Characterization and Wear Behaviors of Electrodeposited Ni-MoS₂/SiC Composite Coating

Round 1

Reviewer 1 Report

Authors have investigated the characterization, wear behavior and other properties of composite coatings. The results are well-presentation and properly explained. Some modifications will improve the quality, presentation, reproducibility of results, and readability of the manuscript. Please consider the following comments:

1.      Lines 96-106: the information on coatings, substrate material, and other chemical materials is better to present in the form of table(s)

2.      What is the rationale behind polishing up to 0.22 µm? What is the acceptable range of surface roughness for the coating of these materials? Please include this information supported by the literature.

3.      Reasoning behind the selection of parameters (table 1) should be included.

4.      Lines 118-128: Steps are numbered but it would be much better to have numbering in stacked order rather in the form of paragraph. Additionally, chemical details should be placed in tabular form.

5.      Line 141-142: Are these test conditions met with some standard. Please mention.

6.      Line 157: please mention the distance among successive five points of micro-hardness

7.      Is the micro-hardness taken vertically from the reference surface (cross-sectional) or horizontally. Please explain in the text.

8.      In addition to current form, results of bonding strength should be presented as like of hardness in the form of graph.

9.      Conclusion number 2, please add the values along with the %ages. Same is in case of conclusion # 3

10.  Breaking down the conclusion # 4 into the bullets will improve the readability.

 

Comments for author File: Comments.pdf

Author Response

Reviewer 1

1. Lines 96-106: the information on coatings, substrate material, and other chemical materials is better to present in the form of table(s).

Author response: Thank you very much for reviewing the paper. It is more intuitive to express it in the form of the tables. We have revised the manuscript according to your comments and suggestions. The changes are marked in the document “Manuscript-Revise.doc”.

It is modified as follows: “Molybdenum disulfide (MoS₂) and silicon carbide (SiC) were commercially purchased from Shanghai Chaowei Nanotech Co., Ltd., China. The 2218 aluminum alloy chosen as the substrate materials was purchased from Dongguan Avis Metal Materials Co., Ltd., China. The chemicals used were commercially purchased. The information of all materials is shown in Tables 1-3.”

Table 1. The coating materials and properties.

Materials	Average particle size (nm)	Specific surface area (m2∙g-1)	Density (g∙cm-3)	Purity (%)
MoS2	600	12.4	1.83	≥99.9
SiC	600	3.2	1.52	≥99.5

Table 2. Chemical composition of 2218 aluminum alloy substrate.

Elements	Fe	Si	Mn	Cu	Mg	Al
wt.%	0.5	0.35	0.28	1.8	2.6	balanced

Table 3. The chemicals.

Chemicals	Purity (%)	Brand
Ni(NH2SO3)2·4H2O	99	Macklin
CH3(CH2)11OSO3Na	98	Aiyan
HBO3	99.5	Nanshi
Na2CO3	99.8	Nanshi
Na3PO4	98	Nanshi
NaOH	96	Nanshi
HNO3	65~68	Aladdin
ZnO	99	Aiyan
FeCl3	97	Nanshi
C6H8O7	99.5	Macklin
NaNO3	99	Nanshi

 

2. What is the rationale behind polishing up to 0.22 µm? What is the acceptable range of surface roughness for the coating of these materials? Please include this information supported by the literature.

Author response: Thank you very much for reviewing the paper. Your comments and suggestions are very helpful to improve the paper and our future research. It is generally accepted that the surface roughness of the substrate has a significant effect on the microstructure, morphology and interfacial bonding strength of the coating. These changes affect the growth trajectory of the coating materials, resulting in enhanced distribution of coating materials inhomogeneity and susceptibility to microcracks and microporosity defects, reducing coating hardness and bond strength. Thus, the friction and wear resistance of the coating is affected. (Hora Paknahad, Farhad Shahriari Nogorani, Effects of substrate roughness on the surface morphology and corrosion properties of Fe- and Ni-aluminide coatings on martensitic stainless steel. Surface & Coatings Technology, 2020, 392,125761; Mona Amiriafshar, Mehran Rafieazad, Xili Duan, Ali Nasiri, Fabrication and coating adhesion study of superhydrophobic stainless steel surfaces: The effect of substrate surface roughness. Surfaces and Interfaces, 2020, 20, 100526; Ali Ostadi Seyyed, Hojjatollah Hosseini Mohammadreza, Ebrahimi Fordoei, The effect of temperature and roughness of the substrate surface on the microstructure and adhesion strength of EB-PVD ZrO₂-%8 wt Y₂O₃ coating, Ceramics International, 2020, 46(2), 2287-2293; Zhiming Li, Shiqiang Qian, Wei Wang, Influence of superalloy substrate roughness on adhesion and oxidation behavior of magnetron-sputtered NiCoCrAlY coatings. Applied Surface Science, 2011, 257(24), 10414-10420). For example, the results of Paknahad et al. showed that the lower the roughness of the substrate, the lower the roughness of the coating. Clear grooves are visible on the coating surface on rough substrates, and the groove surface morphology disappears as the surface roughness decreases. The results of Amiriafshar et al. showed that when the initial surface roughness of the substrate increased, the surface roughness of the electrodeposited coating also increased. As the substrate surface roughness decreases, the adhesion of the coating increases. The results of Seyyed et al. showed that increasing the substrate roughness increases the porosity of the coating and affects the coating microstructure. The surface adhesion of the coating decreases with the increase of substrate surface roughness. The results of Li et al. showed that the surface roughness of the coating increases with the increase of the substrate roughness. The bond strength of the coating increases with the decrease of substrate roughness due to the decrease of internal stress in the coating and defects at the interface. Based on the above research results, combined with the electrodeposition standard GB/T12611 and literature “Hui Wang, Haijun Liu, Yang He, Chunyang Ma, Liangzhao Li, Ni-SiC composite coatings with good wear and corrosion resistance synthesized via ultrasonic electrodeposition. Journal of Materials Engineering and Performance 2021, 30, 1535-1544” and “Jerin K. Pancrecious, J.P. Deepa, Varanya Jayan, Ulaeto Sarah Bill, T.P.D. Rajan, B.C. Pai, Nanoceria induced grain refinement in electroless Ni-B-CeO₂ composite coating for enhanced wear and corrosion resistance of aluminium alloy, Surface & Coatings Technology 356 (2018) 29-37”. We updated the manuscript. The changes are marked in the document “Manuscript-Revise.doc”.

