Development of evaluation technique of high temperature creep characteristics by small punch-creep test method (I)

In this study, a Small Punch Creep(SP-Creep) test using miniaturized specimen(10 x 10 x 0.5mm) is described to develop the new creep test method for high temperature structural materials. The SP-Creep test is applied to 2.25Cr-1Mo(STBA24) steel which is widely used as boiler tube material. The test temperatures applied for the creep deformation of miniaturized specimens are between 550∼600 .deg. C. The SP-Creep curves depend definitely on applied load and creep temperature, and show the three stages of creep behavior like in conventional uniaxial tensile creep curves. The load exponent of miniaturized specimen decrease with increasing test temperature, and its behavior is similar to stress exponent behavior of uniaxial creep test. The creep activation energy obtained from the relationship between SP-Creep rate and test temperature decreases as the applied load increases. A predicting equation of SP-Creep rate for 2.25Cr-1Mo steel is suggested, and a good agreement between experimental and calculated data has been found