- The aim of the paper has to be clarified since the introduction focusses on the use of titanium alloys and the fact they requires carbide tungsten tools to be manufacture. So why do the authors perform tests with carbide tungsten sliding against silicon nitride since this configuration has no industrial application (or at least it has no link with the introduction of the paper) ?

FE model:

- The author have to provide more information about the finite element computation. What is the element type (C3D8 and C3D6 with full integration scheme, C3D8R and C3D6R with a reduce number of integration point…)?

What are the element size of the specimen and of the ball? What are the boundary condition on the YG6X specimen? Is the calculation purely elastic or elastoplastic? Is it run with Abaqus standard (implicit) or Abaqus Explicit? What’s the coefficient of friction used for the computation? Is it the same value for all computation or is it a mean value derived from the experiments?

- The loading steps are not clear and have to be clarified. I understand you just simulate the sliding of the ball in one direction. Since experiments are reciprocating sliding, why do the author not simulate the back and forth? What is the speed of ball? The authors write about a contact pressure of 1.67 MPa and a normal load of 50 N. Do they applied a pressure or a force in the FE model? Why do the author mention a pressure of 1.67 MPa? The radius of the ball is said to be 3mm, so a pressure of 1.67 MPa on a disk of 3mm radius would lead to a force of 47N…

FE analyses:

- According to Fig.5a, and Fig6a, it seems that the stresses are concentrated in just one element. What is the mesh influence on those results? Did the author run Abaqus simulations with smaller elements in order to have more element in contact? Here again, knowing if the finite elements are with full or with reduced integration would help.

- What is the stress presented in fig 5b, 5c, 6b and 6c? Is it von Mises like in Fig8a? Why do the author not present the contact pressure distributions, since this stress is acting directly on friction and wear?

Textured surface:

- I do not understand the table 4. How is calculated the K average values. What’s the differences between K =3, 5 or 7? Why is frequency ranging from 1 to 1.75 when speed and processing times are ranging from 1 to 1.25? What are the units of the coefficients in the table?

- the mean width of the groove are 115µm. But what is the mean depth of the groove? This information may be important to correlate the assumption of “abrasive particle storage” proposed in page 10.

Experiments:

- How is the COF calculated? Is it just the ratio between the tangential and the normal load Ft/Fn? If so, please clearly write it in the paper. As the surface is not flat (because of the surface texture), the “true” Coulomb’s coefficient of friction should consider the real area of contact and the fact that part of the tangential force is due to contact pressure applied on a non-vertical surface.

- What is the maximum sliding speed during the experiments? How long do the friction test last and how many back-and-forth cycles are performed in each configuration?

- How many tests are performed for each configuration? What’s the discrepancies of the results? As an example, for time larger than 25 seconds in fig.8a, could we assumed that the COF for G0, G1 and G2 are equaled and that the textured has no more effect.

- page 10, the author explain “as shown in Figure 10, the depth of the wear scars of G2-90° and G3- 90° was shallower than that of G0 because the groove texture with a certain surface density could effectively store the abrasive particles generated during the wear pro-cess and reduce the grinding on the material surface.” In fact, fig.10 shows that the depth scars of G2-90° and G3-90° are smaller than that of G0, but it does not show that this is linked to the capacity of the groove to store wear particles. It is just an assumption made by the author that have to be proven. May be the author could present some wear section measured along the YG6X grooves at the beginning, at mid test and at the end of test to show if the grooves are effectively filled with wear fragments.

Conclusion:

- the finite element model is not describe with sufficient detail to be confident with its results. Consequently the numerical results do not really contribute to the understanding of the experimental result and on the validation of the assumption made by the author on the effect of the texture surface on friction and wear.

- the conclusions of the paper can be summed up as the texture surface is beneficial when sliding against silicon nitride balls, but not beneficial when sliding against titanium alloys. But the reasons of that difference of behavior are not clearly demonstrated. May be the conclusion of the present study is just that texture surface are good to reduce abrasive wear but are bad when adhesive wear occurs? (and it would be an interesting results)

On the form of the paper:

- Table1: unit have to be given for the processing times

- Figures 5a-d and 6a-d: At what time (or to what position ) correspond the stress field? Adjust the scales of the color map so that each color represent the same stress range for figure a, b, c and d.

