High‐Temperature Corrosion of EB‐PVD Yttria Partially Stabilized Zirconia Thermal Barrier Coatings with an Artificial Volcanic Ash Overlay

• Published in: Journal of the American Ceramic Society
• Main Authors: Mechnich, Peter, Braue, Wolfgang, Schulz, Uwe
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2010
• Subjects: Eyjafjallajokull; Iceland
• Online Access: http://dx.doi.org/10.1111/j.1551-2916.2010.04166.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1551-2916.2010.04166.x; http://onlinelibrary.wiley.com/wol1/doi/10.1111/j.1551-2916.2010.04166.x/fullpdf

High‐temperature interaction of sol–gel‐derived artificial volcanic ash (AVA) matching the bulk composition of the April 15, 2010 Eyjafjallajokull (Iceland) volcanic eruption with a standard 4 mol% (7 wt%) Y 2 O 3 ‐stabilized ZrO 2 (YSZ) electron‐beam physical vapor deposition (EB‐PVD) thermal barrier coating and a corresponding YSZ powder is investigated in order to access possible implications of similar volcanic ashes on the performance of coated turbine engine airfoils. Up to 900°C, AVA deposits and EB‐PVD YSZ do not show significant interaction. Viscous flow above the glass transition of AVA ( T g ∼930°C) yields proceeding wetting of EB‐PVD YSZ coatings. At 1100°C, the YSZ surface is covered by a dense glaze‐like AVA overlay. At 1200°C, AVA is mostly infiltrating the coating, leaving a crystalline plagioclase‐ and hematite‐type residue at the interface. Moreover, some ZrSiO 4 is formed at the expense of YSZ. The overall thermochemical effects on short‐term exposure of the EB‐PVD YSZ coating to a small AVA load were moderate, in particular before complete infiltration. On the other hand, AVA acts as a solvent for the stabilizing Y 2 O 3 beyond 1000°C and a progressive depletion of Y 2 O 3 in the YSZ is observed at the AVA/YSZ interface. Detrimental effects on YSZ phase stability and hence coating lifetime cannot be ruled out for long‐term exposure and higher AVA loads.