Enhancement of weld penetration, fatigue crack growth performance and corrosion resistance of A-TIG welded 304L joints using SiO2–TiO2 binary flux

Activated flux tungsten inert gas (A-TIG) welding is an innovative variant of TIG welding which is widely utilized in industry. In this paper, SiO 2 –TiO 2 binary flux has been applied in A-TIG welding of 304L austenitic stainless steel. The purpose of this work is to study the weld microstructure under A-TIG process and its effect on strength, fatigue crack growth rate (FCGR) and corrosion characteristics of the weld joints. In this study, bead-on-plate A-TIG welding processes were performed on 6 mm-thick 304L plates using mixtures of SiO 2 ,+TiO 2 fluxes at varying compositions of 0%, 25%, 50%, 75%, and 100% TiO 2 . Subsequently, microstructure characterizations (optical microscopy, FE-SEM, EBSD, XRD), mechanical tests (hardness, tensile and fatigue) and corrosion measurements (potentiodynamic polarization and EIS) were conducted. Results demonstrated that SiO 2 flux was proved to produce excellent weld penetration. Despite TiO 2 flux was less effective in increasing the weld penetration but it could enhance fatigue crack growth (FCG) resistance of the weld joints. This improved FCG performance was likely attributed to fine austenitic dendritic grains combined with an increase in δ-ferrite. In addition, TiO 2 flux improved corrosion resistance as indicated by its ability to reduce corrosion current density, i corr and increase both corrosion potential, E corr and pitting potential, E pitt . It seems that better combination of weld penetration, fatigue crack growth and corrosion performances may be attained by suitable proportion of SiO 2 and TiO 2 fluxes.