Thermal barrier coatings failure

Kinetic Monte Carlo and hyperdynamics methods have yet to be applied to processes involved in thermal barrier coating failure or even simpler model metal-ceramic or ceramic-ceramic interface degradation as a function of time. A hindrance to their application is lack of a clear consensus on how to describe the interatomic interactions by an analytic potential function. If instead, for lack of an analytic potential, one must resort to full-blown density functional theory to calculate the interatomic forces, this will become the bottleneck that will limit the size and complexity of systems one may examine, even with multiscale methods. 

Understanding the behavior of the interfaces and bulk materials involved in thermal barrier coating failure due to the extreme environment created in aircraft engines is still in its infancy. This is primarily because the system involves complex interfacial chemistry and the materials issues span large length and time scales. In this review, we have focused on the atomic level characterization. Once that is specified, it will be imperative to draw links between the atomic and the microstructural scales in order to understand the materials failure mechanisms completely. 

Thermal-barrier coatings are used as thermal insulators to lower the temperature of the metallic components. Failure of TBCs is generally the result of thermomechanical processes. These processes are complex and depend on many variables associated with the coating and exposure environment. 

Tawancy H. M., Sridhar N., Abbas N. M., Rickerby D. 1998. Failure mechanism of a thermal barrier coating system on a nickel-base superalloy. Journal of Materials Science 33, 681-686. 

Keywords thermal barrier coatings failure mechanism non-destructive evaluation review. 

Figure 7.44 Several potential ceramic failure mechanisms of Y-PSZ thermal barrier coatings. (A) Spalling due to stresses introduced by thermal cycling (B) Destabilization ofzirconia due to cubic-monoclinic phase transformation (C) Erosion and...

A. Rabiei, A.G. Evans, Failure mechanisms associated with the thermally grown oxide in plasma sprayed thermal barrier coatings, Acta mater. 48 (2000) 3963 3976... 

Failure of the thermal barrier coatings was associated with cracking of the oxide scale in the porous titania-rich layer. 

Thermal barrier systems have a tendency to form an oxide layer between the TC and BC, which leads to significant stress increases in the system, resulting in mechanical failure, like spalling or buckling of coatings. 

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