High voltage electron metallography of stress corrosion cracking of austenitic stainless steels

High voltage electron metallographic studies of stress corrosion cracks nucleated on miniature U-bend specimens of austenitic stainless steels support an anodic dissolution mechanism of cracking. For all the alloys examined crack nucleation occurs at slip traces and a characteristic slotted dissolution morphology is observed in crack tip regions. The crystallography of this attack as determined by stereo-microscopy and trace analysis, reveals the slots to be bounded by {110} planes whilst growing in 〈111〉 directions. Cracking occurs through the network of corrosion slots at the crack tip and the well known features of stress corrosion fracture surfaces can be interpreted by this mechanism.