Abstract
This work investigated the behaviour of introducing ZrSi2 layer between the top coat layer Yttria-stabilized zirconia (YSZ) and the bond coat layer CoNiCrAlY in thermal barrier coatings where ZrSi2 layer helped self-healing of the cracks. Powder mixtures of ZrSi2/8YSZ and ZrSi2/CoNiCrAlY were used to imitate the real case. At 800 degrees C under argon, there was no change in the chemical composition of both ZrSi2 and 8YSZ. ZrSi2 was oxidized in case of treatment in air atmosphere at 800 degrees C with no evidence for any self-healing reactions. At 1000 and 1200 degrees C under argon the formation of ZrSiO4 phase was detected which was a strong evidence of self-healing reaction. ZrSiO4 phase was also detected at 1200 degrees C in air with the appearance of SiO2 phase. A limited interaction was detected at 1000 degrees C between ZrSi2 and CoNiCrAlY under vacuum. Si was detected in the surface of CoNiCrAlY grains and Ni was detected in the composition of ZrSi2. This behavior could contribute to a chemical bonding between ZrSi2 and CoNiCrAlY layers. The obtained data were confirmed by XRD, SEM and EDX analyses.