Evaluation of the Wear Properties and Corrosion Resistance of 52100 Steel Coated with Ni/CrC by Cold Spraying

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors report the preparation of Ni/CrC alloy coatings by cold spraying method. The microstructure of the coatings was characterized by scanning electron microscopy (SEM). Scratch, sliding, potentiodynamic polarization and electrochemical impedance spectroscopy tests showed that the coatings have improved wear and corrosion resistance. The design of this work seems fine, and some analysis results are presented. Major revision should be considered before publication.

 

1. In the section of Introduction, the authors write, "The cold spray (CS) method is renowned for producing low-porosity coatings and preserving powder characteristics, ......". What are the methods to improve the wear and corrosion of coatings? Why choose the cold spray method? What are its advantages over other methods?

2. In the introduction, there is too little coherence between the paragraphs of the paragraphs. In addition, while the authors cite many examples, they need to summarize previous studies and demonstrate the novelty of this work; how does the current work differ from previous reports?

3. Were the working electrodes stabilized at the open circuit potential before the measurements of Tafel polarization curves and Electrochemical Impendence Spectroscopy? If so, for how long was each sample stabilized?

4. Some errors should be noted. Tables 2, 4, 5, 8 and 9 are not three-line tables.

5. In the section of 3.3, the author wrote that "The CPE impedance is defined by, ……". The formula should provide literature support.

6. In section 3.1, I recommend that the authors perform EDS testing on the coated surface to analyze what elements the coating contains.

7. The conclusions should be simplified by directly summarizing the obtained intuition and key parameters.

Author Response

Response to Reviewer 1 Comments

” The authors report the preparation of Ni/CrC alloy coatings by cold spraying method. The microstructure of the coatings was characterized by scanning electron microscopy (SEM). Scratch, sliding, potentiodynamic polarization and electrochemical impedance spectroscopy tests showed that the coatings have improved wear and corrosion resistance. The design of this work seems fine, and some analysis results are presented. Major revision should be considered before publication.”

Dear reviewer,

Thank you very much for your positive feedback and for these valuable comments. We have tried to answer all aspects that were mentioned.

Point 1:  In the section of Introduction, the authors write, "The cold spray (CS) method is renowned for producing low-porosity coatings and preserving powder characteristics, ......". What are the methods to improve the wear and corrosion of coatings? Why choose the cold spray method? What are its advantages over other methods?

Response 1:

We have added additional information in order to improve this section, as can be seen below:

The cold spraying method (CS) is attractive due to the possibility of producing dense coatings with low porosity at very low temperatures. This is possible only through this method, so that even at temperatures of approximately 700 °C, the deposited layer adheres excellently to the surface of the base material while preserving the properties of the powders used as raw materials. Due to these advantages and the wide range of powders with various properties that can be found at established companies in this field, the cold deposition method is excellent both for improving the properties of the materials and for the reconditioning processes of the various components.

Point 2: In the introduction, there is too little coherence between the paragraphs of the paragraphs. In addition, while the authors cite many examples, they need to summarize previous studies and demonstrate the novelty of this work; how does the current work differ from previous reports?

Response 2:

Following your instructions, the authors have made corrections (the paragraphs marked with yellow) to this section so that there is better coherence and, at the same time, a clearer visualisation of the purpose of this work and to better highlight the scientific progress brought by the research carried out.

Point 3: Were the working electrodes stabilized at the open circuit potential before the measurements of Tafel polarization curves and Electrochemical Impendence Spectroscopy? If so, for how long was each sample stabilized?

Response3:

The electrochemical test procedure started by measuring the open circuit potential (OCP) for 1 hour after exposure of the working electrode to the solution at room temperature.

Point 4: Some errors should be noted. Tables 2, 4, 5, 8 and 9 are not three-line tables.

Response4:

The authors fixed this error, as can be seen in the manuscript.

Point 5: In the section of 3.3, the author wrote that "The CPE impedance is defined by, ……". The formula should provide literature support.

Response 5:

We added a new reference

Samantha Michelle Gateman , Oumaïma Gharbi , Hercílio Gomes de Melo , Kieu Ngo , Mirelle Turmine , Vincent Vivier , On the use of a constant phase element (CPE) in electrochemistry, Current Opinion in Electrochemistry, Volume 36, December 2022, 101133

Point 6:  In section 3.1, I recommend that the authors perform EDS testing on the coated surface to analyze what elements the coating contains.

Response 6:

As can be seen in the work, I have attached the EDS testing for the covered surface.

Point 7: The conclusions should be simplified by directly summarizing the obtained intuition and key parameters.

Response 7:

As can be seen in the manuscript, the authors summarize the Conclusions section so that all information is concise and directly based on the results obtained.

Reviewer 2 Report

Comments and Suggestions for Authors

The article is devoted to the study of the properties of Ni/CrC coating on steel 52100. I have several comments and questions for the authors.

