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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.


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.


Liu H.,Shandong Institute of Light Industry | Liu H.,University of Manchester | Guo R.-X.,Zibo Institute of New Materials | Zong Y.,Shandong Institute of Light Industry | And 2 more authors.
Transactions of Nonferrous Metals Society of China (English Edition) | Year: 2010

A comparative study of amorphous electroless Ni-W-P coatings on mild steel substrate treated by a high power diode laser and furnace annealing was presented. Effects of different laser operating parameters and furnace-annealing conditions on microstructures, in terms of crystallisation, pores formation and grain growth, were investigated using SEM/EDX and XRD. Corrosion behaviours of these coatings before and after various treatments were evaluated with anodic polarisation in 0.5 mol/L H2SO4 solution. The results show that the furnace-annealing produces either a mixture of nanocrystallined Ni and amorphous phases or precipitated Ni3P phase distributed in nanocrystallined Ni-based matrix, depending on annealing temperatures, whilst the laser treatment under the operating conditions only produces nanocrystallined Ni-based matrix with Ni3P precipitates. Corrosion performance of the coatings treated by both the laser and the furnace-annealing is dependent on the annealing temperature and laser operating conditions. Corrosion mechanisms of various treated-coatings were discussed in the consideration of phase constitutes and proportion, grain sizes of both Ni and Ni3P phases, pores formation and residual stresses. © 2010 The Nonferrous Metals Society of China.


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.


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.


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.


Liu H.,Shandong Institute of Light Industry | Liu H.,University of Manchester | Viejo F.,University of Manchester | Guo R.X.,Zibo Institute of New Materials | And 2 more authors.
Surface and Coatings Technology | Year: 2010

This paper presents an investigation of amorphous electroless Ni-W-P coatings on mild steel substrate treated by a high-power diode laser. Effects of the laser operating parameters on microstructures, in terms of porosity formation, crystallisation, phase transformation, grain growth, microstrain and residual stress, were investigated using SEM/EDX and quantitative XRD technique. Corrosion behaviors of the coatings before and after laser treatments were evaluated by anodic polarisation in 0.5 M H2SO4 solution and immersion test in 10 wt.% HCl solution. The results showed that the laser treatment produced nanocrystallined Ni phase and Ni3P precipitation with remaining amorphous structure. Corrosion performance of the coatings was significantly improved by the laser treatment. Further, corrosion mechanisms of the as-plated and laser-treated coatings were discussed in the consideration of porosity, integrated intensity ratios of individual phases, grain sizes of both Ni and Ni3P phases, microstrain and residual stress. © 2009.


Liu H.,Shandong Polytechnic University | Liu H.,University of Manchester | Guo R.X.,Zibo Institute of New Materials | Liu Z.,University of Manchester
Surface and Coatings Technology | Year: 2013

An investigation into the relationships between the microstructure and wear behaviour of electroless Ni-W-P coatings with different phosphorus contents (i.e. Ni-4.1 W-11.3 P and Ni-4.9 W-5.9 P in wt.%) and under different thermal treatment processes (i.e. by a furnace and a laser) has been performed. The work shows that the microstructures and morphology of the coatings involving nanocrystallisation, phase transformation, porosity formation and grain growth could be controlled by changing the phosphorus content of the Ni-W-P matrix and by performing different thermal treatments. The best wear resistance for both coatings was achieved with the laser treatment. For laser treatment, the alternation of hard and soft zones resulting from overlapping for large area coverage is beneficial for wear resistance. The wear mechanism is mainly associated with the characteristic of nanocrystalline structure before and after heat treatments, in terms of the volume fraction of various phases, grain size of Ni3P phase and amount of porosity present in the coating. © 2013 Elsevier B.V..


Liu H.,Shandong Polytechnic University | Liu H.,University of Manchester | Guo R.X.,Zibo Institute of New Materials | Liu Y.,University of Manchester | And 2 more authors.
Surface and Coatings Technology | Year: 2012

An investigation of the microstructural and corrosion characteristics of electroless Ni-5.5W-6.5P coatings on steel substrates after laser treatment in argon and air is presented. The microstructural characteristics of the coatings, in terms of crystallisation, grain size, microstrain, porosity as well as surface chemistry, were examined using quantitative X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Electrochemical tests, using potentiodynamic polarisation in 0.5M H 2SO 4 solution and electrochemical impedances spectroscopy (EIS) in 3.5% NaCl solution, were undertaken to evaluate the corrosion behaviour of the coatings. The results indicated that the laser-treated coatings consisted of nanocrystalline Ni and Ni 3P phases, along with retained amorphous phase; further, the dimensions of the Ni crystallites were larger than those of Ni 3P. The laser-treated coating in argon revealed the presence of submicron scale porosity, while no porosity was evident in the coating surface treated by laser in air. The uniform corrosion revealed in 0.5M H 2SO 4 solution is mainly determined by the microstructural characteristics of the coating. Pitting corrosion in 3.5% NaCl solution depended on the amount of porosity on the surface. The laser-treated coating in air exhibited better corrosion resistance in both acidic and chloride environments than that laser-treated in argon. © 2012 Elsevier B.V.

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