Parameter Optimization and Mechanical Properties of Laser Cladding of 316L Stainless Steel Powder on G20Mn5QT Steel
Round 1
Reviewer 1 Report
General comments:
The scientific methodology used by the authors is well-motivated, logical, clear, and sound. The results are analyzed systematically and include sufficient discussion. The conclusions are well-organized, clear, and presented as quantitative information, easy for the reader to digest. For this reason, I would recommend for the editors to accept this article for publication in Coating, with only minor recommendations for improvement.
Specific comments:
1 - The figure captions could be improved. For example, the caption of Figure 2 is repetitive. Please consider using alternative descriptions. E.g. “Figure 2: Laser cladding system: (a) components of experimental setup, (b) schematic of laser cladding process showing scanning direction.”
2 - Figure scale bars are generally difficult to read. Please consider increasing the contrast and perhaps the font size of the scale bars in the figures.
3 – On line 322, did the authors mean to refer to Table 6 instead of Table 7?
4 - Line 117, "According to the test requirements, The constant process..." should be "According to the test requirements, the constant process..."
Author Response
Response to Reviewer 1 Comments
1: The figure captions could be improved.
Response 1: The figure captions have been improved.
2 Figure scale bars are generally difficult to read. Please consider increasing the contrast and perhaps the font size of the scale bars in the figures.
Response 2: Scale bars have been modified.
3 On line 322, did the authors mean to refer to Table 6 instead of Table 7?
Response 3: the Table has been modified.
4 Line 117, "According to the test requirements, The constant process..." should be"According to the test requirements, the constant process..."
Response 4: Line 117 has been modified.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Manuscript ID- coatings-2143584
Title: Parameter optimization and mechanical properties of laser cladding of 316L stainless steel powder on G20Mn5QT steel
Authors have coated/cladding of stainless steel powder on G20Mn5QT steel and studied the changes in microstructural and mechanical properties in detail. The study is organised and has readers' interest—however, Few suggestions and modifications from my side to strengthen the manuscript.
1. The introduction could be improved by explaining some other materials like MoS2 or graphene-based alumina etc. that are being for laser cladding if other sources are consulted, such as those with https://doi.org/10.3390/coatings12121840; https://doi.org/10.3390/coatings12101444;.
2. Please add more literature about laser cladding… introduction part has to be reworked.
3. Scale in figure 1 is not visible.
4. How the levels were chosen (Table 3). Why are these levels representative of research?
5. Which apparatus has been used for getting figure 4.Nothing is clear from Figure 4, is it necessary to provide so many figures, and if it so, please provide clear images by providing some border line for enlarged images.
6. In figure 5 a, the scale is not properly visible, same for figure 5 c.
7. Figure 7, the microhardness of 9 specimens were recorded as a technical result only. It should be compared with the HAZ morphology of other similar processes of heat processing. The detailed study can be available in the following published work. Kindly cite an refer: https://doi.org/10.1016/j.mseb.2020.114832; https://doi.org/10.1080/00084433.2022.2119039; https://doi.org/10.1080/13640461.2021.2014667;https://doi.org/10.1007/s10853-022-0793-6; https://doi.org/10.1016/j.coco.2021.100912
8. Nothing is clear from Figure 13 a. Author can write Time instead of T.
9. Add stress-strain curve of few/all specimens to show the trend of tensile test. Bar graph is just a record of results. It is not preferable.
10. Figure 10, fracture image should be updated in terms of findings level the findings in the image). Refer: https://doi.org/10.1051/metal/2022055; https://doi.org/10.1108/WJE-04-2020-0128
11. Wear results (shown in figure 13) Add generation of the friction force (Fx and Fz) graphs to discuss the effect of frictional force. Refer: https://doi.org/10.3390/coatings12091362
12. Figure in line 310, the spelling of particle is wrong. Please check it.
13. Figure numbering is wrong. I think figure after figure 13, all the numbering is incorrect. Please check and also if it is possible then EDX of the worn surfaces in (figure 13) can be included.
14. What optimization method was used for the analysis in section 3.4? Some brief description about the method could be included.
