High temperature oxidation of AlB12-Al electric spark coatings on Steel 45

The article deals with the study of the resistance of electrospark coatings of the composition AlB12-50 wt.% Al to high-temperature oxidation. The coatings are applied to Steel 45 using an ALIER-52 installation (mode 4). High-temperature oxidation of coated Steel 45 samples was carried out in a Nabertherm furnace, in the temperature range of 500, 600, 700, 800, 900 and 1000oC, in air with exposure at each temperature for 1 hour. The structure of the coatings was studied using a JEOL JSM-6490 LV SEM equipped with an INKA Energy 350XT energy-dispersive spectrometer. The microhardness of the coatings was measured using a PMT-3 microhardness tester (P = 0.5 N). After oxidation, phases of Fe-Al intermetallic compounds, aluminum nitrides of different stoichiometric compositions, AlB12 and Al2O3 were found in the coating. The weight gain of the coated sample was found to be much less than that without the coating; this is explained by the formation of compounds that are resistant to high-temperature oxidation. The developed coatings can be used to protect parts operating under high-temperature oxidation conditions.