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provided higher tribotechnical parameters (wear resistance, friction coefficient
and temperature near the friction zone) of investigated tribo-pairs compared to
ball burnishing or nitriding treatments. It was established that the deformation-
diffusion treatment increases the wear resistance of VT22 titanium alloy in tribo-
pair with BrAZhN 10-4-4 bronze twice and reduces the friction coefficient by
30% compared to nitriding without surface pre-deformation.
It is established that after deformation-diffusion treatment the fatigue
strength approaches the values after strengthening heat treatment of VT22
titanium alloy. The fractographic analysis of the fracture surfaces of the studied
samples revealed a certain correlation, namely: the lower the fatigue strength of
the alloy samples after treatment, the larger area of brittle intergranular fracture
on the fracture surface.
It is shown that the strength of samples of VT22 titanium alloy after all
hardening treatments increases. The samples hardened by deformation-diffusion
treatment were somewhat inferior to the samples after cold surface plastic
deformation and nitriding in terms of the ultimate tensile strength. But, the
plasticity (elongation) of VT22 alloy samples after deformation-diffusion
treatment was the highest. The nature of the fractures indicated the mechanisms
of ductile rupture, namely, the formation of the so-colled dipole void structure
was fixed on fracture surface. A correlation was observed between the size and
depth of the voids (holes) in the surface fracture zone and the strength of VT22
alloys: the treatment that increases the strength the most has the smallest voids
(holes) on the fracture surface.
The technological recommendations for combined deformation-diffusion
treatment of VT22 titanium alloy were developed, which provide the regulated
characteristics of hardened layers while maintaining the volumetric
characteristics of the alloy.
Scientific novelty of the obtained results
1. The low-temperature range of the dependence of the parabolic constant of
nitriding rate was determined, and the activation energy of the process and other