Abstract

Purpose This study aims to investigate the effect of MoS2 powder on tribological properties of sliding interfaces. Design/methodology/approach Loose MoS2 powder was introduced in the gap of point-contact friction pairs, and sliding friction test was conducted using a testing machine. Friction noise, wear mark appearance, microstructure and wear debris were characterized with a noise tester, white-light interferometer, scanning electron microscope and ferrograph, respectively. Numerical simulation was also performed to analyze the influence of MoS2 powder on tribological properties of the sliding interface. Findings MoS2 powder remarkably improved the lubrication performance of the sliding interface, whose friction coefficient and wear rate were reduced by one-fifth of the interface values without powder. The addition of MoS2 powder also reduced stress, plastic deformation and friction temperature in the wear mark. The sliding interface with MoS2 powder demonstrated lower friction noise and roughness compared with the interface without powder lubrication. The adherence of MoS2 powder onto the friction interface formed a friction film, which induced the wear mechanism of the sliding interface to change from serious cutting and adhesive wear to delamination and slight cutting wear under the action of normal and shear forces. Originality/value Tribological characteristics of the interface with MoS2 powder lubrication were clarified. This work provides a theoretical basis for solid-powder lubrication and reference for its application in engineering. Peer review The peer review history for this article is available at:


Authors

Liu, Cong;  Yin, Yanguo;  Tong, Baohong;  Zhang, Guotao

Publons users who've claimed - I am an author

No Publons users have claimed this paper.

Contributors on Publons
  • 2 reviewers
  • pre-publication peer review (FINAL ROUND)
    Decision Letter
    2020/07/28

    28-Jul-2020

    Dear Liu, Cong; Yin, Yanguo; Tong, baohong; Zhang, Guotao; Li, cong min; Li, rongrong

    It is a pleasure to accept your manuscript ilt-04-2020-0150.R2, entitled "Tribological properties of MoS2 powder-lubricated interface" in its current form for publication in Industrial Lubrication and Tribology. Please note, no further changes can be made to your manuscript.

    Please go to your Author Centre at https://mc.manuscriptcentral.com/ilt (Manuscripts with Decisions for the submitting author or Manuscripts I have co-authored for all listed co-authors) to complete the Copyright Transfer Agreement form (CTA). We cannot publish your paper without this.

    All authors are requested to complete the form and to input their full contact details. If any of the contact information is incorrect you can update it by clicking on your name at the top right of the screen. Please note that this must be done prior to you submitting your CTA.

    If you have an ORCID please check your account details to ensure that your ORCID is validated.

    By publishing in this journal your work will benefit from Emerald EarlyCite. As soon as your CTA is completed your manuscript will pass to Emerald’s Content Management department and be processed for EarlyCite publication. EarlyCite is the author proofed, typeset version of record, fully citable by DOI. The EarlyCite article sits outside of a journal issue and is paginated in isolation. The EarlyCite article will be collated into a journal issue according to the journals’ publication schedule.

    FOR OPEN ACCESS AUTHORS: Please note if you have indicated that you would like to publish your article as Open Access via Emerald’s Gold Open Access route, you are required to complete a Creative Commons Attribution Licence - CCBY 4.0 (in place of the standard copyright assignment form referenced above). You will receive a follow up email within the next 30 days with a link to the CCBY licence and information regarding payment of the Article Processing Charge. If you have indicated that you might be eligible for a prepaid APC voucher, you will also be informed at this point if a voucher is available to you (for more information on APC vouchers please see http://www.emeraldpublishing.com/oapartnerships

    Thank you for your contribution. On behalf of the Editors of Industrial Lubrication and Tribology, we look forward to your continued contributions to the Journal.

