Finite element analysis on nano-indentation behavior in columnar 7YSZ EB-PVD thermal barrier coatings

Nano-indentation is an important technique to characterize elastic/plastic deformation of Thermal Barrier Coatings (TBCs). In this paper, the nanoindentation of 7YSZ TBC with columnar grain structure is performed using Finite Element Method (FEM) based on a nonlinear contact model. An indentation model subjected to a quasi-static with rigid indenter and the deformable surface is considered with contact mechanics approach. The FE simulation compares the effect of different indenter shapes (spherical, flat and conical) with a variation of contact friction, columnar friction, and the ratio of columnar gap to the width on elastic/plastic, load-displacement response in detailed. The simulation results showed the clear difference in the load-displacement response for different indenter shapes with a variation of parameters. In all cases, the force acting on the indenter gradually increases with an increase in impression depth. For flat indenter, we observed the largest deformation value resulting in the largest force acting on the indenter compared to spherical and conical ones. Also, the indenter shapes strongly affect the orientation and formation of kink and shear bands. The flat indenter results in a more localized pattern of vonmises stress and compressive stress distribution leading to a larger force for the same magnitude of the displacement.