15. Numbering for Tables is also wrong. Please check and confirm Table 6 in line 338.
16. In table 6 (line 338), units can be included in column 1.
17. Conclusion is too long. Short it into a single paragraph and add future prospects at last of the conclusion.
Author Response
Response to Reviewer 2 Comments
- 1. The introduction could be improved by explaining some other materials like MoS2 or graphene-based alumina etc. that are being for laser cladding if other sources are consulted, such as those with https://doi.org/10.3390/coatings12121840; https://doi.org/10.3390/coatings12101444;.
Response 1: These two references have been added in the Introduction.
- 2. Please add more literature about laser cladding… introduction part has to be reworked.
Response 2: More literature about laser cladding has been added and reworked in the Introduction part.
- 3. Scale in figure 1 is not visible.
Response 3: The scale in Figure 1 has been modified.
- 4. How the levels were chosen (Table 3). Why are these levels representative of research?
Response 4: This is the experimental parameter selected after a large number of experimental studies in the early stage based on the principle of small dilution rate.
- 5. Which apparatus has been used for getting figure 4.Nothing is clear from Figure 4, is it necessary to provide so many figures, and if it so, please provide clear images by providing some border line for enlarged images.
Response 5: Figure 4 was obtained with an optical microscope at low magnification. The purpose of providing so many pictures is to see if there are many defects in the forming interface. Clear pictures have been provided, and border lines are also provided for enlarged pictures.
- 6. In figure 5 a, the scale is not properly visible, same for figure 5 c.
Response 6: The scale has been modified.
- 7. Figure 7, the microhardness of 9 specimens were recorded as a technical result only. It should be compared with the HAZ morphology of other similar processes of heat processing. The detailed study can be available in the following published work. Kindly cite an refer: https://doi.org/10.1016/j.mseb.2020.114832;
https://doi.org/10.1080/00084433.2022.2119039;
https://doi.org/10.1080/13640461.2021.2014667;
https://doi.org/10.1007/s10853-022-0793-6;
https://doi.org/10.1016/j.coco.2021.100912
Response 7: An refer has been cited.
- 8. Nothing is clear from Figure 13 a. Author can write Time instead of T.
Response 8: Has been rewritten.
- 9. Add stress-strain curve of few/all specimens to show the trend of tensile test. Bar graph is just a record of results. It is not preferable.
Response 9: Stress-strain curves have been added.
- 10. Figure 10, fracture image should be updated in terms of findings level the findings in the image). Refer:
https://doi.org/10.1051/metal/2022055;
https://doi.org/10.1108/WJE-04-2020-0128;
Response 10: It has been updated.
- 11. Wear results (shown in figure 13) Add generation of the friction force (Fx and Fz) graphs to discuss the effect of frictional force. Refer: https://doi.org/10.3390/coatings12091362
Response 11: Dear reviewer, I am very sorry because the friction and wear equipment in this paper did not record the graph of friction force and time!
- 12. Figure in line 310, the spelling of particle is wrong. Please check it.
Response 12: Has been rewritten.
- 13. Figure numbering is wrong. I think figure after figure 13, all the numbering is incorrect. Please check and also if it is possible then EDX of the worn surfaces in (figure 13) can be included.
Response 13: The number of the picture has been revised, and the EDX of the worn surface is difficult to provide in a short time, I am very sorry!
- 14. What optimization method was used for the analysis in section 3.4? Some brief description about the method could be included.
Response 14: The method has been provided with a short description.
15. Numbering for Tables is also wrong. Please check and confirm Table 6 in line 338.
Response 15: Has been rewritten.
- 16. In table 6 (line 338), units can be included in column 1.
Response 16: Has been rewritten.
- 17. Conclusion is too long. Short it into a single paragraph and add future prospects at last of the conclusion.
Response 17: Conclusions have been shortened.
