Morphology, Structure, Microhardness and Corrosion Resistance of Ni-W Coating Annealed in Hydrogen and Argon Atmosphere
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JMEPEG (2017) 26:2465–2471 DOI: 10.1007/s11665-017-2658-y
Morphology, Structure, Microhardness and Corrosion Resistance of Ni-W Coating Annealed in Hydrogen and Argon Atmosphere Qiongyu Zhou, Wei Xie, Yadong Zhang, Liang Qi, and Xiaofen Wang (Submitted November 7, 2016; in revised form March 22, 2017; published online May 22, 2017) In this paper, an amorphous Ni-W coating was electrodeposited on the low-carbon steel and then annealed in hydrogen and argon atmosphere. Their characterization was carried out using scanning electron microscopy and x-ray diffraction. The corrosion characterization was carried out using the potentiodynamic polarization (Tafel) and electrochemical impedance spectroscopy. The results show that microcracks inevitably exist on the surface of Ni-W coating when annealed at 750 °C or higher temperature. After annealing treatment, amorphous structure transforms to crystalline and some new phases are precipitated, which is significantly affected by the annealing temperature and atmosphere. The microhardness of annealed Ni-W coatings is much higher than that of as-deposited coating, while an adverse corrosion performance is observed for the annealed Ni-W coatings. The coating annealed in hydrogen at 500 °C shows a huge improvement in hardness and a fairly acceptable corrosion resistance compared with the as-deposited Ni-W coating. Keywords
annealing atmosphere, corrosion resistance, electrodeposition, Ni-W coating
1. Introduction As a desirable engineering material, nickel and nickel alloy possess numerous excellent performance, such as high malleability, superior corrosion resistance and good decorative appearance (Ref 1-3). However, the application of nickel is restricted by its expensive cost. Because the failures (such as corrosion or wear) often occur on the surfaces of materials, therefore preparation of Ni coating is a convenient way to enhance the applications of Ni material for the economic consideration (Ref 4). In recent years, electrodeposition technology, which is really a convenient, practical and inexpensive method, has been widely used for preparing Ni or Ni alloy coating (Ref 5, 6). As the research on electrodeposited Ni coating continues, numerous Ni matrix alloy coatings or composite coatings with better properties were developed, such as Ni-W (Ref 7, 8), Ni-Fe (Ref 9), Ni-Cu (Ref 10), Ni-Zr (Ref 11), Ni-SiC (Ref 12), Ni-diamond (Ref 13), Ni-Mn (Ref 14) and Ni/MWCNT (Ref 15). Among these coatings, Ni-W coating has drawn in much attention as a candidate to replace chromium (Ref 16). Qiongyu Zhou, School of Materials Science and Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, Peoples Republic of China and Institute of Applied Physics, Jiangxi Academy of Sciences, Shangfang Road 108, Nanchang 330029 Jiangxi Province, Peoples Republic of China; and Wei Xie, Yadong Zhang, Liang Qi, and Xiaofen Wang, School of Materials Science and Engineering, Jiangxi University of Science and Technology, Ganzhou 341000, Peoples Republic of China. Contact e-mail: zhouz
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