Wyniki 1-2 spośród 2 dla zapytania: authorDesc:"Robert Albrecht"

Sposób oceny doskonałości struktury krystalicznej monokrystalicznych odlewów łopatek z nadstopu niklu CMSX-4 DOI:10.15199/28.2015.6.1


  Novel method for the measurement of crystalline perfection in single crystal turbine blades made of CMSX-4 superalloy The paper presents novel method for crystal perfection investigation in single crystal turbine blades both as-cast and after heat treatment. The castings were made of CMSX-4 superalloy and cast by the Bridgman method at the withdrawal rate of 3 and 5 mm/min. Evaluation of crystal perfection was based on measurements of alfa angle - the angle between crystallographic growth direction [001] and the main axis of the blade z. The investigation was conducted with the use of X-ray diffraction method called Ω-scan, utilizing prototype OD-EFG diffractometer invented by EFG company (Berlin). The apparatus enables determination of the crystal orientation in the root and airfoil of turbine blade made of nickel based superalloys. The size of the measuring spot was about approx. 2 mm2 and by this size, the orientation of whole surface of turbine blade can be mapped with an accuracy of ±0.01°. It was found that increase of withdrawal rate from 3 to 5 mm/min caused a reduction in the average value of α angle from 6.5 to 4°. The scatter of α angle for both withdrawal rates is similar. Heat treatment of casting resulted in an increase of α angle to 8.5° for withdrawal rate 3 mm/min and 6.5° for 5 mm/min. The scatter of orientation decreased to 1.8 and 1.6° respectively. Key words: nickel-based superalloys, single crystal, turbine blades, CMSX-4, crystal orientation. W pracy przedstawiono ocenę doskonałości struktury krystalicznej monokrystalicznych odlewów łopatek turbiny wysokiego ciśnienia silnika lotniczego w stanie lanym oraz po obróbce cieplnej. Odlewy wytworzono z nadstopu niklu CMSX-4 metodą Bridgmana z prędkością wyciągania formy 3 i 5 mm/min. Podstawą oceny doskonałości struktury krystalicznej odlewów była analiza wyników pomiarów kąta odchylenia pomiędzy kierunkiem wyciągania i kierunkiem kryst[...]

Microstructural characterization of creep in the single crystal superalloy CMSX-4 DOI:10.15199/28.2017.1.3


  Blades and vanes structural components of turbine engines are processed to withstand high temperature during loading conditions of service, fulfilling high standards of quality control and safety for effective use. Therefore, characterization of mechanical properties, such as creep behaviour, are necessary for appropriate control procedures on prediction of exploitation lifetime. The materials mostly used in manufacturing of these components are single crystal nickel-base superalloys. Creep behaviour characterization, composed of creep-rupture tests, were performed on a single crystal rods made of CMSX-4 superalloy obtained at a withdrawal rate of 3 and 5 mm/min. Cylindrical rods were directly solidified in the [001] direction in an ALD Vacuum Technologies investment casting furnace (VIM-IC 2). Then, prepared specimens were tested in tensile creep under constant stress of 248 MPa at a temperature of 982°C. The longitudinal and cross sections from tested samples, were characterized by TEM and X-ray diffraction methods. It was found that all samples showed a similar rupture mechanism. The electron backscatter diffraction (EBSD) measurements showed that octahedral and cubic slip systems were present however, the critical stress was present on {111} planes. It was observed that the cubic slip has the highest calculated Schmid factor along the dendrite cores while the octahedral slip occurs through entire sample volume. Samples obtained at 5 mm/min possess a visible widening of coherent scattering regions as shown in inverse pole figures. The reason of these changes is the fact that higher rate has the greatest probability of creating small angle boundaries, often occurring in the interdendritic channels. Key words: CMSX-4, single crystal, superalloy, creep.1. INTRODUCTION Single crystal superalloys are widely used in the hot section of gas turbines due to their excellent resistant for creep, fatigue and oxidation at high temperature [1]. They ar[...]

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