Solid particle erosion of standard and advanced thermal barrier coatings

• Innovative bilayer TBCs (YAG and Gd containing) have been developed and tested.
• New TBCs erosion resistance was compared with porous and segmented YPSZ TBCs ones.
• Dense segmented TBCs showed in general the highest erosion resistance.
• Advanced YAG bilayer TBCs presented a very interesting erosion resistance.
• Advanced Gd-containing TBCs exhibited the same erosion mechanism as standard TBCs.

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 have 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 was 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.