Study on Microstructure and Mechanical Properties of A100-Y2O3 Coatings on Low-Carbon Steel by Laser Cladding
Round 1
Reviewer 1 Report
The presented article deals with the current issue, and after studying it, it is possible to assess that it is a research article.
- An overview of publications related to the issue of research on the mechanical properties of cladding is sufficient.
- After studying the article, it is not possible to determine why the Y2O3 admixture was chosen, which would be appropriate to justify.
- On the basis of which a percentage of 0.5%, 1.0% and 1.5% was proposed to improve the mechanical properties of the surface. Up to what percentage value is it possible to consider the admixture of Y2O3?
- In Figure 4, is the cross-section of the cladding realistic or only a theoretical assumption? What device was it intended for?
- When determining the change in HV microhardness, the measurement methodology and equipment and material equipment are not described, as well as the repeatability of the measurement.
The results of the presented research are partly very simply described without concrete applications in practice for various other shapes and dimensions of the components. Based on the assessment, I recommend that the authors make minor changes to the article.
Author Response
- An overview of publications related to the issue of research on the mechanical properties of cladding is sufficient.
Answer: Thank you very much for your suggestion, we have rewritten the introduction part of the article.
- After studying the article, it is not possible to determine why the Y2O3 admixture was chosen, which would be appropriate to justify.
Answer: The role of rare earth oxides in coating is mainly to refine grain, which has been reported in related literature. Rare earth oxides in addition to Y2O3, there are other types. We greatly appreciate the reviewer's questions, as we would also like to continue to explore which rare earth oxides are best suited to be added to the laser cladding coating of A100 ultra-high strength steel.
- On the basis of which a percentage of 0.5%, 1.0% and 1.5% was proposed to improve the mechanical properties of the surface. Up to what percentage value is it possible to consider the admixture of Y2O3?
Answer: Our understanding of this question is that you want to understand how to choose the amount of Y2O3 added. We believe that when the content of Y2O3 is low, the mechanical properties of the coating are less improved. Increasing the content of Y2O3 will also improve the mechanical properties of the coating. However, when the content of Y2O3 is too high, agglomeration will occur in the coating, which is not conducive to the improvement of the mechanical properties of the coating. If we do not answer this question properly, please continue to make valuable suggestions.
- In Figure 4, is the cross-section of the cladding realistic or only a theoretical assumption? What device was it intended for?
Answer: Figure 4 is an image of a cross section of the coating under an optical microscope. Figure 3 is the macroscopic morphology of the coating, and the surface forming quality of the coating can be visually seen. Figure 4 is the cross section topography of the coating, and the quality of the interior of the coating can be seen under an optical microscope.
- When determining the change in HV microhardness, the measurement methodology and equipment and material equipment are not described, as well as the repeatability of the measurement.
Answer: Thank you for your questions. We have made the corresponding explanation in the article. The cross-section microhardness of the cladding samples was tested using an HXS-1000 A type digital liquid crystal intelligent microhardness tester from Shanghai Hao Microlight Technology Co., LTD. The microhardness test schematic diagram is shown in Figure 2, and the applied load is 100g and the pressure holding time is 15s.
Author Response File: 
Author Response.doc
Reviewer 2 Report
Study on microstructure and mechanical properties of A100-Y2O3 coatings on Low Carbon Steel by laser cladding.
A100 coatings were prepared by laser cladding to improve the wear resistance of low carbon steel. In this paper, the effects of laser cladding technology and Y2O3 content on microstructure, hardness, and wear resistance of A100 coating were studied, and the mechanism of improving wear resistance was analyzed. The manuscript can be accepted after addressing the following major comments:
1. Please rewrite the abstract and introduction.
2. A thorough check on grammatical errors is recommended.
3. Line 33: What does 4340/300M samples mean? Please elaborate on this in one sentence.
4. Table 1: Check this table. The total weight percentage is not 100.
5. Kindly upload the high-resolution images for Figure 2, Figure 4, Figure 5, Figure 6, Figure 7, Figure 8, and Figure 10. Please focus on the scale bar, and it should be visible.
6. Please explain the figures in the discussion section. For example, you have to explain which phase is present in the corresponding figure for Fig.5(a-d).
