単結晶Ni基超合金の疲労き裂の進展と停止に及ぼす結晶異方性の影響

抄録

Ni-based sigle crystal superalloys are widely used in gas turbine blades due to their excellent high-temperature strength. However, cyclic loading due to mechanical vibrations and thermal stress can cause fatigue crack initiation and subsequent propagation. While prior studies have examined fatigue crack propagation in Ni-based superalloys, few have focused on the arrest of fatigue cracks, particularly considering the effect of crystallographic anisotropy. This study investigates the influence of crystallographic anisotropy on fatigue crack propagation and arrest behavior. Fatigue crack propagation tests were conducted at room temperature using four specimens with different crystal orientations. The results revealed significant effects of crystal anisotropy on crack propagation path, propagation rate, and ΔK_th. Crystal plasticity finite element analysis, incorporating experimentally observed cracks, demonstrated that the damage parameter based on plastic shear strain along the slip plane can effectively evaluate fatigue crack arrest.