Analysis of CMSX-4 single-crystalline turbine blades root by electron and X-Ray diffraction methods

Abstract

The root of single-crystalline turbine blade made of CMSX-4 superalloy were studied. The studied blade was produced by the Bridgman technique in industrial ALD furnace at withdrawal rate of 3 mm/min. The samples for investigations were cut from the blade root parallel to the withdrawal direction. Metallographic sections of longitudinal samples planes were prepared for further investigations. The samples were analysed using scanning electron microscopy and the Laue diffraction studies. The crystal orientations in macro-scale were determined by analysis of the Laue pattern and local crystal orientations were studied by electron backscattered diffraction technique. Morphology of dendrites were examined by analysis of scanning electron microscopy macro-images. Study of subgrain structure was performed by X-ray diffraction topography. The sharp parallel contrast bands, visible on the X-ray topograms, were related with dendrite cores, arranged with the same direction. Additionally, the low angle boundaries were formed in certain samples, visible on the topograms as contrast shifts. Step changes of local crystal orientation in certain areas were observed on the electron backscattered diffraction maps. The electron backscattered diffraction crystal orientation maps were related to the misorientation visualized in topograms.