7. I suggest you combine Figures 6 and 7. It will be easier to understand the comparison of microstructure with and without the addition of Y2O3 coating.
8. Line 180: Mention the figure number. It needs to be clarified to understand the discussion with respect to literature.
9. Correct the heading 3.3.
10. Line 223: Correct the sentence.
11. Can you explain this claim with the help of microstructure? “This in- 236 dicates that the grain size of A100-0%Y2O3 and A100-1.5%Y2O3 coatings is uniform. When 237 the amount of Y2O3 is 0.5% and 1.0%, compared with A100-0%Y2O3 coating, the grains are 238 refined, but because the amount of Y2O3 is relatively small, the degree of grain refining is 239 uneven, resulting in uneven microhardness distribution of A100-0.5%Y2O3 and 240 A100-1.0%Y2O3 coatings.”
Comments for author File: 
Comments.pdf
Please rewrite the abstract and introduction. A thorough check on grammatical errors is recommended.
Many grammatical mistakes are present in this paper. Please thoroughly check it.
Author Response
- Please rewrite the abstract and introduction.
Answer：We have rewritten the abstract and introduction as requested by reviewer.
- A thorough check on grammatical errors is recommended.
Answer：We re-checked the grammar of the article and invited native English speakers to polish the article.
- Line 33: What does 4340/300M samples mean? Please elaborate on this in one
sentence.
Answer：This expression comes from reference No. 9. The researchers deposited 4340 coating on 300M substrate and described the relationship between this coating and substrate as 4340/300m.
- Table 1: Check this table. The total weight percentage is not 100.
Answer：Thanks very much to the reviewer for your careful review. We have re-checked and made modifications.
- Kindly upload the high-resolution images for Figure 2, Figure 4, Figure 5, Figure
6, Figure 7, Figure 8, and Figure 10. Please focus on the scale bar, and it should
be visible.
Answer：Thank you very much for the reviewer's suggestion. We added the scale bar in the corresponding picture according to your suggestion.
- Please explain the figures in the discussion section. For example, you have to
explain which phase is present in the corresponding figure for Fig.5(a-d).
Answer：Thank you very much for the reviewer's suggestion. We have made modifications according to the reviewer's requirements.
- I suggest you combine Figures 6 and 7. It will be easier to understand the
comparison of microstructure with and without the addition of Y2O3 coating.
Answer：Your suggestion is very good, we agree with it, and we have revised it according to your suggestion.
- Line 180: Mention the figure number. It needs to be clarified to understand
the discussion with respect to literature.
Answer：Thanks for your suggestion, we have added the description of the figure number of worn surface morphologies according to your suggestion.
- Correct the heading 3.3.
Answer：We really appreciate your careful review, which is very helpful to our work. We have made changes.
- Line 223: Correct the sentence.
Answer：First of all, we apologize for the language error. Thanks for your correction, we have made the revision.
- Can you explain this claim with the help of microstructure? “This in- 236 dicates that the grain size of A100-0%Y2O3 and A100-1.5%Y2O3 coatings is uniform. When 237 the amount of Y2O3 is 0.5% and 1.0%, compared with A100-0%Y2O3 coating, the grains are 238 refined, but because the amount of Y2O3 is relatively small, the degree of grain refining is 239 uneven, resulting in uneven microhardness distribution of A100-0.5%Y2O3 and 240 A100-1.0%Y2O3 coatings.”
Answer：According to the microhardness test results of the coating, the microhardness of the coating is not uniform when the content of Y2O3 is low. The content of Y2O3 is small, the degree of grain refinement of the coating is not enough, which makes the microstructure of the coating grain size different, so that the microhardness of the coating is not uniform. With the increase of Y2O3 content, the grain refinement degree of the coating is relatively complete, the coating can obtain fine equiaxed grains, and the uniform grain size of the coating makes the microhardness of the coating uniform.
Author Response File: Author Response.doc
Reviewer 3 Report
coatings-2601656-peer-review-v1
Please find comments on each section below:
1) Abstract – Line 18: “The microhardness and wear resistance of the coating were tested by hardness tester and friction and wear tester respectively” – are there any different methods to test hardness or wear? It seems like an unnecessary sentence.
