Investigation of the Nature of the Interaction of Me-MeN-(Me,Mo,Al)N Coatings (Where Me = Zr, Ti, or Cr) with a Contact Medium Based on the Ni-Cr System

Round 1

Reviewer 1 Report

In the manuscript, the authors studied the wear property and microstructure of three coatings belonging to the Me-MeN-(Me,Mo,Al)N system where Me=Zr, Ti, and Cr. The authors have demonstrated that different elements in the (Me,Mo,Al)N system played an important role in affecting the wear property of the coatings. The authors also conducted very detailed TEM analysis of the coatings after the wear test in order to understand the reason behind different tribological performance. There are several issues in the manuscript that I believe are worth authors’ attention.

 

1. The XRD analysis in the manuscript (Line 171 to 173) is too short and lacks significant details. For example, how did authors assign these peaks to different crystal structures? Did they rely on any database? If so, the authors need to include their references including PDF numbers. Upon looking at the data, I found out that the XRD data for coatings M1 is significantly different from the other two (M2 & M3), as the diffraction peaks of (Zr,Mo,Al)N reside at much lower angle compared to the diffraction peaks of (Ti,Mo,Al)N and (Cr,Mo,Al)N. I think detailed explanation of this difference is necessary.
2. Following the first question, the SAED pattern taken from M1 (Fig. 6d) indicates that there are two different metal nitride phases with different lattice spacing. Why does the XRD data only show a single (Zr,Mo,Al)N phase?
3. The third question is related to the element composition analysis. In the manuscript, the authors include several line profiles in regard to the coating composition (Fig. 6c, Fig. 7b, Fig. 7c, Fig. 8c, Fig. 8d, Fig. 9d, Fig. 10c and Fig. 10d). How did they acquire the data? Is it EDX line scan? Also, in these graphs the Y-axis was denoted as “intensity”. What does “intensity” mean? Does it mean the intensity of EDX signals, or is it atomic percentage?
4. Following the third question, the authors mentioned in Line 100 and 101 that the composition “was determined based on the analysis of the studies available and the earlier experimental results”. What exactly are these “studies”? Are the earlier experimental results published? The authors need to include necessary references here.
5. The fifth question is a follow-up of previous two questions. The composition analysis does not include any information about nitrogen. From Line 101 to Line 103, the authors stated that the Mo and Al content in the coatings was 40% and 10% respectively, the content of Ti (or Zr, or Cr) was 50%. These three metals round up at about 100%, but where is nitrogen? Did the authors choose to exclude the nitrogen? What is the reason? I found it extremely confused since the study subjects in the manuscript are nitride coatings, and it is important to include the nitrogen content in the chemical analysis (Fig. 6c, Fig. 7b, Fig. 7c, Fig. 8c, Fig. 8d, Fig. 9d, Fig. 10c and Fig. 10d). I suggest authors change these results to include nitrogen, or at least offer proper explanation that why nitrogen was absent from the data.
6. The authors are advised to change the Y-axis of Fig. 10d, because -10 of intensity does not make sense.
7. In Line 278 and Line 281, please swap the positions of “Figure 6d” and “Figure 6e” so the description in the manuscript matches with the graphs.

Author Response

In the manuscript, the authors studied the wear property and microstructure of three coatings belonging to the Me-MeN-(Me,Mo,Al)N system where Me=Zr, Ti, and Cr. The authors have demonstrated that different elements in the (Me,Mo,Al)N system played an important role in affecting the wear property of the coatings. The authors also conducted very detailed TEM analysis of the coatings after the wear test in order to understand the reason behind different tribological performance. There are several issues in the manuscript that I believe are worth authors’ attention.

 The authors are grateful to the Reviewer for valuable recommendations helping to improve the quality of the manuscript.

1. The XRD analysis in the manuscript (Line 171 to 173) is too short and lacks significant details. For example, how did authors assign these peaks to different crystal structures? Did they rely on any database? If so, the authors need to include their references including PDF numbers. Upon looking at the data, I found out that the XRD data for coatings M1 is significantly different from the other two (M2 & M3), as the diffraction peaks of (Zr,Mo,Al)N reside at much lower angle compared to the diffraction peaks of (Ti,Mo,Al)N and (Cr,Mo,Al)N. I think detailed explanation of this difference is necessary.

 

Due to the recommendations of the Reviewer, we have added a more detailed description of the XRD data, including PDF cards, and lattice parameters.

 

1. Following the first question, the SAED pattern taken from M1 (Fig. 6d) indicates that there are two different metal nitride phases with different lattice spacing. Why does the XRD data only show a single (Zr,Mo,Al)N phase?

 

According to XRD data, we failed to reliably identify two nitride phases with close interplanar spacings due to wide diffraction lines. But with the help of SAED, we were able to identify two phases in the M1 coating.

 

 

1. The third question is related to the element composition analysis. In the manuscript, the authors include several line profiles in regard to the coating composition (Fig. 6c, Fig. 7b, Fig. 7c, Fig. 8c, Fig. 8d, Fig. 9d, Fig. 10c and Fig. 10d). How did they acquire the data? Is it EDX line scan?

