This paper studies dependences of combustion velocities and changes in sample relative lengths from ambient pressure and thermovacuum degassing (TVD) time for the Ti + 0,5C mixture. It was shown that Ti + 0,5C mixture TVD significantly (doubly) increase combustion velocity as well as sample shrinkage. Sample shrinkage occurs under the influence of surface tension due the sufficient quantity of a liquid phase in combustion products that ensure their low viscosity. It was not possible before to obtain pressed samples from the mechanically activated (MA) Ti + C mixture because of their low strength, and therefore to investigate their combustion regularities. To solve this problem, the authors used preliminary granulation of the initial Ti + 0,5C mixture before MA. As a result, dependences of combustion velocity and post-combustion changes in sample lengths from MA time were obtained for the first time ever for the Ti + 0,5C preliminary granulated mixture. It was found that mechanical activation decreases mixture combustion velocity and significantly (triply) increases sample elongation after combustion. Combustion velocity after MA mixture TVD reaches combustion velocity of initial mixtures at the same TVD time. The samples of condensed reaction products from the MA mixture retained a slight elongation (within 8 %) after TVD. X-ray phase analysis revealed no reaction products formed during MA. Combustion products of all mixtures (initial, activated mixture and activated granules) contain the Ti2C phase and Ti traces. X-ray analysis of the initial and MA mixtures shows peaks intensity broadening and reduction of peak intensity to the background intensity ratio after MA thus indicating a higher defect rate in the crystal structure of the components of mixtures. This effect intensifies with an increase in activation time. The study results are interpreted based on the conduction – convection model of reaction wave propagation.

Sintered cemented carbides are very important for modern engineering. It is difficult to point out an industry having no interest in cemented carbides. Their unique properties – hardness, strength, wear resistance, scale resistance, high temperature strength, corrosive resistance – make them suitable for different applications such as metal working, oil-well drilling, mining industry, chipless machining, arms industry, nuclear, space, vacuum and electric engineering, instrumentation, synthetic diamond fabrication process, etc. This paper provides an overview of domestic cemented carbide evolution and fabrication stages. The contribution of national researchers to the development of various cemented carbide grades and their fabrication progress is shown. The outstanding role of Professor G.A. Meerson in the cemented carbide industry development is mentioned. The paper cites the results of many Russian and CIS researchers from such leading institutes as the Russian National Cemented Carbide Research Institute (Moscow, Russia), Ukrainian Institute of Materials Science (Kiev, Ukraine), Institute for Superhard Materials (Kiev, Ukraine), Ural Branch of the Russian Academy of Science (Kirovograd, Russia), Ural Polytechnic Institute (Ekaterinburg, Russia), Tomsk Polytechnic Institute (Tomsk, Russia), Belarusian Institute of Powder Metallurgy (Minsk, Belarus), Institute of Metallurgy and Materials Science (Moscow, Russia), Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences (Chernogolovka, Russia).

Electron microprobe analysis and scanning electron microscopy are used for the first time to systematically study the effect of TiC0,5N0,5 carbonitride doping with V group transition metals (V, Nb, Ta) on the mechanism of contact interaction with the Ni–25%Mo melt (Т = 1450 °С, τ = 1 h, vacuum 5·10–2 Pa). It is found that the dissolution of similar Ti1–nMeV nC0,5N0,5 (n = 0,05) carbonitrides is an incongruent process (alloying metal and carbon predominantly transfer to the melt) with non-monotonic changes in relative velocity and incongruence of carbonitride dissolution for the V–Nb–Ta alloying metal series. The paper suggests an explanation of the effects identified. The causal relationship between the initial composition of Ti0,95MeV 0,05C0,5N0,5 carbonitride (kind of alloying metal) and the composition of K phase (Ti1–n–mMonMeV mCx) precipitated from the melt during the system cooling is analyzed. It is shown that the factor determining the composition of the produced K phase is the ΔT factor (the difference between the crystallization temperatures of Ni/MeVC carbide eutectics and Ni/Mo2C, the most easily-fusible eutectic in these systems). The paper rationalizes the conclusion that the found relationship between the initial carbonitride composition and the composition of K phase formed is a consequence of the microheterogeneous structure of the metal melts. It is demonstrated that this relationship has a relatively general nature and appears in all the studied systems whatever the Group V alloying metal grade and whether the melt contains molybdenum or not.

