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Chen H.,Jiangxi University of Science and Technology | Yang J.-G.,Jiangxi University of Science and Technology | Li J.-H.,Jiangxi University of Science and Technology | Zhang X.-H.,General Research Institute for Nonferrous Metals, China | Peng C.,Central Academe of Hunan Nonferrous Metals Ltd.
Fenmo Yejin Cailiao Kexue yu Gongcheng/Materials Science and Engineering of Powder Metallurgy | Year: 2014

Electroplating Ni-W coatings have been prepared on medium carbon steel substrate using nickel sulphate and sodium tungstate as precursors. The elemental composition, microstructures, phase composition and performance of the coatings were analyzed by SEM, EDS, AFM, XRD, microhardness tester and wear tester. The surface morphologies after wear were observed and the wear mechanism was analyzed. The results show that Ni-W alloy coatings are not found to have obvious flaws and have a good bond with the matrix. The crystalline Ni-W coating is composed of Ni-based solid solution and the coatings before and after heat treatment are crystalline structure. The microhardness of the coatings increases with increasing heat treatment temperature, reaching its maximum value (1100 HV0.3) for heat treatment at 500 ℃, and then decreases for heat treatment at higher temperatures. Due to the low surface roughness of the coating with heat treatment, high microhardness, the crystalline Ni-W coating has strong wear resistance. Source


Peng C.,Central Academe of Hunan Nonferrous Metals Ltd. | Yin Z.-W.,Central Academe of Hunan Nonferrous Metals Ltd. | Wang X.,Central Academe of Hunan Nonferrous Metals Ltd. | Liu Y.,Central Academe of Hunan Nonferrous Metals Ltd. | And 2 more authors.
Fenmo Yejin Cailiao Kexue yu Gongcheng/Materials Science and Engineering of Powder Metallurgy | Year: 2011

The effects of sodium lauryl sulfate (SLS) and 1.4-butynediol (BOZ) on Ni-W electro-deposition, electrodepositing layer quality, targeted inhibition, hardness and corrosion were investigated by complex theory, grain characterization, surface morphology, microstructure and ΦPYMKNH equation. The inhibition mechanism and the cause of hardness decreasing were explored in the present paper. The results show that, when SLS is 0.2 g/L and BOZ is 0.4 g/L, surfactant reaches the critical micelle concentration (CMC), inhibition becomes obvious and the depositing velocity drops quickly. Meanwhile, the Ni-W electrodepositing layers show refine grain and its surface becomes smoother. In addition, corrosion resistance is improved significantly with year corrosion rate (Ke) of 0.0025 mm/y and corrosion resistance of class 2. During the electrodepositing, SLS shows a significant inhibition to tungsten, meaning that tungsten content in the electrodepositing layer and the hardness of the electrodepositing layer decrease with increasing SLS concentration. Small amount of SLS can prevent pinholes and bubbles, while the electroplated layers are dislocated obviously and its surface becomes rough when SLS is 0.4 g/L. However, the dislocated layers and cracks can be removed by adding BOZ. Extraordinary smooth coating is obtained with SLS of 0.2 g/L and BOZ of 0.4 g/L. Source

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