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Article RSE 15008844

Solid particle erosion of standard and advanced thermal barrier coatings

Article

Wear, vol. 348-349, pp. 43-51, Dicembre-2015.

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C. Guardamagna (RSE SpA) , L. Lorenzoni (RSE SpA), A. Moscatelli (Flame Spray), F. Cernuschi (RSE SpA) , S. Capelli (RSE SpA), D.E. Mack (Forschungszentrum Jülich GmbH, IEF-1, Jülich, Germany)

INDUSTRIA 2015 - Energy efficiency in industrial sector

In the frame of the European H2IGCC project, innovative thermal barriers consisting in a double-layered, partially stabilized Yttrium-based Zirconia TBC alternative to the state of the art for use in hot parts of gas turbines have been developed.The solid particle erosion resistance of these innovative TBCs have been investigated under conditions representative of the operation and results have been compared with standard porous and segmented TBCs. In general, better resistance to erosion of segmented TBCs was observed independently from the experimental conditions, while one of the two-layer innovative coatings, due to its peculiar microstructure, showed a very interesting erosion resistance, at least in the case where fine particles have been used as erodent.

The state-of-the-art of the thermal barrier coatings (TBCs), used to protect hot path components from combustion gases, is represented by yttria (partially) stabilized zirconia (YPSZ). Combustion and cooling technology improvements in combination with higher turbine inlet temperature imply that the standard YSZ approaches certain limitations due to sintering and phase transformations at elevated temperatures.

Moreover under high thermal loading early failure of the coating occurs due to attack by calcium-magnesium-alumino-silicate (CMAS) deposits inducing cracking, spallation and delamination of the coating. Alternative refractory materials development, with higher performances than YSZ, was the objective of the UE project H2IGCC: within this project the erosion resistance of porous, dense segmented YPSZ TBCs and innovative TBCs, featured with a bilayer structure, has been tested at impingement angles of 30° and 90°, representative for particle impingement on trailing and leading edges of gas turbine blades and vanes, respectively.

Alumina powders with grain size representative of sand and fly ashes, respectively were chosen as the erodent. A better erosion resistance of dense segmented TBCs regardless of experimental conditions were observed, whereas one of the new bilayer coating, due to its peculiar micro-structure, showed a very interesting erosion resistance, at least with fine erosion particles.

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