Author Response File: Author Response.docx
Reviewer 3 Report
Generally, the introduction lacks a comprehensive review on state of the art specifically in the field that is addressed in the manuscript (wear problems of parts, cladding parameters, and material properties, choice of cladding material) and therefore the paper lacks explaining the motivation behind the work. Experimental part can be better organized to convey the topic more effectively, some details should be given and improved. The experimental work performed is more an engineering research than real scientific one. The subject is generally interesting but the approach in the investigation is scientifically really not on a high leve. I have serious doubts about relevance and applicability of the results presented here because the condition of the material used for substrate preparation is not appropriate for this application. This is so serious that it questions the interpretations of all investigated mechanical properties that were tested. The introduction and presentation of the results in the text is very poor, there are big problems in a sequence of the text and therefore it is usually very difficult to follow. There are a lot of mistakes of different kinds in the results section: in naming, in terminology, and referring. Generally, the explanation of the results has to be better organized to be more fluent. Paper lacks real discussion of the results, and authors rather speculate on some dependances than actual interpreting the results and interconnecting them with the results from the literature. The interpretation given so far does not seem very important from the scientific standpoint of view, it rather has some ordinary engineering significance.
30 row, Sentence “indentation and corrosion damage exceed the 30 standard and need to be repaired or scrapped on time” . It is not clear what is meant by this part of the sentence.
If there exist a standard for axle housing repair, then please refer to the one that you are mentioning. Cite the standard appropriately.
Rows 33-37, sentences are doubled, or some parts of them. Remove the duplicate.
Row 37 Authors should mention and cite only literature that is specifically related to the field, improvement of axle box by coatings. Because for example Plating and vapor depositions are not so suitable for protection against heavy wear, if you don’t agree find and cite appropriate literature, otherwise remove this statement. References 11 and 12 are not relevant at all.
Please cite the information appropriately. Avoid citing at the beginning of the sentence, after a few words. For example, like you did in rows 40, 48, 60, 65, 70. Cite after you mention some information.
Row 44 Sentence “This paper investigates the laser clad repair of G20Mn5QT steel, which requires a 44
low dilution rate and high mechanical…” Remove this sentence from this section, such information is usually written at the end of Introduction section.
Row 46 sentence “Therefore…“ Remove the sentence, … the significance of some investigation does not rely on authors self-opinion about the field, but on the facts from the literature. Therefore, in Introduction authors should address the real need for the investigation, based on the literature review.
Authors should give a more detailed literature review, and explanation why the austenitic steel (316) is an appropriate choice for highly stressed tribological contacts like axle housing. In this manner they should address different properties of the steel that are related to wear resistance and tribological behavior.
In the introduction, authors have to mention why don’t use some metallic layers with higher hardness than steel, like intermetallic coatings, carbides, MMC, stelites, etc.
Sentences are ambiguous and not understandable, rewrite them. Sentence in rows 50-52, “According to the”; row 84-87 “By studying a rational”
Row 53, “steel commonly used for laser cladding repair of rail vehicle structures and structures in corrosive environments” if it is commonly used, why do you cite just one case, one reference? Additionally, the reference [16] cited in that sentence is not appropriate, the paper does not address laser cladding at all! Use appropriate references!
Rows 56-58, sentence “The effect of energy input on the energy efficiency and mechanical properties of 316L parts was investigated using laser metal direct deposition (LMD) technique by some authors [19]” It is not clear to what are authors referring to , by means of energy input, energy efficiency combined with mechanical properties??? What does mean a 316L part?
Inappropriate (wrong) citations detected: row 37 references [11] [12]; row 54 [16], all other references should be carefully checked in the introduction section.
Rows 75,76, “deposited by orthogonal process parameters” Authors should rewrite this sentence, because it is not clear shat does author mean by orthogonal parameter??
The whole second paragraph of the manuscript has different flaws so needs complete reorganization to better convey the idea. The sequence of the covered topics has to be much better organized.
Most of the text written in the third paragraph of the introduction section explains the experimental investigation and as such it does not belong there. It should be moved to the beginning of the experimental section and shortened a little bit.
Row 84-87 Sentence “By studying a rational laser…” This is a result of the presented investigation so it should not be mentioned here, nor in the experimental section. Authors should remove this statement from this section.
In the last part of the Introduction section, authors should explain the motivation to conduct the work that they performed and explain in short (2-3 sentences) the investigation that they performed, the details should be minimized.
Generally, the introduction lacks a comprehensive review on state of the art specifically in the field that is addressed in the manuscript (wear problems of parts, cladding parameters, and material properties) and therefore the paper lacks explaining the motivation behind the work. Therefore, authors should give in the introduction part review on the state of the art regarding the parameters of laser cladding process, and problems that they address in the manuscript. From such a review a motivation for conducting the investigation would be clear.
