Some New Observations on Freckle Formation in Directionally Solidified Superalloy Components

To improve the understanding of freckle formation in superalloys, several directional solidification experiments were carried out in a production-scale Bridgman furnace. During the careful inspections of the many cast specimens, several interesting phenomena were observed, indicating new aspects of freckle formation. Accordingly, several new factors influencing the freckle formation, such as the shadow effect, the edge effect, the step effect, and the crystal orientation effect, are proposed. This will contribute to our current understanding of freckle formation and the future development of new measures to minimize freckle defects in directionally solidified components of superalloys.

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