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This paper presents the results of studies of the structure and properties of coatings produced by cladding 10 mm thick titanium plates with titanium–tantalum powder mixtures using an electron beam extracted into air. A mixture of CaF 2 and LiF salts was used as a flux that protected the heated material from the air atmosphere. The electron beam power was 33.5 kW, the velocity of the sample relative to the beam 10 mm/s, and the beam scanning frequency 50 Hz. High-performance titanium–tantalum layers 2–2.5 mm thick with a tantalum content of 3.9–22.4 wt% were obtained. The surface layers have a dispersed α(α′)+β structure. The tensile strength of the alloy containing 3.9% tantalum is 620 MPa. Increasing the Ta content to 22.4% increases the tensile strength to 735 MPa. For the coating material containing 22.4 wt% Ta, the rate of corrosion in a 68% solution of boiling nitric acid was 190 times lower than that for unclad titanium. The conditions of formation of the layer structure by high-velocity electron-beam cladding of powder materials are significantly different from equilibrium. For this reason, the resulting materials are characterized by a number of features, including a high degree of dispersion of the structural components and inhomogeneous chemical composition.

The paper presents experimental investigations of tungsten surface modification after plasma loads at the multimirror trap GOL-3. Energy loads on tungsten surface varied from 2 up to 4 MJ/m2 per shot with sets from 1 to 9 repetitive irradiations that corresponds to loads higher than tungsten melting threshold and is close to ITER giant ELM loads. Targets surface modification and transverse microsections after irradiation was studied by optical microscopy, SEM and hardness tester. Formation on tungsten surface of three different crack networks with typical cell sizes of 1000, 10 and 0.3 μm and bubbles are identified. The network of large cracks extend perpendicularly to the irradiated sample surface to a depth of 50–350 μm. Erosion depth depends on energy loads – rises from 20 to 200 μm at 2 and 4 MJ/m2 correspondingly. Cracking, development of tungsten surface morphology and droplets splashing are discussed.

We have examined the new phase formation and compositional variations in the coatings produced by detonation spraying of Ti3Al powders in atmospheres of different chemistry. The composition of the spraying atmosphere was varied by changing the O2/C2H2 ratio used for the detonation. In the coatings sprayed at an O2/C2H2 ratio of 0.87 and 1.05, certain deviations of the Al/Ti ratio have been observed relative to the sprayed powder. In these coatings, the Ti3Al phase was found along with TiN and Ti2N formed due to the reaction of the heated particles with nitrogen used for powder injection. The amount of TiN increased with increasing explosive charge and a concomitant rise in the particles temperature. Under O2/C2H2 ratios equal to 1.50 and 2.00, significant losses of Al were detected, the coatings being composed mainly of titanium oxides. This study shows that detonation spraying conditions excluding severe oxidation of Ti3Al can be found as well those facilitating oxidation with an associated loss of Al in the deposits.

Composite WC/Co + MoS 2 coatings were deposited onto steel substrates by Computer Controlled Detonation Spraying using three spraying modes: very cold, cold and normal. Maximal content of MoS 2 in a sprayed powder was 10 wt.%. Characterization of coatings was made with chemical and phase analyses, microhardness measurement, morphology and microstructure investigation. X-ray diffraction study shows that residual MoS 2 exists only in coatings obtained at very cold and cold spraying modes. At normal spraying mode complete decomposition of the solid lubricant occurs during spraying. From the engineering point of view, the coating applied at the cold mode using a powder containing 10 wt.% MoS 2 is the most promising. Such a coating has microhardness of 650 HV 0.2 and a porosity of 10%.

The aim of the work was to clad Ti-Ta-Nb coating on a substrate of pure titanium. Cladding was carried out by non-vacuum electron-beam treatment. As a result a good quality coating thickness of about 2 mm was obtained. Microstructural and microhardness tests were conducted. Dendritic structure and the borders of the former grains of β-phase were revealed. At the microlevel, the coating has a martensitic structure. The average hardness of coating is about 4000 MPa.

This paper presents a brief review of research made by the authors to determine feasibility of using a titanium-based bilayer material in industrial applications. One layer, corrosion preventive, is formed by surface alloying with highly corrosion-resistant doping elements, in particular, Ta, Nb and Zr. These elements have significantly higher corrosion resistance than titanium. Applying them on the titanium substrate allows formation of a coating resistant, in particular, to boiling strong acids. Resistance of obtained coatings in said media is many times higher than that of titanium or stainless steel. The coatings are formed using a high-penetration electron beam ejected to the atmosphere. This article contains references to findings of previous works and offers some new data.

