Romanov, Denis Anatolyevich

Филяков А.Д., Почетуха В.В., Романов Д.А., Ващук Е.С., Громов В.Е.

С использованием рентгеноструктурного анализа, сканирующей и просвечивающей электронной микроскопии исследована микроструктура нового композиционного TiB2 – Ag-покрытия с металлической матрицей, нанесенного методом электровзрывного напыления и модифицированного электронно-пучковой обработкой. Показано, что фазовый состав покрытий зависит от режима напыления, а последующая электронно-пучковая обработка его нормализует. Основными фазами полученного модифицированного покрытия являются Ag, TiB2 и B2O. После электронно-пучковой обработки микроструктура покрытия трансформируется. Наноструктура серебряной матрицы преобразуется в нанокристаллическую структуру со средним размером кристаллов от десятков до сотен нанометров.

Громов В.Е., Ващук Е.С., Романов Д.А., Филяков А.Д., Почетуха В.В.

В настоящем исследовании продемонстрировано влияние электронно-пучковой обработкой на структуру и фазовый состав композиционного покрытия с металлической матрицей системы TiB2–Ag, нанесенное по средствам электрического взрыва. Фазовый состав и структура покрытий были исследованы при помощи методов рентгеноструктурного анализа, сканирующей и просвечивающей электронной микроскопии. Фазовый состав покрытий, полученных электровзрывным методом, варьируется от образца к образцу. Воздействие электронно-пучковой обработки привело фазовый состав покрытий к единообразию. Основными фазами после модификации покрытия электронным пучком являются Ag, TiB2 и B2O. Увеличение плотности энергии и длительности импульса приводит к уменьшению содержания легкоплавкой фазы Ag и образованию медьсодержащих фаз за счет нагрева и плавления медной подложки избыточной энергией электронного пучка. Структура покрытия представлена серебряной матрицей с включениями в виде частиц TiB2. Влияние электронно-пучковой обработки на структуру покрытия носит слабовыраженный характер. Однако под действием электронного пучка микроструктура покрытия трансформировалась в ячеистую кристаллизационную структуру. Наноструктура серебряной матрицы была преобразована в нанокристаллическую структуру со средним размером кристаллов от десятков до сотен нанометров.

Pochetukha V.V., Romanov D.A., Vashchuk E.S., Filyakov A.D., Gromov V.E.

A coating of the TiB2-Ag system was formed through the use of sequential operations of electroexplosive spraying and electron beam processing. The values of electrical conductivity (62.0 MS/m), Vickers microhardness (0.251-0.265 GPa at the point of measurement on a silver matrix and 25-32 GPa at the point of measurement at inclusions of boride phases), nanohardness (4.48 ± 0.76 GPa) were determined), Young’s modulus (116±29 GPa), wear parameter under dry friction-sliding conditions (1.2 mm3/N • m) and friction coefficient (0.5). Switching wear resistance during accelerated tests was 7000 on and off cycles with an electrical resistance of 10.01 - 11.76 LiOhm. The thickness of the coatings is 100 microns. The coatings are formed by a silver matrix with inclusions of titanium borides located in it with three types of sizes: nanocrystalline, submicrocrystalline and microcrystalline. Quantitatively, in the structural composition among titanium borides, titanium diboride and silver (56 wt. %) are formed predominantly (41 wt. %), while other titanium borides account for 3 wt. %. Structural transformations are described using complementary methods of X-ray phase analysis, scanning and transmission electron microscopy.

Romanov D.A., Moskovskii S.V., Pochetukha V.V., Vashchuk E.S., Ivanov Y.F.

Romanov D.A., Sosnin K.V., Pronin S.Y., Pochetukha V.V., Ivanov Y.F., Gromov V.E.

Abstract—An attempt was made to solve the problem of creating a coating for an implant having better biological compatibility than Titanium Grade 5 medical titanium alloy. A coating of Mo–Nb composition was prepared by the electroexplosive method on Titanium Grade 5 medical titanium alloy and formed as a result of the simultaneous electric explosion of foils made of molybdenum and niobium. A set of studies was carried out to determine the structure, phase composition, and properties of the prepared coatings. It is shown that the hardness of the coating surface layer is 60% and the Young’s modulus is 43% higher than the corresponding characteristics of Titanium Grade 5 alloy. The thickness of the layer with high (relative to the substrate) values of hardness and Young’s modulus reaches 80 μm. It was found that the coating wear parameter is 1.8‑fold and the coating friction coefficient is 1.6-fold higher than the substrate wear parameter and friction coefficient. It was determined that, along with coating atoms, the surface layer comprises Al, Ti, V, O, and C atoms, indicating that the coating is doped with the substrate atoms. In the detected coating stratification by elemental composition, the top part of the coating is enriched in niobium atoms, and the bottom part is enriched in molybdenum atoms. The coating was shown to have a polycrystalline structure formed by a molybdenum-based solid solution. The bulk and the grain boundaries compose the second phase comprising α-Ti, Nb, Mo9Ti4, and NbTi4 of various shapes and sizes. The phase composition studies revealed no vanadium or aluminum compounds, which reduce the biocompatibility of coatings. The detected phases comprise only molybdenum, niobium, and titanium, which are bioinert, which allows predicting higher biocompatibility compared to the that of Titanium Grade 5 medical alloy. It is recommended to use the resulting coatings for further clinical tests.

