Friction and wear behavior of pure carbon strip sliding against copper contact wire under AC passage at high speeds

A series of tests on the friction and wear behaviour of pure carbon strip/copper contact wire with alternating current were conducted on a ring-on-block sliding tester at a high speed. The electric current, normal force and sliding velocity have distinct effects on the test results. The worn scar has the smallest size without electric current. The worn scar becomes larger with increasing electric current. Arc ablation pits, dark stream-lines of arc ablation, slipping marks, spalling blocks and the copper-like layer are found on the worn surfaces. Arc erosion, abrasive wear and adhesive wear are main wear mechanisms.     

Sliding wear behavior of ceramic,plasma sprayed on casting aluminum alloy against SiC ball

The wear behavior of Al₂O₃–40% TiO₂ and Cr₂O₃ deposited on a casting aluminum alloy (ASTM A356) by plasma spray against an SiC ball was investigated. It was found that the voids and porosities of the coating surface generated cracks. As the tensile stresses in the coating increased with an increased friction coefficient, the columnar grain of the coating fractured at the critical stress point. It was also found that the cohesiveness of the splats and porosity of the surface both played a role in the wear characteristics. It is suggested that the thermal expansion mismatch of the substrate and coating plays an important role in the wear performance. Tensile, compressive, and thermo-mechanical stress may also occur due to this same thermal expansion mismatch of the substrate and coating. Crack propagation above the interface was observed with a SEM. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of arc discharge on the wear rate and wear mode transition of a copper-impregnated metallized carbon contact strip sliding against a copper disk

Wear of the contact strip on the pantograph of electric railway vehicles is governed mainly by arc discharge occurring simultaneously with break of contact between the strip and trolley wire. As a step to clarify the wear mechanism of metallized carbon contact strips under the occurrence of contact break arc discharge, a detailed sliding wear test of 30 min duration was carried out for the combination of a copper-impregnated carbon strip and a copper disk at a sliding speed of 100 km/h. The worn surfaces of the strip and disk were observed every 5 min. The voltage drop and electric current were measured throughout the test, and the occurrence and energy of the arc discharge were evaluated for each revolution of the disk. The wear process is considered in terms of the wear mode transition, and the effect of arc discharge on the mode transition and wear rate of the strip is discussed.     

Sliding wear transition for the CW614 brass alloy

Dry sliding wear tests were performed on a CW614 brass alloy using a pin-on-ring configuration. Wear kinetics were measured within a load range of 20–80 N and sliding velocity ranging from 1 to 7 m/s. Chemical compositions, morphologies and microstructures of worn surfaces and wear debris were characterised by scanning electron microscope (SEM) and energy dispersive X-ray spectrometer (EDS). Two main wear regimes have been observed: severe wear and mild wear. The results of wear tests and metallographic investigations on worn surfaces have been summarised in a wear mechanism map. It was found that the wear transition is controlled by a critical temperature at the contact surface.     

Experimental study on arc ablation occurring in a contact strip rubbing against a contact wire with electrical current

A series of tests on arc discharge were carried out to better understand the wear mechanism of a contact strip rubbing against a contact wire with electrical current. The arc discharge process was recorded with a high-speed camera. The arc voltage drop and electric current were measured throughout the test. The accumulated arc discharge energy was evaluated. Experimental results show that the wear rate of the contact strip is approximately directly proportional to the accumulated arc discharge energy in logarithmic coordinates. Increasing the normal force can suppress arc discharge and decrease wear of the contact strip.     

Sliding wear behavior of protective coatings for diesel engine components

The use of heat-insulating ceramic coatings on the cylinder walls of diesel engines is currently being considered for certain advanced engine designs. Since a major consideration in such an application is the wear resistance of the coatings, a series of tests has been carried out to determine the sliding wear behavior of several pairs of candidate materials systems, initially at room temperature. The tests were performed using a washer-on-disc specimen configuration and an oscillatory rotation movement to simulate the motion of a piston ring on a cylinder wall. It was determined that each material tested had a different pattern of sliding wear behavior. Impregnation of plasma-sprayed Y₂O₃-ZrO₂ with chromia markedly improved its wear resistance.     

