We present a review of the results of investigations on residual stresses in plasma-vacuum coatings obtained by the physical vapor deposition methods. The data on the character of residual stresses and factors influencing their values and distribution are analyzed. The works are considered that investigate the effect of residual stresses on the physico-mechanical characteristics of the substratecoating system. Recommendations on the further studies of residual stresses in PVD-coatings and the improvement in their level control are presented.Keywords: vacuum plasma coatings, residual stresses, thermal and structural components of stresses, reference potential, intermediate and buffer interlayers, multilayer coating, nanostructural and nanolayer coatings, discontinuous coating. Introduction.One of the peculiar features of modified surface layers of structural materials is the occurrence of residual stresses therein. Residual stresses in functional coatings affect the performance characteristics and life of parts and tools with coatings, as well as the strength characteristics of both the coating itself and the substrate-coating system. The account of these stresses is required, since the residual stresses promote or inhibit fracture processes, depending on the sign, distribution and mode of loading. Therefore, a strong need exists to correctly estimate the level of residual stresses, to reveal the reasons for their occurrence, to establish the manufacturing factors and parameters of the surface architecture that influence their value.The use of coatings obtained by the physical vapor deposition (PVD) method that has started in the sixties of the last century, is gaining further acceptance, particularly for parts and tools operating under conditions of heavy loads and high temperatures.The goal of the work is to review published investigations involving the defining of the physical nature and value of residual stresses in PVD-coatings, the revealing of the characteristics of the coating formation process and the parameters of the surface architecture that influence these stresses, and also the establishing of the relationship between the strength and wear resistance of the substrate-coating system and the level of residual stresses. We hope that this review will make it possible to state the problems and ways for further investigations on the residual stresses in PVD-coatings and to find the methods for attaining such "useful" level of these stresses that will agree with the maximum mechanical properties.Residual Stresses in PVD-Coatings: Value and Distribution, Physical Nature, and Dependence on Manufacturing Parameters. The occurrence of residual stresses is due to different factors, such as the difference in the coefficients of thermal expansion for the substrate and coating materials; the presence of the captured atoms of gas; the condensate imperfection, etc. Assumptions on the physical nature of residual stresses in PVD-coatings are somewhat different. In [1], using the X-ray method, it was determined that res...

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The values of residual stresses in PVD-coatings of titanium, aluminum and niobium nitrides are determined by the flexible specimen method. An experimental-and-calculation procedure for separating the structural and thermal components of residual stresses is proposed that allows one to determine the thermal expansion coefficients of the coating materials and a general level of residual stresses in coatings on a substrate of any material. The dependence of the residual stress on the roughness of the substrate surface is established. The possibility of adjusting the level of residual stresses in coatings by the discrete surface topography formation is shown.Keywords: vacuum plasma coatings, residual stresses, roughness, thermal and structural components of the residual stresses, discrete topography.Introduction. Plasma vacuum deposited (PVD) nitride-based coatings exhibit high hardness and good adhesion to substrates. Owing to their considerable wear-and heat resistance, these are widely used to enhance the performance of cutting and deforming tools, friction pair components, gas turbine engine (GTE) blades. The analysis of the data given in the literature shows that these coatings exhibit considerable residual compressive stresses whose level is from hundreds of megapascals (MPa) to a dozen of gigapascals (GPa) [1-6]. The residual stresses are induced by both the difference in the thermal expansion coefficients of the substrate and coating materials (the thermal component) and the interaction between the growing crystallites (the structural component) [1,7].As argued by the authors of [2,8], the coating stresses due to the structural component (the coating growth stresses) are independent of the substrate material, and the difference between the level of residual stresses in coatings deposited on different substrates is dependent on the thermal component. It is the high level of residual compressive stresses that the crack growth resistance, wear-resistance and corrosion resistance of surfaces modified by vacuum plasma coatings can be related to [9][10][11]. As noted in [12], a high level of residual compressive stresses retards the crack formation processes in coatings during operation of cutting tools, especially under conditions of interrupted cutting. The presence of considerable residual compressive stresses affects positively the characteristics such as fatigue limit [13] and yield strength [14]. At the same time, owing to a high level of residual compressive stresses, the coatings become more brittle, which can result in their spontaneous delamination even prior to the beginning of the operation or to the breakage of adhesion between the substrate and coating during the operation [15][16][17][18][19][20].In this connection, it is necessary to determine the possibilities on the adjustment of the level of the residual compressive stresses in coatings. Attaining this goal is possible by way of improving the coating deposition process and creating the suitable surface architecture. Commonly used methods for adju...

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