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Thermal Conductivity of Composite Materials Copper-Fullerene Soot

Koltsova, T., Bobrynina, E., Vozniakovskii, A., Larionova, T., Klimova-Korsmik, O.

(2022) Materials, 15 (4), статья № 1415.


КРАТКОЕ ОПИСАНИЕ: Copper-based composites strengthened with fullerene soot nanoparticles of 20–30 nm size in concentration up to 23 vol.% were prepared via two methods: mechanical mixing and molecular level mixing. The dependence of thermal conductivity on the carbon concentration was studied. Maxwell’s model describes well the change in the thermal conductivity of the composite obtained by molecular level mixing. However, thermal conductivity of the composite produced by mechanical mixing is significantly lower than the calculated values, due to structural inhomogeneity and residual stresses. Comparison of the thermal conductivity of Cu-fullerene soot composites with that of Cu-based composites described in the literature showed that the prepared materials are not inferior in thermal conductivity to composites containing carbon nanotubes, despite the fact that fullerene soot has a much lower thermal conductivity.

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Spatiotemporal evolution of stress field during direct laser deposition of multilayer thin wall of Ti-6Al-4V

Ivanov, S., Artinov, A., Zemlyakov, E., Karpov, I., Rylov, S., Em, V.

(2022) Materials, 15 (1), статья № 263.


КРАТКОЕ ОПИСАНИЕ: The present work seeks to extend the level of understanding of the stress field evolution during direct laser deposition (DLD) of a 3.2 mm thick multilayer wall of Ti-6Al-4V alloy by theoretical and experimental studies. The process conditions were close to the conditions used to produce large-sized structures by the DLD method, resulting in specimens having the same thermal history. A simulation procedure based on the implicit finite element method was developed for the theoretical study of the stress field evolution. The accuracy of the simulation was significantly improved by using experimentally obtained temperature-dependent mechanical properties of the DLD-processed Ti-6Al-4V alloy. The residual stress field in the buildup was experimentally measured by neutron diffraction. The stress-free lattice parameter, which is decisive for the measured stresses, was determined using both a plane stress approach and a force-momentum balance. The influence of the inhomogeneity of the residual stress field on the accuracy of the experimental measurement and the validation of the simulation procedure are analyzed and discussed. Based on the numerical results it was found that the non-uniformity of the through-thickness stress distribution reaches a maximum in the central cross-section, while at the buildup ends the stresses are distributed almost uniformly. The components of the principal stresses are tensile at the buildup ends near the substrate. Furthermore, the calculated equivalent plastic strain reaches 5.9% near the buildup end, where the deposited layers are completed, while the plastic strain is practically equal to the experimentally measured ductility of the DLD-processed alloy, which is 6.2%. The experimentally measured residual stresses obtained by the force-momentum balance and the plane stress approach differ slightly from each other.

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Design, simulation and optimization of an additive laser‐based manufacturing process for gearbox housing with reduced weight made from alsi10mg alloy

Magerramova, L., Isakov, V., Shcherbinina, L., Gukasyan, S., Petrov, M., Povalyukhin, D., Volosevich, D., Klimova‐korsmik, O.

(2022) Metals, 12 (1), статья № 67.


КРАТКОЕ ОПИСАНИЕ: The gas turbine engineʹs (GTE) development aims for the increasing the efficiency, strength, reliability and safety of its components. To create competitive engines, housing parts and components with high functionality and reduced weight are needed. Especially difficult in the design and production are the gearboxes for aviation GTE. Traditional technologies based on precision casting or material forming operations have significant limitations due to the complexity of fulfilling multiple different requirements. Nowadays, one of the progressive production techniques is additive manufacturing. The article presents the results of computational and experimental studies that substantiate the applicability of laser additive technology to reduce the mass of body parts by up to 15% while ensuring their strength properties. The physical and mechanical characteristics of aluminum alloys acceptable for the manufacturing of housing parts were analyzed. The necessary characteristics of the powder alloy of the Al‐Si system and the technological parameters of the L‐PBF of the modified housing of the gear reducer are established. Using the finite element method (FEM) the L‐PBF process was numerically simulated and the technological modes for synthesis of the AlSi10Mg alloy powder were optimized. With the help of a serial 3D printer ProX320DMP, the prototype of a gear housing was manufactured.

