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The article analyses the current trends in the development of additive manufacturing (AM) technologies. In recent years, the development of additive technologies is one of the industry priorities. Additive technologies, first of all, make it possible to implement effectively any design and engineering ideas in high-tech industries, such as aircraft construction, engine and engine building, rocket engineering, modern electronic devices, etc. The expansion of the range of materials for additive technologies will facilitate their introduction into mass production. Meanwhile, the development of breakthrough scientific and technical solutions in the field of AT is impossible without new powder materials. Currently, there is an evident fundamental problem, namely, the lack of comprehensive scientific research aimed at developing new powder materials for additive technologies, adapting these materials to the requirements of modern additive manufacturing machines and studying the properties of products obtained by additive technology with various variations of technical parameters.

This paper describes the method of shaping the product using 3D technology by means of applying arc heating and consumable material – a wire with a diameter of 1.2 mm. The aim of the work is to study the structure and mechanical properties of the product manufactured using additive 3D technology. Each deposited layer consists of three separate beads: two lateral ones, which provide the set contours of the layer, and one middle one, which fills the space between the two lateral ones. Electric arc surfacing was carried out with the help of a welding robot. The use of a robot made it possible to control the time between layer depositions, thereby controlling grain growth. Also, the use of a robot makes it possible to reproduce a set part as accurately as possible according to a pre-calculated and designed model with a minimum error of repetition of the torch movement of ±0.03 mm. As a result, the structure and mechanical properties of the deposited product were investigated. It is shown that the product manufactured according to the presented technology has a fine-grained ferrite-pearlite structure; the grain size ranges from 7 to 10 numbers. The mechanical properties along and across the deposited layers were studied. The indices practically do not differ. A comparison of their values with normative ones showed that they exceeded normative values by 10–50%. 14 Ref., 3 Tabl., 4 Fig. [ABSTRACT FROM AUTHOR]

Comparative analysis of the influence of modifying additives of boron or titanium carbides on the structure and properties of the metal deposited with PP-Np-25KhFMS flux-cored electrode wire was performed in this study. It is shown that addition of some modifier in the amount of 0.01% does not have any significant influence on the deposited metal structure. Their influence on the structure differs to a certain extent. Boron modifying leads to an essential reduction of the crystallite dimensions, redistribution of nonmetallic inclusions and increase of metal microhardness. Unlike that, introducing titanium carbide microadditives into the weld pool influences the kinetics of metal solidification, which results in elimination of crystallite columnarity and metal structure transformation into the cell one. It is shown that owing to the mentioned changes in the structure, the wear and heat resistance of the metal, deposited with application of both the types of modifiers, is increased. Obtained results can be used at selection of promising methods to improve the service properties of the surfaced parts, which operate under the conditions of thermal force loading and wear at metal friction against metal. 11 Ref., 4 Fig. [ABSTRACT FROM AUTHOR]

The possibility of producing spherical titanium powders by application of the technology of plasma-arc atomization of compact current-conducting Ti wire of Grade 2 of 1.6 mm diameter was experimentally confirmed. Analysis of granulometric composition of the powder showed that the main fraction of the powder is 25…250 μm, making up 95 % of the total powder volume, quantity of particles of <25 μm and 250…315 μm fractions not exceeding 5 %. Parameters of the titanium powder shape were studied. It was shown that the majority of the particles are of a regular spherical shape with sphericity coefficient close to 0.8. The quantity of defective particles is not more than 3 % of the total weight of the powder. It was found that atomization by the wire-anode scheme leads to a considerable increase of wire heating efficiency (by approximately 4 times), compared to the scheme of atomization of neutral wire, which promotes an increase of process efficiency from 2…5 to 12 kg/h. It is shown that application of the technology of plasma-arc spheroidizing of the titanium wire allows producing spherical powders for 3D printing of high-quality products for the aerospace industry by the technologies of selective and direct laser melting and sintering and by the methods of powder (granulated) metallurgy (hot isostatic pressing with subsequent thermomechanical treatment). Ref. 21, Tabl. 2, Fig. 6. [ABSTRACT FROM AUTHOR]

The paper gives the results of investigation of the features of formation of D16 aluminium alloy welds in consumable electrode welding with application of two insulated fi ller wires or embedded elements of diff erent chemical composition. Wires of Zv1201, ZvАК5, ZvАК12 grades of 1.6 mm diameter and embedded elements cut out of V92, V96 and 7056 alloy blanks with diff erent content of zinc were evaluated. It is shown that ZvАК5 wire ensures reduction of the length of solidifi cation cracks and quantity of pores in welded joints, and welded joint strength becomes higher at addition of zinc into the welds. 15 Ref., 5 Tabl., 5 Fig. [ABSTRACT FROM AUTHOR]

