In this study, composite coatings reinforced with boride particles were synthesized on titanium substrates. In this way, both LaB6 and Ti thin films were deposited alternatively with subsequent low-energy high-current electron beam (LEHCEB) processing in a single vacuum cycle. The film thicknesses were selected so that the boron and titanium contents were close to the composition of the TiB2 compound. Upon LEHCEB processing, the effect of energy densities on the microstructures, both chemical and phase compositions, as well as wear resistance of the coatings was considered. It was found that they could comprise mixtures of predominantly TiB2 nanoparticles distributed in the submicrocrystalline titanium matrix at an energy density of 3.5 J/cm2. In this case, wear resistance of the coating significantly exceeded those of the titanium substrate. Increasing the energy density up to 4.5 and 5.5 J/cm2 promoted additional melting of the substrates and dilution of the molten films with titanium from them, reducing the proportions of boron in the coatings. These changes in their chemical compositions led to variations in the observed phases. In addition, the excessive heat input caused the formation of surface discontinuities, deteriorating wear resistance.

The paper deals with the direct synthesis of titanum borides from lanthanum hexaboride layers deposited onto a titanium substrate followed by processing with a microsecond low-energy high-current electron beam (LEHCEB). It is shown how the electron-beam energy density affects the structure and properties of the obtained surface layer. The latter consists of 54 to 41 at.

A promising approach to improve the high-temperature properties of Ni-Al intermetallics is macroalloying with chromium and microalloying with a small amount of rare-earth elements (REE). For powder manufacturing processes such as the combustion synthesis technique, macro- and microalloying can be achieved by employing Cr & REE containing masteralloy powders as one of the starting reagents along with nickel and aluminum powders. This study investigated a process of dysprosium deposition onto the particles of commercial Ni-Cr powder aimed to produce the Ni-Cr-Dy masteralloy powder. The process involves pretreatment of the particle surface by low-energy high-current electron beam (LEHCEB) and uniform magnetron deposition of a thin dysprosium film. The possibility of embedding the dysprosium film into the particle's surface using an additional stage of LEHCEB treatment has been considered. It has been observed that during LEHCEB modification, a change in the particle size distribution, smoothing of the surface, and the formation of an intermetallic Dy3Ni phase in the subsurface layer occurs. A fraction of the obtained Ni-Cr-Dy powders were added to the starting powder blend for the combustion synthesis of Ni-Al-Cr-Dy porous alloys. It has been demonstrated that dysprosium uniformly distributes throughout the intermetallic scaffold of porous alloys and is localized within the Ni3Al phase in the form of enriched regions and separate inclusions.

Self-propagating high-temperature synthesis (SHS) is a powder processing technique used to effectively produce porous Ni-Al-based intermetallics that are characterized by a coarse structure composed of millimeter-sized strut elements. These porous intermetallics possess a low specific surface area, which enhances their longevity and reliability in various high-temperature environments. Modifying the chemical composition of Ni-Al intermetallics by adding a small amount (0.05-0.10 at%) of rare earth elements (REE) is one of the straightforward methods used to enhance the oxidation resistance of cast intermetallics that have never been applied for porous alloys made by the SHS technique. This study examines the cyclic oxidation resistance of porous Ni-Al intermetallics with minor REE content, obtained by applying Al-3.7wt%Dy and Al-4wt%Y masteralloy powders as an additive to the base nickel and aluminum powder mixture. This microalloying strategy enables over two hundred REE carrier particles to participate in the self-assembly of each millimeter-sized strut of the intermetallic scaffold, representing more than 1 % of the total particles involved in the synthesis. The base Ni-Al and microalloyed NiAl-Dy and Ni-Al-Y porous alloys were oxidized cyclically at 1150 degrees C for 100 h. The structures of initial and oxidized alloys were studied using stereological methods and XRD, SEM, and EDS analysis. Microalloying was found to slightly coarsen the porous scaffold by enhancing the formation and merging of the liquid phase within the combustion wave due to the decreased melting temperatures of the Ni-REE eutectics. The results show that microalloying with masteralloy powders allowed a uniform distribution of REE throughout the scaffold of porous intermetallic, resulting in a two-to-five times reduction in the oxidation rate constant, approaching the minimum value of 2 center dot 10-11 g2/cm4/s.

