Structure Formation of Diamond-Containing Coatings during Sintering of Specially-Shaped Grinding Wheels

Round 1

Reviewer 1 Report

In this paper, a new method of applying diamond containing coating on profile surfaces has been suggested. The work is good and authors have thoroughly performed the experiments. I have few minor comments/suggestions as listed below

1. Authors didn't mention the name of organic plasticizer used in the work.
2. Authors should perform Raman characterization for diamond analysis.
3. Authors should perform at least 1-2 functional properties test, either hardness test or wear test, to demonstrate the properties enhancement of coated substrate w.r.t. bare substrate in order reveal the potential of present diamond-containing coatings

Author Response

Dear reviewer,

Thank you for your comments and suggestions. We refer to your remarks and note as follows:

• Composition of the organic plasticizer is the authors' know-how. The plasticizer plays an important part in applying the powder mixture on the steel base by rolling. After rolling, the workpiece is heated in vacuum up to 450°C to remove the organic binding material. The principal problem discussed in the article is structure formation of coatings during sintering. At sintering temperatures, the material under study does not already contain any organic binding substances. Based on this, the authors deemed it possible to omit composition of the organic binding material.
• Raman spectroscopy will undoubtedly yield useful information, especially about the condition of surface of the diamond at fractures of the composite materials. Regrettably, the authors do not have access to a Raman microscope. The authors will aim to find the opportunity of using Raman spectroscopy in further studies.
• With your comment considered, the article has been supplemented with data on the hardness of coatings, and the effect of the hardness of metallic binders on functional properties of diamond-containing coatings has been discussed.

Yours sincerely,

authors of the article

Reviewer 2 Report

This work described in the manuscript of E. Sokolov et al. shows formation of powder diamond-containing coatings with Sn-Cu-Co binders  during sintering of specially-shaped grinding wheels has been studied. 

The authors investigate microstructure, phase  composition, and distribution of elements in metallic binders and interface layers between the binders and steel base. 

The article  can be accepted after minor correction for publication in Coatings. 

page 5 line 138 - Very poorly described figure 3 (b) in the text. It is not known what results from it.

Author Response

Dear reviewer,

Thank you for your comment. Admittedly, the effect of the interface layer on functional properties of the coatings is outlined quite briefly. In page 5 it is noted that "It is the strength of adhesion of diamond-containing coatings to their steel bases that matters much for operability of diamond tools. With regard to this, metallographic studies of the interface regions between the coating binders and the steel bases have been conducted". As a result of the research, it has been found that "The interface layer has no brittle intermetallic iron–tin compounds which can impair the coating to base adhesion strength".

The principal problem discussed in the article is structure formation of coatings during sintering. The authors have a new article planned which will discuss the effect of interface layers on functional properties of diamond-containing coatings with Sn-Cu-Co binders in detail.

Yours sincerely,

authors of the article

Reviewer 3 Report

Diamond coatings are essential work modern working tools. Adhesion and abrasion properties must be improved. In this work, the diamond coating was applied by rolling. The base materials is a diamond-containing powder containing additionally Sn-Cu-Co binders and sintered afterwards. The Co provides adhesion to the steel workpiece with Sn enabling mobility of the powder particles during the low-temperature sintering. A porous coating is the results.

Though the TEM images are impressive, I cannot really follow the reasoning. The values of the porosity must be better explained. I expect here a histogram including the highlighting of the pores in the TEM images. For example, the decrease in porosity with annealing temperature is not visible in the TEM images without further marking of the pores.

Author Response

Dear reviewer,

Thank you for your comments and suggestions. The article has been revised proceeding from your remarks. On Figure 2(a), designations of pores have been added. A histogram has been added, too, to visualize comparison of the samples porosity clearly.

Yours sincerely,

authors of the article

Reviewer 4 Report

In this work, Sokolov et al. introduce a morphological and structural analysis on diamond-containing coatings for abrasive tools with unconventional shapes.

Even if part of the work is obviously protected by a patent of the same authors, discussion is sufficiently exhaustive, and the paper is well-written and organized. The used methodology (analysis as a function of the sintering temperature) is rigorous and correct.

