Advanced Analyses of Heating Elements Manufactured by an Optimized Arc Spraying Process

Round 1

Reviewer 1 Report

The manuscript provides a concise overview of the research, discussing the use of arc spraying for producing heating elements and the analyses conducted on the coatings. However, there are some areas that could be improved to enhance clarity and precision.

1.      Introduction: The manuscript should briefly explain the significance of heating elements in the automotive industry and why investigating simpler spraying technologies like arc spraying is relevant for cost-effectiveness. You can emphasize the need for improving coating characteristics and highlight the alloy NiCr as typical for heating elements.

2.      Objectives: While the manuscript mentions process optimization and advanced preparation methods, it should clearly state the main objectives of the study. For instance, "This study aims to optimize the coating characteristics of heating elements through process modifications in arc spraying and to evaluate the influence of sample preparation on coating analysis results."

3.      Methodology: Provide a concise description of the specific process modifications made in the arc spray process (e.g., alternative pressurizing gases, changes in air cap, and stand-off distance). Also, mention how the coatings were analyzed using SEM, EDS, and resistivity measurements.

4.      Key Findings: The manuscript should provide specific details about the results of the study. For example, "The optimized arc spraying process resulted in coatings with significantly reduced oxygen content and improved morphology compared to the reference plasma-sprayed coatings. The improved microstructure positively impacted surface quality and specific resistivity. However, microcracking was observed in the arc-sprayed coatings and the underlying ceramic coatings, possibly influenced by both sample preparation and inherent characteristics of the arc spray process."

5.      Implications: Elaborate on the significance of the findings for the heating element manufacturing industry. For instance, "The findings suggest that the improved properties of the arc-sprayed coatings, including superior temperature coefficients of resistance and resistivity, hold promise for potential industrial applications in heating element production. However, the technology requires further validation on prototype components and additional tests."

6.      Conclusion: The conclusion section of the manuscript should be more concise. For example, "In conclusion, this study successfully optimized the arc spraying process for heating element coatings, demonstrating improved properties. The study also highlighted the significance of sample preparation methods in coating analysis."

7.      Future Research: Consider briefly mentioning potential future research directions based on the study's findings. For example, "Future research could involve prototyping and testing the technology on actual heating element components to validate its industrial applicability."

The manuscript provides a concise overview of the research, discussing the use of arc spraying for producing heating elements and the analyses conducted on the coatings. However, there are some areas that could be improved to enhance clarity and precision.

1.      Introduction: The manuscript should briefly explain the significance of heating elements in the automotive industry and why investigating simpler spraying technologies like arc spraying is relevant for cost-effectiveness. You can emphasize the need for improving coating characteristics and highlight the alloy NiCr as typical for heating elements.

2.      Objectives: While the manuscript mentions process optimization and advanced preparation methods, it should clearly state the main objectives of the study. For instance, "This study aims to optimize the coating characteristics of heating elements through process modifications in arc spraying and to evaluate the influence of sample preparation on coating analysis results."

3.      Methodology: Provide a concise description of the specific process modifications made in the arc spray process (e.g., alternative pressurizing gases, changes in air cap, and stand-off distance). Also, mention how the coatings were analyzed using SEM, EDS, and resistivity measurements.

4.      Key Findings: The manuscript should provide specific details about the results of the study. For example, "The optimized arc spraying process resulted in coatings with significantly reduced oxygen content and improved morphology compared to the reference plasma-sprayed coatings. The improved microstructure positively impacted surface quality and specific resistivity. However, microcracking was observed in the arc-sprayed coatings and the underlying ceramic coatings, possibly influenced by both sample preparation and inherent characteristics of the arc spray process."

5.      Implications: Elaborate on the significance of the findings for the heating element manufacturing industry. For instance, "The findings suggest that the improved properties of the arc-sprayed coatings, including superior temperature coefficients of resistance and resistivity, hold promise for potential industrial applications in heating element production. However, the technology requires further validation on prototype components and additional tests."

6.      Conclusion: The conclusion section of the manuscript should be more concise. For example, "In conclusion, this study successfully optimized the arc spraying process for heating element coatings, demonstrating improved properties. The study also highlighted the significance of sample preparation methods in coating analysis."

