Influence of Postprocessing on Wear Resistance of Aerospace Steel Parts Produced by Laser Powder Bed Fusion

Round 1

Reviewer 1 Report

Post-processing becomes increasingly interesting for many researchers. The article presents three methods for complex-geometry parts. Good introduction and organization of the work. There are some major concerns:

1 what is the motivation for running wear tests?

2 It seems all three methods only performed once under a given condition. What is the influence of key parameters of those post-processing technologies on the surface quality? It causes low scientific significance of the work and the major weakness of the work.

3 How to convert the experience of a particular example to more general parts?

Author Response

Response to Reviewer 1 Comments

 

Dear reviewer,

Thank you very much for your kind evaluation of our work. We do agree with all your recommendations and have modified the manuscript.

Introduced changes were marked by yellow in the text of the manuscript.

 

Kind regards,

Authors.

 

Point 1: what is the motivation for running wear tests?

Response 1: It is entirely known that surface roughness influences resistance to abrasion wear that is especially relevant for the functional surfaces that work in friction pairs and to ensure tight contact with detachable fasteners of parts. The idea was to search how the obtained surface effect influences wear resistance since the chosen technology based on mechanical types of destruction affects the topology and submicron structure of the surface and subsurface layers differently. Wear resistance is one of the critical exploitation properties of the functional surfaces of the part working in friction pairs or for the parts that should provide tight fixation with movable fixation systems (bolts, screws, nuts). That is especially critical for complex parts that are difficult to subject by classical mechanical polishing or plastic deformation. Grounding is provided in the text of the manuscript and goes like a red thread through the manuscript.

Point 2: It seems all three methods only performed once under a given condition. What is the influence of key parameters of those post-processing technologies on the surface quality? It causes low scientific significance of the work and the major weakness of the work. 

Response 2: Thank you for your kind note. We have conducted in the range of factors and the technology was optimized. However, we did not want to overload the manuscript with unnecessary data. The relevant passages are added.

Point 3: How to convert the experience of a particular example to more general parts?

Response 3: All tests were conducted on the samples. The relevant statement is provided in the text of the manuscript (Lines 162-164).

Author Response File: Author Response.docx

Reviewer 2 Report

In this article, the authors explore several methods for post-processing steel parts manufactured using laser additive manufacturing. The work is interesting and the study is well done, but the manuscript reporting it needs some improvement before it would be ready for publication in an international journal. I recommend that the paper be sent back to the authors for a major revision to address the issues I describe below. After revision, we should review it again and make a decision about its acceptability at that point. 

1. The way the paper is written, it appears in some sections as a large review and others as a research paper. I suspect the authors tried to complete both an extensive review and collect new data in one paper. This is OK (I have done this myself in the past), but it needs to be presented more clearly. For example, there are several sections later in the paper that discuss the results from the literature and not really much from the current paper. It would be best to order the paper something like: (1) Introduction, (2) Literature Review, (3) Materials and Methods, etc.

2. The quality of English writing is good, except the authors should review the paper carefully and make sure that the text is organized in nicely-flowing paragraphs, avoiding short and single-sentence paragraphs. Several areas of the paper need attention on this. 

3. Lines 32-33: "required level". This statement needs expansion. What does "required level" mean? Tolerances? Please discuss this more, since it is both interesting and could cause confusion if not expanded. 

4. When discussing post-processing methods, it would be best to explicitly categorize the methods and sort your background discussion and literature accordingly. For example, simple post-processing simply to remove support material would involve very different considerations than machining the part to final needed tolerances or heat treating it. A simple representative chart laying out the categories would also add value to the paper. Figure 1 is somewhat helpful but it is too specific - need something more general at a higher level that talks about metal part post-processing in general. As researchers in AM, it is important for us to make connections to other manufacturing processes and materials as much as possible so we can normalize using AM and help it gain wider acceptance. 