Section 2 should be named Methods and materials
Row 92-93 sentence ” The substrate material is G20Mn5QT steel” Authors should specify in which condition was the steel. It seems that the structure is obtained by normalization. It should be in a quenched and tempered state. Authors should comment on this because the applicability of all these results comes into the question. Why protect with a softer layer ? What would be the behavior of these samples if the specimen would have been made of quenched and tempered steel?
Row 103 -104 – Equipment for laser cladding should be better explained, it is not clear why you mention CNC machine…
The equipment used in the study should be specified by type and by exact the model, producer etc, as it is specified by the guide for the authors of the journal.
Authors should explain why did they choose the indentation force of 1.98N.
Information specified in Table 4 is not regarded only to Orthogonal process parameters but also to the designation of the samples. Therefore, in order to be more easily to follow the manuscript in the text it should be mentioned that samples designations and performed experiments are given in Table 4.
Use the same naming and designations in Table 3 and Table 4
The number of testing repetitions of tensile test, impact, and shear strength should be given.
Raw 130. Explain which kind of tribological test was performed specify the configuration of the test, movement type. sample and counter body shape and dimensions, type of the counter material, use of lubrication…
Raw 135 , What does authors mean by thickness of the layer was taken, it is not clear. Did all process parameters result in the same thickness of the layers? Results indicate something else. Please explain this in more detail in the text.
The employed tests used for evaluation of tensile strength, and impact are test designed for evaluation of bulk materials. Therefore, authors should explain in the manuscript why do they employed these tests in thei r analysis. How are the bulk mechanical properties related to the tribological behavior of the coating layer.
Section 3 Title – Given that authors did not separate the Results section from the discussion this section should be named appropriately, as Results and discussion.
Figure 4., 5. specify which kind of imaging was used to obtain these images, light optical microscopy, SEM …
Figure 4., 5. Authors should explain the waviness of the substrate / cladding interface. And, explain in the manuscript the details about it.
From cross sectional figures it can be seen that the coating thickness is not the same for all samples, some coatings are considerably thinner. How do you explain this, when you said that the coating thickness is the same?
Row 152, “the forming is uniform” this part of the sentence is unclear. Modify the sentence and clarify the statement.
Rows 153-155 - Authors should explain how do they see the dilution rate from the enclosed images.
Figures 5 c and d, are very poor images, provide better one. The ferrite and perlite microstructure is not visible at all, and the lamellar structure of pearlite cannot be seen.
Authors should explain why did they chose the substrate material in that condition (ferrite/pearlite microstructure) with so low hardness (row 185).For the investigated purposes this kind of steel should be used in quenched and tempered condition. Authors should elaborate on this topic. This is so important and so influential that it can question all the results obtained by tensile test, impact test.
Figure 6. Specify which surface is observed by SEM, on the cross section or from the top.
Rows 200-203, Ambiguous sentence, rewrite it.
Authors should explain how did they ensured that in shear test the shearing occurred on the cladding substrate interface.
Some statements in the manuscript are not based only on the obtained results, but on the results from some other investigation. Therefore, these investigations should be cited. Such sentences are listed in the following and need adequate citing:
· Sentence in rows 204-206 (When the laser power is higher, more energy is absorbed by the substrate, and the melt pool size increases, resulting in a higher dilution rate);
· sentence in rows 206-208 (The shear strength of 316L stainless steel coating obtained by laser cladding with G20Mn5QT carbon steel is higher…).
· sentence in rows 294-296 ‘the high hardness wear particles peel off from the friction surface, the specimen changes from abrasive wear stage to adhesive wear stage, and the friction coefficient increases significantly.”
Rows 220-222 The sentence is repeated. Delete and change appropriately.
Section 3.3.3 Is very difficult to follow. It is very confusing so it needs to be modified in order to be more easy to follow. Try to stick to the main points here.
Unify the naming of the samples, ether sample or specimen. Do this throughout the manuscript.
Use correct expressions (wording) for tribological evaluations. Raw 281 “frictional wear performance test”, these are tribological tests, from which the wear volume and friction coefficients are determined and therefore refer accordingly throughout the manuscript.
Raw 282, and 286 authors refer to wrong figure. There is a mistake you mixed a and b images.
