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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
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