Effect of SiC whiskers on thermal cycling performance of YSZ-Based sealing coating

Abstract

Two types of Y2O3 partially stabilized ZrO2(YSZ)-based agglomerated powders with and without SiC whiskers were prepared by spray granulation, and the flow ability, apparent density and particle size distribution of them were investigated. The thermal cycling performance and failure mechanism of conventional high temperature sealing coating and modified one with additional layer with whiskers, which were sprayed by air plasma spraying (APS), were comparatively analyzed. The results showed that, compared to the powder without whiskers, the flow ability of that with whiskers reduced by 2.32%, and the apparent density and the proportion of 45–150 μm agglomerated powder increased by 1.53% and 2.29%, respectively. The thermal cycling failure mode of conventional high temperature sealing coating was the overall spalling of ceramic coating, and the spalling position originated from the interface of thermally grown oxide (TGO)/ceramic coating. Microstructure observation indicated that the structure integrity of SiC whiskers in the additional layer sprayed by APS was still retained. The whiskers were uniformly distributed and theinterface between bonding coating and ceramic coating exhibited excellent bonding. With the additional layer containing whiskers, the thermal cycling life of the coating was increased by 102.53%. In the thermal cycling process, the “bridging” and “pulling-out” effects of whiskers located at the additional layer consumed considerable energy, which could reduce the driving force of crack growth. Besides, a porous structure of the additional layer after thermal cycling was formed due to “bridging” and “pulling-out” of whiskers, further improving the thermal cycling life of coating with the additional layer.