The article presents the main problems of wear and service life of slide gate valves for trunk pipeline transport of oil and gas industry. One of the possible ways to solve these problems is the application of a thin layer of wear-resistant and corrosion-resistant coatings. Due to the ever-increasing cost of materials, as well as the increased requirements for materials, coating methods have recently become increasingly important. Among the gas-thermal coating methods, the High Velocity Oxygen-Fuel Spray (HVOF) technology is a new and rapidly developing technology that produces high density coatings with porosity less than 1%, with improved hardness and adhesion as well as improved erosion, corrosion and wear resistance properties. This overview article provides a comparative review of the characteristics of carbide coatings produced using different spraying technologies.

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.

In this work, the coatings obtained by a combined method, including Cr₃C₂-NiCr coating applied using a multichamber detonation device and subsequent pulse-plasma treatment, were investigated. This paper presents the results of an investigation of the influence of the pulse-plasma treatment (PPT) exposure distance on the structural-phase state of the surface layer of Cr₃C₂-NiCr-based detonation coatings. It was seen that after the PPT melting and alignment of the structural elements of coatings there were no signs of coating destruction from the impact of plasma pulses. It was established that the microstructure of the coatings was a molten metal–ceramic material based on Cr₃C₂-NiCr. It was also found that after pulse-plasma treatment, Cr₂O₃ chromium oxide phases are found on the surface, and the intensity of Cr₃C₂ peaks increased and new Cr₃C₂ reflexes appeared. It was further found that after pulse-plasma treatment the microstructure became more homogeneous, which led to the densification of the Cr₃C₂-NiCr-based detonation coating. It was established that the pulse-plasma treatment (PPT) contributed to increased hardness of the Cr₃C₂-NiCr coating material, from ~13.4 GPa (before PPT) to ~17.6 GPa (after PPT) and wear resistance twice that of the non-treated coating. The abrasive wear resistance and erosion resistance of Cr₃C₂-NiCr coatings were improved after pulse-plasma treatment.

This work is devoted to the study of the influence of technological parameters of electrolytic-plasma surface quenching (EPQ) on the structure and surface properties of samples of bandage steel 2. In the electrolytic-plasma treatment, we performed the cathode mode in an electrolyte containing an aqueous solution of 20% carbamide (NH₂)₂CO and 20% sodium carbonate Na₂CO₃, on the installation of EPO with appropriate technological processing conditions. According to the electron-optical, X-ray phase studies, the phase composition of the steel after the EPQ was determined this differs from the initial one by the formation of cementite and iron oxides on the surface of the samples. It is established that the microhardness of the bandage steel 2 after the EPQ during heating for 4 seconds increases 2.4 times in comparison with the initial state.

The process of osteointegration depends significantly on the surface roughness, structure, chemical composition, and mechanical characteristics of the coating. In this regard, an important direction in the development of medical materials is the development of new techniques of surface modification and the creation of bioactive ceramic coatings. Calcium-phosphate materials based on hydroxyapatite have been proposed as bioactive ceramic coatings on titanium implants for the effective acceleration of bone tissue healing. To obtain bioactive ceramic coatings, pulse power sources are best suited, namely detonation spraying, in which the energy of the explosion of gas mixtures is used as a source of pulse action. The pulse mode of operation in the detonation spraying method is preferable for the formation of bioactive ceramic coatings. It provides a high velocity of hydroxyapatite particles, which promotes their effective fixation on the titanium substrate, while minimizing the heating of the material. This approach preserves the substrate structure and improves the coating adhesion. Four different types of coatings with varying O₂/C₂H₂ molar ratios, ranging from 2.6 to 3.7, were obtained using detonation spraying. Powders and obtained coatings of hydroxyapatite were studied by Raman spectroscopy and XRD structural analysis. The results of XRD phase analysis showed the partial conversion of the hydroxyapatite phase to the α-tricalcium phosphate (α-TCP) phase during the detonation spraying process. The results obtained by Raman spectroscopy indicate that hydroxyapatite is the main phase in coatings. All hydroxyapatite-based coatings exhibited hydrophobic properties, which was confirmed by contact-angle values above 90° in wettability tests, characteristic of hydrophobic surfaces. The adhesive strength of the coatings was measured by the scratch test method. Tribological tests were conducted using the ball-on-disk method under both dry conditions and in Ringer’s solution. This approach enabled the evaluation of wear resistance and friction coefficient of the coatings in different environments, simulating both lubrication-free conditions and those resembling physiological environments.

Micro-arc oxidation (MAO) coatings were produced on commercially pure titanium Grade 2 using a composite electrolyte containing sodium phosphate (Na₃PO₄) and sodium silicate (Na₂SiO₃), while varying the applied voltage. The surface morphology, phase composition, and structural features of the coatings were examined using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The coatings exhibited a characteristic crater-like microporous surface morphology associated with the micro-arc discharge process. XRD analysis confirmed the formation of mixed TiO₂ phases in the anatase and rutile modifications, with higher voltages promoting the growth of the thermodynamically stable rutile phase. Corrosion and tribological properties were evaluated in a 3.5 wt.% NaCl solution using potentiodynamic polarization and a ball-on-disc test configuration, respectively. The results revealed a substantial improvement in both corrosion resistance and wear performance compared with bare titanium. The coating formed at 300 V demonstrated the highest wear resistance due to its denser microstructure, whereas the coating produced at 350 V exhibited the lowest friction coefficient and the greatest corrosion resistance, attributed to the increased rutile content. Overall, MAO coatings fabricated in the phosphate–silicate electrolyte effectively enhance the combined operational properties of titanium and can be recommended for applications requiring improved wear and corrosion resistance.