PSI - Issue 80

Tomáš Vražina et al. / Procedia Structural Integrity 80 (2026) 244 – 255 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

247

4

Fig.1 Schematics of tested specimens. (a) Cylindrical specimen for Sanicro 25. (b) Flat specimen for FeAlOY.

Table 1. The chemical composition obtained by EDS for both material batches (wt. %). Element Fe Cr Ni Al Y

O

C

W

Nb 0.6

Sanicro25 FeAlOY

Bal. Bal.

21.1

25.7

-

-

-

2.0 2.5

3.4

4.2

-

8.9

3.8

1.4

-

-

Cyclic straining was conducted on 4 polished specimens for both alloys under total strain-controlled loading using a computer-controlled MTS 810 servo-hydraulic testing system operated via the MPE TestSuite software. Tests were performed in laboratory air at room temperature under fully reversed tension- compression conditions (R = −1), corresponding to symmetric cyclic loading. The total strain amplitude range selected for testing spanned from 0.3% to 0.45% as described in Table 2. A constant strain rate of 2 × 10⁻³ s⁻¹ was applied for Sanicro 25 and FeAlOY. Strain measurement and feedback control were achieved using an MTS axial extensometer with a gauge length of 8 mm, securely mounted to the specimen gauge section to ensure accurate strain control throughout the fatigue test. After fatigue test the small samples were extracted from fatigue specimens. Vertical cuts by saw were done in the gauge length.and 2 samples from each fatigue specimen were extracted. One sample for SEM-EBSD (electron backscatterd diffraction) observation and the second for STEM (Scanning transmission electron microscopy) observation also preserving the fractographical surface from the other half of fractured fatigue specimen. Fractographic and microstructural analyses were performed using a Tescan LYRA 3 XMH FEG/SEM. The chemical composition was determined with an UltimMax EDS detector. Grain size and crystallographic orientation were characterized using an EBSD detector, with data acquisition and post-processing conducted in Aztec software. For both materials, EBSD maps we re acquired over areas of 1000 × 1000 µm² with a step size of 1 µm to ensure comparability. The size of high-resolution maps was tailored to specific microstructural features. STEM imaging was conducted using a Thermo Scientific ™ Talos F200i transmission electron microscope equipped with a field emission gun and an EDS detector, with data processed using Velox software.

Table 2. Applied conditions for fatigue testing Testing conditions

Strain amplitude (%)

Period (s)

Frequency (s -1 )

Strain rate (s -1 )