Synthesis of Vanadium Interface for HFCVD Diamond Deposition on Steel Surface

At a Glance

Metadata	Details
Publication Date	2017-07-06
Journal	Materials Research
Authors	Djoille Denner Damm, André Contin, Vladimir Jesús Trava-Airoldi, Getúlio de Vasconcelos, Danilo Maciel Barquete
Institutions	Instituto de Estudos Avançados da Universidade de São Paulo, Universidade Estadual de Santa Cruz
Citations	6
Analysis	Full AI Review Included

Technical Documentation and Analysis: Diamond Coatings on Steel Substrates

Executive Summary

The analyzed research details a successful methodology for depositing Hot Filament Chemical Vapor Deposition (HFCVD) diamond onto AISI D6 steel by utilizing a laser-clad Vanadium Carbide (VC) interlayer. This approach effectively addresses the critical challenges of poor adhesion and high residual thermal stress inherent in direct diamond-to-steel deposition.

Diffusional Barrier Success: A 5 µm thick Vanadium Carbide (V${8}$C${7}$) layer, formed via two-step laser cladding, acts as an effective diffusion barrier against iron, preventing graphitic formation at the interface.
Stress Mitigation: The VC transition zone successfully absorbs thermal mismatch, resulting in a high, stable 5.74 GPa compressive stress in the deposited diamond film, proving excellent film-to-substrate adhesion.
Optimal Morphology: HFCVD yielded high-quality polycrystalline diamond films characterized by fine grains (< 1 µm) and low surface roughness, ideal for demanding hard coating and cutting tool applications.
Process Optimization: Laser Cladding parameters (600 DPI, 100 mm/s) were optimized to achieve strong metallurgical bonding, minimizing porosity and establishing an optimal 37 µm Heat Affected Zone (HAZ).
6CCVD Relevance: This work validates the necessity of engineered intermediate layers for CVD diamond applications on ferrous materials, a requirement directly supported by 6CCVD’s capabilities in custom MPCVD growth and advanced material integration.
Future Improvement: The paper noted residual graphitic phase (1586.45 cm⁻¹ peak), indicating a need for improved purity control—a core advantage of 6CCVD’s specialized MPCVD growth recipes.

Technical Specifications

The following hard data points were extracted from the research paper detailing the optimized deposition process and material characteristics.

Parameter	Value	Unit	Context / Condition
Substrate Material	AISI D6	Steel	Tool steel used for hard coating application.
Interlayer Composition (Dominant)	V${8}$C${7}$	Phase	Ordered vanadium carbide state, primary diffusion barrier.
Interlayer Thickness (LCVC)	5	µm	Achieved with optimized 600 DPI, 100 mm/s parameters.
Heat Affected Zone (HAZ) Depth	37	µm	Transition zone depth for optimal adhesion and stress relief.
Diamond Deposition Method	HFCVD	N/A	Hot Filament CVD technique used for growth.
Deposition Temperature	700	°C	Substrate temperature during HFCVD.
Reactor Pressure	20	Torr	Pressure used during HFCVD growth.
Growth Time	3	hours	Total processing time for the diamond film.
Methane Flow (CH$_{4}$)	6	sccm	Methane precursor flow rate.
Hydrogen Flow (H$_{2}$)	194	sccm	Hydrogen etching gas flow rate.
Diamond Compressive Stress ($\sigma$)	5.74	GPa	Calculated residual stress, confirming high adhesion (Equation 1).
Diamond Raman Shift (v$_{m}$)	1342.13	cm⁻¹	Shift relative to the natural diamond peak (1332 cm⁻¹).
Diamond Grain Size	< 1	µm	Resulting morphology suitable for fine cutting tools.
Maximum HAZ Depth Observed	64	µm	Result of high energy input (900 DPI, 100 mm/s).

Key Methodologies

The synthesis involved a precise, two-stage process combining specialized surface modification (Laser Cladding) with subsequent HFCVD diamond growth.

1. Substrate and Precursor Preparation

Substrate: AISI D6 steel disks (18 mm diameter x 4 mm height) were mechanically sanded (220, 400, 600 grit) and ultrasonically cleaned in acetone.
Precursor: Commercially available 99% pure Vanadium Carbide (VC) powder with an average particle size of 10 µm was used.

2. Two-Step Laser Cladding (LC)

Powder Application: VC powder dispersed in isopropyl alcohol was sprayed onto the substrate surface and dried at 100 °C for 5 minutes.
Laser Processing: A Synrad-SH CO$_{2}$ laser (125 W output power, 200 µm beam diameter, 400 kW/cm² intensity) scanned the powder surface under nitrogen purge.
- Optimal Parameters: Resolution of 600 DPI, scanning speed of 100 mm/s, and one Number of Heating Cycles (NHC).
- Result: Formation of the 5 µm LCVC coating (V${8}$C${7}$, VCrFe${8}$, Fe${2}$O$_{3}$) and a 37 µm HAZ, ensuring strong metallurgical bonding.

