Characterization and Wear Response of Magnetron Sputtered W–B and W–Ti–B Coatings on WC–Co Tools

Round 1

Reviewer 1 Report

The paper is an interesting tribological study of the of W-B and W-Ti-B magnetron sputtered coatings on WC tools, compared to conventional WC-Co inserts. The study was elaborated using confocal microscopy, SEM/EDS, XRD, microhardness, roughness testing, wear and machinability testing as the principal investigation techniques. The subject is within the scope of the Journal and presents industrial interest. The language and grammar needs attention to avoid minor typographical errors and spelling mistakes. The paper is considered suitable for publication provided some minor comments and suggested revisions marked-up in the attached document.

Comments for author File: Comments.pdf

Author Response

At the beginning we want to thank you for your valuable comments and suggestions.

All suggested improvements have been done.

• figure 1 (page 3), figure 3 (page 4/5) and figure 8b (page 9) were enlarged and sharpened. In the caption of figure 10 - “Fig. 9” was changed to “Fig.10”.
• All language corrections were done and introduced in “track changes” mode.
• All missing or used in wrong format units were added and corrected.
• In Table 1. (page 5 )one decimal digit as the most significant one is used.
• In line 209 p. 8 “visible as a picks” was added for explaining.
• References were corrected.

Reviewer 2 Report

The authors present an interesting manuscript with solid results on two sputter coated wear-resistant coatings. The drawn conclusions are based on the measured results. In order to improve the presentation, however, a few minor improvements are recommended:

1. Figures 1 and 5 should be enlarged to improve the visibility of the shown contents.

2. In table 5, the authors might consider using an exponential number format and a reduced number of digits that is representative of measurement errors, e.g. 1.06*10^6 µm³

3. The English language shows some flaws, in particular with the use of articles and between singular and plural, as well as in differentiating between a piece equipment (e.g. a microscope) and a technique in general (e.g. microscopy). It is recommended to seek support with a language editing service.

Author Response

1. Figures 1 and 5 should be enlarged to improve the visibility of the shown contents.

Figures 1 and 5 have been enlarged.

2. In table 5, the authors might consider using an exponential number format and a reduced number of digits that is representative of measurement errors, e.g. 1.06*10^6 µm³

Table 5 has been corrected as follow:

Table 5. Volume of loss material after wear tests.

3. The English language shows some flaws, in particular with the use of articles and between singular and plural, as well as in differentiating between a piece equipment (e.g. a microscope) and a technique in general (e.g. microscopy). It is recommended to seek support with a language editing service.

The English language has been improved by language editing service.

Reviewer 3 Report

in file

Comments for author File: Comments.pdf

Author Response

At the beginning we want to thank you for your valuable comments and suggestions.

• New references (1, 7, 17, 18 ) were added to the introduction
• The hypothesis was formulated (page 2, line 72-74):

“The described properties of (W,Ti)B2 as well as α-WB2 films indicate great potential of using them as protective coatings for cutting tools. So far, there has been no research on the behaviour of such layers under operating condition.”

• All language corrections were done and introduced in “track changes” mode.

Reviewer 4 Report

The article discusses the properties of coatings W-B and W-Ti-B, deposited on a carbide substrate.

The article is poorly written, the English language needs serious correction, examining the coatings using only an optical microscope is not serious. A number of the authors' claims appear controversial. Unfortunately, I cannot recommend this article for publication.

1. "Vickers hardness of 3630 ± 260 HV0.02 (35.6 ± 2.5 GPa)" - a large amount of teutology: Vickers hardness = HV, why specify it simultaneously in two systems?

2. A 30% reduction in flank wear provides at least any coating, even the simplest TiN usually shows the best results.

3. The abstract describes the research methodology in too much detail. We need to pay more attention to the results obtained.

4.Line 30 - why is it only resistant to abrasion? Is it not resistant to other types of wear?

5. Line 33-34 If coatings for cutting tools are being investigated, what is the interest in adhesion to stainless steel? Cutting tools are not made of stainless steel.

6. Line 46 - [12, 13, 14, 3] references must be submitted in ascending order.

7. Line 50 - in ref. [15], "ref." is superfluous.

8. The introduction must be changed. It makes no sense to talk about what research was done. It is necessary to justify the choice of the composition and parameters of the coating.

9. Figure 1. Is this the authors' own development or a standard device? If this is a standard device, I see no point in giving this image (all the more, not very good quality).

