Establishing the relationship between atomized particle sizes and atomization process parameters is important both theoretically and technologically. However, the large number of process parameters complicates this task. A potential solution is to establish simple dependences on the main (defining) parameters (or functional dependences). Determining the mass median particle diameter of a powder batch is particularly difficult, so this study incorporates data from other authors in addition to personal research findings. This study used personal research findings and calculations of the mass median particle diameter of the powders produced at the pilot plant of the Frantsevich Institute for Problems of Materials Science by high-pressure (0.05 to 200 MPa) water atomization of the Al-40.1 Cu-16.9 Fe melt. A series of experiments were performed on the Al-40.1 Cu-16.9 Fe alloy to produce powders by varying the atomization pressure and melt temperature. The dataset included the size distributions of water-atomized powders of pure metals: lead, zinc, copper, stainless and high-speed steels, and copper-phosphorus and ferrosilicon alloys. For comparison, mass median diameters of lead, aluminum, and copper powder particles produced by compressed air atomization at 0.4 to 2.8 MPa were also used. Based on these data, the relationship between the ratio of the mass median particle diameter to the gravitational melt jet diameter, d50/D (inverse degree of atomization), and the Weber number (We) was plotted in logarithmic coordinates. The correlation between the inverse degree of water and gas atomization for liquid metals and alloys and the Weber number followed a linear dependence: lg(d_50/D)=2.0-0.5×lg(We) .

At different temperatures and pressures, some chemical compounds have different types of crystal structures or modifications, the stability of which is determined by the minimum thermodynamic potential [1]. Deformation of the material puts it in a less stable state and can cause polymorphic transformation [2,3]. Silicon carbide has two main modifications - β-SiC (low-temperature - cubic) and α-SiC (high-temperature - hexagonal) [4]. The transition temperature is 2100°C. Transformation under pressure was not investigated. Tapes were rolled from β-SiC powder to the maximum density (rolls with a diameter of 40 mm from the rolling mill had zero exit gap). The maximum normal contact stress did not exceed 0,7 GPa, the temperature did not exceed 40°С. Presses with a diameter of 15 mm were obtained from the original powder and crushed rolling stock. The density of the pressings was 1.05 and 1.23 g/mm3, respectively. The diffraction curves of the samples were taken in discrete scanning mode on a DRON-ZM diffractometer in monochromatized Cu-Kα radiation. The ratio of the atomic radii of carbon and silicon does not allow obtaining simple dense spatial structures [5]. Quantitative analysis of the phase composition of the powders performed using the software package Powdercell 2.4 showed that the phase composition before rolling was ~ 95% β-SiС and ~ 5% α-SiС, while after rolling - ~ 95% α-SiС and ~ 5% β -SiС. The integral width of the α-SiС lines obtained after rolling is significantly greater than the similar characteristic (26 - 46%) in the α-SiС powder supplied by the same company (Qinhuangdao Eno High-Tech Material Development Co. LTD, Китай). Results of X-ray phase analysis of granules from powders | β-SiС and strips rolled at the maximum load showed that polymorphic transformation of β-SiС into α-SiС took place during rolling.

Heat-treated 4Kh4N5M4F2 steel with adjustable austenitic transformation during operation was studied. The temperature range (450–500°C) in which the tempering brittleness of this steel was manifested was established. The impact toughness of the samples after different tempering temperatures and after steel hardening from 1100°C was determined and it was shown that after tempering at 475°C the minimum value of the impact toughness at room temperature (15 J cm2 ) was reached. The role of Ni as a Fe1–xNix replacement element was analyzed, and the segregation along the grain boundaries of the Me6C carbide phase in the solid solution, which caused a decrease in the impact toughness and an increase in the steel brittleness, was recorded.

