OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 crystallizes, forming a coating. Thus, the thickness of the formed ESD coating is determined by the depth of the melt microbath on the cathode at the end of the discharge [23]. The average thickness of the deposited Cu-Ti coatings ranged from 32.3 to 49.3 μm (Table 3). The dependence of the average coating thickness on the copper concentration in the NE had the parabolic form with a maximum for the Cu70 sample. This can be explained by the proximity of this copper to titanium ratio to the eutectic point of the Cu-Ti phase diagram; the secondary structure on the surface of the NE granules for the Cu70 samples had the lowest melting temperature [24]. Fig. 1 shows sections of X-ray diffraction patterns of copper-titanium coatings. The obtained coatings contain copper, αTi, and intermetallics: Ti2Cu, CuTi, and Cu3Ti. With an increase in the proportion of copper granules in the NE, the deposited coatings were enriched with copper and copper-rich intermetallics. The CuTi phase is observed in all coatings. It was also observed in studies on magnetron sputtering [12]. It is known that the hardest phase is Ti2Cu (746.9 ± 67.7 HV), while the CuTi phase is much softer (298.2 ± 20.7 HV) [25]. The hardness of the copper-rich phase Cu3Ti occupies an intermediate position; its hardness is 544.34 HV [26]. In the composition of copper-rich samples (Cu70 and Cu90), the metallic copper phase predominated. Thus, by changing the ratio of copper and titanium granules in the NE, it is possible to vary the phase composition of the deposited coatings. Fig. 2 shows the potentiodynamic polarization curves of the Ti-6Al-4V alloy with and without Cu-Ti coatings in the SBF solution at room temperature. The Tafel slopes of the polarization curves were used to calculate the corrosion potential (Ecorr) and corrosion current density (Icorr), which are presented in Table 4. The results show that Ecorr is decreased with an increase in the copper content in the coating. It was found Ta b l e 3 Thickness and roughness of Cu-Ti coatings Parameters Samples Cu10 Cu30 Cu50 Cu70 Cu90 Average thickness, µm 32.3 ± 9.9 32.4 ± 7.4 43.7 ± 9.4 49.3 ± 8.3 45.2 ± 13.2 Roughness, Ra, µm 6.3 ± 1.4 6.8 ± 1.6 6.9 ± 0.9 7.3 ± 1.1 7.5 ± 1.1 Fig. 1. Results of X-ray analysis of Cu-Ti coatings
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