Mechanism of Ferrite and Grain Boundary Induced Corrosion in Simulated Heat Affected Zone of 316l Austenitic Stainless Steel

Abstract

The microstructure and corrosion resistance evolution of 316L heat-affected zone were studied by simulated welding thermal technology. The different thermal simulation parameters affected the ferrite content and grain boundary characteristics. The residual 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 chromium depleted zone caused by ferrite becomes the nucleation point of pitting corrosion and extends to the austenite matrix along the large angle grain boundary.

Keywords: 316L stainless steel, Simulated welding thermal cycles, Ferrite, Corrosion resistance