Microstructure and Tribological Behavior of Cr-Mn-N Steel with Age-Hardened Near-Surface Layer including CrN and Fe2N Particles Intended for Use in Orthopedic Implants
Round 1
Reviewer 1 Report
I have comments as follows:
1. Please give the step size of the EBSD scanning
2. The preparation of the OM should be provided, for example, the content of the metallographic etchant.
3. There seems to be some confusion in the analysis of SAED in Fig.4(c), the d interplanar distance of 0.086nm is not close to d(200) = 0.181nm. Please check the distance again.
4. The indentation for the first line is missing in line 221.
5. The name of the ordinate and the location of the unit should be uniform. Fig.5, Fig.6, Fig.7, and Fig.8.
Author Response
- Please give the step size of the EBSD scanning
Text added: «Step size of the scanning was 0.5 mm.»
- The preparation of the OM should be provided, for example, the content of the metallographic etchant.
Text added: «after etching with a solution of 60 ml HCl + 20ml HNO3.»
- There seems to be some confusion in the analysis of SAED in Fig.4(c), the d interplanar distance of 0.086nm is not close to d(200) = 0.181nm. Please check the distance again.
Thank you very much for pointing out the error. 1.86 Å is true, as in Table 2.
- The indentation for the first line is missing in line 221.
Thank you. It was corrected.
- The name of the ordinate and the location of the unit should be uniform. Fig.5, Fig.6, Fig.7, and Fig.8.
The ordinate of the Fig.6 corrected.
I thank the referee for his attention to our article and useful comments. All fixes and additions are highlighted in yellow
On behalf of the co-authors,
best wishes
Narkevich.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The authors studied the effect of MTT on the microstructure, the hardening mechanisms, the stress–strain behavior and the tribological characteristics of the near-surface layer of the Cr-Mn-N steel, intended for using as a material for orthopedic implants.
1. The abstract lacks of structure and does not show the significance of the study. A background is also needed for the abstract.
2. 2. Resolution of all images in the manuscript should be improved.
3. 3. The conclusions should be restructured, since they do not reflect all the results obtained.
4. The metallography of Figure 2 should be repeated because the layer formed is not well appreciated; it lacks quality. It is essential to see the layer formed on the substrate surface.
5. More references need to be added; many statements throughout the manuscript need to be substantiated.
5. 6. Information on biocompatibility needs to be included. The authors should provide information on this subject since it is imperative for the reader to know more about this topic.
6. 7. What is the reason for using this steel (Cr-Mn-N steel)? Why not use another substrate?
7. 8. When writing a study, authors must include both their research's advantages and disadvantages. This allows the reader to understand the findings and take them into account when making decisions or drawing conclusions. However, this aspect still needs to be addressed in the study. It is always helpful to have a balanced view of the research, as this can lead to a better understanding of the implications of the findings.
9. The authors mention, "Such dispersed CrN particles were distributed in interlayers between twins (Fig. 3c)". Unfortunately, they are not visible in the image. What is the point of posting an image if we cannot see what is mentioned in the comment?
English is complicated to understand/incomprehensible and must be reviewed by a native speaker
Author Response
- The abstract lacks of structure and does not show the significance of the study. A background is also needed for the abstract.
The annotation is supplemented and shows the summary of the article.
- Resolution of all images in the manuscript should be improved.
The size of the structure elements is extremely small. The image of the structures looks exactly the same as in the article at high magnification.
- The conclusions should be restructured, since they do not reflect all the results obtained.
Conclusions are supplemented.
- The metallography of Figure 2 should be repeated because the layer formed is not well appreciated; it lacks quality. It is essential to see the layer formed on the substrate surface.
Metallography shows ( Fig. 2) the thickness of the modified layer. EBSD indicates grain size. The structure of the near-surface layer was studied by TEM. Fig.3 presents structure after frictional processing. Fig.4 shows structure after frictional and subsequent electron beam processing.
- More references need to be added; many statements throughout the manuscript need to be substantiated.
Links added.
- Information on biocompatibility needs to be included. The authors should provide information on this subject since it is imperative for the reader to know more about this topic.
We made references to works 5-10, the authors of which investigated the biocompatibility of Cr-Mn-N steels.
- What is the reason for using this steel (Cr-Mn-N steel)? Why not use another substrate?
The choice of materials for endoprostheses is not so wide. A number of requirements cannot be combined in one material. In the first place is bioinertness and biocompatibility. Equally important are high strength and low modulus of elasticity. However, at present, the problem of increased wear resistance is most acute. Due to the formation of wear particles in the joint, inflammation begins after 5-15 years. The service life of the endoprosthesis depends on the mass of the person and his physical activity. To remove wear particles, an operation-revision of the endoprosthesis is performed. This can be done no more than 2 times. Therefore, joint replacement operations are best performed in old age (so as not to torment a person with periodic revisions). There is nothing better than our human joints anyway!
- When writing a study, authors must include both their research's advantages and disadvantages. This allows the reader to understand the findings and take them into account when making decisions or drawing conclusions. However, this aspect still needs to be addressed in the study. It is always helpful to have a balanced view of the research, as this can lead to a better understanding of the implications of the findings.
