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Paragraph A

Changes not yet applied. Later legislation changes this provision in ways not yet written into the text below:

The definitions of processes specified in column 1 of the Table are as follows:

(a)

“Chemical Vapour Deposition” (CVD) is an overlay coating or surface modification coating process wherein a metal, alloy composite or ceramic is deposited upon a heated substrate. Gaseous reactants are reduced or combined in the vicinity of a substrate resulting in the deposition of the desired elemental, alloyed or compounded material on the substrate. Energy for this decomposition or chemical reaction process is provided by the heat of the substrate.

1

CVD includes the following processes: out-of-pack, pulsating, controlled nucleation thermal decomposition (CNTD), plasma enhanced or plasma assisted processes.

2

“Pack” means a substrate immersed in a powder mixture.

3

The gaseous material utilized in an out-of-pack process is produced using the same basic reactions and parameters as the pack cementation process, except that the substrate to be coated is not in contact wth the powder mixture.

(b)

“Electron beam physical vapour deposition” (EB PVD) is an overlay coating process conducted in a vacuum chamber, wherein an electron beam is directed onto the surface of a coating material causing vaporization of the material and resulting in condensation of the resultant vapours onto a substrate positioned appropriately, and includes a case where gases are added to the chamber during the processing.

(c)

“Electrophoretic deposition” is a surface modification coating or overlay coating process in which finely divided particles of a coating material suspended in a liquid dielectric medium migrate under the influence of an electrostatic field and are deposited on an electronically coducting substrate.

  • NB:

  • Heat treatment of parts after coating materials have been deposited on the substrate, in order to obtain the desired coating, is an essential step in the process.

(d)

“Pack cementation” is a surface modification coating or overlay coating process wherein a substrate is immersed in a powder mixture, a so-called pack, that consists of:

(1)

the metallic powders that are to be deposited (usually aluminium, chromium, silicon or combinations thereof);

(2)

an activator (normally a halide salt); and

(3)

an inert powder, most frequently alumina.

  • The substrate and powder mixture is contained within a retort which is heated to between 1030 K to 1375 K for sufficient time to deposit the coating.

(e)

“Plasma spraying” is an overlay coating process wherein a gun (spray torch), which produces and controls a plasma, accepts powdered coating materials, melts them and propels them towards a substrate, whereon an integrally bonded coating is formed.

  • For this purpose

1.

“High velocity” means more than 750 metres per second.

2.

“Low pressure” means less than ambient atmospheric pressure.

(f)

“Slurry deposition” is a surface modification coating or overlay coating process wherein a metallic or ceramic powder with an organic binder is suspended in a liquid and is aaplied to a substrate by either spraying, dipping or painting; subsequently air or oven dried, and heat treated to obtain the desired coating.

(g)

“Sputtering” is an overlay coating process wherein positively charged ions are accelerated by an electric field towards the surface of a target (coating material). The kinetic energy of the impacting ions is sufficient to cause target surface atoms to be released and despoited on the substrate.

  • NB:

  • Triode, magnetron or radio frequency sputtering to increase adhesion of coating and rate of despoition are included.

(h)

“Ion implantation” is a surface modification coating process in which the element to be alloyed is ionized, accelerated through a potential gradient and implanted into the surface region of the substrate. The definition includes processes in which the source of the ions is a plasma surrounding the substrate and processes in which ion implantation is performed simultaneously wth electron beam physical vapour deposition or sputtering.

(i)

“Cathodic arc deposition” employs a cathode which is consumable and has an arc discharge established on the surface by a momentary contact of ground trigger. Arc spots form and begin to erode randomly but uniformly the cathode surface creating a highly ionised plasma. The anode can be either a cone attached to the periphery of the cathode through an insulator or the chamber can be used as an anode. Substrates appropriately positioned receive deposits from the ionised plasma. Substrate biasing is used for non-line-of-sight deposition. A gas can be introduced in the vicinity of the substrate surface in order to react during deposition to synthesise compound coatings.