Page 41 - Реферат_Ткачук

39

ABSTRACT
Tkachuk O.V. Scientific bases for increasing functional properties of surface
layers of titanium alloys for medical applications. – A manuscript.
Dissertation for the degree of Doctor of Technical Sciences in specialty 05.02.01 –
Materials Science. – Karpenko Physico-Mechanical Institute of the National Academy
of Sciences of Ukraine, Lviv, 2026.
The dissertation presents a solution of an important scientific and technical problem
– increasing the complex of biocompatibility, wear- and anti-corrosion characteristics of
titanium alloys for medical applications using surface engineering by forming the
appropriate phase-structural state of nitride and oxynitride layers by diffusion saturation
from a controlled gas environment and hydroxyapatite coatings of regulated parameters
by plasma electrolytic oxidation.
The general regularities of the formation of the phase-structural state of the
modified layers on the titanium alloys for medical applications by the diffusion
saturation from a controlled nitrogen-containing gas environment, and its effect on the
wear and corrosion resistance in physiological solutions were established. It was
determined that the wear resistance of nitrided BT6 titanium alloy in a tribo-pair with
UHMWPE in a 10% aqueous solution of chondroitin sulfate is better when a nitride layer
based on the Ti2N phase with lower roughness and surface microhardness is formed on
the surface, the formation of which is provided by the saturation in the range of low
temperatures and long exposures in a rarefied nitrogen. It was shown that the corrosion
resistance of nitrided BT6 titanium alloy in physiological solutions that simulate the
physiological environment of a human body is better when a nitride layer based on
titanium mononitride TiNx is formed on the surface, the formation of which is ensured by
the saturation in the range of high temperatures and short exposures at atmospheric
pressure of the nitrogen.
The stage nitriding regime for commercially pure titanium BT1-0 was developed. It
provides high leveling of tribological and anti-corrosion characteristics of the surface in
physiological solutions. Testing by using the T-24 simulator of the biomechanical human
motion showed that the wear intensity of the UHMWPE cup in a tribo-pair with a nitrided
titanium head is 3 times lower than that of a tribo-pair with CoCrMo. It was established
that the surface nitrided by developed saturation method improves the cytocompatibility
of titanium, which allows to conduct studies in vivo.
The scientific approaches to the formation of oxynitride layers on titanium alloys
from a controlled nitrogen-oxygen-containing gas environment, both in a rarefied
(0.001…0.1 Pa) nitrogen-oxygen-containing gas environment (an air) and saturation in
rarefied nitrogen with the addition of 20 and 30 vol.% of oxygen (nitrogen-oxygen-
containing gas mixture) were developed. The temperature range (500...750 °C) for the
formation of oxynitride layers was established. It was determined that with a decrease
of the oxygen content in the nitrogen-oxygen gas mixture from 30 to 20 vol.%, the corrosion
resistance of oxynitrided titanium is increased regardless of the oxynitriding
temperature. It was established that by influencing the ratio of nitrogen and oxygen in
titanium oxynitride, it is possible to form both oxynitrides of equiatomic composition
and those enriched with nitrogen or oxygen, while changing the surface colour from
violet, gray-violet to golden or green, blue, aquamarine, which has the prospect of use