The Influence of the Highly Concentrated Energy Treatments on the Structure and Properties of Medium Carbon Steel

Round 1

Reviewer 1 Report

This paper describes the effects of combination of electromechanical and ultrasonic treatment on the wear and corrosion behavior of carbon steel AISI 1045. The results shown the surface of carbon steel AISI 1045 had be improved by hardening the surface.

Some suggestions as follow:

1. The author describes “Under the influence of the contact pressure, the material of the surface layer was squeezed out from under the roller. The wavy structure of the surface was formed” and “There is no wavy structure after finishing the surface by means of UT”. The UT is secondary processing so it can improve or eliminate wavy structure. The author can only using ultrasonic treat AISI 1045 maybe find different results.
2. The electric current of EMA and ultrasonic output power affect the surface temperature of the heated material. The temperature at which the surface of the material is heated and the cooling rate affect the changes in the surface structure and hardness of the material. The author only used density of the electric current 400 A/mm2 in EMA, and ultrasonic generator with a power output of 0.3 kW and a frequency of 21.6 kHz, experiments with only two fixed parameters are not complete enough. Suggestion, change the current density and ultrasonic power to obtain different experimental results.
3.  Contact force is also an important experimental parameter. Suggestion, the author use different contact force maybe can find different experimental results on improve material surface.

Author Response

Metals

“The influence of the highly concentrated energy treatments on the structure and properties of medium carbon steel”.

Dear Editor and Reviewers,

Thank you for your useful comments and suggestions on the structure of our manuscript.

Reviewer #1:

1. The author describes “Under the influence of the contact pressure, the material of the surface layer was squeezed out from under the roller. The wavy structure of the surface was formed” and “There is no wavy structure after finishing the surface by means of UT”. The UT is secondary processing so it can improve or eliminate wavy structure. The author can only using ultrasonic treat AISI 1045 maybe find different results.

The works on surface hardening in the process of ultrasonic treatment are carried out, the equipment is serially produced (http://en.utinlab.ru/articles/abrasive-free-ultrasonic-finishing-of-metals-bufo-pulse-ultrasonic-reinforcing-finishing). But the thickness of the hardened layer after only ultrasound treatment is about 100 microns, which is not enough to increase the wear resistance of the product surface. Hence, the EMT is used to increase the thickness of the hardened layer. The similar is described in the article [D. Lesyk, S. Martinez, B. Mordyuk, V. Dzhemelinskyi, А. Lamikiz, G. Prokopenko, Y.V. Milman, K. Grinkevych, Microstructure related enhancement in wear resistance of tool steel AISI D2 by applying laser heat treatment followed by ultrasonic impact treatment, Surf. Coat. Technol., 328 (2017) 344–354. This article investigates the combined effect of laser and ultrasonic treatment on increasing the wear resistance of the steel surface.

The laser treatment requires the use of expensive equipment. Replacing laser technology with the EMT reduces production costs, as the equipment for the EMT is cheaper. The corrosion resistance of the AISI 1045 steel surface increased after the combined treatment. This is the novelty of our work.

We modified the introduction and added a reference to the new article, which was published in the journal Surface and Coatings Technology  [D.A. Lesyk, B.N. Mordyuk, S. Martinez, M.O. Iefimov, V.V. Dzhemelinskyi, Рђ. Lamikiz,Influence of combined laser heat treatment and ultrasonic impact treatment on microstructure and corrosion behavior of AISI 1045 steel,Surface and Coatings Technology,Volume 401,2020, 126275.]. This article investigates the combined effect of laser and ultrasonic treatment on increasing the corrosion resistance of the AISI 1045 steel surface. For this reason, our research is relevant and will be of interest to readers who work in the field of surface engineering.

 

Line 82: Recently, Lesyk et al. [26] studied the combined process of the laser surface hardening and the ultrasonic impact treatment. The highest corrosion resistance enhancement was observed after the combined treatment.

The purpose of this work is the estimate the influence of the combination of the treatments (EMT+UT) on the structure and on the wear and corrosion behavior of AISI 1045 medium carbon steel.

 

2. The electric current of EMA and ultrasonic output power affect the surface temperature of the heated material. The temperature at which the surface of the material is heated and the cooling rate affect the changes in the surface structure and hardness of the material. The author only used density of the electric current 400 A/mm2 in EMA, and ultrasonic generator with a power output of 0.3 kW and a frequency of 21.6 kHz, experiments with only two fixed parameters are not complete enough. Suggestion, change the current density and ultrasonic power to obtain different experimental results.