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Investigation of the technological possibility of laser hardening of stainless steel 14cr17ni2 to a deep depth of the surface

Somonov, V., Tsibulskiy, I., Mendagaliyev, R., Akhmetov, A.

(2022) Metals, 12 (1), статья № 5.


КРАТКОЕ ОПИСАНИЕ: The article presents the results of a research of the process of laser hardening of steel 14Cr17Ni2 (AISI 431) by radiation of a high‐power fiber laser LS‐16. Assessment of the theoretically possible maximum depth in laser processing without additional beam transformations, the use of additional coatings and devices were shown. The results of experiments on increasing the depth of the hardened layer during laser processing by using scanning of the laser beam and optimally selected mode parameters without scanning are demonstrated. The influence of the number of passes on the depth of the hardened layer is investigated. The microstructure of hardened samples was studied and quantitative estimation of structural components was carried out. The microhardness of hardened samples at different modes of laser hardening was measured.

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Microstructure evolution of fenicocral1.3 mo0.5 high entropy alloy during powder preparation, laser powder bed fusion, and microplasma spraying

Semikolenov, A., Kuznetsov, P., Bobkova, T., Shalnova, S., Klimova-Korsmik, O., Klinkov, V., Kobykhno, I., Larionova, T., Tolochko, O.

(2021) Materials, 14 (24), статья № 7870.


КРАТКОЕ ОПИСАНИЕ: In the present study, powder of FeCoCrNiMo0.5 Al1.3 HEA was manufactured by gas atomization process, and then used for laser powder bed fusion (L-PBF) and microplasma spraying (MPS) technologies. The processes of phase composition and microstructure transformation during above mentioned processes and subsequent heat treatment were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and differential thermal analysis (DTA) methods. It was found that gas atomization leads to a formation of dendrites of body centered cubic (BCC) supersaturated solid solution with insignificant Mo-rich segregations on the peripheries of the dendrites. Annealing leads to an increase of element segregations till to decomposition of the BCC solid solution and formation of σ-phase and B2 phase. Microstructure and phase composition of L-PBF sample are very similar to those of the powder. The MPS coating has a little fraction of face centered cubic (FCC) phase because of Al oxidation during spraying and formation of regions depleted in Al, in which FCC structure becomes more stable. Maximum hardness (950 HV) is achieved in the powder and L-PBF samples after annealing at 600◦ C. Elastic modulus of the L-PBF sample, determined by nanoindentation, is 165 GPa, that is 12% lower than that of the cast alloy (186 GPa).

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High-power fiber laser welding of high-strength aa7075-t6 aluminum alloy welds for mechanical properties research

El-Batahgy, A.-M., Klimova-Korsmik, O., Akhmetov, A., Turichin, G.

(2021) Materials, 14 (24), статья № 7498.


КРАТКОЕ ОПИСАНИЕ: The results disclosed that both the microstructure and mechanical properties of AA7075-T6 laser welds are considerably influenced by the heat input. In comparison with high heat input (arc welding), a smaller weld fusion zone with a finer dendrite arm spacing, limited loss of alloying elements, less intergranular segregation, and reduced residual tensile stress was obtained using low heat input. This resulted in a lower tendency of porosity and hot cracking, which improved the welded metal’s soundness. Subsequently, higher hardness as well as higher tensile strength for the welded joint was obtained with lower heat input. A welded joint with better mechanical properties and less mechanical discrepancy is important for better productivity. The implemented high-power fiber laser has enabled the production of a low heat input welded joint using a high welding speed, which is of considerable importance for minimizing not only the fusion zone size but also the dete-rioration of its properties. In other words, high-power fiber laser welding is a viable solution for recovering the mechanical properties of the high-strength AA 7075-T6 welds. These results are en-couraging to build upon for further improvement of the mechanical properties to be comparable with the base metal.