For the first time, the synchrotron X‑ray diffraction is used to study the phase evolution in the Fe-Cr-Al(film)/Zr(substrate) system during its low-energy high-current electron beam (LEHCEB) processing. It is found that surface layer undergoes successive phase transformations with increasing number of pulses and the energy density of LEHCEB. Initially, only Fe-Cr-Al film melting occurs. Next, the gradual film dissolution and the amorphous Fe-Cr-Al-Zr phase formation takes place, followed by the nucleation and growth of FeZr2 intermetallic compound. And finally, the formation the β‑Zr solid solution phase occurs. During the interruption of the LEHCEB process at different stages, it is possible to achieve desired phase composition and surface layer properties.

In this study, W-Zr surface alloys (SAs) were synthesized by low-energy high-current electron beam (LEHCEB) processing of preliminary deposited tungsten films on zirconium substrates in a single vacuum cycle. Then, their microstructure, as well as both chemical and phase compositions were investigated. Also, computer simulation of the dynamics of temperature fields was carried out. After LEHCEB processing of the Zr substrate with the pre-liminary deposited W film, the constituent element distributions were non-uniform over the surface of the W-Zr SA at the energy density of 3.5 J/cm2. Rising the energy density up to 5.5 J/cm2 resulted in a smoother and more homogeneous W-Zr SA. At the energy density of 3.5 J/cm2, the average tungsten content over the surface was 53 +/- 39 at.%, while it was only 26 +/- 2 at.% at 5.5 J/cm2. All W-Zr SAs consisted of the W phase (in different proportions), tungsten-rich solid solutions in the stabilized beta-Zr phase, and the W2Zr intermetallic compound. The contents of the beta-Zr and W2Zr phases enhanced with rising the energy density due to a greater amount of dissolved tungsten. Based on the obtained results, a scheme was proposed describing the formation of the SAs upon LEHCEB processing.

Lasers and electron beams have been widely used to synthesize various surface alloys (SAs) but no data have been reported so far on the molybdenum-zirconium (Mo-Zr) ones. To partially fill this knowledge gap, Mo-Zr SAs were formed by processing molybdenum films on zirconium substrates with low-energy high-current electron beams (LEHCEBs). The effect of the energy density of LEHCEBs on the microstructure, phase composition, nanohardness and corrosion resistance of the Mo-Zr SAs were investigated. Basically, the Mo-Zr SAs consisted of a solid solution of Mo in the beta-Zr phase, Mo2Zr second phase particles (SPPs) and a solid solution Zr in Mo. Increasing in the energy density decreased the concentration of the SPPs and enhanced the content of the beta-Zr phase. Also, it affected the depth of the highest concentration of the SPPs. In the zones of the highest molybdenum contents, the nanohardness values reached 9.4-12.7 GPa, which was higher by 3.2-4.4 times than that of the zirconium substrates. In a 3.5 % NaCl solution at room temperature, the corrosion current densities and the corrosion potentials were greater than those of the zirconium substrates by six and almost two times, respectively.

In this paper, we report our findings on the preparation of a film/alloy/substrate system with the use of a low-energy high-current electron beam (LEHCEB), as a result of sequential growth of molybdenum and chromium films on a zirconium substrate by magnetron sputtering. The system was produced in a single vacuum cycle, by cyclic growth of molybdenum film on a substrate and LEHCEB irradiation, followed by chromium film growth as a final step. We demonstrate that LEHCEB irradiation leads to the formation of Mo–Zr alloy consisting mainly of the high-temperature phase β-Zr. The alloy has the form of a layer 4.2 ± 0.9 μm in thickness, containing molybdenum-enriched regions. Such regions result from the formation of secondary phases: intermetallic compound Mo2Zr and a solid solution of Zr in Mo.

The review summarizes high-energy processing techniques applied for additive manufacturing and surface engineering of cemented carbides and cermets, including laser, electron, and ion beams, as well as plasma and electric discharges. The motivation for writing the review has been the fact that numerous papers have been published in these areas of science, but prospects for such studies in terms of their industrial implementations are unclear at present. In this way, the authors' goal has been to report achievements, challenges and gaps in knowledge for a more meaningful drawing of further research roadmaps. The review includes classifications of up-to-date cemented carbides and cermets in accordance with their compositions, fabrication methods, microstructure, functional properties and typical operating conditions. Then, some patterns of the evaluation of their microstructure and key characteristics are summarized. After that, achievements and challenges of laser and electron-beam additive manufacturing procedures are overviewed. Another topical section is devoted to surface engineering by both conventional methods and high-energy processing procedures. The authors have concluded that the key challenges are difficulties in simultaneous processing of both hard and binder phases without deteriorating their properties in the formed composites, as well as great residual stresses, causing the formation of cracks. To solve these issues, computer simulation methods, implemented for additive manufacturing and surface processing of metallic products, should be adapted for such composite materials. Also, a comparative economic evaluation of the return on investment in such innovative processes should be done for focusing on promising research directions.

