Performance evaluation of activated fluxes for deeper penetration in autogenous A-TIG of AISI304 stainless steel

The activated-TIG (A-TIG) process is a well-established variant of GTAW for achieving deeper penetration in thick sections, having the potential applications in aerospace, automotive, construction, and thermal-power industries. AISI 304 (austenitic stainless steel) is extensively used in these sectors owing to its good weldability, high strength and corrosion resistance for fabrication of tanks, vessels, and piping. A-TIG welding enables single-pass, deliver deep penetration through the use of oxide-based fluxes such as SiO2, TiO2, and CrO3, which modify weld pool behavior by arc constriction and altered Marangoni convection. In the present work, bead-on-plate welds were produced on SS304 at 150 A and 170 A using three different activated fluxes. Among them, CrO3 exhibited the most superior performance owing to its higher oxygen content, achieving complete penetration at 170 A current level. Micro-hardness and wear analysis showed the enhanced mechanical properties of CrO3-assisted weld coupons, although wear rate increased slightly at higher current due to greater heat input. Color metallography correlated these improvements with refined microstructural features. Overall, CrO3 flux delivered maximum penetration (>8 mm), improved hardness (431 HV), and better wear resistance, establishing it as the optimum flux for high-performance A-TIG applications.