The Relationship between Tribo-Magnetization and Wear State during Reciprocating Sliding

Round 1

Reviewer 1 Report

Dear authors,

the paper provides new interesting experimental and theoretical results on tribomagnetisation of 40CrMo steel but the presentation needs some corrections and expansion of the text to improve its quality and readability. Below is the list of suggested corrections/additions:

Line 66 "40CrMo": Please provide also ASTM and/or EN grade of the steel

Line 82 "cuboid": it seems that "plate" will describe better the sample shape.

"40CrMo steel": Please add information about state of this steel (as fabricated, quenched, quenched and tempered at some temperature) and its properties (at least hardness HB or HRC). If you have some information on microstructure of the steel, please give it in this section.
It would be very good if you provide also hardness of 316L  steel used  for pin.

Line 90 "length of 120 mm": Sorry but how the scanning line could be longer than the maximal dimension of the plate? Probably it is 20 mm as it is shown on Fig. 3.

Line 127 Figure 3: Please enlarge the  plots on Fig. 3: legends are practically unreadable.

Plots are very difficult for understanding. Please provide separate simple plots H_min(n), H_max(n) for normal and tangential components. Presence of H(0) points is  strongly recommended. It is also possible to combine Fig. 3 with Figs. 5 and 9 and to rearrange text to keep discussion maximally close to figures.

Eq. 1: Please check correctness of symbols particularly u₀, evidently it should be μ₀.

Eqs. 2 and 3: Sorry but where are magnetic properties of the steel under study or at least of pure α-Fe (with correction coefficient on ferrite content in the steel)  in these equations? Please check these Equations and further mathematics.

Section 3.4 Simulation result: Please discuss here relation between calculated  depth up to 1.4 mm and real depth of the wear stripe (scar) that seems to be in order of micrometers or even nanometers. The nature of experimentally observed asymmetry should be discussed hear.

I recommend also to check and correct English through the text.

Author Response

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Reviewer 2 Report

This paper discussed the tribo-magnetization effect with a pin-on-block reciprocating pair. In addition, in order to evaluate and predict the variation of magnetic field on the surface of wear scar more accurately, an improved magnetic dipole model is established. This paper is detailed, clearly organized, and of high scientific value.

(1) It is difficult to distinguish the lines in Fig. 3. Please enlarge it.

(2)The amount of the wear debris should be increased with an increase in reciprocating cycle and effect on the tribo-magnetization. The proposed magnetic field model seems to be no relation with the amount of the wear debris. In addition, there seem to be no discussion about the wear of the 316L pins. The amount of the debris and the 316L pin wear did not effect on the tribo-magnetization?

Author Response

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Reviewer 3 Report

REVIEW COMMENTS

Manuscript ID: metals-1304378

The relationship between tribo-magnetization and wear state during reciprocating friction

An interesting work. The authors present a work that analyzes the evolution of tribo-magnetization in a reciprocating sliding friction and wear test. The authors observe that there is a relationship between the variation of the tangential and normal magnetic field and the characteristics of the wear scar. This fact makes them conclude that it is feasible to monitor the change of the wear state by monitoring the change of the magnetic field on the friction surface. Likewise, the authors propose an improved magnetic dipole model that allows obtaining by means of numerical simulation the qualitative variation of the magnetic field as a consequence of the wear process. The authors conclude that the simulation results of the model are consistent with the observed wear process.

The work is interesting but some aspects I think need to be improved. I would appreciate it if you would consider the following suggestions:

