Effect of Cr/Al contents on the 475ºC age-hardening in oxide dispersion strengthened ferritic steels

• Main Authors: Wentuo Han, Kiyohiro Yabuuchi, Akihiko Kimura, Shigeharu Ukai, Naoko Oono, Takeji Kaito, Tadahiko Torimaru, Shigenari Hayashi
• Format: Article
• Language: English
• Published: Elsevier 2016-12-01
• Series: Nuclear Materials and Energy
• Subjects: ODS ferritic steel; 475℃ embrittlement; Al and Cr effects; Cr-enriched α′ phase; Hardness evolution
• Online Access: http://www.sciencedirect.com/science/article/pii/S2352179115301162

The age-hardening in oxide dispersion strengthened (ODS) ferritic steels with various additions of Cr (12, 15 and 18wt.%) and Al (0, 5, 7 and 9wt.%) were investigated. After 5000h aging at 475ºC, the hardness increases in all these ODS steels, while the increased level depends on the Cr/Al contents. In 12Cr-ODS steels, the more the Al, the higher the increased hardness is. However, in 18Cr-ODS steels, higher Al addition suppresses the age-hardening. TEM observations of 18Cr-ODS steels reveal that 9Al suppresses the formation of Cr-enriched α' phase, while the 18Cr-5Al-ODS steel comprises a plenty of α′ phases. Adding Zr in ODS steels appears to increase the age-hardening. The susceptibility to age-hardening is remarkably lower in the ODS ferritic steels than in the non-ODS ferritic steel with the similar concentration of Cr.