Carbon Particle In-Situ Alloying of the Case-Hardening Steel 16MnCr5 in Laser Powder Bed Fusion

Round 1

Reviewer 1 Report

Authors presented for the review their article entitled "Carbon Particle In-Situ Alloying of the Case-hardening Steel 16MnCr5 in Laser Powder Bed Fusion". This work is devoted to a relatively novel approach in additive manufacturing - in-situ alloying. Since the list of alloys for powder bed fusion is limited, moreover, composite structures could not be produced using commercial pre-alloyed powders, such approach seems to be a very promising alternative.

My recommendations are as follows: 

1. For Powder Bed Fusion using laser traditionally used the abbreviation L-PBF. I recommend to use it instead of PBF-LB/M.
2. For PSD of the used powders (Fig.2) it is recommended to represent D-numbers - D10, D50, D90.
3. In summary, I recommend to strengthen advantages of the used additive manufacturing method - L-PBF for in-situ alloying with carbon materials. For example, in comparison with Electron Beam Melting or Binder Jetting. 

Author Response

Thank you very much for the detailed review and interest in the presented work.

1. The terminology according to ISO 52900 (PBF-LB/M) was used. We agree, that L-PBF is the more commonly used abbreviation. A sentence for clarification was added in the introduction.
2. An additional table was added with the D10, D50 and D90 of the powders. Figure 2 is still kept as it adds value in showing the partial bimodal distribution beyond the D10, D50 and D90 values. In combination, the PSD is well understandable.
3. This is a very good idea. An additional paragraph is added in the discussion chapter explaining the limits and possibilities of in-situ alloying in electron beam melting and binder jetting.

Reviewer 2 Report

ONLY FEW DETAILS

The powder was atomized using argon gas and lies within the range specified in DIN 208 EN 10084, whereby all main alloying elements are at the lower end of the tolerance: please explain this better, I do not understand why the lower end was an advantage.

The paper is really useful and sound. Only two details to improve: Laser Powder Bed Fusion or SLM or sintered branch, giving very Good patterns and structured microstructures. Recently there were people reaching the limits (in small size). MDPi is very active, that is very good because in some other journals on work is old when is published. I see you did not include the work: A New Approach in the Design of Microstructured Ultralight Components to Achieve Maximum Functional Performance, Materials 14 (7), 1588. After this work, only microstrutured patterns such as yours are the solution.

Carbon has a direct and strong influence on the properties of steels: this is obvious, perhpas it can be modified.

Author Response

Thank you very much for the detailed review and interest in the presented work.

1. The lower end in carbon could have been an advantage when fearing cracks during the process. However, it becomes clear that the material is not prone to cracking even at higher carbon contents. Otherwise, the chemical composition in the lower end is a disadvantage since it would lead to parts with a chemical composition that is out of specification even at low element depletion. An additional sentence was added to clarify.
2. Thank you for the note and the literature advice. A paragraph outlining the combination of the design approach with the microstructure patterns was included. Additionally, the literature is cited and added in the reference section.
3. The sentence was modified.