Criteria for development of new CMAS / volcanic ashes resistant TBCs in thermal gradient and FCT

The evolution of CMAS/VA resistant thermal barrier coatings (TBCs) has been the hot topic in the gas turbine industry and the inevitability is growing exponentially with the constantly increasing turbine inlet temperatures (TIT). Numerous research groups have acquired enormous amount of knowledge on the interactions of TBCs with CMAS, damage mechanisms and methods of analysing the CMAS attack. From all the current knowledge, most substantial parameters which define the CMAS/TBC interactions are shown schematically in Fig.1. Chemical composition and microstructure are illustrated as highly influential parameters in case of CMAS/TBC interaction in Fig.1. Variation in the global CMAS/VA composition means difference in their melting points, viscosities, acidic/basic nature. Any developed novel TBC material will react differently to different CMAS/VA compositions and forms numerous reaction products which might bring a completely new effect in the end. In the presentation novel TBCs such as gadolinium zirconate, alumina and yttria rich zirconia coatings are introduced that were applied by means of EB-PVD method and their interactions with synthetic CMAS and natural volcanic ash was studied in detail. The reaction products heavily depend upon the CMAS chemistry and variy with respect to the crystallinity of the CMAS compound. Please click Additional Files below to see the full abstract