It is modified as follows: “The surface of the 2218 aluminum alloy disc samples (ϕ 50 × 8 mm) was polished by 400, 600, 800 and 1000 grain metallographic sandpapers in a certain order [10,40]. The surface roughness was measured to be ~0.22 μm by a TR 200 surface roughness meter with an accuracy of 0.001 μm (Beijing Saiboruixin technology Co., Ltd., Beijing, China)”.

3. Reasoning behind the selection of parameters (table 1) should be included.

Author response: Thank you very much for reviewing the paper. Your comments and suggestions are very helpful to improve the paper. For electrodeposited functional coatings, the conditions of coating preparation are very critical. It mainly includes the pH value of the plating solution, the temperature of the plating solution, the current density, the stirring speed and the deposition time. The research focuses on the improvement of the friction reduction and wear resistance of the coating in this paper. It can be found that the friction reduction and wear resistance of the coating decreases first, and then increases with the increase of pH value of the plating solution. The too high current density will lead to pitting, pinholes and bubbles in the coating and excessive agglomeration of particles, while the too low current density will lead to reduced deposition rates and even to deposition failure. The high temperature increases the electrodeposition rate and facilitates particle dispersion and deposition. However, if the temperature is too high, the activity of the surfactant will be reduced and the Aminosulfonate will be decomposed leading to experimental failure. The purpose of continuous stirring is to disperse the particles evenly in the plating solution and to prevent particle agglomeration. The deposition time is a key factor to ensure the thickness of the coating, the longer the deposition time, the greater the thickness of the coating obtained. However, for the functional coating of friction reduction and wear resistance, the interfacial bonding strength of the coating is the key to resist frictional shear. The thickness is generally required to be 20~50 μm. Based on the results of the literature “Hui Wang, Haijun Liu, Yang He, Chunyang Ma, Liangzhao Li, Ni-SiC composite coatings with good wear and corrosion resistance synthesized via ultrasonic electrodeposition. Journal of Materials Engineering and Performance 2021, 30, 1535-1544.”, “Sivasakthi P, Sangaranarayanan MV, Influence of pulse and direct current on electrodeposition of Ni-Gd₂O₃ nanocomposite for micro hardness, wear resistance and corrosion resistance applications. Composites Communications 2019, 13, 134-142.”, “Paochang Huang, Kunghsu Hou, Jiajun Hong, Menghung Lin, Gaoliang Wang, Study of fabrication and wear properties of Ni-SiC composite coatings on A356 aluminum alloy. Wear 2021, 477, 203772.”, “Zhou Y, Sun ZP, Yu Y, Li L, Song JL, Xie FQ, Wu XQ, Tribological behavior of Ni-SiC composite coatings produced by circulating-solution electrodeposition technique. Tribology International, 2021, 159, 106933.”, “Pinate S, Leisner P, Zanella C, Wear resistance and self-lubrication of electrodeposited Ni-SiC: MoS₂ mixed particles composite coatings. Surface and Coatings Technology 2021, 421, 127400.” and our pre-experiment, the electrodeposition conditions in Table 1 were finally determined. We updated the manuscript. The changes are marked in the document “Manuscript-Revise.doc”.

It is modified as follows: “Table 4 shows the operating conditions of electrodeposition determined based on the literature [10,11,16,21,25] and pre-experiments.”

4. Lines 118-128: Steps are numbered but it would be much better to have numbering in stacked order rather in the form of paragraph. Additionally, chemical details should be placed in tabular form.

Author response: Thank you very much for reviewing the paper. Your comments and suggestions are very helpful to improve the paper. The reviewer 2 also put forward comments and suggestions for the coating preparation process in conjunction with Figure 1. Combining your comments and reviewer 2's comments, we have revised this section. We updated the manuscript. The changes are marked in the document “Manuscript-Revise.doc”.

It is modified as follows: “The specific process of preparing composite coating is as follows:

Step 1 The aluminum alloy disc samples were etched to remove contaminants and surface oxides in an alkali mixed solution for 2 min.

Step 2 The aluminum alloy disc samples were washed in an acid solution for 30 s.

Step 3 The aluminum alloy disc samples were treated with zinc immersion in the mixed solution for 60 s. Afterwards, the zinc is dezincified in HNO₃ solution for 30 s. Finally, the second zinc immersion was carried out in the mixed solution for 40 s.

Step 4 According to the operating conditions in Table 4 and composite coating requirements, the pretreated aluminum alloy disc samples were subjected to composite coating electrodeposition in plating solution for 60 min.

After each step, the treated aluminum alloy disc samples were ultrasonically cleaned by deionized water for 5 min. Thus, the Ni-MoS₂, Ni-SiC and Ni-MoS₂/SiC composite coatings were achieved. For the convenience of subsequent analysis, the samples of aluminum alloy substrate, Ni-MoS₂ coating, Ni-SiC coating and Ni-MoS₂/SiC coating are denoted as E0, E1, E2 and E3, respectively. The solution composition, operating time and technological process is illustrated in Figure 1.

 

Figure 1. Flow diagram of the technological process.

5. Line 141-142: Are these test conditions met with some standard. Please mention.

Author response: Thank you very much for reviewing the paper. Your comments and suggestions are very helpful to improve the paper. The purpose of this paper is to investigate the tribological properties of different coatings and their improvement of the friction reduction and wear resistance of the 2218 aluminum alloy substrate. The test conditions should be set both within the control parameters of the wear tester and to be able to achieve comparative analysis of the tribological properties of the experimental samples. The load range is 1.5-20 N, temperature is 20-1000 °C, rotation speed is 5-2800 rpm, radius of rotation is 2.5-30 mm in the HT-1000 type high temperature friction and wear tester. The experimental conditions in this paper were determined according to the purpose of the experiment and pre-experimental analysis. We updated the manuscript. The changes are marked in the document “Manuscript-Revise.doc”.

  It is modified as follows: “The dry wear experiments were performed at a rotation speed of 400 rpm, a radius of 6 mm, a load of 2 N, a temperature of 100 °C and a time of 10 min based on the purpose of the experiment and pre-experimental analysis.”