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Numerical analysis of particle trajectories in a gas–powder jet during the laser-based directed energy deposition process

Stankevich, S., Larionov, N., Valdaytseva, E.

(2021) Metals, 11 (12), статья № 2002.


КРАТКОЕ ОПИСАНИЕ: Based on numerical solutions of the equation of motion of a particle in a gas jet modeled by the Reynolds-averaged Navier–Stokes equations, the features of transporting powder particles to the working zone of laser-based directed energy deposition are investigated. The propagation of a gas jet in a confined space in the presence of obstacles in the form of a substrate and a wall of a part is considered. A solution determining the gas-dynamic parameters of the jet is obtained, and the results of calculating its velocity field are presented. The influence of gas-dynamic parameters on the trajectories of the powder particles is analyzed. It is shown that these parameters determine the amount of model material involved in the formation of the geometry of the part.

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Numerical estimation of the geometry of the deposited layers during direct laser deposition of multi-pass walls

Udin, I., Valdaytseva, E., Kislov, N.

(2021) Metals, 11 (12), статья № 1972.


КРАТКОЕ ОПИСАНИЕ: Direct laser deposition (DLD) is a promising additive technology that allows for the rapid and cheap production of metal parts of complex geometry in various sectors of mechanical engineering. Thick-walled metal structures occupy a significant part in mechanical engineering. The purpose of this study was to develop and test an algorithm for predicting the geometry of deposited multi-pass walls. To achieve this goal, the main interrelated processes involved in the formation of a multi-pass wall were described—the process of laser radiation propagation, the process of heat transfer and the process of bead formation. To construct the calculation algorithm, five characteristic types of beads are identified. For these five types, the features of the bead formation and the features of the laser radiation intensity distribution are described. The calculated data were verified. A good match of the calculated data with the geometry of the deposited walls from AISI321 steel, Inconel718 and Ti-6Al-4V alloys was obtained.

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Structure and mechanical properties of shipbuilding steel obtained by direct laser deposition and cold rolling

Mendagaliyev, R., Zotov, O., Korsmik, R., Zadykyan, G., Lebedeva, N., Klimova-Korsmik, O.

(2021) Materials, 14 (23), статья № 7393.


КРАТКОЕ ОПИСАНИЕ: The study of the formation of microstructural features of low-alloy bainite-martensitic steel 09CrNi2MoCu are of particular interest in additive technologies. In this paper, we present a study of cold-rolled samples after direct laser deposition (DLD). We investigated deposited samples after cold plastic deformation with different degrees of deformation compression (50, 60 and 70%) of samples from steel 09CrNi2MoCu. The microstructure and mechanical properties of samples in the initial state and after heat treatment (HT) were analyzed and compared with the samples obtained after cold rolling. The effect on static tensile strength and impact toughness at −40◦C in the initial state and after cold rolling was investigated. The mechanical properties and characteristics of fracture in different directions were determined. Optimal modes and the degree of cold rolling deformation compression required to obtain balanced mechanical properties of samples obtained by additive method were determined. The influence of structural components and martensitic-austenitic phase on the microhardness and mechanical properties of the obtained samples was determined.

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An extended analytical solution of the non-stationary heat conduction problem in multi-track thick-walled products during the additive manufacturing process

Mukin, D., Valdaytseva, E., Turichin, G., Vildanov, A.

(2021) Materials, 14 (23), статья № 7291.