- Figures 5f and 6f: adjust the scale of the vertical axis so that stress variation between two graduations is constant.

- Fig8 and 11: please, use the same color for G0, G1, G2 and G3 in fig a and fig c.

- Page 9, replace “the average value of COF was G2-90° <g3-90° <g0="" <g1-90°”="" by="" “the="" average="" value="" of="" cof="" was="" g3-90°="" <="" g2-90°="" g0="" g1-90°”.="" -="" page="" 11,="" replace="" <g1-90°="" <g3-90°="" <g0”=""> G1-90° > G3-90° > G0”. </g3-90°>

<g3-90° <g0="" <g1-90°”="" by="" “the="" average="" value="" of="" cof="" was="" g3-90°="" <="" g2-90°="" g0="" g1-90°”.="" -="" page="" 11,="" replace="" <g1-90°="" <g3-90°="" <g0”="">- Fig 9 and 12: SEM-EDS analyses would help in the understanding of the wear mechanism. Do the author have the possibility of such analyses? </g3-90°>

Author Response

We feel great thanks for your professional review work on our article. Your suggestions have also benefited the research in this direction, especially in friction simulation. According to your nice suggestions, we have made extensive corrections to our previous draft, the detailed corrections are listed below.

The reviewer’s comment: The aim of the paper has to be clarified since the introduction focusses on the use of titanium alloys and the fact they requires carbide tungsten tools to be manufacture. So why do the authors perform tests with carbide tungsten sliding against silicon nitride since this configuration has no industrial application (or at least it has no link with the introduction of the paper) ?

The authors’ answer : This is because usually the wear resistance of a sample is discussed by rubbing it with a material harder than it is and afterwards measuring the size of the wear marks to evaluate the improvement in wear resistance. In this work, silicon nitride was chosen as the grinding ball because it is inert and is not expected to react with cemented carbide, thus making it possible to study the intrinsic wear resistance of cemented carbide.

The reviewer’s comment: The author have to provide more information about the finite element computation. What is the element type (C3D8 and C3D6 with full integration scheme, C3D8R and C3D6R with a reduce number of integration point…)?

The authors’ answer : The grinding ball model uses a C3D4T four-node thermally coupled

cell, and the carbide model uses a C3D8RT eight-node thermally coupled hexahedral cell, using reduced integration.

The reviewer’s comment: What are the element size of the specimen and of the ball? What are the boundary condition on the YG6X specimen? Is the calculation purely elastic or elastoplastic? Is it run with Abaqus standard (implicit) or Abaqus Explicit? What’s the coefficient of friction used for the computation? Is it the same value for all computation or is it a mean value derived from the experiments?

The authors’ answer : The element size of the specimen and of the ball are 0.4 and 0.3.

YG6X keeps the bottom surface fixed. Pure elasticity calculation, using explicit formula. The coefficient of friction is 0.4 and is obtained from friction experiments with TC4 by non-woven carbide.

The reviewer’s comment: The loading steps are not clear and have to be clarified. I understand you just simulate the sliding of the ball in one direction. Since experiments are reciprocating sliding, why do the author not simulate the back and forth?

The authors’ answer : The first consideration is the computational efficiency, and also

because the friction model is a point contact, in fact, the area always in contact is very small, and multiple back and forth friction can be approximated as a collection through multiple weaving spacing.

The reviewer’s comment: What is the speed of ball? The authors write about a contact pressure of 1.67 MPa and a normal load of 50 N. Do they applied a pressure or a force in the FE model? Why do the author mention a pressure of 1.67 MPa? The radius of the ball is said to be 3mm, so a pressure of 1.67 MPa on a disk of 3mm radius would lead to a force of 47N…

The authors’ answer : The speed of the ball is 66.67mm/s, and the contact pressure set in the

model is set to 1.77Mpa. I am very sorry for the mistake in the writing process.

