Prediction of freckle formation in directionally solidified CMSX-4 superalloy

Freckle defects appearing on the industrial gas turbine blade reduce the high temperature mechanical properties. It is necessary to predict the freckle formation on the castings before the directional solidification. In this paper, the relationship of fluid flow and crystal growth during the vertical directional solidification was analysed. Based on the analysis, a simple method considering the solidification conditions and concaved solidification interface was proposed to predict the freckle formation. The method was verified with specimens and dummy blade under the experimental environments. The validation results show that the method can predict where the freckle may appear on a casting with a large size and complex shape for directionally solidified CMSX-4 superalloy.