КРАТКОЕ ОПИСАНИЕ: An analytical model has been developed for calculating three-dimensional transient temperature fields arising in the direct deposition process to study the thermal behavior of multi-track walls with various configurations. The model allows the calculation of all characteristics of the temperature fields (thermal cycles, cooling rates, temperature gradients) in the wall during the direct deposition process at any time. The solution of the non-stationary heat conduction equation for a moving heat source is used to determine the temperature field in the deposited wall, taking into account heat transfer to the environment. The method considers the size of the wall and the sub-strate, the change in power from layer to layer, the change in the cladding speed, the interpass dwell time (pause time), and the heat source trajectory. Experiments on the deposition of multi-track block samples are carried out, as a result of which the values of the temperatures are obtained at fixed points. The proposed model makes it possible to reproduce temperature fields at various values of the technological process parameters. It is confirmed by comparisons with experimental thermo-couple data. The relative difference in the interlayer temperature does not exceed 15%.

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Characterization of Ni-Cr-Mo alloy phase structures under DLD process

Rashkovets, R.M., Nikulina, A.A., Klimova-Korsmik, O.G., Smirnov, A.I., Veselov, S.V., Kislov, N.G.

(2021) Journal of Physics: Conference Series, 2077 (1), статья № 012015.


КРАТКОЕ ОПИСАНИЕ: Direct laser deposition of Ni-Cr-Mo alloy has been carried out to study the phase structure transformation under various operating parameters. To assess the phase composition SEM, TEM and XRD analysis were performed. It clearly seen that the precipitation of straightening phases (γ' and γ'') depends on the temperature gradients caused by different laser power. The nucleation of γ' phase starts at 750 W while γ'' phase at 1000 W. The changes in temperature gradients lead to different diffusion condition across all the stage of laser power variation and formation of δ-phase, primary MC carbides and Laves phase. δ-phase of all samples did not change the shape and characterized only by plate-like shape.

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Research of trends in the development of laser additive manufacturing in the Russian Federation on the basis of patent information

V V Somonov

(2021) Journal of Physics: Conference Series, 2077 (1), статья № 012020


КРАТКОЕ ОПИСАНИЕ: The article presents the results of the analysis of patent documentation on laser additive manufacturing registered in the territory of the Russian Federation. As a result of the research, the dynamics of patent activity is determined, the top patent holders, the leading countries in the considered technological field are identified, the top of inventors is compiled, the main technological segments for application of patented solutions from the field of laser additive manufacturing are identified.

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Structure and properties of near-α titanium products obtained by direct laser deposition and heat treatment

Shalnova, S.A., Klimova-Korsmik, O.G., Arkhipov, A.V., Yunusov, F.A.

(2021) Journal of Physics: Conference Series, 2077 (1), статья № 012018.


КРАТКОЕ ОПИСАНИЕ: Advanced techniques of obtaining products require careful selection of materials for various industries. Titanium alloys are widely used in the aerospace, shipbuilding and mechanical engineering industries. The development of near-α titanium alloys should be considered a significant achievement in the field of metallurgy and heat treatment (HT) of titanium alloys. This article presents a study carried out with the aim of optimizing heat treatment modes for high-temperature titanium alloys obtained by direct laser deposition (DLD). Heat treatment was carried out in the temperature range (700-1000°C), covering three typical temperature ranges, i.e. the temperature range for the partial decomposition of martensite, the temperature range for the complete decomposition of martensite, and the phase transformation temperature were subsequently selected as the heat treatment temperatures. Based on metallographic analysis, the influence of heat treatment modes on the structure, as well as the tensile properties at room temperature, of TA15 titanium DLD-samples.

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Research of deformation compensation method in laser metal deposition process of 316L stainless steel product

Kovchik, A., Babkin, K., Vildanov, A.

(2021) Journal of Physics: Conference Series, 2077 (1), статья № 012010.


КРАТКОЕ ОПИСАНИЕ: It is exists the problem of big product manufacturing with minimal dimensions tolerances. To solve this problem it is necessary to compensate the deformations influence. In researching of method, it became clear that deformation degree has changed and depended on size and form of part. However, the amount of deformation degree to dimension of part is still independent of size. This fact has observed after production of axis-symmetrical parts. The simple axis-symmetrical part was built up. The dimensions of part was measured, and the compensation coefficient was calculated. The dimensions of part was scaled on this coefficient for compensation of shrinkage effect. After that the experiment was repeated.