10. Fig 3. The description is clearly not enough. What do these images mean? What are they needed for? what is the point in them? 11 images and just one line of description!

11. Fig 5. It is very difficult to see any difference between (b) and (c). Again, it is not clear what is the meaning of these images. Very superficial description!

12. Since there is a much more informative Figure 6, I recommend deleting Figure 5.

13. Figure 8, line 207 "small carbides in matric were observed" - where can you see it? How to understand that these are carbides?

14. What's the point in ri 7? Obviously, after the deposition of the coating, the surface morphology changes, but this should be investigated, at least using an electron microscope, at high magnification, it is desirable to examine a cross section, etc.

15. Lines 215 - 231. As mentioned above, it is not clear why the authors give simultaneously two systems of notation for hardness. What's the point of this?

16. Line 258 - how did the authors understand that this is abrasive wear, and not, for example, adhesive wear?

17. Line 263 - I advise the authors to better understand the theory of cutting. Where they see "build up edge" - there I see only the adhesion of the processed material.

18. Where is the wear-time graph? How many tests were carried out? What are the statistics?

Author Response

1. "Vickers hardness of 3630 ± 260 HV0.02 (35.6 ± 2.5 GPa)" - a large amount of teutology: Vickers hardness = HV, why specify it simultaneously in two systems?

Vickers hardness was specify in two systems kg/mm² and GPa because recently many publication on superhard films use GPa as a hardness unit. This was introduced to help the readers understanding of the article.

2. A 30% reduction in flank wear provides at least any coating, even the simplest TiN usually shows the best results.

A 30% reduction in flank wear is promising result. It was obtained in one cutting condition. Future extended tests may show better results for other cutting condition. P. Dearnley et al. [7] obtaned worst results when examined turing pure titanium with tools covered CrB2, Mo2B5 and WB coatings. Only the WB crystalline coated WC–Co exhibited a better wear resistance (about 40%) compared to uncoated WC–Co, whilst the other boride coated WC–Co variants proved to be significantly worse. J. Paiva et al. [11] showed that the TiB2 coating is efficient only under roughing at low speeds (45 m/min with strong build up edge formation). In contrast, it shows similar wear performance to the uncoated tool under finishing operations at higher cutting speeds when cratering wear predominates. There is no universal coating for various machining condition and new materials for coatings are still wanted.

3. The abstract describes the research methodology in too much detail. We need to pay more attention to the results obtained

The abstract was changed . Some details has been removed.

In this work, α-WB₂ and (W,Ti)B₂ borides were applied as wear-resistant coatings to commercial WC-Co cutting inserts. Properties of coatings deposited by magnetron sputtering on WC-Co tools were studied. The crystal structure and chemical composition were analyzed. Vickers hardness and surface roughness were determined and wear test in semi-dry conditions was performed. The W-B and W-Ti-B coatings deposited on WC-Co substrate were smooth and very hard. However, titanium alloy W-B films with Vickers hardness of 3630 ± 260 HV_0.02 (35.6 ± 2.5 GPa) were characterized by lower adhesion to the substrate, influencing the wear mechanism. Turning tests carried out on 304 stainless steel showed that the W-B film caused less wear compared to uncoated insert. Moreover, when W-B coating was applied, flank wear was reduced by 30% compared to uncoated WC-Co insert. Additionally, coating prevented chipping of the edge during cutting under test conditions. The research shows that W-B film deposited by magnetron sputtering has great potential as a coating for cutting tools for difficult-to-cut materials..

4. Line 30 - why is it only resistant to abrasion? Is it not resistant to other types of wear?Dearnley et al. [9] analysed flank wear of cutting tools. On the base of this work it may be concluded that resistance to abrasion wear is responsible of this type of wear.

5. If coatings for cutting tools are being investigated, what is the interest in adhesion to stainless steel? Cutting tools are not made of stainless steel.

Adhesion was investigated in previous works [4, 10]. Study on films deposited on stainless steel in the same condition as in this work was done. In this work we investigated only WC-Co substrates.

6. Line 46 - [12, 13, 14, 3] references must be submitted in ascending order. Order of reference was changed.

7. Line 50 - in ref. [15], "ref." is superfluous.

As suggested "ref." has been removed.

8. The introduction must be changed. It makes no sense to talk about what research was done. It is necessary to justify the choice of the composition and parameters of the coating.

