Corrosive wear characteristics of bronze friction resisting composites

Abstract

Three groups of bronze based composites with different amounts of slide additive (graphite) and friction additives (SiC and SiO₂) were prepared by powder metallurgy technique. The corrosive wear behaviours of the resulting composites in electrochemical aqueous solutions, namely, acidic rain, neutral rain and wastewater, were comparatively investigated. The corrosive wear mechanisms of the bronze composites were discussed based on examination of the worn surface morphologies of the composite block materials by means of scanning electron microscopy equipped with an energy dispersion spectrometry. The determination of corrosive wear rates was carried out by means of a combination of electrochemical and gravimetric techniques. Increasing both slide and friction additives improved the corrosion resistance of these bronze composites. Samples with 1·5% graphite, 3%SiO₂ and 3%SiC had the highest corrosive wear resistance in neutralised as well as in acid rain due to the high amount of antifriction and slide additives, in addition to low porosity.     

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.     

The tribological properties of bronze–SiC–graphite composites under sea water condition

Bronze–SiC–nickel coated graphite composites were fabricated by powder metallurgy technique (P/M). The tribological properties of composites sliding against AISI321 stainless steel pin were studied under sea water condition. The graphite is an effective solid lubricant in sea water environment. The SiC improved the hardness and tribological properties of composites. The friction coefficient of bronze–SiC–graphite composites increased with the increase of SiC. However, the specific wear rate of bronze–SiC–graphite composites decreased with increasing SiC. Bronze-2 wt% SiC-11.7 wt% nickel coated graphite composite showed the best tribological properties due to the synergistic effects of reinforcements.     

Tribological Properties of PTFE and PTFE Composites at Different Temperatures

The friction and wear properties of polytetrafluoroethylene (PTFE) and its composites with fillers such as bronze, glass fiber, carbon fiber, carbon, graphite, and polymer were studied at ambient temperature and high temperature. The wear resistance and hardness were enhanced by the fillers. Results showed that the wear resistance of all composites was much higher than that of pure PTFE. Pure PTFE has the lowest friction coefficient at ambient temperature (temperature: 23 ± 2°C, humidity: 50 ± 10%) but highest friction coefficient at high temperature (above 100°C). The PTFE composite filled with bronze showed the best wear resistance at ambient temperature but the poorest wear resistance at high temperature. The carbon-graphite- or polymer-filled PTFE composite showed a lower friction coefficient and moderate wear resistance at both ambient and high temperature.     

The effect of lubricant additives on friction and wear studies of polyphenylene sulphide

Polyphenylene sulphide is a polymer with good thermal stability and high crystallinity. This paper summarizes the results of friction and wear studies of polyphenylene sulphide and its composites made with conventional solid lubricants to ascertain the suitability of the material as a matrix for solid lubricant additives. The polymer itself has a high coefficient of friction. Wear rate increases with load and speed. Addition of solid lubricant additives helps in improving the friction and wear of the polymer. Composites with MoS₂-Sb₂O₃ and PTFE gave better results than composites made by the addition of graphite and MoS₂ graphite. Wear rate of these composites increased with load and speed; but load and speed had little effect on friction.     

Influence of counterface roughness on the friction and wear of polytetrafluorethylene- and polyacetal-based composites

The friction of various composites is generally little dependent upon the roughness. When the composites contain glass or carbon fibres, their wear rates are also little dependent upon the roughness. However, the wear rates of PTFE incorporating MoS₂, graphite or bronze and polyacetal incorporating PTFE increase rapidly as the roughness increases beyond a certain critical value characteristic of each of these composites. The roughness-dependency of the wear rate is markedly affected by the transfer during sliding.     

The Wear Resistance of HVOF Sprayed Composite Coatings

The aim of the study was to determine the interactions between standard antiwear zinc dialkyldithiophosphate (ZDTP)-type additives and composite coatings containing hard phases of Al₂O₃, SiC, and TiN in the nickel matrix. The analysis was conducted for selected ceramic materials with different structures and different tribological behavior of ionic, covalent, and metallic bonds. The composite coatings were deposited on C45 steel using the high-velocity oxygen-fuel (HVOF) process. This process efficiently uses high kinetic energy and controlled thermal output to produce dense, low porosity coatings with highly predictable chemistries that are homogeneous in structure. The coatings can operate under harsh service conditions, because they are characterized by higher durability and higher wear and corrosion resistance. It was necessary to determine the interactions between the ZDTP-type antiwear additives (zinc dialkyldithiophosphates) and the coatings. The tribological properties of nickel and nickel-based composite coatings were examined by means of a T-01 M tester functioning in the ball-on-disc configuration during technically dry friction and boundary lubricated friction with lubricants containing 1% ZDTP. The comparative analysis confirmed different tribochemical activity and, accordingly, different tribological effectiveness of the nickel and nickel-based composite coatings during friction.     

