Comparison of Fe₃₀Co₂₀Cr₂₀Ni₂₀Mo_3.5 High Entropy Alloy Coatings Prepared Using Plasma Cladding, High-Speed Laser Cladding, and Deep Laser Cladding

Round 1

Reviewer 1 Report

1. In section 2.1, please also presented SEM images, elemental composition of the steel substrate.

2. The image quality of inset figures in Figure 4 is very low. The figure caption should also be descriptive.

3. Figure 7c does not add any information to the article, it should be removed from the draft.

4. How many times each microhardness test was repeated? please add error analysis in Figure 7a.

5. The discussion should be supported by the published literature. Please compare the results with the published literature.

Author Response

Thank you for your comments concerning our manuscript entitled “Comparison of Fe30Co20Cr20Ni20Mo3.5 high entropy alloy coatings prepared by plasma cladding and laser cladding” (ID: coatings-2512835). Those comments are all valuable and very helpful for revising and improving our paper. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked with different colors in the revised manuscript (highlight). The main corrections in the revised manuscript and the responds are as flowing:

Reviewer 1:

1. In section 2.1, please also presented SEM images, elemental composition of the steel substrate.

Response:

The SEM image of the substrate has been added to Figure 1 of the revised manuscript. The elemental composition of the substrate was listed in Table 1.

2. The image quality of inset figures in Figure 4 is very low. The figure caption should also be descriptive.

Response: The element line scanning results at the interfaces of the three coatings in Figure 4 are shown in Figure 6. The figure caption has also been modified.

3. Figure 7c does not add any information to the article, it should be removed from the draft.

Response: The purpose of adding Figure 7c is to explain the principles of friction experiments and wear volume calculation models. We have moved Figure 7c to Experimental materials and methods. Does this improve the expression effect?

4. How many times each microhardness test was repeated? please add error analysis in Figure 7a.

Response: The microhardness curve is obtained by measuring every 0.1mm from the bottom of the coating upward. Due to the different thicknesses of the three coatings, the number of points taken for each coating also varies. In the coating hardness curve, there are 23 points for PC, 16 points for DLC, and 9 points for HLC. Therefore, we did not repeat measurements for each point. We added the standard deviation of the hardness of the three coatings to make the results more intuitive (Line 214-215). Thanks for your suggestion!

5. The discussion should be supported by the published literature. Please compare the results with the published literature.

Response: We have referred to relevant literature on high entropy alloy cladding and added them to the references.

Special thanks to you for your good comments.

Reviewer 2 Report

In this work the authors studied the microstructure, wear and corrosion properties of a FeNiCoCrMo HEA coating that has been deposited on a Q235 steel substrate with the employment of three methods. In more detail, the authors used plasma clading, high speed laser coating and deep laser coating for the coating deposition. The paper contains a lot of interesting results and is well presented. A few corrections will help to improve this work:

 

1) Authors are kindly requested to check and correct the stoichiometry of the HEA.

2) Lines 73-78 need to be removed from the introduction. Instead a paragraph with the description of the novelty of this work needs to be added.

3) Fig 1 and the relevant discussion needs to move from materials and methods to results.

4) Authors need to explain why DLC has a BCC microstructure while PC and HCL have FCC. This might be related to the solidification rate employed in each process. Relevant discussion will help to improve the microstructural analysis of the coatings.

5) Authors are kindly requested to add the chemical composition of each coating in table 3. There seems to be a discrepancy in the chemical composition of the different coatings. Please explain why.

6) Figure 7c needs to be moved to materials and methods

7) Friction coefficient curves are rather brief. How confident are the authors that after 6 mins the COF reaches the steady state?

8) Ecorr, icorr and Ccorr values between the different coatings show a marginal difference. As a result the claim in line 276-277 is risky. PC and HLC coatings appear to show improved corrosion performance as compared to DLC due to the more noble Epit values. Authors are requested to add Epit values to table 6 and expand the discussion.

