Page 9 - Докторська дисертація_Ткачук

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diffusion saturation from a controlled nitrogen-containing gas environment on their

functional characteristics were established. It was shown that the wear resistance of

nitrided titanium alloy with surface Ti2N layer in a tribo-pair with ultra-high molecular

weight polyethylene in a 10% aqueous solution of chondroitin sulfate, which

simulates the synovial fluid, is 2.5 times higher, and the corrosion resistance in

solutions simulating the physiological environment is 1.5...4 times lower than that of

nitrided alloy with surface TiNx layer. The conditions for the formation of the

corresponding phase-structural state of near-surface layers on titanium alloys BT1-0

and BT6 during gas nitriding according to the functional purpose were outlined.

2. The scientific approaches to the formation of surface layers on titanium

alloys for medical applications by saturation from a controlled nitrogen-oxygen-

containing gas environment were developed. For the first time, the regularities of

oxynitriding under conditions of competing oxide and nitride formation processes

were determined, which makes it possible to control the phase-structural state and

functional properties of surface layers. The determinative influence of the oxygen in

titanium oxynitride on the corrosion resistance in the physiological environment was

established: the highest resistance is provided by the layer of composition TiN0.36O0.64.

3. For the first time, the structural features of the surface layer formed on

titanium alloys by the saturation from controlled nitrogen-oxygen-containing gas

environment were established: the presence of numerous twinning, packaging and

dislocation defects in the (110) planes of the δ-TiNx type phase is a consequence of

the penetration of oxygen into the crystal lattice with the replacement of nitrogen

atoms by oxygen ones and the formation of the TiNxO1-x phase.

4. For the first time, the biocompatibility of surface layers on titanium alloys

for medical applications modified by oxygen and nitrogen was established in vitro. It

was shown that nitrided surface based on titanium mononitride of composition close

to stoichiometric and modified titanium surface with oxygen content of 60…65 at.%

in oxynitride crystal lattice are effective for cell adhesion and proliferation.

5. For the first time, the effectiveness of an alkaline electrolyte (KOH +

hydroxyapatite) (pH=14) for the formation of a hydroxyapatite layer by plasma