The creation of new higher melting temperature materials for gas turbine engines is one of the most important tasks of modern materials. This is due to the fact that nickel superalloys currently used for these purposes have a low melting point about 1400 °C which limits their own maximum working temperature to 1100–1150 °C. Ni alloys can be replaced by natural composites with refractory metals as a matrix and their silicides as intermetallic hardeners. Only three of refractory metal – silicon binary systems exhibit stability to the Me5Si3 silicide, namely Nb5Si3, Re5Si3 and W5Si3, Nb5Si3 is the best compound among other silicides with regard to the combination of high melting point and low density. The use of Nb–Si alloys in additive manufacturing machines is of considerable interest. The paper presents the results of experimental studies on the thermal plasma processing of Nb–16Si alloy powder prepared by mechanical alloying of Nb and Si elemental powders. Nb–16Si (at.%) alloy powder was prepared by mechanical alloying of pure element powders using the Fritsch Pulverisette 4 planetary mill. Spheroidization was carried out on a plasma unit based on vortex-stabilized arc thermal plasma generator. The results of experimental studies conducted confirmed the possibility to perform plasma spheroidization of Nb–16Si alloy powder particles obtained by mechanical alloying. It is shown that the particle surface after spheroidization is rough and reflects the cast structure of the material. Three phase components having different optical contrast are revealed on microsections: Nb5Si3, Nb3Si and Nbss, which is confirmed by X-ray diffraction.

The paper provides the results of alloy development investigation and technology of making compact billets of the Al-Si-Ni-based composite for aerospace equipment components. Composite production included several stages: first, matrix powder was produced by gas atomization and then matrix powder with disperse alloying additives was mechanically alloyed in high-energy machines. The vacuum press, unique equipment located at OJSC «Kompozit» (Korolyov, Moscow region, Russia), was used to develop and test the technology of mechanically alloyed composite degassing in a thin layer (to eliminate material ejection from the container when degassing a large volume of powder) as well as to tryout composite compaction process modes. Cylindrical billets up to 100 mm in diameter and up to 120 mm in height were obtained based on this technology. Kompal-301, a newly developed and patented composite, has significant advantages compared to the SAS-1-50 sintered aluminum alloy due to 1,5 times lower thermal coefficient of linear expansion and 2–3 times higher precision elastic limit with the same density values. The compacted billet has a resulting matrix structure with disperse silicon excess particles distributed quite uniformly over the aluminum solid solution. There are some larger isolated silicon particles in certain structure areas. Unfortunately, they cause lower billet ductility so it is impossible to produce semi-finished products by plastic deformation. However, such a low ductility has no negative effect on the billet production itself.

The article is a continuation of authors’ publications in the field of multi-function protective coatings for strongly heat loaded structural elements of hypersonic systems. The paper suggests a new physical and chemical model of heat-proof coating operation in a high-enthalpy oxidizing gas jet flow. The model considers and eliminates the main causes of surface destruction by the gas flow. The concept is efficiently used to produce a number of Si–TiSi2–MoSi2–B–Y system alloys intended for thin-layer coating formation using any layer deposition method capable of reconstituting the structure, phase composition and morphology of the deposited material. Deposition involves forming a microcomposite layer constructed from the refractory silicide framework with cells filled with a fusible (as compared with the framework phase) eutectic component. This layer transforms into a multilayer system during the high-temperature interaction with oxidizing media (synergetic effect). This multilayer structure contains anti-catalytic, reradiative, anti-erosion, heat-proof, barrier compensating function layers of micron and sub-micron thicknesses. Protection is ensured by a self-healing oxide glassy film formed based on alloyed silica. The self-healing effect consists in the rapid filling of incidental defects by the viscous plastic eutectics and faster (as compared with the known coatings) protection film forming. The branched dendrite cellular refractory framework ensures high resistance to erosion mass loss. The MAI D5 and MAI D5U protective coatings created as part of the presented concept were tested successfully in high-enthalpy oxygen-containing gas flows. The various specimens made of strongly heat-resistant materials were used to depose the coating such as niobium alloys, carbon-carbon and carbon-ceramic composites as well as graphitized carbon materials. The 80–100 μm thick coatings subjected to jet flows with M = 5÷7 and enthalpy 30–40 MJ/kg have shown the protection capacity above 600 s (Tw = 1800 °С), 200 s (Tw = 1900 °С), and 60 s (Tw = 2000 °С) for structural components with sharp edges as well.

