镀铜石墨/铜复合材料的组织和摩擦磨损性能

本实验以电解铜粉为基体,镀铜石墨为润滑相,采用放电等离子烧结技术(SPS)制备镀铜石墨/铜复合材料,研究了镀铜石墨含量对复合材料微观组织、硬度、孔隙率和摩擦磨损性能的影响。结果表明:镀铜石墨均匀分散在Cu基体中能细化晶粒、均匀组织,石墨表面镀铜层能够增强石墨与Cu基体的界面结合。当镀铜石墨含量超过4wt%,复合材料的硬度和孔隙率变化幅度明显增大。镀铜石墨具有细晶强化作用,能提升复合材料的硬度,其含量为4wt%时,复合材料的硬度达到最大值57.8HV,但镀铜石墨含量和孔隙率的共同作用使得复合材料的硬度呈先增大后减小的趋势。随着镀铜石墨含量增加,复合材料孔隙率逐渐增大,摩擦系数、磨损量逐渐减少,镀铜石墨含量为8wt%时,复合材料的摩擦系数、磨损量相比纯铜分别降低63.9%、96.3%。镀铜石墨作为润滑相紧密镶嵌在铜基体中,显著提高了复合材料的摩擦磨损性能。复合材料摩擦磨损机理主要为磨粒磨损、粘着磨损和氧化磨损。     

电铸制备铜-石墨复合材料的研究

在酸性硫酸铜溶液中采用电铸技术制备了铜-石墨复合材料.表面活性剂、微粒浓度、电流密度和搅拌速度等工艺条件对微粒含量具有不同的影响.非离子表面活性剂对微粒共沉积具有较好的效果;随着微粒浓度增大,微粒含量也逐渐增大,最后趋于稳定值;电流密度增大使微粒含量降低;搅拌速度增大时微粒含量存在最大值.铜-石墨复合材料的硬度和摩擦系数随着微粒含量增大而减小,但是磨损量先是减小而后增大.摩擦过程中纯铜发生粘着磨损,铜-石墨复合材料却表现为剥层磨损.     

滑动速度对碳纳米管-银-石墨复合材料电磨损性能的影响

采用粉末冶金法制备了碳纳米管-银-石墨复合材料,研究了圆周速度对复合材料摩擦系数、磨损量的影响。结果表明,当压力一定时,随着速度的加快,机械磨损的摩擦系数减小,而电磨损的摩擦系数增大;复合材料的电磨损量远远大于机械磨损的磨损量,电磨损时磨损量在V=10m/s处出现最小值,而机械磨损的磨损量随速度的加快而减小。     

添加石墨对热压法制备C/C复合材料摩擦磨损性能的影响

以表面酚醛树脂包覆处理过的石墨颗粒,硝酸氧化处理的炭纤维和沥青为原料,经热压烧结制备短切炭纤维增强沥青基C/C复合材料,利用环一块磨损试验机对材料进行了摩擦磨损实验,借助SEM观察样品的磨痕和磨屑,研究了不同石墨含量对样品摩擦磨损性能的影响.结果表明,随着石墨含量的增多,样品的密度和弯曲强度逐渐提高,同时在摩擦磨损表面形成具有自润滑作用的摩擦膜,有利于降低磨损量,并保持摩擦系数的稳定.添加适量的石墨可获得摩擦磨损性能优良的C/C复合材料.     

铜-石墨烧结材料中第三体对摩擦磨损性能的影响

采用粉末冶金技术制备了铜和铜-石墨粉末冶金材料.通过定速摩擦试验机测试了材料的摩擦磨损性能,观察比较了两种材料摩擦学特征和表面摩擦第三体的变化过程.结果表明:摩擦表面第三体状态与材料成分密切相关,并影响材料的摩擦系数和磨损量.纯铜摩擦时,形成的第三体颗粒尺寸大、粘着性强.金属间的粘着撕裂造成摩擦系数剧烈波动和磨损量加大;添加石墨,细化了第三体颗粒尺寸,流动性好的第三体容易覆盖表面的损伤区.这有利于增加真实接触面积,减少应力集中,起到稳定摩擦系数、降低磨损量的作用.     

