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The paper focuses on the study of the combustion kinetics and mechanisms of elemental mixtures in the Zr–Mo–Si–B system, as well as the analysis of phase and structural transformation stages in the combustion wave. A thermodynamic analysis of potential chemical reactions occurring in the combustion wave was carried out. The reaction of ZrB2 formation is preferred in the range of 298–2500 K. Above 2200 K, the formation of MoB becomes more thermodynamically advantageous as compared to MoSi2. Phase stability estimates of combustion products showed that ZrB2, MoSi2 and MoB phases are in equilibrium. Experimental dependences Тc(Т0) and Uc(Т0) are linear, which implies an unchanged combustion mechanism at T0 = 298÷800 K. Preheating leads to an increase in Uc. Similarly, an increase in the proportion of Zr and B in the mixture has a similar effect, i.e. an increase in heat emission and Tc. With a minimum content of Zr and B, the interaction between Mo and Si with the formation of MoSi2 by the reaction diffusion mechanism is decisive. As the proportion of Zr and B increases, the rise of T0 to 750 K does not affect the Tc. Eeff values (50–196 kJ/mol) confirm the significant influence of liquid-phase processes on the combustion kinetics. The mechanism of structure formation was studied. A Si–Zr–Mo melt is formed in the combustion front. The primary grains of ZrB2 and MoB crystallize from this melt as it is saturated with boron. At the same time, the melt spreads over the surface of Zr and Mo particles. This leads to the formation of ZrSix, MoSix films. Core-shell structures are formed behind the combustion front, which disappear as they move towards the post-combustion zone. The phase composition of products is formed in the combustion front in less than 0.25 s.

This study focuses on the combustion kinetics and mechanisms of reaction mixtures in the Mo–Al–B ternary system taken so that the MoAlB MAB phase was formed. The effect of the initial temperature on the key combustion parameters was demonstrated. Reaction mixture preheating was found to weakly affect the maximum combustion temperature. The effective activation energy of self-propagating high-temperature synthesis (SHS) was calculated. Phase diagrams in the Mo–Al–B system were built using the AFLOW and Materials Project databases. The phase composition and structure of the synthesized ceramics with MoAlB lamellar grains 0.4 μm thick and ~2–10 μm long as a main component were studied. The DXRD lines of MoB and Mo2B5 intermediate borides with their total content of ≤3 % were also identified. Scanning electron microscopy and energy dispersive spectroscopy studies revealed that the Al2O3 phase was present in the intergranular pores. A sequence of chemical transformations in the combustion wave was studied, and a hypothesis about the structure formation mechanism was put forward. MoO2 and Al2O3 can be the primary phases during SHS, and the MoAlB phase is formed from the boron-containing aluminum–molybdenum melt. Submicron-sized MoB precipitates are formed in the post-combustion zone due to the partial oxidation of aluminum by the dispersion strengthening mechanism.

The kinetics and the mechanism of oxidation of ceramics based on HfB2 and SiC, manufactured by elemental self-propagating high-temperature synthesis followed by hot pressing were investigated. The synthesis product contained HfC(x) and HfO2 as impurity phases. Depending on the ratio between the main components, the samples were characterized by high structural and chemical homogeneity, porosity of 3–6 vol%, hardness up to 29 GPa, bending strength of 500–600 MPa, fracture toughness of 5.6–8.9 MPa × m1/2, and thermal conductivity of 86.0–89.7 W/(m × K). The oxidation was performed under static conditions at 1650 °C and upon exposure to a high-enthalpy gas flow. A dense layer consisting of HfO2/HfSiO4 grains formed on the surface of the ceramics during both oxidation conditions; the space between the grains was filled with amorphous SiO2–B2O3. The best heat resistance was observed for the ceramics with 16 wt% SiC for static conditions and 8 wt% SiC for gas-dynamic conditions.

As study is performed of the distribution of quantitative characteristics of the steps formed by shear bands (SBs) on the surfaces of deformed samples of massive amorphous alloy Zr60Ti2Nb2Cu18.5Ni7.5Al10 after torsion under high quasi-hydrostatic pressure (HPT) in a Bridgman chamber at room temperature and different deformation values. Histograms are obtained for the distribution of the main characteristics of the SB (power and bulk density) in different zones of disk-shaped samples (geometric center, zone 1; middle of the radius, zone 2; edge, zone 3) on the end surfaces. The dependence of the SB characteristics on the location of the studied area of the sliding steps is established. The minimum value of the bulk density of the SB is observed for all values of n in zone 2. The SB power grows monotonically at a rate that depends on the degree of deformation from zone 1 to zone 3. The maximum height of individual steps is observed in zone 3 (4.1 μm).

