EBSD Study of Delta-Processed Ni-Based Superalloy
, Jessica Calvo 2, Pablo Rodriguez-Calvillo 3, José María Cabrera Marrero 2,4, Marco Antonio Zamora Antuñano 5 and Martha Patricia Guerrero-Mata 6Round 1
Reviewer 1 Report
The influence of deformation temperature and strain rate on recrystallization and delta-phase evolution were investigated by EBSD. Meanwhile, the morphologies of LAGBs and HAGBs in different samples were presented. There some questions as following:
- About 8.95% δ-phase in sample B with yellow color as showed in Fig.8. However, there are some M23C6 carbides on grain boundaries. Maybe the volume fraction of δ-phase value is not precise. Meanwhile, it is suggested that the author need add a SEM photograph of δ-phase.
- The conclusions are too long. The author should modify this part again.
Author Response
Reviewer 1
The influence of deformation temperature and strain rate on recrystallization and delta-phase evolution were investigated by EBSD. Meanwhile, the morphologies of LAGBs and HAGBs in different samples were presented. There some questions as following:
- About 8.95% δ-phase in sample B with yellow color as showed in Fig.8. However, there are some M23C6 carbides on grain boundaries. Maybe the volume fraction of δ-phase value is not precise. Meanwhile, it is suggested that the author need add a SEM photograph of δ-phase.
R= Thank you very much for the comments, suggested changes were made, it was added a new figure 8, and the figure 8 turns to figure 9, see lines 209-226.
2. The conclusions are too long. The author should modify this part again.
R= Thank you very much for the suggestions and observations, see lines 251-270.
Reviewer 2 Report
It is a good paper devoted to the very important material, namely the delta-processed Ni-based superalloy. The control of the microstructure of nickel-based superalloys in manufacturing processes is critical for the development of optimal mechanical properties. The paper could be published after major revisions. In particular, it is good visible in micrographs in Fig. 8 how the phase appearing yellow (δ-phase) surrounds the grains of the phase appearing blue (γ-phase). Such behaviour of grain boundary phase(s) is intimately connected with the so-called complete and incomplete wetting of grain boundaries by the melt or second solid phase (see for example J. Mater. Eng. Perform. 27 (2018) 4989). The morphology of integranular phase strongly influences the overall mechanical properties of a polycrystalline composite (see for example Scripta Mater. 83 (2014) 17). The grain boundary wetting transitions can definitely influence the phenomena observed by the authors. I would strongly propose to discuss these points in the paper.
Author Response
Reviewer 2
It is a good paper devoted to the very important material, namely the delta-processed Ni-based superalloy. The control of the microstructure of nickel-based superalloys in manufacturing processes is critical for the development of optimal mechanical properties. The paper could be published after major revisions. In particular, it is good visible in micrographs in Fig. 8 how the phase appearing yellow (δ-phase) surrounds the grains of the phase appearing blue (γ-phase). Such behaviour of grain boundary phase(s) is intimately connected with the so-called complete and incomplete wetting of grain boundaries by the melt or second solid phase (see for example J. Mater. Eng. Perform. 27 (2018) 4989). The morphology of integranular phase strongly influences the overall mechanical properties of a polycrystalline composite (see for example Scripta Mater. 83 (2014) 17). The grain boundary wetting transitions can definitely influence the phenomena observed by the authors. I would strongly propose to discuss these points in the paper.
R= Thank you very much for the suggestions. The necessary changes were made, a paragraph was added to lines 43-45 and a new cite. Moreover, it was added a new figure 8, and the figure 8 turns to figure 9, see lines 209-226.
Reviewer 3 Report
The authors investigated the influence of delta-processing treatment (DP718) and subsequent deformation at high temperatures on the microstructure of Inconel 718. The samples were compressed below and above δ-solvus temperature at two different strain rates 0.001 s-1 and 0.01 s-1. Microstructural characterization was carried out by the electron backscattered diffraction technique (EBSD) with the result that samples deformed above δ-solvus with high strain rate show an increase in the percentage of low angle grain boundaries (LAGB) due to deformation and a decrease in high angle grain boundaries (HAGB). The δ -phase was found mostly at grain boundaries which leads to a pinning effect and thus a grain growth control during hot deformation.
