WAAM-Fabricated Laminated Metal Composites
Round 1
Reviewer 1 Report
1.This article reported the additive manufacturing of a composite bulk material consisting of dissimilar SG and X10 laminated layers by using wire arc additive manufacturing (WAAM) technique. Variety of mechanical testing were conducted to reveal the mechanical properties of the composites. The amount of work and efforts was huge!
2. The authors claimed that no literature had reported about laminated metal composites (LMC) fabricated by WAAM. In fact, there has been at least one paper published in Mat. Sci. & Eng. in 2020 with the title “Wire arc additive manufacturing of functionally graded material for marine risers”, reported the fabrication of LMC consisting of ER 70S-6 and ER 2209 Duplex S.S. wires using WAAM. In addition, there have been many publications reported on additive manufacturing of bulk metal deposits using arc welding process including GMAW and SAW processes. It is also worthwhile to mention that The Institute MPA-Stuttgart had published a series paper in the 1980s regarding the additive manufacturing (shape welding) of thick-walled pressure vessel and the associated mechanical properties of the weld deposits. The authors should cite some of these paper. Some examples are listed as follows:
S. Chandrasekaran, S. Hari, M. Amirthalingam, Wire arc additive manufacturing of functionally graded material for marine risers, Mat. Sci. & Eng. A (792) 2020, 139530
Panchenko, O.; Kurushkin, D.; Isupov, F.; Naumov, A.; Kladov, I.; Surenkova, M. Gas Metal Arc Welding Modes in Wire Arc Additive Manufacturing of Ti-6Al-4V. Materials 2021, 14, 2457. Wire-arc additive manufacturing
K. Kußmaul, F.W. Schoch and H. Luckow, High Quality Large Components 'Shape Welding' by a SAW Process, Welding Journal, 1983, 17-24.
3. Instead of trade name or company designation, the filler wire SG2 and X90 should be identified with either ISO, EN or AWS designations. Also the chemical compositions of each wire must be listed in a Table.
4. The mechanical properties of the LMC are strongly influenced by the dilution between the unalloyed SG2 and X90 weld beads. The authors should provide information (e.g. EDS-analysis) regarding to which extent the high-alloyed X90 weld beads were diluted by the unalloyed SG2 and how the dilution affected the mechanical properties. This may explain why the hardness of both SG2 and X90 fell almost in the same range as described in line 148 in p.4.
5. The interpass temperature not only affected the weld bead thickness, moreover, it would affect the dilution between SG2 and X90. The decreasing weld bead thickness with subsequent deposition of weld bead on top of each layer implies an increase in dilution between the two dissimilar deposits. This evidence suggests that the applied welding heat input had caused a strong dilution of alloy elements especially in the X90 beads and resulted in decrease in hardness.
6. The range of welding voltage should also be given in Table 1. In addition, the heat input (J/mm) should be calculated (H.I.=I x V/ v) and given in Table 1, too. The abbreviation BPS is a mix of English and German, it is better given as “welding speed, v”.
7. The paragraph regarding the derived yielding and tensile strengths from eq. (1) and (2) in p. 5 is not of significance. These empirical formulas are mainly for the purpose of estimating strength value from hardness for industrial practice but are not relevant to research. Also the 2nd paragraph in p. 8 is irrelevant.
8. Caption of tables must be placed on top of the tables not beneath the tables.
9. In paragraph 4.1., the specimen length 24 cm is not consistent with the dimensions shown in fig. 4. where specimen length is 120mm.
10. Along which cross-section were the tensile specimens taken from? And from which portion of the LMC? It is hard to imagine from figure 4 how the tensile specimens were prepared. On the contrary, figure 7 clearly reveals how the impact specimens were prepared.
11. In p.7, “The rule of mixture” was mentioned in discussion. However, the rule of mixture does not apply in this case since the strength should depend much more on dilution between SG2 and X90 layers than on the volume fraction (or thickness ratio) of the dissimilar deposit layers.
12. The description of the impact specimens after impact test at the end of p.9 was not quantitative. The authors should provide the percentage of ductile fracture/brittle fracture of the fracture surface or width expansion on specimens of different weld deposits.
13. The German term “Probe(n)” must be replaced by “specimen(s)” or “sample(s)” throughout the text!
14. Standard deviation of the impact energy out of 6 Charpy specimens should be given in Table 5. Then, Figure 9 is no more necessary.
15. The first paragraph in p. 11 discussed the possible crack initiation, propagation and delamination in ISO-V-specimens during impact test. However, the evidence provided in micrographs in Figure 10 is quite weak to support the authors’ argument. The authors’ argument should be better supported by a detailed force-displacement curve obtained from an instrumented impact test if this is available. In addition, the scale of figure 10 cannot be read.
16. Since no conclusion could be drawn with respect to the endurance limit of different laminated materials in fatigue test, in addition, figure 13, figure 14 and their associated discussion did not provide substantial information with respect to the fatigue properties, the authors should consider to remove the content of paragraph 4.3.-fatigue test.
17. The article is too long. The content in “5. Discussion” from p. 14 to p.16 is a pure repletion or “in another word” of what has been described and discussed in previous pages and can be dropped from the text.
18. The English text requires a thorough reediting.
19. Considering the interesting topic and the huge amount of work and effort which had made by the authors, the reviewer encourages the authors to further supplement necessary data, condense the content, reorganize and resubmit this article.
Comments for author File: 
Comments.pdf
Author Response
Dear Reviewer,
thank you for your positive feedback on the manuscript and the valuable comments. We overtook all your comments and incorporated them into the manuscript. We highly appreciate your comments which clearly make our manuscript better. Please find our response to each of your comments in the attached Word file.
