Features of Tribooxidation of the High-Entropy Coating (AlCrZrTiTa)N during Dry High-Speed Cutting

Round 1

Reviewer 1 Report

In this work, the high-entropy (AlCrZrTiTa)N coating with the high hardness, elastic modulus and high heat resistance was prepared on cemented carbide ball nose end mill in the hybrid PVD coater using a plasma-enhanced arc source, and excellent cutting performance was demonstrated in dry high-speed cutting tests of SS 304. The research results, the formation mechanisms of friction products and the analysis of friction behavior are all interesting. However, the supporting evidence of some conclusions is insufficient, and the discussion section is too concise, making the manuscript more like a “Letter” than a “Full-length article”. Therefore, authors need to supplement some research in order to reach the bar for publication. Specific comments are included below.

1. Tip: It's more appropriate display Figures after text descriptions.

2. Tip: Some information worth the attention of the reader should be marked on the Figures, such as the “Length of crater wear”, “Wear characteristics”, etc.

3. Please add specific details of coating preparation, such as PVD targets, temperature, air pressure, and other key parameters in “Materials and Methods” section.

4. In the introduction, the author mentioned “(TiZrHfNbTaY)N and (TiZrHfNbTa)N coatings have high hardness 50-60 GPa and elastic modulus more than 300 MPa, they are stable up to 1300 °C [8]”. Firstly, the unit of elastic modulus should be “GPa”. Secondly, the mechanical properties of the studied (AlCrZrTiTa)N coating are very similar to the referenced results, please provide supporting experimental results in revised manuscript.

5. Figure 1 shows the wear running-in stage of AlTiN and HE coatings with cutting length of ~ 1200 m, while, the following are discussed for wear after 130m and 260m. Firstly, the correlation before and after was poor. Authors should state the normal service life of the coating tools, and explain why the coating states after cutting 130 m and 260 m were studied in detail. Secondly, the wear of (AlCrZrTiTa)N coatings gradually stabilized after 400m of cutting and reached a stable wear stage after 700 m. What is the coating protection mechanisms after cutting 130 m and 260 m.

6. Lines 99-100: Please explain what is “The emergence of protective secondary structures”.

7. Line 124: Authors proposed “Other components don’t interact with oxygen”, which only represents the results of the Raman test, due to lack of characterization, this does not necessarily represent the true results. Please revise.

8. Lines 126-127: Are the silicon triboceramics formed on the worn surface of the HE coating after cutting to 260 m?

9. What is the Ta content in the studied coating, and why is there no SAM distribution map of Ta?

10. The protective effects and anti-wear mechanisms of oxide nitride ceramics generated during cutting friction are not discussed in detail. This is the focus and highlight of this study, please add.

11. In the conclusion, the description of “The build-up area occupies 25 and 34 % of the wear hole after cutting 130 m and 260 m” was first mentioned, please add details in the “Results and discussion” section.

• It is recommended to check whether some statements are correct.

Author Response

Thank you very much for the thorough review of the article.

1. Tip: It's more appropriate display Figures after text descriptions.

– Text and figures are placed in a different sequence in our article.

2. Tip: Some information worth the attention of the reader should be marked on the Figures, such as the “Length of crater wear”, “Wear characteristics”, etc.

– In Figure 1. The inscription along the Y axis  has been changed to “Flank wear, m.”

3. Please add specific details of coating preparation, such as PVD targets, temperature, air pressure, and other key parameters in “Materials and Methods” section.

– In text the following deatails were adds: Deposition parameters of the studied coatings were following: Pure N2 gas was fed to the chamber at pressure 4 Pa; current of arc sources –150 A; bias voltage – 100V ; substrate rotation during deposition – 5 rpm.

4. In the introduction, the author mentioned “(TiZrHfNbTaY)N and (TiZrHfNbTa)N coatings have high hardness 50-60 GPa and elastic modulus more than 300 MPa, they are stable up to 1300 °C [8]”. Firstly, the unit of elastic modulus should be “GPa”. Secondly, the mechanical properties of the studied (AlCrZrTiTa)N coating are very similar to the referenced results, please provide supporting experimental results in revised manuscript.

          –300MPa is the wrong value and 300 GPa this is the correct value.

5. Figure 1 shows the wear running-in stage of AlTiN and HE coatings with cutting length of~ 1200 m, while, the following are discussed for wear after 130m and 260m. Firstly, the correlation before and after was poor. Authors should state the normal service life of the coating tools, and explain why the coating states after cutting 130 m and 260 m were studied in detail.Secondly, the wear of (AlCrZrTiTa)N coatings gradually stabilized after 400m of cutting and reached a stable wear stage after 700 m. What is the coating protection mechanisms after cutting 130 m and 260 m.