The subject matter is suitable for publication in Metals but with respect to content and figures there are a lot of open questions and suggestions for improvement:
Figures 3-5:
a) A smaller section with higher magnification would be much more demonstrative. A lot of features, in particular in the deformed regions are much too small to become clear.
a) Legends are missing,
c) y-axes are not comparable and partly seem to be wrong (3a: do you really have a maximum with 0.016%?) Why is the summation of the frequencies unequal to 100%?
x-axes are not comparable. It would be better to omit the few very large grains and extend the axes to the same value.
Did you use the same width for your classification?
Line 128: “average grain size goes down to 10 μm (see Figure 4c)” No, this is not visible from figure 4c
Lines 132: “are forming a sort of necklace around deformed grains” No, the magnification is much too low to see this
Figure 6:
a, c, e) A smaller section with higher magnification would be much more demonstrative. A lot of features, in particular in the deformed regions are much too small to become clear.
Legends are missing,
b, d, f) For better comparison please use the same y-axes
Why is frequency relationship on the y-axis?
Figure 7:
a, c, e) A smaller section with higher magnification would be much more demonstrative. A lot of features, in particular in the deformed regions are much too small to become clear.
Legends are missing,
b, d, f) For better comparison please use the same value of 3.5 for all y-axes,
e.g. for b): cut the first very high column and write the corresponding value next to the column. Otherwise other Sigma boundaries are not detectable in the distribution.
Comparison 3a) - 3b): Contradiction: in a) a huge amount of twins is visible, in b) nearly no sigma 3 boundaries occur
Comparison 3d,f) and corresponding text: Contradiction: in the text 3.5% twins are mentioned for both, in d) and f) nearly no sigma 3 boundaries occur.
Figure 8: Legend is missing
Line 219: “there is a large presence of limits higher than 30° 219 (turquoise)”, Yes, of course it has to be like this, because the angle range is 10° for the first two and minimum 40° for the third. For a meaningful distribution you will have to go on in 10° steps until 60°.
Figure 9:
a) Legend is missing. For a meaningful distribution you will have to use the same class width.
b) Please shorten the x-axis to 60°
Why is frequency ratio on the y-axis?
Figure 10:
a) The meaning of the red grains can be misunderstood
b) Which relative frequency do you mean? If you have 0.08% gamma grains with 1° misorientation, what about the 99.9% other gamma grains? If you have 12% delta grains with 1° misorientation (and few others), what about the other 87% of delta grains?
Lines 224-229: The meaning of this section is unclear.
References to the related work are concentrated on introduction, materials and methods and some basic knowledge like sigma orientation relationships. There is nearly no discussion or comparison with the literature of the results.
Conclusion:
Introductory sentence is missing. Some of the findings like “more LAGBs with increasing strain rate” or “recrystallization may only take place at deformed grains” are self-evident. With respect to the cover story no information about the meaning of the results for this special application is given.
The manuscript exhibits some linguistic and grammatical mistakes and needs revision.
Author Response
Reviewer 3
The authors investigated the influence of delta-processing treatment (DP718) and subsequent deformation at high temperatures on the microstructure of Inconel 718. The samples were compressed below and above δ-solvus temperature at two different strain rates 0.001 s-1 and 0.01 s-1. Microstructural characterization was carried out by the electron backscattered diffraction technique (EBSD) with the result that samples deformed above δ-solvus with high strain rate show an increase in the percentage of low angle grain boundaries (LAGB) due to deformation and a decrease in high angle grain boundaries (HAGB). The δ -phase was found mostly at grain boundaries which leads to a pinning effect and thus a grain growth control during hot deformation.
The subject matter is suitable for publication in Metals but with respect to content and figures there are a lot of open questions and suggestions for improvement:
Figures 3-5:
- a) A smaller section with higher magnification would be much more demonstrative. A lot of features, in particular in the deformed regions are much too small to become clear.
