The purpose of this study is to obtain highly dispersed powder suitable for spheroidization for further application in additive technologies. Volumetric reduction of the FeCl₂–CaCl₂ melt by calcium dissolved in CaCl₂ produced fine iron powder. The process consisted of three stages: preparation of melts containing FeCl₂ and Ca, their mixing and high-temperature aging at 800 °C for 1 hour. At the end of the process the frozen melt was divided into upper and bottom parts. The product from the upper part had a specific surface area of 7,60 m²/g, and for the lower part it was 5,38 m²/g, Average particle size was 157 μm for the former and 124 μm for the latter. After ultrasonic dispersion, it was reduced to 26 μm and 71 μm, respectively. Quantitative X-ray phase analysis showed that the main phase of powder is metallic iron (more than 97 wt.%). Therefore, research originality is the use of volumetric, intensive reduction of iron from chloride melts by calcium dissolved in its chloride. The uniqueness of the study consists in the product obtained, i.e. the main part of reduced iron is in the melt volume as linear aggregates 40 to 600 μm in length, 10 to 50 μm in diameter that are easily broken by ultrasonic dispersion into individual crystals with an average size of 26 μm. The results of the study demonstrated the feasibility of calcium-thermal production of fine iron powder.

The main problem in the production of bimetals (BMs) is the need to ensure adhesive interaction at the contact boundary of layers to prevent their peeling during operation. Hot forging of porous preforms (HFPP) provides the possibility of obtaining high-density powder BMs with a minimum amount of pores both in the volume of the layer material and at the layer interface to increase adhesion strength. Production of hot-forged powder BMs may involve mixing of working layer and substrate charge materials, which can lead to uncontrolled interface «blurring». This study uses the previously proposed method for pre-pressing of hard-to-deform material powder to produce «structural steel – high-speed steel» porous BM preforms. Two-layer cylindrical ∅20×30 mm samples were obtained in order to determine mechanical properties and conduct structural analysis. The BM base material was PK40 steel, and the working layer was atomized powder of M2 high-speed steel featuring satisfactory compressibility properties. The porous preforms of BM samples were pressed in a specially designed mold at a hydraulic press enabling two-sided pressing of two-layer powder moldings with predetermined distribution of layer densities and strengths. Cold-pressed BM preforms were sintered in protective environment, and then subjected to hot repressing using a laboratory drop hammer. Some preforms were examined as sintered. In addition, hot repressing of cold-pressed green preforms was performed. Satisfactory process strength of the working layer material is observed at its porosity (P_wl) in the range from 34 to 45 %. When P_wl > 45 %, powder is not molded, and at P_wl < 34 % the working layer delaminates. The maximum layer bonding strength and thermal shock resistance of BM provides the use of a flow route that involves preliminary sintering of cold-pressed preforms and subsequent hot forging. The optimum pressure of working layer pre-pressing is 145 MPa.

The paper presents the experimentally determined heating temperature of mixed chromium carbide powders and titanium bond under explosive loading on a metal substrate. Pressure of powder mixture compression in shock waves during explosive pressing was 2,5 GPa. The experiment involved recording a thermal cycle on the back side of the coated metal substrate serving as a heat receiving element. It also solved a problem of non-stationary heat conduction until the calculated and experimental thermal cycles coincided. Initial conditions were chosen assuming that the compacted material is uniformly heated to a certain average temperature by the time the shock-wave processes end. Required thermophysical properties of the compacted material were determined by the laser flash method using the LFA 427 unit («Netzsch», Germany). According to calculations, powder mixture heating temperatures were 208 °C and 225 °C for adiabatic approximation and taking into account heat transfer into the environment, respectively. The obtained values were compared with ones calculated by the increase in enthalpy during the shock wave processing (these calculations used solid material densities under normal conditions and final powder material density determined after explosive treatment to be 199 °C and 220 °C, respectively), and it was found that they differ insignificantly. Thus, the assumption of equal material density in a shock wave and solid density does not lead to a significant error and can be used for practical calculations.

