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Article

Tribological Properties of Attapulgite Nanofiber as Lubricant Additive for Electric-Brush Plated Ni Coating

by
Feng Nan
1,2,3,* and
Dong Wang
4,*
1
Hubei Provincial Key Laboratory of Chemical Equipment Intensification and Intrinsic Safety, School of Mechanical and Electrical Engineering, Wuhan Institute of Technology, Wuhan 430205, China
2
Hubei Provincial Engineering Technology Research Center of Green Chemical Equipment, School of Mechanical and Electrical Engineering, Wuhan Institute of Technology, Wuhan 430205, China
3
School of Mechanical and Electrical Engineering, Wuhan Institute of Technology, Wuhan 430205, China
4
College of Mechanical Engineering, Zhijiang College of Zhejiang University of Technology, Shaoxing 312030, China
*
Authors to whom correspondence should be addressed.
Lubricants 2023, 11(5), 204; https://doi.org/10.3390/lubricants11050204
Submission received: 27 March 2023 / Revised: 29 April 2023 / Accepted: 2 May 2023 / Published: 5 May 2023
(This article belongs to the Special Issue Tribology of 2D Nanomaterials)
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Abstract

:
In order to expand the application field of attapulgite in tribology, the tribological properties of attapulgite as a lubricant additive on electric-brush plated Ni coating were investigated using the ball-disc contact mode of a SRV-IV friction and wear tester. The worn surfaces were characterized and analyzed via scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). Results indicated that the friction-reducing and antiwear properties of 150 SN lubricating oil on the Ni coating were remarkably improved by an appropriate amount of attapulgite. Tribofilm mainly composed of Ni, NiO, SiO2, Al2O3, graphite, and organic compounds was formed on the worn surface under the action of attapulgite, which was responsible for the reduction of friction and wear.

Graphical Abstract

1. Introduction

One-third to one-half of the energy used on earth is consumed by friction [1]. Additionally, abrasion caused by friction is a main cause of component failures. Therefore, reducing friction and wear is of great significance for human beings. There are many measures to reduce friction and wear, and using lubricating oil is the most common. With the rapid development of nanotechnology, a variety of nanomaterials have been used as lubricating oil additives to decrease friction and wear owing to their small size effect and excellent physicochemical properties [2,3,4,5,6,7,8].
It is generally believed that large-scale powders cannot be used as lubricating additives because they tend to agglomerate and cause serious abrasive wear. However, it was found that a kind of micrometric natural mineral powder, serpentine, can be utilized as an additive to remarkably improve the tribological properties of lubricating oil [9,10]. Some research has revealed the tribological mechanism of serpentine by means of microscopic characterizations. Zhang et al. [11] found that a tribolayer mainly composed of diamond like carbon (DLC) was formed under the effect of serpentine additive, which was responsible for the improvement in the lubrication performance of lubricating oil. Zhang et al. [12] attributed the reduction of friction and wear to the formation of an amorphous Si–O film. Yu et al. [13] declared that the tribolayer formed on the rubbing surface by serpentine possesses better mechanical properties than the metallic substrate. In addition, some reports have studied the tribological properties of serpentine lubricating additive under different conditions [14,15]. Yin et al. [16] investigated the friction and wear behaviors of steel/bronze tribopairs lubricated by oil with serpentine additive. It was found that the tribological properties of tin bronze were remarkably improved by the addition of serpentine powder into the oil. In the effect of serpentine, a non-conductive tribofilm consisting of metal oxides, oxide ceramic particles, graphite, and organics was formed on the worn tin bronze surface. Moreover, some studies have reported using other natural mineral materials, including kaolin antigorite, as lubricating additives to improve the tribological properties of oils [17,18].
Attapulgite is another natural mineral that has similar crystal structure to serpentine minerals. In recent years, it was found that attapulgite can also be used as an additive to remarkably improve the friction-reducing and antiwear properties of lubricating oil [19,20]. The friction-reducing and antiwear behavior of attapulgite can be attributed to the formation of tribofilm consisting of oxides, ceramics, silicates, and graphite on the rubbing surface. Such tribofilms have good lubricity, high hardness, and a high hardness/elastic modulus ratio [20]. Additionally, some nanomaterials such as nano-La2O3 and nano-Ni have been proved to further improve the friction-reducing and antiwear effect of attapulgite [21,22]. However, the studies are all focused on steel–steel contact. There are few reports on the tribological properties of an attapulgite lubricating additive on other materials. Compared with other mineral materials, attapulgite has the following advantages: (1) The attapulgite materials are natural nanofibers. They can be obtained via simple crystal-bundles separation processing; (2) Attapulgite possesses high reserves in nature; (3) Attapulgite is an environmentally friendly material without toxic and harmful elements. Therefore, attapulgite has promising development prospects in the field of tribology.
Electric-brush plated technology has been applied widely in industry to prepare coatings with abrasion-resistant and corrosion-preventive properties owing to its flexibility, portability, and easy operation. Through a simple and mature process, nanocrystalline Ni coating with high hardness, fine wear, and corrosion resistance can be prepared [23,24]. Additionally, the electric-brush plated Ni coating has been widely applied in the abrasion repairing of mechanical parts such as crankshafts, piston rods, gear shafts, and so on.
In this work, the tribological properties of attapulgite as a lubricant additive on electric-brush plated Ni coating was investigated for the first time. Moreover, the friction-reducing and antiwear mechanism of the attapulgite additive was discussed on the basis of the tribological tests, analysis, and characterization of worn surfaces. The results would provide a reference for the application of attapulgite lubricating additive for the lubrication of electric-brush plated Ni coating. We believe that attapulgite lubricating additive can significantly improve the service life of the electric-brush plated Ni coating under oil lubrication.

