Microstructures of Ni–AlN composite coatings prepared by pulse electrodeposition technology

Applied Surface Science 271 (2013) 7–11

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Microstructures of Ni–AlN composite coatings prepared by pulse electrodeposition technology Fafeng Xia a , Huibin Xu b , Chao Liu c,∗ , Jinwu Wang d , Junjie Ding a , Chunhua Ma a a

School of Mechanical Science and Engineering, Northeast Petroleum University, Daqing 163318, PR China Department of Electronic and Information Engineering, Shanghai Normal University Tianhua College, Shanghai 201815, PR China School of Electronics Science, Northeast Petroleum University, Daqing 163318, PR China d School of Engineering, Northeast Agricultural University, Harbin 150030, PR China b c

a r t i c l e

i n f o

Article history: Received 14 May 2012 Received in revised form 31 October 2012 Accepted 12 December 2012 Available online 20 December 2012 Keywords: Composite coating Pulse electrodeposition Characterization Compact surface

a b s t r a c t Ni–AlN composite coating was fabricated onto the surface of steel substrates by using pulse electrodeposition (PED) technique in this work. The effect of pulse current on the nucleation and growth of grains was investigated using transmission electronic microscopy (TEM), X-ray diffraction (XRD), scanning electronic microscopy (SEM) and atomic force microscopy (AFM), respectively. The results show that the contents of AlN nanoparticles increase with density of pulse current and on-duty ratio of pulse current increasing. Whereas the size of nickel grains decreases with density of pulse current increasing and on-duty ratio of pulse current decreasing. Ni–AlN composite coating consists of crystalline nickel (∼68 nm) and AlN particles (∼38 nm). SEM and AFM observations show that the composite coatings obtained by PED showed more compact surfaces and less grain sizes, whereas those obtained by direct current electrodepositing have rougher surfaces and bigger grain sizes. © 2013 Published by Elsevier B.V.

1. Introduction Composite coatings are coatings formed by components with characteristic dimensionality as nanometer size (1–100 nm) setting in different matrixes [1–5]. Ni–AlN composite coatings have been drawn much attention due to their higher hardness wear resistance, and corrosion resistance in industrial applications [6–11]. Abdel Aal et al. has reported the effect of preparation process on mechanical properties of Ni–AlN coatings [12]. It is well-known that pulse electrodeposition (PED) technique among several preparation methods is a simple and inexpensive method to achieve composite coatings on the surface of steel substrates [13–16]. The optimum technical parameters, wear resistance and corrosion resistance of synthesizing Ni–AlN composite coatings have been systematically investigated in our previous publications [17]. However, the microstructure of Ni–AlN composite coatings is remarkably influenced by preparation process. It is necessary to explore the preparation method and characterization of Ni–AlN coatings fabricated by PED technique deeply. In this study, Ni–AlN composite coatings were prepared on the surface of steel substrates by PED technique. The microstructure of the coatings was characterized. The results provide a

∗ Corresponding author. Tel.: +86 459 6507716; fax: +86 459 6507716. E-mail addresses: xiaff [email protected] (F. Xia), [email protected] (C. Liu). 0169-4332/$ – see front matter © 2013 Published by Elsevier B.V. http://dx.doi.org/10.1016/j.apsusc.2012.12.064

technical basis for modification of the metal surface properties in the future.

