Porosity control for TBCs provided by polymer-ceramics composite powder

The thermal barrier coatings (TBCs) are widely investigated for protecting parts of the turbine, such as blades and combustors. TBCs are typically consisted from two layers, bond coat and top coat. The top coat prevents heat transfer from the combustion gas to the substrate. Recently, the turbine inlet temperature is increasing for the thermal efficiency improvement. Therefore, top coat needs to be capable of lower thermal conductivity.

　Some studies of low thermal conductivity coatings are prepared by using the polymer mixed materials with low thermal conductivity ceramics, such as partially-stabilized zirconia are reported. In these reports, process of evaporate the polymer in the coating is considered to obtain porous thermal barrier coatings.

This study is carried out to control pores in the coating by changing the composition and size of pore-forming polymer materials. In the investigation, three kinds of polymers, polyester (PE), poly-ether-ether-ketone (PEEK), and aromatic polyamide (PI) are prepared for pore-forming materials. These pore-forming materials are combined with Zirconia stabilized yttria (YSZ), for ready to spray materials.

As a result of the investigation, the coating was able to obtain lower thermal conductivity than conventional YSZ coating by atmospheric plasma spraying (APS).