2. Materials and Methods

2.1. Materials

The attapulgite powders (ATP) were purchased from Jiuchuan Nanometer material Science and Technology Ltd. (Huai’an, China). The chemical composition of ATP is SiO2 (58.88 wt%), MgO (12.10 wt%), Al2O3 (9.50 wt%), Fe2O3 (5.20 wt%), K2O (1.04 wt%), CaO (0.4 wt%), TiO2 (0.55 wt%), P2O5 (0.18 wt%), MnO (0.05 wt%), Cr2O3 (0.04 wt%), and H2O (12.06 wt%), indicating that the attapulgite is a kind of silicate mainly composed of some metallic oxides such as SiO2, MgO, Al2O3, and Fe2O3. The powders were purified by the manufacturer, and we did not perform any further treatment. Oleic acid was obtained from Sinopharm Chemical Reagent Ltd. (Shanghai, China). The 150 SN lubricating oil was purchased from Qingdao Compton Technology Co., Ltd. (Qingdao, China). The chemical composition of 150 SN is paraffin hydrocarbon, naphthenic hydrocarbon, alkyl naphthalene, alkyl benzene, polycyclic aromatic hydrocarbons, sulfide, nitride, and oxide.

2.2. Preparation of Electric-Brush Plated Ni Coating

AISI 1045 steel substrate discs (φ24 mm × 8 mm) with a hardness of HRC 27–30 were polished to a roughness below Ra0.3 μm. Then, Ni coating was prepared on the substrate samples through the process shown in Table 1. The composition of Nickel plating solution is displayed in Table 2. The hardness of the coating was measured using a microhardness tester (HVS-1000). When measuring hardness, the applied load was 100 g and loading time was 15 s. At least six points on the coating were selected and the average value was calculated. The hardness of the prepared Ni coating was about 430 HV. The surface roughness of the coating was measured with a MicroXAM surface mapping profilometer (LEXT OLS4000, Olympus, Tokyo, Japan). The surface roughness of the coating was Ra ≈ 0.5 μm.

