Increasing load flexibility of thermal barrier coatings by microstructural design

In industrial gas turbines, atmospheric plasma sprayed (APS) thermal barrier coatings of yttrium stabilized zirconia (YSZ) have been used for decades. These coatings allow turbine efficiency to be maximized by enabling high combustion temperatures that are above the melting point of the structural material of the components. At constant temperatures, these coatings allow long component life. In the future, the turbines will be used to compensate fluctuations in energy supply caused by renewable energy sources. As a result, short cycles and thus load flexibility are becoming increasingly important, but the rapid transients that occur in the process have a negative impact on the service life of the coatings. Therefore, the aim of my PhD thesis is to investigate different coating microstructures to develop a coating system optimized for short load cycles. The results of the development of highly porous APS coatings, coatings with segmentation cracks and columnar structured coatings will be shown and compared to standard APS coatings. Especially the effect of the microstructure on the stress state in the coating during short load cycles will be evaluated. A factor of 2 longer lifetime than standard APS systems is envisaged for these new systems.