The reviewer’s comment: According to Fig.5a, and Fig6a, it seems that the stresses are concentrated in just one element. What is the mesh influence on those results? Did the author run Abaqus simulations with smaller elements in order to have more element in contact? Here again, knowing if the finite elements are with full or with reduced integration would help.

The authors’ answer : There is no simulation for smaller elements. We think the friction

simulation model is mainly point contact, the stress concentration area is very small, and the grid size has very little effect on the results, while also considering the computational efficiency and using reduced integration.

The reviewer’s comment: What is the stress presented in fig 5b, 5c, 6b and 6c? Is it von Mises like in Fig8a? Why do the author not present the contact pressure distributions, since this stress is acting directly on friction and wear?

The authors’ answer : The stress presented in fig 5b, 5c, 6b and 6c are von Mises. Because

my simulation model was obtained based on the references, the analysis of the experimental results was also done with the help of the same analysis method, and it was found that both analyzed the Mises stress, so it was not used to provide the contact pressure distribution.

[1] Lu L, Zhang Z, Guan Y, et al. Comparison of the effect of typical patterns on friction and wear properties of chromium alloy prepared by laser surface texturing[J], 2018, 106: 272-279. https://doi.org/10.1016/j.optlastec.2018.04.020

He C, Yang S, Zheng M J O, et al. Analysis of synergistic friction reduction effect on micro-textured

cemented carbide surface by laser processing[J], 2022, 155: 108343. https://doi.org/10.1016/j.optlastec.2022.108343

The reviewer’s comment: I do not understand the table 4. How is calculated the K average values. What’s the differences between K =3, 5 or 7? Why is frequency ranging from 1 to 1.75 when speed and processing times are ranging from 1 to 1.25? What are the units of the coefficients in the table?

The authors’ answer : The K average values is the average of the summation of experimental

data for a certain level of a factor. R is equal to the maximum value of the K-mean minus the minimum value. For example, the value of 1 time is the average of the summation of the shape values corresponding to Table 1, T1, T6, T11, and T16.

The reviewer’s comment: The mean width of the groove are 115µm. But what is the mean depth of the groove? This information may be important to correlate the assumption of “abrasive particle storage” proposed in page 10.

The authors’ answer : We complementarily measured the depth of the notch, which was

between 5-6 μm. As shown in this figure. It is true that the depth of the groove is an important factor in its ability to store abrasive chips, which is what I'll be looking at next. However, in this paper the recesses are determined based on the morphological values and the depth is not discussed.

The reviewer’s comment: How is the COF calculated? Is it just the ratio between the tangential and the normal load Ft/Fn? If so, please clearly write it in the paper. As the surface is not flat (because of the surface texture), the “true” Coulomb’s coefficient of friction should consider the real area of contact and the fact that part of the tangential force is due to contact pressure applied on a non-vertical surface.

The authors’ answer : The COF is the ratio between the tangential and the normal load Ft/Fn.

we have written it in the paper. Regarding the true Coulomb friction coefficient, thank you very much for your elaboration, indeed this is a very worthy direction to think about, and we did not see a relevant description in other references, we will focus on thinking about this issue in my future experiments.

The reviewer’s comment: What is the maximum sliding speed during the experiments? How long do the friction test last and how many back-and-forth cycles are performed in each configuration? How many tests are performed for each configuration? What’s the discrepancies of the results? As an example, for time larger than 25 seconds in fig.8a, could we assumed that the COF for G0, G1 and G2 are equaled and that the textured has no more effect.

The authors’ answer : The sliding speed in the experiment was 66.67 mm/s, and the friction

test was performed for 30 min with 15,000 reciprocations. Only one set of experiments was conducted for each experiment. Since the experiment is a dry friction rubbing process is violent, the grooves will soon be worn, the grooves do not act for long, and as the friction continues, the friction coefficients of all samples will tend to be equal.

