Diamond coatings on femtosecond-laser-textured stainless steel 316 surfaces for enhanced adherence
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2023-12-17 |
| Journal | Diamond and Related Materials |
| Authors | Zhipeng Wu, Wanting Sun, Aofei Mao, Qiuchi Zhu, Xin Chen |
| Institutions | Institut de Chimie de la MatiÚre Condensée de Bordeaux, Centre National de la Recherche Scientifique |
| Citations | 6 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive SummaryâThis research successfully addresses the critical challenge of poor adherence between diamond coatings and Stainless Steel 316 (SS 316) substrates, typically caused by the large coefficient of thermal expansion (CTE) mismatch.
- Core Innovation: Femtosecond (fs)-laser texturing was employed to fabricate periodic microgrids on SS 316 surfaces, significantly enhancing the adherence of diamond coatings grown via Laser-Assisted Combustion Flame Chemical Vapor Deposition (CVD).
- Adherence Mechanism: Enhanced adhesion is attributed primarily to the stress relief provided by the textured surface, which transitions the residual stress in the coating from compressive (on bare steel) to tensile, combined with improved mechanical interlocking.
- Optimal Performance: By optimizing the fs-laser texturing process, diamond coatings achieved a maximum thickness of 19 ”m and a high quality factor of 96% (as determined by Raman spectroscopy).
- Growth Kinetics: Increasing the microgrid depth (up to 40 ”m) accelerated the diamond growth rate and improved coating quality, likely due to enhanced local heat transfer resulting from the expanded surface area.
- Stress Mitigation: The residual tensile stress in the diamond coating decreased from 1.2 GPa to 0.46 GPa as the microgrid depth increased from 10 ”m to 40 ”m, confirming stronger adhesion with deeper texturing.
- Growth Dynamics: The study revealed the growth dynamics, noting that initial internal carburization and catalytic graphitization of Fe, Co, and Ni are overcome by the deposition of high-quality diamond under favorable gas phase conditions.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Substrate Material | SS 316 | N/A | Austenitic stainless steel (82 wt.% Fe, 18 wt.% Cr, 14 wt.% Ni, 3 wt.% Mo, 2 wt.% Mn, 0.08 wt.% C) |
| Maximum Coating Thickness | 19 | ”m | Achieved on 40 ”m deep microgrids. |
| Maximum Diamond Quality Factor | 96 | % | Calculated from Raman spectra (optimized conditions). |
| Average Grain Size (Max) | 9 | ”m | Achieved after 30 min deposition on 40 ”m microgrids. |
| CVD Substrate Temperature | 720 | °C | Maintained during deposition using water cooling. |
| CVD Laser Power (CO2) | 250 | W | Continuous-wave CO2 laser (10.532 ”m wavelength). |
| Gas Flow Ratio (C2H2:C2H4:O2) | 910:400:1200 | sccm | Precursor mixture for combustion flame CVD. |
| fs-Laser Wavelength | 1030 | nm | Used for surface texturing. |
| fs-Laser Pulse Duration | 408 | fs | Used for surface texturing. |
| fs-Laser Power | 14 | W | Used for surface texturing. |
| Microgrid Pitch Distance | 60 | ”m | Constant spacing between textured lines. |
| Maximum Microgrid Depth | 40 | ”m | Achieved using 75 scanning passes. |
| Residual Stress Range (Textured) | 1.2 to 0.46 | GPa | Tensile stress, decreasing with microgrid depth (10 to 40 ”m). |
| CTE (CVD Diamond) | 3.5x10-6 | /K | Coefficient of Thermal Expansion. |
| CTE (SS 316 Steel) | 10.7x10-6 | /K | Coefficient of Thermal Expansion. |
| Diamond Raman Peak Position | 1332 | cm-1 | Characteristic peak for sp3 crystalline diamond. |
Key Methodologies
Section titled âKey MethodologiesâThe experiment combined femtosecond laser texturing with laser-assisted combustion flame CVD to achieve highly adherent diamond coatings.
- Substrate Pretreatment:
- SS 316 plates were cut and ultrasonically cleaned in acetone.
- fs-Laser Texturing:
- A femtosecond laser (1030 nm, 408 fs pulse duration) was used in ambient air.
- Periodic microgrid patterns were created by scanning the laser spot in two perpendicular directions (pitch 60 ”m).
- Microgrid depth was controlled by the number of scanning passes (25, 45, or 75 passes) to achieve depths of 10, 25, and 40 ”m, respectively.
- Diamond Seeding:
- Textured substrates were ultrasonically seeded in a suspension of nanodiamond slurry (particle size less than 10 nm) mixed with ethyl alcohol.
- Laser-Assisted Combustion Flame CVD:
- Diamond coatings were deposited in open air using a mixture of acetylene (C2H2), ethylene (C2H4), and oxygen (O2).
- A continuous-wave CO2 laser (250 W, 10.532 ”m) was used to promote diamond growth by matching the CH2-wagging vibrational mode of ethylene.
- Substrate temperature was maintained at 720 °C using a water-cooling system.
- Characterization:
- Morphology and Thickness: SEM and cross-sectional SEM (after embedding in conductive silver paint and cutting).
- Interfacial Chemistry: Energy Dispersive Spectrometry (EDS) confirmed the presence of a C/Fe interlayer.
- Phase Constitution: X-ray Diffraction (XRD) confirmed the presence of diamond and the phase transformation of austenite to martensite in the steel.
- Quality and Stress: Raman spectroscopy was used to calculate the diamond quality factor and residual stress based on the 1332 cm-1 peak shift.
Commercial Applications
Section titled âCommercial ApplicationsâThe ability to deposit high-quality, highly adherent diamond coatings on stainless steel opens up applications in domains where steelâs structural integrity must be combined with diamondâs superior surface properties.
- High-Performance Mechanical Components:
- Cutting tools and dies requiring extreme hardness and wear resistance.
- Bearings and sliding components operating in high-load or abrasive environments.
- Corrosion and Chemical Resistance:
- Protecting SS 316 components (used widely in chemical and food processing) from environmental erosion and chemical attack.
- Thermal Management in Harsh Environments:
- Components requiring efficient heat dissipation (high thermal conductivity of diamond) while maintaining the mechanical strength of steel.
- Sensors and Instrumentation:
- Protective coatings for sensors operating under extreme temperature, pressure, or chemical conditions.
- Aerospace and Automotive:
- Durable, lightweight components requiring high surface integrity and low friction.
Tech Support
Section titled âTech SupportâOriginal Source
Section titled âOriginal SourceâReferences
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