Frictional Behavior of MoS₂ Coatings: A Comparative Study of Dynamic and Static Friction in Vacuum and Inert Gases

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In Fig. 13, label of y-axis, [200] is not a plane. Should it be (200)?

In addition, the labelled peaks for the Miller indice of the planes are not enclosed with brackets.

Author Response

We have carefully considered your comments and the authors thank you for constructive remarks

Figure 13 became Figure 5 - The label of y-axis is modified - [200] replaced with (200) and the labelled peaks for the Miller indices of the planes are now enclosed with brackets.

For improvement of the presentation of the results, the structure of the paper is modified in accordance with the comments of the other  reviewers.

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors, thank You for this interesting work! It was a great pleasure for me to review it. Nevertheless, There are some points, that should be improved

1. English style and grammar should be improved. The text is generally understandable, but is hard to read. Please, rephrase some sentences, that were highlighted: this will make the Manuscript more original. Also, I recommend to send the manuscript to professional proofreading
2. In the literature review, and other places where You refer to previously published works, use Your own words, not the fragments from the reference publications. Also, rephrase the test aparatus description, it is very rough
3. Figures 2-6 should be redrawn. It is hard to analyse the CoF usin them: too low accuracy and resolution
4. Lines 247-249. You made a statement about alignment, but did not put any proofe. Please, add them to the manuscript
5. Lines 149-153: what was the duration of the test, or the length of friction path?
6. Please, make full description of test procedures within the 2nd part, including XRD, shear force measurements, calculation methods, mass-spectrometry.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

English is very hard to read. Some highlighted segments look like translated using online services and were not eddited after that. Please, improve the style and grammar of English 

Author Response

We have carefully considered your comments, and the authors thank you for your constructive remarks and questions. We have modified the structure of the manuscript and took into consideration your highlighted segments/proposals (comments 1 and 2)

Comment 3: Figures were redrawn wit webplotdigitizer platform (https://automeris.io/wpd/) for a better accuracy and resolution. The original data were not available. 

Comment 4:  initial Lines 247-249 - with the new structure of the paper, the alignment is proved with XR diffraction.

Comment 5: Initial Lines 149-153  - the test duration was 60 to 80 minutes (addition done)

Comment 6: Full description  of the test procedures  are now in part 2 -Materials and methods

Reviewer 3 Report

Comments and Suggestions for Authors

The article is of interest to the tribology and coatings communities. In general, the work is interesting. Although, it lacks on Novelty and an improved discussion section. The discussion section brings several new results and lacks on comparing the results with previous literature. A better connection between the mass spectrometry and the theoretical formulation is needed. Some questions and comments are provided below to help improve the paper.

 

1. Not enough information was provided to someone be able to replicate the coating deposition. Needs to provide more information.

 

2. Figures 2 to 5 it is suggested to highlight the running-in period, since everything is constant after that.

 

3. Figure 5 shows COF = 0.03 from the y-scale, while in the text that was described as 0.3, which one is correct?

 

4. lines 238-240: “The mean friction coefficient obtained in ambient air with low relative humidity (RH = 25%) is recorded at µ = 0.18.”. No Figure from this test is shown, needs to be included.

 

5. The discussion is a description of the results, and it is barely compared to the literature, it needs to be improved by comparing the results with literature. Needs citation of several values provided.

 

6. Is Figures 9 and 11 SEM image? LOM? Needs to indicate. Is there coating left in the shiny region or is the steel substrate being revealed?

 

7. Figures 10 and 12: If you have a 5 microns coating, why your 3D profilometer scale goes to over 20 microns? It is suggested to calculate the wear rate of the coatings for the different testing conditions.

 

8. lines 462-468 are duplicated text.

 

9. The conclusions are a list of the results. It needs to conclude the work.

 

10. The whole paper needs a better organization of the different sections. There are new results in the discussion section, there are new information on methods, simulation, characterization equipment used that is not present in the materials and methods section.

 

11. The English writing is acceptable, but it is recommended a full review throughout the paper for improvement and for fixing mistakes/typos.

Comments on the Quality of English Language

 

11. The English writing is acceptable, but it is recommended a full review throughout the paper for improvement and for fixing mistakes/typos.

Author Response

We have carefully considered your comments, and the authors thank you for your constructive remarks and questions.

Comment 1: Some additional information was supplied about the deposition of MoS₂ coatings with cold spray process. The coatings were industrial coatings furnished by ASTF  enterprise (Bordeaux/Merignac) with few data.

Comment 2:  initial figures 2 to 5 (now 2–6 to 8) show the permanent friction behavior under vacuum or under a given gas. The running-in-period at the start of each tribological test, prior to the coating orientation, requires detailed study.

Comment 3:   Initial figure 5 (now Figure 8) is modified - the correct value of COF is 0.3.

Comment 4: Initial Lines 238-240 (now lines 390-392). The mean friction coefficient in ambient air with low relative humidity  (RH=25%) is recorded at µ=0.18. This result was obtained by S.Bui in his Ph-D works.  The result is just cited. No figures shown.

Comment 5:  Several citations were added for the discussion of the results.

Comment 6: Initial Figures 9 and 11  (now 3 and 10) are LOM images.

Comment 7: No wear rate was determined.

Comment 8: Initial lines 462-468 cancelled

Comment 9:  The conclusions are replaced with a summary

Comment 10: the paper was reorganized, as also suggested by reviewer 2.

Comment 11: A full review was made by several persons.

Information: All the frictiograms  were redrawn with webplotdigitizer platform  for a better accuracy and resolution  as suggested by reviewer 2. Initial data were not available.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Authors, 

thank You for the work done. 

Good luck!

Author Response

Dear Authors, 

thank You for the work done. 

Good luck!

We improved some results with the comment of reviewer 3  and provide a rebuttal document

Author Response File: Author Response.docx