Microstructure, Esthetics and Engineering Performance of TiN Coatings Deposited by Multi-Arc Ion Plating

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Manuscript ID coatings-3847867

 

 Microstructure, Aesthetics, and Engineering Performance of 2 TiN Coatings Deposited by Multi-Arc Ion Plating

The authors studied simultaneously the requirements for surface strengthening and decorative aesthetics in high-end stainless-steel crafts using TiN coatings deposited on 304L stainless-steel substrates using multi-arc ion plating. The regulatory mechanisms and synergistic evolution laws of nitrogen flow rates 17 (100, 200, and 300 sccm) on the microstructure, decorative properties (color and gloss), and engineering performance (adhesion strength, hardness, wear resistance, and corrosion resistance) of the coatings were investigated.

• Even though the study is not new, using TiN coating on stainless steel and the advantages for using this coating, I still could not find any novelty of this study in your abstract or introduction. You just mentioned the advantages of using this coat.
• I would like to see a paragraph in the abstract mentioning the novelty of your study. Also, I did not see any paragraph in the abstract and introduction mentioning clearly, the objective of your study.
• In materials and methods section, please supply the source of Ti Target
• Please add a reference for surface roughness ( Fig. 4) and substrate adhesion tests(Fig. 6) .
• I think the conclusion is too much and can be summarized in 1-2 paragraphs instead of points.

 

 

Author Response

Comments 1: The authors studied simultaneously the requirements for surface strengthening and decorative aesthetics in high-end stainless-steel crafts using TiN coatings deposited on 304L stainless-steel substrates using multi-arc ion plating. The regulatory mechanisms and synergistic evolution laws of nitrogen flow rates 17 (100, 200, and 300 sccm) on the microstructure, decorative properties (color and gloss), and engineering performance (adhesion strength, hardness, wear resistance, and corrosion resistance) of the coatings were investigated.

Even though the study is not new, using TiN coating on stainless steel and the advantages for using this coating, I still could not find any novelty of this study in your abstract or introduction. You just mentioned the advantages of using this coat.

I would like to see a paragraph in the abstract mentioning the novelty of your study. Also, I did not see any paragraph in the abstract and introduction mentioning clearly, the objective of your study.

Response 1: Thank you for this insightful comment. We agree that the novelty and objectives of our study should be more clearly articulated in both the abstract and the introduction.

We have revised the introduction section (Line 75, Page 2), adding a more explicit statement of the research objectives to highlight the innovative aspects and goals of our work, as well as to enhance the focus and rationality of the research.

We appreciate your valuable feedback, which has helped improve the clarity and impact of our manuscript.

Comments 2: In materials and methods section, please supply the source of Ti Target

Response 2: Thank you for this helpful comment. We agree that providing the source of the Ti target is important for ensuring the reproducibility of the experiment.

In the revised manuscript, the detail has been added to the Materials and Methods section (Line 105, Page 3).

We appreciate your suggestion, which enhances the completeness and transparency of our experimental description.

Comments 3: Please add a reference for surface roughness ( Fig. 4) and substrate adhesion tests(Fig. 6) .

Response 3: Thank you for this suggestion. We have added relevant references to support the surface roughness measurements (Fig. 4) and substrate adhesion tests (Fig. 6) in the revised manuscript.

Comments 4: I think the conclusion is too much and can be summarized in 1-2 paragraphs instead of points.

Response 4: Thank you very much for reviewing our manuscript and providing valuable suggestions. We have carefully considered your suggestion about simplifying the conclusion into 1-2 paragraphs.

We understand your concern about the conciseness of the conclusion. During the revision process, we attempted to condense the conclusion into a paragraph form, but found that this study involves the multi-dimensional effects of nitrogen flow rate on the microstructure, aesthetic performance, and engineering performance of the coating. The conclusion contains four interrelated yet relatively independent important findings. Presenting them in bullet points can more clearly present these complex results, avoid information confusion, and facilitate readers to quickly grasp the key conclusion.

To balance the richness of content with the brevity of expression, we have further refined the language in the conclusion section, eliminating all redundant statements and ensuring that each point is more precise. The current structure best presents the systematic and comprehensive nature of the research.

