Mould walls inclination and dendritic morphology of CMSX-4 blades airfoils

The airfoils of single-crystalline turbine blades were studied. The blades made of industrial CMSX-4 superalloy were obtained by the Bridgman technique. Five different withdrawal rates (1-5 mm/min) were used. Series of as-cast samples were prepared by cutting the airfoils at different distances from the blade root. The metallographic sections, prepared for each cutting planes, were subjected to scanning electron microscopy observations and Laue diffraction studies. Macrostructure images of whole area of airfoil cross-sections were obtained by stitching several obtained SEM images. Morphology of dendrites in different area of cross-sections were analysed. The crystal orientation of each sample were determined by analysis of Laue pattern. It was found that the morphology of dendrites changes in the area, where the dendrite growth is limited by inclined mould walls.