The failure behavior analysis based on finite element simulation of PS-PVD (Gd_0.9Yb_0.1)₂Zr₂O₇/YSZ coatings during burner rig tests

A double-ceramic-layer (DCL) thermal barrier coating consisting of quasi-columnar structured (Gd_0.9Yb_0.1)₂Zr₂O₇ (GYbZ) on top and yttria-stabilized zirconia (YSZ) beneath was deposited by plasma spray-physical vapor deposition (PS-PVD). The as-deposited GYbZ/YSZ coating is composed of a dense continuous layer at the bottom and a columnar layer growing on it. The columnar layer comprises taller coarse columns, shorter tapered columns, and particles filling in the gaps between the columns. The thermal shock behavior of the coating is evaluated in a burner rig at 1300 °C, during which the coating mainly fails in the form of delamination. The coating initially delaminates in the regions where the particles are embedded beneath the taller GYbZ columns tips. Subsequently, delamination occurs in the lower region of GYbZ coating and eventually fails at the TGO/YSZ interface. A finite element model tailored to the microstructural characteristics of the DCL coating was established. Stress distributions of the coating indicate that the discontinuities of the strain tolerance caused by abrupt microstructural or componential changes lead to multiple out-of-plane stress (σ₂₂) concentration spots. The position and procedure of the delamination of GYbZ coating obtained based on the energy release rate of each σ₂₂ concentration spot are consistent with experimental results.