Abstract

The aim of investigations on the chapter was to determine regularities of solid solution hardening of surface layers of titanium alloys depending on the conditions of thermodiffusion saturation in rarified gas medium containing oxygen and determine the correlations between parameters of surface-hardened layers (surface hardness, depth of hardened zone, microstructure) and fatigue properties of titanium alloys under various methods of surface hardening. To achieve the formulated aim, the following methods were used: (a) thermodiffusion saturation of titanium alloys in rarified gas medium containing oxygen in the wide range of temperature-time and gas-dynamical parameters and (b) surface deformation by ultrasonic shock and shot-blasting treatments with rapid annealing of deformed surface by means of induction heating. The positive influence of surface hardening on the fatigue characteristics is decreased under the increasing of l when K is constant. The highest relative gain of fatigue strength (Δσ1) of samples with CTT surface-hardened layers is marked for the low- and middle-strong alloys VT1-0 and OT4-1. Thus for alloy VT1-0, Δσ<sup>1</sup> = 35% under relative gain of surface hardness K = 70% and l = 3 0 μm. For the near-α-alloy OT4-1, Δσ<sup>1</sup> = 38% under relative gain of surface hardness K = 35% and l = 4 5 …50 μm.

Keywords: titanium alloy, oxygen, mass gain, solid-solution hardening, fatigue strength
