Effect of Temperature and Sliding Velocity on the Dry Sliding Wear Mechanisms of Boron Modified Ti-6Al-4V Alloys
Round 1
Reviewer 1 Report
This manuscript explores the effect of temperature and sliding velocity on the dry sliding wear mechanisms of Boron modified Ti-6Al-4V alloys by pin-on-disc experiments with the pin being Ti64 alloy and the EN31 steel disc. The wear results in the article are comprehensive, however, there are still some problems in each part of the paper. Specific comments are given below:
1. Line 123 : “The volume fraction of the TiB,size of α laths, and prior β grain size obtained from the Figure 1 are consistent with the literature studies”, What is the volume fraction of the TiB,size of α laths, and prior β grain size in this manuscript? The specific values should be mentioned.
2. Line 131: The description about “Boron has a good solubility in the liquid Ti” is confused.
3. Line 159 : “An increase in temperature leads to a reduction in the width of the asperities” The discription about the width of the asperities is strange.
4. Line 164 :”debonding of TiB particles” Apart from the SEM image, more evidence is needed to prove the existence of TiB particles.
5. Line 183: “no noticeable oxide peaks are present on the samples tested at 2 m/s” This phenomenon is unexpected, because there are oxide peaks at 1 m/s and 4 m/s. Is there any explanation for this phenomenon?
6. Figure 3,4,5 : Many labeled features are unconvincing, such as the oxidation wear feature in Figure. 3(b). The second verification is recommended.
7. Figure 6 : TiO2 is marked between the two strongest peaks in the third image. Is it a peak? The first image also has this phenomenon, why not be marked? Has the XRD result of the second image been smoothed?
8. Line 278-280 : “Under vacuum, the tendency of adhesion wear increases further due to the “stick and slip” phenomenon while under ambient atmosphere, the oxide layer prevents adhesion wear.” The description is not closely related to the manuscript.
9. Line 272-285 : Many theoretical descriptions in this part are not combined with the experiment result in the manuscript. Many description is not characteristic.
10. Line 283-285 : The causal relationship is unreasonable. The characteristics of abrasive wear and adhesive wear can also be observed in other SEM images of different speed. Are these abrasive wear also caused by adhesive wear?
11. Line 286-303:The delamination phenomenon in Figure. 4 is not obvious actually, but too much theoretical analysis about delamination has been discussed. The description about cracks and voids can not support the experimental results. “The higher value of R z recorded in the profilometry images also demonstrates severe wear due to delamination.” This conclusion is confused.
12. Line 311-312: “ The titanium oxide layer is unstable and ...” More analysises are needed to explain this conclusion.
13. Line 317-321: It’s unnecessary to describe too much other research results at this part.
14. 4.1 Effect of sliding speed and temperature on the wear mechanisms and η : Other speeds also have wear results about high temperature, why only the results of speed 5 m/s are analyzed? A general key conclusion about effect of slidng speed and temperature is lacking here.
15. Line 337-330: The presence about TiO2 and Fe2O3 indicate the existence of MML is implausible.
16. 4.2. Tribo-layer and its effect on wear behavior of Ti alloys: The analysis of other experimental results occupies a large amount of space in this section, while the analysis of this experiment is less. Moreover, the quoted conclusions have less correlation with the experimental results.
17. Line 401 : “TiO layer” is confused.
18. 5.Conclusions :The conclusion of the manuscript is just a simple summary of the experimental results, rather than the key information obtained from the experimental results.
Author Response
Dear Reviewer, We would like to thank you for the thorough review of the manuscript and for constructively criticizing the work. We really appreciate your comments and we believe that the quality of the manuscript is enhanced after incorporating your comments.
Author Response File: 
Author Response.docx
Reviewer 2 Report
It is an original research paper dealing with ‘Effect of temperature and sliding velocity on the dry sliding wear mechanisms of Boron modified Ti-6Al-4V alloys’. It is quite well organized and its language is very satisfactory.
However, there are some issues which is better addressed, prior to acceptance for publication.
For instance, the subsection title: ‘3.1. Microstructure changes due to B addition’ is better modified as follows: ‘3.1. Microstructural changes due to B addition’. or something is like that.
Similarly, the subsection title: ‘4.2. Tribo-layer and its effect on wear behavior of Ti alloys’ is too general, i.e. not specific. Thus, it should be better formulated differently.
Similarly, the following sentence in Conclusion section: ‘At highest s (= 4 m/s), While the increase in s from 2 to 4 m/s causes an increase in η in a few cases and a decrease in other cases depending on the temperature and composition suggesting that multiple factors govern the wear behavior of these alloys.’ is better modified as follows: ‘At highest s (= 4 m/s), while the increase in s from 2 to 4 m/s causes an increase in η in a few cases and a decrease in other cases depending on the temperature and composition suggesting that multiple factors govern the wear behavior of these alloys.’.
