The paper studies the combined electroreduction of lanthanum LaCl₆^3–and cobalt CoCl₄^2– chloride complexes in an equimolar KCl–NaCl melt at a tungsten electrode. As it follows from the results of voltampere measurements, potentials of La and Co reduction at a tungsten electrode coated with preliminary reduced cobalt differ by more than 1,0 V. Therefore, the electrochemical synthesis of La and Co intermetallics is possible only in the kinetic regime. The paper develops the method for the high-temperature electrochemical synthesis of lanthanum and cobalt intermetallic powders in halide melts. The paper determines conditions for realization of the combined electroreduction of La³⁺ and Co²⁺ ions, on the basis of which the paper demonstrates the principal possibility of the direct electrochemical synthesis of lanthanum intermetallics. The paper establishes that the electrosynthesis mechanism is determined by electrolysis conditions. Under potentiostatic conditions (when potentials are more negative than potentials for reduction of the more electronegative element – lanthanum) the combined reduction of La and Co takes place, and the synthesis process is determined by the activation energy of the interaction reaction between lanthanum and cobalt at the cathode. In general, the electrosynthesis of La- and Co-based intermetallics is determined by the following interrelating parameters – the composition of the electrolytic bath and the voltage across it. The paper describes the high-temperature electrochemical synthesis of lanthanum- and cobalt-based ultrafine powders of intermetallics кобальта (Сo₃La₂, Сo₇La₂, Co₁₃La) from chloride melts. 

The paper presents the research findings on the formation of amorphous structures in the Cu–Ti system and their subsequent crystallization by highenergy ball milling (HEBM). Copper powders (PMS-V grade with an average particle size d = 45÷100 μm, GOST 4960-75) and titanium powders (PM99.95, d = 2,0÷4,5 μm, TU 48-19-316-80) were chosen as original components for obtaining Cu-Ti amorphous powders. The high-energy ball milling of Cu + Ti powder mixtures was carried out using the Activator- 2S laboratory planetary ball mill (disc rotation rate – 694 rpm; rotation rate of drums – 1388 rpm) for 1 to 30 minutes. The surface morphology and the micro-, nano- and atomic-crystalline structure of activated Cu + Ti powder mixtures were studied by X-ray diffraction (XRD) methods using the DRON-3M, diffractometer by scanning electron microscopy using the Zeiss Ultra + + microscope (Germany) with energy dispersive analysis, and by high resolution transmission electron microscopy (TEM) using the Titan microscope (USA). Thermal characteristics of phase transformations (temperature, heat of reaction, amorphouscrystalline transition) were determined by differential scanning calorimetry using the DSC 204 F1 instrument in a linear heating mode of up to450 °Cat a rate of 20 deg/min. Amorphous Cu-Ti powders were obtained by using high-energy ball milling for 20 min. According to X-ray diffraction data, the fraction of the amorphous phase in the material was 93 %. TEM-based studies showed that the material consisted mainly of an amorphous phase with an insignificant content of nanocrystalline regions sized from 2 to 8 μm. It was found that crystallization of the Cu–Ti amorphous phase occurred in the temperature range of 336–369 °C with the heat of reaction equal to 79,78 J/g. 

The paper presents experimental results on the possibility of obtaining consolidated powdered hard alloys by the method of explosive compacting without subsequent sintering. Tungsten carbide (WC), chromium (Cr₃C₂) and silicon carbide (SiC) were used as main carbides of alloys; titanium, nickel and copper acted as binder metals. The compression pressure of the powder mixture in shock waves during explosive compacting varied in the range from 5 to 16 GPa, the heating temperature was from 250 to 950°C. The structure, chemical and phase compositions were studied using optical (Axiovert 40MAT, Carl Zeiss), raster (FEI Versa 3D) and transmission (FEI Titan 80-300, Tecnai G2 20F) electron microscopes. The paper demonstrates that powder compositions with a titanium binder are compacted much better than mixtures with copper or nickel. The hardness of materials after explosive compacting reaches 1200 HV. The paper determines a temperature range corresponding to ((0,35÷0,4)t_melt (where t_melt is the absolute melting point of the main carbide of the alloy), transition through which changes the fracture pattern of samples from intercrystalline to transcrystalline. The paper determines that this is due to the formation of strong boundaries between carbide particles and the metal matrix, which constitute interlayers with a thickness of the order of 80–100 nm having its own crystalline structure different from the structure of main components of the alloy.

