Arc Erosion Research Articles

Effect of electrical current on tribological behavior of copper-impregnated metallized carbon against a Cu–Cr–Zr alloy

A block-on-slip ring-type wear tester was used to investigate the tribological behavior of copper-impregnated metallized carbon against a Cu–Cr–Zr alloy under 2 to 6N applied load and 0 to 20A electrical current. The sliding speed was maintained at 25km/h. The wear loss of copper-impregnated metallized carbon increased with greater electrical current. Under a certain applied load, the wear loss with electrical current was minimized. The tribo-layer had an apparent effect on the friction coefficient. The wear mechanisms were complex, consisting of adhesive wear, abrasive wear and arc erosion.

Friction and Wear Behavior of Pantograph Strips Sliding Against Copper Contact Wire with Electric Current

An investigation on friction and wear behaviors of carbon strip and contact wire used in the pantograph-cantenary system is presented. The tests are conducted under laboratory conditions and on a pin-on-disc tester under electric current. The results indicate that electric current have a distinct effect on friction properties of carbon strip rubbing against copper. The wear rate of carbon strip increases with increasing of electric intensity due to the heat and arc discharge generated in the current. Worn surfaces of carbon strip are analyzed by scanning electron microscopy equipped with an energy dispersive X-ray spectroscopy. It is found that the thermal wear, arc erosion and abrasive wear are the dominant wear mechanism occurring in the electrical sliding frictional process, accompanying with material transferring.

開離時アーク放電が集電系材料の質量と表面状態に及ぼす影響

Examination methods that involve a slide between contact wires and contact strips are methods that simulate the actual current-collecting phenomena encountered in the railway field. However, the influence of a breaking arc on the mass and surface of contact materials cannot be clarified by these methods, because the mass change includes the wear and arc erosion that occur during the methods. This paper tries to clarify these problems by using a breaking arc that is generated without using a wire to begin an arc discharge. The breaking arc is generated in this way to resemble the phenomena of arc generation in the railway field.

Tribological behavior of CNTs-Cu and graphite-Cu composites with electric current

CNTs-Cu and graphite-Cu composites were separately prepared by powder metallurgy technique under the same consolidation processing. Tribological behavior of the composites with electric current was investigated by using a pin-on-disk friction and wear tester. The results show that the friction coefficient and wear rate of the composites decrease with increasing the reinforcement content, and increase with increasing the electric current density; the effects of electric current are more obvious on tribological properties of graphite-Cu composites than on CNTs-Cu composites; for graphite-Cu composites the dominant wear mechanisms are electric arc erosion and adhesive wear, while for CNTs-Cu composites are adhesive wear.

Effect of Axial and Transverse Magnetic Fields on the Arc Duration and Material Transfer

Axial and transverse magnetic fields are widely used in many kinds of switches to decrease the arc erosion. In this paper, the influence of these two kinds of magnetic fields on the arc phase transition was studied particularly for AgSnO2 contacts breaking a 28V/25A circuit. The experiments were carried out under resistive and inductive loads in an atmospheric environment. The relationships between flux densities ranging from 0 to 200mT and the arc duration were obtained. It was found that the transverse magnetic field was more efficient in balancing the arc phases and decreasing the arc erosion. The results can be used to guide the design of arc extinguishment systems in DC high power relays.

Fabrication of CuW pseudo alloy by W–CuO nanopowders

CuW pseudo alloy was fabricated with W–CuO nanopowders by sintering and infiltration. The microstructure and phase constituents of the CuW pseudo alloy prepared were characterized by a scanning electron microscope, X-ray diffractometer, and the arc erosion behavior was also evaluated by arcing test. The CuO powders, instead of the induced copper powders, were introduced into W nanopowders. CuW pseudo alloy with uniform structures of Cu and W phases was obtained when 11 wt.% CuO powders were introduced into W nanopowders. In comparison to the conventional CuW pseudo alloy, the sizes of W skeleton and the infiltrated Cu phase were reduced remarkably and both the hardness and electrical conductivity were increased. The arc erosion resistance was increased due to the split characteristic of the cathode spot for the CuW pseudo alloy prepared by W–CuO nanopowders. The appropriate addition of induced copper can improve the distribution of Cu and W phases, and promote the subsequent infiltration of the molten Cu due to pre-wetting the surface of W skeleton.