2. Experimental methods Ni–AlN composite coatings were fabricated by using PED method in this work. The schematic diagram of the basic PED cell is shown in Fig. 1. The precursors used were AlN sols with purity above 99.99%. The AlN nanoparticles had an average primary particle size of 30 nm. One of TEM images of the AlN nanoparticles is shown in Fig. 2, which confirms their nanometer size and shape regularity. The AlN nanoparticle suspensions were prepared by ultrasonically mixing a given amount of particles (AlN nanoparticles: 4–10 g/L). The ultrasonic power was 200 W. After 10 min of ultrasonic mixing, the suspensions became clear and stable, and therefore, suitable for the PED experiments. Nickel plates with dimension of 50 mm × 40 mm × 5 mm were used as anode, and steel substrates with dimension of 50 mm × 20 mm × 1 mm were used as cathode. The anode and cathode were separated at a distance of 60 mm. The electrodes were then placed in the colloidal suspension. The steel plates were polished with emery paper, chemically cleaned and etched, and electroplated by PED. After plating, they were rinsed with distilled water and dried with ethyl alcohol prior to characterization. The frequency of the rectangular pulsed deposition was 500–800 Hz,

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F. Xia et al. / Applied Surface Science 271 (2013) 7–11 Table 2 Preparation parameters of Ni–AlN composite coatings. Density of pulse current (A/dm2 ) On-duty ratio of pulse current (%) Size of nickel grains (nm) Content of nano AlN particles (wt%)

30 20 ∼400 8.9

40 30 ∼280 9.4

40 40 ∼200 10.2

50 60 ∼80 11.7

morphology of the Ni–AlN composite coatings. The foils for HRTEM observations were prepared by mechanical reducing and ion reducing on Gatan-600 double-ion reducing machine. Phase identification for Ni–AlN composite coating samples was carried out by XRD using Cu-K␣ radiation. Scans were recorded over the range of 2 = 20–80◦ at an operating target voltage of 40 kV and tube current of 100 mA with a scan step of 0.02◦ . Using the Scherrer equation, the average grains diameter could be calculated as follows: L= Fig. 1. Schematic diagram of the PED cell used to obtain Ni–AlN composite coatings.

K cos  · FWHM

(1)

where K is the figure factor of the grains (K = 0.89), , the wavelength, FWHM is the breadth of the diffraction peak at half height, and  is the Bragg angle. 3. Results and analysis 3.1. Effect of preparation parameters on Ni–AlN composite coating

Fig. 2. TEM image of the AlN nanoparticles.

the occupational proportion was 20–80%, and the amplitude of the pulse current density was 30–60 A/dm2 . During the PED experiments, the AlN particles in the sol were positively charged. Accordingly, the steel substrate to be coated was used as cathode and a nickel plate was used as anode. The deposition time was varied between 5 min and 50 min to determine the optimum time for obtaining the desired coating thickness. The chemical composition of the electrolyte and the plating process parameters are listed in Table 1. After the PED coating process, the test samples were slowly dried in a humid atmosphere (∼60% humidity). High-resolution transmission electron microscopy (HRTEM) (Tecnai-G2-20-S-Twin), X-ray diffraction (XRD) (Rigaku D/Max-2400 diffractometer), scanning electron microscopy (SEM) (JSM-6460LV), and atomic force microscopy (AFM) (Nanoscope IIIa) were used to examine the quality and Table 1 Chemical composition and plating conditions. Chemicals

Content

Chemicals

Content

NiSO4 NiCl2 H3 BO3 Octyl phenol (OP)

