Effect of Brazing Temperature on the Microstructure and Chosen Properties of WC–10Ni/NiCrBSi Composite Coatings Produced by Vacuum Cladding from Flexible Coated Cloths
Round 1
Reviewer 1 Report
This paper presents investigation of three kinds of WC–10Ni/NiCrBSi composite coatings. This coatings were prepared on the surface of Q235 carbon steel at 1015°C, 1055°C, and 1095°C by vacuum brazing. Authors investigated the microstructure and properties of the composite coatings. With increase of brazing temperature the reaction layer between the solder and the hard phase gradually decreased and disappeared at 1095°C. Size of gray-white massive phases with a large amount of W in the brazing layer decreased gradually. With increase of brazing temperature the Fe content markedly increased in the reaction layer of the matrix and the solder – increasee in brazing temperature was beneficial for metallurgical bonding between the coating and the substrate. Interface bonding strength were enhanced but the microhardness of the composite coating section decreased. The interface bonding strength reached 362.9 MPa.
In my opinion this paper can be interesting to readers of Coatings journal. The paper is it clearly presented and well organized. English of the paper is rather good and meet the requirement of the journal – in my opinion the language of the paper should be a little improved. In my opinion the figures are a good quality. The manuscript can be accepted for publication after minor corrections.
I find some editing mistakes for example:
- In the whole paper, you write the temperature as 1015 °C – you should write a number with the Celsius degree without spaces (1015°C). These errors are on the lines: 12, 16, 22, 44, 61, 73, 74, 118, 128, 131, 132, 141, 150, 171, 172, 200, 202, 244, 253, 255 and 263.
- In the line you write 2×10-3 Pa and should be 2×10-3 Pa – the number -3 is the exponent of power.
- In the line 82 you should erase a dot in front of a word “Table …”.
- Amount of references is also sufficient but some papers cited in the references (9 from all 29) are older then 10 years. Authors should include several modern papers.
- Amount of references is also sufficient but some papers cited in the references (8 from all 29) are wrote by authors from Asia – China and others. Authors should include several modern papers (also from Europe and America).
The presented paper suits the requirements of the Coatings journal and it may be publish after MINOR corrections.
Reviewer
Author Response
Point 1: line 12, 16, 22, 44, 61, 73, 74, 118, 128, 131, 132, 141, 150, 171, 172, 200, 202, 244, 253, 255 and 263.
Comments: In the whole paper, you write the temperature as 1015 °C – you should write a number with the Celsius degree without spaces (1015°C)
Response 1: I am sorry for that, I will correct these errors.
Point 2: line 74
Comments: In the line you write 2×10-3 Pa and should be 2×10-3 Pa – the number -3 is the exponent of power.
Response 2: I am sorry for that, I will modify it.
Point 3: line 82
Comments: you should erase a dot in front of a word “Table …”.
Response 3: I am sorry for that error, I will erase the dot.
Point 4: References
Comments: Amount of references is also sufficient but some papers cited in the references (9 from all 29) are older then 10 years. Authors should include several modern papers. Amount of references is also sufficient but some papers cited in the references (8 from all 29) are wrote by authors from Asia – China and others. Authors should include several modern papers (also from Europe and America).
Response 4: I will modify the references and quote some modern papers from Europe and America.
Author Response File: 
Author Response.docx
Reviewer 2 Report
Compared to the last version of this paper, the quality of the paper is clearly improved which is also due to the much better quality of the English. This is now the quality with which the paper is worth to be submitted to a journal for a first Review. However, I am a little bit disappointed that at some points the authors did not really revise the paper carefully. E.g. they agree that there is no Cr rich phase, that they did a mistake there, but at 2 points this Cr rich phase still appears in the text (see below).
And there are still a few issues concerning the content:
Line 145: Obviously, the increase caused the size of the white massive phases to become smaller. à Increase in which property?
Table 4: As I already remarked in my last comments, it doesn’t make sense to give results of EDX analyses to 0.01 %. Here I would require a reasonable rounding (1 %, in any case not better than 0.1 %). And if these results are then meaningfully presented, you can hardly see a difference in the Si content between B, D and F. I would recommend to delete the statement with the decrease in Si there.
Figure 8: I still recommend to put the intensity values at the left side of the axis.
In your answer you agreed that there is no Cr rich phase and that you delete it. However, it is still there – in line 183 and in line 185.
185: Concerning my question in the last review round: why do you think that Si segregates around the WC particles? If you measure Si at the same positions like W this means that Si is inside the W particles and not around them. Now you write “ It is notable that Si aggregated around the WC particles and tungsten-rich phases. This is because the Si in the NiCrBSi was diffusing and accumulating into the WC particles when it was melted.”
What is now the right description? Si aggregates around the WC particles or diffuses into the WC particles?
Phase formation: I still do not understand the issue with the Ni3Si. You write in your answer to my question:
“Response 13: I will modify the picture to improve the quality. The test area of XRD was the cross section of the sample as shown in Figure 7(a), however, the test area of EDS was the bonding zone of coating to substrate. “
So, in Fig. 7(a) the 1015 °C sample is shown, the XRD shows the results for the 1055 °C sample. The linescan for this sample J-K is across the whole cross section, from region I to region IV and with this covers all different areas of the sample. So unfortunately I cannot understand why “cross section like in the image” and “line scan of the bonding zone” are two different, independent regions.
Besides this, there are still some wrong spaces (e.g. 113 – 2 0N, 132- 109 5°C) and in Fig. 2 (c) there is a capital “C”.
Author Response
Point 1: line 145
Comments: Obviously, the increase caused the size of the white massive phases to become smaller. à Increase in which property?
Response 1: I am sorry that, I will modify to “Obviously, the increase of brazing temperature caused the size of the gray-white massive phases to become smaller.”
Point 2: Table 4
Comments: As I already remarked in my last comments, it doesn’t make sense to give results of EDX analyses to 0.01 %. Here I would require a reasonable rounding (1 %, in any case not better than 0.1 %). And if these results are then meaningfully presented, you can hardly see a difference in the Si content between B, D and F. I would recommend to delete the statement with the decrease in Si there
Response 1: I will delete the statement with the decrease in Si there and give results of EDX analyses to 0.1%.
