Electrochemical Characterization Method of Laves Phase in 9Cr Martensitic Heat-Resistant Steel and Creep Life Prediction
, Ji Li 1,*, Qi Guo 2, Liying Tang 1, Jian Xu 2,*, Rongcan Zhou 1 and Hongjun Zhang 1Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsIn this paper, the authors made an interesting attempt to predict the creep life- time by the electrochemical characteristic (charge density) attributed to the Laves phase amount in the 9%Cr steels.
However, the presented experimental results and their discussion are rather confusing and misleading.
- First, different tests are used, (92 steel after creep tests at 600C, 130 MPa; specimens after long-term service at not specified temperature; 9Cr steel after aging at 650C), however, the obtained Laves phase parameters are not distinguished by testing temperature. It is known that the fraction of Laves phase is lower at higher temperature. Also, the lower contents of W and Mo in 9Cr steel results in lower fraction of Laves phase. Therefore, the results and conclusion 1 concerning the lower fraction of Laves phase in 9Cr steel with thermal ageing are confusing. For example, lines 162-164 – “It can be concluded that the Laves phase can also grow after thermal aging without force acting, but the content is much less than that of the sample after creep”. It is known, that Laves phase is thermally-activated process, and it is the same in aged and crept specimens.
- Second, it is not clear, what points were used to set the equation (page 12) - the creep tests results at 600C or two points after long-term service? These two groups of results show different relationships. How can they be connected? Therefore, the obtained relationship seems to be not reliable.
Also, some other comments:
1. Temperature of normalization is not indicated for T92 steel.
2. Heat treatment before aging is not indicated for 9Cr F/M steel.
3. Page 2, line 56 – “with an ageing time of 24000 h” – “ageing” seems to be replaced by creep.
4. Page 3, line 7, “(solution – quenching treatment)” – why tempering is not indicated?
5. In all figure captures the details of conditions (temperature, creep or aging, MPa – should be indicated).
6. The same is for figures showing the parameters obtained from different tests – for example, Figs. 3, 9, 11,12. The conditions should be indicated on plots.
7. The SEM micrographs of the 9Cr steel after aging with different times were not presented.
8. Page 8, line 174 – “service time” seems to be replaced by “aging time”.
9. Fig. 6, typos in axis Y, “Potentila”
Comments on the Quality of English LanguageEnglish is good.
Author Response
Reply to Reviewer 1:
In this paper, the authors made an interesting attempt to predict the creep life- time by the electrochemical characteristic (charge density) attributed to the Laves phase amount in the 9%Cr steels.
However, the presented experimental results and their discussion are rather confusing and misleading.
Reply: Thank you for your time for reviewing this manuscript and your kind and constructive comments. We have learned a lot from your comments and suggestions not only for the revision of the paper, but also for our future writing of scientific. Revision of the paper has been done on your and other reviewers’ comments.
Our detailed replies to your comments are listed below:
- First, different tests are used, (92 steel after creep tests at 600C, 130 MPa; specimens after long-term service at not specified temperature; 9Cr steel after aging at 650C), however, the obtained Laves phase parameters are not distinguished by testing temperature. It is known that the fraction of Laves phase is lower at higher temperature. Also, the lower contents of W and Mo in 9Cr steel results in lower fraction of Laves phase. Therefore, the results and conclusion 1 concerning the lower fraction of Laves phase in 9Cr steel with thermal ageing are confusing. For example, lines 162-164 – “It can be concluded that the Laves phase can also grow after thermal aging without force acting, but the content is much less than that of the sample after creep”. It is known, that Laves phase is thermally-activated process, and it is the same in aged and crept specimens.
Reply: Thank you for pointing out the problem. The fraction of Laves phase is not only related to temperature, but also to stress. The growth process of Laves phase is actually the diffusion of elements such as W and Mo. Hu et. al[1] found that the formation amount of Laves phase in the aging part is smaller than that in the creep part. Stress facilitates the diffusion of alloy elements, and promotes the nucleation and growth of Laves phase[1,2]. Also, the higher temperature and the lower contents of W and Mo in 9Cr steel results in lower fraction of Laves phase. Therefore, we concluded that the Laves phase content in 9Cr steel is much lower than that in T/P92 steels. The results and conclusion 1 have now been revised in the revised manuscript.
