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Wear resistance and corrosion behavior of Cu-Ti coatings in SBF solution

Vol. 26 No. 3 2024 3 EDITORIAL COUNCIL EDITORIAL BOARD EDITOR-IN-CHIEF: Anatoliy A. Bataev, D.Sc. (Engineering), Professor, Rector, Novosibirsk State Technical University, Novosibirsk, Russian Federation DEPUTIES EDITOR-IN-CHIEF: Vladimir V. Ivancivsky, D.Sc. (Engineering), Associate Professor, Department of Industrial Machinery Design, Novosibirsk State Technical University, Novosibirsk, Russian Federation Vadim Y. Skeeba, Ph.D. (Engineering), Associate Professor, Department of Industrial Machinery Design, Novosibirsk State Technical University, Novosibirsk, Russian Federation Editor of the English translation: Elena A. Lozhkina, Ph.D. (Engineering), Department of Material Science in Mechanical Engineering, Novosibirsk State Technical University, Novosibirsk, Russian Federation The journal is issued since 1999 Publication frequency – 4 numbers a year Data on the journal are published in «Ulrich's Periodical Directory» Journal “Obrabotka Metallov” (“Metal Working and Material Science”) has been Indexed in Clarivate Analytics Services. Novosibirsk State Technical University, Prospekt K. Marksa, 20, Novosibirsk, 630073, Russia Tel.: +7 (383) 346-17-75 http://journals.nstu.ru/obrabotka_metallov E-mail: metal_working@mail.ru; metal_working@corp.nstu.ru Journal “Obrabotka Metallov – Metal Working and Material Science” is indexed in the world's largest abstracting bibliographic and scientometric databases Web of Science and Scopus. Journal “Obrabotka Metallov” (“Metal Working & Material Science”) has entered into an electronic licensing relationship with EBSCO Publishing, the world's leading aggregator of full text journals, magazines and eBooks. The full text of JOURNAL can be found in the EBSCOhost™ databases.

OBRABOTKAMETALLOV Vol. 26 No. 3 2024 4 EDITORIAL COUNCIL EDITORIAL COUNCIL CHAIRMAN: Nikolai V. Pustovoy, D.Sc. (Engineering), Professor, President, Novosibirsk State Technical University, Novosibirsk, Russian Federation MEMBERS: The Federative Republic of Brazil: Alberto Moreira Jorge Junior, Dr.-Ing., Full Professor; Federal University of São Carlos, São Carlos The Federal Republic of Germany: Moniko Greif, Dr.-Ing., Professor, Hochschule RheinMain University of Applied Sciences, Russelsheim Florian Nürnberger, Dr.-Ing., Chief Engineer and Head of the Department “Technology of Materials”, Leibniz Universität Hannover, Garbsen; Thomas Hassel, Dr.-Ing., Head of Underwater Technology Center Hanover, Leibniz Universität Hannover, Garbsen The Spain: Andrey L. Chuvilin, Ph.D. (Physics and Mathematics), Ikerbasque Research Professor, Head of Electron Microscopy Laboratory “CIC nanoGUNE”, San Sebastian The Republic of Belarus: Fyodor I. Panteleenko, D.Sc. (Engineering), Professor, First Vice-Rector, Corresponding Member of National Academy of Sciences of Belarus, Belarusian National Technical University, Minsk The Ukraine: Sergiy V. Kovalevskyy, D.Sc. (Engineering), Professor, Vice Rector for Research and Academic Aff airs, Donbass State Engineering Academy, Kramatorsk The Russian Federation: Vladimir G. Atapin, D.Sc. (Engineering), Professor, Novosibirsk State Technical University, Novosibirsk; Victor P. Balkov, Deputy general director, Research and Development Tooling Institute “VNIIINSTRUMENT”, Moscow; Vladimir A. Bataev, D.Sc. (Engineering), Professor, Novosibirsk State Technical University, Novosibirsk; Vladimir G. Burov, D.Sc. (Engineering), Professor, Novosibirsk State Technical University, Novosibirsk; Aleksandr N. Korotkov, D.Sc. (Engineering), Professor, Kuzbass State Technical University, Kemerovo; Dmitry V. Lobanov, D.Sc. (Engineering), Associate Professor, I.N. Ulianov Chuvash State University, Cheboksary; Aleksey V. Makarov, D.Sc. (Engineering), Corresponding Member of RAS, Head of division, Head of laboratory (Laboratory of Mechanical Properties) M.N. Miheev Institute of Metal Physics, Russian Academy of Sciences (Ural Branch), Yekaterinburg; Aleksandr G. Ovcharenko, D.Sc. (Engineering), Professor, Biysk Technological Institute, Biysk; Yuriy N. Saraev, D.Sc. (Engineering), Professor, V.P. Larionov Institute of the Physical-Technical Problems of the North of the Siberian Branch of the RAS, Yakutsk; Alexander S. Yanyushkin, D.Sc. (Engineering), Professor, I.N. Ulianov Chuvash State University, Cheboksary