    Sincerely,
    Prof. Carsten Gachot
    Editor, Industrial Lubrication and Tribology
    carsten.gachot@tuwien.ac.at

    Decision letter by
    Cite this decision letter
    Reviewer report
    2020/07/28

    Comments and remarks
    1) Related to Fig. 7, the Authors should report in the text what they wrote in the "Authors response to the referee". The interpretation of fig. 7 is not trivial without these information, in particular if the reader is not confident with FEM simulation

    Reviewed by
    Cite this review
    Author Response
    2020/07/24

    Dear Prof. Carsten Gachot,
    Thank you very much for your letter and the comments from the referees about our paper submitted to Industrial Lubrication and Tribology (MS Number ilt-04-2020-0150.R1).
    We have checked the manuscript and revised it according to the comments. We submit the revised manuscript with the correction sections red marked for easy check/ editing purpose. If you have any question, please don’t hesitate to let me know. Thank you very much for all your help and looking forward to hearing from you soon.
    Thank you for this comment. The author neglected to elaborate on the calculation details due to the limitation of manuscript length. In the initial submission, in order to reduce the number of words in the article, the relevant references were deleted. We apologize for our mistake. The related references has been added in this manuscript.
    Sincerely yours,
    Prof. Yin
    Response to Reviewer:
    Thanks for your comments on our paper. We have revised our paper according to your comments.
    Reviewer: 1
    Recommendation: Accept
    Comments:
    (There are no comments.)
    Reviewer: 2
    Recommendation: Accept
    Comments:
    1)The Authors added the EDS and XRD analyses of the wear track. The Authors should better describe the graphs.
    Response: Thanks for the expert's suggestion, which has been added in detail in the manuscript.

    2) Although the pervious remark related to figure 7, it is still not clear from the text what "nodes" are.
    It is not even clear why temperature decreases with a step-down trend. The Authors should clarify this point.
    Response: In the finite simulation, the lower specimen is meshed and many finite small element bodies are generated. In order to quantitatively observe the temperature change in the wear mark of the specimen, four small units at different positions in the wear mark are selected and the temperature in the sliding process is plotted. Since the unit in the wear mark of the lower specimen is selected, (the lower specimen rotates and the upper specimen is fixed), the temperature reaches the maximum when a unit in the wear mark of the lower specimen contacts with the upper specimen. After the contact, the unit is separated from the upper specimen and the temperature decreases slowly. In order to cause unnecessary misunderstanding, it is redefined as selecting four points in different positions of the wear mark to plot the temperature, which are marked as point1, point2, point3, and point4, respectively.

    We tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence the content and framework of the paper. And here we did not list the changes but marked in red in revised paper.
    We appreciate for Editors/Reviewers’ warm work earnestly, and hope that the correction will meet with approval.
    Once again, thank you very much for your comments and suggestions.



    Cite this author response
  • pre-publication peer review (ROUND 2)
    Decision Letter
    2020/07/23

    23-Jul-2020

    Dear Prof. Yin:

    Manuscript ID ilt-04-2020-0150.R1 entitled "Tribological properties of MoS2 powder-lubricated interface" which you submitted to the Industrial Lubrication and Tribology, has been reviewed. The comments of the reviewer(s) are included at the bottom of this letter.

    Although the reviewers have recommended to accept your article, there is a major concern about this article. Almost in the entire part "results and discussion", there is no discussion. No references and citations can be found, which implies that the obtained results have not been discussed in the light of the existing research literature. The authors are advised to use state-of-the-art review articles to provide a real discussion of the obtained results.

    To revise your manuscript, log into https://mc.manuscriptcentral.com/ilt and enter your Author Centre, where you will find your manuscript title listed under "Manuscripts with Decisions." Under "Actions," click on "Create a Revision." Your manuscript number has been appended to denote a revision.

    You will be unable to make your revisions on the originally submitted version of the manuscript. Instead, revise your manuscript using a word processing program and save it on your computer. Please also highlight the changes to your manuscript within the document by using the track changes mode in MS Word or by using bold or coloured text.

    Once the revised manuscript is prepared, you can upload it and submit it through your Author Centre. The deadline for uploading a revised manuscript is 21-Oct-2020 from receiving this email. If it is not possible for you to resubmit your revision within this timeframe, we may have to consider your paper as a new submission.

    When submitting your revised manuscript, you will be able to respond to the comments made by the reviewer(s) in the space provided. You can use this space to document any changes you make to the original manuscript. In order to expedite the processing of the revised manuscript, please be as specific as possible in your response to the reviewer(s).

    IMPORTANT: Your original files are available to you when you upload your revised manuscript. Please delete any redundant files before completing the submission.

    Please note that Emerald requires you to clear permission to re-use any material not created by you. If there are permissions outstanding, please send these to Emerald as soon as possible. Emerald is unable to publish your paper with permissions outstanding.