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Effect of thermal cycles on the microstructure and mechanical properties of cold-resistant steel 09CrNi2MoCu during laser deposition

Mendagaliyev, R., Klimova-Korsmik, O.G., Ivanov, S.Y., Babkin, K.D., Vildanov, A.M.

(2021) Journal of Physics: Conference Series, 2077 (1), статья № 012012.


КРАТКОЕ ОПИСАНИЕ: The formation of microstructure features of cold-resistant bainite-martensite steel 09CrNi2MoCu has been investigated. Thermal cycles during direct laser deposition were studied. The thermal cycles at different points of the deposited samples were investigated. The thermal cycles and CCT diagrams on microstructure formation and mechanical properties have been analyzed. The numerical calculation of the three-dimensional thermal conductivity problem by the finite element method is carried out. The received data of experimentally measured thermal cycles and the calculated data have shown good coincidence of temperature values. On the basis of the obtained data the calculated dependence of inter-layer temperature at depositing the sample with and without a pause is given. The microstructure and mechanical properties of the samples in the initial state and after heat treatment have been studied and compared with traditional hot rolling. The microstructure features at different pauses between passes in different parts of the obtained samples were revealed. The effect on static tensile and impact toughness at -40°C in the bred and heat-treated state was investigated.

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Effect of elevated temperatures on the mechanical properties of a direct laser deposited ti-6al-4v

Ivanov, S., Gushchina, M., Artinov, A., Khomutov, M., Zemlyakov, E.

(2021) Materials, 14 (21), статья № 6432.


КРАТКОЕ ОПИСАНИЕ: In the present work, the mechanical properties of the DLD-processed Ti-6Al-4V alloy were obtained by tensile tests performed at different temperatures, ranging from 20◦C to 800◦C. Thereby, the process conditions were close to the conditions used to produce large-sized structures using the DLD method, resulting in specimens having the same initial martensitic microstructure. According to the obtained stress curves, the yield strength decreases gradually by 40% when the temperature is increased to 500◦C. Similar behavior is observed for the tensile strength. However, further heating above 500◦C leads to a significant increase in the softening rate. It was found that the DLD-processed Ti-6Al-4V alloy had a Young’s modulus with higher thermal stability than conventionally processed alloys. At 500◦C, the Young’s modulus of the DLD alloy was 46% higher than that of the wrought alloy. The influence of the thermal history on the stress relaxation for the cases where 500◦C and 700◦C were the maximum temperatures was studied. It was revealed that stress relaxation processes are decisive for the formation of residual stresses at temperatures above 700◦C, which is especially important for small-sized parts produced by the DLD method. The coefficient of thermal expansion was investigated up to 1050◦C.

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The strength of inconel 625, manufactured by the method of direct laser deposition under sub‐microsecond load duration

Promakhov, V., Schulz, N., Vorozhtsov, A., Savinykh, A., Garkushin, G., Razorenov, S., Klimova‐korsmik, O.

(2021) Metals, 11 (11), статья № 1796.


КРАТКОЕ ОПИСАНИЕ: This paper presents the results of measurements of the spall strength and elastic‐plastic proper‐ties, under dynamic and static loads, of the high‐strength heat‐resistant nickel‐chromium alloy Inconel 625, obtained by the direct laser deposition method. The structural parameters of the obtained samples and the mechanical properties during static tests were studied. According to our information, anisotropy in the structural parameters operates primarily at the level of plastic deformation of alloys. Shock compression of the additive alloy Inconel 625 samples in the range of 6–18 GPa was carried out using a light‐gas gun, both along and perpendicular to the direction of the deposition. The strength characteristics were determined from the analysis of the shock wave pro-files, which were recorded using the VISAR laser velocimeter during the loading of samples. It was found that the value of the spall strength of additive samples does not depend on the direction of deposition, and the Hugoniot elastic limit of samples loaded perpendicular to the deposition direction is about ~10% higher. With an increase in the maximum compression stress, the material’s spall strength increases slightly, but for both types of samples, a slight decrease in the Hugoniot elastic limit was observed as the compression stresses increase. On the basis of the measured wave profiles, shock Hugoniots of the samples of the alloy Inconel 625, loaded both along and perpendicular to the direction of deposition, are constructed in this pressure range.

