Abstract

Purpose - This paper aims to focus on studying the addition of nano-tungsten disulfide (WS2) on fretting wear performance of ultra-high-molecular-weight-polyethylene (UHMWPE).Design/methodology/approach - In this study, the effect of WS2 content on fretting wear performance of UHMWPE was investigated. The fretting wear performance of the UHMWPE and WS2/UHMWPE nanocomposites were evaluated on oscillating reciprocating friction and wear tester. The data of the friction coefficient and the specific wear rate were obtained. The worn surfaces of composites were observed. The transfer film and its component were analyzed.Findings - With the addition of 0.5% WS2, the friction coefficient and specific wear rate increased. With the content increased to 1% and 1.5%, the friction coefficient and specific wear rate decreased. The lowest friction coefficient and specific wear rate were obtained with the addition of 1.5% nano-WS2. Continuingly increasing content, the friction coefficient and wear rate increased but lower than that of pure UHMWPE.Research limitations/implications - The research indicated the fretting wear performance related to the content of nano-WS2 with the incorporation of WS2 into UHMWPE.Practical implications - The result may help to choose the appropriate content.Originality/value - The main originality of the research is to reveal the fretting behavior of UHMWPE and WS2/UHMWPE nanocomposites. It makes us realize the nano-WS2 had an effect on the fretting wear performance of UHMWPE.


Authors

Xin, Xiaocui;  Wang, Yunxia;  Meng, Zhaojie;  Liu, Hao;  Yan, Yunfeng;  Yan, Fengyuan

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  • 2 reviewers
  • pre-publication peer review (FINAL ROUND)
    Decision Letter
    2020/07/01

    01-Jul-2020

    Dear Xin, Xiaocui; Wang, yunxia; Meng, Zhaojie; Liu, hao; Yan, Yunfeng; Yan, Fengyuan

    It is a pleasure to accept your manuscript ilt-04-2020-0151.R2, entitled "Fretting wear behavior of WS2/ ultra-high molecular weight polyethylene nanocomposites" in its current form for publication in Industrial Lubrication and Tribology. Please note, no further changes can be made to your manuscript.

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    Editor, Industrial Lubrication and Tribology
    carsten.gachot@tuwien.ac.at

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    Author Response
    2020/06/25

    1. Author should give more discussions about how to identify the adhesion wear?
      Response: Thanks for your comment. When the surface of the friction pair moves relative to each other, the bonding point formed by the adhesion effect will undergo shear fracture, and the material to be cut will be removed from the surface to form grinding chips or migrate from one surface to another. The obvious characteristic of adhesion is that large pieces of material fall off the worn surface. The sentence of “The worn surface of UHMWPE was characterized by detachment and plastic deformation. It indicated that adhesion occurred between the UHMWPE and the steel ball during the fretting process, which was induced by the softened surface due to the poor heat resistance of UHMWPE” was replaced by “It is obvious the large piece of polymer material removed from the worn surface of UHMWPE, which was the characteristic of adhesion. Therefore, the main wear mechanism of UHMWPE was adhesive wear”



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  • pre-publication peer review (ROUND 2)
    Decision Letter
    2020/06/22

    22-Jun-2020

    Dear Mrs. Wang:

    Manuscript ID ilt-04-2020-0151.R1 entitled "Fretting wear behavior of WS2/ ultra-high molecular weight polyethylene nanocomposites" 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 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.

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

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    Editor, Industrial Lubrication and Tribology
    carsten.gachot@tuwien.ac.at

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

    Comments to the Author
    Author should give more discussions about how to identify the adhesion wear?

    Reviewer: 2

    Comments to the Author
    (There are no comments.)
    Reviewer: 1

    Comments:
    Author should give more discussions about how to identify the adhesion wear?

    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.: No, I would not like my name to appear with my report on Publons

    Reviewer: 2

    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?: 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
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    Reviewer report
    2020/06/05

    Author should give more discussions about how to identify the adhesion wear?

