Role of Ti element in the microstructure and corrosion behavior of nickel-based alloy 825

The influence of Ti content on the microstructure and corrosion behavior of nickel-based alloy 825 in acid oil and gas environments was studied. The pitting corrosion behavior and stress corrosion cracking (SCC) behavior of Alloy 825 were investigated using high-temperature and high-pressure immersion tests, electrochemical tests, and slow strain rate tensile tests. Scanning electron microscopy, electron backscatter diffraction, and 3D microscopy were applied to analyze the microstructure and corrosion performance of the samples. The results showed that the number of inclusions and residual strain increased with the increase of Ti content, and strain concentration was found around the inclusions. The rise in inclusions led to lower pitting potential and a narrower passivation interval. In addition, the enhanced SCC susceptibility of the alloy with higher Ti content may also be attributed to the increase in inclusions.