Coating of Refractory Surfaces with Fine TiO2 Particles via Gas-Dynamic Cold Spraying
, Andrii Toporov 2 and Sergiy Antonyuk 1
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsIn this paper, the deposition of TiO2 particles on the porous surface of the refractory has been studied. The deposition of TiO2 particles onto the porous surface of the refractory material is achieved and the properties of the resulting initial layer is analyzed. The paper is interesting. However, the following problems need to be solved before publication:
1. The introduction focuses too much on the significance to develop a protective layer on the surface of the refractory material. In addition, it is necessary to supplement the current research status on the application of gas-dynamic cold spraying (CGDS) to produce a coating on the refractory using fine titanium dioxide (TiO2) particles. The content about Figure 1 in the introduction should be placed more appropriately in the experimental section.
2. The parameters and equipment used for SEM and CT testing in the results section need to be added to the materials and methods section.
3. (line 333) Why can the slope of the curve in Figure 11 indicate surface stiffness and depth under the same force? How is the modulus of elasticity and hardness calculated from the curves, and are the values accurate and representative (line 349)?
4. (line 499) There are many similar ellipses in the paper. Please carefully check if this expression is correct in scientific papers.
5. Conclusion: please elaborate one by one. In addition, please refine the content, experimental details appeared in the conclusion part are suggested to be deleted, and each conclusion should not be too long.
Comments on the Quality of English LanguageMinor editing of English language required
Author Response
Comments 1: The introduction focuses too much on the significance to develop a protective layer on the surface of the refractory material. In addition, it is necessary to supplement the current research status on the application of gas-dynamic cold spraying (CGDS) to produce a coating on the refractory using fine titanium dioxide (TiO2) particles. The content about Figure 1 in the introduction should be placed more appropriately in the experimental section.
Response 1: Thank you for pointing this out. We agree with this comment. Therefore, we have reduced the amount of information on the need to coat and protect refractories (page 1, paragraph 1, lines 31-35) and added a literature review on the application of gas-dynamic cold spraying to produce a coating on ceramic surfaces with TiO2 particles and other ceramic powders (page 2, paragraph 1, and line 63-93). However, the literature has no information on coating refractories with ceramic particles using cold gas dynamic spray (CGDS). We would like to keep Figure 1 in the introduction to emphasize the purpose of the study. This figure will illustrate, after reviewing the literature on classical particle attachment mechanisms on different surfaces, the distinction of particle attachment mechanisms to a porous substrate.
Comments 2: The parameters and equipment used for SEM and CT testing in the results section need to be added to the materials and methods section.
Response 2: Thank you for pointing this out. We agree with this comment. Therefore, we have added the main parameters of SEM and CT (pages 4, 5, paragraph 2, and lines 129, 155).
Comments 3: (line 333) Why can the slope of the curve in Figure 11 indicate surface stiffness and depth under the same force? How is the modulus of elasticity and hardness calculated from the curves, and are the values accurate and representative (line 349)?
Response 3: Thank you for pointing this out. According to formula 3 (section 2.4, page 8), the numerical value of greater rigidity corresponds to the surface into which the indenter penetrates to a smaller depth ( h ) with the same value of force ( P ).
In nanoindentation tests, the modulus of elasticity and hardness are calculated according to the Oliver and Pharr method (formula 3-9, page 8, paragraph 2) from the indentation load-displacement data by fitting the unloading portion of the load-displacement data to a power-law relationship derived from elastic contact theory. The values of the modulus of elasticity and hardness are obtained by processing data from 12 indentation points for the uncoated grain.
Comments 4: There are many similar ellipses in the paper. Please carefully check if this expression is correct in scientific papers.
Response 4: Thank you for pointing this out. We agree with this comment. We have accordingly changed ellipses all over the paper.
Comments 5: Conclusion: please elaborate one by one. In addition, please refine the content, experimental details that appeared in the conclusion part are suggested to be deleted, and each conclusion should not be too long.
Response 5: Thank you for pointing this out. Agree. The conclusions have been revised (page 23, paragraph 4, lines 593-625).
Reviewer 2 Report
Comments and Suggestions for AuthorsThis paper mainly studies the method of coating fine titanium dioxide (TiO2) particles on the surface of refractories by gas dynamic cold spraying (CGDS) technology. The purpose of this study is to develop a protective coating that can limit the penetration of working medium and prolong the service life of refractories. This research has certain reference value in cold spraying technology, but the work content needs to be further improved.
