Effects of CeO۲ Flux and Shielding Gas In A-TIG Welding on The Microstructure, Corrosion and Passive Film of Super Duplex Phase Stainless Steel ۲۵۰۷

This study explores using CeO۲ flux with Ar and Ar+۵%N۲ shielding gases to enhance the welding process of ۲۵۰۷ super duplex stainless steel through active TIG welding. It discusses their impact on weld geometry, microstructure, pitting corrosion, and passive film in a ۳.۵% NaCl solution, using scanning electron microscopy, cyclic polarization curves, electrochemical impedance spectroscopy, and Mott-Schottky analysis. The results indicate that the proportion of austenite phase in the microstructure resulting from A-TIG welding with CeO۲ flux and Ar gas increased to ۴۹.۱%, compared to ۴۲.۱% in conventional TIG welding, aligning well with the phase balance in the base metal. The microstructure of A-TIG welding with cerium oxide flux and shielding gas mixture, with increased austenite with quasi-spherical shapes, has created a morphology similar to the base metal. When utilizing CeO۲ flux for welding in conjunction with a shielding gas mixture, a significant reduction in grain size occurs, which becomes about four times smaller than the base metal. Moreover, it modifies the shape, size, and distribution of inclusions. This increased corrosion resistance and significantly reduced Icorr and Ipass by approximately ۲۲ times. Additionally, EIS and Mott-Schottky tests indicated decreased point defects in the passive film and a greater propensity to form a dense protective film with higher chemical stability in A-TIG welding, mainly when using a shielding gas mixture. These findings demonstrate the crucial role of cerium in enhancing the welding of super duplex stainless steel, potentially representing a significant breakthrough in the industry.

کلیدواژه ها:

Super-Duplex Stainless Steel ۲۵۰۷ ، Active TIG Welding ، Cerium Oxide Flux ، Corrosion ، Shielding Gas ، Microstructure ، Passive film