    To help support you on your publishing journey we have partnered with Editage, a leading global science communication platform, to offer expert editorial support including language editing and translation.
    If your article has been rejected or revisions have been requested, you may benefit from Editage’s services. For a full list of services, visit: authorservices.emeraldpublishing.com/
    Please note that there is no obligation to use Editage and using this service does not guarantee publication.

    Once again, thank you for submitting your manuscript to the Industrial Lubrication and Tribology and I look forward to receiving your revision.

    Sincerely,
    Prof. Carsten Gachot
    Editor, Industrial Lubrication and Tribology
    carsten.gachot@tuwien.ac.at

    Reviewer(s)' Comments to Author:
    Reviewer: 1

    Comments to the Author
    (There are no comments.)

    Reviewer: 2

    Comments to the Author
    Comments and remarks
    1) The Authors added the EDS and XRD analyses of the wear track. The Authors should better describe the graphs.
    2) Although the pervious remark related to figure 7, it is still not clear from the text what "nodes" are.
    It is not even clear why temperature decreases with a step-down trend. The Authors should clarify this point.
    Reviewer: 1

    Recommendation: Accept

    Comments:
    (There are no comments.)

    Additional Questions:
    Originality: Does the paper contain new and significant information adequate to justify publication?: yes

    Relationship to Literature: Does the paper demonstrate an adequate understanding of the relevant literature in the field and cite an appropriate range of literature sources? Is any signficant work ignored?: yes

    Methodology: Is the paper's argument built on an appropriate base of theory, concepts, or other ideas? Has the research or equivalent intellectual work on which the paper is based been well designed? Are the methods employed appropriate?: yes

    Results: Are results presented clearly and analysed appropriately? Do the conclusions adequately tie together the other elements of the paper?: yes

    Practicality and/or Research implications: Does the paper identify clearly any implications for practice and/or further research? Are these implications consistent withthe findings and conclusions of the paper?: yes

    Quality of Communication: Does the paper clearly express its case, measured against the technical language of the field and the expected knowledge of the journal's readership? Has attention been paid to the clarity of expression and readability, such as sentence structure, jargon use, acronyms, etc.: yes

    Reproducible Research: If appropriate, is sufficient information, potentially including data and software, provided to reproduce the results and are the corresponding datasets formally cited?:

    This journal is participating in Publons Transparent Peer Review. By reviewing for this journal, you agree that your finished report, along with the author’s responses and the Editor’s decision letter, will be linked to from the published article to where they appear on Publons, if the paper is accepted. If you have any concerns about participating in the Transparent Peer Review pilot, please reach out to the journal’s Editorial office. Please indicate below, whether you would like your name to appear with your report on Publons by indicating yes or no. All peer review content displayed here will be covered by a Creative Commons CC BY 4.0 license.: Yes, I would like my name to appear with my report on Publons

    Reviewer: 2

    Recommendation: Accept

    Comments:
    Comments and remarks
    1) The Authors added the EDS and XRD analyses of the wear track. The Authors should better describe the graphs.
    2) Although the pervious remark related to figure 7, it is still not clear from the text what "nodes" are.
    It is not even clear why temperature decreases with a step-down trend. The Authors should clarify this point.

    Additional Questions:
    Originality: Does the paper contain new and significant information adequate to justify publication?: yes

    Relationship to Literature: Does the paper demonstrate an adequate understanding of the relevant literature in the field and cite an appropriate range of literature sources? Is any signficant work ignored?: yes

    Methodology: Is the paper's argument built on an appropriate base of theory, concepts, or other ideas? Has the research or equivalent intellectual work on which the paper is based been well designed? Are the methods employed appropriate?: yes

    Results: Are results presented clearly and analysed appropriately? Do the conclusions adequately tie together the other elements of the paper?: yes

    Practicality and/or Research implications: Does the paper identify clearly any implications for practice and/or further research? Are these implications consistent withthe findings and conclusions of the paper?: yes

    Quality of Communication: Does the paper clearly express its case, measured against the technical language of the field and the expected knowledge of the journal's readership? Has attention been paid to the clarity of expression and readability, such as sentence structure, jargon use, acronyms, etc.: yes

    Reproducible Research: If appropriate, is sufficient information, potentially including data and software, provided to reproduce the results and are the corresponding datasets formally cited?: yes

