Processing science of advanced thermal-barrier systems

Thermal-barrier coatings (TBCs) are complex, defected, thick films made of zirconia-based refractory ceramic oxides. Their widespread applicability has necessitated development of high throughput, low cost materials manufacturing technologies. Thermal plasmas and electron beams have been the primary energy sources for processing of such systems. Electron-beam physical vapor deposition (EBPVD) is a sophisticated TBC fabrication technology for rotating parts of aero engine components, while atmospheric plasma sprays (APS) span the range from rotating blades of large power generation turbines to afterburners in supersonic propulsion engines. This article presents a scientific description of both contemporary manufacturing processes (EBPVD, APS) and emerging TBC deposition technologies based on novel extensions to plasma technology (suspension spray, plasma spray-PVD) to facilitate novel compliant and low thermal conductivity coating architectures. TBCs are of vital importance to both performance and energy efficiency of modern turbines with concomitant needs in process control for both advanced design and reliable manufacturing.