The results of numerical and experimental studies of zirconium irradiated by a low-energy high-current electron beam with an energy density ranging from 2.2 to 5.2 J/cm2 are presented. The dynamics of surface melting is simulated, and the thickness and lifetime of the melt, as well as the cooling rates achieved in zirconium during pulsed electron beam processing, are determined. The structure and properties of zirconium are experimentally studied, it is shown that as a result of processing, a martensitic α'-phase is formed in the layer quenched from the melt. It is established that the formation of the martensitic phase increases the surface nanohardness and wear resistance. The maximum value of the surface layer nanohardness obtained by the processing is twice higher than the initial value.

The review summarizes some achievements of materials scientists in designing high entropy alloys (HEAs) and developing production routs for their industrial implementation, as well as highlights and discusses outstanding challenges in this way. Initially, the generally accepted concept of HEAs and its criticisms have been matched. Then, suggestions for their possible application have been agglomerated. After that, typical designing algorithms for metal products and structures have been considered, focusing on the rational selection of materials. Finally, correspondence of the reported data on both characteristics and properties of HEAs, as well as procedures for their heat treatment, processing and surface engineering, has been correlated with the content of recent reference books on those for conventional metals, steels and alloys. Based on the analysis of these results, some conclusions have been drawn, including generalized knowledge gaps and challenges. Also, further research directions have been proposed.

The paper is devoted to preparation Al@Dy and Al@Y core-shell structures by magnetron sputtering of Dy and Y on an Al powder. A unique powder holder system is used to obtain continuous powder movement and conglomerates destruction during the treatment. It has been established that powder particles treated using the powder holder system have a uniform coating over the entire surface. The powder coating process regularities were studied depending on the deposition time and the powder charge weight. Simple evaluation criteria for powder coating system efficiency and deposited material content based on the deposition rate were proposed. The complex modification consists of the initial core-shell structure formation and subsequent pulsed low-energy high-current electron beam treatment in the surface layer melting mode was demonstrated. The main goal of the electron beam treatment is to provide better adhesion of the “shell” material to the “core” material. Such treatment led to the deposited shell element alloying into the depth of core particles. Moreover, such electron beam treatment led to the synthesis of intermetallic compounds. In further studies, the prepared structures will be used for the uniform distribution of Dy and Y over the frame elements of self-propagating high-temperature synthesized porous materials.

Представлены результаты исследования коррозионной стойкости циркония при воздействии низкоэнергетическим сильноточным электронным пучком с плотностью энергии от 2.2 до 5.2 Дж/см2. Электрохимические результаты показывают, что после облучения НСЭП потенциал коррозии увеличивался в 2 раз, а ток и скорость коррозии уменьшались в 75 раз.

Проведены расчеты температурных полей системы Mo (пленка)/Zr (подложка) при импульсном электронно-пучковом воздействии. Представлены рассчитанные зависимости порогов плавления системы Mo (пленка)/Zr (подложка) от толщины пленки. Порог плавления пленки Mo при увеличении её толщины монотонно увеличивается и стремится к порогу плавления чистого Mo. Порог плавления подложки Zr при увеличении толщины пленки Mo монотонно увеличивается от значения порога плавления чистого циркония до бесконечности. При значениях пленки молибдена не превышающих 8 мкм первой начинает плавится подложка циркония. При дальнейшем увеличении толщины пленки, наоборот, первой начинает плавиться пленка молибдена. Расчитанны зависимости толщины расплавленного слоя подложки из циркония от плотности энергии НСЭП для систем Mo/Zr с толщинами пленок молибдена 0.10, 0.25, 0.50 и 1.00 мкм. При увеличении плотности энергии наблюдается монотонное увеличение толщины расплава. Представлены временные зависимости толщины расплава при плотностях энергии НСЭП 2.5, 3.5, 4.5 и 5.5 Дж/см2 для системы Mo/Zr с толщиной пленки 0.5 мкм.

