Creep-fatigue behavior of nickel-based single crystal superalloy with different orientations: Experimental characterization and multi-scale simulation

In order to clarify the creep-fatigue interaction properties of nickel-based single crystal superalloys with different orientations, mechanical tests of [001], [011] and [111] orientations were conducted at 980Cunder various stress states and microstructural characterization was performed. The results demonstrated that the creep-fatigue life was longest for the [111] orientation, followed by the [001] orientation, and the [011] orientation exhibited the lowest life. Furthermore, as stress levels increased, the life of specimens with different orientations decreased. Damage accumulation in specimens with various orientations was primarily influenced by the formation and growth of material micropores. Fracture analysis revealed that the failure of [001] and [111] oriented specimens resulted from a combination of multi-slip systems and micropore aggregation. Conversely, the fracture of [011] oriented specimens occurred due to a single slip system. Molecular dynamics simulation was employed to analyze the evolution of defects under creep-fatigue loading for different orientation models, further supporting the fracture mechanism. In addition, the life of the specimens was predicted using the crystal plasticity theory based on energy dissipation, and the results were within +/- 1.5 error bands.