Combined Use of Surface Texturing, Plasma Nitriding and DLC Coating on Tool Steel

Round 1

Reviewer 1 Report

I could not find any academic and scientific new points.

I thought that author has just assembled previous methods on roll.

Please add and describe the academic and scientific new points clearly.

Author Response

Reviewer 1

I could not find any academic and scientific new points. I thought that author has just assembled previous methods on roll. Please add and describe the academic and scientific new points clearly.

This work presents important technological novelty, because the use of DLC on textured tools is very challenging. EDT leads to a rough surface and therefore contact pressures at the asperity level are very high, which can lead to spallation. Probably for that reason, in a very recent review about the combined use of surface texturing and solid lubricants, where 269 articles were reviewed, no reference was found for the use of   DLC to protect textured metal forming tools [1]. With that in mind, the rationale of the work involved using an alternative route for DLC synthesis that could result in soft DLC. Despite the expected lower hardness, we hoped that a soft DLC could result in reduced spallation and hopefully withstand high contact pressures with adequate tribological performance, paving a possible way for its future use in textured metalforming tools. This was indeed observed in the results, since the occurrence of spallation was very small and the tribological performance was at least comparable (or superior) to results in the literature regarding friction and wear textured tool materials coated with hard chrome using ball-on-flat tests [2,3]. These results have encouraged further development of this coating and more detailed analysis of the tribological performance, which is under course.   

However, we agree with the reviewer that we had failed to make that more explicit. In the revised manuscript, we have improved the Introduction and added details about the new route for the DLC synthesis. Moreover, in the discussion section, we expanded the analysis towards a broader  perspective to make the scientific contribution of the paper not only to textured forming tools but to any application where the substrate is very rough. Another important scientific contribution was to quantify how DLC deposition changed the surface topography of a very rough substrate.

1. Rosenkranz, A.; Costa , H.L.; Baykara, M.Z.; Martini, A. Synergetic Effects of Surface Texturing and Solid Lubricants to Tailor Friction and Wear – A Review. Wear 2020, Under review.
2. Gonçalves, J.L.; de Mello, J.D.B.; Costa, H.L. Tribological behavior of alternative surface modifications for cold rolling mill rolls. Tribology International 2020, under review, doi:https://doi.org/10.1016/j.wear.2018.12.005.
3. Gonçalves Jr., J.L.; De Mello, J.D.B.; Costa, H.L. Wear in cold rolling milling rolls: A methodological approach. Wear 2019, 426-427 part B, 1523-1535.

Reviewer 2 Report

The authors combined plasma nitriding, DLC coating and surface texturing of steel samples for a potential application as rolls used for texturing of sheets during rolling.

Before publictaion, the manuscript has to be improved significantly.

At the moment it is not possible to review the manuscript completely since nearly all references sources are missing.

However, since I started to read the first pages of the manuscript, I would like to share my comments about the experimental part and some main comments:

Introduction:

In the introduction details of the ε and γ’ phase should be given.

Experimentals:

The authors should indicate the producers of the used measuring devices (e.g. producer of the hardness tester).

There seems to be a repetition on p.2 line 91 and 92.

The authors should clearly indicate the order of process steps nitriding, coating deposition and texturing.

Was symmetric X-ray diffraction used? On which samples was XRD performed (flat, textured, coated samples)?

1. 4 line 157: The reference source is not given.
2. 4 line 163: The authors should indicate how the Poisson’s ratio was determined from nanoindentation experiments.
3. 4 line 167: The meaning of all symbols should be explained? What are E1, E2, ν12 and ν22?
4. 7 Line 232-232: What is the penetration depth of the X-rays? Can diffraction lines of the substrate be expected?

What is the sense of Table 2? It is not reasonable to give values which are not discussed in the manuscript. Only a reasonable number of decimal places should be given for the presented values.

I recommend to introduce subsections in the Experimental part and the Result part for a clearly arrangement of the investigations.

All graphs should have at least two axis which should be labelled.

All labels in the figures and graphs should have a sufficient size in order to be readable. The scale bars in the micrographs are hardly visible.

Author Response

Reviewer 2:

 

The authors combined plasma nitriding, DLC coating and surface texturing of steel samples for a potential application as rolls used for texturing of sheets during rolling.Before publictaion, the manuscript has to be improved significantly.At the moment it is not possible to review the manuscript completely since nearly all references sources are missing.

We sincerely apologise for the error with the references to the Tables and Figures. This occurred when the pdf file was automatically generated because we had used cross references in Word. We have removed all cross references so the problem will not persist.

