Microcrack clustering in stress corrosion cracking of 22Cr and 25Cr duplex stainless steels

• Dealloying in DSS linked to nanocrystalline surface layer induced by grinding.
• Dealloyed layer is precursor to stress corrosion crack initiation in DSS in evaporating seawater.
• Microcrack clustering attributed to local variations in deformation and strain.

A metallographic study of stress corrosion cracks on duplex stainless steel (DSS) and super duplex stainless steel (SDSS) after testing under evaporative seawater conditions has been undertaken with particular focus on the microcrack clusters observed in the ferrite phase. Dealloying in the nanocrystalline layer formed by surface grinding, and subsequent cracking of the dealloyed layer, are considered to be the precursor steps to crack propagation, rather than pitting corrosion. The variable surface density of the crack clusters may reflect localisation of dealloying to regions of heavier grinding that would be expected to produce a finer grain size or more highly strained nanocrystalline layer.