Evolution of porosity, crack density, and CMAS penetration in thermal barrier coatings subjected to burner rig testing

Mack, D.E. and Laquai, R. and Müller, B. and Helle, O. and Sebold, D. and Vaßen, R. and Bruno, G.

Volume: 102 Pages: 6163-6175
DOI: 10.1111/jace.16465
Published: 2019

Degradation of thermal barrier coatings (TBCs) in gas-turbine engines due to calcium–magnesium–aluminosilicate (CMAS) glassy deposits from various sources has been a persistent issue since many years. In this study, state of the art electron microscopy was correlated with X-ray refraction techniques to elucidate the intrusion of CMAS into the porous structure of atmospheric plasma sprayed (APS) TBCs and the formation and growth of cracks under thermal cycling in a burner rig. Results indicate that the sparse nature of the infiltration as well as kinetics in the burner rig are majorly influenced by the wetting behavior of the CMAS. Despite the obvious attack of CMAS on grain boundaries, the interaction of yttria-stabilized zirconia (YSZ) with intruded CMAS has no immediate impact on structure and density of internal surfaces. At a later stage the formation of horizontal cracks is observed in a wider zone of the TBC layer. © 2019 The American Ceramic Society

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