Effect of Nd:YAG Nanosecond Laser Ablation on the Microstructure and Surface Properties of Coated Hardmetals

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The manuscript investigates nanosecond-pulsed Nd: YAG laser ablation for removing AlTiN coatings from WC-Co hardmetal inserts, with LIBS monitoring for process control. The study provides valuable insights into efficient and environmentally friendly coating removal methods. However, the introduction could better highlight the industrial significance and challenges of coating removal across various sectors. Some experimental details and results could be expanded for better clarity.

Specific Comments

1. The introduction would benefit from a more detailed discussion of the industrial relevance of coating removal in different sectors, such as tool manufacturing and aerospace, to emphasize the broader impact of the study. Furthermore, a more in-depth analysis of the current state of research on transient processes during pulsed laser ablation would enhance the introduction. Please consider citing Reference Guo C, Li K, Liu ZL, et al. CW laser damage of ceramics induced by air filament. Opto-Electron Adv 8,240296(2025).
2. The connection between LIBS and process optimization could be clarified. A diagram of the integrated setup would help readers understand the workflow better.
3. While SEM and profilometry results are clear, more analysis on surface roughness and the impact of pulse delays/pulse numbers on substrate damage would improve this section.
4. A brief explanation of the physical processes influencing laser-material interaction at different delays would add value to the results section.
5. The conclusion should more explicitly discuss the broader implications of the findings and propose future research directions, such as exploring other coating materials or laser wavelengths.

Author Response

Comments in the attachment

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Editor,

In the manuscript titled “Effect of Nd:YAG Nanosecond Laser Ablation on the Microstructure and Surface Properties of Coated Hardmetals,” Leal et al. present a laser ablation method to remove coating layers and surface elements. The authors claim that this method provides a cleaner and more effective alternative to conventional chemical stripping techniques.

   In my opinion, this paper is interesting in terms of its approach to surface element removal through laser ablation. However, there are several issues that need to be addressed before the manuscript can be considered for publication. I recommend that the authors carefully consider the comments provided below to improve the manuscript’s readability, scientific rigor, presentation quality, and overall standard. Moreover, it would strengthen the work if the authors discussed and interpreted their results using physical or chemical principles rather than merely reporting the observed outcomes. In other words, the authors should explain the mechanisms underlying their findings (for instance, the large impact depth observed under high laser energy may originate from …).

Major Revision:

1. Please increase the resolution and quality of Figures 3, 5, and 6.
2. Update the reference list by including recent publications from 2023 to 2025.
3. Clarify the cost differences between laser ablation and conventional chemical stripping methods. Is laser ablation a cost-effective alternative?
4. Write out the full name of WC–Co at first mention, and then use the abbreviation thereafter.
5. Rewrite Section 2.2 Experimental Procedure in a more academically appropriate style. The current layout resembles a report format; however, a research paper should follow a more structured narrative format. Please include additional experimental details such as temperature, pressure, and irradiation conditions.
6. In Figure 2, please define the symbol k.
7. Ensure consistency in paragraph length throughout the manuscript. In some sections, paragraphs are as short as three lines, whereas in others, they are considerably longer. Ideally, paragraphs should range between six and ten lines in length.
8. Remove the “Spot Diameter” column from Table 1 and include that information in the table caption.
9. Based on Figure 3, it is evident that the impact area increases with rising laser energy. Please explain this phenomenon in more detail. From a physical standpoint, higher laser energy is expected to increase ablation depth rather than surface area. Although this is partially addressed in Section 3.1 Surface Morphology and Profilometry, further clarification would be beneficial.
10. Does the laser impact induce mechanical dislocation or reduce the mechanical rigidity and strength of the substrate? Please clarify.
11. When the laser interacts with the surface, it is clear that a pit is formed and ablation occurs. However, how are the removed surface elements separated? In other words, what physical or chemical mechanisms govern the evaporation or ejection of surface elements during laser–surface interaction?
12. Please rewrite the conclusion section as one or two cohesive paragraphs focusing on the main findings rather than on experimental details.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

In my opinion, the title of the entire publication has been incorrectly formulated in relation to the research carried out and discussed in the text. Firstly, only two parameters of the device/process were changed (delay and number of shots), while the publication suggests that the entire ablation process has an impact on the material. Secondly, observations of the surface after a certain number of shots and blurred images of cross-sections do not prove any practical changes in the structure and, consequently, in the surface properties.

No properties were measured—the plasma was analyzed and surface development profiles were plotted (without even specifying the roughness parameters)—this is not enough to support the statement in the title of the article.