The reviewer’s comment: Page 10, the author explain “as shown in Figure 10, the depth of the wear scars of G2-90° and G3- 90° was shallower than that of G0 because the groove texture with a certain surface density could effectively store the abrasive particles generated during the wear pro-cess and reduce the grinding on the material surface.” In fact, fig.10 shows that the depth scars of G2-90° and G3-90° are smaller than that of G0, but it does not show that this is linked to the capacity of the groove to store wear particles. It is just an assumption made by the author that have to be proven. May be the author could present some wear section measured along the YG6X grooves at the beginning, at mid test and at the end of test to show if the grooves are effectively filled with wear fragments. The conclusions of the paper can be summed up as the texture surface is beneficial when sliding against silicon nitride balls, but not beneficial when sliding against titanium alloys. But the reasons of that difference of behavior are not clearly demonstrated. May be the conclusion of the present study is just that texture surface are good to reduce abrasive wear but are bad when adhesive wear occurs? (and it would be an interesting results)

The authors’ answer : The sliding speed in the experiment was 66.67 mm/s, and the friction

test was performed for 30 min with 15,000 reciprocations. Only one set of experiments was conducted for each experiment. Since the experiments were dry friction, the friction process was violent and the grooves would soon be worn out, the grooves did not act for long and the coefficient of friction would tend to equalize for all samples as the friction continued. "It is related to the ability of the grooves to store wear particles" is my application of the already summarized mechanism of groove wear reduction, which is actually an accepted fact. Indeed, as you said, our focus was on the variability of texture friction under different grinding balls, and we found this phenomenon, and we will continue to investigate the specific mechanism in the next experiments.

The reviewer’s comment: Table1: unit have to be given for the processing times.

The authors’ answer : The unit of processing times is times. I have made changes in Tables 1

and 4.

The reviewer’s comment: Figures 5a-d and 6a-d: At what time (or to what position ) correspond the stress field? Adjust the scales of the color map so that each color represent the same stress range for figure a, b, c and d.

The authors’ answer : Figures 5a-d and 6a-d: The stress field at the end of the simulation.

The reviewer’s comment: Figures 5f and 6f: adjust the scale of the vertical axis so that stress variation between two graduations is constant.

The authors’ answer : In order to represent the one-to-one correspondence between stress and

surface density, we have modified the figure.

The reviewer’s comment: Fig 8 and 11: please, use the same color for G0, G1, G2 and G3 in fig a and fig c.

The authors’ answer : We have made changes in the paper.

SEM-EDS analyses would help in the understanding of the wear mechanism. Do the author have the possibility of such analyses?

The authors’ answer : Thank you very much for your suggestion, but objective factors led to

not performing the relevant tests. Indeed, as you said, the focus of the article was mainly on the finding that the textured surface is beneficial when sliding against silicon nitride balls, but not against titanium alloys. This phenomenon we are not able to explain and can only make the hypothesis that it is related to stress. The study of this phenomenon will also be the focus of my next work.

Author Response File: Author Response.docx

Reviewer 2 Report

Dear authors,

the paper presents an interesting study of dry friction properties of three different spacing groove textures. The theoretical analysis and FEM results are outlined in order to highlight the research scopes: the experimental evidence has been discussed validating so the rational approaches implemented.

The manuscript deals with an interesting subject which is expected to contribute on the field of materials characterization treated by Coatings journal. I believe the technical content is worthy of publication once following points will be updated:

- to avoid the use of first person in scientific/technical paper;

- a list of symbols and acronyms to be added;

- more details on numerical simulations to be introduced (hypotheses behind the modelling, physical model, boundary conditions);

- how is calculated the contact stress in FE analysis? Which material allowable (tensile, bearing...) should be considered for reserve factor assessment?

Author Response

We feel great thanks for your professional review work on our article. According to your nice suggestions, we have made extensive corrections to our previous draft, the detailed corrections are listed below.

The reviewer’s comment: - to avoid the use of first person in scientific/technical paper.

The authors’ answer : Thank you very much for your suggestion, I did my best to make the changes. More in-depth changes may require the use of editing services.

The reviewer’s comment: - a list of symbols and acronyms to be added.

