The selection of new TBC materials is restricted by few basic requirements such as: high melting point, no phase transformation between room and the operation temperatures, low thermal conductivity, chemical inertness to the combustion gases and environment, thermal expansion match with the metallic substrate, good adherence to the metallic substrate and low sintering rate of the porous microstructure. Among these properties, one of the most important is thermal diffusivity. The number of material that can be used as TBCs is limited and so far only a few materials have been found to basically satisfy these requirements. Recent research has shown that certain rare-earth zirconates, such as La₂Zr₂O₇, have even lower thermal conductivities than 7YSZ, and this has spurred an intensive research in discovering alternative TBC materials. The microstructural characteristics of TBC layers on the basis of a new compound type with pyrochlore structure - La₂Zr₂O₇ was presented in this article. The powder of Co-32Ni-21Cr-8Al-0.5Y type sprayed with the VPS method was used as the base layer. The ceramic layer was sprayed with the APS method. The study performed included microstructural characteristics taking into consideration porosity, presence of cracks, contamination, not melted particles and adhesiveness of layers. It was found that the analysed layer is characterized by uniform thickness distribution, which is approx. 250mm. No vertical or horizontal cracks were found. No delamination effects of individual layers were either noticed. The porosity observed was at the level of approx. 3.5%, but no massive porosity was found. The study of substrate – base layer and base layer – ceramic layer area showed no presence of delamination or oxide contamination in quantities that disqualify the TBC layer.

This work was supported by the Polish Ministry of Education and Science under the research project No PBZ-MNiSW-01/I/2007

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2. XRD characterization of new type of pyrochlore powders for TBC applications
3. Microstructural characterization of Gd₂Zr₂O₇ type of TBC system obtained by APS method
4. Characterization of NiCoCrAlY powders and coating obtained by plasma sparaying for TBC applications
5. Microstructure and thermal diffusivity of La₂Zr₂O₇ powder for TBC aplications
6. Cracks characterization of YSZ and RE zirconates thermal barrier coatings obtained by APS method