High-temperature sulfur corrosion behavior of h-BN-based ceramic coating prepared by slurry method

The heating surface of a coal-fired boiler is susceptible to high-temperature sulfur corrosion. To investigate and address this problem, a h-BN-based ceramic coating was prepared on the surface of a 20CrMn steel sheet using the slurry method. After sintering, the coating had a relatively dense surface with only a small number of microcracks. The coating and the substrate exhibited a metallic damascene structure and were well bonded. The high-temperature-corrosion behavior of the uncoated and ceramic-coated steel sheets in sulfur dioxide (SO2), hydrogen sulfide (H2S), and sulfate environments was investigated. The results show that the coating could effectively prevent inward diffusion of sulfur, and it exhibited high-temperature-corrosion resistance. The high-temperature-corrosion resistance of the coated steel sheet was 8, 7, and 1.7 times that of the uncoated steel sheet in the SO2, H2S, and sulfate environments, respectively. After corrosion in the SO2 and H2S atmospheres, potassium sulfate (K2SO4) crystal grains were formed on the surface of the coating. However, because the coating was relatively dense, thus preventing S diffusion, the presence of K2SO4 was not detected inside the coating.