Comparative Study of the Influence of Heat Treatment and Additive Manufacturing Process (LMD & L-PBF) on the Mechanical Properties of Specimens Manufactured from 1.2709

Round 1

Reviewer 1 Report (Previous Reviewer 2)

The manuscript «Comparative study of the influence of heat treatment and additive manufacturing process (LMD & L-PBF) on the mechanical properties of specimens manufactured from 1.2709» in its current form, according to the reviewer, is not a good enough work for the Crystals journal.

The reviewer considers it possible to send the article in major revision, but notes that it is extremely important to write the relevance and relevance of the study, as well as rewrite the introduction and discussion sections. After making these changes, the work can be evaluated again.

While the reviewer draws attention to the following points:

Introduction section needs to be expanded

The novelty and relevance of the study is not described – The reviewer will not understand the difference between this work and the existing results. https://scholar.google.com/scholar?hl=ru&as_sdt=0%2C5&q=1.2709+additive+manufacturing&btnG=&oq=1.2709+a

It is necessary to describe the scope of Ultra High Strength Tool Steel and the importance of the development of additive technologies for it

Experimental секция описана достаточно подробно – изменения не требуются

Captions for figures 4-6 are not designed according to the journal standard

on structure images, the scale is often not visible or a different scale of compared modes is used

Figure 6 is not mentioned in the text and is not informative at all.

What is the reason for such a large error in the measurement of Young's modulus and fracture strain of LDM specimens after heat treatment?

There is practically no scientific component in the Discussion section, it needs to be significantly expanded and rewritten

Author Response

1. Introduction section needs to be expanded
   1. What exactly is missing, that should be added to the introduction?
2. The novelty and relevance of the study is not described – The reviewer will not understand the difference between this work and the existing results. https://scholar.google.com/scholar?hl=ru&as_sdt=0%2C5&q=1.2709+additive+manufacturing&btnG=&oq=1.2709+a
   1. As mentioned in the introduction, the relevance lies in a better understanding about the influence of the choosen AM-process on the mechanical characteristics of the final part. With this knowledge, a use-case oriented choice on the am-process can be made when working with 1.2709 material.
3. It is necessary to describe the scope of Ultra High Strength Tool Steel and the importance of the development of additive technologies for it
4. Experimental секция описана достаточно подробно – изменения не требуются
   1. -
5. Captions for figures 4-6 are not designed according to the journal standard
   1. Has been redesigned
6. on structure images, the scale is often not visible or a different scale of compared modes is used
   1. The images now have bigger, more readable scales
7. Figure 6 is not mentioned in the text and is not informative at all.
   1. Mentioning in the text added
   2. It shall give the reader an insight about the difference in pores appearing for the individual am-processes
8. What is the reason for such a large error in the measurement of Young's modulus and fracture strain of LDM specimens after heat treatment?
   1. There is one sample that can be identified as an statistical outlier. Explanation has been added to the manuscript
   2. Reason for this rather large deviation in fracture strain couldn’t be find. In future work this will be addressed
9. There is practically no scientific component in the Discussion section, it needs to be significantly expanded and rewritten
   1. Discussion has been expanded.

Reviewer 2 Report (Previous Reviewer 1)

The authors have addressed most of my concerns raised in the previous review. The work can be accepted as currently presented.

Author Response

Language has been checked and in parts of the manuscript changed

Round 2

Reviewer 1 Report (Previous Reviewer 2)

The authors of the article responded to my new comments and partially supplemented the article with new information. Article in its present form may be published

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

In the present study, the authors investigated the differences in the microstructure and mechanical behavior of tensile samples made from two types of additively manufacturing processes, i.e., L-PBF and LMD. Furthermore, the authors investigated the influence of heat treatment on those samples. The study lacks scientific soundness, and I must not recommend accepting the work. The following are some of my primary concerns:

1.       The English need to be corrected in many paragraphs. Sometimes, it isn't easy to follow the grammar. Also, the intext citation of figures shows Error! Reference source not found..in all sections. This manuscript is not adequately prepared.