Ivanov Y.F., Gromov V.E., Guseva T.P., Chapaikin A.S., Vashchuk E.S., Romanov D.A.

The methods of light, scanning, and transmission electron microscopy are used to study the structure, phase composition, and properties of multilayer plasma surfacings made of high-speed steel R18YU in a protective-alloying nitrogen medium, followed by a fourfold high-temperature tempering and additional electron beam processing. After tempering, the deposited layer on the 30KHGSA high-speed steel R18YU has a polycrystalline structure with a cell size of 7–22.5 µm with layers of the second phase along the boundaries and at the joints of the grains. It is shown that the irradiation of surfaised layers with a pulsed electron beam (energy density 30 J/cm2, pulse duration 50 µs, number of pulses 5, and pulse repetition rate 0.3 s–1) leads to the formation of a thin (30–50 µm) surface layer with a cellular crystallization structure. The volume of grains is formed by a solid solution based on α-Fe. Nanoscale (10–45 nm) particles of iron, chromium, and tungsten carbides of complex composition, such as M6C and M23C6, are located in the volume and along the boundaries of the crystallization cells. Fragmentation of the surface layer by a grid of microcracks is revealed, indicating relaxation of thermal stresses formed during high-speed cooling after electron beam processing. The particles have a faceted or globular shape. After irradiation with an electron beam, the wear resistance of the material increases by more than 3 times, while maintaining the microhardness of the modified layer (~5.3 GPa).

Ivanov Y.F., Gromov V.E., Potekaev A.I., Guseva T.P., Chapaikin A.S., Vashchuk E.S., Romanov D.A.

Using plasma surfacing in a nitrogen environment with a PP-R18U non-current-carrying flux-cored wire, the layers up to 10 mm thick were formed on a 30HGSA steel, followed by an additional high-temperature tempering (at 580°C for 1 hour in 4 tempers). It is shown that the deposited layer has a frame-type structure formed by α-iron grains with extended layers of the Fe3W3C (M6C) carbide phase located along the boundaries. Nanosized particles of carbides of the V4C3, Cr7C3, Fe3C, Cr23C6 and WC1–x types are identified in the grain volume. It is found out that high tempering increases the microhardness of the deposited PP-R18U layer by 13% (up to 5.3 GPa) and decreases its wear resistance by 12.3% the friction coefficient by 7.7%.

Filyakov A.D., Pochetukha V.V., Romanov D.A., Vashchuk E.S.

Due to many factors, the electrical explosion spraying process is not stable, which directly causes unstable coating quality and structure. Electron beam treatment may be used to improve the surface and modified structure of coatings sprayed by electrical explosions. In this study, a new TiB2–Ag metal matrix composite coating was deposited by electrical explosion spraying and modified by electron beam treatment. The prepared coatings were characterized by surface macro- and microanalysis, XDR, cross-section SEM, and TEM. The composition of the spray-coating phase differs from sample to sample. The electron beam treatment normalized the phase composition. Ag TiB2 B2O became the main phase in the modified coating. Increasing the pulse energy density and duration leads to a reduction in the low-melting Ag phase and the formation of copper contact phases due to heating and melting of the copper substrate by excess electron beam energy. The coating structure consists of a silver matrix and TiB2 inclusions. The electron beam treatment did not affect the structure; however, the microstructure of the coating transformed into a cellular crystallization structure. The silver matrix nanostructure was transformed into a nanocrystalline structure with an average crystal size ranging from tens to hundreds of nanometers.

Громов В.Е., Филяков А.Д., Романов Д.А., Соснин К.В., Иванов Ю.Ф.

Металлы широко применяются для долговременных ортопедических имплантатов. Это вызвано их высокой прочностью на растяжение и сжатие, высоким пределом текучести, усталостной прочностью, пластичностью, твердостью и ударной вязкостью. Однако металлические материалы не обладают биофункциональными свойствами. Применение титановых сплавов в изготовлении имплантатов ограничивается их низкой твердостью и плохой износостойкостью. В случае применения титанового сплава ВТ6 в качестве имплантата при работе в организме человека выделяются ионы алюминия и ванадия, которые пагубно влияют на организм. В настоящей статье решается проблема устранения воздействия алюминия и ванадия из титанового сплава ВТ6 на организм человека. На поверхности титанового сплава ВТ6 созданы покрытия Ti–Nb–Zr–N. Данные покрытия в будущем предполагается использовать для лучшей приживаемости титановых имплантатов в организме человека. Формирование покрытий включало электровзрывное напыление состава Ti–Nb–Zr, электронно-пучковую обработку и азотирование. Покрытия исследовали методами сканирующей и просвечивающей электронной микроскопии. Полученное покрытие сформировано атомами титана, ниобия, циркония и азота. Алюминий и ванадий не проникают в покрытие из подложки. Такая композиция элементов формируется как на поверхности, так и по всей толщине покрытий. Основными фазами покрытия являются α-Ti, TiN, Ti2N, NbTi4, NbN и Zr2N. Определены микротвердость, модуль Юнга, износостойкость и коэффициент трения покрытий. Проведенный комплекс исследований позволяет рекомендовать полученные покрытия для дальнейших клинических испытаний.

