Thermo-mechanical coupled modeling for analysis of cyclic stress distribution in plasma-sprayed thermal barrier coatings

CHEN Yu-hui1， CHEN Dan-yang2， ZHONG Shun-cong3，4， YANG Tian-xue5，YANG Xiao-xiang3，TU Shan-dong4， XUAN Fu-zhen4
（1. School of Chemistry and Chemical Engineering， Fuzhou University， Fuzhou 350108， China；
2. Zhangzhou Polytechnic University， Zhangzhou 363000， China；
3. School of Mechanical Engineering and Automation， Fuzhou University， Fuzhou 350108， China；
4. Key Laboratory of Safety Science of Pressurized System of Ministry of Education， East China University of Science and Techndogy， Shanghai 200237， China；
5. Fujian Institute of Special Equipment Inspection， Fuzhou 350001， China）

Abstract： Aiming at the stress distribution in the depth direction of the TBCs and the influence of mechanical properties in heating，dwelling and cooling thermal cycles，the oxide layer surface was simplified to sine wave，thermo-mechanical coupled modeling of periodic boundary conditions of air-plasma-sprayed（APS）thermal barrier coatings（TBCs） on Ni-based alloy was investigated. In the computational models，nonlinear relationships（e.g.，convective heat transfer between surrounding environment and coatings，and thermal transfer between the different layers etc.）were considered in the modeling. After the analysis of residual stress influenced by coating creep，the stress redistributed as the change of the thickness of oxide layer，and the results of the cycle and the separate cooling process were compared. The results indicate that the stress significantly is reduced in the dwelling stage because of stress relaxation. The maximum stress occurrs in the peak at the BC/TGO interface and it is amplified at the cooling stage. Moreover，the internal stress in the BC and TGO layer has been increased，when TGO's thickness increased，whilst film adhesion had fallen sharply.
Key words： thermal barrier coatings（TBCs）； thermo-mechanical coupling； creep； finite element analysis