Effects of isothermal oxidation on microstructure and mechanical properties of thermal barrier coatings

Abstract An 8 (wt.) % yttria partially stabilized zirconia (YSZ) coating isothermally oxidized in air at 1100 °C for up to 3000 h was investigated by means of indentation and electron microscopy analyses. It is found that the growth kinetics of thermally grown oxides followed a parabolic law. The apparent porosity within the coatings decreased after isothermal oxidation. The tetragonal prime YSZ phase transformed into cubic and then monoclinic phases during isothermal oxidation. Elastic modulus, microhardness and fracture toughness of the coating increased as oxidation duration prolonged. The correlation between microstructural variation and mechanical properties was discussed.