Characterisation of the microstructure and thermal properties of Gd_2Zr_2O_7 and Gd_2Zr_2O_7/YSZ thermal barrier coatings

摘要

The microstructure of following thermal barrier coatings (TBC) was characterised in this paper: monolayer coatings Gd_2Zr_2O_7 and 8 YSZ; a double ceramic layered (DCL) coating. Coatings were characterised by thicknesses that did not exceed 300 ìm and porosities of approx. 5%. The chemical and phase composition analysis of the DCL layers revealed an external Gd_2Zr_2O_7 ceramic layer approx. 80 ìm thick, a transitional zone approx. 120 (xm thick and an internal 8YSZ layer 100 ìm thick. For the case of the monolayer coating, the Gd_2Zr_2O_7 pyrochlore phase was the only one-phase component. The surface topography of both TBC systems was typical for plasma sprayed coatings, and compressive stress state had a value of approx. 5-10 MPa. Measurements of the thermal parameters, i.e., thermal diffusivity, point to considerably better insulative properties for both new types of layers when compared to the standard 8YSZ layers.