Real-feature Based Study Of Failure Mechanisms Of Thermal Barrier Coatings With Thermal Cycling Loadings

Thermal Barrier Coatings (TBCs) is a protecting layer that sprayed on the top of Super Alloy Substrate, which is widely used in turbines for propulsion and power generation. With low thermal conductivity of TBCs, the super alloy substrate sprayed with TBCs is efficiently protected from high temperature; With the excellent property of erosion resistance of ceramic layer which is the top layer of TBCs, the super alloy substrate is well protected from thermal erosion; With physical layer of TBCs, the substrate underlying is protected from particles and thermal impact of the gas.The TBCs consists of three layers with different material properties, those are Thermal Barrier Coating (TBC) layer, Thermally Grown Oxide (TGO) layer and Bond Coats (BC) layer. The TBCs system undergoes thermal cycling loadings and large thermal gradient, and consequently, intense residual stresses and residual deformations are induced into the imperfection interfaces of the three layers. As a result of the growing residual stresses and the imperfection interfaces, cracks nucleate, propagate and coalescent, which lead to the delamination and the final failure.Based on the Finite Element Method (FEM) and the theory of Cohesive Zone, the failure mechanisms of TBCs with thermal cycling loadings are modeled and analyzed by means of Cohesive Element in ABAQUS. The main points studied are: How do the residual stresses and residual deformations develop; Where and how do the cracks nucleate, propagate and coalescent; What are the mechanisms controlling the final failure of TBCs.