Wear Resistance Mechanism of Sub-Nano Cu₃P Phase Enhanced the Cu-Pb-Sn Alloy

Round 1

Reviewer 1 Report

Comments on coatings-1649057

1. In this manuscript, results are almost well presented, but discussion on the obtained results must be completely provided in this manuscript. As can be seen, a “comprehensive” and “comparative” discussion specially on dry friction, wear rate and wear mechanism of ZCuPb20Sn5-xP alloy (sections 3.1.2. and 3.2 and 3.3) are missed in this work. This should be provided as well.
2. The abstract is not well written. Some details of the experimental processes are missed in the abstract. Please revise this section.
3. The state-of-the-art needs to be described more in “Introduction”. Please revise the last paragraph of this section.
4. The new findings related to this work should be stated in the introduction clearly.
5. There is no description of the future plans for research in the first part of the “Conclusions” section. This should be completed in this section.
6. Recently published references are beneficial for this work. Please check and use new references focused on your work.
7. The quality of Fig. 5 is uneven. Please provide better images with higher definition.
8. Fig.9 b must be improved. Provide graph accoding to a journal standard. Use error bars if necessary.
9. Please provide major findings in the ‘Conclusions” section with a bullet-point style.

Author Response

The expert question has been revised in the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

1. The authors need to justify the novelty with respect to already published articles on the study subject.
2. The literature review section needed major revision as the latest paper cited in current work is from 2019 and has not fully covered all the articles published.
3. Add a reference to line 55.
4. All symbol and acronym used in paper need to defined.
5. Can the author justify the selection of %wt of P in the current study for the readers?
6. How did the authors ensure uniform distribution of P in modified alloys. Can you elaborate it and make it part of your article?
7. The plates number used in testing must be represented in tabulated form for a better understanding of the readers?
8. The composition of oil used in the paper is missing.
9. Why the number of points selected in dry and oil-based tests are different? (Fig 1 and 2).
10. A reduction in friction achieved with the addition of P but need the root cause analysis of reduction will add more value to the article.
11. The image J analysis will add more value to the analysis in the current study.
12. Why the data points in Fig 3 and Fig 4 have nonlinear curve, can you elaborate it in the revised submission.
13. Correct caption of Figure 6.
14. Grammatical and typo errors are there and need correction. Line 114, Line 120, Line 127, Line 133, Line 158, Line 239 etc
15. The reference style of the paper is not uniform and must be consistent with journal guidelines. See line 64.
16. Proof reading of the article is needed to make it acceptable for publication.
17. Hoe the addition of P will affect the hardness of the alloys and what about mechanical properties?
18. Is your results is supported by any published work or any other method used to validate the findings?

