In electrified rail networks, the power required fo rtraction is transferred through the sliding contact between a catenary (copper cable) and a collector (steel). It produces relatively quick wear in the copper cable, which is awkward to replace. The tribological behaviour of a copper-steel couple similar to those in electrified railways has been studied as a function of mechanical, electrical, and environmental parameters. The experimental results obtained in an oxygen atmosphere show that this factor has a major influence on the wear behaviour. While there was a reduction in the average coefficient of friction compared to in argon, under oxygen there was twice the wear found under air, and six times that found under argon. In the absence of an electric current, the nature of the wear was essentially mild adhesive. However, with an electric current at the interface, fluctuations, particularly at high intensities, were recorded in both the coefficient of friction and the electrical contact resistance, and there was severe wear. Discussion of the results is based on examination of the wear surfaces and analysis of the phenomena observed during sliding contact. The oxides reduce the number of metallic junctions, the adhesion area, and th e overall friction coefficient. Their role is analogous to that of a solid lubricant and is underlined by the results obtained under argon. When an electrical current is passed through, the rate of oxidation increases. When debris of great hardness reaches the interface and attains a certain size, it behaves like active particles, making grooves, and considerably increase the wear of the wire. In these conditions, both the friction coefficient and the electrical contact resistance become unstable, while abrasive wear predominates over oxidative wear and largely determines the length of life of the wire.
The influence of oxygen on the friction and wear behaviour of a copper-steel couple under electric current
Tribo Test ; 11 , 1 ; 11-27
2004
17 Seiten, 11 Bilder, 2 Tabellen, 11 Quellen
Aufsatz (Zeitschrift)
Englisch
Anschluss (Kontakt) , Kupferdraht , Stahl , Eisenbahnfahrzeuglauftechnik , Reibung , Verschleiß , Verschleißeigenschaft , Adhäsion , Abrasion , elektrischer Kontakt , Stromabnehmer (Kollektor) , Sauerstoffatmosphäre , Argonatmosphäre , Einflussgröße , Kontaktwiderstand , metallischer Kontaktwerkstoff , Gleitkontakt
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