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ABSTRACT
Lavrys S. M. Increasing the wear resistance of VT22 titanium alloy by
surface deformation-diffusion treatment. – Qualification scientific work as the
manuscript.
Thesis for the Ph.D. in Engineering Sciences in the specialty 05.02.01
«Materials Science» (132 – Materials Science) – Karpenko Physico-Mechanical
Institute of the National Academy of Sciences of Ukraine, Lviv, 2020.
The thesis presents a new solution to the scientific and technical problem of
increasing the wear resistance of VT22 titanium alloy by intensification of gas
nitriding by pre-modification of the surface structure by cold surface plastic
deformation.
The kinetic regularities of thermodiffusion saturation of VT22 titanium
alloy by nitrogen were investigated and the basic kinetic constants of the process
(Кρ, Q, A) for a wide temperature range (750…950°C) were calculated. Obtained
data allow predict the nitriding parameters of VT22 alloy for obtaining regulated
surface hardening.
The correlation dependencies between the cold surface plastic deformation
parameters and the level of surface hardening of VT22 titanium alloy with
different structural states were established. It was found for the first time that the
most effective cold surface plastic deformation was realized in VT22 alloy with
initial two-phase lamellar or globular structures. For the alloy with the initial β-
structure, the cold surface plastic deformation requires higher loads. It is shown
that increasing load provides an increase in the level of surface hardening, and
increasing number of passes – improving the quality of treated surface of VT22
titanium alloy.
The influence of the initial structural state on the nitriding combined with
streng-thening heat treatment of VT22 titanium alloy was shown, which
influences on the phase-structural state and the level of surface hardening of the
modified layers. Thus, for the alloys with the initial equiaxed (α+β)-globular and