Effects of incorporation of micro and nano Al2O3layers on thermal shock behaviour of YSZ thermal barrier coatings

In the present paper, thermal shock behaviour of usual YSZ and layered composite TBCs was evaluated. The layered composite TBCs used in this study were YSZ/micro Al2O3 and YSZ/nano Al2O3 in which Al2O3 was as a topcoat on the YSZ layer. In addition, coating microstructures were investigated using scanning electron microscope; EDS and X-ray diffraction techniques before and after thermal shock test. The results showed that incorporation of a nano Al2O3 oxygen barrier layer caused better thermal shock resistance, while micro Al2O3 layer on the top of YSZ sample resulted in sooner coating failure, compared to the usual TBC coating. Also, the thermal shock behaviour and failure mechanism of mentioned coatings were investigated.