Study On The Effect Of Low Air Pressure And Oxygen On The Friction And Wear Performance Of The Carbon/Copper Contact Pair With Electric Current

Friction and wear occur in almost all relative operating components,and it is often the main cause of energy loss,system failure,etc.Carbon materials with good self-lubrication and conductivity with metal as the moving parts often the first choice of in power transmission,bow net system in the field of rail transit is a kind of typical carbon/metal sliding electrical contact vice,is building the Sichuan-Tibet railway because of its altitude,air pressure is only60% of that in the plain area,oxygen accounted for as low as 15%,Oxygen levels and the vast difference between the pressure and the plains will directly affect the oxidation of carbon/copper interface,the formation of oxide film,affect the current carrying friction interface makes the way of carbon/copper contact vice friction and wear behavior are more complex and changeable,the high altitudes of bow net system operation caused serious security hidden danger,related work to be carried out.Based on building the sliding reciprocating friction and wear test rig carrying tank,and can be closed environment atmosphere in different altitude in China based on differential pressure and oxygen content scope,regulating tank and air pressure,oxygen in the atmosphere fluctuation characteristics of dynamic analysis of contact resistance and friction coefficient,and the wear surface morphology and the interface material composition corresponding relation,The evolution law of electrical contact characteristics of carbon/copper contact pair in bow mesh under low oxygen and low pressure was analyzed,and the abnormal wear mechanism of carbon slide material was revealed.Firstly,the correlation mechanism between oxygen content,air pressure and contact resistance is proved.With the decrease of oxygen content and air pressure,the fluctuation of contact resistance increases but the average value decreases.The fluctuation of contact resistance caused by the change of air pressure is more significant,which is related to the deterioration of self-lubricity of carbon materials and the decrease of the stability of electrical contact characteristics caused by the absence of interface oxide film.Secondly,the influence mechanism of oxygen content and air pressure on friction coefficient is proved.With the decrease of oxygen content and air pressure,the average friction coefficient shows an upward trend.With the decrease of oxygen content and air pressure,the time for friction coefficient to enter stable fluctuation state increases.The formation rate of oxide film plays an important role in forming stable boundary lubrication film and stabilizing friction.Finally,the abnormal wear mechanism under low pressure and low oxygen is revealed.Under different current and contact pressure,the wear amount of carbon slider increases with the decrease of oxygen content and air pressure,and the maximum increase of wear amount is 118%,121%,208%and 134%,respectively.The essential reason is that under low pressure and low oxygen condition,The lack of isolation and lubrication of oxide film and the decline of self-lubricity of carbon materials lead to the aggravation of adhesion wear between carbon and copper,and the accumulation of a large number of abrasive debris on the interface further hinders the transmission of current,resulting in more severe discharge erosion and a sharp increase in the wear of contact pair.