Friction transfer film formation in boundary lubrication

An attempt is made to consider the models of friction transfer film formation in boundary lubrication. The possible role of lubricant in the formation of debris and mass transfer is discussed. Attention is given to the controversial phenomenon of selective transfer in boundary lubrication of copper alloys rubbing against steel. Formation of a porous film providing a very low coefficient of friction is related primarily to direct transfer of soft alloy combined with wear debris deposition, chemical effects being secondary. The structure of a transfer film of soft metal on a hard counterface is related to characteristics of wear particles formed in boundary lubrication and surface effects in a tribosystem. An attempt to simulate mass transfer as a flow of colloidal particles is made. Effectiveness of lubricants containing fine soft particles is discussed when considering them as a possible source of transfer film formation in tribosystems.