Sliding wear behavior of dedicated iron-based SLS materials

Systematic investigation of wear behavior of selective laser sintering (SLS) materials is lacking in SLS/selective laser melting research. The present research is an effort to fill the gap by performing sliding wear tests under plastic and elastic contact conditions upon proprietary iron-based SLS materials: LaserForm and DirectSteel. It is found that LaserForm is a better SLS wear material. It is concluded that wear performance is governed not by the hardness of the materials but by their composition.     

Sliding wear behaviour of Zinc–Nickel alloy electrodeposits

The sliding wear behaviour of zinc–nickel electrodeposited coatings on mild steel substrates was investigated using a spherical pin-on-disc apparatus. The pin materials were alumina and hardened steel. The composition of the coatings was the following: 86 wt% zinc–14 wt% nickel. The friction coefficient of zinc–nickel coating against alumina counter spheres was found to be higher than that against hardened steel counter spheres. The weight loss of zinc–nickel coating after sliding against hardened steel counter spheres was found to be lower than that against alumina counter spheres. The main wear mechanism of the zinc–nickel coating sliding against stainless steel was noted to be severe shearing of the surface layers of the coating due to the ploughing action of the steel pins. For the wear experiments of zinc–nickel coatings against alumina spheres, a surface delamination mechanism is proposed to be the predominant wear mechanism of the coatings.     

Thermal wear and electrical sliding wear behaviors of the polyimide modified polymer-matrix pantograph contact strip

In the present study, the polyimide resin (PI)/cashew-modified resin (YM) polymer-matrix pantograph contact strip (PMPCS) was prepared by using hot repressing, hydro-solidification and dipping treatment processes. The thermal properties of cured resins were studied by thermogravimetry analyzer and differential scanning calorimetry. The thermal wear and electrical sliding wear behaviors of PMPCS against copper were evaluated by a ring block wear tester at elevated temperature under dry sliding conditions and a wear tester which simulated the train motion under laboratory conditions, respectively. Worn surfaces and wear debris of PMPCS were analyzed by scanning electron microscopy and energy dispersive spectrometer, and the wear mechanism was discussed. It has been found that the thermal stability of the PI/YM is superior to that of the YM under the same testing conditions. The results also showed that PI/YM-PMPCS had superior wear resistance than that of YM-PMPCS at elevated temperature and with electrical current. At elevated temperature, the wear mechanism of tribological pair evolved from adhesive wear to oxidative wear with mild delamination wear. Arc erosion wear, oxidative wear, and adhesive wear were the dominant mechanisms of tribological pair during the electrical wearing process.     

Sliding wear behavior of mesocarbon microbeads based carbon materials

The sliding wear behavior of mesocarbon microbeads (MCMBs) based carbon materials was investigated. Samples were sintered at 1300 °C from pure MCMBs without ball-milling (C0) and ball-milled MCMBs doped with 3, 5, 10 wt.% nano-SiC (C3, C5 and C10). The results indicated that C0 sample had poor sliding wear property; ball-milling and doping nano-SiC contributed to the improvement of sliding wear property. The mean friction coefficient values of the C0–C10 samples against H62 brass alloy were 0.38, 0.24, 0.21, and 0.30, respectively. Mass loss increased with increasing sliding time, and C0 and C3 had the highest and lowest mass loss, respectively. The worn surface images showed C0 sample had broad wear tracks and was free from debris layer, while the worn surfaces of C3 and C5 were rather smooth because of the formation of adherent contact films without any significant fracture. These good sliding wear properties were related to small grains, uniform high hardness and large amount of aromatic layers along contact surface.     

Sliding wear behavior of planar random zinc-alloy matrix composites

The friction and wear behavior of planar random zinc-alloy matrix composites reinforced by discontinuous carbon fibres under dry sliding and lubricated sliding conditions has been investigated using a block-on-ring apparatus. The effects of fibre volume fractions and loads on the sliding wear resistance of the zinc-alloy matrix composites were studied. Experiments were performed within a load range of 50–300 N at a constant sliding velocity of 0.8 m s⁻¹. The composites with different volume fractions of carbon fibres (0–30%) were used as the block specimens, and a medium-carbon steel used as the ring specimen. Increasing the carbon fibre volume fraction significantly decreased the coefficient of friction and wear rates of both the composites and the medium-carbon steel under dry sliding conditions. Under lubricated sliding conditions, however, increasing the carbon fibre volume fraction substantially increased the coefficient of friction, and slightly increased the wear of the medium-carbon steel, while reducing the wear of the composite.Under dry sliding conditions, an increasing load increased not only the wear rates of both the composite and the unreinforced zinc alloy, but also those of their corresponding steel rings. However, the rate of increase of wear with increasing load for both the composite and its corresponding steel ring was much smaller than for the unreinforced zinc alloy and its corresponding steel ring. The coefficient of friction under dry sliding conditions appeared to be constant as load increased within a load range of 50–150 N for both the composite and the unreinforced zinc alloy, but increased at the higher loads. Under any load the coefficient of friction of the composite was lower than half that of the unreinforced zinc alloy under dry sliding conditions.     