Point 3: Figure 8
Comments: I still recommend to put the intensity values at the left side of the axis.
Response 3: I am sorry for that, I will put the intensity values at the left side of axis.
Point 4: Line 183 and 185
Comments: In your answer you agreed that there is no Cr rich phase and that you delete it. However, it is still there – in line 183 and in line 185.
Response 4: I am sorry, I will change “With the increase in brazing temperature, the content of the chromium-rich …. uniform” to “With the increase in brazing temperature, the content of the gray-white phases decreased, and the distribution of Cr became relatively uniform.”
Point 5: Line 185
Comments: Concerning my question in the last review round: why do you think that Si segregates around the WC particles? If you measure Si at the same positions like W this means that Si is inside the W particles and not around them. Now you write “ It is notable that Si aggregated around the WC particles and tungsten-rich phases. This is because the Si in the NiCrBSi was diffusing and accumulating into the WC particles when it was melted.”
What is now the right description? Si aggregates around the WC particles or diffuses into the WC particles?
Response 5: I am sorry that the description of Si element in this sentence is not appropriate. I will modify “It is notable that Si aggregated around the WC particles and tungsten-rich phases. This is because the Si in the NiCrBSi was diffusing and accumulating into the WC particles when it was melted” to “It is notable that Si has the same distribution tend as W. This is because the Si in the NiCrBSi was diffusing and accumulating into the WC particles when it was melted.” The right description is Si diffuses into the WC particles.
Point 6: Figure 9
Comments: Phase formation: I still do not understand the issue with the Ni3Si. You write in your answer to my question:
“Response 13: I will modify the picture to improve the quality. The test area of XRD was the cross section of the sample as shown in Figure 7(a), however, the test area of EDS was the bonding zone of coating to substrate. “
So, in Fig. 7(a) the 1015 °C sample is shown, the XRD shows the results for the 1055 °C sample. The linescan for this sample J-K is across the whole cross section, from region I to region IV and with this covers all different areas of the sample. So unfortunately, I cannot understand why “cross section like in the image” and “line scan of the bonding zone” are two different, independent regions.
Response 6: I am sorry that I did not explain this comment well before. Actually, comparing Figure 6(a) and Figure 7(b), you can find that the cross section of the sample consists of three layers: Surface Layer, Hardened Layer and Q235 substrate, so the test area of XRD contains these three areas. However, the test area of EDS was the bonding area between the coating and the substrate only contains the side near the substrate in the Hardened Layer and Q235. As a result, the Ni3Si appears in the surface layer. I will change “The cross-section of the sample with a brazing temperature of 1055℃ was analyzed by X-ray diffraction” to “The cross-section of the sample which contains Surface Layer, Hardened Layer and Q235 substrate Layer with a brazing temperature of 1055℃ was analyzed by X-ray diffraction.”
Point 7: Line 113, 132 Figure 2(c)
Comments: There are still some wrong spaces (e.g. 113 – 2 0N, 132- 109 5°C) and in Fig. 2 (c) there is a capital “C”.
Response 7: I am sorry, I will remove these wrong spaces and modify this “C” to “c”
Author Response File: Author Response.docx
Reviewer 3 Report
The effect of brazing temperature on the microstructure and chosen properties (interface bonding strength, wear resistance and microhardness) of WC–NiCrBSi composite coatings were studied. Despite the idea of such a research is not entirely new (for example, the authors of the present manuscript have recently published an article on the similar topic, and with similar issues, i.e.: X. P. Xu, L. He, C. Z. Xia and J. S. Zou: "Microstructure and Interface Bonding Strength of WC-10Ni/NiCrBSi Composite Coating by Vacuum Brazing" in High Temp. Mater. Proc. 2019; 38: 60–68 [19]), the manuscript does contain novel results. The paper is interesting and useful, well-structured and well readable. The analysis is logical, and the number of references is sufficient, though slightly more up-to-date sources (published in the last three years) could have been cited (currently more than half - 14 items - is from 2004 - 2015).
In general, the presented results are of interest as for scientists and engineers. Therefore, I can recommend it for publication in the journal of Coatings. However, some minor changes are needed:
1. I suggest a slight change in the title, e.g.: “Effect of brazing temperature on the microstructure and chosen properties of…” and updating of older references.
2. It is also necessary to update the reference [19] and to indicate significant differences between the current and already published own articles
Author Response
Point 1: I suggest a slight change in the title, e.g.: “Effect of brazing temperature on the microstructure and chosen properties of…” and updating of older references.
Response 1: Your suggestion is reasonable, I am very grateful, I will change the title to “Effect of brazing temperature on the microstructure and chosen properties of WC-10Ni/NiCrBSi composite coatings produced by vacuum cladding form flexible coated cloths”
I am sorry that I did not cite enough up-to-date sources, I will update the older references.
Point 2: It is also necessary to update the reference [19] and to indicate significant differences between the current and already published own articles
Response 2: I will update the reference [19]. This reference discussed the effect of WC content on the microstructure and mechanical properties of composite coatings. However, this paper study on the effect of brazing temperature on the microstructure and chosen properties of composite coatings.
Author Response File: Author Response.docx
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
The paper presents an investigation of a WC based coating which was prepared at different temperatures. Several experiments were performed to analyze the composition and properties.
The English language has to be edited extensively. For example, the use of tenses is very strange and has to be checked thoroughly and corrected as well as the sentence construction.
The paper is difficult to read, not only because of the weak English but also because of a not well organized structure within the explanations. The order of descriptions within the distinct paragraphs has to be improved. The quality of most of the figures has to be improved. Some open questions have to be addressed.
Introduction:
An a little bit more detailed introduction to the topic would be desirable.
Materials and Methods:
Figure 1: The contrast of the annotation has to be improved (It is hardly possible to read dark red on dark gray.)
The XRD device is using which radiation?
Figure 3: The type of font and the font size should not be different in (a) and (b). What is the scale bar in both sketches?
Results:
3.1:
The authors state: “Firstly, the thickness of the coating gradually decreased with the increasing temperature.” I cannot identify this in Figure 4. It is not possible to see the surface of the samples. The authors also describe that WC is accumulated in the areas near the brazing zone. Unfortunately it is not marked in the images which structures correspond to WC.