– To explain the need to study the initial stage of wear, we have added the following text:

The friction control of cutting tools under surface – damaging conditions means the localization of the majority of external interactions at the maximum dissipation of energy, generated during friction within a thin surface layer. The running-in stage of the tool is the most important, since it determines its long-term wear resistance during cutting. As we have shown earlier, damage accumulates at this stage. This process, as well as the emerging tribooxides, are dissipative structures that dissipate the friction energy supplied from the outside. It has been estimated that a significant portion of frictional energy can be accumulated in the tribo-films [G. Fox-Rabinovich, A. Kovalev, M.H. Aguirre, K. Yamamoto, S. Veldhuis, I. Gershman, A. Rashkovskiy, J.L. Endrino, B. Beake, G. Dosbaeva, D. Wainstein, Junifeng Yuan, J.W. Bunting. Evolution of self-organization in nano-structured PVD coatings under extreme tribological conditions. Appl. Surf. sci. 297 (2014), 22-32 DOI: 10.1016/j.apsusc.2014.01.052]. In addition, dynamically emerging tribooxides radically change the thermal and frictional properties of the surface. We have shown that the nanolaminate structure of such tribooxides prevents the propagation of heat due to the fundamental physical limitations of the propagation of phonon and plasmon oscillations. [A.I. Kovalev, D.L. Wainstein, A. Yu. Rashkovskiy, R.Gago, F.Soldera, and J.L. Endrino, The confinement of phonon propagation in TiAlN/Ag multilayer coatings with anomalously low heat conductivity. Applied Physics Letters (2016) 108, 223106 http://dx.doi.org/10.1063/1.4953230]. Many tribooxides have an extremely low coefficient of friction. Thus, conditions for self-organization are created in rationally engineering protective coatings. Adaptation and self-organization takes place during friction an wear with characteristics of surface and underlying layers evolving significantly during running-in stage. The probability of implementation and the intensity of development of these processes at the initial stage of cutting are essential conditions for the appearance of stable wear. They predetermine the duration of the stage of steady wear. For these reasons, in this article, phase transformations at the initial stage of cutting have been studied in such detail.

6. Lines 99-100: Please explain what is “The emergence of protective secondary structures”.

– This term is applied to the thermodynamics of non-equilibrium phenomena in the case of consideration of phase transformations that occur under conditions of external energy dissipation .

7. Line 124: Authors proposed “Other components don’t interact with oxygen”, which only represents the results of the Raman test, due to lack of characterization, this does not necessarily represent the true results. Please revise.

We added the phrase:

The presence of a single Cr-O vibration peak among other peaks characteristic of metal-nitride interatomic bonds indicates that chromium oxides appear on the surface in the wear flanck at this stage of cutting,. The other components of the HEC nitride do not form oxide structures. In this moment takes place very early stage of chromium tribooxide forming.

One can see on Figure 3 (b) that after further cutting to 260 m chromium, tantalum, and complex zirconium– aluminium triboceramics (Al₂O₃xZrO₂, Mullite) are formed on the worn surface of the HE coating. It should be noted that Raman spectroscopy is intensively used in mineralogy and organic chemistry. It is rarely used in the study of friction and wear. Although the method of phase-structural analysis in conventional optical microscopy is very tempting. This is due to the extreme complexity of interpreting such vibrational spectra.

Moreover, we have added a new section on the study of the crystal structure of triboceramics (Fig 4-a,b)

8. Lines 126-127: Are the silicon triboceramics formed on the worn surface of the HE coating after cutting to 260 m?

Thank you. This is not silicon. But zirconia triboceramic. We have corrected the phrase

“One can see on Figure 3 (b) that after further cutting to 260 m chromium, tantalum, and complex zirconium– aluminium triboceramics (Al₂O₃xZrO₂, Mullite) are formed on the worn surface of the HE coating.”

 

9. What is the Ta content in the studied coating, and why is there no SAM distribution map of Ta?

– We have added tantalum and nitrogen distribution maps to Figure 4. And the following text:

10. The protective effects and anti-wear mechanisms of oxide nitride ceramics generated during cutting friction are not discussed in detail. This is the focus and highlight of this study, please add.

– The protective effect of triboceramics we have previously explained further in the comments to Figure 1

 

11. In the conclusion, the description of “The build-up area occupies 25 and 34 % of the wear hole after cutting 130 m and 260 m” was first mentioned, please add details in the “Results and discussion” section.

In section “Result and Discussion” we add the text: It was found that (AlCrZrTiTa)N ion plasma coating wears out through adhesion mechanism at the running-in stage at high speed dry cutting. The build-up area occupies 25 and 34 % of the wear hole after cutting 130 m and 260 m, correspondingly.

