Effects of Laser Remelting on Microstructure, Wear Resistance, and Impact Resistance of Laser-Clad Inconel625-Ni/WC Composite Coating on Cr12MoV Steel

Round 1

Reviewer 1 Report

1-      The authors should explain what makes this work unique/novel and how it differs from previous research.

2-      .More details, including the model, must be added regarding the laser system that is being used.

3-      Nothing is mentioned in the text about the uncertainty in the measurements, so please discuss this issue in the text.

4-      The authors should explain why they used the Scanning speed of 8 mm/s.

5-      Please explain in the text how the laser light polarization could influence the Microstructure.

Overall the manuscript appears to be clearly and carefully written.

Author Response

Reviewer 1 comments: 

Point 1. The authors should explain what makes this work unique/novel and how it differs from previous research.

Response: Thank you for your constructive comment. We are sorry to have caused you the trouble of reviewing our manuscript. In fact, we explain what makes this work unique in line 71 of the introduction: ‘At present, most researchers have studied LR post-treatment of single-layer coatings to enhance wear resistance, while LR of multilayer composite coatings to improve wear resistance and impact resistance has not been reported’. In short, the most innovative aspect of this work is the study of the effect of laser remelting on the wear and impact resistance of multilayer composite coating.

Point 2. More details, including the model, must be added regarding the laser system that is being used.

Response: Thank you for your helpful comment. We have added more information and details about laser system and experiments in the Section ‘Materials and experimental procedures’ in the revised manuscript.

Point 3. Nothing is mentioned in the text about the uncertainty in the measurements, so please discuss this issue in the text.

Response: Thank you for your constructive comment. For tests that require multiple measurements of data, such as microhardness tests and wear performance tests, we take multiple experimental points to take an average, as specified in the performance characterization tests section of the manuscript.

Point 4. The authors should explain why they used the Scanning speed of 8 mm/s.

Response: Thank you for your helpful comment. We are sorry to have caused you the trouble of reviewing our manuscript. As we have determined in this work the process parameters for laser cladding were: laser power of 1000 W, scanning speed of 6mm/s, spot diameter of 3 mm, powder feed rate of 12 g/min and a defocusing amount of 0. In a large number of basic experiments it was found that the laser remelting test process should have a larger defocusing amount and a slightly faster scanning speed compared to laser cladding. The laser energy density is related to the laser power and scanning speed, so we decided to increase the scanning speed slightly to 8 mm/s and only changed the laser power to determine the appropriate laser energy density for the laser remelting test. This is explained in the revised manuscript.

Point 5. Please explain in the text how the laser light polarization could influence the Microstructure.

Response: Thank you for your helpful comment. We have already explained this in Section 3.3: The analysis suggested that this was mainly due to the fact that in the process of LR, the continuous laser beam irradiated the surface of the formed coating and the coating was remelted at a certain depth to form a new melt pool. The internal microstructure will be remelted and solidified as well. The internal coarse dendrites were broken up to form smaller equiaxed dendrites. Furthermore, the reduced laser energy density in the LR process reduced the temperature gradient in the coating and increased the solidification rate, making the internal microstructure finer.

Author Response File: Author Response.docx

Reviewer 2 Report

The authors introduced an Inconel coating that was fabricated on Chromium Molybdenum Vanadium steel by laser cladding, followed by surface laser remelting with various laser powers. The effects of laser remelting on the microstructure, microhardness, wear resistance, and impact resistance of composite coating was investigated. The results showed that laser remelting did not cause the composite coating to produce new phases. The wear surface of remelted composite coating exhibited the abrasive wear resistance was significantly improved.

The paper is very interesting and perfectly fits the profile of the Coatings journal. I have no fundamental objections to the content of the paper, but I found some errors in this manuscript, and it must be improved.

Weak

The biggest disadvantage of this paper in its current form is the poor quality of the graphic layer, such as charts and photographs. Most drawings need improvement.

Noticed errors

1.       The purpose of the paper was not clearly defined. This should be completed.

2.       Line 37. Bulk citation of multiple sources (more than 2-3) is a bad practice. This should be improved by expanding the information on each cited source. Applies to whole paper.

3.       Chapter 2 lacks specifications for the physical and chemical properties and strength of the materials used.

4.       Figures 6, 7 and 12. The charts are partially illegible. It needs to be improved and increased.

5.       Adding conclusions for further research would certainly increase the value of the paper.

Small errors

(I hope typographic only) do not reduce the value of the paper, but they must be corrected.

