Adhesion of thermal barrier coatings: Influence of the bond coat application technique

The application process is extremely relevant for the adhesion of the bond coat to the substrate. Traditionally applied by Air Plasma Spray or Vacuum Plasma Spray, the recent use of both High Velocity Oxygen Fuel and Cold Gas Spray has improved the quality of the applied bond coatings. This study investigates the adhesion of CoNiCrAlY bond coats applied by Cold Gas Spray and High Velocity Oxygen Fuel in a YSZ Thermal Barrier Coating system. Two bond coat alloys with the addition of Ta and Re applied by CGS are also investigated. The differences in microstructure, general, and fracture characteristics are discussed. Adhesion was assessed by the ASTM - C633 standard test. The findings show that the best adhesion performance was for the TBC system with HVOF sprayed bond coat.