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Materials 2019, 12(6), 870; https://doi.org/10.3390/ma12060870

Defect Creation in the Root of Single-Crystalline Turbine Blades Made of Ni-Based Superalloy

1
Institute of Materials Science, University of Silesia in Katowice, 1A 75 Pulku Piechoty St., 41-500 Chorzów, Poland
2
Department of Materials Science, Rzeszow University of Technology, 2 Wincentego Pola St., 35-959 Rzeszów, Poland
*
Author to whom correspondence should be addressed.
Received: 31 January 2019 / Revised: 1 March 2019 / Accepted: 12 March 2019 / Published: 15 March 2019
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Abstract

An analysis of the defects in the vicinity of the selector–root connection plane occurring during the creation of single-crystalline turbine blades made of CMSX-6 Ni-based superalloy was performed. X-ray diffraction topography, scanning electron microscopy, and positron annihilation lifetime spectroscopy were used. Comparing the area of undisturbed axial growth of dendrites to the area of lateral growth concluded that the low-angle boundaries-like (LAB-like) defects were created in the root as a result of unsteady-state lateral growth of some secondary dendrite arms in layers of the root located directly at the selector–root connection plane. Additional macroscopic low-angle boundaries (LABs) with higher misorientation angles were created as a result of concave curvatures of liquidus isotherm in platform-like regions near selector–root connections. Two kinds of vacancy-type defects, mono-vacancies and vacancy clusters, were determined in relation to the LABs and LAB-like defects. Only mono-vacancies appeared in the areas of undisturbed axial growth. Reasons for the creation of macroscopic LABs and LAB-like defects, and their relationships with vacancy-type defects were discussed. View Full-Text
Keywords: superalloy; Bridgman technique; positron annihilation lifetime spectroscopy (PALS); vacancy-type defects; X-ray topography; defects; lateral growth; dendrite array; low-angle boundaries superalloy; Bridgman technique; positron annihilation lifetime spectroscopy (PALS); vacancy-type defects; X-ray topography; defects; lateral growth; dendrite array; low-angle boundaries
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Krawczyk, J.; Paszkowski, R.; Bogdanowicz, W.; Hanc-Kuczkowska, A.; Sieniawski, J.; Terlecki, B. Defect Creation in the Root of Single-Crystalline Turbine Blades Made of Ni-Based Superalloy. Materials 2019, 12, 870.

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