A case study on CMAS corrosion of an in-situ microstructure modification YSZ TBCs fabricated by EB-PVD

At elevated temperature, the inter-columnar pores of electron beam physical vapor deposited (EB-PVD) thermal barrier coatings (TBCs) may act as infiltration channels for the molten calcium–magnesium–alumino-silicate (CMAS) and, therefore, makes it susceptible to be attacked by CMAS. To enhance the CMAS corrosion resistance of EB-PVD TBCs, a microstructure modification yttria-stabilized zirconia (YSZ) top coat consisting of a low porosity fibrous structure layer on the conventional columnar structure layer was fabricated by in-situ parameter modification. The anti-CMAS corrosion performance of the in-situ modified YSZ coating was evaluated at 1250 °C and the evolution of the microstructure was investigated in detail. The results show that the inter-columnar pores were sealed by the low-porosity and smooth fibrous structure layer. Due to the porosity and the size of the pores of the fibrous structure layer are dramatically reduced, the penetration rate of CMAS is significantly lower in the in-situ microstructure modification coating than in the conventional columnar structure coating, and the interaction between CMAS and YSZ coating was also reduced.