Solidification cracking in duplex stainless steel flux-cored arc welds Part 2 — susceptibility of 22Cr all-weld metals under high restraint

Due to their high strength and corrosion resistance, duplex stainless steels are increasingly used in applications where heavy-wall material is welded under highly restrained conditions. Despite the ferritic solidification and experience shared in most available literature, these alloys are not immune to hot cracking. In this work, different commercial and experimental flux-cored wires of E2209T0 and E2209T1 type were subject to flux-cored arc welding (FCAW) to evaluate the susceptibility to solidification cracking. Impact toughness testing of all-weld metal on restrained plates proved an efficient method to detect and inspect cracks by examining the fracture surfaces. Particles found in cracks and dimples were characterized by means of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). While the start of the observed cracks showed a classic dendritic or dendritic-flat solidification pattern, the end with the last solidified melt was rather smooth. Examination in backscatter mode clearly visualized bismuth to be present in the flat region adhering to manganese sulfide (MnS) particles. Cracks were, however, also detected with bismuth-free wires and wires with low sulfur content. The weld metal chemical composition, source of raw materials, and selected agents for deoxidation could play an important role, while certain formulations with special concepts for slag formation may be less susceptible. The E2209T1 types with more rapidly solidifying slag generally showed higher resistance to solidification cracking than the E2209T0 wires, which also contained substantially higher total amounts of sulfur, phosphorous, boron, oxygen, and bismuth.