高強度Ni基合金のクリープき裂進展特性とその評価パラメータ

抄録

Advanced Ultra Super Critical (A-USC) thermal power plants have been developed. However, many of these components must fit to more severe condition. Estimation of creep crack growth behavior has not been fully accomplished yet because of its dependency on materials’ ductility and loading conditions. Employing CT specimens of a Ni base alloy with side grooves, a few experiments were conducted at 700°C and 675°C. Furthermore, some Finite Element analyses using the NSW model were also performed to clarify creep crack growth behavior and parameters for creep crack propagation. Then, following results were obtained; (1) Both of creep crack length and load line displacement accelerated their rates in the tertiary stage of creep. The deformation in the tertiary stage occupied 70% of the total deformation. (2) Creep J integral, so-called C* parameter, well described creep crack growth behaviors as a power function regardless of testing conditions. (3) When the process zone size was fixed, the creep crack growth behavior greatly depended on the creep ductility at the crack tip.