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

Latin America: The Region without Catalonia

The aim of this article is to analyse the issue of “weak separatism” in Latin America as well as to give an answer to the question why there are no significant separatist movements in this region. The authors provide the definitions of separatism and secessionism as well as an explanation of these phenomena. Moreover, they present an overview of historical and contemporary separatist movements in Latin America. Based on Horowitz’s theory of ethnic separatism, the authors attempt to analyse the separatist movement “The South is My Country” in Brazil and compare it with separatism in Catalonia in Spain, where a referendum on independence from Spain was held in 2017, serving as an impetus for a similar referendum that took place in the South of Brazil. In spite of similar goals of these two separatist movements, the authors argue that there are significant differences in their nature, which are determined by the history and culture of the respective countries

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

Primary crystal orientation of the thin-walled area of single-crystalline turbine blade airfoils

The thin-walled airfoil areas of as-cast single-crystalline turbine blades made of CMSX-4 superalloy were studied. The blades were produced by the industrial Bridgman technique at withdrawal rates of 2, 3 and 4 mm/min. The angle between the [001] crystallographic direction and blade axis, related to the primary orientation, was defined by the Ω-scan X-ray diffraction method at points on the camber line located near the tip of an airfoil and at points of a line located in parallel and near the trailing edge. Additionally, primary crystal orientation was determined by Laue diffraction at the selected points of an airfoil. The influence of mould wall inclination on the primary crystal orientation of the thin-walled areas is discussed. The effect of change in the [001] crystallographic direction, named as "force directing", was considered with regard to the arrangement of primary dendrite arms in relation to the trailing edge and the camber line. It was stated that when the distance between the mould walls is less than the critical value of about 1.5 mm the "force directing" increases as the distance between the walls of the mould decreases. The effect may be controlled by selecting an appropriate secondary orientation using a seed crystal in the blade production process. The model of dendrite interaction with the mould walls, including bending and "deflection", was proposed