On the Control of Elemental Composition, Macro-, and Microstructure of Directionally Solidified Additive Products from Nickel-Based Alloy
Round 1
Reviewer 1 Report
It is a good work on the control of elemental composition, macro- and micro-structure of directionally solidified additive nickel-based alloy. The authors established the influence of heat input and methods of heat removal at the wire-feed EBAM process on the structure of a nickel-based alloy. Minor revisions were suggested.
(a) The chemical composition of superalloy ZhS32 should be given.
(b) The conclusions were too long which need to be improved. Only the main results were suggested to be summarized.
(e) Some typos should be corrected in the manuscript.
Minor revisions were suggested.
Author Response
(a) The chemical composition of superalloy ZhS32 should be given.
The composition of superalloy ZhS32 is given in the last line of Table 4.
(b) The conclusions were too long which need to be improved. Only the main results were suggested to be summarized.
The conclusions have been rewritten to reduce their length and improve the reader's perception.
(e) Some typos should be corrected in the manuscript.
Identified typos have been corrected in the manuscript.
Reviewer 2 Report
The paper concerns a very vital and actual problem of alloys additive manufacturing In my opinion the paper is written very well, the investigations were performed in a very proper manner and the conclusions are of great importance. Also English and presentation are of a good quality.
The following few small doubts and editorial faults were noticed causing my advice for the minor revision: page 6 line 178: directional solidification of the dendritic structure- should be enough; line 183: 3D printing is supressed by the increasing heat input; page 9 line 231 we can conclude the following : the…; page 11 line 261- unknown symbol in place of the phase; lines 272-274: if the following opinion still concerns Al content (it is not completely clear), you are giving another explanation for the reason for Al depletion than in line 258 what makes your intention unclear. Which one or both are valid?
Author Response
page 6 line 178: directional solidification of the dendritic structure- should be enough;
Corrected.
line 183: 3D printing is supressed by the increasing heat input;
Rephrased:
According to [11, 12], zigzag morphology is not implemented in the strategy of multidirectional 3D printing at higher values of heat input.
page 9 line 231 we can conclude the following : the…;
Corrected.
page 11 line 261- unknown symbol in place of the phase;
Corrected.
lines 272-274: if the following opinion still concerns Al content (it is not completely clear), you are giving another explanation for the reason for Al depletion than in line 258 what makes your intention unclear. Which one or both are valid?
The subject of the discussion, tantalum, was lost as a result of editing. Corrected.
Reviewer 3 Report
Dear Authors,
There are some points that need to be clarified and to make corresponding changes in the work according to the comments below.
Kind regards,
Reviewer
1. In the Introduction section, new references should be added, supporting the statements concerning the mentioned different technologies, methods, approaches, etc. 2. It is not appropriate to have equations in the Introduction section. 3. At the end of the Introduction there should be a short paragraph about the purpose of the present work and why this research is necessary and important / what prompted the research.
4. The sentence should be clarified, p.2: “II - Reduction of heat input by reducing the initial beam current IbII by 2/5 of the value of the initial beam current Ib0 in the additive process marked "0" (a recent paper [9] details all aspects of the formation and characteristics of the macro-, micro- and fine structure of this additive product) and all other additive processes, see Figure 1(b);”
5. Figure 1 should be clarified and the labels in Figure 1 should correspond to the text for this figure (p.2). Figure 1 caption should be more informative.6. It should be indicated how the values ​​of heat input presented in Table 1 were calculated (probably from equation 1, which is in the Introduction).
7. The sentence should be clarified, p.3: “As can be seen from the above data, for samples II, IV, V and VI the electron beam current was changed, and for sample III the speed of work table movement was increased, which in turn affects the value of heat input. “ – What is this data? The samples should be defined/ described and their relationship with the labels in the text (p.2) and in Fig. 1 should be correspondent to the conditions in Fig. 1
8. p.3: “Figure 2 shows the dependence of the heat input value calculated by equation (1) on the number of layers deposited and the distance from the substrate.” - How the dependencies on the number of layers deposited and on the distance from the substrate are calculated?
9. Figure 2 caption should be corrected and more informative.10. p.5: “… the highest beam current of 1.6 mA realized in this study during product formation 140 (see Table 1).” – This value of the beam current does not correspond to those indicated in Table 1.
