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We study the effect of grain size of austenitic and ferritic phases and volume fraction of δ-ferrite, which were obtained in different solution-treatment regimes (at 1050, 1100, 1150 and 1200 °C), on hydrogen embrittlement of high-nitrogen steel (HNS). The amount of dissolved hydrogen is similar for the specimens with different densities of interphase (γ-austenite/δ-ferrite) and intergranular (γ-austenite/γ-austenite, δ-ferrite/δ-ferrite) boundaries. Despite, the susceptibility of the specimens to hydrogen embrittlement, depth of the hydrogen-assisted surface layers, hydrogen transport during tensile tests and mechanisms of the hydrogen-induced brittle fracture all depend on grain size and ferrite content. The highest hydrogen embrittlement index IH = 32%, the widest hydrogen-affected layer and a pronounced solid-solution hardening by hydrogen atoms is typical of the specimens with the lowest fraction of the boundaries. Even though fast hydrogen transport via coarse ferritic grains provides longer diffusion paths during H-changing, the width of the H-affected surface layer in the dual-phase structure of the HNS specimens is mainly determined by the hydrogen diffusivity in austenite. In tension, hydrogen transport with dislocations increases with the decrease in density of boundaries due to the longer dislocation free path, but stress-assisted diffusion transport does not depend on grain size and ferrite fraction. The contribution from intergranular fracture increases with an increase in the density of intergranular and interphase boundaries.

The paper studies the structure and microhardness of the heat-affected zone, welding area in low carbon and low alloy steel 09G2S (AISI A516 grade 55), and the coating created by two-pass manual metal arc welding with the addition of titanium carbonitride nanoparticles. It is shown that the microhardness dependence on the distance to the coating surface is divided into four zones. The microstructure of each zone is studied by using the optical and scanning tunneling microscopies. It is found that the formation of highly dispersed acicular ferrite and globular bainite structures in the deposition superheat zone of surfacing is favorable for the improvement of the coating–base metal composition impact toughness.

The possibility of the structural turbulence of plastic flow and ductile fracture in low-carbon and low-alloy steel 09Mn2Si is shown by fracture toughness measurements and uniaxial tension of chevron-notched specimens at 20°C. The conditions for the structural turbulence of plastic deformation of solids are determined which provide high fracture toughness. The decisive functional role is played by the lattice curvature, the appearance of mesoscopic structural states in the lattice interstices at the nanoscale, the activation of self-consistent rotational motion in the hierarchy of mesoscopic structural levels, the presence of free volume, and the possibility of structural transformations at the nanoscale. A nonlinear theory of describing structural turbulence in a deformable solid is discussed.

The paper analyzes the nucleation and growth of bainite in low-carbon low-alloy 09Mn2Si steel doped with titanium carbonitride nanoparticles in impact toughness testing. The analysis shows that such particles segregate at low-angle boundaries, retarding the formation of high-angle ones, and when impacted into the steel, they curve the lattice and generate a new bainite phase at the curvature interstices. The mechanism of bainite nucleation and growth is sympathetic, obeys the angular momentum conservation law, and provides the formation of multilayered packets of bainite plates capable for unlimited thinning to sub-sub-subunits during deformation. Such bainite plates can respond to their stress-strain state by one or another rotation, showing a high relaxation capacity and providing a high impact toughness of the steel at low temperatures.

The paper is devoted to an experimental investigation of a high-temperature deformation in V-alloyed high-nitrogen austenitic Fe-19Cr-22Mn-1.5V-0.3C-0.6N steel processed via different thermo-mechanical treatments. Simple thermo-mechanical processing regimes (cold rolling or rolling with single post-deformation anneal) do not allow to realize a substantial elongation in high-nitrogen steel during high-temperature tensile tests. For fine-grained austenitic structure with an average grain size of 3 µm, the maximal value of elongation to failure of 150% was realized at temperature 950 °C. Using a multi-stage thermo-mechanical treatment included cold rolling and intermediate anneals, a heterophase grain/subgrain structure with high density of deformation-induced defects and precipitates was produced. When heated to a deformation temperature, this deformation-assisted microstructure recrystallizes into a stable fine-grained structure and demonstrates the attributes of superplastic flow (values of elongation to failure higher than 400%) in the temperature range of 850-1000 °C. The maximum elongation of 900% is achieved at temperature of 950 °C and an initial strain rate of 10-4 s-1.

