MECHANISMS OF POSTWELD INTERGRANULAR UNDERCLAD CRACKING

Forged components of ferritic steel are protected by a welded austenit ic clad. Intergranular cracking can take place in the ferritic phase c lose to the ferritic austenitic interface. After developing a fabricat ion technique for these cracks, the formation conditions are studied. Auger electron spectroscopy investigations of specimens containing a r eal crack opened inside the vacuum chamber are used for interpretation . Sulphur segregations embrittle the grain boundaries which are separa ted by different dilatations of the clad and the base metal during the postweld heat treatment.