Fatigue life assessment of a porous casting nickel-based superalloy based on fracture mechanics methodology

Inherent defects induced in casting process seriously affect mechanical performance and fatigue properties of the material. Micro-structural investigations reveal that the grain size and dendrite microstructure are sensitive to casting processes and change materials property. The fatigue performance of the material decreases with porosity and is characterized by distributed voids on grain boundaries. Fatigue cracks nucleated from casting defects dominate the whole fatigue failure process. A developed fatigue micro-crack model based on Paris' law can be used to calibrate low cycle fatigue property of the casting material with different microstructures and agrees with experimental results well.