Evaluation of the Wear Resistance and Electrochemical Behavior of Drill Bits for Drilling Oil and Gas Wells

Round 1

Reviewer 1 Report

 

(1)   There are still some type errors and hard expressions, please check it very carefully. For example, the hardness of the TCI cutter is 12.93 GPa and that of the indenter is 13.41 GPa so the wear rate shown is the material removed from the sample which is of the order of 10-9.  For example, with respect to the friction coefficient, the value observed in Table 1 for the PCD is not properly that of the sample but of the material that was embedded.

(2)   As for PCD cutter, is there crack mechanism? In your wear test, how about the contact pressure? The pressure is one main factor inducing crack and plastic deformation.

(3)   The difference of corrosion resistance for TCI and PCD is resulting from the difference in the composition and microstructure. It is essential to describe the difference in details.

(4)   How about the serving conditions of cutting tool? How about your test conditions? Is there any difference? So some conclusions may have not the sufficient support.

(1)   There are still some type errors and hard expressions, please check it very carefully. For example, the hardness of the TCI cutter is 12.93 GPa and that of the indenter is 13.41 GPa so the wear rate shown is the material removed from the sample which is of the order of 10-9.  For example, with respect to the friction coefficient, the value observed in Table 1 for the PCD is not properly that of the sample but of the material that was embedded.

Author Response

Response to corrections reviewer 1

 

I hope this message finds you well. We would like to express our gratitude for your valuable feedback and suggestions on our manuscript. We have thoroughly reviewed your comments and have made the necessary revisions to address the concerns raised. Here is a summary of the corrections we have made:

 

Typos and Expression: We have meticulously combed through the manuscript to rectify any typos and instances of harsh expressions. For instance, we have clarified that the hardness of the TCI cutter is 12.93 GPa, and that of the indenter is 13.41 GPa. The presented wear rate indicates the material removed from the sample, quantified at approximately 10^-9. We have also clarified that the coefficient of friction value reported in Table 1 for the PCD cutter pertains to the embedded material, not the sample itself. We have cross-referenced this phenomenon with relevant sources and integrated the necessary references.

 

Cracking Mechanism of PCD Cutter: In response to your query about a potential cracking mechanism in the PCD cutter, we have provided a comprehensive explanation. Furthermore, we have elucidated the contact pressure conditions during the wear test. Recognizing the significance of pressure in triggering cracks and plastic deformation, we have augmented our explanation by incorporating detailed images, ranging from macroscopic to microscopic views. The mechanism has been underscored with additional references for robustness.

 

Corrosion Resistance and Microstructure: We have expanded on the differences in corrosion resistance exhibited by the TCI and PCD cutters, attributing these variations to distinctions in composition and microstructure. Our revised manuscript offers an in-depth analysis of these distinctions. To bolster our explanations, we have introduced a comparative study involving a DLC coating.

 

Cutting Tool Service Conditions and Test Parameters: While we acknowledge the variability between the service conditions of the cutting tool and the parameters employed in our testing, we have clarified our intent. Our aim was to acquire laboratory data that could subsequently be compared with results from hard coatings, analogous to the approach adopted in our corrosion analysis.

 

We sincerely appreciate your engagement with our work and your guidance in refining our manuscript. Your insightful comments have undoubtedly enhanced the quality and clarity of our research. Please consider this revised version as our response to your valuable input.

 

Thank you once again for your time and assistance.

 

Best regards,

The authors

Reviewer 2 Report

In this paper, Tungsten carbide inserts (TCI) and polycrystalline diamond compact (PCD) cutters used
in two types of drill bits for drilling oil and gas wells were evaluated by a pin-on-disc test. Results showed that the
polycrystalline diamond compact cutter has a higher hardness, better corrosion, and wear behavior
compared to tungsten carbide..

The paper could be considered for publication in the journal after the following mandatory revisions:

 

1-better define the novelty of the work at the end of the introduction.

2-it should be “used” in the title.

3-the emphasis should be done at the beginning of abstract as to what test is undertaken and what parameters were investigated.

4-make the abstract more quantitative by providing comparison numbers.  

5-Introduciton could be strengthened. Improve the introduction using the following documents:

 

-(2023). Tribology and dynamic characteristics of textured journal-thrust coupled bearing considering thermal and pressure coupled effects. Tribology International, 180, 108292. doi: https://doi.org/10.1016/j.triboint.2023.108292

-(2023). Effect of cutting parameters on the corrosion resistance of 7A04 aluminum alloy in high speed cutting. Vacuum, 212, 111968. doi: https://doi.org/10.1016/j.vacuum.2023.111968

 

6-figure 1 should be deleted.