1. After line 95 in the introduction, the purpose of the study and its scientific novelty should be formulated.

2. The paper poorly describes the research methodology and materials. I recommend giving the chemical composition of AISI 52100 steel. Different countries use different markings and it is difficult for the reader to understand what steel the study is devoted to.

3. The paper talks about Ni/CrC by Cold Spray powder coating. But in section 2 and further in the text it is not indicated what chemical and granulometric composition the powder has. What % Ni is in the powder? I recommend providing a photo of the powder, similar to how it was done in the work https://doi.org/10.3390/ma11050742.

4. How was the surface prepared before coating? The quality of adhesion of the coating to the base metal depends on this.

5. In the microstructure in Figure 2, two phases are visible: dark and gray. Please clarify which is the dark phase in terms of chemical composition and which is the gray phase?

6. The paper does not indicate the size of the samples. We need to clarify this. 

7. How were samples prepared for metallographic analysis?

8. I recommend providing explanatory notes in Figure 2. Coating thickness, phases, base metal.

9. In Figures 3 and 7, the marker color was chosen poorly. The inscriptions are difficult to read. I recommend changing the marker color.

10. I recommend that the hardness of the base metal and coating be given in the article in HRC or HV. Compare the obtained values. Do I understand correctly that the hardness of the coating was higher than that of the base metal (AISI 52100)? Table 2 shows that the hardness of the coating is higher. What is the condition of AISI 52100 steel? The hardness of this steel is very dependent on heat treatment.

11. Increasing the corrosion resistance of Ni/CrC coatings is logical and expected. Nickel and chromium have high corrosion resistance. In this study, more attention should be paid to the quality of adhesion of the coating to the base metal, its hardness and wear resistance.

Author Response

Response to Reviewer 2 Comments

” The article is devoted to the study of the properties of Ni/CrC coating on steel 52100. I have several comments and questions for the authors.”

Dear reviewer,

Thank you very much for your positive feedback and for these valuable comments. We have tried to answer all aspects that were mentioned.

Point 1:  After line 95 in the introduction, the purpose of the study and its scientific novelty should be formulated.

Response 1:

Following the instructions, the authors have added additional information to this section, and we hope that it is now sufficiently improved to support the purpose of this study.

,, With the purpose of enhancing the properties of the base material in terms of layer adhesion, microstructure, hardness, and corrosion resistance, the purpose of this study is to highlight the properties of Cr/C-based powders that have been deposited using the cold spray method. This is in order to provide a more comprehensive picture of the performances that have been obtained by making these deposits.’’

Point 2: The paper poorly describes the research methodology and materials. I recommend giving the chemical composition of AISI 52100 steel. Different countries use different markings and it is difficult for the reader to understand what steel the study is devoted to.

Response 2:

We have attached to the manuscript the table with the chemical composition of AISI 52100 alloy steel as well as its equivalents (table 4).

 Point 3: The paper talks about Ni/CrC by Cold Spray powder coating. But in section 2 and further in the text it is not indicated what chemical and granulometric composition the powder has. What % Ni is in the powder? I recommend providing a photo of the powder, similar to how it was done in the work https://doi.org/10.3390/ma11050742.
Response3:

I have attached to the manuscript the tables with the chemical composition and mechanical properties of WIP-BC1 powders and the specific reference.

Point 4: How was the surface prepared before coating? The quality of adhesion of the coating to the base metal depends on this.

Response4:

We have modified in the manuscript, according to your instructions, the following: The machine-finished surface was abraded by hand with ScotchBriteTM and wiped with ethanol. The bond layer (WIP-BC1) was sprayed onto the surface with the nozzle oriented at 60° to the surface.

Point 5: In the microstructure in Figure 2, two phases are visible: dark and gray. Please clarify which is the dark phase in terms of chemical composition and which is the gray phase?

Response5:

We have corrected these aspects (as you mentioned) and made the appropriate notes on the micrographs. We hope that this is correct and that the images are improved.

Point 6:  The paper does not indicate the size of the samples. We need to clarify this.

Response 6:

As can be seen in the manuscript, we made the appropriate mentions regarding the clarification of the sample dimensions. We have inserted the following text:

”The dimensions of the samples used are between: ø64 x 10 mm for the determination by rotation movement and 30 x 30 x 10 mm for the determination by translation movement; and 20 x 20 x 10 for microsratch and indentation tests. In Figure 1, we can see a sample mounted on the table of CETR UMT-2 tribometer”

And

For the corrosion test, the size of the round samples used is ø12 x 4 mm.

Point 7:  How were samples prepared for metallographic analysis?

Response 7:

Metallographic samples were cut to standard sizes according to wear, microindentation, scratch and corrosion tests. To perform surface and cross-section morphological analyses, rectangular samples were embedded in resin round specimens, after which grinding was performed at different grain sizes, up to grain size 2500P and metallographic etching was performed with Nital reagent, having a chemical concentration of 10% HNO₃.

