Thermal barrier coatings (TBCs) are widely utilized in gas turbine engines for power generation. In recent years, the application of TBCs in automotive has been introduced to improve engine efficiency. Low thermal conductivity and high durability are desired coating properties for both gas turbine engines and automotive. Also, suspension plasma spraying (SPS) permits a columnar microstructure that combines both properties. However, it can be challenging to deposit a uniform columnar microstructure on a complex geometry, such as a gas turbine component or piston head, and achieve similar coating characteristics on all surfaces. This work's objective was to investigate the influence of spray angle on the microstructure and lifetime of TBCs produced by SPS. For this purpose, SPS TBCs were deposited on specimens using different spray angles. The microstructures of the coatings were analyzed by image analysis for thickness, porosity, and column density. Thermal and optical properties were evaluated on each TBC. Lifetime tests, specifically designed for the two applications, were performed on all investigated TBCs. The lifetime results were analyzed with respect to the TBC microstructure and thermal and optical properties. This investigation showed that there is a limit to the spray angle that achieves the best compromise between TBC microstructure, thermal properties, optical properties, and lifetime.

High-entropy alloys (HEAs) represent a relatively new group of multicomponent alloys that have shown great potential for applications requiring tribological and oxidation resistant properties. Consequently, thermally sprayed coatings of different HEA chemistries have received increasing research attention. In this paper, atomized equimolar CrFeCoNi and AlCrFeCoNi feedstocks were used for high velocity air-fuel spraying (HVAF) to produce overlay coatings using two different nozzle configurations. The microstructure, phase constitution and hardness of the coatings were analyzed along with the primary aim of testing the coatings for their oxidation behavior. The performance of the two HEA chemistries was compared with two commercial MCrAlY coatings that are well-established bond coat materials for thermal barrier coatings (TBCs). An investigation was conducted to test the coatings’ performance as bond coats by applying suspension plasma sprayed yttria-stabilized zirconia top coats and evaluating the thermal cycling behavior of the TBCs. The AlCrFeCoNi-coating was found to demonstrate a lower oxidation rate than the CrFeCoNi-coating. However, the AlCrFeCoNi-coating was found to form more rapid oxide scales compared with the commercial bond coat material that also contained reactive elements.