A wear-resistant coating based on a thermodynamically stable high-entropy (AlCrZrTiTa)N nitride oxidizes under extreme tribological conditions to form nanocrystalline and amorphous triboceramics.

At the initial stage of the running-in process we observe films on non-equilibrium oxide CrO₂, but later a complex of tribooxides of mullite (Al₂O₃ · ZrO₂), TaO₂ and also CrO₂ is formed on the surface of the coating.

The method EELFS made it possible to determine the amorphous-nanocrystalline structure of triboceramics based on CrO2 and Al₂O₃·ZrO₂ The nearest atomic surrounding of Cr-Cr, O-O and Cr-O and their subsequent comparison with the available literature data allow us to calculate the equilibrium lattice constants of the CrO₂ unit cell. They are obtained equal to a = 4:3754 Å and c=a = 0:5927.  The triboceramic films on base of nonequilibrium mullite Al₂O₃·ZrO₂ has amorphous structure. In the first coordination sphere, the interatomic distances Zr–O , Al–O were as 1.79 and 1.89 Å .

The emergence of such triboceramics is a consequence of nonequilibrium phase transformations in the process of tribosystem self-organization under extreme external influences (high-speed dry cutting).

For the first time, the ability to self-organize a thermodynamically stable HEC coating on a cutting tool under extreme loads during high-speed dry cutting has been established. A paradoxical phenomenon of the realization of nonequilibrium phase transformations in a thermodynamically stable high-entropy nitride is observed.

Reviewer 2 Report

The authors presented an article about “Features of tribooxidation of the high entropy coating (AlCrZrTiTa)N during dry high-speed cutting.”

The authors conducted a study on coating in this article. While the study is of current importance, it has been written in a way that can be presented at the symposium. It is unprofessional, unworthy of Coatings magazine. The main title sections are written in a very short way and the number of figures that will attract the attention of the reader is very few. These are major shortcomings.

I think the paper is not well organized and appropriate for the “Coatings” journal, but the paper will be ready for publication after major revision.

 

ü  Abstract does not look good. Please briefly mention the importance of the study. Also, please include important numerical results.

 

ü  Introduction part is very short. Please examine more recent scientific articles in detail in the introduction section.

 

ü   What is the problem? Why was the manuscript written? Please explain the reason in the introduction part. In the last paragraph of the introduction, the novelty of the study and the differences from the past in detail should be expressed.

 

ü  The material method part is very poorly written. Not having any figures is unprofessional. This may not be considered ethical for readers. Please expand the material-method section.

 

ü  How were the cutting parameters used during the experiment determined? Please explain in the manuscript.

 

ü  Attach the pictures of the cutting tool and milling machine used in the experiments to the material method section. I would also recommend adding a figure as an experiment schematic.

 

ü  Chemical components for the steel used during the tests should be given in the material method section.

 

ü  Cutting tool features are not mentioned. Please give the general properties of the cutting tool used in the experiment in the material-method section as a table.

 

ü  There are no images related to the coating. It is recommended to put a schematic figure for this part.

 

ü  The findings obtained after the experiments are far from being supported by scientific article comments. The article contains only the test results. Result-discussion section should be rewritten by supporting the obtained comments with citations.

 

ü  How were the phases obtained in the Raman spectra results verified? Please explain by citing the results in the article.

 

ü  Please fix the typographical and eventual language problems in the paper.

 

ü  Cocnlusion section can be written wider by rearranging.

 

*** Authors must consider them properly before submitting the revised manuscript. A point-by-point reply is required when the revised files are submitted.

ü  Please fix the typographical and eventual language problems in the paper.

Author Response

I think the paper is not well organized and appropriate for the “Coatings” journal, but the paper will be ready for publication after major revision.

• significant additions were made to various sections of the article..

 

ü  Abstract does not look good. Please briefly mention the importance of the study. Also, please include important numerical results.

• The article was supplemented with a new methodological section and additional numerical data were added to the abstract. The method EELFS made it possible to determine the amorphous-nanocrystalline structure of triboceramics based on CrO2 and Al₂O₃ZrO₂ The nearest atomic surrounding of Cr-Cr, O-O and Cr-O and their subsequent comparison with the available literature data allow us to calculate the equilibrium lattice constants of the CrO₂ unit cell. They are obtained equal to a = 4:3754 Å and c=a = 0:5927. The triboceramic films on base of nonequilibrium mullite Al₂O₃·ZrO₂ has amorphous structure. In the first coordination sphere, the interatomic distances Zr–O , Al–O were as 1.79 and 1.89 Å .

 

ü  Introduction part is very short. Please examine more recent scientific articles in detail in the introduction section.

• Additional text has been added to the Introduction .

