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The technological and structural properties of spherical granules and the peculiarities of their production processes using industrial technologies of gas atomization, plasma rotating electrode process and plasma‑arc atomization of neutral and current‑carrying wires and rods are considered. It was found that among the considered methods of obtaining spherical granules, the most promising in terms of productivity, energy efficiency and simplicity of the equipment used is the method of plasma‑arc atomization, which, due to the presence of a large number of technological and structural parameters of the process, allows adjusting the particles size distribution and technological properties of the granules in a wide range. Experimental studies have shown that the particles size distribution, shape factor and technological properties of granules made of titanium alloys and stainless steel obtained by plasma‑arc atomization of current‑carrying wire materials at the E.O. Paton Electric Welding Institute of the NAS of Ukraine, together with LLC «R&D PLAZER center», are at the level of the best foreign analogues. A promising direction of increasing the energy efficiency and productivity of the process of obtaining spherical granules for additive manufacturing and granule metallurgy using the technology of plasma‑arc atomization of current‑carrying rods with a diameter of more than 50 mm at reversed polarity by plasma torches with a hollow copper anode is proposed. [ABSTRACT FROM AUTHOR]

A plasma-arc unit of industrial type of up to 50 kW total power for deposition of functional coatings on critical parts and spheroidization of wire materials is presented. A feature of the unit is application of a system of water cooling of plasmatron inner components, modified design of the nozzle and cathode parts and reduction of plasmatron overall dimensions, ensuring a higher productivity of the process, widening of its application areas, improvement of mechanical and technological characteristics of the produced granules and coatings, etc. Presented is the microstructure and results of studying the granulometric composition of the dispersed phase, which are indicative of producing dense coatings with less than 1 % porosity, which form from granules of a spherical shape predominantly in a narrow particle size range of 20…100 μm. 17 Ref., 1 Tabl., 9 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 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 paper is devoted to studying the technological features of plasma-arc spraying by consumable current-conducting wire-anode. The relevance of applying such a process is related to the possibility of spraying directly by atomization of wires without the need to make powders from them. Experimental verification of the results of mathematical prediction of the influence of annular protective flow of compressed air, accompanying the particle-loaded plasma jet, on the results of plasma-arc spraying by compact wire anodes was performed. The key role of increasing this flow rate above 20 m³/h for improvement of the spay-deposited coating formation and quality was established. In spraying of coatings from compact wires porosity decreased with increase of the values of flow rates of accompanying air flow G2, and achievement of this parameter values within 0.5…2.5 %. Conducted experiments allow producing porefree coatings in spraying with wires from М2 copper, Kh20N80 nichrome, NP1 nickel, AMg63 aluminium-magnesium alloy. Studying these experimental results showed that at increase of the rate of accompanying protective air flow G2 from 0 to 40 m³/h, the loss of alloying elements (С, Mn) during spraying by steels wires of 65G and 70 grades decreases by 30…40 % on average. Increase of the parameter of rate G2 of the air flow accompanying the particle-loaded plasma jet influences improvement of the coating adhesion strength and wear resistance. So, at G2 = 20…40 m³/h the adhesion strength at tearing off of coatings from steel 70 along the normal reaches 60…70 MPa, and that of coatings from М2 copper is 40…55 MPa. Wear resistance of coatings under the conditions of boundary friction and resistance at cavitation wear increases at G2 increase from 0 to 40 m3/h, which is manifested in reduction of such wear from 1.35 to 0.32 mg/min. 13 Ref., 9 Fig. [ABSTRACT FROM AUTHOR]

The possibility is considered of producing a steel-titanium joint which forms at complex spray-deposition of a layer of aluminium oxide and a layer of iron powder PZh-1 on titanium with subsequent deposition by a consumable electrode or plasma of a layer of steel using filler wire Zv-08G2S. A new combined method was developed for joining steel to titanium with deposition of protective layers of Al2O3 and iron powder PZH-1 on titanium, with further deposition of a layer of filler wire Zv-08G2S by the plasma process. Ref. 8, Tabl. 2, Fig. 8. [ABSTRACT FROM AUTHOR]