Tribological behaviour of the steel/bronze friction pair (journal bearing type) functioning with selective mass transfer

Abstract

The use of lubricants in the friction pairs that accelerate oxidation processes at the same time with their heating lead to mechanical destruction, as well as to a catalytic and electrochemical effect of the friction surfaces. Also, the current tendency to separate oxidation products and stabilize them in a meta-stable state leads to the same effect. As a result, experimental tests on friction pairs (steel/bronze, journal bearing type), has confirmed that it is useful to be done quickly thermodynamic unstable processes both inside the lubricant (here glycerine) and on the surfaces of the friction pairs, at the beginning of the friction process.This supposes, that in operating conditions unfold physical-chemical processes that are friction favorable, such as polymerized, formation of active substances at the contact surfaces, the formation of colloids and of other compounds with low resistance to tangential stress (shear). The friction in such conditions takes place with the selective mass transfer (SMT), and it is used there where the friction of the mixed layers and adhesion is not safe enough, or the friction pairs durability is not assured.SMT uses the positive effect of friction through the physical-chemical processes that take place in the contact areas of the friction pairs and allows the transfer of some elements of the materials from one surface to the other, forming a thin, superficial layer, with superior properties at minimal friction and wear. The purpose of this paper is to analyze the physical-chemical parameters and the suitable processes for initiation and achieving the selective mass transfer (IASMT) for the steel/bronze pair, which in optimal conditions, forms on the contact surfaces, a thin layer (tribofilm), in whose structure predominate copper. Also, are presents some studies and research concerning the tribological behavior of the surfaces of a friction pair with contact on the surface (journal bearing) which operates with SMT tested on the sliding bearing tribometer.