Fine gas-atomized powders of R6M5K5 tool steel were studied. The spherical powders were produced with two distinct melting procedures, each involving spraying under different modes: at a conventional pressure of 0.6 MPa used to make powders of this steel and a calculated pressure of 2 MPa. To obtain a fine-sized fraction, the powders were sieved through a wire mesh with 50 μm square openings, and the content of this fraction was calculated for each of the two powders. The powders with particle sizes greater than 50 μm were subsequently ground and additionally sieved through a 50 μm mesh. Four types of powders with particle sizes below 50 μm were produced using this method. They varied in particle size distribution and particle shape. Mechanical tests were performed with the powders of this size fraction. The equivalent particle diameter distribution, morphology, and changes in elemental composition of the powders were studied. Distribution characteristics, including d10, d50, and d90, were calculated. The arithmetic mean of flat particle projections was slightly higher for the powder atomized employing the conventional mode (0.6 MPa), measuring 0.914 compared to 0.901 for the powder particles atomized under the calculated mode. The yield of the <50 μm fraction was lower (6 and 55 wt.

Радченко О. К., Гогаєв К. О., Аскеров М. Г., Воропаєв В. С. Кутові параметри осередку деформації під час прокатування металевих порошків (огляд) Зважаючи на складність процесу прокатування порошків, а також те, що існує потреба прогнозування режимів прокатування нових порошків та складних порошкових систем, встановлення кутових параметрів осередку деформації є актуальною задачею. Особливо важливим є знання кутових параметрів при оптимізації режимів прокатування у випадках коли ця операція є останньою при одержанні готового продукту. В огляді розглянуто кутові параметри, що характеризують симетричний осередок деформації при прокатуванні металевих порошків у валках з гладкою поверхнею. Показано, що прокатування металевих порошків є складним процесом, для опису якого в різний час були запропоновані різні кутові параметри. Розглянуто 11 кутів, їх назви, опис, методи визначення та розрахунку. Більшість з них мали кілька назв з яких обрані найбільш вдалі. Для трьох з них запропоновані нові назви, що повніше характеризують їх фізичну сутність. Проаналізовано величини кутів для різних порошків та різних методик їх вимірювання. Встановлені параметри від яких залежать кути, що розглядаються. Найбільш повно досліджено кут захвату порошку. Для кута захвату, за наявними літературними даними, параметри від яких він залежить ранжовані за їхньою значимістю. У порядку зменшення ступеня впливу досліджених параметрів кут захвату залежить від коефіцієнта тертя валок-порошок, коефіцієнта бічного тиску; відносної насипної щільності порошку; ширини бункера та зовнішнього зусилля, що прикладають до порошку. Залишився недослідженим вплив на кут захвату фізико-механічних властивостей матеріалу частинок. До існуючих кутів доданий кут випередження, який у парі з кутом відставання охоплює увесь осередок деформації. Показано, що співвідношення кутів відставання та випередження може бути використане для характеристики таких ознак осередку деформації як симетричність та наявність переднього натягу, а також може характеризувати пластичні властивості матеріалу частинок.

The influence of ground R6M5K5 tool steel powder in mixture with gas-atomized powder on the process properties of the powder mixtures was studied. Both powders were sifted through a 50 μm sieve. The ground powder was present in amounts of 0, 10, 20, 30, 40, 50, and 100

The production of powders with predetermined particle sizes is an important task in various branches of powder metallurgy and is especially relevant in additive manufacturing, where powders with an equivalent particle diameter smaller than 50 μm are used. The following parameters were calculated in the paper: theoretical gas flow speed to produce particles of required size by gas atomization of superheated fluid metal; specific flow rate of the metal flowing out of the metal tundish, and atomization nozzle parameters (such as critical and outlet cross-sectional areas and their ratio). Gas dynamics methods, being widespread in aviation engineering, were used to calculate the nozzle. The supersonic Laval nozzle parameters and gas dynamic parameters for atomization of the molten 10R6M5 tool steel were calculated at gauge gas pressures ranging from 0.5 to 2.0 MPa, allowing fine powders to be produced, including those with a particle size smaller than 50 μm. Graphical dependences were plotted to illustrate the theoretical speed at which particles of required size formed and the gas speed calculated as a function of the gas pressure before the atomization nozzle. A graphical method for determining the cross-sectional areas of the Laval nozzle and the inert gas flow speed for a given gauge pressure in the studied range was proposed. The following parameters for the production of 10R6M5 tool steel powders with a particle size smaller than 50 μm by gas atomization were established: gas flow speed at the nozzle outlet of 525 m/sec, temperature of –140°C, and pressure higher than 16.8 MPa. The calculated critical and outlet cross-sectional areas of the Laval nozzle were 110 and 290 mm2 and their ratio was 0.379.