The friction control of cutting tools under surface – damaging conditions means the localization of the majority of external interactions at the maximum dissipation of energy, generated during friction within a thin surface layer. The running-in stage of the tool is the most important, since it determines its long-term wear resistance during cutting. As we have shown earlier, damage accumulates at this stage. This process, as well as the emerging tribooxides, are dissipative structures that dissipate the friction energy supplied from the outside. It has been estimated that a significant portion of frictional energy can be accumulated in the tribo-films [17]. In addition, dynamically emerging tribooxides radically change the thermal and frictional properties of the surface. We have shown that the nanolaminate structure of such tribooxides prevents the propagation of heat due to the fundamental physical limitations of the propagation of phonon and plasmon oscillations. [18]. Many tribooxides have an extremely low coefficient of friction. Thus, conditions for self-organization are created in rationally engineering protective coatings. Adaptation and self-organization takes place during friction an wear with characteristics of surface and underlying layers evolving significantly during running-in stage. Adaptive processes are the driving forces of evolution in the biological and social world. Energy dissipative non-equilibrium processes, like those present in the living world, constitutes one of the major goals and challenges for future developments in modern material science [19]. Adaptation or self-organization of materials to external influences is a tempting goal when creating new materials.

In engineering systems, similar behavior is typical in particular for tribo-systems through the dynamic re-generation of tribo-films caused by tribo-chemical reactions on the friction surface as a result of interaction with the environment [20]. For instance, the ultra-speed dry machining of steels is a somewhat unique case of extreme tribo-conditions where an adaptive system can exhibit its full potential. Under such conditions, high temperatures (1000-1200 0 C) and heavy loads (3-5 GPa) develop on the friction surface of coated cutting tools. In such an open thermodynamic system, nanolaminate triboceramic films (secondary dissipative structures) dynamically appear on the friction surface. We have repeatedly demonstrated the protective role of such triboceramics for extending the service life of cutting tools with multilayer nanolaminate nitride coatings. However, this effect was observed only when the coatings had an extremely nonequilibrium chemical composition and nanostructure. Considering that alloys or nitrides of high entropy composition are currently declared promising coatings for cutting tools, a paradoxical question arises: can such thermodynamically stable materials exhibit adaptation properties. This work is devoted to the issue of the appearance of triboceramics on the surface of a high-entropy coating on a cutting tool.

The probability of implementation and the intensity of development of these processes at the initial stage of cutting are essential conditions for the appearance of stable wear. They predetermine the duration of the stage of steady wear. For these reasons, in this article, phase transformations at the initial stage of cutting have been studied in such detail.

 

ü   What is the problem? Why was the manuscript written? Please explain the reason in the introduction part. In the last paragraph of the introduction, the novelty of the study and the differences from the past in detail should be expressed.

• It is a pity that the reviewer did not understand anything in the article. It is devoted to the paradoxical problem of instability of a thermodynamically stable high-entropy coating under extreme cutting conditions.

ü  The material method part is very poorly written. Not having any figures is unprofessional. This may not be considered ethical for readers. Please expand the material-method section.

• Additional text has been added to this section.

Deposition parameters of the studied coatingswere following: Pure N₂ gas was fed to the chamber at pressure 4 Pa; current of arc sources –150 A; bias voltage – 100V ; substrate rotation during deposition – 5 rpm.

Ta MNN (1680,0 eV).

The atomic structure of the tribofilms  was investigated using Electron Energy Losses Fine structure (EELFS) analysis [21]. The fine structure of electron losses spectra in the 250 eV range near back-scattered peak (E₀=1500 eV) has been analyzed.  The diameter of spot for investigated micro area was approximately of 100 m. The fine structure of the electron spectra contains information about the structure of the nearest atomic neighbors on the surface. Mathematical spectra processing methods were used to analyze the fine structure of the electron spectra, which allows determining the lengths of the atomic bonds [21]. 

 

 

ü  How were the cutting parameters used during the experiment determined? Please explain in the manuscript.

 This informaton is in the text

ü  Attach the pictures of the cutting tool and milling machine used in the experiments to the material method section. I would also recommend adding a figure as an experiment schematic.

The optical and SEM images of cutting tools are presented on Figure 2. Research equipment is shown in Figure 1

ü  Chemical components for the steel used during the tests should be given in the material method section.

• The high-entropy (AlCrZrTiTa)N coating and chemical composition of HEC phase implies equiatomic concentration of components by definition, 20 at%.

ü  Cutting tool features are not mentioned. Please give the general properties of the cutting tool used in the experiment in the material-method section as a table.