The article was supplemented with the phrase: «The disadvantage of the investigated Cr-Mn-N steel is the high Young's modulus, the value of which is almost two times greater than that of the Ti-6Al-4V alloy and more than three times above that of human bone tissues.»
- The authors mention, "Such dispersed CrN particles were distributed in interlayers between twins (Fig. 3c)". Unfortunately, they are not visible in the image. What is the point of posting an image if we cannot see what is mentioned in the comment?
Fig. 3c Darkfield image in the (00)CrN reflection shows dispersed CrN particles (а scattering of glowing dots).
On behalf of the co-authors, I would like to thank you for your thorough review of the article.
Best regards,
Natalia Narkevich/
Author Response File: Author Response.pdf
Reviewer 3 Report
Dear Authors,
first of all, I would like to thank you for submitting your manuscript to the Metals journal.
The manuscript deals with the study of 17%Cr-19%Mn-0.53%N high-nitrogen austenitic stainless steel modified by mechanical-thermal treatment (MTT) consisted of friction and subsequent electron beam processing. It was found that the microstructure of such produced near-surface layer with thickness of 25 um and average grain size of 3 um was reinforced with CrN and Fe2N nanoparticles as well. Compared to commercially used Ti-6Al-4V alloy, increase in yield strength and wear resistance was documented.
The introduction is clear and provides sufficient theoretical background. All references used in the manuscript are relevant. The most methods used during the experimental work are described adequately and in detail. The structure of the experiment is defined in logical sequence. The results are clearly presented. Authors carried out suitable experimental techniques.
In addition, the topic of the manuscript seems to be very interesting and industrially very important because it has a direct practical application in the orthopedy sector for production of implants.
Based on above, I have only few additional questions, or suggestions for improvements. So, I recommend publishing the article after the minor revision.
Line 60 - Was the chemical composition in Tab. 1 measured by some spectroscopic method, or it is just given from a standard? If it is given from a standard, please give the standard number.
Line 66 – There is written that the first step of surface processing was sliding of the ball. What was the character of sliding? Was there applied some pattern of ball sliding on the surface (lines, or circles)? Was processed entire surface of the steel? What was the width of the sliding track and how many sliding tracks were performed on the steel surface, what was the distance between individual sliding tracks? Did they overlap? Maybe, it could be helpful to add the scheme of sliding pattern to the part Materials and Methods.
Line 71 – What means the abbreviation Pam? It is a pressure unit. But what means the letter “m” there?
Line 119 – I recommend adding legend to the of orientational microscopy figure. The orientation of individual grains is not clear. What was the step size during the EBSD analysis?
Line 205 – I would recommend smoothing the lines of friction of coefficient (COF).
Line 236 – the depths of indents during microhardness testing is given in micrometres, but the x-axis in Fig. 7 is in mm. I recommend using the same units of depth.
Best regards
Author Response
- Line 60 - Was the chemical composition in Tab. 1 measured by some spectroscopic method, or it is just given from a standard? If it is given from a standard, please give the standard number.
Samples of the smelted steel were transferred to the laboratory of the metallurgical enterprise to determine the chemical composition by titration. This method gives more accurate results than spectroscopy and the results were consistent with the Fe-Cr-Mn-N phase diagram.
- Line 66 – There is written that the first step of surface processing was sliding of the ball. What was the character of sliding? Was there applied some pattern of ball sliding on the surface (lines, or circles)? Was processed entire surface of the steel? What was the width of the sliding track and how many sliding tracks were performed on the steel surface, what was the distance between individual sliding tracks? Did they overlap? Maybe, it could be helpful to add the scheme of sliding pattern to the part Materials and Methods.
The part Materials and Method added: «The first one was friction processing, in which the surface layer was deformed with a ball 4 mm in diameter from the 94%WC-6%Co hard alloy, sliding along a linear path under a load of 70 N at a speed of 40 mm/s The reverse movement of the ball was performed without loading. The repeated treatment was performed in the same way. The alternation of a twofold sliding with a transverse displacement by 0.2 mm allowed us to treat the entire surface of the steel plate».
- Line 71 – What means the abbreviation Pam? It is a pressure unit. But what means the letter “m” there?
Thank you for the noticed oversight 0.1 Pa (Pascal).
- Line 119 – I recommend adding legend to the of orientational microscopy figure. The orientation of individual grains is not clear. What was the step size during the EBSD analysis?
Text added: «Step size of the scanning was 0.5 m. The color inset shows only the grain size, but not the misorientation.
- Line 205 – I would recommend smoothing the lines of friction of coefficient (COF).
Figure 5 shows the frictional behavior of materials. I believe that these charts should not be smoothed.
- Line 236 – the depths of indents during microhardness testing is given in micrometres, but the x-axis in Fig. 7 is in mm. I recommend using the same units of depth.
Thank you for the noticed oversight. Bug fixed: x-axis in fig. 7 is in µm.
I thank the referee for a positive assessment of our work, useful comments, and pointing out obvious errors.
On behalf of all contributors
Nanalia Narkevich
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Accept in present form
Moderate editing of English language required
