The Effect of an Ultrasonic Field on the Microstructure and Tribological Behavior of ZrB₂/ZrC+Ni60A/WC Composite Coating Applied by Laser Cladding

Round 1

Reviewer 1 Report

·        The abstract was not excited. The authors must be write in a short with the main important results

·        The novelty of this work in compared to the previous similar work must be inserted

·        In table 2, you can write one time the value of Laser average, Laser scan,  Powder feeding rate, and Ultrasonic as they are the same for all samples

·        The spectrograph was not familiar. Please, support you result in supplementary file with original XRD spectra

·         The label of y-axis in XRD is 2 theta not 2 teta

It is acceptable 

Author Response

The abstract was not excited. The authors must be write in a short with the main important results

• The novelty of this work in compared to the previous similar work must be inserted

Thank you for your comment. In our previous work, the coating was of metallic type (NbMoTaTiNi) and was melted. This is despite the fact that in this work the coating is of composite (ceramic) type and ceramic particles are not melted in the coating. This issue creates a more ideal grain purification. In section 3.1, the explanation about the comparison of the current work with the previous work has been added to the revised version.

• In table 2, you can write one time the value of Laser average, Laser scan,  Powder feeding rate, and Ultrasonic as they are the same for all samples

Thank you for your suggestion. The table is named to introduce the samples marked with MT. The parameters of the laser are the same, this issue was added to the experimental section. But since the naming of samples is related to the change in Ultrasonic power (W), Table 2 has been created.

• The spectrograph was not familiar. Please, support you result in supplementary file with original XRD spectra

XRD analysis by Shimadzu XRD-6100 device; Japan and conducted by the first author of the manuscript at Xijing University. The above laboratory provides the results after analysis with Xpert software, and we do not have access to the Excel file. Thank you for understanding us.

• The label of y-axis in XRD is 2 theta not 2 teta

Thank you for your attention. Was corrected.

Author Response File: Author Response.docx

Reviewer 2 Report

This paper talks about the effect of ultrasonic field on microstructure and tribological behavior of ZrB2/ZrC+Ni60A/WC composite coating applied by laser cladding. The following points need to be clarified:

1.      The introduction is too short, hence needs to be rewritten, i.e. a broader literature review may give readers a better insight about the topic.

2.      It is suggested that the authors should modify the last part of the introduction to: 1) clearly mention the goal and novelty of this work (that needs to be highlighted clearly), 2) mention the methodology used and it is important to place the major hypothesis, 3) mention the structure of the paper or procedure of their work and expected results.

3.      In the abstract the following sentence “The highest level of microhardness and wear resistance was obtained when ultrasonic waves were used during coating” needs to be revised. It should be clearly mentioned how hardness and wear resistance were changing. “highest level” is confusing

4.      How many times did each experiment case was repeated? Figure 2(f) does not show the error bars.

5.      The paper lacks a discussion on the weakness and limitations of the present methodology proposed.

6.      The authors should refrain from summarizing the work in the conclusion; instead, only the main findings should be placed.

7.      In the conclusion the authors could propose an optimized coating process.

Minor editing of English language required

Author Response

This paper talks about the effect of ultrasonic field on microstructure and tribological behavior of ZrB2/ZrC+Ni60A/WC composite coating applied by laser cladding. The following points need to be clarified:

1. The introduction is too short, hence needs to be rewritten, i.e. a broader literature review may give readers a better insight about the topic.

Thank you for your comment, dear reviewer. The introduction was polished. A literature review was added to the introduction section.

2. It is suggested that the authors should modify the last part of the introduction to: 1) clearly mention the goal and novelty of this work (that needs to be highlighted clearly), 2) mention the methodology used and it is important to place the major hypothesis, 3) mention the structure of the paper or procedure of their work and expected results.

Thank you for your good suggestion. The end of the introduction section was modified by the method suggested by the dear reviewer.

3. In the abstract the following sentence “The highest level of microhardness and wear resistance was obtained when ultrasonic waves were used during coating” needs to be revised. It should be clearly mentioned how hardness and wear resistance were changing. “highest level” is confusing

Thank you for your good point. The modified abstract and numerical results were replaced.

4. How many times did each experiment case was repeated? Figure 2(f) does not show the error bars.

Thank you for your comment. Figure 3f (Figure 2f of the pre-revised version) is related to the dimensions of the coat pool, and the dimensions were measured after the image was taken with SEM by Image j software.

5. The paper lacks a discussion on the weakness and limitations of the present methodology proposed.

Thank you for your comment. The manuscript was again reviewed and revised. In fact, this manuscript has tried to highlight the weaknesses and limitations of previous studies conducted by our team (Morteza Taheri). For example, the use of the coating process (laser cladding + ultrasonic) is a solution for the weakness of the laser cladding method, which is addressed in this work. Choosing the composition of the coating material that has the ability to decompose and transform into anti-wear phases during laser cladding is one of the other points of this research. Also, the use of the contact ultrasonic system gave better results than our previous research, which used a non-contact ultrasonic system.

