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6CCVD Research

Laser Texturing of Tungsten Carbide (WC-Co) - Effects on Adhesion and Stress Relief in CVD Diamond Films

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2025-07-30
JournalSurfaces
AuthorsArgemiro Pentian, JosĂ© Vieira da Silva Neto, Javier Sierra GĂłmez, E.J. Corat, Vladimir JesĂșs Trava-Airoldi
InstitutionsNational Institute for Space Research
AnalysisFull AI Review Included

Executive Summary

Section titled “Executive Summary”

This study successfully implemented laser texturing on Tungsten Carbide (WC-Co) substrates to significantly enhance the adhesion and durability of Chemical Vapor Deposition (CVD) diamond films, primarily targeting high-performance cutting tool applications.

  • Adhesion Enhancement: Pyramidal laser texturing (35 ”m features) increased the effective surface area by a factor of 58 (from 0.004 m2/g to 0.232 m2/g), promoting superior three-dimensional mechanical interlocking.
  • Stress Management: The optimized pyramidal geometry effectively dissipated thermal mismatch stresses, resulting in a low compressive residual stress of -1.389 GPa in the diamond film.
  • Interface Robustness: Rockwell indentation tests (150 kg load) confirmed excellent interfacial integrity, showing controlled deformation (sink-in) without the formation of delamination or radial cracks.
  • Process Efficiency: The pyramidal texturing allowed for a 66% reduction in post-deposition cooling time (from 3 hours to 1 hour) while maintaining structural integrity and high film quality.
  • Film Quality: Raman spectroscopy confirmed the high crystalline quality of the deposited diamond, evidenced by a sharp sp3 peak at 1334.45 cm-1, indicating purity and structural stability.

Technical Specifications

Section titled “Technical Specifications”
ParameterValueUnitContext
Substrate CompositionWC-5.8 wt% Co-TNMA 160408 inserts
Texturing Feature Size35”mQuadrangular pyramidal pattern
Laser Wavelength1064nmNanosecond-pulsed laser
Surface Area Increase Factor58-Post-treatment vs. as-received
Post-Treatment Surface Area0.232m2/gBET measurement
Residual Stress (Compressive)-1.389GPaCalculated via Raman spectroscopy
Diamond Raman Peak1334.45cm-1Characteristic sp3 peak
HFCVD Substrate Temperature850°CMeasured by Type J thermocouple
Process Pressure50TorrHFCVD chamber pressure
Gas Concentration (CH4)2%Balance H2 (98%)
Diamond Growth Rate1.08”m/hOver 25 h deposition time
Diamond Film Roughness (Ra)11.55”mMeasured profile roughness
Cooling Time Optimization66%Reduction from 3 hours to 1 hour
Indentation Load150kgRockwell adhesion test

Key Methodologies

Section titled “Key Methodologies”
  1. Laser Surface Texturing: WC-Co substrates were textured using a 1064 nm nanosecond laser to create 35 ”m pyramidal features, enhancing surface topography for mechanical anchoring.
  2. Cobalt Removal: A two-stage chemical process was applied post-texturing to remove surface cobalt and laser-induced re-solidified material:
    • Stage 1: Immersion in Murakami’s solution.
    • Stage 2: Immersion in aqua regia (HNO3/HCl = 1:3).
  3. Nucleation Seeding: Substrates were seeded using a two-step polymer-assisted method involving 4 nm diamond powder dispersed sequentially with anionic (PSS) and cationic (PDDA) polymers to maximize nucleation density.
  4. Diamond Film Growth (HFCVD): Deposition occurred at 850 °C and 50 Torr, utilizing a gas mixture of 98% H2 and 2% CH4, resulting in a 1.08 ”m/h growth rate over 25 hours.
  5. Stress and Quality Analysis: Raman spectroscopy was used to confirm high crystalline quality (peak at 1334.45 cm-1) and quantify residual compressive stress (-1.389 GPa) using the Ager and Drory equation.
  6. Adhesion Testing: Film-substrate adhesion was evaluated using Rockwell indentation (150 kg load, 10 s dwell time) to verify the suppression of interfacial cracks and delamination.

Commercial Applications

Section titled “Commercial Applications”

The robust, stress-relieved diamond coatings developed through this laser texturing technique are highly suitable for industrial applications requiring exceptional durability and interface stability under extreme conditions.

  • High-Performance Cutting Tools: Ideal for machining difficult materials (e.g., composites, non-ferrous alloys) where conventional coatings fail due to thermal stress and poor adhesion.
  • Industrial Tool Production: The 66% reduction in post-deposition cooling time significantly improves manufacturing throughput, making the process viable for large-scale production of diamond-coated inserts (like TNMA 160408).
  • Wear Components: Applicable to mechanical parts subjected to high friction and abrasive wear, benefiting from the enhanced mechanical interlocking and low residual stress.
  • Thermal Management Components: The pyramidal geometry promotes uniform heat dissipation and accelerates heat transfer (58 times greater surface area), potentially benefiting components requiring rapid thermal cycling stability.
View Original Abstract

This study proposes a laser texturing method to optimize adhesion and minimize residual stresses in CVD diamond films deposited on tungsten carbide (WC-Co). WC-5.8 wt% Co substrates were textured with quadrangular pyramidal patterns (35 ”m) using a 1064 nm nanosecond-pulsed laser, followed by chemical treatment (Murakami’s solution + aqua regia) to remove surface cobalt. Diamond films were grown via HFCVD and characterized by Raman spectroscopy, EDS, and Rockwell indentation. The results demonstrate that pyramidal texturing increased the surface area by a factor of 58, promoting effective mechanical interlocking and reducing compressive stresses to −1.4 GPa. Indentation tests revealed suppression of interfacial cracks, with propagation paths deflected toward textured regions. The pyramidal geometry exhibited superior cutting post-deposition cooling time for stress relief from 3 to 1 h. These findings highlight the potential of laser texturing for high-performance machining tool applications.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 1982 - Vapor Deposition of Diamond Particles from Methane [Crossref]
  2. 2023 - A review of thermal properties of CVD diamond films [Crossref]
  3. 1996 - Thermal stresses in diamond coatings and their influence on coating wear and failure [Crossref]
  4. 2022 - Tribological performance of micro textured surface machined by Nd:YAG laser with different incident angle [Crossref]
  5. 2014 - Femtosecond laser surface structuring of carbide tooling for modifying contact phenomena [Crossref]
  6. 2016 - Nano-and microcrystalline diamond deposition on pretreated WC-Co substrates: Structural properties and adhesion [Crossref]
  7. 2012 - CVD diamond films growth on silicon nitride inserts (Si3N4) with high nucleation density by functionalization seeding [Crossref]
  8. 1993 - Diamond growth by hot-filament chemical vapor deposition: State of the art [Crossref]
  9. 1989 - The role of the tungsten filament in the growth of polycrystalline diamond films by filament-assisted CVD of hydrocarbons [Crossref]

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