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
RkJQdWJsaXNoZXIy MTk0ODM1