6. The authors should refrain from summarizing the work in the conclusion; instead, only the main findings should be placed.

 Thank you for your comment. The conclusion was revised and an attempt was made to present only the main results (and not the work summary).

6. In the conclusion the authors could propose an optimized coating process.

Thank you for your good suggestion. In this work, the optimal parameter was added to the conclusion.

Author Response File: Author Response.pdf

Reviewer 3 Report

Dear Authors,

The presented manuscript deals with an interesting topic titled “The effect of ultrasonic field on microstructure and tribological behavior of ZrB2/ZrC+Ni60A/WC composite coating applied by laser cladding”.

The article aimed to study the effects of using ultrasonic fields during the formation of a ZrB2/ZrC-Ni60A/WC composite coating on GTD-111 superalloy, applied using laser cladding technology.

After carefully going through the manuscript, although I found that the work is original and includes relevant research, I have some suggestions to improve this paper, which in my opinion contains some errors and cannot be accepted for publication in its present form. Some of the problems existing in this paper that the authors must pay attention to deal with are;

Overall comments to the author:

1)     The introduction is quite short and very general, I suggest making a table summarizing the current achievements and shortcomings regarding the modification of the surfaces of gas turbine blades.

2)     Materials and method: Authors wrote “The parameters used for laser cladding were selected based on trial and error and previous studies [17,18], presented in Table 2”  - Could you provide more detail on the selection criteria for the parameters used in the experiments, such as laser power and ultrasonic power? What guided these choices?

3)     What the coatings look like after applying them to the samples is not shown?

4)     There is no photo or even a schematic picture of the tribological test stand.

5)     What are the potential implications of the changes in microstructure for the mechanical properties and durability of the coating?

6)     Was the reduced wear resistance for tests with an ultrasonic power of 400 W caused only by the increase in the size of the holes that appeared?

7)     You wrote that 'At the power of 400 W, a slight increase in the hole is observed, which indicates the re-formation of the cavity due to the bursting of the holes.' Is it about the hole cracking or the formation of a new one? This is not precisely explained

8)     Are there any limitations in your methodology or the tools used that might influence the results?

9)     Do you plan to conduct further research to validate or expand upon these findings?

10)  How do your results compare with other available studies on the same topic?

Minor comments to Author:

1)     Separate figure 1d from the remaining figures and mark it as Fig. 2

2)     Page five, line 7, please correct, write MT400 instead of M400

3)     Separate figures 5a and 5b, no description in the picture 5b

4)     Separate figure 6a from 6b and 6c or try to present it more clearly, improve the descriptions of the drawings and explain the COF abbreviations.

Author Response

Dear Authors,

The presented manuscript deals with an interesting topic titled “The effect of ultrasonic field on microstructure and tribological behavior of ZrB2/ZrC+Ni60A/WC composite coating applied by laser cladding”.

The article aimed to study the effects of using ultrasonic fields during the formation of a ZrB2/ZrC-Ni60A/WC composite coating on GTD-111 superalloy, applied using laser cladding technology.

After carefully going through the manuscript, although I found that the work is original and includes relevant research, I have some suggestions to improve this paper, which in my opinion contains some errors and cannot be accepted for publication in its present form. Some of the problems existing in this paper that the authors must pay attention to deal with are;

Overall comments to the author:

• The introduction is quite short and very general, I suggest making a table summarizing the current achievements and shortcomings regarding the modification of the surfaces of gas turbine blades.

Thank you for your comment. The introduction section was generally polished. The results of past research works and their comparison were added to the revised version.

2)     Materials and method: Authors wrote “The parameters used for laser cladding were selected based on trial and error and previous studies [17,18], presented in Table 2”  - Could you provide more detail on the selection criteria for the parameters used in the experiments, such as laser power and ultrasonic power? What guided these choices?

Thank you for the technical questions, dear reviewer. The current research has focused on the effect of the ultrasonic field. In the experimental section, reference is made to the previous work. But in fact, we tried different parameters of laser cladding on ZrB2/ZrC+Ni60A/WC and reached the same range of previous research as presented in Table 2. Now, if we wanted to bring those parameters, it could have been a separate article, and there would have been almost duplicates of our previous research, especially the corresponding author (Morteza Taheri), and it would have diminished the main purpose of this research, which is to investigate the effect of ultrasonic waves. Thank you for understanding us.

3)     What the coatings look like after applying them to the samples is not shown?

Thank you for your comment. The cross-sectional images of the coating along with their dimensions are presented in Figure 3. The area marked with clad zone corresponds to ZrB2/ZrC+Ni60A/WC composite after coating.

4)     There is no photo or even a schematic picture of the tribological test stand.