Author Response

The expert question has been revised in the attachment

Author Response File: Author Response.pdf

Reviewer 3 Report

1. This article is focused on a bulk material, whereas this Journal is on 'Coatings.' How does this work relate to the scope of this Journal?
2. Introduction, page 1, lines 38-39: 'Traditional wear resistant... by the materials'. Sentence is not grammatically correct and needs to be rewritten.
3. Introduction, page 1, line 42: 'bears the same pressure' to what?
4. Introduction, page 1, lines 44-45: 'the oxide film is likely to form'. This applies for dry conditions.
5. Introduction, page 2, line 55: 'Roy' add reference.
6. Introduction, page 2, line 59: Graphite is mainly used to decrease friction, not wear.
7. Introduction: Coefficient of friction refers to a pair on materials. You should always mention the counter-material.
8. Introduction, page 2, lines 75-76: 'For friction, the wear rate... reducing friction'. Sentence is not grammatically correct and needs to be rewritten. Also friction and wear are two different phenomena.
9. Introduction, page 2, lines 88-89: Mention which phase you refer to.
10. Introduction, page 2-3, lines 98-103: 'In order to... more targeted'. Sentence is not grammatically correct and it is also difficult to understand.  Needs to be rewritten.
11. Experimental procedure: paragraphs 2.1 and 2.2 should be merged.
12. Experimental procedure: Why did you considered the 15 min average value of the coefficient of friction and not the steady state?
13. Results: First paragraph of 3.1 'The test data... within the minute' should be moved to experimental procedure as they describe how you analyzed the data.
14. Results, page 4, lines 170-173: The curve does not look linear.
15. Results: Micrographs of the alloy with different P content should be added to explain effect of P on microstructure and tribological properties.
16. Results, page 5, lines 199-200: 'The variation law of the reduction is consistent with the oil lubrication condition'. What do you mean by that?
17. Results: First paragraph of 3.2 'There will be...to obtain the average value' should be moved to experimental procedure as they describe how you analyzed the data.
18. Results, page 6, line 240: It is not 'friction distance', but 'sliding distance'.
19. Results: The wear results cannot be explained based on friction ! As mentioned previously, friction and wear are two different phenomena. You should use microstructural changes and wear mechanisms to explain wear rates and NOT friction values.
20. Results: In 3.1 and 3.2 you explain why friction and wear changes, but you do not provide any experimental evidence to support your hypotheses.
21. Results, Wear mechanisms: How can you asses thickness based on 2D SEM analysis?
22. Figure 5: Microcracks are not evident. This looks more like a tribo-film. What do you mean by Ligou? How to do you know that it is an 'Easy-to-adhere sheet' and what is it?
23. Results, page 10, lines 348-349: How did you measure the 'number and volume of film increase'? Did you use Image analysis software?
24. Results, page 13, line 404: How did you observe dislocations? Your terminology is not correct.
25. I also do not understand how the formation of the secondary phase, reduces the contact (not friction) area. If the contact conditions are the same (load, geometry etc.) then the initial area should be the same. Except, if you mean that during the test and because a material is wearing, the contact area increases. 
26. Figure 9 only shows friction and not wear and it is unclear how you have in one axis load and speed.                

Author Response

The expert question has been revised in the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The revised manuscript looks fine but a professional proofreading is mandatory for this manuscript. 

Author Response

The article has been completed.

Reviewer 2 Report

Dear Editor, Thank you once again for your trust.

Only one paper is added to the introduction section from 2021. The authors need to include more published work in the introduction section to make it more informative and coped with the latest finding.

Kind Regards,

Author Response

The article has been completed.The literature in the article has been perfected, in fact, there is not much literature on this aspect at present.

Reviewer 3 Report

1. Friction does not change the surface unless it is accompanied by wear.
2. You mention that the pressure was set according to the actual application. What is that application.
3. When you refer to coefficient of friction you should mention both materials, as it is a system property. 
4. In your reply you mention that the friction (not friction coefficient) will change the temperature of the wear surface. Do you have any evidence of localized heating up (e.g. formation of oxides)?
5.  What do you mean by 'friction curves under dry and lubricated conditions have the same changing rule'? Are you referring to the experimental deviation? 
6. In Figure 5 you have made no changes. Easy-to-adhere and Ligou (?) remain.
7. Again, you mention that you observed 'dislocations' in your SEM images. This is not correct. Check you terminology.
8. Concerning contact pressure. What you refer to is the formation of debris in your tribo-contact, which results potentially in 3-body abrasion phenomena. I personally believe that the decrease of the friction is due to the formation of a lubricating tribo-layer. The contact pressure does not decrease, as you have the same load distributed over a smaller area.
9. There are several grammatical mistakes in the manuscript. English check is needed.     

Author Response

Already edited.

Author Response File: Author Response.doc

Round 3

Reviewer 3 Report

Dear authors,

After reading the revised version of the article and your point-by-point reply to my comments, I now believe that the manuscript has improved. Some small points still need to be clarified. See my comments below: 

1. I agree that you should not change the title. I am referring to the coefficient of friction. When mention a COF it should be always a pair of materials. Otherwise, you just mention friction instead.
2.   I understand that the MMW-1A machine records the temperature, but no data on the temperature evolution is presented to support this statement. If such data are not available, you should at least add a reference.
3. Again of Figure 5a you indicate Ligou. What is this term? Do you mean abrasive lines? 
4. When you make changes in your manuscript, please highlight them so that it is clear what you have changed/modified.    

Author Response

I am sorry for the confusion I caused you!Please see attachment for my reply.

Author Response File: Author Response.doc