Ni基超合金IN738LCのクリープ損傷過程に及ぼす多軸応力の影響

抄録

Ni based superalloy IN 738 LC is used for the first stage blades of power generation gas turbines and aircraft jet engines. Creep damage occurs preferentially in stress concentration portions. In this study, creep tests have been conducted by using smooth and round bar notch specimens on IN 738 LC to clarify relation between creep damage extension and stress conditions, and crystal misorientation parameters. Creep rupture time of the notch specimen was longer than that of the plain specimens showing notch strengthen effect. Significant difference of void growth behavior between the plain and notch specimens was not observed. The maximum void length took the maximum value within 0.5mm from the notch root in the notch specimen. This corresponds to higher axial tensile stress and axial creep strain yielding at around the notch root. The results of the crystal misorientation measurement suggested that GRODave corresponded to axial creep strain because there was not significantly different in the relationship between GRODave and damage in the smooth specimen and near the notch root of the notch specimen, and the creep strain was equivalent at the same area.