Results from different facilities for plasma-surface interaction (PSI) studies are compared and their relevance to each other and conditions of ITER transient events are discussed. For PSI studies different types of devices were used including open traps, tokamaks, linear plasma machines including quasi-stationary plasma accelerators, electron beams and lasers. The same damage thresholds were demonstrated with different techniques. At energy loads corresponding to ITER transient events (edge localized modes (ELMs), disruptions, etc.) only macroscopic erosion mechanisms are important. They are cracking, droplet formation and macroscopic mass losses of the target. Cracking occurs during cooling stage after irradiations. Details of plasma stream parameters are of secondary importance for cracks formation; only target temperature plays a role. Macroscopic mass losses strongly correspond with melting of a thin surface layer and heat loads play a key role for melting. Heat flux defines the targets surface erosion.

Wide-area (2 cm2) high-power (up to 7 MW) submillisecond electron beam source was applied for generation of intense pulsed heat loads on tungsten sample. Various diagnostics sets were used for in-situ research of the surface damage: IR imaging of the front view of the target, capturing of the reflection pattern of continuous wave laser radiation, recording of intensity of thermal radiation from several spots of the surface. Sample was exposed to a various heat loads near and above melting threshold. Formation of the crack network on the surface and its development with successive pulses was observed. Two-dimensional temperature distribution was obtained after heating at the cooling stage. Melting and spalling of material were shown on severe damaged target. Propagation of the cracks along the surface at a depth of 0.1 – 0.2 mm was revealed with transverse microsections. Circular motion of the molten layer was found with subsequent exposures.

The effect of the initial heat treatment (quenching or tempering) of low-carbon steel (Fe-Mo-Nb-V-C) on special features of the ultrafine-grained structure and microhardness produced by high-pressure torsion was investigated. High-pressure torsion promotes the more apparent refinement of structural elements of the steel (dpr = 55 nm for the quenched state and 74 nm for the tempered state) and an increase in structural homogeneity of microhardness of quenched specimens in comparison with tempered ones. Experimental results reveal a high significance of the initial structural state for the final deformation-processed microstructure and microhardness (radial distribution) of steel specimens.

The effect of initial heat treatment on peculiarities of ultrafine-grained structure and on homogeneity of strength properties (microhardness) through the specimens was studied in low-carbon steel Fe-Mo-Nb-V-C processed by high-pressure torsion. Three initial states, i.e. (I) normalized, (II) quenched and (III) quenched and tempered, with different morphologies and grain sizes were used. A noticeable effect of the initial state on characteristics of ultrafine-grained structure processed by high-pressure torsion was observed: decrease in the initial grain size causes more effective grain refinement and formation of higher value of microhardness in the middle part of disk radii (dav = 91 nm and 700 HV for normilized state, dav = 98 nm and 770 HV for quenched state and dav = 100 nm and 600 HV for initial quenched and tempered state).

The paper presents the results of the investigation of VT6 titanium alloy subjected to electro-explosion alloying with TiB2 and irradiation with pulsed electron beam. It was established that electro-explosion alloying resulted in a high level of roughness of the surface layer with high adhesion of the modified layer and matrix. Further irradiation of the material with electron beam resulted in the smoothing of the surface of alloying and formation of a porous structure with various scale levels in the surface layer. It was also established that the energetic exposure causes the formation of a gradient structure with a changing elemental composition along the direction from the surface of alloying.

The effect of hydrogenation on the strain-hardening behavior and the deformation mechanisms of 〈113〉-oriented single crystals of Hadfield steel was investigated under tension at room temperature. The stages of plastic flow and deformation mechanisms for hydrogen-charged specimens are similar to one in hydrogen-free state: slip → slip + single twinning → slip + multiple twinning. Hydrogen alloying favors to mechanical twinning, micro- and macrolocalization of plastic flow.

We study the effect of high-pressure torsion (6 GPa) for 0 (upset), 1/4, 1/2, and 1 revolutions at room temperature on the microstructure and microhardness of high-nitrogen austenitic steel Fe-18Cr-23Mn-2.7V-0.2C-0.7N (wt %). Slip, twinning, formation of localized microbands, and precipitation hardening are the main deformation mechanisms of steel under HPT. The level of solid solution hardening of steel after deformation remains as high as after quenching. As the result of severe plastic deformation, steel microhardness increases by 1.5 times. Mechanical twinning facilitates strain hardening due to high density of high-angle twin boundaries, prevents the formation of misoriented grain/subgrain structure with common type boundaries and contributes to the homogeneity of the structure and microhardness across the specimens.

