改良9Cr-1Mo鋼環状切欠き試験片のクリープ損傷評価

抄録

Creep damage assessment of steam turbines in ultra-super critical power plants is necessary to maintain reliable operation. The destructive assessment method gives accurate creep damage assessment results, but it is difficult to cut a standard size specimen from steam turbines. Therefore, it is desired to develop a test method and a damage assessment method using a miniature specimen. In this study, creep damaged materials were made by creep tests on round bar notch specimens of the modified 9Cr-1Mo steel (notched tip radius 0.5 mm (R0.5) and 2.0 mm (R2.0)). Large number of voids was observed around 0.5 mm from notch root in R0.5, and it was observed around center of the specimen in R2.0. Creep tests in argon gas were conducted by using a solid bar tensile type miniature specimen with 1 mm diameter taken from the vicinity of the notch root of the creep damaged materials. For miniature specimens collected from the creep damaged materials of R0.5 and R2.0, the rupture time of the miniature specimen became shorter as creep damage increased. It might be possible to apply the miniature specimen for creep damage assessment of damaged materials.