7- materials and methods should be in sub-section.

78-correct this sentence “Figure 2. Photo [of the] cutters [that were] employed. “

9-reference the formula that are used.

10-Improve the English of the whole paper. Some vague sentences are seen throughout the paper.

11-it should be “4. results and discussion”

12-consult the following references in the results/discussion section:

 

-(2023). Experimental investigation of the effect of rotation rate and current speed on the dynamic response of riserless rotating drill string. Ocean Engineering, 280, 114542. doi: https://doi.org/10.1016/j.oceaneng.2023.114542

-(2023). Flow accelerated corrosion of X65 steel gradual contraction pipe in high CO2 partial pressure environments. Arabian Journal of Chemistry, 104935. doi: https://doi.org/10.1016/j.arabjc.2023.104935

 

14-define the passive areas in figure 4.

15-Conclusion is a bit long and tedious. It should be in bullet points.

 

 

Improve the English of the whole paper. Some vague sentences are seen throughout the paper.

Author Response

Response to corrections reviewer 2

 

We are appreciative of your meticulous review and insightful suggestions in response to Reviewer 2's comments. Your feedback has been indispensable in refining our manuscript to meet the journal's standards. We present the adjustments we've made based on your guidance:

 

Novelty Definition: Acknowledging the need to elucidate the novelty of our work, we have refined the introduction with additional references. This enhances the clarity surrounding the original contributions of our study.

 

Title Clarification: We recognize the requirement to use "used" in the title. We've made the necessary alteration to ensure compliance with this directive.

 

Summary Emphasis: As recommended, we have emphasized the specific tests conducted and parameters investigated at the outset of the summary. This addition provides readers with immediate insight into the scope of our study.

 

Quantitative Summary: To offer a more quantitative summary, we've incorporated comparison numbers to augment the understanding of our findings.

 

Strengthening the Introduction: Your provided references have been incorporated into the introduction, bolstering its foundation and aligning with our study's context.

 

Numerical Correction: The unnecessary digit "1" has been removed as instructed.

 

Materials and Methods Structure: To adhere to the formatting requirement, we have restructured the "Materials and Methods" section into subsections. Additionally, we have enhanced the description of the experimental design and detailed the SEM and corrosion equipment employed.

 

Image Description Correction: The sentence "Figure 2. Photo [of the] cutters [that were] used" has been rectified to accurately describe the images.

 

Formula Reference: The utilized formulas have been cross-referenced with appropriate sources.

 

Language Refinement: To address vagueness in sentences, we have undergone English language refinement.

 

Section Numbering: The section heading "4. Results and Discussion" has been retained as originally indicated.

 

Referencing Suggestion: Your recommended references have been reviewed, and those that align with the analysis of results or the introduction have been included as appropriate.

 

Passive Area Clarification: Given the complexities surrounding the determination of passive zones for the materials, we've clarified this in the corrosion analysis by referencing previous literature.

 

Conclusion Structure: Responding to your suggestion, the conclusion has been restructured into bullet points. This revision enhances its readability and conciseness while maintaining a systematic order of the conducted tests.

 

We extend our gratitude for your devoted effort to guide us in enhancing our manuscript. Please consider this revised version as our response to your invaluable insights.

 

Thank you for your continued support and invaluable assistance.

 

Warm regards,

The authors

Reviewer 3 Report

Evaluation of corrosion are the first words of the title of the submitted article. However, only one method has been applied to evaluate the corrosion behavior of both cutters: polarization curves. This method is destructive, applying external polarization, and in the real environment there is not such external polarization. Besides, the polarization curves do not present the Tafel regions and thus, the values of Ecorr and Icorr (table 2) are not correct.

For corrosion evaluation of materials, one simple methos is immersion test: exposed samples of the material for no less than several months, starting the register of the free corrosion potential (at open circuit, without external polarization) since the first hours until no less than 30 days. If there is not change in time after this short period, one should continue the experiment for longer time of the immersion test. During this test, samples (in triplicate) should be removed and characterize the surface (SEM-EDS, XRD for the for the composition of the formed layer, corrosion attack and more).

