Influence of Crystal Orientation on the Freckle Formation in Directionally Solidified Superalloys

De Xin Ma; Michael Mathes; Bin Zhou; Andreas Bührig-Polaczek

doi:10.4028/www.scientific.net/AMR.278.114

Paper Titles

Some Deformation Micromechanisms in Ni-Based Superalloys Evidenced Using TEM In Situ Experiments
p.90

Effect of the Particle Size of γ’ Phase on the Mechanical Properties of Ni Base Superalloy
p.96

Characterization of Residual Stresses in 718 Turbine Discs by Neutron Diffraction and Finite Element Modelling
p.102

Cooling Rate Dependent Morphology of the γ' Precipitates in Nickel-Base Superalloy Udimet 500
p.108

Influence of Crystal Orientation on the Freckle Formation in Directionally Solidified Superalloys
p.114

The Microstructure Changes in IN713LC during the Creep Exposure
p.120

Effect of Elastic Driving Force on the Evolution of Microstructures in the Secondary Creep Stage
p.126

Change in Microstructure at Grain Boundaries with Creep Deformation of Polycrystalline Nickel-Based Superalloy IN-100 at 1273K
p.132

Change in Gamma Prime Morphology and Dislocation Substructures of Single Crystal Nickel-Based Superalloy, CMSX-4, Pre-Crept at 1273K-400MPa with Simple Aging
p.138

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Influence of Crystal Orientation on the Freckle Formation in Directionally Solidified Superalloys

Abstract:

Freckle occurrence is known to be dependent on the casting size and the superalloy components with large cross section are more prone to freckle formation. In our directional solidification experiment of superalloys freckles are observed in some thin samples, while some significantly thicker samples in the same shell mould cluster remain freckle free. The EBSD analysis shows that the samples with freckles have a good <001> axial orientation, while in freckle free samples the primary dendrite stems diverge from the sample axis. In an analogue system the flow behaviour through a mushy zone was simulated, in which the dendrite network was placed in different orientation. The <001> dendrite array shows the lowest resistance to the vertical melt flow. As the dendrite alignment diverges from <001> orientation, the flow speed slows down and reaches the minimum at the <111> orientation. This orientation effect of the interdendritic permeability explains well why the crystal orientation plays such an important role in the occurrence of freckles in superalloy castings.

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