Effect of metastable pitting on stress corrosion cracking in 2205 duplex stainless steel welded joints

The behaviour of metastable pitting and its effect on stress corrosion cracking (SCC) in 2205 duplex stainless steel (DSS) welded joints were investigated through microstructure characterisation, immersion experiments, electrochemical experiments and slow strain rate tensile (SSRT) experiments. The study revealed that the corrosion in the heat-affected zone (HAZ) and weld metal (WM) increased with longer immersion time due to the environment and welding thermal cycle. The majority of the metastable pitting occurred at inclusions in the ferrite phase and ferrite (alpha)/austenite (gamma) interface. Metastable pitting can increase the DSS SCC susceptibility, with cracks typically initiating at the bottom of pits in the ferrite phase and propagating in the direction of slip bands as either transgranular-stress corrosion cracking (TGSCC) and intergranular-stress corrosion cracking (IGSCC).