The effect of age-hardening regime on peculiarities of hydrogen-assisted fracture and tensile properties in two high-nitrogen Fe-23Cr-17Mn-0.1C-0.6N and Fe-19Cr-22Mn-1.5V-0.3C-0.9N steels was studied. A large number of intergranular (austenite/austenite) and interphase boundaries (austenite/coarse particle) provides high fraction of trapping sites for hydrogen atoms in V-alloyed steel. This leads to a change in fracture regime from transgranular brittle mode in coarse-grained V-free steel to intergranular brittle fracture of hydrogen-assisted surface layers in fine-grained V-alloyed steel with coarse (V,Cr)(N,C) particles. The formation of cells (Cr 2 (N,C) particles and austenite) along the grain boundaries due to discontinuous precipitate-hardening reaction facilitates predominantly interphase hydrogen-assisted fracture for both steels. The complex reaction of the particle-strengthening mechanisms including discontinuous precipitation with formation of austenite/Cr 2 (N,C)-plates interfaces or homogeneous nucleation of coherent (V,Cr)(N,C) particles in austenite (age-hardening regime 700 °C, 10 h) promotes mainly transgranular cleavage-like fracture mode under hydrogen-charging. The structural scheme is proposed to describe a change in hydrogen-assisted fracture micromechanisms and tensile properties of the steels with different density and distribution of interphase and intergranular boundaries.

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 microstructure, deformation mechanisms, tensile properties and fracture micromechanisms of ultrahigh-interstitial austenitic Fe-22Cr-26Mn-1.3V-0.7C-1.2N (mass.%) steel were investigated in wide temperature interval. After conventional homogenization and solid-solution treatment, the steel possesses complex hardening which includes grain boundary, solid-solution and dispersion strengthening. In the temperature interval of &minus, 60 to +60 &deg, C, steel demonstrates striking temperature dependence of a yield strength which could be enhanced by the increase in solid-solution treatment temperature. The variation in test temperature does not change the dominating deformation mechanism of the steel, dislocation slip and insufficiently influences tensile elongation and fracture micromechanisms. The insignificant increase in the fraction of brittle cleavage-like component on the fracture surfaces of the specimens in low-temperature deformation regime is promoted by increase in planarity of dislocation arrangement and the gaining activity of mechanical twinning. In high-temperature range (200&ndash, 300 &deg, C) of deformation, a negative strain-rate dependence, serrations on the stress-strain diagrams and improved strain-hardening associated with a dynamic strain aging phenomenon have been observed.

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.

For high-nitrogen Fe-19Cr-21Mn-1.5V-0.3C-0.9N (wt. %) steel water-quenched from the different solution-treatment temperatures (1100oС and 1200oС, 1h), the tensile mechanical properties and fracture micromechanisms were investigated in a temperature range of 77K to 673K. Increase in quenching temperature (QT) provides a partial dissolution of precipitates and increases a solid-solution hardening effect in the steel. A yield strength, tensile strength, strain-hardening coefficient and plasticity are QT-dependent characteristics. Independently on QT and test temperature, steel specimens fracture in ductile transgranular mode except for 77K-temperature, where dimples and some cleavage components are observed on fracture surfaces. The variation in QT allows one to decrease the fraction of cleavage component: 8% for QT=1100oС and 25% for QT=1200oС.

The effect of hydrogen on tensile behavior and fracture mechanisms of V-alloying and V-free high-nitrogen austenitic steels was evaluated. Two steels with the chemical compositions of Fe-23Cr–17Mn–0.1C–0.6N (0V-HNS) and Fe-19Cr–22Mn–1.5V–0.3C–0.9N (1.5V-HNS) were electrochemically hydrogen-charged in NaCl water-solution for 100 hours. According to X-ray diffraction analysis and TEM researches, V-alloying promotes particle strengthening of the 1.5V-HNS. Despite differences in chemical compositions, namely, carbon and nitrogen concentrations, a solid solution hardening is similar for both steels because of precipitate-assisted depletion of austenite by interstitial atoms (carbon and nitrogen) in 1.5V-HNS. For hydrogen-free state, the values of the yield stress and the tensile strength are higher for particle-strengthened 1.5V-HNS as compared to 0V-HNS. Hydrogen-charging increases both the yield stress and the tensile strength of the steels, but hydrogen-assisted fracture micromechanisms are different for 0V-HNS and 1.5V-HNS. Hydrogen-charging drastically reduces a total elongation in 0V-HNS but provides insufficient embrittlement in 1.5V-HNS. Hydrogen-assisted brittle layers form on lateral surfaces of the specimens, and the widths and fracture micromechanisms in them are different for two steels. For 0V-HNS, surface layers of 84 μm in width possess transgranular brittle fracture mechanism (quasi-cleavage mode). For 1.5V-HNS, the brittle surface layers (31 μm width) destroy in intergranular brittle fracture mode. The central parts of steel specimens show dimple fracture similar to hydrogen-free steels. The possible reasons for different hydrogen-induced effects in 0V-HNS and 1.5V-HNS are discussed.

