Laves Phase Precipitation Behavior in HiperFer (High Performance Ferritic) Steel with and without Boron Alloying
Round 1
Reviewer 1 Report
The authors have studied the effect of Boron addition on HiPerFer alloy in terms of microstructure and relevant mechanical properties. The experimental results are well explained. There are minor changes /typos to be corrected and few concerns to be addressed.
1) In figure 1, T dissolution is not visible clearly, what is 115? unit for x axis is given as second in one graph and for Y-axis no unit is given?
2) The authors always discuss about change in diffusion condition w.r.to boron addition. can they elaborate it clearly.
3) In figure 7, what is REM?-BSE. is it SEM.
4) Is there any specific reason that authors prefer to name the amount of deformation as grade instead of strain.
5) Thermodynamically, it is shown that boron does not involve in Laves precipitation. Then how does it accelerate the pptn of Laves. can the seggregation be shown experimentally in the EDS map of GB as the authors had high resolution SEM.
6) what was the morphology of laves phase? does it remained the same with boron addition or TMP or it varied.
7) How many particles were considered for each condition for quantification may be specified. like a minimum of x particles were analysed for each condition.
8) It is not clear to the readers from the BSE image or methodology how the authors estimated the Grain boundary coverage of laves phase.
9) In line 338-339, the authors had missed typo.
10) for figure 8 , figures a and b specific temperature and deformation levels considered may be specified while varying the other.
Author Response
Point 1: In figure 1, T dissolution is not visible clearly, what is 115? unit for x axis is given as second in one graph and for Y-axis no unit is given?
Response 1: The x/y -axis descriptions has ben corrected.
Point 2: The authors always discuss about change in diffusion condition w.r.to boron addition. can they elaborate it clearly.
Response 2: The changes in diffusivity in the GB area due to boron addition is a observed effect according to the literature. This effect is described in detail and referred to in the discussion part of the manuscript.
Point 3: In figure 7, what is REM?-BSE. is it SEM.
Response 3: SEM-BSE has ben corrected.
Point 4: Is there any specific reason that authors prefer to name the amount of deformation as grade instead of strain.
Response 4: The designation “deformation grade” was used in all previous research and therefore should be retained.
Point 5: Thermodynamically, it is shown that boron does not involve in Laves precipitation. Then how does it accelerate the pptn of Laves. can the seggregation be shown experimentally in the EDS map of GB as the authors had high resolution SEM.
Response 5: See please the discussion in chapter 3.3 (292-296). Boron does not participate in the Laves phase formation, however boron occupies the grain boundaries and therefore influences the nucleation. A visualization of the boron segregation on the gran boundaries is very difficult. The best way would be using Nano-SIMS method. Unfortunately, we did not have the opprotunity.
Point 6: what was the morphology of laves phase? does it remained the same with boron addition or TMP or it varied.
Response 6: There is no observed impact of the Laves phase morphology as a result of TMP (previous research) or boron addition (Figure 7).
Point 7: How many particles were considered for each condition for quantification may be specified. like a minimum of x particles were analysed for each condition.
Response 7: The sentence “Twenty to forty thousand intragranular particles were analysed per sample.” has been added into chapter 2.2 Microstructure Analysis.
Point 8: It is not clear to the readers from the BSE image or methodology how the authors estimated the Grain boundary coverage of laves phase.
Response 8: The principle of the ratio determination is described in the chapter 2.2 utilized by ImageJ.
Point 9: In line 338-339, the authors had missed typo.
Response 9: We did not find any typo, sorry.
Point 10: for figure 8 , figures a and b specific temperature and deformation levels considered may be specified while varying the other.
Response 10: The parametrs have been additionally specified in the figure description.
Thank you very much for the time you invested in the revision of our research!
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Very interesting work on strengthening of HiperFer steel. In the research, the authors, based on the analysis of the state of knowledge regarding the influence of boron on steel properties, which they condensed in the introduction, correctly defined the purpose and scope of the research. The presented research methodology is described correctly and legibly, which makes it possible to repeat the experiment.
Researchers analyzed the effect of boron addition at the level of 0.0055% and Laves' phase on creep resistance at elevated temperatures. The very detailed analysis of metallographic results, both qualitative and quantitative, supplemented with a description of the kinetics of the formation and interaction of the Laves phase is fully justified and confirms the formulated conclusions.
In my opinion, the work was done at a high substantive and editorial level and can be published in this journal
Author Response
Thank you very much for the time you invested in the revision of our research!
Reviewer 3 Report
This study attempts to investigate the Laves phase precipitation behavior in HiperFer (high performance ferritic) steel with and without boron alloying by determining the grain boundary coverage ratio of the Laves phase and high temperature mechanical properties. After reviewing the manuscript, the reviewer thinks that this manuscript contains useful information and can be published, however it requires some clarifications and additional information to support the conclusions. The followings are to be clarified.
