The operation modes of a plasmatron for powder coating spraying have been studied. The plasmatron has a node of annular input and a gasdynamic focusing of the powder, and the outlet holes of the nozzle-anode are made in the form of rectangular narrowing-expanding channels (No.34334 RK: IPC H05H 1/42). The dynamics and trajectories of the powder particles in the plasmatron were investigated. The paper analyzes the influence of plasmatron arc current and working gas flow rate on the structure and properties of the obtained coatings. It is established that the phase composition of the sprayed coatings and the initial powder is the same: the main phase is the compound TiN, in addition, the structure contains the phase TiO₂. The results of tribological tests of the coatings under dry friction conditions according to the ball-on-disk scheme are presented. Within the framework of this study, it can be said, from the point of view of obtaining denser coatings with high performance characteristics, that the optimal modes of plasma spraying of TiN powder are a current of 250 A and the working gas flow rate of argon 34 L/min.

This paper investigates the influence of the technological parameters of detonation spraying on the phase composition of NiCr- and Al₂O₃-based coatings. It was determined that the phase composition of Al₂O₃ coatings during detonation spraying strongly depends on the barrel filling volume with the gas mixture. The acetylene–oxygen mixture, which is the most frequently used fuel in the detonation spraying of powder materials, was used as a fuel gas. To obtain a ceramic layer based on Al₂O₃, spraying was performed at an acetylene–oxygen O₂/C₂H₂ mixture ratio of 1.856; the volume of filling of the detonation gun barrel with an explosive gas mixture was 63%. To obtain a NiCr-based metallic layer, spraying was performed at the O₂/C₂H₂ ratio of 1.063; the volume of filling of the detonation gun barrel with an explosive gas mixture was 54%. Based on a study of the effect of the detonation spraying mode on the phase composition of NiCr and Al₂O₃ coatings, NiCr/NiCr-Al₂O₃/Al₂O₃-based multilayer coatings were obtained. Mixtures of NiCr/Al₂O₃ powders with different component ratios were used to obtain multilayer gradient coatings. The structural-phase composition, mechanical and tribological properties of multilayer gradient metal–ceramic coatings in which the content of the ceramic phase changes smoothly along the depth were experimentally investigated. Three-, five- and six-layer gradient coatings were obtained by alternating metallic (NiCr) and ceramic (Al₂O₃) layers. The phase composition of all coatings was found to correspond to the removal of information from a depth of 20–30 μm. It was determined that the five-layer gradient coating, consisting of the lower metal layer (NiCr), the upper ceramic layer (Al₂O₃) and the transition layer of the mechanical mixture of metal and ceramics, is characterized by significantly higher hardness (15.9 GPa), wear resistance and adhesion strength.

The paper considers the research results of structural-phase state and tribological characteristics of detonation coatings based on Ti–Si–C, obtained at different filling volumes of the explosive gas mixture barrel of a detonation gun. The results analysis indicates that the phase composition and properties of detonation coatings strongly depend on the technological parameters of spraying. With an increase of the explosive mixture in the filling volume of the detonation barrel up to 70% of the coatings consist mainly of the TiC phase, because high temperature leads to a strong decomposition of Ti₃SiC₂ powders. Thus, the XRD results confirm that at 70% of the explosive gas mixture’s filling volume, partial decomposition and disintegration of the powders occurs after detonation spraying. We established that detonation coatings based on titanium carbosilicide obtained at the explosive gas mixture’s filling volume at 60% are characterized by high wear resistance and adhesive strength. Thermal annealing was performed after spraying in the temperature range of 700–900 °C for 1 h to reduce microstructural defects and improve the Ti–Si–C coating characteristics. As a result of the heat treatment in the Ti–Si–C system at 800 °C, we observed that an increase in the volume fraction of the Ti₃SiC₂ and TiO₂ phases led to a 2-fold increase in microhardness. This means that the after-heat-treatment can provide a sufficient reaction time for the incomplete reaction of the Ti–Si–C (TSC) coating during the detonation gun spraying. Thus, annealing can provide an equal distribution of elements in the coatings.

