Crack propagation in plasma-sprayed thermal barrier coatings

摘要

Ceramic thermal barrier coatings (TBCs) of yttria stabilized zirconia (YSZ) are increasingly utilized to enhance the performance of advanced gas turbines. In particular, plasma-sprayed TBCs provide a cost effective coating variant with low intrinsic thermal conductivity, which is further reduced by high porosity and numerous cracks. However, the thermally favourable defect structure has considerable disadvantages with respect to mechanical TBC integrity. To study the microstructural aspects of TBC failure in more detail, crack propagation experiments have been carried Out with a miniature mechanical testing device mounted in a scanning electron microscope. Cracks were propagated in a stable fashion parallel and normal to the spraying splats. Fractography studies reveal that the cracks essentially follow the pre-existing flaw structure. The results are correlated with the toughness behaviour. Effects of crack bridging are discussed.