Creep strength and nano-macro structure of high-Cr martensitic steel

Tanno, Takashi  ; Otsuka, Satoshi   ; Kaito, Takeji ; Yano, Yasuhide  ; Koyama, Shinichi  ; Tanaka, Kenya; Oba, Yojiro*; Onuma, Masato*

The 9Cr-ODS martensitic steel is under development as first candidate material for fast reactor long life fuel cladding. It should have high temperature strength, irradiation resistance and productibility. The 11Cr-ODS steels with additional corrosion resistance by Cr enrichment are also under development. And the evaluation of their applicability for cladding material is in progress. Trial manufacture, creep test and nano/macro structure evaluation of several ODS steels were carried out to modify the chemical composition and manufacturing process of the 11Cr-ODS steel. Uni-axial creep strength of manufactured 11Cr-ODS steels were equal to or higher than that of 9Cr-ODS steel. The strength of 11Cr-ODS steels with 0.3wt% Ti was slightly higher than that with 0.2wt% Ti. The size and number density of dispersed-oxide depended on the amount of added Ti and extra-oxygen.