Point 8: I recommend providing explanatory notes in Figure 2. Coating thickness, phases, base metal.

Response 8:

We have corrected these aspects and made the appropriate notes on the micrographs. We hope that it is now correct and that we have managed to improve these details.

Point 9: In Figures 3 and 7, the marker color was chosen poorly. The inscriptions are difficult to read. I recommend changing the marker color.

Response 9:

Dear reviewer, Thank you very much for your observations. We have updated figures 2, 3, 5, 7 and 10 with a more readable scale bar. Unfortunately, we cannot modify the color of the measurements because these values are given by the equipment software. The images are 300 dpi and can be zoomed in very well. Please accept this form.

Point 10: I recommend that the hardness of the base metal and coating be given in the article in HRC or HV. Compare the obtained values. Do I understand correctly that the hardness of the coating was higher than that of the base metal (AISI 52100)? Table 2 shows that the hardness of the coating is higher. What is the condition of AISI 52100 steel? The hardness of this steel is very dependent on heat treatment.

Response 10:

Dear reviewer, Thank you very much for your suggestions. As can be seen in the paper, we fixed this aspect and attached the changes made below.

The following text has been added: ”To evaluate the Rockwell hardness and Young modulus, were carred out five microindentation tests on four coated 52100 steel samples and one uncoated steel sample for 20 N vertical loading, and the final data are presented in Table 5. The coated samples exhibit greater hardness values compared to the base material, indicating an enhanced resistance to wear.”

Table 5. Data obtained after performing microindentation tests.

Sample		1	2	3	4	Uncoated
load [N]		20				20
Rockwell Hardness [HRC]	1	69.60	65.80	72.23	70.44	49.31
	2	68.36	61.74	72.97	59.37	50.96
	3	73.87	68.07	67.19	65.95	47.28
	4	70.72	69.23	70.97	71.64	52.45
	5	63.88	64.79	76.26	69.03	48.59
	Av	69.29	65.92	71.92	67.29	49.72
Young modulus [GPa]	1	155.47	152.82	162.22	166.88	199.86
	2	154.38	159.67	169.53	153.40	208.04
	3	160.55	160.00	165.44	162.03	221.24
	4	155.92	157.04	160.25	165.28	211.39
	5	166.72	160.88	168.86	163.77	209.69
	Av	158.61	158.08	165.26	162.27	210.04

Point 11: Increasing the corrosion resistance of Ni/CrC coatings is logical and expected. Nickel and chromium have high corrosion resistance. In this study, more attention should be paid to the quality of adhesion of the coating to the base metal, its hardness and wear resistance.

Response 11:

The research carried out on corrosion resistance confirms the data from the specialised literature regarding the performances achieved by Ni Cr/C coatings and, at the same time, is intended to highlight the superior properties of the deposited layer, coming as a complement to the research carried out on adhesion of the coating to the base metal, its hardness, and wear resistance. These analyses are part of a large research project coordinated by the Northeastern University of Boston (USA), where the aim of the research was to test the influence of the deposited layers in terms of microstructure, mechanical properties, and corrosion behaviour, as well as impact applications.

Reviewer 3 Report

Comments and Suggestions for Authors

The provided characterization of wear and corrosion resistance of the coatings prepared by cold spray methods is of common interest, mainly from the point of practical applications.

There are some minor points that could be specified/explained in more detail in order to improve the clarity of the text describing the obtained results, and relevance of the derived conclusions.

The comments/suggestions are summarized in the commented manuscript text enclosed.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

The quality of English varies significantly throughout the text (Introduction section is fine, but the subsequent description of the obtained results, especially those related to the wear tests,  should be improved..)

Author Response

Response to Reviewer 3 Comments

” The provided characterization of wear and corrosion resistance of the coatings prepared by cold spray methods is of common interest, mainly from the point of practical applications.

There are some minor points that could be specified/explained in more detail in order to improve the clarity of the text describing the obtained results, and relevance of the derived conclusions.

The comments/suggestions are summarized in the commented manuscript text enclosed.

The quality of English varies significantly throughout the text (Introduction section is fine, but the subsequent description of the obtained results, especially those related to the wear tests,  should be improved..)”

 

Dear reviewer,

Thank you very much for your positive feedback and for these valuable comments. We have tried to answer all aspects that were mentioned and to improve the manuscript as you desired.

 

Response:

First of all, we would like to thank you for the corrections that you made to the entire paper. As can be seen in the manuscript, the authors tried to revise the entire paper, and we managed to respond in an appropriate way to the mentions made, so that the research paper is improved to meet your standards.

Typing errors have been corrected, tables have been updated, and the figures have been revised as requested by you and the other reviewers.

If there are still inconsistencies, please respectfully mention them to us so that we can correct them in the next review.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The revised manuscript can be accepted for publication.

Reviewer 2 Report

Comments and Suggestions for Authors

The authors significantly corrected the article and responded to questions and comments. I recommend publication in this version.