Efficient Preparation of Nanoparticles Reinforced Nickel-based Composite Coating with Highly Preferred (220) Orientation

This paper reports a phenomenon that the grain orientation gradually evolves to (220) with the deposition current density increasing when preparing nanoparticles reinforced nickel-based composite coatings by jet electrodeposition (JED). During the preparation of Ni-SiC composite coatings, the deposition current density increases from 180 A/dm 2 to 220 A/dm 2 , and TC(220) gradually increases from 41.4% to 97.7% correspondingly. The Ni-SiC composite coating with highly preferred (220) orientation has superior corrosion resistance and adhesion force. With the increase of TC(220), the surface roughness is reduced from Ra1.210 μm to Ra0.119 μm, the self-corrosion potential increases from -0.747 V to -0.477 V, the corrosion current density decreases from 54.52 μA·cm 2 to 2.76 μA·cm 2 , the diameter of corrosion pits that after 10 days of immersion in 3.5 wt% NaCl solution decreases from 3.3~22.2 μm to 153~260 nm, and the adhesion of the coating is increased from 20.5 N to 61.6 N. The research results can provide theoretical and technical support for the preparation of new composite coatings with high efficiency, low cost, high adhesion and strong corrosion resistance.


Introduction
With the continuous development of modern industry, the wear resistance and corrosion resistance of more and more key components of high-end equipment are required, so the high-performance composite coatings are usually required to be prepared on the key component surface. Nanoparticles reinforced metal matrix composite coatings have great application potential in mechanical parts surface strengthening due to their excellent hardness, abrasion resistance, corrosion resistance and high temperature oxidation resistance. It is widely concerned by researchers.
Ruiqian Li et al. [1] produced the Ni-SiO2 composite coating by electrodeposition and found that the addition of SiO2 nanoparticles improved the wear resistance of the coating. Baosong Li et al. [2] prepared the Ni-W/TiN coating by pulse electrodeposition and observed that the doped TiN nanoparticles could promote nucleation and caused obvious changes in microstructure, thus improving the hardness and corrosion resistance of the coating. Yongqi Tao et al. [3] fabricated the Ni-B-Sc coating by conventional electrodeposition and detected that the grain boundary and phase boundary area increased due to the addition of Ni2Sc nanoparticles. However, nanoparticles usually exist in the form of agglomeration in the plating solution because of their high surface energy. It is difficult to break the agglomeration of nanoparticles by conventional electrodeposition, so the prepared composite coatings have defects such as rough surface and poor adhesion [4,5].
Jet electrodeposition (JED) is a kind of unconventional electrodeposition. The high-speed jet liquid improves the transmission speed of ions in the deposition process compared with conventional electrodeposition (CED). The ions are evenly distributed by high-speed flushing, which reduces the concentration polarization and improves the upper limit value of current density in the process of electrodeposition [6,7].
Meanwhile, the agglomeration of the nanoparticles is broken up during the high-speed flushing, and the nanoparticles are distributed uniformly in the coating. Therefore, using jet electrodeposition to prepare nanoparticles reinforced composite coating, the advantages of high deposition efficiency, uniform distribution of nanoparticles and good surface quality of coating can be obtained [8][9][10].
During electrodeposition, the preferred orientation (texture) often occurs, which means significant amounts of grains exhibit the same common orientation characteristics in the deposition layer. It is called highly preferred orientation if almost all of grains are assembled in one certain orientation. Through controlling the preferred orientation of the grains in the deposition layer, the properties of deposition layer can be improved, and even deposition layer has some special functions. Haibo Gao et al. [11] made Co-Ni films with preferred (220) orientation by controlling the variation of Co and Ni ratio, which showed superior photocatalytic performance. Alexandre Ponrouch et al. [12] prepared preferentially oriented (100) platinum nanowires and thin films by changing the deposition potential, which exhibited efficient electro-catalytic properties. Jiwon Kim et al. [13] manufactured Bi2Te3-xSex thin films by pulse electrodeposition. Through changing the duty cycle of current, thin films had the preferred orientation of (110), and displayed superior thermoelectric performance.
In recent years, the research on the preferred orientation of nickel coatings by conventional electrodeposition has attracted much attention. J.A. Calderón et al. [14] carried out the experiment about preparing Ni-SiC composite coatings. It was found that with the increase of SiC content, the grain orientation of the coatings gradually evolved from (200) to (111), and corrosion resistance of the coating was improved with the grain orientation of (111). Yuantao Zhao et al. [15] performed the research on Ni-xAl-yTi composite coatings. They claimed that as the content of Al and Ti particles increased, the orientation of (200) decreased while (111) increased, and the preferred (111) orientation coating showed better corrosion resistance than preferred (200) orientation. Morteza Alizadeh et al. [16] undertook the analysis about Ni-Cu/Al2O3 composite coatings. They reported the structure of coatings gradually evolved to preferred (111) orientation when the content of Al2O3 increased, and the hardness, wear resistance and corrosion resistance of coatings were improved. Jianhua Deng et al. [17] demonstrated that with the addition of 1,4-bis(2-hydroxyethoxy)-2-butyne (BEO), the grains preferred orientation of Ni/diamond composite coatings changed to (200), and the wear resistance of the coating was also enhanced.
The above studies on the preferred orientation of nickel-based composite coatings mainly focused on (111) and (200), and research about the highly preferred (220) orientation of Ni-SiC composite coatings has not been reported. This paper reveals the principle of efficient preparation nanoparticles reinforced nickel-based composite coating with highly preferred (220) orientation, and then explores the effect of deposition parameters on the structure of nanoparticles reinforced nickel-based composite coatings，finally investigates the microstructure, corrosion resistance and the adhesion force of the Ni-SiC composite coating with highly preferred (220) orientation. Some innovative theoretical and technological achievements have been made.

