Influence of filler metal on the microstructure of dissimilar welds between UNS S32205 duplex stainless steel and ASTM A517 Quench and tempered steel

In this study, the microstructure in different regions of dissimilar welding sections of type 2205 duplex stainless steel (DSS) to type A517 high-strength quenched and tempered (QTLA) steel was investigated using optical microscopy (OM) and scanning electron microscopy (SEM). The joints were fabricated using gas tungsten arc welding by two types of filler metals including ER309LMo and ER2209. The metallographic analysis and X-ray diffraction (XRD) revealed that the weld metals were completely free of common destructive phases and no trace of sigma phase and chromium nitride was found. The ER309LMo weld metal has austenitic with lathy ferrite microstructure and ER2209 weld metal sample has an austenitic continues networks in the matrix of primary ferrite. The studies by SEM from joint interface of A517 side revealed, in both welding samples, the unmixed zone formed and in the case of ER309LMo addition to this zone, a decarburization layer is also visible. HAZ of 2205 steel is non-width and with coarse primary ferrite grains and this region in A517 steel side has been width and with not-tempered martensite microstructure.The ER309LMo and ER2209 weld metal’s hardness respectively were about 240 and 300 vickers.