250 g/L 50 g/L 30 g/L 1 mg/L

CTAB AlN nanoparticles Temperature (◦ C) pH

0.5 mg/L 4–10 g/L 25–30 4–6

The metal ions and AlN nanoparticles were directionally deposited on the surface of the cathode using a single-directional pulse current. The content of AlN nanoparticles and the size of nickel grains in the composite coatings obtained from different pulse parameters are shown in Table 2. Fig. 3 shows the effect of density of pulse current and on-duty ratio of pulse current on the content of AlN nanoparticles and the size of nickel grain. It is seen from Fig. 3(a) that the contents of AlN nanoparticles increase with density of pulse current and on-duty ratio of pulse current increasing. It is because of that the cathode overpotential increases and the electric field intensifies with increasing average current density. Thus, the electrostatic gravitation between the cathode and Ni2+ ions becomes stronger and the deposition velocity of Ni2+ ions get faster, which enhances the capability of Ni2+ to coat the AlN nanoparticles and increase the content of AlN nanoparticles in the plated coating. Moreover, it is also found from Fig. 3(b) that the size of nickel grains decreases with density of pulse current increasing and on-duty ratio of pulse current decreasing. The nickel grains and dispersed AlN nanoparticles in the composite coatings obtained from different pulse parameters were observed by HRTEM and shown in Fig. 4. It is seen from Fig. 4(a), the nickel grains (marked with arrows) are large and the size almost reaches the nanometer scale when the average current density is relatively low and the pulse interval is short. Based on the principle of PED method, high-amplitude and narrow pulse of current can accelerate the nucleation and restrain the growth of the crystalline grains. So it can be seen from Fig. 4(b) that the nanosized nickel grains (marked with arrows) dispersed in Ni–AlN composite coatings are homogenous in size. The reason can be explained as follows. On the one hand, when pulsed deposition was made, the existence of the pulse interval can hinder the growth of the crystalline grains and change the growth direction [18,19]. Therefore, the grains were prevented from growing into bulks. On the other hand, the size of grains of the deposited coating depends on the velocity of nucleation and growth. The increase in nucleation velocity and decrease in growth velocity lead to the formation of nanosized crystalline grains [20].

F. Xia et al. / Applied Surface Science 271 (2013) 7–11

14

%)

(a)

9

AlN particles (wt

12

Content of nano

10

m 2)

50

(%

cu se

ul

ati

(A /d

oo

30

45

20

yr

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fp

40

se cu

ut

f pul

-d

ity o

On

D e ns

50 40

35

rre

6 30

nt

70 60

)

8

(b)

Fig. 5. XRD patterns of Ni–AlN composite coatings at different electrodepositing conditions: (a) frequency 500 Hz, on-duty ratio of pulse 80%, density of pulse current 30 A/dm2 ;(b) frequency 800 Hz, on-duty ratio of pulse 30%, density of pulse current 50 A/dm2 .

450

3.2. Effect of pulse current on XRD patterns of Ni–AlN composite coatings

350 300 250 200

50 30

m 2)

50

20

(%

cu se

ul

Fig. 5 shows the XRD patterns of Ni–AlN composite coatings, which reveal the presence of AlN particles in the Ni–AlN coatings. For Ni, the diffraction peaks at 44.82◦ , 52.21◦ , and 76.77◦ correspond to (1 1 1), (2 0 0), and (2 2 0). For AlN, the diffraction peaks at 31.84◦ , 34.98◦ , and 37.82◦ correspond to (1 0 0), (0 0 2), and (1 0 0). According to the XRD data, the average grain size for Ni and AlN in the coating calculated using Eq. (1) are approximately 152 and 73 nm, respectively, whereas the experimental average grain size for Ni and AlN in the coating are ∼68 and ∼38 nm, respectively.

oo

30

45

(A /d

a ti

rre n t

fp

40

se c u

yr

f pul

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D e ns

50 40

35

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60

nt

70

100

)

150

-d

Size of nickel gra

ins (nm)

400

Fig. 3. Effect of density of pulse current and on-duty ratio of pulse current on the content of AlN nanoparticles and the size of nickel grain: (a) content of AlN nanoparticles; (b) size of nickel grain.

3.3. Effect of electrodepositing conditions on the surface morphology of Ni–AlN composite coatings Ni–AlN composite coatings obtained under different electrodepositing conditions are shown in Fig. 6. Composite coatings obtained by pulse current electrodeposition showed more compact surfaces with smaller grain sizes, whereas those obtained by direct current electrodepositing had rougher surfaces and bigger grain sizes. This result is ascribed to the current density which is

Fig. 4. HRTEM images of Ni–AlN composite coatings at different electrodepositing conditions: (a) frequency 500 Hz, on-duty ratio of pulse 80%, density of pulse current 30 A/dm2 ; (b) frequency 800 Hz, on-duty ratio of pulse 30%, density of pulse current 50 A/dm2 .