In other our articles we have already evaluated the effect of current density, linear speed, feed rate, and contact force with different parameters. Therefore, the optimal of them were determined earlier. N.G. Dudkina, I.N. Zakharov, V.S. Ermolov, A. Yu. Ivannikov. Dependence of microhardness of a regular discrete structures of the surface layer of a mild steel on the conditions of electromechanical treatment Probl. Mashinostr. Nadezhn. Mashin, 5, (2006)  pp. 62-68. (in Russian). So the purpose of this work was to study the surface structure, corrosion rate and wear rate of AISI 1045 steel in comparison with the effect of the EMT and the combined treatment (EMT + UT).

We modified the part “2.2. The Electromechanical Treatment”.

 

3. Contact force is also an important experimental parameter. Suggestion, the author use different contact force maybe can find different experimental results on improve material surface.

Yes, you are right. Previously, we studied the effect of loading on surface hardening of AISI 1045 steel during the EMT process. It was determined that load increase leads to increase of surface waviness. This can be used to restore the geometric dimensions of a piece after wear. But in this study, our goal was to study the structure of the white layer after the EMT using high resolution electron microscopy. Previously, there were no such results in works on the EMT processing of steels. The main highlight of the article is the study of the effect of the combined effect of the EMT and the UT on the corrosion rate of the surface of AISI 1045 steel.

Reviewer 2 Report

The authors have prepared understandable and clear paper. As a reviewer I find this topic scientifically relevant and the work itself interesting and valuable. My reservation is that authors completely neglected the effect of treatment on the surface roughness. Authors should include roughness measurements before and after each treatment. Each process changes the topography, which can also have significant impact on both wear and corrosion properties.

Does EMT and UT have influence on geometry change of treated surface? On figure 6c it can be seen that treated layer after EMT + UT is less thick than only  EMT (figure 6b).

Machining tolerances on the figure 1 are quite strict (32 -0,06 -0,085). Was influence of EMT and UT on geometry taken into the account? As it is stated WEL is 250 ± 25 µm, where difference of 25 µm is close to the tolerance limit. If ENT and UT significantly influence on geometry change this could also have influence on wear test. Please address this issue.

 

Additional remarks:

Test sample is firstly denoted as bearing (page 3 line 96) and later on as bush (page5 line 157). Please unify denotation.

Author Response

Metals

“The influence of the highly concentrated energy treatments on the structure and properties of medium carbon steel”.

Dear Editor and Reviewers,

Thank you for your useful comments and suggestions on the structure of our manuscript.

Reviewer #2:

 

1. The authors have prepared understandable and clear paper. As a reviewer I find this topic scientifically relevant and the work itself interesting and valuable. My reservation is that authors completely neglected the effect of treatment on the surface roughness. Authors should include roughness measurements before and after each treatment. Each process changes the topography, which can also have significant impact on both wear and corrosion properties.

Thanks for your helpful comments.

We modified the text of the manuscript and wrote more about the effect of the surface roughness on the wear rate.

 

2. Does EMT and UT have influence on geometry change of treated surface? On figure 6c it can be seen that treated layer after EMT + UT is less thick than only  EMT (figure 6b).

We modified the part “2.4. Analysis of Surface”.

Measurements of roughness, depth of the WEL, and effective grain size were made with the image analyzer, having software of VideoTest Structure 4.0 (VideoTest OOO, St. Petersburg, Russia).

 

The measurement of the average depth of the WEL has been updated.

Line 213: The average depth of the WEL is 240 ± 20 µm.

The measurement of the average depth of the WEL was carried out and discussed.

Line 224: The average depth of the WEL after the additional UT was 210 ± 10 µm. During the UT the surface layer was heated, for this reason, the average depth of the WEL decreased.

3. Machining tolerances on the figure 1 are quite strict (32 -0,06 -0,085). Was influence of EMT and UT on geometry taken into the account? As it is stated WEL is 250 ± 25 µm, where difference of 25 µm is close to the tolerance limit. If ENT and UT significantly influence on geometry change this could also have influence on wear test. Please address this issue.

The diameter of the specimens after the EMT increased from 20 to 40 µm, because the wavy structure was formed. The inner diameter of the conterfaces was more than the outside diameter of the test specimens after the EMT. For this reason, the specimens after the EMT could be used in the wear test.

4. Additional remarks:

Test sample is firstly denoted as bearing (page 3 line 96) and later on as bush (page5 line 157). Please unify denotation.

We modified the capture of the figure 4.

