Stress-Strain Response and Fatigue Lifetime of EEQ-111 Superalloy in Cyclic Loading at High Temperatures

0582280 - ÚFM 2025 RIV NL eng C - Konferenční příspěvek (zahraniční konf.)
Šulák, Ivo - Obrtlík, Karel
Stress-Strain Response and Fatigue Lifetime of EEQ-111 Superalloy in Cyclic Loading at High Temperatures.
Procedia Structural Intergrity. Vol. 52. Amsterdam: Elsevier, 2024 - (Aliabadi, M.; Khodaei, Z.), s. 154-164. ISSN 2452-3216.
[FDM 2023 - International Conference on Fracture, Damage and Structural Health Monitoring /21./. London (GB), 12.09.2023-14.09.2023]
Institucionální podpora: RVO:68081723
Klíčová slova: EEQ 111 superalloy * high temperature * cyclic stress-strain behaviour * fatigue lifetime
Obor OECD: Materials engineering

The material under investigation was polycrystalline Sulzer’s nickel-based superalloy EEQ-111 which is equivalent to the original
GTD-111 developed in the late 1970s. The EEQ-111 superalloy is typical with coarse polyhedral dendritic grains with an average
grain size of (2.48 ± 0.87) mm. The microstructure consists of γ channels, a bimodal distribution of nano-sized coherent γ´
precipitates, γ/γ´ eutectic, and MC and M23C6 carbides. The proportion of casting defects in the material is minimal due to the
application of hot isostatic pressing. Low cycle fatigue experiments were executed on solid cylindrical specimens with a gauge
length and diameter of 15 mm and 6 mm, respectively. A symmetrical push-pull cycling under strain control mode was utilized at
800 °C and 900 °C using servo-hydraulic testing machine MTS 810. Hysteresis loops, fatigue hardening/softening curves, and
fatigue lifetime curves in Coffin-Manson, Basquin, and total strain amplitude representations were obtained. Analysis of fracture
surfaces and secondary cracks from metallographic sections revealed the preferential initiation sites of fatigue cracks that are
independent of temperature. In contrast, the fatigue crack propagation is purely transgranular at 800 °C, whereas a mix of
transgranular and intergranular crack propagation can be found at 900 °C indicating grain boundary weakening.
Trvalý link: https://hdl.handle.net/11104/0352921