6. Line 157: please mention the distance among successive five points of micro-hardness.

Author response: Thank you very much for reviewing the paper. Your comments and suggestions are very helpful to improve the paper. The surface microhardness of the samples was obtained using a THV-5 Vickers hardness tester according to the GB/T 4340. The distance between the center of the measurement point and the edge of the specimen is not less than 2.5 times the diagonal distance of the indentation, and the distance between the two test points is not less than 3 times the diagonal distance of the indentation. We updated the manuscript. The changes are marked in the document “Manuscript-Revise.doc”.

It is modified as follows: “A digital Vickers hardness tester (THV-5, Beijing Time High Technology Co., Ltd., Beijing, China) was applied to measure the microhardness of all samples. In this work, the load applied was 200 g and the holding time was 15 s. For the validity of the results, at least 5 points were measured at different locations according to GB/T 4340.”

7. Line 157: Is the micro-hardness taken vertically from the reference surface (cross-sectional) or horizontally. Please explain in the text.

Author response: Thank you very much for reviewing the paper. Your comments and suggestions are very helpful to improve the paper. The microhardness in this paper refers to the surface hardness of the samples. Therefore, it is measured perpendicular to the surface of the coating. We updated the manuscript. The changes are marked in the document “Manuscript-Revise.doc”.

It is modified as follows: “The average value was taken as the surface microhardness of the sample.”

8. In addition to current form, results of bonding strength should be presented as like of hardness in the form of graph.

Author response: Thank you very much for reviewing the paper. According to your comments and suggestions, we have added the Figure 5 (b) for the bonding strength of composite coatings. We updated the manuscript. The changes are marked in the document “Manuscript-Revise.doc”.

Figure 5. Mechanical properties of the E0, E1, E2 and E3 samples.

(a) Microhardness, (b) Bonding strength.

9. Conclusion number 2, please add the values along with the %ages. Same is in case of conclusion # 3.

Author response: Thank you very much for reviewing the paper. Your comments and suggestions are very helpful to improve the paper. We updated the manuscript. The changes are marked in the document “Manuscript-Revise.doc”.

It is modified as follows:

(2) The surface microhardness of Ni-MoS₂, Ni-SiC and Ni-MoS₂/SiC composite coating samples is 274.9 HV, 407.48 HV and 356.9 HV, which is 111.92%, 214.12% and 175.13% higher than that of 2218 aluminum alloy substrate sample, respectively. It mainly depends on the strengthening effect of coating particles, grain refinement effect and fine microstructure.

(3) The tribological behaviors of all composite coating samples are significantly enhanced. The wear rate of Ni-MoS₂, Ni-SiC and Ni-MoS₂/SiC composite coating samples is 5 mg/N∙m, 2.8 mg/N∙m and 4 mg/N∙m , and decreased by 28.87%, 60.17% and 43.10%, respectively. The average friction coefficient of corresponding samples is 0.2677, 0.4387 and 0.3153, and reduced by 59.73%, 34.01% and 52.56%, respectively. Therefore, the Ni-MoS₂/SiC composite coating sample is better from the viewpoint of comprehensive friction reduction and wear resistance.”

10. Breaking down the conclusion # 4 into the bullets will improve the readability.

Author response: Thank you very much for reviewing the paper. Your comments and suggestions are very helpful to improve the paper. We updated the manuscript. The changes are marked in the document “Manuscript-Revise.doc”.

It is modified as follows:

(4) The predominant wear mechanism of 2218 aluminum alloy substrate is severe adhesive wear and abrasive wear, which show poor wear resistance.

(5) The Ni-MoS₂ composite coating sample is mainly characterized by mild abrasive wear, flake spalling and tearing. The Ni-SiC composite coating sample shows the abrasive wear, particles shedding and debris piled up. However, the Ni-MoS₂/SiC composite coating sample exhibits the typical mild abrasive wear, spalling, pits and tearing.

Thank you again for your review of the paper.

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript entitled “Characterization and wear behaviours of electrodeposited Ni- 2 MoS2/SiC composite coatings” includes the development of Ni-MoS2, Ni-SiC and Ni-MoS2/SiC composite coatings on the 2218 aluminium alloy by an electrodeposition technique to improve the wear resistance against steel materials. Subsequently, surface morphologies, microstructure, microhardness and its adhesion to the substrate were investigated. The tribological behaviours of the composite coatings were also investigated under dry sliding friction. Author’s presented the data in systematic manners along with all the essential evidences, however, it requires minor and mandatory revisions for future acceptance in the coatings.

• There is need to include latest literature related to the electro-deposition technique in the introduction section.

• Why the samples were initially polished to the roughness of 0.22 μm. Kindly justify it.

• Kindly mentioned the parametric selection method, which has been used to conduct the electro-deposition process at fixed levels.  

• It would be more effective to include the processing and holding time spans in the Figure 1.

• The specifications and least count of the experimental facilities as well as the measurement instruments are also missing, and the use of pictorial view of the experimental facility would be more effective.

• Kindly check the title 3.1. “Composite Catings”.

• Measurement methodology used to identify the coating thickness is not reported in the manuscript. 

• There is a need to provide schematic illustrations of the process mechanism.

• The scientific reasoning of the results and mechanisms is missing.

• In Figure 6.a. and c, is it correct to present the data in line graph format? Kindly check and justify. 

• The conclusion should be concise.

Author Response

Reviewer 2

1. There is need to include latest literature related to the electro-deposition technique in the introduction section.

Author response: Thank you very much for reviewing the paper. Your comments and suggestions are very helpful to improve the paper. We have added three literatures “Pattraporn Krajaisri, Rachakorn Puranasiri, Pongpak Chiyasak, Aphichart Rodchanarowan, Investigation of pulse current densities and temperatures on electrodeposition of tin-copper alloys, Surface & Coatings Technology 2022, 435, 128244”, “Mohammed Fuseini, Moustafa Mahmoud Yousry Zaghloul, investigation of electrophoretic deposition of PANI nano fibers as a manufacturing technology for corrosion protection, Progress in Organic Coatings 2022, 171, 107015.”and “Mohammed Fuseini, Moustafa Mahmoud Yousry Zaghloul, Statistical and qualitative analyses of the kinetic models using electrophoretic deposition of polyaniline, Journal of Industrial and Engineering Chemistry, 2022, 113, 475-487”. We updated the manuscript. The changes are marked in the document “Manuscript-Revise.doc”.