Sliding wear performance of reinforced A413 alloy at elevated temperatures

Dry sliding wear behaviour of Al–Si A413 alloy with and without intermetallics has been studied at ambient and elevated temperatures. It is observed that as the temperature is increased, the wear rate decreased. The reduction in wear rate is mainly attributed to the formation of glazing layers at elevated temperature and is observed in both A413 alloy with and without intermetallics. The wear due to oxidation is predominant during high temperature sliding.     

Dual-rotary fretting wear behavior of 7075 aluminum alloy

Friction and wear behavior of dual-rotary fretting (DRF) combined by torsional and rotational fretting modes have been investigated. Such fretting mode is essentially achieved by changing tilt angles of the rotary axis and varying rotary angular displacement amplitudes The DRF behavior has been characterized from the dynamic behavior, wear damage, third-body behavior, wear mechanisms. The running condition fretting map (RCFM) of DRF fretting wear was established by using the tilt angles and angular displacement amplitudes. The evolution of the wear volume vs the tilt angle under varied angular displacement amplitudes was quantificationally measured. In addition, the competition between the local wear and fatigue (cracking, wear) has been discussed in detail. The results indicated that the damage of 7075 aluminum alloy induced by DRF was strongly dependent upon the tilt angle and the angular displacement amplitude.     

KFC铜合金引线框架带材的连续挤压制造技术

针对目前KFC铜合金引线框架带材主要生产方法中存在的生产工艺流程长、设备投资大、产品成品率低和成本高等问题,提出KFC铜合金引线框架带材的连续挤压制造技术,并通过企业的生产运行,验证了该方法的技术可行性和工艺可行性,使企业的产品生产效率、质量和品种等多方面水平得到提高,尤其具有良好的节能减排优势.     

Sliding wear behavior of Fe-based bulk metallic glass at high temperature

In the past decade Fe-based bulk metallic glasses (BMGs) have attracted increasing attention due to their beneficial properties, including high glass forming ability (GFA), high strength and hardness and high fracture toughness in both fundamental science and engineering application. Most research using these materials has been conducted at room temperature environment, and research that assesses their behavior especially at high temperature has been scarce. We present the results of high temperature effect on the friction and wear behavior of Fe-based bulk metallic glass (BMG), and we tested that this material may satisfy wear and oxidation resistance at high temperature as well as to explore the high temperature wear mechanism of the Fe-based BMG. The dry sliding tribological behaviors of Febased BMG against Si₃N₄ ceramic were conducted with a pin-on-disc friction and wear tribometer. The morphology of the worn surfaces of Fe-based BMG was examined by scanning electron microscopy (SEM) and the chemical composition characterized with energy dispersive spectroscopy (EDS) to observe the wear characteristics and investigate the wear mechanisms. The overall average friction coefficient value generally decreased with increasing temperature, and the glass transition and the formation of protective oxide film played an important role in the tribological behavior of BMG. The wear resistance of Fe-based BMG was not only from their hardness but also from the formation protective oxide layer. Analysis of the worn surface revealed abrasion, plastic deformation and oxidation during sliding test.     

Sliding wear behavior of hardfacing alloys in a pressurized water environment

In this study, sliding wear behavior of newly developed Fe-base Co-free hardfacing alloy (Fe–Cr–C–Si) was investigated and compared to that of Stellite 6 and Fe-base NOREM 02 in the temperatures ranging from 300 to 575 K under a contact stress of 103 MPa (15 ksi) in pressurized water. The weight loss of Fe–Cr–C–Si was equivalent to that of Stellite 6 over all temperatures range in 100-cycle wear test. The weight loss of Fe–Cr–C–Si 1000-cycle wear test increased almost linearly with increasing temperature up to 575 K. The weight loss of NOREM 02 was nearly equivalent to that of Stellite 6 below 475 K, however, galling occurred above 475 K in 100-cycle wear test. It was also found that the lubrication effect of pressurized water on the sliding wear behavior of the alloys was negligible under the present test conditions.     