In presented work the literature review on current developments in the field of tungsten borides and alloying them with titanium was made to show the potential of these layers in industry applications. The influence of  deposition parameters and also composition of coatings on their properties were studied in previous work of our team. For example the effect of target sputtering power and ambient gas pressure were studied in :

2016. Chrzanowska , Ł. Kurpaska, M. Giżyński, J. Hoffman, Z. Szymański and T. Mościcki, "Fabrication and characterization of superhard tungsten boride layers," Ceramics International 42, p. 12221–12230, 2016.

- substrate temperature:

2018. Chrzanowska-Giżyńska, P. Denis, S. Woźniacka and . Ł. Kurpaska, "Mechanical properties and thermal stability of tungsten boride films deposited by radio frequency magnetron sputtering," Ceramics International 44, pp. 19603-19611, 2018.

and composition:

2020. Moscicki, R. Psiuk, H. Slominska , N. Levintant-Zayonts, D. Garbiec, M. Pisarek, P. Bazarnik, S. Nosewicz and J. Chrzanowska-Giżyńska, "Influence of overstoichiometric boron and titanium addition on the properties of RF magnetron sputtered tungsten borides," Surface and Coatings Technology 390, p. 125689, 2020.

In experimental procedure (line 89-91 p.2) the sentence:

“On the base of our earlier studies on sputtering power and gas pressure [11], substrate temperature [10] and composition [4] optimal parameters of deposition were chosen.”  was added.

9. Figure 1. Is this the authors' own development or a standard device? If this is a standard device, I see no point in giving this image (all the more, not very good quality).

Currently it is not standard device. Quality of figure was improved.

10. Fig 3. The description is clearly not enough. What do these images mean? What are they needed for? what is the point in them? 11 images and just one line of description!

The deposited coatings are smooth across measured area. All elements are uniformly distributed and the mcro-segregation of elements was not observed. Exact analysis of presented composition is described and discussed below figure 3. (line162-170 p.6)

11. Fig 5. It is very difficult to see any difference between (b) and (c). Again, it is not clear what is the meaning of these images. Very superficial description! Since there is a much more informative Figure 6, I recommend deleting Figure 5.

The photos have been sharpened and now more details can be seen. Figure 5 caption has been changed. Figure 6 shows only waviness and impurities on 1x1 mm area at big magnification on Z axis. The observed area of Figure 5 is about 10 times larger (100x100 um) what cased that microstructure can be observed.

The caption of figure 5 was changed:

Surface topography after polishing: (a) WC-Co; (b) sample surface after deposition W-B coating on WC-Co substrate; (c) topography of the W-Ti-B-film on WC-Co substrate (confocal microscope).

12. Figure 8, line 207 "small carbides in matric were observed" - where can you see it? How to understand that these are carbides?

The WC grains have characteristic sharp shape. Explanation has been added (line 216):

In case of WC-Co insert small carbides with characteristic sharp shape in matrix were observed (Figure 7a).

13. Line 258 - how did the authors understand that this is abrasive wear, and not, for example, adhesive wear?

The appearance of the surface after turning test indicates abrasive wear. Characteristic scratches on surface are visible, no particles of the cut material are present.

14. Line 263 - I advise the authors to better understand the theory of cutting. Where they see "build up edge" - there I see only the adhesion of the processed material.

The description has been modified. The adhesive wear mechanism may led to build up edge and  this kind of wear was observed. Additional figure c’ was added with example of build up edge.

The adhesive wear was stated in case of the coated insert. Figure 10b and c show adhere material. In Figure 10c and 10c’ profile of the cutting edge after machining is presented. The change in insert geometry caused by build-up was  observed in two cases. This mechanism is caused by pressure welding of the chip to the insert. It is most common during machining of sticky materials with low cutting speed. To prevent this kind of wear highest speed should be applied.

15. Where is the wear-time graph? How many tests were carried out? What are the statistics?

The turning tests were done for one cutting lengh. The test was repeated 5 times and results of measured flank wear with standard deviation are shown in Table 6.

The English language in manuscript has been improved by professional language editing service. All language corrections were done and introduced in “track changes” mode.

Round 2

Reviewer 4 Report

Author's Notes

I didn't see any fundamental changes in the article. Unfortunately, I have no reason to change my mind and recommend this article for publication. 

1. "Vickers hardness of 3630 ± 260 HV0.02 (35.6 ± 2.5 GPa)" - a large amount of teutology: Vickers hardness = HV, why specify it simultaneously in two systems?