It is modified as follows: “Among these methods, the electrodeposition method has received much attention owing to its low cost, ease of implementation and applicability to various geometries [11-15].”

2. Why the samples were initially polished to the roughness of 0.22 μm. Kindly justify it.

Author response: Thank you very much for reviewing the paper. Your comments and suggestions are very helpful to improve the paper and our future research. It is generally accepted that the surface roughness of the substrate has a significant effect on the microstructure, morphology and interfacial bonding strength of the coating. These changes affect the growth trajectory of the coating materials, resulting in enhanced distribution of coating materials inhomogeneity and susceptibility to microcracks and microporosity defects, reducing coating hardness and bond strength. Thus, the friction and wear resistance of the coating is affected. (Hora Paknahad, Farhad Shahriari Nogorani, Effects of substrate roughness on the surface morphology and corrosion properties of Fe- and Ni-aluminide coatings on martensitic stainless steel. Surface & Coatings Technology, 2020, 392,125761; Mona Amiriafshar, Mehran Rafieazad, Xili Duan, Ali Nasiri, Fabrication and coating adhesion study of superhydrophobic stainless steel surfaces: The effect of substrate surface roughness. Surfaces and Interfaces, 2020, 20, 100526; Ali Ostadi Seyyed, Hojjatollah Hosseini Mohammadreza, Ebrahimi Fordoei, The effect of temperature and roughness of the substrate surface on the microstructure and adhesion strength of EB-PVD ZrO₂-%8 wt Y₂O₃ coating, Ceramics International, 2020, 46(2), 2287-2293; Zhiming Li, Shiqiang Qian, Wei Wang, Influence of superalloy substrate roughness on adhesion and oxidation behavior of magnetron-sputtered NiCoCrAlY coatings. Applied Surface Science, 2011, 257(24), 10414-10420). For example, the results of Paknahad et al. showed that the lower the roughness of the substrate, the lower the roughness of the coating. Clear grooves are visible on the coating surface on rough substrates, and the groove surface morphology disappears as the surface roughness decreases. The results of Amiriafshar et al. showed that when the initial surface roughness of the substrate increased, the surface roughness of the electrodeposited coating also increased. As the substrate surface roughness decreases, the adhesion of the coating increases. The results of Seyyed et al. showed that increasing the substrate roughness increases the porosity of the coating and affects the coating microstructure. The surface adhesion of the coating decreases with the increase of substrate surface roughness. The results of Li et al. showed that the surface roughness of the coating increases with the increase of the substrate roughness. The bond strength of the coating increases with the decrease of substrate roughness due to the decrease of internal stress in the coating and defects at the interface. Based on the above research results, combined with the electrodeposition standard GB/T12611 and literature “Hui Wang, Haijun Liu, Yang He, Chunyang Ma, Liangzhao Li, Ni-SiC composite coatings with good wear and corrosion resistance synthesized via ultrasonic electrodeposition. Journal of Materials Engineering and Performance 2021, 30, 1535-1544” and “Jerin K. Pancrecious, J.P. Deepa, Varanya Jayan, Ulaeto Sarah Bill, T.P.D. Rajan, B.C. Pai, Nanoceria induced grain refinement in electroless Ni-B-CeO₂ composite coating for enhanced wear and corrosion resistance of aluminium alloy, Surface & Coatings Technology 356 (2018) 29-37”. We updated the manuscript. The changes are marked in the document “Manuscript-Revise.doc”.

It is modified as follows: “The surface of the 2218 aluminum alloy disc samples (ϕ 50 × 8 mm) was polished by 400, 600, 800 and 1000 grain metallographic sandpapers in a certain order [10,40]. The surface roughness was measured to be ~0.22 μm by a TR 200 surface roughness meter with an accuracy of 0.001 μm (Beijing Saiboruixin technology Co., Ltd., Beijing, China)”.

3. Kindly mentioned the parametric selection method, which has been used to conduct the electro-deposition process at fixed levels.

Author response: Thank you very much for reviewing the paper. Your comments and suggestions are very helpful to improve the paper. For electrodeposited functional coatings, the conditions of coating preparation are very critical. It mainly includes the pH value of the plating solution, the temperature of the plating solution, the current density, the stirring speed and the deposition time. The research focuses on the improvement of the friction reduction and wear resistance of the coating in this paper. It can be found that the friction reduction and wear resistance of the coating decreases first, and then increases with the increase of pH value of the plating solution. The too high current density will lead to pitting, pinholes and bubbles in the coating and excessive agglomeration of particles, while the too low current density will lead to reduced deposition rates and even to deposition failure. The high temperature increases the electrodeposition rate and facilitates particle dispersion and deposition. However, if the temperature is too high, the activity of the surfactant will be reduced and the Aminosulfonate will be decomposed leading to experimental failure. The purpose of continuous stirring is to disperse the particles evenly in the plating solution and to prevent particle agglomeration. The deposition time is a key factor to ensure the thickness of the coating, the longer the deposition time, the greater the thickness of the coating obtained. However, for the functional coating of friction reduction and wear resistance, the interfacial bonding strength of the coating is the key to resist frictional shear. The thickness is generally required to be 20~50 μm. Based on the results of the literature “Hui Wang, Haijun Liu, Yang He, Chunyang Ma, Liangzhao Li, Ni-SiC composite coatings with good wear and corrosion resistance synthesized via ultrasonic electrodeposition. Journal of Materials Engineering and Performance 2021, 30, 1535-1544.”, “Sivasakthi P, Sangaranarayanan MV, Influence of pulse and direct current on electrodeposition of Ni-Gd₂O₃ nanocomposite for micro hardness, wear resistance and corrosion resistance applications. Composites Communications 2019, 13, 134-142.”, “Paochang Huang, Kunghsu Hou, Jiajun Hong, Menghung Lin, Gaoliang Wang, Study of fabrication and wear properties of Ni-SiC composite coatings on A356 aluminum alloy. Wear 2021, 477, 203772.”, “Zhou Y, Sun ZP, Yu Y, Li L, Song JL, Xie FQ, Wu XQ, Tribological behavior of Ni-SiC composite coatings produced by circulating-solution electrodeposition technique. Tribology International, 2021, 159, 106933.”, “Pinate S, Leisner P, Zanella C, Wear resistance and self-lubrication of electrodeposited Ni-SiC: MoS₂ mixed particles composite coatings. Surface and Coatings Technology 2021, 421, 127400.” and our pre-experiment, the electrodeposition conditions in Table 1 were finally determined. We updated the manuscript. The changes are marked in the document “Manuscript-Revise.doc”.