Row 282 What you mean by the Break-in ? Running in?
Row 287 “all samples have similar curves, ”This is not true”
Row 289 The friction coefficients of samples 2 and 3 have different evolution than other samples. Other samples after the Running in period show a decrease in coefficient of friction after the You have to comment on that in a right way.
Section 3.3.5. The explanation of tribological results and their discussion is on a very low level. Authors have to organize better the results explanation in this section and use adequate references connected with tribological testing of similar materials and prepare a better discussion of the obtained results.
Rows 294-296 ‘the high hardness wear particles peel off from the friction surface, the specimen changes from abrasive wear stage to adhesive wear stage, and the friction coefficient increases significantly.” Which results or literature information supports this statement? You should more carefully analyze the results and use literature citing for explanations.
The results of layers mechanical properties should be brought in connection with the results of tribological tests.
Figure 13. caption title is not appropriate “Tensile fracture morphology”
Row 319 “polar difference method” should be explained in more details in Methods part of the work. This is important so the reader can more easily follow the research.
Conclusion should be changed according the all changes made in the manuscript.
Author Response
Response to Reviewer 3 Comments
- 30 row, Sentence “indentation and corrosion damage exceed the 30 standard and need to be repaired or scrapped on time” . It is not clear what is meant by this part of the sentence. If there exist a standard for axle housing repair, then please refer to the one that you are mentioning. Cite the standard appropriately.
Response 1: Since it is mentioned that the relevant information of the axle box is confidential, the introduction of this part of the content has been removed, and other information has been added as required.
- Rows 33-37, sentences are doubled, or some parts of them. Remove the duplicate.
Row 37 Authors should mention and cite only literature that is specifically related to the field, improvement of axle box by coatings. Because for example Plating and vapor depositions are not so suitable for protection against heavy wear, if you don’t agree find and cite appropriate literature, otherwise remove this statement. References 11 and 12 are not relevant at all. Please cite the information appropriately. Avoid citing at the beginning of the sentence, after a few words. For example, like you did in rows 40, 48, 60, 65, 70. Cite after you mention some information.
Response 2: Duplicates have been removed and appropriate references have been cited as required.
- Row 44 Sentence “This paper investigates the laser clad repair of G20Mn5QT steel, which requires a 44 low dilution rate and high mechanical…” Remove this sentence from this section, such information is usually written at the end of Introduction section.
Response 3: This part has been modified.
- Row 46 sentence “Therefore…“ Remove the sentence, … the significance of some investigation does not rely on authors self-opinion about the field, but on the facts from the literature. Therefore, in Introduction authors should address the real need for the investigation, based on the literature review.
Response 4: The sentence has been removed.
- Authors should give a more detailed literature review, and explanation why the austenitic steel (316) is an appropriate choice for highly stressed tribological contacts like axle housing. In this manner they should address different properties of the steel that are related to wear resistance and tribological behavior.
Response 5: A more detailed review of the literature has been given.
- In the introduction, authors have to mention why don’t use some metallic layers with higher hardness than steel, like intermetallic coatings, carbides, MMC, stelites, etc.
Sentences are ambiguous and not understandable, rewrite them. Sentence in rows 50-52, “According to the”; row 84-87 “By studying a rational”
Response 6: It has been explained why higher hardness materials are not used and the sentence has been rewritten.
- Row 53, “steel commonly used for laser cladding repair of rail vehicle structures and structures in corrosive environments” if it is commonly used, why do you cite just one case, one reference? Additionally, the reference [16] cited in that sentence is not appropriate, the paper does not address laser cladding at all! Use appropriate references!
Response 7: Modified as requested.
- Rows 56-58, sentence “The effect of energy input on the energy efficiency and mechanical properties of 316L parts was investigated using laser metal direct deposition (LMD) technique by some authors [19]” It is not clear to what are authors referring to , by means of energy input, energy efficiency combined with mechanical properties??? What does mean a 316L part?
Response 8: The sentence has been modified.
- Inappropriate (wrong) citations detected: row 37 references [11] [12]; row 54 [16], all other references should be carefully checked in the introduction section.
Response 9: References have been revised.
- Rows 75,76, “deposited by orthogonal process parameters” Authors should rewrite this sentence, because it is not clear shat does author mean by orthogonal parameter?
