Search

The paper studies the effect of electrolytic hydrogen charging on the plastic flow, strength properties, ductility, and fracture mechanisms in austenitic stainless steels Cr17Ni13Mo3C0.01, Cr18Ni10TiC0.12, and Cr18Ni9C0.17 with different stacking fault energies. The investigated steels are subjected to warm ABC-pressing and thermomechanical processing, including cold rolling and annealing, to produce the ultrafine-grained structure of different morphologies, such as ultrafine-grained (submicrocrystalline), misoriented grain-subgrain and mixed (grain and subgrain) structures of submicron scale. The strength properties of the steels after warm pressing and rolling with annealing exceed 3.5–6.0 times the properties of the quenched steels with coarse-grained structure. Electrolytic hydrogen charging of the studied steels with submicron-sized structure reduces the yield strength irrespective of the grain/subgrain size, structure, steel composition, and its stacking fault energy. The formation of a highly defective grain-subgrain structure with high dislocation density suppresses the effect of hydrogen embrittlement in Cr17Ni13Mo3C0.01 and Cr18Ni10TiC0.12 steels, in which no or a small volume fraction of strain-induced α′ martensite forms in tension. The tempering of the highly defective structure and the formation of a large fraction of high-angle misorientations in the stable Cr17Ni13Mo3C0.01 steel enhances the effect of hydrogen embrittlement in the specimens as compared to the specimens with a grain-subgrain structure with a high density of dislocations and low-angle boundaries. The hydrogen embrittlement effects are most pronounced in ultrafine-grained (submicrocrystalline) Cr18Ni10TiC0.12 and Cr18Ni9C0.17 steels with predominantly grain structure, which undergo induced γ→α′ phase transformation.

In this paper, we studied the phase and elemental composition of the surface layer of die steel 5KhNM subjected to electro-explosive sputtering deposited composite TiC–Ni–Mo coating and subsequent pulsed irradiation with a high-intensity submillisecond electron beam. The modes of electron-beam processing providing the formation of a dense, with a mirror gloss, surface layer with a submicrocrystalline structure based on titanium carbide and intermetallic compounds based on Mo, Ni, and Ti are determined. The electron-beam processing of an electro-explosive coating in the melting mode is shown to lead to the formation of a structurally uniform and concentration-uniform surface layer. TiC–Ni–Mo coatings have a 1.26 times higher wear resistance compared to die steel 5KhNM used as a substrate. The microhardness of the formed coatings is 450–2400 HV, the nanohardness is 25.5 GPa, and the modulus of elasticity is E = 398 GPa.

The electroexplosive method is used to obtain Ti-Zr coatings on the titanium dental implant surface (alloy VT6). Scanning and transmission electron microscopy as well as X-ray diffraction analysis are used to determine the elemental and phase composition; the morphology and defect substructure of the coating is studied. Hardness and Young’s modulus, friction coefficient and wear resistance of the formed coating are determined. The coating formed by electric explosion is found to be multielement and multiphase and to have a submicro-nanocrystalline structure.

Tensile properties, work-hardening, microstructure and fracture mechanisms were studied in two vanadium-containing high-nitrogen austenitic steels, Fe-19Cr-21Mn-1.3V-0.22C-0.81N and Fe-17Cr-10Mn-7Ni-1.0V-0.09C-0.65N, in low-temperature deformation regime. Vanadium-alloying provides several concurrent effects – decreases a solid solution hardening in the steels (softening effect) due to formation of nitrides(carbonitrides), causes precipitate hardening by vanadium-based particles (hardening effect) and suppresses grain growth during solid solution treatment (hardening effect). The yield stresses at room temperature deformation and 77 K-deformation are analyzed taking into account the contributions from these softening/hardening mechanisms. As a result of complex hardening and softening effects, both steels possess high tensile properties, show striking temperature dependences of the yield strength, an ultimate tensile strength and an elongation (the ultimate tensile strength and elongation at 77 K reaches 2600 MPa and 14% for Fe-19Cr-21Mn-1.3V-0.22C-0.81N steel) in low-temperature deformation regime. Striking temperature dependence of the yield strength for particle-containing steels is in accordance with deformation behavior of high-nitrogen particle-free steels with high solid-solution strengthening. In spite of similarities in temperature dependence of strength properties and deformation mechanisms with precipitate-free high-nitrogen steels, V-containing steels do not undergo ductile-to-brittle transition during deformation at cryogenic temperatures and they fracture in ductile manner even during tensile deformation at 77 K. Deformation microstructures at different strain levels and test temperatures are studied in order to reveal the dominating structural parameters responsible for fracture micromechanisms. Despite the activation of mechanical twinning and planar dislocation slip as dominating deformation mechanisms during tension at 77 K, precipitate-hardened high-nitrogen steels show rather high elongation values of 14–15% and ductile fracture with dimple micromechanism. Vanadium-based precipitates of ≈ 300 nm in diameter do not cause strong precipitate hardening, but strongly influence dislocation arrangement and suppress low-temperature brittle fracture in high-nitrogen austenitic steels.

