Investigation of Detonation-Sprayed NiCr–Al Coatings Tested under Real Operating Conditions of a Thermal Power Plant

Abstract

This study presents the experimental results of high-temperature oxidation testing under actual operating con ditions in a thermal power plant of gradient and homogeneous composite NiCr–Al coatings produced by the detonation spraying method. To characterize the degradation mechanisms of the tested coatings, systematic analyses were performed, including phase composition evaluation, and detailed microstructural examination using scanning electron microscopy (SEM). The evolution of oxide layers and elemental redistribution across the coating thickness were also assessed to clarify the influence of coating architecture on protective perfor mance. The experimental results demonstrated that the gradient composite NiCr–Al coatings exhibit superior resistance to high-temperature oxidation compared to homogeneous coatings. The gradient architecture effec tively preserved structural integrity and promoted a more uniform distribution of aluminum and chromium within the coating thickness. This compositional optimization facilitated the formation of continuous and ad herent protective oxide layers, predominantly Al2O3 and Cr2O3, which significantly reduced oxidation kinet ics and inhibited coating degradation. In contrast, the homogeneous NiCr–Al coatings showed noticeable aluminum depletion, crack formation, and oxide scale spallation after prolonged exposure to high temperature industrial conditions. The findings of this study confirm that gradient NiCr–Al coatings deposit ed by detonation spraying represent a promising protective solution for components operating in severe high temperature and corrosive environments, offering improved durability and extended service life for industrial and energy related applications.