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$\beta$-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.
Al-Cr coatings were prepared on Ni-based superalloy K417G by pack cementation method. Hot corrosion resistance of the coatings beneath deposits of 25 NaCl+75 Na2SO4 (mass) at 900℃ was investigated. The average Cr content of the formed two layered Al-Cr coating prepared by two step process was ca. 20 mass, of which the outer zone was com-posed of β-NiAl with a little AlCr2 phase. In the contrast, a three layered coating was formed for the AlCr coating prepared by one step progress, of which Cr mainly existed in the outer zone (8 mass) and the middle zone (3 mass). The Al-Cr coating with high Cr content possessed much better resistance to hot corrosion at 900℃ beneath deposits of 25 NaCl+75 Na2SO4.
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