| Nowadays, the driving power of the electric railway locomotive has been up to 8000～10000 kW, which is transmitted to the running train through the pantograph strip rubbing against the contact line. The pantograph strip/contact wire system works in such a poor condition that wear of the pantograph strip and contact wire materials is severe due to discharge and temperature. The service life of pantograph/catenary system mainly depends on the wear life of the pantograph strip and contact wire materials. In China, most of the pantograph strips of electrified railway locomotive need to be imported from foreign countries. Therefore, the running and maintenance costs are very expensive. The wear life of imported pantograph strips is also very short, only 8-10×104 km/piece. Therefore, the study on friction and wear properties and electrical characteristics of pantograph strip/contact wire couples can provide important guidance and theoretical basis for development and selection of pantograph strip materials in domestic electric locomotive.The pantograph strip/contact wire materials as the contact couples, which is commonly used in the electrified railway, has been tested simulatively on AC and DC friction and wear testers. In this paper, sliding friction and wear properties of several pantograph strip/contact wire materials are studied under different support stiffness, normal load, sliding speed and electric current. And the effects of the support stiffness and the normal load on the electrical contact performance of pantograph strip/contact wire couples are discussed in the same conditions. By observing the temperature change and arc discharge during testing, the mechanism for arc discharge and the main factors affecting arc discharge intensity in the pantogragh/catenary system are explored in the paper. The effects of the temperature and the arc discharge intensity of the contact couple on the friction and wear performance of the pantograph strip/contact wire couple are systematically studied. By use of micro-hardness tester, temperature controller, digital cameras, surface profiler, scanning electron microscopy and energy dispersive X-ray apparatus, and so on, the temperature rise of contact couple and the occurrence of off-line arc discharge were observed effectively, and friction and wear behaviors of pantograph strip/contact wire materials were studied. The main conclusions obtained are as follows: 1. When the support stiffness k=19 000 N/m and the normal load Fn=160 N, the intensity and the frequency of arc discharge between the contact couple are suppressed. The wear rate of pin sample, the worn surface roughness and the surface damage are significantly decreased. The friction coefficient is stable. The appropriate support stiffness and normal load reduce the vibration and shock of the pantograph strip/contact wire during the high-speed sliding process. Their good contact makes off-line probability and arc discharge intensity of contact couple be controlled. Therefore, materials damage of the contact couple due to arc ablation is reduced. Then the appropriate contact force and support stiffness can keep a good contact of pantograph strip/contact wire extend the service life of pantograph strip/contact wire contact material, ensure a stable current-receiving condition of the locomotive and the stable running for the train.2. The intensity of arc discharge is studied by arc picture during testing. The current-receiving quality of the pantograph strip/contact wire system is measured according to the average current and the current loss rate in the circuit. The greater average current, the smaller the electric current loss is and the better the current-receiving quality of the circuit is, and vice versa.3. Spark discharge and arc discharge occurred in the process of electric sliding friction. When the contact couple is off-line, arc and spark discharge appears because of the breakdown of gas between the contact couple. The different discharge phenomena are mainly caused by its polarity, the contact area and material properties. Discharge intensity increases with increasing electric current and sliding speed, decreases with increasing normal load. It increases firstly and then decreases with increasing spring stiffness. Frictional heat, Joule heat and arc heat lead to temperature rise of contact couple. The temperature rise of the friction surfaces is very low, only 38℃in the absence of electric current. After the electric current is added, the contact temperature increases rapidly. The temperature of the contact couple is up to about 110℃when the electric current is 50 A.4. The friction coefficient firstly increases with increasing contact temperature, then decreases rapidly, and finally stabilizes. But the friction coefficient increases slightly with increasing arc discharge intensity. The effect of contact temperature on friction coefficient is more significant than that for the arc discharge. The wear volume of carbon strip increases slowly with increasing contact temperature, and increases linearly with increasing discharge intensity. The arc discharge has more significant effect on the friction coefficient than the temperature rise. The wear volume of carbon strip increases slowly with increasing contact temperature, and increases linearly with increasing discharge intensity. The arc discharge has more significant effect on the wear volume of carbon strip than the temperature rise. The main wear mechanisms without arc discharge include adhesive wear, oxidation wear, which is mainly caused by the temperature rise. The major wear mechanisms during arc discharge are arc erosion, oxidation wear and adhesive wear, which are caused by arc discharge. Abrasive wear and material transfer take place in the process of sliding friction and wear. Therefore, cooling measures should be applied in pantograph/catenary systems to reduce the thermal wear of contact couple materials. Especially, off-line arc discharge of the contact couple should be suppressed to the maximum extent to avoid the damage of material caused by arc erosion, so as to extend the service life of pantograph strip.5. The friction coefficient of the pure carbon strip rubbing against copper contact wire is kept at 0.24～0.35 under AC and high speed. The friction coefficient with electric current is much lower than that without electric current. In the case, the wear rate of carbon strip is characterized by a small area, a shallow depth of worn track and a minimum surface roughness. The wear rate of carbon strip with electric current is nearly 10 times as many as without electric current. The worn area and the depth of worn track significantly increase. In addition, the surface roughness under electric current is 2 to 3 times of the surface roughness without electric current. And in the sliding direction, the black stream-line due to arc ablation appears on the worn surface. The sliding velocity and the normal load have a slight influence on the wear volume of the pantograph strip material, and high temperature wear and arc erosion caused by electric current are the major factors affecting carbon strip wear. The wear mechanisms of pure carbon strip rubbing against copper contact wire are abrasive wear, arc erosion and oxidation wear, accompanied by material transfer.6. In the conditions of copper-impregnated metal carbon rubbing against stainless steel and the pure carbon rubbing against pure copper, the friction coefficient is stable and low. The wear volume is also small. These friction couples are appropriate for pantograph strip/contact wire couple. However, the friction coefficient and the wear volume of copper-impregnated metal carbon rubbing against copper couple are greater than those of former two couples. Adhesion and squeal noise occur in the process of sliding friction. For the pantogragh/catenary system, arc discharge, screaming and adhesion should be avoided in the process of pantograph strip rubbing against contact line to decrease wear volume of pantograph strip/contact wire materials and control surroundings noise.
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