The effect of severe plastic deformation by rotary forging on the mechanical properties and the corrosion resistance of a pseudo-α-titanium PT-7M alloy is studied. The corrosive character of fracture the fine-grained alloy under hot salt corrosion (HSC) conditions is found to change: pitting corrosion at the onset of recrystallization processes changes into intercrystalline corrosion. The HSC resistance of the fine-grained PT-7M titanium alloy is shown to depend on the structure–phase state of grain boundaries, whose intense migration with developing recrystallization leads to “sweeping out” of corrosion-hazardous alloying elements (aluminum, zirconium) from the crystal lattice of the titanium alloy.

The research has been conducted into the impact that structural-phase state of grain boundaries in α-titanium alloy Ti-5Al-2V has on strength, plasticity and susceptibility to intercrystalline corrosion (ICC). It is found that during Equal Channel Angular Pressing (ECAP) performed at elevated temperatures there is a change in local concentration of alloying elements (aluminum, vanadium) along α-Ti grain boundaries. The current study proves that by controlling the structure of α-titanium alloy Ti-5Al-2V through ECAP it is possible to enhance its strength and resistance to hot salt intercrystalline corrosion. Plasticity of ultrafine-grained (UFG) alloy samples at room temperature is comparable with plasticity of a coarse-grained material, while plasticity of an UFG alloy at elevated temperatures is 2–3 times bigger than plasticity of a coarse-grained material.

Проведены исследования влияния интенсивного пластического деформирования (ИПД) на структурно-фазовое состояние границ зерен псевдо-alpha-титанового сплава Ti-4Al-2V (промышленное обозначение ПТ3В). Установлено, что повышение прочности, пластичности и коррозионной стойкости титанового сплава связано с формированием ультрамелкозернистой структуры. Показано, что повышение коррозионной стойкости в условиях горячей солевой коррозии обусловлено диффузионно-контролируемым перераспределением атомов алюминия и ванадия на границах зерен титана, сформированных в процессе теплой ИПД. DOI: 10.21883/PJTF.2017.10.44617.16580

The influence of severe plastic deformation on the structural-phase state of grain boundaries in a Ti–4Al–2V (commercial PT3V grade) pseudo-alpha-titanium alloy has been studied. It is established that increase in the strength, plasticity, and corrosion resistance of this alloy is related to the formation of an ultrafine- grained structure. In particular, it is shown that an increase in the resistance to hot-salt intergranular corrosion is due to diffusion-controlled redistribution of aluminum and vanadium atoms at the grain boundaries of titanium formed during thermal severe plastic deformation.

The structure and properties of TiN-Cu coatings with a broad range of copper concentrations (C Cu = 0.6–20 at %), which were fabricated by the ion-plasma vacuum-arc deposition on a TT10K8B hard-alloy tool, including its cutting resistant tests, were investigated. The introduction of copper into the coating composition diminishes crystallites of the nitride phase from 100 to 20 nm. The hardness of coatings increases from 20 to 40 GPa, with an increase in C Cu to 7–8%. The further increase in the copper content, which is accompanied by diminishing crystallites of the nitride phase, is characterized by a decrease in hardness to 14–15 GPa, which is associated with the influence of soft plastic metal. Resistant cutting tests of steel 35KhGSA of removable multifaceted plates (RMP) with the TiN-Cu coatings indicate that the optimally selected composition (TiN-7-8 at % Cu) increases RMP resistance more than by a factor of 6 and 2.5 as compared with tools without the coating and with the TiN coating deposited according to the basic technology, respectively.