Effect of Post-Processing Treatment on Fatigue Performance of Ti6Al4V Alloy Manufactured by Laser Powder Bed Fusion

Round 1

Reviewer 1 Report

In this paper, the authors present microstructure and properties of Ti6Al4V processed by laser powder bed fusion, and then treated by HIP technology. I read it with great curiosity, because it is a topic that I deal with myself and which has been very exploited in recent years.The paper is generally nicely and clear written, the experiments are relevant and well described, and the topic is useful. The paper is extensive and covers the topic enough to count as an acceptable contribution. In terms of subject matter, the manuscript itself absolutely matches the journal. Its structure, layout, language used by the authors - all this is perfectly adequate. The abstract is extensive, it presents the essence of LPBF and HIP, the scope of research and conclusions.

The introduction is structured, successively presents the research topics that the authors raised in the work. The literature was also selected correctly - the authors cite many studies related to the subject of their work.

The subject of the article is already quite well known - both the technology itself and its use have been widely described in the literature, also with the use of Ti6Al4V. The subject of  LPBF and the use of additive manufacturing is often discussed, but nevertheless it is a continuous and uninterrupted source of knowledge and is a very good material for research. A slight change in parameters, production conditions or settings of the printing device means that we obtain results that are often much different than other scientists. Therefore, in-depth knowledge of the process, depending on the material used, is crucial.   Research methodology described in an orderly and comprehensive manner. The results are presented correctly, the authors study the microstructure and mechanical properties, reveal the differences between differently treated samples. Which allow to draw specific conclusions. In terms of content, the article and the content presented in it are acceptable.  

My main complaint about this work is its lack of originality.  And although the article itself is really noteworthy, it does not add anything new to the state of knowledge we currently have. I have the impression that it is a duplication of many others already published, in terms of content, the order of subsections, and the way of presenting the results. Of course, this is not an objection that eliminates the work from further procedures, but a journal of such importance should publish works more significant for the discipline.

In such a situation - although I positively assess the work of the authors - I leave the decision to publish to the editorial team.

 

 

 

 

 

 

 

Comments for author File: Comments.pdf

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

The manuscript presents the use of post-treatments to improve the fatigue life of L-PBF-ed Ti6Al4V. The introduction presents the state-of-art, with the use of HIP to improve mechanical properties and its inefficiency in reduce the material surface roughness condition, demanding other surface post-treatments, such as machining, shot peening, and others. L-PBF-ed Ti6Al4V were HIP-ed and HT-ed, and exposed to different surface treatments (sand blasting, E-blasting, tribofinishing, and machining). The samples were analyzed regarding microstructures, strength, and rotating bending fatigue life. The work contributes to the scholars by presenting experimental data and a deep discussion about the L-PBF-ed Ti6Al4V fatigue life improvement by post treatments.

 

Some points could be improved or edited by the authors, as listed:

 

Line 28: Keep 450 and MPa in the same line.

Line 225: is the wavelength in micrometers or nanometers?

Line 231: Keep 100 and MPa in the same line.

Line 272: Figure 2. Add a scale bar in the images.

Line 293: Figure 3. Add the measuring unit (mm) in the drawings or in the image subtitle.

Line 349: the sentence “(non-heat treated specimen)” is not necessary at this point in the manuscript. Please delete it.

Line 350: the sentence “without any thermal treatment” is not necessary at this point in the manuscript. Please delete it.

Line 412: Keep 512.5 and MPa in the same line.

Line 415: Keep 850 and °C in the same line.

 

Line 419: in the English system, it is not used point as a thousands separator (14.000). Retype it with a coma or none.