Principle of efficient preparation of nanoparticles reinforced nickel-based composite coating by jet electrodeposition (JED).
The experimental device for jet electrodeposition is shown in Figure 1a. The pure titanium rod connects to the positive pole of DC power supply and the substrate connects to the negative pole of DC power supply. The pure titanium rod acts as the current transfer electrode, which transfers the current to nickel balls, making nickel balls become anode. Nickel atoms are oxidized into a large amount of Ni2+, which are used to supplement the Ni2+ constantly consumed in the plating solution. The titanium rod is not consumed in experiments because the chemical properties of titanium rod is more stable than those of nickel balls. Due to the titanium rod is closer to the upper surface of the substrate, the unconsumed titanium rod can play a role in providing a stable electric field environment, and the deposited coatings have better uniformity. The plating solution in the liquid storage tank is heated by a water bath to maintain a constant temperature. During the preparation process, firstly the composite plating solution is transported to the anode cylinder through the inlet pipe by a diaphragm pump.
Then the plating solution in the anode cylinder is impacted on the substrate through the nozzle at a high speed for deposition. Finally, the plating solution flows back to the liquid storage tank through the outlet pipe.
The schematic diagram of preparation principle of nanoparticles reinforced nickelbased composite coatings by JED is illustrated in Figure 1b. Most of the nanoparticles exist in the plating solution as agglomeration, which mainly are surrounded by water molecules and ion clusters. Since mainly chemical reaction is the redox of Ni2+ during electrodeposition, so the model is simplified into nanoparticles agglomeration surrounded by a large number of Ni2+. When the nanoparticles agglomeration is impacted the substrate at a high speed, the nanoparticles agglomeration are divided into many individual nanoparticles due to reacting force. According to the composite codeposition theory [18,19], some nanoparticles are adsorbed on the substrate, among which the strongly adsorbed nanoparticles are deposited and the weakly adsorbed nanoparticles are washed away. Meanwhile, under the condition of high deposition current density, a large amount of Ni2+ near the cathode are reduced to Ni atoms, and then Ni atoms are deposited on the substrate. The stacking of Ni atoms and nanoparticles covering substrate defects rapidly, and eventually the nanoparticles reinforced nickel-based composite coating with smooth surface is formed. Figure 1c, the thickness of the coating increase gradually when the nozzle moves back and forth along the path at a certain scanning speed. The required thickness and shape of the composite coating has been obtained by controlling the nozzle path and deposition time.

