The Effect of Interpass Temperature on the Mechanical Properties and Microstructure of Components Made by the WAAM Method from Inconel 718 Alloy

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The authors studied the impact of temperature on deposition of components using Cold Metal Transfer-Wire Arc Additive Manufacturing technology. They proposed 2 overlay weld wall structures were created: by applying an interpass temperature of 100°C and without additional cooling. Conducted research did not show no changes in microstructure due to the application of interpass temperature were confirmed. However, they noticed that applying an interpass temperature reduces the average ultimate tensile strength. In the submitted manuscript, TEM analysis were also carried out, where it was found that the presence of strengthening phases γ’/ γ’’ in both components.  However, it was noticed that a larger amount of the strengthening phase γ’’ was present in the component manufactured without the application of interpass temperature.

 The presented research results are worth attention, but some issues require improvement.

 1.      Abbreviations should not appear in the abstract. They are unnecessary, especially since the mentioned abbreviations do not appear a second time in the abstract. Please use abbreviations for the first time in the section, for example "Introduction" and "Materials and Methods".

2.      Please justify why the authors used the electrolytic etching in solution of oxalic acid and not the quite popular Kalling's reagent?

3.      In my opinion, Figures 1-3 are unnecessary. If the authors want to keep them, please change the description for example: "Figure 2. Geometric dimensions specimen for tensile test" and "Figure 3. geometric dimensions specimen for notch toughness" as well as refer to the standards numbers.

4.      Figures 4 and 5 are described quite generally. Please describe them in more detail. It may be worth noting certain characteristic features in the microstructure - dendrite arrangement.

5.      The abbreviations in Table 3 “UTS” and “YS0.2” should be explained in the methodology and not in the abstract.

6.      The undoubted advantage of this manuscript is that the authors analyzed samples from TEM studies. However, the description of TEM results is quite poor. Please describe in more detail and refer to the literature of other authors if there is any.

Author Response

Dear reviewer,

thank you for your valuable comments. We accepted or justifyied all comments and responded to every one of them below. We are sure that performed changes based on your comments will improve quality and readability of the manuscript.

 

Comments 1: Abbreviations should not appear in the abstract. They are unnecessary, especially since the mentioned abbreviations do not appear a second time in the abstract. Please use abbreviations for the first time in the section, for example "Introduction" and "Materials and Methods".

Response 1: Abbreviations from the abstract were removed and relocated to other sections as suggested.

Comments 2: Please justify why the authors used the electrolytic etching in solution of oxalic acid and not the quite popular Kalling's reagent?

Response 2: Since austenitic stainless steel is often studied at our university, where electrolytic etching is commonly used, the same procedure was therefore applied to inconel 718 as the first choice, since it has an austenitic structure as well. The results achieved were satisfactory and we did not look for other solutions.

Comments 3:  In my opinion, Figures 1-3 are unnecessary. If the authors want to keep them, please change the description for example: "Figure 2. Geometric dimensions specimen for tensile test" and "Figure 3. geometric dimensions specimen for notch toughness" as well as refer to the standards numbers.

Response 3: Descriptions of the Figures 2 and 3 in the submitted manuscript (now Figures 4 and 5) were changed as suggested

Comments 4: Figures 4 and 5 are described quite generally. Please describe them in more detail. It may be worth noting certain characteristic features in the microstructure - dendrite arrangement.

Response 4: Results of microstructure analysis were explained in more detail

Comments 5: The abbreviations in Table 3 “UTS” and “YS0.2” should be explained in the methodology and not in the abstract.

Response 5:  The abbreviations in Table 3 “UTS” and “YS0.2” are now explained in the section 2 (Materials and Methods)

Comments 6: The undoubted advantage of this manuscript is that the authors analyzed samples from TEM studies. However, the description of TEM results is quite poor. Please describe in more detail and refer to the literature of other authors if there is any.

Response 6: Results of TEM analysis were described in more detail and additional images were inserted, all TEM images have been re-edited to improve readability, discussion section (now section 4) was added for better explanation of results

Reviewer 2 Report

Comments and Suggestions for Authors

This study explored the effects of interpass temperature on the properties of WAAM-processed IN 718. This study is timely and useful, but the manuscript itself needs some improvements before it could be considered for publication. The major issues are the lack of details in the Materials and Methods section and lack of significant discussion before the conclusions. 

Specific comments: 

1. The organization of the paper is generally good, with the exception of some very short paragraphs. In several places, only a single sentence occupies a paragraph. The paragraphs should be reorganized so that they are all about the same size in order to make the manuscript easier to read. The text also needs some additional polishing. 