It is modified as follows: “Table 4 shows the operating conditions of electrodeposition determined based on the literature [10,11,16,21,25] and pre-experiments.”

4. It would be more effective to include the processing and holding time spans in the Figure 1.

Author response: Thank you very much for reviewing the paper. Your comments and suggestions are very helpful to improve the paper. We have revised the Figure 1. We updated the manuscript. The changes are marked in the document “Manuscript-Revise.doc”.

Figure 1. Flow diagram of the technological process.

5. The specifications and least count of the experimental facilities as well as the measurement instruments are also missing, and the use of pictorial view of the experimental facility would be more effective.

Author response: Thank you very much for reviewing the paper. Your comments and suggestions are very helpful to improve the paper. The equipment and instruments used in the study included the HT-1000 high temperature friction and wear tester (Zhongke Kaihua Technology Development Co., Ltd., Lanzhou, China. Technical indicators are as follows: Load of 1.5-20 N; Rotation speed of 5-2800 rpm; Temperature range of ~1000 °C, 0.2% FS; Rotation radius of 2.5-30 mm; Friction coefficient dynamic display accuracy of 0.2% FS; Friction force dynamic display accuracy of ±0.002 N.), electronic balance (FA2204C, Shanghai Yueping Scientific Instrument Co., Ltd., Shanghai, China. Weighing capacity of 200 g; Accuracy of 0.1 mg), ultrasonic cleaners (F-050, Shenzhen Fuyang Technology Group Co., Ltd., Shenzhen, China. Technical indicators are as follows: Temperature of ~80 °C; Time of 1-30 min; Ultrasonic power of 360 W.), TR 200 surface roughness meter (Beijing Saiboruixin technology Co., Ltd., Beijing, China, GB/T 4340. Technical indicators are as follows: Measurement parameters includes Ra and Rq (0.005-16 μm), Rz, Rt, Rp and Rm (0.02-160 μm); Measuring range of 160 μm for Z-axis and 17.5 mm for X-axis; Resolution of 0.002-0.008/±20-80 μm; Sampling length of 0.25 mm, 0.8 mm and 2.5 mm; Stylus is natural diamond with a cone angle 90° and tip radius 5 μm; Accuracy of 0.001 μm.) WS-2005 automatic scratching instrument for coating adhesion (Zhongke Kaihua Technology Development Co., Ltd., Lanzhou, China, JB/T 8554. Technical indicators are as follows: Loading rate of 10-100 N/min; Scratch speed of 1-10 mm/min; Scratch length of 2-6 mm; Automatic loading range of 0-200N with an accuracy 0.3N; Coating thickness detection range of 0.2-150 μm; Diamond indenter with a cone angle 120° and tip radius 0.2 mm.), THV-5 Vickers hardness tester (Beijing Time High Technology Co., Ltd., Beijing, China, GB/T 4340. Technical indicators are as follows: Pressure head surface angle of 136°; Automatic loading, holding and unloading; Holding time of 1-99 s.), WYK-5010 DC regulated voltage and current power supply (Yangzhou Jintong Eletronics Co., Ltd., Yangzhou, China. Technical indicators are as follows: Output voltage of 0-50 V; Output current of 0-10 A.), DF-101S collector type thermostatic heating magnetic stirrer (Gongyi Yuhua Instrument Co., Ltd., Zhenfzhou, China. Technical indicators are as follows: Rotation speed of 0-2600 rpm; Temperature range of ~400 °C.), scanning electron microscope (SEM, MIRA3, TESCAN, Czech Republic. Technical indicators are as follows: Acceleration voltage of 0.2~30 kV; Magnification: x1~ X1,000,000; Secondary electronic image resolution of1.0 nm (30 kV).) and 3D optical microscope (DVM6, Germany. Technical indicators are as follows: 10 megapixel high-resolution camera；Optical magnification ratio of 16:1; Viewing angle of ±60°; Load platform rotation of ±180°; Maximum magnification of 2350 times.). The experimental facilities and the measurement instruments are as follows. We have added the corresponding the experimental facilities and the measurement instruments specifications in the paper. Common equipment and instruments were used in the study, and the tests were carried out according to the appropriate standards. We have added the corresponding standards and technical specifications to the paper.

 “The surface roughness was measured to be ~0.22 μm by a TR 200 surface roughness meter with an accuracy of 0.001 μm (Beijing Saiboruixin technology Co., Ltd., Beijing, China). The electrodeposition device consists of a WYK-5010 DC regulated voltage and current power supply with an output voltage of 0-50 V and output current of 0-10 A (Yangzhou Jintong Eletronics Co., Ltd., Yangzhou, China) and a DF-101S collector type thermostatic heating magnetic stirrer with a rotation speed of 0-2600 rpm. The tester with a load of 1.5-20 N, a rotation speed of 5-2800 rpm and a temperature of room temperature-1000 °C. The wear mass loss was received by using an electronic balance with an accuracy of 0.1 mg and a weighing capacity of 200 g (FA2204C, Shanghai Yueping Scientific Instrument Co., Ltd., Shanghai, China). A digital Vickers hardness tester (THV-5, Beijing Time High Technology Co., Ltd., Beijing, China) was applied to measure the microhardness of all samples. In this work, the load applied was 200 g and the holding time was 15 s. For the validity of the results, at least 5 points were measured at different locations according to GB/T 4340. The average value was taken as the surface microhardness of the sample. The bonding strength of the composite coatings was obtained using an automatic scratch instrument with a loading rate of 10-100 N/min, a scratch rate of 1-10 mm/min and a scratch length of 2-6 mm (WS-2005, Zhongke Kaihua Technology Development Co., Ltd., Lanzhou, China). In this case, the diamond indenter with a 120˚ conical shape and a tip radius of 200 μm was employed.”  We updated the manuscript. The changes are marked in the document “Manuscript-Revise.doc”.

