Damage Grading Evaluation of Thermal Barrier Coatings under CMAS Corrosion

Thermal barrier coatings (TBCs) material has excellent high-temperature resistance and heat insulation performance, which plays a vital role in improving the working efficiency and running life of the engine. During the flight, the engine will inhale dust particles in the air. These particles are mostly from siliceous debris, which are usually called calcium magnesium aluminum silicate (CMAS). At present, CMAS corrosion has become one of the important problems affecting the service life of thermal barrier coatings. In this study, conventional yttrium oxide stabilized zirconia (YSZ) coatings and ytterbium oxide and yttrium oxide co-stabilized zirconia (YbYSZ) coatings were prepared by atmospheric plasma spraying. The two coatings were examined under thermal cycling-CMAS coupling conditions and divided into six life stages. The failure modes, CMAS permeation behavior, crack characteristics and mechanical properties of the two coatings at different life stages were evaluated systematically. The experimental results show that the YbYSZ coating has a longer life than YSZ coating under the thermal cycling and CMAS coupling condition, which increases by about 83% compared with the conventional YSZ coating. In the whole life stage, the porosity of YbYSZ coating is always higher than that of YSZ coating. The phase transition is not the reason for the failure and spalling of the coatings. The crack length of the two coatings showed an increasing trend, but the crack length of the YSZ coating was higher than that of the YbYSZ coating, and the crack density of the two coatings showed a “saddle shape”, which was more obvious for the YSZ coating. The YbYSZ coating shows better mechanical properties under the thermal cycling-CMAS coupling condition with the evolution of life.