 

Yes, these data were obtained by the EDX method, but not along the line in automatic mode, but by points in manual mode with a certain step. We added data on the used EDX method to the methodology. We incorrectly indicated the intensity on the graphs, the Y-axis corresponds to the atomic percentages of the elements. We've fixed it.

 

 

Also, in these graphs the Y-axis was denoted as “intensity”. What does “intensity” mean? Does it mean the intensity of EDX signals, or is it atomic percentage?

 

"intensity" on all images was replaced by "concentration, at%"

 

 

1. Following the third question, the authors mentioned in Line 100 and 101 that the composition “was determined based on the analysis of the studies available and the earlier experimental results”. What exactly are these “studies”? Are the earlier experimental results published? The authors need to include necessary references here.

 

Relevant references have been added.

 

1. The fifth question is a follow-up of previous two questions. The composition analysis does not include any information about nitrogen. From Line 101 to Line 103, the authors stated that the Mo and Al content in the coatings was 40% and 10% respectively, the content of Ti (or Zr, or Cr) was 50%. These three metals round up at about 100%, but where is nitrogen? Did the authors choose to exclude the nitrogen? What is the reason? I found it extremely confused since the study subjects in the manuscript are nitride coatings, and it is important to include the nitrogen content in the chemical analysis (Fig. 6c, Fig. 7b, Fig. 7c, Fig. 8c, Fig. 8d, Fig. 9d, Fig. 10c and Fig. 10d). I suggest authors change these results to include nitrogen, or at least offer proper explanation that why nitrogen was absent from the data.

 

This situation is related to the fact that the lighter the element, the worse it is qualitatively and especially quantitatively determined by the EDX method, and especially against the background of heavy elements. Therefore, we forcibly excluded nitrogen even in those rare cases when it sometimes appeared in the spectra. When analyzing EDX with the SEM method, nitrogen is felt better due to the fact that the volume from which the characteristic X-rays are generated is significantly larger than in the case of TEM. Also, more modern Silicon Drift Detectors (SDD) are more sensitive, which could slightly improve the detection of light elements, but, unfortunately, we only use the previous generation Si-Li detector with nitrogen cooling.

 

1. The authors are advised to change the Y-axis of Fig. 10d, because -10 of intensity does not make sense.

 

We incorrectly indicated the intensity on the graphs, the Y-axis corresponds to the atomic percentages of the elements. We've fixed it.

 

1. In Line 278 and Line 281, please swap the positions of “Figure 6d” and “Figure 6e” so the description in the manuscript matches with the graphs.

 

The typo has been corrected. Thank you!

Reviewer 2 Report

This manuscript employed high-resolution transmission electron microscope to systematically investigate the microstructure evolution, fracture mode, oxidation behavior of three Me-MeN-(Me,Mo,Al)N coatings under different cutting conditions. It shows beautiful characterization micrographs, and the authors have analyzed the results correctly. I suggest a minor revision before acceptance.

 

1. The introduction could be more concise.

 

2. The error bars should be added in Fig. 1g.

 

3. The scale bars in Fig. 3a should be consistent with Fig. 3b and 3c.

 

4. In results and discussions section, I suggest the authors add a 3.5 section to summarize the identical rules and differences of three coatings (M1, M2 and M3) under the processes of fracture, diffusion, and oxidation.

Author Response

This manuscript employed high-resolution transmission electron microscope to systematically investigate the microstructure evolution, fracture mode, oxidation behavior of three Me-MeN-(Me,Mo,Al)N coatings under different cutting conditions. It shows beautiful characterization micrographs, and the authors have analyzed the results correctly. I suggest a minor revision before acceptance.

 The authors are grateful to the Reviewer for valuable recommendations helping to improve the quality of the manuscript.

1. The introduction could be more concise.

 The introduction has been shortened - some of the information has been removed, and some has been moved to the Materials and Methods section.

1. The error bars should be added in Fig. 1g.

 Error bars are added to the hardness data (because 12 measurements were taken and the average value was determined), the data on the critical fracture load are presented from the results of one test, therefore error bars are not indicated.

1. The scale bars in Fig. 3a should be consistent with Fig. 3b and 3c.

 Figure 3 has been modified, and a map of the distribution of the main elements has also been added.

Reviewer 3 Report

Dear Authors,

Below you can find my impression of the submitted manuscript after the careful lecture. I am able to identify some certain interesting points in this work and it makes it possible to accept it for publication after revision. 

1 a lot of the figures/graphs are not possible to read in a version of manuscript - the legends are too small. 

Fig 1, d-f

Fig 6 c

Fig 7 b,c

Fig 8, c,d

Fig 9, d

Fig 10, c,d

Fig 1-g - error bars are missing. How many repetitions have been made? 

Fig 2 - what is the meaning of the red dot line? Need to be explained clearly in the text and in the description of the graph.

XRD - impossible to read and distinguish anything there. What about the card identification numbers? Which database has been used? And the description of the peaks? Any texture indication? A lot of interesting information from XRD is missing. 

In the references are a lot of self-citations.  Author: Alexey Vereschaka is self-cited in an unacceptable manner (23! from 86 citation records ~27%). I am not even checking the other co-workers because this number can be even higher. 