Response 10: The sentence has been modified.
- The whole second paragraph of the manuscript has different flaws so needs complete reorganization to better convey the idea. The sequence of the covered topics has to be much better organized.
Response 11: The second paragraph has been rewritten.
- Most of the text written in the third paragraph of the introduction section explains the experimental investigation and as such it does not belong there. It should be moved to the beginning of the experimental section and shortened a little bit.
Response 12: The third paragraph of the introduction was revised as required.
- Row 84-87 Sentence “By studying a rational laser…” This is a result of the presented investigation so it should not be mentioned here, nor in the experimental section. Authors should remove this statement from this section.
Response 13: Modified as requested.
- In the last part of the Introduction section, authors should explain the motivation to conduct the work that they performed and explain in short (2-3 sentences) the investigation that they performed, the details should be minimized.
Response 14: A short introduction to the motivation for the work has been given.
- Generally, the introduction lacks a comprehensive review on state of the art specifically in the field that is addressed in the manuscript (wear problems of parts, cladding parameters, and material properties) and therefore the paper lacks explaining the motivation behind the work. Therefore, authors should give in the introduction part review on the state of the art regarding the parameters of laser cladding process, and problems that they address in the manuscript. From such a review a motivation for conducting the investigation would be clear.
Response 15: Modified as requested.
- Section 2 should be named Methods and materials.
Response 16: has been renamed.
- Row 92-93 sentence ”The substrate material is G20Mn5QT steel” Authors should specify in which condition was the steel. It seems that the structure is obtained by normalization. It should be in a quenched and tempered state. Authors should comment on this because the applicability of all these results comes into the question. Why protect with a softer layer ? What would be the behavior of these samples if the specimen would have been made of quenched and tempered steel?
Response 17: Modified as requested.
- Row 103 -104 – Equipment for laser cladding should be better explained, it is not clear why you mention CNC machine…
Response 18: It has been modified.
- The equipment used in the study should be specified by type and by exact the model, producer etc, as it is specified by the guide for the authors of the journal.
Response 19: Improvements have been made as required.
- Authors should explain why did they choose the indentation force of 1.98N.
Response 20: This paper does not specify how much pressure to use, the main thing is to be able to measure the microhardness values of the substrate and the coating.
- Information specified in Table 4 is not regarded only to Orthogonal process parameters but also to the designation of the samples. Therefore, in order to be more easily to follow the manuscript in the text it should be mentioned that samples designations and performed experiments are given in Table 4. Use the same naming and designations in Table 3 and Table 4. The number of testing repetitions of tensile test, impact, and shear strength should be given.
Response 21: Improvements have been made as required.
- Raw 130.Explain which kind of tribological test was performed specify the configuration of the test, movement type. sample and counter body shape and dimensions, type of the counter material, use of lubrication…
Response 22: Improvements have been made as required.
- Raw 135 , What does authors mean by thickness of the layer was taken, it is not clear. Did all process parameters result in the same thickness of the layers? Results indicate something else. Please explain this in more detail in the text.
Response 23: The cladding thickness of 2 mm refers to the thickness of the molten cladding after wire-cutting and turning of the specimen.
- The employed tests used for evaluation of tensile strength, and impact are test designed for evaluation of bulk materials. Therefore, authors should explain in the manuscript why do they employed these tests in their analysis. How are the bulk mechanical properties related to the tribological behavior of the coating layer. Section 3 Title – Given that authors did not separate the Results section from the discussion this section should be named appropriately, as Results and discussion. Figure 4., 5. specify which kind of imaging was used to obtain these images, light optical microscopy, SEM …
Response 24: An explanation of why these tests were used has been included in the manuscript. Part 3 has been named Results and discussion. Figures 4 and 5 have been used for a more detailed description.
- Figure 4., 5. Authors should explain the waviness of the substrate / cladding interface. And, explain in the manuscript the details about it.
From cross sectional figures it can be seen that the coating thickness is not the same for all samples, some coatings are considerably thinner. How do you explain this, when you said that the coating thickness is the same?
Response 25: The wave at the substrate/cladding interface has been explained. The different thickness of the cladding layer in the figure is the thickness before processing, while the previously mentioned cladding layer thickness of 2 mm is the thickness after processing.
