Effect of Plasma Pretreatment on Thermal Durability of Thermal Barrier Coatings in Cyclic Thermal Exposure

Abstract

Plasma pretreatment on the top and bond coats was performed and its influence on the thermal durability of thermal barrier coating (TBC) system was investigated through cyclic thermal exposure. Two types of bond coat were prepared by different methods, namely, air plasma spray (APS) and high-velocity oxy-fuel (HVOF), and two kinds of feedstock powder were employed for preparing the top coat in APS process. The better thermal durability was achieved in the vertically cracked TBC with the surface modified bond coat or with the bond coat prepared by APS process. The hardness and fracture toughness values of TBCs increased because of densification of the top coat during cyclic thermal exposure, and the bond coat prepared by HVOF process showed higher values than that by APS process. The TBCs with the surface modified bond coat were more efficient in improving adhesive strength than those without plasma pretreatment on the bond coat. The relationship between microstructure evolution and thermomechanical characteristics of TBCs with plasma pretreatment was discussed in cyclic thermal exposure.