Features of the Formation of Surface Structures under Dry Friction of Al-30Sn Composite against Steel

Round 1

Reviewer 1 Report

This paper studied the features of the frictional interaction and friction mechanism of a sintered Al-30Sn composite according to the scheme pin-on-disk friction experiment. The work is interesting, but some descriptions are too long and readability is poor, and there are still many inappropriate sentences.

In my opinion, in the present form it cannot be accepted for publication, authors need revise the manuscript, again.

-Paragraph 2 in section 2.1: “the sintered samples were subjected to equal channel angular pressing (ECAP) with route A”, Please give the method of ECAP with route A using graphic.

- in section 2.2: Please give the tribological tests unit and experimental principle  using graphic method.

-Figure 2: This figure is compression curve, but it can’t explain some information clearly, so some other figure can be given, such as the yield strengthσ0.2 and ductility under different Al-30Sn composites handling methods, the local magnification the figure at deformation of 1-2% . Besides show the line using number of ECAP passes 0,1,2,4 directly, not 1,2,3,4.

-in section 4 discussion: I don't think this section is very logical. Paragraph 2-9 is redundant and not closely related to the content of the study in my opinion. Some content cuts are suggested. Besides, give some sections according to the content discussed to make this paper more logical and readable.

-Figure 7: The image of the friction track surface should be given separately.

-Figur9 and Figure 10: I suggest the drawing statements are the same as the abscissa in Fig.7, using sliding distance.

-in section 5: “The effect of tin as a solid lubricant on the process of frictional interaction of the investigated friction pair during the stage of steady state friction is insignificant. As a result, the value of friction force between the coupled bodies is high and depends on the structure of the discrete transferred layer.”  Whether the effect is related content of Sn? Because this opinion was also mentioned in paragraph 6 in section 1.

Author Response

The text of the manuscript has been significantly shortened and revised.

 

1. [Paragraph 2 in section 2.1: “the sintered samples were subjected to equal channel angular pressing (ECAP) with route A”, Please give the method of ECAP with route A using graphic.] Equal channel angular pressing is a well-known method used to harden and change the structure of various materials. The routes of its implementation are described in detail by many authors. Therefore, we think that it should not be presented as an illustration. When describing it, we provided several references, including our work, which presents in detail the scheme of ECAP with route A implementation.

 

2. [in section 2.2: Please give the tribological tests unit and experimental principle using graphic method.]

An image of the testing scheme has been added.

 

3. [Figure 2: This figure is compression curve, but it can’t explain some information clearly, so some other figure can be given, such as the yield strengthσ0.2 and ductility under different Al-30Sn composites handling methods, the local magnification the figure at deformation of 1-2% . Besides show the line using number of ECAP passes 0,1,2,4 directly, not 1,2,3,4.]

The flow stress values of the investigated composites at different strains (σ_0.2 and σ₄₎ have been added to Table 1. The necessary information about the number of ECAP passes has been added In Figure 3 and the text of the manuscript.

 

4. [in section 4 discussion: I don't think this section is very logical. Paragraph 2-9 is redundant and not closely related to the content of the study in my opinion. Some content cuts are suggested. Besides, give some sections according to the content discussed to make this paper more logical and readable.]

The section 4 “Discussion” has been significantly modified.

 

5. [-Figure 7: The image of the friction track surface should be given separately.]

The necessary edits have been made to this Figure.

 

6. [-Figure 9 and Figure 10: I suggest the drawing statements are the same as the abscissa in Fig.7, using sliding distance.]

Captions for these Figures have been corrected.

 

7. [-in section 5: “The effect of tin as a solid lubricant on the process of frictional interaction of the investigated friction pair during the stage of steady state friction is insignificant. As a result, the value of friction force between the coupled bodies is high and depends on the structure of the discrete transferred layer.” Whether the effect is related content of Sn? Because this opinion was also mentioned in paragraph 6 in section 1.]

