Research on thermal creep behavior of Chinese low-activation ferritic/martensitic steel

•Thermal creep behavior of CLF-1 steel is studied based on application of CN HCCB TBM.•Microstructure of CLF-1 steel reflects that the size and type of precipitates between as-received and crept samples are not changed.•CLF-1 steel reflects clear creep stage from the curve, the Larson-miller parameter shows CLF-1 steel is similar to Eurofer97 and even better than F82H. A series of thermal creep experiments are conducted on Chinese low-activation ferritic/martensitic steel (CLF-1 steel) at a temperature of 550, 575, and 600 °C with various normal stress (from 150 to 300 MPa), respectively. The results are analyzed by creep curves, microstructure, and creep properties. Finished samples display adequate fracture surface in short creep rupture tests (within 3000 h). The comparative creep curve shows no difference related to the thickness of CLF-1 steel plate (10 and 30 mm). Microstructure images before and after creep reflect a tempered lath martensite structure and carbides decorating both in prior austenitic grain boundaries and lath boundaries. Comparison is discussed between 30 mm plate and 10 mm plate. All current results reflect that all CLF-1 steel samples shows good creep behavior and proves that a series excellent progress of CLF-1 steel R&D work has been successfully achieved. Besides, collected data will contribute a lot to the design and R&D work of the Chinese Helium Cooled Ceramic Breeding Test Blanket Module (CNHCCB-TBM).