Thermomechanical fatigue performance of additively manufactured Inconel 939

Thermomechanical fatigue performance of additively manufactured Inconel 939

Článek WoS

Additively manufactured nickel-based superalloy Inconel 939 (IN939) was subjected to in-phase and out-of-phase thermomechanical fatigue loading in the temperature range of 400-800 degrees C. Horizontally and vertically built cylindrical specimens were subjected to a three-step heat treatment and subsequently tested with mechanical strain amplitudes in the range of 0.3-0.9%. A constant heating and cooling rate of 10 degrees C/s was utilised, making the cycle period 80 s. Representative hysteresis loops, fatigue hardening/softening curves, cyclic stress-strain curves, and fatigue life curves are reported. The results show that, regardless of the load cycle, the horizontally built IN939 exhibits lower lifetimes than the vertically built alloy. This stems from a distinctive (001) texture in the building direction, which influences the stress response of the material. Higher stress amplitude values observed for horizontally built material contribute to faster fatigue crack initiation and propagation. The SEM observation revealed that, regardless of the building direction, the damage is mainly intergranular for in-phase loading and mixed for out-of-phase loading. Plastic strain localisation into persistent slip markings and formation of nanotwins was typical for out-of-phase loading. In contrast, dense dislocation networks and stacking fault formation within gamma precipitates were observed for in-phase loading.

Additively manufactured nickel-based superalloy Inconel 939 (IN939) was subjected to in-phase and out-of-phase thermomechanical fatigue loading in the temperature range of 400-800 degrees C. Horizontally and vertically built cylindrical specimens were subjected to a three-step heat treatment and subsequently tested with mechanical strain amplitudes in the range of 0.3-0.9%. A constant heating and cooling rate of 10 degrees C/s was utilised, making the cycle period 80 s. Representative hysteresis loops, fatigue hardening/softening curves, cyclic stress-strain curves, and fatigue life curves are reported. The results show that, regardless of the load cycle, the horizontally built IN939 exhibits lower lifetimes than the vertically built alloy. This stems from a distinctive (001) texture in the building direction, which influences the stress response of the material. Higher stress amplitude values observed for horizontally built material contribute to faster fatigue crack initiation and propagation. The SEM observation revealed that, regardless of the building direction, the damage is mainly intergranular for in-phase loading and mixed for out-of-phase loading. Plastic strain localisation into persistent slip markings and formation of nanotwins was typical for out-of-phase loading. In contrast, dense dislocation networks and stacking fault formation within gamma precipitates were observed for in-phase loading.

Nickel-based superalloy, Laser powder bed fusion, High-temperature fatigue, Deformation mechanisms, Persistent slip bands, Intergranular damage, Microtwinning

Nickel-based superalloy, Laser powder bed fusion, High-temperature fatigue, Deformation mechanisms, Persistent slip bands, Intergranular damage, Microtwinning

ŠULÁK, I.; GÁLÍKOVÁ, M.; BABINSKY, T.; POCZKLAN, L.; KUBENA, I.; GUTH, S.

01.07.2026

Elsevier

International Journal of Fatigue

208

July 2026

Spojené království Velké Británie a Severního Irska

12

https://www.sciencedirect.com/science/article/pii/S0142112326000721