Transactions of Nonferrous Metals Society of China The Chinese Journal of Nonferrous Metals

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中国有色金属学报(英文版)

Transactions of Nonferrous Metals Society of China

Vol. 22    No. 8    August 2012

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Microstructure and depositional mechanism of Ni-P coatings with nano-ceria particles by pulse electrodeposition
ZHOU Xiao-wei1, SHEN Yi-fu1, JIN Hui-ming2, ZHENG Ying-ying1

1. College of Materials Science and Technology, Nanjing University of Aeronautics and Astronautics,
Nanjing 210016, China;
2. College of Mechanical Engineering, Yangzhou University, Yangzhou 225127, China

Abstract:Nano-CeO2 (RE) particles were co-deposited into Ni-P binary composite coatings by applying pulse current (PC) under ultrasonic (U) field. Morphology, chemical content and crystal microstructure were characterized by environmental scanning electron microscopy (E-SEM) with energy dispersive X-ray analysis (EDXA), XRD diffractometry and transmission electron microscopy (TEM). Experimental results show that Ni-P coating reinforced with 15g/L nano-CeO2, in amorphous state and with compact structure, can be improved in the microhardness from HV0.2580 to HV0.2780 by annealing at 600 °C for 2 h. The highest content of codeposited Ce and deposition rate can reach 2.3% and 68 μm/h, respectively. Furthermore, the effect of RE adsorption and pulse overpotential on depositional mechanism was investigated. n-CeO2 particles or Ce4+ ions with strong adsorption capacity acted as the catalytic nucleus to improve densification effectively. During annealing at 600 °C for 2 h, n-CeO2 particles will uniformly adsorb on crystal grain to preferentially pad and heal up gaps of cracking Ni boundaries, promoting dispersion strengthening with refiner-grained structure.

 

Key words: Ni-P coating; pulse electrodeposition; overpotential; depositional mechanism; CeO2

ISSN 1004-0609
CN 43-1238/TG
CODEN: ZYJXFK

ISSN 1003-6326
CN 43-1239/TG
CODEN: TNMCEW

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