Filtern
Erscheinungsjahr
Dokumenttyp
- Zeitschriftenartikel (9)
- Beitrag zu einem Sammelband (9)
- Vortrag (8)
- Posterpräsentation (2)
Schlagworte
- Creep (9)
- Superalloys (8)
- CMSX-4 (3)
- Nickel alloys (3)
- Nickel-base superalloys (3)
- Rafting (3)
- Creep damage (2)
- Dendritic structure (2)
- Misfit (2)
- Porosity (2)
Eingeladener Vortrag
- nein (8)
Creep damage of single-crystal nickel base superalloys: mechanisms and effect on low cycle fatigue
(2010)
The main mechanisms of creep damage of single-crystal nickel-base superalloys are the loss of the interface coherency, coarsening of the γ / γ'-microstructure, precipitation of topologically closed packed phases and growth of porosity. This degradation deteriorates the mechanical properties such as yield stress, creep lifetime and especially low-cycle fatigue life, which can be reduced nearly by a factor of 10. The degradation kinetics during creep was characterised quantitatively on the superalloy CMSX-4. A new non-destructive testing technique was applied to cover a wide test parameter range with few specimens in a relatively short time: repeated load annealing of wedge shaped specimens.
A new technique for investigation of interfacial dislocations in nickel-base superalloys by scanning electron microscopy is presented. At high temperatures the pressure of interfacial dislocations against the γ/γ'-interface causes grooves. This 'fingerprint of the dislocation network' is visualized by deep selective etching, which removes the γ'-phase down to the γ/γ'-interface. Compared with transmission electron microscopy, the proposed method has important advantages: observation of large sample areas, no superposition of dislocations lying in different specimen depths, possibility of three-dimensional view of dislocation configurations, information about the dislocation mobility, reduced time for preparation and visualization. The method can be applied for multiphase materials where the interface is grooved by interfacial dislocations.