碳纤维含量对碳纤维／中铜石墨复合材料减摩耐磨性能的影响

在干磨擦条件下，对不同碳纤维含量的碳纤维／中铜石墨复合材料，进行了５０ｈ的摩擦磨损试验并借助扫描电镜观察了综们的磨面，结果表明，随碳纤维 增加，碳纤维．中铜石墨复合材料的摩擦系数和磨损量均明显减少。     

氧化铝短纤维、石墨混杂增强ZL108复合材料的摩擦特性

采用挤压铸造法制备了氧化铝短纤维(80％Al_2O_3·20％SiO_2)、石墨(Gr)混杂增强铝基复合材料。对其组织、强度、摩擦磨损特性等进行了研究。发现由氧化铝短纤维和石墨混杂增强的铝基复合材料具有优良的摩擦性能。这种复合材料随着其中石墨含量的增加,摩擦系数明显降低。在短纤维含量较高的铝基复合材料中,石墨的作用尤为突出。在大载荷下,石墨能显著降低短纤维增强铝基复合材料的摩擦系数和磨损量。从实验和分析来看,石墨改变了复合材料的磨损类型。     

含NbSe2的铜基电接触复合材料的制备及其真空摩擦学性能研究

本研究采用粉末冶金工艺制备出含纳米NbSe₂(1wt%~9wt%)的铜-石墨自润滑复合材料。在微摩擦试验机及超低温摩擦试验机上进行摩擦磨损实验, 通过X射线衍射仪(XRD)、扫描电子显微镜(SEM )等分析其物相、形貌及磨痕, 并探讨了该复合材料在大气、真空试验条件下的磨损机理。结果表明: NbSe₂的加入显著提高铜基复合材料的摩擦学性能; 真空干摩擦条件下不含NbSe₂复合材料的摩擦系数有所增大, 但添加NbSe₂(5.5wt%)的自润滑复合材料摩擦系数更小(μ=0.185), 承载能力更高, 其磨损是粘着磨损、接触疲劳磨损共同作用的结果。     

铜-石墨复合材料的摩擦学性能和磨损机理

采用机械合金化后冷压成型和放电等离子烧结两种不同工艺分别制备铜-石墨复合材料,在销盘式实验机上进行材料的摩擦实验,并通过扫描电镜、X射线光电子能谱仪(XPS)分析摩擦表面的形貌和化学性质。结果表明:随着石墨含量的增加,复合材料的摩擦系数与磨损率显著下降;随烧结温度的升高,摩擦系数与磨损率都呈下降趋势。摩擦系数与磨损率的显著改善是由于在磨损过程中形成一层覆盖表面的润滑膜。当形成的润滑膜几乎覆盖住整个磨损表面时,该润滑膜能够抑制滑动界面处金属与金属接触,使摩擦磨损特性得以改善。     

C/C复合材料与石墨材料干态摩擦磨损行为

在M-2000型摩擦磨损实验机上,以GCr15钢为配副,对石墨材料和C/C复合材料在干态条件下的滑动摩擦进行研究。结果表明:C/C复合材料的摩擦系数和体积磨损均比石墨材料的低。具有光滑层炭结构 (SL) 的C/C复合材料的摩擦系数和体积磨损量比具有粗糙层结构 (RL) 的C/C复合材料低;低密度石墨的摩擦系数和体积磨损量比高密度石墨材料高。随时间延长,RL结构的C/C复合材料摩擦系数在60、80、200 N时有小幅度的增长,另三种则下降; SL结构的C/C复合材料摩擦系数除60 N外基本保持平稳;石墨材料的摩擦系数随时间延长表现出增长趋势。SEM观察表明: RL结构的C/C复合材料摩擦表面随载荷增加而趋向完整,SL结构的C/C复合材料的摩擦表面随载荷增加变化不大。而高密度石墨摩擦表面比密度低的石墨完整。C/C复合材料比石墨更适宜用作航空发动机轴间密封材料。      

Effect of the SiC particle size on the dry sliding wear behavior of SiC and SiC–Gr-reinforced Al6061 composites

