Effects of secondary orientation on fatigue crack initiation in a single crystal superalloy

Effects of secondary orientation on plastic deformation and crack initiation in a nickel-based single crystal superalloy were investigated based on in-situ scanning electron microscope fatigue tests and crystal plasticity finite element simulations. Specimens in 2 kinds of secondary crystal orientations were tested at 600 degrees C. The results show that specimens exhibit different crack initiation modes. For specimen [001]/ [010], the crack initiated from a region of high density slip traces at an angle of 45 degrees to the load axis and propagated along the 45 degrees slip line. For specimen [001]/ [110], the crack initiated from a slip line that is perpendicular to the loading axis and propagated along the horizontal direction. A crystal plasticity finite element model is used to predict the cyclic plastic behavior of nickel-based single crystal superalloy. The slip line distributions, the location of the crack initiation, the crack propagating direction, and the crack deflection position are preferably predicted in comparison to the experimental results.