Creep Damage Repair of a Nickel-Based Single Crystal Superalloy Based on Heat Treatment
Round 1
Reviewer 1 Report
Dear Authors,
Thank you for this interesting study that seems to include a lot of experimental work and data analysis.
Please find below some comments:
- In the first sentence in the Abstract paragraph as well as in many sentences in the Introduction section, there are a lot of “and” words that are used as connecting bonds between phrases. However, this situation creates a confusing sentence with no clear meaning and not obvious cohesion, which makes it difficult the understanding the meaning. Please try to change the “and” words with others that depict in a better way the connection of the phrases.
- In the introduction section, since the authors refer to repair issues of airplane engine parts, it could be also interesting to address some of the following references that refer to Additive Manufacturing processes that are used also for repairing purposes in the Aeronautical Industry:
- Bikas,P. Stavropoulos,G. Chryssolouris, "Efficient machining of aero-engine components: challenges and outlook", International Journal of Mechatronics and Manufacturing Systems(IJMMS), Vol. 9, No. 4, pg. 345-369, (2017)
- Stavropoulos, P.Foteinopoulos, A. Papacharalampopoulos, H. Bikas, "Addressing the challenges for the industrial application of additive manufacturing: Towards a hybrid solution", International Journal of Lightweight Materials and Manufacture, Volume 1, Issue 3, pg. 157-168, (2018)
- Maybe the scope and the goal of the presented work should be pointed out in a better and more clear way at the end of the introduction section. Also the outline-structure of this work could be also added. Please find the below literature as indicative examples of a document with clearly presented structure. You may also address them:
- Ntouanoglou, P. Stavropoulos, D. Mourtzis,"4D Printing Prospects for the Aerospace Industry: A Critical Review", 18th Machining Innovations Conference for Aerospace Industry, (MIC 2018), Procedia Manufacturing,Volume 18, pp.120-129, 28-29 December, Garbsen Germany (2018)
- Komineas, P. Foteinopoulos, A. Papacharalampopoulos, P. Stavropoulos,"Build Time Estimation Models in Thermal Extrusion Additive Manufacturing Processes", 15th Global Conference on Sustainable Manufacturing, (GCSM) , Vol. 21, pg. 647-654 , 25-27 September, Haifa, Israel,(2017)
- Regarding the experimental work: The test artefact has been designed and selected according to existing ISO/Standards? If no, don’t you think that it could be better to select an ISO-designed artefact?
- Line 283: Delete an extra space after γ’
- Figure 9: The color labeling what it shows?
- Overall, it is good work, that needs to address the aforementioned comments and try to make clearer the scope of the work. Having read the manuscript it is obvious what the authors have examined. In addition please find below, two more papers related to this work that can also be used:
- Sekihara, Masaru & Ichikawa, Kunihiro & Imano, Shinya & Kagiya, Yukio & Ito, Akihiro & Chuujou, Kouji. (2011). Refurbishment of Creep Damage Using Re-Heat Process for Ni-Based Superalloy under Bending Load. Journal of the Society of Materials Science, Japan. 60. 202-209. 10.2472/jsms.60.202.
- Omprakash, Cm & Boddapati, Srivathsa & Kamaraj, M. & Satyanarayana, D.. (2015). Creep Damage Evaluation of DS CM247 Nickel Base Superalloy Using Alternate Current Potential Drop Technique. Transactions of the Indian Institute of Metals. 69. 10.1007/s12666-015-0768-5.
Thank you.
Author Response
All replies are in the attached word document.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
This article should be drastically revised and rewritten. The reasons are as follows;
- There is a little originality on this article. I wonder what new results are.
- The contents of this article are mixed up the Result and Discussion. They had better combine them as a section of Result and Discussion.
- In section of discussion, authors discuss the effect of heat treatment using equation (10) and (11), but they could not explain their results in Table 6. And they should reconsider that these equations (4) to (11) are required or not.
- In addition, although authors explain the effects of the restoration on high temperature creep properties by using dislocation mechanisms, they could not show the evidences of dislocation mechanisms. Authors had better show their evidences such as dislocation images taken by TEM and so on. If they do not observe the TEM, they should discuss the dislocation mechanisms in the super alloys by referring to the evidences on dislocation behaviors which are published by many authors.
- The introduction is quite long. It should be rewritten more clearly.
- Minor errors; lack of reference [26].
Comments for author File: Comments.pdf
Author Response
All replies are in the attached word document.
Author Response File: Author Response.pdf
Reviewer 3 Report
Creep damage repair of a Nickel-based single crystal superalloy based on heat treatment
Abstract:
Line 12: should you say accelerated creep interruption test?
- Test materials and methods
It would be nice if you explicitly show in Figure 1a,b what are g phases and what g’ phases.
