Fracturing in 14MoV6-3 Steel Weld Joints—Including Base Metals—After a Short Time in Service

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

(1) The title does not seem to represent the contents perfectly.  "Fracture behavior of 14MoV6-3 steel weld joints including base metal after service" might be better.

(2) Mo and V in the base metals shown in Table 1 are not satisfying the DIN specification.  Some interpretation seems necessary.

(3) Geometry of the test specimens must be provided because the tensile test results for the welded joint must have been influenced by it.

(4) Please clarify what "d" denotes in eq. (1).

(5) Symbols in all figures are not clear.  Some improvement such as the employment of curves seems necessary.

(6) What does the value of Reduction of area for DIN standard mean?  If it is a minimum requirement, both materials do not satisfy this requirement.

(7) It would be better to add the value of Reduction of area in Table 6 for representing actual material ductility although it might depend on the specimen geometry, either round bar or some plate-type specimen.

(8) It seems that the conclusion regarding the necessity of additional qualification of welding method is not so persuasive because the failure occurred in the used base metal, rather than weld metal or HAZ.  The reviewer thinks that the tests including the used welded joints might be important to evaluate the integrity of the welded components.

(9) No.1 reference is missing.

 

Comments on the Quality of English Language

There are many imperfect expressions needing elaboration starting from the first sentence in the abstract.  Some ones are difficult to even understand, such as the third sentence in page 3 and the last sentence in page 6.  Extensive modifications throughout the paper seem desirable.

 

Author Response

Dear Reviewer,

We would like to sincerely thank you for your thoughtful and detailed comments on our manuscript titled "Fracture in base metals of 14MoV6-3 steel weld joints after short service period." We truly appreciate the time and effort you have invested in reviewing our work.

Once again, we are grateful for your constructive feedback and we believe the revisions we have made have significantly improved the manuscript. We look forward to hearing your thoughts on the revised version.

Thank you for your understanding and consideration.

Please find below a list of manuscript changes and corrections.

Best regards,

dr Dikić Stefan

University of Belgrade

Faculty of Technology and Metallurgy

Comment 1: we have accepted your suggestion.

Comment 2: In the previous version, we have used DIN standard instead of appropriate EN standard. In that manner, the ranges for V content are inadequate in previous manuscript version. Now we made corrections. Vanadium content suits to EN 10216-2 specifications. Regarding molybdenum, values ​​for chromium were by mistake entered in the field for molybdenum and vice versa.

Comment 3: We just added a technical drawing of test specimen.

Comment 4: We have declared "d" as pipe diametar.

Comment 5: We have corrected all the figures.

Comment 6: Once again, we made correction. Instead of DIN standard, now we use adequate EN standard which specifies reduction of area - 40%.

Comment 7: Regarding your suggestion to include the reduction of area values, we would like to clarify that, in our laboratory practice, we do not typically determine these values for tensile tests of welded joints. In that manner, at this moment we are not able to provide these values.

Comment 8: 

Regarding your point about the necessity of additional qualification of the welding method, we understand your concern. The failure observed in our study occurred in the base metal rather than the weld metal or the Heat-Affected Zone (HAZ), which suggests that the welding method is not the primary cause of the failure.

However, we would like to emphasize that the focus of our study was on evaluating the influence of the base metal on fracture behavior. We agree that tests involving welded joints are crucial to evaluate the overall integrity of the welded components. Our conclusion regarding the need for additional qualification of the welding method is based on the observed interaction between the weld and base metal, and we believe that ensuring the integrity of the welded joint as a whole is critical for the reliability of welded structures, especially in applications under stress.

Comment 9: We have checked once again our manuscript. Reference no.1 is indexed in third row of introduction.

 Once again, thank you for your thoughtful comments and for your careful review of our manuscript. We greatly appreciate your feedback.

Reviewer 2 Report

Comments and Suggestions for Authors

The authors aim to evaluate the reliability of steel pipes by repairing and welding old and new pipes using different welding techniques, such as Gas Tungsten Arc Welding (GTAW) and Manual Metal Arc Welding (MMAW). However, the manuscript lacks scientific evidence to support its claims, and the organization needs significant improvement. Detailed comments on these aspects are provided in the attached document.