    This journal is participating in Publons Transparent Peer Review. By reviewing for this journal, you agree that your finished report, along with the author’s responses and the Editor’s decision letter, will be linked to from the published article to where they appear on Publons, if the paper is accepted. If you have any concerns about participating in the Transparent Peer Review pilot, please reach out to the journal’s Editorial office. Please indicate below, whether you would like your name to appear with your report on Publons by indicating yes or no. All peer review content displayed here will be covered by a Creative Commons CC BY 4.0 license.: Yes, I would like my name to appear with my report on Publons

    Decision letter by
    Cite this decision letter
    Reviewer report
    2020/07/23

    Comments and remarks
    1) The Authors added the EDS and XRD analyses of the wear track. The Authors should better describe the graphs.
    2) Although the pervious remark related to figure 7, it is still not clear from the text what "nodes" are.
    It is not even clear why temperature decreases with a step-down trend. The Authors should clarify this point.

    Reviewed by
    Cite this review
    Author Response
    2020/07/14

    Dear Prof. Carsten Gachot,
    Thank you very much for your letter and the comments from the referees about our paper submitted to Industrial Lubrication and Tribology (MS Number ilt-04-2020-0150).
    We have checked the manuscript and revised it according to the comments. We submit the revised manuscript with the correction sections red marked for easy check/ editing purpose. If you have any question, please don’t hesitate to let me know. Thank you very much for all your help and looking forward to hearing from you soon.
    Sincerely yours,
    Prof. Yin
    Response to Reviewer:
    Thanks for your comments on our paper. We have revised our paper according to your comments.

    Reviewer: 1
    1)The lubrication using MoS2 power directly has been studied previously, but author did not mention them. A comparison must be given to highlight the true contribution of this study.
    Response: Thank you for this comment. A previous study used MoS2 as the lubricating medium in investigating the effect of physical properties of the powder under plane contact on lubrication characteristics. The researchers of this study primarily analyzed lubrication characteristics of the lubricant and demonstrated that the powder can be introduced in frictional clearance without special treatments while physical properties of the powder significantly influenced its lubrication characteristics. However, studies on friction and wear characteristics of MoS2 powder lubrication under point contact are limited. Therefore, this study primarily investigates friction and wear properties of MoS2 lubrication and its wear mechanism. The results showed that the steel surface changes from severe cutting and adhesive wear to delamination and slight cutting wear under the lubrication of MoS2 powder. The emphasis of this study differs from the focus of previous studies with the same MoS2 powder lubrication. Hence, different conclusions are obtained.

    2) EDS is suggested to identify the coverage of tribofilm on the used counter surface and the worn substrate surface. It can help for understanding its role in friction and wear reducing.
    Response: Thank you for your advice. EDS surface scanning and XRD analysis have been added to the manuscript. This study primarily investigated tribological characteristics and determined that the formation of friction film significantly influences tribological characteristics of mating pairs. At present, the author intends to explore this research topic further and conduct an in-depth investigation on the formation process of friction film in a future study. The formation and evolution of friction film were examined using EDS, XPS, and XRD. Thanks again for the expert's valuable suggestions.

    Reviewer:2
    1)The most important general comment is related to the theoretical part. The calculation is not described in details, and also the output does not have any direct correlation with the experimental part. If this theoretical part will not be improved, I suggest to remove it from the manuscript.
    Response: Thank you for this comment. The author neglected to elaborate on the calculation details due to the limitation of manuscript length. The numerical simulation has been added in this manuscript. The numerical simulation has been described in this paper by applying dynamic simulation settings according to test conditions to explore the influence of MoS2 powder on friction temperature, stress, and plastic deformation under the same conditions. Although the simulation has some limitations, it can also reflect the difference to some extent.

    2)The noise during the sliding process has been measured. The Authors should describe the apparatus related to this procedure.
    Response: Thanks for the expert's suggestion, which has been added in detail in the manuscript.
    An electret condenser microphone (PCB 378A04, PCB Piezotronics MTS Systems Corporation, USA) with sensitivity of 450 mV/Pa was placed approximately 50 mm from the sliding interface and used to collect noise signals of the friction system. The dynamic sound pressure and frequency ranges of the microphone are 15–130 dB and 3.75 Hz–20 kHz, respectively. Signals acquired from the microphone are analyzed synchronously in the DASP-acoustics data acquisition system (China Orient Institute of Noise and Vibration). Detected data were recorded automatically by a computer connected to the tribology testing machine during the experiment.

