Creep behavior modeling of nickel-based superalloy foil structures in gas foil bearings

Gas foil bearings are self-acting aerodynamic bearings that use nickel-based superalloy foil structures as the load-carrying element. This type of bearing has great potential in high-temperature and high-speed turbomachinery but faces serious challenges in maintaining a long service life in extreme environments. Creep behaviors of foil structures are inevitable when the bearings are exposed to high temperatures for prolonged periods. In this paper, we innovatively propose a finite element model to investigate the steady-state creep behavior of foil structures, considering both the creep effects and nonlinear contact behaviors. Uniaxial creep tests are conducted using miniature specimens to obtain the material constants in the Norton creep model of Inconel 718. The reasonability of the model is verified by comparing predictions with the ANSYS simulation results, demonstrating its ability to accurately describe the evolution of creep displacement, stress, and strain in foil structures. The significant differences in creep displacements at different positions of the foil structure are explained by analyzing the distributions of equivalent stress and principal stress. Overall, the bump foil exhibits more pronounced creep displacements than the top foil, especially in the peak region of bumps and the flat segment between adjacent bumps near the free end.