Microstructure and Mechanical Properties of a Fiber Welded Socket-Joint Made of Powder Metallurgy Molybdenum Alloy
Round 1
Reviewer 1 Report
The paper is written weld and clearly presents obtained results. The quality of presented results is fine. My main remark concerns EDS measurements of oxygen content. Please specify oxygen measurement methodology during EDS analysis
Please see: http://adsabs.harvard.edu/abs/2012AGUFM.V23C2831K
Some small typewriting errors and clarification in text are marked in pdf file. Please check also references.
Below other remarks not listed in pdf file
Section 2
The NS Mo alloy was prepared through powder metallurgy and hot rolling – wat is the final density of NS Mo alloy is it porous
Section 3.2
Please explain the porosity observed in welded joint (on fig.8), support some comparison between analysed heat inputs regarding porosity, and sintered base NS Mo alloy or in example state that this issue is discussed in the next part of manuscript (3.4.1)
References
Symbol [J] appears at the end of some references, probably some font effort, please check carefully each reference
Comments for author File: 
Comments.pdf
Author Response
Detailed responses to reviewer 1
Title: Microstructure and mechanical properties of NS-Mo socket-joints made by laser welding.
Response to Reviewer’s comments (highlighted with yellow in manuscript)
Thank you for your time and professional suggestions.
(1)
Comments:
Please specify oxygen measurement methodology during EDS analysis.
Response:
Agree.
Before the EDS analysis, the sample was polished on a polishing machine and was cleaned with alcohol. Oxygen was detected by a non-standard method. For the convenience of qualitative comparison, the EDS test conditions of different samples were the same.
(2)
Comments:
Some small typewriting errors and clarification in text are marked in pdf file, please check also references.
Response:
Please see
Line 16;
Line 21;
Line 25;
Line 115;
Line 147.
(3)
Comments:
The NS Mo alloy was prepared through powder metallurgy and hot rolling-what is the final density of NS Mo alloy, is it porous?
Response:
Agree.
The NS-Mo is not a porous material. It is prepared by using powder metallurgy. In the later phase of sintering process of powder metallurgy, small residual pores cannot be thoroughly eliminated, resulting in a compactness of about 99.6% [36].
[36] Han, S. l.; Song, Y. q.; Cui, S. Effect of Sintering Parameters on Properties and Microstructure of Mo-Cu Alloys. Chinese journal of rare metals. 2009, 33, 666-669.
Please see
Lines 70-71.
(4)
Comments:
Please explain the porosity observed in welded joint (on fig.8), support some comparison between analyzed heat inputs regarding porosity, and sintered base NS Mo alloy or in example state that this issue is discussed in the next part of manuscript(3.4.1).
Response:
Agree.
Previous studies on Electron beam welding (EBW) of powder metallurgy Mo alloy also observed significant porosity defects in welded joint [34, 35]. High-pressure gas might be retained in micro-pores inside materials in the extrusion process of powder metallurgy materials under 180~200 MPa. During fusion welding, the high-pressure residual gases might be released into molten pool and expanded due to sudden change of both pressure and temperature. Controlling the compactness and impurities of base metal should be an important measure for inhibiting the occurrence of porous defects during the fusion welding of powder metallurgy materials.
[34] Stütz Markus, Oliveira D , Rüttinger, Matthias, et al. Electron Beam Welding of TZM Sheets. Mater. Sci. Forum, 2017, 879, 1865-1869.
[35] Alexander-Morrison G M , Dobbins A G , Holbert R K , et al. Metallurgical examination of powder metallurgy uranium alloy welds. J. Mater. Energy Syst. 1986, 8, 70-79.
Please see
Lines 48-50;
Lines 53-54;
Lines 57-59.
(5)
Comments:
Symbol [J] appears at the end of some references, probably some font effort, please check carefully each reference.
Response:
Agree.
The manuscript has been revised according to your comments.
Please see:
Lines 268-346.
