分别利用真空等离子沉积和超音速火焰喷涂技术制备含有Y和含Y氧化物的NiCoCrAl涂层,用差热分析和光学及电子显微镜研究两种涂层在Ar-16.7%O2,Ar-3.3%H2O和Ar-0.2%H2-0.9%H2O气氛中1100℃时的氧化动力学和断面微观结构,通过第一性原理计算对比在不同气氛中含Y氧化物对涂层氧化的影响机理.结果表明:对于NiCoCrAl+Y涂层,Y倾向于向界面扩散并在界面富集导致Al2O3膜生成更多有利于内氧化的孔洞,水蒸气更会对内氧化产生促进作用.而对于NiCoCrAl+Y(O)涂层,由于Y在涂层制备过程中被氧钉扎,导致NiCoCrAl+Y(O)涂层在上述气氛中生成了平直而均匀的Al2O3层,不同气氛对其氧化行为影响较小.上述研究进一步揭示NiCoCrAl涂层中活性元素Y的存在状态和氧化气氛中的水蒸气对氧化铝组织结构和生长速率有重要影响.
NiCoCrAl coatings containing Y and Y oxide were made using vacuum plasma deposition and high-velocity oxygen fuel respectively, high temperature oxidation dynamics and cross-section microstructures of NiCoCrAl+Y and NiCoCrAl+Y(O) coatings in Ar-16.7%O2, Ar-3.3%H2O and Ar-0.2%H2-0.9%H2O at 1100℃ were investigated by differential thermal analysis (DTA) and optical and electron microscope.The influencing mechanism of Y oxide on the oxidation of coatings at different atmosphere was compared by computation using First-Principles.The results show that Al2O3 layer on NiCoCrAl+Y coatings has more holes for internal oxidation on account of the element Y diffusion and enrichment on the interface.In addition, steam can promote the internal oxidation.While a thinner and uniform alumina form on NiCoCrAl+Y(O) coatings because element Y is pinned by oxygen atoms during the preparation of coatings.Water vapor has less influence on protective alumina formation on the NiCoCrAl+Y(O) coating.Therefore, oxidation behavior of NiCoCrAl coatings vary in composition and structure in different oxidizing atmosphere.Besides, Y and Y-enrichment oxides have key influences on the microstructure and the growth rate.
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