Impact of Peak Material Volume of Polycrystalline CVD Diamond Coatings on Dry Friction Against Aluminum
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-05-07 |
| Journal | JOM |
| Authors | M. Prieske |
| Institutions | Bremen Institute for Applied Beam Technology |
| Citations | 3 |
| Analysis | Full AI Review Included |
Technical Documentation: Optimized Polycrystalline CVD Diamond for Dry Tribology
Section titled âTechnical Documentation: Optimized Polycrystalline CVD Diamond for Dry TribologyâThis document analyzes the findings of the research paper âImpact of Peak Material Volume of Polycrystalline CVD Diamond Coatings on Dry Friction Against Aluminumâ and outlines how 6CCVDâs advanced MPCVD capabilities can meet and exceed the material requirements for high-performance dry forming and tribological applications.
Executive Summary
Section titled âExecutive SummaryâThe research successfully identified the critical surface topology parameterâPeak Material Volume (Vmp)ârequired for achieving ultra-low friction and wear rates in dry tribological contact between CVD diamond coatings and aluminum (EN AW 5083).
- Critical Parameter Identified: The Peak Material Volume (Vmp) is the primary predictor for minimizing aluminum abrasion and achieving a low coefficient of friction (COF).
- Performance Target: To minimize wear, the Vmp of the diamond coating surface must be maintained below 0.04 ml/m2.
- Optimal Material: Microcrystalline Polycrystalline CVD Diamond (PCD) with subsequent mirror-polishing achieved the best results, demonstrating the lowest wear rate (4.5 x 10-9 mm3/Nm).
- Friction Stability: The highly polished coating (CVDD 10.25p) exhibited the most constant and lowest COF (0.12-0.13) throughout the 99,900-cycle test.
- Methodological Insight: Standard roughness parameters (Ra, Rq) were found to be insufficient for predicting tribological performance; precise control over the Vmp parameter is essential for engineering dry forming tools.
- 6CCVD Value Proposition: 6CCVD specializes in producing high-purity PCD and SCD materials with custom post-processing, including mirror polishing (Ra < 1nm) necessary to achieve the required ultra-low Vmp values for competitive dry forming applications.
Technical Specifications
Section titled âTechnical SpecificationsâThe following table summarizes the critical performance metrics and material parameters derived from the tribological investigation.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Target Application | Dry Forming/Shaping | N/A | Aluminum alloy EN AW 5083 counter body |
| Tribometer Test Type | Oscillating Ball-on-Plate | N/A | Dry contact, 99,900 cycles |
| Hertzian Contact Stress | 759 | MPa | Simulating sheet metal forming conditions |
| Test Velocity | 50 | mm/s | N/A |
| Critical Topology Parameter | Peak Material Volume (Vmp) | ml/m2 | Primary factor correlating to low wear and friction |
| Recommended Vmp Target | < 0.04 | ml/m2 | Required to minimize aluminum wear rate |
| Lowest Achieved Vmp | 0.001 | ml/m2 | Achieved by mirror-polished CVDD 10.25p |
| Lowest Aluminum Wear Rate | 4.5 x 10-9 | mm3/Nm | Achieved by mirror-polished CVDD 10.25p |
| Lowest Friction Coefficient (COF) | 0.12 - 0.13 | N/A | Achieved by mirror-polished CVDD 10.25p |
| Best Surface Roughness (Sa) | 0.02 | ”m | Achieved by mirror-polished CVDD 10.25p |
| Raman Quality Factor (Q) | 0.8 - 0.9 | N/A | High quality factor (sp3 concentration) |
Key Methodologies
Section titled âKey MethodologiesâThe experiment utilized atmospheric pressure CVD diamond coatings deposited on K10 hard metal (WC-Co) substrates, followed by various surface post-treatments.
- Substrate Preparation: K10 hard metal discs (20.3 mm diameter) were etched using Murakami reagent and Caroâs reagent to remove cobalt and prepare the surface.
- Nucleation: Substrates were nucleated using a dispersion of 0.25 ”m to 0.50 ”m diamond powder in isopropanol via ultrasonic bath treatment.
- Deposition Method: Laser-based plasma CVD process at atmospheric pressure was used.
- Process Gas Parameters:
- Total gas flow: 2 standard liters per minute (slm) of CH4/H2 mixture.