The authors’ Answer :

English explanation	Abbreviations
laser scanning confocal microscopy	LSCM
scanning electron microscope	SEM
coefficient of friction	COF
Ti6Al4V	TC4
electrical discharge machining	EDM
laser texturing	LST
Untextured YG6X carbide	G0
YG6X carbide with 0.25 mm texture spacing	G1
YG6X carbide with 0.50 mm texture spacing	G2
YG6X carbide with 0.75 mm texture spacing	G3
The friction subsets slide perpendicular to the grooves of the G1 sample	G1-90°
The friction subsets slide perpendicular to the grooves of the G2 sample	G2-90°
The friction subsets slide perpendicular to the grooves of the G3 sample	G3-90°
The friction subsets slide against the grooves of the G sample at 45 degrees	G3-45°

The reviewer’s comment: - more details on numerical simulations to be introduced (hypotheses behind the modelling, physical model, boundary conditions).

The authors’ answer : We have added details to the model in the paper. The sliding ball

model uses a C3D4T four-node thermally coupled cell, and the carbide model uses a C3D8RT eight-node thermally coupled hexahedral cell, using reduced integration. The element size of the specimen and of the ball are 0.4 and 0.3. The YG6X was fixed and restrained, and a pressure of 1.67 MPa was applied to the sur-face of the titanium alloy hemisphere. Finally, a Velocity/Angular Velocity analysis type was established for TC4, and the velocity was set to 66.67mm/s according to this analysis step. Pure elasticity calculation, using explicit formula. The coefficient of friction is 0.4 and is obtained from friction experiments with TC4 by non-textured carbide.

The reviewer’s comment: - how is calculated the contact stress in FE analysis? Which material allowable (tensile, bearing...) should be considered for reserve factor assessment?

The authors’ answer : The stress presented in fig 5b, 5c, 6b and 6c are von Mises. It can be obtained directly by simulation software. The simulation of the friction process does not take into account the plastic deformation of the material, but mainly considers the stress changes in the carbide when the grinding ball passes through the groove. The input material mechanical parameters are only the modulus of elasticity and Poisson's ratio.

Author Response File: Author Response.docx

Reviewer 3 Report

Dear Authors,

The tribological pattern of femtosecond laser-textured YG6X carbide samples were analyzed under 3 groove texture spacing, two friction subsets and two friction directions. The manuscript managed to present a new matter in the field. The novelty of the manuscript encourage readers to follow it but there are some modifications that the authors should consider them.

-Abstract should present a comprehensive overview of the manuscript. The current abstract should be modified and it is recommended to rewrite it.

-Introduction should be extended and the authors should use further updated references particularly from the journal.

- The section of experiment should be extended and be more comprehensive so that readers can be aware of more details.

-Finite Element Method is a practical technique to analyze mechanical mediums. There is no enough expression of FEM in the manuscript. It is understandable that the authors used Abaqus software but the authors should dedicate a sub-section to present the significance of FEM as a strong tool.

-There are many English language errors that should be modified. A good manuscript needs a good presentation.

Regards

Author Response

The reviewer’ s comment: -Abstract should present a comprehensive overview of the manuscript. The current abstract should be modified and it is recommended to rewrite it.

The authors’ answer : I have rewritten the abstract based on your suggestion. Details are as follows or see this paper.

This paper investigates the use of laser surface texturing (LST) to improve the tribological properties of YG6X cemented carbide. Three different spaced groove textures were processed on the surface of YG6X carbide samples using a femtosecond laser. Friction experiments and friction simulations were performed under two friction subsets and two friction directions. Testing results showed that, when the area density was 46%, the texture surface was beneficial when sliding against Si₃N₄, but not beneficial in reducing coefficient of friction when sliding against Ti6Al4V titanium alloy. At area densities of 23% and 15.3%, the texture surface was beneficial when sliding against Si₃N₄, but not beneficial when sliding against Ti6Al4V titanium alloy. When selecting the friction direction at 45° to the area density of 15.3%, the texture surface was not beneficial when sliding against Si₃N₄ and Ti6Al4V titanium alloy. Sliding with Si₃N₄, the higher the stress value the more easily the material was destroyed, leading to an elevated coefficient of friction and wear area. Sliding with Ti6Al4V titanium alloy, the higher the stress value of Ti6Al4V titanium alloy, the more easily Ti6Al4V titanium alloy wore and generated a large amount of abrasive chips.

The reviewer’ s comment: -Introduction should be extended and the authors should use further updated references particularly from the journal.

