Thermal insulation capability and adhesion strength of thick thermal barrier coatings

Thermal insulation and adhesion strength of thick thermal barrier coating produced using unpyrolyzed powder (Un TTBC) were compared with those of conventional YSZ TBCs, thick TBC (TTBC), dense vertically cracked TTBC (DVC TTBC). Many researchers have focused on extending the service life of TTBCs by improving its microstructure, however, having vertical cracks seems very promising. The thermal insulation capacity was evaluated using temperature drop and the adhesion strength of coatings was evaluated. The results indicate that Un TTBC and DVC TTBC have 35% and 25% higher adhesion strength respectively, compared to TTBC. Also, the results of thermal insulation test show that DVC TTBC coatings have the lowest thermal insulation capability with 0.28 ºC/μm and Un TTBC coatings have the highest thermal insulation capability with 0.40 ºC/μm. The adhesion strength of the Un TTBC was the highest because of presence of non-melted areas with sub-micron dimensions which prevent the cracks to grow.

Keywords:

Thick thermal barrier coating , unpyrolyzed powder , dense vertically cracked , adhesion strength , thermal insulation capability