Thank you for your suggestion. Schematic of the wear test was added in Figure 2b.

5)     What are the potential implications of the changes in microstructure for the mechanical properties and durability of the coating?

Thank you for your beautiful question. Exactly the point mentioned by the respected reviewer is the main goal of our research. In fact, by applying the ultrasonic field during laser cladding, we intended to improve the microstructural properties of the coating and thus improve the tribological properties. The results of our research showed that ultrasonic refines the grains. Grain refinement means reducing grain size, reducing grain aspect, tendency to form equiaxed grains, and reducing porosity. The above set of cases showed that the tribological properties were improved. The mechanism for all of the above is in the manuscript and has been polished a bit.

6)     Was the reduced wear resistance for tests with an ultrasonic power of 400 W caused only by the increase in the size of the holes that appeared?

Thank you for your careful reading of this manuscript. As mentioned by dear reviewer, the most important reason for reducing the tribological behavior of the coating with the increase of ultrasonic power from 300 W is the creation of holes, the mechanism of which is explained in the manuscript (excessive increase of cavitation effect and formation of new holes). It seems that the most important reason is these holes. Because the grain size is slightly reduced at 400 W compared to 300 W, but the wear results at 400 W are weaker than at 300 W.

7)     You wrote that 'At the power of 400 W, a slight increase in the hole is observed, which indicates the re-formation of the cavity due to the bursting of the holes.' Is it about the hole cracking or the formation of a new one? This is not precisely explained

Thank you for your comment. New explanations about this were added to the manuscript. “In fact, at a power of 400 W, cavitation causes excessive pressure on the holes, which will burst with a new wave of disturbance in the melting pool. This disturbance will be accompanied by the formation of new holes, which will turn into porosity soon after solidification.”

"8)     Are there any limitations in your methodology or the tools used that might influence the results?

Thank you for your expert comment. There are definitely limitations. I (Morteza Taheri) with the help of my team have been focusing on the coating of superalloys used in gas turbine blades for several years. In each study, we have tried to solve the shortcomings and limitations of the previous ones. Our goal is a coating that achieves two main goals: firstly, to be flawless, and secondly, to have a refined microstructure. I write some of these restrictions. Whatever parameter we choose for the laser, it will probably not be the input parameter. Because a large amount of laser radiation is reflected from the surface. Should we place the ultrasonic field in a contact or non-contact manner? Our research has shown that the type of contact we used in this research has a better effect. Pulsed or continuous? In previous studies, we have presented that pulsed laser produces better refined grains due to better solidification conditions. Our effort has always been to remove limitations in further research.

9)     Do you plan to conduct further research to validate or expand upon these findings?

I really thank the honorable reviewer for these key questions. Yes. I think I answered in the previous question that my goal is to expand the research on the coating of superalloys with the laser cladding technique. My goal is to modify the microstructure. In order to increase the resistance to corrosion and wear. My future research is mainly focused on two things: firstly improving the coating material, and secondly improving the method through laser hybrid methods. In the first case, I move towards special composite compounds and even cermets. I want to use these compounds in nano dimensions as well. In the second case of hybrid methods with laser. Such as magnetic field + laser cladding methods, magnetic field + ultrasonic field + laser cladding, and other methods. Also, pre-coating methods such as shot blast, pre-heat and post-heat effect, effect of heat treatment cycle after coating, etc.

10)  How do your results compare with other available studies on the same topic?

Thank you for your comment. A section of research comparison was added to the manuscript (especially in the introduction section). The comparison of the results in this field comes down to two cases: the first case is the selection of a suitable material for coating which has a very good wear behavior. Corrosion behavior will also be investigated in future research. The second case was the type of coating. Comparing our research with other researches that did not use the hybrid method (laser cladding+ultrasonic) has shown better microstructural characteristics that lead to better mechanical behavior. The expansion of the equiaxed grain area at the top and bottom of the coating is one of the most important achievements of this research compared to other researches.

Minor comments to Author:

• Separate figure 1d from the remaining figures and mark it as Fig. 2

Thank you for your comment. The above was done.

• Page five, line 7, please correct, write MT400 instead of M400

Thank you for your attention. The above item was corrected.

• Separate figures 5a and 5b, no description in the picture 5b

Thank you for your suggestion. Since pictures 6a and 6b (Figure 5 of the version before the revision) are related to hardness results, I would like to thank the honorable reviewer for accepting the figures in their current state.

• Separate figure 6a from 6b and 6c or try to present it more clearly, improve the descriptions of the drawings and explain the COF abbreviations.

Thank you for your comment. COF modification was added in the revised version. “coefficient of friction (COF)”

Figures 7a-b (Figure 6 before the revised version) are related to the wear results. Especially Figure 7b, which shows the average COF results of sample 7a.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

The paper is revised as requested

Minor editing of English language required