The authors’ answer : We have cited more articles from this journal in our paper.

The reviewer’ s comment: - The section of experiment should be extended and be more comprehensive so that readers can be aware of more details.

The authors’ answer : We have added details to the experiment in the paper. The K average

Values is the average of the summation of experimental data for a certain level of a factor. R is equal to the maximum value of the K-mean minus the minimum value. The COF is the ratio between the tangential and the normal load Ft/Fn. The sliding speed in the experiment was 66.67 mm/s, and the friction test was performed for 30 min with 15,000 reciprocations. We mainly present the friction experiment details in 2.2, where the parameters of the friction simulation and the experimental parameters correspond.

The reviewer’ s comment: -Finite Element Method is a practical technique to analyze mechanical mediums. There is no enough expression of FEM in the manuscript. It is understandable that the authors used Abaqus software but the authors should dedicate a sub-section to present the significance of FEM as a strong tool.

The authors’ answer : We have added details to the model in the paper. The grinding ball

model uses a C3D4T four-node thermally coupled cell, and the carbide model uses a C3D8RT eight-node thermally coupled hexahedral cell, using reduced integration. The element size of the specimen and of the ball are 0.4 and 0.3. YG6X keeps the bottom surface fixed. Pure elasticity calculation, using explicit formula. The coefficient of friction is 0.4 and is obtained from friction experiments with TC4 by non-textured carbide.

The reviewer’ s comment: -There are many English language errors that should be modified. A good manuscript needs a good presentation.

The authors’ answer : Thank you very much for your suggestion, I did my best to make the changes. More in-depth changes may require the use of editing services.

Round 2

Reviewer 1 Report

The reviewer’s comment: The aim of the paper has to be clarified since the introduction focusses on the use of titanium alloys and the fact they requires carbide tungsten tools to be manufacture. So why do the authors perform tests with carbide tungsten sliding against silicon nitride since this configuration has no industrial application (or at least it has no link with the introduction of the paper) ?

Reviewer: Ok.

The reviewer’s comment: The author have to provide more information about the finite element computation. What is the element type (C3D8 and C3D6 with full integration scheme, C3D8R and C3D6R with a reduce number of integration point…)?

The authors’ answer : The grinding ball model uses a C3D4T four-node thermally coupled cell, and the carbide model uses a C3D8RT eight-node thermally coupled hexahedral cell, using reduced integration.

Reviewer: Ok

The reviewer’s comment: What are the element size of the specimen and of the ball? What are the boundary condition on the YG6X specimen? Is the calculation purely elastic or elastoplastic? Is it run with Abaqus standard (implicit) or Abaqus Explicit? What’s the coefficient of friction used for the computation? Is it the same value for all computation or is it a mean value derived from the experiments?

The authors’ answer : The element size of the specimen and of the ball are 0.4 and 0.3. YG6X keeps the bottom surface fixed. Pure elasticity calculation, using explicit formula. The coefficient of friction is 0.4 and is obtained from friction experiments with TC4 by non-woven carbide.

Reviewer: the computation options are wrong regarding what the authors try to show in their paper. Experiments exhibit wear marks, which are not representative of fatigue contact. Therefore, the stresses in the vicinity of the worn area exceed the yield stress and plasticity occurs. Consequently, the authors cannot obtain a realistic stress state with a computation in pure elasticity. Their computations overestimate the stresses.

Authors must, at least, explained their computations are made under the purely elastic deformation assumption and stresses may be overestimated.

The reviewer’s comment: The loading steps are not clear and have to be clarified. I understand you just simulate the sliding of the ball in one direction. Since experiments are reciprocating sliding, why do the author not simulate the back and forth?

The authors’ answer : The first consideration is the computational efficiency, and also because the friction model is a point contact, in fact, the area always in contact is very small, and multiple back and forth friction can be approximated as a collection through multiple weaving spacing.

Reviewer: as plastic strain may occur, the surface is not the same during the back and forth movements. However, since the authors run their computations in pure elasticity, the reviewer understand that his remark is not taken into consideration.