The effect of the structural transformations during non-vacuum electron-beam cladding of amorphous boron powder on the hydroabrasive wear resistance of the surface layers of a chromium-nickel austenitic steel is studied. It is shown that the cladding yields a coating with densely arranged borides. An x-ray method is used to show that the modified layer consists virtually fully of Fe2 B iron borides. This structure raises the hydroabrasive strength of steel 12Kh18N9T by a factor of 1.5 – 2.

A temperature dependence of the tensile mechanical properties, microstructure and fracture mechanism of high-nitrogen Fe-(19-23)Cr-(17-21)Mn-(0-3)V-(0.1-0.3)C-(0.5-0.9)N vanadium-free and vanadium-containing steels was investigated. For all steels, the 0.2% offset yield strength and strain-hardening drastically increase with a decrease in test temperature. This is associated with high interstitial solid solution strengthening of the steels and more pronounced twinning and stacking-fault formation during straining below room temperature. For the vanadium-free steel, a ductile-to-brittle transition was evaluated: at 77K specimens destroy by cleavage mechanism while at room temperature steels show ductile fracture. Vanadium-alloying provides a particle strengthening of the steels and, at the same time, reduce solid-solution strengthening. Increase of vanadium concentration fully or partially suppress brittle fracture of the steels at 77K. Particle strengthening changes interstitial solid-solution effect, dislocation arrangement and slip/twinning relation in vanadium-containing high-nitrogen steels compared to vanadium-free one.

Features of the structure of a layered material welded by explosion of high-strength titanium alloy and tool roller steel with an intermediate layer of the structural low-carbon steel have been studied. The structural transformations occurring in materials upon their dynamic interaction have been analyzed. Particular attention is paid to the structure of vortex zones formed at the interfaces of billets of various steels, as well as structural steel and titanium-based alloy. The structural analysis methods made it possible to fix stable and metastable joints appearing upon the explosive welding of various metals. To reveal features of structural transformations caused by prolonged heating, billets of titanium alloy and structural steel were also joined by diffusion welding. It has been shown that, in the course of the diffusion welding process, a continuous layer of stable brittle intermetallic compounds is formed along the entire interface of the welded materials. In the explosively welded materials, the intermetallic phases are distributed locally and, thus, they have a weaker embrittlement effect.

This paper studies the effect of electrolytic hydrogen charging on the plastic deformation and fracture of Hadfield steel single crystals oriented for tension along the ‹111› and ‹144› directions, which the major deformation mechanism is mechanical twinning. Electrolytic hydrogen charging for five hours at a current density of 100 A/m2 slightly affects the stages of plastic flow, deformation mechanism, and the value of uniform elongation of ‹111› and ‹144› single clreystals. Hydrogen saturation causes shear microlocalization and a decrease of the strain hardening coefficient in twinning in one system, but slightly affects the strain hardening characteristics in multiple twinning. Hydrogen charging increases the fraction of the brittle component on fracture surfaces and leads to microand macrocracking near the fracture zone on the lateral surface of deformed specimens. It has been found experimentally that the stress relaxation rate in loaded ‹111› single clreystals after hydrogen saturation decreases. Mechanisms of describing this phenomenon have been proposed.

