Evaluation of creep properties using small punch creep test for modified 9Cr-1Mo steel

In the pressure vessel of a very-high-temperature reactor (VHTR), creep damage, which has a fatal adverse effect on safe operation, occurs due to long-term operation at a higher temperature. In this paper, only the small punch creep test (SPCT) was used to evaluate the creep properties of modified 9Cr-1Mo steel, which is considered a suitable candidate material for VHTR pressure vessels. Since the test outputs of SPCT are displacement and load, we converted those outputs into the strain and stress of conventional uniaxial creep tests (UCTs). The Norton, Larson-Miller and Monkman-Grant creep models were constructed using the conversion data from SPCT and the triangular relationship among the three creep models was successfully demonstrated. Finally, those three models were constructed using long-term UCT with the same material and temperature, and the validity of this study was verified by comparing it with SPCT results.