- Second, it is not clear, what points were used to set the equation (page 12) - the creep tests results at 600C or two points after long-term service? These two groups of results show different relationships. How can they be connected? Therefore, the obtained relationship seems to be not reliable.
Reply: Two points after long-term service were used to set the equation (page 12). It is known that the charge density of Laves phase in T92 fracture samples is 0.0069 C/cm2, so we assume that P92 steel breaks when the charge density of Laves phase reaches this value. By extrapolating the data of P92 50000h and 82000h specimens to reach the dissolved charge density value of the T92 fracture specimen, as shown in Figure 12(a). We emphasize that the accuracy of this prediction method is still uncertain due to the few data points at present. It is suggested to increase the sample size in the next step and establish a more accurate creep life prediction model based on big data.
Also, some other comments:
- Temperature of normalization is not indicated for T92 steel.
Reply: The standard heat-treatment for T92 steel is normalization at 1050 oC for 1 h. We have expanded on the normalization temperature of T92 steel in the revised manuscript.
- Heat treatment before aging is not indicated for 9Cr F/M steel.
Reply: The 9Cr F/M steels were quenched after solid solution treatment at 1050℃ for 1 h and tempered at 730℃ for 3 h, and then aged at 650℃ for a series of times (0 h, 1000 h, 2000 h, 3500 h, 5000 h, and 6500 h). We have expanded on the heat treatment before aging for 9Cr F/M steel in the revised manuscript.
- Page 2, line 56 – “with an ageing time of 24000 h” – “ageing” seems to be replaced by creep.
Reply: Thank you for pointing out the problem. T92 steel was crept for 24000 h at a temperature of 600 ℃ and a pressure of 130 MPa. The word has now been carefully revised in the revised manuscript.
- Page 3, line 7, “(solution – quenching treatment)” – why tempering is not indicated?
Reply: Thank you for the suggestion. The tempering has now been indicated in the revised manuscript.
- In all figure captures the details of conditions (temperature, creep or aging, MPa – should be indicated).
Reply: Thank you for the suggestion. The details of conditions have now been mentioned in all figure captions in the revised manuscript.
- The same is for figures showing the parameters obtained from different tests – for example, Figs. 3, 9, 11,12. The conditions should be indicated on plots.
Reply: Thank you for the suggestion. The details of conditions have now been mentioned in the relating figures in the revised manuscript.
- The SEM micrographs of the 9Cr steel after aging with different times were not presented.
Reply: Thank you for the suggestion. The SEM micrographs of the 9Cr steel after aging with different times have now been presented in the revised manuscript (see Figure 5).
Figure 5. SEM images of the 9Cr F/M specimens after ageing at 650 ℃ for different time under the backscatter electron mode. (a) 9Cr F/M-0 h, (b) 9Cr F/M-1000 h, (c) 9Cr F/M-2000 h, (d) 9Cr F/M-3500 h, (e) 9Cr F/M-5000 h, (f) 9Cr F/M-6500 h
- Page 8, line 174 – “service time” seems to be replaced by “aging time”.
Reply: Thank you for pointing out the problem.
- Fig. 6, typos in axis Y, “Potentila”
Reply: Thank you for pointing out the problem. The word “Potentila” has been corrected as “Potential” in the revised manuscript.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe paper reads about characterization of phases in Fe-Cr steels subjected to the internal pressure creep test being compared to the specimens taken from a power plant. This subject can be topical for the applied scientists dealing with creep behavior of ferritic martensitic steels. I have a few comments to the manuscript:
1) The authors distinguish three steels (T92, P92 and 9Cr F/M). However, the chemical composition of T92 and P92 steels in identical so actually they represent the same material. The difference is that T92 steel was studied in laboratory while P92 was taken from a power plant. To avoid the confusion, I advise authors to denote that actually they studied two materials, while one of them was labelled in two different ways to specify their origin.
2) Please, clarify what is the purpose of considering 9Cr F/M steel when the prediction of its lifetime can not be validated?
3) Methodical section needs in update - please, specify the models and manufacturers of the characterization techniques used as well as software - with the used version number. A scheme of the the internal pressure creep test would also be helpful.
4) Some technical flaws such as mismatch between terms "9Cr F/M" (text) and "9Cr FM" (Table 1) should be corrected. The references should be corrected to comply with the MDPI style. Ref [18] - authors' names are missing. Caption of Fig. 1 contains information ("20 spots were observed for each specimen") which was already provided in the Methodical section. Technical information in Fig. 7 should be replaced with a professional quality marker.
