Coating apparatus – Gas or vapor deposition – Multizone chamber
Patent
1987-12-07
1989-04-25
Bueker, Richard
Coating apparatus
Gas or vapor deposition
Multizone chamber
118715, 118724, 118725, 118730, C23C 1600
Patent
active
048237345
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an installation for the densification of porous pieces by chemical vapor infiltration of a refractory material other than carbon.
The field of application of the invention, therefore, is the production of composite pieces with refractory matrix in a material different from carbon, for example in silicon carbide or alumina.
Industrial installations are already known to be used for densifying porous pieces by chemical vapor deposition of carbon in order to produce composite pieces in carbon-carbon.
These installations however have proved unsuited for the infiltration of materials such as silicium carbide or alumina. One reason for this is that the infiltration of such materials requires the use of reactant gases or implies the production of reaction products such as hydrochloric acid which are chemicals difficult to manipulate. Another reason is the difficulty to perform uniform infiltrations without any undesirable deposits.
It is the object of the present invention to propose an installation permitting the densification of porous pieces with a refractory material such as silicium carbide or alumina, in the conditions of safety and reliability expected at industrial level.
This object is reached With an installation of the type comprising a graphite armature defining a reaction chamber, an inductor surrounding the armature and heating the reaction chamber by induction, a sealed enclosure containing said armature and inductor, means for supplying reactant gases to the reaction chamber, means for supplying inert gas to the enclosure, and means for removing gases from said reaction chamber and said enclosure, installation wherein, according to the invention, the armature constitutes a tight structure inside the enclosure and is connected outside said enclosure with the reactant gases supplying means, the enclosure is supplied with inert gas in order to keep up a permanent flow of inert gas in the space around the armature inside the enclosure, and the removal of gases from the reaction chamber and of inert gas from the enclosure is achieved via respective outlet conduits which join up outside the enclosure, so that substantially equal pressures are maintained in the enclosure, inside and outside the reaction chamber.
The tight structure of the armature prevents the reactant gases and the reaction products from coming into contact with parts of the infiltration furnace outside the armature, and in particular the metallic inductor, which parts could be attacked by these gases. The sweeping through of the enclosure outside the armature with a neutral gas creates a protection by forming a cushion around the reaction chamber. Furthermore, the fact of keeping the pressures equal in the enclosure, both inside and outside the armature, prevents any leak of neutral gas into the reaction chamber, which would interfere with the infiltration process, or any leak of the aggressive or dangerous reactant gases or reaction products in the enclosure, outside the reaction chamber.
Preferably, the gas removing means comprise a pumping device with water ring, such as a water ring pump, to which are connected the outlet pipes. With such a pumping device, removal of the corrosive products, such as hydrochloric acid, is made possible without the need for expensive protection systems normally required in other pumping devices such as vane pumps.
The invention will be more readily understood on reading the following description with reference to the accompanying drawings in which :
FIG. 1 is a very diagrammatical view of a known installation for the chemical vapor infiltration of carbon;
FIG. 2 is a diagrammatical view of an embodiment of the installation according to the invention for the chemical vapor infiltration of silicium carbide; and
FIG. 3 is a partial view showing in more detail the gas removing device of the installation according to FIG. 2.
Referring first to FIG. 1, this very diagrammatically shows a prior art furnace for the chemical vapor infiltration of carbon. A graphite armature 1 is
REFERENCES:
patent: 3925577 (1975-12-01), Fatzer
A. J. Caputo et al., "Development of a New, Faster Process for the Fabrication of Ceramic Fiber-Reinforced Ceramic Composites by Chemical Vapor Infiltration", Ceramic Engineering and Science Proceedings, vol. 6, No. 7/8, Jul.-Aug. 1985, pp. 694-706, Figure 1.
Bueker Richard
Societe Europeenne de Propulsion
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