OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 24 No. 4 2022 Ta b l e 3 Corrosion parameters of coatings calculated from the slopes of polarization curves Parameters Samples AISI304 Si2.6 Si6.0 Ecorr., V –0.68 –0.57 –0.603 Icorr, µA 27.5 13.1 15.1 Rp, kΩ 2.5 10.1 10.7 the lowest corrosion current density. The calculated polarization resistance of the deposited coatings was four times higher than that of the original AISI304 steel. Despite the high corrosion resistance of AISI304 steel, due to the high chromium content (Table 2), it can be concluded that the use of electrospark Fe-Ti-Si coatings can significantly improve its anti-corrosion properties. Figure 4, a shows the average values of microhardness measured on the surface of the coatings. The hardness of the coatings decreased from 12.86 to 10.05 GPa with the growth of powder charge in the anode mixture. Thus, the application of Fe-Ti-Si coatings can significantly increase the surface hardness of AISI304 steel (1.9 GPa). The high hardness of the coatings is primarily due to the presence of the Ti5Si3 phase, which hardness is 9.5 GPa [17, 18]. The higher hardness of the deposited coatings is explained by the structure refinement up to the amorphous state, due to the high cooling rates of the material after the completion of the discharge during ESD [19]. Figure 4, b shows the dynamics of the friction coefficient of the coatings compared to stainless steel AISI304. It follows from this that the application of Ti-Si coatings makes it possible to reduce the friction coefficient of AISI304 steel by 20 % from 0.9 to 0.73. With an increase in the powder content in the anode mixture, the average values of the friction coefficient slightly decreased from 0.73 to 0.71. With an increase in the silicon content in the anode mixture, the average values of coating wear rate increased from 1.07∙10–6 to 1.45∙10–6 mm3/Nm, which is consistent with the hardness data (Fig. 4, a). In general, the application of Fe-Ti-Si coatings makes it possible to increase the wear resistance of the AISI304 steel surface from 4.6 to 6.2 times. a b Fig. 4. Microhardness (a), coefficient of friction and wear rate at a load of 10 N (b)
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