Vol. 26 No. 3 2024 5 CONTENTS OBRABOTKAMETALLOV TECHNOLOGY Sukhov A.V., Sundukov S.K., Fatyukhin D.S. Assembly of threaded and adhesive-threaded joints with the application of ultrasonic vibrations...................................................................................................................................... 6 Baraboshkin K.A., Adigamov R.R., Yusupov V.S., Kozhevnikova I.A., Karlina A.I. Thermomechanical rolling in well casing production (research review)......................................................................................................................... 24 Dwivedi R., Somatkar A., Chinchanikar S. Modeling and optimization of roller burnishing of Al6061-T6 process for minimum surface roughness, better microhardness and roundness................................................................................ 52 Ilinykh A.S., Pikalov A.S., Miloradovich V.K., Galay M.S. Experimental studies of rail grinding modes using a new high-speed electric drive...................................................................................................................................................... 66 Karlina Yu.I., Konyukhov V.Yu., Oparina T.A. Assessment of the possibility of resistance butt welding of pipes made of heat-resistant steel 0.15C-5Cr-Mo................................................................................................................................... 79 Gimadeev M.R., Stelmakov V.A., Shelenok E.A. Product life cycle: machining processes monitoring and vibroacoustic signals fi lterings.................................................................................................................................................................... 94 EQUIPMENT. INSTRUMENTS Zakovorotny V.L., Gvindjiliya V.E., Kislov K.V. Information properties of frequency characteristics of dynamic cutting systems in the diagnosis of tool wear....................................................................................................................... 114 Ablyaz T.R., Blokhin V.B., Shlykov E.S., Muratov K.R., Osinnikov I.V. Features of the use of tool electrodes manufactured by additive technologies in electrical discharge machining of products....................................................... 135 Sidorov E.A., GrinenkoA.V., ChumaevskyA.V., Panfi lovA.O., Knyazhev E.O., NikolaevaA.V., CheremnovA.M., Rubtsov V.E., Utyaganova V.R., Osipovich K.S., Kolubaev E.A. Patterns of reverse-polarity plasma torches wear during cutting of thick rolled sheets..................................................................................................................................... 149 MATERIAL SCIENCE Semin V.O., Panfi lov A.O., Utyaganova V.R., Vorontsov A.V., Zykova A.P. Corrosion properties of CuAl9Mn2/ER 321 composites formed by dual-wire-feed electron beam additive manufacturing................................ 163 Dewangan R., Sharma B.P., Sharma S.S. Investigation of hardness behavior in aluminum matrix composites reinforced with coconut shell ash and red mud using Taguchi analysis............................................................................ 179 Saprykina N.А., Saprykin A.А., Sharkeev Y.P., Ibragimov E.А. The eff ect of technological parameters on the microstructure and properties of the AlSiMg alloy obtained by selective laser melting......................................................... 192 Burdilov A.A., Dovzhenko G.D., Bataev I.A., Bataev A.A. Methods of synchrotron radiation monochromatization (research review).................................................................................................................................................................. 208 Burkov A.A., Dvornik M.A., Kulik M.A., Bytsura A.Yu. Wear resistance and corrosion behavior of Cu-Ti coatings in SBF solution..................................................................................................................................................................... 234 Pugacheva N.B., Bykova T.M., Sirosh V.A., MakarovA.V. Structural features and tribological properties of multilayer high-temperature plasma coatings........................................................................................................................................ 250 Sharma B.P., Dewangan R., Sharma S.S. Characterizing the mechanical behavior of eco-friendly hybrid polymer composites with jute and Sida cordifolia fi bers.................................................................................................................... 267 Kornienko E.E., Gulyaev I.P., Smirnov A.I., Plotnikova N.V., Kuzmin V.I., Golovakhin V., Tambovtsev A.S., Tyryshkin P.A., Sergachev D.V. Fine structure features of Ni-Al coatings obtained by high velocity atmospheric plasma spraying.................................................................................................................................................................... 286 EDITORIALMATERIALS 298 FOUNDERS MATERIALS 307 CONTENTS

