Controlled Pre-Corrosion Attack and Ultrasonic Fatigue Endurance of Titanium Alloy Ti-6Al-4V

Abstract

Ultrasonic fatigue tests were carried out on titanium alloy Ti-6Al-4V on the base material and the pre-corroded specimen to assess the pre-corrosion effect on the fatigue life of this alloy. The pre-corrosion was obtained by immersion of specimens in an acid solution: hydrochloric acid with 1.4 of pH during 8 and 16 minutes. All ultrasonic fatigue tests were performed following a predetermined sequence to attain the nominal applied load. Infrared images were taken at the neck section of specimens during ultrasonic fatigue testing, revealing that temperature is higher for the specimens with pre-corrosion and it increases with the time of pre-corrosion. It was observed that pits generated by pre-corrosion were associated with stress concentration, temperature increase and fatigue endurance decrease. Fracture surfaces were analyzed to determine the crack initiation and propagation and the stress intensity factor range threshold KTH was obtained for both: the pre-corroded and non pre-corroded specimens.