High-Temperature Low Cycle Fatigue of Nickel-Based Superalloy IN738 LC

0571149 - ÚFM 2025 RIV CH eng J - Journal Article
Šulák, Ivo - Chlupová, Alice - Obrtlík, Karel
High-Temperature Low Cycle Fatigue of Nickel-Based Superalloy IN738 LC.
Defect and Diffusion Forum. Roč. 422, neuvedeno (2023), s. 27-32. ISSN 1012-0386
Institutional support: RVO:68081723
Keywords : Inconel * precipitates * microstructure * high-temperature fatigue * hysteresis loop * fractography
OECD category: Materials engineering

Polycrystalline cast nickel-based superalloy IN738LC is employed for critical parts of gas
turbine components in the power industry, aircraft engines, and the marine sector. These components
undergo severe degradation by low cycle fatigue caused by thermal gradients, particularly during
start-up and shut-down periods. The present work reports the cyclic deformation behaviour and
fatigue damage of IN738LC during high-temperature isothermal fatigue. Cylindrical specimens were
cyclically deformed under strain control with constant total strain amplitude in symmetrical cycling
at 800 °C and 950 °C in air. The microstructure is typical of coarse dendritic grains with carbides,
eutectic, and shrinkage pores. SEM imaging revealed a γ matrix with coherent L12 γ′ precipitates with
bimodal morphology. Cyclic hardening/softening curves, cyclic stress-strain response, and fatigue
life diagrams were determined. An increase in testing temperature is associated with a significant
decrease in stress amplitude and an increase in plastic strain amplitude. The fatigue life gradually
decreases with increasing temperature. The fracture surfaces and polished sections parallel to the
specimen axis were examined to study damage mechanisms in cyclic loading at high temperatures.
Permanent Link: https://hdl.handle.net/11104/0342454