HT-1000                     FA2204C             F-050

  

WS-2005                 THV-5        WYK-5010         DF-101S

    

TR 200                     MIRA3, TESCAN                 DVM 6

6. Kindly check the title 3.1. “Composite Catings”.

Author response: Thank you very much for reviewing the paper. It is a clerical error. It is modified as follows: “Characterization of Composite Coatings.” Simultaneously, we have proofread the manuscript. We updated the manuscript. The changes are marked in the document “Manuscript-Revise.doc”.

7. Measurement methodology used to identify the coating thickness is not reported in the manuscript.

Author response: Thank you very much for reviewing the paper. Your comments and suggestions are very helpful to improve the paper. The thickness of the coating was obtained when the cross-section microstructure was measured by scanning electron microscopy. Thank you again for your review of the paper.

8. There is a need to provide schematic illustrations of the process mechanism.

Author response: Thank you very much for reviewing the paper. Your comments and suggestions are very helpful to improve the paper. We have added a schematic illustration. We updated the manuscript. The changes are marked in the document “Manuscript-Revise.doc”.

It is modified as follows: “To better illustrate the electrodeposition mechanism of coating particles, the electrodeposition process of the Ni-MoS₂/SiC composite coating is shown in Figure 5. The dispersed SiC and MoS₂ particles in the plating solution are wrapped by Ni ions through weak adsorption, which causes the particles to be transported towards the cathode (aluminum alloy substrate) under electric field forces due to their positive charge. Afterwards, the charged particles pass through the boundary layer and gradually diffuse to the cathode surface. And then, the particles are adsorbed on the surface of the aluminum alloy substrate to achieve electrodeposition. In the continuous electrodeposition process, the particles in the diffusion layer on the surface near the cathode are continuously reduced. The continuous magnetic stirring effect can cause the charged particles to transfer to the diffusion layer by migration and diffusion, thus ensuring continuous electrodeposition.”

Figure 5 A schematic illustration of electrodeposition process.

9. The scientific reasoning of the results and mechanisms is missing.

Author response: Thank you very much for reviewing the paper. Your comments and suggestions are very helpful to improve the paper. The measurement instruments commonly used in this field of research were used in this study, and the corresponding test and analysis standards and specifications were followed in the test and analysis. The surface morphology, the elemental distribution, the microstructure of the coating cross-section and the coating thickness of the coatings were characterized by SEM (SEM, MIRA3, TESCAN, Czech Republic) and energy spectrum analysis.

“It is believed that this composite coating structure is due to the fact that MoS₂ particles attached to the substrate not only become nucleation sites for Ni growth, but also result in higher current density on the surface. Ni ions prefer to nucleate on the particle surface rather than around the particle, resulting in nodular structures. Shourije et al. [43] and He et al. [31] have reported the strong influence of conducting particles on the local current distribution and its growth kinetics during the electrodeposition process. In addition, the MoS₂ particles enhance the denseness of the composite coating structure. The presence of MoS₂ particles hinders the growth of Ni ions, resulting in smaller Ni grains. The similar structural morphology has been also observed by Zhou et al. [44] and He et al. [31]. The addition of SiC particles increases the number of nucleation sites of Ni crystals while effectively inhibiting the growth of Ni grains [10,45]. Gyawali et al. [46] and Huang et al. [16] have described the similar structural morphology of Ni-SiC coatings prepared by electrodeposition methods. The combined effect of the two coating particles enhances the nucleation sites of Ni ions and the growth of Ni grains is inhibited. However, the refinement of the Ni grains is inferior to that of the E2 sample, which could be attributed to the addition of MoS₂ particles leading to a change in the current distribution, thus attenuating the inhibitory effect of the SiC particles. It can be concluded that the coatings thickness mainly depends on the properties of the deposited particle and the electrodeposition rate. The internally structure of all composite coatings is compact, integral and consequent, tightly fitted with the 2218 aluminum alloy substrate.”; The surface hardness and bonding strength of coatings were obtained by THV-5 Vickers hardness tester and WS-2005 automatic scratch tester according to GB/T4340 and JB/T8544 standards. “The increase in hardness is chiefly attributed to the strengthening of the co-deposited particles, the finer structure and the grain refinement due to the hindrance of dislocation migration and grain growth [16,25]. The interfacial bonding strength depends mainly on the surface properties of the substrate, the pretreatment of the substrate surface, the characteristics of the coating materials and the electrodeposition conditions.” The worn surface morphology was analyzed by scanning electron microscopy (SEM, MIRA3, TESCAN, Czech Republic) and three-dimensional optical microscopy (DVM6, Germany), and the wear depth was measured. “It can be clearly observed that the wear surface exhibits obvious wide and deep grooves along the sliding direction, and there is typical plastic deformation and plastic flow, which is mainly due to the lower hardness of the 2218 aluminum alloy substrate. It can be assumed that the softer MoS₂ is released on the contact surface under the experimental conditions, forming a good lubricating layer and filling the grooves to some extent [57]. Considering the high surface hardness of the E1 sample, this is the reason why this sample has very good friction reduction and wear resistance properties. It can be concluded that the improved tribological behaviors of the E2 sample is mainly attributed to its increased surface microhardness. Tribological properties are mainly dependent on the improvement of surface hardness of the composite coating and the combined friction reduction and wear resistance properties of the coating materials. However, the groove-filling ability of MoS₂ is diminished by the plowing effect of the hard particles. The tearing and flake spalling marks of the composite coating are significantly reduced.”. We updated the manuscript. The changes are marked in the document “Manuscript-Revise.doc”.

10. In Figure 6.a. and c, is it correct to present the data in line graph format? Kindly check and justify.

Author response: Thank you very much for reviewing the paper. Your comments and suggestions are very helpful to improve the paper. The bar graphs express the wear rate and average friction coefficient for different samples, and the line graphs are only for a more visual representation of the differences between the test samples. Since they are different samples, this presentation may create some ambiguity in understanding. Based on your comments and suggestions, we have removed the line graph format. We updated the manuscript. The changes are marked in the document “Manuscript-Revise.doc”.

It is modified as follows.

Figure 7. Variation of wear rate and friction coefficient of E0, E1, E2 and E3 samples. (a) Wear rate; (b) Friction coefficient vs. time; (c) Average friction coefficient.