1.       Pages 2/3 and 3/4. Bad pagination.

2.       Table2. Is: Scanning speed(mm/s); should be: Scanning speed (mm/s)

3.       Table2. Is: Laser energy density(J/mm²); should be: Laser energy density (J/mm²)

4.       Line 137. Is: 9.8N; should be: 9.8 N. Applies to whole paper.

 

5.       Table 4. Is: Impact energy(J); should be: Impact energy (J)

Author Response

Point 1. The purpose of the paper was not clearly defined. This should be completed.

Response: Thank you for your constructive comment. We are sorry to have caused you the trouble of reviewing our manuscript. In fact, we explain and completed the purpose of the paper: ‘In this work, considering the complexity of mold steels subjected to high impact and high friction forces in service, an Inconel625-Ni60-Ni60/25%WC (Inconel625-Ni/WC) composite coating was fabricated on the surface of Cr12MoV steel by LC. Subsequently, LR was applied to improve the microstructure, wear resistance, and impact resistance of the composite coating. The results obtained in this study can provide a useful reference for surface laser repair and strengthening of components with high friction and impact performance requirements (e.g. Cr12MoV stamping die parts).’

Point 2. Line 37. Bulk citation of multiple sources (more than 2-3) is a bad practice. This should be improved by expanding the information on each cited source. Applies to whole paper.

Response: Thank you for your helpful comment. We have checked the literature citations and made some adjustments in the revised manuscript.

Point 3. Chapter 2 lacks specifications for the physical and chemical properties and strength of the materials used.

Response: Thank you for your constructive comment. We have added some notes to the section on the chemical composition and physical properties of the material in the revised manuscript.

Point 4. Figures 6, 7 and 12. The charts are partially illegible. It needs to be improved and increased.

Response: Thank you for your helpful comment. We have reviewed and re-drawn some of the images like Figures 6, 7, and 12 in the revised manuscript.

Point 5. Adding conclusions for further research would certainly increase the value of the paper.

Response: Thank you for your helpful comment. We have re-examined the content of the manuscript and made some revisions that we hope will further improve the quality of the manuscript.

Point 6. Small errors

Pages 2/3 and 3/4. Bad pagination. 

Table2. Is: Scanning speed(mm/s); should be: Scanning speed (mm/s)

Table2. Is: Laser energy density(J/mm²); should be: Laser energy density (J/mm²)  

Line 137. Is: 9.8N; should be: 9.8 N. Applies to whole paper.

Table 4. Is: Impact energy(J); should be: Impact energy (J)

Response: Thank you for your helpful comment. We have checked the above problems and made the appropriate modifications in the revised manuscript.

Author Response File: Author Response.docx

Reviewer 3 Report

The manuscript presents an interesting investigation of multilayer laser cladding coating with additional laser remelting in order to increase the coating's wear and impact resistance. However, the manuscript includes several serious flaws that must be corrected. Therefore the manuscript is suggested for rejection alternatively new submission.

Numerous suggestion are provided below with hope to be of help to the authors in rewriting the manuscript. a PDF-file is attached too, with numerous comments, suggestions and corrections.

INTRODUCTION

Introduction does not introduce into the subject.

- Cr12MoV steel is not introduced following general-to-specific  writing method and with improper references [1,2,3].  A much better way would be to present description of cold working steel and this steel from some basic, capital books or handbooks references about tool steels.

- References [1,2,3] are however very welcome in a next paragraph focusing on surface coating and processing of Cr12MoV steel. References [4,7,12] appears not to contribute to the subject - they consider neither tools steels nor Ni-based laser cladded coatings.

- Laser cladding is not introduced following general-to-specific  writing method and with improper references.  A much better way would be to present description of laser cladding from some basic, capital books, handbooks or review papers references about laser cladding. Reference [11] is however a good one here.

- Laser remelting is in similar way not introduced by following general-to-specific  writing method and with improper references. A much better way would be to present description of cold working steel and this steel from some basic, capital books or handbook or general review papers references about Laser remelting.

- Wear resistance of laser cladded/remelted coatings is not introduced. This is not allowing a proper presentation of the achieved test results and their discussion.

- Impact resistance of laser cladded/remelted tyest samples is not introduced. This is not allowing a proper presentation of the achieved test results and their discussion. In particular, focus to be on the samples'  coating and position of the V-notch.

