The effect of chemical composition of filler metal on properties of dissimilar joint between AISI316 and AISI430 steels welded by GTAW

In this research, the effect of different filler metals on microstructure and mechanical properties of dissimilar joint between AISI316 and AISI430 stainless steels was studied. For this purpose, GTAW process with ER308L, ER309L and ERNiCrMo4 filler metals with diameter of 2.4 mm were used. Microstructure and fracture surfaces of the welded samples were analyzed by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and ferritoscopy. Also, the mechanical properties of the joint were evaluated by tension, impact and microhardness tests. The results show that the microstructure in the welded sample with ER308L filler metal was austenitic with lathy and skeletal ferrite and Widmanstatten austenite. In the welded sample with ER309L filler metal the microstructure was composed from austenite with skeletal ferrite and in the welded sample with ERNiCrMo4 filler metal was fully austenitic. In tension test, all samples fractured from AISI430 base metal in a ductile manner. ER309L filler metal indicated low impact energy of about 49 J and ER308L and ERNiCrMo4 filler metals indicated higher impact energy of about 120 and 73 J, respectively. The fracture of the weld metal in the welded samples with ER308L and ERNiCrMo4 filler metals was ductile and in the welded sample with ER309L filler metal was brittle. The results of microhardness test indicated that ER308L and ERNiCrMo4 filler metals had higher microhardness as compared with ER309L filler metal due to the presence of alloying elements, finer microstructure and higher grain boundaries.