We investigate the melting ranges of the base Zr–Si mixture (eutectic composition) depending on the content of the heterophase powder component in the ZrB2–ZrSi2–MoSi2 and the HfB2–HfSi2–MoSi2 systems in the amount of 30–90 wt % obtained by self-propagating high-temperature synthesis (SHS). The range of the melting point of the Zr–Si mixture was 1420–1440°C; addition of the ZrB2–ZrSi2–MoSi2 SHS powders resulted in an increase of the melting onset temperature Tm0 to 1460–1560°C and in the complete melting temperature Tmelt to 1480–1670°C. Addition of the HfB2–HfSi2–MoSi2 powders influenced only slightly the Tm0 value (1390–1430°C), but resulted in the increase in Tmelt to 1510–1550°C. The X-ray phase analysis shows that the remelted samples contain the following phases: ZrB2/HfB2, ZrSi2/HfSi2, MoSi2, and Si; here, the number of phases was directly proportional to the SHS powder content in the Zr–Si mixture. The ingots are characterized by a homogeneous structure consisting of the silicon matrix and ZrSi2/HfSi2 and MoSi2 grains, with inclusions of ZrB2/HfB2.

Mo5SiB2-based ceramics were fabricated from elemental powders by forced SHS compaction and hot pressing of SHS-produced powders and specific features of product patterning were characterized by XRD, time-resolved XRD, SEM/EDS, and TEM/EDS. Best results were obtained upon hot pressing of SHS-produced Mo–Si–B powders: resultant material was single-phased Mo5SiB2 with a mean grain size of 2–10 μm.

The work is devoted to studying the melting ranges of the base Zr – Si eutectic composition depending on the content of the heterophasic powder component in the ZrB2 – ZrSi2 – MoSi2 and HfB2 – HfSi2 – MoSi2 systems in an amount of 30 – 90 % obtained by the method of self-propagating high-temperature synthesis (SHS). The melting range of the mixture Zr – Si was 1420 – 1440 °C, while the addition of SHS-powders ZrB2 – ZrSi2 – MoSi2 led to an increase in the melting onset temperature Тmelt.onset to 1460 – 1560 °С and the complete melting temperature Tmelt.complete to 1480 – 1670 °C. The addition of HfB2 – HfSi2 – MoSi2 powders had a weak effect on the values of Тmelt.onset (1390 – 1430 °С), but led to an increase in the values of Tmelt.complete to 1510 – 1550 °С. X-ray phase analysis showed that the remelted samples contained ZrB2/HfB2, ZrSi2/HfSi2, MoSi2 phases and Si, with the number of phases being directly proportional to the content of SHS powders in the composition of the Zr – Si mixture. The ingots were characterized by a homogeneous structure consisting of a silicon matrix, ZrSi2/HfSi2, MoSi2 disilicide grains, with ZrB2/HfB2 diboride inclusions.

This work is devoted to the fabrication of ZrB2–ZrSi2–MoSi2-based composite powder ceramics by self-propagating high-temperature synthesis (SHS) according to the scheme of magnesium thermal reduction from oxide feedstock and its subsequent hot-pressing (HP) consolidation. The combustion of reaction mixtures has rather high adiabatic temperatures in a range of 2060–2120 K and burning rates in a range of 8.3–9.4 g/s. The end product yield of the magnesiothermal reduction is 34–38%. The resulting powder contains 13–47% ZrB2, 21–70% ZrSi2, 2–32% ZrSi, and 10–18% MoSi2, depending on the composition of the initial reaction mixture; has high structural homogeneity; and consists of composite polyhedral particles with an average size on the order of 8 μm. The structure of ceramics consolidated by HP from the SHS powder is homogeneous and includes needle ZrB2 grains distributed in the ZrSi2 matrix, MoSi2 inclusions of various morphologies, and inclusions of ZrSiO4 silicate distributed over the ZrSi2 grain boundaries. The HP-formed samples have a high degree of homogeneity of the chemical composition and residual porosity of 2.5–7.4%.

