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.
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%Na_2SO_4 （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 ofβ-NiAl with a little AlCr_2 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%Na_2SO_4.
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