Line 177: Test principle: Bearing is radially loaded against shaft

Reviewer 3 Report

Dear authors, 

Thanks for sharing you work with the rest of the community.

The paper describes appropriately the response of Aisi 1045 to high energy surface modification (EMT and EMT + UT) , in terms of the obtained microstructure, hardness, wear resistance and corrosión resistance. 

The materials and methods are properly described so that other research groups may reproduce them. Explanations are clear and the paper is easy to read. It would be welcome the Figures to have a better resolution. 

On the more specific comments:

Line 126. Could you asses the importance of the water in the quenching of the WET? Were was the water jet directed to? 

 

Line 159. Is pressure calculated by Hertzian contact equations? 

 

Figure 6. Could you please note the names for the numbers in the text?  Is it that there is more perlite in EMT and EMT + UT? If so, was it produced by the surface conditioning and how? 

 

Table 2. What dispersion descriptor are +/- values related to? 

 

Table 2. Why not use HV instead of MPa? 

 

Line 254. Previously MPa were used instead of GPa.

 

Line 263. Is there missing a Figure 8 with the COF? 

 

Could you please answer these questions in the, revised version of the text in the cases that may apply? 

 

Thanks again for your very nice work and look forward to reading the future work on fatigue behaviour.

 

Best regards

 

 

 

Author Response

Metals

“The influence of the highly concentrated energy treatments on the structure and properties of medium carbon steel”.

Dear Editor and Reviewers,

Thank you for your useful comments and suggestions on the structure of our manuscript.

Reviewer #3:

The paper describes appropriately the response of Aisi 1045 to high energy surface modification (EMT and EMT + UT) , in terms of the obtained microstructure, hardness, wear resistance and corrosión resistance. 

The materials and methods are properly described so that other research groups may reproduce them. Explanations are clear and the paper is easy to read. It would be welcome the Figures to have a better resolution. 

On the more specific comments:

1. Line 126. Could you asses the importance of the water in the quenching of the WET? Were was the water jet directed to? 

We modified the text in the part  “2.2. The Electromechanical Treatment”.

Line 120:The water jet was supplied to the point of contact between the surface of the specimen and the roller. Therefore, the surface was simultaneously cooled to accelerate the hardening process, as well as the roller was cooled to increase its resource.

 

2. Line 159. Is pressure calculated by Hertzian contact equations? 

No. We use the standard model, in which the pressure is uniform. The pressure is the ratio of the normal load to projected area. The projected area is the multiplication of the nominal diameter of shaft and the length of the bearing. (https://en.wikipedia.org/wiki/Bearing_pressure#CITEREFSG2003).

 

3. Figure 6. Could you please note the names for the numbers in the text?  Is it that there is more perlite in EMT and EMT + UT? If so, was it produced by the surface conditioning and how? 

Thank you. We modified the text.

The information about the microstructure of the numbered zone was added to the part “3.1. Macrostructure and Microstructure”.

Line 210: Fig. 6 shows optical microscopy of the cross-sections of the base metal, the electromechanically treated steel, and the electromechanically and ultrasonically treated steel. Fig. 6 a shows ferrite-pearlite structure of the AISI 1045 steel. Fig. 6 b, c recovers the white etched layer (WEL) in the surface of the cross-section after the EMT. The average depth of the WEL is 240 ± 20 µm. The heat affected zones are observed between the WELs. The heat affected zones are being formed while the roller moves longitudinally and some part of the previously fabricated WEL is heated the second time. The ferrite-pearlite structure is detected in the HAZ.

4. Table 2. What dispersion descriptor are +/- values related to? 

The table shows average values of the microhardness. The dispersion allows to estimate the maximum and the minimum values of the microhardness.

2. Table 2. Why not use HV instead of MPa? 

There is now a trend towards reporting Vickers hardness in SI units (MPa or GPa), particularly in academic papers (https://www.gordonengland.co.uk/hardness/hvconv.htm). One should divide by 9.807 to convert MPa to HV.

3. Line 254. Previously MPa were used instead of GPa.

Thank you. We modified the text.

The GPa was changed to the MPa.

4. Line 263. Is there missing a Figure 8 with the COF? 

Thank you. We modified the text.

Line 280: Spalling and delamination may cause unstable wear behavior, resulting in large fluctuation in the wear rate, as shown in Fig. 10.

Could you please answer these questions in the, revised version of the text in the cases that may apply? 

Thank you. We modified the text.

Thanks again for your very nice work and look forward to reading the future work on fatigue behaviour.

Thank you for the suggestion, such studies and the residual stress assessment are already planned.

