In this paper, Ni–Cr–Al coatings were deposited using the detonation spraying method. The aim was to investigate how technological parameters influence coating structure formation, phase composition and tribological performances. We observed that the degree to which the barrel is filled with an O₂/C₂H₂ gas mixture strongly influences the chemical composition of manufactured coatings. High degrees of barrel filling led to a decrease in aluminum content in the coating. Filling degrees of 40% and 50% produced sprayed coatings in which only Ni–Cr phases could be found. When the filling degree was reduced up to 25%, Ni–Al phases began to form in the sprayed coatings. Gradient Ni–Cr–Al coatings were produced by gradually reducing the filling degree from 50% to 25%. These coatings are characterized by Ni–Cr near the substrate level with Ni–Cr and Ni–Al phases at higher levels. The results obtained confirm that gradient Ni–Cr–Al coatings exhibit high hardness as well as good wear resistance.

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.

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.

In this study, the mechano-chemical properties of aromatic polymer polyetheretherketone (PEEK) samples, irradiated by high energy electrons at 200 and 400 kGy doses, were investigated by Nanoindentation, Brillouin light scattering spectroscopy and Fourier-transform infrared spectroscopy (FTIR). Irradiating electrons penetrated down to a 5 mm depth inside the polymer, as shown numerically by the monte CArlo SImulation of electroN trajectory in sOlids (CASINO) method. The irradiation of PEEK samples at 200 kGy caused the enhancement of surface roughness by almost threefold. However, an increase in the irradiation dose to 400 kGy led to a decrease in the surface roughness of the sample. Most likely, this was due to the processes of erosion and melting of the sample surface induced by high dosage irradiation. It was found that electron irradiation led to a decrease of the elastic constant C₁₁, as well as a slight decrease in the sample’s hardness, while the Young’s elastic modulus decrease was more noticeable. An intrinsic bulk property of PEEK is less radiation resistance than at its surface. The proportionality constant of Young’s modulus to indentation hardness for the pristine and irradiated samples were 0.039 and 0.038, respectively. In addition, a quasi-linear relationship between hardness and Young’s modulus was observed. The degradation of the polymer’s mechanical properties was attributed to electron irradiation-induced processes involving scission of macromolecular chains.

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.