Crystal perfection studies of single crystal superalloy turbine blades by X-Ray diffraction methods

In the paper the crystal structure of single crystal CMSX-4 blade casts, applied in high pressure turbine of aircraft engines was analyzed. The longitudinal section of blade, cast at withdrawal rate of 3 mm/min was used as a sample. During the conducted research, following X-ray diffraction methods were applied: EFG -scan, Auleytner X-ray topography and analysis of diffraction reflex profile (“rocking curve”). The authors determined crystal orientation in entire blade casts on the basis of set criterion concerning values of angle — deviation of [001] direction from the direction of cast withdrawal. Conclusions concerning the crystal structure quality of the blade were drawn based on results from three different research methods. Local changes in crystal orientation on the surface of blade cast, also areas with significant structure defect degree and the presence of internal stresses were characterized

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

Characterization of casting defects in the single crystal turbine blade airfoil

In the paper turbine blades made from single crystal CMSX-4 superalloy were investigated by X-ray diffraction methods (topography, -scan mapping) complemented by scanning electron microscopy observations. By the X-ray diffraction topography method several misorientation defects were visualized as well as dendrites arrangement. It was discussed that tip of the airfoil and thin walled area of the turbine blades located near the trailing edge can accumulate more growth defects than other airfoil part, due to the complex shape of the mould

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

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

Dendrite growth in selector-root area of single crystal CMSX-4 turbine blades

The single crystal turbine blades made of CMSX-4 nickel-based superalloy were studied. The turbine blades were obtained by the Bridgman technique with withdrawal rate of 5 mm/min. The samples, cut-off from root part of blades and containing the fragment of the selector, were studied. The effect of selector geometry on the dendrites growth and defects formation in the selector-root area of the blade were analyzed. The Laue diffraction, scanning electron microscopy, and X-ray diffraction topography were applied. It was found that, during crystallization of the selector, the dendrite cores, after reaching the surface of mould, may bend, if the angle between dendrite cores and the mould surface was equal to 12 . When the angle was equal to 24 the growth of dendrites has been stopped. It can be stated that the defects, which appeared in the selector were inherited by the root part

Effect of creep on crystallographic orientation in single crystal superalloy

The creep-rupture tests were performed on a single crystal rods made of CMSX-4 superalloy obtained at withdrawal rates of 3 and 5 mm/min. After the rupture the microstructure and fracture surface were examined and correlated with X-ray crystal rotation measurements by the -scan method. The conclusions about the crystal lattice rotation during creep test were provided