Effect of Post-Heat Treatment on the AISI M4 Layer Deposited by Directed Energy Deposition
Round 1
Reviewer 1 Report
The Manuscript needs some major reviews to be accepted: 1. Introduction, line 37: "process ability" is not a mechanical property of the material. Please, improve it; 2. Introduction section: in the SoA description, the term "post-heat treatment" is used too many times and it is too general in describing the previous research activities. Please add more details concerning the post-heat treatment performed by the different Authors which you have cited; 3. DED means a family of AM technologies (e.g. DED technologies can be equipped with laser or electron beam source, can use powder or wire as raw material). Please, specify your case (is it a Laser Metal Deposition technology?); 4. Preparation of Specimens section: an indication of the number of printed samples is missing. Also, Table 2 should be referenced in this section. Please, improve it; 5. In Table 2, there is no indication of the pre-heating temperature employed during the sample manufacturing. Please, improve it or add this process parameter into "Preparation of specimens" section; 6. Post-heat treatment conditions section, line 119: post-heat treatments affect the mechanical properties of the sample produced by DED, not the DED process. Please, improve it; 7. In Figure 3 the 4 different paths corresponding to the 4 post-heat treatment conditions are missing. Please, improve it; 8. Post-heat treatment conditions section, lines 136-137 and lines 146-148: an indication on the number and location of the performed cross-sections and hardness measurements is missing. Please, improve the text (an additional Figure could be useful): 9. Microstructure prediction by cooling rate section, lines 159-160: Figure 4 shows the detected temperatures during the sample cooling phase, not the cooling rate. Please, provide some data concerning the obtained cooling rates and indicate how the temperature has been measured; 10. Microstructure section: there is no indication related to the presence of defects. Have you detected cracks or pores? Please, improve it; 11. Labels in Figure 5 are too small. Please, improve them; 12. Hardness section, lines 223-225: in line 101 and Figure 2 it is explained that the sample is detached by the substrate before performing post-heat treatment. There is no indication of the post-heat-treatment performed for D2 substrate. Do you have post-heat treated also the substrate? If yes, please improve the text. Also a description related to the followed methodology for hardness measurements performed for D2 substrate is missing.
Author Response
Please see the attachment
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Overview
Although the structure and the scientific soundness of the work is correct, the weak points of this draft are the poor elaboration of the introduction (neglecting most of the relevant published works, even those of the same authors), and lack of discussion about the importance of the findings in the context of the state of the art. Moreover, the low significance of the achieved results in comparison to the finding of already published reports reduces the novelty and potential interest of the current draft.
Tittle:
The reviewer suggests to substitute “M4” by “M4 steel” or “AISI M4” in the title to broaden paper visibility.
Introduction
Authors state “Moreover, tool steels used in high-hardness cold presses require high toughness in addition to high hardness and wear resistance, and the durability (i.e., hardness, wear behavior, and toughness) of tool steels deposited through DED should be evaluated; however, no study in this regard has been conducted.” Nevertheless, the authors contributions Metals 2019, 9, 282; doi:10.3390/met9030282, or Shim et al. Surf. Coat. Technol. 2017, 328, 219–230. are examples of the contrary. It seems clear that such papers should be included in the introduction. Moreover, some other published works that can be considered are the following:
- Hashemi et al. Oxidative wear behaviour of laser clad High Speed Steel thick deposits: Influence of sliding speed, carbide type and morphology,Surface and Coatings Technology, 315,2017, 519-529, https://doi.org/10.1016/j.surfcoat.2017.02.071
Jo et al. Experimental analysis on multilayer cladding using AISI-M4/H13 metal powders for enhancement of wear resistance and shockproof characteristics. Journal of the Korean Society for Precision Engineering 36, Issue 11, 2019, 1059-1064
Rahman et al. Development and characterization of multilayer laser cladded high speed steels, Additive Manufacturing, 24, 2018, 76-85
Rahman et al. Directed energy deposition and characterization of high-carbon high speed steels, Additive Manufacturing, 30, 2019,100838
Zhang et al. Laser additive manufacturing of M2 high-speed steel, Materials Science and Technology Volume 34, 2018 - Issue 1
- Tuominen et al Microstructural and abrasion wear characteristics of laser-clad tool steel coatings Surface Engineering, 32, 2016
Results
For each characterization test, number of repetitions, mean values and standard deviations should be provided (It is surprising that this information is not provided if other publications of same authors are observed).
Authors should discuss the work findings in comparison with previous reports (from other authors and from previous research of current authors, such as Metals 2019, 9, 282; doi:10.3390/met9030282). What do these results mean within the scope of different steels and treatment alternatives for die manufacturing and performance?
References
The references in the draft do not follow the metals template or the Instructions for Authors (the authors should not submit a draft without formatting it according the journal template). In addition, the low number of references makes difficult to contextualize the addressed problem and the work results.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Dear Authors, in my opinion, the Manuscript has been improved and it is ready for publication.
Regards
