Preparation of (Gd0.9Sc0.1)2Zr2O7/YSZ thermal barrier coatings and their corrosion resistance to V2O5 molten salt

Gd0.9Sc0.1)(2)Zr2O7/YSZ thermal barrier coatings (TBCs) were produced by air plasma spray (APS). Compared with agglomerated particles for thermal spray, (Gd0.9Sc0.1)(2)Zr2O7 coatings had the same phase structure and a close chemical composition. (Gd0.9Sc0.1)2Zr2O7/YSZ TBCs revealed a lamellar microstructure, and the (Gd0.9Sc0.1)(2)Zr2O7 coating had some porous zones with many fine particles among the splats. Hot corrosion tests in V2O5 at 700-1000 degrees C indicated that the coating was highly resistant to molten salt penetration, resulting from the formation of a continuous dense reaction layer on the surface. The thickness of the reaction layer was similar to 0 mu m, independent on the corrosion temperature and time. After corrosion at 700 degrees C, the layer consisted of (Gd, Sc)VO4 and Sc2O3 doped ZrV2O7, while at higher temperatures, it was composed of (Gd,Sc)VO4 and monoclinic ZrO2. The mechanism by which these corrosion products formed is clarified based on phase diagrams and Lewis acid-base rule.