However, since I started to read the first pages of the manuscript, I would like to share my comments about the experimental part and some main comments:

Thank you for that.

Introduction:In the introduction details of the ε and γ’ phase should be given.

This was added to the Introduction

Experimentals: The authors should indicate the producers of the used measuring devices (e.g. producer of the hardness tester).

We have added this information to the revised manuscript.

There seems to be a repetition on p.2 line 91 and 92.

Thanks, that was corrected.

The authors should clearly indicate the order of process steps nitriding, coating deposition and texturing.

We have added a sentence to make the sequence clearer.

Was symmetric X-ray diffraction used? On which samples was XRD performed (flat, textured, coated samples)?

XRD measurements were carried out in a ground specimen after plasma nitriding and DLC deposition. Since the amorphous DLC film does not present crystalline phases, the Bragg–Brentano θ-2θ configuration was used to assess the phases present in the substrate in the steel substrate and nitrided layer.  The penetration depth of the X-ray measurements was estimated using the mass absorption coefficient (MAC) tool of the X’Pert High Score Plus software giving a value of approximately 7 μm.

1. 4 line 157: The reference source is not given.

This and all the other reference problems have been corrected

2. 4 line 163: The authors should indicate how the Poisson’s ratio was determined from nanoindentation experiments.

The Poisson’s ratio value was not calculated from the nanoindentation experiments. In order to calculate the initial Hertian pressure we obtained the DLC Poisson’s ration from the literature [1]

[1] Cho, S.-J.; Lee, K.-R.; Yong Eun, K.; Hee Hahn, J.; Ko, D.-H. Determination of elastic modulus and Poisson’s ratio of diamond-like carbon films. Thin Solid Films 1999, 341, 207-210, doi:https://doi.org/10.1016/S0040-6090(98)01512-0.

1. 4 line 167: The meaning of all symbols should be explained? What are E1, E2, ν12 and ν22?

We apologise for the mistake in the notation for ν12 and ν22. It has been corrected and the Poisson’s ratios have been defined.

1. 7 Line 232-232: What is the penetration depth of the X-rays? Can diffraction lines of the substrate be expected?

The penetration depth of the X-rays was around 7 μm, that’s why the diffraction lines of the substrate were not seen. We have clarified this in the revised manuscript.

What is the sense of Table 2? It is not reasonable to give values which are not discussed in the manuscript. Only a reasonable number of decimal places should be given for the presented values.

We agree with the reviewer and have largely simplified Table 2.

I recommend to introduce subsections in the Experimental part and the Result part for a clearly arrangement of the investigations.

Done

All graphs should have at least two axis which should be labelled.

Sorry, we have added a vertical axis and axis title to Figure 6.

All labels in the figures and graphs should have a sufficient size in order to be readable. The scale bars in the micrographs are hardly visible.

The figures have been changed accordingly.

Reviewer 3 Report

This article was well written and experimental results were reasonable and complete. Therefore, I recommend this paper can be accepted for publication in Coatings. 

Author Response

Reviewer 3

This article was well written and experimental results were reasonable and complete. Therefore, I recommend this paper can be accepted for publication in Coatings. 

Thank you.

 

 

 

Round 2

Reviewer 1 Report

This revised one is well revised on the basis of comments.

Author Response

Thank you for your work and help.

Reviewer 2 Report

The manuscript contains still some flaws. It seems that the recommendations given in the previous revision were not considered completely. I propose to check them again carefully.

The preparation of the samples is not clearly described. In section 2.2 the experimental parameters of the plasma nitriding step and the DLC coating deposition seemed to be mixed (p.3 lines 129 to 139). It is also not clear if both process steps were performed in the same device.

The labbels in the figures are not all visible. Sometimes units are missing. Even discrepancies in the scale bars are present (fig.7).

For some reference sources in section 3.1 still errors occurred.

It is not clear how the penetration depth of X-rays was defined and for which material it was calculated. The penetration depth of Cu radiation in Fe3N should much smaller than 7um.

All given values (e.g. XPS or Raman) should have a reasonable number of decimal places. Furthermore, also the errors for the given values should be indicated.

What is the experimental evidence for the presence of martensite. The diffraction lines shown in Fig. 6 could also attributed to bcc-Fe.

What is the benefit of the DLC coating? Which experiments give evidence for a lubrictiy due to the DLC layer? I miss a comparison of the COF with “EDT dry” or “EDT+plasma nitriding dry” or “EDT+plasma nitriding lubricated”.

Author Response

Please see the attachment.

Author Response File: Author Response.docx