Yours sincerely,
The authors
Author Response File: Author Response.pdf
Reviewer 2 Report
- what means the number 188.65 (row 149) and number 179.65 (row 150). they are marks of steel or the values of some properties? To explain, please.
- Table 6 is not correct to view. Part of this is out of page.
- is not mention about Figure 12 (S-N-curves) in text
Author Response
Dear Reviewer,
thank you for your positive feedback on the manuscript and the valuable comments. We overtook all your comments and incorporated them into the manuscript. We highly appreciate your comments which clearly make our manuscript better. Please find our response to each of your comments in the attached Word file.
Yours sincerely,
The authors
Author Response File: Author Response.pdf
Reviewer 3 Report
Paper presents the idea of laminate composite manufacturing via welding technique. Authors fabricated layered metal composite components using WAAM method. Paper suits the scope of Metals and should be interesting for the readers (if accepted). The paper needs revision. Moreover some questions were raised during reading the paper:
- Please, show in the methodology the design of the welding torch. It seems interesting how you changed the welding wires.
- The goal of your study is a little bit blurred. Please state it clearly in the end of the introduction.
- Authors should investigate the quality of the manufactured component. Does each weld pass present sufficient fusion? Were the components pores free?
- Provide the nominal chemical compositions of the filler materials. Provide information about nomial mechanical properties of weld metal. Make it in table form and place it at the beginning of "materials section" - now it is partly stated in tab. 4. Compare your research results, with the nominal data, given by the manufacturer (in the filler certificate).
- It is well known that temperature influences the Charpy results. Please state clearly the temperature of fracture testing.
- The paper should include the macrostructure of weld passes, figure 2 should be compared with specimens fabricated from SG2 and X90 fillers.
- Authors use the inappropriate phrase "specimens consisting of bulk high strength steel" - this is should be named "deposited metal" or "weld metal" - this is not a "bulk steel" - steel is manufactured via plastic forming while your component has different as-welded microstructure / properties.
- In conclusion, the authors state that: 'two wires, a ductile steel and a high strength steel wire" - of course, it is an unprecise phrase. These are "deposits made of ductile steel type wire" ... etc. Please improve it in whole paper.
- Please comment on the dilution. Maybe you should weld 2 or 3-layers of each material? Generally, each layer is a mixture consisting of 2-grades of wires. You should comment on that.
- The quality of specimens (pores, lack of fusion etc) strongly affects the mechanical properties of weld joints. The same in WAAM, could decrease fatigue or strength of your samples - what do you think? Can you assure that your specimens have high quality?
- Improve the quality of table 6 - it is partly cut.
- Paper does not contain a discussion of the results with the up to date literature. Even your topis is novel you should compare obtained results with the literature data.
- Do not use "left" / "right" in figures captions, you should use a) or b). Please check it in revised manuscript captions and body text.
- Table captions should be positioned above the table, not below. Improve it.
- Figure 2 - use dots as decimals, not commas.
Author Response
Dear Reviewer,
thank you for your positive feedback on the manuscript and the valuable comments. We overtook all your comments and incorporated them into the manuscript. We highly appreciate your comments which clearly make our manuscript better. Please find our response to each of your comments in the attached Word file.
Yours sincerely,
The authors
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Reviewer Comments on Reviewer Comments on metals-1440795v2
1. The reviewer recognized the effort made by the authors in improving the article.
2. The authors had accepted the most of the suggestions proposed by the reviewer and had revised the article accordingly. For example, one more publication had been cited for recognizing the contribution of other authors in developing the WAAM process; results of EDS analysis across the laminated weld beads had been added to reveal the dilution between dissimilar weld beads and to support the finding in hardness test as well as in tensile test; as well as the content had been substantially condensed.
3. The curves showing the EDS-line scan of Ni and Cr distribution in Fig.4(b) should be distinguished with a clearer indication. The legends of Ni- and Cr-curve reveal the same color in the draft.
4. The length of the tensile specimen should better be expressed consistently in unit in mm.
5. The German term “Probe” needs to be revised in Fig. 11 and in Table 7.
6. Based on the revised content, the reviewer recommends this article for publication.
Author Response
The authors thank the reviewer for the careful review and very valuable inputs improving the manuscript.
Reviewer's comment 3. The curves showing the EDS-line scan of Ni and Cr distribution in Fig.4(b) should be distinguished with a clearer indication. The legends of Ni- and Cr-curve reveal the same color in the draft.
Figure 4 has been updated correspondingly.
Reviewer's comment 4. The length of the tensile specimen should better be expressed consistently in unit in mm.
The unit has been changed to [mm].
Reviewer's comment 5. The German term “Probe” needs to be revised in Fig. 11 and in Table 7.
Fig. 11 and Table 7 have been updated.
Reviewer's comment 6. Based on the revised content, the reviewer recommends this article for publication.
Thank you.
Reviewer 3 Report
Thank you for your responses. I accept your explanations.
Minor remarks:
- fig 4d - please present eg. the spectrum 1 concentration and deviation in one column use plus/minus for Std. dev.
- table 3 and 4 - the unit of hardness measurements should be stated according to ISO standard. It can not be presented in "MPa" but "HV3"!
Congratulate on the interesting idea of your research!
#Rev
Author Response
The authors appreciate the valuable comments of the reviewer. Thank you very much!
Minor remarks:
Reviewer's comment 1: fig 4d - please present eg. the spectrum 1 concentration and deviation in one column use plus/minus for Std. dev.
Figure has been updated.
Reviewer's comment 2: table 3 and 4 - the unit of hardness measurements should be stated according to ISO standard. It can not be presented in "MPa" but "HV3"!
Table 3 and 4 hav been updated.
Reviewer's comment 3: Congratulate on the interesting idea of your research!
Thank you very much!