What is meant with: “The liquid solder lacking WC above the coating was lost during the brazing process, resulting in a gradual decrease in coating thickness.”
The contrast of the annotations in Figure 4 – yellow text on yellow ground – has to be changed. The scale bare is quite small.
3.2:
I guess that the images show the microstructure measured at room temperature and not at the brazing temperatures of more than 1000 °C as it is written in lines 97/98.
Figure 5: several features are marked in these images. However, it is not described in the caption what they mean. E.g. a table could be added there which summarizes these findings. Again, there is a bad choice of colors for the annotations and fonts and font sizes.
Please mark the “white vesicular WC particles” in Figure 4.
“Comparing Fig. 5(a), (b) and (c), it was found that when the brazing temperature was 1015℃ and 1055℃, and the near-seam section of the coating was divided into four regions: I, II, III and IV.”
This statement appears strange since in the text above the authors already describe that there are these 4 zones. Please think of rewriting this paragraph.
The authors detect a “gray-white massive phase”. What is it? (ok, it is described later. Perhaps one could state there that this is revealed in the following section.)
I do not understand why “zone II” disappears if the process is done at the highest temperature.
Line 129: “a large amount of Si and B diffused from the interface into…” From which interface?
Line 138: “light elements B and C were not marked”. The elements were not marked or not measured? Of cause it is not so easy to measure the light elements with EDS, however other methods like Auger electron spectroscopy could be used. A statement that the “areas likely contain a number of B and C interstitial atoms” appears quite doubtful to me. I would like to have a proof.
The authors describe that the WC particles did not undergo any transformation (line 132). A bit later they state that Cr causes a dissolution of WC (135), later again that WC itself did not decompose (207). This I do not understand. Is there a transformation or not? And if so, where is it seen in the images/data?
Line scans/Figure 6: I am wondering how representative a single line scan is in such an inhomogeneous material with locally distributed phases. Which general conclusions can be derived from such a measurement?
Why does Si segregate around the WC particles?
Figure 6: the images appear distorted. What is the meaning of the numbers behind the elements?
Figure 7: What is the “relative strength”? Units and numbers: it is relative strength / a.u. or relative strength (a.u.), the same holds for the x-axis. How do the XRD measurements of the other two samples look like – what is the difference to the presented curve?
3.4:
“Simultaneously, because of the sedimentation of the WC particles in the coating, the WC content in the surface layer was greatly reduced, so the hardness in the surface layer was lower.”
Where is it seen in Figure 8 that the hardness of the surface layer decreased with increasing temperature? In my eyes the values for the surface layer are quite the same independent on the temperature.
Figure 8: different fonts on the axes.
Author Response
Point 1: Introduction
Comment: An a little bit more detailed introduction to the topic would be desirable?
Response 1: I will add the following details.
The flexible "coated cloth" technology originated in the 1960s and 1970s and was invented by American scientists R. Goldsmith and E. J. Breton [10, 11]. The main process of the flexible "coated cloth" technology is: mixing the powdery hard particles, the bonding metal and the organic binder through a stirring device, and then the hard particle powder and the binder metal powder are wrapped in an organic binder by other molding processes. thereby a material having a good flexibility is produced. In this paper , WC-NiCrBSi composite coating was prepared by vacuum brazing on the surface of substrate Q235 by combining vacuum brazing technology and flexible "coated cloth" technology.
Point 2: Materials and Methods
Figure 1
Comment: The contrast of the annotation has to be improved (It is hardly possible to read dark red on dark gray.)
Response 2: I am sorry for the weird colour choice, I will change the colour of the annotation in Figure 1 to black.
Point 3: Materials and Methods
Comment: The XRD device is using which radiation?
Response 4: Sorry, I forgot to indicate it in this paper, the radiation of XRD device is Cu Kα radiation (λ = 1.54 Å). I will add the radiation type.
Point 4: Materials and Methods
Figure 3
Comment: The type of font and the font size should not be different in (a) and (b). What is the scale bar in both sketches?
Response 4: I am sorry that I ignored this detail and I will change the font and size to the same.
I will give the scale bar of shear test sketch. However, the microhardness test sketch was not drawn to scale, it is simply intended to indicate the general distribution of hardness test points in the sample.
Point 5: Results
3.1
Comment: The authors state: “Firstly, the thickness of the coating gradually decreased with the increasing temperature.” I cannot identify this in Figure 4. It is not possible to see the surface of the samples. The authors also describe that WC is accumulated in the areas near the brazing zone. Unfortunately it is not marked in the images which structures correspond to WC.
The contrast of the annotations in Figure 4 – yellow text on yellow ground – has to be changed. The scale bare is quite small.
Response 4: I am sorry, Figure 4 did not indicate my argument very well. I will change 3.1 to the following.
3.1. Micromorphology at different temperatures
Fig. 4(a) had shown Micromorphology of the coating with a soldering temperature of 1055℃. In the process of brazing, the NiCrBSi solder liquefied, while WC particles did not decompose. Due to the density of WC was higher than that of NiCrBSi and the gravity of WC, WC settled downward and accumulated in areas near the brazing zone. As the brazing temperature increased, the fluidity of the solder increased, and the resistance of solder to WC sedimentation decreased, therefore, the deposition of WC particles was more and more sufficient, and the amount of liquid solder without WC particles above the coating increased. As can be seen in Fig.4(b), these liquid solders flowed to the back of the sample due to the lack of support from the WC particles and this process led to a reduction in coating thickness.
Figure 4: (a) Micromorphology of the coating with a soldering temperature of 1055℃ (b) The front and back morphology of samples, these liquid solders flowed to the back of the sample due to the lack of support from the WC particles.
Point 5: Results
3.1
Comment: What is meant with: “The liquid solder lacking WC above the coating was lost during the brazing process, resulting in a gradual decrease in coating thickness.”
Response 5: I am sorry that I did not make it clear. What I wanted to express is that “as the brazing temperature increased, the fluidity of the solder increased, and the resistance of solder to WC sedimentation decreased, therefore, the deposition of WC particles was more and more sufficient, and the amount of liquid solder without WC particles above the coating increased. These liquid solders flowed to the back of the sample due to the lack of support from the WC particles and this process led to a reduction in coating thickness”. I will modify it.