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Using a trial sample on stainless steel 316l in a direct laser deposition process

Vildanov, A., Babkin, K., Mendagaliyev, R., Arkhipov, A., Turichin, G.

(2021) Metals, 11 (10), статья № 1550.


КРАТКОЕ ОПИСАНИЕ: Direct laser deposition technology is used for the manufacture of large-size products with complex geometries. As a rule, trial samples with small dimensions are made to determine the deposition parameters. In order for the resulting products to have the required performance characteristics, it is necessary to minimize the number of internal macrodefects. Non-fusion between the tracks are defects that depend on the technological mode (power, speed, track width, etc.). In this work, studies have been carried out to determine the power level at which non-fusion is formed, dwell time between the tracks on the model samples. This paper considers the issue of transferring the technological parameters of direct laser deposition from model samples to a large-sized part, and describes the procedure for making model samples.

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Features of filler wire melting and transferring in wire-arc additive manufacturing of metal workpieces

Voropaev, A., Korsmik, R., Tsibulsky, I.

(2021) Materials, 14 (17), статья № 5077.


КРАТКОЕ ОПИСАНИЕ: In this paper, we present the results of a study on droplet transferring with arc space short circuits during wire-arc additive manufacturing (WAAM GMAW). Experiments were conducted on cladding of single beads with variable welding current and voltage parameters. The obtained oscillograms and video recordings were analyzed in order to compare the time parameters of short circuit and arc burning, the average process peak current, as well as the droplets size. Following the experiments conducted, 2.5D objects were built-up to determine the influence of electrode stickout and welding torch travel speed to identify the droplet transferring and formation features. Moreover, the current–voltage characteristics of the arc were investigated with varying WAAM parameters. Process parameters have been determined that make it possible to increase the stability of the formation of the built-up walls, without the use of specialized equipment for forced droplet transfer. In the course of the research, the following conclusions were established: the most stable drop transfer occurs at an arc length of 1.1–1.2 mm, reverse polarity provides the best drop formation result, the stickout of the electrode wire affects the drop transfer process and the quality of the deposited layers. The dependence of the formation of beads on the number of short circuits per unit length is noted.

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The features of martensitic transformation in 12% chromium ferritic–martensitic steels

Bazaleeva, K., Golubnichiy, A., Chernov, A., Ni, A., Mendagaliyev, R.

(2021) Materials, 14 (16), статья № 4503.


КРАТКОЕ ОПИСАНИЕ: An anomaly in martensitic transformation (the effect of martensitic two-peak splitting in the temperature-dependent thermal expansion coefficient) in complex alloyed 12% chromium steels Fe-12%Cr-Ni-Mo-W-Nb-V-B (ChS-139), Fe-12%Cr-Mo-W-Si-Nb-V (EP-823) and Fe-12%Cr-2%W-V-Ta-B (EK-181) was investigated in this study. This effect is manifested in steels with a higher degree of alloying (ChS-139). During varying temperature regimes in dilatometric analysis, it was found that the splitting of the martensitic peak was associated with the superposition of two martensitic transformations of austenite depleted and enriched with alloying elements. The anomaly was subsequently eliminated by homogenization of the steel composition due to high-temperature aging in the γ-region. It was shown that if steel is heated to 900◦C, which lies in the (α + γ) phase region or slightly higher during cooling, then the decomposition of austenite proceeds in two stages: during the first stage, austenite is diffused into ferrite with carbides; during the second stage, shear transformation of austenite to martensite occurs.