2.3. Friction and Wear Test

0.2 wt%, 0.4 wt%, 0.6 wt%, and 0.8 wt% of ATP were put in a certain amount of 150 SN. In order to obtain good dispersity in the oil, 5.0 wt% (percent of ATP) of oleic acid was also added in the oil to have the ATP modified. The structural formula of oleic acid is CH3(CH2)7CH=CH(CH2)7COOH, which is an organic surface modifier with long carbon chains. The long carbon chains were grafted onto the surface of attapulgite nanoparticles during mechanical stirring. Therefore, the lipophilicity of attapulgite nanoparticles was significantly enhanced. The attapulgite nanoparticles can be fully dispersed in oil to avoid agglomeration and forming large particles. The mixtures of ATP, oil, and oleic acid were well-mixed through ball mill at 200 r/min for 2 h. Eventually, the 150 SN with an added 0.2 wt%, 0.4 wt%, 0.6 wt%, and 0.8 wt% of ATP were prepared.
An SRV-IV oscillating friction and wear tester was used to evaluate the tribological properties of the oils. During the tribological tests, the upper AISI 52,100 steel balls (φ10 mm) with a hardness of HRC 59–62 slide reciprocally at an amplitude of 1 mm, a frequency of 10 Hz, and a temperature of 50 °C against the stationary discs for 30 min. Firstly, the tribological properties of 150 SN with different added contents of ATP were investigated at a load of 50 N. After determining the optimum content of ATP, the effect of the load on the tribological properties of ATP was studied. The selected loads were 10, 20, 50, and 100 N. Each tribology test was repeated 3 times to minimize data scatter. The friction coefficient curve was recorded by the computer connected to the SRV friction and wear tester and the average value was calculated. The wear volume of each disc was measured with a MicroXAM surface mapping profilometer for at least three times and the mean value was calculated.

2.4. Characterization and Analysis

The phase composition of ATP was characterized by X-ray Diffraction (XRD) (Advance 8, Bruker, Mannheim, Germany). A few attapulgite powders were uniformly dispersed into alcohol via ultrasonic. Then, a little suspension was dropped onto copper mesh. After alcohol volatilization, the microstructure of ATP was observed using TEM. The morphologies and elemental contents of the Ni coating and worn surfaces on the discs were analyzed via SEM (Nova Nano 650, FEI, Hillsboro, OR, USA) equipped with EDS. The cross-sectional morphology of the coating was analyzed via SEM (Nova Nano 650). The grain size distribution of the ATP powders was measured through a laser particle size analyzer (Malvern, MAL1066490, UK). The chemical state of typical elements on the worn surfaces was characterized using XPS (ESCALAB 250Xi, Thermo Scientific, Waltham, MA, USA). The XPSPEAK 4.1 software was utilized to fit the XPS data. The binding energy resolution was approximately ±0.2 eV.

3. Results

3.1. Characterization of ATP and Electric-Brush Plated Ni Coating

The XRD spectrogram of ATP is shown in Figure 1a. Characteristic diffraction peaks of attapulgite (d(110), d(200), d(040), d(231), etc.) can be obviously seen on the XRD spectrogram. This indicates that the chemical formula of the ATP was (Mg, Al, Fe)5Si8O20(OH2)4·4H2O (JCPDS No. 21-0957). The ATP contained almost no other impurities. The TEM morphology displayed in Figure 1b indicates that the ATP particles had a nano-fibrous morphology with a diameter of about 50 nm. The length of nanoparticles was nonuniform. Some nanoparticles were about 1 μm. Few nanoparticles were as short as below 100 nm. In addition, the nanoparticles exhibited good dispersion. Only a small amount of nanoparticles gathered together.
Figure 2a shows the surface morphology of the prepared Ni coating. The Ni coating surface was compact and smooth. Additionally, several typical cauliflower-like structures can be seen on the surface. There were few holes, burrs, cracks, and other macro defects in the coating. The corresponding EDS analysis result of prepared Ni coating shown in Figure 2b indicates that only Ni and C elements can be detected on the coating surface.
Figure 3 shows cross-sectional SEM morphology of the electric-brush plated Ni coating. It was found that the thickness of the prepared Ni coating is 21.4 μm. Additionally, the adhesion between coating and substrate is fine.
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Figure 3. Cross-sectional SEM morphology of the electric-brush plated Ni coating. The grain size distribution of the ATP powders is displayed in Figure 4. It was found that the particle size of most powders was from 150 to 900 nm.
Figure 3. Cross-sectional SEM morphology of the electric-brush plated Ni coating. The grain size distribution of the ATP powders is displayed in Figure 4. It was found that the particle size of most powders was from 150 to 900 nm.
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Lubricants 11 00204 g004 550
Figure 4. Grain size distribution of the ATP powders.
Figure 4. Grain size distribution of the ATP powders.
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3.2. Friction and Wear Behavior