Powder processing of the P6M5K5 alloy in rolls of the rolling mill has been performed. There was no contamination, and the oxygen content was not increased during the processing. Processing of the sprayed powder of the P6M5K5 alloy was carried out on a two-roll press DUO 180 with a speed of rotation of 10 rpm. Only one of the rolls was rotating, which made it possible to carry out a combination of three types of impact on the material - compression, impact, and abrasion. The gap between the rolls was zero. The number of processing passes varied from 5 to 20. For the use of powder in 3D printers, the optimal fractional composition of the powder is from 50 μm to 160 μm. The fractional composition of the powder was measured by its dispersion on a vibrating sieve analyzer of the ROTAP type. Since the process of destruction of any brittle material depends on their initial properties, the grinding of this material on a rolling mill cannot be quantitatively unambiguous. In processing the powder, rolling of the powder dominated, and the particles themselves were not easily destroyed. The reason for this turned out to be insufficient rigidity of the DUO 180 rolling mill for this powder. As a result of the processing of the P6M5K5 powder in the rolling state, the fluidity of the powder significantly decreased by more than 2 seconds from 22 s to 20 s, which is 10%. This is evidence that a rolling process took place, which led to a decrease in the number of satellites. Five cycles of processing the powder in the rolling mill were enough to reduce the fluidity by 10%. Increasing the number of processing cycles to 20 did not change the fluidity of the powder, but led to its slight grinding. Keywords: P6M5K alloy powder, rolling, grinding, fractional composition of the powder.

There are five 3D printing methods that use metal or alloy powders. The most promising methods are powder bed fusion, directed energy deposition, and binder jetting. General requirements for the powders and their most important characteristics (particle size and shape, powder flowability), as well as the chemical composition of nickel alloy powders from two manufacturers, are addressed. Features peculiar to the behavior of powders in use of two types of recoater (as a blade or a roller) are analyzed. It is shown that the d90 size does not meet the actual requirements and dmax needs to be taken into account instead. Powders with nonspherical particles (mixtures of spherical and nonspherical particles) are known to be reused, but there are still no clear recommendations for their use. Inadequate attention is paid to the shape of powder particles. In additive manufacturing processes, powders with nonspherical particles (produced by grinding and other methods) have been already used but, in most cases, the shape indicators or their dispersion are not determined. Basic criteria for the particle shape that correlate with the powder flowability should be identified. The standard flowability value (determined by flow test) does not adequately characterize the dynamic behavior of powders, nor does it allow the powders with significantly different bulk densities and particle material to be compared, and thus requires adjustment. The most important characteristic for the processes considered is the ability of powders to form a thin flat layer in certain conditions. A new characteristic of the powder dynamic behavior has been proposed: spreadability. It includes two criteria: build plate coverage ratio and powder dynamic flow angle, each having its drawbacks. To date, there is no accepted technique for testing spreadability, nor is there an agreed indicator that would characterize it. There is only an understanding that a research method should best reproduce the powder behavior in a 3D printer in operation. Methods such as powder drum rotation (GranuDrum instrument) or long-established classification of pharmaceuticals by flowability, which was tried to be applied to metal powders, are involved. According to the classification, excellent flowability is inherent in powders having an angle of repose varying from 25 to 30 deg, Hausner ratio lower than 1.11, and Carr index lower than 5–15. The validity of this application requires thorough verification. The advantages and disadvantages of the following basic methods for producing powders of various metals and alloys used in 3D printers are addressed: gas atomization of melts in crucibles without vacuum and with vacuum melting or induction melting, plasma atomization using feedstock rods, rotation electrode gas or plasma atomization, etc. Gas atomization as a commercial method remains the most popular. Powders of greater quality made from reactive elements allow the production of new high-quality parts but also involve additional costs.

