Average Temperature Limits of the Dry Sliding Surface of Steel under High-Density Electric Current

Dry sliding of AISI 1020 steel samples against a hardened steel counterbody under electric current was carried out according to the “pin-on-ring” scheme. It was found that the surface layer was plastically deformed in sliding with a current density of higher than 80 A/cm 2 . This led to the formation of a tribolayer, and the thickness of the tribolayer reached 20 μm as the current density increased to 280 A/cm 2 , when catastrophic wear began. At the same time, an increase in the average contact temperature was observed, which was found by using five thermocouples, placed on the sample axis, as well as using the infrared thermography method. It was established that the average steel/steel contact temperature does not exceed 400°C under the current density of 200–600 A/cm 2 in the contact. Sliding under a current density lower than 80 A/cm 2 did not lead to noticeable plastic deformation of the surface layer, the tribolayer was absent, and the wear was close to zero. It was shown that the plastic deformation of the tribolayer led to the formation of two sectors on the sliding surface of the AISI 1020 steel sample. One of the sectors showed signs of deformation according to the viscous fluid mechanism without visible signs of adhesion. Traces of adhesion and plastic displacement by asperities of the counterbody were visible on another sector of the friction surface. The electrical conductivity of the contact decreased but did not reach zero in the mode of catastrophic wear. The contact temperature did not reach 400°C. The impossibility of a noticeable increase in the contact temperature is associated with a strong heat removal due to high wear intensity. Therefore, it can be assumed that setting external impact (high ambient temperature, pressure, current density, etc.), leading to an increase in the contact temperature to 350–400°C, will necessarily cause catastrophic wear of steel or other metals.