In this work, the influence of modifications of SHS-process on the microstructure and performance characteristics of composite ceramics MoSi2-HfB2-MoB with two-level structure was studied. Partial texturing of MoSi2 grains in samples obtained by force SHS pressing technology was revealed. The effect of preliminary mechanical activation on the macrokinetic parameters of combustion and on the microstructure of the synthesized ceramics was studied. A significant grinding of the synthesized ceramics grain and an increasing of physical-mechanical properties are achieved by increasing the velocity and lowering the combustion temperature of the activated mixtures. The sample obtained by hot pressing of SHS powder from MA reaction mixture showed the most optimal combination of hardness (19.5 GPa), porosity (0.4%) and oxidation resistance (1.82∙10-6 mg/(cm2∙s)).

The results of a study of the kinetics and mechanism of heterogeneous and compact ceramics oxidation in the ZrSi2-MoSi2-ZrB2 system at air temperature of 1400 °C are presented. The ceramics were obtained by the hot-pressing of composite powders that were manufactured by self-propagating high-temperature synthesis following the magnesiothermal recovery approach. Oxidation kinetics are described using a power function with index n > 2 , confirming the significant influence on the evolution process in the structure of the formed oxidation coating. The oxidation mechanism includes the formation of a two-layer structure consisting of a continuous silicate film, of which the outer part contains magnesium and a sublayer based on the ZrSiO4 phase, with the scheelite structure encapsulating the ZrB2 and MoSi2 grains. The influence of the ZrSi2, MoSi2 and ZrB2 phases on the structural-morphological peculiarities of the appearing oxide films and the effectiveness of its protective action are revealed.

This work is devoted to the fabrication of heterophase powder and consolidated ceramics based on hafnium and molybdenum borides and silicides by combining self-propagating high-temperature synthesis (SHS) and hot pressing (HP). Composite ceramic HfB2–HfSi2–MoSi2 SHS powders are fabricated according to the magnesium-thermal reduction flowsheet from oxide raw materials, in which the combustion wave has temperatures of 1750–2119 K and rather high mss combustion rates of 8.4–9.3 g/s. The structure of synthesized SHS powders consists of relative coarse MoSi2 grains up to 10 μm in size, submicron elongated HfB2 grains mainly located inside the MoSi2 grains, and rounded Si precipitates. The composition with a lower boron concentration contains numerous polyhedral HfSi2 grains smaller than 10 μm in size. The resulting powders have an average particle size of ~6 μm with a maximal size up to 26 μm. The phase compositions of the ceramics consolidated by the HP method and synthesized SHS powders are identical. The microstructure of compact samples consists of faceted elongated HfB2 grains 0.5–10.0 μm in size, polyhedral HfSi2 and MoSi2 grains up to 8–10 μm in size, and silicon interlayers. The consolidated ceramics have a high structural and chemical homogeneity, low residual porosity of 1.1–1.7%, high hardness of 11.7–12.6 GPa, and thermal conductivity of 62–87 W/(m K).

The paper focuses on obtaining heterophase powder ceramics and consolidated ceramics based on borides and silicides of hafnium and molybdenum by combining the methods of self-propagating high-temperature synthesis (SHS) and hot pressing (HP). Composite ceramic SHS powders HfB2–HfSi2–MoSi2 were obtained according to the scheme of magnesium-thermal reduction from oxide raw materials where the combustion wave is characterized by temperatures of 1750–2119 K and high mass combustion rates of 8,4– 9,3 g/s. The structure of synthesized SHS powders consists of relatively large MoSi2 grains up to 10 μm in size and submicron elongated HfB2 grains located mainly inside the MoSi2 grains and rounded Si precipitates. The composition with a lower concentration of boron contains a large number of polyhedral HfSi2 grains with a size of less than 10 μm. The resulting powders are characterized by an average particle size of ~6 μm with a maximum size up to 26 μm. Phase compositions of ceramics consolidated by the HP method and SHS synthesized powders are identical. The microstructure of compact samples consists of faceted HfB2 elongated grains 0,5– 10,0 μm in size, polyhedral HfSi2 and MoSi2 grains up to 8–10 μm in size and silicon interlayers. Consolidated ceramics has a high structural and chemical homogeneity, low residual porosity of 1,1–1,7 %, high hardness of 11,7–12,6 GPa and thermal conductivity of 62–87 W/(m·K).

