Horokh D. Regularities of formation, structural features and properties of ion-plasma nitride coatings TiSiN/NbN and TiSiN/CrN

The dissertation is devoted to the creation of multilayer coatings of nanometer scale based on TiSiN/NbN TiSiN/CrN that meet modern requirements for surface protection of structural materials operating at elevated temperatures, fatigue and thermal fatigue loads, as well as to identify the features of the synthesis processes, elemental and phase composition, substructure and properties of multilayer coatings obtained by vacuum arc deposition. Determination of the relationship between the structure and mechanical and tribological properties of coatings. The aim of the work is to determine the conditions for the formation of nitride multilayer protective coatings and to develop recommendations for specific physical and technological processes of their deposition. The work is of significant fundamental and practical interest for physical materials science and surface physics To achieve this goal, the following tasks had to be accomplished: 1. To obtain (TiSi)N/NbN, (TiSi)N/CrN coatings using plasma methods under different deposition modes. 2. To investigate the effect of synthesis conditions on the elemental composition of the resulting coatings. 3. To study the structure, surface topology, nature of chemical interatomic bonding, microhardness and elastic modulus of the obtained coatings. 4 To study the effect of thermal annealing on the structural state and physical and mechanical properties, in particular microhardness. 5 Determine the adhesive strength and fracture mechanism of multilayer coatings. Object of research: technological processes and physical factors that affect the formation of multilayer nitride coatings with nanometer layer thicknesses deposited by vacuum arc method, the relationship of structural characteristics with physical and mechanical properties of coatings. The subject of the study is the elemental and phase composition, structural state, mechanical properties and tribotechnical characteristics of multilayer nitride coatings of nanometer scale (TiSi)N/NbN, (TiSi)N/CrN. Methods of formation and research Currently, the most promising coating methods are vacuum ion-plasma methods, among which reactive magnetron sputtering and vacuum arc deposition are widely used for deposition of wear-resistant nitride coatings. Along with the main advantage of the magnetron method - drip-free sputtering - it has a number of significant disadvantages: relatively high operating pressure to maintain the discharge and a narrow range of basic parameters (pressure, current) under which optimal coating deposition conditions are realized. And, as a result, the low energy of the particles involved in the nitride synthesis reactions, which leads to high porosity of the coatings and their relatively low adhesion to the substrate. When using the vacuum arc deposition method, based on the generation of highly ionized metal plasma flows by an arc discharge, coatings are formed on the surface of samples as a result of condensation of the plasma flow of the eroding cathode material. Any electrically conductive material can be used as the evaporated material: metal, alloy or metal-based composite. In the presence of a discharge gap of reaction gas, a layer is synthesized on the substrate based on compounds of elements of the cathode material and working gas (nitrides, oxides, carbides). The high degree of ionization of the vacuum-arc plasma (20-100 %) and the ability to control the parameters of the coating synthesis process in a wide range (working gas pressure, discharge current, bias voltage, etc.) allow for a targeted influence on the structural and physical and mechanical characteristics of the resulting condensates. To study the morphology, crystal structure, elemental composition, structural and phase state, mechanical and tribotechnical properties of multilayer coatings, we will use scanning electron microscopy (SEM), X-ray microanalysis using an energy dispersive spectrometer (EDS), and X-ray diffraction analysis (XRD), measurement of microhardness and nanohardness, application of the sclerometry method to obtain a complete picture of the wear pattern, friction coefficient and adhesive strength, and fracture processes of coatings, as well as laboratory tests of coated samples at the V.N. Bakul Institute of Superhard Materials of the National Academy of Sciences of Ukraine.