High-temperature crack growth in a Ni-base superalloy during sustained load
Journal article, 2014

he high-temperature sustained load crack growth behaviour of a Ni-base superalloy was investigated using a combination of mechanical testing in controlled atmosphere, fractographical and microanalytical investigations, and finite element modelling. The results show that the local crack front geometry is un- even on two scales – jaggedness on the scale of 100 μm was observed in all specimens, whereas mm- scale waviness could occasionally be observed. The jaggedness can be explained by a percolation-type crack growth along weaker grain boundaries, whereas the large-scale waviness is presumably due to larger regions of the material having specific grain texture with high crack growth resistance. The un-even crack front is shown to potentially have considerable effects on the loading conditions at the crack tip, whereas ligaments of un-cracked material in the crack wake are deemed to have less effect on the crack tip loading due to their low area fraction. The ligaments fail intergranularly in the wake as the crack grows in the present case, as opposed to by creep fracture as previously proposed. Finally, the plastically deformed regions about the crack and crack tip are shown not to exhibit any elevated oxygen levels, implying that the damage in these regions is purely mechanical.

Sustained load crack growth

Superalloy

Mechanical properties

Grain boundaries

Author

Magnus Hörnqvist

Chalmers, Applied Physics, Materials Microstructure

Leif Viskari

Chalmers, Applied Physics, Materials Microstructure

Katie L. Moore

University of Oxford

Krystyna Marta Stiller

Chalmers, Applied Physics, Materials Microstructure

Materials Science & Engineering A: Structural Materials: Properties, Microstructure and Processing

0921-5093 (ISSN)

Vol. 609 131-140

Subject Categories

Materials Engineering

Other Engineering and Technologies

Other Materials Engineering

Metallurgy and Metallic Materials

Areas of Advance

Materials Science

DOI

10.1016/j.msea.2014.04.102

More information

Latest update

10/15/2018