The kinetics and mechanism of high-temperature oxidation of dense heterophase ZrSi2-MoSi2-ZrB2 ceramics at a temperature of 1650 °C are studied. The ceramics were fabricated by hot pressing of composite powders prepared by self-propagating high-temperature synthesis with magnesiothermic reduction. The oxidation kinetic curve is described by the power-law function, which indicates that the evolutionary changes in the structure of the formed oxide films significantly affect the course of the oxidation process. The oxidation mechanism involves formation of a multi-layered structure of heterogeneous oxide film, partial dissociation of the ZrSiO4 phase, and formation of secondary MoB and Mo5Si3 compounds. The influence of the ZrSi2, MoSi2 and ZrB2 phases on the structural and morphological features of the formed oxide films and the efficiency of their protective action are shown. Silicon is reduced and zirconium is simultaneously oxidized to ZrO2 in the ZrSi2-ZrSiO4 system at temperatures above 1620 °C in the absence of oxygen or in low-oxygen environment.

This study focuses on the investigation of the macrokinetic features of SHS (combustion synthesis) of elemental mixtures Mo–Hf–Si–B, in particular the mechanisms of structure and phase formation in the combustion front as well as the structure and properties of consolidated ceramics. Two routes for the fabrication of the composite SHS powder in system MoSi 2 –HfB 2 –MoB were used: (1) synthesis using Mo–Si–B and Hf–B mixtures followed by mixing of the combustion products and (2) synthesis using the four-component Mo–Hf–Si–B mixture. Dense ceramic samples with a homogeneous structure and low residual porosity (0.8–3.6%) were prepared by hot pressing of SHS powders. Although the particles size distribution and phase composition of SHS powders are similar for both synthesis routes, the structure and properties of both the composite SHS powders and hot-pressed ceramics differ considerably. Synthesis using the four-component Mo–Hf–Si–B mixture allows one to produce hierarchically ordered nanocomposite material with improved mechanical properties: hardness up to 17.6 GPa and fracture toughness up to 7.16 MPa m 1/2 .

The structure and properties of pre-alloyed Ni41Al41Cr12Co6 spherical powders (the 40–160 μm fraction) produced using the plasma rotating electrode processing technology were studied. The evolution of the fine structure of pre-alloyed Ni41Al41Cr12Co6 spherical powders under heating at 20, 350, …, 850 °C was investigated. Disk-shaped chromium-rich pre-precipitation zones 5–30 nm in size were detected in the temperature range of 450, …, 650 °C; they precede the formation of the dispersed chromium precipitate. Prism-shaped chromium nanocrystals with the characteristic longitudinal dimension ranging from 15 to 100 nm, whose nucleation process starts at prismatic dislocation loops, were found to be formed at 750, …, 850 °C. The Young's modulus, hardness, and elastic recovery of powder material were determined by nanoindentation measurements. The resulting powders are characterized by bulk density of 3.8 g/cm3, excellent flow rate (3.5 s), and the angle of repose of 19.6°. Keywords: Plasma rotating electrode processing (PREP), Spherical powders, Nickel aluminide, Precipitation hardening, Intermetallic alloys, Nucleation and growth

The work is dedicated to researching into combustion kinetics and mechanism as well as the stages of the chemical transformations during self-propagating high-temperature synthesis of ZrB2-SiC based ceramics. Dependences of the combustion temperature and rate on the initial temperature (T0) have been studied. It has been shown that the stages of the chemical reactions of ZrB2 diboride and SiC carbide formation do not change within the range of T0 = 298–700 К. The effective activation energy of the combustion process amounted to 170–270 kJ/mol, from which it has been concluded that chemical interaction through the melt plays a leading role. The stages of the chemical transformations in the combustion wave have been studied by dynamic X-ray diffraction. First, ZrB2 phase forms from Zr-Si melt saturated with boron, and SiC phase is registered later. The SHS method has successfully been used in order to obtain ZrB2-SiC composite powders and compact ceramics with a silicon carbide content of 25–75%. The ceramics are characterized by a residual porosity of 1.5%, hardness up to 25 GPa, the elastic modulus of 318 ± 21 GPa, elastic recovery of 36% and thermal conductivity of 54.9 W/(m × K) at Troom.

The goal of this study was to produce biocompatible ceramic materials in the Ti–C–Co–Ca3(PO4)2–Ag–Mg system by combustion mode synthesis. The influence of cobalt on combustion parameters of the mixture, structure, and properties of the products was investigated. Compact ceramics consist of a combined grain frame of nonstoichiometric titanium carbide (TiC0.5–TiC0.6) with the titanium phosphate (Ti3POx) phase homogeneously distributed along grain boundaries and local isolations of calcium oxide (CaO). The introduction of cobalt promotes the formation of a complex phosphide CoTiP and TiCo intermetallic compound. Alloying with silver and magnesium leads to the formation of a silver-based solid solution.