Figure 5 shows the tribological properties of 150 SN with different added amounts of ATP at 50 N. Under the lubrication of 150 SN, the friction coefficient and wear volume were 0.214 and 50.12 × 10−3 mm3, respectively. With the addition of ATP, the friction coefficient and wear volume for 150 SN were both decreased. When the amount of ATP was 0.4 wt%, the friction coefficient and wear volume were 0.169 and 42.58 × 10−3 mm3, respectively, which were the lowest. Therefore, the optimum amount of ATP is 0.4 wt%. Under the effect of 0.4 wt% ATP, the friction coefficient and wear volume of oil were reduced by 21% and 16%, respectively.
Furthermore, the effect of load on the tribological properties of 150 SN and 150 SN with added ATP was investigated. Figure 6 shows the friction coefficient curves under the lubrication of 150 SN and 150 SN with added ATP. At the initial stage of the friction test, the friction coefficients of the two kinds of oils both showed a significant increase, which may be attributed to the running-in of the friction pair. Under the lubrication of 150 SN, the friction coefficient fluctuated greatly at 10 and 20 N due to the effect of the cauliflower-like structure. When the load increased to 50 and 100 N, the friction coefficient became more stable than that at 10 and 20 N. Throughout the tribological test, the friction coefficients at 50 and 100 N were basically the same. The friction coefficients both remained around 0.20 after 1200 s. Overall, the friction coefficient at low loads was higher than that at high loads. Additionally, the friction coefficient at 10 N was the highest. As for 150 SN with added ATP, the friction coefficients at all loads were more stable and lower than that at 150 SN. The friction coefficient at 50 and 100 N was more stable than that at 10 and 20 N, which was similar to 150 SN. Additionally, the friction coefficient at all loads can basically achieve stability after 400 s, which is apparently shorter than 150 SN. Similarly, the friction coefficient at low loads was higher than that at high loads. The friction coefficient at 20 N was the highest and at 50 N was the lowest.
The average friction coefficient and wear volume under the lubrication of 150 SN and 150 SN with added ATP at different loads is shown in Figure 7. Under the lubrication of 150 SN, the friction coefficient decreased gradually along with the increased load, while for 150 SN with added ATP, the friction coefficient at 20 N was the highest and at 50 N was the lowest. In addition, the friction coefficient of 150 SN with added ATP was lower than that of 150 SN at all selected loads. From Figure 7b, it can be seen that the wear volume increased gradually along with the increased load for both the two oils. Additionally, the wear volume of 150 SN with added ATP was lower than that of 150 SN at all selected loads. In summary, the friction-reducing and antiwear properties of 150 SN can be remarkably improved by adding moderate ATP at all selected loads. The friction-reducing and antiwear effect of ATP is most obvious at the applied load of 10 N. At 10 N, the average friction coefficient for 150 SN was decreased from 0.26 to 0.18, which is a 30.8% reduction. The wear volume for 150 SN was decreased from 21.8 × 10−3 mm3 to 10.2 × 10−3 mm3, which is a 53.2% reduction.