Point 6: Results
3.2: [P4,96] “The micromorphology of the coating interface at the brazing temperatures of 1015℃, 1055℃ and 1095℃ was shown in Fig. 5.”
Comment: I guess that the images show the microstructure measured at room temperature and not at the brazing temperatures of more than 1000 °C as it is written in lines 97/98.
Response 6: I am sorry that I did not make it clear. I will modify it to “The micromorphology of the coating interfaces which brazed at 1015℃, 1055℃ and 1095℃ were shown in Fig. 5.”
Point 7: Results
Figure 5
Comment: several features are marked in these images. However, it is not described in the caption what they mean. E.g. a table could be added there which summarizes these findings. Again, there is a bad choice of colors for the annotations and fonts and font sizes.
Response 7: I am sorry for the bad choice of colors, I will modify the colors for the annotations and fonts and font sizes, and add a table.
Point 8: Results
Figure 4
Comment: Please mark the “white vesicular WC particles” in Figure 4.
Response 8: I will change Figure 4, the “white vesicular WC particles” can be clearly seen in the new Figure.
Point 9: Results
3.2:[4,104] “Comparing Fig. 5(a), (b) and (c), it was found that when the brazing temperature was 1015℃ and 1055℃, and the near-seam section of the coating was divided into four regions: I, II, III and IV.”
Comment: This statement appears strange since in the text above the authors already describe that there are these 4 zones. Please think of rewriting this paragraph.
Response 9: sorry, I will change this paragraph to “Comparing Fig. 5(a), (b) and (c), it was found that Zone II became narrower with the increase of the brazing temperature, disappearing at the 1095℃.”
Point 10: Results
[4,109]: “…At the same time, the size of the gray-white massive phase…”
Comment: The authors detect a “gray-white massive phase”. What is it? (ok, it is described later. Perhaps one could state there that this is revealed in the following section.)
Response 9: Ok, I will add a description here.
Point 10: Results
Comment: I do not understand why “zone II” disappears if the process is done at the highest temperature.
Response 10: well, the disappear of “zone II” means that the “gray-white massive phases” and
“WC particles” are separate. The generation of these phases is due to the dissolution of WC caused by Cr replacing C in WC. As the brazing temperature increases, the elemental activity is enhanced and the WC dissolution is more sufficient, therefore, “zone II” disappears.
Point 11: Results
[5,129]: “a large amount of Si and B diffused from the interface into …”
Comment: “a large amount of Si and B diffused from the interface into…” From which interface?
Response 11: Sorry, I did not express my meaning clearly, this interface is the interface between “carbide cloth” and “solder cloth”. I will add this description to the text.
Point 12: Results
[5.138]: “light elements B and C were not marked”
Comment: The elements were not marked or not measured? Of cause it is not so easy to measure the light elements with EDS, however other methods like Auger electron spectroscopy could be used. A statement that the “areas likely contain a number of B and C interstitial atoms” appears quite doubtful to me. I would like to have a proof.
Response 12: The EDS was used to measure the light element B and C, unfortunately, the result is ridiculous. Your doubt is reasonable, I will delete this conjecture in the paper.
Point 13: Results
[5,132]: “the WC particles alone did undergo …”
[5,135]: “Cr causes a dissolution of WC…”
[7,207]: “…the WC itself did not decompose”
Comment: Line 138: “light elements B and C were not marked”. The elements were not marked or not measured? Of cause it is not so easy to measure the light elements with EDS, however other methods like Auger electron spectroscopy could be used. A statement that the “areas likely contain a number of B and C interstitial atoms” appears quite doubtful to me. I would like to have a proof.
Response 13: I am sorry that I did not make it clear. The melting point of WC is 2870℃，therefore the separate WC particles did not undergo any transformation under vacuum conditions of 1100℃, however, they may form a dissolution after mixing with the NiCrBSi. The affinity of Cr to C was higher than that of W and C, and W in WC could be preferentially replaced. Therefore, Cr in NiCrBSi was also a cause of dissolution of WC.
The W in the gray-white massive phase can prove this point.
Point 14: Results
Figure 6: line scans
Comment: I am wondering how representative a single line scan is in such an inhomogeneous material with locally distributed phases. Which general conclusions can be derived from such a measurement?
Response 14: The coatings showed little change from the direction of vertical and line scanning. What I want from the single line scan is the distribution of elements around the WC particles and this distribution at the cross section of the substrate and coating.
Point 15: Results
[6,147]: “…in which Si diffused and aggregated to the WC particles…”
Comment: Why does Si segregate around the WC particles?
Response 15: In the vacuum brazing process, due to the high content of the melting element in the "solder cloth", a large amount of Si and B diffused from the interface between “carbide cloth” and “solder cloth” into the hard zone in order to achieve the balance of the element concentration in the coating:
Point 16: Results
Figure 6
Comment: The images appear distorted. What is the meaning of the numbers behind the elements?
Response 16: I am sorry for the strange proportion of the picture, I will change it. The numbers behind the elements are the quantity of intensity and its unit is CPS.
Point 17: Results
Figure 7
Comment: What is the “relative strength”? Units and numbers: it is relative strength / a.u. or relative strength (a.u.), the same holds for the x-axis. How do the XRD measurements of the other two samples look like – what is the difference to the presented curve?
Response 16: I am sorry for the error in the description. I will change “relative strength…” to “Intensity (a.u.)” and change “diffraction angle…” to “2θ(°)”.
Point 17: Results
3.4:[7,184] “Simultaneously, because of the sedimentation of the WC particles in the coating, the WC content in the surface layer was greatly reduced, so the hardness in the surface layer was lower.”
Comment: Where is it seen in Figure 8 that the hardness of the surface layer decreased with increasing temperature? In my eyes the values for the surface layer are quite the same independent on the temperature.
Response 17: I am sorry that I have analyzed the data incorrectly. I will delete the text of this error.
Point 18: Results
Figure 8
Comment: different fonts on the axes.
Response 17: I will modify the axes.
Author Response File: Author Response.docx
Reviewer 2 Report
The paper is about a subject of interest, the vacuum cladding. However, there are some points that should be correctly addressed before the paper is
acceptable. For example, introduction and references could be improved. In introduction, the authors could explain better the state of the art, the industrial application of the process and so on.