The experimental approach to repairing steel pipes is original. However, the study lacks a clear scientific framework, and further justification is needed to highlight its novelty in comparison to existing literature.

The manuscript does not clearly define a research gap. It primarily reports experimental findings without demonstrating how they advance the field. A stronger literature review and a well-defined problem statement are necessary to establish the research gap.

The study does not present significant new insights or findings that contribute substantially to the existing knowledge. The results appear more like a technical report rather than a scientific study. The authors should focus on formulating a stronger research hypothesis and providing a comparative discussion with previously published work.

The study should adhere to standard experimental methodologies, ensuring reproducibility and scientific rigor. Specific concerns about the experimental design, data collection, and analysis are addressed in the attached comments.

The conclusions are not well-supported by the presented evidence. The discussion does not sufficiently link the experimental results to the research objectives. The authors should strengthen their argument by providing a more detailed analysis and discussion of the findings. Additional comments are included in the attached document.

The references do not appropriately support the study’s claims. Many cited works appear unrelated or do not provide sufficient context for the research. A revision of the literature review is necessary to include more relevant and recent references. Further details are provided in the attached comments.

The quality of data presentation needs improvement. Specific issues with tables and figures, including clarity, labeling, and relevance, are detailed in the attached comments.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

the quality of the English is poor. need improvement

Author Response

Dear Reviewer,

We would like to sincerely thank you for your thoughtful and detailed comments on our manuscript titled "Fracture in base metals of 14MoV6-3 steel weld joints after short service period." We truly appreciate the time and effort you have invested in reviewing our work.

Once again, we are grateful for your constructive feedback and we believe the revisions we have made have significantly improved the manuscript. We look forward to hearing your thoughts on the revised version.

Due to lack of time for revision, we gave our best to provide an improvement of our manuscript, regarding your suggestions.

We made some corrections in introduction and conclusion section. Regarding comment 4, we accepted your suggestions, except from the last one. At this moment, we don’t have samples with fracture surfaces, so we are unable to provide macrographs.

Regarding comment 6, we have updated our reference list, and provided more scientific articles in bibliography.

All new parts of text, that we added, are marked in red.

Thank you for your understanding and consideration.

Please find below a list of manuscript changes and corrections.

Best regards,

dr Dikić Stefan

University of Belgrade

Faculty of Technology and Metallurgy

Reviewer 3 Report

Comments and Suggestions for Authors

Introduction

The introduction is very extensive and concerns well-known general issues in relation to steel. In the introduction, apart from two sentences, there is nothing about the problems of welding "old" and new steels, including 14MoV6-3 steel. The problems studied by the Authors are known and have already been described by many scientists! So please definitely shorten the general part and cite the results of research by other authors on welding joints of "old" and new "power" steels.

Moreover, the second part of the statement that "Obligatory qualification of welding technology is done in accordance with the standardized procedure (19), but it is required only on steel that was not in service - new steel" is incorrect. In the case of repair welding of pressure equipment and pipelines, the relevant regulations in many countries require the development of a WPQR of repair welding before repair.

 

Table 1

In Table 1 "DIN 17175 [16]", but in the list of literature it is stated: "16. SRPS EN 10216-2:2020 Seamless steel tubes for pressure purposes…." ???

Same problem: GTAW-wire [17] and MMA-electrode [17] there is a scientific article "17. Zieliński A, Zieliński A, Dobrzański J, Dziuba-Kałuża M. Structure of welded joints…." ??? Why not a manufacturer's catalog or certificate? Please correct.

 

Table 4

Same problem as in Table 1: "Mechanical properties of used filler materials [23]", but in the list of literature instead of a filler manufacturer's catalog there is a scientific publication: "23. Easterling K. Physical Metallurgy of Welding …." ???

 

Table 5

In Table 5 "DIN 17175 [16]", but in the list of literature it is stated: "16. SRPS EN 10216-2:2020 Seamless steel tubes for pressure purposes…." ???