Romanov D.A., Pochetukha V.V., Moskovskii S.V., Sosnin K.V., Ivanov Y.F., Gromov V.E.

Romanov D.A., Sosnin K.V., Pronin S.Y., Ivanov Y.F., Gromov V.E.

Romanov D.A., Pochetukha V.V., Gromov V.E., Sosnin K.V., Ivanov Y.F.

Copper-based Ag–Co–N coatings are fabricated by a combined method, which includes electroexplosive spraying, electron-beam treatment, and nitriding. The nanohardness, the wear resistance under dry sliding friction conditions, the coefficient of friction, the electrical conductivity, and the electroerosion resistance of the coatings are investigated, and their structure and phase composition are analyzed.

Romanov D.A., Pochetukha V.V., Sosnin K.V., Moskovskii S.V., Gromov V.E., Bataev V.A., Ivanov Y.F., Semin A.P.

The article is concerned with analyzing the structure and properties of the Ni–C–Ag–N coating formed on copper by the complex method combining the electroexplosive spraying of coating, its irradiation by a pulsed electron beam and a subsequent nitriding in plasma of a gas discharge of low pressure. The structural constituents of coating's surface after the electroexplosive spraying as well as after the electron-beam processing and nitriding are studied. It is shown that a coating's thickness amounts to ≈90 μm. The wear resistance of a copper sample with the deposited coating exceeds that of the copper without the coating by ≈ 1.6 times. The friction coefficient of samples with the coating (μ = 0.5) is less than that of the copper without the coating (μ = 0.679) by ≈ 1.35 times. It is established that the hardness of the coating increases as the substrate is approached and reaches the maximum value of ≈1780 MPa (the hardness of substrate is 1300 MPa). By means of micro-X-ray-spectral analysis it is detected that the main chemical element of the coating is silver, but copper, nickel, carbon and nitrogen are present in a considerably smaller quantity. It is established by the methods of diffraction electron microscopy that the main phases of the coating are solid solutions.

Ivanov Y.F., Pochetukha V.V., Romanov D.A., Gromov V.E., Peregudov O.A.

The aim of this work is to analyze the structure and properties of a coating of the SnO2–In2O3–Ag–N composition formed on copper by a complex method combining electroexplosive spraying, irradiation with a pulsed electron beam, followed by nitriding in the plasma of a low-pressure gas discharge. It is shown that the thickness of the coating is ≈100 μm. The wear resistance of a coated copper specimen exceeds that of uncoated copper by a factor of 2.8. The friction coefficient of the coated specimens is μ = 0.479, which is a factor of 1.4 lower than that of uncoated copper μ = 0.679 ± 0.048. It is found out that hardness of the coating increases closer to the substrate and reaches a maximum value of ≈ 1400 ± 98 MPa (the substrate hardness is 1270 MPa). According to the micro X-ray spectral analysis, the main chemical element of the coating is silver; copper, tin, indium, oxygen and nitrogen are present in much smaller amounts. It is revealed by the XRD analysis that the main phases of the coating are copper- and silver-based solid solutions.

Romanov D.A., Pochetukha V.V., Gromov V.E., Sosnin K.V.

WN–WC–W2C0.84–Ag coatings are fabricated by a combined method, which combines electroexplosive spraying, nitriding, and electron-beam treatment. The structure, phase composition, nanohardness, Young’s modulus, wear resistance under dry sliding friction conditions, friction coefficient, electrical conductivity, and electroerosion resistance of the coatings are investigated.

Bashir K., Gupta D., Jain V.

Nevskii S.A., Bashchenko L.P., Sarychev V.D., Granovskii A.Y., Shamsutdinova D.V.

The combined effect of inclined electric fields and a transverse acoustic field on the Kelvin–Helmholtz instability of the interface of viscous electrically conductive liquids is studied using the example of air – water and argon – iron systems. An inclined electric field, regardless of the effect of sound vibrations, leads to the increased Kelvin–Helmholtz instability in the micrometer wavelength range. The most intense increase in the disturbances of the interface is observed at the angle of inclination of the electric field π/3. This opens up new opportunities for the development of technologies for accelerated cooling of rolled products and surfacing materials by regulating the drop transfer of material. The combined effect of acoustic and electric fields has an ambiguous effect on the Kelvin–Helmholtz instability. In the case of an air – water system, sound vibrations lead to suppression of the Kelvin–Helmholtz instability, while a tangential electric field with a strength of 3·106 V/m enhances this effect, and a normal field, on the contrary, weakens it. For the argon – iron system, sound vibrations lead to the complete disappearance of the viscosity-conditioned maximum and to a significant decrease in the growth rate of disturbances at the interface, which corresponds to the first maximum. Application of a horizontal electric field with a strength of 3·107 V/m significantly weakens the effect of suppressing the Kelvin–Helmholtz instability, while in a vertical field, on the contrary, increases it. It was established that the restoration of the first hydrodynamic maximum in a normal electric field is possible with a ratio of specific electrical conductivities σ greater than 0.012, regardless of the presence of a sound field. A change in the influence of the vertical electric field from a stabilizing to a destabilizing one is possible with a ratio of σ from 0.015 or more.