The work aimed at preparation of the MgB2 doped with alloying metals (Al, Cu, Ag, Zn) by SHS in a mode of thermal explosion. The measured combustion temperatures fell within the range 940–1030°С. Detailed XRD analysis has shown that, among other selected metals, it is solely Al that can enter the MgB2 lattice. According to time-resolved XRD results, the formation of final product (Mg, Al)B2 in the Mg–Al–B system involved no intermediate phases. But in the Mg–Cu–B system, the volume reaction additionally yielded MgB4, Cu2Mg, and CuMg2 due to the presence of the liquid phase. In final products, the agglomerates of MgB2 grains had a size of 500–1000 nm, while the size of Cu2Mg and CuMg2 inclusions was within 0.5–2 μm.

The aim of this work was to study the kinetics and oxidation mechanism of MoSi 2 -MoB SHS-ceramics in the temperature range of 600–1200 °C. Due to the low rate of change in the mass of samples during the initial stage of oxidation, the kinetic curves at 600 °C suggest that the oxidation process occurs according to a parabolic rate law. At this temperature, MoO 2 and MoO 3 are formed in samples with the greatest MoB content due to its oxidation, and their intensive evaporation only begins after 700 °C. A thin film consisting of a mixture of Mo, Si and B oxides forms on the sample surface as a result of oxidation with a minimum MoB content. The presence of B 2 O 3 in the oxide film leads to the formation of a borosilicate barrier layer, which prevents oxygen diffusion to the sample surface and MoO 3 evaporation. At temperatures of 900 and 1200 °C, the oxidation process proceeds according to a logarithmic law. At these temperatures, an oxide film based on SiO 2 is formed on the surface layer, which in the case of the maximum MoB content sample, is a mixture of B 2 O 3 -SiO 2 oxides in an amorphous state. At lower MoB concentrations, the formed SiO 2 film has a crystalline structure and contains boron. In addition, during oxidation of the materials at the maximal temperature, a Mo 5 Si 3 silicide layer is formed at the interface between the oxide layer of B 2 O 3 -SiO 2 or B-SiO 2 and the sample material due to the oxidation of MoSi 2 , whose thickness and continuity increase with increases of the temperature and duration of oxidation.

The structure and mechanical behavior of NiAl-based intermetallic alloys alloyed with Hf, Cr and Co at their total content (Cr+Co)=18 at% were studied. The alloys were prepared by centrifugal SHS casting from oxide raw materials. The mechanism of precipitation hardening is shown to take place at the Cr/Co ratios >0.5, leading to the formation of chromium-based inclusions and nanosized precipitates in the NiAl dendrite body. The resulting alloys have a three-level hierarchical structure with oxygen, nitrogen, and carbon impurity contents of 0.129, 0.0045, and 0.04 wt%, respectively, and the ultimate compressive strength at room temperature equal to 2300 MPa.

The structure and mechanical properties of the Ni41Al41Cr12Co6 intermetallic alloy prepared by vacuum induction remelting (VIR) of the SHS semi-product are studied. The evolution of the microstructure of the Ni41Al41Cr12Co6 alloy heated in the temperature range of 20–850 °C was investigated. Noticeable dissolution of Cr inclusions at temperatures above 550 °C is observed; the dissolution stage is preceded by fragmentation of dispersed Cr inclusions into nanocrystallites. The thermomechanical properties of the Ni41Al41Cr12Co6 alloy were determined in the temperature range of 400–1100 °C. VIR is found to increase high-temperature creep resistance and thermal stability of the Ni41Al41Cr12Co6 alloy to a certain extent.

In this work, we investigate the oxidation resistance of the coatings manufactured by reactive impregnation of Cf/C-SiC composites with a melt derived from layers of ZrSi2-MoSi2-ZrB2 powder composition synthesized by SHS and alternating layers of SHS powders and elemental Si. Oxidation resistance tests were conducted in static conditions at 1650 °C in air and under an air plasma torch at 2200 °C. The performance of the coatings in these conditions is defined by the emergence and evolution of the heterogeneous oxide films based on zirconia-modified borosilicate glass. The protective oxide layers effectively inhibit the oxygen influx and further oxidation of the substrate. The increase of temperature above 1750−1800 °C resulted in evaporation of the glass phase from the surface and formation of porous thermally insulating ZrO2-based layer with Mo/MoO2, Mo3Si, and Mo5Si3 inclusions. The gradient of temperature across the coatings’ thickness allows for a partial retainment of the glassy phase in the coatings’ lower layers due to the decrease of partial pressures of boron and silicon suboxides, resulting in an additional degree of protection against oxygen diffusion. The specimens were characterized in terms of the temperature and time boundaries of their performance, mass loss kinetics, catalytic activity, and spectral emissivity of the coatings. The limiting factors of the coatings’ performance are outlined.

