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Article
Peer-Review Record

Mechanisms of Oxidation Degradation of Cr12 Roller Steel during Thermal Fatigue Tests

Metals 2020, 10(4), 450; https://doi.org/10.3390/met10040450
by David Bombač 1,2,*, Marius Gintalas 3,4,5, Goran Kugler 1 and Milan Terčelj 1,*
Reviewer 1: Anonymous
Reviewer 2: Anonymous
Reviewer 3: Anonymous
Metals 2020, 10(4), 450; https://doi.org/10.3390/met10040450
Submission received: 3 March 2020 / Revised: 23 March 2020 / Accepted: 24 March 2020 / Published: 28 March 2020
(This article belongs to the Special Issue Thermal Fatigue Behavior of Roller Steel)

Round 1

Reviewer 1 Report

In this paper the authors analyzed Mechanisms of oxidation degradation of Cr12 roller steel during thermal fatigue tests. Several experiments and test condition have been tested and a qualitative analysis of microstructure have been done. Still the research is interesting in the present it is very difficult to really understand how was designed and to appreciate the founded results.

Here you can find different revision that are needful to better presents the results:

Introduction

The state of art needs a higher revision too many citations in single sentence (as example line 36). Please avoid citation that are not coherent with the purpose of your research and specify better what is the main contribution to the research of the authors that are cited.

Experimental methods

Please add a flowchart or a graphical description of the research, experimental condition tested and methods selected to measure the results obtained. Moreover different information about the methods are presented in the Results chapter (as example line 135-139 the methods of how results are analyzed is reported, this part have to be included in the experimental methods chapter)

Results and discussion

Divide this two section and please in the second one try to give a global point of view about the effort of your research and a reasons to the founded results.

Conclusion

Too long you have to be more syntetic and cleat, do not repeating the abstract, or just listing experimental results. but provide a clear scientific justification for your work

Author Response

Please see the attachment.

Reply to all 3 reviewers is given in the same  attachment. Corrections in the paper were marked red where extensive changes were done. Some minor mistakes and misspellings were not marked.

Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript is well writen and drawn the conclusions by mainly experiments and observatios and simulations.

However the manuscript is too lengthy and compliceted and difficult to follow the whole results contained in the manuscript.

Thus, this reviewer's recommendation is "major revision needed". Following is the major point to revise.

Please shoten it simply or split into two or three papers. Please reconsider the structure of the manuscript contetnts.

Following is minor points to revise:

  1. In Fig. 13,  please check the location of a) - e)
  2. Please address the validity of thermal stress simulations using some measurement technology of strain gauge measurement result or digital image correlation measurement.

Author Response

Please see the attachment.

Reply to all 3 reviewers is given in the same  attachment. Corrections in the paper were marked red where extensive changes were done. Some minor mistakes and misspellings were not marked.

Author Response File: Author Response.pdf

Reviewer 3 Report

Highly assessing the research and its description, I have only minor remarks:

Page 2: Gleeble 1500D thermomechanical simulator; please give the company name and country

Page 2: FEI NanoSEM; please give the model, is it complete>

Page 3: Modulus; a small letter and not a capital one

Page 6: EDX; properly EDS

Page 9: elements of the carbides cluster are not cracked; improper, not elements

Page 14: 300µm; add a space between a value and a unit

Page 14: cracks are completely the cooled surface; unclear

Page 14: it is important to note the importance; improper

Page 15: varies and was measured; various tenses, incorrect

Page 15:  Observation of the sample at the lowest maximum temperature (500 °C) leads to a negligible oxide layer thickness.; the observation cannot lead to the thickness...

Page 19: where crack nucleation and carbide crushing is shown.; carbide crushing?

Page 19: has reduced role; contribution?

Page 19: You can also see surface bulges or elevations on the surface where the crack canal begins; the "You" form should not be used.

Page 20: carbide pathway; what is it, please define

Page 22: crack peak stress; as above

Page 25: the formation of two bricks in the matrix in the favourable oxidation direction; unclear, what is it the brick?

Page 29: The formation of oxidation in two sub-brunches; unclear, and rather formation of oxides

Page 29: both sub-branches follow the range in the matrix; please define what is a sub-branch

Page 30: oxide of the lamellae on the left side is extensive massive; extensive massive? improper

Page 31: influence crack growth.; influences

Page 31: Areas with depleted Cr content in the vicinity of eutectic carbides and within a narrow band along the primary carbides were observed. The amount of Cr in these areas was about 4-5 wt %. compared to the expected range of 7-9 wt % in the matrix.
Content of Mo in primary carbides varied and was determined in the range of 3-8 wt %. The determined content of Mo in eutectic carbides is lower and is only in the range of 2.1-2.9 wt %.

Remark: both sentences are not conclusions.

Page 32: The observed oxidation area of the eutectic matrix is larger compared to the oxidation of eutectic carbides.; as above.

Page 32: bellow; rather `below`

Generally: the conclusions are too large, please shorten this section and do not repeat the results.

Author Response

Please see the attachment.

Reply to all 3 reviewers is given in the same  attachment. Corrections in the paper were marked red where extensive changes were done. Some minor mistakes and misspellings were not marked.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Please rewrite the discussion by taking in consideration that

Here you must respond to what the results mean. You need to make the Discussion corresponding to the Results, but do not reiterate the results. Here you need to compare the published results by your colleagues with yours (using some of the references included in the Introduction). Never ignore work in disagreement with yours, in turn, you must confront it and convince the reader that you are correct or better.

Author Response

We are grateful for comment and have reorganised Discussion. Some results that were previously in Discussion were removed and where applicable moved to the Results.

References cited in Introduction were discussed in more detail, however by authors knowledge non went as deep as current paper. Therefore only general confirmations of previous knowledge were discussed. However, even contrary results by ref. [27] are possible if chemical conditions permit.

Following was added to the discussion:

Thermal stress, shape and size of the eutectic, content of Cr in the matrix and eutectic carbides, orientation of the eutectic lamellae (perpendicular to the cooled surface), occurrence of cracks in eutectic carbides and temperature accelerate the oxidation of the matrix. The oxidation progress of carbides and the matrix adjacent to carbides depends on the local chemical composition. The oxidation intensity of crack tips depends not only on the depletion of Cr, but also on the Mo content. If the Mo content in the carbides is lower, the oxidation front will align along the carbides and the oxidation rate is expected to accelerate. The results obtained confirm that the matrix generally oxidizes faster. As shown in Figure 15b, carbides can oxidize at a similar rate to the matrix due to local variations in chemical composition, especially Mo content. In some cases, carbides could oxidize faster than the matrix, depending on the local chemical composition, which complements the observations of Kim et al. [34]. Large oxidation tongues in the present study contrast with oxidation studies [4,15,22,23,28,34-38] and tribological tests [3,9-11,14,16,25,26,33,35,39-57]. This is attributed to test conditions where thermal cycles play an important role in O diffusion and confirms the theory of Lao et al. [27] that the condition under isothermal testing in the highly plastic deformed region during sliding wear is not comparable to the behavior during hot rolling.

We hope revised Disscussion enjoys your approval.

Reviewer 2 Report

Thank you very much for the revised manuscript.

This manuscript is well writen for sicentific publication and have a value to publish.

This reviewer's recommendation is "accept as is for publication".

 

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