Influence of the electrical sliding speed on friction and wear processes in an electrical contact copper–stainless steel A. Bouchoucha a,* , S. Chekroud b , D. Paulmier c a Laboratoire de Me ´canique, De ´partement de Ge ´nie Me ´canique, Faculte ´ des Sciences de l’Inge ´nieur, Universite ´ Mentouri Constantine, Constantine 25000, Algeria b De ´partement de Physique, Universite ´ Mentouri Constantine, Constantine25000, Algeria c Laboratoire de Physique et Me ´canique des Mate ´riaux, CNRS-UMR 7554, Equipe ERMES, ENSEM-INPL, 2 Avenue de la Fore ˆt de Haye, 54516 Vandoeuvre-les-Nancy Cedex, France Received 8 June 2003; received in revised form 13 September 2003; accepted 14 September 2003 Abstract Among the various parameters that influence the friction and wear behaviour of a copper–stainless steel couple crossed by an electrical current and in a dry contact is the sliding speed. The tests were carried out under ambient environment and the sliding speed was in the range of 0.2–8 ms 1 . The electrical current intensity was varied from 0 to 40 A and held constant during each experiment. The normal load was maintained constant corresponding to an average Hertzian stress of 10 7 Pa. It appears that the friction coefficient and the wear rate increase at first with the speed, reach their maximums, then slowly decrease and tend to constant values. Over the entire range of sliding speeds two types of wear are observed. These latters are essentially mild wear as long as hard debris do not appear at the interface and severe wear when debris consisting of oxides or oxide metal mixture become big enough, they are removed from the surface and have abrasive effect. The results are discussed in terms of observations of wear debris size and composition, wear track study, metallographic study of worn surfaces and friction and electrical contact resistance records. # 2003 Elsevier B.V. All rights reserved. Keywords: Friction; Wear; Sliding speed; Electric contacts; Abrasion; Oxide films 1. Introduction The copper–steel couple was used to transfer the electrical current from the catenary (copper) to the col- lector (steel) but, previously the noticed high wear rate has led to the present use of the copper–graphite couple. However, it is interesting to highlight the friction and wear processes in the case of copper–steel couple. These depend on the using conditions [1], especially on the sliding speed which appears as an important operating parameter determining the useful service life of the couple. The sliding speed has an effect to increase the interface temperature by heating. Indeed, the local temperatures can attain values leading to the thermal softening of the copper. This affects the metallic struc- ture [2] and the mechanical properties of the surface layers [3]. High and moderate sliding speeds, in pre- sence of an electrical current, favour the formation of hard oxides and in addition to the adhesive wear, the abrasive one occurs at the interface. The results are discussed essentially taking into account the theoretical analysis and experimental phenomenon due to the friction. Applied Surface Science 223 (2004) 330–342 * Corresponding author. Tel.: þ213-31632434; fax: þ213-31632434. E-mail address: bouchoucha.ali1@caramail.com (A. Bouchoucha). 0169-4332/$ – see front matter # 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2003.09.018