Tribochemistry and Lubrication of Alkaline Glass Lubricants in Hot Steel Manufacturing

Reviewer 1 Report

The authors have tried to give an overview of research done in the field alkaline glass lubricants in their review article "Tribochemistry and Lubrication of Alkaline Glass Lubricants in Hot Steel Manufacturing". It's an interesting field of research and a good review of research done in this field in recent years will be a nice addition and contribution the field. I have following comments:

Minor comments:

1. Line24, Keywords are missing.
2. Line 59-61, authors have left comments from the journal template unchanged.
3. Line 144, harsh not hash I believe.
4. Line 384-397, again the comments from template have left unchanged. 

Major comments:

5. Reading through the article, I am confused if it's at all a review article. With sections like Experiments, Results and Discussion and Theoretical simulations, it appeared to me as if it's a novel research article.

6. The authors need to read and cite many more articles from the field to make it look like a proper review article. In its current form, reviewers have mostly cited their work. It appears more like a book chapter than a review article.

Author Response to Reviewer1:

Minor comments:

• Line24, Keywords are missing.

Authors reply: The key words of “alkaline glass lubricants; hot steel manufacturing; tribochemistry, lubrication” have been added in lines 24-26 in the manuscript.

• Line 59-61, authors have left comments from the journal template unchanged.

Authors reply: The comments from the journal template at lines 59-61 (60-62 in updated manuscript) has been deleted.

• Line 144, harsh not hash I believe.

Authors reply: this word has been corrected as “harsh” line 145 and 229.

• Line 384-397, again the comments from template have left unchanged.

Authors reply: The comments from the journal template at lines 384-397 were added because of formatting changes to our original submission by the editorial office. The additional information has been corrected as:

Funding: This project is supported by Australian Research Council Discovery Projects DP170103173 and Linkage Project LP160101871.

Acknowledgements: This work was supported by computational resources provided by the Australian Government through University of Wollongong (UOW) under the National Computational Merit Allocation Scheme (NCMAS). The authors also would like to thank the Australia National Computational Infrastructure (NCI) for computing time on High Performance Computing Cluster through UOW/NCI Partner Share Scheme.

Conflicts of Interest: The authors declare no conflict of interest.

Major comments:

• Reading through the article, I am confused if it's at all a review article. With sections like Experiments, Results and Discussion and Theoretical simulations, it appeared to me as if it's a novel research article. The authors need to read and cite many more articles from the field to make it look like a proper review article. In its current form, reviewers have mostly cited their work. It appears more like a book chapter than a review article.

Authors reply: This work was aimed to submit as a combined feature-review article. But in the Article Type, there is no option for this type of article, except Review, Addendum, Book review, Brief Report, Case Report, Comment, Commentary, Communication, Concept Paper, Conference Report, Creative, Discussion, Editorial, Essay, Expression of Concern, Guideline, Hypothesis, Interesting Images, Letter, New Book Received, Opinion, Perspective, Proceedings, Project Report, Reply, Short Note, Technical Note, Technical Report, Viewpoint. So we decided to choose Review article.

More articles from the field have been added to enhance the review part of the article. The additional information has been addressed as the following.