Reviewer 4 Report

I couldnt follow the micro hardness profile as the numbers are in MPa. I dont think its common to report the hardness that way.

It would be beneficial to see what phase transformation has happened in the WEL and HAZ and corresponds that to the observed hardness. If the layer is fully martensitic with poor ductility, how does that behave under any other loading than wear?

I also didnt see the importance of hardening 1045 by this method. Is there a cost saving vs. using a conventional induction surface hardening?

Comments for author File: Comments.pdf

Author Response

Metals

“The influence of the highly concentrated energy treatments on the structure and properties of medium carbon steel”.

Dear Editor and Reviewers,

Thank you for your useful comments and suggestions on the structure of our manuscript.

Reviewer #4:

1. I couldnt follow the micro hardness profile as the numbers are in MPa. I dont think its common to report the hardness that way.

There is now a trend towards reporting Vickers hardness in SI units (MPa or GPa) particularly in academic papers (https://www.gordonengland.co.uk/hardness/hvconv.htm). One should divide by 9.807 to convert MPa to HV.

2. It would be beneficial to see what phase transformation has happened in the WEL and HAZ and corresponds that to the observed hardness. If the layer is fully martensitic with poor ductility, how does that behave under any other loading than wear?

In an earlier work we showed that the presence of the HAZ with ferrite-pearlite structure reduces the wear of the coating. During the wear test of the hardened specimen, the HAZ with the ferrite-pearlite structure is worn out first. The wear and grease products are trapped in this area and the wear rate is reduced. Therefore, the presence of the HAZ with ferritic-pearlite structure contributes to increase of surface wear resistance in comparison with the surface, which is hardened throughout the area.

3. I also didnt see the importance of hardening 1045 by this method. Is there a cost saving vs. using a conventional induction surface hardening?

The EMT allows to perform the hardening process on a lathe. Therefore, the hardening is carried out on the same equipment. There is no need to use additional rooms or equipment. In addition, the EMT allows strengthening of local areas, for example, cutter slots or fillets of shafts. It is also possible to strengthen large-sized items or items with complex geometry.The microstructure of the white layer, formed during the hardening of the EMT and the laser hardening, is the same. Therefore, the EMT can replace the laser hardening, because the cost of the equipment is several times lower. We modified the text in the part “Results and Discussion”. Line 307.

 

Round 2

Reviewer 1 Report

The author has corrected doubts in this article. Related reference materials are also added in the text. The author stated in the reply “But in this study, our goal was to study the structure of the white layer after the EMT using high resolution electron microscopy.” In this way, study the structure of the white layer after the EMT is goal. But the white layer structure has been described insufficiently. The structure variation in the EMT process, for example grain size, phase transformation ect,. It is recommended that the author supplement these analysis data.

Author Response

Thanks for your helpful comments.

We modified the part “3.1. Macrostructure and Microstructure” of the manuscript and wrote more about the structure of the white etched layer.

Line 226: In the previous study [27] the optical microscopy could not examine the structure of the WEL. In addition, the modelling of the electromechanical treatment [28] showed that the heating temperature of the surface layer was more than 1000 K. As a result, the γ-iron dissolved carbon and did so by consuming the cementite. Consequently, the austenite was formed in the surface layer. The cooling rate during the EMT process indicated that it exceeded 104 K/s, there was not enough time for the reverse transformation and the carbon could not diffuse out of its lattice. The austenite was distorted into tetragonal shape. The martensite was formed with the strained lattice. It was assumed that the martensite had grain size less than 0.5 µm and could not be examined by means of the optical microscopy.

In this study, we used high-resolution scanning electron microscopy for examination of the structure of the WEL. Fig. 7 shows the microstructure of the WEL. The lath martensite is formed after the EMT of the surface of the AISI 1045. The length of the lath is 0.50 ± 0.25 µm and the average thickness is 100 ± 25 nm. The length and the thickness of the structure in the WEL are less than 0.5 µm each. For this reason, the optical microscopy could not be used for examination of the structure of the WEL. The comparison of the structure of the WEL after the EMT and after the laser

treatment [26] showed that these types of the highly concentrated energy treatments gave the similar structure of the lath martensite in the surface layer of the AISI 1045 steel.

Reviewer 4 Report

Thanks for revising the content according to the suggestions.

Author Response

Reviewer #4:

Thanks for revising the content according to the suggestions.

Thanks for your interesting and helpful comments.

Round 3

Reviewer 1 Report

The author has corrected doubts in this article.

I accept the author's explaination