UDC 621.791The paper presents the results of studying the formation of structure and properties of metals when using additive technologies, such as arc and laser surfacing of highly alloyed nickel alloys. The main problem of nickel-chromium alloys during treatment with highly concentrated energy sources (welding, surfacing, soldering, plasma and laser treatment) consists in low strength and heat resistance after heating to high temperatures and rapid cooling, which is typical for these methods. The maximum high-temperature strength of such alloys is achieved after quenching and subsequent aging resulting in the formation of finely-dispersed ′ γ -phase precipitates, which inhibit plastic deformation. However, the achieved level of high-temperature strength of nickel alloys is often reduced significantly as a result of thermal effects and unfavorable structural changes during subsequent treatment (welding, surfacing). The paper presents the results of studying the structure, phase composition and properties of EP648 alloy during argon-arc surfacing. A comparison with the EP648 alloy structures obtained by laser surfacing is provided. It was established that argon-arc welding of EP648 alloy in combination with ultrasonic treatment creates an additional effect of increasing phase dispersion, which leads to an increase in hightemperature strength of the alloy.

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This paper investigates the effect of cold working via layer-by-layer peening on the microstructure and properties of a 308LSi steel workpiece produced by the wire deposition welding with a consumable electrode following the principle of 3D printing. The microstructure, phase composition and mechanical properties of the metal are studied before and after the workpiece synthesis. In the microstructure of the workpieces produced by peening, there is, in addition to austenite, a small quantity of fine-dispersed carbides and residual δ-ferrite in the interdendritic spaces. It is demonstrated that the use of layer-by-layer cold working in the process of deposition welding enables eliminating transcrystallization of the deposited metal, promotes an increase in the microstructure’s degree of dispersion and a more uniform distribution of fine-dispersed carbides in the volume of the dendrites. It is found that these structural features of the deposited metal in the additive manufacturing of a workpiece with layer-by-layer peening lead to an enhancement of the strength characteristics as compared to the material produced by the conventional wire deposition welding. Meanwhile, the level of the ductility characteristics remains high.

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The paper considers the influence of a change in the heat rate of a source with time by means of slope control, using the example of plasma-jet hard facing, as well as changes in the original structure due to laminated cool post weld upsetting of the pads, using the example of plasma-jet heat-facing with a consumable electrode (Plasma-MIG). It was found that the formation of the structure is accompanied by metal deposits transcrystallization. It is shown that the use of vibratory actions on the liquid bath by slope control modulating during plasma surfacing contributes to the partial suppression of transcrystallization of the metal deposit: the direction of columnar crystallites growth changes relative to the previous layer, contributes to the refinement of the pine-tree structure, which leads to a change in mechanical characteristics. The best properties are observed when surfacing with slope control with a frequency of 15000 Hz. The use of laminated cool post weld upsetting during the plasma-jet hard-facing by consumable electrode reduces the transcrystallization of the metal deposit. It forms dendritic crystals of an equiaxial form, which leads to the reduction of the morphological grain flow, and the strength characteristics of the fused on alloy exceeds the level of the metal durability fused on without post weld upsetting and materials obtained by traditional technologies. However, the moldability characteristics remain at a high level.