G 40
CAP. 60]
Import and Export (Strategic Commodities) Regulations
[1988 Ed.
[Subsidiary]
Technical Note:
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 materials on the substrate. Energy for this decomposition or chemical reaction process is provided by the heat of the substrate.
N.B.
1.
2.
3.
CVD includes the following processes-"out-of pack", pulsating, controlled nucleation thermal decomposition (CNTD)/ plasma enhanced or plasma assisted.
"Pack" denotes a substrate immersed in a powder mixture.
The gaseous material utilized in the 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 with 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 vapourization of the material and resulting in condensation of the resultant vapours onto a substrate positioned appropriately.
N.B.
The addition of gases to the chamber during the processing is an ordinary modification to the process.
(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 electrically conducting substrate.
N.B.
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 1030K to 1375K 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.
N.B. 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 applied 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 deposited on the substrate.
N.B.
Triode, magnetron or radio frequency sputtering to increase adhesion of coating and rate of deposition are ordinary modifications to the process.
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