Influence of parameters in the magnetron sputtering process (HiPIMS) on the mechanical and antibacterial properties of silver-doped DLC coatings
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2025-05-20 |
| Journal | Archives of Civil and Mechanical Engineering |
| Authors | Artur Albert Kozera, Z. SĆomka, Joanna KacprzyĆska-GoĆacka, RafaĆ ChoduĆ, Daniel PaÄko |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Silver-Doped DLC Coatings
Section titled âTechnical Documentation & Analysis: Silver-Doped DLC CoatingsâExecutive Summary
Section titled âExecutive SummaryâThis documentation analyzes the research on silver-doped Diamond-Like Carbon (DLC) coatings deposited via High-Power Impulse Magnetron Sputtering (HiPIMS) for antiwear and antibacterial applications.
- Core Achievement: The study successfully created multilayer Cr-CrN-DLC(Ag) coatings on 316L steel substrates, achieving 100% bactericidal efficacy against both Escherichia coli and Staphylococcus aureus across all tested silver concentrations.
- Methodology: HiPIMS was used, controlling the silver content (ranging from 0.3% to 16%) by varying the Ag target pulse frequency (200 Hz to 800 Hz).
- Mechanical Trade-off: Increasing silver content led to a significant decrease in mechanical properties, with hardness dropping from ~14 GPa (pure DLC) to ~4 GPa (16% Ag content). This is attributed to the reduction of sp3 carbon bonds and the introduction of a soft metallic silver phase.
- Optimal Parameters: The DLC(Ag) layer deposited at 200 Hz (0.3% Ag) provided the best balance, retaining high mechanical properties (Hardness ~12 GPa) while maintaining full bactericidal activity.
- Structural Impact: Silver doping caused surface morphology changes, including the formation of silver clusters and aggregates, which grew larger as silver concentration increased.
- 6CCVD Value Proposition: 6CCVD provides high-purity MPCVD diamond (SCD/PCD) materials that can serve as superior, ultra-hard substrates for advanced coating systems, mitigating the mechanical degradation observed when doping soft substrates.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Substrate Material | 316L Steel | N/A | 25 mm diameter, 5 mm height |
| SCD/PCD Layer Thickness Range | 1.15 - 2 | ”m | Cr-CrN-DLC(Ag) multilayer coatings |
| Ag Target Pulse Frequencies | 200, 400, 600, 800 | Hz | HiPIMS deposition variable |
| Silver Content Range | 0.3 - 16 | % | Increases linearly with pulse frequency |
| Hardness (Pure DLC) | ~14 | GPa | Highest measured value |
| Hardness (DLC(Ag)-800 Hz) | ~4 | GPa | Lowest measured value (16% Ag) |
| Youngâs Modulus Range | 150 - 220 | GPa | Decreases with increasing Ag content |
| Optimal Mechanical Performance | 200 | Hz | Lowest Ag content (0.3%), highest hardness |
| Bactericidal Efficacy | 100 | % | Against E. coli and S. aureus (all Ag-doped samples) |
| Deposition Temperature | < 200 | °C | Maintained during DLC(Ag) layer deposition |
| Graphite Target Power (Pâ) | 9.24 | kW | Constant power supply |
| Silver Target Power (Pâ) | 0.36 | kW | Constant power supply |
Key Methodologies
Section titled âKey MethodologiesâThe multilayer Cr-CrN-DLC(Ag) coatings were deposited using High-Power Impulse Magnetron Sputtering (HiPIMS) in a chamber containing three circular magnetrons.
- Substrate Preparation: 316L steel substrates were ion-etched in Crâș plasma and heated to 200 °C.
- Target Materials:
- Two 4â magnetrons used pure Chromium (99.99% purity) and Graphite (99.99% purity).
- One 2â magnetron used a Silver target (99.99% purity).
- Base Layer Deposition (Cr and CrN):
- Cr layer: Ar 100%, Substrate polarization Ubias = -50 V, Pressure 5x10-3 mbar.
- CrN layer: Ar 85%, Nâ 15%, Ubias = -150 V, Pressure 5x10-3 mbar.
- DLC(Ag) Layer Deposition:
- Graphite target parameters (constant): Ubias = -50 V, Pâ = 9.24 kW, Pulse duration tâ = 60 ”s, Frequency F = 1000 Hz.
- Silver target parameters (variable): Ubias = -50 V, Pâ = 0.36 kW, Pulse duration tâ = 30 ”s.
- Variable Parameter: Voltage pulse frequency applied to the Ag target was varied (200, 400, 600, 800 Hz) to control silver content.