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 Wear resistance and corrosion behavior of Cu-Ti coatings in SBF solution Alexander Burkov а, Maxim Dvornik b, Maria Kulik c, *, Alexandra Bytsura d Khabarovsk Federal Research Center FEB RAS, 153 Tihookeanskaya st., Khabarovsk, 680042, Russian Federation a https://orcid.org/0000-0002-5636-4669, burkovalex@mail.ru; b https://orcid.org/0000-0002-1216-4438, maxxxx80@mail.ru; c https://orcid.org/0000-0002-4857-1887, marijka80@mail.ru; d https://orcid.org/0009-0005-4750-7970, alex_btsr@mail.ru Obrabotka metallov - Metal Working and Material Science Journal homepage: http://journals.nstu.ru/obrabotka_metallov Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science. 2024 vol. 26 no. 3 pp. 234–249 ISSN: 1994-6309 (print) / 2541-819X (online) DOI: 10.17212/1994-6309-2024-26.3-234-249 ART I CLE I NFO Article history: Received: 20 May 2024 Revised: 22 June 2024 Accepted: 08 July 2024 Available online: 15 September 2024 Keywords: Cu-Ti coating Electrospark deposition SBF solution Coefficient of friction Corrosion Wear Funding The work was supported by the Russian Science Foundation grant No. 23-23-00032. ABSTRACT Introduction. Currently, titanium and its alloys have become the most popular metal implantable biomaterials. However, the main disadvantage of titanium alloys is low wear resistance due to high viscosity. It is known that copper-titanium coatings effectively improve the antibacterial properties of titanium alloy and at the same time increase its wear resistance. Purpose of the work is to study the effects of a solution simulating body fluid on corrosion properties, friction coefficient and the wear of copper-titanium coatings obtained by electrospark deposition method of the Ti-6Al-4V alloy. Method. A non-localized electrode consisting of copper and titanium granules in various ratios was used to form copper-titanium coatings on a titanium alloy by electrospark deposition. The structure of the coatings was examined using a DRON-7 X-ray diffractometer in Cu-Kα radiation and an X-max 80 energy dispersive spectrometer. The antibacterial activity of the deposited Cu-Ti coatings was studied on a non-pathogenic gramnegative culture of Escherichia coli. Polarization tests in SBF solution were carried out using a P-40X potentiostat with an impedance measurement module. The metal content in the SBF solution after immersion of the samples was measured using an ICP-MS 2000 mass spectrometer. The tribological characteristics of the coatings according to the ASTM G99-17 standard using the “ball-on-disk” scheme with sliding friction in the SBF solution at loads of 10 and 25 N were examined. Results and discussions. It is shown that the bactericidal activity of Cu-Ti coated samples to a non-pathogenic culture of Escherichia coli increased monotonously with an increase in copper content. With copper concentration increasing, the corrosion current density of the coatings increased from 3.455 to 17.570 μA/cm2. It is shown that the SBF solution accelerates the wear of a titanium alloy many times over due to its interaction with the electrolyte via the oxidative wear mechanism. The use of Cu-Ti coatings allows reducing the friction coefficient and greatly decreasing the wear of Ti-6Al-4V alloy in the presence of an electrolyte. For citation: Burkov A.A., Dvornik M.A., Kulik M.A., Bytsura A.Yu. Wear resistance and corrosion behavior of Cu-Ti coatings in SBF solution. Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science, 2024, vol. 26, no. 3, pp. 234– 249. DOI: 10.17212/1994-6309-2024-26.3-234-249. (In Russian). ______ * Corresponding author Kulik Maria A., Junior Researcher Khabarovsk Federal Research Center FEB RAS, 153 Tihookeanskaya st., 680042, Khabarovsk, Russian Federation Tel.: +7 4212 22-69-56, e-mail: marijka@mail.ru Introduction Titanium and titanium alloys are used in many sectors of the national economy due to its outstanding mechanical properties (high strength, low density) and corrosion resistance [1]. Currently, titanium and its alloys have become more popular metal implantable biomaterials, compared to stainless steels and cobalt alloys, due to its better mechanical properties, high corrosion resistance and biocompatibility [2]. Titanium alloys are primarily used for orthopedic and dental implants. The failure rate of titanium implants is known to be 5–10 % over 15 years [3]. Bioinertness is one of the main reasons for poor osseointegration of titanium alloys. Therefore, for the successful use of titanium alloys in dentures or artificial joints, some obstacles still need to be overcome.

