Mechanical Behavior of Tribochemical Films Under a Cyclic Tangential Load in a Ball-Flat Contact

Abstract

This paper describes an experimental investigation of some mechanical properties of four tribochemical films. Experiments have been performed for a contact between a 52100 steel flat covered with a film formed in boundary lubrication on a plane on plane tribometer. Measurements have shown that the tangential stiffness is reduced by the presence of film. The values of elastic shear modulus obtained for all films in the contact conditions are of the same order and similar to those of high molecular weight polymers. The study of contact degradation under cyclic microsliding have shown that the friction coefficient increase with the number of cycles, even for low amplitude microslidings (lower than 10 nm) when surface modifications are not yet observed. These results pointed out the existence of two types of films which present different friction and wear behaviors probably related to their plastic properties and to the boundary conditions.