1. It is recommended to describe the experimental result of nitrogen concentration in the Table 1. And it’s measuring techniques should be notified in the 2.1 Materials Preparation part of the manuscript.
2. Change the style of units; ø 5 x 9 mm3, ø 6.4 x 30 mm, ø 6.8 x 15 mm3 which are used to indicate the cylindrical type of samples size in the manuscript.
3. It is advisable to revise the Figure 1 because it is not properly representing the manuscript context. What is the meaning of “115 in the y axis and 600, 3, 60 in the x axis? If inset is used in the Figure, then inset should be separately explained in the Figure text.
4. The detail processing route (“_4”) should not be referring, because it is important conditions of this study. It should be described in the manuscript at page 3 of line 102.
5. Reviewer think that OM is common than LOM at Line 127.
6. It is recommended to describe the brief LB etching methods at Line 128 and to provide the corresponding references in the manuscript.
7. Authors calculated the chemical compositions of the Laves phase using TCFE8 database. Reviewer wonder why authors didn't do experimental analysis of the Laves phase to compare with theoretically calculated results!
8. It is advisable to make a labelling for each picture of Figure 4, Figure 5, Figure 7, and Figure 8. Furthermore, give a picture explanation for each label in the Figure text. Figure 9 is a good example!
9. What is “REM-BSE” in Figure 7? And REM-BSE method should be mentioned in 2.2 Microstructure analysis.
10. Is there higher magnification of SEM images to validate the size of Laves precipitates? It is too small to confirm the size of the Laves with SEM images in Figure 7.
In summary, based on the above-mentioned reviewer’s report, the reviewer judge on this manuscript is “Mandatory for Major Revision”.
Comments for author File: Comments.pdf
Author Response
Point 1: . It is recommended to describe the experimental result of nitrogen concentration in the Table 1. And it’s measuring techniques should be notified in the 2.1 Materials Preparation part of the manuscript.
Response 1: The nitrogen information have been added.
Point 2: Change the style of units; ø 5 x 9 mm3, ø 6.4 x 30 mm, ø 6.8 x 15 mm3 which are used to indicate the cylindrical type of samples size in the manuscript.
Response 2: The unit style has been unified.
Point 3: It is advisable to revise the Figure 1 because it is not properly representing the manuscript context. What is the meaning of “115 in the y axis and 600, 3, 60 in the x axis? If inset is used in the Figure, then inset should be separately explained in the Figure text.
Response 3: Figure 1 has ben revised. The x/y axis description has been corrected. 600/3/60 s are the holding times in the process route.
Point 4: The detail processing route (“_4”) should not be referring, because it is important conditions of this study. It should be described in the manuscript at page 3 of line 102..
Response 4: The processing for the mechanical testing is described properly and in addition referred in the manuscript. According to the outlined forging process of the dilatometer specimens (Figure 1), the most important final rolling pass of the plate materials was performed.
Point 5: Reviewer think that OM is common than LOM at Line 127.
Response 5: LOM to OM has ben corrected.
Point 6: It is recommended to describe the brief LB etching methods at Line 128 and to provide the corresponding references in the manuscript.
Response 6: The description of the LB etching method has been added.
Point 7: Authors calculated the chemical compositions of the Laves phase using TCFE8 database. Reviewer wonder why authors didn't do experimental analysis of the Laves phase to compare with theoretically calculated results!
Response 7: T he mean particle diameters are way below the range of 1 µm. In this case it is not possible to have the “pure” chemical composition of precipitates, because of the interaction volume. The matrix contribution is comparably high. Therefore, a relevant comparison of formed LP in B0 and B55 or proove of no implementation of boron into LP formation is not possible. However, due to the short holding time of 60 s after deformation, chemical composition is closer to the LTL composition. The evolution of the chemical composition of formed LP is discussed in detail in other research published by our group.
Point 8: It is advisable to make a labelling for each picture of Figure 4, Figure 5, Figure 7, and Figure 8. Furthermore, give a picture explanation for each label in the Figure text. Figure 9 is a good example!
Response 8: The labelling has been added.
Point 9: What is “REM-BSE” in Figure 7? And REM-BSE method should be mentioned in 2.2 Microstructure analysis.
Response 9: The SEM-BSE method was ment. It has been corrected.
Point 10: Is there higher magnification of SEM images to validate the size of Laves precipitates? It is too small to confirm the size of the Laves with SEM images in Figure 7.
Response 10: The SEM images in Figure 7 have been chosen to show the representative overview of the microstructure. That means the diffrences in GB and GI precipitate density and distribution as well as the PFZs of both alloys.
Thank you very much for the time you invested in the revision of our research!
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
Regarding the previous review, the authors responded and corrected my inquiries. The answers and corrections are reasonable. Therefore, reviwer think the revised manuscript is acceptable and suitable to publish for Metals.
