通过水溶液镀Cr后再用AlCl3-EMIC (氯化1-甲基3-乙基咪唑)离子液体镀Al, 制备Cr/Al复合镀层, 其后通过低温扩散热处理制备Al-Cr涂层. 用OM, SEM, BSE, EDS和XRD研究了短时间热处理时, 热处理温度对Al-Cr涂层组成和结构的影响. 结果表明, Cr/Al复合镀层在540 ℃时即可发生明显的互扩散, 形成Al-Cr合金层. 通过对复合镀层中Cr和Al镀层厚度的控制, 可以得到不同组成的Al-Cr合金涂层. 6.5 μm Cr/15 μm Al的复合镀层经640 ℃/960 min热处理, 表面形成以Al8Cr5为主的合金涂层; 1.6 μm Cr/15 μm Al的复合镀层经 600 ℃/30 min热处理, 可得到以Al4Cr为主的Al-Cr涂层.
The Al-Cr coating exhibits a good steam oxidation resistance and can act as tritium permeation barrier. It is necessary to prepare Al-Cr coating at low temperatures to avoid detrimental effect on the mechanical properties of the substrate. In the present study, a new process was proposed to prepare Al-Cr coating by electrodeposition of Cr/Al composite coatings firstly, and then heat treatment at low temperatures. The Cr/Al composite coatings were obtained by electrodepositing Cr from aqueous solution followed by electrodepositing Al from AlCl3-EMIC ionic liquid. Effects of the temperature of heat treatment on the composition and phase of alloy layers were studied by using OM, SEM, BSE, EDS and XRD. The results showed that an Al-Cr alloy layer at the Cr/Al interface was formed even at low temperature of 540 ℃ by the interdiffuse between Al and Cr coating. The different Al-Cr alloy layers could be formed by controlling the thickness of Cr and Al in Cr/Al composite coatings. For 6.5 μm Cr/15 μm Al composite coating, the main phase was Al8Cr5 for 960 min heat treatment at 640 ℃, and for 1.6 μm Cr/15 μm Al composite coatings treated at 600 ℃ for 30 min, the main phase of alloy layer was Al4Cr.
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