Potekaev A.I., Gromov V.E., Ivanov Y.F., Klopotov A.A., Abzaev Y.A., Yuriev A.B., Shlyarova Y.A., Kulagina V.V.

Meng F., Zhou Y., Zhang H., Wang Z., Liu D., Cao S., Cui X., Nong Z., Man T., Liu T.

Wear-resistant coatings applied to the surface of copper and copper alloys through diverse advanced technologies can substantially enhance their wear resistance and broaden their application spectrum. This paper provides a comprehensive review of the development and current research status of wear-resistant coatings fabricated on copper and its alloys. It presents the research findings on the preparation of wear-resistant coatings using both one-step methods (such as laser cladding, electroplating, thermal spraying, cold spraying, electro-spark deposition, etc.) and two-step methods (chemical plating and heat treatment, electrodeposition and laser cladding, laser cladding and in situ synthesis, etc.). This paper provides an in-depth examination of the characteristics, operating principles, and effects of various coating techniques on enhancing the wear resistance of copper and copper alloys. The advantages and disadvantages of different coating preparation methods are compared and analyzed; meanwhile, a prospective outlook on the future development trends is also offered.

Bashir K., Gupta D., Jain V.

Ivanov Y.F., Gromov V.E., Yuryev A.B., Minenko S.S., Semin A.P., Chapaikin A.S.

Lepeshkin A.R., Fedin M.A., Kuvaldin A.B., Kondrashov S.S., Suleymanov R.F., Ilyinskaya O.I.

We discussed an integrated approach to mathematical modeling and study of electromagnetic field parameters in a two-layer and three-layer conducting medium during induction heating of a cylindrical steel product with melting of a conductive metal coating, providing a joint study of processes considering two Curie points occurring in the induction heating device and in the product with conductive coating.

Filyakov A.D., Pochetukha V.V., Romanov D.A., Vashchuk E.S., Gromov V.E.

The microstructure of a new TiB2 – Ag metal matrix composite coating deposited by electrical explosion spraying and modified by electron beam treatment is studied using x-ray diffraction analysis and scanning and transmission electron microscopy. It is shown that the phase composition of the coating depends on the deposition mode, and the subsequent electron beam treatment normalizes it. The main phases of the resulting modified coating are Ag, TiB2 and B2O. After the electron beam treatment, the microstructure of the coating transforms. The nanostructure of the silver matrix is transformed into a nanocrystalline structure with an average crystal size of tens to hundreds of nanometers.

Cruz-Cruz I., Hernández-Maya R., Reséndiz-Hernández J.E., Olvera-Trejo D., Martínez-Romero O., Ulloa Castillo N.A., Elías-Zúñiga A.

Gromov V.E., Ivanov Y.F., Yuriev A.B., Minenko S.S., Gostevskaya A.N.

The structure of four-layer coatings with a total thickness of 9 mm made of high-speed molybdenum steel S2-9-2 (W2Mo9Al) was studied. The coatings were obtained on a substrate of 41CrMo4 (30CrMnSi) steel by plasma cladding using a powder wire in a mixture of argon and nitrogen. The structure of the coating was studied by electron microscopy and energy-dispersive x-ray spectroscopy (EDS) on sample sections. It is shown that the microhardness of the deposited layer varies in the range of 5.2 – 6.6 GPa. This is due to the formation of an inhomogeneous structure in the deposited layer consisting of grains of an iron-based solid solution, at the joints and along the boundaries of which are inclusions of eutectic enriched mainly with Mo, Cr, and W. Grain sizes vary between 5 and 20 μm. A sub-grain structure is observed in the grain volume, indicating substructural hardening of the deposited layer. The sizes of the sub-grains vary between 1.5 and 2.5 μm. The layer of the alloy S2-9-2 deposited on 41CrMo steel exhibits a framework-like structure. The main alloying elements of the clad layer are Fe, Mo, Cr, W, and Al.

Zhao H., Zhao X., Hui Z., Wang X., Shi H., Huang X.

The present study establishes an experimental platform for investigating arc erosion and explores the erosion characteristics of Ti3AlC2 material under a voltage of 10 kV in SF6/N2, SF6/CO2, and N2/CO2 environments. Our findings reveal that the arc energy and duration exhibit a gradual increase in the sequence of SF6/N2, SF6/CO2, and N2/CO2, while the breakdown strength decreases. Scanning electron microscopy (SEM) and a three-dimensional laser confocal microscope were employed to observe uneven erosion morphology. Additionally, high-speed camera footage captures the arc bending and drifting phenomenon caused by Rayleigh-Taylor instability between the arc and gas. X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) analysis were utilized to characterize the composition of eroded surfaces. Erosion models were proposed for each mixed atmosphere along with comprehensive discussions on their underlying mechanisms. This work expands the application scope of MAX phase materials while providing a theoretical foundation for designing electrical contact materials.

Bashchenko L.P., Bendre Y.V., Kozyrev N.A., Mikhno A.R., Shurupov V.M., Zhukov A.V.

