3D Data for Fatigue in Superalloys
11
4 Targeted 3D Data
The microstructural configuration (neighborhood) is demonstrated to be influential
to the initiation of fatigue cracks [6, 7, 9, 82]. A postmortem analysis of fatigue
samples is a good way to identify systematic microstructural characteristics that
result in fatigue cracks. Samples of René 88DT were cycled with fully reversed
loading and then interrupted at 80% lifetime (R = −1, 1 Hz, peak load 758 MPa)
such that the regions surrounding the initiated fatigue cracks could be investigated.
Previous work has shown that this polycrystalline superalloy spends much of its life
(80%) initiating cracks [82], before they propagate into the next few grains and then
begin short crack-type growth.
A dataset was gathered in the TriBeam system from a region where a typical
fatigue crack had initiated. The FIB was used to clean a 250-μm-wide region after
femtosecond laser ablation using a 15 nA, 30 kV Ga + beam at an angle of 3 ◦ to
the surface. Although EBSD maps containing high-quality diffraction patterns are
obtainable from the laser-ablated surface in René 88DT, FIB cleaning was still
performed in order to guarantee that small and thin twin features (<1 μm) were
well resolved. The total collection time per slice was 53 min, with 28 min EBSD
collection, 20 min FIB, and the balance stage movements and SEM imaging. The
dataset is comprised of 127 slices collected at a 0.75 μm slice thickness and 0.3 μm
EBSD resolution.
Both the 3D fatigue crack location and the microstructural neighborhood at the
surface and subsurface were reconstructed. Twin boundaries are visible adjacent to
the crack initiation location in Fig. 7, as expected based on the room temperature
Fig. 7 A region containing a crack (a) was identified and a targeted 3D dataset collected beneath
(b) in order to investigate the microstructure and local loading conditions leading to failure. The
3D dataset is 200 × 120 × 90 μm with a 0.75 μm slice thickness and 0.3 μm EBSD resolution.
The crack initiating twin related domain (c) and the crack path (d) are shown along with the
microstructure surrounding the crack path (e)
11
4 Targeted 3D Data
The microstructural configuration (neighborhood) is demonstrated to be influential
to the initiation of fatigue cracks [6, 7, 9, 82]. A postmortem analysis of fatigue
samples is a good way to identify systematic microstructural characteristics that
result in fatigue cracks. Samples of René 88DT were cycled with fully reversed
loading and then interrupted at 80% lifetime (R = −1, 1 Hz, peak load 758 MPa)
such that the regions surrounding the initiated fatigue cracks could be investigated.
Previous work has shown that this polycrystalline superalloy spends much of its life
(80%) initiating cracks [82], before they propagate into the next few grains and then
begin short crack-type growth.
A dataset was gathered in the TriBeam system from a region where a typical
fatigue crack had initiated. The FIB was used to clean a 250-μm-wide region after
femtosecond laser ablation using a 15 nA, 30 kV Ga + beam at an angle of 3 ◦ to
the surface. Although EBSD maps containing high-quality diffraction patterns are
obtainable from the laser-ablated surface in René 88DT, FIB cleaning was still
performed in order to guarantee that small and thin twin features (<1 μm) were
well resolved. The total collection time per slice was 53 min, with 28 min EBSD
collection, 20 min FIB, and the balance stage movements and SEM imaging. The
dataset is comprised of 127 slices collected at a 0.75 μm slice thickness and 0.3 μm
EBSD resolution.
Both the 3D fatigue crack location and the microstructural neighborhood at the
surface and subsurface were reconstructed. Twin boundaries are visible adjacent to
the crack initiation location in Fig. 7, as expected based on the room temperature
Fig. 7 A region containing a crack (a) was identified and a targeted 3D dataset collected beneath
(b) in order to investigate the microstructure and local loading conditions leading to failure. The
3D dataset is 200 × 120 × 90 μm with a 0.75 μm slice thickness and 0.3 μm EBSD resolution.
The crack initiating twin related domain (c) and the crack path (d) are shown along with the
microstructure surrounding the crack path (e)