Characterization of the strain in the thermal barrier coatings caused by molten CaO-MgO-Al2O3-SiO2 using a digital image correlation technique

The strain field of the thermal barrier coatings (TBCs) corroded by molten CaO-MgO-Al2O3-SiO2 (CMAS) is investigated using the digital image correlation (DIC) techniques. The results indicate that the strain in TBCs is compressive and it increases during cooling from 1250 to 25 degrees C. The cracks induced by CMAS form at the YSZ/BC interface at 300-400 degrees C. These cracks can be observed even without CMAS as temperature decreases to 100 degrees C. The DIC measurements show that the critical strains for the failure of TBCs with and without CMAS are 0.7% and -1.6%, respectively, and these results can be predicted by using a theoretical model. (C) 2017 Elsevier B.V. All rights reserved.