Welding of 304L Stainless Steel to 409 Stainless Steel with GMAW Process Using ER316LSi and ER309LMo Filler Metals

Dissimilar welding of AISI 304L austenitic stainless steel to AISI 409 ferritic stainless steel with GMAW process usingtwo Ar-O2 and Ar-CO2 shielding gas mixtures was studied. ER316LSi and ER309LMo filler metals were chosen by considering 5 and 15% delta ferrite according to the Schaeffler equations and diagram. Based on the observations, both filler metals accompanied by Ar-2%O2 shielding gas resulted in acceptable weldments. Yield strength and UTS of tensile samples were 288 and 424 MPa, respectively. All tensile samples fractured in the ferritic base metal. Microhardness test results demonstrated that the maximum hardness of 190-200 HV was obtained from ER316LSi weld metal. The minimum hardness of 145 HV was found in the HAZ of 409 side mainly due to the grain coarsening. Microstructural examinations revealed needle-like precipitates formed perpendicular to each other in the HAZ of 409 stainless steel. It seemed that the pre-existing TiC precipitates evolved into the needle shape precipitates as a result of rapid heating and cooling rates during the welding process.