 

Conclusions

1. a) Please indicate in the conclusions the type of steel tested.
2. b) "Also, in all cases, yield strength is above level requested by standard" - which standard?
3. c) Please correct the final text of the conclusions regarding the recommendation by the Authors to perform WPQR repair welding, because in practice it is currently carried out on most power installation repairs.

 

References

a) Please check the numbering of all literature, because there is no item no. 1!!!

b) Item no.20. “20. ISO 15614-8 2016: Specification and Qualification of Welding Procedures for Metallic Materials - Welding procedure test- Part 8: Welding of tubes to tube - plate joints” concerns “tubes to tube-plate joints”. The authors examine welded pipe joints. What is this standard for?

c) References to literature in the text do not correspond to the items in the list of publications.

Author Response

Dear Reviewer,

We would like to sincerely thank you for your thoughtful and detailed comments on our manuscript titled "Fracture in base metals of 14MoV6-3 steel weld joints after short service period." We truly appreciate the time and effort you have invested in reviewing our work.

Once again, we are grateful for your constructive feedback and we believe the revisions we have made have significantly improved the manuscript. We look forward to hearing your thoughts on the revised version.

Thank you for your understanding and consideration.

Please find below a list of manuscript changes and corrections.

Best regards,

dr Dikić Stefan

University of Belgrade

Faculty of Technology and Metallurgy

Regarding your comments:

1. Moreover, the second part of the statement that "Obligatory qualification of welding technology is done in accordance with the standardized procedure (19), but it is required only on steel that was not in service - new steel" is incorrect. In the case of repair welding of pressure equipment and pipelines, the relevant regulations in many countries require the development of a WPQR of repair welding before repair.
2. c) Please correct the final text of the conclusions regarding the recommendation by the Authors to perform WPQR repair welding, because in practice it is currently carried out on most power installation repairs.

What we wanted to say is that even though WPQRs are mandatory for reparation welding in the most of the countries, none of them considers use of material which was already subjected to working conditions, and have suffered microstructural changes. All the microstructural changes caused by exposure to high temperatures, lead to occurrence of creep, which might cause fracture. In that manner, we hope that we have managed to clarify these statements in revised manuscript.

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Most of the comments seem to have been addressed properly.  It is further recommended to indicate the values of Ls in Figure 3 (maximum allowable value and actual values if possible.)

Author Response

Dear Colleague,

We thank You very much for Your comments and efforts to provide us suggestions in order to improve this paper.

In short time available for answers to reviews, duties for just finished projects and together with situation on Belgrade University, we are aware that our answers should have been done in better manner and we hope that it did not cause inconveniences to You.

We have accepted your suggestion and made correction on Figure 3.

Best regards,

Dikić Stefan

Reviewer 2 Report

Comments and Suggestions for Authors

Cooment to the author: 

Thank you for your revised submission. However, I would like to express concern regarding your response to the review process.

Firstly, your cover letter indicates that, due to time constraints, you were unable to prepare a detailed point-by-point response to the reviewer comments. A thorough and respectful revision process requires authors to address each reviewer comment explicitly. This step is critical not only for clarity but also to demonstrate your engagement with the scientific discourse. I strongly recommend that you allocate sufficient time to properly address all reviewer concerns in future submissions.

Additionally, the absence of fracture surface evidence following mechanical testing is a significant omission. This type of data is fundamental in materials research, especially when drawing conclusions related to mechanical behavior. The explanation that this evidence is “not available” is unsatisfactory and raises questions about the rigor of the experimental work. If such data truly cannot be provided, a clear justification must be given, and its implications for the reliability of your conclusions should be discussed transparently.

While the manuscript has potential and the topic is relevant, I encourage you to treat the revision process with the seriousness it deserves. Reviewers dedicate time and expertise to improving the quality of submissions, and that effort should be met with an equally diligent response.

Please provide a complete and detailed rebuttal addressing all reviewer comments and ensure any missing experimental evidence is either included or convincingly justified.

