Creep-fatigue crack growth behaviour based on EBSD observations for notched specimen made of directionally solidified Ni-base superalloy

摘要

In order to characterise the creep-fatigue crack growth behaviour of a directionally solidified Ni-base superalloy, an investigation into damage behaviour based on the electron backscattered diffraction (EBSD) method using notched specimens has been carried out. The average misorientation in the vicinity of notches increases linearly up to the initiation of cracks with the increasing creep strains under creep or creep-fatigue conditions, whereas under fatigue conditions fatigue cracks grew without an increase in misorientation. The stress holding time clearly influenced the growth behaviour of creep-fatigue cracks and the appearance of misorientation development. However, it was shown that the relationship between the average misorientation and the relative notch opening displacement was independent of test conditions such as temperatures, stresses and stress wave forms.