Once again, we would like to thank you for your valuable suggestions. They have been very helpful in improving the quality of our paper.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The paper “Microstructure, Aesthetics, and Engineering Performance of TiN Coatings Deposited by Multi-Arc Ion Plating” addresses the issue of improving the homogeneity and technical performance of titanium nitride coatings.

There are numerous studies in this area, which highlights the relevance of this work. However, although they all address the effect of nitrogen flow rate on some specific properties of TiN coatings, they do not systematically investigate its effect on both decorative (color and gloss) and technical properties (morphology, crystal structure, preferred orientation, and chemical composition) through microstructure modulation. The present studies using 304L stainless steel as a substrate with varying nitrogen flow rates from 100 to 300 cm³/min under controlled deposition temperature, target current, substrate bias, and deposition time fill this gap. The obtained results provide a scientific basis and technical support for the design and production of high-quality stainless steel products, promoting the integration of material science and advanced manufacturing.

The research methodology includes determination of the mechanisms of influence of nitrogen flow rate on the microstructure, decorative properties and technical characteristics of TiN coating. It was found that at a nitrogen flow rate of 200 cm³/min, the coating demonstrated a homogeneous and dense columnar crystalline structure, as well as a rich golden hue with a high surface gloss. In contrast, excessively low (100 cm³/min) or high (300 cm³/min) nitrogen flow rate resulted in the formation of large particles and blurring of grain boundaries due to uncontrolled droplet ejection or target poisoning, respectively, which led to deterioration in both appearance and technical characteristics. The presented evidence and arguments answer the main research question. The analysis of the mechanisms allowed us to determine the optimal values ​​​​to obtain compliance with not one, but several parameters at once.

The paper uses appropriate references and the tables do not require improvement.

As improvements to the presentation of the material and description of the figures, it is proposed to clarify the following issues:

1. The paper indicates an improvement in the aesthetic appearance if the use of excessively low (100 cm³/min) or high (300 cm³/min) nitrogen flow rates (resulting in the formation of large particles and blurring of grain boundaries) is avoided, but no photographs are provided to allow such an assessment. In this case, it would be appropriate to indicate an improvement in the homogeneity of the coating application or to add photographs of the material's appearance to the paper.
2. It is not clear from Figure 4a how the matte rough structure manifests itself; in the image the surface only differs in color and it can be assumed that they have an acceptable aesthetic appearance.
3. Figure 6 needs to be described in more detail. It is not clear enough to which of the ordinate axes one or the other curve belongs. It is also necessary to explain (possibly in the figure itself) why one of the curves cannot be written further and breaks off. What phenomenon is this associated with?

Comments for author File: Comments.pdf

Author Response

Comments 1: The paper indicates an improvement in the aesthetic appearance if the use of excessively low (100 cm3/min) or high (300 cm3/min) nitrogen flow rates (resulting in the formation of large particles and blurring of grain boundaries) is avoided, but no photographs are provided to allow such an assessment. In this case, it would be appropriate to indicate an improvement in the homogeneity of the coating application or to add photographs of the material's appearance to the paper.

Response 1: Thank you for your comment. We agree on the importance of including visual evidence to support the aesthetic evaluation. We would like to clarify that actual appearance photographs of the coatings prepared under different nitrogen flow rates have already been included in Figure 4a (chromaticity diagram with sample images). These images allow for a clear visual comparison of the color uniformity and surface gloss among the TiN-100, TiN-200, and TiN-300 coatings.

Comments 2: It is not clear from Figure 4a how the matte rough structure manifests itself; in the image the surface only differs in color and it can be assumed that they have an acceptable aesthetic appearance.

Response 2: Thank you for raising this important point. We agree that the visual differences in surface texture are not fully distinguishable from the color images in Figure 4a alone, as the photographs primarily reflect differences in hue and saturation.

The assessment of a "matte and rough" structure for TiN-100 was concluded through a comprehensive analysis combining quantitative roughness measurements (Figure 4b), surface topography (Figure 5), and microstructure observation (Figure 1), in addition to chromaticity data. The high surface roughness (1.351 μm) and the presence of macroscopic particles and defects lead to diffuse light scattering, resulting in the matte visual effect, which is a key characteristic differentiating it from the glossy TiN-200 sample.

To clarify this in the manuscript, we have added relevant statements in Section 3.2 (Line 220, Page 7).

