Silicon Nitride Seal for Thermal Barrier Coating in Gas Turbines for Extended Engine Life

In a Gas Turbine Engine thermal barrier coatings (TBCs) which comprise ceramic material such as YSZ (Yttrium stabilized Zirconia), insulate turbine and combustor engine components from the hot gas stream (800 C), and improve the durability and energy efficiency of these engines. YSZ is a preferred choice as a TBC in Jet engine and other Gas Turbine applications due to its heat tolerance and chemical inertness. However, YSZ and other TBC’s with rare-earth zirconia grows  in columnar geometry (image) so that there are spaces between the columns where CMAS (Ca, Mg, Al, Si and their oxides) and volcanic ash can enter and initiate corrosion, resulting in reliability issues.  An innovative way to prevent this corrosion process is to seal the columnar structure and fill the pores. We are proposing to use Si3N4 as the sealing material. Silicon nitride is inert, refractory in nature with high melting point (~1900 C) and therefore suitable for high temperature ceramic applications.  What makes silicon nitride highly suitable is the moisture and oxygen barrier property.  Once an effective seal has been put in place with silicon nitride CMAS and volcanic ash issues would be greatly minimized or eliminated thus improving reliability and extending the life of the Gas Turbine Engines.