Thermal conductivity and stability of multilayered thermal barrier coatings under high temperature annealing conditions

Pyrochlore oxides have most of the relevant attributes for use as next generation thermal bather coatings (TBCs) such as phase stability, low sintering kinetics and low thermal conductivity. One of the issues with the pyrochlore oxides is their lower toughness and therefore higher erosion rate compared to the current state of the art TBC material, yttria (6-8 wt.%) stabilized zirconia (YSZ). In this work, sintering characteristics were investigated for novel multilayered coating consisted of alternating layers of pyrochlore oxide viz. Gd2Zr2O7 and t' low k (rare earth oxide doped YSZ). Thermal gradient and isothermal high temperature (1316 degrees C) annealing conditions were used to investigate sintering and cracking in these coatings. The results are then compared with that of relevant monolayered coatings and a baseline YSZ coating. (C) 2014 Elsevier Ltd. All rights reserved.