Analysis of surface and subsurface of sliding electrical contact steel/steel in magnetic field

This paper reports the analysis of the surface and subsurface after the friction tests of a steel/steel sliding couple. Experiments were carried out on a pin-on-disc tribometer in ambient environment with a 10-mm-diameter pin under a normal load N=63 N and sliding linear speed v=0.38 m/s. During sliding, a DC electric current was passed through the contact. Simultaneously, an AC magnetic field was applied perpendicularly to the friction area. Experimental results showed that the presence of electric current and magnetic field around the tribocontact modifies the mechanical properties of the surface and subsurface. The mean friction coefficient changes from μ≈0.16 without electric current and magnetic field to μ≈0.26 with them, and its variation reduces considerably. The worn surfaces were smoother with magnetic field application than that without it, and the modification of subsurface structure was observed. The magnetic field and the electric current modify the mechanical and chemical properties of this ferromagnetic material in the sliding contact by interaction with cyclic contact stresses and increasing the temperature on the contact surface. We have characterized this interaction by an increase of the microhardness, the activation of oxidation on the surfaces, the difference of contact noise level and the changes induced in subsurface structure.