Methods of structural surface engineering in solving problems of multifactorial improvement of materials performance
Authors: Belozerov Valeriy , Volkov Oleh , Knyazev Serhii , Knyazeva Hanna , Konotopska Tetiana , Kraevska Zhanna , Subbotina Valeria , Subbotin Oleksandr , Fedorenko Hanna 
Published: December 2023

Problem. Structural surface engineering encompasses a complex of scientific disciplines and technological methods of directed change of physical and chemical properties of materials surface layers by modification, deformation, application of films, coatings, protective layers, with the help of various combined methods. In the course of the study several different methods of structural engineering of the surface are considered for solving problems of multifactor increase of the level of exploitation characteristics of materials. The methods described in the article are characterized by different physics of the process on the way to obtaining the result, but are aimed at modifying the structure and properties of the surfaces to which they are applied. Goal. Consideration of different methods of influence on the surface of ferrous and non-ferrous alloy objects, analysis of their influence on the modification of the structural state and properties of the surface layers that were investigated, discussion of the peculiarities of each of the considered technologies. Method. The first direction includes technologies that include a friction component, namely thermofriction treatment (TFT) for thermofriction hardening (TFH), supplementary thermofriction hardening (STH) or thermofriction welding (TFW). The second direction is the technology involving the use of anodic-cathodic electrolysis mode in alkali-silicate electrolyte – micro-arc oxidation (MAO). The third direction is the technology of vacuum-arc PVD-method, which involves obtaining chromium coatings. The article describes the features and results of application of such technologies, as well as the expediency of using this or that method for materials of different classes, schemes of the corresponding installations are presented. Results. The result of additional hardening of U8A steel surface from the microhardness level of 7.2 GPa to 14.7 GPa by DTFZ method after its thermal hardening practically to the maximum possible level is shown. The microstructure of the cross section of the pre-hardened U8A steel sample after DTFZ is presented, where the degree and character of surface hardening can be reliably seen. It is emphasized that in previous studies a consistently effective hardening of steels of various classes was achieved, up to a level of 22 GPa in 65G steel. The structure and properties of coatings on low-alloy aluminum alloys AB and AD1 formed in alkali-silicate electrolyte in the anodic-cathodic mode of MDO in the process of application of the microarc oxidation method have been studied. It is shown that the method of MDO in alkali-silicate electrolyte allows to obtain coatings with thickness up to 300 μm, coating growth rate ~ 2 μm/min and coating hardness 10-20 GPa. The coatings have high adhesion to the substrate, have a layered structure, the properties of the coatings are determined by the properties of the base layer. The coatings have a crystalline structure and consist of the following phases: γ-Al2O3, α-Al2O3, mullite (3Al2O3⋅2SiO2), the ratio between the phases depends on the electrolysis conditions. It is established that phase formation begins with the γ-Al2O3 phase, which in the process of further growth of the coating turns into the α-Al2O3 phase or interacts with silicon oxide to form the mullite phase. The possibility of obtaining high-quality chromium nitride-based hard coating by vacuum-arc sputtering is shown.