Author Response
Point 1: Introduction and reference
Comment: Introduction and references could be improved. In introduction, the authors could explain better the state of the art, the industrial application of the process and so on.
Response 1: I will add the detail of the flexible "coated cloth" technology.
Author Response File: Author Response.docx
Reviewer 3 Report
First, and although English is not my native language, I do not believe that the presented paper corresponds to the English standard Coatings journal uphold to. Therefore, I believe that a major English revision should be conducted.
I believe that the paper refers to an interesting topic and the scientific contributions are valid and interesting, nonetheless some extensive changes should be done on the document since a lot of experimental details are missing debilitating the results analysis, hindering the paper quality.
Please find below some detailed remarks regarding the different sections of the paper:
Abstract:
· The authors refer to delamination in the interface and afterwards state that there is a difference in bonding strength. This is confusing and no results presented on this paper are related to delamination. What does the authors mean with delamination? If there is delamination, then the coating won’t withstand sheer tests….
Introduction:
· Introduction should be more extensive, with more references to other authors work regarding these technique/materials. I believe that this introduction does not frame the readers to the scientific contributions provided within the text.
· The comparison between vacuum cladding and other processing techniques is not clear (ex. Welding).
Materials and Methods:
· This is the sections that I believe needs to be completely re-written since a lot of important details are missing and it is overall confusing. Most of the details missing make significant change on the materials processing characteristics and might influence the result analysis…
· Materials and Methods
o Missing steel substrate composition and mechanical characteristics
o Missing WC-10Ni and NiCrBSi powders composition and particle characteristics (shape, size, distribution, etc)
o How was the mixture done? Technique, duration… How was the mixture evaluated for homogeneity, …?
o What was the brazing cycle duration, heating rate? …
o How many samples were produced? Only one for each temperature? For statistical analysis it should be done at least 3-5 samples to ensure that the experimental variations were considered…
o How were the cloths prepared and what parameters were used?
o Was any load applied on the carbide cloth, solder cloth multilayers structure?
o Thickness of the cloths? Dimensions, etc….
o Missing the initial characterization of the cloths prior to brazing… (porosity evaluation, dispersions, dimensions,….)
o Table 1 has two WC-10Ni(5-15um) columns….
o How was the XRD done? Directly on the surface of the coating? What was the anode material?
o Scale on Figure 1 and 2
o Missing the distance between microhardness lines and indentations.
Results:
· Line 84. The thickness of the coating is not referred anywhere neither images showing the thickness evolution…
· A wettability study of the soldering paste should be interesting… At least heating soldering paste on top of the substrate to check if the wets or not.
· Line 120 and 121. D and F have 15% of Fe… That is not a “small amount of Fe”. Please correct the description.
· Line 126-128 The phrase “Simultaneously, due to the presence of WC particles in the hard zone, the difference in element concentration between the interface and the hard layer increases” does not make any sense either in English or scientifically…
· Line 151-154 – What is crystal segregation? This phrase also does not make sense…
· Figure 6 exhibit clearly a relation of location between the presence of Si and W (that are present in the same zone), as well as, when the presence of Ni is identified there is no Si and W. This should be referenced in the text clearly and the reason for this.
· As for the XRD the results make no sense. In Figure 6 the Si location is exactly different from the Ni and then on the XRD it is identified the presence of a Ni3Si phase… Another doubt is if the XRD analysis is on the surface how can the x-ray penetration see the substrate? What is the thickness of the coating….
· Line 187-189 – On the images presented before (Figure 4) no segmentation is observed… Can you present SEM imagens clearly showing the WC particle segmentation? If the WC particles would sediment, then the wear results should be worse for the higher temperatures (where the WC would sediment more). Can the authors comment on this?
· Line 195-196. Is the films delaminate how can they present these values of sheer strength? Can the authors clarify this?
· The paragraph from line 205-209 is not necessary and should be used for the introduction where the justification for the NiCrBSi coating and it’s importance should be referred.
· Overall analysis: With a more detailed materials and methods section, the Results section should be more supported. I believe that the extra details on the material section could help to further explain some of the phenomena identified. Please add some more comments regarding this on the Results section.
Conclusions:
· Same reference to delamination as on the Abstract. No evidence is presented in the paper and since the authors present a sheer strength of 362.9 MPa this makes no sense…
Bibliography:
· The two last references (14 and 15) are not referenced in the text….
Author Response
Point 1: Abstract
Comment: The authors refer to delamination in the interface and afterwards state that there is a difference in bonding strength. This is confusing and no results presented on this paper are related to delamination. What does the authors mean with delamination? If there is delamination, then the coating won’t withstand sheer tests….
Response 1: I am sorry, I did not accurately express what I mean. What the figure 5 show is
the micromorphology of the bonding area of the coatings and substrate and What I want to express is that there are different reaction layers in this area. There is no split here. I will modify the description in the paper.
Point 2: Introduction
Comment: Introduction should be more extensive, with more references to other authors work regarding these technique/materials. I believe that this introduction does not frame the readers to the scientific contributions provided within the text.
Response 2：I will add a description of the flexible "coated cloth" technology, and the current research status of this study at home and abroad.
Point 3: Introduction
Comment: The comparison between vacuum cladding and other processing techniques is not clear (ex. Welding)
Response 3: I am sorry for not having this contrast clearly. I will indicate in this paper that, Compared with other technologies, coatings prepared by the combination of vacuum cladding and the flexible "coated cloth" technology have the characteristics of low internal stress, controllable thickness, higher surface hardness and better wear resistance. At the same time, flexible metal cloth can overcome the problem of complicated structure and location of workpiece.
Point 4: Materials and Methods
Comment: This is the sections that I believe needs to be completely re-written since a lot of important details are missing and it is overall confusing. Most of the details missing make significant change on the materials processing characteristics and might influence the result analysis…
4.1 Missing steel substrate composition and mechanical characteristics
Response 4.1: I am sorry the I did not given the mechanical characteristics of steel substrate in the text. I will add it.
4.2 Missing WC-10Ni and NiCrBSi powders composition and particle characteristics (shape, size, distribution, etc)
Response 4.2: The WC-10Ni powder was prepared by sintering agglomerates of WC particles and Ni. I will add a table for the composition of NiCrBSi powders, and the microscopic morphology of 30-45μm WC-10Ni powders 5-15μm WC-10Ni powders and BNi2 powders.