So, this part of the study has not been performed and thus, the conclusion for the corrosion resistance is out.

 

Author Response

Response to corrections reviewer 3

 

I trust this message finds you well. We extend our sincere appreciation for your insightful feedback and suggestions, which have been instrumental in refining our manuscript. Following your guidance, we have made the necessary revisions to address the concerns highlighted in Reviewer 3's comments. Allow us to present an overview of the corrections made:

 

Corrosion Assessment Methodology: We acknowledge the discrepancy between the title and the single method employed to assess corrosion behavior – polarization curves. We concur that this method, while valuable, introduces a bias that diverges from real-world conditions. Further, we appreciate your insight on the Tafel regions, which has prompted us to re-evaluate our Ecorr and Icorr values (table 2). To this end, we have repositioned the focus of the article to primarily address wear due to friction, while considering corrosion as a secondary aspect. New citations have been incorporated to validate this shift in emphasis. Additionally, the analysis of wear mechanisms arising from the wear test has been augmented.

 

Alternative Corrosion Evaluation Method: Your suggestion regarding the immersion test for corrosion evaluation is well-received. We acknowledge the practicality of this method in capturing longer-term corrosion effects. The proposed procedure involves exposing material samples for an extended duration while monitoring the free corrosion potential, followed by surface characterization through techniques such as SEM-EDS and XRD. However, in line with our revised focus on wear behavior, we have refrained from conducting this specific corrosion evaluation. As such, the discussion and conclusion related to corrosion resistance have been updated to align with the modified scope of our study.

We deeply value your engagement with our work, which has undoubtedly enhanced the clarity and rigor of our research. Please consider this revised version as our response to your constructive input.

Thank you once again for your invaluable time and guidance.

 

Warm regards,

The authors

Reviewer 4 Report

The PCD cutters exhibited better wear resistance, higher hardness, and better corrosion resistance, which is expected for this type of material. On the other hand, TCI exhibited lower corrosion resistance due to the exchange of electrons with the electrolyte through the cobalt present in the material. Although each insert has a specific application for well drilling, PCD cutters can be applied in more aggressive environments due to their corrosion and wear behavior, but the cost of these is at least five times more than TCI inserts. For this reason, it is necessary to look for a material with similar characteristics and is more affordable; an option would be the DLC coatings, which are under investigation.

 

The manuscript provides a concise overview of the study, mentioning the materials evaluated (tungsten carbide inserts and polycrystalline diamond compact cutters), the test methods used (pin-on-disc test and electrodynamic polarization technique), and the main findings (better wear resistance, higher hardness, and better corrosion resistance of PCD cutters compared to TCI). However, the manuscript could benefit from adding more specific details about the study's scope and significance.

Context and Objectives: The manuscript lacks a clear statement of the research objectives and the problem being addressed. It would be helpful to include a sentence or two explaining the motivation behind evaluating corrosion and wear resistance of these cutters and why this evaluation is essential for the drilling industry.

Test Methods: The manuscript briefly mentions the pin-on-disc test and electrodynamic polarization technique, but it would be beneficial to provide a sentence explaining the significance of these test methods and how they are relevant to assessing corrosion and wear resistance in the context of drill bits.

Specific Findings: The manuscript states that PCD cutters have higher hardness and better corrosion and wear behavior compared to TCI. However, it would be valuable to quantify these improvements, providing specific data or percentage differences to highlight the significance of the findings.

Cost Consideration: The manuscript mentions the cost difference between PCD cutters and TCI inserts but does not elaborate on the cost implications for the drilling industry. It would be helpful to briefly discuss the potential impact of the cost difference on drilling operations and how it influences the choice of cutter materials.

Recommendations and Future Directions: The manuscript concludes by suggesting the investigation of DLC coatings as an alternative material. It would be beneficial to expand on this point, explaining why DLC coatings are a potential option, and what advantages they may offer in terms of wear and corrosion resistance and cost-effectiveness compared to PCD and TCI.

The PCD cutters exhibited better wear resistance, higher hardness, and better corrosion resistance, which is expected for this type of material. On the other hand, TCI exhibited lower corrosion resistance due to the exchange of electrons with the electrolyte through the cobalt present in the material. Although each insert has a specific application for well drilling, PCD cutters can be applied in more aggressive environments due to their corrosion and wear behavior, but the cost of these is at least five times more than TCI inserts. For this reason, it is necessary to look for a material with similar characteristics and is more affordable; an option would be the DLC coatings, which are under investigation.