The effect of size of silicon carbide particles on the dry sliding wear properties of composites with three different sized SiC particles (19, 93, and 146 μm) has been studied. Wear behavior of Al6061/10 vol% SiC and Al6061/10 vol% SiC/5 vol% graphite composites processed by in situ powder metallurgy technique has been investigated using a pin-on-disk wear tester. The debris and wear surfaces of samples were identified using SEM. It was found that the porosity content and hardness of Al/10SiC composites decreased by 5 vol% graphite addition. The increased SiC particle size reduced the porosity, hardness, volume loss, and coefficient of friction of both types of composites. Moreover, the hybrid composites exhibited lower coefficient of friction and wear rates. The wear mechanism changed from mostly adhesive and micro-cutting in the Al/10SiC composite containing fine SiC particles to the prominently abrasive and delamination wear by increasing of SiC particle size. While the main wear mechanism for the unreinforced alloy was adhesive wear, all the hybrid composites were worn mainly by abrasion and delamination mechanisms.     

The effect of graphite addition on the mechanical and tribological properties of pitch-based granular carbon composites

The present work deals with the effect of graphite addition on selected mechanical and tribological properties of pitch-based granular carbon composites. Three pitches (a commercial impregnating coal tar pitch, an air-blown pitch and a thermally treated coal tar pitch) and anthracite particles as reinforcing material were used to prepare carbon composites to be tested as carbon brake pads. These carbon composites show good compression strength (from 25.8 to 94.2 MPa) but unstable and high friction coefficients (>0.5). Experimental results have showed that small amounts of graphite addition (2.5 and 5.0 wt%) lead to carbon materials with more stable and lower friction coefficient (<0.3). So, graphite addition promoted the reduction in the wear rate. Finally, compressive strength of carbon composites prepared with modified pitches significantly increases after addition of small amounts of graphite with values from 94 to 128.8 MPa.     

Experimental investigation on tribological behaviours of PA6, PA6-reinforced Al<Subscript>2</Subscript><Emphasis Type="Italic">O</Emphasis><Subscript>3</Subscript> and PA6-reinforced graphite polymer composites

This article reports on the preparation, characterization and experimental investigation of polyamide 6 (PA6) reinforced with alumina oxide (Al₂O₃) and graphite composites. The test specimens were prepared in an injection-moulding machine by varying the weight proportions of Al₂O₃ and graphite particles blended with PA6. The tribological properties of the composites were observed by using pin-on-disc wear test rig under dry sliding conditions. The worn surfaces of the composites were examined using scanning electron microscope. The addition of Al₂O₃ and graphite significantly enhanced the tribological properties of PA6. The PA6 containing 30 wt% Al₂O₃ and 20 wt% graphite revealed the best tribological behaviours due to the stronger interfacial bonding characteristics with improved wear resistance. Further, the thermal stability of Al₂O₃ and graphite particles was studied through thermogravimetric analysis test. It was also found that further addition of Al₂O₃ and graphite in PA6 had no significant improvement in wear resistance, the co-efficient of friction and heat generation.     

不同纳米材料与石墨混合填充PTFE复合材料摩擦磨损性能

利用MM-200型磨损试验机考察了载荷对纳米SiO₂、TiO₂、Al₂O₃与石墨混合填充PTFE复合材料摩擦磨损性能的影响,采用扫描电子显微镜观察分析磨损表面形貌及磨损机理。结果表明,纳米材料及其与石墨混合都可以不同程度地提高PTFE的耐磨性,而它们对PTFE耐磨性的提高程度各不相同,其中以纳米SiO₂-石墨填充PTFE复合材料的磨损质量损失最小,纳米Al₂O₃-石墨填充PTFE复合材料的磨损质量损失较大;填充PTFE复合材料同钢对磨时的摩擦系数表现出不同的性能,纳米SiO₂-石墨填充PTFE的摩擦系数与纯PTFE相差不大。     

