Scientists over the world develop, improve and apply different types of nano-coatings that are meant to increase the lifetime of details and to get the required exploitation characteristics. One of the essential characteristics of the slidingfriction pairs is the lifetime which is largely determined by the process of wear. The given calculation model for friction surfaces with nano-coatings is described by a separate section of the probability theory - random field theory using standardized 3D surface roughness parameters, detail’s physical-mechanical characteristics, sliding surface constructive-kinematic parameters. The wear process is explained using fatigue theory approach.