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Liu H.,Shandong Polytechnic University | Guo R.X.,Zibo Institute of New Materials | Bian J.S.,Shandong Polytechnic University | Liu Z.,University of Manchester
Crystal Research and Technology | Year: 2013

This paper presents a comparative study of nanocrystallisation and the wear resistance of electroless plated Ni-P/Ni-W-P duplex coatings with a single Ni-W-P coating before and after high- power diode laser treatment. Effects of the laser operating parameters on microstructures, in terms of crystallisation, porosity formation, phase transformation and grain growth, were investigated using scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX) and quantitatively X-ray Diffraction (XRD). Microhardness and wear behaviour of the coatings before and after laser treatment were evaluated by measurement of coating surface and cross-section hardness as well as un-lubricated friction and wear tests. The results revealed that in the case of laser treatment, the Ni-P/Ni-W-P duplex coatings offered better wear resistance than the single Ni-W-P coating, while the as-plated, single Ni-W-P coating showed better wear resistance than the Ni-P/Ni-W-P duplex coatings. Adhesive wear mechanism prevails in the laser-treated coatings when subjected to wear test against hardened steel material. The effects of microstructural characteristics in the coatings, in particularly the grain size of Ni 3P phase and the degree of crystallisation, on the adhesive wear behaviour have been investigated and found to be dominant besides the effect of hardness. This paper presents a comparative study of nanocrystallisation and the wear resistance of electroless plated Ni-P/Ni-W-P duplex coatings with a single Ni-W-P coating before and after high- power diode laser treatment. Effects of the laser operating parameters on microstructures, in terms of crystallisation, porosity formation, phase transformation and grain growth, were investigated using scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDX) and quantitatively X-ray Diffraction (XRD). Microhardness and wear behaviour of the coatings before and after laser treatment were evaluated by measurement of coating surface and cross-section hardness as well as un-lubricated friction and wear tests. The results revealed that in the case of laser treatment, the Ni-P/Ni-W-P duplex coatings offered better wear resistance than the single. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Liu H.,Shandong Polytechnic University | Liu H.,University of Manchester | Guo R.-X.,Zibo Institute of New Materials | Liu Z.,University of Manchester
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2012

Characteristics of microstructures of electroless Ni-P/Ni-W-P duplex coatings were investigated using SEM/EDX and XRD analysis techniques. Microhardness and wear behaviour of the coatings before and after laser crystallization were evaluated by measurements of hardnesses of coating surface and cross-section, and by unlubricated friction and wear experiments. The results indicate that it is possible to prepare electroless Ni-P/Ni-W-P duplex coatings by sequential immersion in two different plating baths. After laser crystallization, the microstructures of electroless Ni-P/Ni-W-P duplex coatings present the characteristics of higher degree of crystallization and larger grain size for outer layer Ni-W-P than inner Ni-P, but outer layer has a higher hardness. The wear resistance of laser-treated duplex coatings in a given process parameter conditions is superior to the as-plated ones. Laser treatment was performed directly in air without argon protection, which provides the possibility for application of industrialized production. © 2012 The Nonferrous Metals Society of China. Source


Liu H.,Shandong Polytechnic University | Liu H.,University of Manchester | Guo R.X.,Zibo Institute of New Materials | Viejo F.,University of Manchester | And 2 more authors.
Transactions of the Institute of Metal Finishing | Year: 2013

An investigation has been undertaken of the influence of the mixed nanocrystalline and amorphous microstructure on the corrosion behaviour of electroless Ni-5·5W-6·5P (wt-%) deposits on steel substrates. The effects of annealing temperature on microstructure evolution were investigated. The corrosion behaviour of the deposits was evaluated by potentiodynamic polarisation in 0·5M H2SO4 solution and EIS measurements in 3·5%NaCl solution. Relationships between the microstructure and corrosion mechanisms of the as plated and the annealed deposits were considered by reference to microstructural information, including degree of crystallisation, grain sizes of both nickel and Ni3P phases, porosity development, microstrains and residual stresses. © 2013 Institute of Metal Finishing. Source


Liu H.,Shandong Polytechnic University | Liu H.,University of Manchester | Guo R.X.,Zibo Institute of New Materials | Viejo F.,University of Manchester | Liu Z.,University of Manchester
Surface and Coatings Technology | Year: 2012

This paper presents an investigation of microstructures in mixstructural electroless Ni-W-P coatings annealed by a laser and a furnace. Effects of the annealing temperature and the laser scanning velocity on microstructural characteristics, in terms of degree of crystallisation, grain size, microstrain and residual stress, were investigated using SEM/EDX and XRD techniques. Microhardness of the coatings before and after the heat treatments was evaluated by Vickers measurements. The results showed that the laser treatment at 8 to 14mm/s and the furnace annealing at 200 to 700°C resulted in incomplete crystallisation and the size of Ni 3P phase was larger than that of the Ni phase while the Ni 3P crystallisation reaction occurred at 14mm/s for laser annealing or at 400°C for furnace annealing. The laser annealing was useful for precipitation of Ni 3P phase and produced higher microhardness as compared to the furnace annealing. The phenomena were discussed considering the effect of heating and cooling rates in laser and furnace annealing on the degree of crystallisation, grain sizes of both nickel and Ni 3P phases, microstrain and residual stress. © 2011. Source


Liu H.,Shandong Institute of Light Industry | Guo R.-X.,Zibo Institute of New Materials | Li S.,Shandong Institute of Light Industry | Zong Y.,Shandong Institute of Light Industry | He B.-Q.,Shandong Institute of Light Industry
Zhongguo Youse Jinshu Xuebao/Chinese Journal of Nonferrous Metals | Year: 2011

The evolution of microstructures, in terms of degree of crystallisation, grain size and lattice strain of electroless Ni-W-P coating with high phosphorous (13.3%) content during laser and furnace annealing was investigated by quantitative XRD method and morphological observation of SEM. The results show that, during the annealing crystallization of the amorphous coating, the volume fraction of Ni3P exceeds that of Ni, and the volume fraction difference between the two phases increases remarkably at 700°C, but the remaining amorphous phase still exists in the coating. The grain size of Ni3P is larger than that of Ni between 400°C and 500°C, the grain size of both phases is reversed above 500-700°C and are in the range of nanoscale. The lattice strain of as-plated deposit is the maximum and decreases with the increase of temperature. The characteristics of microstructures of the coating treated by laser is consistent with the deposit annealed by furnace between 400°C and 500°C. The grain size of Ni3P and phases difference increase with the increase of the scanning velocity. Source

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