Thermal Barrier Coatings: The Basics
Andrea Scrivani, Gabriele Rizzi
Thermal barrier coatings (TBCs) are widely used surface treatments typically consisting of a top coat of Y2O3 air plasma sprayed partially stabilized ZrO2, and a McrAlY bond coat (where M is Ni, Co, or NiCo), which can be deposited using different thermal spray processes such as air plasma spray (APS), vacuum plasma spray (VPS), and high-velocity oxyfuel (HVOF) [1-3]. Another example is a top coat of Y2O3 partially stabilized ZrO2 deposited using electron-beam physical vapor deposition (EBPVD), and an aluminum alloy bond coat deposited using chemical vapor deposition (CVD). For many metallic components, adequate creep properties (creep resistance, thermal efficiency, thermal shock resistance, etc.) can only be achieved with the use of nickel and cobalt superalloy base material plus adequate coatings and surface treatments to obtain resistance to oxidation and corrosion at high temperature. Repair of components means restoring their original properties. Therefore, these surface treatment processes are not only used during manufacture, but also during repair.