11. p.6: “The shape and dimensions of Product VI are most similar to those of the other additive products.” – This statement is incorrect based on the visual picture alone (Figure 3). 12. p.6: “The general regularities of the material macrostructure of the additive products formed in the EBAM process with the marking I - VI have been established: ….” – the figures on which these conclusions are based should be added /cited. 13. p.6: angle Ψ should be labeled/shown in the figure. 14. p.6: “Notably, in additive product III, directional dendrite growth is interrupted at 25 mm from the substrate (see Figures 4(c) and 5(c)).” – This should be marked /indicated on the corresponding figures. 15. p.6: “However, in our case, exceeding the initial heat input of 2.6 kJ/mm leads to excessive melting of the additive product, resulting in unsatisfactory final product size and shape.” – This value does not correspond to those given in Table 1 for this case. 16. p.7 - Figure 6 caption should be more informative. 17. p.7: “The carbide phases are enriched in chromium, niobium, tantalum, tungsten and rhenium. The dendrites and interdendritic space contain all the alloying elements, while the dendrite axes contain 1.5 times more tungsten and rhenium.” – It should be clarified where this follows from. 18. p.8: In Figure 6, the phases should be marked. 19. p.8 - Figure 7 caption should be more informative. 20. p.8: “As can be seen in Figure 7, there is a gradual increase in the PDAS for each of the 6 samples.” – Incomplete and incorrect statement; should be clarified. 21. p.10 – Table 4 caption should be more informative. 22. p.11: “In our opinion, the identified reduced by 0.61- 0.81 % wt, relative to the minimum allowable grade composition, is due to the selective precipitation of carbide phases during the preparation of metallographic thin sections. X-ray fluorescence analysis was performed on their surfaces.” – should be clarified.23. The conclusions should be rewritten, summarized and shortened.
24. The References section should be enriched and new sources of other authors added - 8 out of 14 cited References are of the co-authors of this manuscript (Ref. N 4, 7-12, 14).
25. It is recommended that the Results and discussion section be structured into subsections according to the presented results.26. The level of English use must be improved.
The level of English use must be improved.
Author Response
- In the Introduction section, new references should be added, supporting the statements concerning the mentioned different technologies, methods, approaches, etc.
Corrected.
- It is not appropriate to have equations in the Introduction section.
Corrected.
- At the end of the Introduction there should be a short paragraph about the purpose of the present work and why this research is necessary and important / what prompted the research.
Corrected
- The sentence should be clarified, p.2: “II - Reduction of heat input by reducing the initial beam current IbII by 2/5 of the value of the initial beam current Ib0 in the additive process marked "0" (a recent paper [9] details all aspects of the formation and characteristics of the macro-, micro- and fine structure of this additive product) and all other additive processes, see Figure 1(b);”
Corrected.
- Figure 1 should be clarified and the labels in Figure 1 should correspond to the text for this figure (p.2). Figure 1 caption should be more informative.
Corrected.
- It should be indicated how the values of heat input presented in Table 1 were calculated (probably from equation 1, which is in the Introduction).
Corrected.
- The sentence should be clarified, p.3: “As can be seen from the above data, for samples II, IV, V and VI the electron beam current was changed, and for sample III the speed of work table movement was increased, which in turn affects the value of heat input. “ – What is this data? The samples should be defined/ described and their relationship with the labels in the text (p.2) and in Fig. 1 should be correspondent to the conditions in Fig. 1
Corrected.
- p.3: “Figure 2 shows the dependence of the heat input value calculated by equation (1) on the number of layers deposited and the distance from the substrate.” - How the dependencies on the number of layers deposited and on the distance from the substrate are calculated?
A number of actual values of technological parameters, including acceleration voltage, electron beam current and worktable movement rate are recorded in additive forming processes by means of software with reference to a specific layer. The set of calculated values according to formula (1) for each of the layers allow to plotting the dependencies of the linear energy on the number of formed layers. Comparing the actual height of the additive product with the calculated values of the heat input in each of the layers allow to plotting the dependence of the heat input on the distance to the substrate.
- Figure 2 caption should be corrected and more informative.
Corrected.
- p.5: “… the highest beam current of 1.6 mA realized in this study during product formation 140 (see Table 1).” – This value of the beam current does not correspond to those indicated in Table 1.
Mistake was corrected.
- p.6: “The shape and dimensions of Product VI are most similar to those of the other additive products.” – This statement is incorrect based on the visual picture alone (Figure 3).
Corrected.
- p.6: “The general regularities of the material macrostructure of the additive products formed in the EBAM process with the marking I - VI have been established: ….” – the figures on which these conclusions are based should be added /cited.
Corrected. The revised manuscript summarizes the identified qualitative and quantitative characteristics of the macrostructure of additive products.
- p.6: angle Ψ should be labeled/shown in the figure.
As an example, on Figure 4 showed the corners Y÷÷.
- p.6: “Notably, in additive product III, directional dendrite growth is interrupted at 25 mm from the substrate (see Figures 4(c) and 5(c)).” – This should be marked /indicated on the corresponding figures.
In Figure 4(c), the area under discussion is highlighted with a closed dashed line, and explanations have been made in the manuscript text.