2) Introduction – Line 31: what do the authors mean by “comprehensive properties”?
3) Materials and methods – Line 105: is there any effect of the deionized water that could potentially increase the potential corrosion of the substrate material?
4) Materials and methods – Lines 112-116: were the process parameters optimized? How were they determined?
5) Materials and methods – Lines 115-116: why the authors used 0.5%, 1% and 1.5% addition of reinforced ceramics? Was there any scientific justification?
6) Figure 1 and Figure 2 could be presented in one figure to avoid free space. Please add the professional scale bar.
7) Table 1: please make sure that the total content presented in the Table 1 is 100%
8) Materials and methods – Lines 135: How many indentations were made by condition? Or how many measuring profiles were performed to obtain the microhardness distribution?
9) Line 141: what authors mean by analytical balance? What is the accuracy of such a method?
10) Results and discussion – Line 146: “quality of the cladding sample is good” – it is not a scientific description. What do the authors mean by “good” surface quality? How the quality of the surface was assessed? How did the authors know that there are no cracks? Were the claddings subjected to microscopic inspection?
11) Figure 4: Please enlarge the cross-section of clads and measure the HAZ to investigate the effect of reinforcement addition on HAZ depth and the geometry of the clad. Please enlarge the scale bar.
12) Line 153: how the authors assess the degree of wettability?
13) Figure 5/XRD analysis: Please enlarge the font. It is hard to read.
14) Figure 5: The authors stated, that there are no changes in phase composition. However, some additional peaks are visible in Figures c-d. Please discuss.
15) Figure 6: the authors discuss the grain refinement, however, the SEM images are presented in different magnifications. Please add the professional scale bars to clearly distinguish the differences in the microstructure. The microstructural features described by the authors should be indicated in the Figures.
16) EDS mapping analysis: the observations performed by the authors could not be supported by Figure 8 because of its poor quality. One cannot distinguish Y distribution on the grain boundaries. To confirm the authors' statements, the EDS mapping analysis should be performed under significantly higher magnification.
17) Hardness measurements: the authors claimed, that for 0% and 1.5% the variance is small while for 0.5% and 1% the variance is “relatively large”. However, the variance differences between these conditions is ranging from 6 to 9HV, which is definitely within measurement error. Please comment.
18) The authors discussed the hardness improvement in terms of grain refinement. One should highlight the importance of Y-reinforcement in hardness enhancement. Since the authors claim that Y is distributed on the grain boundaries, it surely strengthens the material. However, it has to be confirmed by the authors.
19) Wear analysis: the microstructural features described by the authors should be indicated in the Figures.
20) Figure 11: since the addition of reinforcement may change the weight of the specimen, the results should be presented in terms of relative weight changes, not weight loss.
21) The discussion part of this paper should be improved. The total number of 20 papers used in the whole paper does not reflect that the state of the art, as well as obtained results, were analysed sufficiently.
General comments: The paper needs to be significantly improved to be considered for eventual publication. The results are interesting, however, the presentation of the data in the form of graphs as well as SEM images must be reconsidered.
The language should be significantly improved. There are numerous repetitions or non-formal statements used throughout the manuscript.
Author Response
- Abstract – Line 18: “The microhardness and wear resistance of the coating were tested by hardness tester and friction and wear tester respectively” – are there any different methods to test hardness or wear? It seems like an unnecessary sentence.
Answer: Thank you for your comments. This sentence is misstated and we have corrected it.
- Introduction – Line 31: what do the authors mean by “comprehensive properties”?
Answer: A100 Ultra high strength steel has excellent strength, fracture toughness and fatigue strength. A100 ultra-high strength steel has good comprehensive mechanical properties. Our expression is not rigorous enough, and we have made corresponding modifications.
3) Materials and methods – Line 105: is there any effect of the deionized water that could potentially increase the potential corrosion of the substrate material?
Answer: First of all, deionized water has removed chemical ions compared with ordinary water, and its corrosion ability to the substrate is very weak. In addition, the substrate dries immediately after removal from the deionized water to avoid corrosion.
4) Materials and methods – Lines 112-116: were the process parameters optimized? How were they determined?
Answer: After the first draft of this paper was completed, it was revised by the team, resulting in errors. We apologize for this error. The issue of laser cladding process parameters will be discussed in another article.