We consider structural changes occurring upon electron-beam hardening in air of rail steel M76. The microhardness of the hardened zone (thickness about 1.2 mm) is 800 – 900 HV. The short-term drawback using electron beam provides reduction of the microhardness to 400 – 700 HV. Electron-beam hardening also provides a 2-3 fold increase in the wear resistance of steel under the effect of abrasive particles. The data thus obtained make it possible to recommend the method of electron-beam treatment to strengthen the side edge of rail heads.

Special features of plastic deformation and fracture of excess cementite segregated under the conditions of high-temperature carbon supersaturation of steel are studied by the methods of light and scanning electron microscopy. It is shown that regularly oriented flakes of excess cementite with a lamellar structure are formed within the former austenite grains. The cementite flakes oriented along the, rolling plane fracture by a brittle mechanism forming numerous fragments. The behavior of free cementite under the conditions of cold rolling depends on the orientation of the flakes in the specimen. The mutual shift of the layers allows coarse cementite formations to deform under the action of compressive stresses without cracking.

This paper presents the results of structural investigations and results of tribological and microhardness tests of the coating obtained by electron beam cladding of a Ni-Cr-Si-Fe-B self-fluxing alloy on low-carbon steel. After electron beam treatment high-quality dense layer with a thickness of 1.2-1.8 mm was obtained. The structure of the coating consisted of dendrite crystals based on y-Ni-solid solution and eutectic with complex composition. Microhardness of the coating achieves 370 HV. Wear-resistance of the coating obtained by electron-beam cladding technique was 1.6-fold higher than that of low-carbon carburized steel.

The structure and microhardness of surface layers, obtained by non-vacuum electron beam cladding of Ti-Mo-C powder mixture on a steel substrate after different types of heat treatment, were investigated. After cladding samples were heat treated in a furnace at 200...500 °C, as well as quenched at 860 ° C and then underwent high-temperature tempering. Heat treatment of cladded coatings induced tempering of martensite and precipitation of cementite particles (Fe3C). Transmission electron microscopy of the samples after heating and holding at 300 ° C revealed precipitation of nanosized cubical TiC particles. The formation of hard nanosized particles led to the surface layer microhardness growth. The highest level of microhardness (which was 1.2...1.5-fold higher in comparison with coating microhardness after heat treatment) was achieved after heating of the claded material at 300 °C and 400 °C Additional quenching of samples at 860 °C did not increase the microhardness level.

Conjugated polymer-based organic photovoltaic devices (OPVs) have been intensively studied, since they are advantageous over regular inorganic devices. However, there is still no complete understanding of the functionality of conjugated polymer-based organic active layers. Due to this, research into the processes of microstructure formation will improve morphology control and optimization and enhance performance and productivity. In this study we used in situ measurements of conductivity and X-ray diffraction analysis in grazing incidence X-ray diffraction (GIXD) geometry to investigate the structure of light-sensitive layers produced by coating from solutions and based on poly(3-hexylthiophene) (P3HT) mixtures as donors with various fullerene acceptors: [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) and indene-C60 bisadduct (ICBA). The structure of films produced by coating from solutions was studied by large-angle GIXD. Ex situ and in situ methods (under external voltage applied) were used to detect high compatibility between the donor and acceptor for ICBA-based films. The time dependences of changes in current and intensity of the (100) peak of P3HT demonstrate that the maximum emerges simultaneously. A two-step increase in intensity of the (100) peak of P3HT was observed for films containing PCBM as an acceptor. In situ studies of the structure confirm that the joint donor–acceptor structure is formed as the solvent evaporates. Atomic force microscopy studies of the surface roughness of films containing different acceptors demonstrate that they are characterized by different morphologies.

1. Among the materials investigated the pitting formation process takes place most intensely in the M2 plasma coating. The resistance of the PG-SR4 coating to contact-fatigue failure is at the level of a similar characteristic of U8 steel with bainite structure after isothermal processing. 2. The controllable thermoplastic hardening of the U8 steel with subsequent treatment to bainite results in an increase in its fracture toughness, increases the resistance to contact-fatigue failure in comparison with normal isothermal processing. 3. For increasing the resistance to contact-fatigue of protective coatings, it is necessary to reduce their porosity, increase their cohesion strength and the strength of bonds with the base metal.

It is known that steels with different structures can have different wear rates at the same strength. The present work concerns the effect of the shape, dispersity, and presence of defects in carbides on the wear rate of steel U8 in friction against rigidly and nonrigidly fastened abrasive particles.

Bands of localized plastic flow 20–30 μm wide and up to 3000 μm long are formed in deep drawing of steel 18YuA. The development of the bands is completed with the formation of cracks due to exhaustion of the reserve of plastic properties in the steel. The special features of the process of localized flow in drawing steel 18YuA are considered.