The reviewer’s comment: What is the speed of ball? The authors write about a contact pressure of 1.67 MPa and a normal load of 50 N. Do they applied a pressure or a force in the FE model? Why do the author mention a pressure of 1.67 MPa? The radius of the ball is said to be 3mm, so a pressure of 1.67 MPa on a disk of 3mm radius would lead to a force of 47N…

The authors’ answer : The speed of the ball is 66.67mm/s, and the contact pressure set in the model is set to 1.77Mpa. I am very sorry for the mistake in the writing process.

Reviewer: Ok

The reviewer’s comment: According to Fig.5a, and Fig6a, it seems that the stresses are concentrated in just one element. What is the mesh influence on those results? Did the author run Abaqus simulations with smaller elements in order to have more element in contact? Here again, knowing if the finite elements are with full or with reduced integration would help.

The authors’ answer : There is no simulation for smaller elements. We think the friction simulation model is mainly point contact, the stress concentration area is very small, and the grid size has very little effect on the results, while also considering the computational efficiency and using reduced integration.

Reviewer: FEA may lead to severe overestimation of stresses when only a single node of the mesh is loaded. The error may be even larger when reduced integration is used because of the poor interpolation of the results from the integration points to the nodes (which is the case in the present study). Finally the element size in the surface area may also strongly affect the accuracy of the computations. Author have to test the effect of the element size on the stress distributions and refine their mesh so that more than one element is in contact on each surface (more than one element of the ball, more than one element in the specimen).

The reviewer’s comment: What is the stress presented in fig 5b, 5c, 6b and 6c? Is it von Mises like in Fig8a? Why do the author not present the contact pressure distributions, since this stress is acting directly on friction and wear?

The authors’ answer : The stress presented in fig 5b, 5c, 6b and 6c are von Mises. Because my simulation model was obtained based on the references, the analysis of the experimental results was also done with the help of the same analysis method, and it was found that both analyzed the Mises stress, so it was not used to provide the contact pressure distribution.

He C, Yang S, Zheng M J O, et al. Analysis of synergistic friction reduction effect on micro-textured cemented carbide surface by laser processing[J], 2022, 155: 108343. https://doi.org/10.1016/j.optlastec.2022.108343

Reviewer: Ok. The reviewer understands that it is quite common to observe von Mises stress in the literature related to wear. Nonetheless, friction in ABAQUS uses the Coulomb’s friction model, which depends on the contact pressure and not on the von Mises stress. The authors might take this remark in consideration for their next paper.

The reviewer’s comment: I do not understand the table 4. How is calculated the K average values. What’s the differences between K =3, 5 or 7? Why is frequency ranging from 1 to 1.75 when speed and processing times are ranging from 1 to 1.25? What are the units of the coefficients in the table?

The authors’ answer : The K average values is the average of the summation of experimental data for a certain level of a factor. R is equal to the maximum value of the K-mean minus the minimum value. For example, the value of 1 time is the average of the summation of the shape values corresponding to Table 1, T1, T6, T11, and T16.

Reviewer: Ok

The reviewer’s comment: The mean width of the groove are 115µm. But what is the mean depth of the groove? This information may be important to correlate the assumption of “abrasive particle storage” proposed in page 10.

The authors’ answer : We complementarily measured the depth of the notch, which was between 5-6 μm. As shown in this figure. It is true that the depth of the groove is an important factor in its ability to store abrasive chips, which is what I'll be looking at next. However, in this paper the recesses are determined based on the morphological values and the depth is not discussed.

Reviewer: Ok. Even if the influence of the depth is not discussed, the author may at least provide the value of the groove depth in the paper.

The reviewer’s comment: How is the COF calculated? Is it just the ratio between the tangential and the normal load Ft/Fn? If so, please clearly write it in the paper. As the surface is not flat (because of the surface texture), the “true” Coulomb’s coefficient of friction should consider the real area of contact and the fact that part of the tangential force is due to contact pressure applied on a non-vertical surface.

The authors’ answer : The COF is the ratio between the tangential and the normal load Ft/Fn. we have written it in the paper. Regarding the true Coulomb friction coefficient, thank you very much for your elaboration, indeed this is a very worthy direction to think about, and we did not see a relevant description in other references, we will focus on thinking about this issue in my future experiments.