    3)In the "Numerical simulation" section there is no information about the technique the Authors used for this calculation. Is this FEM? What are the main parameter and approach they used?
    Response: Thank you for your comment. Numerical simulation with finite element method was specifically added in detail in the manuscript.

    4)In fig 3 the CoF and the noise vs time are reported. It is clearly evident that in the case of MoS2 the CoF is very stable from the beginning of the test. On the other and, the noise takes some time to reach the steady state, even if it should be directly correlated to the friction. What can be the reason of these different trends?
    Response: Thank you for your comment. It's really interesting what the experts mentioned. This problem is also found in the test. The friction coefficient of the friction pair with MoS2 has been stable since the beginning. However, the measured friction noise in the rising stage at the initial sliding stage or the “noise running-in period” is likely related to the pressing and adaptation processes of the powder in the initial stage between friction pairs, that is, the formation of the initial friction film at the contact position. The formation process of friction film via in situ observation technology (intermittent microscopic measurement) will be the focus of a future investigation.

    5)In the numerical calculation, the temperature of the contact decreases with sliding time. What is the reason of this?
    Response: Only one sliding circle is selected for comparative analysis due to the limited solution time. The temperature of a single node reaches the maximum at the moment of contact with the steel ball. The temperature shows a gradual downward trend when the contact of the single node is separated from the steel ball.

    6)As already reported, it does not seem that the simulation helps in the comprehension of the experimental evidences.
    Response: Thank you for your comment. Numerical simulation is carried out according to test conditions. Changes in wear marks in the disc with and without MoS2 powder lubrication were observed. For example, the amount of plastic deformation of wear mark reflects the change of wear quality to a certain extent. The increase in friction temperature is closely related to oxidation wear to a certain extent.

    7)In fig. 7, what does Nodal# represent?
    Response: We apologize for our mistake. Nodal was originally used in Figure 7 to represent nodes. The same element nodes were selected in the finite element simulation for comparison. Hence, Figure 7 has been modified.

    8)The Authors report on a tribofilm that forms on the wear track. Is this film present on the ball as well?
    Response: Thank you for your questions. Under the current experimental conditions, it is found that there is no friction film on the steel ball, so there is no characterization of the steel ball.

    9)The observation of a tribofilm on the wear track and its evolution is probably the most interesting results. The Authors report a chemical analysis with EDX. However, EDX is not sensitive to chemical bonds. Are they able to use a spectroscopic analysis sensitive to chemical bonds? I.e. XPS, Raman, or others. This should be very interesting, for example to see if oxides from MoS2 are present.
    Response: Thank you for your comment. EDS surface scanning and XRD analysis have been added to the manuscript. No oxygen element was found in the experimental study. Therefore, as mentioned before, the formation process of friction film will be the foci of a future investigation. In situ observation techniques were used and the formation and evolution of tribofilm were explored via EDS, XPS, and XRD.

    We tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence the content and framework of the paper. And here we did not list the changes but marked in red in revised paper.
    We appreciate for Editors/Reviewers’ warm work earnestly, and hope that the correction will meet with approval.
    Once again, thank you very much for your comments and suggestions.



    Cite this author response
  • pre-publication peer review (ROUND 1)
    Decision Letter
    2020/06/22

    22-Jun-2020

    Dear Prof. Yin:

    Manuscript ID ilt-04-2020-0150 entitled "Tribological properties of MoS2 powder-lubricated interface" which you submitted to the Industrial Lubrication and Tribology, has been reviewed. The comments of the reviewer(s) are included at the bottom of this letter.

    The reviewer(s) have recommended major revisions to the submitted manuscript, before it can be considered for publication. Therefore, I invite you to respond to the reviewer(s)' comments and revise your manuscript.

    To revise your manuscript, log into https://mc.manuscriptcentral.com/ilt and enter your Author Centre, where you will find your manuscript title listed under "Manuscripts with Decisions." Under "Actions," click on "Create a Revision." Your manuscript number has been appended to denote a revision.

