Abstract
The failure behavior of thermal barrier coatings (TBCs) involves multilayered systems infiltrated with calcium–magnesium–alumino-silicates (CMAS). The metastable tetragonal phase is mainly composed of 7YSZ (7 mol.% Y2O3-stabilized ZrO2), and it destabilizes into the Y-lean tetragonal phase, which may be induced by CMAS infiltration, and transforms into a monoclinic phase during cooling. The phase transformation leads to volume expansion around the CMAS-rich layer. Furthermore, it is shown that the spalling of the coating system emerges when the surface of the coating system is subjected to significant residual stress. In this study, a double-cantilever beam model is established to describe the macroscopic phenomenon of thermal buckling induced via CMAS. The result of the buckle height is used to demonstrate the consistency of the experiment and finite element simulation. The experimental parameters are imported into a multilayer cantilever beam model to analyze the interfacial stresses due to CMAS infiltration. The finite element results indicate that the phase transformation leads to damage in the coating system wherein the interfacial stresses due to phase transformation are 27% higher than those in the model without phase transformation.
Highlights
Thermal barrier coatings (TBCs) are widely applied in aerospace engineering to protect metallic substrates and other engine parts from high-temperature exposure
The depth h( Th ) of the infiltrated region can be expressed in terms of the depth R( Th ) of the CMAS-rich layer obtained via experiments and expansion due to CMAS infiltration, which can be related to the period of holding time
The results suggest that the simulation solutions are in good agreement with the corresponding experimental results in terms of the buckle height of the YSZ specimens induced by CMAS infiltration
Summary
Thermal barrier coatings (TBCs) are widely applied in aerospace engineering to protect metallic substrates and other engine parts from high-temperature exposure. Arrow (II) indicates Y depletion due to the interaction between YSZ phase cannot transform into a monoclinic phase upon cooling, and it is often referred to and CMAS at high temperatures. Tetragonal phase and extracts the yttrium from stabilized zirconia This denotes that the Aircraft engines encounter particulate debris in atmosphere and volcanic ash at grain boundary of zirconia becomes unstable because of the Y depletion region induced cruise altitude. After 10 h of thermal exposure, only 3.71 wt.% of Y2O3 was observed in the top region of YSZ This indicated destabilization due to the molten volcanic ash that infiltrates the YSZ top region via chemical reaction: yttria is depleted by CMAS. The residual interfacial stress of TBCs is determined using the corresponding multilayer cantilever beam model
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