In this study, the authors have analyzed the effect of nanosized particles of titanium carbonitride Ti-C-N and non-stoichiometric nitride TiN1–x on the structure and properties of coatings on 09Mn2Si steel formed by arc welding, utilizing MP-3 electrodes. It was shown, that adding of TiN1–x modifying powders into the weld pool effectively increased the fatigue durability and impact toughness at negative temperatures.

The structure and microhardness of the heat-affected zone of low-carbon and low-alloy steel 09G2S, the melting zone and the coating obtained by manual electric arc welding using electrodes modified with nanoparticles of titanium carbonitrides have been investigated. It is shown that the dependence of microhardness on the distance from the coating surface has 4 stages. The microstructure of all zones has been studied using optical and scanning tunneling microscopes and its effect on the impact strength of the coating-substrate composition is discussed.

The experimental evidence for the realization of a superplastic behavior with 900% elongation in V-alloyed high-nitrogen austenitic Fe-19Cr-22Mn-1.5V-0.3C-0.6N steel was proposed. Using thermomechanical processing, a misoriented grain/subgrain austenitic microstructure with a high density of deformation-assisted defects and precipitates was developed in the steel. During high-temperature tensile deformation in a temperature interval from 850 to 1000 &deg, C and strain-rate range from 4 &times, 10&minus, 4 s&minus, 1 to 6 &times, 3 s&minus, 1, this microstructure demonstrated the characteristics of superplastic flow: elongation in the interval 400&ndash, 900%, strain-rate sensitivity exponent m = 0.40&ndash, 0.49, grain boundary sliding mechanism. The maximum elongation to failure (900%) was reached at deformation temperature 950 &deg, C and strain rate 4 &times, 1.

Austenitic stainless steels are frequently used for hydrogen applications due to their high ductility at low temperatures and lower hydrogen environment embrittlement compared to ferritic steels. We study the effect of electrochemical hydrogen saturation up to 40 h on tensile behavior and fracture mechanisms in high-nitrogen austenitic 17Cr–24Mn–1.3V–0.2C–1.3N steel. Hydrogen saturation weakly influences the characteristic of stress–strain curves, but decreases steel ductility, yield stress, and ultimate tensile stress. Hydrogenation provides a change in steel fracture peculiarities—a hydrogen-assisted thin brittle surface layer of ≈5 μm and ductile subsurface layer of 50–150 μm in width in hydrogen-saturated specimens. The subsurface layer shows ductile transgranular fracture with elongated dimples and flat facets. The central parts of fracture surfaces for hydrogenated specimens show ductile fracture mode similar to hydrogen-free state, but they include numerous secondary cracks both for central part and for transition zone between ductile central part and subsurface layer associated with highest hydrogen saturation. The possible reasons of decrease in hydrogen-associated ductility and change in fracture character are discussed.

Using different solid solution treatments, two structural states were produced in high-interstitial austenitic Fe-19Cr-22Mn-1.6V-0.4C-0.8N and Fe-22Cr-26Mn-1.3V-0.7C-1.2N (all in wt %) steels. Room temperature tensile properties of both steels are determined by a combination of several factors: solid-solution hardening of austenite with carbon and nitrogen, size and distribution of precipitates and grain size. Increase in solid-solution temperature from 1100 to 1200°C increases solid-solution hardening, decreases the particle strengthening effect in the steels and causes grain growth. The relation of these factors governs the value of a yield strength, ultimate tensile strength and elongation in the steel’s specimens.

