Investigation of the Processes of Fatigue and Corrosion-Fatigue Destruction of Pseudo-α Titanium Alloy

The paper describes the results of fatigue and corrosion-fatigue tests of the pseudo-alpha titanium alloy PT-3V, which is actively used in nuclear engineering for the manufacture of heat exchange equipment for modern nuclear power plants. Alloy PT-3V has an inhomogeneous coarse-crystalline structure with precipitates of beta-phase particles along the grain boundaries of lamellar shape. It is shown that smooth specimens tested according to the bending-with-rotation loading scheme do not show a noticeable decrease in the cyclic fatigue life when exposed to a neutral corrosive environment (3% aqueous NaCl solution). However, specimens with a notch (stress concentrator) tested according to the cantilever bending loading scheme demonstrate sensitivity to the action of a corrosive environment at the stages of initiation and growth of fatigue cracks, as evidenced by a significant decrease in the number of cycles before crack initiation, as well as before specimen failure, in comparison with tests in air. Fractographic analysis of fractures of smooth specimens and specimens with a concentrator after fatigue and corrosion-fatigue tests has been carried out. The main stages of the initiation and growth of fatigue cracks are revealed. It has been established that a decrease in the resistance to the initiation and propagation of corrosion-fatigue cracks during testing of notched specimens may be due to the effect of hydrogen embrittlement, accelerated by stress concentration.