The development and research of new materials for machine parts of the mining and metallurgical complex by the method of surfacing with flux cored wire has a lot of attention nowadays. Flux cored wires are widely used for surfacing of steels with high wear resistance, in which reduced tungsten in the form of ferroalloys, ligatures and metal powder of various degrees of purity are used as fillers. However, due to the scarcity and high cost of tungsten, its rational use is an urgent task. For practical application, the technology of surfacing with tungsten-containing flux cored wire is of interest; using it the maximum extraction of tungsten into the deposited layer is achieved due to reduction processes in the arc. In order to increase the beneficial use of tungsten, the technologies of indirect alloying with tungsten during surfacing under the flux of flux cored wires, in which tungsten oxide is used as a filler on the one hand, and reducing agent – on the other, deserve consideration. It can be expected that during arc discharge, tungsten and (or) chemical compounds of tungsten with reducing agents can be formed during the surfacing process. This paper presents the results of a comparative analysis of the thermodynamic processes of tungsten oxide reduction by carbon, silicon, aluminum and titanium during arc discharge occurring during surfacing with flux cored wires under a layer of flux. The thermodynamic analysis of 41 reactions in standard states showed that the presence of reducing agents (carbon, silicon, aluminum, titanium) in the flux cored wire used for surfacing will contribute to the formation of silicides and tungsten carbides, and, possibly, tungsten itself. It was determined that the best state for the participation of tungsten oxide in reactions in the arc is WO3(g) gaseous state.

Potekaev A.I., Gromov V.E., Yuriev A.B., Ivanov Y.F., Konovalov S.V., Minenko S.S., Semin A.P., Chapaikin A.S., Litovchenko I.Y.

Using the methods of scanning and transmission electron microscopy, the structural-phase states in the transition zone of a layer of fast-cutting S-2-9-2 steel (European standard) surfaced on 14331 medium-carbon steel (CSN standard) is investigated after tempering and electron-beam treatment. As a result of surfacing, a carbide network structure is formed, while there is no network in the transition zone. A plate-like martensitic structure is observed to form in the transition zone. The carbide phase particles measuring up to tens of nanometers demonstrate different morphology in the transition zone. They localize along the grain boundaries of martensitic crystals and austenitic interlayers and on dislocations in the bulk of the martensitic plates.

Zhou R., Liu Y., Li M., Cao J., Cheng J., Wei D., Li B., Wang Y., Jia D., Jiang B., Valiev R.Z., Zhou Y.

Yuriev A.B., Ivanov Y.F., Gromov V.E., Potekaev A.I., Abzaev Y.A., Klopotov A.A., Minenko S.S., Chapaikin A.S., Semin A.P.

Using the methods of advanced material physics, the structural-phase state of a layer of high-entropy high-speed non-equiatomic molybdenum tool steel formed by electric arc surfacing in a nitrogen atmosphere is studied. The thermodynamical and mechanical (elastic moduli) properties of the surfaced layer are examined in a temperature interval of 300–1400°C, and a phase-composition diagram is presented. It is observed that a temperature increase is accompanied by an α→γ polymorphic transformation, followed by a decrease in the content of carbide phases and elastic moduli.

Perinskaya I.V., Perinsky V.V., Rodionov I.V., Kuts L.E.

The research deals with effects of ion implantation using protons at energy of 30 keV and dose of 3 × 1013 ions/cm2, ion-implanted doping element (sulfur) at energy of 75 keV and dose of (1–6) × 1014 ions/cm2, sulfur ions at energy of 30 keV and dose of 4 × 1016 ions/cm2, and annealing in a carbon-containing atmosphere (CO2) at 500°С on the characteristics of monocrystalline gallium arsenide. The authors propose a mechanism aimed to increase electron mobility in the surface layer to 4500–5000 cm2/(V s) based on the gas phase nanocluster synthesis during proton irradiation and subsequent filling of the bulk of the structure with sulfur ions, including activation annealing under a layer of nonporous carbon coating synthesized by the ions accelerated into a carbon-containing atmosphere. The proposed method promotes new possibilities for ion implantation to be applied in monolithic microwave integrated circuit (MMIC) design and technology.

Ma G., Chen S., Wang H.

He C., Feng F., Wang J., Huang B., Lian Y., Song J., Chen Z., Liu X.

Yttria dispersion-strengthened tungsten composites with enhanced thermal and mechanical properties were fabricated by powder metallurgical methods in this work. The processing route involves the doping of yttria particles in the tungsten powders by liquid-liquid doping process, followed by hot pressing and two-step high-energy-rate forging (HERF). The microstructure, thermal conductivity, mechanical properties and thermal shock resistance of the hot-pressed W-Y 2 O 3 composites and the HERF processed W-Y 2 O 3 composites were comparatively investigated. The bending strengths of the HERF processed W-Y 2 O 3 composites increased significantly compared with that of the hot-pressed W-Y 2 O 3 billets. The HERF W-Y 2 O 3 material presented a ductile behavior even at room temperature with a maximum flexural strain of 4.4% and a yield stress of 2324.5 MPa. At 100°C, the material also exhibits evident plasticity with a flexural strain of 5.9% and the yield stress is up to 1931.9 MPa. The thermal conductivity of the W-Y 2 O 3 composite is 170 W/mK, which is close to the deformed pure W. The thermal shock response of the HERF processed W-Y 2 O 3 is also evaluated by applying edge-localized mode like high heat loads (100 pulses) with an energy density of 0.16–1 GWm −2 at various temperatures in an electron beam facility. The thermal shock results indicate that the cracking threshold of the HERF processed W-Y 2 O 3 at RT is between 0.55 GWm −2 and 0.66 GWm −2 . The cracking threshold of the HERF W-Y 2 O 3 at 100°C and above is higher than 1 GWm −2 . • A two-step high-energy-rate forging (HERF) was used to optimize W-Y 2 O 3 composites. • High strength and thermal conductivity, and low DBTT (100°C) were reported. • One of the highest thermal shock resistance among W-based materials was displayed. • This W-Y 2 O 3 composite is strongly desired in extreme conditions like fusion reactors.

