OBRABOTKAMETALLOV technology Vol. 26 No. 2 2024 Ta b l e 5 Results of energy-dispersive spectroscopy Coverage Element, weight % O Al Ti Fe Fe2O3 30.1 – – 69.9 Al2O3 + 10% Fe2O3 45.7 49.2 – 5.1 Ti + 10 % Fe2O3 39.6 – 54.1 6.3 Ta b l e 6 Phase of composite coatings Coverage Phase Spatial group Composition, % Fe2O3 Fe3O4 74:Imma 100 Al2O3 + 10 % Fe2O3 α-Al2O3 167:R-3c 54 γ-Al2O3 227:Fd3m 39 Fe3O4 227:Fd-3m 7 Ti + 10 % Fe2O3 TiO2 136:P42/mnm 91 Fe3O4 227:Fd-3m 9 The results of energy dispersive spectroscopy (EDS), confirmed the expected elemental composition of the witness specimens. The composition corresponds to the composition of the initial powders. The results of the study of the phase composition of the coatings are summarized in Table 6. When coating from a composition of Al2O3 + 10 % Fe2O3 powders, a structure consisting of α-Al2O3, γ-Al2O3 and Fe3O4 solid solution phases is formed. The coating obtained from the composition of powders Ti + 10 % Fe2O3 consists of phases TiO2 and Fe3O4. The transition of the Ti phase into the TiO2 phase is due to the oxidation of titanium, which occurs during the formation of the coating. Figure 5 shows the results of measuring the emissivity of experimental specimens of coatings at 450 °С. The dips in the region of 4.25 μm are caused by absorption of carbon dioxide, in the region of 1.82, 3.3, 5.9 and 6.5 μm are caused by steam. Among the experimental specimens obtained, the coating Fe2O3 at 450 °C showed the highest emissivity in the infrared range ε3-7 μm = 0.7 and ε4-5 μm = 0.8. Composite coatings of Al2O3 + 10 % Fe2O3 and Ti + 10 % Fe2O3 have ε3-7 μm = 0.59 and 0.57 , respectively, and ε4-5 μm = 0.67 and 0.66 at 450 °C. Coating Fe2O3 has the main peak of IR radiation in the region of 3–4 μm, which is more promising for use in the baking industry, because the radiation of this spectral range most deeply penetrates into the dough, accelerating the cooking process. According to the results of the analysis of the results of thermal cycling of experimental specimens, it was revealed that the appearance of coatings did not change. The appearance of the coating specimens after thermal cycling is shown in Figure 6. The specimens underwent 300 cycles of thermal cycling without cracks and delaminations. The analysis of X-ray phase diagram showed that after thermocycling there were no changes in the crystal lattice, which indicates a high resistance of coatings to operational temperature changes. The results are presented in Figure 7.
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