Certain statements are not supported by the results presented and certainly require detailed explanations:

1. Chapter 2, Materials and Methods, lines 106-113;
   Lack of specific ablation process output data (laser operating parameters) for the second harmonic (532 nm) – what was the maximum (rated) energy value in a single pulse, where was it measured, and to what extent was this value limited by the optical path? The atmosphere used in the process (vacuum, gas, partial oxygen pressure) has not been specified?
2. Chapter 2, Materials and Methods, verses 122-123;
   What type of calibration was used instead of direct measurement of energy density on the surface of the workpiece - the mere statement of the use of calibration (or calibration curves) is insufficient.
3. Chapter 3, Results, Figure 2;
   The results of the full chemical composition analysis (EDS) are not provided, considering the correction method and measurement errors, or any modes used. The recording of numerical results should be limited to only one decimal place (or none), and the value should be given with a period instead of a comma. There is a lack of carbon (TiCN and the WC-Co substrate), and it is known that it should be detected in this system.
4. Chapter 3, Results, lines 151-152;
   How was the diameter of the spot on the sample surface determined? Later images show that it is not a symmetrical spot but rather an ellipse.
5. Chapter 3, Results, lines 164-176;
   I do not understand the relevance of these studies because they do not concern the process of layer removal. It is known that a higher energy pulse will reach the surface of the workpiece and thus remove the coating layers - it would have been sufficient to provide only the parameters of such a beam without the entire analysis. Furthermore, no changes relevant to the subject of the research can be observed in the SEM images, and even if the images of spots on the surface explain anything, the set below (x2000) does not really add anything - it would be better to provide a set of roughness parameters and explain how and why they change; there is no set of images for 5000x magnification (version 168). It would be best to provide a specific set of ablation parameters for a situation in which the pulse reaches the substrate but does not melt it, showing the structure in cross-section.
6. Chapter 3, Results, lines 177-178;
   Is this really the optimal range? Based on what value or characteristic was this statement made?
7. Chapter 3, Results, line 180;
   (…) the microstructural and compositional stability of the substrate (…); What is the evidence for such a categorical statement?
8. Chapter 3, Results, lines 197-200;
   The author does not explain what the NIST database is, but as can be seen, it forms the basis for the detection of individual elements in LIBS analysis.
9. Chapter 3, Results, lines 204-206;
   (…) The brown line corresponds to the lower of energy delay of 120 µs; this energy was increased from 20 to 20 until reaching the maximum energy, which corresponds to 20 (blue line) (…); This statement is probably incorrect or grammatically incorrect.
10. Chapter 3, Results, line 248;
    The caption under Figure 5 is incorrect; variant (d) is missing. The SEM images are of poor quality and illegible—the effects of the laser beam cannot be observed on them. Again, an image of the cross-section of the impact/melting area would explain much more than the analysis of surface profiles.
11. Chapter 3, Results, paragraph from line 257;
    Again, as before, I do not understand the rationale behind this analysis. Why was linear fitting used at all if there is clearly an increase of a different nature? In what units is the slope value given? This entire analysis does not contribute anything to the justification of the measurements, and it is well known that the delay directly affects the energy value and energy density measured on the machined surface.
12. Chapter 3, Results, Figure 7, lines 305-313;
    The use of surface EDS analysis is pointless, as it does not indicate whether and how the beam reacts with the substrate. Only cross-sectional analysis would indicate the possible impact of laser pulses on the structure (observed changes) and the expected properties of the substrate (evolution of chemical composition). The images in Figure 7 clearly suggest that the spot is not symmetrical. The final statement (lines 311-313) is not supported by the analysis results shown, and there is no evidence for such a categorical conclusion.

Comments on the Quality of English Language

The article requires thorough editorial and grammatical correction:

1. The correct spelling of Nd:YAG is confused and incorrectly written in many places (Nd-YAG, ND-YAG, etc.)
2. Introduction chapter, lines 37-41;
   The statement is written in an ungrammatical way and loses its meaning
3. Introduction chapter, lines 45-47;
   Does the topographical development of the surface not improve adhesion? What scale of development does this statement refer to?
4. Caption under Figure 1, line 119;
   (...)This equipment is equipped (...) - grammatically incorrect wording
5. Magnifications in microscopic methods are written as: x200 or x50k, not X 200 - requires correction throughout the text.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Thanks for the revision. It would be better to compare the processing mechanism in the work (Tailoring sapphire–invar welds using burst femtosecond laser. Light: Advanced Manufacturing, 2026. 10.37188/lam.2026.003)

Author Response

The authors would like to thank the referee for their time and effort to evaluate the article.

Reviewer 2 Report

Comments and Suggestions for Authors

Dear Editor,

The authors have addressed all of my concerns. However, the layout of their response letter made it difficult to clearly link each response to the corresponding section of the manuscript. Moreover, while the answers were somewhat brief, they were generally acceptable. I confirm that this manuscript can now be accepted for publication; however, for future submissions, it would be beneficial for the authors to improve the layout and organization of their response letters.

Author Response

We appreciate the reviewer their suggestion to publish the manuscript; we also appreciate the feedback regarding the layout and organization of our response letter. We recognize that clearer structuring, with each comment explicitly linked to the corresponding manuscript section, would have improved readability. We will implement this recommendation in future submissions. The authors would like to thank the referee for their time and effort in evaluating the article

Reviewer 3 Report

Comments and Suggestions for Authors

Thank you for clarifying the problematic issues from the original review.

I accept your arguments and recommend the manuscript for publication.

Author Response

The authors would like to thank the referee for their time and effort to evaluate the article.