Results are encouraging and novel: authors clearly demonstrate to have found a solution to ensure both mechanical robustness and resistance to wear, thus overcoming the limitations of electroplated diamond-containing coatings and coatings obtained by vacuum brazing.

In my opinion, the paper deserves publication in Coatings after minor revision. I suggest to improve the paper by addressing two minor issues:

• Authors should improve the “readability” of SEM images shown in Fig. 2 and Fig. 7. For instance, in Fig. 2(a), Cu particles, pores, and liquid Sn in the 700-740°C sintering temperature images should be indicated with arrows or lines, in the same way as the image reported for the 820°C sintering temperature. In fig. 7, authors should indicate the diamond faces and the binder particles in fig 7(a), as well as the diamond particles in Fig 7(b).
• I suggest the authors to elaborate a little bit more on the formation of pits, cracks and fractures during sintering, as mentioned in the introduction. Do they have any suggestion on a possible technological solution to prevent from the formation of such defects? Few lines should be added, for instance in the discussion section, describing the possible reasons for the defect formation and the possible ways to reduce the defect density.

Author Response

Dear reviewer,

Thank you for your comments and suggestions. The article has been revised proceeding from your remarks. On Figure 2(a), designations of pores have been added. A histogram has been added, too, to visualize comparison of the samples porosity clearly.

1. Dear reviewer,

Thank you for your positive opinion about the article and suggestions on its improvement. The article has been revised proceeding from your comments:

- Designations of pores and structural constituents of the materials have been added to Figure 2.

- Designations to improve "readability" of the images have been added to Figure 8 (previously, Figure 7).

• In the Discussion section, assumptions on the causes of defects in coatings have been put forward, and ways to prevent the defects have been suggested (pages 7-8).

Yours sincerely,

authors of the article

Reviewer 5 Report

The manuscript seams to be interesting for readers. It presents the original author's findings related to manufacturing of grinding surfaces with various shapes containing diamonds. The authors are studying mechanical properties of developed coatings like hardness, porosity, structure, but they haven't mentioned its durability at all. In the manuscript, there is shown an intriguing effect of diamonds surface wetting by a liquified phase of  cobalt. The authors also claim  that  this fraction of cobalt phase is responsible for an adhesion enhancement of the developed surface coating as well. However, as it was mentioned, they don't  present any experimental evidence. There are only presumption that appearing of the cobalt phase between the iron core of the tools and the coating will significantly result in the endurance. Before possible publication, it will be better to introduce some information to the manuscript that the developed coating really work. I have no objection to the presented experimental evidence of the effect. But, in my opinion, the lack of information about the strength is a weak point of the manuscript.  Further, despite the English grammar seams to be correct, the stile of writing is very heavy. Moreover, the introduction part pointing the manuscript goals can be improved as well.

Author Response

Dear reviewer,

Thank you for your comments. Admittedly, the effect of the interface layer on functional properties of the coatings is outlined quite briefly. The principal problem discussed in the article is structure formation of coatings during sintering. The authors have a new article planned which will discuss the effect of interface layers on functional properties of diamond-containing coatings with Sn-Cu-Co binders in detail.

Yours sincerely,

authors of the article

Round 2

Reviewer 5 Report

Ok, I accept the author's viewpoint presented in the response letter. However, I do not understand why they had paid so much attention to the adhesion strength of the diamond containing coating to steel in the introduction section. And farther, they hadn't wanted to present any experimental results showing if it really works or not.  As I had mentioned before, structural analyses had been presented correctly.   But the lack of such information is the manuscript's weak point. Regarding this, I uphold my earlier decision to major in manuscript revision. However, the final decision needs to up taken by the editors.

Author Response

Dear reviewer,

Thank you for your positive opinion on the structural analysis presented in the article. We have elaborated the article in line with your comments. In Section 3.2, clarification on the necessity of strong coating to steel adhesion has been added. At the end of the article, results of tests of the grinding wheels have been provided.

Yours sincerely, authors of the article