    You will be unable to make your revisions on the originally submitted version of the manuscript. Instead, revise your manuscript using a word processing program and save it on your computer. Please also highlight the changes to your manuscript within the document by using the track changes mode in MS Word or by using bold or coloured text.

    Once the revised manuscript is prepared, you can upload it and submit it through your Author Centre. The deadline for uploading a revised manuscript is 20-Sep-2020 from receiving this email. If it is not possible for you to resubmit your revision within this timeframe, we may have to consider your paper as a new submission.

    When submitting your revised manuscript, you will be able to respond to the comments made by the reviewer(s) in the space provided. You can use this space to document any changes you make to the original manuscript. In order to expedite the processing of the revised manuscript, please be as specific as possible in your response to the reviewer(s).

    IMPORTANT: Your original files are available to you when you upload your revised manuscript. Please delete any redundant files before completing the submission.

    Please note that Emerald requires you to clear permission to re-use any material not created by you. If there are permissions outstanding, please send these to Emerald as soon as possible. Emerald is unable to publish your paper with permissions outstanding.

    To help support you on your publishing journey we have partnered with Editage, a leading global science communication platform, to offer expert editorial support including language editing and translation.
    If your article has been rejected or revisions have been requested, you may benefit from Editage’s services. For a full list of services, visit: authorservices.emeraldpublishing.com/
    Please note that there is no obligation to use Editage and using this service does not guarantee publication.

    Once again, thank you for submitting your manuscript to the Industrial Lubrication and Tribology and I look forward to receiving your revision.

    Sincerely,
    Prof. Carsten Gachot
    Editor, Industrial Lubrication and Tribology
    carsten.gachot@tuwien.ac.at

    Reviewer(s)' Comments to Author:
    Reviewer: 1

    Comments to the Author
    Authors did a nice work about the lubrication of MoS2 power with considerations of the impacts on friction, wear, noise, tempareture, roughness and interfacial stress. Some of these factors are critical in real industrial applications. I recommoned minor revision before publication.
    1) The lubrication using MoS2 power directly has been studied previously, but author did not mention them. A comparison must be given to highlight the true contribution of this study.
    2) EDS is suggested to identify the coverage of tribofilm on the used counter surface and the worn substrate surface. It can help for understanding its role in friction and wear reducing.

    Reviewer: 2

    Comments to the Author
    Response of the referee
    Manuscript id: ilt-04-2020-0150
    Title: Tribological properties of MoS2 powder-lubricated interfaceThis work deals with the tribological
    This work deals with the effect on the tribological properties of MoS2 powder added between sliding counterparts made of steel. The Authors found that the addition of MoS2 decreases both friction, wear and related noise. In particular, they found that the powder forms a tribolayer at the surfaces that is continuously replaced during sliding. They also calculated the strain and the temperature of the contacting point during the motion of the disc.

    Comments and remarks
    1) The most important general comment is related to the theoretical part. The calculation is not described in details, and also the output does not have any direct correlation with the experimental part. If this theoretical part will not be improved, I suggest to remove it from the manuscript.
    2) The noise during the sliding process has been measured. The Authors should describe the apparatus related to this procedure.
    3) In the "Numerical simulation" section there is no information about the technique the Authors used for this calculation. Is this FEM? What are the main parameter and approach they used?
    4) In fig 3 the CoF and the noise vs time are reported. It is clearly evident that in the case of MoS2 the CoF is very stable from the beginning of the test. On the other and, the noise takes some time to reach the steady state, even if it should be directly correlated to the friction. What can be the reason of these different trends?
    5) In the numerical calculation, the temperature of the contact decreases with sliding time. What is the reason of this?
    6) As already reported, it does not seem that the simulation helps in the comprehension of the experimental evidences.
    7) In fig. 7, what does Nodal# represent?
    8) The Authors report on a tribofilm that forms on the wear track. Is this film present on the ball as well?
    9) The observation of a tribofilm on the wear track and its evolution is probably the most interesting results. The Authors report a chemical analysis with EDX. However, EDX is not sensitive to chemical bonds. Are they able to use a spectroscopic analysis sensitive to chemical bonds? I.e. XPS, Raman, or others. This should be very interesting, for example to see if oxides from MoS2 are present.
    Reviewer: 1

    Comments:
    Authors did a nice work about the lubrication of MoS2 power with considerations of the impacts on friction, wear, noise, tempareture, roughness and interfacial stress. Some of these factors are critical in real industrial applications. I recommoned minor revision before publication.
    1) The lubrication using MoS2 power directly has been studied previously, but author did not mention them. A comparison must be given to highlight the true contribution of this study.
    2) EDS is suggested to identify the coverage of tribofilm on the used counter surface and the worn substrate surface. It can help for understanding its role in friction and wear reducing.

