Effect of gas tungsten arc welding on the microstructural, mechanical and corrosion properties of Ti-stabilized 439 ferritic stainless steel

In the present study, the gas tungsten arc welding was employed on Ti-stabilized 439 ferritic stainless steel using 308L austenitic stainless steel filler electrode. The formation of retained austenite (RA) at ferrite grain boundary and ferrite grains inside the grain boundary were observed through optical microstructure and it's further confirmed by X-ray diffraction analysis. In heat affected zone (HAZ), the grains coarsening occurred near the fusion boundary due to elevated temperature. The scanning electron microscopy shows the formation of peppery structure inside the ferrite grains in HAZ and the peppery structures consisted of carbide precipitates. The micro-hardness of weld zone is higher than the HAZ and base metal ascribed to the formation of RA at ferrite grain boundary. The tensile test results in higher strength of WZ because of formation of mixed microstructure. The potentiodynamic polarization test was used for corrosion study and the WZ depicted higher corrosion resistance as compare to base metal.