Abstract
Ca50Mg10Al10Si30 (CMAS) corrosion induced microstructure evolution and composition development in yttria-stabilized zirconia (YSZ) thermal barrier coatings prepared by electron-beam physical vapor deposition (EB-PVD), have been investigated by means of analytical electron microcopy, Raman spectroscopy and X-ray diffraction. The corroded YSZ still mainly consists of t-ZrO2 and no harmful monoclinic zirconia formation occurs; however, the feathery and columnar morphology of the as-deposited YSZ coating transforms into an equiaxed grain structure with dramatic grain coarsening and significant CMAS infiltration. The CMAS corrosion induces dissolution of YSZ into the molten CMAS, spinel MgAl2O4 formation both in the intergranular gaps and inside YSZ grains, and anorthite (CaAl2Si2O8) precipitates in the intergranular gaps with reduced Mg and Ca content in the infiltrated amorphous CMAS. These results show that CMAS with a high content of calcium can induce significant grain coarsening and microstructure evolution that has a detrimental effect on primary function of the YSZ coating.
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