Search

The small punch (SP) creep test using a TEM disk-type specimen (φ3 × t0.25 mm) was applied to the fusion zone (FZ), the coarsened grain heat-affected zone (CGHAZ), the fine grain HAZ (FGHAZ), the tempered HAZ (THAZ) and the base metal (BM), respectively, which were removed from the joint of 8Cr - 2W - VTa steel welded by an electron beam welding, in order to investigate the creep properties of such local regimes. Experimental results revealed that the SP creep rupture of the FGHAZ was accompanied by creep void formation even if the rupture time was relatively short and its creep rupture strength was inferior to those of the other regimes. This reduction in rupture strength seemed to be attributable to the microstructural changes during the welding thermal cycles, which were represented by the annihilation of clear lath martensitic structure and the change in precipitate distribution. [ABSTRACT FROM AUTHOR]

Highlights • Lifetime of F82H-BA07 is very similar to that of commercial 9Cr-1Mo steel as indicated by similarity in tensile properties. • Lifetime in the air is 1/4 times shorter than that in vacuum. • Manson's modified universal slope method gives good estimation for lifetime of F82H at temperature below 823 K. • Fatigue lifetime in low cycle region in the air can be summarized using the universal slope dividing Nf by a factor, and the factor increases with the test temperature. Abstract Reduced activation ferritic/martensitic (RAFM) steels are assumed as structural material of blanket design activities. Determining the design limit is essential for the RAFM steels to qualify their use in fusion blankets. This work investigates fatigue properties of a RAFM steel, F82H at elevated temperature up to 823 K in the air and a vacuum condition. The tests were carried out with axial strain controlled condition using cylindrical specimen, and the results were summarized using the Manson's modified universal slope method, which can describe fatigue lifetime as a function of tensile properties. Manson's modified universal slope method gives good estimation for lifetime of F82H at temperature below 823 K. However, F82H-IEA demonstrated shorter lifetime than the estimation. The lifetime at vacuum condition was successfully described using universal slope method. On the other hand, the lifetime in the air was 1/3 or shorter than that in vacuum condition. It is notable that a heat of F82H prepared for IEA round robin tests demonstrated 1/5 of shorter lifetime than the latest F82H. [ABSTRACT FROM AUTHOR]