A method for assessing the powder explosibility was developed using analysis of dispersed powder distribution in reaction vessels, combustion propagation, and comparative tests of atomizers. Dependences of the maximum explosion pressure on the concentration of dispersed particles and oxygen content in mixtures with nitrogen and other inert gases determined with a 4-L experimental facility of the Frantsevich Institute for Problems of Materials Science (IPM) were examined. The experimental data were used to study the effect of reaction vessel sizes on the maximum explosion pressure and maximum rate of explosion pressure rise. The applicability of the cube root law for geometrically similar vessels, the similarity criteria for dispersed gas flows (including the homochronism criterion for turbulent flows) being obeyed, was shown. The metal powders were categorized in accordance with the modified explosion index based on combustibility and explosibility characteristics and calculated in relative units with regard to the explosion hazard of silicon powders. The irregular gas distribution substantially affected the accuracy of the explosion characteristics. In compliance with the IPM method, the explosion characteristics are corrected by the concentration factor, characterizing the dispersed powder distribution in the reaction vessel. Incomplete disintegration of powder particle aggregates by a mushroom-shaped atomizer and their incomplete combustion (apparatus of the United States Bureau of Mines) led to underestimation of the maximum explosion pressure and overestimation of the lower concentration ignition limit, while the dispersed powder concentration was calculated as the ratio between the dispersed powder weight and vessel volume.

The effect of the chemical structure of interpolyelectrolyte complexes (IPEC) based on polymers of natural origin (pectin--chitosan+, pectin--cationic starch (starch+), carboxymethylcellulose (CMC-)-cationic β-cyclodextrin (β-CD+), anionic starch (starch-)-cationic starch (starch+) on the structure, morphology, thermomechanical and antimicrobial properties of silver-containing nanocomposites obtained by thermochemical reduction of Ag+ ions in interpolyelectrolyte-metal complexes (IMC) was studied. Thermochemical reduction of Ag+ ions in the IMC bulk for 30 min at 150 °C led to formation of silver-containing nanocomposites and this fact was confirmed by wide-angle X-ray scattering method. Transmission electron microscopy showed that different sized of silver nanoparticles were formed depending on the chemical structure of IPEC. The average size of silver nanoparticles was found to be 4.7 nm for pectin--Ag-chitosan+; 5.3 nm for pectin--Ag-starch+; 6.3 for CMC--Ag-β-CD+ and 9 nm for starch--Ag-starch+, correspondingly. The nanocomposites having smaller average nanoparticle size exhibited higher antimicrobial activity against S. aureus and E. coli strains. Pectin--Ag-chitosan+ nanocomposites formed by thermochemical reduction of Ag+ ions showed that the diameter of the inhibition zone against S. aureus and E. coli strains was 19.7 and 32.6 mm, respectively, whereas these values were 15.6 and 14 mm, respectively, for the same nanocomposites obtained by chemical reduction using ascorbic acid.

The results of researches on steel 4H4N5M4F2 modes thermo-deformation processing optimization are given. It is established that incomplete annealing (750 °С ± 20 °С in comparison with full annealing 860 °С) in cast and forged condition promotes to improve the machining of blanks for the manufacture of matrices. It is shown that the use of incomplete annealing, namely partial recrystallization promotes the formation of spheroidized rather than lamellar carbide phase, which leads to a decrease in the characteristics: strength threshold, yield strength, hardness 900 MPa, 800 MPa, 32 33 HRC in the cast state and 1200 MPa, 1050 MPa, 38 39 HRC in forged condition, respectively. This increases the fracture toughness: 180 J/cm2 in the cast state and 130 J/cm2 in the forged state. The optimized mode of forging at the temperature of 1170 ± 20 °С and heat treatment (hardening at 1100 ± 5 °С and tempering at 595 ± 5 °С) of steel 4H4N5M4F2 allowed to increase impact strength five times in comparison with cast experimental steel, and also to increase strength threshold of 100 MPa. Forged steel 4H4N5M4F2 has slightly lower heat resistance compared to cast, which hardens at temperatures above 630 °C during operation of the die steel tool. After operation of the extruder wheels made of investigated forged steel and forged steel 4H5MF1S, which was used at the enterprise in copper processing, the properties of both steels were determined. The investigated forged steel 4H4N5M4F2 is characterized by an increase in the strength threshold by 200 MPa and hardness by 6 HRC. After operation (production of 60 tons of copper products of M1 grade) the tool (wheel extruder) from H13 steel (analog 4H5MF1S) had micro and macrocracks on the side and inner parts, and in the investigated steel 4H4N5M4F2 such defects were absent. Thus, the studied steel is characterized by increased stability. Keywords: steel, heat treatment, forging, structure, physical and mechanical properties.

