High temperature strength and nano/meso structure evaluation of High Cr-ODS steels

Tanno, Takashi  ; Otsuka, Satoshi   ; Yano, Yasuhide  ; 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, because of its superior high temperature strength, irradiation resistance and productivility. 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 manufacturing, high temperature tensile test, creep test and nano/meso 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 residual -ferrite fraction in 11Cr-ODS steels was also controlled at the same level as that of the 9Cr-ODS steel. The creep strength had a linear correlation with the dispersion condition, which is defined by the size and number density of dispersed-oxide.