5) May the electron diffraction patterns be provided and indexed for TEM data (Fig. 4) to distinguish between the Laves phase/carbides? Anyway, the justification of how authors indicated these phases in TEM images should be specified - the sentence "identified as Laves phase and carbides as previously mentioned" (line 146) is not informative.
Comments on the Quality of English LanguageMinor polishing of English is advised.
Author Response
Reply to Reviewer 2:
The paper reads about characterization of phases in Fe-Cr steels subjected to the internal pressure creep test being compared to the specimens taken from a power plant. This subject can be topical for the applied scientists dealing with creep behavior of ferritic martensitic steels. I have a few comments to the manuscript:
Reply: Thank you for your time for reviewing this manuscript and your kind and constructive comments. Revision of the paper has been done on your and other reviewers’ comments.
Our detailed replies to your comments are listed below:
1) The authors distinguish three steels (T92, P92 and 9Cr F/M). However, the chemical composition of T92 and P92 steels in identical so actually they represent the same material. The difference is that T92 steel was studied in laboratory while P92 was taken from a power plant. To avoid the confusion, I advise authors to denote that actually they studied two materials, while one of them was labelled in two different ways to specify their origin.
Reply: Thank you for the suggestion. We have modified it into two materials in the revised manuscript ( see the Materials and Methods section).
2) Please, clarify what is the purpose of considering 9Cr F/M steel when the prediction of its lifetime can not be validated?
Reply: The purpose of considering 9Cr F/M steel is to verify the general applicability of quantitative detection of Laves phase in other 9% Cr martensitic stainless steels by the electrochemical method. However, since there is no long-aging 9Cr F/M steel taken from the power plant, the life prediction cannot be verified.
3) Methodical section needs in update - please, specify the models and manufacturers of the characterization techniques used as well as software - with the used version number. A scheme of the internal pressure creep test would also be helpful.
Reply: Thank you for the suggestion. Software in our article, such as Image J, was open-source software and no version number was needed. A scheme of the internal pressure creep test information was added in the revised manuscript.
Table 2. Sample information of internal pressure creep tested T92
|
No. |
Status |
Time（h） |
Creep life loss（%） |
|
1 |
as-received |
0 |
0 |
|
2 |
creep interrupt sample |
1700 |
7 |
|
3 |
creep interrupt sample |
5000 |
20 |
|
4 |
creep interrupt sample |
12800 |
53 |
|
5 |
creep interrupt sample |
18600 |
77 |
|
6 |
creep fracture sample |
24000 |
100 |
4) Some technical flaws such as mismatch between terms "9Cr F/M" (text) and "9Cr FM" (Table 1) should be corrected. The references should be corrected to comply with the MDPI style. Ref [18] - authors' names are missing. Caption of Fig. 1 contains information ("20 spots were observed for each specimen") which was already provided in the Methodical section. Technical information in Fig. 7 should be replaced with a professional quality marker.
Reply: Thank you for the suggestions. The term "9Cr F/M" has now been carefully corrected throughout the whole manuscript. The references have now been corrected to comply with the MDPI style. The repeated information ("20 spots were observed for each specimen") in the Methodical section has been removed from the caption of Fig. 1 in the revised manuscript. The technical information in Fig. 7 has been replaced with a professional quality marker.
5) May the electron diffraction patterns be provided and indexed for TEM data (Fig. 4) to distinguish between the Laves phase/carbides? Anyway, the justification of how authors indicated these phases in TEM images should be specified - the sentence "identified as Laves phase and carbides as previously mentioned" (line 146) is not informative.
Reply: Thank you for the suggestions. The major elemental composition of two kinds of precipitates has been provided to distinguish between the Laves phase/ carbides in Fig. 4. Since the Laves phase contains higher W and/or Mo contents than the carbides, it has a clearer Z-contrast. Depending on the contrast in TEM images, the darker particles are enriched in W and Mo, identified as Laves phase; and the lighter particles are enriched in Cr, which are con-firmed as carbides. The reason for indicating these phases in TEM images has been specified in the revised manuscript.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe article is devoted to the study of creep patterns. And it is largely aimed at solving practically significant problems. Before publishing the article, it is worth making a number of modifications.
