铜包石墨含量对铜锰铝复合材料摩擦磨损性能的影响

为改善铜锰铝合金的烧结性能,并提高其在干摩擦下的摩擦磨损性能,以铜包石墨作为自润滑相加入到铜锰铝合金中,采用等离子真空压力烧结方法制备铜锰铝/石墨复合材料,分析铜包石墨含量对复合材料的密度、硬度的影响,探讨不同复合材料在干摩擦和油润滑条件下的摩擦磨损性能.结果表明:相比真空和氢气还原气氛下的烧结方式,等离子体烧结铜锰铝...     

Studies on high temperature wear and its mechanism of Al-Si/graphite composite under dry sliding conditions

Wear behaviours of aluminum silicon alloy and Al-Si/graphite composite were investigated at ambient and elevated temperatures. The trend showed a decrease in wear rate with increase in temperature. The reduction in wear rate was mainly attributed to the formation of glazing layer and oxide layer at higher temperature. This was invariably observed in alloy and composites. In addition, the presence of graphite in composite offered better wear resistance for all temperatures under consideration. The wear due to oxidation was predominant during high temperature sliding.     

Dry sliding wear behaviour of an aluminium alloy–granite particle composite

In the present study, the effect of granite reinforcement on the dry sliding wear behaviour of an aluminium–silicon alloy (BS:LM6) was investigated using a pin-on-disc machine. The composite was prepared using liquid metallurgy technique wherein 10 wt.% granite particles were incorporated in the matrix alloy. Sliding wear tests were conducted at applied loads in the range 0.2–1.6 MPa and speeds of 1.89, 3.96 and 5.55 m/s. The matrix alloy was also prepared and tested under identical conditions in order to see the influence of the dispersoid phase on wear behaviour. It was observed that the composite exhibited lower wear rate than that of the matrix alloy. Increasing applied load increased the wear rate. In the case of the composite, the wear rate decreased with speed except at higher pressures at the maximum speed; the trend reversed in the latter case. On the contrary, the matrix alloy exhibited minimum wear rate at the intermediate test speed. Seizure pressure of the composite was significantly higher than that of the matrix alloy, while temperature rise near the contacting surfaces and the coefficient of friction followed an opposite trend. SEM examination of the worn surfaces, subsurface regions and debris enabled to understand the operating wear mechanisms.     

Wear Behavior of Al-Si Alloy Impregnated Graphite Composite

Pin-on-disk type unidirectional sliding wear experiments for an Al-Si alloy impregnated graphite composite (pin) in contact with a bearing steel (disk) were conducted at various contact loads in wet and dry air to investigate the wear behaviors in detail. The pin-lifting phenomena of the composite as observed. The height was constant at lower loads and increased with load. The entrance of wear particles into the contacting surfaces brought about the pin lifting. Mixtures of graphite powder and wear particles adhered to the sliding surface of the bearing steel, resulting in the formation of wide, compacted surface films. The mean thickness of the films increased with load to a few micrometers. The composite exhibited better wear resistance than the matrices in wet air and the wear rate decreased especially at high loads. The wide, compacted films together with the pin-lifting phenomena prevent metal-to-metal contact, achieving a good anti-wear condition. On the other hand, the surface films that adhere in a scaled fashion in dry air have little wear reduction effect.     

Tribological Properties of Lubricating Films on the Al-Si Alloy Surface via Laser Surface Texturing

Dimpled textures were prepared by using a pulse solid laser on the surface of Al-Si alloy. The combination of laser surface texturing (LST) and MoS₂ solid lubricant as well as their tribological properties were investigated in this article. The obtained friction and wear data were critically analyzed to investigate how the parameters of texture influence the tribological performance of Al-Si alloy. Furthermore, morphological investigations of the transfer layers on the worn surfaces were performed and the wear mechanisms are discussed. The results show that the combination of LST and solid lubricant improves the tribological characteristics of Al-Si alloy. The friction coefficient of Al-Si alloy: steel friction pairs can be reduced to 0.15 under dry friction. The lubrication mechanism is attributed to a synergetic effect of providing solid lubricant and traps wear debris in the dimples. It was found that the optimum density of structure was 37% for excellent tribological properties.     

