Page 5 - Thesis_Lavrys

5

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