Process for the formation of wear- and scuff-resistant carbon coatings

At a Glance

Metadata	Details
Publication Date	2023-01-23
Journal	Lincoln (University of Nebraska)
Authors	Gerard W. Malaczynski, Xiaohong Qiu, J. V. Mantese, Alaa A. Elmoursi, Aboud H Hamdi
Institutions	Cranbrook Academy of Art, Los Alamos Medical Center
Analysis	Full AI Review Included

Technical Documentation & Analysis: Wear- and Scuff-Resistant Carbon Coatings (US Patent 5,458,927)

This analysis connects the requirements for high-performance, wear-resistant carbon coatings achieved via Plasma Source Ion Implantation (PSII) to the advanced material solutions offered by 6CCVD. While the patent focuses on Diamond-Like Carbon (DLC) coatings, 6CCVD provides bulk, high-purity MPCVD diamond materials (SCD and PCD) that offer superior mechanical, thermal, and tribological performance for demanding engineering applications.

Executive Summary

Core Achievement: Development of an efficient, high-volume Plasma Source Ion Implantation (PSII) process for forming adherent, hard, low-friction carbon coatings (Diamond-Like Carbon, DLC) on complex, three-dimensional metal alloy workpieces.
Target Application: Enhancing the wear and scuff resistance of silicon-containing aluminum alloys (e.g., A390) used in automotive powertrain components (pistons) to eliminate the need for heavy iron liners.
Process Methodology: A sequential, four-step plasma immersion treatment: 1) Argon sputtering for oxide removal, 2) Carbon ion implantation (CH₄/C₂H₂) to form underlying metal carbides (75 nm to 150 nm deep), 3) Argon sputtering to remove coincidentally deposited graphitic material, and 4) Final low-energy deposition of amorphous hydrogen-containing carbon (DLC).
Key Material Properties: The final coating is an amorphous, hydrogen-containing carbon layer, 1 µm to 10 µm thick, characterized by high hardness and lubricity due to an appreciable fraction of sp³ bonds.
Technical Advantage: The PSII method ensures uniform coating and implantation on all unmasked surfaces, overcoming the line-of-sight limitations of traditional PVD/CVD techniques, making it suitable for high-volume manufacturing.

Technical Specifications

The following parameters were extracted from the patent describing the PSII process for DLC coating formation:

Parameter	Value	Unit	Context
Substrate Material	A390 Aluminum Alloy	N/A	Hypereutectic Al-Si alloy (17% Si)
Carbon Implantation Depth	75 to 150	nm	Forms underlying aluminum and silicon carbides
Final DLC Coating Thickness	1 to 10	µm	Adherent, amorphous hydrogen-containing carbon
Carbon Ion Dose (Implantation)	2 to 5 x 10¹⁷	ion/cm²	Required dose for carbide formation
Implantation Voltage Range	5 to 40 (Suitably 20)	kV	Negative pulses applied to workpiece
Implantation Pulse Duration	10 to 30	µs	Short duration, high frequency pulses
Argon Sputter Pressure (Oxide/Graphite Removal)	0.2 to 2.0 (Suitably 0.4)	mtorr	Subatmospheric pressure
Argon Sputter Voltage	1 to 10 (Suitably 1.2)	kV	Accelerates Ar⁺ ions for sputtering
DLC Deposition Pressure (C₂H₂)	2 to 70 (Suitably 4.5)	mtorr	Lower energy deposition step
DLC Deposition Voltage	600	V	Negative pulses (30 µs duration)

Key Methodologies

The process relies on sequential immersion of the workpiece in different plasma compositions and the application of high-voltage negative pulses to control ion kinetic energy for cleaning, implantation, and deposition.