Friction and wear behaviour of an Al-Si alloy against steel lubricated with N- and O-containing organic compounds

The friction and wear properties of an Al-Si alloy against AISI 52100 steel were investigated with a block-on-ring wear tester lubricated with a liquid paraffin base oil containing organic additive compounds, such as ethylenediamine, ethyleneglycol, ethanolamine, and N,N-dibutylethanolamine. The boundary film formed on the rubbed surface of the Al-Si alloy was then examined using FT-IR microscopy and XPS. The friction and wear tests revealed that ethylenediamine, ethanolamine and N,N-dibutylethanolamine additives provide good lubrication in the Al-Si alloy-on-steel system, especially N,N-dibutylethanolamine. FT-IR microscopy and XPS revealed the possible formation of a chemically stable five-ring complex of aluminium or silicon with diamine and ethanolamine.     

Effect of the Graphite Content on the Tribological Behavior of Al/Gr and Al/30SiC/Gr Composites Processed by In Situ Powder Metallurgy (IPM) Method

The influence of graphite content on the dry sliding wear characteristics of Al6061/Gr composites along with Al6061/30SiC/Gr hybrid composites has been assessed using a pin-on-disc wear test. The composites with different volume fraction of graphite particles up to 13% were processed by in situ powder metallurgy (IPM) technique. The porosity and hardness of the resultant composites were also examined. It was found that an increase in the graphite content reduced the porosity, hardness, and friction coefficient of both types of composites. The hybrid composites were more porous and exhibited higher hardness and lower coefficient of friction at identical graphite contents. The increased graphite content in the range of 0–13 vol.% resulted in increased wear rate of Al/Gr composites. The Al/30SiC composite exhibited a lower wear rate as compared with the base alloy and graphite addition up to 9 vol.% improved the wear resistance of these hybrid composites. However, more graphite particles addition resulted in increased wear rate. SEM micrographs revealed that the wear mechanism was changed from mostly adhesive in the base alloy sample (Al/0Gr) to the prominently abrasive and delamination wear for Al/Gr and Al/SiC/Gr/composites.     

Effectiveness of an externally added solid lubricant on the sliding wear response of a zinc–aluminium alloy,its composite and cast iron

The role played by an externally added solid lubricant like graphite towards controlling the sliding wear behaviour of a zinc-based alloy has been examined in this study. The influence of dispersing hard silicon carbide particles in the alloy was also investigated by testing the composite in identical test conditions. The wear performance of the zinc-based alloy and its composite was compared with that of a gray cast iron. Wear tests were performed in oil lubricated environment. Composition of the lubricant was changed by adding various quantities of graphite (particles) to the oil. The study suggests that the wear response (in terms of wear rate, frictional heating and friction coefficient) of the samples improved in the presence of suspended graphite particles in the oil lubricant. However, this improvement was noticed up to a critical content of graphite particles only and the trend reversed at still higher graphite contents. The zinc-based (matrix) alloy revealed highest wear rate. Dispersoid silicon carbide particles showed a significant improvement in the wear performance of the matrix alloy. The cast iron performed in between the matrix alloy and composite. The frictional heating and friction coefficient were the highest for the composite while the cast iron and the matrix alloy showed a mixed response. Examinations of wear surfaces, subsurface regions and debris particles helped to substantiate the observed wear response of the samples.     

AZ91D镁合金微动磨损特性研究

采用液压高精度材料试验机考察了平面一球面接触的AZ91D镁合金摩擦副的微动磨损行为，分析了位移幅值、法向载荷和频率等参数对摩擦因数和磨损体积的影响，考察了不同实验条件下的磨斑形貌，并探讨了其磨损机理。结果表明：AZ91D镁合金的微动区域可分为部分滑移区、混合区和滑移区3个区域，粘着磨损、疲劳磨损和磨粒磨损分别是3个区域的主要磨损机制；磨损体积随着位移幅值和法向载荷的增加而增大，但却随着频率的增大而减小。在微动部分滑移区和混合区，摩擦因数随着位移增大迅速增加；在微动滑移区，摩擦因数随法向载荷的增大而减小，而位移幅值和频率对摩擦因数的影响较小。     

Tribological behavior of metal matrix composites

The wear and friction behavior of continuous graphite fiber reinforced metal matrix composites was investigated. Composite materials were tested against 4620 steel at 54 m s^?1 at room temperature in air without lubricant. The graphite fibers studied included rayon-, pitch- and polyacrilonitrile (PAN)-based fibers. Both high modulus and high strength PAN-based fibers were examined. The fibers were incorporated into copper- and silver-based alloys by means of a liquid metal infiltration technique. The results of this study indicate that the type of graphite fiber in the composite is the most significant factor in the wear and friction behavior of metal matrix composites. In some high modulus fiber tin-bronze composites the fiber fraction influences the wear rate but not the coefficient of friction. Neither the matrix alloy nor the composite tensile strength per se correlate with the friction and wear properties; however, there are specific trends for the various matrix alloys.     