1. Expand the abstract and state in it the main results obtained in the work.
2. Expand the introduction section. Now it is very short and does not reflect the relevance of the work well. You should also write more clearly at the end of the introduction section the goals of the work. Review in more detail.
3. In the methodology section, indicate how many samples were tested in each experiment.
4. In describing Figure 4 you are talking about different sizes of the Laves phase for different samples. However, only one Laves phase is visible in the photographs. In order to make your words more convincing, it would be good to provide a few photographs where the Laves phases are visible. Or provide a photograph with lower magnification, which will show several phases of Laves.
5. In Figure 5 and in its description you talk about the average particle size of the Laves phase. But it would be worthwhile to immediately provide data on how different the sizes of the Laves phase are within the same sample. What is the particle size dispersion of the Laves phase at different aging times?
6. It would be good to expand the conclusions a little and give numerical values for the percentage change in the Laves phase content at different test times. Show links to properties. Also describe in more detail the possibility of practical use of the results obtained.
Author Response
Reply to Reviewer 3:
The article is devoted to the study of creep patterns. And it is largely aimed at solving practically significant problems. Before publishing the article, it is worth making a number of modifications.
Reply: Thank you for your time for reviewing this manuscript and your kind and constructive comments. Revision of the paper has been done on your and other reviewers’ comments.
Our detailed replies to your comments are listed below:
- Expand the abstract and state in it the main results obtained in the work.
Reply: Thank you for the suggestion. The abstract has been expanded in the revised manuscript.
- Expand the introduction section. Now it is very short and does not reflect the relevance of the work well. You should also write more clearly at the end of the introduction section the goals of the work. Review in more detail.
Reply: Thank you for the suggestion. The introduction has been expanded in the revised manuscript.
- In the methodology section, indicate how many samples were tested in each experiment.
Reply: Thank you for the suggestion. The number of samples tested for each experiment has now been indicated in the revised manuscript.
- In describing Figure 4 you are talking about different sizes of the Laves phase for different samples. However, only one Laves phase is visible in the photographs. In order to make your words more convincing, it would be good to provide a few photographs where the Laves phases are visible. Or provide a photograph with lower magnification, which will show several phases of Laves.
Reply: Thank you for the suggestions. A photograph with several Laves phase has been replaced (see Figure 4) in the revised manuscript.
Figure 4. The TEM images of the microstructure of (a) T92 specimen with creep ageing for 5000 h at 600 ℃, 130 MPa. (b) 9Cr F/M specimen after ageing at 650 ℃ for 5000 h. The major elemental composition (at. %) of the two precipitates is also given in the figure.
- In Figure 5 and in its description you talk about the average particle size of the Laves phase. But it would be worthwhile to immediately provide data on how different the sizes of the Laves phase are within the same sample. What is the particle size dispersion of the Laves phase at different aging times?
Reply: Thank you for the suggestions. The size dispersion of the Laves phase at different ageing times has been added in the revised manuscript.
Figure 7. The size dispersion of the Laves phase in 9Cr F/M specimens after ageing at 650 ℃ with different time.
- It would be good to expand the conclusions a little and give numerical values for the percentage change in the Laves phase content at different test times. Show links to properties. Also describe in more detail the possibility of practical use of the results obtained.
Reply: Thank you for the suggestions. The conclusions have been expanded in the revised manuscript.
Author Response File: Author Response.pdf
Reviewer 4 Report
Comments and Suggestions for AuthorsQuantitative evaluation of Laves phase in 9Cr heat resistant steels creep-deformed and annealed for varying times based on electrochemical method was demonstrated together with suggestion on its possible application in predicting remaining life of the steels. The key idea of the manuscript is interesting and deserves attention of the researchers in the field. Although there is a doubt on if the authors claimed in the manuscript is really applicable to predict the remaining life of the heat-resistant steels in service, the concept proposed in the manuscript appears meaningful and, therefore, publication of the manuscript is recommended. The manuscript is well written and easy to read. Some minor comments are as follows,
(Line 21) Please correct 'high press parts' to 'high pressure parts'.
(Line 150) After the sentence, 'This may be attributed to differences in the composition of the two materials', it would be good to add one more sentence giving more detailed explanation including the composition of C and Mo/W.
