OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 24 No. 2 2022 Fig. 1. Distribution of chromium diboride powder particles by diameter: 1 – integral; 2 – differential Ta b l e 2 Chemical composition of AISI 304 steel Element Fe Cr Ni Mn Cu P C S Concentration, wt. % 66.3‒74 18 8 ≤ 2 ≤ 1 ≤ 0.045 ≤ 0.03 ≤ 0.03 was 600 s. To ensure reproducibility of the results the cathode weight gain was studied for three samples from each series. The structure of the formed coatings was studied using a Sigma 300 VP scanning electron microscope (SEM) equipped with an INCA Energy dispersive spectroscopy (EDS) analyzer and a DRON-7 X-ray diffractometer in Cu-Kα radiation. The roughness of the coatings was measured on a TR 200 profi lometer. The contact angle of wetting with water was measured at room temperature according to the sessile drop method [20]. Polarization tests were carried out in a three-electrode cell in a 3.5% NaCl solution using a P-2X galvanostat (Electro Chemical Instruments, Russia) with a scanning rate of 10 mV/s. A standard Ag/AgCl electrode served as a reference electrode, and a paired ETP-02 platinum electrode was used as a counter electrode. Before recording the samples were held for 30 minutes to stabilize the current of open circuit potential. Cyclic oxidation resistance tests were carried out in a muffl e furnace at a temperature of 900 °C in air. Cube samples with an edge of 6 mm were kept at a given temperature for ~6 hours, then removed and cooled in a desiccator to room temperature. The total testing time was 100 hours. During the oxidation resistance test, the samples were placed in ceramic crucibles to take into account the mass of exfoliated oxides. The change in the weight of the samples was measured using a laboratory balance with a sensitivity of 10–4 g. The weight gain Δm for steel AISI 304 and coatings after the oxidation resistance test was calculated by formula: , w m S where Δw – weight gain and S – sample area.
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