High-temperature performance of self-healing SiC-YSZ thermal barrier coatings deposited by using various plasma spray concepts

In this study, a novel self-healing concept is considered in order to increase the lifetime of thermal barrier coatings (TBCs) in modern gas turbines. For that purpose, the sub-micrometersized SiC healing particles were introduced to YSZ topcoat by using various plasma spray concepts, i.e.: hybrid SiC suspension/YSZ powder, intermixed SiC powder/YSZ suspension or intermixed SiC powder/YSZ solution. All topcoats were sprayed by hybrid water stabilized plasma torch (H-WSP 500) on previously deposited NiCrAlY bondcoats produced by conventional APS. The coatings were subjected to thermal conductivity measurements by laser flash method, isothermal oxidation testing up to 200h under 1100°C and finally to thermal cyclic fatigue (TCF) lifetime testing under 1100°C. Then, the microstructural testing of coatings was performed by SEM, in as-produced state and after high-temperature studies. This was done to analyze the self-healing phenomena and its influence on high-temperature performance of newly developed TBCs.

Key words: thermal barrier coatings, self-healing effect, thermal conductivity, isothermal oxidation, thermal cyclic fatigue