    Reviewed by
    Cite this review
    Author Response
    2020/05/30

    Reviewer 1
    question 1. In fig. 2, it would be clearer if in the spectrogram the characteristic features of MoS2 and polyethylene will be marked in the graph.
    Response: Thanks for your suggestion. The morphology, Raman spectrum and XRD patterns in Fig.2 only refers to nanofiller WS2 rather than nanocomposites. The characteristic peaks and planes have been marked in Raman spectrum and XRD patterns.
    Question 2. In par. 2.1, the authors should better specify in the discussion if they refer to MoS2 features.
    Response: Thanks for your suggestion. In paragraph 2, we aimed at characterize the microstructure of WS2. In last paragraph, the specified discussion was given in last paragraph.
    Question 3. At line 25 of page 5, the authors to a fractured surface. Do they refer to a cross section?
    Response: Thanks for your comments. Yes. Fractured surface refers to cross section. It has been made by the following process: the samples were cut into slices, and cool down to liquid nitrogen few minutes and then broken with tweezers.
    Question 4. The Authors should define UP1, UP2, etc.
    Response: Thanks for your comment. The sentence of “According to the above method, composites with different mass fractions of nano-WS2 (0.5%, 1%, 1.5%, 2% and 3%) were prepared respectively and were named as UPE-1, UPE-2, UPE-3, UPE-4, and UPE-5. Pure UHMWPE samples were also prepared for comparison in the experiment and was named as UPE.” has been revised for “According to the above method, composites with different mass fractions of nano-WS2 (0.5%, 1%, 1.5%, 2% and 3%) were prepared respectively and were named as UP1, UP2, UP3, UP4, and UP5. Pure UHMWPE samples were also prepared for comparison in the experiment and was named as UP.”

    Figure 4. The friction coefficient and specific wear rate of UHMWPE and its nanocomposites: (a) Friction coefficient; (b) Average friction coefficient and (c) Specific wear rate.

    Figure 5. Thermal properties of UHMWPE and its nanocomposites

    Figure 9. Raman curves of the transfer films after fretting against UHMWPE composites.
    Question 4. In fig. 4 all the curves show an initial increasing trend. The Authors should discuss this point and propose am explanation.
    Response: Thanks for your suggestion. The sentence of “As can be seen from Fig. 4(a), the friction coefficients of UHMWPE and its nanocomposites increased dramatically during the initial period, then kept steady.” Has been revised for “As can be seen from Fig. 4(a), the friction coefficients of UHMWPE and its nanocomposites increased dramatically during the initial period, then kept steady. It was believed that the contact areas between the counterpart and the polymer increased during the initial fretting wear periods, and then the frictional heat produced and resulted in a severe adhesion, which led to dramatic fluctuations in friction coefficients.”
    Question 5. Both CoF and wear appear higher in the case of 0.5% addition. Have the Authors an explanation of this evidence?
    Response: Thanks for your comment. Many factors affect the friction, such as amplitude, load, frequency, humidity and so on. In addition, the dispersion of nanoparticles in the collective will also affect the friction and wear. The experiment was conducted at 10N, 50 micron and 100HZ.The experimental results show that the friction coefficient and wear rate of 0.5%WS2 composite material are higher than other samples. As for the specific reasons, we need to carry out in-depth research in the future.
    Reviewer 2.
    Question 1. SEM images shown in Fig. 3 cannot distinguish WS2 and substrate material, other analysis technique should be added combining with SEM measurements.
    Response: Thanks for your suggestion. The element of W in fractured surface of composite were presented as follows.