The study has been conducted in line with the current approach to investigation of materials obtained by considerably deep surface alloying of the titanium substrate with Ta, Nb, and Zr. The thickness of the resulting alloyed layer was equal to 2 mm. The coating was formed through weld deposition of a powder with the use of a high-voltage electron beam in the air. It has been lately demonstrated that manufactured such a way alloyed layers possess corrosion resistance which is significantly higher than the resistance of titanium substrates. It has already been shown that such two-layered materials are weldable. The study objective is to investigate the feasibility of rolling for necking the sheets with the Ti-Ta-Nb anticorrosion coating with further fourfold decrease in their thickness. The research is also aimed at investigation of the material properties after rolling. Anticorrosion layers were formed both on CP-titanium and on VT14 (Ti-4Al-3Mo–1 V) durable titanium alloy. The results of chemical composition determination, structure examination, X-ray phase analysis and mechanical properties observations (including bending properties of the alloyed layers) are presented in the paper. The combination of welding, rolling, and bending enables the manufacture of corrosion-resistant vessels and process pipes which are made from the developed material and find technological application.

A number of experimental studies of melt motion and droplet ejection caused by pulsed plasma load include the measurements of the shape of surface after the solidification of target. The measured shape may be different from the one during the heating stage because of melt motion. In present paper the evolution of this perturbations is treated as capillary waves on the melt surface. The dispersion relation for capillary waves taking into account viscosity and limited depth of liquid was used. The numerical estimations for the melt surface behavior are done for tungsten samples irradiated at BETA facility.

In this study, the non-vacuum electron beam (EB) technology was used to clad commercially pure (CP-) Ti with Ta and Nb. The microstructure of the samples was characterized using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). The cladded layers were 1.7–2.7 mm thick and had a dense defect-free structure. Compositional inhomogeneity caused by dendritic liquation was observed in the cladded layers. High cooling rates during non-vacuum EB cladding led to the formation of the α’, α”, β, and ω metastable phases in the samples. The nanoscale ω phase was found in the regions with a high amount of Ta and Nb. Due to the increase in the Nb and Ta content, the microstructure of the samples was refined, and the microhardness increased from 330 HV to 400 HV. The impact toughness of the materials with cladded layers remained at a sufficiently high level (180–250 J/cm2). Corrosion tests carried out in hot nitric acid revealed that the addition of 15% Ta and 11.3% Nb to Ti decreased the corrosion rate from 0.104 mm/year to 0.004 mm/year, which was related to an increase in the fraction of Ta and Nb oxides in the oxide film. The produced materials can be recommended as a relatively cheap alternative for nuclear waste recycling when a hot solution of nitric acid is used.

The research was devoted to studying unlubricated tribological behaviors of γ-TiAl-based coatings in the temperature range 25–400 °C. These γ-TiAl-based intermetallic coatings alloyed with Fe or Mn were formed on CP-Ti workpieces using a non-vacuum electron beam deposition. The microstructure, phase and elemental analyses proved the formation of γ-TiAl and appearance of the ternary phases (Laves and G-phases). It was shown that friction coefficients obtained for three materials were barely different but their fluctuations were strongly dependent on surface oxidation and the phase composition. It was found that the Ti-45Al-8Mn (at.%) coatings consisting mainly of γ and α2 phases had lower wear resistance in comparison with the Ti-42Al-7Fe (at.%) and Ti-57Al-13Fe (at.%) coatings. Whereas the Ti-57Al-13Fe (at.%) coating contained γ and G phases possessed better wear resistance as compared to that of Ti-42Al-7Fe (at.%) coating with the structure represented by the γ matrix and a eutectic (α2 + Laves phases). The microprobe analysis, scanning electron and optical microscopy, and XPS measurements revealed the formation of highly oxidized mechanically mixed layers after the sliding tests. The Ti-45Al-8Mn (at.%) coating subsurface consisted of Al2O3, Al, TiO2, and Ti sub-oxides, whereas for both Ti-Al-Fe coatings the formation of an initial oxide film consisted of a titanium dioxide (rutile structure), alumina, and a low amount of iron oxide (hematite structure) was revealed. Thermal softening of the counter body provoked the iron oxide growth in the wear traces of the coatings alloyed with Fe. Tribooxidation behaviors of Ti-Al-Fe coatings may be interpreted as an example of adaptation the as-deposited structure and phases to high-temperature sliding condition and therefore these coatings can be recommended for protection of the titanium alloy components.