Представлены результаты исследований по формированию многокомпонентного Fe-Cr-Al-Zr поверхностного сплава на Zr подложке с помощью низкоэнергетического сильноточного электронного пучка (НСЭП). Сплав формировался путем напыления пленки Fe-Cr-Al заданного состава на подложку с последующей НСЭП обработкой с различной плотность энергии полученной системы пленка/подложка в едином вакуумном цикле. Исследована морфология и элементный состав образцов с поверхностным сплавом. Показано, что при плотности энергии НСЭП равной 2.3 Дж/см2 происходит плавление в основном только напыленной Fe-Cr-Al пленки, при этом содержание циркония в поверхностном слое минимально и составляет 4.1 ат.%. На поверхности сплава наблюдались дефекты типа трещин и раковин. Увеличение плотности энергии приводит к более интенсивному перемешиванию материала пленки с подложкой и формированию бездефектной поверхности. При этом происходит увеличение содержания циркония в поверхностном сплаве до 54 ат. %, однако относительное содержание Fe, Cr и Al в сформированном поверхностном сплаве сохраняется и аналогично содержанию этих элементов в напыляемой пленке.

Представлены результаты исследований по формированию Mo-Zr поверхностного сплава на Zr подложке с помощью низкоэнергетического сильноточного электронного пучка (НСЭП). Сплав формировался путем чередования операций напыления пленки молибдена на подложку и последующей НСЭП обработки с различной плотность энергии полученной системы пленка/подложка в едином вакуумном цикле. Исследована морфология, элементный состав, а также распределение молибдена по глубине образцов с поверхностным сплавом. Обнаружено, что для рассматриваемых режимов формирования поверхностного сплава происходит образование сетки трещин и пор на поверхности образцов. Показано, что с увеличением плотности энергии НСЭП при формировании поверхностного сплава поверхность становится более однородной, количество пор уменьшается, и при плотности энергии 5.5 Дж/см2 полностью отсутствуют. Исследование элементного состава показало, что увеличение плотности энергии приводит к легированию молибденом на большую глубину и формированию более однородного по толщине поверхностного сплава.

The results of crack formation in a Cr–Zr surface alloy formed by a low-energy high-current electron beam are presented. The morphology and elemental composition of the surface alloy in the area of crack formation are investigated. It is shown that cracks propagate along the surface regardless of the location of pits and grooves, which indicates a greater dependence of cracking on the internal stresses rather than the roughness or other structural factors. It is found out that the distribution of elements affects the cracking of the surface alloy, which is indicated by its nearly equiatomic elemental composition in the area of crack formation.

The paper presents the results of numerical simulation of the distribution of thermal fields during the formation of Cr-Zr surface alloy using a pulsed low-energy high-current electron beam (LEHCEB). The melting thresholds of the Cr-Zr system for different thicknesses of Cr films were calculated. The melting threshold of the Cr-Zr system increases linearly with increasing Cr film thickness. A linear regression dependency model of the melting threshold on the film thickness is proposed. Evaporation thresholds of the Cr-Zr system for different thicknesses of Cr films were calculated. The evaporation threshold of the Cr-Zr system increases linearly with increasing Cr film thickness. A linear regression dependency model of the evaporation threshold on the film thickness is proposed. The value of the LEHCEB energy density at which the lifetime of the film and substrate are equal is calculated. This value is a maximum value for the effective formation of Cr-Zr. A model of the LEHCEB energy density, at which the lifetime of the film and the substrate are equal, in the form of a third-degree polynomial is proposed.

The paper investigates the regularities of the formation of Cr-Zr surface alloy using a low-energy high-current electron beam (LEHCEB). The influence of the electron-beam processing parameters and the magnetron deposition parameters on the elemental composition of the formed Cr-Zr surface alloy is estimated. It is shown that, for all considered modes, there is a general tendency to a decrease in the chromium content in the surface alloy with an increase in the energy density or the LEHCEB processing pulse number. The thickness increasement of the chromium film applied in one cycle or the surface alloy total thickness increasement leads to an increase in the chromium content in the surface alloy. The LEHCEB processing parameters, namely the energy density and the number of pulses, have a greater effect on the chromium content during the formation of the Cr-Zr surface alloy in comparison to the magnetron sputtering parameters, namely the deposited film thickness and the formed surface alloy thickness. A linear regression model that describes the chromium content in the surface alloy depending on the film thickness, the surface alloy total thickness, the number of pulses and the pulse energy density is proposed.

The study of the surface alloy NiAl formed by irradiating a three-layer system of alternating layers of Ni and Al with a total thickness of 2.5 μm by a low-energy high-current electron beam with a different number of pulses is presented. The influence of the number of irradiation pulses on the morphology of the obtained surface alloys, their microhardness, and the structure of the transition layer on transverse sections is studied. It is found that with an increase in momentum the surface layer becomes smooth and cracks are reduced to a certain number of pulses. The microhardness values of the surface alloys obtained are close and, on average, 1.5 times higher than that of the initial sample.