TBC's help protect gas turbine blades from the increasingly harsh operating environment of the military and commercial aircraft engine. Turbine engines are being pushed beyond the use temperature of available metallic systems, generally exceeding 2600 F in engines. The TBC's allow a 300 F improvement in the temperature capability of the engine parts. However, durability and reliability issues limit the benefits that can be derived from TBC's.
Stresses occur at the interface between the ceramic and the bond coat.
The adhesion quality of the TBC to the substrate is considered to be one of the limiting factors for use of these materials. Thermal barrier coatings often need to retain their integrity when subject to thermal cycling through large temperature ranges, despite significant thermal expansion misfit with the substrate. This is achieved by deliberately incorporating either aligned porosity or microcrack arrays. These methods for incorporating compliance also result in low strength and toughness. Eventually, the coating spalls away and exposes the substrate.