OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 4 2024 The microstructure of Inconel 625 specimens obtained using EBAM and WAAM technologies is shown in Figure 2, a–d. This fi gure shows micrographs taken with an optical microscope in the center of the specimen. An elongated cellular structure with brightly colored particles in the interdendritic regions can be seen. The presence of dendritic structure is also clearly visible in all specimens. For horizontal specimens for both technologies, the dendrites have long fi rst-order axes, while the second-order axes are practically absent. For vertical specimens, the cooling rate is lower and second-order axes have time to form; the embryos of third-order axes can be seen in some places. The diff erence in dendrite development is clearly visible for EBAM technology (Fig. 2, a and Fig. 2, b). In addition, it is evident from the shown microstructure, that the grains are textured. The texture is more developed for vertical specimens due to the higher cooling rate. a b c d Fig. 2. Microstructure of specimens obtained using various additive technologies: a – horizontal specimen obtained using EBAM technology; b – vertical specimen obtained using EBAM technology; c – horizontal specimen obtained using WAAM technology; d – vertical specimen obtained using WAAM technology Certainly, diff erent cooling rates lead to the formation of diff erent grain sizes in the specimens. At the same time, in general, the same tendency is observed for all technologies under study. The grains have a dendritic structure; the grains are elongated in the direction of heat removal. The length of grains increases with distance from the substrate. For vertical specimens the cooling rate is lower and the grain length on the obtained specimens can reach 0.8–0.9 mm (vertical EBAM specimens). For horizontal specimens, the grain length reaches 0.3–0.5 mm. These data are in agreement with the results of other researchers. In [6], a specimen of Inconel 625 fabricated using the SLM technology had a grain length of about 1 mm. Specimens of Inconel 718 produced using the direct laser additive fusion process in the work [32] had a grain length of 3 mm. The authors of [11, 16], showed that the equiaxed grains are mainly located at the bottom, close to the Inconel 625 substrate. When moving away from the substrate, the grains elongate, texture appears and the length of the grains increases signifi cantly. Our results are in good agreement with the data of these authors.
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