Evaluation of Porosity in AISI 316L Samples Processed by Laser Powder Directed Energy Deposition

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

Please comment on the effect of reflectivity of 316 SS powders by laser on the loss of energy for fusion.

Can you please show some metallography or SEM pictures of the cross section of the porosity containing samples?

Author Response

Thanks for the review the revision are detailed in the file

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The article presents the results of research on the influence of the main parameters of the DED-LB/Powder process on porosity. The authors considered the effects of laser power, powder mass flow rate, and movement speed on the pore distribution and sizes. Moreover, the thermal history was simulated on a macro scale for further analysis.

The introduction is based on a broad literature review and contains information necessary to determine the research's relevance and the problem's topicality.

The article's section on materials and research methods was correctly described; only Figure 2's readability needs improvement. The test results are clearly presented in three-dimensional drawings and charts.

The discussion of the research results is enriched by the integration of relevant literature data, underscoring the research's relevance and contribution to the field.

The conclusions contain a summary of the research and include the most critical observations obtained from the study.

Author Response

Thanks for the review the revision are detailed in the file

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

The paper is well prepared with good quality images. It is worth publishing after addressing the major points highlighted in the attached PDF. 

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Author Response

Thanks for the review the revision are detailed in the file

Author Response File: Author Response.pdf

Reviewer 4 Report

Comments and Suggestions for Authors

This paper presents an experimental and numerical investigation aimed at understanding the mechanisms behind the generation of pores on AISI 316L stainless steel when processed by DED-Laser.

Overall, the contents of the paper are interesting and well aligned with the scope of the journal, but some modifications should firstly be made before the paper can be ready to publication,

1)       Both the Abstract and Introduction require the novelty of the overall work to be more clearly presented. There are several available studies on the analysis of porosity in additively manufactured metals (such as stainless steel alloys). Therefore, if the novelty is more clearly expressed in the paper, it will help it stand out from the remaining studies on similar topics.

2)       The state-of-the-art is comprehensive. One way to further improve it would be to include some comments on the effects that shielding gases may have on porosity. (e.g. 10.1177/0954405420911768)

3)       Please add units to the schemes of Figure 1.

4)       The rationale for the utilized processing parameters should be explained in finer detail, namely clarifying what the authors mean by ‘satisfactory outcomes in terms of dimensional accuracy’ (line 127). Moreover, the variations employed on travel speed are relatively much smaller than those considered for laser power.  

5)       Please explain why a rotation of 90º was used between layers. Typically, rotations of 67º or 63.5º are used to avoid repeating the positions of near consecutive laser vectors.

6)       Why is the heat generation rate not considered in the heat balance presented in equation (1)?

7)       What were the experimental procedures used for confirming the forced and natural convection coefficients and emissivity value used in the simulations?

8)       Were the porosity assessments confirmed with any other experimental measurement techniques, such as the Archimedes method or micrograph analysis?

9)       The analysis of porosity with the effect of laser power seems fine to me, but I still advise the authors to add some comments on possible geometric deviations that may occur due to excessive waviness caused by the higher melt pool volumes.

10)    The correlation between experimental and finite element results shown in Figure 8 is not so evident. Section 3.2.1 should be revised to improve clarity on how finite element results mostly based on temperature can be used for predicting the volume regions where concentrations of pores due to lack of fusion are expected.

Comments on the Quality of English Language

The paper is very well written under a fine overall structure. Still, I recommend proofreading the paper just to correct some minor misspelling issues (such as the word Figure 6c in line 334).

Author Response

Thanks for the review the revision are detailed in the file

Author Response File: Author Response.pdf

Round 2

Reviewer 4 Report

Comments and Suggestions for Authors

No further comments.

Comments on the Quality of English Language

No further comments.