Effects of test environment on high temperature fatigue properties of reduced activation ferritic/martensitic steel, F82H

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.