Abstract
The longevity and the cost of thermal energy storage (TES) components in solar power plants is a matter of great concern. To address this issue, three kinds of thermal spray coatings (Ni-5Al, NiCoCrAlY, and CoNiCrAlY) were successfully deposited on the low-alloy steel (P91) substrate by high velocity oxygen fuel (HVOF) spraying process. The corrosion performance of the prepared coatings in Solar Salt (at 565 °C for 15 days) was evaluated in detail by gravimetric analysis, field emission scanning electron microscopy (FESEM), and X-ray diffraction (XRD). Results revealed that all three coatings were quite dense and the substrates were generally well protected by the coatings. Compared with Ni-5Al and NiCoCrAlY coatings, the CoNiCrAlY coating exhibited the best corrosion performance owing to the formation of a dense oxide layer on the surface. Further, it was revealed that despite containing corrosion-resistant composition in NiCoCrAlY coating, the presence of a large number of phase interfaces could be the vulnerable regions that may result in local corrosion failure. Moreover, increasing the content of aluminum and using pre-alloyed powder may be an excellent solution to improve the performance of Ni-5Al coating.
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