To examine the deformation behavior of the coatings, a UMIS nanoindenter (Based Model, CSIRO) with a Berkovich indenter tip was used to indent the coatings at a high load of 400 mN. The(AlCrZrTiTa)N coating has the hardness and elastic modulus 46 and 270 GPa, respectively

 

ü  There are no images related to the coating. It is recommended to put a schematic figure for this part.

• The thickness of the coating studied was around 3μm for the film characterization.

This existing text does not require any outline

ü  The findings obtained after the experiments are far from being supported by scientific article comments. The article contains only the test results. Result-discussion section should be rewritten by supporting the obtained comments with citations.

• The part Results and discussion has been significantly revised and expanded. Added section on the study of the atomic structure of triboceramics.

ü  How were the phases obtained in the Raman spectra results verified? Please explain by citing the results in the article.

• each reference (article) in its title contains the name of the phase that was identified on the Raman spectra: ZrO, Al2O3, TiO2, γ-Al2O3, AlCrN coating, AlCrTiN coating, single-crystal aluminum nitride., tantalum oxide, TiN, CrN, TiAlN coatings, TaN/Ta hard coating. These articles contained standard or proprietary experimental data for the interpretation of Raman spectra.

.ü  Please fix the typographical and eventual language problems in the paper.

ü  Cocnlusion section can be written wider by rearranging.

• the Conclusions has been significantly revised and expanded:
• It was found that (AlCrZrTiTa)N ion plasma coating wears out through adhesion mechanism at the running-in stage at high speed dry cutting. The build-up area occupies 25 and 34 % of the wear hole after cutting 130 m and 260 m, correspondingly.
• A wear-resistant coating based on a thermodynamically stable high-entropy (AlCrZrTiTa)N nitride oxidizes under extreme tribological conditions to form nanocrystalline and amorphous triboceramics.
• At the initial stage of the running-in process we observe films on non-equilibrium oxide CrO₂, but later a complex of tribooxides of mullite (Al₂O₃ ZrO₂), TaO₂ and also CrO₂ is formed on the surface of the coating.
• The method EELFS made it possible to determine the amorphous-nanocrystalline structure of triboceramics based on CrO2 and Al₂O₃ZrO₂ The nearest atomic surrounding of Cr-Cr, O-O and Cr-O and their subsequent comparison with the available literature data allow us to calculate the equilibrium lattice constants of the CrO₂ unit cell. They are obtained equal to a = 4:3754 Å and c=a = 0:5927. The triboceramic films on base of nonequilibrium mullite Al₂O₃·ZrO₂ has amorphous structure. In the first coordination sphere, the interatomic distances Zr–O , Al–O were as 1.79 and 1.89 Å .
• The emergence of such triboceramics is a consequence of nonequilibrium phase transformations in the process of tribosystem self-organization under extreme external influences (high-speed dry cutting).
• For the first time, the ability to self-organize a thermodynamically stable HEC coating on a cutting tool under extreme loads during high-speed dry cutting has been established. A paradoxical phenomenon of the realization of nonequilibrium phase transformations in a thermodynamically stable high-entropy nitride is observed.

Reviewer 3 Report

Rejected. My comments are in the file attached.

Comments for author File: Comments.pdf

Author Response

• The reviewer did not understand the title and purpose of this article. It is not devoted to the features of cutting stainless steels, but to the paradoxical phenomenon of adaptation of a thermodynamically stable coating based on HEC nitride during its transformation with the formation of triboceramics on the wear surface. The results of Auger microscopy and other methods of electron spectroscopy, as well as Raman spectroscopy, have never required the statistical processing that the reviewer requires. The reviewer has no experience in applying structural methods for the analysis of phase transformations at the atomic and electronic levels. And it requires statistical processing of such results.
• “• Scanning Auger Mapping (SAM: is confusing, this is a regular scanning.”

–The reviewer does not have his own experience in electron spectroscopy. And for this reason he is embarrassed. Other examples of our work in the area of Auger and Plasmon electron microscopy: G. Fox-Rabinovich, A. Kovalev, S. Veldhuis, K. ; A. I. Kovalev, A. Yu. Rashkovskiy, D. L. Wainstein, R. Gago, F. Soldera, J. L. Endrino. Influence of electronic structure, plasmon-phonon and plasmon-polariton excitations on anomalously low heat conductivity in TiAlN/Ag nanoscale multilayer coatings. Curr.Appl.Phys. 16 (2016) 459-468  http://dx.doi.org/10.1016/j.cap.2016.01.012

 In the 2. Materials and Methods, the authors added text about the method AEM: The Auger electron spectroscopy investigations were carried out using multifunctional electron spectrometer ESCALAB MK2 (VG) Auger gun Leg 2000) and EMU-50 source of monochromatic electrons (E0 ¼ 0e100 eV, FWHM ¼ 17 meV).. The samples were cleaned using Ar ions in the preparation chamber of spectrometer at a pressure of 10⁵ Pa, an accelerating voltage of 8 kV and a current of 20 mA.. The parameters of spectra acquisition were selected to provide high energy resolution of the spectrum full width at half maximum (FWHM) about 20 meV for high resolution electron energy loss spectroscopy (HREELS) investigations. Auger electron microscopy (AEM) was applied for imaging of elements distributions on the HEC coatings in wear area at a primary electron energy E0 =1450 eV. Resolution of images was 256 256 pixels at 10000 magnification. The topographic contrast was suppressed by image acquisition software.