    Additional Questions:
    Originality: Does the paper contain new and significant information adequate to justify publication?: yes

    Relationship to Literature: Does the paper demonstrate an adequate understanding of the relevant literature in the field and cite an appropriate range of literature sources? Is any signficant work ignored?: No

    Methodology: Is the paper's argument built on an appropriate base of theory, concepts, or other ideas? Has the research or equivalent intellectual work on which the paper is based been well designed? Are the methods employed appropriate?: yes

    Results: Are results presented clearly and analysed appropriately? Do the conclusions adequately tie together the other elements of the paper?: yes

    Practicality and/or Research implications: Does the paper identify clearly any implications for practice and/or further research? Are these implications consistent withthe findings and conclusions of the paper?: yes

    Quality of Communication: Does the paper clearly express its case, measured against the technical language of the field and the expected knowledge of the journal's readership? Has attention been paid to the clarity of expression and readability, such as sentence structure, jargon use, acronyms, etc.: yes

    Reproducible Research: If appropriate, is sufficient information, potentially including data and software, provided to reproduce the results and are the corresponding datasets formally cited?:

    This journal is participating in Publons Transparent Peer Review. By reviewing for this journal, you agree that your finished report, along with the author’s responses and the Editor’s decision letter, will be linked to from the published article to where they appear on Publons, if the paper is accepted. If you have any concerns about participating in the Transparent Peer Review pilot, please reach out to the journal’s Editorial office. Please indicate below, whether you would like your name to appear with your report on Publons by indicating yes or no. All peer review content displayed here will be covered by a Creative Commons CC BY 4.0 license.: Yes, I would like my name to appear with my report on Publons

    Reviewer: 2

    Recommendation: Major Revision

    Comments:
    Response of the referee
    Manuscript id: ilt-04-2020-0150
    Title: Tribological properties of MoS2 powder-lubricated interfaceThis work deals with the tribological
    This work deals with the effect on the tribological properties of MoS2 powder added between sliding counterparts made of steel. The Authors found that the addition of MoS2 decreases both friction, wear and related noise. In particular, they found that the powder forms a tribolayer at the surfaces that is continuously replaced during sliding. They also calculated the strain and the temperature of the contacting point during the motion of the disc.

    Final response: Major revision

    Comments and remarks
    1) The most important general comment is related to the theoretical part. The calculation is not described in details, and also the output does not have any direct correlation with the experimental part. If this theoretical part will not be improved, I suggest to remove it from the manuscript.
    2) The noise during the sliding process has been measured. The Authors should describe the apparatus related to this procedure.
    3) In the "Numerical simulation" section there is no information about the technique the Authors used for this calculation. Is this FEM? What are the main parameter and approach they used?
    4) In fig 3 the CoF and the noise vs time are reported. It is clearly evident that in the case of MoS2 the CoF is very stable from the beginning of the test. On the other and, the noise takes some time to reach the steady state, even if it should be directly correlated to the friction. What can be the reason of these different trends?
    5) In the numerical calculation, the temperature of the contact decreases with sliding time. What is the reason of this?
    6) As already reported, it does not seem that the simulation helps in the comprehension of the experimental evidences.
    7) In fig. 7, what does Nodal# represent?
    8) The Authors report on a tribofilm that forms on the wear track. Is this film present on the ball as well?
    9) The observation of a tribofilm on the wear track and its evolution is probably the most interesting results. The Authors report a chemical analysis with EDX. However, EDX is not sensitive to chemical bonds. Are they able to use a spectroscopic analysis sensitive to chemical bonds? I.e. XPS, Raman, or others. This should be very interesting, for example to see if oxides from MoS2 are present.

