Abstract
AbstractThe 444-type heat-resistant ferritic stainless steel is widely utilized in automotive exhaust pipes and solid oxide fuel cells, due to its excellent properties at elevated temperature. To meet the demands of significantly harsh service environments, rare earths were added in 444-type ferritic stainless steel. For the purpose of evaluating the effect of rare earths on pitting corrosion initiation, the metastable pitting corrosion behavior in 444-type ferritic stainless steel was studied through potentiodynamic polarization and potentiostatic polarization tests. The results demonstrated that pitting corrosion was initiated at the inclusion/alloy interface. The cerium alloying in 444-type ferritic stainless steel decreased the amount of preferential dissolution sites. The beneficial effect of Ce on pitting corrosion resulted from the formation of stable cerium oxides, as well as from the reduction in the amount and size of inclusions in 444-type ferritic stainless steel. In addition, electrochemical impedance spectroscopy test results revealed that cerium alloying enhanced the polarization resistance of passive films through insignificant thickness alteration.
Highlights
IntroductionThe 444-type ferritic stainless steel demonstrates satisfactory mechanical properties, such as favorable anti-
The 444-type ferritic stainless steel demonstrates satisfactory mechanical properties, such as favorable anti-Rare earths are reported to enhance the performance of materials under high-temperature conditions for manifolds
Kim et al found that the addition of Ce in austenitic stainless steel improved the Cr-deletion of (Fe, Cr) oxide inclusions and led the pits to grow towards the alloy matrix, increasing the pitting corrosion resistance [12]
Summary
The 444-type ferritic stainless steel demonstrates satisfactory mechanical properties, such as favorable anti-. It was disclosed that rare earths modified the type and shape of inclusions, which had a positive effect on the mechanical properties of steel. Cerium effect on pitting corrosion initiation of 444-type ferritic stainless steel 577 pitting corrosion. Few studies aimed to study the effect of rare earths on the inclusions and corrosion behavior of 444-type ferritic stainless steel. It was necessary to study the relationship between inclusions and corrosion behavior in 444-type ferritic stainless steel containing rare earths. The mechanism affecting the pitting initiation was discussed, based on electrochemical corrosion measurements and inclusion surface morphology observation. Prior to each electrochemical measurement, the exposed surface was cathodically polarized at −1.0 VSCE for 10 min, to eliminate the oxides formed in air to ensure reproducible conditions. The elemental distribution and morphology of inclusions were analyzed through electron microprobe analysis (EPMA)
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