Honglong Wang

Evolution of the Thermal Conductivity of Sm 2 Zr 2 O 7 Under CMAS Attack

One impact of the reaction of thermal barrier coatings (TBCs) in gas turbine engines with volcanic ash or other debris (CMAS) is a change in the thermal conductivity. In this study, the effective thermal conductivity of the potential TBC material Sm2Zr2O7 was determined after CMAS reaction below and above the melting temperature of the CMAS. The conductivities of Sm2Zr2O7, CMAS, and the reaction layer were determined separately. The phase content and microstructure were characterized with scanning electron microscopy and X-ray diffraction. The change in microstructure and formation of Ca2Sm8(SiO4)6O2 led to an increase in the effective conductivity, which would reduce the effectiveness of the TBC.

DEGRADATION OF SM2ZR2O7 THERMAL BARRIER COATING CAUSED BY CALCIUM-MAGNESIUM-ALUMINUM-SILICON OXIDE (CMAS) DEPOSITION

Rare earth zirconates are promising materials for use as thermal barrier coatings in gas turbine engines. Among the lanthanide zirconate materials, Sm2Zr2O7 with the pyrochlore structure has lower thermal conductivity and better corrosion resistance against calcium-magnesium-aluminum-silicon oxide (CMAS). In this work, after reaction with CMAS, the pyrochlore structure transforms to the cubic fluorite structure and Ca2Sm8(SiO4)6O2 forms in elongated grain.