Microcrack initiation behavior around film cooling holes in a Ni-based single crystal: In situ observation and crystal plastic analysis

The microcrack initiation behavior around the film cooling holes (FCHs) of a Ni-based single crystal was investigated by in situ tensile experiments and crystal plasticity simulations, in which the hardening effect was considered. The effect of FCHs on the tensile strength and plasticity localization was determined according to experimental results. Multisource microcracks that initiated along the slip bands around the FCHs and the kink shear bands were observed. The macrocrack path characterized the features of instantaneous and crystallographic fractures, as confirmed by the fracture surface morphology. The slip bands along which the crack initiated were determined by identifying the activation type of the octahedral slip family using the crystal plasticity finite element method (CPFEM). The simulation results were found to be in excellent agreement with the experimental results. Plastic deformation mainly occurred around the FCHs where the dominant slip systems were activated, which were defined as the dominant slip sectors in this study. The resolved shear stress (RSS) induced microcracks around the FCHs along the (-11-1) [011], (-1-11) [011], (1-1-1) [0–11], and (111) [0–11] slip bands in the dominant slip sectors.