Effect of Recrystallization on Crack Initiation and Propagation during Creep in a Directionally Solidified Ni-Based Superalloy

Abstract

Crack initiation and propagation during creep test in a recrystallization (RX) grain containing directionally solidified (DS) nickel-base superalloy was studied by employing electronic backscattered diffraction (EBSD) technique. Creep samples were locally deformed and then heat treated to get local RX at the center of the gauge length. Creep test was carried out at 980 °C/235 MPa. It was found that during creep test, precipitate free zones (PFZ) were formed along the RX grain boundary and the cracks were initiated and propagated along the interface (a) between PFZ and RX grains, (b) between PFZ and the matrix or (c) within PFZ. It indicated that the crack initiation and the propagation were crystal orientation dependent.