The process of porous iron powder spheroidization in microwave discharge and combined microwave and DC discharge modes in nitrogen and helium plasma was studied with powder particle sizes ranging from 45 to 85 μm. The powder was obtained by air spraying and subsequent hydrogen annealing. Plasma spraying produced hollow spheroidized particles with a wall thickness from 1 to 10 μm. The share of spheroidized powder particles in their total volume was determined. It was found that microwave power rising from 1.5 to 5 kW leads to a linear increase in the spheroidization degree of iron powder particles. When working in the hybrid plasmatron mode, microwave radiation conditions are combined with a DC discharge and make it possible to increase the plasma temperature. When the ratio of microwave and DC discharge power is 1 : 1, virtually 100 % iron powder spheroidization is obtained. The metallographic study of spheroidized particles showed that their final size differs from the initial one by about 10 times. It was found that iron powder oxidation occurs regardless of the spheroidization mode. This is due to the insufficient purification degree of plasma gases. The structure of particle surfaces when using nitrogen or helium as a plasma gas is different. Experiments showed that the use of helium is more preferable, since the particles have only a slight roughness in comparison with the particle structure during nitrogen spheroidization.

The paper presents the results obtained when studying particles of aluminum-modifier-quartz composites by different physicochemical methods after mechanochemical treatment (MCT) in a planetary centrifugal mill. Graphite (C), polyvinyl alcohol (PVA) and stearic acid (SA) were used as modifiers. To increase the dispersibility of plastic metal powders in the composition (modifier metal), MCT was carried out in the presence of quartz with its mass fraction in the composite ranging from 5 to 20 %. The most significant grinding of aluminum particles was observed with an increase in the graphite content from 5 to 20 %, and SiO2 from 5 to 10 % in the composition of aluminum-modifier-quartz composites. The particle size decreases, while the crystallite size increases with an increase in the quartz content in the composite during the Al–SA–SiO2 system MCT. Al–SA–5%SiO2 showed the maximum defectiveness of aluminum after MCT. For the Al–PVA–SiO2 composition after MCT, an increase in the particle size and, accordingly, a decrease in the specific surface were observed at sufficiently low crystallite size values. It was shown that with an increase in the quartz content in the system, the defective crystal structure of aluminum particles increases as a result of MCT. In this case, the synthesized powder material is a composite formation of aluminum and quartz particles bound by a polymer obtained from polyvinyl alcohol. As a result of Al–modifier–SiO2 mixture MCT, powder activity increases due to the accumulation and redistribution of defects in aluminum particles, as well as changes in the surface structure occurring after modifying additives penetration into the oxide layer to be destroyed. A conceptual model for the transformation of the surface layer and subgrain structure of aluminum particles as a result of MCT is presented.

The TiC + Al binder metal matrix composites were obtained by self-propagating high-temperature synthesis (SHS) in the reactive powder mixtures of titanium, carbon (carbon black) and aluminum. It was found that a steady-state wave combustion occurs when the aluminum powder content in reactive mixtures does not exceed 50 wt.%. Loose SHS cakes obtained during synthesis were crashed and screened to get lumpy, nearly equlaxial composite powders favorable to good flowability necessary for powder application in cladding and spraying of wear-resistant coatings. The synthesis products were studied by scanning electron microscopy, X-ray diffraction (XRD) and local energy-dispersive X-ray spectroscopy (EDX). It was found that the average size of carbide inclusions in the composite structure depends on the content of thermally inert aluminum powder in the reaction mixtures. The titanium carbide lattice parameter determined by XRD turned out to be slightly below the known values for equiatomic titanium carbide. However, no any dependence of the lattice parameter on the aluminum content in composites was found. TiC inclusions in the composite structure were investigated by EDX spectroscopy. Titanium content in the carbide was close to that in equiatomic titanium carbide. Titanium carbide contains up to 2.5 wt.% aluminum in addition to titanium and carbon. Aluminum dissolution in the carbide lattice can influence the lattice parameter.

The TiN/TiAl3/Ti2AlN composite material was obtained by filtration combustion of the porous TiAl intermetallic samples in gaseous nitrogen. X-ray phase analysis of combustion products provided data to calculate the weight content of each phase as follows: 42 wt.% TiN, 35 wt.% TiAl3, 20 wt.% Ti2AlN and 3 wt.% TiAl. The synthesized composite material containing Ti2AlN МАХ phase features good electrical conductivity of a metallic nature. Specific electrical resistance of the synthesized material was measured by a standard 4-point procedure at constant current in the temperature range 300–1300 K in vacuum 2·10–3 Pa. It was found that specific electrical resistance grows linearly from 0.35 to 1.25 μΩ·m as temperature rises. Subsequent measurements of this indicator at the following heating/cooling cycles demonstrated full agreement of obtained results. This fact indicates that the material has stable electrophysical properties in the investigated temperature range.

