Heat insulating capacity of Sm₂Zr₂O₇ coating added with high absorptivity solids

Rare earth zirconates has the potential to be a new generation of ceramic top coat material in thermal barrier coatings (TBCs). However, the heat insulating capacity of rare earth zirconates will weaken with the temperature rising because of infrared radiation. In order to evaluate the shielding effect of the coatings for infrared radiation, single layer coatings (SLC), double layer coatings (DLC) and triple layer coatings (TLC) with pure Sm₂Zr₂O₇ (SZO) layer and Sm₂Zr₂O₇–15 vol%NiCr₂O₄ (SZO-15%NCO) layer were deposited by atmospheric plasma spraying (APS). The phase, microstructure and heat insulating capacity of the coatings were investigated. The results show that the powders and coatings are only composed of spinel-type and pyrochlore type SZO. The coatings are in a well compact state. The SLC has the lowset ΔT (213 ℃), while the highest ΔT (225 ℃) is obtained in TLC. Due to high absorptivity and conductivity of NCO, both positive and negative effects on heat insulating capacity generate in the SZO-15vol%NCO layer. The DLC shows a slightly higher ΔT (216 ℃), which is 3 ℃ higher than that in SLC. Compared with SLC and DLC, ΔT in TLC increases by 12 ℃ and 9 ℃, respectively. It indicates that suitable arrangement of heat insulation layer and absorption layer can effectively obstruct radiation, which can improve effectively the insulating capacity of the coatings.