4.3 How was the mixture done? Technique, duration… How was the mixture evaluated for homogeneity, …?
Response 4.3: I am sorry that no specific mixing parameters have been given. The powders was mixed for hours with a QM-5 roller ball mill, unfortunately, there was on test to assess homogeneity.
4.4 What was the brazing cycle duration, heating rate? …
Response 4.4: I am sorry that I ignored it. I will add a Figure of the brazing curve.
4.5 How many samples were produced? Only one for each temperature? For statistical analysis it should be done at least 3-5 samples to ensure that the experimental variations were considered…
Response 4.5: Actually, there were 3 simples being prepared for each temperature, and the test of mechanical properties is repeated more than 5 times. I will make it clear in the text.
4.6 How were the cloths prepared and what parameters were used?
Response 4.6: Preparation of “coated clothes” were divided into 3 steps, the first step was to mix the three different powders by a QM-5 roller mill for 5 hours according to the proportion required , the second step was to roll the mixed powders repeatedly into 1mm thick “Carbide cloth” and “Solder cloth” ,By using a self-grinding mill, the third step is to cut clothes to the size of 70×30mm. I will add a schematic diagram of self-grinding mill.
4.7 Was any load applied on the carbide cloth, solder cloth multilayers structure?
Response 4.7: There is no load applied on the carbide cloth, solder cloth multilayers structure.
4.8 Thickness of the cloths? Dimensions, etc….
Response 4.8: I am sorry that I did not make it clear in the text, the dimensions of the coating are 70×30×1mm
4.9 Missing the initial characterization of the cloths prior to brazing… (porosity evaluation, dispersions, dimensions,….)
Response 4.9: I will add the microscopic morphology of both “Carbide cloth” and “Solder cloth”.
4.10 Table 1 has two WC-10Ni(5-15um) columns….
Response 4.10: I am sorry for the mistake, these two columns are actually WC-10Ni(5-15um) column and WC-10Ni(30-45um) column. I will correct it.
4.11 How was the XRD done? Directly on the surface of the coating? What was the anode material?
Response 4.11: What was tested by XRD is the side face of the sample with both coating and substrate. The anode material is Cu.
4.12 Scale on Figure 1 and 2
Response 4.12: I will specify the scale of Figure 1 and 2.
4.13 Missing the distance between microhardness lines and indentations.
Response 4.13: The distance between microhardness lines is 2mm and the distance between indentations was marked in the figure of Microhardness of composite coatings section.
Point 5: Results
Line 84
Comment: The thickness of the coating is not referred anywhere neither images showing the thickness evolution…
Response 5: I am sorry for that, I will re-written 3.1 and provide appropriate date and analysis.
Point 6: Results
Comment: A wettability study of the soldering paste should be interesting… At least heating soldering paste on top of the substrate to check if the wets or not.
Response 6: NiCrBSi is a common solder and has good wettability to carbon steel.
Point 7: Results
Line 120 and 121
Comment: D and F have 15% of Fe… That is not a “small amount of Fe”. Please correct the description.
Response 7: I am sorry for that mistake, I will correct it.
Point 8: Results
Line 126 and 128 “Simultaneously, due to the presence of WC particles in the hard zone, the difference in element concentration between the interface and the hard layer increases”
Comment: It does not make any sense either in English or scientifically…
Response 7: I am sorry what I really wanted to express is that: the presence of WC-10Ni in the “Carbide cloth” compared to the “Solder cloth” resulted in a difference in elemental density between them. I will correct it.
Point 8: Results
Line 151-154
Comment: What is crystal segregation? This phrase also does not make sense…
Response 8: I am sorry what I really wanted to express is that: as can be seen form the result of scanning lines, Si aggregated around WC particles and tungsten rich phases. This is because the Si in the NiCrBSi was diffusing and accumulating into the WC particles, when it was melted. Subsequently, in the process of heat preservation, due to the crystallization of the isothermal solidification, part of g-Ni solution without Si formed and the remaining liquid with Si non-isothermally curdled. I will correct it.
Point 9: Results
Figure 6.
Comment: Figure 6 exhibit clearly a relation of location between the presence of Si and W (that are present in the same zone), as well as, when the presence of Ni is identified there is no Si and W. This should be referenced in the text clearly and the reason for this.
Response 9: I am sorry, Line 151-154 is to explain this relation, but I did not express my meaning explicitly, I will change here to “It is notable that Si aggregated around WC particles and tungsten rich phases. This is because the Si in the NiCrBSi was diffusing and accumulating into the WC particles, when it was melted. Subsequently, in the process of heat preservation, due to the crystallization of the isothermal solidification, part of γ-Ni solution without Si formed and the remaining liquid with Si non-isothermally curdled”.
Point 10: Results
3.3 Phase composition of composite coating
Comment: As for the XRD the results make no sense. In Figure 6 the Si location is exactly different from the Ni and then on the XRD it is identified the presence of a Ni3Si phase… Another doubt is if the XRD analysis is on the surface how can the x-ray penetration see the substrate? What is the thickness of the coating….
Response 10: I am sorry that I did not specify the XRD test area in the text, actually, what was tested by XRD is the side face of the sample with both coating and substrate.
Ni3Si phase is formed during non-isothermal solidification and is dispersed inside the coating，so it corresponds to some points in Figure 6. However, it is hard to specify where it is.
Point 11: Results
Line 187-189
Comment: On the images presented before (Figure 4) no segmentation is observed… Can you present SEM imagens clearly showing the WC particle segmentation? If the WC particles would sediment, then the wear results should be worse for the higher temperatures (where the WC would sediment more). Can the authors comment on this?
Response 11: The SEM image follow shows the WC particle segmentation. I am sorry that I did not describe the wear test accurately. In this paper, the wear test is carried out after cutting the surface of the coating by 1mm, which means that the wear resistance here is actually the resistance of “Hardened layer”.
Point 12: Results
Line 195-196
Comment: Is the films delaminate how can they present these values of sheer strength? Can the authors clarify this?
Response 12: There is no split in coatings. What the figure 5 show is the micromorphology of the bonding area of the coatings and substrate and What I want to express is that there are different reaction layers in this area.