Line 106: The average size …. Missing: of what? γ? γ’?
Line 110: I believe that polishing does not remove residual stresses. Have you checked that with XRD measurements of surface residual stresses?
Line 114: electrochemical / chemical corrosion? Do you mean etching? The same means for line 138, and elsewhere.
Line 133: what means AC? Air cooled? Explain abbreviations when you mention them for the first time.
How did you measure elongation of the specimen during the accelerated creep test?
Figure 2: dimensions are written with decimal comma, in text with decimal point.
3.1. High temperature creep test results
What is stress of elastic deformation of DD6 at 1050°C? Where is the limit for yield stress at 1050°C?
Table 2: it is not clear, how do you evaluate creep strain? From 0 to 20, 40…100h? Or from 0 to 20, from 20 to 40 h… The data does not fit with Figure 3b.
Figure 3b: Why don’t you start graph at 0-0 x-y axes? How many specimens were creep tested at one interruption time?
It would be nice if you explicitly show in Figures 3c,d what are g phases and what g’ phases.
3.2. Microstructure after different creep interruption test time
Figure 4: why don’t you show us microstructures with a unit scale of 200 nm, instead of 1 mm. then we could compare microstructure at all different heat treatment conditions.
Line 213: Mpa ® MPa
Lines 218, 219: To explain symbols in equations 1,2, you should write in text fraction fAγ’ and fVγ’.
Table 3: why is no data for γ at rupture?
Line 240: explicitly write down, what symbols ǁ mean regarding to load. Do you mean perpendicular to load, when you write ǁ?
Line 266: when you say large number of dislocations, do you have any proof? TEM? Any reference?
Line 272: do you explain the increase of g’ phase with the end of secondary creep interval?
3.3. Microstructure after restoration heat treatment
Line 278: Why did you perform air cooling after solution heat treatment?
Figure 5: Figures a,c,e,g does not show us anything – no visual differences.
Line 298, 322, 347: us same designations everywhere: AC – air cooling.
At the end of this chapter you could add a T-t graph of solution heat treatment followed with two aging heat treatments, perhaps for specimen obtained at interruption time of 70 h, where you incorporate characteristic microstructures of the specimen before and after each stage of heat treatment.
3.4. Secondary high temperature …
Lines 350, 353, 356: Mpa ® MPa
Table 5: it is not clear: creep life without restoration… means, that if you interrupt creep testing after 20 hours, and then continue with creep testing, the specimen would rupture after 82 hours (102 h)? How many tests were done? Please explain more clearly.
Line 362: the same comment as for Table 5 also fo : The cumulative creep life…. Where are the data?
Line 367: What about strain at fracture? Any comment?
Figure 8: Why don’t you start graphs at 0-0 x-y axes?
Line 373: H ® h
- Discussion
No literature comparison and evaluation.
4.1. The effect of restoration…
Table 6: missing data for initial stage and for creep stage, before solution heat treatment.
Lines 411-458: no data, just theory
4.2. Effect of restoration heat treatment…
Figure 9: missing description, it is not clear, like Table 5
Line 471: missing explanation, why creep life is lower than… Explanation regarding number of creep stop-starts and their effect on creep life…
- Conclusions
Someone could expect, regarding the title, that after heat treatment DD6 restore initial creep properties, and not those after interruption of creep process.
Comments for author File: Comments.pdf
Author Response
All replies are in the attached word document.
Author Response File: Author Response.pdf
Reviewer 4 Report
Minor, the paper is very interesting and format is OK, with some changes I humbly suggested in the attached file, it would be one of the best.
I encourage you to make all of them, they are needed.
Comments for author File: Comments.pdf
Author Response
All replies are in the attached word document.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments
(1) The title "Test results and discussion" should be changed in "Results and discussion".
(2) There are many small errors on typesetting. Please check them.
(3) I wonder how authors improve equation (1) to (11) except equation (9). There are no change in all of them. It looks like the same one before and after the revision. Please show us how the equations are improved in the revise article.
Author Response
Dear reviewer，
Thank you very much for your careful review and valuable comments! We will reply to your comments one by one.
(1) The "test results and discussion" has been modified to "results and discussion";
(2) The typesetting of the full text has been carefully checked and revised;
(3) The formulas (1) to (11) are not modified, but the missing and unclear symbols in the formula are supplemented and explained. The reason why air cooling is used in the recovery heat treatment is explained, and the modified part has been marked yellow in the paper.
Thanks again!
Reviewer 3 Report
A lot of effort has been put into repairing this article. The explanations are now clear and the additional images are very effective. Only Figure 9b needs to be corrected - the starting point of the graph should be 0-0 for the x-y axis.
Author Response
Dear reviewer，
Thank you very much for your careful review and valuable comments. Figure 9 has been modified and replaced.
Thanks again!
