Concentrated Solar Power Testing of Plasma-Sprayed Hybrid Thermal Barrier Coatings

Abstract

Multilayered thermal barrier coatings (TBC) are commonly used in systems exposed to extensive heat, such as jet engines or gas turbines. The testing of coatings’ performance is usually carried out using electric or gas furnaces. Concentrated solar power (CSP) could provide a cost-effective and environmentally friendly alternative using natural energy source. Moreover, it can also simulate material exposure in real applications, e.g., in solar power plant. In this study, the possibility of using concentrated solar power to test the performance of TBCs prepared by hybrid water/argon-stabilized plasma technology was studied for the first time. Testing procedure was carried out in three stages. In stage I, the procedure was optimized for multilayered TBC and then one selected condition was used in stage II and stage III also for hybrid TBCs. In service, TBC top-coat layer may be exposed also to so-called CMAS air-borne particles occurring in the atmosphere which may melt at elevated temperatures and penetrate the coating microstructure, inducing crystallographic and volumetric changes therein. Therefore, testing with the presence of CMAS particles was also included in this study to observe its influence on the coating microstructure under solar irradiation for potential environmental barrier coatings applications, e.g., solar power plants in desert areas. Changes in the coating microstructures were studied using SEM analysis and X-ray diffraction. The interaction of the coatings with melted CMAS particles was observed using EDS analysis. The results show that the CSP may be a suitable method for TBCs testing, if provided with several adjustments, especially regarding temperature control and measurement. In general, the tested TBCs withstood the CSP testing without significant morphological changes when tested without CMAS particles, while suffered from severe damage during the CSP testing with CMAS particles applied on the surface.