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 The main disadvantage of titanium alloys is low wear resistance, which leads to the release of wear products into the patient body. Another disadvantage of titanium is the lack of antibacterial properties, which can lead to infection or inflammation during clinical use and even to unsuccessful implantation [4, 5]. Antibacterial coating can reduce infections and inflammations caused by surgical contamination [6]. Copper-titanium coatings are known to effectively improve the antibacterial properties of titanium alloy and at the same time increase its wear resistance [7, 8]. Cu-Ti coatings are applied by magnetron sputtering [9–12], plasma spraying [6] and electrospark deposition (ESD) [13]. ESD is a high-energy process, the main advantages of which are the metallurgical bond of the formed coating to the substrate, the ability to select the coating thickness (from several units to several tens of micrometers), low thermal effect on the base material and simple equipment that does not require vacuum [14]. ESD technology is based on many low-voltage electrical discharges passing between the electrode and the workpiece in a gas environment. During the discharge, a microbath of molten metal on the cathode surface is formed, into which the material is transferred from the anode, the so-called polar transfer. As a result of convective and diffusion mixing of the anode and cathode materials, high adhesion of the coating to the substrate is provided. Due to the short discharge lifetime ≤ 10−4 s the low thermal effect on the substrate is ensured [15, 16]. In this work, a non-localized electrode was used, which ensured automation of ESD processing. The concept of a non-localized electrode is based on the use of a set of millimetersized granules as a source of deposited material [17–19]. Previously, we deposited Cu-Ti coatings by the method of electrospark deposition (EGD) using a non-localized electrode [20, 21] and studied its wear behavior under dry sliding conditions. However, there is no information in the literature on the corrosion and tribological behavior of copper-titanium coatings in physiological solutions, despite the fact that a significant effect of electrolytes on the friction coefficient, wear mechanism of materials and corrosion properties is known. The purpose of the work is to study the effects of a solution simulating body fluid (SBF) on corrosion properties, friction coefficient and the wear rate of copper-titanium coatings obtained by electrospark deposition method of the Ti-6Al-4V alloy. Research methodology Copper-titanium coatings were prepared by the EGD method using a non-localized electrode (NE) as an anode. It consisted of a set of cylindrical granules (d = 4 ± 0.5 mm, h = 4 ± 1 mm) of titanium VT1-00 and copper M0. The composition of five NEs with different ratios of titanium and copper granules is presented in Table 1. Cylinders (h = 10 mm, d = 12 mm) made of industrial titanium alloy Ti-6Al-4V were used as a substrate (cathode). Before applying the coatings, the substrates were processed on P600 abrasive paper, then alternately washed in water and alcohol using an ultrasonic bath and dried in a drying oven at 90 °C. The sets of granules were poured into a titanium container, in the center of which the substrate was placed. The substrate and container were connected to the negative and positive leads of the pulse generator, respectively. The substrate and container with granules were rotated in opposite directions with a frequency of 60 rpm using motors. The pulse generator operating parameters were as follows: pulse duration 100 μs, repetition frequency 1 kHz, voltage 30 V, current pulse amplitude 110 A. Surface oxidation and nitriding during coating application were eliminated by feeding argon into space of the container with granules. Each set of granules was run in on a non-replaceable cathode for ~2 hours. The processing of one sample lasted 10 minutes. The method of deposition of Cu-Ti coatings is described in detail in [19–21]. Ta b l e 1 Composition of a set of granules for coating Sample designation Cu10 Cu30 Cu50 Cu70 Cu90 Cu, at. % 10 30 50 70 90 Ti, at. % 90 70 50 30 10

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 X-ray analysis of the samples was performed on a DRON-7 X-ray diffractometer at a scanning rate of 0.05°s−1 using a copper tube. The antibacterial activity of the deposited Cu-Ti coatings was studied on a non-pathogenic gram-negative culture of Escherichia coli cultivated on meat-peptone agar (MPA). Test samples were placed in sterile Petri dishes (d = 100 mm). 0.04 ml of the cultured culture with a concentration of 105 COE/ml was dropped onto the surface of each sample. The samples were incubated for 24 hours at a relative humidity of ≥ 90 %, the temperature was maintained at 36 °C. Then, bacteria were washed off the surface of the samples with a phosphate buffer solution (1.6 ml). To count the colonies of surviving bacteria, suspensions were obtained, which were then applied to a Petri dish with MPA and incubated for 24 hours at a temperature of ~ 36 °C. Corrosion and tribological tests were carried out in an SBF solution (Table 2), the composition of which is close to human blood plasma [22]. Polarization tests were carried out using a P-40X potentiostat equipped with an impedance measurement module (Electro Chemical Instruments, Russia). The reference electrode was an Ag/AgCl electrode, the auxiliary electrode was an ETP-02 platinum electrode, and the working electrode was titanium sample with coating. The sample exposure area was 1 cm2. The scanning rate in the range of −0.8–0 V was 4 mVs−1. The concentration of metals in the SBF solution after immersion of the samples was measured using a mass spectrometer with inductively coupled plasma (ICP-MS 2000). Cu-Ti coating samples with an exposed surface area of 2.88 cm2 were immersed in 50 ml of SBF solution at room temperature for 24 h. Ta b l e 2 Ion concentration in SBF solution Ions HPO4 2− Mg2+ Ca2+ HCO3− K+ Na+ Cl− Concentration, mg/l 1.00 1.50 2.50 4.20 5.00 14.00 148.80 Tribological tests were carried out according to the ASTM G99 – 17 standard using the “ball on disk” scheme with sliding friction in SBF solution; a disk made of high-speed steel M45 was used as a counterbody at a rotation speed of 3 rpm, with a sliding circle diameter of 5 cm, under loads of 10 and 25 N. A peristaltic pump supplied SBF solution to the friction zone at a rate of 1 ml∙min−1. For each sample, 5 measurements of the friction coefficient and wear rate were made. The microstructure of the surface of worn coatings was studied using a Vega 3 LMH scanning electron microscope (SEM). An X-max 80 energy dispersive spectrometer (EDS) (Oxford Instruments, UK) was used for microanalysis of the surface of samples after wear testing. Results and its discussion Under the influence of electric discharges occuring between copper and titanium granules, its surface layers melt and intensive exchange of material occurs between it. Preliminary running-in of NE leads to the formation of a secondary structure on the surface of all granules, represented by a copper-titanium layer similar to the coating on the substrate. During the EGD treatment of samples, discharges occur between the granule and the substrate and the copper-titanium composition of the secondary structure of the granule is transferred to substrate surface, and not pure copper or titanium, as in the case of traditional ESD processing of titanium alloy with a copper electrode or vice versa. In addition, unlike traditional ESD, when using NE, the formed Cu-Ti erosion particles remain in the system and can re-participate in the process of coating formation. When an electric discharge passes between the granule and the substrate, a melt microbath is formed on the cathode, into which the molten granule material is transferred and mixed with the substrate material. During the discharge, a dynamic equilibrium on the cathode is formed, in which more material enters to melt microbath than leaves it as erosion result. After the discharge is complete, the microbath material