- Characterization: Mechanical properties were assessed using nanoindentation (Hardness, Youngâs Modulus) and scratch testing (Adhesion, critical forces Fcâ, Fcâ, Fcâ). Chemical composition and phase were analyzed via EDS and Raman spectroscopy.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe research demonstrates the critical need to balance the functional requirements (antibacterial activity) with mechanical integrity (hardness, adhesion). The observed decrease in hardness of the DLC(Ag) layer highlights the limitations of using softer substrates or relying solely on the coating for structural strength.
6CCVD offers advanced MPCVD diamond materials that provide a superior foundation for replicating or extending this research into high-performance, durable applications.
Applicable Materials
Section titled âApplicable MaterialsâTo replicate or extend this research, 6CCVD recommends the following materials, which offer significantly higher intrinsic hardness and thermal stability than 316L steel:
- Optical Grade SCD (Single Crystal Diamond): Ideal for applications requiring the highest possible hardness (up to 100 GPa) and ultra-low surface roughness (Ra < 1nm). SCD substrates would minimize the mechanical degradation seen in the DLC layer, making them suitable for high-precision biomedical tools or micro-electromechanical systems (MEMS).
- High-Purity PCD (Polycrystalline Diamond): Available in large formats (up to 125mm diameter), PCD offers excellent thermal conductivity and mechanical robustness, serving as a durable platform for large-area antibacterial coatings in industrial or medical environments.
- Custom Substrates: 6CCVD can provide custom diamond substrates (SCD or PCD) up to 10mm thick, engineered specifically to withstand the high-energy plasma environments used in HiPIMS or other PVD coating processes.
Customization Potential
Section titled âCustomization PotentialâThe success of the DLC(Ag) coating relies on precise layer control and integration. 6CCVD provides comprehensive services to support the development of such multilayer systems:
| Requirement from Paper | 6CCVD Capability | Benefit to Researcher |
|---|---|---|
| Substrate Dimensions (25 mm diameter) | Custom Plates/Wafers up to 125mm (PCD) | Enables scaling of antibacterial coatings for larger components or devices. |
| Multilayer Integration (Cr-CrN-DLC(Ag)) | Internal Metalization Services (Au, Pt, Pd, Ti, W, Cu) | 6CCVD can integrate custom adhesion layers (e.g., Ti/W) and conductive layers required for advanced diamond-based coating stacks. |
| Surface Finish (Critical for adhesion/biofilm) | Ultra-Polishing (SCD: Ra < 1nm; PCD: Ra < 5nm) | Provides a pristine, low-defect diamond surface, optimizing the adhesion (Fcâ) of the subsequent Cr-CrN and DLC(Ag) layers. |
| Thickness Control (1.15 ”m - 2 ”m coatings) | Precise CVD Thickness Control (0.1 ”m - 500 ”m) | Ensures the SCD/PCD substrate thickness meets specific thermal or structural requirements for the final device. |
Engineering Support
Section titled âEngineering SupportâThe relationship between sp3/sp2 hybridization and mechanical properties is central to this research. 6CCVDâs in-house PhD team specializes in tailoring diamond material properties (purity, crystal orientation, doping) to meet demanding application requirements.
We offer consultation services for similar Antiwear and Antibacterial Coating projects, focusing on:
- Selecting the optimal diamond grade (SCD vs. PCD) to maximize the overall system hardness and thermal performance.
- Designing custom metalization stacks to ensure robust adhesion between the diamond substrate and the functional DLC or metallic layers.
- Providing Boron-Doped Diamond (BDD) materials for electrochemical applications where intrinsic conductivity is required alongside extreme hardness.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Abstract In the present work, DLC coatings, well known for their antiwear properties, were modified by introducing to the structure an additive metal with antibacterial propertiesâsilver. Diamond-like coatings doped with silver were deposited on Cr-CrN layers created on steel 316L. To create the coatings, high-power impulse magnetron sputtering (HiPIMS) was used. The work carried out was divided into doping of DLC layers with silver and obtaining coatings with different contents of this metal by modifying the frequency of the voltage pulses applied to the silver target magnetron and investigating of the surface morphology, chemical and phase composition, mechanical properties and antibacterial activity. Light microscopy was used to analyse the surface morphology. The mechanical properties of the coatings were investigated using nanoindentation and the scratch method. Analysis of the antibacterial properties was carried out using two bacterial strains: Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive). The results showed that silver-doped DLC at a magnetron pulse frequency of 200 Hz had the best mechanical properties compared to other silver-doped coatings and possessed bactericidal activity.