    Question 2. The optical images in Fig. 6 is not clear enough to characterize the topographies of the entire worn region. Higher resolution pictures or 3D pictures imaged such as white-light interferometer are suggested to be given. The topic of this study is to detect the influence of WS2 content on the fretting performance, but the details of fretting wear scar depending on the WS2 content were missed in the analysis and discussion. Higher resolution pictures or 3D pictures may provide more information about the difference of wear status, such as the variation of stick area, caused by the various WS2 contents.
    Response: Thanks for your suggestion. The optical image of sample presented the entire worn surface of sample. Since the magnification of the light mirror is determined by the lens, it is difficult to achieve both full and special clarity under our experimental conditions. We provide the optical image to present the whole picture, and the more detailed wear morphology can be observed by SEM, where the different magnification images of the worn surface were presented.
    In fact, the worn surface of UHMWPE was adhesion. With addition 0.5% WS2, the adhesion became more severe, which result in the increasing friction coefficient and wear rate. When the content of WS2 was 1.5%, the worn surface was smooth and clean and there was a little wear debris. Continuing increasing the content to 3%, the crack initiated due to the aggregation of WS2. Meanwhile, the large amounts of debris appeared on worn surfaces, which indicated the wear mechanism transformed to abrasion.
    The sentence of “When the asperities of the steel ball fretting against the nanocomposites, the stress concentration generated around the agglomerated nano-WS2, which lead to initiation of the cracks” has been replaced by “When the asperities of the steel ball fretting against the nanocomposites, the stress concentration generated around the agglomerated nano-WS2, which lead to initiation of the cracks. In brief, the worn surface of UHMWPE and 0.5% WS2/UHMWEP was adhesion. With the content increasing to 1.5%, the worn surface was smooth. With addition of 3% WS2, the wear mechanism transformed to abrasion.”
    Question 3. The formation of wave-like pattern on the worn surfaces is not clear. The cross-section profiles of these worn regions are suggested to be added.
    Response: Thanks for your suggestion. The amplitude of the fretting is small, making the wear area was very small. Therefore, it is difficult to mechanically prepare the cross section in this small worn region. It is clear to observe the wave-like patterns in Fig. 7.
    Question 4. Author indicated that the wear mechanism was adhesion. The evidence is not enough.
    Response: Thanks for your comment. The main wear mechanism of UHMWPE and 0.5% WS2/UHMWPE was adhesion. The characteristic has been marked in Fig. 7a and 7b.

    Question 5. The topographies of the balls after the tests must be given and analyzed.
    Response: Thanks for your suggestion. The topographies of the balls have been supplemented.

    Figure 8. The worn surfaces of the steel ball fretting against of UHMWPE and its nanocomposites: (a, a1) UPE; (b, b1) UPE-3; (c, c1) UPE-5 and EDS element analysis of UPE-3 (b2) and UPE-5 (c2).
    The sentence of “Figure 8(a) showed the SEM image of the steel ball for the pure UHMWPE. It was found that, the worn surface of the steel ball was smooth and clean and the transfer film was invisible. After fretting against the 1.5% WS2/UHMWPE nanocomposite, a thin and uniform transfer film formed on the steel ball (Fig. 8(b)).” Have been replaced by “Figure 8(a, a1) showed the SEM image of the steel ball for the pure UHMWPE. It was found that, the worn surface of the steel ball was smooth and clean and there was no sign of material transfer to steel ball. For UP3 and UP5 (Fig.8b and 8c), the material transfer occurred and the transfer films formed on the steel balls. For UP3, after fretting wear test, a thin and uniform transfer film formed on the steel ball (Fig. 8(b)), while the transfer film was not fully covered the entire contact area of ball and it was uneven when it terms to UP5 (Fig.8(c)).
    Question 6. Author should check the format of reference.
    Response: Thanks for your comment. The references have been revised in manuscript.



    Cite this author response
  • pre-publication peer review (ROUND 1)
    Decision Letter
    2020/05/14

    14-May-2020

    Dear Mrs. Wang:

    Manuscript ID ilt-04-2020-0151 entitled "Fretting wear behavior of WS2/ ultra-high molecular weight polyethylene nanocomposites" 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 12-Aug-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
    Response of the referee
    Manuscript id: ilt-04-2020-0151
    Title: Fretting wear behavior of WS2/ ultra-high molecular weight polyethylene nanocomposites
    This work deals with the effect of MoS2 additivation of polyethylene on its tribological properties. The composite material was produced by sintering a powder with 0.5-1.5-2-35 of MoS2. The material was tested by linear reciprocating motion at high frequency, in order to study the pitting induced by a steel ball. Depending on the MoS2 percentage, different behaviour was observed. With respect to non-additivated powder, the CoF and wear is higher in the case of 0.5%, while it is lower in all the other percentage. The minimum CoF and wear were observed in the case of 1.5%. Higher percentage induced a worsening of the mechanical properties of the material with respect to 1.5%.

    Comments and remarks
    1) In fig. 2, it would be clearer if in the spectrogram the characteristic features of MoS2 and polyethylene will be marked in the graph.
    2) In par. 2.1, the Authors should better specify in the discussion if they refers to MoS2 features.
    3) At line 25 of page 5 the Authors to a fractured surface. Do they refer to a cross section?
    4) The Authors should define UP1, UP2, etc.
    5) In fig. 4 all the curves shows an initial increasing trend. The Authors should discuss this point and propose am explanation.
    6) Both CoF and wear appear higher in the case of 0.5%additivation. Have the Authors an explanation of this evidence?

    Reviewer: 2

    Comments to the Author
    Authors studied the tribological performance of UHMWPE depending on the addition of nano-WS2 with different components. As the authors announced, this study is something new because few research has concerned this field. Based on the compared tests, the addition of nano-WS2 at a constant of 1.5% has a limited contribution to the friction reducing and wear resistance increasing. The results provide new method to minimize the friction and fretting wear of UHMWPE, so I recommend it can be published with major modification.
    1) SEM images shown in Fig. 3 cannot distinguish WS2 and substrate material, other analysis technique should be added combining with SEM measurements.
    2) The optical images in Fig. 6 is not clear enough to characterize the topographies of the entire worn region. Higher resolution pictures or 3D pictures imaged such as white-light interferometer are suggested to be given. The topic of this study is to detect the influence of WS2 content on the fretting performance, but the details of fretting wear scar depending on the WS2 content were missed in the analysis and discussion. Higher resolution pictures or 3D pictures may provide more information about the difference of wear status, such as the variation of stick area, caused by the various WS2 contents.
    3) The formation of wave-like pattern on the worn surfaces is not clear. The cross-section profiles of these worn regions are suggested to be added.
    4) Author indicated that the wear mechanism was adhesion. The evidence is not enough.
    5) The topographies of the balls after the tests must be given and analyzed.
    6) Author should check the format of reference.
    Reviewer: 1

    Comments:
    Response of the referee
    Manuscript id: ilt-04-2020-0151
    Title: Fretting wear behavior of WS2/ ultra-high molecular weight polyethylene nanocomposites
    This work deals with the effect of MoS2 additivation of polyethylene on its tribological properties. The composite material was produced by sintering a powder with 0.5-1.5-2-35 of MoS2. The material was tested by linear reciprocating motion at high frequency, in order to study the pitting induced by a steel ball. Depending on the MoS2 percentage, different behaviour was observed. With respect to non-additivated powder, the CoF and wear is higher in the case of 0.5%, while it is lower in all the other percentage. The minimum CoF and wear were observed in the case of 1.5%. Higher percentage induced a worsening of the mechanical properties of the material with respect to 1.5%.

    Comments and remarks
    1) In fig. 2, it would be clearer if in the spectrogram the characteristic features of MoS2 and polyethylene will be marked in the graph.
    2) In par. 2.1, the Authors should better specify in the discussion if they refers to MoS2 features.
    3) At line 25 of page 5 the Authors to a fractured surface. Do they refer to a cross section?
    4) The Authors should define UP1, UP2, etc.
    5) In fig. 4 all the curves shows an initial increasing trend. The Authors should discuss this point and propose am explanation.
    6) Both CoF and wear appear higher in the case of 0.5%additivation. Have the Authors an explanation of this evidence?

    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

    Reviewer: 2

    Comments:
    Authors studied the tribological performance of UHMWPE depending on the addition of nano-WS2 with different components. As the authors announced, this study is something new because few research has concerned this field. Based on the compared tests, the addition of nano-WS2 at a constant of 1.5% has a limited contribution to the friction reducing and wear resistance increasing. The results provide new method to minimize the friction and fretting wear of UHMWPE, so I recommend it can be published with major modification.
    1) SEM images shown in Fig. 3 cannot distinguish WS2 and substrate material, other analysis technique should be added combining with SEM measurements.
    2) The optical images in Fig. 6 is not clear enough to characterize the topographies of the entire worn region. Higher resolution pictures or 3D pictures imaged such as white-light interferometer are suggested to be given. The topic of this study is to detect the influence of WS2 content on the fretting performance, but the details of fretting wear scar depending on the WS2 content were missed in the analysis and discussion. Higher resolution pictures or 3D pictures may provide more information about the difference of wear status, such as the variation of stick area, caused by the various WS2 contents.
    3) The formation of wave-like pattern on the worn surfaces is not clear. The cross-section profiles of these worn regions are suggested to be added.
    4) Author indicated that the wear mechanism was adhesion. The evidence is not enough.
    5) The topographies of the balls after the tests must be given and analyzed.
    6) Author should check the format of reference.

    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?: No

    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?: No

    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

    Decision letter by
    Cite this decision letter
    Reviewer report
    2020/05/14

    Authors studied the tribological performance of UHMWPE depending on the addition of nano-WS2 with different components. As the authors announced, this study is something new because few research has concerned this field. Based on the compared tests, the addition of nano-WS2 at a constant of 1.5% has a limited contribution to the friction reducing and wear resistance increasing. The results provide new method to minimize the friction and fretting wear of UHMWPE, so I recommend it can be published with major modification.
    1) SEM images shown in Fig. 3 cannot distinguish WS2 and substrate material, other analysis technique should be added combining with SEM measurements.
    2) The optical images in Fig. 6 is not clear enough to characterize the topographies of the entire worn region. Higher resolution pictures or 3D pictures imaged such as white-light interferometer are suggested to be given. The topic of this study is to detect the influence of WS2 content on the fretting performance, but the details of fretting wear scar depending on the WS2 content were missed in the analysis and discussion. Higher resolution pictures or 3D pictures may provide more information about the difference of wear status, such as the variation of stick area, caused by the various WS2 contents.
    3) The formation of wave-like pattern on the worn surfaces is not clear. The cross-section profiles of these worn regions are suggested to be added.
    4) Author indicated that the wear mechanism was adhesion. The evidence is not enough.
    5) The topographies of the balls after the tests must be given and analyzed.
    6) Author should check the format of reference.

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    Reviewer report
    2020/05/10

    Response of the referee
    Manuscript id: ilt-04-2020-0151
    Title: Fretting wear behavior of WS2/ ultra-high molecular weight polyethylene nanocomposites
    This work deals with the effect of MoS2 additivation of polyethylene on its tribological properties. The composite material was produced by sintering a powder with 0.5-1.5-2-35 of MoS2. The material was tested by linear reciprocating motion at high frequency, in order to study the pitting induced by a steel ball. Depending on the MoS2 percentage, different behaviour was observed. With respect to non-additivated powder, the CoF and wear is higher in the case of 0.5%, while it is lower in all the other percentage. The minimum CoF and wear were observed in the case of 1.5%. Higher percentage induced a worsening of the mechanical properties of the material with respect to 1.5%.

    Final response: minor revision

    Comments and remarks
    1) In fig. 2, it would be clearer if in the spectrogram the characteristic features of MoS2 and polyethylene will be marked in the graph.
    2) In par. 2.1, the Authors should better specify in the discussion if they refers to MoS2 features.
    3) At line 25 of page 5 the Authors to a fractured surface. Do they refer to a cross section?
    4) The Authors should define UP1, UP2, etc.
    5) In fig. 4 all the curves shows an initial increasing trend. The Authors should discuss this point and propose am explanation.
    6) Both CoF and wear appear higher in the case of 0.5%additivation. Have the Authors an explanation of this evidence?

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