几种静环的耐磨性和磨损失效分析

通过热压工艺制造了一种颗粒增强青铜基材料作为航天航空液压泵中的静环。对比了其它用于航天航空液压泵上的几种静环(浸铜石墨和填充聚四氟乙烯)对同一种材料(12CrN i3)制成的动环的耐磨性和磨损机制,并对磨损失效进行了分析。结果表明,颗粒增强青铜基材料的耐磨性远优于浸铜石墨和填充聚四氟乙烯,是用于航天航空液压泵静环的有前景的材料。     

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。     

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.     

SiC颗粒增强铝基复合材料的摩擦磨损性能

制备了不同粒度和含量siC的铝基复合材料,与santana2000轿车用HFM605型非金属摩擦片材料配成摩擦副,于不同压力和速度条件下在MM-200型摩擦磨损试验机上进行干摩擦试验,研究了其摩擦磨损性能。结果表明:摩擦因数随摩擦压力的增大而下降;比较而言,在高速高压时摩擦因数最低;复合材料中SiC粒度和含量对摩擦因数影响不大;随着siC粒度减小、含量增大,复合材料的耐磨性能逐渐提高;热处理可以明显提高复合材料的摩擦因数和耐磨性能。     

Tribological behaviour of SiC?TiC?TiB2 composites under unlubricated sliding conditions

The friction and wear behaviour of eight different SiC TiC TiB₂ composite materials, with a practically constant SiC:TiC ratio of 1 and an increasing amount of TiB₂, was determined comparatively in oscillating sliding tests at room temperature under unlubricated conditions. The influence of the relative humidity (RH) of the surrounding air was investigated in tests in dry, normal, and moist air. All tests were performed against SiC balls and Al₂O₃ balls as counterbodies. The friction was affected by RH but barely at all by the composition of the composites. The wear resistance of the composites was found to be improved considerably by addition of TiB₂ in the range 20–60%. The highest wear resistance of the system was found when Al₂O₃ was used as the counterbody material.     

Synergetic Effect of Lubricant Additive and Reinforcement Additive on the Tribological Behaviors of PEEK-Based Composites under Seawater Lubrication

Polyetheretherketone (PEEK)-based composites reinforced with lubricant additive (polytetrafluoroethylene, PTFE) and reinforcement additives including carbon fiber (CF), glass fiber (GF), and bronze powder were prepared using a hot-press molding technique. The synergetic effects of different additives on the tribological behaviors of PEEK-based composites sliding against 316 steel under seawater lubrication were investigated systematically using a ring-on-block test rig. The results showed that lubricant additive PTFE can decrease the friction coefficient and consequently improved the wear resistance of PEEK under seawater lubrication, especially when the volume fraction of PTFE was about 20%. It was also found that the incorporation of CF can further improve the wear resistance of PEEK blended with 20% PTFE, especially under high load and high sliding speed. This suggested that a synergistic effect on improving the wear resistance of PEEK existed between PTFE and CF, which originated from good lubrication of PTFE, good reinforcement of CF, and good interfacial combination between CF and PEEK-20%PTFE. However, two other reinforcement additives of GF and bronze powder had an antagonistic effect but not a synergetic effect with PTFE; that is, the incorporation of the two additives greatly deteriorated the wear resistance of PEEK blended with 20% PTFE.     

Friction and Wear Behavior of Copper Matrix Composites Reinforced with SiC and Graphite Particles

The objective of this paper is to investigate the friction behavior and wear mechanism of copper matrix composites reinforced with SiC and graphite particles. The results indicate that a graphite-rich mechanically mixed layer (MML) formed on the tribo-surface was responsible for the good tribological properties of the hybrid composites at low normal loads. When graphite content was high enough for delamination wear to take place at high load, wear resistance deteriorated. A continuous supply of graphite to the tribo-surface is an important precondition for the formation of a graphite-rich MML and the benefit of its anti-friction properties for the copper hybrid composites.     

Wear properties of Saffil/Al,Saffil/Al2O3/Al and Saffil/SiC/Al hybrid metal matrix composites

The purpose of this study is to investigate the wear properties of Saffil/Al, Saffil/Al₂O₃/Al and Saffil/SiC/Al hybrid metal matrix composites (MMCs) fabricated by squeeze casting method. Wear tests were done on a pin-on-disk friction and wear tester under both dry and lubricated conditions. The wear properties of the three composites were evaluated in many respects. The effects of Saffil fibers, Al₂O₃ particles and SiC particles on the wear behavior of the composites were elucidated. Wear mechanisms were analyzed by observing the worn surfaces of the composites. The variation of coefficient of friction (COF) during the wear process was recorded by using a computer. Under dry sliding condition, Saffil/SiC/Al showed the best wear resistance under high temperature and high load, while the wear resistances of Saffil/Al and Saffil/Al₂O₃/Al were very similar. Under dry sliding condition, the dominant wear mechanism was abrasive wear under mild load and room temperature, and the dominant wear mechanism changed to adhesive wear as load or temperature increased. Molten wear occurred at high temperature. Compared with the dry sliding condition, all three composites showed excellent wear resistance when lubricated by liquid paraffin. Under lubricated condition, Saffil/Al showed the best wear resistance among them, and its COF value was the smallest. The dominant wear mechanism of the composites under lubricated condition was microploughing, but microcracking also occurred to them to different extents.     

