Wear of sintered composites based on bearing steel at boundary friction with current collection against copper

摘要

© 2018, National University of Science and Technology MISIS. All rights reserved. The possibility of creating a composite of steel-graphite by sintering using the simplest technology has been studied at temperature lower than 1000 °C in the electric furnace without vacuum. The main research aim was to estimate ability of such composite to show high wear resistance at sliding against copper counterbody under the influence of electric current with a contact density higher than 100 A/cm 2 . Powder steel has been obtained by recycling of grinding wastes of bearing production. Composites had low mechanical properties and high specific electric resistance. The high through porosity was shown by optical metallography. Tribotech-nical loading of composites has been carried out according to the contact scheme “pin-on-ring” with a sliding velocity of 5 m/s and with a contact pressure of 0.09 MPa. It has been noted that dry friction of these composites has caused transfer layer emergence on the sliding surface of copper counterbody. As a result there was reduction of sliding electric contact conductivity and increase in the general copper sliding surface roughness. Impregnation by industrial oil of composites porous framework led to significant increase in specific surface contact electric conductivity and to linear wear intensity decrease comparing with the same characteristics of dry contact. Catastrophic wear under these conditions began at the contact current density of 150 – 200 A/cm 2 . It has been shown that the placing of lead plate and composite in the specimen holder and implementation of their joint sliding under the influence of electric current caused additional contact electric conductivity increase and wear intensity decrease to values of 3 – 11 μm/km at the contact current density about 250 A/cm 2 . Catastrophic wear in the presence of a lead plate and industrial oil in contact zone began at the contact current density of 250 – 300 A/cm 2 . Contact characteristics dependence on graphite concentration was not evidently observed. It has been established that every friction mode did not lead to copper sliding surface deterioration. It was concluded that the use of the restored bearing steel has the perspective for creation of current collection materials demonstrating high wear resistance under the influence of electric current of high contact density.