3. HFCVD Diamond Deposition

Equipment: The diamond film was grown using Hot Filament CVD.
Recipe: The substrate temperature was maintained at 700 °C, and the reactor pressure was 20 Torr.
Gas Mixture: 6 sccm Methane (CH${4}$) and 194 sccm Hydrogen (H${2}$). (Note: Higher CH$_{4}$ concentration, up to 3%, was tested to improve graphitization for stress relief.)
Duration: 3 hours.

4. Characterization

Microscopy: Morphology and thickness analyzed via FEG-SEM (Field Emission Scanning Electron Microscopy).
Composition: Element distribution confirmed by EDS (Energy Dispersive X-ray Spectroscopy) and phase identification by XRD (X-ray Diffractometry, Cu-K$\alpha$ radiation).
Quality/Stress: Residual thermal stress (5.74 GPa compressive) and film purity verified using Raman spectroscopy (325 nm excitation).

6CCVD Solutions & Capabilities

6CCVD’s advanced MPCVD technology is ideally suited to replicate, refine, and scale the production of high-performance diamond coatings on specialized substrates, offering superior purity control and customization over HFCVD methods.

Applicable Materials

The requirements defined by this research—specifically the need for a highly robust, low-roughness, fine-grained hard coating suitable for demanding mechanical applications—is best met by 6CCVD’s Polycrystalline Diamond (PCD) materials.

Core Recommendation: Microcrystalline Polycrystalline Diamond (PCD) Wafers and Plates.
- Benefit: 6CCVD MPCVD systems offer tighter control over nucleation density and grain size compared to HFCVD, allowing for precise engineering of the required sub-micron grain structure (< 1 µm) and low surface roughness (Ra < 5 nm).
- Purity Improvement: The researchers noted residual graphitic phases (1586.45 cm⁻¹). 6CCVD’s high-purity MPCVD reactors can significantly minimize sp² inclusion, guaranteeing high-quality, high-adhesion PCD films while maintaining necessary residual stress control.

Customization Potential

The research highlights the critical importance of dimensionally precise coatings and integrated transition layers (VC cladding). 6CCVD offers full vertical integration to meet these engineering demands:

Required Capability	6CCVD Solution	Technical Advantage
Custom Substrate Handling	Specialized Fixturing	Capability to handle challenging, non-standard materials (e.g., AISI D6 Steel) and complex geometries required for integration with cladding processes.
Interface Engineering	Custom Metalization Services (Ti/W/Pt/Au, etc.)	While the paper used VC cladding, 6CCVD offers in-house Ti/Pt/Au and other metalization schemes to create robust chemical or mechanical transition layers prior to diamond growth, potentially eliminating the need for external laser cladding post-processing.
Dimension & Thickness	Wafers up to 125 mm; Thickness 0.1 µm - 500 µm	Capability to scale the reported 5 µm film thickness to large-area plates (up to 125mm PCD) or specialized hard coatings up to 500 µm, with custom laser cutting for specific tooling dimensions.
Surface Finish	Sub-nanometer Polishing	Polishing services achieving Ra < 5 nm on inch-size PCD, significantly surpassing the “low surface roughness” achieved in the paper, extending wear life for cutting tools.

Engineering Support

This study demonstrates an application requiring intricate knowledge of thermal expansion matching and chemical diffusion barriers. 6CCVD’s in-house PhD engineering team specializes in tailoring diamond growth recipes to solve these complex material challenges.

We provide comprehensive consultation for projects involving advanced hard coatings, heat spreading, and structural components on dissimilar materials. Our expertise can assist researchers and engineers in selecting the optimal MPCVD recipe (e.g., optimizing methane concentration and growth rate) to manage film stress and enhance crystallinity for similar High-Performance Hard Tooling and Wear Resistance projects.

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

View Original Abstract

Laser cladding of vanadium carbide powder developed an interlayer on AISI D6 steel as a diffusional barrier and to relief thermal residual stress.Laser cladding experiments varied resolution (DPI) and scanning speed (mm/s).CVD diamond deposition on this interface went on by HFCVD technique.The coatings were characterized by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM-FEG) and Raman spectroscopy.Ordered state V 8 C 7 phase prevailed in the interlayer.The thickness of heat-affected zone (HAZ) and Laser Cladding Vanadium Coating (LCVC) were 37 µm and 5 µm, respectively, in the best layer produced.The diamond film showed good quality and morphology.The Raman peak at 1342,13 cm -1 shows the residual stresses level undertaken at the film-substrate interface and the corresponding adhesion, demonstrating the suitability of the VC laser cladding process to CVD diamond films deposition.

Tech Support

Original Source

DOI: https://doi.org/10.1590/1980-5373-mr-2016-1053

References

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