High temperature lubricants, as summarised in Fig. 1, can be divided into five different types depending on their working temperature range, molecular structure, thermal stability and reactivity with atmosphere.[4] Oil-based lubricants with an oil-in-water mixture are classified as the conventional lubricants and commonly used in hot rolling of steel because of the reduction in rolling force due to a lower friction and a longer life of the work roll from the reduced roll wear.[5-7] Nevertheless, their thermal decomposition at high temperature, cost and usage of fossil fuel from the environmental perspective are the drawbacks of this type of lubricant.[8] Apart from soluble additives of phosphorus, chlorine and sulphur, the solid lubricant in fine powders can be applied to tribological surfaces. The well-known lamella solid lubricants such as graphite, h-BN, transition-metal dichalcogenides (MX₂ with M = W, Mo, Nb, Ga and X = S, Se, Te), mica and talc are also often formulated in the lubricant to enhance its lubricating performance due to the weak Van der Waal interaction between 2D layers.[9] However, transition-metal dichalcogenides degrades rather quickly in moist and oxidizing environment. Moreover, most these 2D materials lose their intrinsic lubricity above 500°C due to thermal degradation.[10,11] Solid lubricants of soft metals (Au, Ag, Pb, In, Sn), single (B₂O₃, Re₂O₇, MoO₃, TiO₂) and mixed oxided (CuO-Re₂O₇, CuO-MoO₃, PbO-B₂O₃, CoO-MoO₃, Cs₂O-MoO₃, NiO-MoO₃, Cs₂O-SiO₂…), fluorides (CaF₂, BaF₂, SrF₂, LiF, MgF₂) and sulfates of alkaline earth metals (CaSO₄, BaSO₄, SrSO₄) have also been considered as alternatives.[12,13] The self-lubricating of ternary ceramic and its composite coating materials containing different solid lubricants such as Ni-CoCrAlY-Cr₂O₃-Ag-Mo, VN-Ag, NbN/Ag, TaN/Ag… performed well from room temperature to 1000°C.[14-16] In comparison with liquid and grease, solid lubricants can withstand a high pressure while being relatively insensitive with temperature.[13] However, this type of lubricant still have major shortcomings which include: i) poor thermal conductivity; ii) relatively high and unstable friction coefficient; having short wear life and difficult replenishment, iv) degradation during service, and v) irreversible structural-chemical changes.[13] At extreme temperature, the melt products that can function effectively are glasses such as alkali phosphates, borates and silicates. These glasses gain lubricity when they transition into viscous melt above their melting point to produce a tribofilm that reduce friction, wear and oxidation. The last type of lubricant is reactive gases, such as gaseous halogen-substituted methane derivatives, which are used under extreme conditions with excessive chemical reactions that are manifested in corrosive wear.[17] This paper is focused on a series of glass lubricants with regard to their tribological performance and the underlying mechanochemical mechanism for the tribofilm formation between sliding steel surfaces at high temperatures.

Figure 1 Working temperature range of different lubricant classes

New References

1. Schey, J.A. Tribology in Metalworking: Friction, Lubrication, and Wear. Journal of Applied Metalworking 1984, 3, 173-173, doi:10.1007/BF02833697.
2. Shirizly, A.; Lenard, J.G. The effect of lubrication on mill loads during hot rolling of low carbon steel strips. J. Mater. Process. Technol. 2000, 97, 61-68, doi:https://doi.org/10.1016/S0924-0136(99)00339-8.
3. Shirizly, A.; Lenard, J.G. The effect of scaling and emulsion delivery on heat transfer during the hot rolling of steel strips. J. Mater. Process. Technol. 2000, 101, 250-259, doi:https://doi.org/10.1016/S0924-0136(00)00401-5.
4. Azushima, A.; Xue, W.; Yoshida, Y. Influence of Lubricant Factors on Coefficient of Friction and Clarification of Lubrication Mechanism in Hot Rolling. ISIJ Int. 2009, 49, 868-873, doi:10.2355/isijinternational.49.868.
5. Allam, I.M. Solid lubricants for applications at elevated temperatures. Journal of Materials Science 1991, 26, 3977-3984, doi:10.1007/BF02402936.
6. Bay, N.; Azushima, A.; Groche, P.; Ishibashi, I.; Merklein, M.; Morishita, M.; Nakamura, T.; Schmid, S.; Yoshida, M. Environmentally benign tribo-systems for metal forming. CIRP Annals 2010, 59, 760-780, doi:https://doi.org/10.1016/j.cirp.2010.05.007.
7. Feher, R. Graphite-Based Lubricants. In Encyclopedia of Lubricants and Lubrication, Mang, T., Ed. Springer Berlin Heidelberg: Berlin, Heidelberg, 2014; 10.1007/978-3-642-22647-2_187pp. 758-769.
8. Friedman, P.A.; Luckey, S.G. 4 - High-temperature lubricants for superplastic forming of metals. In Superplastic Forming of Advanced Metallic Materials, Giuliano, G., Ed. Woodhead Publishing: 2011; https://doi.org/10.1533/9780857092779.1.72pp. 72-82.
9. Voevodin, A.A.; Muratore, C.; Aouadi, S.M. Hard coatings with high temperature adaptive lubrication and contact thermal management: review. Surf. Coat. Technol. 2014, 257, 247-265, doi:https://doi.org/10.1016/j.surfcoat.2014.04.046.
10. Erdemir, A. Solid Lubricants and SelfLubricating Films: CRC Press. In Modern Handbook of Tribology, 2001.
11. Shi, X.; Zhai, W.; Wang, M.; Xu, Z.; Yao, J.; Song, S.; Wang, Y. Tribological behaviors of NiAl based self-lubricating composites containing different solid lubricants at elevated temperatures. Wear 2014, 310, 1-11, doi:https://doi.org/10.1016/j.wear.2013.12.002.
12. Zhu, S.; Bi, Q.; Yang, J.; Liu, W.; Xue, Q. Ni3Al matrix high temperature self-lubricating composites. Tribol. Int. 2011, 44, 445-453, doi:https://doi.org/10.1016/j.triboint.2010.11.016.
13. Zhu, S.; Cheng, J.; Qiao, Z.; Yang, J. High temperature solid-lubricating materials: A review. Tribol. Int. 2019, 133, 206-223, doi:https://doi.org/10.1016/j.triboint.2018.12.037.
14. Johnson, R.L.; Swikert, M.A.; Buckley, D.H. High Temperature Lubrication In Reactive Atmospheres. CORROSION 1960, 16, 395t-398t, doi:10.5006/0010-9312-16.8.101. 

