Effect of Solution Treatment Temperature on Microstructural Evolution, Precipitation Behavior, and Comprehensive Properties in UNS S32750 Super Duplex Stainless Steel
Round 1
Reviewer 1 Report
The paper studies some phase transformation processes in SAF2507 superduplex stainless steel.
The eutectoidal decomposition process of ferrite phase in duplex stainless steels is well known and have been investigated by several authors. In this metallurgical process the ferrite decomposes to sigma phase and secondary austenite. Therefore, the ferrite/austenite phase ratio decreases. It is associated with the dramatical decrease of the ductility and corrosion resistance.
The studied task of the paper is the opposite metallurgical process, namely the solution treatment of SDSS.
The applied investigation methods are appropriate, the evaluation of theresults is correct.
The conclusions are not surprising. They confirm previous findings from other researchers.
Author Response
Dear Reviewer，
Thank you for your letter and comments regarding our manuscript. We've responded point by point to your comment. Please see the attachment.
Once again, thank you very much for your comments, suggestions and consideration.
Yours sincerely
Junhe Li，Zhanbing Yang, Wei Shen, Fuming Wang, Ping Lin
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The work faces the challenge of solution temperature optimization in a super duplex stainless steel of common use, UNS S32750. Really it is a topic already faced in literature even if not in the so exstensive form as in the present work. The comments are coherent with the experimental observations and can be taken as a further reinforcement of what is already known about that alloy. However there are some minor changes that are required before the work bu suitable for publication:
1) the name SAF2507 is the Sandvik trade mark that doesn't exist any more as the patent has expired. Authors should use the actual standard name all over the paper.
2) as observed above the present topic was already faced in literature. See for instance: Cervo, P. Ferro, A Tiziani. 2010. "Annealing temperature effects on super duplex stainless steel UNS S32750 welded joints. I : microstructure and partitioning of elements". Journal of Materials Science. Vol. 45, pp. 4369-4377. doi: 10.1007/s10853-010-4310-1;R. Cervo, P. Ferro, A Tiziani, F. Zucchi. 2010. " Annealing temperature effects on super duplex stainless steel UNS S32750 welded joints. II: Pitting corrosion resistance evaluation". Journal of Materials Science. Vol. 45; p. 4378-4389; P. Ferro. A dissolution kinetics model and its application to duplex stainless steels. Acta Materialia 61 (2013) 3141-3147.
Author are asked to better highlight the originality of their work compared to the previous ones
3) In the introduction sigma phase ratio should be changed with sigma phase fraction
4) how was measured the alloy chemical composition? What are the tolerances? please specify in the text.
5) Does the holding time include the time required to reach the target temperature? In fact, this last should be different according to the imposed oven temperature. Please specify in the text.
6) The measure of sigma phase fraction using optical micrographs promotes uncertainties because of the chemical attack that increase the thickness of grain boundaries. The lower the sigma phase particle size the higher the uncertainty. Did you take into account such effect?
7) In micrograph 2b is very hard to detect the sigma phase, probably you need to increase the contrast...moreover colored micrographs will help to better visualize the different phases. Please improve the micrographs in this sense.
8) Line 142: it is stated that 'the stabilizing effect of N on austenite begins to weaken with the rise of the temperature'. Why? Is this an authors' supposition? Please prove this sentence or add a reference in which that demonstrated.
9) Line 155: It seems not true that Cr in austenite increase significantly. Please specify better in the text.
10) Authors use often the words 'obvious' and 'obviously' that is in my opinion are not appropriate in a scientific paper, as nothing is obvious and should be demonstrated
11) There are some typos to be corrected
12) Lines 325-326: please rephrase the sentence because it is not clear as it is
13) Conclusions must be more concise, in the present form they are too long
Author Response
Dear Reviewer，
Thank you for your letter and comments regarding our manuscript. We've responded point by point to your comment. Please see the attachment.
Once again, thank you very much for your comments, suggestions and consideration.
Yours sincerely
Junhe Li，Zhanbing Yang, Wei Shen, Fuming Wang, Ping Lin
Author Response File: Author Response.pdf
Reviewer 3 Report
The article presents the results of research on the influence of temperature on the microstructure of SAF2507 super duplex stainless steel. At the same time, the influence of changes in the microstructure of SAF2507 steel on its mechanical properties and corrosion resistance was analyzed.
Detailed comments:
Introduction sufficiently describes the current state of knowledge and justifies the research topic. However, I believe that the Authors, both in the Introduction and in the title, misuse the following phrases:
effect of solution temperature (title)
the solid solution treatment temperature (line 48-49)
the solid solution treatment (line 50)
solid solution treatment parameters (line 61)
It is not known what kind of solution it is about. The duplex steel structure includes two solid solutions: α - ferrite, γ - austenite. I believe this should be for the SAF2507 steel, not the solution.
Table 1: The description should be completed - wt%.
Line 90-91: Please complete the description of how the electrochemical corrosion process was carried out.
Line 95: EDS stands for Energy Dispersive Spectroscopy, not energy spectroscopy.
Line 100-103: Specify the devices on which the hardness and impact strength tests were carried out.
Line 104-114: Provide details of the equipment on which the electrochemical corrosion tests were performed.
Line 118: The term "solution temperature" is incomprehensible.
Figure 2: The steel symbol is incomplete.
Line 139-140: The σ phase is the intermetallic phase and can dissolve in the ferrite. However, the statement that austenite dissolves in ferrite is wrong. Austenite and ferrite differ only in the type of unit cell in the lattice and lattice remodeling takes place, not dissolution.
Line 133-144: The word solution is incomprehensible. This note applies to the entire article.
Figure 3. In the figure caption, the same information is given twice. In the description of the y-axis in Fig. (b) it should be stated what ratio it is.
Figure 4: In the description of the y-axis, the share of which element is presented in the graph should be given
Line 163: Which drawing is it? No reference to Figures 5 and 6 in the text.
Figures 2, 7 and 8: On what basis do the authors identify the phases marked in the drawings? This requires the presentation of research results or reference to literature.
Line 210-215: This statement requires a reference to the literature.
Line 287-306: Why is the electrochemical corrosion parameter not specified?
Figure 15: In the description of figure the same information is given twice.
Author Response
Dear Reviewer，
Thank you for your letter and comments regarding our manuscript. We've responded point by point to your comment. Please see the attachment.
Once again, thank you very much for your comments, suggestions and consideration.
Yours sincerely
Junhe Li，Zhanbing Yang, Wei Shen, Fuming Wang, Ping Lin
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
The authors did a good job. They responded to all my comments and suggestions and revised the manuscript significantly.
I believe that it can be published in this form.
A small note to the authors:
My misunderstanding of the use of the word 'solution' has been cleared up.
Note to answer 14.
It is obvious to me that the authors have adequate knowledge and experience in identifying these phases in the microstructure image and they do it well. However, I believe that in this case it is good to refer to the literature when describing the microstructure. Then there will be no doubts and the description will be more professional.