Vickers hardness was specify in two systems kg/mm² and GPa because recently many publication on superhard films use GPa as a hardness unit. This was introduced to help the readers understanding of the article.

Any tech-savvy reader can easily match one system to another. Did the authors use two different methods for measuring hardness? If yes, then it is necessary to explain why this is needed.

1. A 30% reduction in flank wear provides at least any coating, even the simplest TiN usually shows the best results.

A 30% reduction in flank wear is promising result. It was obtained in one cutting condition. Future extended tests may show better results for other cutting condition. P. Dearnley et al. [7] obtaned worst results when examined turing pure titanium with tools covered CrB2, Mo2B5 and WB coatings. Only the WB crystalline coated WC–Co exhibited a better wear resistance (about 40%) compared to uncoated WC–Co, whilst the other boride coated WC–Co variants proved to be significantly worse. J. Paiva et al. [11] showed that the TiB2 coating is efficient only under roughing at low speeds (45 m/min with strong build up edge formation). In contrast, it shows similar wear performance to the uncoated tool under finishing operations at higher cutting speeds when cratering wear predominates. There is no universal coating for various machining condition and new materials for coatings are still wanted.

I have been in the business of cutting tool coatings for over 25 years. In particular, he was engaged in turning and milling titanium alloys. Even fairly simple coatings based on ZrN can reduce flank wear by 2 or more times. 30% is the level of statistical error.

Despite the fact that only 5 tests were carried out (according to the authors), a decrease in wear by 30% may well be a statistical error. Such a decrease can make some sense if it is confirmed by hundreds of experiments (in this case, it is possible to really determine and eliminate the statistical error)

 " W-B film deposited by magnetron sputtering has great potential as a coating for cutting tools" - while wear has decreased by only 30%

2. The abstract describes the research methodology in too much detail. We need to pay more attention to the results obtained

The abstract was changed . Some details has been removed.

In this work, α-WB₂ and (W,Ti)B₂ borides were applied as wear-resistant coatings to commercial WC-Co cutting inserts. Properties of coatings deposited by magnetron sputtering on WC-Co tools were studied. The crystal structure and chemical composition were analyzed. Vickers hardness and surface roughness were determined and wear test in semi-dry conditions was performed. The W-B and W-Ti-B coatings deposited on WC-Co substrate were smooth and very hard. However, titanium alloy W-B films with Vickers hardness of 3630 ± 260 HV_0.02 (35.6 ± 2.5 GPa) were characterized by lower adhesion to the substrate, influencing the wear mechanism. Turning tests carried out on 304 stainless steel showed that the W-B film caused less wear compared to uncoated insert. Moreover, when W-B coating was applied, flank wear was reduced by 30% compared to uncoated WC-Co insert. Additionally, coating prevented chipping of the edge during cutting under test conditions. The research shows that W-B film deposited by magnetron sputtering has great potential as a coating for cutting tools for difficult-to-cut materials..

Line 30 - why is it only resistant to abrasion? Is it not resistant to other types of wear?

Dearnley et al. [9] analysed flank wear of cutting tools. On the base of this work it may be concluded that resistance to abrasion wear is responsible of this type of wear.

 Why does abrasion occur? How do the authors distinguish abrasive wear (due to abrasive grains) from adhesive wear (due to the formation and rupture of adhesive bonds between the workpiece material and the tool material)?

If coatings for cutting tools are being investigated, what is the interest in adhesion to stainless steel? Cutting tools are not made of stainless steel.

Adhesion was investigated in previous works [4, 10]. Study on films deposited on stainless steel in the same condition as in this work was done. In this work we investigated only WC-Co substrates.

1. Line 46 - [12, 13, 14, 3] references must be submitted in ascending order. Order of reference was changed.
2. Line 50 - in ref. [15], "ref." is superfluous.

As suggested "ref." has been removed.

3. The introduction must be changed. It makes no sense to talk about what research was done. It is necessary to justify the choice of the composition and parameters of the coating.

 It is not enough just to add two short phrases about "great potential for using". Why was this wear-resistant coating chosen? Why is it better than TiN, ZrN, (Ti, Al) N or even a large number of different coatings?