7.      Future Research: Consider briefly mentioning potential future research directions based on the study's findings. For example, "Future research could involve prototyping and testing the technology on actual heating element components to validate its industrial applicability."

Author Response

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Author Response File: Author Response.docx

Reviewer 2 Report

Dear authors of the article!

The article needs to be radically finalized, reworked in accordance with the indicated remarks. The article presented by the authors is practically unreadable and does not carry any significant, new information. The article needs to be radically revised, supplemented with numbers and graphs of the dependences of adhesive and cohesive strength on technological parameters. The article also needs to be supplemented with graphs of the dependence of the porosity of coatings on technological parameters. Below are the comments, the authors need to give a detailed answer for each remarks in the text of the article.

Remarks:

1. At the end of the paragraph "Introduction", indicate clearly the "Purpose of the work."

2. What is the scientific novelty of research. Specify in the text of the article.

3. Figure 1, it is necessary to add a photo of the process of arc deposition of Ni, Cr wires, as well as plasma deposition of Al2O3. This will make the article more presentable and interesting. In addition, it will confirm the fact of receiving the results.

4. What is the adhesion and cohesion of the coatings? How was the adhesion of coatings determined (what method was used, technique). Indicate in the text of the article, this is very important.

5. It is necessary to make a three-dimensional model (maybe a graph in three axes) of the dependence of adhesion / cohesion of coatings on the main technological parameters of arc / plasma spraying.

6. What is the porosity of the coatings? How the porosity of coatings was determined (what method was used, technique). Indicate in the text of the article, this is very important.

7. It is necessary to make a three-dimensional model (maybe a graph in three axes) of the dependence of the porosity of coatings on the main technological parameters of arc / plasma spraying.

8. What is the optimal thickness of NiCr and Al2O3 coatings. How does coating thickness affect adhesion? Specify in the text of the article.

9. What exactly gives arc surfacing of Ni and Cr wires. Why do you need to do it? What is the advantage of arc surfacing compared to other methods (HVOF, supersonic methods, etc.). Specify in the text of the article.

10. The article is submitted to a materials science journal, it is necessary to add coating structures (so that the grain size is visible) and submit a phase analysis. Specify in the text of the article.

11. How does the structural state of the coating of materials affect the adhesive strength? Specify in the text of the article.

Author Response

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Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Accept

Author Response

Thank you again for your input!

Reviewer 2 Report

Dear authors of the article!

I don't have any high requirement regarding your article. I just want your article to be of interest to a wide range of readers. The article has weaknesses. You offer technology for producing layered composites (coatings). But, it is necessary to prove that the proposed technology is superior to plasma spraying, high-speed flame spraying and other gas-thermal methods. But you do not provide any evidence of the superiority of the proposed technology over others. Therefore, I asked you to include coating properties (cohesion and adhesion) in the article. And provide a comparison of these properties (adhesion and cohesion of coatings obtained using different technologies), which will confirm that your technology is better than other similar technologies.

I also don’t understand what the problem is with inserting photographs of the technological process for obtaining the coating. This would decorate the text of the article and would confirm the fact that you actually received coverage using the technology you proposed. It’s just from Figure 6 and Figure 10 that it’s difficult to understand what technology was actually used. Coatings obtained by plasma spraying of wire look the same as in Figures 6 and 10. But plasma spraying technology is more than 80 years old. In addition, Figures 6 and 10 show that there are many defects and pores. Therefore, I asked to indicate in the table the percentage of pore content in the coatings. Pores in the coating, it's a stress concentrator. These stresses, when the coating is loaded, will lead to the occurrence of microcracks. Therefore, it is necessary to determine the percentage of porosity content in coatings. To determine the porosity of coatings, the well-known method of hydrostatic weighing is used.

Summarizing everything written above, I ask the authors of the article to add at least summary tables of adhesion/cohesion of coatings, as well as porosity. For example, HVOF technology (NiCr coating, or an analogue - adhesion (numbers) MPa). Arc Spraying technology (NiCr coating – adhesion (numbers) MPa).

Author Response

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Author Response File: Author Response.docx