Santosh S., Kevin Thomas J., Pavithran M., Nithyanandh G., Ashwath J.

• Laser machining of Cu-Al-Fe high temperature shape memory alloy was carried out. • Cu-Al-Fe shape memory alloys was fabricated by vacuum induction melting. • Effect on the laser machining parameters (Power, Cutting Speed, Stand Off Distance and Gas Pressure) on the alloy have been analyzed. • Laser power and cutting speed had the maximum influence on material removal rate and surface roughness. The term 'shape memory alloys' (SMAs) refer to a group of metallic materials that have the ability to return to a previously defined shape when subjected to the appropriate thermal or loading cycles. They are now being employed in different real-life applications. Cu-Al-Fe is a High Temperature Shape Memory Alloy (HTSMA) and could replace Ni-Ti SMAs. Conventional machining technologies are not efficient enough in machining SMAs, and thus the properties of the SMAs are affected. One of the most successful technologies for processing these alloys is Laser Beam Machining (LBM). This work shows an investigation of the effect of process variables in laser machining on SMA. Differential scanning calorimetry, X-Ray Diffraction, Optical Microscopy, Scanning Electron Microscopy, and Hardness tests were used to analyze the laser-machined material. It has been found that power was the highest influencing variable which affects Material Removal Rate (MRR) and Surface Roughness (Ra), and the second most influencing parameter was cutting speed. DSC thermograms confirm that the Shape Memory Effect (SME) and the transition temperatures of the SMA have not been much affected after machining. The hardness of the machined surface slightly increased after machining, owing to the formation of a re-solidified layer.

Lu Y., Turner R., Brooks J., Basoalto H.

• Steady and non-steady state sections have different weld pool geometries. • Significant difference in cooling rates experienced in the steady and non-steady state sections. • Similar microstructures and textures were observed, while grain sizes are largely varied in steady and non-steady state sections. • Different states lead to a significant difference in measured porosity. • The use of electron beam welding significantly affected the performance of joints. A detailed microstructural characterisation of the emerging weld-line grain structure, for bead-upon-plate welds in Ti-6Al-4V (Ti64) of differing plate thickness, was performed. The microstructure studied was formed during both steady state and non-steady state sections within the weld path, with the non-steady state portion being taken from the end of the plate as the weld bead and heat source overhang the edge of the plate. This allows for the effects of welding process conditions on the microstructural evolution to be determined. The weld pool geometry and 3D tomography of the weld-induced defects have been investigated. Detailed characterisation of microstructure and texture for different welding parameters and for steady and non-steady states have been used to identify physical parameters for the microstructure predictions that are difficult to obtain otherwise. The different states significantly affect the weld crown shape and formation, weld toe, weld bead depth and width. However, the heat affected zone (HAZ) remains unchanged. Regarding the microstructural evolution, both the steady and non-steady states have similar microstructure and texture. No defects were observed in the steady state section of welds, but sub-surface spherical pores have been observed in the non-steady state section of a weld. Finite element modelling to simulate the thermal-metallurgical-mechanical fields within the steady and non-steady state sections of the welds was considered, and the cooling rates predicted within steady state and non-steady sections were interrogated to improve the theoretical understanding of the microstructure and defect formation differences in these Ti64 EB weld regions.

Zhang M., Wang C., Mi G., Ouyang Q.

SiC p /Al matrix composite (SiC p /AMCs) has been widely used in aerospace field of structural frames, but it is difficult to realize the lightweight connection of complex structural parts. Understanding the fracture mechanism from the source will provide a decisive insight into the preparation (e.g. additive manufacturing) and processing (e.g. welding) of new high strength lightweight aluminum matrix composite. In this work, the fracture characteristics and the correlative damage mechanisms near fracture crack tip in a notorious SiC/2A14Al joint was conducted by in-situ scanning electron microscopy tensile test and transmission electron microscopy . The sandwich eutectic microstructure Mg 2 Si–Al–AlCu of clean interface and micron scale heterogeneous heterostructure inhibited the crack propagation . The sandwich eutectic microstructure disperses the extra stress caused by deformation, and the dislocation multiplies and moves at the interface of Mg 2 Si–Al and Al–AlCu phase, which slows down the stress concentration at the interface and avoids catastrophic crack propagation. Based on the fracture crack initiation source characterization of the joint, a rapid solidification process strategy was designed to further improve the mechanical properties of the joint, and the joint with tensile strength of 255 MPa was successfully prepared. Under the premise of ensuring full penetration and the same heat input, it is easier to obtain satisfactory tensile strength with high laser power - high velocity welding parameters, which is due to the suppression of the Al 4 C 3 . This work can be regarded as a breakthrough in the research of high strength aluminum matrix composites guided by reverse failure analysis strategy.