3.3. Worn Surface Analysis

The morphologies of the worn surfaces lubricated with 150 SN and 150 SN with added ATP at 50 N are displayed in Figure 8. Under the lubrication of 150 SN, it is obvious that the cauliflower-like structure of the Ni coating disappeared. There existed a large area of material peeling and some pits on the worn surface of Ni coating, while for 150 SN with added ATP, the worn surface became much smoother and flatter. Only shallow furrows and a few pits could be seen on the worn surface of Ni coating.
Figure 9 and Table 3 show the element composition and content on the worn surfaces displayed in Figure 6. C and Ni elements can be detected on the worn surface lubricated with 150 SN. There is no Fe element on the worn surface, indicating that the Ni coating is not completely worn off. In addition, the Ni content on the worn surface is lower than that on the substrate. As for the worn surface lubricated with 150 SN with added ATP, besides C and Ni elements, the new elements of O, Si, and Al can be found on it. Moreover, the Ni content of the worn surface lubricated with 150 SN with added ATP is basically the same as that with 150 SN. The above results demonstrate that tribofilm consisting of Ni, C, O, Si, and Al has formed on a worn surface under the lubrication of the 150 SN with added ATP.
XPS analysis on the worn surface lubricated with 150 SN with added ATP was performed to further confirm the composition of the formed tribofim. The results are presented in Figure 10. The analysis of the Ni2p3/2 peak indicates that Ni (853 eV) and NiO (854.1 eV) exist in the tribofilm [25,26,27]. The spectrum of C1s can be fitted into three subpeaks at 283.6, 284.8, and 285.5 eV, corresponding to graphite, C-C (pollution carbon), and organic compounds [14,27]. The subpeaks of O1s at around 530, 531.2, 532.3, and 533.4 eV are associated with NiO, Al2O3, SiO2, and organic compounds, respectively [14,25,27]. In addition, the spectrum of Si2p can be identified SiO2 (103.2 eV) [14,27]. The spectra of the Al2p peak suggests that Al2O3 (74.5 eV) can be found in the tribofilm [27]. Hence, it can be confirmed from XPS analysis results that the tribofilm formed on the worn surface of Ni coating is mainly composed of Ni, NiO, Al2O3, SiO2, graphite, and organic compounds.