 

 

1. The authors have their own view and concept of interpretation of self-organization of PVD coatings during cutting. The authors have extensive experience in the study of non-equilibrium processes during cutting, including the cutting of austenitic steels and alloys: German Fox-Rabinovich at all, The Relationship between Cyclic Multi-Scale Self-Organized Processes and Wear-Induced Surface Phenomena under Severe Tribological Conditions Associated with Buildup Edge Formation, Coatings 2021, 11, 1002. https://doi.org/10.3390/coatings11081002; Guerman Fox-Rabinovitch, Goulnara Dosbaeva, Anatoly Kovalev, Iosif Gershman, Kenji Yamamoto. Edinei Locks, Jose Paiva, Egor Konovalov and Stephen Veldhuis. Enhancement ofMulti-Scale Self-Organization Processes during Inconel DA 718 Machining through the Optimization of TiAlCrSiN/TiAlCrN Bi-Nano-Multilayer Coating Characteristics. Materials 2022, 15, 1329. https://doi.org/10.3390/ma15041329

 

– The authors have their own rich experience in studying the features of oxidation of such wear-resistant coatings: G.K. Dosbaeva, S.C. Veldhuis, K. Yamamoto, D.S. Wilkinson, B.D. Beake, N. Jenkins, A. Elfizy, G.S. Fox-Rabinovich, Oxide scales formation in nano-crystalline TiAlCrSiYN PVD coatings at elevated temperature, Int. Journal of Refractory Metals & Hard Materials 28 (2010) 133–141, doi:10.1016/j.ijrmhm.2009.09.003;; , Dmitry Wainstein and Anatoly Kovalev, Tribooxidation as a Way to Improve theWear Resistance of Cutting Tools, Coatings 2018, 8, 223; doi:10.3390/coatings8060223;

A.I. Kovalev, Vladimir Olegovich Vakhrushev, Egor Pavlovich Konovalov, German Simonovich Fox-Rabinovich, Features of the Oxidation of Multilayer (TiAlCrSiY)N/(TiAlCr)N Nanolaminated PVD Coating during Temperature Annealing, 2023 Coatings 13(2):287, DOI:10.3390 /coatings13020287.

– The authors have made numerous additions to the article to improve its understanding by readers.

Reviewer 4 Report

The material presented in the manuscript is quite interesting. However, the description is very brief; the article is more of a patent description than a scientific journal publication.

For a journal publication, the article should be expanded. It is necessary to increase the experimental part. After all, of the experimental research methods, only Raman Spectroscopy, Scanning Auger spectroscopy and Cutting testing are described. And the article does not say anything about electrochemical methods, although the results of such a study would be very interesting. Since the coating had an amorphous nanocrystalline microstructure, very important information could be given by an X-ray study or (even better) an electron diffraction investigation. I no longer mention the computational modeling of the coating, which could also decorate the scientific publication.

Author Response

The material presented in the manuscript is quite interesting. However, the description is very brief; the article is more of a patent description than a scientific journal publication.

For a journal publication, the article should be expanded. It is necessary to increase the experimental part. After all, of the experimental research methods, only Raman Spectroscopy, Scanning Auger spectroscopy and Cutting testing are described. And the article does not say anything about electrochemical methods, although the results of such a study would be very interesting. Since the coating had an amorphous nanocrystalline microstructure, very important information could be given by an X-ray study or (even better) an electron diffraction investigation. I no longer mention the computational modeling of the coating, which could also decorate the scientific publication.

• The authors have made numerous additions to the article to improve its understanding by readers.
• To determine the amorphization of triboceramics, the authors used the method of analysis of the nearest atomic surrounding EELFS of the thinnest films similar to EXAFS. These studies were additionally presented in the article at the suggestion of the reviewer.
• Unfortunately, we do not have methods of electrochemical analysis and did not pursue the goal of studying the corrosion resistance of cutting tools.

