Thermal Barrier Coatings

Thermal barrier coatings (TBCs) are typically a duplex-type coating system which consists of a so-called metallic bond coat and a ceramic topcoat. The bond coat protects the substrates from oxidative and corrosive attack and improves the bonding between ceramic topcoat and substrate. This chapter focuses on the atmospheric plasma spraying (APS)-type TBCs that are frequently used in combustion chambers or on the vanes and blades of stationary engines. This more widespread use of APS TBCs mainly results from the much higher costs involved with the production of electron beam-physical vapor deposition (EB-PVD) coatings, which requires significantly more expensive equipment and higher investment costs. The chapter provides some details of the effort to seek ceramics that replace yttria-stabilized zirconia (YSZ) TBCs. It explains the two major manufacturing routes for TBCs namely EB-PVD and APS. The chapter discusses some basic properties of YSZ-based TBCS and the failure of YSZ-based TBC systems.