Author Response

Thank you for your comments concerning our manuscript entitled “Comparison of Fe30Co20Cr20Ni20Mo3.5 high entropy alloy coatings prepared by plasma cladding and laser cladding” (ID: coatings-2512835). Those comments are all valuable and very helpful for revising and improving our paper. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked with different colors in the revised manuscript (highlight). The main corrections in the revised manuscript and the responds are as flowing:

Reviewer 2:

1. Authors are kindly requested to check and correct the stoichiometry of the HEA.

Response:

The labeling of Fe₃₀Ni₂₀Co₂₀Cr₂₀Mo_3.5 HEA in the manuscript refers to the amount added according to the atomic ratio of each element when preparing powder. Fe₃₀Ni₂₀Co₂₀Cr₂₀Mo_3.5 represents the atomic ratio of each element rather than the percentage of atomic content.

2. Lines 73-78 need to be removed from the introduction. Instead a paragraph with the description of the novelty of this work needs to be added.

Response:

We have added the prime novelty statement of the article in lines 75-81. Thank you very much for your suggestion.

3. Fig 1 and the relevant discussion needs to move from materials and methods to results.

Response:

Figure 1 and the relevant discussion have been moved to section 3.1.

4. Authors need to explain why DLC has a BCC microstructure while PC and HCL have FCC. This might be related to the solidification rate employed in each process. Relevant discussion will help to improve the microstructural analysis of the coatings.

Response:

Due to the low dilution rate of HLC and PC, the elemental content of these two coatings is not different from that of Fe₃₀Ni₂₀Co₂₀Cr₂₀Mo_3.5 HEA powder. This can be seen from the results of line scanning (Figure 8) and EDS (Figure 9 and Table 4). Therefore, these two coatings maintain the same crystal structure as the powder after rapid solidification. DLC has a very high dilution rate, and the coating area contains a large amount of Fe element. Under the high heat input cladding process, the cooling rate of the melt pool is slow, thus forming the crystal structure of BCC. We added relevant discussions on lines 189-198.

5. Authors are kindly requested to add the chemical composition of each coating in table 3. There seems to be a discrepancy in the chemical composition of the different coatings. Please explain why.

Response:

This suggestion is very valuable to us. We have added the reasons for the differences in the content of Mo and Cr elements at grain boundaries and within grains (lines 206-210).

6. Figure 7c needs to be moved to materials and methods.

Response:

Figure 7c has been moved to materials and methods.

7. Friction coefficient curves are rather brief. How confident are the authors that after 6 mins the COF reaches the steady state?

Response:

During the preparation process of the samples used for friction and wear tests, the surface roughness and flatness of each sample cannot be guaranteed to be the same. Therefore, the performance of each sample varies at the beginning of the experiment. Therefore, the friction coefficient of 0-6 minutes was discarded when calculating the average friction coefficient.

8. Ecorr, icorr and Ccorr values between the different coatings show a marginal difference. As a result the claim in line 276-277 is risky. PC and HLC coatings appear to show improved corrosion performance as compared to DLC due to the more noble Epit values. Authors are requested to add Epit values to table 6 and expand the discussion.

Response:

We have added E_pit in Table 6, and the relevant discussion is in lines 285-288. Thank you very much for your advice, which has made our work more perfect!

Special thanks to you for your good comments.

Reviewer 3 Report

Comments for coatings-2512835

 

Title: Comparison of Fe30Co20Cr20Ni20Mo3.5 high entropy alloy coatings prepared by plasma cladding and laser cladding

 

This study examined three types of Fe30Ni20Co20Cr20Mo3.5 high entropy alloy (HEA) coatings applied to Q235 steel plates using plasma cladding and laser cladding. The coatings were analyzed for microstructure, crystal structure, element distribution, microhardness, wear resistance, and corrosion resistance. The deep laser cladding coating (DLC) had the smallest grain size and the best microhardness and wear resistance. The high-speed laser cladding coating (HLC) had the best corrosion resistance, while the plasma cladding coating (PC) showed improved corrosion resistance compared to Q235. The different coatings exhibited varying corrosion types.

High entropy alloy coatings focused on Fe30Co20Cr20Ni20Mo3.5 composition have garnered interest due to their unique composition and properties. This manuscript highlights the potential of different modification / cladding techniques in tailoring the properties of high entropy alloy coatings for various purposes.