- Row 152, “the forming is uniform” this part of the sentence is unclear. Modify the sentence and clarify the statement.
Response 26: The sentence has been modified to express that the specimen is better formed under the process parameters.
- Rows 153-155 - Authors should explain how do they see the dilution rate from the enclosed images.
Response 27: According to the formula of dilution rate, the greater the melting depth under normal circumstances, the greater the dilution rate will also become, and it has been proved in the previous single-pass test that the dilution rate will be greater when the laser power is higher than when the laser power is lower.
- Figures 5 c and d, are very poor images, provide better one. The ferrite and perlite microstructure is not visible at all, and the lamellar structure of pearlite cannot be seen.
Authors should explain why did they chose the substrate material in that condition (ferrite/pearlite microstructure) with so low hardness (row 185).For the investigated purposes this kind of steel should be used in quenched and tempered condition. Authors should elaborate on this topic. This is so important and so influential that it can question all the results obtained by tensile test, impact test.
Response 28: Figures 5c and d have been re-provided better. Since the study in this paper is for the G20Mn5QT cast steel used in rail vehicles, the hardness values are only as large as those tested in the manuscript. Other conditions of the substrate are not studied at this time and further studies will follow if necessary.
- Figure 6. Specify which surface is observed by SEM, on the cross section or from the top. Rows 200-203, Ambiguous sentence, rewrite it.
Response 29: SEM images have been made in the manuscript to explain and rewrite the ambiguous sentences.
- Authors should explain how did they ensured that in shear test the shearing occurred on the cladding substrate interface.
Response 30: Due to the obvious difference in color between the substrate and the coating, it is easy to distinguish the cross section between the coating and the substrate.
- Some statements in the manuscript are not based only on the obtained results, but on the results from some other investigation. Therefore, these investigations should be cited. Such sentences are listed in the following and need adequate citing:
Sentence in rows 204-206 (When the laser power is higher, more energy is absorbed by the substrate, and the melt pool size increases, resulting in a higher dilution rate);
sentence in rows 206-208 (The shear strength of 316L stainless steel coating obtained by laser cladding with G20Mn5QT carbon steel is higher…).
sentence in rows 294-296 ‘the high hardness wear particles peel off from the friction surface, the specimen changes from abrasive wear stage to adhesive wear stage, and the friction coefficient increases significantly.”
Response 31: Improvements have been made as required.
- Rows 220-222 The sentence is repeated. Delete and change appropriately.
Section 3.3.3 Is very difficult to follow. It is very confusing so it needs to be modified in order to be more easy to follow. Try to stick to the main points here.
Unify the naming of the samples, ether sample or specimen. Do this throughout the manuscript.
Use correct expressions (wording) for tribological evaluations. Raw 281 “frictional wear performance test”, these are tribological tests, from which the wear volume and friction coefficients are determined and therefore refer accordingly throughout the manuscript.
Response 32: Improvements have been made as required.
- Raw 282, and 286 authors refer to wrong figure. There is a mistake you mixed a and b images.
Response 33: It has been revised as requested.
- Row 282 What you mean by the Break-in ? Running in?
Response 34: It has been modified.
- Row 287 “all samples have similar curves, ”This is not true”
Response 35: It has been modified.
- Row 289 The friction coefficients of samples 2 and 3 have different evolution than other samples. Other samples after the Running in period show a decrease in coefficient of friction after the You have to comment on that in a right way.
Response 36: Improvements have been made as required.
- Section 3.3.5. The explanation of tribological results and their discussion is on a very low level. Authors have to organize better the results explanation in this section and use adequate references connected with tribological testing of similar materials and prepare better discussion of the obtained results.
Response 37: Improvements have been made as required.
- Rows 294-296 ‘the high hardness wear particles peel off from the friction surface, the specimen changes from abrasive wear stage to adhesive wear stage, and the friction coefficient increases significantly.” Which results or literature information supports this statement? You should more carefully analyze the results and use literature citing for explanations.
Response 38: Improvements have been made as required.
- The results of layers mechanical properties should be brought in connection with the results of tribological tests. Figure 13. caption title is not appropriate “Tensile fracture morphology”
Response 39: Improvements have been made as required.
- Row 319 “polar difference method” should be explained in more details in Methods part of the work. This is important so the reader can more easily follow the research.
