9–12% Cr Heat-Resistant Martensitic Steels with Increased Boron and Decreased Nitrogen Contents

Round 1

Reviewer 1 Report

This paper reviews the effects of B/N content on the creep resistance in various high Cr-F/M steels. The review is very comprehensive and informative. I would recommend accepting it after some minor revisions. See some comments below:

1. “It is consisted in the increasing the” please correct the grammar.

2. “Although Co is not included in the precipitates, addition of 3% Co provides increasing the amount of MX carbonitrides and M23C6 particles, especially around PAG boundaries. Also Co has effect on the chemical composition of precipitates, increasing the V content in MX particles, and Fe, Cr and W content in M23C6 particles.” Can the author provide citations and some explanations in the text? Also there are grammatical errors in these sentences.

3. In Figure 8a, why do the data (140 ppm B / 34 ppm N by Abe) show significantly worse than the other two B/N-modified steels? Should steels with high B and low N content outperform the other modified steels in terms of the creep resistance, please comment on that.

4. My main question, in general, is that when comparing the mechanical properties and the effects of B/N on the creep behaviors, it’s really hard to ensure that all other experimental parameters were kept constant. For example, the mechanical test setup could vary; the B/N content could affect other microstructures during heat-treatments which then affects the creep behaviors, and in that case the B/N content might not be the root cause of the variation. My main concern is that other parameters not well-controlled could result in variations that are more significant than the variation caused by the B/N content. I understand it is not easy to cross-compare different work in the literature, but can the author comment on this?

5. In the introduction part, the author mentioned the variation of dislocation mobility due to the effects of precipitates and grain boundaries, which is one of the key factors on the varying creep behavior of various steels. However, in the review, discussions on dislocation line and dislocation network are limited while the focus has been put mainly on the precipitates. Can the author expand on the reviews of dislocations as a result of B/N content, if available in the literature?

6. Overall this is a fantastic review article and I will add it to my reading list. Please double check with a native speaker to minimize the grammatical errors.

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The paper is a good technical report/review of new heat-resistant martensitic steels with increased boron and decreased nitrogen content and could provide a basic insight into this field for readers.

 

English is good (acceptable), for easier reading avoid excessive use of passive (present or past tense would fit better and will make the text more understandable).

 

Some remarks:

In Fig. 1b Abbreviation HAB is not explained (high angle boundary?)

Line 84 The addition of 3W … – should be 3%W?

Line 187 The term “vacuum pressure” is not appropriate (even if it is sometimes used)

Scale is missing in Fig. 9b (it is the same as in Fig. 9a?).

Lines 369-373 The phrases here are circular definitions (i.e. lower minimum creep rate leads to lower minimum creep rate …) and should be reformulated.

 

Conclusions are in fact not the conclusions (rather Summary or a list). Some concluding remarks are necessary to be added here.

 

After these amendments, the paper can be recommended for publication.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The present work give a review on the creep strength and related microstructural features of the 9% Cr and 10-12% Cr martensitic steels with a high B and a low N content. The factors determining the optimal B/N ratio in steels are considered. The relationships between the stability of lath structure and precipitates of M23C6, Laves, and MX phases and the creep strength of steels are considered. Further perspectives of this modification of alloying by high boron and low nitrogen are outlined.I think this is a good review.

The heat treatment part is rough, which is recommended to be supplemented.

Author Response

Please, see the attachment.

Author Response File: Author Response.pdf