Abstract
UDC 544.558+66.088
DOI https://doi.org/10.52577/eom.2026.62.2.01
A possibility of using hybrid plasma electrolytic treatment on the surface of commercially pure titanium to improve its functionality is demonstrated, consisting of sequential chemical-thermal treatment, polishing, and micro-arc oxidation. Chemical-thermal treatment was performed in an electrolyte based on ammonium chloride and glycerol at a temperature of 900 °C. Subsequent polishing for 1 min in an ammonium fluoride solution at a temperature of 90 °C ensured the removal of the oxide layer formed on the surface during diffusion saturation and did not have a significant effect on the modified substrate, in which the phases TiC, Ti8C5, Ti2N, and Ti3O were identified. Microarc oxidation of commercially pure titanium in the initial state in the aluminate system for 30 min in the initial state allowed to synthesize an oxide ceramic-like coating on the surface, represented by the phases γ-Al2O3, α-Al2O3, TiO, TiO2, and α-Ti3O5 and characterized by a maximum microhardness of 1360 ± 60 HV. After hybrid plasma electrolytic treatment (microarc oxidation was carried out under similar conditions), the following phases were detected in the coating composition: γ-Al2O3, α-Al2O3, TiC, TiN, Ti2N, C4, TiO, TiO2, β-Ti3O5, α-Ti3O5, and Fe3O4. The presence of strengthening phases of titanium carbide and nitride increased the maximum microhardness of the coating to 1600 ± 15 HV. At the same time, a carbonitride layer was preserved in the surface layer of the base material, with a maximum microhardness of 900 ± 20 HV. Corrosion tests under potentiodynamic measurements in a 3.5% sodium chloride solution showed the synergistic effect of the hybrid modifying treatment to shift the corrosion potential from –0.283 to –0.035 V and an increase of the polarization resistance by 2.6 times. Moreover, the corrosion current density on the material surface without treatment and after hybrid plasma electrolytic treatment was the same, within the error limits, and amounted to 0.018 μA/cm2.
Keywords: plasma electrolytic processing, chemical-thermal treatment, polishing, microarc oxidation, microhardness, corrosion resistance, titanium.