Conclusion should be changed according the all changes made in the manuscript.
Response 40: Improvements have been made as required.
Author Response File: Author Response.docx
Reviewer 4 Report
1. What is the size of the axle box, and is it feasible to do PVD with that size ? The authors mentioned the axle application and cites some literature [12] on PVD coatings. The author must clarify if the axle size is suitable for PVD coatings. if not, The authors need to revise the introduction/background with optimal citations.
2. What is the present working life of the Axle box, and what are the improvement figures with the proposed coatings?
3. How the shear strength testing was prepared ? The methodology needs more explanations and details for each type of characterization.
4. What is the white region at the interface of Sample 7 of Figure 4? What is the significance of numerics in the popup image of each sample?
5. Figure captions need to be self-contained and should revise with full details of the figure.
6. Figure 4: The resolution of a few sub-figures is not good, so it's difficult to identify if there is not any porosity in sample 8 and sample 5. Please consider re-taking figures with good quality.
7. What is the difference in porosity of each sample, and does it really affect properties ?
8. What is the reason for variations/similarities in shear strength? how many samples were considered for each type?
9. Is there any relation between porosity and elongation after fracture and tensile strength? What is the signification of elongation after a fracture as per the proposed application of axle box ?
10. The authors need to provide the co-relation of microstructure with evaluated properties in each subsection of section 3.
11. Table 6: Captions of all the tables need to be revised with full information. Captions should be self-contained.
Author Response
Response to Reviewer 4 Comments
- What is the size of the axle box, and is it feasible to do PVD with that size ? The authors mentioned the axle application and cites some literature [12] on PVD coatings. The author must clarify if the axle size is suitable for PVD coatings. if not, The authors need to revise the introduction/background with optimal citations.
Response 1: As it is mentioned in the paper that the axle box is secret-related, the keyword of the axle box is required to be removed. I am very sorry, but the content of the introduction has been further revised.
- What is the present working life of the Axle box, and what are the improvement figures with the proposed coatings?
Response 2: At present, due to the confidentiality of the mentioned axle box, the information about the axle box cannot be provided yet.
- How the shear strength testing was prepared ? The methodology needs more explanations and details for each type of characterization.
Response 3: As can be seen in Figure 3(d) of the article, the coating is cut from the substrate by the cutter of the shearing device at a certain speed, and the shear strength can be calculated by the computer and has been explained in the method.
- What is the white region at the interface of Sample 7 of Figure 4? What is the significance of numerics in the popup image of each sample?
Response 4: The white area is the cladding layer. In order to see the fusion line clearly, the color of the coating was adjusted to white when shooting. The numbers for each sample only indicate cladding samples under different parameters.
- Figure captions need to be self-contained and should revise with full details of the figure.
Response 5: Figure details have been modified.
- Figure 4: The resolution of a few sub-figures is not good, so it's difficult to identify if there is not any porosity in sample 8 and sample 5. Please consider re-taking figures with good quality.
Response 6: Figure 4 has been adjusted for resolution.
- What is the difference in porosity of each sample, and does it really affect properties ?
Response 7: The porosity of each sample has little difference and has little effect on performance.
- What is the reason for variations/similarities in shear strength? how many samples were considered for each type?
Response 8: The shear strength is mainly related to the laser energy input, and the shear strength has little difference under the same laser power, and three samples are prepared for each group.
- Is there any relation between porosity and elongation after fracture and tensile strength? What is the signification of elongation after a fracture as per the proposed application of axle box ?
Response 9: Porosity and elongation at break are not related to tensile strength because the axle box body is subject to collision during service and therefore requires better plasticity and toughness than the substrate.
- The authors need to provide the co-relation of microstructure with evaluated properties in each subsection of section 3.
Response 10: Since this paper mainly explores the relationship between parameter optimization methods and the influence of parameters on performance, the relationship between microstructure and performance is not discussed, and the relationship between microstructure and performance will continue to be explored subsequently.
- Table 6: Captions of all the tables need to be revised with full information. Captions should be self-contained.
Response 11: Table 6 has been modified.
Author Response File: Author Response.docx
Round 2
Reviewer 4 Report
The authors have addressed the queries to some extent. No further comments.
