High-Resolution Diffraction Imaging of Misorientation in Ni-Based Single Crystal Superalloys
In the present work, the novel high-resolution X-ray diffraction technique for imaging misorientation and mosaicity in single crystal superalloys is introduced. The technique is based on classical X-ray diffraction topography geometries combined with high
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Abstract
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In the present work, the novel high-resolution X-ray diffraction technique for imaging misorientation and mosaicity in single crystal superalloys is introduced. The technique is based on classical X-ray diffraction topography geometries combined with high-resolution diffraction and post-processing of obtained data including color coding and 3D projections of each diffraction images. For the investigations, the single crystal rods were produced from CMSX-4 superalloy at a withdrawal rate of 1, 3, 5, and 7 mm⋅min−1. The high spatial and angular resolution of the method allows to visualize the complex nature of mosaicity present in single crystal superalloys. It was observed that mosaics blocks differ in size and misorientation on the multi-scale level from the small present in dendrite arms, through single dendrites, group of dendrites, up to subgrains. Measurements of misorientation were done on cross and longitudinal sections of the castings. It was proved that increasing withdrawal rate influences the mosaicity structure and mechanisms of its evolution. Solidification at withdrawal rates from 1 to 5 mm⋅min−1 possesses higher misorientation between dendrites. With higher misorientation between dendrites, when the widening of solidification front occurs, the mosaicity spreads across the casting in the form of misoriented dendrite lines as the solidification progress by growing long secondary dendrite arms. Also, it was stated that 3–5 mm⋅min−1 rates possess a higher possibility of creation of subgrains or selector grains defects in the casting.
Single crystal Ni-based superalloys X-ray diffraction imaging Misorientation Mosaicity
R. Albrecht (&) M. Zubko Institute of Materials Science, University of Silesia, 75 Pułku Piechoty 1A, 41-500 Chorzów, Poland e-mail: [email protected] K. Gancarczyk D. Szeliga Department of Materials Science, Rzeszow University of Technology, Al. Powstancow Warszawy 12, 35-959 Rzeszow, Poland
Introduction The materials design for high-pressure turbine blades is a vast challenge for the scientist since the first commercially built gas turbine [1]. Such materials must withstand operation under severe conditions such as heavy mechanical loads, high temperature, and oxidizing gas environments. Since the early days of development, it became clear that nickel-based alloys are the most promising group of materials possessing excellent high-temperature properties [2]. Nowadays, the commercially used superalloys contain approximately ten chemical elements with rare earth additions and well-controlled level of impurities. The exact chemical composition of superalloys evolves with its manufacturing technology [3]. The manufacturing process of the turbine blades critical components became sophisticated to the level of single crystals casting from multi-component alloys. The nomenclature was taken directly from a typical single crystal growth process, however, the technology and microstructure behind superalloys are much different [4, 5]. The obtained single cry
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