In situ synthesis and electrical properties of CuW–La2O3 composites

CuW–La2O3 composites were fabricated using an in-situ synthesis. The breakdown voltage in vacuum, moving trajectory of cathode spots, electrical conductivity, and hardness of CuW–La2O3 composites were carefully examined. The microstructures were characterized by a scanning electron microscope (SEM). The results show that CuW–La2O3 composites have the maximum hardness of 220HB and the electrical conductivity of 45% IACS when the content of La2O3 is 0.75wt.%. In comparison with CuW alloy, the dielectric strength, arc life and the arc mobility of the CuW–La2O3 composites increased by 36.9%, 9.7% and 46.6%, respectively. As a result, the addition of La2O3 is useful to improve the properties of CuW alloys and the in situ synthesized CuW–La2O3 composites should have excellent arc erosion resistance.

Study on Electrical Sliding Wear Property of Cu/MoS<sub>2</sub>/Mo Composites

In this paper, the Cu/MoS2/Mo composites were prepared by the powder metallurgy technology. The friction wear test was tested by the HST-100 High Speed Electric-tribometer. The microstructure and wearing surface morphology were examined by SEM and EDS. The electrical sliding wear behavior of the composites was discussed. The results indicated that the dense composites are obtained; the wear mechanisms of Cu/MoS2/Mo are mainly abrasive wear and adhesive wear with arc erosion; the effects of current intensity and sliding velocity on the wear property of the composites are complicated, and the composites show the best property when the current intensity is 60A and the sliding velocity is 40m/s.

Effect of electrical current on tribological property of Cu matrix composite reinforced by carbon nanotubes

Cu matrix composite reinforced with 10% (volume fraction) carbon nanotubes (CNTs/Cu) and pure Cu bulk were prepared by powder metallurgy techniques under the same consolidation processing condition. The effect of electrical current on tribological property of the materials was investigated by using a pin-on-disk friction and wear tester. The results show that the friction coefficient and wear rate of CNTs/Cu composite as well as those of pure Cu bulk increase with increasing the electrical current without exception, and the effect of electrical current is more obvious on tribological property of pure Cu bulk than on that of CNTs/Cu composite; the dominant wear mechanisms are arc erosion wear and plastic flow deformation, respectively; CNTs can improve tribological property of Cu matrix composites with electrical current.

Vacuum Arc Motion Characteristics on CuWCr Composites

The CuWCr composites were respectively fabricated by the mixture of W and Cr and WCr alloyed powders, followed by sintering and infiltration. Vacuum arcs on CuWCr composites were observed by a digital high-speed video camera. The morphologies of the composites before and after arc erosion were characterized by a scanning electron microscope. The results show that the microstructure CuWCr composites prepared by WCr alloyed powders becomes finer and more uniform, and, thus, has good characteristics of diffusive arcs and arc erosion resistance. In addition, the composite prepared by WCr alloyed powders has excellent electrical properties such as high breakdown voltage, low chopping current and long arc life. Arc erosion zones of the CuWCr composite fabricated by WCr alloyed powders become more dispersive and uniform on the surfaces with some shallow erosion pits. During the course of arc evolution, the dispersed arcs are caused by the split of electrical arc.

Effect of temperature and arc discharge on friction and wear behaviours of carbon strip/copper contact wire in pantograph–catenary systems

A series of tests on friction and wear performance of pure copper rubbing against carbon strip under electric current have been carried out on a modified pin-on-disc friction and wear tester. The results indicate that there are temperature rise and arc discharge in the electrical sliding processes. The temperature rise of contact pairs and the intensity of arc discharge increase with the increasing of electric current. However, the friction coefficient increases firstly due to the accumulation of wear debris, and then decreases with the increasing of electric current due to the accumulation of electric heat and friction heat on contact interface. The increase in wear volume of the carbon strip is mainly caused by high temperature of contact pairs and arc discharge phenomenon. The test results also show that the wear volume of pin specimen with arc discharge is much greater than that without arc discharge under the same temperature. Therefore, the thermal wear due to high temperature has a distinct influence on the service life of pantograph contact strip and arc erosion even has more significant influence. Cooling measures should be applied in pantograph/catenary systems. Especially, off-line arc discharge of the contact couple should be suppressed to the maximum extent to extend the service life of pantograph contact strip.