Comments 3: Figure 6 needs to be described in more detail. It is not clear enough to which of the ordinate axes one or the other curve belongs. It is also necessary to explain (possibly in the figure itself) why one of the curves cannot be written further and breaks off. What phenomenon is this associated with?

Response 3: Thank you for this suggestion. We agree that the original description of Figure 6 could be improved for better clarity.

In the revised manuscript, we have modified Figure 6 to clearly differentiate the curves corresponding to the left and right ordinate axes using distinct colors. Additionally, the explanation regarding the sudden termination of the acoustic emission curve has been revised and elaborated in the manuscript text (Line 241, Page 8).

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

In the manuscript “Microstructure, Aesthetics, and Engineering Performance of 2 TiN Coatings Deposited by Multi-Arc Ion Plating,” the authors review the process of optimizing the properties of TiN coatings produced by multi-arc ion plasma spraying. This topic is relevant due to the difficulties that arise in establishing a correlation between deposition parameters (e.g., nitrogen rate), the microstructure formed, and the final set of properties. This topic becomes especially relevant in those conditions when one of the requirements to the formed coating is the need to simultaneously achieve perfect aesthetic characteristics and outstanding engineering properties. In this paper, the authors conduct a systematic study of the influence of deposition rate on the microstructure, and consequently on the decorative and functional properties of coatings. The manuscript itself is well-written and competently structured. However, there are a number of comments on the manuscript, the correction of which will significantly improve the quality of the article:

1. Line 70. It would be logical to summarize at the end of the paragraph an intermediate summary of the results that were obtained during the analysis of the articles cited.
2. The Materials and Methods section states that 15 mm thick samples were used, but does not further explain how such a significant thickness affects the deposition processes and thermal regimes. Were preliminary experiments conducted to determine the optimal substrate thickness to minimize thermal deformation or influence deposition kinetics?
3. Line 87. Why do you use this particular grade of steel in your study. Please add an explanation.
4. There is a typographical error in the caption to Fig. 2 and Fig. 1: for image (c) in both cases, “(b) TiN-300” is given. It should be corrected to “(c) TiN-300”.
5. Line 210. Further clarification is required as to which range of adhesion values are considered optimal for the purposes intended by the authors.
6. Line 221. The difference between the Lc2 values for TiN-200 and TiN-300 is only 8%. This raises the question: what should be the optimal values of the Lc2 indicator in the adhesion study? A similar question concerns the Lc3 index, since the difference in this index between all three samples is also insignificant.
7. The authors provide a clear explanation of the nonlinear dependence of coating thickness on nitrogen flux on page 5 (lines 152-159). They attribute the increase in thickness at 200 sccm to ensuring the completeness of the reaction, and its decrease at 300 sccm to the phenomenon of target poisoning and a decrease in atomization efficiency. However, this explanation is not fully utilized to interpret all the data. Along with the thickness, the nitrogen content of the coating decreases from 200 to 300 sccm (from 25.52 wt.% to 24.32 wt.%, Table 1). Although the authors state this fact (page 4, lines 137-138), they do not offer an explanation for it. It is recommended to deepen the discussion in Section 3.1 by linking the two facts.
8. It makes sense at the end of Section 3.3 to make an intermediate conclusion that due to the thicker coating and uniform distribution of crystals in the TiN-200 sample, better mechanical characteristics can be observed in comparison with the other two samples. However, at the same time, it is necessary to clearly indicate what range of characteristics the authors were aiming at when studying each of these characteristics. It may also make sense to compare with other coatings.
9. It makes sense at the end of Section 3.3 to make an intermediate conclusion that due to the thicker coating and uniform distribution of crystals in the TiN-200 sample, better mechanical characteristics can be observed in comparison with the other two samples. However, at the same time, it is necessary to clearly indicate what range of characteristics the authors were aiming at when studying each of these characteristics. It may also make sense to compare with other coatings.
10. Add the uncertainties to the results obtained in Sections 3.2-3.4.
11. References to Figures 4b, 5, 8b are after Figures 4b, 5, 8b themselves. The first references should always be given before the figures.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Many thanks for answering my comments

Reviewer 3 Report

Comments and Suggestions for Authors

I think the manuscript can be accepted.