Unveiling the mechanism of yttrium significantly improving high-temperature oxidation resistance of super-austenitic stainless steel S32654

Aiming at serious catastrophic oxidation problem of super-austenitic stainless steel S32654, the influence of different rare earth elements on its oxidation behavior was comparatively investigated at 1200 degrees C. The mechanism of Y significantly improving high-temperature oxidation resistance of S32654 was unveiled. The results demonstrated that Y played much better beneficial roles than Ce and La in the initial formation of oxide layer: (1) Y promoted Cr segregation to steel surface to combine with O; (2) its preferential oxidation provided nucleation cores for Cr 2 O 3 . Both roles jointly promoted the selective oxidation of Cr and then the formation of protective Cr-rich oxide layer. This provided good prerequisites for inhibiting the formation and volatilization of MoO 3 . Additionally, Y cation segregation to oxide grain boundaries further promoted the selective oxidation of Cr and Si to form more protective oxide layer. These beneficial roles of Y essentially eliminated the synergistic effects of MoO 3 volatilization and lamellar Cr 2 N precipitation on catastrophic oxidation. Accordingly, the oxidation resistance of Y-bearing S32654 was improved by 22%-45%. (c) 2022 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

Automated summary

This study comparatively investigated the influence of different rare earth elements on the oxidation behavior of super-austenitic stainless steel S32654 and unveiled the mechanism of Y significantly improving its high-temperature oxidation resistance. Y played a key role in the initial formation of the oxide layer and served as a protective agent through selective oxidation during the oxidation process. Y cation segregation further promoted the formation of the oxide layer. These actions eliminated the negative effects of MoO3 volatilization and lamellar Cr2N precipitation on oxidation, thereby enhancing the oxidation resistance of S32654.