OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 24 No. 4 2022 a b Fig. 8. Microstructure and chemical composition of non-deformable particles of type 1: a – coating of composition 1; b – coating of composition 2 tion 1, dendrites have a fine structure with closely spaced secondary branches, and this testifies to high solidification rates (Fig. 8, a). The dendritic branches are enriched with silicon and carbon, and the interdendritic spaces are enriched with boron (Table 4 and Fig. 8, a). Most likely, the dendritic branches consist of chromium ferrite with dispersed particles of Cr23C6 carbides, CrSi, Cr3Si, and (Cr,Fe,Mn)5Si3 silicides, and the interdendritic spaces consist of chromium ferrite with disperse FeB and Fe2B boride particles. In the coating of composition 2, the particles that have solidified before collision with the substrate are characterized by a coarser dendritic structure (Fig. 8, b). Ta b l e 4 The results of local chemical analysis of the areas, marked in Fig. 8, at.% Coating composition 1 (Fig. 8, a) Area No. B C Si V Cr Mn Fe 1 3.39 0.23 2.40 1.28 5.70 3.70 83.30 2 7.52 0.00 1.10 1.47 6.12 3.53 80.26 Coating composition 2 (Fig. 8, b) Area No. B C Si V Mn Fe Ni 1 8.55 2.11 3.91 0.30 4.58 73.65 6.90 2 17.16 2.42 3.59 0.24 3.63 66.17 6.80 In austenite, in the dendritic branches, a larger number of disperse nickel, manganese and iron silicide particles are formed, with Fe2B iron borides concentrated in the interdendritic spaces (Fig. 8, b and Table 4). The presence of silicon and chromium in the inner layer will ensure the formation of a Cr2O3 + SiO2 protective film during oxidation, which is known to be a reliable protection from high-temperature oxidation. Conclusion Compositions of layers in multilayer high-temperature coatings protecting the surface of piercing mandrels are proposed. The first layer, 150 to 200 μm thick, is produced by plasma spraying of self-fluxing Fe-Cr-Mn-V-SiC-B and Fe-Ni-Mn-Si-C-В powders and characterized by high hardness (up to 1400 HV 0.05) due to the
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