The effect of electrodeposition conditions and post-annealing on nanostructure of Co-W coatings

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• 作者：N. Tsyntsaru^a ; ^{natalia.tintaru@mtm.kuleuven.be} ; H. Cesiulis^b ; A. Budreika^b ; X. Ye^a ; R. Juskenas^c ; J.-P. Celis^a
• 关键词：Cobalt&ndash ; tungsten alloys ; Electrodeposition ; Structure ; Grain size ; Thermal stability
• 刊名：Surface and Coatings Technology
• 出版年：2012
• 期刊代码：106_02578972
• 类别：ms
• 出版时间：25 May, 2012
• 卷：206
• 期：19-20
• 页码：4262-4269
• 文件大小：1386 K

摘要

Nanocrystalline Co-W alloys were electrodeposited at 60 掳C from citrate-borate electrolyte at pH 6.7 and 8.0. The effect of electrodeposition conditions in the direct (DC) and pulse (PC) current modes on tungsten content in the alloys and their structure was investigated. The tungsten content in the alloys was varied between 13 and 36 at.%, and it defines the grain size of the Co-W coatings irrespectively on the deposition mode or current density allowing us to obtain this particular content of alloy. A grain size of 27-40 nm was obtained for a lower content of tungsten, and 3-6 nm is characteristic for as-deposited coatings containing more than 23 at.%W. The formation of W solid solution in the Co and Co₃W phases is discussed. The transition from nanocrystalline to polycrystalline structure of the Co-W coatings with an as-deposited grain size of 3-6 nm was obtained by annealing. In coatings containing 24.5 at.%W, a well developed polycrystalline structure of Co₃W appears at 400 掳C with {200}, {201} and {220} textures which remain stable up to 1000 掳C. The grain size of the coatings containing 24.5 at.%W increases from 3-5 nm up to 26-30 nm after annealing at 400 掳C. Whereas, Co-W coatings with a tungsten content of 34.4 at.%maintain their nanocrystallinity at 400 掳C, and transforms to the polycrystalline structure at 600 掳C with an increase of grain size up to 45 nm.