Mechanism of abrasive wear of Al-Si hypoeutectic alloycontaining 5 vol% fly ash

Fly ash, an inexpensive resource material, has been introducedinto Al-Si hypoeutectic alloy (A356) to make low-cost compositeswith decreased density and improved hardness and abrasive wearbehavior. The mechanisms of abrasive wear of stir-cast A356-5vol% fly ash composite were discussed based on the results ofwear tests of composites and the A356 base alloy. Scanningelectron microscopy was used to investigate the morphology ofthe worn surfaces, wear debris for both composite and A356 basealloy. The subsurface of the worn samples was also observed.These morphology observations provide a method to understand theabrasive wear and friction mechanism of the composites showing that the base alloy wears primarily by microcutting but thecomposite wears by microcutting and delamination caused by crackpropagation below the rubbing surface through interfaces of flyash and silicon particles with the matrix.     

含石墨镍基复合材料的摩擦学性能研究

用粉末冶金制备石墨wt．％含量为0，3，6,9的镍基白润滑合金，研究不同石墨含量对材料摩擦学性能的影响。     

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.     

Scuffing Behavior of Al-Si Alloy Modified by Fine Particle Bombarding and Powder Impact Plating Hybrid Surface Treatment

The occurrence of scuffing is widely observed on tribological components made of Al-Si alloys. The object of this study is to investigate the scuffing behavior of Al-Si alloy modified by fine particle bombarding (FPB) and powder impact plating (PIP) hybrid surface treatment. FPB treatment, PIP treatment, and hybrid treatment consisting of FPB and PIP were conducted on Al-Si alloy samples. The surface morphology, microstructure, and hardness of the samples were examined. Block-on-ring tests were performed to investigate the scuffing resistance of the samples. The test results show that the scuffing resistance of Al-Si alloy depends on the surface hardness and friction coefficient. Scuffing resistance is improved by FPB treatment, which increases the surface hardness by nanocrystallization and reduces the friction coefficient by decreasing the surface roughness and producing a microdimpled surface. PIP treatment reduces the friction coefficient by generating an Sn coating on the surface of the sample, thereby improving the scuffing resistance. After FPB and PIP hybrid surface treatment, the surface hardness is increased and the friction coefficient is further reduced. Therefore, the sample modified by hybrid surface treatment exhibits the highest scuffing resistance.     

石墨填充聚醚酰亚胺摩擦学性能分析

在M-200摩擦试验机上进行不同含量石墨填充PEI基复合材料的摩擦磨损试验,利用扫描电子显微镜分析了断口和磨损表面的显微结构,并分析了磨损机制。考察了表面硬度随含量填充量的变化规律。试验结果表明:石墨在复合材料基体中呈片状结构,磨损过程中易形成转移膜,从而改善了摩擦磨损情况,其中填充质量分数10%石墨的PEI基复合材料摩擦因数最低,填充30%石墨的复合材料磨损率最低,材料表面硬度随着填充石墨含量的增加而降低,石墨填充量在5%～30%之间表面硬度下降平缓,当填充量超过30%时,材料表面硬度下降剧烈。     

Friction and wear of carbon nanohorn-containing polyimide composites

Polyimide (PI)-based composites containing single-wall carbon nanohorn aggregate (NH) were fabricated using the spark plasma sintering (SPS) process. For comparison, composites with carbon nanotube (NT) and traditional graphite (Gr) were also fabricated. The NH was produced using CO₂ laser vaporization and a graphite target and the NT was produced by a chemical synthesis method. We evaluated the friction and wear properties of the PI-based composites with a reciprocating friction tester in air using an AISI 304 mating ball. NH drastically decreased the wear of PI-based composites; the specific wear rate of composite with NH of only 5 wt% was of the order of 10⁻⁸ mm³/Nm, which was two orders of magnitude less than that of PI alone. The wear reduction ability of NT seemed to be slightly inferior to that of NH, although it was considerably better than that of Gr. NH and NT lowered the friction of composites. The friction coefficient of composite with 10 wt% NH was less than 0.25, although it was slightly higher than that of composite with 10 wt% Gr. There was no clear difference in the friction reduction effect of NH and NT. The further addition of Gr to composites with NH or NT rather deteriorated the antiwear property of composites, although the friction coefficient was slightly reduced. The transferred materials existed on the friction surface of the mating ball, sliding against composites with three types of carbon filler. These transferred materials seemed to correlate with the low friction and wear properties of composites.     