Author Response

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Author Response File: Author Response.pdf

Reviewer 3 Report

The paper focus on “Effect of surface condition in fatigue performance of Ti6Al4V 2 alloy processed by Laser Powder Bed Fusion”  A few interesting results were obtained. Still, some modifications or clarifications should be made:
1. Abstract, The abstract does not reflect the research results of the paper, there are too many background and method introductions, and the experimental conclusive data description is insufficient, which needs to be rewritten

 

2、. Introduction. A brief introduction of the AM technology and the material used in the study is needed, but the introduction section is too long , which needs to be rewritten

 

3. Results: The number of repetitions of tensile and fatigue samples? whether the surface state has been tested for each repeated sample, and whether the as-built sample has been directly subjected to fatigue testing. If surface turning is not performed, the surface state will not meet the fatigue testing standards. Will it affect the accuracy of fatigue testing? Is there any deviation and comparability in this comparative value

4 discuss. Fig.13 .The figure shows the starting position of fatigue crack generation, but can the characteristic image of the starting position be further enlarged and described in more detail? At the same time, can surface defects and stress generation be added to the main mechanism of crack initiation? There is more description and discussion of the results in the article, and the discussion on the mechanism of crack generation is not deep enough

5 Conclusions. The structure of the paper is not concise enough and needs further modification

Author Response

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Author Response File: Author Response.pdf

Reviewer 4 Report

The authors have studied the effect of post-processing treatment on the mechanical performance of Ti6Al4V samples manufactured by Laser Powder Bed Fusion technology. The research is well designed and presented clearly. A good comparative analysis of existing publications concerning the tasks set in the work is performed. The methodological section of the manuscript is presented in sufficient detail. The authors used the modern equipment for tests of samples as well as visualization and assistance in the interpretation of the obtained results. They found that that machined surfaces presented a fatigue behavior comparable to the wrought material offering a fatigue limit superior to 450 MPa, whereas alternative surface treatments showed a fatigue behavior equivalent to the cast material.

However, some shortcomings should be corrected to make the manuscript acceptable for publication in Journal of Manufacturing and Materials Processing.

(1) The title of the manuscript should be corrected (“in” should be replaced with “on”). Besides, the single word “condition” is not appropriate in this context. The title of the manuscript may be as follows: “Effect of post-processing treatment on fatigue performance of Ti6Al4V alloy manufactured by Laser Powder Bed Fusion”. The same concerns the heading of sub-section 4.2.

(2) The term “sample/specimen” should be unified.

(3) The term “fatigue hipped samples” is confusing. It seems that it should be “hipped fatigue samples” or “HIP-processed fatigue samples”.

(4) In Figure 2, scale bars should be provided for both the images.

(5) In Figure 3 for both the positions (a) and (b), the building direction should be indicated. The text in the figure body cannot be recognized.

(6) Line 297: Spelling should be checked for “established”.

(7) In sub-section 3.2, instead of the terms “stress” and “strain”, the terms “engineering stress” and “engineering strain” should be used.

(8) In Table 3, the heading “Load (MPa)” should be replaced with “Stress amplitude (MPa)”.

(9) Figure 8: The word “surface” is missed in the figure caption.

(10) It is expected that the authors replace the vertical axis name “Maximum Stress (MPa)” with “Stress amplitude (MPa)” in Figure 11. The horizontal axis name “Cycles to failure N (log)” is confusing, as in this case, one should perceive “log” as the measurement unit. Instead, the horizontal axis name may be as follows: “Number of loading cycles N (cycles)” or “Lifetime N (cycles)”, as this is a general graph containing data of broken and unbroken specimens. Besides, it goes without saying that the horizontal scale is logarithmic. The same comments concern Figure 15.

(11) Figure 13: In my opinion, the structure of the figure is irrational due to the different magnification of the images. It would be better if the authors presented two images (low magnification and high magnification) for each mode. However, I do not insist on this.

In my opinion, English language of this manuscript should be improved.

Author Response

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Author Response File: Author Response.pdf

Round 2

Reviewer 3 Report

vThe paper focus on “Effect of surface condition in fatigue performance of Ti6Al4V 2 alloy processed by Laser Powder Bed Fusion”  A few interesting results were obtained，it canbe accept in prensent conditions

Reviewer 4 Report

All the reviewer’s comments were taken into account by the authors. The manuscript can now be accepted for publication in Journal of Manufacturing and Materials Processing.

Minor editing of English language required.