The ligature for finishing of base steel 3H3M3Ftype for obtaining steel 4H3N5M3Ftype with adjustable austenitic transformation is developed in the article. The phase-structural state of steel in the cast state is investigated. The uniform distribution of alloying components on the body of grains is shown. It was found that the investigated hardened steel is softening above the tempering temperature of 620 °C, because the heat resistance of steel decreases (below 40 HRC). It was developed a 3H3M3F base steel ligature for steel production with adjustable austenitic transformation of 4H3N5M3F brand. Ingots (ligature of the Fe―Ni―Mo―V―Mn system) weighing 25 kg were obtained. The ligature was obtained by means of an induction furnace in a casting mold. The temperature of the metal in the furnace before release was 1550 °C. The duration of refining did not exceed 20 minutes. The phase-structural state of cast steel is studied. The uniform distribution of alloying components on the body of grains is shown, as well as the absence of coarse carbide eutectic in metal. This allows to reduce energy-intensive technological operations (diffusion annealing, forging) for the die toolsmanufacture. The presence of martensitic structure in the steel in the cast state of the investigated ingot requires the main thermal operation — annealing. It is established that incomplete annealing at a temperature of 750 ± 20 °C under the condition of partial recrystallization of the investigated steel allows to improve the mechanical processing (cutting) for the production of the die tool. It was determined that the investigated hardened steel hardens above the tempering temperature of 620 °C, because the heat resistance of steel decreases (below 40 HRC). Thus, a die tool of the investigated steel for hot deformation, capable of operating up to the temperature of 620 °C. Keywords: steel, ligature, temperature, structure, hardness.

In the work, the heat treatment conditions of 4H4N5M4F2 die steel for hot deformation are investigated. The physico-mechanical properties of the investigated ingot steel were determined after quenching 1100 ± 5 °С and tempering. Given the importance of cooling regimes after tempering, various cooling regimes (in oil, in a furnace, in air) were investigated. Physical-mechanical properties of cast steel 4X4H5M4F2 after tempering at 550 ± 5 °C and 600 ± 5 °C were determined. The optimal tempering regime for steel at 550 ± 5 °C with air cooling was established: the ultimate strength of 1860 MPa and the yield strength of 1760 MPa. The optimal tempering regime for steel at 600 ± 5 °C with air cooling has been established: the ultimate strength is 1600 MPa, the yield strength is 1500 MPa, and the heat resistance is 48.5 HRC. It was established that twofold hardening and tempering of steel at 600 ± 5 °C temperature with oil cooling leads to an increase in its fracture toughness (75 J/cm2) compared with the fracture toughness after air cooling (30 J/cm2). It is established that the temperature range of tempering brittleness of the studied steel is 465 ‑ 495 °С. The optimized temperature regime of tempering of the investigated steel (590 ± 5 °С) made it possible to increase the impact strength by a factor of two (up to 30 J/cm2) in the temperature range 465 ‑ 495 °С. A pilot test of the punch tool made from the investigated steel was carried out. During hot pressing of the AK7ch aluminum alloy, the life of the dies was at the level of forged steel 4Kh5MF1S with a nitrided surface layer, which was used at the factory. After the operation of both matrices (hot deformation), samples were cut and tested for hardness and toughness. The latter turned out to be higher for the forged steel, however, the service life of the matrices from both steels was at the same level.

Structural organization and antimicrobial properties of nanocomposites based on chitosan, anionic β-cyclodextrin (βCD) and Ag nanoparticles, being formed by the chemical reduction method from interpolyelectrolyte-metal complexes (IMC) chitosan-Ag + -anionic βCD have been investigated. It is defined that chemical reduction of Ag + ions by NaBH 4 in the interpolyelectrolyte complex results to formation silver-containing nanocomposites. The antimicrobial investigation of the elaborated nanocomposites revealed they possess a high antimicrobial activity against S. aureus and E. coli strains.