Author Response File: Author Response.pdf
Reviewer 2 Report
This article deals with made of NS-Mo alloy parts welded by laser method. Authors reports microstructure and mechanical properties of fabricated two joints variants. It is worth notice presented work is interesting and can be useful especially for industry community. However before publishing in Materials journal reviewed manuscript must be strongly improved as follows:
1. The title of manuscript must be more simple e.g. “Microstructure and mechanical properties of NS-Mo joints made by laser welding”
2. The first sentence of abstract sounds strange grammatically – please improve it.
3. Please define Keywords more precisely and suitably, e.g. what Mo alloy, what properties, etc.
4. Line 72 – “hot-rolled powder metallurgy” – what does it mean?, please clarify it.
5. Line 74 – Magnification of b) micrograph should be more corresponded with “…which presents fine grains with rolled morphology.”
6. Line 77 – How were end plug and tube preheated?
7. Fig.2a – please give information what kind of a fit was used – medium fit, clearance fit, fine fit, etc.
8. Fig.3b – please show the detail b) more clearly.
9. Table 1 – What was Defocusing distance used for (preheating was made by the first laser passing)? What was the real laser spot size? How was welding speed calculated? Please explain how was HI calculated – what was standards used for it?
10. Why was two different power laser for joint 1 and 2 used (due to size of spot laser was different for each joint)? – please explain it.
11. Rotational speed of assembled the end plug and the tube as a basic technological parameter should be given.
12. Line 104 – “…varies only by a factor of about 2, while the welding speed varies by a factor of 30.” – in my opinion “a factor” is not suitable term. The laser power and the welding speed for two heat inputs are simply two times and thirty times higher respectively.
13. Line 106 – How was the surface morphology defined? Did you research roughness, waviness of surface of “weld seams”?
14. Fig.4 – Rather “Direction of rotations” should be used.
15. Fig.5, Fig.7 - Why the shape of the joints is not the same around the circumference? It is mean the kinematic parameters (acceleration/deceleration, laser shutter on/off delay, etc.) selected improperly (especially for lower welding speed). How were the weld width and depth measured – please add suitable paragraph in Materials and methods section.
16. Fig.6b – The metallurgical quality of joint #2 is unacceptable. What are reasons of that?
17. Table 2 - The shape coefficient of grains for Joint 1 and Joint 2 must be added.
18. Line 169 – please use oC as the temperature unit – please check throughout the article.
19. Fig.10 – Was the average microhardness shown in these figures? – please comment it in figure description.
20. Fig.11 – The elastic deformations line must be straight. The Young’s modulus should be the same for all variants. Did you use extensometer? Please correct it.
21. Fig.5 and 12 are duplicated – please delete the second one.
22. Fig.13 – How was the content of oxygen measured? Please notice that EDS method is not suitable for this. Was a measuring method standardized?
23. Fig.13, 14 – The morphology of fractures should be independent of the observation area Please explain how can be homogeneity of microstructure and shape of weld joints improved. The welding speed should be given in cm per min (see Table 1).
Moreover English requires grammar and terminology correction – please check carefully the article.
Author Response
Detailed responses to reviewer 2
Title: Microstructure and mechanical properties of NS-Mo socket-joints made by laser welding.
Response to Reviewer’s comments (highlighted with green in manuscript)
Thank you for your time and professional suggestions.
Detailed responses can be found in the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
The authors have reported the fiber lase welding of powder metallurgy nanostructured Mo alloy. The role of heat input was investigated by examining the microstructure of fusion zone. When heat input decreased, the tensile strength of welded joint increased. The welding under low heat input reduced the segregation of MoO2, which caused a poor strength of welded joint.
The nanostructured Mo alloy is important material for the cladding tube in nuclear fuel. Therefore, the results in the present manuscript are highly useful for the development of nuclear technologies. So I believe the manuscript meets all criteria necessary for Metals. But, before the acceptance, the authors should address the comments listed below.
(1) What is the abbreviated TZM? The authors should give the full name before using TZM.
(2) The full name of HAZ is given after the first appearance of abbreviated word in p.2 line 58. The authors should the full name before using HAZ.