11. The conclusion should be concise.

Author response: Thank you very much for reviewing the paper. Your comments and suggestions are very helpful to improve the paper. We have rewritten the conclusions according to comments and suggestions. We updated the manuscript. The changes are marked in the document “Manuscript-Revise.doc”.

It is modified as follows:

The Ni-MoS₂, Ni-SiC and Ni-MoS₂/SiC composite coatings were prepared by an electrodeposition method. The surface morphologies, microstructure, mechanical properties and tribological behaviors were investigated. The main conclusions are summarized as follows:

(1) Compared with 2218 aluminum alloy sample, the surfaces of the composite coating samples are rough. The coating materials are irregularly and relative uniformly distributed on the surface, the microstructure is compact, integral and consequent, tightly fitted with the substrate, without visible microcracks and pinhole defects. The thickness of composite coating samples is different due to the different coating materials and their effects on the deposition rate.

(2) The surface microhardness of Ni-MoS₂, Ni-SiC and Ni-MoS₂/SiC composite coating samples is 274.9 HV, 407.48 HV and 356.9 HV, which is 111.92%, 214.12% and 175.13% higher than that of 2218 aluminum alloy substrate sample, respectively. It mainly depends on the strengthening effect of coating particles, grain refinement effect and fine microstructure.

(3) The tribological behaviors of all composite coating samples are significantly enhanced. The wear rate of Ni-MoS₂, Ni-SiC and Ni-MoS₂/SiC composite coating samples is 5 mg/N∙m, 2.8 mg/N∙m and 4 mg/N∙m, and decreased by 28.87%, 60.17% and 43.10%, respectively. The average friction coefficient of corresponding samples is 0.2677, 0.4387 and 0.3153, and reduced by 59.73%, 34.01% and 52.56%, respectively. Therefore, the Ni-MoS₂/SiC composite coating sample is better from the viewpoint of comprehensive friction reduction and wear resistance.

(4) The predominant wear mechanism of 2218 aluminum alloy substrate is severe adhesive wear and abrasive wear, which show poor wear resistance.

(5) The Ni-MoS₂ composite coating sample is mainly characterized by mild abrasive wear, flake spalling and tearing. The Ni-SiC composite coating sample shows the abrasive wear, particles shedding and debris piled up. However, the Ni-MoS₂/SiC composite coating sample exhibits the typical mild abrasive wear, spalling, pits and tearing.

Thank you again for your review of the paper.

Author Response File: Author Response.pdf

Reviewer 3 Report

Review of the manuscript "Characteristics and Wear Characteristics of Ni-2 MoS2/SiC Electrodeposited Composite Coatings" by Yutao Yan, Lifeng Lu, Yuqiu Huo, and Yong Zhao.

The paper presents the results of studies of Ni-MoS2, Ni-SiC and Ni-MoS2/SiC coatings deposited by electrolysis on aluminum alloy 2218. The material of the article is well presented, the analysis technique and results are well illustrated, all conclusions are consistent with the results. I believe that the manuscript can be published in the form in which it is presented.

As a recommendation to the authors:

1. To fig. 4 add data on the distribution of elements in the cross section of the coating.

2. Fig.5. It makes sense to indicate in the caption to the figure that this is not the hardness of samples, but of coatings. The hardness of the substrate (sample E0) should be marked on the diagram not with a column, but with a horizontal line - the hardness of the substrate. It will be more correct.

Author Response

Reviewer 3

1. To fig. 4 add data on the distribution of elements in the cross section of the coating.

Author response: Thank you very much for reviewing the paper. The purpose of Figure 4 is to analyze the microstructure, thickness and interfacial bonding of the coating. The research focuses on the tribological behaviors of the coating, which is directly related to the surface properties of the coating. Therefore, we have measured and analyzed the surface morphology, surface hardness and interfacial bonding strength of the coatings. The distribution of the coating materials is relatively uniform according to the electrodeposition process used and the elemental analysis of the coating surface. The elemental distribution of the coating surface can be observed and analyzed in Figure 3 in this paper.

2. Fig.5. It makes sense to indicate in the caption to the figure that this is not the hardness of samples, but of coatings. The hardness of the substrate (sample E0) should be marked on the diagram not with a column, but with a horizontal line - the hardness of the substrate. It will be more correct.

Author response: Thank you very much for reviewing the paper. Your comments and suggestions are very helpful to improve the paper. The graphical representation of the study results is important for understanding. Based on your comments and suggestions, we have revised Figure 5. We updated the manuscript. The changes are marked in the document “Manuscript-Revise.doc”.

 It is modified as follows.

Thank you again for your review of the paper.

Reviewer 4 Report

The paper seeks to introduce an approach “Characterization and wear behaviors of electrodeposited Ni-MoS2/SiC composite coatings”. However, the authors should consider improving upon the quality to further highlight and emphasize.

1.     Based on the understanding of what should be included in the abstract, consider adding one or two lines highlighting the importance of the study.

2.    Consider tabulating all the materials used with their physical and chemical properties.

3.    The introduction needs to be improved by relating to the mechanics of the studied materials and their mechanical characteristics. The references to be included are: 10.1007/s10853-022-06994-3, 10.1016/j.polymertesting.2017.09.009, 10.1177/07316844211051733, 10.1016/j.compstruct.2021.114698, 10.3390/polym14132662, 10.1016/j.jiec.2022.06.023, 10.1016/j.porgcoat.2022.107015.

4.    Put space between each variable and its corresponding unit. For instance, in the description of the materials and chemicals section, almost all the various units are attached to the variable which is not acceptable.

5.    How and what was used to polish the samples for the coatings. The author only mentioned in line 108 that the sample was polished without stating the method and material used for the polishing.

6.    In your SEM analysis, what are the accelerating voltage, scale bar, and the working disk (magnification) used?

7.    Are these labelled samples (E0, E1, E2, and E3) an average number or an absolute number of sets of samples?

8.    The author needs to take good care of the English grammar especially singular and plural forms of the English grammar.

Author Response

Reviewer 4

1. Based on the understanding of what should be included in the abstract, consider adding one or two lines highlighting the importance of the study.