In presented work the literature review on current developments in the field of tungsten borides and alloying them with titanium was made to show the potential of these layers in industry applications. The influence of  deposition parameters and also composition of coatings on their properties were studied in previous work of our team. For example the effect of target sputtering power and

ambient gas pressure were studied in :

1. Chrzanowska , Ł. Kurpaska, M. Giżyński, J. Hoffman, Z. Szymański and T. Mościcki, "Fabrication and characterization of superhard tungsten boride layers," Ceramics International 42, p. 12221–12230, 2016.

- substrate temperature:

1. Chrzanowska-Giżyńska, P. Denis, S. Woźniacka and . Ł. Kurpaska, "Mechanical properties and thermal stability of tungsten boride films deposited by radio frequency magnetron sputtering," Ceramics International 44, pp. 19603-19611, 2018.

and composition:

1. Moscicki, R. Psiuk, H. Slominska , N. Levintant-Zayonts, D. Garbiec, M. Pisarek, P. Bazarnik, S. Nosewicz and J. Chrzanowska-Giżyńska, "Influence of overstoichiometric boron and titanium addition on the properties of RF magnetron sputtered tungsten borides," Surface and Coatings Technology 390, p. 125689, 2020.

In experimental procedure (line 89-91 p.2) the sentence:

“On the base of our earlier studies on sputtering power and gas pressure [11], substrate temperature [10] and composition [4] optimal parameters of deposition were chosen.”  was added.

4. Figure 1. Is this the authors' own development or a standard device? If this is a standard device, I see no point in giving this image (all the more, not very good quality).

Currently it is not standard device. Quality of figure was improved.

 This drawing has never been published before? (If published, an appropriate reference is needed). What is the peculiarity of this method, if it differs from the standard one?

5. Fig 3. The description is clearly not enough. What do these images mean? What are they needed for? what is the point in them? 11 images and just one line of description!

The deposited coatings are smooth across measured area. All elements are uniformly distributed and the mcro-segregation of elements was not observed. Exact analysis of presented composition is described and discussed below figure 3. (line162-170 p.6)

 This can be written in one line. These images do not contain any information relevant to the reader.

6. Fig 5. It is very difficult to see any difference between (b) and (c). Again, it is not clear what is the meaning of these images. Very superficial description! Since there is a much more informative Figure 6, I recommend deleting Figure 5.

 In my opinion, the image quality has decreased.

The photos have been sharpened and now more details can be seen. Figure 5 caption has been changed. Figure 6 shows only waviness and impurities on 1x1 mm area at big magnification on Z axis. The observed area of Figure 5 is about 10 times larger (100x100 um) what cased that microstructure can be observed.

After processing, Fig 5 b c became completely unacceptable. These images are absolutely insufficient for any kind of analysis.

The caption of figure 5 was changed:

Surface topography after polishing: (a) WC-Co; (b) sample surface after deposition W-B coating on WC-Co substrate; (c) topography of the W-Ti-B-film on WC-Co substrate (confocal microscope).

7. Figure 8, line 207 "small carbides in matric were observed" - where can you see it? How to understand that these are carbides?

The WC grains have characteristic sharp shape. Explanation has been added (line 216):

In case of WC-Co insert small carbides with characteristic sharp shape in matrix were observed (Figure 7a).

"with characteristic sharp shape" - characteristic for what? Label them in the image, research them if they are important for the topic of the article. Otherwise, it is not clear why the image in Fig. 7 is needed.

8. Line 258 - how did the authors understand that this is abrasive wear, and not, for example, adhesive wear?

The appearance of the surface after turning test indicates abrasive wear. Characteristic scratches on surface are visible, no particles of the cut material are present.

 That is, the authors believe that if there is no buildup of the processed material, then there is no adhesive wear?

9. Line 263 - I advise the authors to better understand the theory of cutting. Where they see "build up edge" - there I see only the adhesion of the processed material.

The description has been modified. The adhesive wear mechanism may led to build up edge and  this kind of wear was observed. Additional figure c’ was added with example of build up edge.

The adhesive wear was stated in case of the coated insert. Figure 10b and c show adhere material. In Figure 10c and 10c’ profile of the cutting edge after machining is presented. The change in insert geometry caused by build-up was  observed in two cases. This mechanism is caused by pressure welding of the chip to the insert. It is most common during machining of sticky materials with low cutting speed. To prevent this kind of wear highest speed should be applied.

 I don't see the build up edge in the images shown, I only see the build up (adherent). I invite the authors to take a closer look at the theory. With the cutting conditions used by the authors, the build up edge should not be formed in principle. If it is formed, it must be proven by appropriate research.

