Comparative analysis of mechanical properties and corrosion resistance of AISI 304L steel welded by conventional and pulsed GTAW processes

AISI 304L steel is specified as a base metal for welded joints in various equipment, due to its good resistance to sensitization. In some applications the operating temperature exceeds 450°C. The pulsed GTAW process is an alternative to the conventional one, as it alleviates the harmful effects of successive thermal cycles in multipass welding. However, it requires greater investments, raising questions about the metallurgical gains of this alternative. In this context, this article compared the resistance to pitting corrosion and the toughness of AISI 304L Steel welded by the two processes. For this, thermal aging was carried out at a temperature of 450°C for a period of up to 24 hours and, later, microstructural characterizations were carried out by optical (OM) and scanning electron microscopy (SEM-EDS), and magnetic permeability. The mechanical properties were evaluated by microhardness and impact toughness tests on the metallic joints, and compared with each other under the indicated aging conditions. The evaluation of the material's susceptibility to pitting corrosion was performed using the cyclic potentiodynamic polarization technique in an aqueous solution containing 3.5% NaCl. The results indicated higher toughness values in the pulsed GTAW samples for all proposed conditions. In addition, the longer aging time caused a decrease in toughness, possibly due to the formation of intermetallic phases. However, in the as-welded condition, the conventional GTAW showed greater resistance to pitting corrosion. The results, therefore, suggest that the choice between the processes considers, primarily, economic factors. (author)