Creep-fatigue Behavior and Life Evaluation of Hastelloy XR Perforated Plate for High Temperature Gas-cooled Reactor

In this paper, creep-fatigue behavior of Hastelloy XR, candidate material for High Temperature Gas-cooled Reactor (HTGR), was clarified based on experimental data of uniaxial round bar specimen and perforated plate at 950℃. Applicability of creep-fatigue life evaluation methods for these data was also examined. In the strain-controlled uniaxial creep-fatigue tests with hold time up to 30 min, rapid relaxation due to creep was observed. The stress after relaxation during hold time was almost within 20% of the initial stress. In the creep-fatigue tests of perforated plate on the basis nominal-strain control, stress relaxation during hold time was slower than that in uniaxial tests, due to the effect of elastic-follow-up behavior. The life reduction of perforated plate was about 1/5, larger reduction when compared with that in the uniaxial tests. In the uniaxial tests, predicted lives on the basis of the linear damage rule of fatigue and creep were almost within a factor of 3 of experimental life, for both cases of time-fraction and ductility exhaustion rules for creep damage. In the perforated plate test, predicted lives, on the basis of the detailed inelastic analysis were also within a factor of 3 of experimental life. An applicability of a simplified creep-fatigue life evaluation method based on elastic analysis to the perforated plate was discussed.