(Line 253) What is the meaning of the sentence, 'Hinders dislocation and subgrain boundary movement mainly depend on various strengthening mechanisms in 9% Cr martensitic steels'? Please correct it.
(Line 325) It is difficult to agree to the statement, 'On the contrary, the electrochemical method can directly quantify the degree of microstructural evolution of the material without destroying the tube'. There is no way to do the suggested evaluation on the tubes which are actually in service without destructing it. It would be good if authors could put more effort on this issue.
Author Response
Reply to Reviewer 4:
Quantitative evaluation of Laves phase in 9Cr heat resistant steels creep-deformed and annealed for varying times based on electrochemical method was demonstrated together with suggestion on its possible application in predicting remaining life of the steels. The key idea of the manuscript is interesting and deserves attention of the researchers in the field. Although there is a doubt on if the authors claimed in the manuscript is really applicable to predict the remaining life of the heat-resistant steels in service, the concept proposed in the manuscript appears meaningful and, therefore, publication of the manuscript is recommended. The manuscript is well written and easy to read. Some minor comments are as follows,
Reply: Thank you for your time for reviewing this manuscript and your kind and constructive comments. We would like to express our gratitude to the reviewer for the positive feedback and recommendation for the manuscript publication. Revision of the paper has been done on your and other reviewers’ comments.
Our detailed replies to your comments are listed below:
(Line 21) Please correct 'high press parts' to 'high pressure parts'.
Reply: Thank you for the suggestion. ‘high press parts’ has been corrected to 'high pressure parts' in the revised manuscript.
(Line 150) After the sentence, 'This may be attributed to differences in the composition of the two materials', it would be good to add one more sentence giving more detailed explanation including the composition of C and Mo/W.
Reply: Thank you for the suggestion. More detailed explanation about the composition of the two materials has been expanded in the revised manuscript.
(Line 253) What is the meaning of the sentence, 'Hinders dislocation and subgrain boundary movement mainly depend on various strengthening mechanisms in 9% Cr martensitic steels'? Please correct it.
Reply: This sentence means: The strengthening mechanisms of 9%Cr heat-resistant steel include precipitated phase strengthening, solid solution strengthening, dislocation strengthening, grain boundary strengthening, etc., which promote each other to hinder the dislocation movement and subgrain boundary migration, and thus obtain high microstructure thermal stability. The sentence has been corrected in the revised manuscript.
(Line 325) It is difficult to agree to the statement, 'On the contrary, the electrochemical method can directly quantify the degree of microstructural evolution of the material without destroying the tube'. There is no way to do the suggested evaluation on the tubes which are actually in service without destructing it. It would be good if authors could put more effort on this issue.
Reply: Thank you for the suggestion. The electrochemical method can directly quantify the degree of microstructural evolution of the material with a minor damage the tube. The traditional methods need advanced facilities and the sample must be cut from the studied materials. However, the electrochemical method is easily conducted, and has the potential to realize in-site detection without cutting the tube , which brings great conveniences for the steel performance evaluation in operating plants. We have added some discussion about this issue in the revised manuscript.
References:
- Hu, P.; Yan, W.; Sha, W.; Wang, W.; Shan, Y.; Yang, K. Microstructure Evolution of a 10Cr Heat-Resistant Steel during High Temperature Creep. Journal of Materials Science & Technology 2011, 27, 344-351, doi:https://doi.org/10.1016/S1005-0302(11)60072-8.
- Yin, H.; Ge, W.; Yin, F.; Zhao, J.; Yang, G.; Bao, H.; Zhou, L. Effect of stress on the nucleation and evolution of Mo-rich Laves phase in 9.5Cr-1.5MoCoVNbNB heat-resistant steel during tensile rupture at 620 °C. Materials Characterization 2023, 196, 112565, doi:https://doi.org/10.1016/j.matchar.2022.112565.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors partially answered the comments. Some comments remain still actual.
Previous comment: <<- Second, it is not clear, what points were used to set the equation (page 12) - the creep tests results at 600C or two points after long-term service? These two groups of results show different relationships. How can they be connected? Therefore, the obtained relationship seems to be not reliable.>>
As it can be seen from Fig. 14a, the results after different testing conditions (creep 130 MPa, 600C and service operation at uncertain temperature and stress) give the different relationships. It seems that they should be written as two different relationships between charge density and time, the one per certain condition.