10. Where is the wear-time graph? How many tests were carried out? What are the statistics?

The turning tests were done for one cutting lengh. The test was repeated 5 times and results of measured flank wear with standard deviation are shown in Table 6.

 A graphical presentation of the results for cutting tests is preferred as it provides more information for the reader.

The English language in manuscript has been improved by professional language editing service. All language corrections were done and introduced in “track changes” mode.

Author Response

I didn't see any fundamental changes in the article. Unfortunately, I have no reason to change my mind and recommend this article for publication. 

Dear Reviewer,

Thank you for your valuable comments. In first response we didn’t want to fundamentally change our manuscript because we receive 3 positive opinions from the three remaining reviewers. Additionally we had to do professional English proof reading, when we had only 5 day for a response.

Please understand our situation.  In this round we have 4 days on this answer only. Due to COVID-19 (permits, limited number of researchers in laboratories, long waiting times for tests),  we don’t able to conduct new research. However, we will try to respond to the comments as well as possible.

The English language in manuscript has been improved by professional language editing service. All corrections have been introduced in “track changes” mode.

1. Any tech-savvy reader can easily match one system to another. Did the authors use two different methods for measuring hardness? If yes, then it is necessary to explain why this is needed.

  Due to measuring method, appropriate units have been used. Other (additional) units have been rejected.

2. I have been in the business of cutting tool coatings for over 25 years. In particular, he was engaged in turning and milling titanium alloys. Even fairly simple coatings based on ZrN can reduce flank wear by 2 or more times. 30% is the level of statistical error.

Despite the fact that only 5 tests were carried out (according to the authors), a decrease in wear by 30% may well be a statistical error. Such a decrease can make some sense if it is confirmed by hundreds of experiments (in this case, it is possible to really determine and eliminate the statistical error)

 " W-B film deposited by magnetron sputtering has great potential as a coating for cutting tools" - while wear has decreased by only 30%

Yes, You are right. However, borides (especially alloyed tungsten borides) are very promising material due to their properties. They are very hard or even super hard H>40 GPa and alloying of them allow to increase the flexibility and resistance for cracking. The most recent studies are a basic research. Please look for examples in:

1. Fuger, et al., "Influence of Tantalum on phase stability and mechanical properties of WB2," MRS Communications 9(1), pp. 375-380, 2019
2. Moscicki, et al, "Influence of overstoichiometric boron and titanium addition on the properties of RF magnetron sputtered tungsten borides," Surface and Coatings Technology 390, p. 125689, 2020.
3. Moraes, et al, Ternary TM-diborides coating films, patent no. US 2020/0332407 A1, Pub. Date Oct 22, 2020

However, there is a little mention of application of these coatings. Earlier we deposited similar coatings on the wire drawing dies with a tungsten carbide seat. In this case the time of work of tools increased above 200%. Therefore, the research on cutting tools with such coatings seemed to be promising. The research presented in the article showed that despite very promising results of basic research, further research on the conditions of layer deposition on tools is still necessary. 30% decrease in wear confirms this thesis.

3. Why does abrasion occur? How do the authors distinguish abrasive wear (due to abrasive grains) from adhesive wear (due to the formation and rupture of adhesive bonds between the workpiece material and the tool material)?

Thank you for paing attention to this issue. The term “abrasive wear” has been replaced with more general “wear”.

Flank wear is marked by tiny grooves that run parallel to the cutting direction.

4. The introduction must be changed. It makes no sense to talk about what research was done. It is necessary to justify the choice of the composition and parameters of the coating.

 It is not enough just to add two short phrases about "great potential for using". Why was this wear-resistant coating chosen? Why is it better than TiN, ZrN, (Ti, Al) N or even a large number of different coatings?

As it was mentioned above  tungsten borides and ternary transition metal-diborides possess very high application potential. The ternary TM-diboride coating films showing exceptionally high phase stability and mechanical properties, even at high temperature or even after exposition to high temperatures. For example addition of tantalum cause an increase in hardness H>40 GPa with conservation of very high fracture toughness kIc  ~3.5 MPa√m. In the figures below the comparison with other coatings taken from literature are presented.

As it shown in figure not alloyed WB2 coating is super hard (41 GPa) and resistant to cracking K_Ic=3.7 MPa√m

With appropriate selection of deposition conditions, similar properties can be obtained for W-Ti-B2.