This study aimed to obtain biocompatible ceramic materials in the Ti–C–Co–Ca 3 (PO 4 ) 2 –Ag–Mg system in combustion mode. The influence of cobalt additive on the combustion parameters, as well as the structure and properties of the electrode materials, was studied. Compact ceramics consists of a rigid frame of nonstoichiometric titanium (TiC 0,5 –TiC 0,6 ) carbide grains with titanium phosphate (Ti 3 PO (x) ) phase evenly distributed along the grain boundaries and with local precipitations of calcium oxide (CaO). The addition of cobalt leads to the formation of TiCo intermetallide and a complex CoTiP phase. Introduction of silver and magnesium causes the formation of a silver-based solid solution. Particular attention was devoted to studying the erosive capacity of the electrode materials during the pulsed electrospark deposition (PED) onto a titanium surface. The as-deposited coatings, which were 10 μm thick with a roughness Ra = 5–6 μm, exhibited high mechanical properties, as well as a sufficiently high level of biocompatibility and bioactivity. The silver additive enabled achieving a high antibacterial effect but resulted in a small inhibitory effect of osteoblastic proliferation and differentiation.

The study focuses on investigation of the combustion kinetics and mechanisms, as well as the phase- and structure formation processes, during elemental synthesis of ceramics based on zirconium diboride and silicide doped with aluminum. The effect of the degree of dilution with an inert component and initial temperature T 0 on the combustion kinetics of the Zr–Si–Al–B mixture is studied. An increase in T 0 in the range of 298–700 K causes a directly proportional rise in the combustion temperature T c and rate U c , which demonstrates that staging of the reactions of formation of zirconium boride and silicide remains invariant. The effective activation energy E eff of the combustion process is 225 kJ/mol, suggesting that the liquid-phase processes have a decisive effect on the reaction kinetics. The interaction of zirconium with boron and silicon runs through the Zr–Si–Al–B melt that is formed in the combustion zone. Staging of chemical transformations during phase and structure formation of SHS products is studied. The primary ZrB 2 grains crystallize from the melt in the combustion zone; the ZrSi silicide phase is formed with a delay of no longer than 0.5 s. Compact ceramics with composition ZrB 2 –ZrSi–ZrSi 2 –ZrSiAl 2 synthesized by forced SHS- pressing showing a great potential for high-temperature applications both as a construction material and as a precursor for ion-plasma deposition of coatings.

This article is devoted to the investigation into the combustion kinetics and mechanism of reaction mixtures in Zr–Si–B and Zr–B systems formed according to the forced SHS-pressing of compact ceramic materials, as well as to studying their heat resistance. It is shown that dependences of the combustion temperature and rate on the initial temperature (T0) for compositions in the Zr–Si–B system are linear; i.e., staging of chemical reactions of formation of zirconium diboride and disilicide remains invariable with an increase in T0. The values of effective activation energy of SHS process, which evidence the leading role of the reaction interaction of zirconium with boron and silicon in the melt, are calculated. Staging of chemical transformations in the combustion wave of the Zr–Si–B system is investigated: initially the ZrB2 phase is formed by crystallization from the melt, and then the ZrSi2 phase appears with a delay of 0.5 s; unreacted Si crystallizes after 1 s. The phase composition of synthesis products, in which the main component is ZrB2 diboride, and zirconium disilicide, Si, and ZrB12 boride are contained depending on the composition of the reaction charge, is investigated. Compact samples having high hardness and low residual porosity are fabricated according to forced SHS-pressing technology. High-temperature oxidation of SHS samples results in the formation of SiO2–ZrO2–B2O3 oxide films and ZrSiO4 complex oxide on their surface depending on the composition, which serve the effective diffusion barrier and lower the oxidation rate.

NiAl-based electrodes of a required size were fabricated by combined use of centrifugal SHS casting and induction remelting in an inert atmosphere and characterized by modern analytical methods. Thus produced electrode materials exhibiting high chemical purity and low content of impurity gases (0.005 wt % O, 0.0001 wt % N) can be recommended for use in centrifugal plasma sputtering of micro granules via the plasma rotating electrode process (PREP).

