Thermal insulation performance of 7YSZ TBCs adjusted via Al modification

ZrO 2 -7 wt% Y 2 O 3 (7YSZ) thermal barrier coatings (TBCs) with three different structures were prepared by atmospheric plasma spraying (APS), electron beam physical vapor deposition (EB-PVD) and plasma spray-physical vapor deposition (PS-PVD). Al films were deposited onto the top 7YSZ TBCs by magnetron sputtering, and the Al-deposited 7YSZ TBCs were subjected to vacuum heat treatment. The effects of Al modification on the thermal insulation properties of 7YSZ TBCs were investigated. The results showed that Al modification could significantly improve the thermal insulation of 7YSZ TBCs at 1000 °C. Moreover, the maximum improvement of thermal insulation for PS-PVD 7YSZ TBCs was approximately 100 °C, but the improvement decreased with increasing temperature. This is mainly because with increasing temperature, the rate of radiation heat transfer increases, and the effects of convection heat transfer and thermal conductivity on thermal insulation are weakened. At the same temperature, Al modification of PS-PVD 7YSZ TBCs provides better temperature insulation than those of APS 7YSZ TBCs and EB-PVD 7YSZ TBCs because of its wider and deeper inter-columnar gaps. When the temperature was 1200 °C, Al modification still caused a good insulation effect in PS-PVD 7YSZ TBCs; the improvement was approximately 50 °C, but in APS and EB-PVD 7YSZ TBCs, the insulation effect disappeared. Graphical Abstract