Coating processes – With post-treatment of coating or coating material – Heating or drying
Patent
1998-05-13
2000-08-29
Meeks, Timothy
Coating processes
With post-treatment of coating or coating material
Heating or drying
4273762, 4273763, 4273797, 4274301, 427431, B05D 118, B05D 302
Patent
active
06110535&
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of incorporating a molten metal-based composition in porous substrates.
In the present case, the term "metal-based" is used to mean more particularly a composition comprising one or more metals, preferably having a melting temperature that is lower than 2000.degree. C., and capable of forming refractory carbides having a melting temperature greater than 2200.degree. C. Such metals are, in particular, silicon, titanium, zirconium, hafnium, and vanadium.
APPLICATION OF THE INVENTION
A particular field of application is incorporating a metal-based composition, and in particular a composition based on metallic elemental silicon (hereinafter an "Si-based" composition) in substrates of composite material, in particular of thermostructural composite material.
Thermostructural composite materials are characterized by mechanical properties which make them suitable for constituting structural parts, and by their ability to retain these properties at high temperatures. They are constituted by a fibrous reinforcing fabric made of refractory fibers and densified by a refractory matrix. Well known thermostructural composite materials are carbon-carbon (C--C) composites in which the reinforcing fabric is made of carbon fibers and the matrix is made of carbon, and ceramic matrix composites (CMCs) in which the reinforcing fabric is made of carbon fibers or of ceramic fibers and the matrix is made of ceramic, with the ceramic material constituting the fibers and/or the matrix frequently being silicon carbide, SiC.
Parts made of thermostructural composite material are generally fabricated by making a fiber preform and densifying it with the matrix. Well known densification methods include liquid densification which consists in impregnating the preform with a matrix precursor in the liquid state and then transforming the precursor by heat treatment, and densification by chemical vapor infiltration, or a combination of both methods. In which case, densification is performed initially using a liquid and subsequently by chemical vapor infiltration, or vice versa, or indeed by alternating a plurality of times between the two methods.
Whatever the densification method used, parts made of thermostructural composite material inevitably present residual internal pore space that is open, i.e. in communication with the outside of the part.
Thermostructural composite materials are used in a variety of fields where use is made of their ability to retain very good mechanical strength at high temperatures, in particular in the aviation, space, friction, and nuclear fields.
In aviation and in space, these materials are used in particular for jet engine flaps, nozzles, and coatings for protecting spacecraft against heating in the dense layers of the atmosphere. In the friction field, C--C composites are commonly used at present for aircraft brake disks, and their use for land vehicles which is presently restricted to F1 racing cars, will develop. In the nuclear field, C--C composite bricks have been developed in particular to form protective coatings for the walls of plasma confinement chambers in nuclear fusion reactors.
In those various applications, the properties of parts made of thermostructural composite materials can be improved by incorporating a metallic composition, and in particular an Si-based composition, in the residual internal pore space of the parts.
Thus, for parts made of composite material containing carbon, siliciding by incorporating a molten Si-based composition leads to internal silicon carbide protection against oxidation being formed by reaction between the carbon of the composite material and the molten silicon. The improvement in resistance to oxidation of composites containing carbon is particularly important in the aviation and space fields and in the friction field. In addition, for brake disks, siliciding provides particular friction behavior.
In the nuclear field, siliciding bricks for lining plasma confinement chambers significantly improves the ability of the C--
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Bernard Bruno
Laxague Michel
Rey Jacques
Barr Michael
Meeks Timothy
Societe Nationale d'Etude et Construction de Moteurs D'Aviation
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