The paper is dedicated to the study of PDC (polycrystalline diamond compact) diamond composites, which are widely used in drilling, tool and construction industries. They constitute a complex composition of diamond and cermet phases. The diamond phase consists of diamond grains of various grain-size compositions and shapes, and forms a strong, solid scaffold. The cermet phase acts as a binder. The presence of catalyst metals in the diamond layer of PDC two-layer composites deteriorates their performance properties, since the difference in the coefficient of thermal expansion between diamond grains and the catalyst can lead to material cracking during cutting, and the high temperature during the manufacture of the diamond tool and its utilization in the cutting area can lead to the reverse diamond-graphite phase transition. The paper describes the process of metal etching from the surface of the tool working area by two etching methods: electrochemical and chemical, for the purpose of improving wear characteristics of PCD diamond composites obtained using catalytic metals (cobalt and tungsten). The electrochemical etching was carried out in sulfuric acid under various current regimes and concentration; chemical etching was carried out in a mixture of hydrochloric and nitric acids and in a mixture of hydrofluoric and nitric acids. Post-etching in depth distribution of chemical composition in PCD samples was studied using the scanning electron microscopy. It was established that electrochemical etching was kinetically more active, and chemical etching was promising for industrial applications. The abrasive tests of PCD samples carried out before and after the etching showed no significant effect of both electrochemical and chemical etchings on their abrasive property. 

The paper studies the microstructure and mechanical characteristics of samples of medium-grained (WC–8Co), submicron (WC– 8Co–1Cr3C2) and ultrafine (WC–8Co–0,4VC–0,4Cr3C2) hard alloys produced by liquid-phase sintering of powders of appropriate dispersity. The paper shows that a decrease in the average grain diameter from 1,65 to 0,37 μm leads to an increase in hardness of resulting alloys from 1356 to 1941 HV. At the same time, the cracking resistance decreases from 19,0 to 8,5 MPa·√ —m and strength decreases from 2080 MPa to 1210 MPa. Comparison with the literature data showed that alloys considered in this paper are highly competitive in hardness and crack resistance with analogues produced by sintering under pressure, hot pressing, electric spark and induction sintering. At the same time, the bending strength of alloys produced by liquid phase sintering was 1,5–2,5 times lower than for alloys produced by pressure sintering or pressing, due to the presence of pores with a maximum diameter estimated at 40 μm. The paper analyses obtained results and the literature data against the theoretical regularities. It is shown that in general, dependences of hardness, cracking resistance and strength on the average grain diameter of produced alloys and their analogues correspond to conventional regularities based on the Hall–Petch and Orovan–Griffiths laws, despite the existence of theoretical prerequisites for deviating from them. 

The paper reviews literature on the structure, properties, production processes, and fields of application of materials based on the MAX phase Cr₂AlC. It was noted that the most promising method for production of such materials was self-propagating high-temperature synthesis (SHS), with SHS metallurgy being one of its directions. A mixture of AR grade chromium III and chromium VI oxide powders, ASD-1 grade aluminum, and carbon was used as the base charge during studies. The adiabatic combustion temperature and the composition of final products were calculated using the special THERMO program. The experiments were carried out in the SHS reactor with a volume of V = 3 dm³ at the initial inert gas pressure (Ar) Р₀ = 5 MPa. The experiments focused on the influence of the starting reagent ratio on parameters of the high-temperature synthesis (burning rate, pressure gain, and yield of the target product), composition and microstructure of target products. The paper develops a scientific approach to the production of cast materials by SHS metallurgy under gas pressure in the Cr–Al–C system consisting of the Cr₂AlC MAX phase, and Cr₅Al₈ and Cr₃C₂ phases. The paper studies structural-phase states of target products. It was experimentally established that by varying the content of starting reagents (aluminum and carbon) in the charge, it was possible to produce a significant effect on synthesis regularities, the composition and microstructure of final products. As the carbon content in the base mixture increases (above the stoichiometric content), the content of the MAX phase Cr₂AlC in the final product increases as well and content of Cr₅Al₈ reduces. An increase in the aluminum content (above stoichiometric) in the base mixture leads to an increase in the MAX phase Cr₂AlC content in the final product and to a reduction in the Cr₃C₂ phase content. 

