PSI - Issue 43

Vít Horník et al. / Procedia Structural Integrity 43 (2023) 136–141 Author name / Structural Integrity Procedia 00 (2022) 000 – 000

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at low-stress amplitudes. The scatter of the fatigue lifetime corresponds to the defect size previously documented by Kunz et al. (2012). The optimization of the casting procedure or addition of HIP treatment leads to significant suppressing of the casting defects and subsequently the improvement of high-cycle fatigue performance.

Fig. 5. Fracture surfaces of IN 738LC superalloy specimens after cycling at 900 °C

a) σ a = 260 MPa, N f = 1.6 × 10

5 cycles; b) σ

a = 200 MPa, N f = 2.9 × 10

6 cycles, defect size = 2.6 mm.

Fig. 6. Fracture surfaces of IN 738LC superalloy specimens after cycling at 950 °C

a) σ a = 200 MPa, N f = 5.2 × 10

5 cycles; b) σ

a = 160 MPa, N f = 5.0 × 10

6 cycles, defect size = 955 µm.

The influence of testing temperature on crystallographic stage I regime fatigue crack propagation was observed on the fracture surfaces. The facets were observed on the fracture surfaces of all specimens fractured at 800 °C. The crack