Pipe Surface Coating Using Hollow Cathode Plasma for Uniform DLC

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Solution Overview

Problem

Existing methods for coating both internal and external surfaces of hollow workpieces simultaneously face challenges such as non-uniform external coatings, lower external coating thickness, and rapid decay of high ion density plasma, leading to poor quality coatings.

Innovation Solution

A method utilizing a hollow cathode effect with a multi-dimensional chamber and coaxial positioning of workpieces to maintain a controlled plasma intensity and focusing, allowing for simultaneous coating of internal and external surfaces with adjustable bias voltages and gas flow to achieve uniform diamond-like carbon (DLC) coatings.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If high ion density plasma is used for rapid deposition, then deposition rate increases, but plasma decays rapidly after exiting the hollow cathode source

Engineering Contradiction:

Improvedeposition rateVSAvoidplasma duration

Core Design Contradiction:

ProductivityVSDuration of action of stationary object

Solution Approach 1:

The plasma is generated and maintained in a controlled hollow cathode region before reaching the coating surface. By pre-establishing the high ion density plasma in this confined space and immediately directing it onto the surface, the system captures the deposition benefit before plasma decay occurs

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The hollow cathode source is nested within the vacuum chamber, creating a contained plasma generation zone. This nested structure allows the high ion density plasma to be generated and maintained in a controlled environment, extending its effective duration by preventing premature expansion and decay

Inventive Principle:

Principle #7Nested doll (Nesting)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach results in high deposition rates and uniform coating thickness on both surfaces, enhancing the quality and durability of the coatings, suitable for applications requiring corrosion resistance and thermal stability.

Implementation Method 1

Conditions are established to maintain a hollow cathode effect within the spacing between the interior surface of the chamber and the exterior surface of the workpiece... The interior surface of the chamber and the exterior surface of the workpiece are biased as cathodes... anodes are located at opposite ends of the hollow cathode effect region

Methodology Applied

Scientific EffectHollow cathode effect: Electric Glow Discharge

Implementation Method 2

Plasma Enhanced Chemical Vapor Deposition (PECVD) methods of coating external surfaces of a workpiece within a vacuum chamber are well known

Methodology Applied

Scientific EffectPlasma enhanced chemical vapor deposition: Plasma Enhanced Chemical Vapour Deposition

Data Source

PatentUS8343593B2Method of coating inner and outer surfaces of pipes for thermal solar and other applications

Publication Date: 2013.01.01 ARMORLUBE LLC

AI summary

A method of coating at least one exterior surface of at least one workpiece is disclosed. The method may be used for coating inner and outer surfaces of pipes. A hollow workpiece is positioned within a chamber. A spacing between a multi-dimensional interior surface of the chamber and an exterior surface of the workpiece is fixed. Conditions are established to maintain a hollow cathode effect within the spacing and within the hollow workpiece. The conditions include biasing anodes at opposite ends of a hollow cathode effect region, and biasing the interior surface of the chamber and the workpiece as cathodes. The interior surface and the workpiece may be maintained at a common bias voltage or, in at least one embodiment, at differing voltages.