The paper studies the effect of doping with manganese powder on the production of (Al–2%Mn)–10%TiC and (Al–5%Cu– 2%Mn)–10%TiC nanostructured composite alloys by self-propagating high-temperature synthesis (SHS) of TiC titanium carbide nanoparticles from Ti + C charge in the melt of matrix alloys. First, manganese metal powder was added to the matrix bases of Al and Al–5%Cu composite alloys in the amount of 2 wt%. This improved aluminum base tensile strength from 81 MPa (for the original A7 grade aluminum) to 136 MPa and aluminum-copper base tensile strength to 169 MPa. It was found that when aluminum was doped with manganese only, the SHS reaction proceeded weakly and not completely, and the carbide phase size in the resulting alloy (Al–2%Mn)–10%TiC varied from nanoscale to several micrometers. When 10% Na₂TiF₆ halide salt was added to the SHS charge, the SHS process intensified, but the resulting alloy contained a considerable amount of pores, inclusions of unreacted charge and large agglomerates of TiC ceramic nanosized particles. Similar results were obtained in cases of using Ti + C and Ti + C + 10%Na₂TiF₆ SHS charges, but with joint doping of matrix aluminum with copper and manganese, providing more uniform distribution of the TiC nanodispersed phase. The best results were obtained by reducing the Na₂TiF₆ salt additive to 5 % of the SHS charge mass, which facilitated smoother and complete synthesis of predominantly TiC nanosized particles and the formation of a non-porous uniform microstructure of (Al–5%Cu–2%Mn)–10%TiC composite alloy with an ultimate tensile strength of 213 MPa and 6,6 % elongation.

The possibility of joining ceramic materials with a Ta substrate was explored in the conditions of self-propagating high-temperature synthesis (SHS). The sample used in experiments consisted of Ta foils, Ti + 0,65C pellet, 5Ti + 3Si pellet, and a Ti + 2B igniting tape laid between them. The sample was installed onto a BN base and covered by a chamotte brick (SiO₂ + Al₂O₃) plate with a weight of 3,36 kg placed on top in order to reduce heat sink. Experiments were performed in a closed reactor under 1 atm of Ar. Samples were preheated from the bottom, after which SHS reaction was initiated from the butt. Temperature was monitored with three W/Re thermocouples. Depending on heating rate, temperature gradient along the sample depth had a value of 50–150 deg/mm. The samples obtained exhibited strong joining between Ta foil and Ti + 0,65C and also between the two pellets. The upper foil did not stick to the 5Ti + 3Si pellet, which can be explained by low temperature at the interface (1600 °C). At the Ta–TiC interface, the formation of Ti–Ta and (Ti, Ta)C interlayers was observed. The studies conducted demonstrate the possibility of Ta foil joining with ceramic materials under SHS conditions. Main conditions for this joint are the presence of a liquid phase and Ti + 0,65C combustion temperature matching the Ta substrate melting temperature. The results may be useful for deposition of multilayer functional coatings and functionally graded materials.

The paper provides experimental research and mathematical models of wave synthesis and thermal explosion in a thin-layer CuO–B–glass system. It is found that burning front propagation has a multi-source behavior and its rate depends on reacting layer thickness by the parabolic law with a maximum at d = 4·10^–4 m. Increased reacting layer thickness improves thermal explosion properties in this system, and dilution with an inert component makes it possible to obtain copper coatings featuring good electrical conductivity. X-ray phase analysis and optical microscopy demonstrated that the coating consists of metallic copper drops fused together and surrounded by boron-lead silicate glass melt. Coatings have high electrical conductivity comparable with that of metals. It is found that layer thickness increased over 4·10^–4 m results in a significantly reduced layer propagation rate due to initial mixture loosening under the evaporation effect of water vapors and gases adsorbed on powders, and, as a consequence, it results in reduced heat transfer in the burning front. These coatings are not electrically conductive. Mathematical models of wave synthesis and thermal explosion in a thin-layer CuO–B–glass system using macroscopic approximation. Process dynamics are numerically calculated. Theoretical estimates correspond satisfactorily to experimental values. Thermophysical and thermokinetic process constants are determined by the inverse problem method. Experimental data obtained and mathematical models developed made it possible to obtain prototypes of electric film heaters with high electrical conductivity and operating temperature.

The paper presents the results obtained when studying static tensile strength of aluminum-based cast dispersion-hardened composites with a different content of the Al₂O₃ strengthening phase. The investigated materials are manufactured using a fundamentally different technology for the production of cast dispersion-hardened aluminum composites based on the process of burning out the aluminum melt when interacting with oxygen or an oxygen-nitrogen mixture. The fractographic patterns of static failure surfaces are stidued on samples failed at maximum stress values. It is found that samples with the low Al₂O₃ content have a purely viscous failure pattern consisting mainly of a single fibrous zone. The fracture pattern shows a radial area with a solid phase doubled, while a tripled Al₂O₃ content causes viscous failure by the separation and shear mechanism alternated with brittle cleavage failure signs. The fracture profile diagrams of samples containing 10 % and 30 % of solid phase inclusions reveal no sharp relief differences, but demonstrate a completely different failure pattern. However, in both cases profile diagrams feature no any abrupt jumps in the relief or extreme profile values, so it is possible to assert that failure processes are stable. This is not true for the 20 % Al₂O₃ sample failure showing a rather significant one-time drop. Optical microscopy reveals features of changes in the failure surface relief and the difference in the location and number of fracture origins in the studied samples.

