Stability of plasma-sprayed thermal barrier coatings: The role of the waviness of the bond coat and the thickness of the thermally grown oxide layer

• Stresses in top coat obtained from 3D and 2D models are significantly different.
• Waviness induces appreciable stresses within thermal barrier coatings.
• Waviness influences thickness of thermally grown oxide layer for stress conversion.

In this paper, the effect of the waviness of the bond coat and the thickness of the thermally grown oxide (TGO) layer on the stability of plasma-sprayed thermal barrier coatings is investigated. Large numbers of three-dimensional finite element calculations were performed using a plasma-sprayed MCrAlY + YSZ thermal barrier coating as a modeled system and a cosine surface to represent an irregular top-coat/bond-coat interface. Thermal cooling stresses in critical locations (the top coat and the interfaces between the top coat, the TGO, and the bond coat) were evaluated assuming a stress-free initial state and elastic (the substrate, the thermally grown oxide and the top coat) and elastic–ideal plastic (the bond coat) material behavior. The results of this investigation, which have been discussed by taking into account interfacial geometries typical of manufactured coatings, indicate that the waviness could markedly affect the service lifetime and thus should be considered in both theoretical studies and further experimental endeavors.