Improved Tribocorrosion Resistance by Addition of Sn to CrFeCoNi High Entropy Alloy

Round 1

Reviewer 1 Report

Dear Authors! I delighted reading your manuscript "Improved Tribocorrosion Resistance by Addition of Sn to CrFeCoNi High Entropy Alloy" and after the reviewing I came to the conclusion that it can be accepted in present form or (what is better) after minor editing. My comments are mainly terminological and conceptual, but only advisory. 

1. I am in general sceptical about the perspectives of HEAs in view of practical applications especially in competition with "traditional" alloys. On the other hand, I fully support fundamental research such as represented in your article. I would recommend to reinforce the introduction section with the examples of successful commercialization of HEAs if exist.
2. I would omit discussion of biomedical application in the context of these particular alloys - Ni causes allergy, Sn is referred as carcinogenic and mutagenic.
3. Taking into account the experimental error in the determination of phase volume fractions I would not use terms "matrix" and "secondary" phase. "Matrix" has connotation from composite science assuming also the presence of reinforcement what is not the case in the system studied. I would consider to use the terminology from dual-phase steels science.
4. The cracks ascribed to the brittle Ni-Sn phase only are not visible in depth. I would use terms "apparently" and "seem" when you discuss this issue.

Good luck and Merry Christmas!    

Author Response

Thank you for your reading of our manuscript, and the thoughtful comments.  Our response to these is below:

1) We agree that there are significant barriers to the implementation of HEAs in practical applications, but that this does not invalidate scientific inquiry in this area.  We are not able to provide details of successful commercialisation of HEAs, but, as this is an important aspect, we have added some text to note this

Changes: text added, lines 56-57

2) The reviewer has raised an important point here, and we will remove the biomedical reference

Changes: text removed / changes, lines 30, 45 & 49

3) This is a very good point, and we agree the terms are misleading, and should be changed.  We have changed the description to be that the material is dual-phase, and altered the terminology accordingly.

Changes: Text altered on lines 19, 162, 167, 169, 216

4) Thank you, it does appear that an increased degree of caution is appropriate here.

Changes: Text added on lines 198 and 199

And we wish you a Merry Christmas too!    

Reviewer 2 Report

The paper reports the tribo-corrosion resistance of CrFeMnNi High Entropy Alloys (HEAs) with and without Sn element. The paper shows the new aspect of HEAs, however, the revision must be necessary for the acceptance. The followings should be considered before the acceptance.
Mandatory
(1) Table 2
"0" at the same element pair should be changed to the blank.
(2) Fig. 5
Is it necessary to show EDS data in Fig. 5? The EDS analysis results were already shown in Table 1.
(3) Fig. 4 and Fig. 5
Is it necessary to show both SEM-SE image (Fig. 4b) and SEM-BSE image (Fig. 5) in the separated figures to explain the indents of HEAs with Sn element? Modify the explanation and figures in the revised paper.
Optional comments
(1) Please add the information for the casting process for the fabrication of cylindrical samples. High frequently melting using ceramic crucibles under Ar atmosphere? Can the oxydation during melting and cooling be ignored in the present study?
(2) line 210-213
Is it better that the sentences about the volume fraction ratio of FCC and Ni-Sn phase move to the line 161. Please consider.

Author Response

Thank you for the comments on our manuscript, which we are very pleased to see and act on.  Our response, point by point, is given below:

1) Table 2 – thank you, this is correct, of course

Changes: Zeros removed from Table 2

2) Fig.5 – Rather than have redundant information, we agree it is best to remove the data (see also next comment).

Changes: See changes for point 3

3) Figs 4 and 5 – Thank you for this observation.  Our purpose in Figure 5 was to show the locations for the EDS measurements, but, agreeing that this information is not needed, the simplest solution to this repeat of images showing essentially the same information is to remove Figure 5,

Changes: Figure 5 is removed, figures are renumbered and references to them changed.

4) Thank you, we are happy to add the casting process details (suction casting in the arc melter).  Oxidation should be reduced, due to the procedures used (we have added details of this), but cannot be excluded at some level, and we have acknowledged this.

Changes: Details added, lines 82-86

5) Volume fraction information – we are happy to address this earlier, and have moved the information as suggested, referring to it again in the later text.

Changes: Text added, lines 167-169, 211-212

Round 2

Reviewer 2 Report

The paper was revised to address the reviewers' comments appropriately. The revised paper was judged to accept in the Journal.