5. The ending of Section 1 (Introduction) is weak and should be expanded. It is very important to show the novelty of the work - simply discussing methods and trying existing methods is not necessarily novel. I should note that I DO agree that what the authors present is novel and worth publishing - my concern is with the presentation and not with the quality of their study. 

6. Figure 2: Panels (c) and (d) should be replaced by higher-resolution images if possible

7. Section 2.1. Are the authors able to show examples of the actual final samples? If the final samples are represented in Figure 2, please make this more clear. 

8. Table 6 and Table 7 need to be improved - I believe that the two rows associated with AM are for examples with and without heat treatment but it took me several minutes to understand this from the presented tables. Please use three full rows for each table to ensure clear communication (e.g., AM (without HT), AM (with HT), cast)

9. I feel like the discussion relies too much on the literature review and not enough on the actual presented results. The Conclusion section also suffers from this. Please focus the discussion on this and only bring in the literature to give context or compare with your data at the end. Since you did an extensive review, perhaps a new subsection dedicated to comparing to literature data would be appropriate. 

Good luck with your revision and I look forward to seeing the revised manuscript 

 

Author Response

Response to Reviewer 2 Comments

 

Dear reviewer,

Thank you very much for your kind evaluation of our work. We do agree with all your recommendations and have modified the manuscript.

Introduced changes were marked by green in the text of the manuscript.

 

Kind regards,

Authors.

 

Point 1: The way the paper is written, it appears in some sections as a large review and others as a research paper. I suspect the authors tried to complete both an extensive review and collect new data in one paper. This is OK (I have done this myself in the past), but it needs to be presented more clearly. For example, there are several sections later in the paper that discuss the results from the literature and not really much from the current paper. It would be best to order the paper something like: (1) Introduction, (2) Literature Review, (3) Materials and Methods, etc.

Response 1: Thank you for your kind suggestion. We would like to notice that some reviewers recommend introducing some kind of overview of the research domain when others ask to ground the chosen field and subject of the research. We have tried to combine two of the approaches to make a more understandable motivation. We found that our introduction has not enough material for a separate section of the literature overview, and this kind of structure is not recommended by the authors’ guidelines of the journal. It makes it quite difficult then to satisfy the recommendation of everyone. We probably did not get the point, but if the reviewer means that we should move our short overview (lines 54-83) to the discussion section, we are ready to assist. Our introduction contains three main parts – grounding actuality of the research, short overview, grounding chosen post-processing methods.

Point 2: The quality of English writing is good, except the authors should review the paper carefully and make sure that the text is organized in nicely-flowing paragraphs, avoiding short and single-sentence paragraphs. Several areas of the paper need attention on this.

Response 2: Thank you for your kind evaluation. We have tried to revise it to make the paragraphs larger. We hope it corresponds to your kind advice.

Point 3: Lines 32-33: "required level". This statement needs expansion. What does "required level" mean? Tolerances? Please discuss this more, since it is both interesting and could cause confusion if not expanded.

Response 3: Thank you for your question; the relevant description is added.

Point 4: When discussing post-processing methods, it would be best to explicitly categorize the methods and sort your background discussion and literature accordingly. For example, simple post-processing simply to remove support material would involve very different considerations than machining the part to final needed tolerances or heat treating it. A simple representative chart laying out the categories would also add value to the paper. Figure 1 is somewhat helpful but it is too specific - need something more general at a higher level that talks about metal part post-processing in general. As researchers in AM, it is important for us to make connections to other manufacturing processes and materials as much as possible so we can normalize using AM and help it gain wider acceptance. 

Response 4: Figure 1 is revised.

Point 5: The ending of Section 1 (Introduction) is weak and should be expanded. It is very important to show the novelty of the work - simply discussing methods and trying existing methods is not necessarily novel. I should note that I DO agree that what the authors present is novel and worth publishing - my concern is with the presentation and not with the quality of their study. 

Response 5: Thank you for your kind suggestion. You are right; we did rephrase this statement.

