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Fourth-generation single crystal nickel base superalloy for jet engine turbine blades application. 3D imaging and metrology of microstructure elements

Ziętara Maciej, Kruk Adam, Cempura Grzegorz, Gruszczyński Adam, Czyrska-Filemonowicz Aleksandra

Inżynieria Materiałowa

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2020

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Vol. 41, nr 3

12--17

EN

Fourth-generation single crystal nickel base superalloy (PWA 1497) used for turbine blades application were subjected to three-dimensional micro- structural analysis. The FIB-SEM tomography was performed on the as received and creep deformed samples in order to visualize and quantify the microstructure elements of γ and γ’ phases. The results of 3D microstructural quantitative analysis were compared with the complementary results obtained by means of 2D TEM analysis. It was demonstrated that for modern single crystal nickel base superalloys, the measurements of the relative area fraction (A A) of γ’ phase in 2D images are adequate for measurements of the volume fraction (V V ) of this phase (A A ≅ V V ). Microstructural changes of the investigated superalloy revealed in 3D space were found to be much more complex than images of this microstructure obtained by electron microscopy techniques in two-dimensional space (2D).

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Microstructure analysis in the creep process of a gas turbine blade of the turbine engine

Błachnio J., Kułaszka A., Ziętara M., Czyrska-Filemonowicz A.

Combustion Engines

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2016

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R. 55, nr 2

41--45

EN

The technical condition of gas turbine blades of the turbine engine has a significant impact on the reliability and life span of the turbine and the entire engine. In order to assess the blades’ technical condition, a visual method, with the use of optoelectronic devices, is used. In order to verify this assessment, metallographic tests are conducted. The paper presents the results of microstructural tests of the turbine rotor blades made of nickel-based monocrystalline super alloys. The aim of these tests was to determine the consequences of impacting high exhaust gas temperature and stresses occurring during operation on the stability of the blade microstructure. The progress level of the blade microstructure changes in the post-operational stage for different sections towards the blade vertical axis and was compared with the blade microstructure on delivery made of the same super alloy. A varied degree of the microstructure degradation for different blade sections was shown. The changes typical of the high-temperature creep process – γ' phase directional growth (rafting), were observed only for the thinnest walls of the upper section of the turbine blade leaf.

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Characterization of microstructure evolution during high temperature creep of CMSX-4 superalloy by TEM, HRSTEM and high spatial resolution EDX mapping

Dubiel B., Czyrska-Filemonowicz A.

Inżynieria Materiałowa

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2013

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Vol. 34, nr 3

153--156

EN

Microstructural analysis ofCMSX-4 single nickel-base superalloy have been performed to investigate the mechanisms controlling its creep deformation at high temperature. The attention was focused on the examination of the dislocation networks and the chemical elements partitioning between the y and y' phases. The results of TEM investigations shown that in the primary creep stage at 950°C/185 MPa the dislocation networks are formed by reactions between dislocations. Initially unstable networks are converted into stable conﬁgurations, containing dislocations, which cannot move by slip. High spatial resolution EDX mapping allowed the investigation of chemical composition at nanoscale. It was determined, that heat treated CMSX-4 superalloy the y phase contains Co, Cr, Re as well as Ni and W. The content of Ni and W in y phase is smaller than in y' phase, which contains also Al, Ti and Ta. During the high temperature creep of CMSX-4 the morphological change of the y' particles from cubes to plates, called rafting, occurs. The increased concentration of Co and Cr at y-y' interfaces in CMSX-4 with rafted microstructure was observed. It was postulated that the observed segregation can be related with the diffusion of Co and Cr, associating dissolution of vertical y phase channels during rafting.

PL

W celu zbadania mechanizmów wysokotemperaturowego pelzania monokrystalicznego nadstopu niklu CMSX-4 przeprowadzono badania zmian mikrostruktury metodami mikroskopii elektronowej. Szczególną uwagę zwrócono na budowę siatek dyslokacyjnych oraz podział pierwiastków chemicznych pomiędzy fazy y i y'. Wyniki badań metodami TEM wykazały, że w pierwszym stadium pełzania w 950°C/185 MPa tworzą się siatki dyslokacyjne na skutek reakcji pomiędzy dyslokacjami. Początkowo niestabilne siatki dyslokacyjne ulegają przebudowie do konﬁguracji stabilnych, zawierających dyslokacje, które nie mogą się poruszać przez poślizg. Mapy rozmieszczenia pierwiastków uzyskane za pomocą STEM-EDX z wysoką rozdzielczością przestrzenną umożliwiły zbadanie składu chemicznego w nanoskali. Stwierdzono, że w nadstopie CMSX-4 w stanie obrobionym cieplnie faza y zawiera Co, Cr, Re oraz Ni i W. Zawartość Ni i W w fazie y jest mniej sza niż w fazie y', która zawiera również Al, Ti i Ta. Podczas wysokotemperaturowego pełzania w mikrostrukturze nadstopu CMSX-4 zachodzi zmiana kształtu wydzieleń fazy y' z sześciennego na płytkowy, nazywana raftingiem. Po raftingu na granicach międzyfazowych y-y' zaobserwowano zwiększone stężenie Co i Cr. Segregacj a Co i Cr do granic y-y' jest prawdopodobnie związana z rozpuszczaniem się pionowych kanałów fazy y podczas raftingu.