 

After a careful peer-reviewing process, I must inform you that, the subject of this paper is interesting and can be considered for publication in the MDPI/Coating journal after a MAJOR REVISION. I believe that the paper contains relevant information for the scientific community focused on recent advances in HEA coatings and their modification processes. I believe that the results are informative but must be well organized and improved in the next revision(s). Therefore, there are some questions about this submission and some revisions are necessary for this work. The major/minor issues are indicated as follows:

 

1. Authors must provide more information on the specific plasma cladding and laser cladding techniques used in this study. How were the coatings prepared and what exact parameters were used during the various three types of cladding processes (plasma cladding, high-speed laser cladding and deep laser cladding)?

2. It would be helpful to know the specific testing methods and equipment used to determine the microstructure, crystal structure, element distribution, microhardness, wear resistance, and corrosion resistance of the coatings. This information would provide more context for the results obtained.

3. Please provide more details on the experimental setup for measuring microhardness and wear resistance. What load and duration were used in the microhardness tests? What type of wear test was conducted and what were the testing conditions?

4. Authors should explain the reasoning behind selecting Fe30Ni20Co20Cr20Mo3.5 as the composition for the high entropy alloy coatings. Were there any specific properties or applications that influenced this choice?

5. It would be beneficial to include additional characterization techniques, such as scanning electron microscopy (SEM) or energy-dispersive X-ray spectroscopy (EDS), to further analyze the microstructure and element distribution of the coatings.

6. Please provide more insight into the mechanism behind the improved microhardness, wear resistance, and corrosion resistance observed in the high entropy alloy coatings. Are there any specific alloying elements or microstructural features that contribute to these enhanced properties?

7. Please provide more information on the corrosion testing methodology. What type of solution or environment was used to simulate corrosion conditions? Were any electrochemical techniques employed, such as potentiodynamic polarization or electrochemical impedance spectroscopy?

8. It would be helpful to include some discussion on the limitations and potential future directions of this study. Are there any challenges or areas for improvement that should be addressed in further research?

9. Can authors discuss how the results obtained in this study compare to previous research on high entropy alloy coatings? Are there any notable differences or similarities in terms of the properties achieved or the deposition techniques used?

10. Please ensure that the statistical significance of the results is addressed. Were multiple samples tested for each coating type, and if so, what was the variability observed?

 

11. Please highlight all three types of plasma cladding; high-speed laser cladding and deep laser cladding in the title. Alternatively, modify the title to clearly highlight the methods used for the readers.

 

12. Higher magnification (macro-scaled) inset images are beneficial for Fig. 3.

 

13. ICDD reference codes must be provided for all detected phases in XRD results (e.g., Fig. 4).

 

14. EDS spectra is also required for all A-F analysis points on Fig. 6.

 

15. There is no description of the future plans for research in the first part of the “Conclusions” section. This should be completed in this section.

 

16. Recently published references are beneficial for this work. Please check and use new references focused on your work:  doi.org/10.1002/adem.202001047; doi.org/10.3390/coatings12030372 

17. Comments and related discussion on corrosion pit size and related mechanism in Fig. 11 is incomplete. Please revise.

 

 

Author Response

Thank you for your comments concerning our manuscript entitled “Comparison of Fe30Co20Cr20Ni20Mo3.5 high entropy alloy coatings prepared by plasma cladding and laser cladding” (ID: coatings-2512835). Those comments are all valuable and very helpful for revising and improving our paper. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked with different colors in the revised manuscript (highlight). The main corrections in the revised manuscript and the responds are as flowing:

Reviewer 3:

1. Authors must provide more information on the specific plasma cladding and laser cladding techniques used in this study. How were the coatings prepared and what exact parameters were used during the various three types of cladding processes (plasma cladding, high-speed laser cladding and deep laser cladding)?

Response:

We listed the parameters of the three cladding processes in Table 1, and added two parameters: carrier gas flow rate and shielding gas flow rate during cladding.

2. It would be helpful to know the specific testing methods and equipment used to determine the microstructure, crystal structure, element distribution, microhardness, wear resistance, and corrosion resistance of the coatings. This information would provide more context for the results obtained.

Response:

Thank you very much for your suggestion. We have supplemented information on all testing equipment.

