High-temperature oxidation-resistant glass-ceramic/YSZ composite coatings for gas turbine engine applications

Oxidation behavior of a novel double-layered thermal barrier coating (TBC) system consisting of glass-ceramic-25 wt.% yttria-stabilized zirconia (YSZ) bond coat and 8 wt.% YSZ top coat was investigated at 900 degrees C and 1000 degrees C for 100 h. Developed TBC system showed changes in phase, microstructure, and mechanical properties with increasing temperature. Zircon formation in the glass-ceramic during oxidation (1000 degrees C, 100 h) enhanced oxidation resistance of the TBC system. Weight gain per unit surface area was about 0.085 mg/cm(2) after 100 h at 1000 degrees C during oxidation test; whereas, it was much lower (similar to 0.04 x 10(-2) mg/cm(2)) at 900 degrees C after same period of time. Tetragonal zirconia (t-ZrO2) top coat changed to both cubic and tetragonal phases after 100-h exposure at 1000 degrees C. Nanohardness and Young's modulus values of bond coat and top coat were increased with increasing temperature.