Thermal cycling behavior and failure mechanism of LaTi 2Al 9O 19/YSZ thermal barrier coatings exposed to gas flame

Abstract

As a potential thermal barrier coating (TBC) material, lanthanum titanium aluminum oxide (LaTi 2Al 9O 19, LTA) possesses excellent phase stability between room temperature and 1600 °C and desirable thermo-physical properties, but its thermal cycling performance is rather poor partially due to the low fracture toughness. In this work, LTA/yttria stabilized zirconia (YSZ) double ceramic layer TBC was prepared and its thermal cycling lifetime was assessed by a gas burner facility at a coating surface temperature of 1300 ± 50 °C. Chipping of LTA layer, which was different from the failure mechanism of the traditional plasma-sprayed TBCs, was visible in the center part of the TBC after about 3000 cycles, equaling to a holding time of 500 h at 1300 ± 50 °C. The failure of the LTA layer was mainly due to the decomposition and sintering of LTA exposed to extremely high-temperature gas flame. Followed by another 1000 cycles, the YSZ layer was also cracked along its interface to the bond coat.