2. In Section 2, we need more technical details about:

-  The WAAM setup itself, including more details about the build plate

- Shielding gas information

- Actual photos of the samples before testing

- Where did the information in Table 1 come from?

- More details about the cutting and grinding phases

- More information about the waterjet cuts made. 

- More information about the testing equipment used. 

The Materials and Methods section is not detailed enough to reproduce the experiments. Also, if any experimental design was used, this needs to be outlined in detail. 

3. There is a lot of confusion in the presentation about just exactly how many samples were tested for each experiment. The authors need to add a table to the paper with the list of experiments done and an exact sample count for each one.

4. The results of the statistical analysis are presented, but the setup and methods used for calculating the p-values need to have a much more detailed presentation. The presentation should be so detailed that a causal reader can reproduce the experiments just from reading the paper. 

5. Please provide all the raw data, either tabulated in the paper itself or attached as a supplemental document.  

6. In the bar plots, what do the error bars represent? (% error, standard deviation, standard error?)

7. The TEM images need improvement, as many of them are too dark to see what is going on. I suggest the authors increase the contrast and increase brightness to make them clearer. 

8. There is very little discussion of results. An additional section needs to be added to the paper to resolve this issue. 

9. Less serious than the other issues, but the background review is weak and ignores a lot of good related literature. If the authors have time, I recommend addressing this to increase the quality of the manuscript. 

Comments on the Quality of English Language

Needs some improvement, see my comments to the authors

Author Response

Thank you for your valuable comments. We accepted your comments and responded to every one of them below. We are sure that performed changes based on your comments will improve quality and readability of the manuscript.

 

Comments 1: The organization of the paper is generally good, with the exception of some very short paragraphs. In several places, only a single sentence occupies a paragraph. The paragraphs should be reorganized so that they are all about the same size in order to make the manuscript easier to read. The text also needs some additional polishing. 

Response 1: The paragraphs of the manuscript were mostly reorganized. We believe that manuscript structure is better now.

Comments 2:  In Section 2, we need more technical details about:

-  The WAAM setup itself, including more details about the build plate

- Shielding gas information

- Actual photos of the samples before testing

- Where did the information in Table 1 come from?

- More details about the cutting and grinding phases

- More information about the waterjet cuts made. 

- More information about the testing equipment used. 

The Materials and Methods section is not detailed enough to reproduce the experiments. Also, if any experimental design was used, this needs to be outlined in detail. 

Response 2: WAAM setup scheme was added as Figure 1.

• information about shielding gas was added
• actual photo of samples after abrasive water jet cutting was added as Figure 3. Actual photo of sample after milling process is not available anymore since they were used for destructive testing.
• information regarding origin of chemical composition in Table 1 was added
• information about cutting and grinding was added.
• Samples after abrasive water jet cutting is shown in Figure 3. We added the designation of cutting machine and explanation why the cuts were made by abrasive water jet.
• All equipment information used in experiment was added.
• Materials and Methods section was re-edited and explained more in detail for better reproducibility of the experiment.

Comments 3:  There is a lot of confusion in the presentation about just exactly how many samples were tested for each experiment. The authors need to add a table to the paper with the list of experiments done and an exact sample count for each one.

Response 3: Number of samples were added into each table with results for particular test. Number of samples for destructive testing is easy to track, however the microscopic analysis and TEM analysis comes with many documentations from more places.

Comments 4: The results of the statistical analysis are presented, but the setup and methods used for calculating the p-values need to have a much more detailed presentation. The presentation should be so detailed that a causal reader can reproduce the experiments just from reading the paper. 

Response 4: Information about the statistical software used including test type and significance levels were added.

Comments 5: Please provide all the raw data, either tabulated in the paper itself or attached as a supplemental document.  

Response 5: Raw data were added to tables 3 and 4.

Comments 6: In the bar plots, what do the error bars represent? (% error, standard deviation, standard error?)

Response 6: Error bars explanations was added to paragraph right before Figure 2.

Comments 7:  The TEM images need improvement, as many of them are too dark to see what is going on. I suggest the authors increase the contrast and increase brightness to make them clearer. 

Response 7: Thank you for this comment, images were enhanced for better readability.

Comments 8: There is very little discussion of results. An additional section needs to be added to the paper to resolve this issue. 

Response 8: Discussion section (now section 4) was added.

Comments 9: Less serious than the other issues, but the background review is weak and ignores a lot of good related literature. If the authors have time, I recommend addressing this to increase the quality of the manuscript. 

Response 9: We agree that introduction can be improved, however, due to the time pressure from the editors and significant changes of the manuscript required by reviewers, there was not enough time to implement more literature review and to fulfil this request. We are very sorry for that.

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have done an acceptable revision of the manuscript. I recommend acceptance of the current version.