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

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 Fig. 2. Polarization plots of Cu-Ti coatings and Ti-6Al-4V alloy in SBF solution Ta b l e 4 Copper concentration in the composition of Cu-Ti coatings and its corrosion parameters in SBF solution Parameter Samples Ti-6Al-4V Cu10 Cu30 Cu50 Cu70 Cu90 Ecorr, V −0.38 −0.23 −0.34 −0.33 −0.36 −0.61 Icorr, μA/cm2 9.00 3.46 7.05 8.75 8.45 17.57 Copper concentration, at.% – 12.5 24.3 36.8 61.4 74.1 that the Cu10–Cu70 coatings have a higher corrosion potential than the substrate, i.e. these coatings are more noble. Because of this, a galvanic couple can be formed between the coating and the substrate, where the substrate will undergo anodic corrosion. The corrosion current density determines the corrosion rate of the material. With an increase in the titanium concentration in the coatings, Icorr decreased from 17.570 to 3.455 μA/cm2. It was shown that for all coatings except Cu90, I corr was lower than that of the Ti-6Al-4V alloy. Thus, polarization tests indicate an increase in the corrosion resistance of the Ti-6Al-4V alloy when using ESD Cu-Ti coatings with a copper content of less than 70 at. %. The corrosion resistance of Cu-Ti compositions is usually associated with the passivation film of Cu2O, which is resistant to the effects of Cl − ions due to the formation of insoluble copper (I) chloride [27]. For a more detailed research of the corrosion characteristics for all samples, electrochemical impedance spectroscopy (EIS) was used, which can be classified as a non-destructive testing method due to the low voltage and low current flowing through the sample [28]. Fig. 3 shows the experimental results on EIS. As a rule, the capacitive arc on the Nyquist plot is explained by charge transfer reactions occurring at the metal/solution interface or associated with the features of the surface passive layer. It is known that with an increase in the radius of the capacitive arc, charge transfer is hindered, which has a positive effect on the corrosion resistance of the material [29]. The radius of the capacitive arc of the samples increased in the series: Cu90, Cu70, Cu50, Cu30, Cu10 (Fig. 3 a, b). That is, charge transfer became more difficult

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 monotonically with a decrease in the copper concentration in the Cu-Ti coatings. At the same time, all samples with Cu-Ti coatings had a smaller radius of the capacitive arc than the untreated substrate. As follows from the Bode impedance diagram, the spectrum of the Ti-6Al-4V alloy in the mid-frequency range (10−1–103 Hz) has a wide linear region, which indicates the formation of a single-layer passive layer in the SBF solution (Fig. 3 b). In the coatings, the linear region narrowed with increasing copper concentration, which indicates the formation of additional passive layers. It is shown that with an increase in the copper concentration in the NE, the capacitance of the barrier layer on the coating surface decreases, as indicated by a decrease in the slope of the corresponding curves in the logarithmic coordinates. It is known that, in the general case, the anticorrosive properties of the material are in direct proportion to the resistance of the barrier layer and inversely dependent on its capacitance [30]. The compactness of the formed oxide film is determined by the convexity magnitude in the mid-frequency range on the Bode phase angle graph (Fig. 3 c). For the Ti-6Al-4V alloy, the convexity value was higher than 75°. It is known that the phase angle а b c Fig. 3. Impedance plots of Cu-Ti coatings in Nyquist coordinates (a), total Bode impedance (b) and phase angle (c)