Point 6: Figure 2: Panels (c) and (d) should be replaced by higher-resolution images if possible

Response 6: Thank you, the subfigures were replaced. If it is not OK, we are ready to remove them from the manuscript.

Point 7: Section 2.1. Are the authors able to show examples of the actual final samples? If the final samples are represented in Figure 2, please make this more clear.

Response 7: Unfortunately, the used samples (20 × 20 × 20 mm) and parts for the searching effect were conveyed to our industrial partner in the contract frame after realizing the project.

Point 8: Table 6 and Table 7 need to be improved - I believe that the two rows associated with AM are for examples with and without heat treatment but it took me several minutes to understand this from the presented tables. Please use three full rows for each table to ensure clear communication (e.g., AM (without HT), AM (with HT), cast)

Response 8: Thank you for your advice; we have modified the tables.

Point 9: I feel like the discussion relies too much on the literature review and not enough on the actual presented results. The Conclusion section also suffers from this. Please focus the discussion on this and only bring in the literature to give context or compare with your data at the end. Since you did an extensive review, perhaps a new subsection dedicated to comparing to literature data would be appropriate. 

Response 9: Thank you for your kind comment. We have tried to improve it and hope that it corresponds to your recommendations in the current version.

Point 10: Good luck with your revision and I look forward to seeing the revised manuscript 

Response 10: Thank you once again for your help in improving the manuscript.

Author Response File: Author Response.docx

Reviewer 3 Report

The manuscript technologies 1005374 with the title "Post-Processing of Laser Additively Manufactured Aerospace Steel Parts" has been reviewed.

The manuscript presents results of abrasive surface smoothening applied to demonstrator parts from the aerospace industry manufactured in steels by the Additive Manufacturing (AM) technology of Laser Powder Bed Fusion. Surface roughness, topography and wear resistance are analyzed. Experimental procedures, results and conclusion are presented very clearly and unmistakably. The relevant literature is considered and the novelty and industrial relevance of this research work is clearly pointed out and put into larger perspective. The structure and outline of this manuscript are very strict, which makes it easy to read and understand. Graphical representations are of high quality and the important features discussed in text are obvious.

Congratulations to the authors for this well written manuscript!

 

Only three minor suggestions are made for improvement:

- in order to increase probability of this article to be found in search engines, the international standardized terminology according to ISO 52900 for the exact AM process should be added to keywords: "laser powder bed fusion"

- the numbers on scales in fig.8 a-e are hard to read. They should be added in larger font size

- it would be interesting if the authors could add one or two sentences as a future outlook. How could surface smoothness probably be improved further, in order to hopefully surpass the aerospace industry demands?

Author Response

Response to Reviewer 3 Comments

 

Dear reviewer,

Thank you very much for your kind evaluation of our work. We do agree with your recommendations and have modified the manuscript.

Introduced changes were marked by blue in the text of the manuscript.

 

Kind regards,

Authors.

 

Point 1: - in order to increase probability of this article to be found in search engines, the international standardized terminology according to ISO 52900 for the exact AM process should be added to keywords: "laser powder bed fusion".

Response 1: Thank you for your kind suggestion, we have added this term in the abstract, key words and although the manuscript. Should we also add it in the title as follows?

NOW: Influence of Ultrasonic Post-Processing on Wear Resistance of Laser Additively Manufactured Aerospace Steel Parts (14 words)

CAN BE: Influence of Ultrasonic Post-Processing on Wear Resistance of Aerospace Steel Parts Produced by Laser Powder Bed Fusion (17 words)

Point 2: - the numbers on scales in fig.8 a-e are hard to read. They should be added in larger font size

Response 2: The subfigures are revised.

Point 3: - it would be interesting if the authors could add one or two sentences as a future outlook. How could surface smoothness probably be improved further, in order to hopefully surpass the aerospace industry demands?

Response 3: The paragraph on the Future outlook statement is added at the end of the conclusions.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Dear Authors, 

Thanks for your revisions. They have addressed my concerns sufficiently and I recommend acceptance of the paper.