Experimental research on behavior of rolled tungsten plates under intense transient heat loads generated by a powerful (a total power of up to 7 MW) long-pulse (0.1–0.3 ms) electron beam with full irradiation area of 2 cm2 was carried out. Imaging of the sample by the fast CCD cameras in the NIR range and with illumination by the 532 nm continuous-wave laser was applied for in-situ surface diagnostics during exposure. In these experiments tungsten plates were exposed to heat loads 0.5–1 MJ/m2 with a heat flux factor (Fhf) close to and above the melting threshold of tungsten at initial room temperature. Crack formation and crack propagation under the surface layer were observed during multiple exposures. Overheated areas with excessive temperature over surrounding surface of about 500 K were found on severely damaged samples more than 5 ms after beam ending. The application of laser illumination enables to detect areas of intense tungsten melting near crack edges and crack intersections.

In the present study the effect of the thermal-mechanical processing regime—cold high-pressure torsion (HPT) at room temperature, cold HPT followed by annealing at 773 K (500 °C), and warm HPT at 723 K (450 °C)—on the peculiarities of the microstructure and microhardness of a Mo-Nb-Ti-V-0.08C microalloyed steel was analyzed. HPT processing resulted in high deformation and refinement of the initial structure and produced an ultrafine-grained microstructure featuring different morphologies with fine (

In the present research a novel method of increasing in mechanical characteristics (wear resistance, friction coefficient, Young's modulus and nanohardness) of titanium implants is proposed. A complex processing was used including electroexplosion spraying of hafnium coating and subsequent electron-beam processing combined with nitriding. Electroexplosion spraying was carried out in the modes ensuring the formation of microrelief on the boundary with titanium substrate. Electron beam processing of hafnium coating surface allowed its smooth surface to be provided and the coating to be nanostructurized. Smooth surface makes the coating a more commercially profitable for selling the medical products and nanostructurization ensures a high level of mechanical and biolodical properties. The obtained coating of Ti-Hf-N system contributes to the increase in wear resistance by the factor of 17.4 and simultaneous increase in friction coefficient by 7%. The coating also ensures the increase in nanohardness by the factor of 2.05 and the increase in the Young modulus by 13% in comparison with Ti-6Al-4V alloy. Nitriding allowed the strengthening of hafnium coating by nitrides. In the coating 40–50 μm in thickness hafnium is distributed homogeneously and is presented in the phases of HfN, Hf and HfTiN2. The comparison of the phases being formed in the coating and the structural components of coatings' surface depending on processing mode is made. After combined processing the surface of the coating is presented by three different structural components. The proliferative activity of fibroblasts and antimicrobial activity were studied as biological properties of the coating in the present research. The structure of the coating is studied by the methods of modern physical materials science. The complex analysis carried out enables one to recommend the coating for subsequent tests on experimental animals (rabbits) and further commercial production of strengthened titanium implants. To study osteointegration the samples of the experimental implants with bioinert coatings obtained in the present research are to be introduced into rabbits' osseous tissue in future.