Dual plasma synthesis and characterization of a stable copper–ethylene glycol nanofluid

This article addresses the issue of metallic nanoparticle suspension (nanofluid) stabilization without the use of traditional surface-stabilizing agents such as surfactants. A dual plasma process for the single-step synthesis of a copper–ethylene glycol nanofluid is presented. The process uses a combination of low-pressure pulsed cathodic arc erosion to generate metal nanoparticles and in-flight radio-frequency glow discharge plasma functionalization for surface stabilization. The surface-stabilized nanoparticles are collected in situ by a falling film of ethylene glycol, the vapours of which are used for plasma functionalization. Little to no agglomeration is observed in the suspension, although this process is shown to occur when the produced suspensions are heated to temperatures well beyond the range of effectiveness of typical surfactants. This thermally induced agglomeration is demonstrated to be fully reversible. The stability of the suspension is confirmed by UV–Vis absorption spectrometry and electron microscopy. The particles synthesized are also shown to be re-dispersible in aqueous media. Though no heat transfer enhancement was observed due to the low nanoparticle loading, this study demonstrates for the first time that high temperature-stable nanofluids containing metal nanoparticles can be synthesized in a single-step, without manipulation outside the controlled synthesis environment and without the post-addition of surfactants.

Tribological properties of Cu-La 2O 3 composite under different electrical currents

A new type of Cu-La 2O 3 composite was fabricated by internal oxidation method using powder metallurgy. Sliding wear behavior of the Cu-La 2O 3 composite was studied on a pin-on-disc wear tester under various electrical currents and applied loads. The worn surfaces were characterized using scanning electron microscopy and energy dispersive spectroscopy to probe the wear mechanisms. The results indicated that applied load had a significant effect on the wear rate of the Cu-La 2O 3 composite pins. The wear rate displayed the minimum value at the load of 50 N during electrical sliding processes. The corresponding wear mechanism was identified to be adhesive wear, abrasive wear, oxidation wear and arc erosion.

Sliding Wear Behaviour of Cu-10Fe-3Ag <i>In Situ</i> Composite

A deformation-processed Cu-10Fe-3Ag in situ composite was made by consumable arc melting and casting followed by extensive deformation. A superior combination of mechanical strength and electrical/thermal conductivity was achieved with the composite since Fe filaments existed in the copper matrix. The effects of sliding speed and electrical current on sliding wear behavior and microstructure of the composite were investigated on wear tester. Worn surfaces of the Cu-10Fe-3Ag in situ composite were analyzed by scanning electron microscopy (SEM). Within the studied range of electrical current and sliding speed, the wear rate increased with the increasing electrical current and the sliding speed. Compared with Cu-10Fe in situ composite under the same conditions, the Cu-10Fe-3Ag in situ composite had much better wear resistance. Adhesive wear, abrasive wear and arc erosion were the dominant mechanisms during the electrical sliding processes.

Effects of Arc Discharge on Wear Properties of Carbon-Carbon Composites Sliding against Cu Trolley under Electric Current

Influence of arc discharge to the contact strip of carbon-carbon composites was orthogonally studied on the HST-100 tribo-tester under electric current, which simulated working conditions of the pantograph-wire system used in electric railway. The regression equation between specific wear rate and arc discharge were obtained and analyzed through the non-linear regression and orthogonal design. The results of the experiments show that a power function between specific wear rate and arc discharge was obtained. Microstructure and phase composition were observed and analyzed by scanning electron microscope(SEM), energy dispersive X-ray spectrum(EDS) and temperature sensor. The results revealed that the arc discharge dissipation seriously affects tribological characteristics of the carboncarbon composites. The temperature of some local contact points beyond their melting point with the electric arc heat effect, and give rise to the desposite carbon and friber carbon were vaporazated, which form the lubrication film on the wear surface, and with the augmant of the arc discharge, the area of lubrication film of carbon was decrease. Therefore, the main wear form of the arc erosion of the carbon-carbon composites is evaporate erosion and material transfer.

