目的 研究超音速喷涂45CT涂层抗KCl+K2SO4+Na2SO4熔融盐腐蚀性能,了解45CT涂层在熔融盐中的防护及失效机制.方法 将试样置于KCl+K2SO4+Na2SO4混合熔盐中,获得样品在熔盐中不同温度下的腐蚀动力学规律.采用XRD、SEM、EDS对高温腐蚀产物成分、结构、形貌进行分析.结果 45CT涂层在熔融盐中的主要腐蚀产物为Cr2O3、NaCrO2.在600℃和650℃下,涂层能较好地保护基体,涂层上腐蚀产物层较薄;而在700℃下,涂层退化严重,涂层内有大量金属硫化物,基体中的Fe向涂层扩散.结论 在高温条件下,涂层易发生硫化,导致涂层与氧化膜的弱结合.随着测试温度升高,涂层在KCl+K2SO4+Na2SO4熔融盐中的热腐蚀越严重,涂层失效加快.
The work aims to study corrosion property of 45CT coating prepared by HOVF in KCl + K2SO4+ Na2SO4 molten salt, and understand the protection and failure mechanisms of 45CT coating in molten salt. The samples were immersed in KCl+K2SO4+Na2SO4 mixed molten salt to obtain corrosion kinetic of the samples in the molten salt at different temperatures. The composition, structure and morphology of high temperature corrosion products were investigated by using XRD, SEM and EDS. Main corrosion products of the 45CT coating corroded molten salt were identified as Cr2O3 and NaCrO2. The coating could protect the substrate effectively and the layer of corrosion products on it was thinner at 600℃ and 650℃. However, the coating degraded seriously at 700℃ and a lot of sulfides were detected in the coating. Fe in the substrate diffused toward the coating. Sulphidation occurs easily in 45CT coating at high temperature, leading to weak bonding between the oxide film and coating. As temperature increases, hot corrosion of 45CT coating in KCl+ K2SO4+Na2SO4 molten salt becomes more serious and results in faster coating degradation.
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