Effect of shielding gas composition on intergranular corrosion of stabilized ferritic stainless steel GMA welds
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The effect of shielding gas composition on intergranular corrosion of the fusion zone formed by bi-stabilized ferritic stainless steel plates (AISI 441) and ER430Ti and ER430LNb filler metals during gas metal arc welding was investigated. Double loop electrochemical potentiokinetic reactivation tests were conducted to examine the influence of the shielding gas content (Ar + 2%O2, Ar + 8%CO2 and Ar + 25%CO2) on intergranular corrosion of the ferritic stainless steel welds. It was possible to observe an increase in the tendency toward sensitization with the increase in the CO2 content in the shielding gas, especially with the ER430Ti filler metal. Analysis of the formed precipitates by means of optical microscope, scanning electron microscope an energy-dispersive X-ray spectroscopy allowed to notice that high levels of CO2 blended in the shielding gas increase the intergranular precipitates and lead to significant intergranular corrosion, which was induced by the Cr-depletion zone formation, especially for the welds produced with the ER430Ti filler metal.
KeywordsIntergranular corrosion GMAW Shielding gas Ferritic stainless steel Stabilized filler metal
The authors acknowledge the financial support from CNPq, CAPES and FAPEMIG, the infrastructural support from Laprosolda/UFU, EMC/UFG, LabMic/UFG and LCMM-DEFIS/UFMA and, finally, thank ArcelorMittal Inox Brasil S/A for laboratorial analyses and for donating the base and filler metals.
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