This work is devoted to the study of the formation of nanostructured multilayer coatings (TiZr/Nb)N on the surface of an AISI 321 steel substrate depending on the deposition parameters of the Arc-PVD method. The results of the X-ray diffraction analysis showed the formation of solid solution (TiNb)N and ZrN in the multilayer coatings with an FCC structure, ε-NbN with a hexagonal structure, as well as with a small volume fraction of the ε-Ti₂N and β-Nb₂N phase. On the basis of phase composition data, it is possible to assume that an increase in the number of bilayers leads to a decrease in the nitrogen concentration in the bilayers and, consequently, to a decrease in the volume fraction of ε-NbN and β-Nb₂N nitrides. In all investigated systems obtained at −100 V and −200 V bias potentials, ε-NbN is the main phase. The study of the element distribution over the thickness of the (TiZr/Nb)N coating confirms the results of the X-ray diffraction analysis. The use of the structure model in the form of alternating layers allows for significantly improving the adhesion characteristics of the protective coating, as well as ensuring their high hardness. Based on the experimental results, it is possible to analyze changes in the mechanical and tribological properties of multilayer coatings depending on the number of applied bilayers. The results of the study of the elastic modulus and hardness of multilayer coatings (TiZrNb)N with different numbers of bilayers showed that a large number of bilayers (small thickness of each individual layer) shows the lowest value of hardness. It is assumed that as the bilayer thickness decreases, the coating characteristics are closer to the monolayer alloy than to the multilayer structure.

Как известно ранее, карбиды, силициды и карбосилициды металлов обладают уникальным сочетанием высокой твердости, коррозионной стойкости и износостойкости [1]. Однако получение таких фаз традиционными методами связано с высокой температурой и продолжительностью их синтеза. В то же время технология получения защитных покрытий из таких композиций ограничена. Газотермические методы (электрическая дуга, газовое пламя, плазма, детонация и т. Д.) Являются одними из наиболее широко используемых [2–5]. Во всех газотермических методах при нанесении материалов покрытия на подложку используются высокотемпературные газовые потоки, в которых частицы материала нагреваются и приобретают высокую скорость. Образование покрытия происходит, когда эти частицы взаимодействуют с подлежащим покрытию субстратом. Важным преимуществом газотермических методов покрытия является то, что они позволяют наносить различные материалы покрытия (металлы и их сплавы, оксиды, бориды, карбиды и т. Д.). Анализ классических газотермических методов нанесения покрытий показывает, что наиболее высокие прочностные свойства обеспечивают детонационные покрытия [6]

The high-temperature oxidation of homogeneous and gradient coatings based on Ni-Cr-Al obtained by detonation spraying is investigated. To assess the resistance to high-temperature oxidation of Ni-Cr-Al coatings, cyclic tests were carried out at a temperature of 1000 °C for 50 cycles. The assessment of high-temperature oxidizing ability was carried out by measuring the weight gain of samples after each cycle. After high-temperature oxidation tests, the morphology and chemical composition of the coating structure in the cross-section were investigated using SEM/EDS. The phase composition of the samples was studied by X-ray diffraction (XRD) phase analysis. Visual analysis of the sample surface under study after high-temperature oxidation showed that the surface of homogeneous or gradient Ni-Cr-Al coatings remained undamaged. The results of X-ray phase analysis showed the peaks of Al₂O₃ in Ni-Cr-Al gradient coatings are more expressed and intense compared to homogeneous coatings of Ni-Cr-Al. Gradient coatings also retain an increased chromium content compared to homogeneous Ni-Cr-Al coatings. This increased chromium content can slow down mixing or diffusion between different phases of the material at their boundary, which, in turn, contributes to increasing the resistance of the gradient coating to oxidation.