Point 13: Results
Line 205-209
Comment: it is not necessary and should be used for the introduction where the justification for the NiCrBSi coating and it’s importance should be referred.
Response 12: I am sorry, this is really superfluous, I will delete it.
Point 14: References
Comment: The two last references (14 and 15) are not referenced in the text….
Response 12: I am sorry, the two last references is hard to find, they are in line 134, unfortunately, I mistakenly wrote them as [13,14]
Author Response File: Author Response.docx
Reviewer 4 Report
an EBSD would be vvery interesting to study the distribution of phases. It would be interesting a study by nanoindentation
Author Response
Point 1: an EBSD would be vvery interesting to study the distribution of phases. It would be interesting a study by nanoindentation
Response 1: Thank you very much for your suggestion, I will use these analysis methods in subsequent research.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
With the revised version of the paper the authors tried to answer some of the remarks and at some points the paper is improved. However, it is still very difficult to read this work, not only because of a weak quality of the English, but some paragraphs are written in a complicated and “confuse” way. In my last report I already wrote that “The English language has to be edited extensively. For example, the use of tenses is very strange and has to be checked thoroughly and corrected as well as the sentence construction.” However, unfortunately, this has not been done. Why?
At some points it is written - e.g. “test the properties at different brazing temperatures”. You did not do any test at these temperatures I guess. All experiments are done at RT?! This should be clarified.
To my opinion, before accepting this paper, a professional English editing is essential and the authors should consider to restructure some of the paragraphs. It appears that the authors did not really proof read their own work. For example in the introduction (version with corrections) line 40/41 and 55/56 contains the same sentence.
Line 428 (version without corrections marked):
“NiCrBSi powders of type BNi-2 shown in table 2 were selected as solder that the composition of it , the solidus and liquidus temperatures of it were 917℃ and 999℃, respectively, and the powder diameter was less than 45μm.”
This sentence doesn’t make much sense.
These are only two examples from the first two pages which demonstrate that a further revision is required in case the paper will be accepted for publication.
The introduction has improved – although it is strange to me that the authors note from which institutions the work which is cited comes from. I would delete this.
I am still wondering why in Fig. 2a the carbide cloth and the solder cloth have different dimensions (and there is no scale bar). Does it mean that the solder is not covered everywhere by the carbide?
The new figure 5 has a bad quality. The numbers should not be written at the axis, since they mean time durations and not time “points”.
Results:
Lines 489 etc:
“As the brazing temperature increased, the fluidity of the solder increased, and the resistance of solder to WC sedimentation decreased, therefore, the deposition of WC particles was increasingly sufficient, and the amount of liquid solder without WC particles above the coating increased.”
What does it mean that the “deposition of WC particles was increasingly sufficient”? Sufficient for what?
Line 513:
“At the same time, the size of the gray-white massive phase which revealed in the following section gradually decreased …”
This sentence doesn’t make sense – what does it mean – phase which revealed …?
The EDS evaluation at page 24 – this paragraphs should be ordered somehow. Why do you start with B, D, F? Why are these three points compared? Of course, since it is assumed that they have the same composition, but this should be introduced somehow. Then if these three positions are compared, they should be noted in the table underneath each other.
Line 524: “The characteristic regions B, D, and F were mainly composed of Ni, Fe and a small amount of Si and Cr.”
At position B, the amount of Fe is less than that of Si and Cr. The statement only holds for position D and F. Is pos B equivalent to D and F? (By the way – presenting results for EDS to 0.01 % is not reasonable.)
543 “The areas A, C, E and G formed complex phase compounds composed of chromium rich phase, tungsten rich phase”
Point G contains 7 % of Cr. Why is this a chromium rich phase? (btw, this is also not a sentence)
Line 551 “It is notable that Si aggregated around WC particles and tungsten rich phases.”
The Si signal is detected at the positions where W is detected. Why does this mean that Si aggregates “around” the WC particles? In the next sentence it is also written that Si is diffusing into the WC particles?
Figure 9: you explained to me that the numbers besides the elements are the intensities. This information should be noted within the figure.
Figure 10: the quality of this figure is worse than it was before. How sure are you about the Ni3Si? Since the EDS shows that at the positions where there is Ni there is hardly any Si. And if you get a sharp XRD signal this requires sufficient large crystals?
On the other hand, you state that there is a Cr rich phase, which is also written in the conclusions. From this phase, however, there is no XRD signal although Cr is clearly visible in the EDS analysis.
So – you state the presence of Ni2Si from XRD which is not visible in EDS and you state a Cr rich phase from EDS, which is not visible in XRD. Why do you think this that this makes sense?
Line 585 – “It could be seen from Fig. 8 …” You certainly mean Fig. 11 … You state that the microhardness is reduced if the brazing temperature is increased. Where do you see this in the results? Between the depth of 0 and 0.6 um the green curve is slightly lower than the other two, but then it becomes as high as the other. As you wrote the signal is very noisy due to the measurement at WC or between the particles. I repeat my question if several measurements have been done at different positions in such an inhomogeneous material?
Author Response
Point 1:
Comments: At some points it is written - e.g. “test the properties at different brazing temperatures”. You did not do any test at these temperatures I guess. All experiments are done at RT?! This should be clarified.
Response 1: I am sorry that I did not clarify it, I will change the title to “Microstructure and properties of WC-NiCrBSi composite coatings produced by vacuum cladding from flexible coated cloths”, and change “3.1…” to “3.1.Microstructure”, “3.2 Interface morphology and element distribution at different temperatures” to “3.2 Interface morphology and element distribution”, “3.4…” to “3.4 Microhardness of composite coatings section”, “3.5…” to “Bonding strength between coating and substrate”, “3.6…” to “3.6 Wear resistance of composite coating”.
Point 2: Introduction
Comments:To my opinion, before accepting this paper, a professional English editing is essential and the authors should consider to restructure some of the paragraphs. It appears that the authors did not really proof read their own work. For example in the introduction (version with corrections) line 40/41 and 55/56 contains the same sentence.
Line 428 (version without corrections marked)
“NiCrBSi powders of type BNi-2 shown in table 2 were selected as solder that the composition of it , the solidus and liquidus temperatures of it were 917℃ and 999℃, respectively, and the powder diameter was less than 45μm.”
This sentence doesn’t make much sense.