 

The manuscript provides a concise overview of the study, mentioning the materials evaluated (tungsten carbide inserts and polycrystalline diamond compact cutters), the test methods used (pin-on-disc test and electrodynamic polarization technique), and the main findings (better wear resistance, higher hardness, and better corrosion resistance of PCD cutters compared to TCI). However, the manuscript could benefit from adding more specific details about the study's scope and significance.

Context and Objectives: The manuscript lacks a clear statement of the research objectives and the problem being addressed. It would be helpful to include a sentence or two explaining the motivation behind evaluating corrosion and wear resistance of these cutters and why this evaluation is essential for the drilling industry.

Test Methods: The manuscript briefly mentions the pin-on-disc test and electrodynamic polarization technique, but it would be beneficial to provide a sentence explaining the significance of these test methods and how they are relevant to assessing corrosion and wear resistance in the context of drill bits.

Specific Findings: The manuscript states that PCD cutters have higher hardness and better corrosion and wear behavior compared to TCI. However, it would be valuable to quantify these improvements, providing specific data or percentage differences to highlight the significance of the findings.

Cost Consideration: The manuscript mentions the cost difference between PCD cutters and TCI inserts but does not elaborate on the cost implications for the drilling industry. It would be helpful to briefly discuss the potential impact of the cost difference on drilling operations and how it influences the choice of cutter materials.

Recommendations and Future Directions: The manuscript concludes by suggesting the investigation of DLC coatings as an alternative material. It would be beneficial to expand on this point, explaining why DLC coatings are a potential option, and what advantages they may offer in terms of wear and corrosion resistance and cost-effectiveness compared to PCD and TCI.

Author Response

Response to corrections reviewer 4

 

We are grateful for your thoughtful feedback and constructive suggestions regarding Reviewer 4's comments. Your insights have been instrumental in refining our manuscript to better communicate the significance and scope of our study. Here, we present the enhancements we've made in response to your guidance:

 

Context and Objectives: We acknowledge the need for a clear articulation of our research objectives and the problem we seek to address. As such, we have bolstered the introduction by providing a more explicit description of the motivation behind evaluating the corrosion and wear resistance of tungsten carbide inserts (TCI) and polycrystalline diamond compact cutters (PCD). We now highlight the relevance of this evaluation to the drilling industry, emphasizing its importance for enhancing tool performance under challenging operating conditions.

 

Test Methods: Your recommendation to elucidate the importance of the test methods used has been duly noted. We've integrated a sentence that underscores the significance of the pin-on-disc testing and electrodynamic polarization technique. By establishing the relevance of these methods in assessing corrosion and wear resistance within the context of drill bits, we enhance the readers' understanding of our experimental approach. We've also acknowledged the limitations of completely emulating service conditions.

 

Specific Findings: We understand the value of quantifying our findings to emphasize the improvements observed. As a result, we've provided a more detailed explanation of the calculation of the wear rate, with explicit clarification regarding the PCD insert's immersion in the indenter. Although specific percentages were not included due to the aforementioned clarification, we've ensured a comprehensive understanding of the comparison. Additionally, we've mentioned the possibility of future work involving a comparison with Diamond-like Carbon (DLC) coatings, particularly in the context of corrosion testing.

 

Cost Consideration: Your point about addressing the cost implications of the studied materials is well-received. While specific references about individual insert costs were challenging to locate, we've incorporated a brief discussion regarding the substantial cost differences in production between PCD cutters and TCI inserts. We've reframed the context to reflect the impact on drilling operations and the material selection process.

 

Recommendations and Future Directions: The inclusion of a broader discussion on DLC coatings has been further emphasized, as suggested. We've expanded on this point to elucidate why DLC coatings are an appealing alternative, particularly in terms of their potential advantages in wear and corrosion resistance, as well as cost-effectiveness. We've reiterated our intention to investigate DLC coatings in future work and to compare their performance with the results obtained in our study.

 

We extend our gratitude for your unwavering commitment to improving our manuscript. Please consider this revised version as our response to your invaluable insights.

 

Thank you for your continued guidance and support.

 

Warm regards,

The authors

Round 2

Reviewer 1 Report

As all my comments have been responded, I recommend this work to be accepted.

Reviewer 2 Report

The revised version of the paper can be accepted for publication. 

Reviewer 4 Report

Accept

Accept