Sustainable Combined Process for Improving Surface Integrity and Fatigue Strength of Heat-Treated 42CrMo4 Steel Shafts and Axles
, Galya Duncheva 1,2,*, Angel Anchev 1,2, Vladimir Dunchev 1,2, Kalin Anastasov 2,3 and Mariana Ichkova 1
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors
Comments from Reviewer
Manuscript ID: metals-3697377-peer-review-v1
Sustainable combined process for improving surface integrity and fatigue strength of heat-treated 42CrMo4 steel shafts and axles
The current form's presentation of methods and scientific results is satisfactory for publication in the Metals journal. Some comments apply to the entire article. Please take this into account when making corrections. The minor and significant drawbacks to be addressed can be specified as follows:
Minor and major comments:
- Lines 168-171. The authors provide certain conditions. What was the reason for their use and the corresponding structures?
- Some abbreviations are explained several times in the text. It is sufficient to do it the first time: reference condition (RC) – lines 224 and 491.
- Fig. 4. Were the results shown in the figure repeated? How many times?
- Fig. 5. Is this the same area, i.e., before and after treatment? To what extent do these photos reflect the entire structure of the tested materials?
- Fig. 6. "|Phase analysis"? What technique and equipment were used to perform these measurements?
- “3.3.3. residual” ---> “3.3.3. Residual"
- Fig. 15. Did the authors investigate the surface composition of the tested materials? SEM–EDX and AFM-EDX?
- The authors should clearly define the study's objectives and indicate the elements of scientific novelty. I'm not convinced by what the authors wrote: "a sustainable combined process, including sequential dry hard turning and dry smoothing DB of the heat-treated axles and shafts made of 42CrMo4 steel (and similar)." Especially since only one material was tested? What do the authors mean by writing "and similar"? What does this similarity consist of?
Sincerely,
The reviewer.
Author Response
Please see the attached file.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe paper shows a very deep and interesting research related to the influence of heat treatment on fatigue properties and crack propagation of 42CrMo4 steel parts. During the researc,h I found the following issues:
- Please provide the aim of your work in the abstract and its background.
- Provide more information about the microstructure of the 42CrMo4 steel parts after different types of heat treatment, specifically those mentioned in the introduction.
- Provide a supplier of the material.
- Put the heat treatment parameters in a dedicated table.
- What type of device was used to determine the chemical composition of the material?
- Table 3 - What do those values in the indexes mean?
- What kind of standards have you used for the research? How does using only one sample per measurement series correspond with this standard? Such an approach makes your results unreliable...
- You showed that the increase of burnishing force leads to better surface properties, but at the same time causes a decrease in fatigue life (100N and 150N) - it is against the fatigue theory - please elaborate on this phenomenon.
- The amount of retained austenite is unrealistically high. Provide full XRD results, with e.g. phase maps.
- You used the Basquine law for megacycles, where it is inadequate. Also, please put the source of the b parameter.
- Lines 601-604 - you mentioned LCF, but there is no data of that kind of test in your article.
- The word "Element" is mostly related to chemical composition. Please use words such as "parts", components, etc.
- Figure 8 - What does the "flood" mean?
Author Response
Please see the attached file.
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe manuscript “Sustainable combined process for improving surface integrity and fatigue strength of heat-treated 42CrMo4 steel shafts and axles” addresses an actual problem related to development of surface treatment techniques for increasing fatigue durability of steel shafts and axels. To address the problem, a combined process of sequential dry hard turning and dry diamond burnishing (DB) was utilized for enlarging fatigue limit of heat-treated 42CrMo4 steel. At the first stage, an optimization of dry hard turning was carried out aimed at reducing the average roughness Ra. At the second stage, a dry DB parameters were selected from three alternative DB processes at variation of burnishing forces of 50, 100, and 150 N. It was shown that with increasing burnishing force, the average roughness decreased, while the microhardness and the surface axial residual stresses increased. However, at enlarged burnishing forces of 100 and 150 N the fatigue limit decreased. In addition, it was established that dry DB at a force of 50 N increases the rotating bending fatigue limit by 20 MPa, while the fatigue life enlarges by a factor of 70.
The state of the art is well described with the number of cited references of 36.
Experimental techniques are clearly described. The experiments might be reproduced elsewhere.
Results are clearly reported. However, there is some lack of statistics. In addition, some trends are to be added to the figures 12 and 13.
There is a discussion section that interpret obtained results with their comparison with literature data.
The conclusions clearly summarize the main outcomes of the study.
The manuscript might be accepted for the publication in the journal of metals. However, it requires a major revision. The following aspects are to addressed by the authors.
Page 1, line 31. “They are made of tough-plastic alloys”. What does this mean?
Page 1, line 35. “because the external load vector rotates 35 around the shaft (axle) axis”. What does this mean?
Page 1, line 37. “and they are exposed to the environment”. All of us are exposed to environment!
Page 1, line 40. “for more responsible shafts”. What does this mean?
Page 2, line 72. “to provide a suitable surface texture”. What does “suitable” mean?
Page 2, line 94. “DB provides a 5.66% higher fatigue limit 94 than DR”. 5% is within an error range. Is it really a significant (meaningful) difference?
Page 4, Figure 1. Specimen geometry: (a) tensile test; (b) impact toughness test. The manuscript discusses the issues of surface treatment. Impact toughness is a bulk property. How is was possible to modify the material in the notch tip?
Page 6, line 216. “complete destruction.” Destruction seems to be an incorrect term.
Page 6, line 217. “One specimen was used for each experimental point”. Is it statistically correct?
Page 7, line 258. “disintegration of austenite, respectively”. Disintegration seems to be an incorrect term.
Page 7, line 265. “greatly complicates the breakdown of martensite”. Breakdown seems to be an incorrect term.
Page 7, line 270. “The resulting structure has a lower free energy”. Did you measure it?
Page 11 Figure 7. ANOVA main effects. And what is the main effect of ANOVA?
Page 12, line 370. “However, subsequent DB dramatically improves the SI by transforming the residual axial and hoop stresses into compressive stresses of significant magnitude (up to –937 MPa for axial stresses and up to –592 MPa for hoop stresses)”. What does improve SI mean in the context of this sentence?
Page 13, Figure 12. “Residual axial stress distribution depending on the finishing”. The trends are to be added to the experimental points.
The same is related to figure 13.
Page 17, line 532. “After the destruction of the modified layer”. Destruction seems to be an incorrect term.
Because of many abbreviations, the authors are welcome to make a nomenclature.
Comments on the Quality of English LanguageEnglish language is to be improved.
Author Response
Please see the attached file.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsIn my opinion the corrected work can be accepted for publication.
Reviewer 3 Report
Comments and Suggestions for AuthorsMost of the reviewer's comments were addressed. Some concerns were just formally responded. The manuscript was just slightly modified. In fact, the manuscript might be better improved, if the comments were deeper responded.