Please elaborate on all underlined issues.

 

With my best regards,

Author Response

Dear Authors,

Below you can find my impression of the submitted manuscript after the careful lecture. I am able to identify some certain interesting points in this work and it makes it possible to accept it for publication after revision. 

The authors are grateful to the Reviewer for valuable recommendations helping to improve the quality of the manuscript.

1 a lot of the figures/graphs are not possible to read in a version of manuscript - the legends are too small. 

Fig 1, d-f

Fig 6 c

Fig 7 b,c

Fig 8, c,d

Fig 9, d

Fig 10, c,d

The images indicated by the Reviewer have been re-edited to increase the font size.

Fig 1-g - error bars are missing. How many repetitions have been made? 

Error bars are added to the hardness data (because 12 measurements were taken and the average value was determined), the data on the critical fracture load are presented from the results of one test, therefore error bars are not indicated.

Fig 2 - what is the meaning of the red dot line? Need to be explained clearly in the text and in the description of the graph.

The red dotted line indicates the value of limit wear on the flank face VB_max = 0.3 mm. Added to the caption.

XRD - impossible to read and distinguish anything there. What about the card identification numbers? Which database has been used? And the description of the peaks? Any texture indication? A lot of interesting information from XRD is missing.

We took into account the comments of the Reviewer and added a more detailed description of the XRD data, indicating PDF cards. 

In the references are a lot of self-citations.  Author: Alexey Vereschaka is self-cited in an unacceptable manner (23! from 86 citation records ~27%). I am not even checking the other co-workers because this number can be even higher. 

The number of self-citations has been significantly reduced.

 

Round 2

Reviewer 1 Report

After reviewing the revised manuscript, I have a few concerns,

 

1.     The authors stated the reason of excluding nitrogen from the EDX data, which is the difficulty in quantification of light elements in a matrix consists of both heavy and light elements. I can only partially agree. The authors included the results of oxygen to demonstrate the oxidation reaction of the coatings. However, oxygen is only slightly heavier than nitrogen. If the quantification of nitrogen was deemed not reliable by the authors, how would they justify the reliability of EDX data in regard to the oxygen content? I suggest authors either include the nitrogen in the final result, or offer proper explanation in the manuscript stating why they exclude the nitrogen, which is one of the major elements forming the coating.

2.     The authors stated that the EDX was obtained by manually selecting multiple spots in a pre-determined line across the sample. Did the authors control the spacing between each spot? Although I do not believe that it is necessary to keep the distance between those spots strictly the same, I DO believe that authors need to revise all the linear EDX data. Instead of smooth curves, the authors should plot the data taken from every spot, and connect the spots using straight lines. In this way, the data will be presented more accurately, and will correspond to the method better.

Author Response

After reviewing the revised manuscript, I have a few concerns,

 The authors are grateful to the Reviewer for their help in improving the manuscript

1. The authors stated the reason of excluding nitrogen from the EDX data, which is the difficulty in quantification of light elements in a matrix consists of both heavy and light elements. I can only partially agree. The authors included the results of oxygen to demonstrate the oxidation reaction of the coatings. However, oxygen is only slightly heavier than nitrogen. If the quantification of nitrogen was deemed not reliable by the authors, how would they justify the reliability of EDX data in regard to the oxygen content? I suggest authors either include the nitrogen in the final result, or offer proper explanation in the manuscript stating why they exclude the nitrogen, which is one of the major elementsforming the coating.

The authors fully agree with the Reviewer that it would be of interest to study the nitrogen content in the composition of coatings along with the oxygen content. At the same time, the EDX method is not well suited for accurate and unambiguous nitrogen content. In particular, due to the low resolution of the EDX method and the superposition of the Lα (0.452 keV) lines of titanium and the Kα (0.392 keV) lines of nitrogen, we were unable to show the presence of nitrogen in the Ti–TiN–(Ti,Mo,Al)N coating.

At the same time, the nitrogen content in the coating was determined many times during previous studies and is 48 - 52 at% (this information has been added to the manuscript). Thus, the authors considered it possible to exclude the nitrogen content curve from the graphs. While nitrogen and oxygen are light elements with similar atomic masses, oxygen is still slightly heavier and its identification using the EDX method provides more accurate results.

2. The authors stated that the EDX was obtained by manually selecting multiple spots in a pre-determined line across the sample. Did the authors control the spacing between each spot? Although I do not believe that it is necessary to keep the distance between those spots strictly the same, I DO believe that authors need to revise all the linear EDX data. Instead of smooth curves, the authors should plot the data taken from every spot, and connect the spots using straight lines. In this way, the data will be presented more accurately, and will correspond to the method better.

The graphs have been modified in accordance with the recommendations of the Reviewer. The measurement points have been marked and the data points are now connected by a straight dotted line. At the same time, the designation of data on graphs significantly complicates perception, moreover, these values are not an exact percentage, but reflect only the conditional concentration of elements. At the same time, graphs allow you to see the trend in the content of elements along the line.

Round 3

Reviewer 1 Report

The authors have made substantial improvement on the quality of the manuscript. I recommend acceptance of the revised version.