Formation of a dense and continuous Al(2)O(3) layer in nano thermal barrier coating systems for the suppression of spinel growth on the Al(2)O(3) oxide scale during oxidation

A continuous and thin Al(2)O(3) layer would act as an infiltration barrier to diminish the growth of spinels in thermal barrier coating systems. Therefore, isothermal oxidation of normal NiCrAlY/YSZ. nano NiCrAlY/ YSZ and nano NiCrAIY/YSZ/nano Al(2)O(3) coatings was investigated at 1000 degree C. These samples were then subjected to thermal cycles at 1150 degree C. The microstructural characterisation showed that the spinel growth in the nano NiCrAIY/YSZ/nano Al(2)O(3) coating was much lower than the other coatings. This observation can be related to the formation of a fully continuous Al(2)O(3) layer on the nano NiCrAlY coating during pre-oxidation at 1000 degree C and also to the presence of a nano Al(2)O(3) layer over the YSZ coating.