The possibility of producing spherical powders by application of the technology of plasma-are sputtering of current-con- ducting wire of 1.6 mm dia. from low-carbon steel was experimentally confirmed. It was found that at different parameters of plasma are sputtering in the general case the main fraction of the powder is 25...250 μm fraction, which amounts to 95 % of the powder overall volume, quantity of particles of < 25 and 250. ..315 μm fractions in optimum sputtering modes is at a rather low level and is not more than 5 %. The plasma-are sputtering mode was selected, which will ensure a change of the granulometric composition towards increase of the content of fine fractions (< 80 μm), which are in great demand in the field of additive 3D printing technologies: current — 280 A; wire feed rate — 12.0 m/min; arc gap length — 8 mm; plasma gas flow rate — 50 1/min; concurrent gas flow rate — 60 m³/h; gap between plasma-forming and compression nozzle — 1 mm; cathode immersion depth — 1 mm. The shape and structure of the atomized particles was studied, most of which generally have a regular spherical shape. Here, the sphericity coefficient depends on process parameters and is ‘equal to 0.7...0.9 on average at optimal sputtering modes. In the total mass of the obtained spherical powders the share of satellites and isolated particles of an irregular shape is close to 1...3 %. [ABSTRACT FROM AUTHOR]

The results of studying the formation of welded joint in electric arc surfacing on copper by the wires, providing a deposited metal based on iron and nickel, which according to the authors and publications in the technical literature have a high resistance to different types of wear at elevated temperatures. The modes were selected and technologies of arc surfacing on a copper basis by selected wires were developed, which provide a satisfactory formation of the deposited metal and its fusion with the base metal. According to the results of experiments on electric arc surfacing on copper, as well as the study of macro- and microstructure of deposited specimens, it was shown that the best results in terms of welding and technological properties are provided by the use of nickel-based wire. The permissibility of individual defects that were found in the deposited metal and on the fusion line of the base and deposited metal during studies will be determined by the operating conditions of specific parts. [ABSTRACT FROM AUTHOR]

Unevenness of wearing of working surfaces of parts, operating under friction, is a common cause for beginning of renovation and replacement times. One of the methods to avoid this problem is formation of surfaces of a variable composition and properties by arc surfacing. The work presents comparative analysis of the hardness and structure of the metal, deposited with pre-application of titanium and boron carbides on the processed surfaces. These materials were selected, proceeding from their impact on the deposited metal mechanical properties. The hardness, structure and composition of the deposited metal were studied. Hardness dependence on the heat input and material consumption in individual zones of the bead cross-section was analyzed. Regularities were established between accumulation in the formed beads of material pre-applied on the processed surface and the significance of structural transformations. A similar influence of both the carbides on the deposited metal structure was found. Bead metal hardness is 1.5 times higher at B4 C application, than in the case of using TiC. X-Ray spectral microanalysis revealed the influence of free carbon, formed as a result of compound decomposition, on the structural transformation in the deposited metal. It was found that the largest accumulations of bainite are characteristic for zones with the highest carbon content. It was determined that pre-application of carbides, using the most common surfacing materials, allows producing deposited metal, matching by its properties the metal deposited with PP-Np-152 wire. [ABSTRACT FROM AUTHOR]

The investigation of the formation process of pseudoalloy coatings of the copper-aluminium system under the conditions of electric arc spraying is performed. Regression equations reflecting the dependence of the average particle size of the products of wire spraying, the content of oxides and porosity of the coatings on the wire feed rate, voltage at the electrodes, compressed air consumption and spraying distance are obtained using mathematical planning of the experiment. As determined, the main ways to control the size of the sprayed particles during the simultaneous spraying of copper and aluminium wires is to change the compressed air consumption and heat input into the sprayed materials and gas jet. As a result of studying the structure and phase composition of the spraying products, it is found that in the process of simultaneous spraying of copper and aluminium wires as a result of the interphase interaction of their melts pseudoalloy particles are formed, which are a conglomerate of copper-aluminium. Analysis of the study's results of coatings formation during the spraying of copper and aluminium wires show that heterogeneous pseudoalloy coatings are formed for the entire selected range of electric arc spraying parameters. The coatings consist of lamellas of the initial components of copper and aluminium with the presence of oxide layers of copper. The coatings also contain admixtures of the intermetallic phases Cu9Al4 and CuAl2, which are formed during the formation of the coating layer on the substrate. The content of oxides in the coatings is in the range of 10-17% vol., the porosity of the coatings is 4-8% vol. As a result of the performed investigation, the ways of controlling the structure and consequently the properties of pseudoalloy copper-aluminium coatings by changing the parameters of electric arc spraying are established. [ABSTRACT FROM AUTHOR]

