Development of refractory silicate-yttria-stabilized zirconia dual-layer thermal barrier coatings

Development of advanced thermal barrier coatings (TBCs) is the most promisi ng approach for increasing the efficiency and performance of gas turbine en gines by enhancing the temperature capability of hot section metallic compo nents. Spallation of the yttria-stabilized zirconia (YSZ) top coat, induced by the oxidation of the bond coat coupled with the thermal expansion misma tch strain, is considered to be the ultimate failure mode for current state -of-the-art TBCs. Enhanced oxidation resistance of TBCs can be achieved by reducing the oxygen conductance of TBCs below that of thermally grown oxide (TGO) alumina scale. One approach is incorporating an oxygen barrier havin g an oxygen conductance lower than that of alumina scale, Mullite, rare ear th silicates, and glass ceramics have been selected as potential candidates for the oxygen barrier. This paper presents the results of cyclic oxidatio n studies of oxygen barrier/YSZ dual-layer TBCs.