The Relationship between Surface and In-Depth Hardness for the Nitrocarburizing Treatment Process

Round 1

Reviewer 1 Report

I have reviewed the submission and have not been satisfied with the original form of the prepared manuscript and therefore I cannot recommend publication of the submission in its original form. However, the authors may want to follow the recommendations in their revised manuscript:

The writing of English should be improved; I suggest the authors get editing help from someone with full professional proficiency in English.
Microscopic images of the initial steel structure, post-heat treatment, and nitrocarburized structures must be given.
The method of removing the compound layer should be given in detail.
What are the numbers in Tables 3 and 4 based on? Please explain.
Conclusion and discussion should be separated.
Modify the sections of different parts of the article.
Correct the horizontal axis of Figure 8 a.
The literature review is not sufficient and authors must review and cite more papers in the field of predicting the thickness and properties of surface layers and especially newly published ones. Doing this, review and citing the following refs could be helpful:
[1] Ceramics International, 40, 2014, 5515-5522, DOI 10.1016/j.ceramint.2013.10.141
[2] Neural Computing and Applications, 23, 2013, 779-786, DOI 10.1007/s00521-012-0994-2

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript entitled: 'The Relationship Between Surface and In-depth Hardness, for the Nitrocarburising Treatment Process' deals with the inhomogeneous hardness distribution along the surface. I have the following concerns with the present manuscript.

• Error bars should be introduced for the data in Table 1, 3, 5, 6, and 7.
• The quality of the figures should be improved (especially for the schematics).
• The manuscript includes too much data without much scientific implication.
• The implication of such variation in the hardness profile along the surface in terms of the material's performance or life should be connected or discussed scientifically.
• Section number 6 should be Summary and not Discussion.
• Typos in the manuscript should be checked carefully.
• The English language needs attention.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

REVIEW

on article

The Relationship Between Surface and In-depth Hardness, for the Nitrocarburising Treatment Process

Mihaly Réger, Richárd Horváth, Attila Széll, Tamás Réti, Viktor Gonda and Imre Felde

SUMMARY.

The article considers the well-known problem of determining the function of changing the hardness of a metal subjected to nitrocarburizing in-depth during measurements by the indentation method. Despite the widespread use of nitrocarburizing in technological operations to increase the strength and wear resistance of the surface of machine elements, the problem has not been fully investigated and has good scientific and practical importance. Indeed, it is attractive to use simple indentation techniques to determine the entire hardness versus depth curve and to understand the ability of a part to resist fatigue or wear.

From this point of view, the problem under consideration is relevant and of scientific interest.

The authors proposed a mathematical model showing the dependence of the change in hardness with depth on the example of nitrocarburized samples of tool steel for hot working. The tool steel samples were heat treated. Depth hardness was measured on polished sections perpendicular to the surface with a load of HV0.2 (1.962 N) by the Vickers method with a step of 50 μm. The resulting model allows, by determining the surface hardness, to evaluate the change in hardness along with the depth of the part.

The reference list contains 15 items.

At the same time, the article has several inaccuracies.

COMMENTS.

1. The authors have to redo the Abstract and bring it in line with the requirements of the Metals journal. The scientific problem is poorly defined. The results are practically not reflected. Editors strongly encourage authors to use the following style of structured abstracts, but without headings: (1) Background: Place the question addressed in a broad context and highlight the purpose of the study; (2) Methods: Describe briefly the main methods or treatments applied; (3) Results: Summarize the article's main findings; and (4) Conclusions: Indicate the main conclusions or interpretations. The abstract should be an objective representation of the article.
2. The review of references is very poor, with only 15 sources.
3. Line 24. The definite article "The" is double used
4. The article establishes that it is best to approximate the distribution of hardness over depth using the function (4). This expression is not supported by theoretical calculations or numerical analysis. Authors need to convincingly prove the applicability of this formula.
5. In equation (5), it is not clear what the designation of the variables in the formula is.
6. Figures 8а and 8c. Check the abscissa labels.
7. The Discussion section does not contain an in-depth analysis of the results. I recommend that the authors compare the data obtained with the results of other authors.
8. In fact, Formula 4 establishes a relationship between the upper A1 and lower A2 boundaries and does not depend on the geometry of the part being measured. How can this be applied to parts with complex geometries, such as gears, shafts, crankshafts, and others? In these details, cementation penetrates unevenly.
9. There is no Conclusions section in the article. I recommend doing this section, because many readers first read the Abstract and Conclusion, and only then the whole article.

In general, the article is devoted to an interesting scientific problem that will undoubtedly attract the attention of readers. However, there are many inaccuracies in the article.

I recommend the article for publication after a major correction.

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

In the reviewed paper, the relationship between surface and indentation hardness for the nitrocarburizing treatment process is presented.  

However, the usefulness of the proposed mathematical model, in a symbolic way, was confirmed experimentally, as the authors themselves confirm at the very end of their paper.
It would be advisable to confirm the functionality of the mathematical model for other surface treatment processes. For example, data from numerous publications in this field could be taken. 
Apart from the scientific side, the caption of Fig. 8a was not correctly written in English

Author Response

Dear Reviewer,

First of all, let us express our thanks for the thorough and detailed review!

Literature has been extended as requested. The abscissa labels were corrected (Fig. 8a). 

Round 2

Reviewer 1 Report

The revised manuscript could be considered for publication in Metals.

Author Response

Dear Reviewer,

The spelling check and correction of typos were done.

Thank you for your detailed work, and support for publishing this article.

Reviewer 2 Report

The authors have satisfactorily addressed my comments and the manuscript may now be accepted for publication in the present form.

Author Response

Dear Reviewer,

Thank you for your detailed work, and support for publishing this article.

(The spelling check and correction of typos were done.)

Reviewer 3 Report

All my comments were taken into account and corrected in the text of the article. The article looks much better. I recommend the article for publication

Author Response

Dear Reviewer,

Thank you for your detailed work, and your recommend for publishing this article.

Reviewer 4 Report

    Thank you for sending the revised version of the article. Indeed, in many points, the quality of the article has been somewhat improved. However, when writing that the mathematical model has been symbolically confirmed by test results, I expected that the authors in the revised version would provide photos of the microstructures of the investigated steels, after heat treatment and after nitrocarburizing, and that an in-depth analysis would be carried out.  Also, when describing the conditions for removing the surface layer after heat treatment, it is not specified how the parameters were chosen and how it was found that the layer was removed.  
In conclusion, I personally believe that the photographs of microstructures confirming the results obtained and used for modeling should be presented in the paper.

Author Response

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Author Response File: Author Response.pdf

Round 3

Reviewer 4 Report

After corrections and additional explanations by the authors, accepts the article for publication