Abstract:

Thermal barrier coatings (TBCs) are multilayer structures that are critical components in modern gas turbine engines. They enable increased turbine inlet temperatures, reduce cooling requirements and allow life extension of expensive superalloy components in both power and propulsion turbines. TBC is a system comprising of metallic bond coats that provide both adhesion of the ceramic to the substrate and oxidation protection to the superalloy, followed by a thick and compliant ceramic coating principally made of yttria stabilized zirconia. Such two layer TBCs are now pervasive in the industry. Due to sustained thermal exposure as well as extrinsic threats through particle erosion, foreign object damage and infusion of ash and sand, TBC’s undergo mechanical, thermo-mechanical and thermo-chemical changes. As the turbine operation temperatures increase, so do the types of damage mechanisms with concomitant performance challenges. New materials and coating architectures are sought to address these multifunctional requirements but complexities in processing arises. In this presentation, we will introduce the concept of integrating layered materials design and multilayer manufacturing concepts that will enable future TBC systems to concurrently combat various failure mechanisms. Of particular importance in this strategy is that the plasma spray process through its ability to manufacture coatings in layers and enabling optimization properties of these layers during the assembly, will allow novel architectures to be realized. In this paper, we will present examples of a TBC system with optimized through thickness properties achieved via process nuances while also judiciously incorporating new compositions. The results point to a new regime of process enabled design of layered and graded coatings.