The effect of annealing on the evolution of an ultrafine-grain structure and carbides in a 06MBF steel (Fe–0.1Mo–0.6Mn–0.8Cr–0.2Ni–0.3Si–0.2Cu–0.1V–0.03Ti–0.06Nb–0.09C, wt %) has been studied. The grain–subgrain structure (d = 102 ± 55 nm) formed by high-pressure torsion and stabilized by dispersed (MC, M3C, d = 3–4 nm) and relatively coarse carbides (M3C, d = 15–20 nm) is stable up to a temperature of 500°C (1 h) (d = 112 ± 64 nm). Annealing at a temperature of 500°C is accompanied by the formation in regions with a subgrain structure of recrystallized grains, the size of which is close to the size of subgrains formed by high-pressure torsion. The average size and distribution of dispersed particles change weakly. The precipitation hardening and the increase in the fraction of high-angle boundaries in the structure cause an increase in the values of the microhardness to 6.4 ± 0.2 GPa after annealing at 500°C as compared to the deformed state (6.0 ± 0.1 GPa). After 1-h annealing at 600 and 700°C, the microcrystal size (d = 390 ± 270 nm and 1.7 ± 0.7 μm, respectively) increases; the coarse M3C (≈ 50 nm) and dispersed carbides grow by 5 and 8 nm, respectively. The value of the activation energy for grain growth Q = 516 ± 31 kJ/mol upon annealing of the ultrafine-grained steel 06MBF produced by high-pressure torsion exceeds the values determined in the 06MBF steel with a submicrocrystalline structure formed by equal-channel angular pressing and in the nanocrystalline α iron.

The phase transformations of the alloy Ti-40 mas % Nb after tempering and severe plastic deformation are studied. The phase transformations of the alloy according to the type and conditions of external influences are analyzed using methods of XRD, SEM and optical metallography. It is determined that inverse phase transformation of the metastable α''-phase to equilibrium β-phase is carried out after severe plastic deformation. Complete phase transformation α'' → β is typical for the mode, which consists of three pressing operation with the change of the loading axis in cramped conditions, followed by a multi-pass rolling in grooved rolls.

The purpose of the research was to form a Ti-Ta-N- system bioinert coating on Ti6Al4V alloy surface as well as to study its structure and properties. The main contribution of the research is in the following. Electro-explosion spraying of tantalum coating on VT6 titanium alloy surface was pioneered in the research. After that the processing of the coating by low-energy high-current electron beam and subsequent nitriding was carried out in a single technological cycle. It has been established that a nanocrystalline coating based on tantalum, nitrogen and titanium was formed as a result of the technological operations. The phase composition of the coatings has been detected. The variations in crystal lattice parameters being formed in coating of phases and coherent scallering regions of these phases depending on power density of electron beam have been determined. Structural characteristics of the coatings at nano- and microlevel have been detected. Tests of coatings for nanohardness, the Young modulus, wear resistance and friction factor have been carried out. By all technical characteristics Ti-Ta-N-system coating exceeds titanium of VT6 grade. The cause of the increase in mechanical characteristics of the Ti-Ta-N-system coating is their nanostructural state and strengthening phases. Tests for proliferation activity of fibroplasts and antimicrobial activity have shown better results in comparison with VT6 titanium alloy as well. It is due to escape of vanadium ions from VT6 alloy into nutrient cell medium and their destructive effect on cell cultures. Variations in proliferation and antimicrobial activity develop due to amplification of cell proliferation. A complex of the obtained characteristics makes it possible to recommend Ti-Ta-N-system coating for its application as a bioinert coating on different implants in furure.

The structural transformations of the Cr-Ni austenitic steel surface layers during non-vacuum electron beam cladding of the amorphous boron and wetting agents (Cr, Ni, Fe) were investigated. Gas- and hydroabrasive wear resistance of the obtained materials was evaluated. It was shown that the modified layer almost completely consisting of the complex borides (Cr,Fe)хBy is formed during the cladding. The structure provides improving the wear resistance of the steel by 2-5 times. The thickness of the formed layers is 2.5-2.7 mm. The coating formed by beam current 23 mA with Fe as wetting agent has the best set of properties.

The influence of the cladding rate on the structure and microhardness parameter of coatings obtained by non-vacuum electron beam treatment of Ni-Cr-Si-B powder mixtures was investigated. Modified layers characterized by the gradient structure and consist of dendritic grains and a eutectic located at the grain boundaries. It was found that the lowest microhardness level (300 HV) was characteristic of the coatings obtained when the workpiece was moving relative to an electron beam with a speed of 10 mm per second. This treatment regime allowed obtaining high-quality coatings 2.5 mm in thickness. However, a large thickness of fusion penetration led to the interfusion of the base metal with a coating material and a decrease in the concentration of alloying elements in the coating. Reducing the lifetime of the liquid phase during treatment prevented intensive diffusion processes. Increasing the treatment velocity to 20 mm per second doubled the cladded layer microhardness (up to 650 HV).