Bao T., Zhou Z., Gao P., Dong X., Chen J., Zhao S., Liu P., Yin G.

The development of advanced technology to promote osteo-integration of metallic implants and to solve bacteria-associated infection is one of the urgent clinical requirements. A multilayer polyelectrolyte coating composed of phosphonate/quaternary amine block polymer (pDEMMP- co -pTMAEMA), polymethacrylic acid (PMAA) and polyethylenimine (PEI) was designed as the dual functional coating. Through a layer-by-layer technology, stable coatings were constructed on Ti alloy plate (TC4) substrates based on the strong covalent binding between phosphonate group and metallic substrate, and the electrostatic interaction between oppositely charged polymers. The polymeric coating enabled a high-efficiency sustained release of recombinant human bone morphogenetic protein 2 (rhBMP-2) from the TC4 substrates and promoted the trans-differentiation of C2C12 cells to osteoblast cells. Meanwhile, the polycationic component in the polyelectrolyte coating significantly improved the antibacterial properties of titanium alloy surface. The polyelectrolyte coating demonstrated here is a promising candidate to increase the osteo-integration and antibacterial property of metallic implants. • A multilayer polyelectrolyte coating was designed as the dual functional coating for TC4 substrates. • Through a layer-by-layer technology, stable coatings were constructed on TC4 substrates. • The polymeric coating enabled a high-efficiency sustained release of rhBMP-2 from the TC4 substrates. • The polycationic component in the polyelectrolyte coating improved the antibacterial properties of TC4 substrates surface.

Romanov D.A., Pochetukha V.V., Gromov V.E., Sosnin K.V.

WN–WC–W2C0.84–Ag coatings are fabricated by a combined method, which combines electroexplosive spraying, nitriding, and electron-beam treatment. The structure, phase composition, nanohardness, Young’s modulus, wear resistance under dry sliding friction conditions, friction coefficient, electrical conductivity, and electroerosion resistance of the coatings are investigated.

Romanov D.A., Pochetukha V.V., Sosnin K.V., Moskovskii S.V., Gromov V.E., Bataev V.A., Ivanov Y.F., Semin A.P.

The goal of the research is to analyze the structure and properties of the coating SnO 2 –In 2 O 2 –Ag–N formed on copper by a complex method. The method of coating formation combined the electroerosion spraying, irradiation by pulsed electron beam and subsequent nitriding in plasma of a gas discharge of a low pressure. It is shown that the thickness of the coating amounts to ≈100 μm. The wear resistance of a copper sample with the deposited coating is ≈ 2.8 times higher than that of copper without the coating. The friction coefficient of samples with the coating (μ = 0.479) is ≈ 1.4 times less than that of copper without the coating (μ = 0.679). It is established that the coating hardness increases as the substrate is approached and reaches its maximum value of ≈1400 MPa (substrate hardness is 1270 MPa). By means of micro-X-ray- spectral analysis it is detected that the main chemical element of the coating is silver, with copper, tin, indium, oxygen and nitrogen being present in a much smaller quantity. By the methods of X-ray phase analysis it is revealed that the main phases of the coating are copper-and silver base solid solutions. Tests for the electroerosion resistance showed that the coatings meet the requirements of standards for electromagnet starters with the category of application AC-3 of direct action.

Wu P., Zhao C., Qiu R.

Contactor is widely used in power system. It is used to connect and disconnect the main circuit frequently to ensure the safe operation of the system. The long-term use of contactor will inevitably lead to the problem of loss. When the loss reaches the fault threshold, the abnormal operation of the equipment may lead to potential safety hazards of the electrical system. Therefore, it is of great significance to study the life prediction and state evaluation of contactors for the safe operation of electrical system [1]. Aiming at the problem of life prediction of contactor, the feasibility of life prediction scheme of contactor is studied, which provides a new idea for on-line life prediction of contactor.

Wang X., Zhou H., Wei Y., Zhang A., Zhu L.

Ag–C composite coating exhibits excellent electrical and thermal conductivities, good arc mobility, and low contact resistance, making it has a good prospect in switch contact of high voltage isolators. At present, the electro-deposition method is mainly used to prepare Ag/C composite coatings. However, the production efficiency of the electro-deposition method is low and the obtained coatings are thin. The electrical explosion spraying, due to its simplicity and high efficiency, has attracted significant attention in coating preparation. In this study, a new method that confines Ag and graphite powders in a tube for electrical explosion spraying was proposed. Powder electrical explosion spraying was used for preparing an Ag/C composite coating by employing a self-designed device. The heating behavior of the powder during exploding, macroscopic morphology, micromorphology, deposition efficiency, and thickness of the coatings, as well as the deposition behavior of the sprayed particles, were investigated. After a single spraying, a dense and uniform Ag/C composite coating was obtained at the charging voltage of 13 kV and a spray distance of 18 mm. The results show that the coating area is approximately 39.25 mm2, the coating thickness was 50 μm, and the deposition efficiency was 35%. the coatings have good adhesion with the substrate. the interface between the coating and the substrate appeared as an inter-diffusion of elements, which was typical of a metallurgical bonding interface. Graphite is evenly distributed in the coating. Furthermore, the underlying deposition behavior of the coating was carefully characterized.