A complex production technology of electrodes from the powder alloy based on titanium aluminide TiAl, which includes the stages of fabrication of the powder alloy by calcium hydride reduction, treatment of the powder in a ball hard alloy mill with the addition of Y2O3 as a structural modifier, and the hydrostatic formation and sintering of a billet, is proposed. Formation and sintering processes are investigated for experimental samples and the alloy microstructure is investigated at all stages of process flowchart. The electrode for the plasma centrifugal spraying of the granules is fabricated using this technology.

The quantitative characteristics of steps formed by shear bands (SB) on the surface of deformed samples of bulk amorphous Zr60Ti2Nb2Cu18.5Ni7.5Al10 alloy were studied after high pressure torsion (HPT) and after rolling. It was found that the SB design depends on deformation mode. The deformation value decisively affects the SB power (the step height).

An integrated process for producing electrodes of TiAl-based powder alloy is proposed with the following stages: powder alloy production by hydride-calcium recovery, powder treatment in a carbide ball mill with Y2O3 added as a structure modifier, workpiece hydrostatic molding and sintering. Experimental samples were used to study molding and sintering processes and examine alloy microstructure at all stages of the processing chain. An electrode for plasma centrifugal disintegration of granules was produced using this technology.

The technique of centrifugal SHS was used to fabricate an alloy with a composition close that of commercially available alloy 48Ti–48Al–2Nb–2Cr by using Ti–Al–Nb2O5–Cr2O3–CaO2 thermite mixtures. The synthesized alloy exhibited a uniform structure and a composition close to that of commercial prototype. Its main drawback is the presence of undesired admixtures of O, N, P, Ca, C, and Si. Further efforts should be oriented on diminishing a contamination level.

Alloy powder of the Ti–47Al–2Nb–2Cr composition (at %) with a structure of TiAl (60 wt %) and Ti3Al (40 wt %) is prepared by the calcium-hydride method. The mode of calcium-hydride synthesis is optimized for the Ti–50Al (at %) model alloy. It is established that the reduction temperature should be no lower than 1100°C, while the excess of the CaH2 reducing agent should be no lower than 15 wt %. The main physicochemical and manufacturing properties of the synthesized Ti–47Al–2Nb–2Cr powder alloy, which provide the formation of dense compact items during its subsequent consolidation processes, are determined using modern analytical methods.

A complex manufacturing method of billets from material based on high-boron nickel aluminide is proposed. The method includes manufacturing the semifinished alloy products using a combined method of self-propagating high-temperature synthesis and centrifugal casting from oxide feedstock and subsequent vacuum induction remelting with the introduction of Al-based foundry alloys containing nanosized ZrO2 and modifying the structure. The evolution of the microstructure and phase composition is investigated at all production stages. A cast ZrO2-modified cylindrical billet, which possess high purity in regards to gas impurities (O 0.005 wt % and N 0.0001 wt %) and is suitable for the further production of powders by the plasma rotating electrode process, is fabricated according to the proposed technology.

The results of a study focused on combustion synthesis of the biocompatible ceramic material TiC–Ti3POx–CaO is reported. The effect of tricalcium phosphate (TCP) additives on the combustion process of the (100% – X)(Ti+0.5C)+X% Ca3(PO4)2 mixture, and the phase and structure formation of synthesis products, was studied. Parallel chemical reactions between Ti and C and between Ti and Ca3(PO4)2 occur in the combustion wave. It was shown that the resulting melt is based on titanium, and TCP forms the reactionary surface by capillary spreading onto the carbon black surface. The SHS product consists of an interconnected skeleton of nonstoichiometric titanium carbide grains with the titanium phosphate (Ti3POx) phase distributed uniformly along the grain boundaries, with inclusions of calcium oxide (CaO). The presence of the CaTiO3 phase is indicative of the interaction between calcium oxide and unreacted titanium in the post-reaction zone. Dense ceramic materials consisting of round-shaped grains of nonstoichiometric titanium carbide TiC0.55–TiC0.6, titanium phosphate (Ti3POx) and calcium oxide (CaO) were produced using the forced SHS- pressing technology. Increasing the TCP concentration reduces the size and hardness, but increases the residual porosity of structural components.