The widespread use of polymeric semiconductor compositions for creating flexible and inexpensive solar cells can be achieved by providing the higher values of the coefficient of efficiency. The cost-effective production of polymer solar cells is expected at the efficiency of them not less than 10 %, while now its real level does not exceed 4 %. Many laboratories work to develop semiconductor compositions of organic materials as donors and acceptors which are fullerene derivatives or nanosize particles of semiconductor inorganic compounds [1-6]. The prospect of polymer used depends on the photovoltaic materials and the polymer purity and to a greater extent on the structure of the films formed from the compositions under development. In the search for ways to achieve higher performance of solar cells it is essential to optimize the technology of polymeric composition preparation, of which the active layer is formed, as well as optimization of the layer formation. In order to get information about the relationship between the structure of formed layer and its photovoltaic characteristics it is suggested to analyze the structure of the active layer simultaneously with the monitoring of its current-voltage characteristics. The study of the material structure directly in the process of its evolution seems an urgent task, since the majority of modern methods of structure investigation (light and electron microscopy, X-ray analysis) is not able to detect structural changes occurring in a short period of time. The most useful tool for monitoring the structure of polymer active layer is high intensity X-ray diffraction.

The effect of solid solution temperature (1100 and 1200°C) on microstructure, phase composition and temperature dependence of 0.2% offset yield strength R0.2, in the temperature range of 77 to 673 K was studied for high-nitrogen austenitic Fe–19Cr–21Mn–1.5V–0.3C–0.9N (wt. %) steel. Increase in solid solution temperature provides a partial dissolution of (V, Cr)(N, C) particles and increases a concentration of carbon and nitrogen in austenite. A complex effect of solid solution hardening and particle strengthening provides strong temperature dependence of the yield strength in the steel independently on solid solution temperature. The mechanisms, responsible for the variation in the yield strength with test temperature and solution treatment, are described on the basis of the microstructural parameters of the steel.

The influence of hydrogen-charging on microstructure and microhardness of a high-nitrogen austenitic Fe– 19Cr–21Mn–1.5V–0.3C–0.8N (wt. %) steel processed by high-pressure torsion (HPT) was investigated. X-rays diffraction data indicate that hydrogenation of HPT-deformed specimens leads to an additional broadening of X-rays lines and their shifting, which testify to the formation of the stacking-faults and high residual stresses. Hydrogen-charging of HPT-processed steel promotes to γ–e martensitic transformation. Due to hydrogen-induced phase hardening, the microhardness of HPT-deformed specimens increases up to 6.8 GPa in hydrogen-charged condition (6.5 GPa in hydrogen-free one). After following exposure of hydrogen-charged specimens for 170 h at air condition, the release of hydrogen atoms occurs, and the X-rays lines shift back to positions corresponded to hydrogen-free HPT-processed specimens.

Nanocomposite materials on the basis of ultra-high-molecular-weight polyethylene and multilayer carbon nanotubes (MCNTs), the concentration of which varied from 0.1 to 1 wt %, were prepared by combined deposition from solution. The presence of carbon nanotubes in the polymer matrix leads to structural changes strongly affecting the physical properties of composites. The interrelation between the macroscopic behavior under deformation and the microstructure of the composite was studied in situ by X-ray structural analysis with the application of synchrotron radiation. The results indicate that the martensite transformation of the orthorhombic phase of ultra-high-molecular-weight polyethylene into the monoclinic one induced by the deformation and the relative content of the metastable phase are determined by the presence of carbon nanotubes.

