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Effect of a circular notch on [001] tensile creep behavior of the Ni-base superalloy single crystal LEK 94 at 1020 °C

  • Ni-base superalloy single crystals have been used in turbine blades for hot sections of gas turbines for over four decades. In order to increase the efficiency of the turbines, a continuous increase in the inlet temperature of combustion gases into the turbine has driven the design of turbine blades to complicated shapes and the presence of a complex pattern of cooling channels. These three-dimensional shapes, together with the inhomogeneous distribution of stresses along the blade, induce an also complicated triaxial stress state, which does not compare to uniaxial tests that are performed to characterize high temperature properties such as creep. A round notch on a test piece represents a simple configuration that generates a quasi-isostatic stress state across the notch. In the present contribution, the effect of a sharp round notch on the microstructural micromechanisms within the notched region cylindrical bars, loaded along [001] at 1020 °C and 160 MPa net stress, is studied. ToNi-base superalloy single crystals have been used in turbine blades for hot sections of gas turbines for over four decades. In order to increase the efficiency of the turbines, a continuous increase in the inlet temperature of combustion gases into the turbine has driven the design of turbine blades to complicated shapes and the presence of a complex pattern of cooling channels. These three-dimensional shapes, together with the inhomogeneous distribution of stresses along the blade, induce an also complicated triaxial stress state, which does not compare to uniaxial tests that are performed to characterize high temperature properties such as creep. A round notch on a test piece represents a simple configuration that generates a quasi-isostatic stress state across the notch. In the present contribution, the effect of a sharp round notch on the microstructural micromechanisms within the notched region cylindrical bars, loaded along [001] at 1020 °C and 160 MPa net stress, is studied. To this end, a series of interrupted creep tests is conducted on plain and notched bars and the microstructure is compared. Results are discussed in terms of degree microstructural coarsening, and dislocation activity. The effect of notch generation via grinding is also discussed in these terms. The presence of carbides evolving in from residual carbon is also shown and discussed. .Funding by the German Research Association (DFG) [grant number AG 191/1] is acknowledgezeige mehrzeige weniger

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Metadaten
Autoren/innen:Leonardo Agudo Jácome
Dokumenttyp:Vortrag
Veröffentlichungsform:Präsentation
Sprache:Deutsch
Jahr der Erstveröffentlichung:2018
Organisationseinheit der BAM:5 Werkstofftechnik
5 Werkstofftechnik / 5.1 Materialographie, Fraktographie und Alterung technischer Werkstoffe
DDC-Klassifikation:Technik, Medizin, angewandte Wissenschaften / Ingenieurwissenschaften / Ingenieurwissenschaften und zugeordnete Tätigkeiten
Freie Schlagwörter:Creep; Electron microscopy; Microstructure; Multiaxial stress state; Superalloy single crystals
Themenfelder/Aktivitätsfelder der BAM:Material
Material / Degradation von Werkstoffen und Materialien
Veranstaltung:DGM-Arbeitskreis mechanisches Werkstoffverhalten bei hoher Temperatur
Veranstaltungsort:Hochschule Augsburg, Germany
Beginndatum der Veranstaltung:20.09.2018
Enddatum der Veranstaltung:20.09.2018
Verfügbarkeit des Dokuments:Datei im Netzwerk der BAM verfügbar ("Closed Access")
Datum der Freischaltung:26.09.2018
Referierte Publikation:Nein