- Materials and methods – Lines 115-116: why the authors used 0.5%, 1% and 1.5% addition of reinforced ceramics? Was there any scientific justification?
Answer: We sincerely thank reviewers for asking this question. Because we have the same question when we read the literatures, how the amount of additions in the literature is determined. Unfortunately, there are few reasons given in the literatures for determining the amount of addition. Some research results show that a small amount of rare earth oxides can play the role of refining grains, while agglomeration occurs when the amount of rare earth oxides is too large. At present, the research work of laser cladding A100 ultra-high strength steel is relatively few. This article is also a preliminary exploration of the effect of Y2O3 content on A100 ultra-high strength steel coating. According to the suggestions of reviewers, we will further study the addition amount of Y2O3 in future work.
- Figure 1 and Figure 2 could be presented in one figure to avoid free space. Please add the professional scale bar.
Answer: We made the modification according to the reviewer's suggestion.
- Table 1: please make sure that the total content presented in the Table 1 is 100%
Answer: Thanks to the reminding of the reviewers, we made the revision.
- Materials and methods – Lines 135: How many indentations were made by condition? Or how many measuring profiles were performed to obtain the microhardness distribution?
Answer: The upper hardness of the coating has the greatest effect on protecting the substrate. Therefore, we measure the hardness of the upper part of the coating and find the average hardness. The coating microhardness test schematic diagram is shown in Figure 1.
Fig 1. Schematic diagram of coating microhardness test
9) Line 141: what authors mean by analytical balance? What is the accuracy of such a method?
Answer: The mass loss of worn specimens is measured by an analytical balance. The accuracy of the analytical balance can reach 0.0001 g. The results of analytical balance measurement are accurate and reliable.
10) Results and discussion – Line 146: “quality of the cladding sample is good” – it is not a scientific description. What do the authors mean by “good” surface quality? How the quality of the surface was assessed? How did the authors know that there are no cracks? Were the claddings subjected to microscopic inspection?
Answer: The macroscopic crack defects are observed through the macroscopic morphology. Laser cladding coatings are prone to defects such as cracks, pores and teardrops (i.e., discontinuity) at the macro level. It can be seen from the macroscopic morphologies that the A100-Y2O3 cladding coatings does not have the above defects, which is usually considered to be a good coating molding quality.
11) Figure 4: Please enlarge the cross-section of clads and measure the HAZ to investigate the effect of reinforcement addition on HAZ depth and the geometry of the clad. Please enlarge the scale bar.
Answer: First of all, we apologize for the inconvenience caused by the quality of the picture. We have made modifications according to the reviewer's suggestions. Rreviewer's advice is very important, and just like the reviewer's advice, the melting height and depth are usually one of the focuses of the research. The effect of Y2O3 on the melting depth and height of the coating was analyzed.
- Line 153: how the authors assess the degree of wettability?
Answer: According to the definition of wettability, that is, the ability or tendency of a liquid to spread over a solid surface. Determine the spreading ability (i.e., wettability) of the coating by comparing the melting width and melting height of the coating.
13) Figure 5/XRD analysis: Please enlarge the font. It is hard to read.
Answer: We apologize for the poor reading experience. We have made modifications as suggested by reviewers.
14) Figure 5: The authors stated, that there are no changes in phase composition. However, some additional peaks are visible in Figures c-d. Please discuss.
Answer: The backside and impurities in the XRD testing process will cause the presence of miscellaneous peaks in the XRD results. Often, miscellaneous summits are ignored by researchers. It can be seen from the XRD results of the coating that the diffraction intensity of other peaks mentioned by the reviewer is very weak, so it is treated according to miscellaneous peaks.
15) Figure 6: the authors discuss the grain refinement, however, the SEM images are presented in different magnifications. Please add the professional scale bars to clearly distinguish the differences in the microstructure. The microstructural features described by the authors should be indicated in the Figures.
Answer: We have made corresponding modifications according to the reviewer's requirements.
16) EDS mapping analysis: the observations performed by the authors could not be supported by Figure 8 because of its poor quality. One cannot distinguish Y distribution on the grain boundaries. To confirm the authors' statements, the EDS mapping analysis should be performed under significantly higher magnification.
