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A method was proposed for increasing the oxidation resistance of promising wrought Ti2AlNb ortho-alloys by depositing γ-TiAl-based coatings. Using original vacuum pulse-arc melting of 100 μm thick granule layers, coatings with different Al/Ti ratios and a thickness of 50–60 µm were obtained on the surface of the Ti50Al25Nb25 alloy. Granules Ti50Al44Nb4.9Mo1B0.1 (at.%), 20–60 μm in size, were employed. To vary Al content, initial granules and their mixture with Al powder were used. Excellent adhesion of the coatings is ensured by the similar chemical composition and structure of the substrate and coatings, as well as micro-metallurgical reactions between granules and the substrate that occur during treatment. The resulting coatings had a submicron gradient structure consisting of TiAl and Ti3Al intermetallic compounds. During oxidation at 850 °C for 10 h, an oxide layer consisting of a mixture of α-Al2O3, TiO2, and AlNbO4 was formed on the coating surfaces. With an increase in the annealing duration to 100 h, a dense α-Al2O3 oxide layer, approximately 0.5 µm thick, was formed over the primary oxide mixture, the quality of which was higher in coatings enriched with aluminum. [ABSTRACT FROM AUTHOR]

Marine and coastal infrastructures usually suffer from synergetic effect of corrosion and wear known as tribocorrosion, which imposes strict requirements on the structural materials used. To overcome this problem, novel composite wear- and corrosion-resistant xTiC-Fe-CrTiNiAl coatings with different TiC content were successfully developed. The coatings were obtained by the original technology of electrospark deposition in a vacuum using xTiC-Cr2Ti-NiAl (x = 0, 25, 50, 75%) electrodes. The structure and morphology of the coatings were studied in detail by XRD, SEM, and TEM. The effect of TiC content on the tribocorrosion behavior of the coatings was estimated using tribological and electrochemical (under stationary and wear conditions) experiments, as well as impact testing, in artificial seawater. The TiC-free Fe-Cr2Ti-NiAl coating revealed a defective inhomogeneous structure with transverse and longitudinal cracks. Introduction of TiC allowed us to obtain coatings with a dense structure without visible defects and with uniformly distributed carbide grains. The TiC-containing coatings were characterized by a hardness and elastic modulus of up to 10.3 and 158 GPa, respectively. Formation of a composite structure with a heavily alloyed corrosion-resistant matrix based on α-(Fe,Cr) solid solution and uniformly distributed TiC grains led to a significant increase in resistance to stationary corrosion and tribocorrosion in artificial seawater. The best 75TiC-Fe-CrTiNiAl coating demonstrated the lowest corrosion current density values both under stationary (0.03 μA/cm2) and friction conditions (0.8 μA/cm2), and was characterized by both a 2-2.5 times lower wear rate (4 × 10−6 mm3/Nm) compared to AISI 420S steel and 25TiC-Fe-CrTiNiAl and a high fracture toughness. [ABSTRACT FROM AUTHOR]

Zn-containing TiO 2 -based coatings with Na, Ca, Si, and K additives were obtained by plasma electrolytic oxidation (PEO) of Ti in order to achieve an effective and broad bactericidal protection without compromising biocompatibility. A protocol has been developed for cleaning the coating surface from electrolyte residues, ensuring the preservation of the microstructure and composition of the surface layer. Using high-resolution transmission electron microscopy, three characteristic microstructural zones in the PEO-Zn coating are well documented: zone 1 with a TiO 2 -based nanocrystalline structure, zone 2 with an amorphous structure, and zone 3 around pores with an amorphous-nanocrystalline structure. The excellent cytocompatibility of PEO-Zn samples was confirmed by three different methods: monitoring the proliferation of MC3T3-E1 cells, assessing the viability of sheep osteoblast cells using calcein-AM staining and fluorescence microscopy, and incubation with spheroids based on primary osteoblast cells and mouse embryonic fibroblast NIH3T3 cells. The PEO-Zn coatings absorb >60% of the incident light over the UV and Vis-NIR spectral ranges. After 24 h, the PEO-Zn coatings completely inactivate four types of strains: Gram-positive Staphylococcus aureus CSA154 and ATCC29213 and Gram-negative Escherichia coli K261 and U20, and also prevent E. coli U20 and K261 biofilm formation. The superior antibacterial activity is associated with the synergistic effect of Zn 2+ ions in safe concentration and reactive oxygen species (ROS) generated in response to either UV irradiation or soft short-term X-ray irradiation. The X-ray irradiation-induced ROS formation by a PEO coating is reported for the first time. The enhanced bactericidal activity after X-ray irradiation compared to UV illumination is attributed to the more intense ROS generation in the first few hours. The results obtained significantly expand the possibilities of using PEO coatings on the surfaces of titanium implants.