Reviewer: Ok

The reviewer’s comment: What is the maximum sliding speed during the experiments? How long do the friction test last and how many back-and-forth cycles are performed in each configuration? How many tests are performed for each configuration? What’s the discrepancies of the results? As an example, for time larger than 25 seconds in fig.8a, could we assumed that the COF for G0, G1 and G2 are equaled and that the textured has no more effect.

Reviewer: Ok

The reviewer’s comment: Page 10, the author explain “as shown in Figure 10, the depth of the wear scars of G2-90° and G3- 90° was shallower than that of G0 because the groove texture with a certain surface density could effectively store the abrasive particles generated during the wear pro-cess and reduce the grinding on the material surface.” In fact, fig.10 shows that the depth scars of G2-90° and G3-90° are smaller than that of G0, but it does not show that this is linked to the capacity of the groove to store wear particles. It is just an assumption made by the author that have to be proven. May be the author could present some wear section measured along the YG6X grooves at the beginning, at mid test and at the end of test to show if the grooves are effectively filled with wear fragments. The conclusions of the paper can be summed up as the texture surface is beneficial when sliding against silicon nitride balls, but not beneficial when sliding against titanium alloys. But the reasons of that difference of behavior are not clearly demonstrated. May be the conclusion of the present study is just that texture surface are good to reduce abrasive wear but are bad when adhesive wear occurs? (and it would be an interesting results)

The authors’ answer : The sliding speed in the experiment was 66.67 mm/s, and the friction test was performed for 30 min with 15,000 reciprocations. Only one set of experiments was conducted for each experiment. Since the experiments were dry friction, the friction process was violent and the grooves would soon be worn out, the grooves did not act for long and the coefficient of friction would tend to equalize for all samples as the friction continued. "It is related to the ability of the grooves to store wear particles" is my application of the already summarized mechanism of groove wear reduction, which is actually an accepted fact. Indeed, as you said, our focus was on the variability of texture friction under different grinding balls, and we found this phenomenon, and we will continue to investigate the specific mechanism in the next experiments.

Reviewer: Ok even if it’s not easy to draw conclusion with only one test and a finite element computations that are not confident due to their assumptions and poor mesh quality…

The reviewer’s comment: Table1: unit have to be given for the processing times.

The authors’ answer : The unit of processing times is times. I have made changes in Tables 1 and 4.

Reviewer: Ok

The reviewer’s comment: Figures 5a-d and 6a-d: At what time (or to what position ) correspond the stress field? Adjust the scales of the color map so that each color represent the same stress range for figure a, b, c and d.

The authors’ answer : Figures 5a-d and 6a-d: The stress field at the end of the simulation.

Reviewer: Ok

The reviewer’s comment: Figures 5f and 6f: adjust the scale of the vertical axis so that stress variation between two graduations is constant.

The authors’ answer : In order to represent the one-to-one correspondence between stress and surface density, we have modified the figure.

Reviewer: Ok

The reviewer’s comment: Fig 8 and 11: please, use the same color for G0, G1, G2 and G3 in fig a and fig c.

The authors’ answer : We have made changes in the paper.

Reviewer: Ok

SEM-EDS analyses would help in the understanding of the wear mechanism. Do the author have the possibility of such analyses?

The authors’ answer : Thank you very much for your suggestion, but objective factors led to not performing the relevant tests. Indeed, as you said, the focus of the article was mainly on the finding that the textured surface is beneficial when sliding against silicon nitride balls, but not against titanium alloys. This phenomenon we are not able to explain and can only make the hypothesis that it is related to stress. The study of this phenomenon will also be the focus of my next work.

Reviewer: Ok

Author Response

Please check attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

Dear authors,

thanks for the answers. For me, the paper is fine.

Best regards.

Author Response

Dear Reviewer,

Thank you for your approval.

Round 3

Reviewer 1 Report

The authors have answer to all of my question.

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Dry Friction Properties of Friction Subsets and Angle Related to Surface Texture of Cemented Carbide by Femtosecond Laser Surface Texturing

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