Oxidation Behavior of an Austenitic Steel (Fe, Cr and Ni), the 310 H, in a Deaerated Supercritical Water Static System
Round 1
Reviewer 1 Report
The manuscript is focused on studying the oxidation behavior of 310 H steel in Deaerated Supercritical Water Static System. The 310 H is one of the critical materials for the supercritical water-cooled nuclear reactor. The objective of the manuscript is well described. The experimental data well support the conclusion of the manuscript. The highlight of the paper is the experimental design and execution to get the results on the oxidation behavior. The following are the concern with the reviewer.
- Many Figures are not explained in detail; therefore, it is not easy to understand—for example, Fig. 3. The authors have presented 3 Figures, a b and c. What a –c Figures indicate. Is the line in the microstructure shows the thickness? If yes, please indicate in the Figure. Also, the dimensions in the Figures are not easily visible. The reviewer encourages the authors to modify the Figure captions for all the figures and give more details about the respective Figures.
- Authors indicate the presence of the Chrome oxide and spinel compound based on EDS. Authors need to be explicit about how they identified these compositions based on EDS. It would be helpful for the reader if the Authors presents the EDS maps and explain the presence of different compounds.
- Authors claim that grain size decreased when exposed to the supercritical temperature and pressure. From the microstructure, it is difficult to rationalize. Also, the grain calculated for an unoxidized sample is ~ 24.6 um, and when it is exposed to the operating conditions, the grain size increased to 26.7 um, which is expected. I am sure where/which samples authors want to say the Grain size decreased.
- Authors need to present the microstructure with carbide precipitated on the grain boundary. With the given microstructure, it is difficult to say the carbide precipitations.
- There are many spelling mistakes. Reviewer encourages to update the English language in the revised version.
Author Response
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Author Response File: 
Author Response.pdf
Reviewer 2 Report
The paper experimentally investigated the corrosion behavior of Fe-Cr-Ni steel in water at a supercritical temperature of 550 °C and a pressure of 250 atm during long-term exposure. This study provides some information which is important for understanding the possibility of using Fe-Cr-Ni steel in new nuclear SCWR reactors. The advantages of the paper include the authors' detailed corrosion studies by different methods and a comparison of the results. At the same time, there are still some problems to be solved in the manuscript. Therefore, the article can be recommended for publication only after mandatory revision according to the following suggestions:
- The authors do not mention the problem of changing the mechanical properties of austenitic steels due to radiation exposure.
- In chromium and chromium-nickel steels, after long exposures at temperatures of 500 - 800 °C (depending on the chemical composition), a sigma phase may precipitate (for example, Long-term annealing resistance of ferritic chromium steels subjected to high-temperature nitriding. Russian Metallurgy (Metally). 2019 (2019) 427-430). How the authors consider this point?
- Lines 193-195. This information is already available in Section 2 Materials and Methods.
- Lines 201-203. The authors write: ‘The microstructural analysis after exposure in water at supercritical temperature was leading to grain decrease and carbides appearance at 202 grains boundaries’. Is there a mistake here? Has the grain size decreased rather than increased? And where are the carbides in the figure? How did the authors identify them?
- Figure 5 does not provide any information. It is enough to give the microhardness values in the text of the paper. And you need to give any measure error.
- Lines 214-216. The authors write that an increase in microhardness was observed after oxidation. What is the reason for this?
- Line 240. Figure 10 is not listed in the paper.
- Line 251. What figures do you mean?
- Line 307. Figure 10a is not listed in the paper.
- In some figures, the caption is not complete: the parts (a, b, c etc.) of Figure 3 and Figure 4 are not indicated.
Author Response
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Author Response File: Author Response.pdf
Reviewer 3 Report
a good study of 310 H austenite alloy for SCWR. weight gain oxidation kinetics and metallographic anlaysis give more understanding of the studied material. I would suggest some additional inputs such as EDS data and XRD if possible.
1. Introduction:
A short introduction about the material candidate for SCWR. I suggest to add some literature results on other different materials used for SCWR (why austenite, why is it better to use it than ferrite for example). what components of 310H attracts the interest of this austenite alloy for SCWR
2. Materials and Methods:
line 90: has at 25 C, a conductivity. (add the comma after C)
3.Results and discussion
3.1 oxidation kinetic
good illustration and description of the weight gain oxidation kinetics.
3.2 Metallographic analysis
line 180: indicate if this is an optical micrograph
line 197: same comment as line 180
you talk about EDS in section 3.2, I didn't see any graph
is there any images on the thickness of the oxide layers as well (with higher magnification).
have you seen any bulk phase transformation of austenite to ferrite or martensite?
did you do XRD on the surface of the oxidized samples
other sections: Ok
Conclusion:
some additional information would benifit your work, specially the comments in section 3.2
Please modify the temperature in all the manuscript with a space between the number and the degree celsius. example: 550 °C
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The manuscript can be recommended for publication in the revised form.
Author Response
We are thanking for interesting comments and indications helping us to deliver a better version of our manuscript.
Reviewer 3 Report
Thank you for the revised version.
Lines 215 through 221:
About the EDS analysis. It is better to show a SEM image showing the area of the EDS point scan or line scan you took. it is interesting to see the interface of Cr oxide and spinel oxide as well as its sequence.
Line 245: Microhardness tests made from oxide to alloy? or only on the alloy region
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
