Effect of irregular microcracks on the hot corrosion behavior and thermal shock resistance of YSZ thermal barrier coatings

The durability and service performance of thermal barrier coatings (TBCs) is influenced by its microstructure. One type of yttria stabilized zirconia coating containing irregular microcracks (mc-YSZ) was prepared by atmospheric plasma spraying (APS) method in this study, and the differences in hot corrosion behavior and thermal shock resistance between the conventional YSZ coating and the mc-YSZ coating were investigated. Results showed that the presence of irregular microcracks facilitated the penetration of corrosive salt (V2O5 and Na2SO4) and accelerated the hot corrosion reaction. The deflection effect of irregular microcracks in the early stage of hot corrosion could suppress the propagation of cracks generated by corrosion; but irregular microcracks would merge with corrosion cracks in the later stages of corrosion and aggravate the failure of the coatings. Thermal shock tests showed no significant difference of the thermal shock lifetime between YSZ coating and mcYSZ coating, which proved that this irregular microcrack could not effectively improve the strain tolerance. The present study provides a reference for the structure design of thermal barrier coatings: when designing the structure of the coating, the appearance of that irregular microcracks should be avoided.

Automated summary

The presence of irregular microcracks in yttria stabilized zirconia coatings was found to accelerate hot corrosion reaction and aggravate coating failure, but has no significant effect on the strain tolerance of the coatings.