Answer: In order to further analyze the distribution of Y element. The distribution of elements within grain boundaries and grains was analyzed by EDS points. The analysis results show that Y element is concentrated in the grain boundary.
17) Hardness measurements: the authors claimed, that for 0% and 1.5% the variance is small while for 0.5% and 1% the variance is “relatively large”. However, the variance differences between these conditions is ranging from 6 to 9HV, which is definitely within measurement error. Please comment.
Answer: Thank the reviewer for this point of view. In order to avoid the error caused by one measurement, we measured the same coating five times and calculated the average microhardness and variance. The variance can represent the difference between each microhardness measurement of the coating. The smaller the variance, the closer the measured values are each time, indicating that the microhardness value of the coating fluctuates little, and it can also indicate that the microhardness of the coating is relatively uniform. The more uniform the microhardness of the coating, the more uniform the microstructure of the coating.
18) The authors discussed the hardness improvement in terms of grain refinement. One should highlight the importance of Y-reinforcement in hardness enhancement. Since the authors claim that Y is distributed on the grain boundaries, it surely strengthens the material. However, it has to be confirmed by the authors.
Answer: First of all, the reviewer's suggestions are very helpful to improve the analysis of the microhardness of the coating. First of all, the reviewer's suggestions are very helpful to improve the analysis of the microhardness of the coating. We believe that the grain of the coating is obviously refined after adding Y2O3. The improvement of the microhardness of the coating is due to the washing strengthening effect brought by the grain refinement of the coating and the precipitation strengthening effect of Y2O3 itself.
19) Wear analysis: the microstructural features described by the authors should be indicated in the Figures.
Answer: Thanks to the reviewer for the improvement suggestions, we have made modifications according to the suggestions.
20) Figure 11: since the addition of reinforcement may change the weight of the specimen, the results should be presented in terms of relative weight changes, not weight loss.
Answer: The coating is weighed by an analytical balance and the weight of the coating is recorded before the friction and wear test, and then the friction and wear test begins. After the unpredictable wear test is completed, clean the wear chips of the worn coating to avoid the wear chips sticking to the coating. The worn coating is then weighed with an analytical balance and the weight of the worn coating is recorded. The weight difference before and after wear is the wear weightlessness of the coating. The wear weightlessness is one of the common methods to measure the wear resistance of coating.
21) The discussion part of this paper should be improved. The total number of 20 papers used in the whole paper does not reflect that the state of the art, as well as obtained results, were analysed sufficiently.
Answer: Thank you very much for your suggestions. We added 4 literatures to support the question raising and analysis of this paper.
Author Response File: Author Response.doc
Round 2
Reviewer 2 Report
The manuscript has been revised, and now this can be accepted for publication.
The quality of English looks good after the revision.
Author Response
Thank you for your review. Your review comments are very helpful to improve the quality of our paper.
Reviewer 3 Report
1) Please ensure, that SEM images get proper descriptions. Probably text is missing.
2) EDS mapping is not acceptable since it does not provide any information. The scanning resolution is definitely too low thus I do not recommend showing these results.
3) Table 2 - confidence intervals are missing
The paper might be considered for publication by the editor.
-
Author Response
Dear Editor and Reviewer,
Here below is our description on revision according to editor and reviewers comments. If the paper still needs improvement, please let us know, we are willing to continue to improve our work according to your suggestions.
Answer the questions from Reviewer.
- Please ensure, that SEM images get proper descriptions. Probably text is missing.
Answer: Thank the reviewer for reminding us. We give a complete description of the SEM information.
- EDS mapping is not acceptable since it does not provide any information. The scanning resolution is definitely too low thus I do not recommend showing these results.
Answer: According to the reviewer's suggestion, we removed the results of EDS mapping.
3) Table 2 - confidence intervals are missing
Answer: The reviewer's opinion is very valuable. We really did not consider the confidence interval when measuring the geometry of the cross section of the coating. According to the literature and common research methods, only the geometric size data of the coating is also correct and scientific. However, it's more rigorous to think about confidence intervals. Thanks to the reviewers for their valuable suggestions, which will be very helpful to our future work.
Author Response File: Author Response.doc