Structural sparsely-doped titanium alloys are developed with the purpose of lowering the finished product cost. Possibility of application of tungsten electrode argon-arc welding (AAW) for sparsely-doped pseudo-β-titanium alloy Ti–2.8Al–5.1Mo–4.9Fe was evaluated. Influence of different kinds of argon-arc welding on weld formation and mechanical properties of Ti–2,8Al–5,1Mo–4,9Fe alloy joints were assessed. The effect of complete penetration AAW, semi-submerged AAW AAW with feeding unalloyed titanium welding filler wire VT1-00sv was studied. It was found that the structure of metal of the weld and HAZ in welded joints of sparsely-doped titanium alloy Ti–2.8Al–5.1Mo–4.9Fe made by AAW consists mainly of β-phase with precipitates of metastable α-phase. Lowering of AAW heat input for Ti–2.8Al–5.1Mo–4.9Fe alloy has a positive impact on the joint strength. So, among the welded joints made without changing the weld metal composition, the joints made by semi-submerged arc welding have the highest strength of 972 MPa and the highest impact toughness on the level of 5.7 J/cm2 . 15 Ref., 3 Tabl., 3 Fig. [ABSTRACT FROM AUTHOR]

The effect of the SiO2 nanopowder's adding into the welding bath on the wear resistance and structure of low-alloyed weld metal is studied. Silicon dioxide is fixed by preliminary spraying onto the surface of the alcohol solution, by applying a mixture of nanopowder with fluxes or a paraffin pencil and SiO2. Hardfacing is carried out on the templates of steel 09Г2С with wires Нп- 30ХГСА under flux АН-60 and Св-08Г2С under flux АН-348А. For correct comparison surfacing regime is constant. Test of durability are carried out for friction conditions of metal by metal according to the scheme of shaftpads. The amount of wear received as a result of test is determined by weighing or measuring of templates before friction process and after it. The dependence of changes nature in the weld metal on the adding method of additional materials is revealed. The most noticeable increasing of hardness is observed with adding of nano-oxide in a mixture with flux АН-60 with spray technology and using the wire Нп-30ХГСА. Templates welded with the same wire with adding of nanopowder fixed with paraffin to weld bath have maximum wear resistance. The efficiency of adding schemes depends on welded metal's alloying schemes: during hardfacing with wire increasing of hardness and wear resistance is not observed. Adding of silicon nanoxide in mixture with flux causes the formation of a fine structure with ferrite-carbide composition. The combination of ferrite with different morphologies is recorded: there is polygonal ferrite at the borders of grains which grows outrageous ferrite and divergent plates of needle-shaped ferrite. The number of cementitious secretion increases because of adding the silicon dioxide nanopowder in a mixture with paraffin. Proportionality of hardness increasing to grinding of ferrite-carbide structural component and of wear-resistance increasing to number of cementitious secretions is found. [ABSTRACT FROM AUTHOR]

A series of electric explosions of single wires and bunches of copper, titanium and tungsten in propane-butane was carried out and the respective time dependencies of voltage and current were analyzed. The products of the exploded refractory metals and their chemical compounds with carbon, deposited in the form of coating on a structural surface, were investigated by means of optical and scanning electron microscopy and X-ray diffractometry. The process of resistive heating of Cu is characterized by a sharp, and, most importantly, monotonous increase in voltage to a peak value while the voltage curves of Ti and W are characterized by the formation of a flat plateau followed by a peak of overvoltage slightly lower than the one for Cu. These features are due to the difference of the resistivity and the temperature coefficients of resistance in the liquid state for refractory conductors and high-conductive Cu, which can absorb during resistive heating 1.5-2 times more energy accumulated by the condenser than Ti and W. Relatively thick bunches of tested metals (twisted wires 0.3 mm in diameter) explode with the energy deposition that does not exceed the sublimation energy, and form liquid metal microdrops and agglomerated spherical particles less than 100 nm in size. The presence of the electric arc may be due to the heterogeneous heating of the cross section of thick bunches, as compared to a single wire, and the development of electroemission from the surface of the refractory conductors. The study of the obtained coatings shows that an increase in the energy input into Ti and W during the resistive heating, which can be realized either by changing the parameters of the electric circuit, or by the electro explosion of conductors insulated with dielectric varnish, is conducive to the formation of different carbides, in particular, stabilized high temperature carbide phases, to reducing the amount of pure metal in the coating, reducing the average particle sizes of destroyed conductors and to smoothing the surface relief of the coating. The calculated mass balance of the system reveals that the weight of the coating increases in proportion to the number of electroexplosions, despite the fact that a certain quantity of destroyed electric wires does not participate in the formation of the coating and falls to the bottom of the reactor as powder. The mass growth of the coatings composed of the Ti and W destruction products is determined by the sublimation energy and the density ratio of pure metals and carbide phases provided the same modes of wire electroexplosion and the uniform geometry of conductors. [ABSTRACT FROM AUTHOR]