Author Response File: Author Response.docx

Reviewer 2 Report

The manuscript is a review of an important area of lubrication and should be published. I did find a few minor changes.

line 57: Change to Experimental Studies

lines 59-61 should be deleted

lines 384-387 should be deleted

Author Response to Reviewer2:

line 57: Change to Experimental Studies

Authors reply: The heading of “Experiment” has been changed to “Experimental Studies”

lines 59-61 should be deleted

Authors reply: The comments from the journal template at lines 59-61 (60-62 in updated manuscript) has been deleted.

lines 384-387 should be deleted

Authors reply: The comments from the journal template has been revised. The revised information is mentioned in the response to the comment #5 of Reviewer 1.

Following are the new references added for extra review

Author Response File: Author Response.docx

Author Response to Editor:

It has been reviewed by experts in the field and we request that you make major revisions before it is processed further.

Please revise the manuscript according to the reviewers' comments and upload the revised file within 10 days. Use the version of your manuscript found at the above link for your revisions, as the editorial office may have made formatting changes to your original submission. Any revisions should be clearly highlighted, for example using the "Track Changes" function in Microsoft Word, so that changes are easily visible to the editors and reviewers. Please provide a cover letter to explain point-by-point the details of the revisions in the manuscript and your responses to the reviewers' comments. Please include in your rebuttal if you found it impossible to address certain comments. The revised version will be inspected by the editors and reviewers. Please detail the revisions that have been made, citing the line number and exact change, so that the editor can check the changes expeditiously. Simple statements like ‘done’ or ‘revised as requested’ will not be accepted unless the change is simply a typographical error.

Authors reply: The authors have replied to all reviewer’s comments.

The cover letter has been submitted to indicate the revisions in the manuscript, as well as our responses to the reviewers' comments.

Please carefully read the guidelines outlined in the 'Instructions for Authors' on the journal website https://www.mdpi.com/journal/lubricants/instructions and ensure that your manuscript resubmission adheres to these guidelines. In particular, please ensure that abbreviations have been defined in parentheses the first time they appear in the abstract, main text, and in figure or table captions; citations within the text are in the correct format; references at the end of the text are in the correct format; figures and/or tables are placed at appropriate positions within the text and are of suitable quality; tables are prepared in MS Word table format, not as images; and permission has been obtained and there are no copyright issues.

Authors reply: The abbreviation of “MD” of “molecular dynamics” has been defined in parentheses the first time they appear in the abstract.

Permission has been obtained and there are no copyright issues for Figures 1-6. Particularly,

For Figure 1 from Reference 7 by Wan et. al., which is an open access article distributed under the terms of the Creative Commons CC BY license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

For Figure 2 from Reference 10 by Tran et. al., a copyright request has been sent to Taylor & Francis publisher to get an approval. The request has been attached in the resubmission.

For Figure 3 from Reference 19 by Le et. al., a copyright request has been sent to Elsevier publisher to get an approval.

For Figure 4 from Reference 21 by Ta et. al., a copyright request has been approved by ACS in both print and electronic formats. The approval is attached in the resubmission.

For Figure 5 from Reference 23 by Tran et. al., a copyright request has been sent to Elsevier in both print and electronic formats.

For Figure 6 from Reference 20 by Ta et. al., a copyright request has been approved by ACS in both print and electronic formats. The approval is attached in the resubmission.