Author Response

Dear Colleague,

We thank You very much for Your comments and efforts to provide us suggestions in order to improve this paper.

In short time available for answers to reviews, duties for just finished projects and together with situation on Belgrade University, we are aware that our answers should have been done in better manner and we hope that it did not cause inconveniences to You.

Please find below a list of answers and changes/corrections made in manuscript.

Best regards,
On behalf of all authors,

Dikić Stefan

Comment 1. Lack of Novelty and Scientific Evidence:

The manuscript does not present novel insights or scientific findings. It merely reports experimental data without critical analysis or new contributions to the field. The research lacks a clear hypothesis or aim beyond describing weld joint performance.

Our response:

Our research is based on problems that engineers constantly encounter, during maintenance of power plants. During exploitation at elevated temperatures, steels undergo significant degradation, caused by accelerated diffusion processes. Under such conditions, coarsening of the precipitates and grain growth occur, which facilitates the occurrence of creep. Heat energy introduced into material during reparation, might cause further degradation of material.  Therefore, regular inspection of the welded joint using the metallographic replica method is required. In practice, even though creep starts in Base metal, inadequate welding technology might cause occurrence of creep in Heat affected zone.

Metallographic replica allows monitoring of creep process, but it does not provide information about changes in mechanical properties of material, especially during early stage of degradation of microstructure and early creep stage. Our research was focused on determining the influence of repair welding and short exploitation time on reduction of mechanical properties.

It is well known that if the steel is exposed to elevated temperatures during long times, it will lead to certain decrease of strength. Until now, we did not manage to find quantification of that decrease after short exposure to elevated temperatures and effect of reparation welding. Our opinion is that this topic is for some reason underestimated, so we gave our best to clarify our aims and concept, and all the changes in text were marked.

 

Comment 2. Poor Manuscript Presentation:

The manuscript lacks clarity and is poorly organized. The formatting throughout is inconsistent, and the text does not follow a proper structure. The manuscript should be revised to meet the journal's standards for presentation.

Our response:

We made a lot of changes in manuscript, especially in Introduction and Conclusions in order to clarify the aims of our research. All the changes were marked in text.

 

Comment 3. Introduction and Literature Review: 

The introduction to the welding techniques (GTAW + MMA) is shallow and does not effectively set the context for the study. A more comprehensive literature review is needed to highlight gaps in research and how this study attempts to address them.

Our response:

Selected welding processes are not innovative but widespread and most commonly used in welding especially in power plants. The point of the work was not in the welding process as such, but in the difference in the amount of heat input. It is well known that GTAW process leads to higher heat input compared to MMA process. In that way, except from higher efficiency of combination GTAW for root and MMA for filler layer lead lower heat input.

 

Comment 4. Figures and Tables:

• Figures 6 and 7: The type of etching agent and magnification should be removed from the image itself. The details of the chemical etching agent should be added in the Materials and Methods section. Additionally, the microbar should be included for clarity.
• Figures 4 and 5: Distinguishing between the plots is difficult. These figures need to be clearer and more easily interpreted, perhaps using different colors or line styles.
• Figure 3: The graph plotting is not appropriate. It would be more effective to plot the data with lines and symbols to improve readability.
• Macrographs of the fractured samples are missing and should be included to support the findings related to fracture behavior.

Our response:

• We have accepted you suggestions and made changes on figures 6 and 7. We removed etching agent and magnification, and have added microbar as you suggested.
• We have selected a higher scatters and different colors in order to make it more clear on figures 4 and 5.
• The same as with previos comment, we decided to chose scateer marks with higher contrast in order to make it more clear.
• In our practice, after each test we analyze fracture surfaces. In this specific case, it was clear that fractures were ductile. As ductile fracture surfaces were expected, all the analyzis and calculations of deformation and strength were done, we kept samples for 30 days in accordance with our internal procedure

 

Comment 5. Conclusions:

The conclusions should be presented in bullet points for clarity and brevity. The current paragraph-style conclusions do not clearly summarize the significant results obtained from the study.