4. Discussion

It can be indicated from the above experimental results that ATP can obviously improve the friction-reducing and antiwear properties of 150 SN for electric-brush plated Ni coating. Under the lubrication of 150 SN, the cauliflower-like structure of Ni coating is constantly worn away at first, due to the poor lubricity of oil. Along with the Ni coating continuing to be worn out, the cauliflower-like structure disappears, and a large area of material peeling and some pits appear on the worn surface. As for 150 SN with added ATP, a protective tribofilm is formed on the worn surface under the action of ATP. This behavior is directly related to the crystal structure of attapulgite and friction heat and high pressure. The chemical formula of attapulgite is (Mg, Al, Fe)5Si8O20(OH2)4·4H2O. It possesses a layered chain structure formed by a continuous Si-O tetrahedral layer and a discontinuous Mg(Al)–OH/O octahedral layer, as shown in Figure 11 [20,28]. Active oxygen atoms and unsaturated bonds (Si–O, Si–OH, Mg–O, Mg–OH, Al–O, Al–OH) exist in the tetrahedral layers and octahedral layers. Therefore, attapulgite possess several good physicochemical properties, including high surface activity and adsorption ability. During the friction procedure, attapulgite particles suspended in oil can be easily absorbed and deposited onto the Ni coating surface. Then, following tribochemical reactions among Ni coatings, attapulgite particles and oil occur under the effect of high contact stress and shearing force: (1) Microstructural instability of attapulgite occurred, leading to the release of plentiful active oxygen atoms, which take reaction with the Ni coating to form NiO [22,26]; (2) Some unsaturated bonds decomposed and recombined to form SiO2 and Al2O3 [22]; (3) The cracking of oil could form graphite and organic compounds. Finally, tribofilm mainly composed of Ni, NiO, Al2O3, SiO2, graphite, and organic compounds was formed on the rubbing surface. The tribofilm can fill and repair the wear region to reduce the surface roughness of the rubbing surface, thus reducing friction and wear. In addition, as the thickness of the tribofilm continuously increases, the metal–Ni coating friction pair changed into a tribofilm–tribofilm friction pair. The tribofilm is mainly composed of ceramic phases including NiO, Al2O3, and SiO2, which possess some excellent physicochemical properties, such as high strength, favorable antioxidation, and anticorrosion properties. Moreover, the ductility of such metallic oxides is low. Therefore, under the same tribology test conditions, the contact area of the tribofilm–tribofilm friction pair is smaller than that of the metal–Ni coating friction pair [29]. Consequently, the friction and wear can be remarkably reduced. However, the content and microstructure of each substance in the tribofilm cannot be determined; thus, the formation mechanism of tribofilm needs further research and exploration.
It was found that the optimum content of attapulgite additive in oil is 0.4 wt% when the load is 50 N.
It can be seen from Figure 6 that the friction coefficient under the lubrication of 150 SN fluctuated greatly at 10 and 20 N. This is attributed to the high roughness of the coating surface caused by the cauliflower-like structure. When the load increased to 50 and 100 N, the hardness of the coating was not high enough to resist the shear and extrusion of heavy loads. The cauliflower-like structure was quickly worn away to bring about significant reduction of coating surface roughness. Thus, the friction coefficient became more stable than light loads. Under the lubrication of 150 SN with added ATP, tribofilm can form on the worn surface to reduce coating surface roughness. Therefore, the friction coefficient was more stable and lower. Compared with the Ni coating, the ability of tribofilm to bear heavy loads is stronger. Thus, the friction coefficient and wear loss of 150 SN can be remarkably reduced even at the heavy load of 100 N. The tribological properties of attapulgite additive under different loads are dissimilar, which may be attributed to the competition between the formation and abrasion of tribofilm. With the increase in load, the energy provided by friction increases. However, at the same time, wear is also intensified [30,31]. It was found that the friction-reducing and antiwear effect of ATP was most obvious at the applied load of 10 N. This result demonstrates that the formation of tribofilm occupies a dominant position at the applied load of 10 N. The contact mode of the friction pair is ball on disc. Therefore, the contact stress of the friction pair was high. Thus, the energy provided by friction was high. If the contact mode changes to another form that cannot provide such high energy, it is doubtful that attapulgite still possesses friction-reducing and antiwear effects for the electric-brush plated Ni coating. This requires further research.

5. Conclusions

(1) The attapulgite nanofibers can be used as additives to improve the tribological properties of 150 SN for electric-brush plated Ni coating. The oil with an added 0.4 wt% attapulgite was found to be the most efficient in reducing friction and wear under the ball-disc model at a load of 50 N, a frequency of 10 Hz, and a temperature of 50 °C.
(2) The attapulgite additive can improve the friction-reducing and antiwear properties of oil at all selected loads—10, 20, 50, and 100 N. Under the lubrication of 150 SN, the friction coefficient decreased gradually along with the increased load, while for 150 SN with added ATP, the friction coefficient at 20 N is the highest and at 50 N is the lowest.
(3) Under the action of attapulgite, tribofilm mainly composed of Ni, NiO, Al2O3, SiO2, graphite, and organic compounds formed on the worn surface of Ni coating, which contributed to the decrease in friction and wear.

Author Contributions

Conceptualization, F.N.; methodology, F.N.; software, D.W.; validation, F.N.; formal analysis, D.W.; investigation, F.N.; resources, F.N.; data curation, D.W.; writing—original draft preparation, F.N.; writing—review and editing, D.W.; visualization, D.W.; supervision, D.W.; project administration, F.N.; funding acquisition, F.N. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the National Natural Science Foundation of China (51705511) and the Scientific Research Foundation of the Wuhan Institute of Technology (K202013).

