初晶Si面积比增大。复合材料的内层由于聚集了大量初晶Si而具有较高的硬度和较优的耐磨性。复合材料的断裂方式为脆性断裂,含共晶Si的中层在断裂中比含块状初晶Si的内层经历了更多的塑性变形。     

Tribological properties and thermal-stress analysis of C/C-SiC composites during braking

The tribological properties and thermal-stress behaviors of C/C-SiC composites during braking were investigated aiming to simulate braking tests of high-speed trains. The temperature and structural fields of C/C-SiC composites during braking were fully coupled and simulated with ANSYS software. The results of tribological tests indicated that the C/C-SiC composites showed excellent static friction coefficient (0.68) and dynamic friction coefficient (average value of 0.36). The highest temperature on friction surface was 445 °C. The simulated temperature field showed that the highest temperature which appeared on the friction surface during braking was about 463 °C. Analysis regarding thermal-stress field showed that the highest thermal-stress on friction surface was 11.5 MPa. The temperature and thermal-stress distributions on friction surface during braking showed the same tendency.     

Preparation and properties of Cu matrix composite reinforced by carbon nanotubes

Cu matrix composites reinforced by carbon nanotubes(CNTs) were prepared. The effect of carbon nanotubes on mechanical and tribological properties of the Cu matrix composites were investigated. The chemical method for coating CNTs was reported. The morphology of the fracture surfaces and worn surface were examined by SEM.The results show that Cu/coated-CNTs composites have higher hardness, much better wear resistance and antifriction properties than those of the reference Cu alloy (Cu-10Sn) and Cu/uncoated-CNTs composite sintered under the same conditions. The optimal mechanical properties of the composites occurred at 2. 25%(mass fraction) of CNTs. The excellent wear resistance and anti-friction properties are attributed to the fiber strengthening effect of CNTs and the effect of the spherical wear debris containing carbon nanotubes on the tribo-surface.     

Wear performance of spark plasma sintered Co/WC and cBN/Co/WC composites

The present study investigates the efficiency of spark plasma sintering (SPS) technique on the tribological behavior of tungsten carbide composites, and aims to develop the wear resistance of these composites by addition of cubic boron nitride (cBN). Wear tests of spark plasma sintered 6(wt.%)Co/WC, 25(vol%)cBN/6Co/WC and conventionally fabricated 6(wt.%)Co/WC as a reference sample were performed by ball-on-disk contact with dry and rotational sliding at room temperature in order to determine the friction coefficient and wear rate. Wear mechanisms were explained by using SEM observations and the wear rates were computed by a surface profilometer. In all cases, the major wear mechanisms were observed gradually in the form of microcraking, material removal by grain pull out, and generation and spalling of a tribochemical layer. Based on the experimental results, the addition of cBN considerably enhanced the wear resistance of tungsten carbides. In addition, these results revealed that SPS process has outstanding potential for the fabrication of tungsten carbides with high wear properties for tribological applications.     

Tribological Properties of Al Alloy Particle Composites

In recent years, a variety of particle dispersed aluminum alloy composites have been synthesized. The tribological properties of these materials include sliding wear, friction, seizure resistance and abrasive wear (of composites containing solid lubricant as well as hard ceramic particles). The potential high-performance applications of Al-alloy-graphite composites include pistons for internal combustion engines and bearings. For such applications, the low stress abrasive wear rates of composites, containing high volume fractions (0.20–0.35), are comparable to that of heat treated 1045 steel.     

摩擦条件对化学混杂复合镀层Ni-P-Gr-SiC摩擦性能的影响(英文)

研究化学复合镀层Ni-P-Gr-SiC的摩擦磨损性能,主要研究石墨复合量、载荷及转速对复合镀层摩擦性能的影响。采用SEM和EDAX对磨损表面和截面进行磨痕形貌和成分分析。结果表明,由于石墨和碳化硅两相颗粒的协同作用,复合镀层显示出良好的减摩性能和耐磨性。分析表明,摩擦试样的亚表层形成的富石墨机械混合层对摩擦体系保持良好的摩擦性能起到重要作用,同时碳化硅颗粒的承载作用有效避免富石墨机械混合层在摩擦剪切力作用下的断裂。