2.       The introduction section lacks all the essential details necessary to showcase the study's novelty. It is just two paragraphs, and it’s unclear if there are previous studies dealing with comparing mechanical properties/microstructure for parts made from PBF and LMD. Are their other studies dealing with such assessment? Why have you selected 1.2709 maraging steel? How will the present study advance the scientific knowledge in the field? The motivation for the current work is not clear.

 

Just a simple search shows the following articles which should be part of the introduction section:

https://doi.org/10.1016/j.matchar.2020.110842

https://doi.org/10.1007/s11771-021-4677-y

https://link.springer.com/article/10.1007/s00170-021-07635-w

 

3.       Sections: 2.1, 2.2, 2.3, and 2.4 should be part of the introduction section (not material and methods).

4.       Section 2.5 on the experimental procedure lacks enough details for replicating or reproducing the work. The deposition parameters used for the fabrication of the part must be given in full.

5.       Figure 2: why did you choose different orientations for the tensile test samples cut out for the LMD and PBF-made blocks? What are the dimensions for the tensile sample cut-outs shown in the figure? Do you think that sample orientation does not influence tensile test results? Please improve the quality of figures 2 and 3.

6.       Figure 4: optical micrographs are insufficient in providing enough details regarding the microstructure. You must include SEM images and clearly describe the various microstructural features in photos and discussions.

7.       The authors fail to discuss any noticeable differences observed after heat treatment of the samples (i.e., Figure 4). The images are just poor.

8.       Can you also include a sample grey-scale microstructural image to support the defect distribution shown in Figures 5 and 6? Also, the readability of the scale/title in figure 5-7 is poor. Can you include the scale bar in Figure 6.

9.       Why are there significant differences in the hardness (i.e., Figure 7), while the tensile test results are almost identical in all aspects (i.e., Figure 9). Something must be checked. There is no result on the strain distribution obtained from DIC measurements. How about more details about the resolution of DIC measurements?

10.   Dimensions should be provided for Figure 8a. Also, the quality of the figure is poor.

11.   Can you scientifically discuss the reason for the sharp increase in properties after the heat treatment? The discussion on the influence of EDM cutting is not convincing.

12.   The present study is inconclusive and could not answer the question: of whether there is a significant difference in mechanical properties when different additive manufacturing processes or heat treatments are used to make samples?

 

The reason is that the scientific soundness of the work is very weak. Careful scientific assessment can only be done when the deposition parameters are chosen wisely. The measurements are comparable when there is a logic behind the variation in process history or parameters. Consequently, the manuscript lacks a conclusion section. The authors could have been more interesting if the authors chose to vary the LMD and PBF deposition parameters for each sample and present more details about microstructural features (e.g., detailed SEM). It does not make sense to simply compare the microstructure morphology and mechanical properties for samples made from two processes which significantly vary in terms of thermal history, material buildup rate, stacking directions, etc. The properties and microstructure are obviously going to be different. Therefore, I am not sure if the comparison of the current results is affected by the negligence of the material build-up direction or, for instance the location for hardness tests and surface roughness assessments.

Comments for author File: Comments.pdf

Reviewer 2 Report

The article «Comparative study of the influence of heat treatment and additive manufacturing process (LMD & L-PBF) on the mechanical properties of specimens manufactured from 1.2709» is not without flaws.

 

I recommend the authors to make a major revision of the article, including based on these comments:

I recommend giving the more general name of the alloy 1.2709 in the title (Tool Steel for example)

The introduction does not sufficiently describe the current state of the problem. More reference needs to be given. The relevance of the study is not obvious. The goal is vaguely formulated.

It is not clear on the basis of what parameters these heat treatment modes were selected.

To analyze the macrostructure, it is necessary to show the results with a large expansion, including with the help of a SEM

The analysis of the defects is not detailed enough

Error in reference "Error! Reference source not found.," - there is no way to match sources

 

Conclusions are too general