The paper studies how microalloying with amorphous boron (Bam) influences the structure and properties of boride coatings. Two factors are found to strongly affect the structure and phase formation in composite coatings produced by electron beam surfacing, especially when using thermoreactive powders: (i) high reactive diffusion between the composite and substrate components, which causes the coating structure degradation, and (ii) slight deviations from phase concentrations and equilibrium crystallization, which give rise to such nonequilibrium phases in the coating structure under the electron beam as ferroboron, ferrotitanium and binary eutectics. The above findings suggest the possibility of controlling the structure formation and phase composition by varying the electron beam surfacing parameters. The parameters, among others, include the crystallization rate varied by the introduction of different modifiers, the proportion of components and granulometric composition of the fused powder mixture.

Efficiency of electron beam welding carried out on electron beam facility with the plasma cathode is shown at manufacturing tips oxygen lance from dissimilar materials. Composites of powder additives and technological regimes of welding allowing are optimized to receive qualitative welded seams between homogeneous (copper - copper) and dissimilar materials (copper - steel).

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.

Effect of age hardening regime (at the temperatures of 700 and 800°C for 10 min to 10 h) on phase composition and microhardness of high-nitrogen steels was investigated. Before age hardening treatments, specimens of V-free and V-alloyed steels, Fe–23Cr–17Mn–0.1C–0.6N (0V-HNS) and Fe–19Cr–22Mn–1.5V–0.3C–0.9N (1.5V-HNS), were water-quenched after 1200°C (for 0.5 h) to produce supersaturated solid solution of interstitial atoms (nitrogen and carbon) in austenite (7% ferrite in 0V-HNS, no ferrite and

New high-interstitial austenitic Fe–19Cr–22Mn–1.6V–0.4C–0.8N (mass. %) and Fe–22Cr–26Mn–1.3V–0.7C–1.2N steels were designed. A combination of high interstitial content (C + N = 1.2 mass. % and C + N = 1.9 mass. %, C/N = 0.5–0.6) and V-alloying of these steels provides a complex hardening mechanism (a solid-solution hardening, a particle strengthening and a grain boundary hardening). Increase in solid-solution temperature in the interval 1100–1230 °C forces solid-solution hardening, causes grain growth and changes a distribution and volume fraction of the precipitates in austenite. The relation of these factors governs the value of a yield strength, an ultimate tensile strength and an elongation in the high-interstitial steels. The variation in particle strengthening with solid-solution temperature has minor effect on the yield strength of the steels, but the distribution of precipitates strongly influences a tensile fracture micromechanism of the steels. The effect of solid-solution temperature on fracture peculiarities is described based on microstructural analysis of the steels.

The study on structure and mechanical properties of surfaced coatings and welded joints of 09Mn2Si steel formed with the use of a standard electrode as well as one modified by adding titanium carbonitride nanoparticles was carried out. Optical and scanning electron microscopy, microhardness measurement were employed to investigate the structure at welding with a standard electrode, as well as to illustrate changes resulting from the electrode modification through adding titanium carbonitride nanoparticles. Evaluation of mechanical properties was performed by conducting tests on static, cyclic and impact loading. It is shown that welding with the use of the modified electrode gives rise to decreasing the size of ferrite grains and increasing impact toughness and fatigue life.

The wear resistant composite coatings on the basis of titanium borides, which are synthesized from thermoreactive powder components of a boron-containing mixture at electron beam surfacing, are interesting for applications today.

The paper studies how microalloying with amorphous boron (Bam) and zirconia (ZrO2) influences the structure and properties of boride coatings. Two factors are found to strongly affect the structure and phase formation in composite coatings produced by electron beam surfacing, especially when using thermoreactive powders: (i) high reactive diffusion between the composite and substrate components, which causes the coating structure degradation, and (ii) slight deviations from phase concentrations and equilibrium crystallization, which give rise to such nonequilibrium phases in the coating structure under the electron beam as ferroboron, ferrotitanium and binary eutectics.

In this paper, we investigate the microstructure and microhardness of high-nitrogen austenitic steel after high-pressure upset and high-pressure torsion (6 GPa) at room temperature. As the result of deformation, steel microhardness increases by 1.5 times after high-pressure torsion per one revolution while the distribution of microhardness is quasi-homogeneous across the disks. The level of solid solution hardening of steel remains high after deformation processing, and the main mechanisms determining fragmentation of the steel structure are slip, twinning, formation of localized deformation microbands, and precipitation hardening.

