Effect of ferrite and grain boundary characteristics on corrosion properties of thermal simulated 316 L heat affected zone.

The microstructure and corrosion resistance evolution of 316 L heat-affected zone were studied by simulated welding thermal technology. The different thermal simulation parameters affected the ferrite content and grain boundary characteristics. The ferrite content and grain boundary characteristics in thermal simulation samples were studied by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). Combining the electrochemical test, it was observed that the Cr-depleted zone existed at the austenite/ferrite interface and the high angle grain boundary (HAGB) of the austenite interface usually became the nucleation point of pitting corrosion. • Retained ferrite can be found due to chromium aggregation during welding thermal cycle. • Cr-depleted zone and random high angle grain boundary are conducive to pitting nucleation. • Corrosion extends from ferrite/austenite phase boundary to austenite matrix. [ABSTRACT FROM AUTHOR]