As shown in
(Location of Figure 1)

Experimental parameters of preparation of nanoparticles reinforced nickel-based composite coating by JED.
Because of the high hardness and stability of SiC nanoparticles, Ni-SiC composite coatings have been widely used. This paper focused on the properties of Ni-SiC composite coatings. The composition of plating solution and experimental parameters are shown in Table 1.The purity of SiC nanoparticles is 99.99% and the average particle size is about 50 nm，and the SEM and EDS figures are shown in figure S1.
(Location of Table 1)

Testing details.
The grain orientation and grain size of nanoparticles reinforced nickel-based

The grain orientation evolution of Ni-SiC composite coating during JED.
In the process of JED, the deposition layer is rapidly formed on the surface of the substrate with the condition of high current density by means of high-speed jetting.  (220). It can be seen that with the increase of the deposition current density from 180 A/dm2 to 220 A/dm2, the coating orientation shows a trend of gradual evolution to Ni(220).
The preferred orientation coefficient (texture coefficients) of different crystal planes in coating of these coatings are calculated by formula (1) [20], where TC(hkl) is the texture coefficient of (hkl) orientation, I(hkl) is measured intensity of (hkl) reflection, I0(hkl) is powder diffraction intensity of nickel (PDF#70-0989), and n is the There is a critical value for the injection speed. When the injection speed exceeds this value, the nickel structure cells tend to adsorb on the substrate with random crystalline planes instead. The critical value has a negative correlation with the deposition current density, that is, the smaller the deposition current density, the larger the critical value (Figure 2f-2h).
Under the condition of high deposition current density, the nickel structure cells nucleate rapidly, and the number of crystal nucleus with (220) orientation is larger than that of with (111) orientation and (200) orientation. Therefore, the crystal nucleus with (220) orientation dominate the growth process. Eventually, the average size of (220) orientation grains is obviously larger than that of (111) orientation grains and (200) orientation grains (Figure 2i).
In order to explore the effect of nanoparticles in the preparation of nickel-based composite coatings with highly preferred (220) orientation, the pure Ni coating ( Figure   S2-S3)、Ni-TiO2 composite coating (Figure S4-S5) and Ni-Al2O3 composite coating ( Figure S6-S7) are also prepared by JED. The deposition current density is 220 A/dm2 and the injection velocity is 1.76 m/s. The results show that all of the three coatings are all highly preferred (220) orientation structure, which shows that nanoparticles have little effect on the orientation of the grains in the coating. This paper will carry out subsequent analysis based on Ni-SiC composite coating.

The morphology of Ni-SiC composite coating with highly preferred (220)
orientation. Figure 4 shows the morphology of a Ni-SiC composite coating with highly preferred (220) orientation prepared by JED (TC(220) = 97.7%). As shown in Figure   4a, the surface (Area C) and section (Area f) of the coating are observed. It is obvious that the surface of Ni SiC composite coating with highly preferred (220) orientation is compact and flat (Figure 4c, Figure 4f), and there is no dome-like or hill valley like structure [16,[22][23][24]. The surface roughness of the coating is Ra0.119 μm (Figure 4b).
SiC nanoparticles have no agglomeration inside the coating (Figure 4d, Figure 4g) and are evenly distributed in different areas of the coating (Figure 4e, Figure 4h). Figure 5 shows the morphology of a Ni-SiC composite coating prepared by CED ( Figure S8, Table S1). The XRD pattern of the coating is shown in Figure S9 (TC(220) = 40.7%).
(Location of Figure 4) As shown in Figure 5a, the surface (Area C) and section (Area f) of the coating are also observed. Unlike Figure 4c and Figure 4f, the surface of Ni SiC composite coating prepared by CED is coarse and fluctuant (Figure 5c, Figure 5f). The surface roughness of the coating is Ra1.210 μm (Figure 5b). SiC nanoparticles have obvious agglomeration inside the coating (Figure 5d, Figure 5g) and the content varies greatly at different areas (Figure 5e, Figure 5h).
(Location of Figure 5) The high speed jetting process in JED can make SiC nanoparticles evenly distributed in the coating. At the same time, the highly preferred (220) orientation structure makes the coating has better surface quality, which is beneficial to significantly improve the corrosion resistance of Ni-SiC composite coating.