Microstructure of coatings obtained by manual arc welding with commercial electrode MP-3 and experimental electrode modified with carbonitride nanoparticles was studied using scanning tunnel microscopy. It was found that microdispersed additives lead to structure refinement and bianite formation. Using dihedral angle measurements relative energies of ferrite/ferrite and ferrite/cementite grain boundaries were estimated. It was shown that the average relative grain boundary energy for experimental electrode coating is more than two times less than the corresponding value for commercial electrode coating. This phenomenon might be related to the increase of ferrite/cementite boundary portion. The decrease in grain boundary energy is correlated with the impact toughness increase of specimens with experimental electrode coating.

In this paper, the mechanical properties and fracture mechanisms of the high-nitrogen austenitic steel Fe– 17Cr–10Mn–7Ni–0.95V–0.8N–0.1C (in wt %) processed by different thermomechanical treatments are investigated. Cold rolling and short-time solid solution hardening contribute to the formation of a rather homogeneous fine-grained structures in the steel, which possess high strength, sufficient plasticity and exhibit excellent product of strength and elongation (σYS = 540–570 MPa, σUTS = 900–950 MPa, EL = 36–37%, PSE=33–35 GPa %) in comparison with cold-rolled specimens possessing high strength properties, but extremely low elongation (σYS = 1200 MPa, σUTS = 1650 MPa, EL=1%, PSE=1.7 GPa %).

The paper discusses the application of electron beam equipment based on a plasma cathode gun for three-dimensional surface modification of metals and alloys. The effect of substrate surface preparation on the adhesion strength of gas thermal coatings has been investigated.

Characteristics of CWS containing petrochemicals ignition by single hot particle in disk shape established experimentally. The main components of fuel composition are coal 45 %, water 45 %, used engine oil 10 %. The main parameters of local heat sources are: material – steel, diameter 10–12 mm, high 4–8 mm. As a result of experimental study is established limit (minimum) conditions for ignition of CWS containing petrochemicals by hot particle and the impact of local heat source parameters on the main process characteristic – ignition delay time.

The Institute of Strength Physics and Materials Science (Siberian Department, Russian Academy of Sciences) has developed a process for electron-beam deposition of powdered composite materials on metallurgically-produced parts. A unique electron-beam deposition device, the LUNa-10, for reinforcement of blower nozzles used in blast-furnace casting and for reinforcement of crystallizers in continuous steel casting machines was developed and placed into service at the West Siberian Metallurgical Combine (Novokuznetsk). This paper describes some characteristics of the electron-beam deposition process for composite coatings, and the properties of such coatings as a function of composition and purpose.

Electron-beam deposition (EBD) is an advanced technique intended for the formation of protective coatings that exhibit high strength and wear, and fatigue resistance. The investigation of the structure of coated materials and the development of mesoscale plastic deformation shows that these properties depend heavily on EBD modes. It is proposed that the latter can be optimized by: (i) choosing the electron-beam parameters that ensure a uniform structure of the coating, appropriate width and proper structure of the transient zone, (ii) the trial-and-error method of selecting such deposited powder composition that ensure high strength properties, and (iii) mechanical test aimed at distinguishing the coatings whose performance has been advantageously increased by EBD.

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.

The paper presents experimental research results on how microdisperse refractory Ti compounds entered into compositions of welding rods and flux cored wires can influence the structure and properties of deposited coatings. It is shown that welding electrodes based on microdisperse titanium carbonitrides and titanium aluminum nitrides make possible composite coatings of high hardness with high wear resistance and high fracture ductility.

High-nitrogen austenitic steels are perspective materials for an electron-beam welding and for producing of wear-resistant coatings, which can be used for application in aggressive atmospheres. The tensile behavior and fracture mechanism of high-nitrogen austenitic steel Fe-20Cr-22Mn-1.5V-0.2C-0.6N (in wt.%) after electrochemical hydrogen charging for 2, 10 and 40 hours have been investigated. Hydrogenation of steel provides a loss of yield strength, uniform elongation and tensile strength. The degradation of tensile properties becomes stronger with increase in charging duration - it occurs more intensive in specimens hydrogenated for 40 hours as compared to ones charged for 2-10 hours. Fracture analysis reveals a hydrogen-induced formation of brittle surface layers up to 6 [mu]m thick after 40 hours of saturation. Hydrogenation changes fracture mode of steel from mixed intergranular-transgranular to mainly transgranular one.