Fatigue life and initiation mechanisms in wrought Inconel 718 DA for different microstructures

Meriem Abikchi (1, 2) , Thomas Billot (3) , Jérôme Crépin (1) , Arnaud Longuet (2) , Caroline Mary (2) , Thilo F. Morgeneyer (1) , André Pineau (1)

1 MAT - Centre des Matériaux
2 SNECMA Villaroche [Moissy-Cramayel]
3 SNECMA Gennevilliers [Colombes]

Wrought Inconel 718 DA superalloy disk zones present a wide range of behavior in fatigue life due to the variability of the microstructure. In order to link the effect of the forging conditions and achieved microstructure to the fatigue life, two microstructures have been tested in fatigue. Fatigue tests under strain control were performed at 450°C. Grain size distributions and phase distributions were characterized in the specimens and related to fatigue failure initiation modes. Fatigue crack initiation was seen to occur on large grains in stage I for the larger grain material whereas for the material with slightly smaller grains initiation from internal nitrides caused failure via so-called fish-eye cracks. The different steps of these failure modes are discussed using data from the literature to gather the ingredients for a quantitative assessment of the fatigue lifetime using fracture mechanics.

Mots clés: Inconel 718; Microstructure; Fatigue; Crack initiation; Propagation mechanism

Domaines: Sciences de l'ingénieur [physics]; Matériaux

Meriem Abikchi, Thomas Billot, Jérôme Crépin, Arnaud Longuet, Caroline Mary, et al.. Fatigue life and initiation mechanisms in wrought Inconel 718 DA for different microstructures. 13th international conference on fracture, Jun 2013, Beijing, China. 11 p. ⟨hal-00853448⟩