CHARACTERIZATION OF WELD SOLIDIFICATION CRACKING IN A DUPLEX STAINLESS-STEEL (REPRINTED FROM METALLOGRAPHY, VOL 23, PG 1-19, 1989)

Weld solidification cracking in the duplex stainless steel SAF 2205 ha s been investigated and compared with that of alternate duplex and aus tenitic stainless steels. Varestraint weldability testing showed SAF 2 205 to exhibit a lower cracking susceptibility than that of the duplex stainless steel Ferralium 255 but greater than that of a Type 304 aus tenitic stainless steel which solidified as ferrite and exhibited Ferr ite Number 8 (FN 8) in the weld fusion zone. The high augmented strain levels required to induce cracking in these three alloys during Vares traint testing indicated a high resistance to solidification cracking at strain levels normally encountered in structural weldments. Crackin g susceptibilities of the duplex and Type 304/FN-8 stainless steels we re appreciably lower than that of a Type 304L stainless steel which so lidified entirely to austenite and exhibited less than FN 1 in the wel d fusion zone. Microstructural characterization of SAF 2205 using conv entional black-and-white and two different color metallography techniq ues showed solidification cracks to be associated with ferrite grain b oundaries. Color metallography was also effective in revealing the fus ion zone solidification structure and delineating second phases, inclu ding inter-and intragranular austenite and fine Cr2N precipitates. Fra ctographic analysis of solidification crack surfaces from SAF 2205 Var estraint samples revealed dendritic and flat topographies, and confirm ed a solidification versus solid-state cracking mechanism.