Structure of the Contact Layers of Steel and Their Deterioration in Dry Sliding Against Steel Under High-Density Electric Currents at Different Turn Ratios of a Supply Transformer

The structural states of the contact layers of C235 steel in dry sliding against C45 steel are studied under a high-density alternating electric current. A sliding electrical contact is made in the secondary winding circuit of a power transformer. The electrical conductivity of this contact decreases with a decrease in the turn ratio. At the same time, the wear resistance and the current density corresponding to the onset of catastrophic wear also decrease. The formation of FeO on the contact surface is shown. The FeO content is observed to increase with the decreasing turn ratio. This is one of the reasons for the decrease in the contact electrical conductivity. Another reason is an increase in the displacement current and a corresponding increase in the excitation of the FeO atomic lattice with a decrease in the turn ratio. The peculiarities of the sliding surface morphology are presented in order to identify the mechanism of the contact layer deterioration and find other reasons for the decrease in the contact electrical conductivity with the decreasing turn ratio. However, the surface layer morphology does not change with the changing turn ratio in sliding under a current density higher than 100 A/cm2. Two sectors appear on the nominal contact area. The boundary between the sectors is quite distinct and is perpendicular to the sliding direction. The sector directed towards the running up contact surface of the counterbody has traces of adhesion, plowing, etc., which generally appear during plastic deformation of the contact surface. The other sector shows the signs of deformation similar to that of a viscous liquid. No traces of adhesion are observed.