OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 7 2 5 beam, which leads to excessive melting of previously formed layers (Fig. 11, b). In the case of forming only the first layers of the manufactured product, they lead to bending of the substrate (Fig. 11, c). When applying a layer, material expansion occurs, which is limited by the colder deposited solidified layer, causing elastic compressive deformation. This leads to shrinkage of the material, causing a bending angle, and accumulates tensile residual internal stress in the growing direction. Heat input values selected for steel wire deposition are high for copper wire deposition. This leads to complete melting of the fed material and its subsequent spreading on already deposited layers (Fig. 12, a). This increases the thickness of the product, which is an undesirable phenomenon (Fig. 12, b). Low heat input values are also undesirable for the formation of a defect-free product. This manifests in needle-like whole remnants of wire on the vertical wall (Fig. 12, c). а b c Fig. 12. Images of defects (complete melting (a), increased thickness (b) and wire non-melting (c)) during copper wire deposition, resulting from improperly selected parameters for bimetal fabrication using EBAM When printing with set fixed parameter values for a bimetallic specimen with a smooth interface, it is necessary to control the heat input values from the very beginning until the last layer of the manufactured product. Controlling heat input values at each layer will help avoid the occurrence of discontinuities and delamination at the layer boundaries, which can lead to crack formation [19, 20]. In addition, insufficient or excessive energy input into the melt pool will lead to clumping of the fed material, which causes poor surface quality and disruption of the product geometry (Fig. 13). When applying the first layers to the substrate for manufacturing bimetallic specimens with any interface design, it is necessary to use a high heat input value. As the layer increases, it is necessary to reduce the heat input value. With this approach, sufficient heating of the material and a stable melt pool will occur. Thus, based on the properties of the materials used, changing technological parameters is necessary for the manufacturing of defect-free metal products by additive manufacturing methods (Figs. 14‑15). Conclusions 1. Defect-free specimens of composite materials consisting of copper alloy and iron alloy were fabricated by the wire electron beam additive manufacturing method. To obtain heterogeneous materials, simultaneous and continuous metal feeding was performed into the 3D printing zone from two wire feeders. Fig. 13. Defects observed during copper wire deposition in EBAM bimetal fabrication due to improperly selected parameters
RkJQdWJsaXNoZXIy MTk0ODM1