Arc Erosion of Silver/Tungsten Contact Material under Low Voltage and Small Current and Resistive Load at 400Hz and 50Hz

Using a self-developed ASTM test system of contact material electrical properties under low voltage (LV), small-capacity, the current-frequency variable and a photoelectric analytical balance, the electric performance comparison experiments and material weighing of silver-based electrical contact materials, such as silver/tungsten and silver/cadmium oxide contact materials, are completed under LV, pure resistive load and small current at 400Hz/50Hz. The surface profiles and constituents of silver/tungsten contact material were observed and analyzed by SEM and EDAX. Researches indicate that the form of the contact material arc burnout at 400Hz is stasis, not an eddy flow style at 50Hz; meanwhile, the area of the contact burnout at 400Hz is less than that of 50Hz, and the local ablation on the surface layer at 400Hz is more serious. Comparing the capacities of the silver-based contact materials with different second element such as CAgW50, CAgNi10, CAgC4 and CAgCdO15 at 400Hz, no matter what the performances of arc erosion resistance or welding resistance, it can be found that the capacities of the silver/tungsten material is the best.

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.

Effect of Fe on microstructures and vacuum arc characteristics of CuCr alloys

In order to clarify the effect of Fe addition on vacuum arc characteristics of CuCr alloys, the CuCr50, CuCr45Fe5 and CuCr40Fe10 alloys were prepared by vacuum sintering and infiltrating, and the simulated electrical breakdown experiment was undertaken in a vacuum interrupter. The characteristics of the motion of vacuum arcs were analyzed by a digital high-speed video camera and the erosion morphology was characterized by a scanning electron microscope (SEM). The results show that Fe additions can strengthen the Cr phase, promote the first breakdown phase to transfer from Cr to Cu and increase the strength of the alloy breakdown voltage by 80%. Meanwhile, Fe additions can still retain the arc stability of CuCr50 alloys during the generation and extinguishing process, decrease the chopping current, and prolong the arc life. Furthermore, the characteristics of the split and motion of cathode spots on the surface of the CuCr40Fe10 alloy were improved, which prohibits the concentrated arc erosion.

Effect of Arc Discharge on Friction and Wear Behaviors of Stainless Steel/Copper-Impregnated Metalized Carbon Couple under Electric Current

Friction and wear tests of stainless steel rubbing against copper-impregnated metalized carbon with electric current were carried on the pin-on-disc tester. The result indicates that arc discharge occurs in the process of experiments, and the intensity of arc discharge of interface increases with increasing of electric current and sliding velocity. As increasing of the arc discharge intensity, friction coefficient shows a tendency of slightly increase. While the rate of copper-impregnated metalized carbon material increase significantly with the increase of arc discharge intensity. Through observing the worn surface morphology of pin samples, it is found that the abrasive wear is dominant at small arc discharge due to worn particles and arc ablation craters, but arc erosion and oxidation wear are the main wear mechanisms in condition of large arc discharge due to arc discharge and its producing high temperature. The materials transfer of contact couple occurs in the process of friction and wear.

A detailed 87SR/ 86SR isotopic curve for the mid-Cincinnatian (Upper Katian–Lower Hirnantian, Upper Ordovician), NE North American Shelf (Ontario, Canada) transition to the Hirnantian glaciation

We examined the Sr-isotopic composition of one species of well-preserved brachiopod species from the mid-Cincinnatian (Upper Katian–Lower Hirnantian, Upper Ordovician) in closely spaced samples from one borehole on the western shelf of the Upper Ordovician Appalachian low latitude retroarc basin in southwestern Ontario. The section spans the transition from passive margin carbonate ramp through anoxic shales into foredeep orogenic clastics and encompasses the transition into the late Ordovician glaciation. The primary nature of the Sr-isotopic composition of the shells shows several stable Sr-isotopic excursions that refine the Upper Ordovician Sr-isotopic curve, and indicate several marked changes that may be related to the competing influences of island arc and ophiolite nappe emplacement and erosion, increasing continental crust erosion during the Taconic orogeny and the glacio-eustatic drop in sea-level related to the onset of the late Ordovician Hirnantian glaciation. These changes begin with low Sr isotope ratios (~ 0.7090) consistent with the overall trends but the ratios then change to much more positive, reaching high Sr isotope ratios (~ 0.7084) not elsewhere attained until the end Silurian. These and other minor fluctuations are attributed to periodic increases in Sr isotope ratios in the semi-isolated Taconic retroarc basin caused by rivers draining unroofing continental thrust sheets and earlier Ordovician carbonate cover rocks, with their higher Sr isotope ratios, together with increased continental erosion during regression associated with the onset of the main phase of the late Ordovician glaciation and possible glacial/interglacial phases.