Mechanical and tribological properties of short-fiber-reinforced SiC composites

The short-carbon-fiber-reinforced SiC (C_sf/SiC) composites were prepared by hot-pressing sintering with Si, Al and B as sintering additives. The effects of fiber volume fraction on the mechanical and tribological properties of the C_sf/SiC composites were investigated. The results show that the bending strength values of the composites containing a certain content of the short carbon fibers are higher than that of the monolithic SiC. The friction coefficients of the composites decrease with increasing short carbon fibers content. Except of the composite containing 53 vol% short carbon fibers, the wear rates of the composites decrease with increasing short carbon fibers content, and are lower than that of the monolithic SiC drastically.     

石墨含量对铜基滑动轴承材料摩擦特性影响的数值模拟

采用离散元软件建立了不同石墨含量铜基滑动轴承材料的数值模型,模拟了铜基复合材料与45#钢摩擦副的滑动摩擦过程,探究了石墨含量对铜基轴承材料的抗压强度和摩擦学行为的影响.结果表明:随着石墨含量的增多,材料的抗压强度持续降低;铜基石墨复合材料与45#钢滑动摩擦过程中会在45#钢表面附着转移石墨颗粒,转移石墨颗粒的形成可以有...     

Wear Behavior of Bronze Hybrid MMCs Coatings Produced by Current Sintering on Steel Substrates

In this work, a bronze matrix (90 wt% Cu + 10 wt% Sn) was reinforced with SiC and graphite particulates using mechanical alloying and a subsequent current sintering technique. The mechanically ball-milled bronze hybrid matrix composite powders reinforced with 5.0 wt% SiC and 5.0 wt% graphite were cold-compacted on a 1040 steel substrate under a pressure of 300 MPa. The compacted structure was sintered at atmospheric conditions to nearly a full density within 10 min using current sintering, in which the powders were heated by a low voltage and high current and compressed simultaneously. The samples were sintered at three different applied currents (1,500, 1,700, and 1,900 A) to provide dense and well-bonded coatings on steel substrates. Microhardness testing and optical and scanning electron microscopes (SEM) were used for microstructural characterization of the hybrid composites. The tribological characterization of the resulting composites was tested by a block-on-disk method for determination of the wear loss and friction coefficient behaviors against a steel disk. It was pointed out that increasing applied current during the sintering/coating process resulted in obtaining high-hardness and wear-resistant hybrid composite coatings.     

Impact of Viscoelasticity on the Tribological Behavior of PTFE Composites for Valve Seals Application

In this article, we studied and explored the impact of viscoelasticity on the friction and wear behavior of pure polytetrafluoroethylene (PTFE), carbon–graphite PTFE composite, and glass fiber–MoS₂ PTFE composite. Tests were carried out using a specific reciprocating tribometer for valve seal application. The worn surfaces of the PTFE composites and the transfer films formed on the counterface were examined with a scanning electron microscope (SEM). Experimental results revealed that the addition of filler materials was effective in reducing the wear volume in all composites studied. In addition, the friction coefficient and wear resistance showed high sensitivity to the viscoelastic behavior of the PTFE seal. SEM investigation showed that the incorporation of particulate fillers into the PTFE matrix could dramatically reduce and stabilize the transfer films to the counterface, so they largely decreased the wear of the PTFE composites.     

石墨含量对铜基石墨自润滑复合材料摩擦过程中石墨润滑膜的影响

为研究石墨含量对铜基石墨自润滑复合材料摩擦过程中形成石墨润滑膜的影响,采用粉末冶金法制备了不同石墨含量的铜基石墨自润滑复合材料,测试了复合材料的力学性能,用自制环-块摩擦试验机测试评估了材料的耐磨性能,用光学显微镜实时原位观察了摩擦表面组织形貌的变化,用扫描电镜对磨痕进行观察和分析,通过能谱仪成分扫描分析接触面石墨润滑膜的覆盖率。结果表明:随着复合材料中石墨含量的增加,材料的力学性能逐渐降低,石墨润滑膜的覆盖率先升高后降低,磨损量先减小后增大;当石墨体积分数为14%时,石墨润滑膜的覆盖率最高,磨损量最小,耐磨性能最好。