Volodymyr Posuvailo

The modern approaches to the formation of wear-resistant and bioactive coatings on titanium alloys by plasma electrolytic oxidation are summarized, the influence of electrolytes and additives on the coating properties is analyzed, and combined methods and prospects for biomedical applications are evaluated.

The Gibbs energies of the reactions between titanium nitrides and the components of the electrolyte plasma during the synthesis of oxide-ceramic coatings on nitrided titanium have been calculated. It is shown that atomic and molecular oxygen interact with titanium nitride, forming titanium oxide and nitrogen. An increase in temperature and the size of discharge channels leads to a slowdown in the growth rate of oxide-ceramic coatings due to a decrease in the oxidizer content in plasma discharges. X-ray diffraction analysis and scanning electron microscopy were used to study the structure and phase composition of oxide-ceramic coatings based on nitrided VT1-0 and VT6 alloys. It is proposed to limit the coating synthesis time on nitrided VT1-0 and VT6 titanium alloys to 20–30 min to obtain oxide-ceramic coatings with low porosity and increased microhardness.

Methods of modeling silicon carbide particles of asymmetric shape as well as the methods of image analysis of the surface layer of an aluminum alloy reinforced with silicon carbide particles have been developed. 3D modeling of the distribution of silicon carbide particles of different sizes and filling percentages in the surface layer of the aluminum alloy was carried out. The distribution of silicon carbide areas in different cross-sectional planes and with different volumetric filling of the strengthened layer was established.

The microhardness and abrasive wear resistance of cast Al-Si alloys after plasma-electrolytic oxidation (PEO) in a weakly alkaline basic electrolyte (3 g/L KOH + 2 g/L Na₂SiO₃), as well as with the addition of H₂O₂, were determined. X-ray analysis showed that the PEO layer comprises two oxide phases, namely α-Al₂O₃ and γ-Al₂O₃, as well as sillimanite -Al₂O₃ · SiO₂ and a small percentage of mullite -3 Al₂O₃ · 2SiO₂. Silicon is present in the structure of the oxide layer, and its percentage is greater than that of the alloys in their initial state. It has been shown that the characteristics of PEO layers on AK9 and AK12 silumins synthesized in an electrolyte of basic composition increase (microhardness up to 900–1000 HV and abrasive wear resistance by 14–57 times). The formation of PEO layers in the base electrolyte with the addition of 3 g/L of hydrogen peroxide intensifies the synthesis process and promotes the formation of high-temperature oxide phases (in particular, corundum). The abrasive wear resistance of both silumins with PEO layers synthesized in such an electrolyte increases by 30–70%.