Steels with adjustable austenitic transformation during the exploitation (RAPE) are designed for applied in the temperature range of 800 – 950 °C, which corresponds to the austenitic structure, but at the lower temperature range (630 – 650 °C) tempering fragility of the second kind occurs, which makes it difficult to operate. This is inconvenient when the die tool works in a wide range of temperatures during deformation of various metals and alloys. An improved steel composition (4H4N5M3F2) (RAPE) for press molds for hot pressing of copper and its alloys at temperatures of 630 – 650 °C is proposed. Steel was obtained by electroslag remelting, it was heat treated and the properties were determined. It is shown that the heat resistance of the investigated steel is higher by 2 HRC than the heat resistance of steels grade 4H5MF1S and 3H3M3F, which are used under the same operating conditions. The yield strength and impact strength of steel 4H4N5M4F2 considerably exceeds the characteristics of steel 3H3M3F (high –grade rolled products). The annealing temperature limits, which allow obtaining the necessary technological properties of steel, were established. It is shown that the steel structure consists of two areas: dark (obviously it is released martensite) and light (the area with a lower content of the carbide component). With an increase in tempering temperature from 640 to 660 °C, the hardness (HV) of the dark and light components decreases from 478.6 to 459.8 and from 427.8 to 376.0, respectively. The heat resistance of the investigated steel after quenching and tempering in optimal conditions increased to 650 °C (41 HRC).

В останні десятиліття використання магнітних наночастинок було поширене на багато видів застосувань і областей, таких як традиційні електричні, оптичні і магнітні області, і розширилося до декількох нових застосувань, включаючи магнітокеровані біосепарацію і біокаталіз, також сорбцію токсичних аніонів та катіонів, напр., As (V), Cr (VI) і U (VI). Основною екологічною проблемою, у зв´язку з промисловим використанням барвників, є забруднення стічних вод. Як природні сорбенти на даний час досить перспективними є полімери на основі β-циклодекстрину (β-ЦД), за рахунок їх унікальної здатності формувати комплекси-включення з різноманітними органічними речовинами. Отримання магнітокерованих полімерів на основі β-ЦД має забезпечити швидке та достатньо просте відділення та видалення забруднюючих речовин із забрудненого середовища шляхом дії зовнішнього магнітного поля без додаткового центрифугування або фільтрації.

Показано, що структура загартованої сталі 40Х3Н5М3Ф при нагріванні від кімнатної температури до температури експлуатації (800С) змінюється: мартенситна структура перетворюється на аустенітну.Залежність кількости аустеніту від температури близька до експоненційної.Підтверджено, що в інтервалі температур експлуатації

The paper examines the mechanisms that contribute to the strength of green compacts produced and tested in different thermal conditions (different homological temperatures of Sn, Zn, Cu, Ni, and Mo powders compacted and tested in normal conditions). The role of powder particle shape is demonstrated using scanning electron microscopy to analyze images of the particles and fracture patterns of the compacts. Partial plastic fracture is found only in the Sn powder sample. When plastic powders with irregular, branched particles (Cu, Ni) are compacted, the mechanism of adjusting particle surfaces to one another prevails and leads to all three mechanical components: interlocking, entangling, and seizing. When plastic powders with spherical particles are compacted, deformation of particles prevails. The ratio of the tensile strength of compacts (σb.i) determined indirectly to the tensile strength (σb) of particulate material shows a semilogarithmic dependence on the ratio of compacting pressure (P) to the yield stress (σ0.2) of the particulate material. The dependence of the ratio of σb.i to the elastic modulus on the homological temperature of compacting and testing divides into two linear dependences for spherical and nonspherical particles.

Modern approaches to calculating the strength of green compacts by van der Waals forces (σVW) are reviewed. Respective components (σVW) are calculated and green tensile strength (σtl.av) is experimentally determined for test powders of metals (Al, Zn, Cu, Ni, and Mo) and one nonmetal (FeSi). Comparison of σtl.av/σVW ratios shows that σtl.av and σVW are of one order for the atomized zinc powder, and σVW is greater than σtl.av for the atomized copper powder, though σtl.av is greater than σVW by two to three orders for most powders with irregular shape of particles. This difference can be attributed to the effect of shape and mechanical interlocking or seizure of particles when compacted. To predict the green strength, it is necessary to take into account both the shape of particles (or relative apparent density of the powder) and the forming temperature.