Mechanisms of postweld intergranular underclad cracking

Forged components of ferritic steel are protected by a welded austenitic clad. intergranular cracking can take piace in the ferritic phase close to the ferritic austenitic interface. After developing a fabrication technique for these cracks, the formation conditions are studied. Auger electron spectroscopy investigations of specimens containing a real crack opened inside the vacuum chamber are used for interpretation. Sulphur segregations embrittle the grain boundaries which are separated by different dilatations of the clad and the base metal during the postweld heat treatment.