- Argon plasma flame flow: 26 slm.
- CH4/H2 ratio varied from 1% to 5%.
- Deposition Temperature: Varied from 750 °C to 1050 °C.
- Deposition Time: Varied from 12 minutes to 40 minutes.
- Post-Treatment: Coatings were either left untreated, mechanically polished (âpâ), or rubbed against another diamond layer (ârâ) to modify surface topology.
- Characterization: Surface roughness parameters (DIN EN ISO 25178) were measured using 3D laser microscopy. Diamond quality (sp3/sp2 ratio) was assessed via Micro-Raman spectroscopy (514 nm excitation).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe findings confirm that achieving optimal dry tribological performance requires precise control over diamond crystal size, film thickness, and, critically, post-deposition surface finishing to minimize the Peak Material Volume (Vmp). 6CCVD is uniquely positioned to supply materials engineered to these exact specifications.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate or extend this research, 6CCVD recommends materials optimized for ultra-low roughness and high purity:
| 6CCVD Material Recommendation | Rationale & Application |
|---|---|
| High-Purity Polycrystalline CVD Diamond (PCD) | Ideal for high-volume dry forming tools. We offer custom crystal sizes (microcrystalline, similar to the paperâs successful samples) and thicknesses up to 500 ”m, grown on various substrates (including WC-Co). |
| Optical Grade Single Crystal Diamond (SCD) | For applications requiring the absolute lowest friction and wear. SCD offers superior initial surface quality and can be polished to Ra < 1 nm, ensuring Vmp values significantly lower than the 0.04 ml/m2 threshold. |
| Custom Substrates | While the paper used K10 hard metal, 6CCVD can deposit PCD/SCD films on custom substrates, including Si, Mo, W, or specialized ceramics, tailored to the clientâs thermal and mechanical requirements. |
Customization Potential for Tribology Engineers
Section titled âCustomization Potential for Tribology EngineersâThe key to the paperâs success was the mirror-polished surface (CVDD 10.25p, Vmp = 0.001 ml/m2). 6CCVD offers industry-leading post-processing capabilities essential for achieving these results:
- Ultra-Low Roughness Polishing: We guarantee surface roughness down to Ra < 5 nm for inch-size PCD plates and Ra < 1 nm for SCD, ensuring the Vmp parameter is minimized for optimal dry friction performance.
- Custom Dimensions: While the paper used 20.3 mm discs, 6CCVD can supply PCD plates/wafers up to 125 mm in diameter, suitable for scaling up industrial dry forming processes.
- Thickness Control: We provide precise thickness control for PCD coatings from 0.1 ”m up to 500 ”m, allowing engineers to optimize cost and performance based on expected tool life.
- Metalization Services: If the application requires integration into complex tooling, 6CCVD offers in-house metalization capabilities (Au, Pt, Pd, Ti, W, Cu) for reliable bonding and electrical contact.
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD team specializes in the relationship between MPCVD growth parameters, crystal morphology, and resulting surface topology. We can assist clients in defining the precise material specifications needed for similar Dry Metal Shaping and Forming projects:
- Vmp Optimization: We consult on growth recipes and polishing techniques specifically targeting the required Vmp value (< 0.04 ml/m2) to ensure maximum tool life and minimum COF.
- Quality Assurance: We provide detailed surface metrology reports, including 3D roughness parameters (Sa, Spk, Vmp, etc.) according to DIN EN ISO 25178, guaranteeing the material meets the critical tribological requirements identified in this research.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract For economic and environmental reasons, dry forming is of increasing interest due to the shortening of process chains, cost savings and reduction of environmental pollution. The aim of these investigations is to examine to what extent chemical vapor deposited (CVD) diamond coatings are suitable for dry forming of aluminum and to identify the surface topology requirements for a low friction coefficient and low wear. Nine different surface topologies of CVD diamond coatings were tested in an oscillating ball-on-plate tribometer test against aluminum balls with a Hertzian contact stress of 759 MPa and 99,900 cycles. It could be concluded that the peak material volume (Vmp) of the diamond coating is the most important factor for achieving a low abrasion of aluminum as well as a low friction coefficient against aluminum. The Vmp should be smaller than 0.04 ml/m 2 . Microcrystalline CVD diamond with a post-treated surface has great potential for dry forming of aluminum.