1. Lines 2-3: Being rigorous, the authors perform a “reciprocating sliding test” or a “reciprocating sliding” friction and wear test, not a “reciprocating friction” test. Correct it, please.
2. Line 10: Both in the line 10, and in other sections of the manuscript, the authors refer to "frictional behavior". However, the authors do not measure friction in the tests, therefore, they do not characterize friction behavior. In my opinion, it would be more correct to refer to "tribological behavior", rather than "frictional behavior". (Note: Tribology is the science of interacting surfaces in relative motion. It includes the study of friction and wear)
3. Lines 81: Indeed, austenitic stainless steel is not ferromagnetic under normal conditions. However, magnetization of this steel can occur because of plastic deformation that can lead to the transformation of austenite into martensite (TRIP: Transformation-Induced Plasticity). It is to be expected that plastic deformation of the pin will occur in the contact area. Have the authors verified that there has not been a magnetization of the pin during the test that could have an effect on the results? Explain it, please.
4. Lines 86-87: What roughness parameter has been measured? Ra? Indicate it, please.
5. Lines 131-133: In figure 3 it is impossible to observe that up to 200 reciprocating cycles the fluctuation amplitudes are very weak and after 200 reciprocating cycles they gradually increase. It could be interesting to include an additional figure with a smaller number of conditions (for example: 50, 100, 150, 200, 250, 300 350 and 400 reciprocating cycles) to show more clearly the variation of the fluctuation amplitudes with the number of cycles.
6. Lines 136-137: It is impossible to observe the indicated change of the curve in figure 3. It might be interesting to include an additional figure for a number of cycles around 2500 (for example: 1500, 2000, 2500, 3000 and 3500 reciprocating cycles).
7. Lines 138-139: The same suggestion explained in point 4.
8. Lines 142-143: It is impossible to observe the indicated change of the curve in figure 3. It might be interesting to include an additional figure for a number of cycles around 7000 (for example: 6000, 6500, 7000, 7500 and 8000 reciprocating cycles).
9. Lines 188-189. Lines 192-193. Lines 196-197: The authors describe the characteristics of the wear debris and their possible influence on the behavior of the tribological pair. However, section 2.2 state: "During the experiment, both the pin and block specimen were separated after a certain number of reciprocating strokes, and wear debris on the specimen was carefully removed to reduce the impact of its own residual magnetic field.” When was wear debris removed from the specimen? The frequency of removal of wear debris can influence the results? Explain it please.
10. Lines 281-283: What would be the results of the simulation if the typical plane dipole theory had been used instead of the improved magnetic dipole model proposed by the authors? It would be interesting for the authors to show the comparison of the results with both models so that readers can appreciate the advantages of the proposed model.

Author Response

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Round 2

Reviewer 3 Report

REVIEW COMMENTS

Manuscript ID: metals-1304378_v2

The relationship between tribo-magnetization and wear state during reciprocating friction

The manuscript has significantly improved. I am grateful that the authors have taken into account the suggestions made by this reviewer. The added figures allow to observe more clearly the variation of the magnetic field during the reciprocal sliding as a function of the number of cycles. Also, the addition of simulation results using the typical plane dipole theory allows the reader to understand more clearly the differences with the improved magnetic dipole model proposed by the authors. However, in my opinion, there are still some details that should be corrected. I would appreciate if you would consider the following suggestions:

1. Lines 81: This reviewer asked if the authors verified that pin magnetization does not occur in the tests, since this magnetization can influence the results. The authors reply that they have indeed taken this fact into account and that they measured the magnetic field on the surface of the pin before and after the tests. In these measurements they observed that the pin did not appear magnetized after the test. Correct, the explanation is adequate but I think it would be appropriate to include this explanation in the paper so that readers are sure that the possible magnetization of the pin has been taken into account in the tests.
2. Lines 82-84: Indicate correctly the Brinell hardness designation, please. According to the ISO 6506-1 standard, the hardness value is indicated first (for example 174) and then the hardness symbol (HBW). Therefore, it would correctly be 174 HBW and not HB174.
3. Line 88: I think it is convenient to indicate in the text that the roughness parameter measured has been Ra (in the manuscript only the numerical value is indicated, not which parameter it corresponds to).
4. Line 123: "Reciprocating sliding" instead of "reciprocating friction". Correct it throughout the manuscript.
5. Lines 128-129: A graph of changes in the normal magnetic field appears in the revised version of the manuscript (Figure 3 (b)). Obviously it is a mistake. Take it off, please.

Author Response

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