- a) Legends are missing,
- c) y-axes are not comparable and partly seem to be wrong (3a: do you really have a maximum with 0.016%?) Why is the summation of the frequencies unequal to 100%?
x-axes are not comparable. It would be better to omit the few very large grains and extend the axes to the same value. Did you use the same width for your classification?
Line 128: “average grain size goes down to 10 μm (see Figure 4c)” No, this is not visible from figure 4c
Lines 132: “are forming a sort of necklace around deformed grains” No, the magnification is much too low to see this
R= Thank you very much for the observations, we agreed about remove the histograms in figures 3-5, see lines 127-153. The histogram had the aim of be evidence for the average gran size, it is not relevant.
Figure 6:
a, c, e) A smaller section with higher magnification would be much more demonstrative. A lot of features, in particular in the deformed regions are much too small to become clear.
Legends are missing,
b, d, f) For better comparison please use the same y-axes
Why is frequency relationship on the y-axis?
R= Thank you very much for the observations, we agreed about remove the histograms in figure 6, see lines 153-171. The histogram had the aim of be evidence for the average gran size, it is not relevant.
Figure 7:
a, c, e) A smaller section with higher magnification would be much more demonstrative. A lot of features, in particular in the deformed regions are much too small to become clear.
Legends are missing,
b, d, f) For better comparison please use the same value of 3.5 for all y-axes,
e.g. for b): cut the first very high column and write the corresponding value next to the column. Otherwise other Sigma boundaries are not detectable in the distribution.
Comparison 3a) - 3b): Contradiction: in a) a huge amount of twins is visible, in b) nearly no sigma 3 boundaries occur
Comparison 3d,f) and corresponding text: Contradiction: in the text 3.5% twins are mentioned for both, in d) and f) nearly no sigma 3 boundaries occur.
R= Thank you very much for the suggestions, improvements were made see lines 180-195.
Figure 8: Legend is missing
R= Thank you very much for the suggestions, improvements were made see lines 224-226.
Line 219: “there is a large presence of limits higher than 30° 219 (turquoise)”, Yes, of course it has to be like this, because the angle range is 10° for the first two and minimum 40° for the third. For a meaningful distribution you will have to go on in 10° steps until 60°.
Figure 9:
- a) Legend is missing. For a meaningful distribution you will have to use the same class width.
- b) Please shorten the x-axis to 60°
Why is frequency ratio on the y-axis?
R= Thank you very much for the observations, we agreed about remove the histograms in figure 9 which turns to 10, see lines 233-237. The histogram it is not relevant.
Figure 10:
- a) The meaning of the red grains can be misunderstood
- b) Which relative frequency do you mean? If you have 0.08% gamma grains with 1° misorientation, what about the 99.9% other gamma grains? If you have 12% delta grains with 1° misorientation (and few others), what about the other 87% of delta grains?
Lines 224-229: The meaning of this section is unclear.
References to the related work are concentrated on introduction, materials and methods and some basic knowledge like sigma orientation relationships. There is nearly no discussion or comparison with the literature of the results.
R= Thank you very much for the suggestions, improvements were made see lines 243-244. Figure 10 turns to 11. Suggested changes were made, it was added a new figure 8, and the figure 8 turns to figure 9, see lines 209-226. In addition, a paragraph was added to lines 43-45 and a new cite. Another paragraph was added to lines 212-219 and a new cite, as well.
Conclusion:
Introductory sentence is missing. Some of the findings like “more LAGBs with increasing strain rate” or “recrystallization may only take place at deformed grains” are self-evident. With respect to the cover story no information about the meaning of the results for this special application is given.
The manuscript exhibits some linguistic and grammatical mistakes and needs revision.
R= Thank you very much for the feedback. The improvement was made, see lines 251-270
Finally, the review of the English language was carried out. A native review.
Author Response File: 
Author Response.pdf
Round 2
Reviewer 2 Report
After revision the paper is acceptable for publication as it is
Reviewer 3 Report
All corrections and suggestions for improvement have been implemented by the authors.