The Auger electron spectroscopy investigations were carried out using multifunctional electron spectrometer ESCALAB MK2 (VG) Auger gun Leg 2000) and EMU-50 source of monochromatic electrons (E0 ¼ 0e100 eV, FWHM ¼ 17 meV).. The samples were cleaned using Ar ions in the preparation chamber of spectrometer at a pressure of 10⁵ Pa, an accelerating voltage of 8 kV and a current of 20 mA.. The parameters of spectra acquisition were selected to provide high energy resolution of the spectrum full width at half maximum (FWHM) about 20 meV for high resolution electron energy loss spectroscopy (HREELS) investigations. Auger electron microscopy (AEM) and electron microscopy was applied for imaging of elements distributions on the HEC coatings in wear area at a primary electron energy E0 =1450 eV. Resolution of images was 256 256 pixels at 10000 magnification. The topographic contrast was suppressed by image acquisition software.

Round 2

Reviewer 1 Report

1. There are many formatting errors in the manuscript. The Figures, Text, and Label format in revised manuscript need to be further polished, revised and unified, you can refer to the format of other “Coatings” published papers. Please take it seriously, an academic paper should not only be rigorous and scientific in content, but also ensure the quality of the paper writing and picture production

2. Many comments are not well solved, such as comment 1, 2, 4, and 6. Please explain "The emergence of protective secondary structures" mentioned in Comment 6 in order to facilitate readers' understanding.

• The English language needs polishing.

Author Response

1. There are many formatting errors in the manuscript. The Figures, Text, and Label format in revised manuscript need to be further polished, revised and unified, you can refer to the format of other “Coatings” published papers. Please take it seriously, an academic paper should not only be rigorous and scientific in content, but also ensure the quality of the paper writing and picture production

– Figures and figure captions formatted

2. Many comments are not well solved, such as comment 1, 2, 4, and 6. Please explain "The emergence of protective secondary structures" mentioned in Comment 6 in order to facilitate readers' understanding.
3. Tip: It's more appropriate display Figures after text descriptions.

– Text and figures are placed in a different sequence in our article.

2. Tip: Some information worth the attention of the reader should be marked on the Figures, such as the “Length of crater wear”, “Wear characteristics”, etc.

– In Figure 1. The inscription along the Y axis  has been changed to “Flank wear, m.”

4. In the introduction, the author mentioned “(TiZrHfNbTaY)N and (TiZrHfNbTa)N coatings have high hardness 50-60 GPa and elastic modulus more than 300 MPa, they are stable up to 1300 °C [8]”. Firstly, the unit of elastic modulus should be “GPa”. Secondly, the mechanical properties of the studied (AlCrZrTiTa)N coating are very similar to the referenced results, please provide supporting experimental results in revised manuscript.

          –300MPa is the wrong value and 300 GPa this is the correct value. We've made this change

6. Lines 99-100: Please explain what is “The emergence of protective secondary structures”.

– This term is applied to the thermodynamics of non-equilibrium phenomena in the case of consideration of phase transformations that occur under conditions of external energy dissipation

• We add to the text: This process, as well as the emerging tribooxides, are dissipative structures that dissipate the friction energy supplied from the outside. It has been estimated that a significant portion of frictional energy can be accumulated in the tribo-films [17].

Reviewer 2 Report

• It is a pity that the reviewer did not understand anything in the article….

 

I blame the authors for their response to a comment. I only suggested the necessary corrections for the symposium, so that a work of poor quality, which could hardly be considered, can be published in an important journal of a valuable publisher.

 

The authors need to correct this style.

Comments for author File: Comments.docx

Author Response

1. I blame the authors for their response to a comment. I only suggested the necessary corrections for the symposium, so that a work of poor quality, which could hardly be considered, can be published in an important journal of a valuable publisher.

We took into account all 14 comments and advice of the reviewer. And with gratitude made all corrections and additions. Our reaction was and remains harsh to the remark: «What is the problem? Why was the manuscript written? Please explain the reason in the introduction part. In the last paragraph of the introduction, the novelty of the study and the differences from the past in detail should be expressed.»

In order to further clarify the topic of the article and the novelty, we have significantly expanded the introduction, we made an addition to the conclusions: The emergence of such triboceramics is a consequence of nonequilibrium phase transformations in the process of tribosystem self-organization under extreme external influences (high-speed dry cutting).

For the first time, the ability to self-organize a thermodynamically stable HEC coating on a cutting tool under extreme loads during high-speed dry cutting has been established. A paradoxical phenomenon of the realization of nonequilibrium phase transformations in a thermodynamically stable high-entropy nitride is observed.

The article has a hidden meaning and an implicit criticism of the fashion for high-entropy materials, which are promoted as extremely stable. We have shown that they, like conventional materials, are subject to change. under external conditions very far from equilibrium

We apologize to the reviewer for the harsh response to one of his comments.

Reviewer 3 Report

see, the file attached. My decision is the same, but encourage the authors to improve it.

