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采用粉末包埋法在Ni基高温合金K417G上制备Al-Cr涂层,并研究其在25%NaCl+75%Na2SO4(mass%)盐膜下900℃的热腐蚀特性.采用两步法沉积的Al-Cr涂层为双层结构,外层为β-NiAl相和少量AlCr2相,平均Cr含量约为20 mass%;内层为互扩散带.而采用一步法沉积的Al-Cr涂层具有三层结构,外层和中间层均为β-NiAl相,它们之间的主要差别是外层Cr含量为8 mass%左右,中间层Cr含量为3 mass%左右,内层也是互扩散带.热腐蚀试验结果表明,低Cr含量的Al-Cr涂层氧化膜易剥落,抗热腐蚀性能较差;高Cr含量的Al-Cr涂层表面能形成较完整的氧化膜,抗热腐蚀性能明显优于低Cr含量的涂层.
The Al-Cr coating was prepared on the Ni-based superalloy K417G by powder embedding method and its corrosion behavior at 900 ℃ under 25% NaCl + 75% Na2SO4 (mass%) salt film was investigated. The Al-Cr coating has a double-layered structure with an outer layer of β-NiAl phase and a small amount of AlCr2 phase, with an average Cr content of about 20 mass%; the inner layer is an interdiffusion zone, whereas the Al-Cr coating deposited by the one- The three-layer structure, the outer layer and the middle layer are both β-NiAl phases. The main difference between them is that the content of Cr in the outer layer is about 8 mass%, the content of Cr in the middle layer is about 3 mass%, and the inner layer is also an interdiffusion zone. The results of hot corrosion test show that the Al-Cr coating with low Cr content is easy to peel off and the thermal corrosion resistance is poor. The surface of the Al-Cr coating with high Cr content forms a complete oxide film with obvious anti-hot corrosion performance Better than low Cr coating.