多层股钢丝绳直线张拉状态下接触磨损机理研究

为了解多层股钢丝绳内部接触磨损情况,通过不同方法对其在直线张拉状态下的力学特性进行了研究。基于Costello的普通钢丝绳弹性理论,建立了拉力作用下直线状态钢丝绳的受力模型,以18×7+IWS多层股钢丝绳为例,计算得出多层股钢丝绳不同层绳股的应力变化情况;根据钢丝绳的空间几何结构,分析钢丝在接触状态下的受力情况,研究了钢丝接触应力的大小和钢丝间的滑动位移量对钢丝接触状态和钢丝疲劳磨损的影响;利用Abaqus对钢丝绳进行有限元静力学分析,研究了绳股钢丝间的应力变形情况;最后在DIC-MTS试验台进行了钢丝绳直线状态下的拉伸实验,从力学角度分析了多层股钢丝绳疲劳损伤的主要原因,对上述理论分析进行了验证,并得出了多层股钢丝绳在使用中其失效先从内部磨损开始,继而扩展断裂的结论。     

Sliding wear of cast zinc-based alloy bearings under static and dynamic loading conditions

The lubricated wear behaviour of cast journal bearings, produced from a series of zinc-based alloys and SAE 660 bronze as a reference material, was investigated under both static and dynamic loading conditions using a bearing test rig. All of the zinc-based alloys had higher wear resistance than the SAE 660 bronze. Among the zinc-based alloys, the wear resistance of the monotectoid-based alloys was superior to those based on near-eutectoid composition, and the best wear performance under both static and dynamic loading conditions was obtained with ZnAl40Cu2Si1 alloy. Copper content affected the wear resistance of monotectoid zinc-based alloys. Under dynamic loading conditions, it increased with increasing copper content up to 2%, but declined thereafter. Tensile properties and hardness of the monotectoid alloys were also affected by their copper content. Loading conditions had a strong influence on the wear rate. Under static loading conditions, as-cast zinc-based alloys showed higher wear resistance than the equivalent heat-treated alloys, but this behaviour was reversed for dynamic loading. Possible reasons for this are briefly discussed.     

Sliding wear behavior of nanocrystalline nickel coatings: Influence of grain size

In the present study the sliding wear behavior of pulse electrodeposited nanocrystalline Ni coatings as a function of grain size including bulk annealed Ni has been systematically studied using pin-on-disc configuration against the WC-Co counter body. The sliding wear has been analyzed with respect to wear rate, coefficient of friction, subsurface deformation and composition of wear debris. The result indicates that the sliding wear rate and coefficient of friction of Ni decreases with decreasing grain size. The subsurface beneath the worn pin surface is composed of a near surface shear region and beneath it a region of bulk plastic deformation. The ratio of the depth of the shear region to the depth of bulk deformed region decreases with decreasing grain size indicating a greater localization of near surface deformation with decreasing grain size.     

Sliding wear behavior of electron beam surface-melted 0–2 tool steel

Studies were carried out on the dry sliding wear behavior of electron beam melted surface layers on a type 0–2 tool steel and on annealed and conventionally hardened 0–2 steel specimens for comparison. Wear tests were conducted in a flowing argon atmosphere at a sliding speed of 20 cm s^?1 and a load of 10 N against a 52100 bearing steel ring. Wear surface morphology was studied along with subsurface structure using optical and electron microscopy methods. The study concentrated on the wear of this steel after different processing treatments. Electron beam surface melting and subsequent rapid solidification in situ of the steel produced a highly refined martensitic microstructure having higher hardness values and better wear resistance than obtained using conventional quench hardening of that steel. Carbide distribution and martensite phase morphology were affected by this surface melting process; those microstructural characteristics influenced the wear behavior. Variations in electron beam power and surface speed during melting were explored in terms of their effect on the resulting surface layer. The wear test system used was computer interfaced and controlled, permitting continuous measurements of wear depth and friction force.