Tribological Performance of Microwave-Heat-Treated Copper–Graphite Composites

Copper–graphite composite is a tribological composite that can be used in sliding electrical contact applications requiring low friction and wear in addition to high electrical conductivity. The graphite powder (5 wt%) was mixed with the copper powder, and then composite was fabricated through powder metallurgy (P/M) route. P/M product generally requires secondary operations such as rolling, extrusion, etc. to improve their mechanical properties. Post-heat-treatment technique is also applicable to improve the properties of P/M components. Microwave-post-heat-treatment research studies are gaining momentum nowadays due to the improved quality of products with reduced time, energy, and associated cost. Microwave post-heat treatment of copper–graphite composites for different heat treating duration was carried out in a hybrid microwave heating setup. Microstructural studies were carried out using SEM with EDAX. Microwave-heat-treated samples exhibited reduced porosity, improved density, and hardness. In order to understand the friction and wear properties of microwave-heat-treated copper–graphite composites, pin-on-disk wear experiments were conducted. For comparison, untreated copper–graphite composites were also subjected to similar studies. Microwave-heat-treated samples exhibited reduced coefficient of friction and specific wear rate when compared to the untreated ones. The wear mechanism of untreated composites was observed to be plastic deformation characterized by large wear fragments, whereas the mechanism of heat-treated composite was delamination observed through peel off tribolayer.     

Tribological behavior of graphite-containing nickel-based composite as function of temperature,load and counterface

Nickel-based graphite-containing composites were prepared by powder metallurgy method. Their mechanical properties at room temperature and friction and wear properties from room temperature to 600 °C were investigated by a pin-on-disk tribometer with alumina, silicon nitride and nickel-based alloy as counterfaces. The effects of graphite addition amount, temperature, load, sliding speed and counterface materials on the tribological properties were discussed. The micro-structure and worn surface morphologies were analyzed by scanning electron microscope (SEM) attached with energy dispersive spectroscopy (EDS). The results show that the composites are mainly consisted of nickel-based solid solution, free graphite and carbide formed during hot pressing. The friction and wear properties of composites are all improved by adding 6–12 wt.% graphite while the anti-bending and tensile strength as well as hardness decrease after adding graphite. The friction coefficients from room temperature to 600 °C decrease with the increase of load, sliding speed while the wear rates increase with the increasing temperature, sliding speed. The lower friction coefficients and wear rates are obtained when the composite rubs against nickel-based alloy containing molybdenum disulfide. Friction coefficients of graphite-containing composites from room temperature to 600 °C are about 0.4 while wear rates are in the magnitude of 10^?5 mm³/(N m). At high temperature, the graphite is not effective in lubrication due to the oxidation and the shield of ‘glaze’ layer formed by compacting back-transferred wear particles. EDS analysis of worn surface shows that the oxides of nickel and molybdenum play the main role of lubrication instead of graphite at the temperature above 400 °C.     

Dry-Sliding Tribological Properties of Bronze–Graphite Composites

Bronze-uncoated and nickel-coated graphite composites were fabricated by powder metallurgy route. The tribological behaviors of composites sliding against AISI52100 steel ball under dry sliding condition were studied using a ball-on-disk tribometer. The nickel-coated graphite composites showed much better tribological properties in comparison with bronze and uncoated graphite composite. The friction coefficient of nickel-coated graphite composites decreased with increasing nickel-coated graphite content. However, the specific wear rate increased with the increase in nickel-coated graphite. The composite containing 15?wt% nickel-coated graphite showed the best self-lubricating properties because the compacted and stable mechanical mixed layer was formed on the worn surfaces. The wear mechanism of bronze 663 is adhesive wear and abrasive wear. The uncoated nickel-coated graphite composite shows the adhesive wear and delamination characteristics. However, the wear mechanism of nickel-coated composites is mildly abrasive wear.     

Improvement on Sliding Wear Behavior of Al/Cast Iron Tribopair by CNT's Reinforcement of an Al Alloy

The results presented in this work show the wear characterization of Al-Si matrix composites reinforced by multiwall carbon nanotubes (MWCNTs) under dry reciprocating sliding conditions against a grey cast iron (GCI) The wear resistance is investigated as a function of the carbon nanotube (CNT) content that varied from 2 to 6 wt%. The results demonstrated that the CNT content plays a relevant role in the wear behavior by substantially reducing the wear loss of Al-Si CNT composites. Further, it reduces the wear loss of the grey cast iron counterface. A physical model able to explain the improved behavior in both mating materials is depicted from experimental results.