Influence of Niobium or Molybdenum Addition on Microstructure and Tensile Properties of Nickel-Chromium Alloys
Round 1
Reviewer 1 Report
This study is very interesting and well-written, but before publication, some remarks should be made:
1. Page 2, the sentence "Studies with Be-free Ni-Cr alloys have been also considered for dental applications [ref]." contains an unknown reference. Please, check it.
2. The XRD patterns obtained in this work can not be used for identification of Nb3Ni particles. The authors should provide the XRD patterns sufficient for distinguishing of these particles.
Author Response
1. The reference was inserted in revised text after the mentioned phrase.
2. This observation is correct and the revised text was carefully changed. In this sense, the new Table containing EDS results of commercial Ni-Cr alloy, and as-cast Ni-Cr-Mo and Ni-Cr-Nb alloys have indicated the contents of Ni, Cr, Mo (or Nb) of phases formed in these ternary alloys during solidification.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Dear authors
To confirm the existence of the Ni3Nb phase, please provide a chemical analysis in selected areas where the occurrence of this phase is presumed.
If this phase is voluminous, then only the most intense line according to the pattern can appear on the diffractogram. In this case, the diffraction does not give an unambiguous answer because the solution shows that the lines of both phases overlap. Other research techniques must confirm occurrence of this phase.
From the equilibrium binary systems can be read that Ni8Nb phase can appear in the structure, hence why it is stated that is Ni3Nb?
In line 119 is written Ci Cr, where should be Ni-Cr.
Figure 5 should be titled representative tensile......
In line 133 it is written that four thermogravimetric curves are illustrated in figure 4 while it presents only three analysis. Moreover why the authors didn't presents a TG analysis of commercial alloy?
Line 174 it can not be stated that "minor Ni3Nb peaks" where this peak represents the background of the analysis.
Line 178 the author mentioned that on figure 2 there is a eutectic at grain boundaries, however, the Figure 2a is poor quality and too small magnification. Please change a micrograph for better quality and with higher magnification.
Line 212 reference should be to the table 3 not 4
In the discussion section authors mentioned about the elastic modulus, so the results should be presented in table 3 or 4 too.
Authors present information about the hardness of commercial Ni-Cr alloy, however not presents tensile strength results. Please provide information about the tensile strength of commercial Ni-Cr alloy.
Can not be stated that the addition of Nb cause improvement in hardness or tensile strength because the results of mechanical properties of commercial alloy and an alloy with 8% of Nb presents similar results.
Authors present that the mechanical properties improved as a result of the increase of the amount of Ni3Nb phase during solidification. How was it measured? Did some computer image analysis of precipitation in the structure was made? please provide the results by which it can be stated.
Author Response
We would like to thank the reviewer for yours comments.However, we need for 10 more days in order to check the thermal analsysis of commercial Ni-Cr alloy and perform the computer image analysis of different Ni-Cr-Nb alloys evaluated in this work.
Nevertheless, we are sending the revised text containing the revised text in concordance to all the reviewer' comments as follow:
Authors’ answers:
1. In order to identify the elemental contents in Niss (ss-solid solution) and the Ni3Nb formation, the Table 3 with EDS analysis in selected areas was inserted in revised text, which present the contents (Ni, Cr, Nb, Mo and others) of phases formed in as-cast Ni-Cr-Nb alloys.
2.Information on overlapping peaks and the use of monolithic samples were inserted in revised text, and the term “minor” was changed to “traces”, which were confirmed to be the Ni3Si after EDS analysis as mentioned in revised text. In this regard, a new reference on overlapping peaks in NiNb alloy was also inserted in revised text.
3. The Ni8Nb and Ni3Nb phases contains close to 11.1 and 25 at.-% Nb, respectively. According to the EDS results, the Nb-rich regions presented 17-18 at.-% Nb, indicating to be the Ni3Nb. Information on their enthalpies of formation were also inserted in revised text.
4. It was changed from Ci-Cr to Ni-Cr.
5. The caption of Figure 5 was changed to: Representative tensile curves of the as-cast Ni-Cr-Mo and Ni-Cr-Nb alloys investigated in this work.
6. The TG analysis of commercial Ni-Cr alloy has been checked and its TG curve will be included in the final revised text.
7. This observation is correct and the revised text was carefully changed. So, the term “minor Ni3Nb peaks” were changed to “traces”, which were furtherly confirmed by EDS analysis to be the Ni3Nb phase, as it is indicated in revised text.
8. A new SEM image with higher quality and resolution of commercial Ni-Cr alloy was inserted in revised text
9. This information was corrected in revised text.
10. In revised text, the values of elastic module were inserted in Table 5.
11. Information on mechanical properties of commercial Ni-Cr alloy are presented in text: The commercial Ni-Cr alloy evaluated in this work presented the yield strength (offset 0.2%) and ultimate tensile strength of 417 MPa and 550 MPa, respectively.
12. This consideration is correct and the text was carefully revised, comparing the mechanical properties of commercial Ni-Cr alloy with the Ni-Cr-Mo and Ni-Cr-Nb alloys evaluated in this work.
13. A new text was included in revised text. Information on computer image analysis will be done and included in final version.
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Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
The improved manuscript, in my opinion, can be accepted for publication.
