Nonlinear Thermo-Mechanical Coupled Modeling for the Analysis of Stress Distribution in Air-Plasma-Sprayed Thermal Barrier Coatings

Abstract

Thermo-mechanical coupled modeling of air-plasma-sprayed (APS) thermal barrier coatings (TBCs) on Ni-based alloy was investigated. In the computational models, the stress distribution in the depth direction of the TBCs and also the influence of mechanical properties in heating, dwelling and cooling thermal cycles, were investigated. Nonlinear relationship (e.g., convective heat transfer between surrounding environment and coatings, and thermal transfer between the different layers etc.) was considered in the modeling. The results showed that the stress significantly reduced in the dwelling stage because of stress relaxation. The maximum stress occurred in the peak at the BC/TGO interface and it was amplified at the cooling stage. Moreover, the internal stress in the BC and TGO layer had a slight increase when TGOs thickness increased whilst the stress in the TBC and Sub were essentially unchanged. In the present work, the cracks in BC coating and the BC/TGO interface cracks were simulated as well. The failure mechanism I/II of TBCs had been investigated and the results showed that there was no stress concentration in the vicinity of cracks near the peak at the top coating layer, however, due to crack propagation, factures happened near the peak at the BC/TGO interface.