Effect of doped nano-CeO₂ on thermal insulation properties of ZrO₂-Y₂O₃ thermal barrier coatings

The agglomerated powders consisting of nano ceramic particles ZrO₂-8wt%Y₂O_3，YSZ and doped respectively with 25wt% and 50wt% nanoscale CeO₂ in the nano-YSZ were used as insulation top materials，and NiCrAlY(Ni-25Cr-5Al-0.5Y，wt %) alloy was used as the bonding coating. Thermal barrier coatings of the three kinds of materials were prepared on the GH30 high temperature alloy surface by an atmospheric plasma spray (APS) process. The morphology and microstructures of the coating doped with 25wt%CeO₂ in the nano-YSZ powders were characterized using scanning electron microscopy ( SEM) and X-ray diffraction ( XRD) . The thermal conductivity of the three kinds of coatings were measured at room-temperature and 300，500 and 700℃. Thermal insulation property of the as-received coatings was also examined under the same edge conditions. The results show that a relatively stable t-phase (t-ZrO₂、t-Zr_0.82Y_0.18O_1.91、t-Zr_0.82Ce_0.18O₂) and c-phase (c-CeO₂) form and the closed pores and microcracks are also observed in the coating. Moreover , the thermal barrier coatings doped with nano-CeO₂ reduce the thermal conductivity and accordingly，the thermal insulation property can be developed with the amount of CeO₂ increased. For CeO₂/ZrO₂ -Y₂O₃ coating ( CYZ，doped with 25wt%CeO₂) with 400μm thickness，the temperature drop of the matrix alloys increases by 10.7% compared to nano-YSZ coating. As the mass fraction of CeO₂ increased from 25wt% to 50wt%，the thermal insulation property increases by 7.1%.