(3) The authors should give the information of fiber laser in Materials and Methods. What is the central wave length? Is the fiber laser CW or pulse laser? If it is a pulse laser, the authors should comment the pulse width and repetition rate.
(4) In Fig.13, the authors should present the EDS spectra.
Author Response
Detailed responses to reviewer 3
Title: Microstructure and mechanical properties of NS-Mo socket-joints made by laser welding.
Response to Reviewer’s comments (highlighted with pink in manuscript)
Thank you for your suggestions.
(1)
Comments:
What is the abbreviated TZM? The authors should give the full name before using TZM.
Response:
Agree.
It was reported that molybdenum-titanium-zirconium (TZM) alloy joint produced by using tungsten inert gas arc welding (GTAW) presented not only coarse columnar grains in FZ but also remarkably reduced joint strength which took up about 40% of that of base metal (BM) [17].
Please see:
Lines 50-53.
(2)
Comments:
The full name of HAZ is given after the appearance of abbreviated word in p.2 line 58. The authors should the full name before using HAZ.
Response:
Agree.
The width of FZ zone of EBW joint and GTAW joint was 0.8mm and 1.7mm respectively, while the width of heat affected zone (HAZ) of EBW joint and GTAW joint was significantly different.
Please see:
Lines 54-56.
(3)
Comments:
The authors should give the information of fiber laser in Materials and Methods. What is the central wave length? Is the fiber laser CW or pulse laser? If it is a pulae laser , the authors should comment the pulse width and repetition rate.
Response:
Agree.
The welding tests were conducted by using IPG YLS-4000 fiber laser continuous welding (CW) system, as illustrated in Fig. 3, with a maximum output of 4 kW, a central wave length of 1070 nm and a focal spot size of 0.2 mm in diameter.
Please see:
Lines 78-80.
(4)
Comments:
In Fig. 13, the authors should present the EDS spectra.
Response:
Agree.
The Fig.13 has been revised as follow.
Figure 13. SEM images and EDS results in fusion zone of NS-Mo alloy welded joints. Heat input: (a) 250 J/cm; (b) 3600 J/cm.
Please see:
Line 215.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The article was significantly improved. However some points still require improvement as follows:
1. Line 140 – Please use “Microstructure observations” as subsection title.
2. Table 2 – please add Standard Deviation for Joint 1 and Joint 2 shape coefficients. Moreover add information in Materials and Methods section how was defined shape coefficient and give method of its calculation.
3. Line 164 – Please use “Microhardness measurements”.
4. Line 173, 174 – Please give temperature without decimal places.
5. Line 182 – The subsection title should be “Tensile strength”.
6. Figure 12 – Please improve the caption, e.g. Views of failure path of …
7. Line 206 – This subsection contains only EDS measurements results. Please presents suitable documentation for calculation of GBs content in FZ of joints. Moreover the title require modification. Now it sounds improperly.
Please notice English still requires strongly improving. I recommend mandatory professional proofreading.
Author Response
Detailed responses to reviewer 2
Title: Microstructure and mechanical properties of NS-Mo socket-joints made by laser welding.
Response to Reviewer’s comments (highlighted with green in manuscript)
Thank you for your time and professional suggestions.
Detailed responses can be found in the attachment.
Author Response File: Author Response.pdf
Round 3
Reviewer 2 Report
The article still requires major revision as follows:
1. Table 2 – please use singular form, i.e. “Standard deviation of grain shape coefficient”. It must be clear how was the grain shape coefficient calculated - an equation with description must be given in Materials and Methods section.
2. Line 206 – The subsection still contains only EDS measurements results. Please add graphic documentation supported information presented in 212-214 lines. The subsection title requires modification.
Please improve English before publishing.
Author Response
Detailed responses to reviewer 2
Title: Microstructure and mechanical properties of NS-Mo socket-joints made by laser welding.
Response to Reviewer’s comments (highlighted with green in manuscript)
Thank you for your time and professional suggestions.
Detailed responses can be found in the attachment.
Author Response File: Author Response.pdf