3. Please provide more details on the experimental setup for measuring microhardness and wear resistance. What load and duration were used in the microhardness tests? What type of wear test was conducted and what were the testing conditions?

Response:

We have added the model of the testing equipment and more detailed testing parameters in lines 110-113.

4. Authors should explain the reasoning behind selecting Fe30Ni20Co20Cr20Mo3.5 as the composition for the high entropy alloy coatings. Were there any specific properties or applications that influenced this choice?

Response:

The powder used for cladding in this article is alloyed HEA powder prepared by gas atomization method. Due to the extremely high melting point of Mo element, which is close to the gasification temperature of Fe, it is very difficult to increase the content of Mo in the process of preparing powder. Therefore, we chose Fe₃₀Ni₂₀Co₂₀Cr₂₀Mo_3.5 as the composition for the high entropy alloy coatings.

5. It would be beneficial to include additional characterization techniques, such as scanning electron microscopy (SEM) or energy-dispersive X-ray spectroscopy (EDS), to further analyze the microstructure and element distribution of the coatings.

Response:

Based on the original test, we have added SEM images of the microstructure of the Q235 substrate.

6. Please provide more insight into the mechanism behind the improved microhardness, wear resistance, and corrosion resistance observed in the high entropy alloy coatings. Are there any specific alloying elements or microstructural features that contribute to these enhanced properties?

Response:

We have added discussions and relevant references on the mechanism behind the improved microhardness, wear resistance, and corrosion resistance. This is very helpful for our research!

7. Please provide more information on the corrosion testing methodology. What type of solution or environment was used to simulate corrosion conditions? Were any electrochemical techniques employed, such as potentiodynamic polarization or electrochemical impedance spectroscopy?

Response:

We added more information on the corrosion testing methodology. Including the model of electrochemical workstation, test method and parameters.

8. It would be helpful to include some discussion on the limitations and potential future directions of this study. Are there any challenges or areas for improvement that should be addressed in further research?

Response:

We have added the future plans for research in the first part of the “Conclusions” section.

9. Can authors discuss how the results obtained in this study compare to previous research on high entropy alloy coatings? Are there any notable differences or similarities in terms of the properties achieved or the deposition techniques used?

Response:

We added a comparison of the mechanical properties of Fe₃₀Ni₂₀Co₂₀Cr₂₀Mo_3.5 HEA and CrMnFeCoNi HEA coatings.

10. Please ensure that the statistical significance of the results is addressed. Were multiple samples tested for each coating type, and if so, what was the variability observed?

Response:

The performance of the samples in the manuscript has been retested at least three times. No significant differences were observed.

11. Please highlight all three types of plasma cladding; high-speed laser cladding and deep laser cladding in the title. Alternatively, modify the title to clearly highlight the methods used for the readers.

Response:

We changed the title of the manuscript to ‘Comparison of Fe₃₀Ni₂₀Co₂₀Cr₂₀Mo_3.5 high entropy alloy coatings prepared by plasma cladding high-speed laser cladding and deep laser cladding’.

12. Higher magnification (macro-scaled) inset images are beneficial for Fig. 3.

Response:

We added high-power SEM images of three coatings in Figure 5.

13. ICDD reference codes must be provided for all detected phases in XRD results (e.g., Fig. 4).

Response:

The ICDD reference codes of BCC and FCC are added in line 179.

14. EDS spectra is also required for all A-F analysis points on Fig. 6.

Response:

We added EDS spectrum of point A-F to figure 6.

15. There is no description of the future plans for research in the first part of the “Conclusions” section. This should be completed in this section.

Response:

We have added the future plans for research in the first part of the “Conclusions” section.

16. Recently published references are beneficial for this work. Please check and use new references focused on your work: org/10.1002/adem.202001047; doi.org/10.3390/coatings12030372

Response:

These two references are very helpful to us. Thank you very much for your suggestion.

17. Comments and related discussion on corrosion pit size and related mechanism in Fig. 11 is incomplete. Please revise.

Response:

We deleted the Simulation results of simplified electrochemical corrosion model, because the simulation results are not meaningful for the discussion of corrosion mechanism.

Special thanks to you for your good comments.

Round 2

Reviewer 3 Report

Accept as is.