Kinetics of boundary layers in non-conformal contact under non-stationary conditions

Abstract

The tests were carried out according to the roller-on-roller scheme on an SMC-2 rig, the specimens being cylindrical rollers of steel 45 with hardness HRC 32. The studies were performed in the mode of frequent starts and stops: acceleration 4 s, stop 3.5 s, the cycles following one another without pauses. The total rolling speed was 1.91 m/s, the slip 20 %, the contact stress 550 MPa, the total number of operating cycles N = 2350. The lubricant layer thickness was determined by the voltage drop method in the normal glow discharge mode.   A mechanism of the formation and adaptation of boundary adsorption layers on friction surfaces under conditions of frequent starts and stops has been revealed, which consists in the fact that activation of the metal surfaces under multi-cycle action and polarization of hydrocarbon molecules by the electric field of the solid phase initiate the formation of the layer, while its subsequent failure exposes the nascent metal surface, and the escape of electrons from it (exoelectron emission) creates conditions for the formation of anions and radicals and the growth of chemisorbed films. The obtained dependences of the boundary layer thickness on the number of operating cycles make it possible to predict the lubrication regime of non-conformal friction units under conditions of frequent starts and stops and to choose the concentration of the fullerene additive in a justified way.