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F. Xia et al. / Applied Surface Science 271 (2013) 7–11

Fig. 6. Surface morphology images of Ni–AlN composite coatings at different electrodepositing conditions: (a) direct current[19] , (b) pulse current.

Fig. 7. AFM images of samples: (a) Ni coating[19] , (b) Ni–AlN coating.

higher under pulse current electrodeposition than in direct current electrodepositing condition [21]. Moreover, cathode polarization is also stronger in the former. According to electrodeposition theories, a stronger cathode polarization causes a faster crystal nucleation rate and increased number of nuclei. Compared with direct current electrodeposition [19–21], the coating fabricated by using PED has a compact surface and fine grains.

compact morphology. Nanosized nickel grains with uniform size are homogenous in coatings. XRD results demonstrate that the average diameters of Ni grains and AlN particles in the composite coating were approximately 68 and 38 nm, respectively.

3.4. AFM images of Ni–AlN composite coatings

The authors gratefully acknowledge the National Natural Science Foundation of China (grant no. 51101027), National Key Technology Support Program (2012BAH28F03), Program for New Century Excellent Talents in Heilongjiang Provincial University (NCET) and Program for Young Backbone Teachers in Heilongjiang Province University (grant no. 1251G004).

Fig. 7 shows the AFM images of the coatings. The Ni coating in Fig. 7(a) and the Ni–AlN coating in Fig. 7(b) were deposited under the same pulse current. The Ni–AlN coating exhibits a compact surface morphology in the micro-regions, and the grain size in the Ni coating is greater than that in the Ni–AlN composite coating. This result is attributed to the decrease in nickel grain size caused by the presence of AlN nanoparticles. By contrast, the Ni–AlN coating prepared by PED has more AlN particles and fewer aggregations. 4. Conclusions Ni–AlN composite coatings were prepared on the surface of steel substrates by PED method and the effect of preparation conditions on content of AlN nanoparticles, microstructures and surface morphology of the coating were systematically investigated in this work. The contents of AlN nanoparticles increase with density of pulse current and on-duty ratio of pulse current increasing. And the size of nickel grains decreases with increasing density of pulse current and decreasing on-duty ratio of pulse current, exhibiting

Acknowledgments

References [1] M.J. Jiao, X.X. Wang, Electrolytic deposition of magnesium-substituted hydroxyapatite crystals on titanium substrate, Materials Letters 63 (2009) 2286–2290. [2] C.T. Kwok, P.K. Wong, F.T. Cheng, H.C. Man, Characterization and corrosion behavior of hydroxyapatite coatings on Ti6Al4V fabricated by electrophoretic deposition, Applied Surface Science 255 (2009) 6736–6744. [3] D. Qiu, L. Yang, Y. Yin, A. Wang, Preparation and characterization of hydroxyapatite/titania composite coating on NiTi alloy by electrochemical deposition, Surface and Coatings Technology 205 (2011) 3280–3284. [4] T.J. Hilton, Can modern restorative procedures and materials reliably seal cavities? In vitro investigations. Part 1, American Journal of Dentistry 15 (2002) 198–203. [5] S.E. Rodil, J.J. Olaya, S. Muhl, B. Bhushan, G. Wei, The influence of the magnetic field configuration on plasma parameters and microstructure of niobium nitride films, Surface and Coatings Technology 201 (2007) 6117–6122.