The paper presents the results of investigation of CrN/AlN system coatings obtained by magnetron-ion reactive sputtering. Coating versions with a periodic nanocomposite structure with a layer period L = 1,5÷3,2 nm and a relative Cr content in the Cr/(Al + Cr) coating range of 68–85 % are studied. It is found that the coatings have a dense morphology and a columnar grain structure, which is typical for them. For all the samples, diffraction maxima corresponding to the cubic lattice are observed, being a superposition of the two compositions of CrN and AlN coatings. No peaks corresponding to AlN with a hexagonal structure type are recorded. Neither CrAlN peaks are found, that means that no homogeneous coating is formed. Experimental studies of the microhardness, modulus of elasticity, plasticity index and wear resistance of coatings obtained under different spraying conditions are conducted. Measurements showed that the microhardness and modulus of elasticity of the coatings obtained vary between H = 32÷42 GPa and E = 350÷420 GPa, respectively. The maximum plasticity index value H/E = 0,115 is reached at L = 3,2 nm, which corresponds to the coating versions with the greatest hardness. However, the H/E = 0,1 values are also fairly high with a minimum layer period (L = 1,5 nm) and a high Cr content. Abrasive wear coefficients of the coatings obtained vary in the range kс = (2,0÷2,8)·10–13 m3/(N·m). The minimum values of wear are reached at the maximum period of coating layers, i.e. with the greatest hardness, which agrees well with the classical theory of wear. At the same time, high wear resistance is observed at a low L, which indicates a correlation of the values of H/E and kс. Based on the experimental data, a group of neural network models is built that establish the relationship between the deposition process mode parameters (current on magnetrons) with the elemental composition of coatings, as well as the period of coating layers and relative chromium content with the physical and mechanical properties and abrasion resistance of CrN/AlN coatings.

The paper describes single and crosswise (double) surfacing of Hardox 450 steel using the C–Mn–Si–Cr–Nb–W flux-cored wire, and the analysis of the microhardness, phase composition, and defective substructure of built-up layers. The microhardness profile is obtained at a distance from the surface. It is shown that a high-strength surface layer with a microhardness of 10,2 GPa is formed as a result of surfacing. Material microhardness decreases to 6 GPa at a greater distance from the surface of the built-up layer. An increase in the number of built-up layers up to 2 causes thickening of the hardened layer. The paper shows that the microhardness value of this layer does not depend on the number of built-up layers of the weld flux-cored wire. The paper describes the study of the phase composition and defective substructure of a built-up layer by transmission electronic diffraction microscopy methods. It is shown that the thickness of the hardened layer varies from 6,0–6,5 to 7,5 mm for single and double surfacing. It was found that the increase in the built-up layer microhardness was attributable to the formation of a multiphase submicro- and nanosized structure with hardening preconditioned by the hardening effect and the presence of submicron-sized niobium carbide inclusions, the morphology of which essentially depended on the place of formation in the steel structure. It was found that the contact area between the surfacing and the base metal was similar to the structure of the original steel, but hardening of the transition layer occurred due to the presence of carbide phase particles formed by elements of the flux-cored wire.