Coatings with Columnar Microstructures for Thermal Barrier Applications

Columnar‐structured thermal barrier coatings (TBCs) manufactured by electron beam‐physical vapor deposition (EB‐PVD) are well known to exhibit high strain tolerance. However, as EB‐PVD is a high‐vacuum process, it is expensive. Suspension plasma spraying (SPS) and plasma spray‐physical vapor deposition (PS‐PVD) are alternatives for the manufacture of similar microstructures. Herein, the state of the art of manufacturing columnar‐structured TBCs by SPS and PS‐PVD is outlined. Both processes have been investigated and further developed at Forschungszentrum Jülich for many years. The mechanisms leading to the formation of columnar‐structured coatings are described and differentiated from EB‐PVD. Examples are given for SPS and PS‐PVD columnar microstructures and their life performance. Columnar‐structured ceramic coatings are highly strain tolerant and thus ideal for thermal barrier systems, for example, in modern gas turbines. Suspension plasma spraying and plasma spray‐physical vapor deposition processes are cost‐effective novel processes to manufacture them.