The Influence of Surface Roughness on Freckle Formation in Directionally Solidified Superalloy Samples

A series of directional solidification experiments with superalloy CMSX-4 was carried out with various surface profiles. The results obtained clearly demonstrate the influence of surface features on the occurrence of freckles. The rough surfaces exhibit less freckling tendencies than smooth surfaces. For a notch depth larger than the critical layer beneath the surface, the freckle formation can be completely suppressed. The freckle formation is...