Hassan T., Cheema K.M., Mehmood K., Tahir M.F., Milyani A.H., Akhtar M.

This research utilizes a hybrid technology through resonant line-level control phase-shifted full-bridge (HR-LLC-PSFB) dc–dc converter. In this research, a line level control (LLC) auxiliary circuit is used to achieve zero-current soft-switching turned-off operation of a controlled switch. The zero-voltage soft-switching turned-on operation is achieved by using the transformers’ magnetic branch energy and the energy reflected by the output filter inductor. The effective turn’s ratio of the isolating transformers is used to reduce the inverter circuit’s voltage stresses. The effect of voltage overshoots and freewheeling circulating current in rectifying branches is improved by implementing an energy recovery circuit with an output filter. A closed loop coordination proportional integral derivative (PID) controller is proposed to generate the pulse width modulation (PWM) control signal to transmit smooth power by controlling output voltage and current values. The droop constant current charging (CCC) and reduced constant current charging (RCCC) technique is proposed for the charging process. Simulations performed in MATLAB and results substantiate the proposed work superiority in comparison to other topologies.

Wang Y., Zhuo L., Yin E.

Tungsten‑copper (W Cu) composites/pseudo alloys with excellent properties are extremely desirable for applications as electrode materials, functional graded materials, electronic packaging materials, electrical contacts, as well as other aerospace and military candidates. This paper reviewed the recent progress on fabrication techniques, microstructure and property regulation that ensure high-performance W Cu alloys. Besides the well-developed traditional powder metallurgy including the parameter modification, powder pre-treatment and severe plastic deformation post-treatment, extensive novel sintering or manufacturing techniques including microwave sintering, spark plasma sintering, field-assisted sintering and additive manufacturing of W Cu alloys are reviewed, along with various chemical methods for nano-powder synthesis. Subsequently, the microstructure and property regulation by pure metal elements and introduction of second phases with great details are provided. Based on the review with all-sided perspectives for W Cu alloys, future developments and potential research challenges for W Cu alloys are summarized and proposed finally. • Traditional powder metallurgy for fabrication of W-Cu alloys is reviewed concisely. • Novel sintering or manufacturing techniques of W-Cu alloys are provided. l Various chemical methods for nano-powder synthesis are summarized. • Microstructure and property regulation are analyzed and discussed with great details. • Future developments and potential research challenges are summarized and proposed from five different perspectives.

Liu X., Li Z., He J., Xiao Q., Yang W., Chen D.

Stable and low contact resistance is the basic requirement of each connector in electrical contact. There are many factors that affect contact resistance and investigated by many previous studies. In this work, the effect of wear debris to electrical contact endurance at different relative humidity is studied by fretting test. The contact resistance evolution curve at different relative humidity indicates that the wear debris is more effective to electrical contact resistance. The composition of the wear debris is analyzed by x-ray photoelectric spectroscopy. It is clearly revealed that wear debris give a sharp rise to contact resistance. In addition, measured results illuminated that the contact resistance is greatly reduced with the wear debris washed. Higher relative humidity can restrain the generation of debris to a certain extent. Physical model of debris formation is established to evaluate ultimate lifetime of contactor.

Li P., Wen W., Li B., Li B., Huang Y., Chen L.

• Transient interruption characteristics of mechanical DCCB with current commutation drive circuit (CCDC) are revealed. Its mathematical model is deduced, and verified by simulation and experiment. • With investment as optimization goal, parameters design methodology for DCCB is proposed, in which, the coordination between high-voltage capacitor and CCDC is considered. • The modularized serial topology and integrated serial topology, for high-voltage mechanical DCCB with CCDC are introduced. By discussing performances of the two topologies, modularized serial topology is recommended for high-voltage DCCB with CCDC. With rated voltage of multi-terminal direct current (MTDC) power transmission system varying from ±160 kV to ±500 kV and even ±800 kV, high-voltage direct current circuit breaker (DCCB) is in urgent demand. With remarkable features of low operating losses, free-maintenance, and relative small investment, DCCBs based on mechanical vacuum switch (MVS) and current commutation drive circuit (CCDC) are recognized to have bright prospects in practical engineering. However, parameters design and serial topology selection for high-voltage mechanical DCCB with CCDC are still open problems. Motived by this, parameter design method for a modularized DCCB with CCDC is proposed. Then, parameters of 500 kV DCCBs with two typical serial topologies, namely, modularized serial topology and integrated serial topology, are optimized, and simulations are conducted in PSCAD/EMTDC for verification. In the end, performances of the two serial topologies, including dynamic voltage balancing, fault-tolerance capability and cost, are discussed. According to research results, modularized design methodology is recommended for high-voltage DCCB with CCDC.