Ductile fracture mechanisms in shielded metal-arc and gas tungsten-arc welds of Type 347 stainless steels

摘要

.The ductile fracture behavior of two different weldsof Type 347 stainless steel, which are made by SMAW (shieldedmetal arc welding ) and GTAW (gas tungsten arc welding)processes was characterized by J-integral testing andmicrostructural evaluation techniques. Both welds by SMAW andGTAW processes showed significantly low fracture toughnesscompared with that of the base metal. Metallographic andfractographic examinations revealed that differentmicromechanisms are operative in the fracture process of the twowelds. In the SMAW weld , the fracture was dominated by voidinitiation and growth at the inclusions that are homogeneouslydistributed in the matrix. On the other hand, in the GTAW weld, alarge number of Nb(CN) particles precipitated on theaustenite/ferrite interface as long rod shapes and the fractureproceeded by void initiation at these particles and accompanyingdecohesion of the interface. It is recommended that the C and Nbcontents be reduced in weld metal itself as well and that thewelding atomosphere be controlled.