The following explanation has been added in introduction:

“Also, tungsten borides and ternary transition (TM) metal-diborides possess very high application potential. The ternary TM-diboride coating films showing exceptionally high phase stability and mechanical properties, even at high temperature or even after exposition to high temperatures [2]. Addition of TM such as Ta or Ti cause that coatings possess fracture toughness kIC (~3.5 MPa√m)  higher than well-known coatings such us (Ti,Al)N, CrN/TiN, Ti-Si-N, TiN, and TiB2 and at the same time they are super hard (H>40 GPa)[2]. So far, there has been no research on the behavior of such layers under operating conditions.”

5. Figure 1. Is this the authors' own development or a standard device? If this is a standard device, I see no point in giving this image (all the more, not very good quality).

  This drawing has never been published before? (If published, an appropriate reference is needed). What is the peculiarity of this method, if it differs from the standard one?

The drawing has not been published yet. Figure 1 has been done based on the Skoda-Sawin station manual and has been modified. The method is not standard and therefore a scheme and description of the stand have been presented. However, such devices were owned by research and industrial centers in the past and has been normalized to polish norm. The stand allows you to flexibly change the parameters of the wear test. It is possible to carry out tests in dry friction and lubrication conditions for various loads. It is also possible to measure the volume of wear at the stand. However, due to the small depths of wear the volume of used material was measured on a confocal microscope, which ensured more accurate measurements. A characteristic feature of the method is the change of the contact surface during the wear test.

6. Fig 3. The description is clearly not enough. What do these images mean? What are they needed for? what is the point in them? 11 images and just one line of description!

Fig 3. The description is clearly not enough. What do these images mean? What are they needed for? what is the point in them? 11 images and just one line of description!

  This can be written in one line. These images do not contain any information relevant to the reader.

The figures with distribution of boron, oxygen and titanium have been rejected. Maps of tungsten distribution are presented as an example of uniform distribution of elements.

The sentence has been added: “As it is shown on exemplary distribution of tungsten (Figure 3a,b) there is no the mcro-segregation of elements.”

7. Fig 5. It is very difficult to see any difference between (b) and (c). Again, it is not clear what is the meaning of these images. Very superficial description! Since there is a much more informative Figure 6, I recommend deleting Figure 5.

 In my opinion, the image quality has decreased.

After processing, Fig 5 b c became completely unacceptable. These images are absolutely insufficient for any kind of analysis.

Due to reviewer suggestion Figure 5 and description of Fig. 5  have been removed from the article.

8. Figure 8, line 207 "small carbides in matric were observed" - where can you see it? How to understand that these are carbides?

"with characteristic sharp shape" - characteristic for what? Label them in the image, research them if they are important for the topic of the article. Otherwise, it is not clear why the image in Fig. 7 is needed.

The WC grains have characteristic sharp shape. Explanation has been added (line 221):

According suggestion WC grains have been label in Figure 6 and description has been changed

In the case of WC-Co insert, small carbides in the matrix with characteristic sharp shape for WC grains were observed (Figure 6a). After deposition of W-B coating, the surface morphology changed, however single carbides were still observed (Figure 6b).

9. Line 258 - how did the authors understand that this is abrasive wear, and not, for example, adhesive wear?

 The appearance of the surface after turning test indicates abrasive wear. Characteristic scratches on surface are visible, no particles of the cut material are present.

 That is, the authors believe that if there is no buildup of the processed material, then there is no adhesive wear?

 I don't see the build up edge in the images shown, I only see the build up (adherent). I invite the authors to take a closer look at the theory. With the cutting conditions used by the authors, the build up edge should not be formed in principle. If it is formed, it must be proven by appropriate research.

You’re right, adhesive wear occurs and is shown in the Figure b. The description has been clarified.

10. Where is the wear-time graph? How many tests were carried out? What are the statistics?

The turning tests were done for one cutting lengh. The test was repeated 5 times and results of measured flank wear with standard deviation are shown in Table 6.

 A graphical presentation of the results for cutting tests is preferred as it provides more information for the reader.

The graphical presentation of the results has been added.

Figure 10. Flank wear VB of cutting edges WC-Co and WC-Co coated with W-B film after turning tests at constant cutting condition v_c = 80 m/min, a_p = 1.5 mm, p = 0.09 mm/rev and cutting length 70 mm.