Author response: Thank you very much for reviewing the paper. Your comments and suggestions are very helpful to improve the paper. It is modified as follows: “The application of aluminum alloy materials is greatly limited due to their poor friction reduction and wear resistance. Therefore, to enhance the tribological behaviors of aluminum alloy materials, the Ni-MoS₂, Ni-SiC and Ni-MoS₂/SiC composite coatings were prepared on the 2218 aluminum alloy by an electrodeposition technique”. We updated the manuscript. The changes are marked in the document “Manuscript-Revise.doc”.

2. Consider tabulating all the materials used with their physical and chemical properties.

Author response: Thank you very much for reviewing the paper. Your comments and suggestions are very helpful to improve the paper. We updated the manuscript. The changes are marked in the document “Manuscript-Revise.doc”.

It is modified as follows: “Molybdenum disulfide (MoS₂) and silicon carbide (SiC) were commercially purchased from Shanghai Chaowei Nanotech Co., Ltd., China. The 2218 aluminum alloy chosen as the substrate materials was purchased from Dongguan Avis Metal Materials Co., Ltd., China. The chemicals used were commercially purchased. The information of all materials is shown in Tables 1-3.”

Table 1. The coating materials and properties.

Materials	Average particle size (nm)	Specific surface area (m2∙g-1)	Density (g∙cm-3)	Purity (%)
MoS2	600	12.4	1.83	≥99.9
SiC	600	3.2	1.52	≥99.5

Table 2. Chemical composition of 2218 aluminum alloy substrate.

Elements	Fe	Si	Mn	Cu	Mg	Al
wt.%	0.5	0.35	0.28	1.8	2.6	balanced

Table 3. The chemicals.

Chemicals	Purity (%)	Brand
Ni(NH2SO3)2·4H2O	99	Macklin
CH3(CH2)11OSO3Na	98	Aiyan
HBO3	99.5	Nanshi
Na2CO3	99.8	Nanshi
Na3PO4	98	Nanshi
NaOH	96	Nanshi
HNO3	65~68	Aladdin
ZnO	99	Aiyan
FeCl3	97	Nanshi
C6H8O7	99.5	Macklin
NaNO3	99	Nanshi

 

3. The introduction needs to be improved by relating to the mechanics of the studied materials and their mechanical characteristics. The references to be included are: 10.1007/s10853-022-06994-3, 10.1016/j. polymertesting.2017.09.009, 10.1177/07316844211051733, 0.1016/j.compstruct.2021.114698, 10.3 390/polym14132662, 10.1016/j.jiec.2022.06.023, 10.1016/j.porgcoat.2022.107015.

Author response: Thank you very much for reviewing the paper. We have downloaded and read the literatures you mentioned. Based on the relevance of the literature study to the study in this paper, we have cited the following literature. “Mohammed Fuseini, Moustafa Mahmoud Yousry Zaghloul, Investigation of electrophoretic deposition of PANI nano fibers as a manufacturing technology for corrosion protection, Progress in Organic Coatings 2022, 171, 107015.” and “Mohammed Fuseini, Moustafa Mahmoud Yousry Zaghloul, Statistical and qualitative analyses of the kinetic models using electrophoretic deposition of polyaniline, Journal of Industrial and Engineering Chemistry, 2022, 113, 475-487”. We updated the manuscript. The changes are marked in the document “Manuscript-Revise.doc”.

4. Put space between each variable and its corresponding unit. For instance, in the description of the materials and chemicals section, almost all the various units are attached to the variable which is not acceptable.

Author response: Thank you very much for reviewing the paper. Your comments and suggestions are very helpful to improve the paper. According to your comments and suggestions, we have proofread the manuscript sentence by sentence. We updated the manuscript. The changes are marked in the document “Manuscript-Revise.doc”.

5. How and what was used to polish the samples for the coatings. The author only mentioned in line 108 that the sample was polished without stating the method and material used for the polishing.

Author response: Thank you very much for reviewing the paper. Your comments and suggestions are very helpful to improve the paper. It is modified as follows: The surface of the 2218 aluminum alloy disc samples (ϕ 50 × 8 mm) was polished by 400, 600, 800 and 1000 grain metallographic sandpapers in a certain order [10,40]. The surface roughness was measured to be ~0.22 μm by a TR 200 surface roughness meter with an accuracy of 0.001 μm (Beijing Saiboruixin technology Co., Ltd., Beijing, China. GB/T4340).” Technical indicators of TR 200 surface roughness meter are as follows: Measurement parameters, Ra and Rq (0.005-16 μm), Rz, Rt, Rp and Rm (0.02-160 μm); Measuring range, 160 μm for Z-axis, 17.5 mm for X-axis; Resolution, 0.002-0.008/±20-80 μm; Sampling length, 0.25 mm, 0.8 mm and 2.5 mm; Stylus, natural diamond, cone angle 90° and tip radius 5 μm; Accuracy, 0.001 μm). We updated the manuscript. The changes are marked in the document “Manuscript-Revise.doc”.

6. In your SEM analysis, what are the accelerating voltage, scale bar, and the working disk (magnification) used?

Author response: Thank you very much for reviewing the paper. Your comments and suggestions are very helpful to improve the paper. The conditions for the SEM images used in the paper are as follows. The coating surface morphologies were measured at an accelerating voltage of 20 kV, magnifications of 200 X and 1000 X and corresponding to a scale of 200 μm and 50 μm. The cross-section images were measured at an accelerating voltage of 20 kV, a magnification of 5000 X and a scale of 100 μm. The worn surface morphologies were measured at an accelerating voltage of 20 kV, a magnification of 1500 and a scale of 50. Thank you again for your review of the paper.

7.  Are these labelled samples (E0, E1, E2, and E3) an average number or an absolute number of sets of samples?

Author response: Thank you very much for reviewing the paper. Your comments and suggestions are very helpful to improve the paper. The data used in this paper are the average of the measured data of the experimental samples. Thank you again for your review of the paper.

8. The author needs to take good care of the English grammar especially singular and plural forms of the English grammar.

Author response: Thank you very much for reviewing the paper. Your comments and suggestions are very helpful to improve the paper. We have proofread the manuscript sentence by sentence. We updated the manuscript. The changes are marked in the document “Manuscript-Revise.doc”.

Thank you again for your review of the paper.

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors addressed all queries very nicely and in detail. 

So I recommend it to publish in the present form