Investigation of microstructure and corrosion resistance of AISI 304 stainless steel joint with ER308 and ERNiCr-3 filler metals by GTAW

In this study, the effect of two different filler metals (ERNiCr-3 and ER308) on microstructure and corrosion resistance of gas tungsten arc welded AISI 304 has been investigated. The microstructure of the joints was investigated by optical and scanning electron microscope. The microhardness of samples was investigated to determine the mechanical properties of the welds. Also, the electrochemical corrosion resistance of the samples was studied by Tafel polarization and impedance analysis in 1 M hydrochloric acid. The results showed the niobium-rich carbides in the welded specimen by ERNiCr-3 filler, also this sample exhibited a higher hardness and corrosion resistance. The exchange current density and the polarization radius of the ERNiCr-3 filler metal were 0.069 mA and 244 V, and those of ER308 filler metal were 0.121 mA and 66 V, respectively. The higher hardness and corrosion resistance is attributed to the formation of hard niobium-rich carbides in the weld zone, which eliminates the formation of chromium carbides. (authors)