-  The motivation of why to use of multi layer coatings instead of single layer coatings is not provided.

MATERIALS AND EXPERIMENTAL PROCEDURES

- Dry reciprocating sliding wear testing does need deeper description and references. A photograph of the tribometer with close up of the test contact would be fine to have.  Surface roughness of the test samples must be described. Humidity during testing must be described.

-   Impact testing - the test samples must be clearly shown with respect to coating and position of the V-notch.

RESULTS AND DISCUSSION

- Figure 6 must be completed/proved with photographs of the indentation lines on the sample cross sections.

- Wear resistance - cannot be done without a previous introduction of dry sliding reciprocating wear.  Ceramic ball to plane bar contact normally includes formation of  a pillow with a glaze layer that decide about friction and wear. SEM/EDS analysis of the wear track on the test ceramic balls must be completed. First then, one can state about wear mechanisms.

- Impact resistance - Figure 17. provides a detailed view of the fracture of the samples. But there is no general picture of how the sample broke, considering coating and position of the V-notch.

CONCLUSIONS

Can be written after completions as above.

Comments for author File: Comments.pdf

Moderate editing.

Author Response

Point 1.- Cr12MoV steel is not introduced following general-to-specific  writing method and with improper references [1,2,3].  A much better way would be to present description of cold working steel and this steel from some basic, capital books or handbooks references about tool steels.

- References [1,2,3] are however very welcome in a next paragraph focusing on surface coating and processing of Cr12MoV steel. References [4,7,12] appears not to contribute to the subject - they consider neither tools steels nor Ni-based laser cladded coatings.

- Laser cladding is not introduced following general-to-specific  writing method and with improper references.  A much better way would be to present description of laser cladding from some basic, capital books, handbooks or review papers references about laser cladding. Reference [11] is however a good one here.

- Laser remelting is in similar way not introduced by following general-to-specific  writing method and with improper references. A much better way would be to present description of cold working steel and this steel from some basic, capital books or handbook or general review papers references about Laser remelting.

Response: Thank you for your helpful comment. This part of the introduction has been reorganised and some changes have been made

Point 2.- Wear resistance of laser cladded/remelted coatings is not introduced. This is not allowing a proper presentation of the achieved test results and their discussion.

- Impact resistance of laser cladded/remelted tyest samples is not introduced. This is not allowing a proper presentation of the achieved test results and their discussion. In particular, focus to be on the samples'  coating and position of the V-notch.

-  The motivation of why to use of multi layer coatings instead of single layer coatings is not provided.

Response: Thank you for your constructive comment. We have made the relevant modifications. The reason for adding Inconel 625 layers to form a multilayer coating is to improve the impact resistance of the coating because of the excellent ductility of the Inconel 625 material. This is illustrated in a separate, related work that has been submitted for publication. Furthermore, this thesis is only intended to investigate the effect of laser remelting on the wear and impact resistance of multilayer coatings.

Point 3.-  Dry reciprocating sliding wear testing does need deeper description and references. A photograph of the tribometer with close up of the test contact would be fine to have.  Surface roughness of the test samples must be described. Humidity during testing must be described.

-   Impact testing - the test samples must be clearly shown with respect to coating and position of the V-notch.

Response: Thank you for your constructive comment. The friction test has been further illustrated and completed in the revised manuscript. The schematic diagram of the impact test has been modified to make it more specific.

Point 4.- Figure 6 must be completed/proved with photographs of the indentation lines on the sample cross sections.

- Wear resistance - cannot be done without a previous introduction of dry sliding reciprocating wear.  Ceramic ball to plane bar contact normally includes formation of  a pillow with a glaze layer that decide about friction and wear. SEM/EDS analysis of the wear track on the test ceramic balls must be completed. First then, one can state about wear mechanisms.

- Impact resistance - Figure 17. provides a detailed view of the fracture of the samples. But there is no general picture of how the sample broke, considering coating and position of the V-notch.

Response: Thank you for your constructive comment. The relevant pictures have also been modified and improved.

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

In response to my previous suggestions and concerns, the authors have made reasonable changes to the manuscript. Overall, the manuscript reads well and clarifies the authors' work. In my opinion, the manuscript contains currently all information and is ready for publishing in the Journal " Coatings " as a regular article.  

Overall the manuscript appears to be clearly and carefully written

Author Response

我们重新检查和审查了稿件，并对修订后的稿件进行了一些词汇和语法上的更改。