MoS_2和石墨对Ni-Cr基复合材料摩擦学性能的影响

用粉末冶金方法制备Ni-Cr基自润滑复合材料,研究了固体润滑剂MoS_2和石墨对复合材料的机械性能和摩擦学性能的影响。结果表明,随着MoS_2含量的增加,复合材料的显微硬度明显降低;MoS_2添加量从10%(质量分数,下同)增加到15%,复合材料摩擦系数和磨损率的变化并不明显。随着石墨含量的增加,复合材料的显微硬度呈逐渐降低的趋势,在400℃和800℃的摩擦系数呈升高趋势,石墨添加量为10%时室温摩擦系数最小。同时添加5%MoS_2和10%石墨时,复合材料的摩擦系数保持在0.48-0.65,石墨与MoS_2之间存在着协同效应,但是磨损率比添加单一润滑剂时高一个数量级。     

Friction and wear of epoxy/TiO2 nanocomposites: Influence of additional short carbon fibers, Aramid and PTFE particles

An epoxy-based nanocomposite containing graphite powder (7 vol%) and nano-scale TiO₂ (4 vol%) was developed for tribological evaluation. A series of composites containing additional fillers such as short carbon fibers (SCF), Aramid and polytetrafluoroethylene (PTFE) particles was developed and evaluated in adhesive and low amplitude oscillating wear modes. The incorporation of SCF and Aramid particles resulted in a remarkable improvement in the sliding wear resistance. However, SCF impaired the low amplitude oscillating wear resistance. The further addition of PTFE to the SCF filled nanocomposites reduced the friction and wear under both wear conditions. However, an adverse effect of PTFE was found for the Aramid particles filled nanocomposites. Under sliding conditions, the lowest wear rate and coefficient of friction showed the 2–4 vol% PTFE filled SCF nanocomposite. Aramid particles containing nanocomposites (without PTFE) exhibited the best wear and friction behavior under low amplitude oscillating wear conditions among the selected composites. The wear mechanisms were studied by scanning electron microscopy.     

Tribological properties of powder metallurgy – Processed aluminium self lubricating hybrid composites with SiC additions

In this experimental study, aluminium (Al)-based graphite (Gr) and silicon carbide (SiC) particle-reinforced, self-lubricating hybrid composite materials were manufactured by powder metallurgy. The tribological and mechanical properties of these composite materials were investigated under dry sliding conditions. The results of the tests revealed that the SiC-reinforced hybrid composites exhibited a lower wear loss compared to the unreinforced alloy and Al–Gr composites. It was found that with an increase in the SiC content, the wear resistance increased monotonically with hardness. The hybridisation of the two reinforcements also improved the wear resistance of the composites, especially under high sliding speeds. Additionally, the wear loss of the hybrid composites decreased with increasing applied load and sliding distance, and a low friction coefficient and low wear loss were achieved at high sliding speeds. The composite with 5 wt.% Gr and 20 wt.% SiC showed the greatest improvement in tribological performance. The wear mechanism was studied through worn surface and wear debris analysis as well as microscopic examination of the wear tracks. This study revealed that the addition of both a hard reinforcement (e.g., SiC) and soft reinforcement (e.g., graphite) significantly improves the wear resistance of aluminium composites. On the whole, these results indicate that the hybrid aluminium composites can be considered as an outstanding material where high strength and wear-resistant components are of major importance, predominantly in the aerospace and automotive engineering sectors.     

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.     

Effects of atomic oxygen exposure on the tribological performance of ZrO2-reinforced polyimide nanocomposites for low earth orbit space applications

The effects of atomic oxygen exposure on pure polyimide and nano-ZrO₂ reinforced polyimide composites were investigated in a ground-based simulation facility. The experimental results indicated that the surface structure of both pure polyimide and ZrO₂/polyimide composites were destroyed by atomic oxygen attack, but the addition of nano-ZrO₂ particles in polyimide could obviously decrease the mass loss, which showed that ZrO₂ could enhance the atomic oxygen resistance. The results of ZrO₂/polyimide composites before and after atomic oxygen exposure showed that atomic oxygen irradiation aggravated the friction and wear of the ZrO₂/polyimide composites. The wear mechanism was mainly abrasive particles wear arising from the ZrO₂-rich layer on the surface of composites. The ZrO₂/polyimide composites with 1 wt% nano-ZrO₂ owns the lowest varying rate of the friction coefficient and wear rate before and after atomic oxygen exposure, which showed stable friction and wear properties and was expected to become a kind of potential tribological materials for practical spacecraft designation.