The tin content in the studied material was deliberately chosen to be high (30 wt.% or about 15 vol.%), which exceeds its content in industrial alloys. In this paper, tin as a lubricant is shown to be ineffective under the dry friction of the composite against steel at a pressure of 1 MPa. At the same time, we do not deny its positive effect in increasing the wear resistance of aluminum alloys under dry friction conditions, since it contributes to the plasticization of the surface layers of aluminum-tin alloys.

Reviewer 2 Report

The manuscript describes, “Features of the Formation of Surface Structures Under Dry Friction of Al-30Sn Composite Against Steel” which is suitable for Journal of Coating. Anyhow, the reviewer would like to make the following comments

 1- How did the authors morphology of aluminium and tin in the sentences “Moreover, the tin inclusions and aluminum grains matrix have the flattened shape in the shear plane of the sample after ECAP with route”

2- How has the cross section of samples been prepared? Need more details
3- The reference values for etching solutions are missing and the sliding distance of tribology tests are missing.
4- The authors assumed that the friction coefficient is constant due to properties and composition of the friction surfaces that are not changed during the measuring. By hypothesis, how to control the oxidation reaction during the wear test as the local temperature increased sharply.
5- It is vague. ‘If the sliding distance is large enough’ what do you mean large enough? How much distance is large enough
6- How did you calculate the %mass of elements in the samples (table 2)?
7- The authors stated that increase in the ductility and strengthening of Al-30Sn composite are due to removal of the structural defects. So, I recommend that the density value of the samples should be calculated.
8- I could not find any hardness value of samples.

 

Author Response

1. [How did the authors morphology of aluminium and tin in the sentences “Moreover, the tin inclusions and aluminum grains matrix have the flattened shape in the shear plane of the sample after ECAP with route”]

This section in the text of the manuscript has been modified.

 

2. [How has the cross section of samples been prepared? Need more details]

The cross sections plane was chosen in the central part of the samples to avoid the presence of surface defects. This information has been added.

 

3. [The reference values for etching solutions are missing and the sliding distance of tribology tests are missing.]

The concentration of nitric acid in ethanol was selected experimentally. Etching time information has been added. The sliding distance was different with varying the test modes. This information has been added to the figures captions.

 

4. [The authors assumed that the friction coefficient is constant due to properties and composition of the friction surfaces that are not changed during the measuring. By hypothesis, how to control the oxidation reaction during the wear test as the local temperature increased sharply.]

The fact that the friction coefficient is constant due to properties and composition of the friction surfaces that are not changed during the measuring is not assumed by the authors. This fact is assumed by to the well-known law of Amontons–Coulomb, and it was mentioned in the text of the manuscript. During the friction process, the composition and structure of the surface layers of the counterbodies change greatly, including due to oxidation processes. Moreover, these arguments are present in large numbers in the description of our results in sections 3 and 4.

 

5. [It is vague. ‘If the sliding distance is large enough’ what do you mean large enough? How much distance is large enough.]

This means that the sliding distance is large enough for the friction pair to reach the stage of steady state friction. This stage begins in our case after the sliding distance of 200-300 m. The required information has been added to the text.

 

6. [How did you calculate the %mass of elements in the samples (table 2)?]

The %mass of elements were calculated using LEO EVO 50 scanning electron microscope (Carl Zeiss AG, Germany) with energy-dispersive analysis (EDX), which is indicated in Materials and Methods section. This information has been added to the caption for Table 2.

 

7. [The authors stated that increase in the ductility and strengthening of Al-30Sn composite are due to removal of the structural defects. So, I recommend that the density value of the samples should be calculated.]

The information about the porosity of the sintered and processed by ECAP composite has been added.

 

8. [I could not find any hardness value of samples.]

The hardness of the studied samples was not measured in this work. Mechanical tests were determined by testing the samples for compression. Since their strength noticeably increases after the ECAP processing, it can be said with certainty that their hardness also significantly increases.

Reviewer 3 Report

The work is well written and the results well discussed. It can be published without revisions.

Author Response

Thank you

Round 2

Reviewer 1 Report

Authors corrected some mistakes and added some explanations, the manuscript was much improved. In my opinion, it can be accepted for publication in the present form.