Comments for author File: Comments.pdf

Author Response

The reviewer, in addition to the comments in the first review, added new comments and advice.

The reviewer repeatedly insists on additional research and discussions with the authors of other articles that are outside the scope of this work. The reviewer strongly imposes the need for a discussion with an article that, in terms of topic and meaning, has nothing to do with the behavior of high-entropy coatings when cutting steel. The reviewer proposes to study microstresses in our coating according to the Stoney’s method for thin transparent coatings using the method of optical interferometry. This strong advice in our case cannot be implemented due to two circumstances: HEC coatings are not transparent; Structural stresses, adhesion of the coating are not the aim of this work. Our coating was applied by PVD deposition. And the reviewer insistently demands to compare this instrumental coating with transparent photoelastic circular disks made of PSM-1 . This advice is incredible and unacceptable.

1. Figure 1 must be eliminated, are simple pictures of lab devices. No special meaning.

– We agree with you, however we added this drawing at the request of another reviewer. Many requirements of the reviewers conflict  each other and the authors are confused, but they strive to improve the text of the article.

1. Figure 2: how many results did you check, only one tool? Please, this is key, check for instance the new trends in testing tool, as it is proposed in https://doi.org/10.1177/0954406215616145 with better performance than ISO testing standards. Coating for cutting tools is a real business and it must follow long and statistical testing.

• This work was not intended to bring a new HEC coating to market and test its full life cycle as done by Fernández-Valdivielso, A., López de Lacalle, L., Urbikain, G., & Rodriguez, A. ( 2016). Detecting the key geometrical features and grades of carbide inserts for the turning of nickel-based alloys concerning surface integrity. Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science, 230(20), 3725–3742. doi:10.1177/0954406215616145. The authors are grateful to the referee for suggesting new methods for testing coated cutting tools. The authors devoted their early work to this issue, which were published in the chapter "Geometrical adaptation of cutting tools" in book: Self-organization during friction: Advance Surface Engineered materials, edited by G.S. Fox-Rabinovich and G.E. Tottrn, Taylor and Francis Group. Boca Raton, NY, USA (2006) 412-455. The purpose of this work is to determine the ability of HEC coating to self-organize by forming triboceramics on the surface under extreme cutting conditions. For this reason, the authors do not consider it appropriate to include in the article a discussion on topics that are far from the purpose of the work. In this work, 8 cutting inserts were studied, for which the width of the wear hole was determined at various cutting times from 130 to 1200m. These data are plotted in Figure 2. This phrase was added to the 2 Materials and methods

1. Figure 3-a, no scale. We have added the designation of the type of insert and the manufacturer in the caption to the figure. This is enough to understand the dimensions of the insert: Optical image of cutting insert type DNMM-OR Sandvic Coromant.
2. Raman spectroscopy and Auger electron microscopy were used. Please define the equipment and resolution, is it similar to Renishaw ones?

• All data on equipment for Auger microscopy and Raman spectroscopy are given in the Materials and Methods section. Figure 1 shows photographs of equipment
• We add to the text of 2. Materials and Methods: When recording Raman spectra, the device automatically determines the wavelength of laser radiation, the line half-width in the current climatic conditions, and adjusts the intensity and energy scales of the recorded spectra.
• Calibration of an Auger electron spectrometer using ISO 17973:2016 International Standard is performed by using of copper, gold and silver reference standard samples in order to measure the kinetic energies of selected Auger electron peaks. These reference materials are chosen as they provide one Auger electron peak in the high energy range, one in the middle range and one at low energies. Standard spectrometer control operations made it possible to align the instrument. The Auger electron spectroscopy investigations were carried out using multifunctional electron spectrometer ESCALAB MK2 (VG) Auger gun Leg 200) and EMU-50 source of monochromatic electrons (E0 ¼ 0e100 eV, FWHM ¼ 17 meV).. The samples were cleaned using Ar ions in the preparation chamber of spectrometer at a pressure of 10⁵ Pa, an accelerating voltage of 8 kV and a current of 20 mA.. The parameters of spectra acquisition were selected to provide high energy resolution of the spectrum full width at half maximum (FWHM) about 20 meV for high resolution electron energy loss spectroscopy (HREELS) investigations. Auger electron microscopy (AEM) and electron microscopy was applied for imaging of elements distributions on the HEC coatings in wear area at a primary electron energy E0 =1450 eV. Resolution of images was 256 256 pixels at 10000 magnification. The topographic contrast was suppressed by image acquisition software.

Reviewer 4 Report

I recommend the manuscript for publication.

Author Response

Thank you very much for your work. Most of the comments of the reviewers contradicted each other. And it was very difficult for us to maneuver between them.

With best wishes!