Features of Deterioration of the Contact Surface of C235 Steel and Its Wear in Dry Sliding Against Steel under Alternating Current

Abstract

Dry sliding of model samples of C235 steel against 45 steel under alternating current with a density of up to 120 A/cm² using the pin-on-ring configuration was investigated. The possibilities of increasing wear resistance by changing one of the geometric parameters (height) of the sample (pin) were studied and the temperature of the sample holder at different points was investigated. It was shown that this temperature can exceed 150°C in the sample mounting zone. The increase in the temperature of the sample holder and the wear intensity were nonlinear in accordance with a curve close to an exponential function with increasing current density. Sliding at a current density higher than 100 A/cm² occurred under conditions of catastrophic wear. Formation of a transfer layer with a thickness of about 20 μm was observed on the contact surface of the samples. Using X-ray phase analysis, it was found that the transfer layer contains more than 70% FeO. The analysis of wear surfaces allowed us to reveal the mechanism of contact layer deterioration, which was presented as the division of the nominal contact area into two sectors. The boundary between the sectors was quite clear and perpendicular to the sliding direction. The sector directed towards the oncoming contact surface of the counterbody had traces of adhesion, plowing, etc., which usually appear during sliding without current. The other sector had signs of deformation similar to the deformation of a viscous liquid. Traces of adhesion were not observed here. The friction coefficient decreased with increasing current density and did not change its behavior upon transition to the catastrophic wear mode. The presented regularities were observed at a qualitative level regardless of the height of the samples. Only the heating temperatures of the sample holder differed quantitatively. The results of the work will be useful in creating a real friction unit operating in sliding current collection with a high current density.