The article presents the results obtained in the corrosion resistance study of TiB2/TiN eutectic alloy powder in HCl and HNO3 mineral acids. Experiments were carried out on samples synthesized in the combustion mode and then ground in an agate vessel. The morphology, size distribution and specific surface area of particles were determined in the obtained powder samples. Corrosion resistance experiments were conducted with varying acid concentration from 0.2 to 6.0 M and process temperature from 25 to 80 °C. Chemical analysis of the studied products of interaction with an aggressive medium was carried out to determine the content of main elements in them (titanium, boron, nitrogen) using methods developed for refractory compounds. As a result of the work carried out, it was shown that samples have the greatest resistance when interacting with solutions of diluted acids at room temperature, and their resistance decreases as acid concentration and/or process temperature rises. It was found that interaction with the acid occurs with both TiB2 and TiN phases in all cases considered in the paper. At the same time, the reaction involving the TiB2 phase was faster. For the first time deep corrosion and corrosion resistance of the alloy in HCl and HNO3 media were measured at room temperature and 1.0 M acid concentration. Based on the obtained data, the investigated alloy was classified as a «resistant» material. Corrosion resistance by a ten-point scale in HCl and HNO3 media was «4» and «5», respectively.

The study covers the effect of compaction pressure during semi-dry pressing of zirconia nanopowder partially stabilized with yttria in a steel mold on the phase composition and microstructure of compacts and samples sintered at 1400 °C for 2 hours. An aqueous solution of polyvinyl alcohol was used as a temporary process binder. According to X-ray fluorescence analysis, the content of yttria in the powder synthesized by sol-gel technology (precipitation with aqueous ammonia solution from water-ethanol solutions of the corresponding reagents with the agar-agar additive) was 3.2 mol.%. The paper provides the results obtained when studying compacts and sintered samples by Raman spectroscopy, optical and atomic force microscopy. It was found that the increase in their density is not a monotonous process. There is a critical compaction pressure interval of Р = 400÷450 MPa where a sharp change in the material porosity, pore shape and size, microstructure and phase composition occurs. A monoclinic phase was observed in compacted samples along with tetragonal zirconia. Its content varies with a variation in Р values. The grinding of material grains is associated with the agglomerate destruction process and actively occurs in the interval of Р = 350÷550 MPa. A similar effect was observed by other researchers during zirconia nanopowder compaction who suggested that the nanopowder system response to the effect of pressure is related to the influence on the water component (in this case, the temporary process binder) and is due to the transition of one water form to another at 10–25 °С and 400–700 MPa.

The paper presents the results obtained when studying the structure of surfacing materials based on martensitic-aging Fe–Cr– Ni–Мо и Fe–Co–Ni–Мо alloys obtained by plasma powder surfacing. Silicon was chosen as an alloying element, which made it possible to significantly improve the technical and economic performance of martensitic-aging materials. A comparison of martensitic-aging steels with high-carbon steels showed that the former provide an advantage as a wear-resistant material due to their increased resistance to crack propagation. Microscopic analysis, X-ray diffraction analysis and electron microprobe analysis were used for the research. Surfacing materials were tested for wear and internal friction. Silicon oxide particles and chromium and molybdene silicides involved in the process of alloying material strengthening were found during the experiments. Silicide particle density was determined that varies depending on the amount of silicon in the material. The effect of the silicon content on the material hardness was considered. The data obtained on the structure and phase composition of Fe–Cr–Ni–Мо и Fe–Co–Ni–Мо compounds doped with silicon in both the initial and aged states made it possible to suggest a structural-physical model of their hardening in the course of aging. Results of the experiments showed that the heat treatment process actively influences the wear rate and weight wear reducing their values that is typical for both Fe–Cr–Ni–Мо and Fe–Co–Ni–Мо alloys. Based on these data, a structural-technological model of wear was obtained for the surfacing materials studied.

Recent decades jewelry manufacturers put into practice using of non-precious alloys in order to decrease the production costs. Nevertheless, the large number of customers has allergic (sensitizing) body reaction on jewelries. Applying of non-sensitizing coating is able to decrease negative influence of jewelry material on human body. One of the biologically inert materials toward to human body tissues is zirconium. In the present work we examined the zirconium-based coatings applied by magnetron sputtering. Eleven coating regimes of AISI 430 steel substrates by zirconium oxynitride were investigated. Coatings corrosion test in Hank’s solution, microhardness measurements, color performance in CIE 1976 L*a*b* and RGB color spaces were carried out. The coating width was 0.4–1.2 μm. It was established that coatings have microhardness 2.5–3.0 GPa and can simulate jewelries colors. Using energy dispersive X-ray spectroscopy, it was evaluated that coatings consist of Zr, N and O. We select the sputtering regimes which provides metallic type coatings with the high optical reflectivity in the energy range near the infrared part of spectrum (<1.7 eV) and has golden color with a high lightness. It was experimentally proved that coatings are not corroding in Hank’s solution. The allergy patch test of jewelry with zirconium oxynitride coating demonstrate a good result on respondents with sensitizing reaction to non-precious alloys jewelry. The obtained results allow us to recommend the application of a zirconium-based coating magnetron sputtering in manufacturing of the non-precious alloys jewelry.