- p.6: “However, in our case, exceeding the initial heat input of 2.6 kJ/mm leads to excessive melting of the additive product, resulting in unsatisfactory final product size and shape.” – This value does not correspond to those given in Table 1 for this case.
Corrected.
- p.7 - Figure 6 caption should be more informative.
Corrected.
- p.7: “The carbide phases are enriched in chromium, niobium, tantalum, tungsten and rhenium. The dendrites and interdendritic space contain all the alloying elements, while the dendrite axes contain 1.5 times more tungsten and rhenium.” – It should be clarified where this follows from.
Corrected. It was decided to exclude a detailed discussion of the composition of the individual phases from this manuscript.
- p.8: In Figure 6, the phases should be marked.
The description of the peculiarities of the phase composition of additive products is beyond the scope of the present study. Basically, these features are presented in [9]. Here we note that carbide phases (the light component in Fig. 6) are localized in the interdendritic space, as well as eutectic g/g¢ and, possibly, Laves phases.
- p.8 - Figure 7 caption should be more informative.
Corrected.
- p.8: “As can be seen in Figure 7, there is a gradual increase in the PDAS for each of the 6 samples.” – Incomplete and incorrect statement; should be clarified.
Corrected.
- p.10 – Table 4 caption should be more informative.
Corrected.
- p.11: “In our opinion, the identified reduced by 0.61- 0.81 % wt, relative to the minimum allowable grade composition, is due to the selective precipitation of carbide phases during the preparation of metallographic thin sections. X-ray fluorescence analysis was performed on their surfaces.” – should be clarified.
Corrected.
- The conclusions should be rewritten, summarized and shortened.
Conclusions have been rewritten.
- The References section should be enriched and new sources of other authors added - 8 out of 14 cited References are of the co-authors of this manuscript (Ref. N 4, 7-12, 14).
New references gave been added.
- It is recommended that the Results and discussion section be structured into subsections according to the presented results.
Corrected.
- The level of English use must be improved.
Corrected.
Reviewer 4 Report
The manuscript describes the microstructure of directionally solidified Ni-based superalloys processed by EBAM.
The manuscript needs to be carefully revised before suggesting publication in this journal.
Before identifying gamma prime like Ni3Al and then use the symbol γ’.
Introduction = English needs to be polished to improve the flow of the text.
Please provide references for this sentence “Additive manufacturing eliminates the need for molds and, because of the high temperature gradient, it is possible to increase the speed of obtaining products.”
The final part of the introduction needs to report more details.
The possible industrial advantages of the directionally solidified Ni-based alloys must be included in the introduction.
Please provide a Table with the chemical composition of the current alloy in materials and method
Please provide a scale bar for Figure 3.
For figure 4, it is possible to observe the direction grain growth along z-axis. It would be useful to provide information about the grains size to enhance the discussion. From the images, more than single crystal, the material seems formed by different columnar grains. Clarifying this point is very important. See, for instance, the paper published on Materials “A Single Crystal Process Window for Electron Beam Powder Bed Fusion Additive Manufacturing of a CMSX-4 Type Ni-Based Superalloy”
It would be useful to provide the SEM images also for the last layer.
The correlation of the data with the current literature should be improved.
English needs to be polished. It is not appropriate to start a sentence with “And” in an academic journal. Moreover, several sentences can be modified to improve the flow of the discussion.
When using an abbreviation, it is important to define it before. For example EBAM, It is defined in the abstract but should also be defined in the introduction.
AlNi3 or Ni3Al?
Starting a sentence with "and", it is not appropriate in an academic journal.
Several sentences could be modified to improve the flow of the discussion.
Author Response
Before identifying gamma prime like Ni3Al and then use the symbol γ’.
The section introduces the gamma prime phase designation: The Ni3Al intermetallic compound (has the well-established designation g¢-phase) also provides intermetallic hardening.
Introduction = English needs to be polished to improve the flow of the text.
Corrected.
Please provide references for this sentence “Additive manufacturing eliminates the need for molds and, because of the high temperature gradient, it is possible to increase the speed of obtaining products.”
Corrected.
The final part of the introduction needs to report more details.
Introduction has been rewritten.
The possible industrial advantages of the directionally solidified Ni-based alloys must be included in the introduction.
Corrected.
Please provide a Table with the chemical composition of the current alloy in materials and method
The chemical composition of the alloy is given in subsection 3.4 introduced in the revised manuscript. This subsection discusses the peculiarities of the elemental composition of the material of additive products as a function of heat input and in comparison with the composition of the ZhS32 alloy. For clarity and ease of comparison, the actual compositions of additive products and the grade composition of ZhS32 alloy are summarized in a single Table 4. The elemental composition of additive products is not discussed earlier in the manuscript. Presenting the grade composition of ZhS32 alloy in a separate table in Section 2 complicates both the authors' presentation of the material and the readers' perception of it.
