Effect of ultrafine powders in lubricants on performance of friction pairs

The effect of ultrafine powders (UFPs) of metals and metal alloys in lubricants on surface properties of steel-to-steel friction pairs was analyzed. It was found that the UFP operation mechanism depended on the origin of metals and their chemical affinity for the material of rubbing surfaces. It was shown that copper alloys had a special significance since they could undergo phase transformations with precipitation of active copper under a load, resulting in appearance of secondary ultrafine composite structures on rubbing surfaces and a dynamic equilibrium between wear and wear-compensation processes. The copper concentration in those structures was determined by the chemical composition of the ultrafine alloys and stability of their crystal lattices. It was proposed to interpret the wear-compensation process by analogy with the principle of an oriented growth of layers.