Kinetics of the SHS process, stages of chemical transformations and structure formation of ceramic materials in the Cr–Al–Si–B multicomponent system were investigated. The effect of reaction mixtures composition and initial temperature on the combustion rate U c and combustion temperature T c , which reduce with increasing Al content, was studied. An increase in the initial temperature of the SHS process causes a linear increase of U c and T c in the range of T 0 =290–750 K. This is evidence to the fact that each composition is characterized by the similar combustion mechanism, when the stages of chemical reactions of product formation remain unchanged. However, an increase in T 0 above 750 K, probably, may lead to exponential character of U c growth. Furthermore, an increase in Al content increases the proportion of the Al–Si eutectic melt. The dissolution of Cr particles in this melt becomes the rate-limiting stage of the combustion process, thus reducing the effective activation energy approximately from ~290 to ~110 kJ/mol. The stages of chemical transformations in the combustion wave were studied; the mechanism of structure formation was proposed. Firstly, the Al–Si eutectic mixture undergoes contact melting followed by formation of the reactionary surface as the melt spreads over the Cr and B particles surface. The melt is saturated with these elements followed by crystallization of CrB and Cr(Si,Al) 2 grains. In the Cr- and B-rich areas and low melt concentration, the formation of CrB may occur by solid-phase interaction supported via gas-transport reaction. Dynamic X-ray diffraction confirmed the sequential formation of chromium monoboride CrB and after chromium silicide Cr 5 Si 3 or chromium alumosilicide Cr(Si,Al) 2 . Force SHS–pressing was used to fabricate ceramic targets for magnetron sputtering of multicomponent coatings.

Cast NiAl/Ni20Al3B6 composites containing 2.3–3.5 wt % B have been prepared by centrifugal SHS for the first time. The composite materials comprised of a solid-solution matrix based on NiAl with inclusions of Ni20Al3B6 and complex boride (Mo, Cr)B. Best results were achieved at centrifugal accelerations 150–200 g in open air. Cast materials based on NiAl and τ-borides seem promising for use in turbine power units.

The goal of this work is to investigate the combustion mechanisms of reactions in the Mo–Si–B system and to obtain ceramic materials using the SHS method. It is concluded that the following processes are defined by the SHS for Si-rich Mo–Si–B compositions: silicon melting, its spreading over the surfaces of the solid Mo and B particles, followed by B dissolution in the melt, and formation of intermediate Mo 3 Si-phase film. The subsequent diffusion of silicon into molybdenum results in the formation of MoSi 2 grains and molybdenum boride phase forms due to the diffusion of molybdenum into B-rich melt. The formation of MoB phase for B-rich compositions may occur via gas-phase mass transfer of MoO 3 gaseous species to boron particles. The stages of chemical interaction in the combustion wave are also investigated. The obtained results indicate the possibility of both parallel and consecutive reactions to form molybdenum silicide and molybdenum boride phases. Thus the progression of combustion process may occur through the merging reaction fronts regime and splitting reaction fronts regime. Molybdenum silicide formation leads the combustion wave propagation during the splitting regime, while the molybdenum boride phase appears later. Finally, targets for magnetron sputtering of promising multi-phase Mo–Si–B coatings are synthesised by forced SHS compaction method.

Coatings on steel Kh12MF are fabricated by the force of electric-spark treatment by the TiB2-20% NiAl electrode and carbon-containing materials. Kinetics of their formation, the phase composition, mechanical and tribological properties, roughness, and durability to high-temperature oxidation are investigated. When depositing the coating using the TiB2-20% NiAl electrode, the effect of a disproportionate increase in the substrate erosion, which is observed with an increase in the energy of a single pulse and leads to lowering the content of boride phases in the coating is discovered. The subsequent electric-spark treatment of the boride coating using an electrode made of fine-grain dense graphite led to a noticeable improvement of tribological properties of the coating having no noticeable effect on its durability to high-temperature oxidation. In the case of applying an electrode made of the silicicated composition material, the coating durability to high-temperature oxidation increased substantially, but no improvement of tribological properties was observed.

The effect of the degree of room-temperature plastic deformation by high-pressure torsion on the tendency to plastic flow in the Zr60Cu18.5Nb2Ni7.5Al10Ti2 and Zr52.5Cu17.9Ni14.6Al10Ti5 bulk amorphous alloys has been studied by Vickers microindentation and precision measurements of the relative height of the “pileup” at the base of the indent. Three stages of the dependence of plasticity on the number of full revolutions of the moving anvil upon high pressure torsion of the alloys have been established.