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Front Cover of J Am Ceram Soc – Corrosion Test of TBCs

A new publication by Daniel E. Mack, Oliver Helle, Doris Sebold, and Robert Vaßen (all IEK-1) and colleagues from Bundesanstalt für Materialprüfung (BAM) Berlin (R. Laquai, B. Müller, G. Bruno) has appeared in the Journal of the American Ceramic Society.

The paper deals with the degradation of porous thermal barrier coatings (TBC) under attack by molten deposits at high temperature gradient conditions.

Simultaneous deposition of calcium-magnesium-aluminium-silicates (CMAS) during cyclic testing under extreme temperature gradients relevant to application in gas turbines is achieved in a unique burner rig facility. Infiltration by the molten slag as well as formation and growth of cracks are analyzed by state of the art electron microscopy and X‐ray refraction techniques. The combination of those advanced techniques allows the study of progressing degradation of the ceramic microstructure in the course of continued corrosive and thermo-mechanical attack.

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

An image showing a specimen under test in the unique burner rig facility is selected for the front cover of the journal:

Mack DE, Laquai R, Müller B, Helle O, Sebold D, Vaßen R, and Bruno G. Evolution of porosity, crack density, and CMAS penetration in thermal barrier coatings subjected to burner rig testing. J Am Ceram Soc. 2019;102:6163–6175.