Damage evaluation based on EBSD method for nickel-base superalloy notched specimen under creep and/or fatigue conditions

Abstract

In order to characterize the creep and/or fatigue crack initiation and growth behavior of Ni-base superalloys, an investigation into damage behavior based on the EBSD (Electron BackScattered Diffraction) method using notched specimens has been carried out. The misorientation in the vicinity of notches increased with the increase in the creep or creep-fatigue damage characteristically depending on a CC (Conventional Casting) or a DS (Directionally Solidified) superalloy. The stress holding time clearly influenced the creep and/or fatigue crack growth behavior and the appearance of misorientation development. However, it was shown that the relationship between the average misorientation in grain and the RNOD (Relative Notch Opening Displacement) was independent of the creep and/or fatigue conditions. It is concluded that the misorientation analysis of damaged samples based on the EBSD method allows the prediction of the initiation and the growth behaviors of the creep and/or fatigue crack.