The paper studies the structure, elemental and phase composition of the diamond-matrix interface in a diamond tool for abrasive wheel dressing manufactured using a new hybrid technology that combines thermal diffusion metallization of diamond with chromium and sintering of a matrix based on WC–6%Co carbide powder mixture with copper impregnation in a single cycle of vacuum furnace operation. During matrix sintering, the compact arrangement of chromium powder particles around diamond grains and the shielding effect of copper foil create favorable conditions that ensure the thermal diffusion metallization of diamond. Scanning electron microscopy, X-ray diffraction, and Raman spectroscopy show that temperature-time modes and sintering conditions specified in the experiment provide for a metal coating chemically bonded to diamond that is formed on the diamond surface and consists of chromium carbide phases and cobalt solid solution in chromium providing durable diamond retention in the copper-impregnated carbide matrix. In this case, matrix structure and microhardness except for areas directly adjacent to the diamond-matrix interface remain the same as for the matrix of a powder mixture sintered without chromium. Comparative tests of similar diamond dressing pens were carried out and showed the high effectiveness of the hybrid technology in obtaining diamond-containing composites intended for tool applications. It is shown that the specific productivity of a pen prototype made using the hybrid technology was 51,50 cm³/mg when dressing a grinding wheel of green silicon carbide that is 44,66 % higher than the similar indicator for the sametype check pen made by the traditional method.

The comparative study covers the features of formation, thermal stability of structure and mechanical properties of heatresistant Ni and Fe based alloys obtained using additive technologies (AT) by direct metal laser sintering, selective laser melting. It is found that alloys obtained by direct metal laser sintering have a cellular structure formed with small pores up to 200 nm in size, in contrast to alloys obtained by selective laser melting having elements with a globular and lamellar morphology and not completely melted areas as well as large pores about 5 μm in size. The study reveals a possible effect of nanophase hardening due to the presence of nanosized particles of chromium silicides in the material. A comparative analysis of the mechanical properties of studied materials is carried out. It is shown that the iron-based alloys have higher strength and lower ductility compared to nickel alloys. All studied samples obtained by selective laser melting demonstrate higher strength characteristics in comparison with alloys obtained by laser metal deposition. As a result of short-term annealing at a temperature of 900–1000 °C for 1 h leads to a significant reduction in the plasticity and strength of iron-based AT alloys during tensile and compression tests at room and elevated temperatures. During compression tests at t = 900 °C, iron-and nickel-based alloys obtained by laser metal deposition have similar strength characteristics. Unlike iron-based alloys, additional annealing of nickel-based AT alloys has virtually no impact on its strength properties.

The study focuses on the radiation resistance of a composite filled with fine tungsten powder having the 200–500 nm particle size. The studied composite is designed to provide radiation protection of electronic equipment. A sample with the test material was exposed to continuous spectrum X-ray radiation to an absorbed dose of 3 MGy. A characteristic of radiation resistance was sample microhardness measured before and after X-ray irradiation. Scanning electron microscopy was used to study the microstructure of a sample transverse cleavage after irradiation, and it was found that the sample had no visible defects in its structure. This result can be explained by uniform energy dispersion from local stresses due to high degree of composite filling with tungsten powder having a high thermal conductivity coefficient. The study of sample microhardness showed its 10 % increase attributable to the radiation hardening effect where increasing strength results in a simultaneous increase in microhardness. Experiments proved that this effect is manifested with an increase in the absorbed radiation dose.

Magnetron sputtering was used to obtain single-layer MoSi₂, MoSiB and multilayer MoSiB/SiBC coatings. Coating structures were studied using X-ray phase analysis, scanning electron microscopy and glow discharge optical emission spectroscopy. Mechanical properties of the coatings were determined by nanoindentation. The coatings were tested for oxidation resistance and thermal stability at temperatures between 600 °С and 1200 °С. It was found that single-layer MoSiB coatings have a hardness of 27 GPa, elasticity modulus of 390 GPa and elastic recovery of 48 % and exhibit short-term oxidation resistance up to 1500 °С inclusive due to a SiO₂-based protective film formed on their surfaces. MoSi₂ coatings have hardness comparable to that of MoSiB but slightly lower oxidation resistance. Multilayer MoSiB/SiBC coatings feature 23–27 GPa hardness and oxidation resistance limited to 1500 °С, but at the same time they have higher elastoplastic properties as compared to MoSiB.