These are only two examples from the first two pages which demonstrate that a further revision is required in case the paper will be accepted for publication.
Response 2: I will seek the help of a professional English editor and delete “ In this paper…” (line 40/41).
Point 3:
Comments: The introduction has improved – although it is strange to me that the authors note from which institutions the work which is cited comes from. I would delete this.
Response 3: I will delete the institutions of authors.
Point 4: Figure 2
Comments: I am still wondering why in Fig. 2a the carbide cloth and the solder cloth have different dimensions (and there is no scale bar). Does it mean that the solder is not covered everywhere by the carbide?
Response 4: Figure 2 was used to show the flexibility and tailorability of the “coated cloth”. Actually, as shown in Figure 4, the solder is covered everywhere by the carbide .
Point 5: Figure 5
Comments: The new figure 5 has a bad quality. The numbers should not be written at the axis, since they mean time durations and not time “points”.
Response 5: I am sorry for that mistake, I will modify it.
Point 6: 3.1. microstructure
Line 438-441 “As the brazing temperature increased, the …above the coating increased.”
Comments: What does it mean that the “deposition of WC particles was increasingly sufficient”? Sufficient for what?
Response 6: I am sorry that I did not express it clearly, the “deposition of WC particles was increasingly sufficient” means that “WC particles can sink more fully in the liquid solder”
I will modify “As the brazing temperature… coating increased” to “As the brazing temperature increased, the fluidity of the solder increased, therefore, WC particles could sink more fully in the liquid solder, leading to the increasing amount of liquid solder without WC particles above the coating.”
Point 7: 3.2 Interface morphology and element distribution
Line 462: “At the same time, the size…. Gradually decreasing”
Comments: This sentence doesn’t make sense – what does it mean – phase which revealed …?
Response 7: What I want to express in this sentence is that the increase in brazing temperature caused the size of white massive phase to become smaller.
I will delete “which revealed in the following section”
I will modify this sentence to “Obviously, this increase caused the size of white massive phases to become smaller.”
Point 8: 3.2 interface morphology and the element distribution
Comment: The EDS evaluation at page 24 – these paragraphs should be ordered somehow. Why do you start with B, D, F? Why are these three points compared? Of course, since it is assumed that they have the same composition, but this should be introduced somehow. Then if these three positions are compared, they should be noted in the table underneath each other.
Response 8: I am sorry that I did not express this clearly, the point B, D, F are located at Ni-based solid solutions in the layer III on the samples prepared at different brazing temperatures. I will add this to the text, and adjust the order of the rows in the table 4 so that they can be better compared.
Point 9: 3.2 interface morphology and the element distribution
Comment: At position B, the amount of Fe is less than that of Si and Cr. The statement only holds for position D and F. Is pos B equivalent to D and F? (By the way – presenting results for EDS to 0.01 % is not reasonable.)
Response 9: B, D, F are located at the similar region on the samples prepared at different brazing temperature, the compositions of them are similar.
I will change “The results were shown in Table 4. The characteristic regions B, D and F were mainly composed of Ni, Fe and a small amount of Si and Cr” to “As can be seen in Table 4. The characteristic regions B, D, and F were mainly composed of Ni and a little of Fe, Si and Cr.”
Point 10: 3.2 interface morphology and the element distribution
Line 494-495 “The areas A, C, E and G formed complex phase compounds composed of chromium rich phase, tungsten rich phase.”
Comments: Point G contains 7 % of Cr. Why is this a chromium rich phase? (btw, this is also not a sentence)
Response 10: I am sorry that I made an obvious mistake here, I will modify “The characteristic regions A, C, and E …the bond strength at the coating interface” to “the characteristic areas A, C, E and G (gray-white massive phases) were composed of a large number of W, some Cr, Ni and a small amount of Si, Fe. A large amount of W content caused the hardness of these phases to be high, leading the bond strength at the bonding surface of the coating to the substrate to decrease.”
Point 11: line 502-503 “It is notable that Si aggregated around WC particles and tungsten rich phases.”
Comments: The Si signal is detected at the positions where W is detected. Why does this mean that Si aggregates “around” the WC particles? In the next sentence it is also written that Si is diffusing into the WC particles?
Response 11: This conclusion was obtained by comparing the position of the line scan (Figure 8) and the result of the scan (Figure 9).
I will modify “This is because the Si in the NiCrBSi was diffusing and accumulating into the WC particles, when it was melted” to “This is because the Si in the NiCrBSi was diffusing and accumulating to the WC particles, when it was melted”
Point 12: Figure 9
Comments: you explained to me that the numbers besides the elements are the intensities. This information should be noted within the figure.
Response 12: I am sorry that I did not make it clear, I will add a label next to the Y-axis.
Point 13: Figure 10
Comments: the quality of this figure is worse than it was before. How sure are you about the Ni3Si? Since the EDS shows that at the positions where there is Ni there is hardly any Si. And if you get a sharp XRD signal this requires sufficient large crystals?
On the other hand, you state that there is a Cr rich phase, which is also written in the conclusions. From this phase, however, there is no XRD signal although Cr is clearly visible in the EDS analysis.
So – you state the presence of Ni2Si from XRD which is not visible in EDS and you state a Cr rich phase from EDS, which is not visible in XRD. Why do you think this that this makes sense?
Response 13: I will modify the picture to improve the quality. The test area of XRD was the cross section of the sample as shown in Figure 7(a), however, the test area of EDS was the bonding zone of coating to substrate.
As shown in response 10, I made a mistake, actually, there is no Cr rich phase, I will modify it.
Point 14: Line 535-536 “It could be seen from Fig. 11 that as the brazing temperature increased, the microhardness of the interface decreased,”
Comments: You state that the microhardness is reduced if the brazing temperature is increased. Where do you see this in the results? Between the depth of 0 and 0.6 um the green curve is slightly lower than the other two, but then it becomes as high as the other. As you wrote the signal is very noisy due to the measurement at WC or between the particles. I repeat my question if several measurements have been done at different positions in such an inhomogeneous material?
Response 14: I am sorry I did make it clear, the reduction of microhardness that I pointed out was for region “interface” (between the depth of -0.2 and 0.1 um). As shown in Figure 6. (b), each microhardness value was obtained by subtracting the average value after three measurements.