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 value for an ideal capacitor is 90°.At this phase angle value, there is an ideally dense oxide film on the surface that can effectively inhibit charge transfer processes [31]. For all samples with copper-titanium coatings, the largest phase angle values were lower than 60°. This indicates that the oxide film formed on the surface of copper-titanium coatings was looser compared to the titanium alloy. Moreover, the coatings have two convexity maxima, which indicate a more complex oxide film compared to the titanium alloy. Comparing the convexity width on the phase angle graphs, it can be concluded that it decreases monotonically with increasing copper concentration in the coatings. Thus, the stability of the oxide film formed on the samples decreased with decreasing titanium concentration. In general, the results of impedance spectroscopy are in good agreement with the polarization data of the samples (Table 4). Thus, in the SBF solution, coppertitanium coatings Cu10–Cu70 have better corrosion resistance compared to the titanium alloy, but the barrier films formed on it are more permeable than on the Ti-6Al-4V alloy. Table 5 shows the concentration of dissolved copper ions after immersion of Cu-Ti coated samples in SBF solution for 24 h. It can be found that the concentration of copper ions was in the range of 98.6 to 484.9 μg/L; the minimum concentration was characteristic of Cu50 sample, and the maximum concentration was characteristic of Cu70 sample. According to the works on copper-titanium alloy (Ti – 5 wt. % Cu), the release of copper ions into 0.9 wt. % NaCl solution after anodizing was in the range of 52 to 239 μg/L [32], and after acid etching it was in the range of 26 to 386.9 μg/L [33], despite the fact that the copper concentration in the alloy was several times less than in the case of our coatings. The safe concentration of copper in drinking water, according to the World Health Organization, is < 2 mg/L [34]. Thus, the copper concentration released into the SBF solution from the developed Cu-Ti coatings is many times lower than the permissible values and therefore it can be used as biocompatible coatings. Another significant element is aluminum, which is released from the Ti-6Al-4V alloy and accumulates in the body of patients with implants. Despite the low concentration of aluminum in the Ti-6Al-4V alloy (~ 6 wt. %), it was released from the surface of the samples in quantities comparable to copper. Ta b l e 5 Content of metals released from the samples into the SBF solution Samples Concentration of metals, µg/dm3 Al Ti V Cu Cu10 188.45 1.67 6.15 193.98 Cu30 57.98 3.71 4.39 243.50 Cu50 54.14 1.17 6.82 98.55 Cu70 198.02 0.90 3.88 484.92 Cu90 98.37 5.17 4.69 145.15 The antibacterial activity (AA) of the samples with copper-titanium coatings was calculated using the method [35] in accordance with expression (1): ( ) 100 A B AA A − × = , (1) where: A is the number of bacterial colonies in the Petri dish for the reference metal; B is the number of bacterial colonies in the dish for the bactericidal metal. According to the calculations, the antibacterial activity of Cu-Ti coatings to the culture of non-pathogenic Escherichia coli monotonously increased from 25.5 ± 4.2 to 62.8 ± 5.4 % (Fig. 4). In real conditions of use, a longer contact (> 24 h) of the environment with the surface of copper-titanium coatings will lead to its complete disinfection. The result of the experiment showed that all deposited Cu-Ti coatings exhibited bactericidal activity. The highest concentration of copper in the Cu90 sample resulted in the

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 highest bactericidal activity. The Cu50 sample is the most optimal in terms of low concentration of released copper ions and sufficient antibacterial activity. The results of tribological tests of copper-titanium coatings in comparison with Ti-6Al-4V alloy in SBF solution at normal loads of 10 and 25 N are shown in Figure 5. It was found that with an increase in the applied load from 10 to 25 N, the average values of the friction coefficient (COF) of the titanium alloy Ti6Al-4V decreased from 0.45 to 0.36 (Fig. 5 a). Similarly, the friction force during the wear of Cu-Ti coatings decreased with an increase in the specific load. Thus, the average COF values of Cu-Ti coatings at load of 10 N were in the range from 0.39 to 0.55, while at 25 N it was in the range from 0.28 to 0.40 (Table 6). This leads to the conclusion that part of the applied load is compensated by the pressure of the oncoming liquid flow. The highest values of COF at both loads were observed for the Cu70 sample, while the lowest values of COF were for Cu50 sample. The use of the latter allows reducing the friction force of the Ti-6Al-4V alloy by 14–21 %. Previously, at a load of 25 N, we found that COF of copper-titanium coatings without SBF was much higher and was in the range from 0.73 to 0.96. Moreover, COF of the coatings under dry friction was significantly higher than that of the Ti-6Al-4V alloy [19]. Fig. 5 b shows the diagrams of wear rate values of titanium alloy samples with copper-titanium coatings in SBF solution. The wear rate of samples with Cu-Ti coatings was within the range from 0.71×10−5 to 2.70×10−5 mm3/Nm under a load of 10 N and from 0.70×10−5 to 1.79×10−5 mm3/Nm under a load of 25 N. Under both loads, the Cu50 coating had the highest wear resistance, which is explained by its lowest friction coefficient. Under a load of 10 N, the wear rate of the Ti-6Al-4V alloy in SBF solution was 3.58×10−4 mm3/ Nm, and under 25 N it was 3.99×10−4 mm3/Nm. Thus, the wear resistance of the alloy was 13 to 57 times lower than that of the coatings. It is characteristic that the wear of the Ti-6Al-4V alloy under dry sliding conditions at 25 N was 0.75×10−4 mm3/Nm [20], which is 5.3 times lower than that in the SBF solution, which is consistent with the results of work [36]. Thus, the SBF solution repeatedly accelerates the wear of the titanium alloy due to its interaction with the electrolyte according to the oxidative wear mechanism [36]. Oxidative products, and primarily rutile, can act as abrasive particles, accelerating the wear of the titanium alloy. Comparison of the wear intensity of Cu-Ti coatings under a load of 25 N showed that most of the samples also had increased wear in the SBF solution compared to the dry sliding mode, with the exception of the Cu50 and Cu70 coatings, which had very close wear values in SBF and dry environments. Thus, the use of Cu-Ti coatings for products made of titanium alloy Ti-6Al-4V allows reducing its wear many times over and lowering the coefficient of friction when used in SBF solution. Fig. 4. Antibacterial activity (AA)