    Additional Questions:
    Originality: Does the paper contain new and significant information adequate to justify publication?: yes

    Relationship to Literature: Does the paper demonstrate an adequate understanding of the relevant literature in the field and cite an appropriate range of literature sources? Is any signficant work ignored?: yes

    Methodology: Is the paper's argument built on an appropriate base of theory, concepts, or other ideas? Has the research or equivalent intellectual work on which the paper is based been well designed? Are the methods employed appropriate?: The part related to simulation is not well described and it does not seem it can be related to the experimental evidences. The Authors are asked to clarify this point.

    Results: Are results presented clearly and analysed appropriately? Do the conclusions adequately tie together the other elements of the paper?: See above for the simulation

    Practicality and/or Research implications: Does the paper identify clearly any implications for practice and/or further research? Are these implications consistent withthe findings and conclusions of the paper?: Yes

    Quality of Communication: Does the paper clearly express its case, measured against the technical language of the field and the expected knowledge of the journal's readership? Has attention been paid to the clarity of expression and readability, such as sentence structure, jargon use, acronyms, etc.: Yes

    Reproducible Research: If appropriate, is sufficient information, potentially including data and software, provided to reproduce the results and are the corresponding datasets formally cited?: Not the part about simulation

    This journal is participating in Publons Transparent Peer Review. By reviewing for this journal, you agree that your finished report, along with the author’s responses and the Editor’s decision letter, will be linked to from the published article to where they appear on Publons, if the paper is accepted. If you have any concerns about participating in the Transparent Peer Review pilot, please reach out to the journal’s Editorial office. Please indicate below, whether you would like your name to appear with your report on Publons by indicating yes or no. All peer review content displayed here will be covered by a Creative Commons CC BY 4.0 license.: Yes, I would like my name to appear with my report on Publons

    Decision letter by
    Cite this decision letter
    Reviewer report
    2020/06/22

    Response of the referee
    Manuscript id: ilt-04-2020-0150
    Title: Tribological properties of MoS2 powder-lubricated interfaceThis work deals with the tribological
    This work deals with the effect on the tribological properties of MoS2 powder added between sliding counterparts made of steel. The Authors found that the addition of MoS2 decreases both friction, wear and related noise. In particular, they found that the powder forms a tribolayer at the surfaces that is continuously replaced during sliding. They also calculated the strain and the temperature of the contacting point during the motion of the disc.

    Final response: Major revision

    Comments and remarks
    1) The most important general comment is related to the theoretical part. The calculation is not described in details, and also the output does not have any direct correlation with the experimental part. If this theoretical part will not be improved, I suggest to remove it from the manuscript.
    2) The noise during the sliding process has been measured. The Authors should describe the apparatus related to this procedure.
    3) In the "Numerical simulation" section there is no information about the technique the Authors used for this calculation. Is this FEM? What are the main parameter and approach they used?
    4) In fig 3 the CoF and the noise vs time are reported. It is clearly evident that in the case of MoS2 the CoF is very stable from the beginning of the test. On the other and, the noise takes some time to reach the steady state, even if it should be directly correlated to the friction. What can be the reason of these different trends?
    5) In the numerical calculation, the temperature of the contact decreases with sliding time. What is the reason of this?
    6) As already reported, it does not seem that the simulation helps in the comprehension of the experimental evidences.
    7) In fig. 7, what does Nodal# represent?
    8) The Authors report on a tribofilm that forms on the wear track. Is this film present on the ball as well?
    9) The observation of a tribofilm on the wear track and its evolution is probably the most interesting results. The Authors report a chemical analysis with EDX. However, EDX is not sensitive to chemical bonds. Are they able to use a spectroscopic analysis sensitive to chemical bonds? I.e. XPS, Raman, or others. This should be very interesting, for example to see if oxides from MoS2 are present.

    Reviewed by
    Cite this review
    Reviewer report
    2020/06/11

    Authors did a nice work about the lubrication of MoS2 power with considerations of the impacts on friction, wear, noise, tempareture, roughness and interfacial stress. Some of these factors are critical in real industrial applications. I recommoned minor revision before publication.
    1) The lubrication using MoS2 power directly has been studied previously, but author did not mention them. A comparison must be given to highlight the true contribution of this study.
    2) EDS is suggested to identify the coverage of tribofilm on the used counter surface and the worn substrate surface. It can help for understanding its role in friction and wear reducing.

    Reviewed by
    Cite this review
All peer review content displayed here is covered by a Creative Commons CC BY 4.0 license.