We have studied the tribological behavior of a XC 48 steel/XC 48 steel sliding couple in the presence of an A.C. magnetic field. Experiments were conducted on a pin-on-disc tribometer in ambient atmosphere under an applied normal load P=62.85N and sliding speed v=0.38m/s. The magnetic field was applied to the pin and remained constant during each test. Experimental results showed that the presence of a magnetic field around the tribocontact modifies the tribological behavior through changes of the mechanical properties of the subsurface. The surface microhardness increases in magnetic field and modifies the tribocontact rheology. The modifications induced in the contact surface and subsurface of XC 48 steel, by the magnetic field H=0 to 8kA/m after 30min of sliding, were analyzed by Vickers microhardness measurement, scratch testing with acoustic emission detector, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS).