Self-Lubricating Effect of FeWO₄ Tribologically Synthesized from WC-(Fe-Mn-C) Composite during High-Speed Sliding against a HSS Disk

Round 1

Reviewer 1 Report

Reviewer Comments: I want to congratulate the authors for the manuscript titled as “Self-lubricating effect of FeWO4 tribologically synthesized from WC-(Fe-Mn-C) composite during high-speed sliding against a HSS disk”. However, it is realized that there are important missings and overlooked sides of the paper. Hence, I am recommending rejection of this article because of the following critical issues:

1. The language of paper is very poor. Sentences are written without proper meaning. English proofread is required.
2. Authors have not carefully examine the phenomena behind their outcomes.
3. SEM images are not clear; their scale bars are missing, and it does not provide any proper information.
4. Application and novelty is missing in the article.
5. Results are explained without any proper references. Improve the results and discussion and conclusion parts. The results and discussion section should be widened with more focusing point of the findings. And these sentences should be supported with the literature studies. Results and discussion and conclusion parts are inadequate according to citation and analyze in detail. There should be the importance of the study in detail, comparison results with other approaches in literature, the success of the prediction and computational results. To put the current work in a broader context, some high-quality literatures should be cited.
6. Conclusion section is not given the article. It is necessary to more clearly show the novelty of the article and the advantages of the proposed method. Add qualitative and quantitative results of your work. What is the difference from previous work in this area? Show practical relevance.
7. Introduction section is quite sufficient. It is not written in scientific perspective. This section should be widened, its present form too short. In this section, more literature papers have to be included to explain the subject better. Some giving citations need to be check such as [1-7], as they may not provide the required information in a sentence. Now the list of references needs to be supplemented with at least several more references published over the past 5 years. At the last paragraph of the introduction, please clearly show the general outline of the paper and show the importance of the study along with the main aim.
8. The whole representation of the article is very poor. Especially Fig 1, 2, 6, and 7, these figures representation should be improve. These graphs are need frame, and in XRD graphs, PDF or JCPDS card no is missing.
9. There is no information at which point in the test the friction coefficient was measured. Was the friction coefficient stable during the test? Can you show an example of the course of coefficient of friction (or friction torque or friction force) during the test? How many times have you repeated the tests for the same configuration? I cannot find information on the wear test time

Author Response

Please see attached.

Author Response File: Author Response.pdf

Reviewer 2 Report

Review of Manuscript for Journal Lubricants

A Self-lubricating effect of FeWO4 tribologically synthesized from WC-(Fe-Mn-C) composite during high-speed sliding against a HSS disk by Nikolai Savchenko, Irina Sevostyanova and Sergei Tarasov submitted to be considered in Journal Lubricants

In this work WC-(Fe-Mn-C) composites with γ-iron and γ+α matrices were sintered and then tested at sliding speeds in the range 7-37 m/s. Authors report that friction coefficient gets reduced when tested at a speed of 37 m/s. The formation of iron tungstate FeWO4 on the worn surface is responsible of the mechanochemical mechanism. No wear reduction is observed. The underlying 25-65μm of thickness layer was composed of only heat-affected WC and recrystallized γ-iron grains.

Reviewer comments

1. Language needs to be improved throughout the manuscript
2. The aim of the paper is not clear.
3. Conclusion section is missing
4. Fig 10 is confusing. Speed? Squared and triangle symbols 1 and 2 do represent…?
5. Discussion on the nature of the void particles and the wear mechanism would be valuable.
6. EDS results are not discussed
7. Page 8 line 179, Why he particles contain less tungsten?
8. Page 4 line 109, There is no much difference between WC-Mn4 and WC-Mn20 in terms of wear rate… Description of the wear rate graph is confusing. Explain better.

Author Response

Please see attached.

Author Response File: Author Response.pdf

Reviewer 3 Report

Dear Authors,

some few comments on wording that might be improved (at least I was not sure to have understood those wordings properly). Some formulae seem not to be complete.

My comments are added as "notes" in the pdf, few typos are marked in yellow.

One general point: could you please clarify "wear" of the HSS-disc: was it worn too, how much ?

thanks, all the best

Comments for author File: Comments.pdf

Author Response

Please see attached.

Author Response File: Author Response.pdf

Reviewer 4 Report

This paper experimentally investigate the tribological behaviors of WC-(Fe-Mn-C) composite against a HSS disk at high sliding speed and concluded that the composition of FeWO4 generated during the tribological process serves as a solid lubricant to reduce the friction and wear. This study may be of interest in the fields of self-lubricating solids, but some problems should be addressed.

The suggestions are listed as follows:

1. on Page 3, it is stated “α is the contact radius of the real contact area to be determined from an equation as follows (4)”. Here, it seems that “(4)” indicates Reference [4].

Equation (2) is in the same form as Equation (1) and should be corrected.

2. On page 6, it is stated “Given that FeWO4 may serve as a solid lubricant it becomes possible understanding the CoF behavior as a function of sliding speed (Figure 2)”.

The conclusion is based on what?

“If so then the amounts of FeWO4 grow with the sliding speed (temperature) as expected and provide friction reduction as shown in Figure 2b.”

There is no Figure 2b.

4. The sliding speed for Figure (5) is in the range of 7-20 m/s or fixed at 20 m/s?

What’s the main factor that causes the differences in worn surfaces presented in Figures (4) and (5). The structure-property or the sliding speed?

5. There must be some relationships between the surface topographies (Figure 5), plastic deformation (Figure 6), and friction and wear behaviors. But the paper only presents the experimental phenomenon. Please discuss more details on the reasons that lead to the results.

6. The Discussion Section should be based on the experiments presented and those on Y-TZP should be deleted.

7. The paper should be polished by a native speaker.

Author Response

Please see attached.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Authors have improved the manuscript and made the corrections required. I think it can be accepted in present form.

No more comments.

Reviewer 2 Report

Reviewer 2
Review of Manuscript for Journal Lubricants
A Self-lubricating effect of FeWO4 tribologically synthesized from WC-(Fe-Mn-C) composite during high-speed sliding against a HSS disk v2 by Nikolai Savchenko, Irina Sevostyanova and Sergei Tarasov submitted
to be considered in Journal Lubricants In this work WC-(Fe-Mn-C) composites with γ-iron and γ+α matrices were sintered and then tested at
sliding speeds in the range 7-37 m/s. Authors report that friction coefficient gets reduced when tested at a speed of 37 m/s. The formation of iron tungstate FeWO4 on the worn surface is responsible of the mechanochemical mechanism. No wear reduction is observed. The underlying 25-65μm of thickness layer was composed of only heat-affected WC and recrystallized γ-iron grains. 

Authors provided a proper answer to all coments. This reviewer suggest the article be ACCEPTED for publication in Lubricants.

Reviewer 4 Report

The authors have addressed my concerns and the paper can be accepted as it is.