The corrosion resistance of Ni-SiC composite coating with highly preferred
(220) orientation.
In this paper, the corrosion resistance of Ni-SiC composite coating is tested, including electrochemical test and full immersion corrosion test. Figure 6 reports the electrochemical test results of Ni-SiC composite coatings in 3.5 wt% NaCl solution.
The dynamic polarization curves are shown in Figure 6a. As can be seen from this   (220) increase from 41.4% to 97.7%. The higher the impedance value, the stronger the corrosion resistance of the coating. Figure 6d shows the Bode plots of log(f) vs. Angle of the Ni-SiC composite coatings. For the Ni-SiC composite coatings, the higher phase angle at middle high frequency for the chemical conversion treated specimen corresponds to a capacitive behavior, that is to say the conversion coating has good dielectric property to avoid the ionic flow of electrolyte [25]. When the frequency is in the range of 100~105 Hz, the phase angle of Ni-SiC composite coating prepared by CED is minimum, and the phase angle of Ni-SiC composite coating prepared by JED increases with the increase of TC(220).
The EIS data is fitted by calculated by electrical equivalent circuit (EEC). The corrosion process of Ni-SiC composite coating can be replaced by EEC of R(Q(R(QR))) when the oxide layer on the substrate surface is taken into account [26]. As observed in , where w is the angular frequency (rad s-1), Y0 is the CPE admittance, j is the imaginary number ( 1 − ), and n with a value of 0-1 represents the relaxation dispersion. When the value of n is 1, the CPE is a pure capacitor with a capacitance of Y0. It is believed that the smaller the n value is and the more defects will be on the surface as well as the pitting corrosion is more likely to occur [25,27].
(Location of Figure 6) The fitting results is shown in Table 2. It can be seen that the Rc and Rct of Ni-SiC composite coating prepared by CED is 1.476×102 Ω/cm-2 and 1.476×102 Ω/cm-2, respectively. Compared with that of other coatings, these parameters is the minimum value, which means this coating has the worst corrosion resistance. The Ni-SiC composite coatings prepared by JED increase with TC (220) from 41.4% to 97.7%, the Rc of the coatings increase from 4.423×103 Ω/cm-2 to 7.025×103 Ω/cm-2, and the Rct increase from 1.267×104 Ω/cm-2 to 5.989×104 Ω/cm-2. It is proved that the corrosion resistance of Ni-SiC composite coating increases with the increase of TC(220).
(Location of Table 2) The full immersion corrosion tests of Ni-SiC composite coatings are carried out.
The corrosion solution was 3.5 wt% NaCl solution, and the corrosion time was 1 day, 3 days, 5 days and 10 days, respectively. The surface of the coatings after immersion corrosion are observed, and the surface morphologies of different corrosion times are shown in Figure S10-S12 and Figure 7. reduced and the diffusion rate of corrosion pits is reduced. Therefore, the Ni-SiC coating with highly preferred (220) orientation shows excellent corrosion resistance.

The adhesion force of Ni-SiC composite coating with highly preferred (220)
orientation.
The adhesion force is an important index to judge the performance of coating. The higher the adhesion force of the coating, the less easy it will fall off, and the longer the service life will be. In this paper, the adhesion of Ni-SiC composite coatings and substrate is quantitatively measured by scratch method. Figure 8a shows

Conclusions
(1) The grain orientation of Ni-SiC composite coatings prepared by JED gradually evolves to (220) with the increase of current density. The Ni-SiC composite coating with highly preferred (220) orientation is prepared at current density of 220 A/dm2, while the orientation coefficient reached to 97.7%.
(2) In the process of JED, the high-speed jetting fluid makes the nanoparticles break the agglomeration state and disperse evenly into the coating. Under the condition of high current density, the deposition layer quickly to fill the defects of the substrate and form a compact and flat composite coating on the surface. The surface roughness of Ni-SiC composite coating with highly preferred (220) orientation is 90.2% lower than that of Ni-SiC composite coating prepared by CED.
(3) The corrosion resistance of Ni-SiC composite coatings increases with the increase of TC(220). Compared with the corrosion resistance of coating prepared by CED, the corrosion resistance of coating with highly preferred (220) orientation prepared by JED has a 36.1% increase in corrosion potential and a 94.9% decrease in corrosion current density.