Casting micro-porosity growth in single-crystal superalloys

Finite element (FE) analysis is employed to investigate casting micro-porosity growth in nickel-base single-crystal superalloys. Based on finite deformation rate-dependent crystallographic constitutive equation, the simulation of casting micro-porosity in three-dimensional unit cell model is carried out under variation in a range of parameters including triaxiality, Lode parameter, type of slip systems activated and Loading orientation. The FE results show that large local cumulative shear strain around casting micro-porosity plays an important role for driving casting micro-porosity growth, the high casting micro-porosity volume fraction corresponds to large cumulative shear strain. The type of slip systems activated has remarkable effect on casting micro-porosity growth, so it is very important to determine the operative slip systems for predicting the life of hot section. The growth of casting micro-porosity is related to crystallographic orientation, because different orientation is associated with different Schmid factor, the Young's modulus and slip systems activated. That is to say, according to load case of hot section, to choice a properly crystallographic orientation is necessary.