Our response:

We agree that conclusions were not clear. In that manner we made changes in order to make it more clear even though we did not present in bullet points.

 

Comment 6. References and Citations:

• The reference list is not formatted correctly and includes numerous mistakes. Reference [1] is missing from the list, and several references include data sets, theses, and reports, rather than scientific articles. The authors should ensure all references are correctly formatted and relevant to the study.
• The manuscript cites several reports but does not provide sufficient scientific evidence or data to back up the claims. It is essential to cite studies that directly support the findings rather than relying on general literature.
•  

Our response:

We have corrected all the refference list mistakes. We also added new scientific references in our list, in order to back up our claims.

 

Comment 7. Methodology and Units:

• Equations 1, 2, and 3: The references for these equations are missing.
• Units: The manuscript uses inconsistent units, which should be standardized across the document.
• The methodology lacks clarity, particularly regarding the criteria used for selecting welding parameters. This section needs more detail to justify the experimental setup.

Our response:

• Reference was already in the text, just above the equations.
• We have accepted corrections. All the units are now uniform across the manuscript.
• Welding parameters were set in accordance with our previous experience in repair welding, and parent material manufacturer suggestions. In revised version of manuscript those comments were added and marked.

 

Comment 8. Grammar and Language: 

The manuscript contains several grammatical issues and awkward phrasing, making it difficult to follow. A complete language revision is needed to improve clarity and readability.

Our response:

We accepted your suggestions. Our manuscript grammar and language were revised by third party.

 

Comment 9. Structure and Flow:

• The structure of the manuscript is disorganized. The authors should present the microstructure section first, followed by the mechanical testing results.
• The manuscript contains unconstructive statements, and there is no clear link between the experimental data and the conclusions. The authors should focus on providing a coherent and scientifically grounded discussion

Our response:

The reason why we did not started with Microstructures in chapter Results is explained in answer for Comment 10. The fact that fracture occurred in base metal and not in weld metal or Heat Affected Zone, leads to present organization of paper. In all other circumstances, we would document microstructures in all zones, as You suggested.

Comment 10. Microstructure Section:

The microstructure after welding is critical to understanding the mechanical properties of the welded joint. This section should be detailed, as it is essential to correlate the microstructure with the observed fracture behavior. The authors should emphasize this aspect and provide clear micrographs, including microbars for clarity.

Our response:

We agree that microstructures are critical to understanding. On the other hand, the pinpoint of this paper was related to occurrence of fracture in base metal. It is assumed, that since there is no evidence of influence of microstructure on fracture itself, we think that there is no need to show microstructures from other zones of weld joint.

 

Additional Comments:

• The number of experiments conducted in the study is not specified, and it is unclear how robust the results are. The authors should report the experimental setup in more detail to ensure reproducibility.
• Table 5: There are spelling mistakes in the third row, and the decimal separator in the fourth column is inconsistent (comma instead of a period).

Our response:

• Three specimens were tested for each set of conditions. We have added this information to the experimental part.
• Changes were made in revised manuscript and were marked in the text.

Reviewer 3 Report

Comments and Suggestions for Authors

General: The Authors have highlighted and investigated the problem, but the research results do not indicate a way to solve the problem. The main conclusion for users – be careful. At the same time, there are only standard welding materials for new steels with appropriate mechanical properties of the deposit metal on the market. Please write a few words of comment.

Line 401: No. of position 35 and 27. Please correct.

Author Response

Dear Colleague,

We thank You very much for Your comments and efforts to provide us suggestions in order to improve this paper.

In short time available for answers to reviews, duties for just finished projects and together with situation on Belgrade University, we are aware that our answers should have been done in better manner and we hope that it did not cause inconveniences to You.

The idea for this paper/research came directly from the fact that fracture always occurs in used steel. Qualification of welding technology can not give the answer on the level of deterioration of strength during service of one construction. Therefore, one of the goals of this paper was to point out the awareness that there is a need to quantify the decrease of strength and that it can be done in this manner.

Best regards,
On behalf of all authors,

Dikić Stefan