High-energy milling in planetary mills has found widespread application for tasks such as mechanical alloying/activation, synthesis of composite powder mixtures, and recycling of chip waste. The transfer of mechanical energy to the processed material depends, among other factors, on the technological parameters of mechanical processing, which determine the motion of the grinding bodies and, consequently, the energy-force characteristics of the process. To study the effect of the gear ratio on the energy-force conditions of mechanical processing, a discrete element model of grinding body motion in a planetary mill was developed, numerically implemented, and validated. Model parameters were determined to ensure reasonable agreement between the experimental and calculated structures of instantaneous images of grinding body motion in the steady-state operation of the mill. Using the model, a series of numerical experiments were conducted, varying the gear ratio K from 1 to 2. It was shown that increasing K within this range changes the motion pattern of the grinding bodies from a rolling mode to a combination of rolling and free flight. This transition reduces the number of collisions while simultaneously increasing their force characteristics. An analysis of the changes in total energy loss during “body–body” and “body–chamber” collisions was performed. It was established that as K increases from 1 to 2, the total energy loss during collisions primarily increases due to greater energy loss in “body–body” collision pairs. The developed models and the obtained numerical estimates of the effect of the gear ratio on the energy-force characteristics of collisions can be utilized to design optimized mechanical processing technology in planetary mills.

This study examines the effect of quenching and tempering on the structure and mechanical properties of hot-deformed powder steels containing ultrafine particles. The research analyzes the structural transformations and mechanical responses during quenching and tempering, focusing on the relationship between heat treatment conditions and the resulting material properties. The experiments involved variations in quenching temperature and tempering time, allowing the identification of optimal conditions for achieving a favorable combination of strength and ductility. The findings highlight the potential to achieve a homogeneous microstructure and high mechanical performance, making these materials suitable for high-load applications. This study underscores the significance of tailoring heat treatment parameters to control both microstructural and mechanical characteristics, thereby broadening the industrial applicability of powder steels.

The finite element method is employed to analyze the distribution of residual stresses in axisymmetric preforms of a gas compressor seal at the final stage of compaction. A computational scheme is presented, based on the obtained data on equivalent stress isolines. The dependence of the stress-strain state on the contact conditions between the compact and the die during pressing is examined. The obtained data illustrate equivalent stress isolines (MPa) according to the Mirolyubov criterion. It was established that in various sections, the stress state approaches the critical limit, which may lead to visible fracture of the briquette and delamination of its lateral surface. This finding confirms the results of previous studies on obtaining high-density powder compacts via single-step cold pressing. When solving the problem of producing a high-density powder component, the initial input data included a previously known stress distribution in the compacted briquette. Such data can be obtained from widely established methodologies, particularly for cold pressing in rigid dies for components with complex geometries. The stress-strain state of the powder briquette was computed at the contact surface between the compact and the rigid die under high and infinite friction conditions. In certain regions, significant stress levels can provoke hidden or visible failure, such as rupture of the “terminal layer” or delamination of the lateral surface. The results of numerical investigations are also applicable to low-modulus powder materials compacted in massive dies. The described method for calculating residual stresses was developed using a specialized IBM software program and was utilized for stress state analysis of compacted preforms under elastic unloading conditions.

The crystalline structure of carbon fibers (CF) based on polyacrylonitrile (PAN) and viscose precursors, treated in the tempe­rature range of 1500 to 2800 °C, was studied using X-ray diffraction analysis and Raman spectroscopy. The objective of the study was to obtain data on the structure of low-modulus viscose-based fibers, which are widely used as fillers in composite materials, and to compare the characteristics of CF derived from different precursors. An empirical dependence of the intensity ratio of the D and G lines (I_D/I_G) of the Raman spectra on the treatment temperature was established for carbon fibers based on viscose and PAN. The crystallite sizes L_a and L_c of both types of CF obtained at different treatment temperatures were evaluated. It was revealed that as the treatment temperature increases, the crystallite sizes L_a and L_c grow, while the interlayer spacing d₀₀₂​ decreases, indicating an increase in the degree of graphitization. It was found that viscose-based carbon fibers exhibit a less ordered crystalline structure compared to PAN fibers processed under the same conditions. Additionally, the true density and elastic modulus of viscose-based CF were investigated, showing lower values than those of PAN fibers treated at the same temperature. These differences in the properties and structure of CF are attributed to the microtextured nature of viscose fibers. However, during treatment at 2800 °C, CF undergo partial graphitization, which significantly reduces structural differences between fibers of both types. Nevertheless, despite the similarity in crystalline structure, viscose-based CF, even after high-temperature treatment, does not become analogous to PAN-based fibers.

The results of studies of thermophysical and operational characteristics of heat-resistant glass-ceramic coating on 12Cr18Ni10Ti steel in high-speed air plasma flow are presented. The coating was obtained using the slurry-firing technology. The heat treatment was carried out in air at 1400 K for 3 min. The structure of the coating is represented by a matrix based on barium silicate glass with Cr₂O₃ particles evenly distributed within it. The outer layer of the coating, ~3÷5 µm thick, contains many highly dispersed crystals of BaSi₄O₉ doped with Cr and Mo, indicating the surface glass phase crystallization. The heat capacity, thermal diffusivity and thermal conductivity of the coating in the temperature range of 293–573 K and at a pressure of 10⁵ Pa vary in the ranges of 0.68–0.75 J/(g·K), 0.47–0.43 mm²/s and 1.198–1.222 W/(m·K), respectively. The average values of coating’s specific mass loss and entrainment rates during air plasma flow at a velocity of ~3.5 km/s and heating of the surface to 1593 K were 7.2 mg/cm² and 25.9 mg/(cm²·h). The spect­ral emissivity of the coating at a wavelength of 890 nm and the rate of heterogeneous recombination of flux atoms and ions on its surface were 0.85±0.02 and 14±3 m/s. Glass phase provides effective protection of steel from high-temperature oxidation and self-healing of defects. Refractory Cr₂O₃ particles along with surface’s glass phase crystallization increase the resistance of the coating to erosion entrainment in the high-speed air plasma flow, its emissivity and catalyticity. The reduction of the thermal conductivity of the coating to 0.04±0.01 W/(m·K) at a temperature of 1054±10 K and a pressure of ~200 Pa is experimentally established and confirmed by numerical modelling. The explanation of the effect is presented.

The oil production process is often accompanied by various failures at oil production facilities, which leads to serious economic losses. Failures in oil production systems not only increase repair and maintenance costs, but also lead to loss of productivity, which has a negative impact on the economic efficiency of projects. A pipeline failure is considered to be its complete or partial shutdown due to a violation of its tightness or tightness of the shut-off valves, or due to blockage of the flow section. The most common causes of complications in oil production are: corrosion of oil and gas equipment, formation of asphalt-resin-paraffin deposits (ARPD) and inorganic salt deposits on the working surface of oil and gas equipment. There are a large number of methods aimed at preventing each of the previously mentioned complicating factors. It is noteworthy that the use of protective coatings can be a measure of prevention of corrosion processes, ARPD, and inorganic salt deposits. This article will review the literature, which will consider what properties, composition and structure protective coatings should have to prevent corrosion, ARPD and salt deposits, as well as what testing methods can be used to evaluate the ability of a protective coating to prevent these complicating factors.