Degradation Behavior of Nanostructured Coatings Deposited by High-Velocity Arc Spraying Process in an Actual Environment of a Coal-Fired Boiler

FeCr-based nanostructured coatings were deposited on a 301S stainless steel substrate by the high-velocity arc spraying process in the current work. The oxidation behavior of the coatings exposed to elevated temperatures (700°C and 900°C) under laboratory conditions as well as in an actual industrial environment of a coal-fired boiler (at 700 ± 10°C) was investigated. X-ray diffraction, scanning electron microscopy/energy-dispersive analysis, and transmission electron microscopy techniques were used to characterize the coating as well as to analyze the corrosion products for elucidating the corrosion mechanisms. The microhardness of the coating was found to be 520–1100 HV. The (FeCr)-based nanostructured coating showed good adherence to the 310S substrate and excellent oxidation resistance during the exposures with no tendency for spallation of its oxide scales in both environments. The nanosized grain morphology of the coating facilitated the formation of protective scales, which is continuous, adherent, and nonporous due to the higher diffusivity of alloying elements in the coatings. It precludes high-temperature oxidation by acting as a diffusion barrier between the environment and the coating.