The paper studies the effect of mechanical activation conditions (MA) on the microstructure and phase composition of Ta–Hf–C reaction mixtures and products derived from them by self-propagating high-temperature synthesis (SHS). The mechanical activation of Ta–Hf-C reaction mixtures was carried out in centrifugal planetary mills with different drum rotation speeds. It was found that an increase in the drum rotation speed from 250 to 900 rpm reduced the heterogeneity scale of the reaction charge, reduced the size of coherent scattering regions of tantalum and hafnium by an order of magnitude, and led to an increase in the strain degree of their crystal lattices by 1,5–2,0 times. It was experimentally established that initiation of the SHS reaction in the activated Ta–Hf–C mixture at an initial temperature Т₀ Т₀ = 800 K only, when the adiabatic combustion temperature reached 3274 K. The single-phase carbide (Ta,Hf)C with a lattice parameter а = 0,44787 nm corresponding to 18,0 at.% of HfC dissolved in TaC, was obtained from reaction mixtures activated under optimal regimes. The content of hafnium oxide in products does not exceed 1 %. The structure of samples is characterized by high porosity (more than 30 %) and a small carbide grain size (less than 10 μm), which made it possible to obtain the (Ta,Hf)C powder by milling the SHS product in a ball mill.

The paper describes the production of «TiC – steel binder» metal matrix composites by self-propagating high-temperature synthesis (SHS) in reaction powder mixtures of titanium, black carbon (soot), and HSS powders in laminar burning mode. Composite powders with various steel binder contents were prepared by milling and screening the synthesis products. The synthesis products were studied by optical and scanning electron microscopy, X-ray diffraction analysis, and electron probe microanalysis. It was found that an average size of carbide inclusions in the structure of the metal matrix composite depends on the content of the heat inert steel powder in reaction mixtures and can be controlled over a wide range. The lattice parameter of the titanium carbide formed in the SHS process is smaller than that of equiatomic TiC. The main reason for decrease in the lattice parameter is the non-stoichiometric carbide composition preconditioned by the carbon deficit. According to the results of the electron probe microanalysis, titanium carbide inclusions in the composite structure additionally contain up to 1 at% of iron and other alloying elements. The dissolution of iron and alloying elements leads to a certain increase in the carbide lattice parameter, which partially compensates for decrease in the lattice parameter caused by the carbon deficit. According to the results of the X-ray microanalysis, ferrite as a main phase in the metal binder has an ultra-equilibrium content of alloying elements. SHS products annealed at700 °Cresult in decomposition of retained austenite and dissolution of alloying element carbides in ferrite. 

New generation superalloys based on Ni intermetallics exhibit high thermomechanical stability at high temperatures and are widely used in modern industry. The production of such materials by self-propagating high-temperature synthesis (SHS) has an advantage over traditional metallurgical production methods due to reaction heat utilization. The creation of coatings and surfacing based on NiAl intermetallic on the surface of W products in the SHS process is of great practical interest. This paper describes experiments on the interaction of a W substrate and a Ni–Al-based melt in the SHS regime. When connecting the W substrate to the NiAl intermetallic during the SHS process, a gradient welded joint with a thickness of 200–400 μm with a complex structure is formed. During the SHS reaction, the formation of a Ni and Al melt occurs, in which surface layers of the W substrate are diffused. During cooling, the tungsten-based phase dendrites (84–86 at% W and 16–14 at% Ni) and the NiAl-based pseudobinary eutectic dendrites (β-phase) which include W-containing phase precipitates of less than 50 nm in size and needlelike Ni3Al inclusions (γ′-phase) crystallize in the subsurface layer. A structured ternary eutectic W + Ni + Ni3Al (α + γ + γ′) containing particles of a solid solution based on Ni3Al intermetallic of about 100 nm in size was found in the transition layer. The paper demonstrates a modification of the W substrate surface with the formation of globular W precipitates (α-phase), which significantly increases the surface area.