Hydration Tolerant, low Thermal Conductivity (K) Thermal Barrier Coatings

ABSTRACT: Thermal barrier coatings (TBC) are currently employed to protect gas turbine engine components. Thermally exposed TBC systems have been observed to be affected by moisture. This spallation mechanism, Moisture Induced Delayed Spallation (MIDS), occurs at room temperature while the coatings are not exposed to the thermal-mechanical inputs that typically drive TBC failure. Future TBC systems will benefit from improved TBC reliability which can be achieved by development of an advanced high temperature protective coating system designed to improve, among other characteristics, the durability of coating in the presence of moisture. In Phase I, DVTI demonstrated TBC systems which included modification of the TBC elastic modulus, incorporation of an advanced TBC bond coat having an improved CTE mismatch between the bond coat and the TGO, reduced TGO growth rates and also modifications to TBC top coats which potentially limit access of moisture into the bond coat. In Phase II, based on positive effects shown in Phase I, these enhanced coating properties will be more fully developed into an advanced TBC system which will then be systematically varied to create an analytical model which explores the effects of these elements on the reliability of TBC systems subject to moisture exposure. BENEFIT: This research is anticipated to result in thermal barrier coating systems with enhanced resistance to hydration induced coating failure and thus improved reliability. Development of advanced TBC coating systems using DVD processing techniques will not only enable new TBC coating systems that will meet the needs of current and future engines used in military aircraft, it will also enable low cost deposition of these coatings. The DVD deposition technique enables coatings not previously possible with existing processing approaches. DVD coaters can be small with low capital costs and tailorable volumes so that small volumes of parts can still be coated at low cost. The high deposition rates of DVD and the soft vacuum required (with quick pump down times) can provide nearly assembly line like part coating. These features also facilitate quick and easy repair options at repair depots. It is also envisioned that a single piece of equipment could be used to deposit the entire TBC system (both bond coat and top coat) in a single step. DVD"s compositional and morphological flexibility also enables other advanced TBC systems and other functional coating such as those for erosion protection, hot corrosion resistance and environmental barrier coatings.