Effects of heat treatment on adhesion strength of thermal barrier coating systems

• CoNiCrAlY and YSZ (ZrO2 + Y2O3) powders were used as coating materials.
• HVOF and APS techniques were used to produce the thermal barrier coatings (TBCs).
• The TBC specimens were subjected to heat-treatment tests.
• Adhesion strength of as-sprayed and heat-treated samples was investigated.
• Heat treatment of the coatings led to an increase in the adhesion strength of TBCs.

Thermal barrier coatings (TBCs) are widely used as protective and insulative coatings on hot section components of gas turbines and their applications, like blades and combustion chambers. The quality and performance properties of TBCs are of great importance in terms of their resistance to service conditions. In a TBC system, there is a close relationship between the adhesion properties of coating layers. The adhesion strength of TBCs varies depending on the coating technique used and the surface treatments. In this study, CoNiCrAlY and YSZ (ZrO2 + Y2O3) powders were deposited on stainless steel substrate. High Velocity Oxy-Fuel (HVOF) and Atmospheric Plasma Spraying (APS) techniques were used to produce the bond coats. The ceramic top layers on CoNiCrAlY bond coats were produced by the APS technique. The TBC specimens were subjected to heat-treatment tests. Adhesion strength for top coat/bond coat interface of as-sprayed and heat-treated samples was investigated. The results showed that the heat treatment of the coatings in different temperatures led to an increase in the adhesion strength of TBCs.