Please provide a scale bar for Figure 3.
Scale bars make it extremely difficult to visualize additive manufacturing images. As an alternative to scale bars, the dashed lines in all additive manufacturing images show the overall dimensions of 56×41×11 mm3 (length × height × width) specified for 3D printing of additive products.
For figure 4, it is possible to observe the direction grain growth along z-axis. It would be useful to provide information about the grains size to enhance the discussion. From the images, more than single crystal, the material seems formed by different columnar grains. Clarifying this point is very important. See, for instance, the paper published on Materials “A Single Crystal Process Window for Electron Beam Powder Bed Fusion Additive Manufacturing of a CMSX-4 Type Ni-Based Superalloy”
The reviewer correctly notes that the material structure of additive products is directionally crystallized. Obtaining products with a directional structure and investigating the characteristics of such a structure was the aim of the present study. A discussion of the correspondence between directional and single crystal structures has been added to the text of the manuscript.
It would be useful to provide the SEM images also for the last layer.
Added.
The correlation of the data with the current literature should be improved.
Corrected.
English needs to be polished. It is not appropriate to start a sentence with “And” in an academic journal. Moreover, several sentences can be modified to improve the flow of the discussion.
Corrected.
When using an abbreviation, it is important to define it before. For example EBAM, It is defined in the abstract but should also be defined in the introduction.
Corrected.
AlNi3 or Ni3Al?
Both these designations are found in the literature. For unification with the previous publication it was corrected to Ni3Al.
Round 2
Reviewer 3 Report
The needed changes according to the comments of the reviewer have been made by the authors in the revised manuscript.
Minor changes still need to be made in English.
Minor changes still need to be made in English.
Author Response
Changes have been made to the text of the manuscript. Changes are highlighted in color.
Reviewer 4 Report
The authors improved the current version of the manuscript by performing several points highlighted in the previous revisions.
However, in my opinion, the authors should determine the dimensions of columnar grains in Figure 4. The term grains is not reported throughout the text. A clear difference between dendritic structures and grains should be described.
Please provide how many dendrites were used to calculate the PDAS and how the XRF analysis's standard deviation is determined.
After the improvement of these parts of the manuscript, the manuscript could be suitable for publication.
Author Response
Determining the size of columnar grains in the form of directionally crystallized colonies of dendrites was not within the scope of the present study. Experience from previous studies shows that the results of such measurements on macroscopic images (shown in Figure 4 of the monograph) give a very large error. Due to the presence of only azimuthal mutual disorientations of directionally crystallized columnar grains, the boundaries between them are revealed either by optical metallography (see, for example, Figure 5 of the manuscript) or by EBSD analysis using SEM (see, for example, Figure 3 in [Fortuna S., Gurianov D., Nikonov D., Fortuna S., Gurianov D., Gurianov D., Nikonov D., Gurianov D., Nikonov D., Gurianov D., Nikonov S., Ivanov K., Mironov Y., Vorontsov A. Characteristics of the macro-, micro- and fine structure of the nickel superalloy product material formed by the method of electron beam additive manufacturing. Materials. 2022, 15(24), 8882. DOI10.3390/ma15248882]). Evaluation of the transverse dimensions of directionally crystallized dendrite colonies by optical metallography shows that the sizes range from 42.0 to 3125.9 μm. In our opinion, for products with a directional structure, the mechanical properties along the directional structure under creep conditions are not determined by the transverse dimensions of the columnar grains, but by the volume fraction of directionally crystallized colonies of dendrites with mutual disorientation less than 10 degrees.
In the manuscript, the authors deliberately avoid using the term "columnar grains". This is for the following reasons. The grain structure is characterized by the accumulation of dislocations and other defects of crystal structure along the grain boundaries. In the investigated material, the defective substructure along the boundaries of the dendrite colonies is not revealed by TEM and SEM. In the directionally crystallized structure, the dendrite colonies have only azimuthal disorientations relative to each other. As mentioned above, azimuthal disorientations are only seen in metallographic studies or in EBSD analysis by SEM.
Most likely, the boundaries between dendrite colonies in directionally crystallized structures are coherent. However, a separate set of structural studies is required to confirm this.
For each of the additive products, the PDAS was determined at 20 points along the height of the product. To determine the PDAS, three dendritic colonies at each height were considered and the distance between parallel growing primary dendritic arms was measured. Each dendritic colony contains approximately 50-60 such arms. Thus, at least 18.000 measurements of distances between primary dendritic arms were made.
The elemental composition of the material of the additive products was determined by taking the arithmetic mean of three parallel measurements. Arithmetic means and standard deviations were calculated using Niton XL3t GOLDD++ software (Thermo Scientific Portable Analytical Instruments, Inc., USA).