On the other hand, the relationship between the charge density and the content of Laves phase seems to be not confirmed by the study of 9Cr F/M steel – it can be seen that the charge density increases whereas the area fraction of Laves phase does not change.
Previous comment: <<6. The same is for figures showing the parameters obtained from different tests – for example, Figs. 3, 9, 11,12. The conditions should be indicated on plots.>>
The text on the graphs is still confusing. The points from different testing conditions are combined on graphs. And only “creep at 600 C, 130 MPa” is indicated for both T92 and P92 steels. Whereas this only applies to T92 steel. The description for P92 steel should be added.
Comments on the Quality of English Language
Fugure 6 capture: The scatter bars in the figure indicate the standard derivation of the data. "derivation" seems to be "deviation"
Author Response
Reply to Reviewer 1:
The authors partially answered the comments. Some comments remain still actual.
Reply: Thank you again for your valuable suggestions to improve the quality of our manuscript. According to your nice suggestions, we have made extensive corrections to our previous manuscript, the detailed corrections are listed below:
Previous comment: <<- Second, it is not clear, what points were used to set the equation (page 12) - the creep tests result at 600C or two points after long-term service? These two groups of results show different relationships. How can they be connected? Therefore, the obtained relationship seems to be not reliable.>>
As it can be seen from Fig. 14a, the results after different testing conditions (creep 130 MPa, 600C and service operation at uncertain temperature and stress) give the different relationships. It seems that they should be written as two different relationships between charge density and time, the one per certain condition.
Reply: Indeed, the results after different testing conditions give the different relationships. However, the composition of T92 and P92 is the same, but the parts used are different, one is pipe (P92) the other is tube (T92). Therefore, the creep properties of both materials can be deemed as identical. On the other hand, the service temperature of T92 and P92 is the same, and only the stresses are different. The stress in the internal pressure creep test is relatively high, mainly to accelerate the creep failure. In addition, the stress will also promote the formation of Laves phase. So, we try to judge the creep lifetime of the materials through a single variable of the charge density of Laves phase. The current experimental data show that this variable as the basis can fit the two sets of data well (i.e., the charge density of Laves phase in internal pressure creep and field materials), which indicates the charge density of Laves phase is a promising variable for predicting the residual life of T/P92. It should be pointed out that this method is only a tentative approach up to now due to the limited data points, and we are still on the groping stage. The above discussion has been added to the revised manuscript.
On the other hand, the relationship between the charge density and the content of Laves phase seems to be not confirmed by the study of 9Cr F/M steel – it can be seen that the charge density increases whereas the area fraction of Laves phase does not change.
Reply: As described in the results section (page 12), it can be concluded that the average diameter of Laves phase precipitated in the beginning is small, and it gradually increased with creep time as the area fraction remained almost unchanged. The charge density of Laves phase contains the information on the particle size relative to the area fraction, and an increase in charge density without an obvious change in the area fraction of the Laves phase corresponds to an increase in the size of the Laves phase, namely coarsening of Laves phase particle. This also agrees with the average diameter data in Fig. 6c. We agree that more studies would be useful to establish a more accurate relationship in the next step.
Previous comment: <<6. The same is for figures showing the parameters obtained from different tests – for example, Figs. 3, 9, 11,12. The conditions should be indicated on plots.>>
The text on the graphs is still confusing. The points from different testing conditions are combined on graphs. And only “creep at 600 C, 130 MPa” is indicated for both T92 and P92 steels. Whereas this only applies to T92 steel. The description for P92 steel should be added.
Reply: Thanks for your suggestion. P92 steel taken from the fossil power plant pipe at a temperature of about 600 °C and a pressure of about 67 MPa. The description for P92 steel has been added in the revised manuscript.
Figure 6 capture: The scatter bars in the figure indicate the standard derivation of the data. "derivation" seems to be "deviation"
Reply: Thanks for your careful checks. We are sorry for our carelessness. We have corrected the "derivation" into "deviation".
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe authors generally revised the article and took my comments into account. The article has been well revised. The article may be published in my opinion.
Author Response
The authors generally revised the article and took my comments into account. The article has been well revised. The article may be published in my opinion.
Reply: I really appreciate your review and approval of this article.
Author Response File: 
Author Response.docx
Round 3
Reviewer 1 Report
Comments and Suggestions for AuthorsThe authors responded to all comments.
