Microstructure, Hardness, and Tensile Properties of Vacuum Carburizing Gear Steel
Round 1
Reviewer 1 Report
The reviewer comments of the paper «Microstructure, hardness and tensile properties of vacuum carburizing gear steel»
- Reviewer
The authors presented an article «Microstructure, hardness and tensile properties of vacuum carburizing gear steel». Reviewed article is very interesting and write at good scientific level. However, there are several points in the article that require further explanation.
Comment 1:
The introduction is well written. However, after the purpose of the article, describe briefly what has been done in each section of the article.
Comment 2:
Give all devices used in the article in parentheses (manufacturer, city, country).
Redraw figure 1. The centerline has shifted. Also, increase the resolution.
Also need to improve figures 3, 4, 5, 6, 7, 8, 9, 10. Increase the resolution of these figures.
Are all the formulas in the article original? If not, show the relevant citations.
Are all the formulas in the article original? If not, show the relevant citations. In formula 5 it is better to use formula editor instead of exp.
Comment 3:
Add to the nomenclature section all chemical elements found in the text of the article, for example:
Mn Manganese
etc.
Comment 4:
The reference list must be drawn up in accordance with the MDPI requirements.
The article is interesting and written at a good scientific level. Authors should carefully study the comments and make improvements to the article step by step. After changes can an article be considered for publication in the "Metals".
Author Response
Thank you for your comments, Please see the response in the following file.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The current study investigates the effect of austenitizing temperature on several properties of steel at elevated temperatures followed by quenching and tempering processes. Evaluated properties include hardness and tensile properties. The authors report that the fracture is premature when the austenitizing temperature is increased however hardness was similar. The highest fracture occurred at the lower level of temperature used for austenitizing due to fine microstructure and retained austenite changing to martensite. Austenitizing temperature increase did not seem to have any effect on the strain hardening, finally the authors claim that among the austenitizing temperature tested, 840 C is most suitable austenitizing temperature for optimal properties of the analysed steel material
Line 33 needs a reference
Line 65 avoid using bulk citations without giving them full credit, i.e. discuss what they have done, what were their main findings and how is your different from them and how does your current study brings new knowledge to the field
Table 1 needs referencing
Which standard was used to test the specimens?
Line 129-134 the authors needs to provide proper explanation for why this phenomena is observed with change of temperature, what did past studied report on similar studies, did the temperature rise had any influence or not, why so, and also is it because temperature change is small (less than 100 Celsius for example?
Line 167-169 the authors should try and support this with references or report what previous studies found and compare it with their own results.
Line 166-169 needs rephrasing please check
How many times was the hardness measured and at which locations in the specimens
Line 178 varied slightly (please add values here, add the range to be more clear)
Line 178 explain this slight variation in hardness, is it due to operator error or something else?
Have the authors tried using higher temperatures to see if this might have an influence on the hardness values?
Line 196-197 why this, please explain this observation.
Line 205-207 please support this claim/conclusion with references from previous studies if possible
Figure 5 needs some arrows or text to tell the reader what to look for in them
Line 242 lease explain why brittle fracture occurs here and support with references if possible
Looking at table 3 it is odd to see that tensile elongation is best at 820 Celsius, how many times was each test repeated? It could be error in the machine or operator or setup, have the authors checked for these issue?
Author Response
Thank you for your comments, Please see the response in the following file.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The authors have improved the article according to the comments. The article can be published. However, there is a problem with Figure 1 that is important to solve at the stage of editing.
Author Response
Thank you for your comments, We have changed the Manuscript.
Author Response File: Author Response.pdf
Reviewer 2 Report
Authors have not answered many of the questions in first review properly. this has to be addressed again and provide sufficent answers.
For example Table 1 needs a reference on the table caption
many of the answers are very short and seems the authors did not make effort to provide sufficent justification or explanation.
Looking at table 3 it is odd to see that tensile elongation is best at 820 Celsius, how many
times was each test repeated? It could be error in the machine or operator or setup, have the authors checked for these issue?
the authors did not answer this questions:
Line 166-169 needs rephrasing please check
The authors appear not to have checked all questions carefully and therefore, can not be accepted.
Line 178 explain this slight variation in hardness, is it due to operator error or something
else?
Author Response
Sorry about that. This time the authors have checked all the questions carefully.
Author Response File: Author Response.pdf
Round 3
Reviewer 2 Report
Authors have answered all comments
This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.
Round 1
Reviewer 1 Report
Thanks for the manuscript!
The aim of the presented research is to investigate the microstructure and tensile properties of case-hardened gear steel after vacuum carburization and re-austenitization to 820 - 900 ° C, followed by oil quenching and tempering.
