Effect of Annealing Treatment on Corrosion Resistance of Ti-19Zr-11Nb-2Ta Alloy in Acid Fracturing Service

Using high-temperature and high-pressure corrosion simulation experiments, the corrosion behavior of Ti-19Zr-11Nb-2Ta alloy in acid fracturing service was studied. The corrosion morphology and mechanism of Ti-19Zr-11Nb-2Ta alloy in acidic solutions were studied by X-ray diffractometer(XRD), scanning electron microscope (SEM) and optical microscope(OM). The results show that below 120 ℃, hydrofluoric acid can easily destroy the passive film on the cast alloy surface and suppress its regeneration, leading to severe surface corrosion. However, at the same temperature range, the cast alloy exhibits certain corrosion resistance in hydrochloric acidowing to the protective passive film. Annealing treatment can improve the corrosion resistance of the cast alloy, but the corrosion resistance first increases and then decreases with the rise of annealing temperature. The corrosion resistance of the alloy after 700 ℃ annealing treatment is best, which improves significantly than that of the cast alloy. This is attributed to the fact that annealing optimizes the grain structure, increases the number of grains and strengthens grain boundaries effects, thereby improving the corrosion resistance of the alloy