Surface Oxide Removal (Argon Sputtering):
- Gas: Argon (Ar).
- Pressure: Low subatmospheric (0.2 mtorr to 2 mtorr).
- Energy Application: High voltage negative pulses (1 kV to 10 kV) or RF-induced DC self-bias (500 V to 2000 V) applied to the workpiece.
- Purpose: Accelerate Ar⁺ ions to sputter clean the surface, removing oxygen atoms and surface oxides (e.g., Al₂O₃, SiO₂).
Carbon Ion Implantation:
- Gas: Carbon-containing gas (Methane, CH₄, and/or Acetylene, C₂H₂).
- Pressure: 0.2 mtorr to 6 mtorr.
- Energy Application: High voltage negative pulses (5 kV to 40 kV, suitably 20 kV).
- Purpose: Implant positive carbon and hydrocarbon ions into the surface to form metal carbides (Al/Si carbides) for adhesion, while coincidentally depositing a thin, extraneous layer of graphitic material.
Graphitic Layer Removal (Argon Sputtering):
- Gas: Argon (Ar).
- Pressure: 0.2 mtorr to 2 mtorr.
- Energy Application: High voltage negative pulses (suitably 1.2 kV).
- Purpose: Bombard the surface with Ar⁺ ions to sputter and remove the non-adherent graphitic layer, exposing the carbide-containing surface for the final deposition step.
DLC Deposition:
- Gas: Acetylene (C₂H₂) and/or Methane (CH₄).
- Pressure: 2 mtorr to 70 mtorr (Suitably 4.5 mtorr).
- Energy Application: Lower energy negative pulses (suitably 600 V).
- Purpose: Deposit the final, adherent, hard, hydrogen-containing amorphous carbon layer (1 µm to 10 µm thick) for wear and scuff resistance.

6CCVD Solutions & Capabilities

The research demonstrates the critical need for materials exhibiting extreme hardness, low friction, and chemical inertness in high-wear environments (tribology). While DLC coatings offer a solution, 6CCVD provides bulk MPCVD diamond materials that deliver superior, intrinsic performance for the most demanding applications, including advanced tribological testing and high-power thermal management.

Applicable Materials

For applications requiring the highest level of wear resistance, thermal stability, and friction reduction, 6CCVD recommends the following materials:

6CCVD Material	Key Properties	Application Relevance to Wear/Scuff Resistance
Optical Grade Single Crystal Diamond (SCD)	Highest purity, extreme hardness (100 GPa), lowest friction (Ra < 1 nm polish).	Ideal for precision tribological test fixtures, ultra-low friction bearings, and counter-surfaces where minimal wear is paramount.
Polycrystalline Diamond (PCD)	High hardness, large area capability (up to 125 mm wafers), cost-effective for large components.	Excellent for large-scale wear plates, industrial tooling, and components requiring robust, uniform hardness over broad areas.
Boron-Doped Diamond (BDD)	Electrically conductive, chemically inert.	Suitable for electrochemical sensors or electrodes integrated into complex systems where wear resistance must be combined with electrical functionality.

Customization Potential

The PSII process is designed for complex, three-dimensional parts. 6CCVD supports the integration of bulk diamond into such systems through extensive customization capabilities:

Custom Dimensions and Shapes: 6CCVD provides SCD and PCD plates/wafers up to 125 mm in diameter. We offer precision laser cutting and shaping services to match the unique geometries required for complex automotive or industrial components.
Thickness Control: We supply SCD and PCD materials with precise thickness control, ranging from 0.1 µm films up to 500 µm wafers, and substrates up to 10 mm thick, ensuring optimal material volume for specific mechanical loads.
Advanced Metalization: For integrating diamond components into systems requiring electrical contact, heat sinking, or bonding, 6CCVD offers in-house metalization services, including Ti/Pt/Au, W, Cu, and Pd. This is critical for mounting diamond components adjacent to or replacing the high-wear surfaces discussed in the patent.
Ultra-Low Roughness Polishing: To achieve the lowest possible friction coefficients necessary for tribological applications, 6CCVD guarantees surface roughness (Ra) < 1 nm for SCD and < 5 nm for inch-size PCD.

Engineering Support

The challenges addressed in this research—achieving high adhesion and superior wear resistance in extreme environments—are core competencies of 6CCVD’s in-house PhD engineering team.

Material Selection for Tribology: Our experts can assist researchers and engineers in selecting the optimal diamond grade (SCD vs. PCD) and surface finish required to replicate or extend this research, particularly when transitioning from DLC coatings to bulk diamond solutions.
Integration Consultation: We provide technical consultation on mounting, bonding, and thermal management strategies for integrating high-performance diamond materials into complex Wear- and Scuff-Resistant Carbon Coating projects.

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

View Original Abstract

A process for forming an adherent diamond-like carbon coating on a workpiece of suitable material such as an aluminum alloy is disclosed. The workpiece is successively immersed in different plasma atmospheres and subjected to short duration, high voltage, negative electrical potential pulses or constant negative electrical potentials or the like so as to clean the surface of oxygen atoms, implant carbon atoms into the surface of the alloy to form carbide compounds while codepositing a carbonaceous layer on the surface, bombard and remove the carbonaceous layer, and to thereafter deposit a generally amorphous hydrogen-containing carbon layer on the surface of the article.

Tech Support

Original Source

DOI: None