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

At a Glance

Metadata	Details
Publication Date	2025-07-30
Journal	Surfaces
Authors	Argemiro Pentian, José Vieira da Silva Neto, Javier Sierra Gómez, E.J. Corat, Vladimir Jesús Trava-Airoldi
Institutions	National Institute for Space Research
Analysis	Full AI Review Included

Technical Analysis and Documentation: Laser Texturing for Enhanced CVD Diamond Adhesion

Executive Summary

This document analyzes the research on laser texturing of Tungsten Carbide (WC-Co) substrates to enhance the adhesion and structural integrity of Chemical Vapor Deposition (CVD) diamond films, a critical requirement for high-performance machining tools.

Core Achievement: Pyramidal laser texturing (35 µm pattern) was proven highly effective in optimizing the WC-Co interface for CVD diamond deposition.
Adhesion Mechanism: The texturing process resulted in a 58-fold increase in effective surface area (0.004 m²/g to 0.232 m²/g), maximizing mechanical interlocking between the substrate and the diamond film.
Stress Relief: The pyramidal geometry successfully converted thermal mismatch stresses into beneficial compressive residual stresses, measured at -1.4 GPa.
Process Efficiency: The optimized geometry reduced the critical post-deposition cooling time required for stress relief from 3 hours to just 1 hour, representing a 66% increase in thermal cycle efficiency.
Structural Integrity: Rockwell indentation confirmed superior interface robustness, showing controlled sink-in deformation and the complete suppression of delamination or radial cracking under concentrated loads.
Material Quality: Raman spectroscopy verified the high crystalline quality of the resulting polycrystalline diamond (PCD) film, suitable for demanding industrial applications.

Technical Specifications

The following hard data points were extracted from the research paper detailing the substrate preparation, deposition parameters, and resulting film properties.

Parameter	Value	Unit	Context
Substrate Material	WC-5.8 wt% Co	-	TNMA 160408 inserts
Laser Wavelength	1064	nm	Used for nanosecond-pulsed texturing
Texturing Pattern Geometry	Quadrangular Pyramidal	-	Pattern size: 35 µm
Surface Area Increase Factor	58	-fold	Achieved post-texturing and chemical treatment
Residual Compressive Stress	-1.4	GPa	Measured at the cutting edge via Raman analysis
Optimized Cooling Time	1	h	Reduced from conventional 3 h (66% efficiency gain)
Substrate Deposition Temperature	850	°C	Measured by Type J thermocouple during HFCVD
Reactor Pressure	50	Torr	HFCVD chamber operating pressure
Methane Concentration (CH₄)	2	%	Process gas ratio (balance 98% Hydrogen)
Diamond Growth Rate	1.08	µm/h	Measured over 25 hours of deposition
Final Film Roughness (Ra)	11.55	µm	Limits application to fine finishing operations
Diamond Quality Peak	1334.45	cm^-1	Characteristic Raman peak confirming high sp³ purity

Key Methodologies

The experiment successfully integrated laser texturing, chemical etching, and Hot Filament CVD (HFCVD) to produce highly adherent diamond coatings.

Substrate Preparation: WC-5.8 wt% Co inserts (TNMA 160408) were used as substrates.
Laser Texturing: Substrates were textured using a 1064 nm nanosecond-pulsed laser to create 35 µm quadrangular pyramidal patterns.
Cobalt Removal (Chemical Treatment): A two-stage process was used to remove surface Cobalt and re-solidified material:
- Immersion in Murakami’s solution (K₃[Fe(CN)₆] + KOH + H₂O).
- Immersion in aqua regia (HNO₃/HCl at 1:3 ratio).
Seeding (Nucleation Enhancement): Inserts were immersed for 30 minutes in a solution containing 4 nm diamond powder dispersed with an anionic polymer (PSS), followed by 30 minutes in a cationic polymer (PDDA) solution.
Diamond Growth (HFCVD):
- Reactor setup used five 0.85 mm diameter tungsten filaments positioned 3.2 mm from the insert.
- Gas mixture: 98% H₂ and 2% CH₄.
- Process parameters: 50 Torr pressure, 850 °C substrate temperature.
Characterization: Techniques included SEM/EDS (morphology, Cobalt analysis), BET (surface area quantification), Raman spectroscopy (residual stress calculation via Ager and Drory equation), and Rockwell indentation (adhesion testing).

6CCVD Solutions & Capabilities

6CCVD specializes in providing high-quality MPCVD diamond materials that meet or exceed the requirements for advanced tooling and scientific applications demonstrated in this research. We offer the materials and processing expertise necessary to replicate, optimize, and scale this technology.

Applicable Materials

The research successfully utilized Polycrystalline Diamond (PCD) films. 6CCVD offers superior MPCVD-grown PCD materials optimized for mechanical and thermal applications.

Material Recommendation: Industrial Grade Polycrystalline Diamond (PCD) plates or wafers.
Thickness Control: The paper achieved a film thickness of approximately 27 µm. 6CCVD provides precise thickness control for PCD films ranging from 0.1 µm up to 500 µm, allowing engineers to specify optimal coating depth for tool life and cost efficiency.
Boron Doped Diamond (BDD) Potential: For applications requiring enhanced thermal dissipation or electrochemical stability, 6CCVD offers Boron-Doped Diamond (BDD) films, which can be integrated into similar textured substrates.

Customization Potential

The success of this research relies heavily on precise substrate geometry and interface preparation. 6CCVD supports the integration of our diamond films onto complex, pre-textured substrates.

Research Requirement	6CCVD Custom Capability	Benefit to Customer
Substrate Size/Geometry	Custom Plates up to 125 mm (PCD)	We supply diamond plates in custom dimensions, ready for laser cutting or integration onto large-scale WC-Co inserts or tooling components.
Post-Deposition Finish	Ultra-Low Roughness Polishing	The paper noted high roughness (Ra = 11.55 µm) limits fine finishing. 6CCVD offers polishing services for inch-size PCD down to Ra < 5 nm, enabling high-precision cutting applications.
Metalization Layers	Custom Metalization Services	Although not required in this study, 6CCVD offers in-house metalization (Au, Pt, Pd, Ti, W, Cu) for subsequent brazing or electrical contact integration, crucial for complex tool assembly.
Global Logistics	DDU and DDP Shipping	We ensure reliable, global delivery of sensitive diamond materials, simplifying the supply chain for international research and manufacturing partners.

Engineering Support

The optimization of diamond film adhesion and residual stress for high-performance machining tools is a core competency of 6CCVD.

Application Focus: 6CCVD’s in-house PhD team can assist with material selection and deposition parameter optimization for similar High-Performance Machining Tool projects, ensuring the final diamond coating maximizes the benefits of substrate texturing.
Process Optimization: While the paper used HFCVD, 6CCVD specializes in MPCVD, which typically yields cleaner, higher-quality diamond films with superior control over grain size and morphology, further enhancing the mechanical interlocking achieved by texturing.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

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 µm) 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

Original Source

DOI: https://doi.org/10.3390/surfaces8030054

References

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