A surface layer in deformable material is an independent structural level of deformation which plays a significant functional role in a part behavior at the operation of this part. It is conditioned on not only by a certain influence of a surface layer state upon performance of a part, but also by peculiarities of its deformation. The surface layer deformation gains special significance during friction of mating ground parts. At friction the basic changes of material take place in a thin (up to some micrometers) in a surface layer. The localization of stresses and their pulse character at fricion results in the generation of deformation defects. These defects arising on the surface move then to a certain depth conditioning the development of plastic deformation. The structure and properties of a deformed layer are defined by an initial state of material, conditions of loading, temperature and environment in which a couple of friction operates. The experimental investigations carried out of the surface layer formation in parts ground revealed various mechanisms of their behavior at friction affecting substantially the wear resistance of parts in couples of friction. The investigation results allow choosing substantiated scientifically the conditions and modes for finishing friction surfaces ensuring the formation of wear resistant thin nearsurface structures that will increase considerably machinery life and efficiency of technological operations of their finish grinding.