Tailoring of self-healing thermal barrier coatings via finite element method

In this paper, the multi-layer structured self-healing thermal barrier coatings (TBCs) have been designed and optimized on the basis of design criteria of the typical double layer NiCrAlY/YSZ TBCs. The self-healing layer 20%wt.TiC + xAl2O3 + (80 wt.%-x) YSZ (TAZ) has been embedded between the NiCrAlY and YSZ layer. Based on the better thermal insulation and remission of thermal expansion misfit, the optimized x and the thickness ratio of each layer for the designed self-healing TBCs has been obtained. And the self-healing effect of the TBCs under high temperature service condition was also simulated. The detailed self-healing mechanism has been discussed systematically. The investigation results indicate that there are three factors which will promote the self-healing effect of the designed multi-layer structured self-healing TBCs, i.e. the larger compressive stress induced around the crack, the filling of the self-healing matter in the crack and the reduction of formation rate of the TGO layer. In addition, the existence of self-healing cracks which are near to the interface will also change the stress distribution along the top-coat/self-healing layer interface evidently.