OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 7 2 5 for printing with copper wire on already deposited steel layers, it is necessary to minimize heat input. Thus, for printing bimetallic specimens based on iron and copper alloys, a fixed heat input value is set for each of the materials under consideration. The heat input value when depositing layers of copper M1 is 0.09 kJ/ mm, which is 2.5 times less than the heat input value when depositing layers of copper alloy Cu-9 Al-2 Mn. The heat input value when depositing layers of iron alloy 321 is 0.17 kJ/mm, which is 1.5 times less than the heat input value when depositing layers of iron alloy 0.09 C-2 Mn-Si. This difference is due to the variation in thermophysical properties of the materials used. It should be noted that when applying the first layers to the substrate for each bimetallic specimen with a sharp interface, the heat input values are higher than the fixed ones. At such values, intensive heating of the substrate material occurs in the first layers of the specimen, which contributes to the stable formation of the melt pool. A common feature of the change in heat input values along the height of the printed specimen with a sharp interface is a sharp decrease during the transition from deposition of iron alloy to deposition of copper alloy. When forming a smooth interface between dissimilar materials, iron and copper wires were fed simultaneously. It was necessary to gradually change the ratio of feed rates of iron and copper wires into the melt pool: the feed rate of the copper alloy wire into the melt pool needed to be increased simultaneously with decreasing the feed rate of the iron alloy wire until it completely stopped (Fig. 5). During the printing process, in the zone with a gradual change in the feed rate of wires of dissimilar materials, a structure with a smooth interface is formed. During the feeding of only iron alloy wire when the copper alloy feed rate is υcopper = 0, a part of the additively grown steel is formed. The beginning of the smooth interface formation is accompanied by the introduction of copper alloy wire by the second feeder with a ratio of feed rates of the materials υsteel > υcopper approximately 1 to 4. At this stage, the area with additively grown steel predominates until the ratio of feed rates of the materials becomes equal υsteel = υcopper. The formation of the smooth interface is completed when the volume of iron alloy wire introduced is reduced, when the ratio of feed rates of the materials is υsteel < υcopper approximately 3 to 4. In the IV stage, only copper alloy wire is fed at iron alloy feed rate υsteel = 0, forming a part of additively grown copper. Thus, when manufacturing a vertical wall with a gradual change in feed rate, the formation of a smooth interface can be observed. Fig. 5. Schematic of the wire-feed electron beam additive manufacturing process for fabricating bimetallic specimens with a smooth interface between iron and copper alloys
RkJQdWJsaXNoZXIy MTk0ODM1