The subject of the research is within the scope of the journal and it is worthy of investigation. The manuscript is interesting for readers and other researchers. Its novelty is ensured by the researched materials and the applied approach. I found there all the necessary information related to the research and the evaluation of the results. I rate the article positively, but some formal improvements need to be made before publishing the manuscript. These are:
- Page 2 – It is more appropriate to use „wt. %“ in the title of Table 1 (instead of „mass%“).
- Page 2 – Figure 1 - from a technical point of view, the axis is missing because it is a cylindrical type of sample.
- - Please check ... in some cases, there is no blank space between the number and the unit (eg page 3, line 90 "(1.96N)"; ... page 11, line 290 - "γis" ... etc.)
- Figure 3 – please, provide a detailed view on emphasised area, minimally at Fig. 3c
- Please, unify the header of Table 2 – add a description for „Ms“ similar to other parameters.
- Equation (3) - please, use the same type of text style as for equations (1) and (2)
- Page 9, line 227 – correct „Tynestudied“ ...
- Figure 8 – there is a confusing label of individual images - probably the label has been shifted relative to the images themselves.
- Page 11, Equation (4) – for the fracture stress, use the same designation in the equation and also in the explanation below the equation (with regard to the subscript).
- Page 12, line 301 – below equation (5) – I think there should be f0 and fγ.
- Page 12, line 307 – improve spelling „austneitized“.
- In the conclusions, based on the results of the presented research, the authors should provide practical advice for users of the given type of steel and its processing, which would be focused on real practice.
Reviewer 2 Report
Dear authors,
many thanks for submitting your manuscript to the journal Metals.
The topic is generally of interest to the readership, but the novelty of your results is low and some of the conclusions seem scientifically questionable.
You state that vacuum carburising may result in coarse grain size when high carburizing temperatures are applied. But, you did apply the very common temperature of 930°C. You discuss your findings in mechanical properties in very close detail, but you did not discuss the accuracy of your measurements and the expected large scatter in brittle materials at all. The reason for the intergranular fracture remain unclear as you did not discuss the most common cause for that phenomenon - grain boundary segregation - at all.
In general, there remain doubts whether any new information on the behaviour of case hardening steels can be drawn from these experimental results.
Reviewer 3 Report
The reviewer comments of the paper «Effect of austenitizing temperature on microstructure and tensile properties of vacuum carburizing gear steel»
- Reviewer
The authors presented an article «Effect of austenitizing temperature on microstructure and tensile properties of vacuum carburizing gear steel». However, there are several points in the article that require further explanation.
Comment 1:
The introduction is not convincing enough.
Try to reinforce the relevance of your research. It is important to more clearly define why they chose hardening steel 16CrMnH for research. Are there any foreign analogues of this steel? Why is this steel important for wheels?
It is necessary to more clearly define the "white spots". That has not been previously investigated by other scientists. Now the stated purpose of the article does not have sufficient validity.
It will be helpful to add an article: DOI: 10.3390/ma13225059
However, at the end of the article, list briefly what has been done in each section of the article.
Now, both in the purpose of the article, abstract and in the title, nothing is said about measuring hardness. This must be taken into account.
Comment 2:
- Experimental
Give vacuum carburizing furnace - what brand? (Manufacturer, city, country). Likewise for all instruments used in research.
Show in Figure 1 the roughness of the surfaces. If you want to show the centering holes, it is best to do this with a local cut. It is necessary to complete a sketch in accordance with a unified system for design documentation.
Comment 3:
- Result and Discussion
The quality of Figures 3 and 5 needs to be improved.
It would be useful to show a diagram of phase transformations. And show compliance with Figure 3.
All abbreviations encountered for the first time in the text should be explained. For example, "scanning electron microscope (SEM)". What is XRD, etc.?
Figure 4, 5, 6 should explain what 820, 840, etc. are. Possibly in the caption. To make the curves more obvious it is useful to change the HV scale from 300 to 800. Thus, redraw figure 4.
Why does Figure 5 only cover (a) 820, (b) 840 ℃? It is useful to show the full range of temperatures.
Explain in the text what is the difference between Engineering and True for Figures 5 and 6. This must be clearly explained to the reader in the text of the article. What is the difference between specimen or any conditions for these figures?
Redraw these figures in a single scale: stress (0 ... 2000), strain (0 ... 0.030).
What are the letters in Figure 8? It needs to be adjusted.
Comment 4:
It will be useful to add a section of Nomenclature in which to sign all the physical quantities and abbreviations encountered in the article. There are many physical quantities in the text and such a section will help to find the description of the necessary element.
For example,
E : Elasticity modulus,
MVC : Microvoid coalescence
etc.
Comment 5:
Conclusions.
In addition, it is necessary to more clearly show the novelty of the article and the advantages of the proposed method. What is the difference from previous work in this area? Show practical relevance. Conclusions should reflect the purpose of the article.
The article is interesting. Authors should carefully study the comments and make improvements to the article step by step. After major changes can an article be considered for publication in the "Metals".
