A hollow cathode high density plasma process for internally coating cylindrical substrates

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A hollow cathode high density plasma process for internally coating cylindrical substrates

Lusk, D. / Gore, M. / Boardman, W. / Casserly, T. / Upadhyaya, D. / Tudhope, A.

A new and exciting technique for performing material deposition on the inside of cylindrical substrates, in particular pipes, will be described. Using the hollow cathode effect (HCE), a high density plasma can be generated within such cylindrical substrates by using Plasma Enhanced Chemical Vapor Deposition (PECVD). As the pipe itself is the vacuum chamber, such high density plasmas can be maintained by using asymmetric bipolar direct current (DC) pulsed power. Very high deposition rates can thus be achieved of the order of 1 micron/min. A vast number of applications can greatly benefit from this novel process, on both a large and small scale. Examples of such applications would be industrial piping, offshore drilling, chemical delivery systems, gun barrels and medical devices. A future application of this process would be in drug delivery systems. The films generated from this vacuum deposition technique can be optimized for whatever a specific application requires. In general these films have high corrosion, erosion and wear resistant properties but changing the process parameters can improve any of these properties. Details of the actual process and deposition system will be described in detail as well as how the technology works and how such high density plasmas can be maintained for various lengths and diameters of pipe. Results of the testing of these films by various techniques will be shown with the main properties of interest being hardness, adhesion, layer thickness, wear and corrosion resistance.