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 Figure 6 shows SEM images of wear track of Cu-Ti coatings after tribological testing in SBF solution. It shows that on the worn surface of the Ti-6Al-4V alloy, as a result of plowing up, were formed tracks that look like wide grooves and scratches, which indicate abrasive wear. At the same time, there are signs of adhesive wear, such as areas with delamination and strong deformation. The images clearly show that the worn surface of the Ti-6Al-4V alloy is rougher, and the surface of the Cu-Ti coatings is smoother. The smoothest surface was observed in the case of the Cu50 sample (Fig. 6 c), and the most relief one was observed in the case of the least wear-resistant Cu90 coating (Fig. 6 e). In contrast to dry friction in the SBF solution, no oxide wear flakes were observed on the surface of the coatings. This indicates that, during friction in liquid, the oxidative products are actively removed from the friction zone. Therefore the protective tribooxide layer is not preserved, which is expressed in increased wear rate values, compared to dry friction. Wear products were preserved only in surface depressions such as pores and cracks. According to the results of EDS analysis, the wear products contain iron, tungsten and chromium, which were deposited on the coating surface as a result of intensive wear of the counterbody made of high-speed steel M45 (Table 7). A significant amount of oxygen indicates oxide accumulations, which is a consequence of oxidative wear [37]. The presence of Cl, S and P elements is explained by the participation of the SBF solution in the formation of wear products. The oxygen concentration decreased in the wear products with an increase in the copper content in the coatings, which is explained by a higher standard electrode potential of copper compared to titanium. Thus, the main wear mechanism of copper-titanium coatings was a combination of oxidation and abrasive wear, while for titanium alloy the adhesive wear mechanism was more typical. a b Fig. 5. Friction coefficient (a) and wear rate (b) of Cu-Ti coatings and Ti-6Al-4V alloy in SBF solution under various loads Ta b l e 6 Averaged COF values of samples with coatings in SBF solution Load, N Samples Ti-6Al-4V Cu10 Cu30 Cu50 Cu70 Cu90 10 0.449 0.430 0.480 0.387 0.548 0.425 25 0.361 0.346 0.358 0.284 0.399 0.320

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 Fig. 6. SEM photos of the worn surface of Cu-Ti coatings after wear testing in SBF solution: a – Cu10; b – Cu30; c – Cu50; d – Cu70; e – Cu90; f – Ti-6Al-4V а b c d e f Ta b l e 7 Composition of wear products on the surfaces of coatings and Ti-6Al-4V alloy Element Concentration, at.% Cu10 Cu30 Cu50 Cu70 Cu90 Ti-6Al-4V C 25.38 5.67 22.72 13.08 16.71 7.16 O 53.95 63.5 50.1 43.3 42.68 20.09 Al 0.47 0.19 0.33 4.37 P 0.07 0.07 0.08 S 0.1 0.19 0.12 0.14 0.11 Cl 0.22 0.59 0.41 0.18 0.35 0.32 Ti 1.59 12.28 11.99 37.90 26.03 63.87 V 0.53 0.87 3.2 Cr 0.22 0.7 0.4 0.16 0.37 Fe 18.02 12.61 8.43 0.39 9.86 0.88 Cu 0.38 3.02 5.62 3.93 3.24 W 0.07 0.44 0.14 0.22 Conclusions Copper-titanium coatings on titanium alloy blanks were prepared by the method of electric spark deposition using a non-localized electrode consisting of copper and titanium granules in different ratios. The copper concentration in the coatings monotonically increased with its content in the electrode. It is shown

OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 that with an increase in the copper concentration, the corrosion current density of the coatings increased from 3.455 to 17.570 μA/cm2. It is found that in the SBF solution, copper-titanium coatings Cu10–Cu70 have a higher corrosion potential and better corrosion resistance compared to the Ti-6Al-4V alloy, but the passivation films formed on it are more permeable than on the Ti-6Al-4V alloy. All compositions of the CuTi coatings showed bactericidal activity towards the non-pathogenic culture of Escherichia coli. It is shown that the electrospark deposition of Cu-Ti coatings reduces the surface wear of the titanium alloy Ti-6Al-4V in SBF solution many times over. Despite the lubricating effect, the wear in the SBF solution is more severe for the Ti-6Al-4V alloy and copper-titanium coatings compared to wear under dry friction conditions due to the intensive removal of the antifriction tribooxide layer. The combined action of abrasive wear and oxidation accelerated by the electrolyte was the main wear mechanism of the copper-titanium coatings, while for the Ti-6Al-4Valloy, adhesive wear was more characteristic. References 1. Geetha M., Singh A., Asokamani R., Gogia A. Ti based biomaterials, the ultimate choice for orthopaedic implants – a review. Progress in Materials Science, 2009, vol. 54, pp. 397–425. DOI: 10.1016/j.pmatsci.2008.06.004. 2. Gepreel M.A.H., Niinomi M. Biocompatibility of Ti-alloys for long-term implantation. Journal of the Mechanical Behavior of Biomedical Materials, 2013, vol. 20, pp. 407–415. DOI: 10.1016/j.jmbbm.2012.11.014. 3. Sánchez-López J.C., Rodríguez-Albelo M., Sánchez-Pérez M., Godinho V., López-Santos C., Torres Y. Ti6Al4V coatings on titanium samples by sputtering techniques: Microstructural and mechanical characterization. Journal of Alloys and Compounds, 2023, vol. 952, p. 170018. DOI: 10.1016/j.jallcom.2023.170018. 4. Banerjee R., Das S., Mukhopadhyay K., Nag S., ChakraborttyA., Chaudhuri K. Involvement of in vivo induced cheY-4 gene of Vibrio cholerae in motility, early adherence to intestinal epithelial cells and regulation of virulence factors. FEBS Letters, 2002, vol. 532, pp. 221–226. DOI: 10.1016/S0014-5793(02)03678-5. 5. Olmedo D., Fernández M.M., Guglielmotti M.B., Cabrini R.L. Macrophages related to dental implant failure. Implant Dentistry, 2003, vol. 12, pp. 75–80. DOI: 10.1097/01.ID.0000041425.36813.A9. 6. Zhao L., Chu P.K., Zhang Y., Wu Z. Antibacterial coatings on titanium implants. Journal of Biomedical Materials Research. Part B: Applied Biomaterials, 2009, vol. 91, pp. 470–480. DOI: 10.1002/jbm.b.31463. 7. Tian J., Xu K., Hu J., Zhang S., Cao G., Shao G. Durable self-polishing antifouling Cu-Ti coating by a micronscale Cu/Ti laminated microstructure design. Journal of Materials Science & Technology, 2021, vol. 79, pp. 62–74. DOI: 10.1016/j.jmst.2020.11.038. 8. Zhang J.Q., Cao S., Liu Y., Bao M.M., Ren J., Li S.Y., Wang J.J. Tribocorrosion behavior of antibacterial Ti– Cu sintered alloys in simulated biological environments. Rare Metals, 2022, vol. 41, pp. 1921–1932. DOI: 10.1007/ s12598-021-01943-6. 9. Adamiak B., Wiatrowski A., Domaradzki J., Kaczmarek D., Wojcieszak D., Mazur M. Preparation of multicomponent thin films by magnetron co-sputtering method: The Cu-Ti case study. Vacuum, 2019, vol. 161, pp. 419–428. DOI: 10.1016/j.vacuum.2019.01.012. 10. Jin X., Gao L., Liu E., Yu F., Shu X., Wang H. Microstructure, corrosion and tribological and antibacterial properties of Ti–Cu coated stainless steel. Journal of the Mechanical Behavior of Biomedical Materials, 2015, vol. 50, pp. 23–32. DOI: 10.1016/j.jmbbm.2015.06.004. 11. Wojcieszak D., Kaczmarek D.,AntosiakA., Mazur M., Rybak Z., RusakA., Szponar B. Influence of Cu–Ti thin film surface properties on antimicrobial activity and viability of living cells. Materials Science and Engineering: C, 2015, vol. 56, pp. 48–56. DOI: 10.1016/j.msec.2015.06.013. 12. Zhu Y., Yan M., Zhang Q., Wang Q., Zhuo H. Effects of the prefabricated Cu-Ti film on the microstructure and mechanical properties of the multiphase coating by thermo plasma nitriding on C17200 Cu alloy. Coatings, 2019, vol. 9, p. 694. DOI: 10.3390/coatings9110694. 13. Wang Z.Q., Wang X.R. Microstructure and flame-retardant properties of Ti-Cu coating on Tc11 prepared via electrospark deposition. Material Engineering and Mechanical Engineering: Proceedings of Material Engineering and Mechanical Engineering (MEES 2015). World Scientific, 2016, pp. 1283–1291. DOI: 10.1142/ 9789814759687_0144. 14. Radek N. Experimental investigations of the Cu-Mo and Cu-Ti electro-spark coatings modified by laser beam. Advances in Manufacturing Science and Technology, 2008, vol. 32, pp. 53–68.

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