Data Availability Statement

The data presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. Characterization of ATP: (a) XRD; (b) TEM.
Figure 1. Characterization of ATP: (a) XRD; (b) TEM.
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Figure 2. Characterization of the electric-brush plated Ni coating: (a) SEM; (b) EDS.
Figure 2. Characterization of the electric-brush plated Ni coating: (a) SEM; (b) EDS.
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Figure 5. Tribological properties of 150 SN with different added amounts of ATP (50 N, 10 Hz, 30 min).
Figure 5. Tribological properties of 150 SN with different added amounts of ATP (50 N, 10 Hz, 30 min).
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Figure 6. Friction coefficients as a function of sliding time for (a) 150 SN; (b) ATP at different loads (50 N, 10 Hz, 30 min).
Figure 6. Friction coefficients as a function of sliding time for (a) 150 SN; (b) ATP at different loads (50 N, 10 Hz, 30 min).
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Figure 7. Effect of load on (a) average friction coefficient; (b) wear volume for 150 SN and ATP (10 Hz, 30 min).
Figure 7. Effect of load on (a) average friction coefficient; (b) wear volume for 150 SN and ATP (10 Hz, 30 min).
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Figure 8. SEM images of the worn surfaces lubricated with (a) 150 SN; (b) ATP (50 N, 10 Hz, 30 min).
Figure 8. SEM images of the worn surfaces lubricated with (a) 150 SN; (b) ATP (50 N, 10 Hz, 30 min).
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Figure 9. EDS analysis results of the worn surfaces lubricated with (a) 150 SN; (b) ATP (50 N, 10 Hz, 30 min).
Figure 9. EDS analysis results of the worn surfaces lubricated with (a) 150 SN; (b) ATP (50 N, 10 Hz, 30 min).
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Figure 10. XPS patterns of worn surface lubricated with ATP: (a) Ni2p3/2; (b) C1s; (c) O1s; (d) Si2p; (e) Al2p (50 N, 10 Hz, 30 min).
Figure 10. XPS patterns of worn surface lubricated with ATP: (a) Ni2p3/2; (b) C1s; (c) O1s; (d) Si2p; (e) Al2p (50 N, 10 Hz, 30 min).
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Figure 11. Crystal structure model of attapulgite.
Figure 11. Crystal structure model of attapulgite.
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Table
Table 1. Process flow and parameters of electro-brush plating.
Table 1. Process flow and parameters of electro-brush plating.
ProcessSolutionVoltage/VPlating Time/minMovement Velocity of Plating pen/m·min−1
1Electrical cleaningElecting cleaning solutions+1216~8
2Intense activationNo. 2 activation solutions−120.58~10
3Slight activationNo. 3 activation solutions−180.56~8
4Pre-platingPre-plating nickel solutions+1218~10
5PlatingNickel plating solutions+12510~12
Table
Table 2. Major components of Nickel plating solutions.
Table 2. Major components of Nickel plating solutions.
ComponentAmount
NiSO4·6H2O20 g·L−1
CH3COONH440 g·L−1
(NH4)3C6H5O745 g·L−1
NH3·H2O/(adjust pH to 7.3~7.5)100~130 mL·L−1
Table
Table 3. Elemental content of Ni coating and worn surfaces on it (50 N, 10 Hz, 30 min).
Table 3. Elemental content of Ni coating and worn surfaces on it (50 N, 10 Hz, 30 min).
Atomic%
CNiOSiAl
Substrate57.8042.20000
Lubricated with 150 SN64.1435.86000
Lubricated with 150 SN with added ATP 55.4736.216.920.630.78
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Nan, F.; Wang, D. Tribological Properties of Attapulgite Nanofiber as Lubricant Additive for Electric-Brush Plated Ni Coating. Lubricants 2023, 11, 204. https://doi.org/10.3390/lubricants11050204

AMA Style

Nan F, Wang D. Tribological Properties of Attapulgite Nanofiber as Lubricant Additive for Electric-Brush Plated Ni Coating. Lubricants. 2023; 11(5):204. https://doi.org/10.3390/lubricants11050204

Chicago/Turabian Style

Nan, Feng, and Dong Wang. 2023. "Tribological Properties of Attapulgite Nanofiber as Lubricant Additive for Electric-Brush Plated Ni Coating" Lubricants 11, no. 5: 204. https://doi.org/10.3390/lubricants11050204

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