F. Xia et al. / Applied Surface Science 271 (2013) 7–11 [6] A. Ratna Phani, S. Santucci, Structural characterization of nickel tantalum oxide synthesized by sol–gel spin coating technique, Materials Letters 47 (2001) 20–24. [7] K.L. Morgan, Z. Ahmed, F. Ebrahimi, The effect of deposition parameters on tensile properties of pulse-plated nanocrystalline nickel, Materials Research Society Symposia Proceedings 634 (2001) B3.11.1–B3.11.6. [8] L. Benea, P.L. Bonora, A. Borello, S. Martelli, F. Wenger, P. Ponthiaux, J. Galland, Composite electrodeposition to obtain nanostructured coatings, Journal of the Electrochemical Society 148 (2001) C461–C465. [9] S.M. Arifuzzaman, S. Rohani, Experimental study of brushite precipitation, Journal of Crystal Growth 267 (2004) 624–629. [10] T. Arima, K. Milyata, Y. Inagaki, K. Idemitsu, Oxidation properties of Zr–Nb alloys at 500–600 ◦ C under low oxygen potentials, Corrosion Science 47 (2008) 435–446. [11] Y. Chen, W. Liu, C. Ye, L. Yu, S. Qi, Preparation and characterization of selfassembled alkanephosphate monolayers on glass substrate coated with nanoTiO2 thin film, Materials Research Bulletin 36 (2001) 2605–2612. [12] A. Abdel Aal, M. Bahgat, M. Radwan, Nanostructured Ni–AlN composite coatings, Surface and Coatings Technology 201 (2006) 2910–2918. [13] X.H. Chen, J.C. Peng, X.Q. Li, F.M. Deng, J.X. Wang, W.Z. Li, Tribological behavior of carbon nanotubes-reinforced nickel matrix composite coatings, Journal of Materials Science Letters 20 (2001) 2057–2060. [14] B. Yin, G. Liu, H. Zhou, J. Chen, F. Yan, Sliding wear behavior of HVOF-sprayed Cr3 C2 –NiCr/CeO2 composite coatings at elevated temperature up to 800 ◦ C, Tribology Letters 37 (2010) 463–469.

11

[15] C. Huang, L. Du, W. Zhang, Preparation and characterization of atmospheric plasma-sprayed NiCr/Cr3 C2 –BaF2 ·CaF2 composite coating, Surface and Coatings Technology 203 (2009) 3058–3063. [16] E. Sánchez, A. Moreno, M. Vicent, M.D. Salvador, V. Bonache, E. Klyatskina, I. Santacruz, R. Moreno, Preparation and spray drying of Al2 O3 –TiO2 nanoparticle suspensions to obtain nanostructured coatings by APS, Surface and Coatings Technology 205 (2010) 987–992. [17] F.F. Xia, M.H. Wu, Z.Y. Jia, Z. Li, Ultrasonic-electrodeposited nano Ni–AlN composite layers and characterization, in: Technology and Innovation Conference International, vol. 6–7, Hangzhou, China, 2006, pp. 35–38; P. Gupta, G. Tenhundfeld, E.O. Daigle, D. Ryabkov, Electrolytic plasma technology: science and engineering—an overview, Surface and Coatings Technology 201 (2007) 8746–8760. [18] W. Xue, Q. Zhu, Q. Jin, M. Hua, Characterization of ceramic coatings fabricated on zirconium alloy by plasma electrolytic oxidation in silicate electrolyte, Materials Chemistry and Physics 120 (2010) 656–660. [19] F.F. Xia, C. Liu, F. Wang, M.H. Wu, J.D. Wang, H.L. Fu, J.X. Wang, Preparation and characterization of Nano Ni–TiN coatings deposited by ultrasonic electrodeposition, Journal of Alloys and Compounds 490 (2010) 431–435. [20] G. Wu, N. Li, D. Zhou, K. Mitsuo, Electrodeposited Co–Ni–Al2 O3 composite coatings, Surface and Coatings Technology 176 (2004) 157–164. [21] L. Chen, L. Wang, Z. Zeng, J. Zhang, Effect of surfactant on the electrodeposition and wear resistance of Ni–Al2 O3 composite coatings, Materials Science and Engineering A 434 (2006) 319–325.