Thus, the language of the manuscript should be polished.
In addition, the discussion of the existing literature on Ti-alloys is not sufficient, therefore the following sentence in Introduction Section: ‘Titanium containing 6 wt% Aluminium and 4 wt% Vanadium (also referred to as Ti6Al4V or Ti64 alloy) is a workhorse of Ti alloys because of its superior mechanical properties (e.g., yield strength, fracture toughness, fatigue and creep resistance) and hence extensively used in aerospace, biomedical, and automotive industries [1].’ should be better re-written as follows: ‘Titanium containing 6 wt% Aluminium and 4 wt% Vanadium (also referred to as Ti6Al4V or Ti64 alloy) is a workhorse of Ti alloys because of its superior mechanical properties (e.g., yield strength, fracture toughness, fatigue and creep resistance) [1]. Hence, it is extensively used in aerospace, biomedical, and automotive industries like other commercial Ti-alloys [1-8].’ and some related papers discussing properties and application areas of Ti-alloys should be cited, such as the following:
2. Han J., Zhang G.-Y., Chen X.-Y., Liu B., Cai Y.-C., Zhang X., Tian, Y.-B. Fabrication and study of innovative Ni-added Ti–6Al–4V through directed energy deposition. Materials Science & Engineering A 2022, 856, 143946, doi: 10.1016/j.msea.2022.143946.
3. Yang Z.-Y., Wen F.-M., Sun Q., Chai L.-J., Ma X.-K., Zhu M.H. Strength-ductility improvement achieved by introducing heterostructured martensite in a Ti-6Al-4 V alloy, Materials Characterization 2022, 192, 112230, doi: 10.1016/j.matchar.2022.112230.
4. Cam G., Ipekoglu G., Bohm K.-H., Kocak M. Investigation into the microstructure and mechanical properties of diffusion bonded TiAl alloys. J. Mater. Sci. 2006, 41 (16), 5273-5282, doi:10.1007/s10853-006-0292-4.
5. Cam G., Clemens H., Gerling R., Kocak M. Diffusion bonding of fine grained gamma-TiAl sheets. Z. Metallkd. 1999, 90 (4), 284-288.
6. Polishetty A., Nomani J., Littlefair G. Effect of transus based heat treatment on material characterization of wrought and additive titanium alloy Ti-6Al-4 V. Materials Today: Proceedings 2022, 59, 1749-1753, doi:10.1016/j.matpr.2022.04.332.
The rest of the reference numbers in the original submission, starting from [2], should be altered accordingly.
Apart from these issues the manuscript seems OK.
Author Response
We would like to thank the reviewer for appreciating the work and finding it suitable for publication. Also suggesting a few important and relevant references on the work.
Author Response File: Author Response.docx
Reviewer 3 Report
This work focuses on the wear mechanisms of a Ti-based alloy, to which boron was also added. The article is well-written and gives a good impression. It was carefully prepared and the material is presented logically. The effect of added boron was found to be different under different wear test conditions, which gives this work both scientific/practical value and originality. The microstructural analysis of the alloys after tests is very thorough. I am convinced that ths work deserves publicaton and has a potential to be cited.
Author Response
We sincerely appreciate the reviewer's comments for finding the manuscript suitable for publication.
Author Response File: Author Response.docx
Round 2
Reviewer 1 Report
Most of the comments were well answered and the manuscript has been improved, however, the discussion of Section 4.1 still needs to be modified further. The title of the article is "Effect of temperature and sliding velocity on the dry sliding wear mechanisms of Boron modified Ti-6Al-4V alloys ", so temperature and sliding velocity are key points the author would like to discuss in depth. The two variables are mixed together in the discussion, so the logic in Section 4.1 is confusing. It is suggested to adjust and modify the writing logic. There are also some details that still need to be worked out:
About comments 15: In the wear process, the generation of oxide is reasonable, but the generated oxide does not necessarily form a mechanical mixed layer (MML). If just a small amount of oxide, MML will not be exist. This sentence is not rigorous enough.
4.1 Section: The description logic of the two variables (temperature and sliding velocity) in Section 4.1 is not clear. To explore the effect of sliding velocity variation, the temperature did not remain consistent when comparing the results of experiments. If the two variables change at the same time, is the experiment result influenced by temperature or sliding velocity?
Line 260 and Line 264-265：This front part talks about low temperature and low speed, but the later description “Therefore, the wear surface features presented in Figures 3a, b, and c...” is not completely consistent with the front part. The Figure b belongs to high temperature condition.
5.Conclusions: A summary of high temperatures have been added, but the general key conclusion about effect of sliding velocity is still lacking here. The conclusion of the manuscript should be closely related to the topic.
Author Response
Dear Reviewer, We would like to thank you for critically reviewing the manuscript. Your comments have not only improved the quality of the manuscript but also provided more insight to extend the work further. We sincerely appreciate it
Author Response File: Author Response.docx