1. The format of references should be unified.
2. Figure 9(a) lacks a ruler.
3. The CFD simulation mentioned in line 363 obtained the distribution of overpressure and temperature (Figure 12), the Y-component (along the Laval nozzle axis),and the Z-component (tangential to the substrate surface) of gas velocity (Figure 13), along with the magnitude of particle velocity (Figure 14) was mislabeled.
4. The conclusion is too complicated and needs to be simplified.
5. There is an extra line of space in line 444. Please check whether there are similar errors in the article.
6. In the introduction, the summary of the research status of cold spraying is not enough, so it is necessary to increase the elaboration of its research status to prove the advantages of using cold spraying.
7. How to prove that the coating has good adhesion at the pore?
8. What is the thickness of the coating made by cold spraying?
Author Response
Comments 1: The format of references should be unified.
Response 1: Thank you for pointing this out. We agree with this comment. We have accordingly edited the reference format in the paper.
Comments 2: Figure 9(a) lacks a ruler.
Response 2: Thank you for pointing this out. We agree with this comment and have made a ruler in Figure 9(a).
Comments 3: The CFD simulation mentioned in line 363 obtained the distribution of overpressure and temperature (Figure 12), the Y-component (along the Laval nozzle axis), and the Z-component (tangential to the substrate surface) of gas velocity (Figure 13), along with the magnitude of particle velocity (Figure 14) was mislabeled.
Response 3: Thank you for pointing this out. We agree with this comment and have changed links to figure numbering (page 14, paragraph 3, and lines 400-402, 411).
Comments 4: The conclusion is too complicated and needs to be simplified.
Response 4: Thank you for pointing this out. Agree. The conclusions have been revised (page 23, paragraph 4, lines 593-625).
Comments 5: There is an extra line of space in line 444. Please check whether there are similar errors in the article.
Response 5: Thank you for pointing this out. Agree. We have made changes to the paper text.
Comments 6: In the introduction, the summary of the research status of cold spraying is not enough, so it is necessary to increase the elaboration of its research status to prove the advantages of using cold spraying.
Response 6: Thank you for pointing this out. We agree with this comment. Therefore, we have reduced the amount of information on the need to coat and protect refractories (page 1, paragraph 1, lines 31-35) and added a literature review on coating ceramic surfaces using cold spraying. (page 2, paragraph 1, and lines 63-93).
Comments 7: How to prove that the coating has good adhesion at the pore?
Response 7: Thanks for your question. Unfortunately, we did not conduct adhesion tests specifically, but nanoindentation tests indirectly confirm good adhesion of the layer. The results of nanoindentation in the pore indicate it (Fig.12). There are no pop-up effects on the force-displacement curves, which suggests a smooth indenter stroke and the absence of chipping in the coating layer. Moreover, the form of the imprint on the coated sample (Fig.10a) does not correspond to the Berkovich tip shape, which indicates that the surface layer formed by the particles is elastically-plastically deformed and adheres well to the surface of the fireclay.
Comments 8: What is the thickness of the coating made by cold spraying?
Response 8: Thanks for your question. Since the structure of the substrate is porous, the layer thickness varies in different areas. Fine pores (up to 5 max particle diameters) are completely bricked up by a layer of particles. The coating thickness on the grain ranges from 0.4 to 1.5 µm. During the spraying of TiO2 particles, the substrate velocity was adjusted so to prevent the formation of a closed particulate layer on the surface, enabling the investigation of pore filling mechanisms.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe article will certainly be of interest to readers who are working on research in a similar field.
In the introduction, the authors approached the issue and used available and new literature for this.
The research materials and methods were chosen correctly and I have no comments about them. All the information provided is understandable. I have no comments on them.
The conclusion is very well written and contains a summary of the achieved research results. Perhaps it would be useful to separate the individual facts with a password.
Author Response
Comments 1: The conclusion is very well written and contains a summary of the achieved research results. Perhaps it would be useful to separate the individual facts with a password.
Response 1: Thanks a lot for your review. The conclusions have been revised (page 23, paragraph 4, lines 593-625).
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsAccept in present form.