The application of electron-beam processing enabled to obtain the mirror luster of electroexplosive coating surface of CuO-Ag system, to reduce the roughness without the loss of the composite material, to homogenize the surface layer of the coatings to the whole thickness of the coating being equal to 40 μm. The utilization of the selected regimes of pulsed electron—beam processing results in the realization of the processes of surface layer structurization of electroexplosive coating of CuO-Ag system. The phase composition of electroexplosive coating of CuO-Ag system after electron—beam processing presents the following phases: Ag, Cu2O, Cu64O and Cu. The electroexplosive coating of CuO-Ag system fail after 3000 cycles of switching on / switching off in the course of the accelerated electroerosion resistance tests. During the accelerated electroerosion resistance tests the electrical resistance is acceptable to the weak—current electrical contacts and is within the interval from 5.8 to 14.8 μOhm. The wear resistance tests have shown that EES of copper is accompanied by ≈3.3-fold increase in wear resistance of the modified layer; in this case, ≈1.3-fold increase in the fiction coefficient is observed. Nanohardness of coating layer varies within 280 MPa to 290 MPa at the average hardness value being 866.5 MPa. Young modulus varies within 24.3 GPa to 71.7 GPa at the average value of the modulus of 49.6 GPa.

For the first time, electroerosion-resistant coatings of the CuO–Ag system were obtained by electro-explosive spraying. The coating structure was investigated by atomic force microscopy and scanning electron microscopy. The formed coating is a homogeneous composite material consisting of a silver matrix and CuO inclusions located in it. The composite electro-explosive coating of CuO–Ag system is obtained on copper electric contact of contactor KPV-604. Tests of sprayed coatings for electrical erosion resistance under arc erosion conditions were carried out. A formation mechanism of hierarchical levels of the structure of electro-explosive coatings was suggested. The mechanism is based on theoretical concepts of the formation and evolution of fractal aggregates with diffusion-limited and cluster-cluster aggregations of the CuO. Based on the electrical properties of silver and copper oxide, the dependence of electrical contact resistance on the number of on/off cycles in the process of testing for electrical erosion resistance is substantiated.

Structural changes developing in surface layers of plates from steel 20 in the process of explosive welding are studied with the help of light metallography and scanning and transmission electron microscopy. Mathematical simulation is used to compute the depth of the action of severe plastic deformation due to explosive welding of steel plates on the structure of their surface layers.

The paper explores the effect of a modifier based on ultrafine powders of refractory metal oxides on the change of structural state, phase composition and mechanical properties of cast iron of ИЧХ28Н2 (Russian grade). It was shown that the modifier added to the melt does not change the phase composition of ferrite-austenitic matrix and carbides and is not carbide-forming. Material microstructure changes only due to the presence of a large amount of crystallization nuclei during the casting cooling. It was established that the modification increases the ultimate stress limit by 53%, plasticity by 10.7%, corrosion resistance by 15%, and leads to the reduction of friction factor and linear wear due to the decreasing of structural elements: carbide phase and austenitic-carbidic eutectic.

We present several possible microstructure development scenarios in Ti3SiC2-Cu composites during mechanical milling and Spark Plasma Sintering (SPS). We have studied the effect of in situ consolidation during milling of Ti3SiC2 and Cu powders and melting of the Cu matrix during the SPS on the hardness and electrical conductivity of the sintered materials. Under low-energy milling, (3–5) vol.%Ti3SiC2-Cu composite particles of platelet morphology formed, which could be easily SPS-ed to 92–95% relative density. Under high-energy milling, millimeter-scale (3–5) vol.%Ti3SiC2-Cu granules formed as a result of in situ consolidation and presented a challenge to be sintered into a bulk fully dense sample; the corresponding SPS-ed compacts demonstrated a finer-grained Cu matrix and more significant levels of hardening compared to composites of the same composition processed by low-energy milling. The 3 vol.% Ti3SiC2-Cu in situ consolidated and Spark Plasma Sintered granules showed an extremely high hardness of 227 HV. High electrical conductivity of the Ti3SiC2-Cu composites sintered from the granules was an indication of efficient sintering of the granules to each other. Partial melting of the Cu matrix, if induced during the SPS, compromised the phase stability and uniformity of the microstructure of the Ti3SiC2-Cu composites and thus it is not to be suggested as a pathway to enhanced densification in this system.